JP6442248B2 - Damping valve and shock absorber - Google Patents

Description

  The present invention relates to a damping valve and a shock absorber.

  Some shock absorbers used in vehicle suspensions include a damping valve that can vary the damping force. Such a shock absorber includes a cylinder, a piston that divides the cylinder into an extension side chamber and a pressure side chamber, a piston rod that is connected to the piston at one end and is movably inserted into the cylinder, and a damping valve. The other damping valve is separated from and seated on a passage communicating the extension side chamber and the pressure side chamber provided in the piston and an annular valve seat surrounding the outlet end of the passage provided in the piston. A disc valve that opens and closes, a back pressure chamber that applies a pressure guided from the expansion side chamber or the pressure side chamber to the back surface of the disc valve, and an electromagnetic pressure control valve that uses a solenoid that controls the pressure in the back pressure chamber. (For example, refer to Patent Document 1).

  In the shock absorber configured in this way, the damping force at the time of expansion and contraction is controlled by controlling the pressure in the back pressure chamber by the electromagnetic pressure control valve. In the closed state where the valve is seated on the valve seat, liquid can pass back and forth between the expansion side chamber and the pressure side chamber through the fixed orifice provided in the disc valve, and the piston speed moves at a low speed. In this case, the shock absorber exerts a damping force mainly at the fixed orifice.

  JP 2001-12530 A

  Considering the ride comfort in a vehicle shock absorber, there are cases where it is desired to reduce the damping force when the piston speed is in a low speed range. Until the valve is opened, the damping force is exerted by the fixed orifice. To reduce the damping force, it is necessary to increase the opening area of the fixed orifice. If the opening area of the fixed orifice is increased, the damping force can certainly be reduced, but the maximum value of the damping force is determined by the fixed orifice, so that the damping force adjustment range is significantly reduced. Become.

  If the orifice is not provided, the damping force adjustment range becomes large. However, even if the damping force is fully soft, the damping force becomes too large and the riding comfort in the vehicle is deteriorated.

  Furthermore, in the conventional damping valve, when the pressure fluctuation of the back pressure chamber that urges the disc valve occurs, the urging force that urges the disc valve changes abruptly, so the damping force changes abruptly and the ride comfort in the vehicle is increased. There is a problem that makes it worse.

  Therefore, the present invention was devised to improve the above-described problems, and the object of the present invention is to reduce the damping force and increase the damping force adjustment range when the piston speed is in the low speed range. It is to provide a damping valve and a shock absorber that are possible, and to provide a damping valve and a shock absorber that can alleviate a sudden change in damping force.

  In order to solve the above-described object, the problem-solving means in the present invention provides a valve disk including a passage and a valve seat surrounding an outlet end of the passage, and a first clearance between the valve seat and the valve seat. An annular first leaf valve that is stacked on the disk and opens and closes the passage by being attached to and detached from the valve seat, and a second leaf valve that is stacked on the opposite valve disk side of the first leaf valve via a second gap And urging means for applying a variable urging force to the second leaf valve toward the valve disc side.

  According to the hydraulic shock absorber of the present invention, it is possible to reduce the damping force when the piston speed is in the low speed range and to increase the damping force adjustment range.

It is sectional drawing of the buffer which applied the damping valve in one Embodiment. It is a partial expanded sectional view of the buffer which applied the damping valve in one embodiment. It is an expanded sectional view of the damping valve in one embodiment. It is a figure explaining the damping force characteristic of the buffer which applied the damping valve in one embodiment.

  The present invention will be described below based on the illustrated embodiment. As shown in FIG. 1, the damping valve in one embodiment is applied to both the extension side damping valve and the compression side damping valve of the shock absorber D, and the extension side passage 3 and the pressure side passage 4 as the passages and the extension side. Piston 2 as a valve disk provided with annular extension side valve seat 2d and pressure side valve seat 2c surrounding the outlet ends of side passage 3 and pressure side passage 4, respectively, and extension side valve seat 2d as a first gap. An extension side first leaf valve Ve1 as an annular first leaf valve that is stacked on the piston 2 with a side first clearance, and a pressure side first clearance as a first clearance in the pressure side valve seat 2c are provided in the piston 2. The pressure side first leaf valve Vp1 as the annular first leaf valve to be stacked and the extension side second gap as the second gap on the counter piston side which is the counter valve disk side of the extension side first leaf valve Ve1. Laminated An annular second leaf valve Ve2 serving as a second leaf valve having an annular shape and a pressure-side second clearance serving as a second clearance are stacked on the non-piston side on the counter-valve disk side of the pressure-side first leaf valve Vp1. A variable urging force is applied to the pressure side second leaf valve Vp2 as the second leaf valve and the expansion side second leaf valve Ve2 toward the piston 2 side, and the pressure side second leaf valve Vp2 is variable toward the piston 2 side. And an urging means for applying an urging force. Of course, the damping valve of the present invention may be embodied only in the expansion side damping valve of the shock absorber D or only in the compression side damping valve.

  On the other hand, the shock absorber D is capable of moving in the axial direction a cylinder 1 filled with a fluid such as hydraulic oil, the above-described damping valve housed in the cylinder 1, and a piston 2 as a valve disk constituting the damping valve. An extension side chamber R1 and a pressure side chamber R2 partitioned by a piston 2 by being inserted into the cylinder 1 and a piston rod 7 that is movably inserted into the cylinder 1 and connected to the piston 2 are provided. When the piston 2 moves relative to the cylinder 1 in the axial direction which is the vertical direction in FIG. 1, the flow of the liquid passing through the expansion side passage 3 is controlled by the expansion side first leaf valve Ve1 on the compression side. A resistance is applied to the flow of liquid passing through the passage 4 by the compression-side first leaf valve Vp1 to exert a damping force.

  A free piston that slides in the cylinder 1 is provided below the cylinder 1 in FIG. 1, and a gas chamber is formed in the cylinder 1 by the free piston. The piston 2 is connected to one end of a piston rod 7 movably inserted into the cylinder 1, and the piston rod 7 penetrates the inner periphery of an annular rod guide (not shown) provided at the upper end of the cylinder 1. Then, it protrudes out of the cylinder 1. In addition, between the piston rod 7 and the cylinder 1, the inside of the cylinder 1 is in a liquid-tight state with a seal (not shown). Since the shock absorber D is set to a so-called single rod type, the volume of the piston rod 7 that enters and exits the cylinder 1 as the shock absorber D expands and contracts is the volume of the gas in the gas chamber described above. The free piston is compensated by expanding or contracting and moving the free piston up and down in the cylinder 1. Thus, the shock absorber D is set to a single cylinder type, but instead of installing a free piston and a gas chamber, a reservoir is provided on the outer periphery or outside of the cylinder 1, and the volume compensation of the piston rod 7 is performed by the reservoir. May be performed.

  Further, in this example, the urging means in the damping valve includes an expansion side spool Se that urges the expansion side second leaf valve Ve2, an expansion side back pressure chamber Ce that presses the expansion side spool Se with internal pressure, and a compression side. Via a pressure-side spool Sp for energizing the second leaf valve Vp2, a pressure-side back pressure chamber Cp for pressing the pressure-side spool Sp with internal pressure, and a pressure-side pilot orifice Pp as a pressure-side resistance element that provides resistance to the flow of liquid passing therethrough. A communication passage 24 communicated with the compression-side back pressure chamber Cp via an expansion-side pilot orifice Pe as an expansion-side resistance element that communicates with the expansion-side back pressure chamber Ce and gives resistance to the flow of liquid passing therethrough; The extension side pressure introduction passage Ie that allows only the flow of liquid from the side chamber R1 to the compression side back pressure chamber Cp, and the compression side pressure that allows only the flow of liquid from the compression side chamber R2 to the extension side back pressure chamber Ce. The introduction passage Ip, the adjustment passage Pc connected to the communication passage 24, and the pressure side discharge passage Ep that allows only the liquid flow from the adjustment passage Pc to the extension side chamber R1 while communicating with the downstream side of the adjustment passage Pc to the extension side chamber R1. A downstream side of the adjustment passage Pc to the pressure side chamber R2, and an extension side discharge passage Ee that allows only a liquid flow from the adjustment passage Pc to the pressure side chamber R2, and an upstream of the adjustment passage Pc provided in the adjustment passage Pc. And an electromagnetic pressure control valve 6 for controlling the pressure.

  Hereinafter, the damping valve and the shock absorber D will be described in detail. In this case, the piston rod 7 forms a piston holding member 8 that holds the piston 2 and a hollow receiving portion L that is connected to the piston holding member 8 at one end and receives the electromagnetic pressure control valve 6 together with the piston holding member 8. The solenoid valve housing cylinder 9 is formed of a rod member 10 having one end connected to the solenoid valve housing cylinder 9 and the other end projecting outward from the upper end of the cylinder 1.

  The piston holding member 8 includes a holding shaft 8a on which an annular piston 2 is mounted on the outer periphery, a flange 8b provided on the outer periphery of the upper end in FIG. 1 of the holding shaft 8a, and a cylindrical shape provided on the outer periphery of the upper end of FIG. Socket 8c. The piston holding member 8 has an annular hole 8d that opens from the tip of the holding shaft 8a and extends in the axial direction and communicates with the inside of the socket 8c, and a ring 8 provided at the lower end of the flange 8b in FIG. 1 so as to surround the holding shaft 8a. A groove 8e, a port 8f that communicates the annular groove 8e with the socket 8c, a horizontal hole 8g that communicates the annular groove 8e with the longitudinal hole 8d, and an extended side that opens from the outer periphery of the holding shaft 8a and communicates with the longitudinal hole 8d. An extension side pilot orifice Pe as a resistance element, a pressure side pilot orifice Pp as a pressure side resistance element, a screw portion 8i provided on the outer periphery of the lower end in FIG. 1 of the holding shaft 8a, and a vertical hole 8d formed at the upper end of the flange 8b. And a groove 8j that communicates therewith.

  In the vertical hole 8d provided in the holding shaft 8a, a communication path 24 is formed which communicates the expansion side pilot orifice Pe and the pressure side pilot orifice Pp in the vertical hole 8d with a cylindrical annular groove 23a provided on the outer periphery. The separator 23 to be inserted is inserted. An annular valve seat 23b surrounding the opening at the lower end is provided at the lower end of the separator 23 in FIG. The vertical hole 8d allows the pressure side chamber R2 to communicate with the socket 8c through the separator 23, but the expansion side pilot orifice Pe and the pressure side pilot orifice Pp are separated by the separator 23 into the pressure side chamber R2 and the socket through the vertical hole 8d. 8c is not connected. Further, the lateral hole 8g also communicates with the communication passage 24, and the lateral hole 8g is also prevented from communicating with the pressure chamber R2 and the socket 8c through the vertical hole 8d by the separator 23.

  The above-mentioned extension side resistance element and compression side resistance element only have to give resistance to the flow of liquid passing therethrough, so that not only the orifice but also other restriction such as a choke passage, a leaf valve, A valve that provides resistance, such as a poppet valve, may be used.

  An annular recess 8k is provided on the outer periphery of the upper end in FIG. 1 of the socket 8c, and a through-hole 8m that leads from the recess 8k into the socket 8c is provided in the socket 8c. An annular plate 22a is attached to the recess 8k, and the annular plate 22a is urged by a spring member 22b from above in FIG. 1 to close the through hole 8m.

  The solenoid valve housing cylinder 9 includes a top-cylindrical housing cylinder portion 9a and a cylindrical connecting portion that has an outer diameter smaller than that of the housing cylinder portion 9a and extends upward from the top of the housing cylinder portion 9a in FIG. 9b and a through-hole 9c that opens from the side of the accommodating tube portion 9a and communicates with the inside. Then, the piston holding member 8 is integrated with the solenoid valve housing cylinder 9 by screwing the socket 8c of the piston holding member 8 to the inner periphery of the housing cylinder portion 9a of the solenoid valve housing cylinder 9, and these solenoid valves The housing cylinder 9 and the piston holding member 8 form a housing portion L in which the electromagnetic pressure control valve 6 is housed in the housing tube portion 9a, and a part of an adjustment passage Pc described later in detail is provided in the housing portion L. . The accommodating portion L is connected to the communication path 24 by the port 8f, the annular groove 8e, and the lateral hole 8g, and the port 8f, the annular groove 8e, and the lateral hole 8g form a part of the adjustment passage Pc. ing. In addition, since the accommodating part L should just be connected to the communicating path 24, it does not employ | adopt the port 8f, the annular groove 8e, and the horizontal hole 8g, but the path | route which communicates with the accommodating part L directly to the communicating path 24 is used. However, the use of the port 8f, the annular groove 8e, and the lateral hole 8g has an advantage that the processing of the passage that communicates the accommodating portion L and the communication passage 24 is facilitated.

  As described above, when the piston holding member 8 is integrated with the electromagnetic valve housing cylinder 9, the through hole 9c faces the recess 8k, and cooperates with the through hole 8m to communicate the housing portion L with the extension side chamber R1. The non-return valve 22 that allows only the flow of liquid from the inside of the accommodating portion L to the extension side chamber R1 is formed by the annular plate 22a and the spring member 22b. Therefore, the pressure side discharge passage Ep is formed by the through hole 9 c, the recess 8 k, the through hole 8 m, and the check valve 22.

  Further, a check valve 25 that is attached to and detached from an annular valve seat 23b provided at the lower end in FIG. 1 of the separator 23 is provided in the vertical hole 8d of the piston holding member 8. While preventing the flow of the liquid which goes to the accommodating part L from the R2 side, only the flow of the liquid which goes to the compression side chamber R2 from the accommodating part L is permitted. Therefore, the extended-side discharge passage Ee is formed in the vertical hole 8d by the separator 23.

  The rod member 10 has a cylindrical shape, and the inner circumference at the lower end in FIG. 1 has an enlarged diameter, allows insertion of the connecting portion 9b of the solenoid valve housing cylinder 9, and enables the connecting portion 9b to be screwed. A screw portion (not shown) is provided. Thus, the piston rod 7 is formed by integrating the rod member 10, the electromagnetic valve housing cylinder 9 and the piston holding member 8.

  A harness H for supplying power to a solenoid, which will be described later, is inserted into the rod member 10 and the connecting portion 9b of the solenoid valve housing cylinder 9. It extends outward and is connected to a power source.

  As shown in FIG. 3, on the outer periphery of the holding shaft 8 a provided on the piston holding member 8, together with the annular piston 2, a pressure side first annular spacer 60 serving as a first annular spacer on the upper side of the piston 2 in FIG. The first leaf valve Vp1, the pressure side second annular spacer 61 as the second annular spacer, the pressure side second leaf valve Vp2, the pressure side spacer 62 as the spacer, the pressure side annular plate 63 as the annular plate, and the pressure side plate stopper 64 And the pressure side spool Sp and the pressure side chamber 11 forming the pressure side back pressure chamber Cp are assembled, and the lower side of the piston 2 in FIG. One leaf valve Ve1, an extended second annular spacer 66 as a second annular spacer, an extended second leaf valve Ve2, an extended spacer 67 as a spacer, an annular plug Shin-side annular plate 68 as over bets, and the extension side plate stopper 69, the extension side spool Se, and the extension side chamber 12 to form the expansion side back pressure chamber Ce assembled.

  In this case, the piston 2 is formed by overlapping the upper and lower discs 2a and 2b, and an extension side passage 3 and a pressure side passage 4 that connect the extension side chamber R1 and the pressure side chamber R2 are formed. Yes. In this way, by forming the piston 2 with the discs 2a and 2b divided into the upper and lower sides, the complicated-side expansion side passage 3 and compression side passage 4 can be formed without drilling, and the cost is low. And the piston 2 can be manufactured easily. Further, as shown in FIG. 3, at the upper end of the disk 2a, there are an annular window 2e communicating with the pressure side passage 4, and an annular pressure side valve seat 2c provided on the outer peripheral side of the annular window 2e and surrounding the pressure side passage 4. An inner peripheral sheet portion 2f provided on the inner periphery of the annular window 2e is provided. On the other hand, at the lower end of the disk 2b on the lower side, an annular window 2g communicating with the extension side passage 3, an annular extension side valve seat 2d provided on the outer peripheral side of the annular window 2g and surrounding the extension side passage 3, An inner peripheral sheet portion 2h provided on the inner periphery of the annular window 2g is provided.

  As shown in FIG. 3, the extension-side first leaf valve Ve <b> 1 has an annular shape to allow insertion of the holding shaft 8 a of the piston holding member 8. Further, the extension side first leaf valve Ve1 is sandwiched between the piston 2 and the extension side chamber 12 and fixed to the holding shaft 8a of the piston holding member 8, and the outer circumference is allowed to be bent. More specifically, the back side of the extension side first leaf valve Ve1 is provided with an extension side second annular spacer 66 having an outer diameter smaller than that of the extension side first leaf valve Ve1, and the extension side first leaf is interposed. When the valve Ve1 is bent downward in FIG. 3, the outer peripheral side is allowed to be bent from the portion supported by the extended second annular spacer 66. When the valve Ve1 is bent upward in FIG. Deflection on the outer peripheral side of the portion supported by the spacer 65 is allowed.

  Further, an extension side second leaf valve Ve2 is stacked below the extension side second annular spacer 66 on the opposite side of the valve disk in FIG. 3, and the extension side second leaf valve Ve2 is also the extension side first leaf. Similar to the valve Ve1, the inner periphery is sandwiched between the piston 2 and the extension side chamber 12 and fixed to the holding shaft 8a of the piston holding member 8, and the outer periphery is allowed to bend. The extension side second leaf valve Ve2 is directly sandwiched between an extension side second annular spacer 66 and an extension side spacer 67 whose outer diameter is smaller than the outer diameter of the extension side second leaf valve Ve2. In addition, the outer periphery of the portion supported by these is allowed to bend.

  And the extending | stretching side 1st leaf valve Ve1 comprised in this way is laminated | stacked below the piston 2 in FIG. 3 via the extending | stretching side 1st annular spacer 65 laminated | stacked on the inner peripheral seat part 2h of piston 2. As shown in FIG. . In a state where no load is applied to the extension side first leaf valve Ve1, an extension side first gap is formed between the extension side first leaf valve Ve1 and the extension side valve seat 2d. The length in the vertical direction in FIG. 3 of the extension side first gap can be adjusted by replacing the extension side first annular spacer 65 with a different thickness or changing the number of extension side first annular spacers 65 stacked. it can. In addition, the extension side first clearance between the extension side first leaf valve Ve1 and the extension side valve seat 2d is such that the height of the inner peripheral seat portion 2h is set higher than the height of the extension side valve seat 2d. Alternatively, the extended first annular spacer 65 can be eliminated and the extended first leaf valve Ve1 can be directly laminated on the inner peripheral seat portion 2h. However, the length of the extension side first gap can be easily adjusted by providing the extension side first annular spacer 65.

  Further, the extension side second leaf valve Ve2 is stacked below the extension side first leaf valve Ve1 in FIG. 3 via the extension side second annular spacer 66. In a state where no load is applied to the extension side second leaf valve Ve2, an extension side second gap is formed between the extension side second leaf valve Ve2 and the extension side first leaf valve Ve1. The length in the vertical direction in FIG. 3 of the extension side second gap can be adjusted by exchanging with the extension side second annular spacer 66 having a different thickness or changing the number of extension side second annular spacers 66 stacked. it can. By providing the extended second annular spacer 66, it is possible to easily adjust the length of the extended second gap.

  Further, an extension side annular plate 68 is slidably mounted on the outer periphery of the extension side spacer 67. The axial length of the extension-side annular plate 68 is shorter than the axial length of the extension-side spacer 67, and the extension-side annular plate 68 can move in the up-down direction while being in sliding contact with the outer periphery of the extension-side spacer 67. It can be done. Further, an extension side plate stopper 69 that is annular and has an outer diameter set larger than the inner diameter of the extension side annular plate 68 is provided below the extension side spacer 67 in FIG. The extension side chamber 12 is stacked below the side plate stopper 69. Further, the inner diameter of the expansion side annular plate 68 is set to be smaller than the outer diameter of the inner peripheral sheet portion 2 h provided in the piston 2. The outer diameter of the expansion side annular plate 68 is set to be larger than the inner diameter of the expansion side valve seat 2d. The extension-side annular plate 68 can move in the vertical direction in FIG. 3, which is the axial direction, between the extension-side second annular spacer 66 and the extension-side plate stopper 69.

  The expansion side annular plate 68 has a higher bending rigidity than the expansion side second leaf valve Ve2. Therefore, the axial length (thickness) of the expansion side annular plate 68 is longer than the axial length (thickness) of the expansion side second leaf valve Ve2, but not only the rigidity is increased by the axial length. The extension side annular plate 68 may be formed of a material having higher rigidity than the extension side second leaf valve Ve2.

  When the expansion side annular plate 68 is pressed by the urging means from the side opposite to the piston, which is the back side, specifically, the pressure in the expansion side back pressure chamber Ce and the expansion side spool Se, The extension side second leaf valve Ve2 is pushed up and bent together with the extension side second leaf valve Ve2. The expansion side second leaf valve Ve2 bends as described above when the urging force from the urging means is applied from the back side through the expansion side annular plate 68. However, the urging force increases and the outer periphery is expanded. If it bends so that it may displace more than a 2nd clearance gap, it will contact | abut to the expansion side 1st leaf valve Ve1. When the extension side second leaf valve Ve2 presses the extension side first leaf valve Ve1, the extension side first leaf valve Ve1 bends, and when the displacement of the outer periphery due to this bending becomes equal to or greater than the extension side first gap, the extension side first The leaf valve Ve1 is seated on the extension side valve seat 2d, and the extension side passage 3 is closed.

  If the extension side first leaf valve Ve1 is bent until it is seated on the extension side valve seat 2d, the extension side annular plate 68 is supported by the inner peripheral seat portion 2h and the extension side valve seat 2d. The pressure in the pressure chamber Ce and the urging force by the expansion side spool Se are received by the expansion side annular plate 68, and further deformation of the expansion side first leaf valve Ve1 and the expansion side second leaf valve Ve2 is suppressed, The extension side first leaf valve Ve1 and the extension side second leaf valve Ve2 are not overloaded. Further, since the expansion side annular plate 68 is slidably mounted on the expansion side spacer 67, the expansion side first leaf valve Ve1 and the expansion side second leaf valve Ve2 are separated from the expansion side valve seat 2d. 3 is moved downward in FIG. 3 with respect to the expansion side spacer 67, the bending operation of the expansion side first leaf valve Ve1 and the expansion side second leaf valve Ve2 in the direction away from the piston 2 is performed. There is no hindrance.

Subsequently, the extending side chamber 12 includes a cylindrical mounting portion 12a fitted to the outer periphery of the holding shaft 8a of the piston holding member 8, a flange portion 12b provided on the outer periphery of the lower end in FIG. A sliding contact cylinder 12c extending from the outer periphery of the portion 12b toward the piston 2 side, an annular groove 12d provided on the inner periphery of the mounting portion 12a, and a notch 12e communicating from the outer periphery of the mounting portion 12a to the annular groove 12d. Has been. When the extension side chamber 12 is assembled to the holding shaft 8a, the annular groove 12d faces the pressure side pilot orifice Pp provided on the holding shaft 8a. Note that an extension side plate stopper 69 is interposed between the attachment portion 12a and the extension side spacer 67 in the extension side chamber 12, but the extension side plate stopper 69 is eliminated and the extension portion 12a is extended to the extension side. The lower limit of movement of the annular plate 68 may be regulated. However, when the expansion side chamber 12 is assembled to the holding shaft 8a of the piston holding member 8, if it is necessary to adjust the pressure side pilot orifice Pp and the annular groove 12d to face each other, the expansion side plate stopper 69 is used. It is possible to adjust the position of the extension side chamber 12 with respect to the piston holding member 8.

  An extension side spool Se is accommodated in the sliding contact cylinder 12c. The extension side spool Se is in sliding contact with the inner periphery of the sliding contact cylinder 12c, and can move in the axial direction within the sliding contact cylinder 12c. The extension-side spool Se includes an annular spool body 13 and an annular protrusion 14 that rises from the inner periphery of the upper end of the spool body 13 in FIG. The inner diameter of the annular protrusion 14 is set to be smaller than the outer diameter of the extended-side annular plate 68 so that the annular protrusion 14 can come into contact with the lower surface in FIG. It has become.

  When the expansion side spool Se is assembled to the expansion side chamber 12 and the expansion side chamber 12 is assembled to the holding shaft 8a as described above, the expansion side chamber 12 extends to the lower side in FIG. 3, which is the back side of the expansion side second leaf valve Ve2. A side back pressure chamber Ce is formed. The inner diameter of the spool body 13 is larger than the outer diameter of the mounting portion 12a, but this is set to a diameter that is in sliding contact with the outer periphery of the mounting portion 12a. It can also be sealed.

  In addition, an annular groove 12d is provided on the inner periphery of the mounting portion 12a of the extension side chamber 12, and a notch 12e is provided from the outer periphery of the mounting portion 12a to the annular groove 12d. When assembled to the holding shaft 8a, the annular groove 12d faces the pressure side pilot orifice Pp provided on the holding shaft 8a, and the expansion side back pressure chamber Ce communicates with the pressure side pilot orifice Pp.

  Further, the expansion side chamber 12 is provided with a pressure side pressure introduction passage Ip that opens from the outer periphery of the flange portion 12b, and communicates the compression side chamber R2 into the expansion side back pressure chamber Ce. An annular plate 15 is laminated on the upper end in FIG. 3 of the flange portion 12b of the extension side chamber 12, and the annular plate is provided by a spring member 16 interposed between the annular plate 15 and the spool body 13 of the extension side spool Se. 15 is pressed against the flange portion 12b to close the pressure side pressure introduction passage Ip. Note that the pressure side pressure introduction passage Ip is considered so as not to cause resistance to the flow of the passing liquid.

  When the pressure side chamber R2 is compressed and the pressure is increased during the contraction operation of the shock absorber D, the annular plate 15 is pressed by the pressure and is separated from the flange portion 12b to open the pressure side pressure introduction passage Ip. During the expansion operation of the shock absorber D in which the pressure in the side back pressure chamber Ce becomes higher than the pressure side chamber R2, the pressure side pressure introduction passage Ip is closed by being pressed against the flange portion 12b, and only the liquid flow from the pressure side chamber R2 is allowed. It functions as a check valve body of the pressure check valve Tp. The pressure-side check valve Tp sets the pressure-side pressure introduction passage Ip as a one-way passage that allows only the flow of liquid from the pressure-side chamber R2 to the extension-side back pressure chamber Ce.

  The spring member 16 plays a role of pressing the annular plate 15 against the flange portion 12b, and constitutes the compression side check valve Tp together with the annular plate 15 which is a check valve valve body, and the extension side spool Se is connected to the extension side second leaf. It also plays a role of energizing toward the valve Ve2. By energizing the extension side spool Se with the spring member 16, the extension side second leaf valve Ve2 is bent and the extension side spool Se is separated from the piston 2 and pushed downward in FIG. Even if the deflection of the second side leaf valve Ve2 is eliminated, the spring member 16 is biased so that the extension side spool Se follows the extension side second leaf valve Ve2 and quickly returns to its original position (see FIG. 3). To the position shown). Although it is possible to urge the expansion side spool Se with a separate spring member, the compression side check valve Tp and the spring member 16 can be shared, and the number of parts can be reduced and the structure can be simplified. There is. The outer diameter of the extension side spool Se is set to be larger than the inner diameter of the annular protrusion 14, and the annular protrusion 14 comes into contact with the extension side annular plate 68. The side back pressure chamber Ce is always biased toward the expansion side second leaf valve Ve2.

  As shown in FIG. 3, the compression-side first leaf valve Vp1 stacked above the piston 2 has an annular shape so as to allow the holding shaft 8a of the piston holding member 8 to be inserted, like the extension-side first leaf valve Ve1. The inner circumference is sandwiched between the piston 2 and the pressure side chamber 11 and fixed to the holding shaft 8a of the piston holding member 8, and the outer circumference is allowed to bend. More specifically, a pressure side second annular spacer 61 having an outer diameter smaller than that of the pressure side first leaf valve Vp1 is interposed on the back side of the pressure side first leaf valve Vp1, and the pressure side first leaf valve Vp1 is In the case of bending upward in FIG. 3, bending on the outer peripheral side is allowed from the portion supported by the pressure side second annular spacer 61, and in the case of bending downward in FIG. 3, it is supported by the pressure side first annular spacer 60. Deflection on the outer peripheral side of the part is allowed.

  In addition, a pressure side second leaf valve Vp2 is stacked above the pressure side second annular spacer 61 on the side opposite to the valve disk in FIG. 3, and the pressure side second leaf valve Vp2 is also the same as the pressure side first leaf valve Vp1. Further, the inner circumference is sandwiched between the piston 2 and the pressure side chamber 11 and fixed to the holding shaft 8a of the piston holding member 8, and the outer circumference is allowed to bend. The pressure side second leaf valve Vp2 is directly sandwiched between a pressure side second annular spacer 61 and a pressure side spacer 62 whose outer diameter is smaller than the outer diameter of the pressure side second leaf valve Vp2. Deflection on the outer peripheral side than the portion to be applied is allowed.

  And the pressure side 1st leaf valve Vp1 comprised in this way is laminated | stacked on the upper side in FIG. In a state where no load is applied to the pressure side first leaf valve Vp1, a pressure side first gap is formed between the pressure side first leaf valve Vp1 and the pressure side valve seat 2c. The vertical length of the pressure side first gap in FIG. 3 can be adjusted by replacing the pressure side first annular spacer 60 with a different thickness or changing the number of stacked pressure side first annular spacers 60. The pressure-side first clearance between the pressure-side first leaf valve Vp1 and the pressure-side valve seat 2c is set so that the height of the inner peripheral seat portion 2f is higher than the height of the pressure-side valve seat 2c. It can also be formed by eliminating the annular spacer 60 and laminating the pressure side first leaf valve Vp1 directly on the inner peripheral seat portion 2f. However, the length of the pressure side first gap can be easily adjusted by providing the pressure side first annular spacer 60.

  Furthermore, the pressure side second leaf valve Vp2 is stacked above the pressure side first leaf valve Vp1 in FIG. In a state where no load is applied to the pressure side second leaf valve Vp2, a pressure side second gap is formed between the pressure side second leaf valve Vp2 and the pressure side first leaf valve Vp1. The vertical length in FIG. 3 of the pressure side second gap can be adjusted by exchanging the pressure side second annular spacer 61 with a different thickness or changing the number of stacked pressure side second annular spacers 61. By providing the pressure side second annular spacer 61, the length of the pressure side second gap can be easily adjusted.

  Further, a pressure side annular plate 63 is slidably mounted on the outer periphery of the pressure side spacer 62. The axial length of the pressure side annular plate 63 is shorter than the axial length of the pressure side spacer 62, and the pressure side annular plate 63 can move in the vertical direction while being in sliding contact with the outer periphery of the pressure side spacer 62. ing. Further, a pressure side plate stopper 64 having an annular shape whose outer diameter is set larger than the inner diameter of the pressure side annular plate 63 is provided above the pressure side spacer 62 in FIG. 3. The compression side chamber 11 is stacked above the substrate. The inner diameter of the pressure side annular plate 63 is set to be smaller than the outer diameter of the inner peripheral sheet portion 2 f provided on the piston 2. The outer diameter of the pressure side annular plate 63 is set to be larger than the inner diameter of the pressure side valve seat 2c. The pressure side annular plate 63 can move in the vertical direction in FIG. 3, which is the axial direction, between the pressure side second annular spacer 61 and the pressure side plate stopper 64.

  The compression-side annular plate 63 has a higher bending rigidity than the compression-side second leaf valve Vp2. Therefore, although the axial length (thickness) of the compression side annular plate 63 is longer than the axial length (thickness) of the compression side second leaf valve Vp2, not only the rigidity is increased by the axial length but also the compression side annular plate 63 is compressed. The compression side annular plate 63 may be formed of a material having higher rigidity than the second leaf valve Vp2.

  When the pressure side annular plate 63 is pressed by the urging means from the counter-piston side on the back side, specifically, the pressure in the pressure side back pressure chamber Cp and the pressure side spool Sp, the pressure side annular plate 63 is pressed against the pressure side second leaf. The valve Vp2 is pushed down and bends together with the pressure side second leaf valve Vp2. The pressure-side second leaf valve Vp2 bends as described above when the urging force from the urging means is applied through the pressure-side annular plate 63 from the back side. If it bends so that it may displace, it will contact pressure side first leaf valve Vp1. When the pressure-side second leaf valve Vp2 presses the pressure-side first leaf valve Vp1, the pressure-side first leaf valve Vp1 bends, and when the displacement of the outer periphery due to this bending becomes greater than or equal to the pressure-side first gap, the pressure-side first leaf valve Vp1 It sits on the valve seat 2 c and closes the pressure side passage 4.

  When the pressure side first leaf valve Vp1 is bent until it is seated on the pressure side valve seat 2c, the pressure side annular plate 63 is supported by the inner peripheral seat portion 2f and the pressure side valve seat 2c. The pressure and the urging force of the pressure side spool Sp are received by the pressure side annular plate 63, and further deformation of the pressure side first leaf valve Vp1 and the pressure side second leaf valve Vp2 is suppressed, and the pressure side first leaf valve Vp1 and the pressure side first The two leaf valve Vp2 is not overloaded. Further, since the pressure side annular plate 63 is slidably attached to the pressure side spacer 62, the pressure side first leaf valve Vp1 and the pressure side second leaf valve Vp2 are bent in a direction away from the pressure side valve seat 2c. 3 moves upward in FIG. 3 with respect to the pressure side spacer 62, so that the bending operation of the pressure side first leaf valve Vp1 and the pressure side second leaf valve Vp2 in the direction away from the piston 2 is not hindered.

  Subsequently, the compression side chamber 11 includes a cylindrical mounting portion 11a that is fitted to the outer periphery of the holding shaft 8a of the piston holding member 8, a flange portion 11b that is provided on the outer periphery of the upper end of the mounting portion 11a in FIG. A sliding contact cylinder 11c extending from the outer periphery of 11b toward the piston 2 side, an annular groove 11d provided on the inner periphery of the mounting portion 11a, and a notch 11e communicating from the outer periphery of the mounting portion 11a to the annular groove 11d. ing. When the pressure side chamber 11 is assembled to the holding shaft 8a, the annular groove 11d is opposed to the extension pilot orifice Pe provided on the holding shaft 8a. The pressure side plate stopper 64 is interposed between the mounting portion 11a and the pressure side spacer 62 in the pressure side chamber 11, but the pressure side plate stopper 64 is eliminated and the pressure side annular plate 63 is moved by the mounting portion 11a. The upper limit may be regulated. However, when the pressure side chamber 11 is assembled to the holding shaft 8a of the piston holding member 8, if it is necessary to adjust the extension side pilot orifice Pe and the annular groove 11d to face each other, the pressure side plate stopper 64 is provided. By providing, the position of the compression side chamber 11 with respect to the piston holding member 8 can be adjusted.

  A pressure side spool Sp is accommodated in the sliding contact cylinder 11c. The pressure-side spool Sp is in sliding contact with the inner periphery of the sliding contact cylinder 11c and can move in the axial direction within the sliding contact cylinder 11c. The pressure-side spool Sp includes an annular spool body 17 and an annular protrusion 18 that rises from the outer periphery of the lower end of the spool body 17 in FIG. The inner diameter of the annular protrusion 18 is set to be smaller than the outer diameter of the pressure-side annular plate 63 so that the annular protrusion 18 can come into contact with the upper surface in FIG. Yes.

  When the pressure-side spool Sp is assembled to the pressure-side chamber 11 and the pressure-side chamber 11 is assembled to the holding shaft 8a in this way, the pressure-side back pressure chamber Cp is located on the upper side in FIG. 3, which is the back side of the pressure-side second leaf valve Vp2. Is formed. The inner diameter of the spool body 17 is larger than the outer diameter of the mounting portion 11a. However, the spool body 17 is set to a diameter that is in sliding contact with the outer periphery of the mounting portion 11a so that the compression side back pressure chamber Cp is sealed with the compression side spool Sp. It is also possible to make it.

  Further, an annular groove 11d is provided on the inner periphery of the mounting portion 11a of the pressure side chamber 11, and a notch 11e is provided from the outer periphery of the mounting portion 11a to the annular groove 11d. The annular groove 11d is opposed to the extension side pilot orifice Pe provided on the holding shaft 8a so that the compression side back pressure chamber Cp communicates with the extension side pilot orifice Pe. The compression side back pressure chamber Cp communicates with the expansion side back pressure chamber Ce through the communication passage 24 formed in the vertical hole 8d of the holding shaft 8a and the compression side pilot orifice Pp by communicating with the expansion side pilot orifice Pe.

  Further, the compression side chamber 11 is provided with an expansion side pressure introduction passage Ie that opens from the outer periphery of the flange portion 11b, and allows the expansion side chamber R1 to communicate with the compression side back pressure chamber Cp. An annular plate 19 is laminated at the lower end of the flange portion 11b of the compression side chamber 11 in FIG. 3, and the annular plate 19 is attached by a spring member 20 interposed between the annular plate 19 and the spool body 17 of the compression side spool Sp. The extension side pressure introduction passage Ie is closed by being pressed against the flange portion 11b. Note that the extension side pressure introduction passage Ie is designed not to cause resistance to the flow of the passing liquid.

  When the expansion side chamber R1 is compressed and the pressure increases when the shock absorber D is extended, the annular plate 19 is pressed by the pressure and is separated from the flange portion 11b to open the expansion side pressure introduction passage Ie. During the contraction operation of the shock absorber D in which the pressure in the compression side back pressure chamber Cp becomes higher than that of the expansion side chamber R1, it is pressed against the flange portion 11b to close the expansion side pressure introduction passage Ie, and only the liquid flow from the expansion side chamber R1 is allowed. It functions as a check valve body of the extending check valve Te. By this extension side check valve Te, the extension side pressure introduction passage Ie is set as a one-way passage that allows only the flow of liquid from the extension side chamber R1 toward the compression side back pressure chamber Cp.

  Here, as described above, the communication path 24 communicates with the inside of the housing portion L through the annular groove 8e, the port 8f, and the lateral hole 8g provided in the piston holding member 8. Therefore, the expansion side back pressure chamber Ce and the pressure side back pressure chamber Cp are not only communicated with each other via the expansion side pilot orifice Pe, the compression side pilot orifice Pp and the communication path 24, but also via the expansion side pressure introduction path Ie. The expansion side chamber R1 communicates with the compression side chamber R2 via the pressure side pressure introduction passage Ip, and further communicates with the accommodating portion L through the port 8f and the lateral hole 8g.

Returning, the spring member 20 plays a role of pressing the annular plate 19 against the flange portion 11b, and constitutes the extension-side check valve Te together with the annular plate 19 which is a check valve valve body, and the compression-side spool Sp is connected to the compression-side spool Sp. It also plays a role of energizing towards the two leaf valve Vp2. By energizing the compression side spool Sp by the spring member 20, from a state in which the compression side spool Sp is pushed upward in FIG. 3 to be spaced apart from the piston 2 flexed pressure side second Rifubaru blanking V p2 is the pressure side second Even if the deflection of the leaf valve Vp2 is eliminated, the pressure side spool Sp follows the pressure side second leaf valve Vp2 and quickly returns to the original position (position shown in FIG. 3) because it is biased by the spring member 20. be able to. Although it is possible to urge the compression side spool Sp with a separate spring member, the extension side check valve Te and the spring member 20 can be used in common, and the number of parts can be reduced and the structure can be simplified. There is. The outer diameter of the pressure-side spool Sp is set to be larger than the inner diameter of the annular protrusion 18 so that the annular protrusion 18 contacts the pressure-side annular plate 63. The pressure-side spool Sp is a pressure-side back pressure chamber. Since it is always urged toward the pressure side second leaf valve Vp2 by the pressure of Cp, it is not necessary to install it if it is a spring member for the purpose of energizing only the pressure side spool Sp.

  The expansion side spool Se receives the pressure of the expansion side back pressure chamber Ce and urges the expansion side second leaf valve Ve2 toward the piston 2 via the expansion side annular plate 68. In a state where the two leaf valve Ve2 is in contact with the extension side first leaf valve Ve1, the extension side first leaf valve Ve1 is also urged toward the piston 2. The pressure receiving area that receives the pressure of the extension side back pressure chamber Ce of the extension side spool Se is the difference between the area of the circle having the outer diameter of the extension side spool Se as the diameter and the area of the circle having the inner diameter of the annular protrusion 14 as the diameter. Become.

Similarly, the pressure side spool Sp receives the pressure of the pressure side back pressure chamber Cp and urges the pressure side second leaf valve Vp2 toward the piston 2 via the pressure side annular plate 63, and further pressurizes the pressure side second leaf valve Vp2. In a state where the pressure side first leaf valve Vp1 is in contact with the pressure side first leaf valve Vp1, the pressure side first leaf valve Vp1 is also urged toward the piston 2. The pressure receiving area that receives the pressure of the pressure side back pressure chamber Cp of the pressure side spool Sp is a difference between the area of the circle having the outer diameter of the pressure side spool Sp as the diameter and the area of the circle having the inner diameter of the annular protrusion 18 as the diameter. In the case of slow衝器D of this embodiment, the pressure receiving area of the extension side spool Se is is made larger than the pressure receiving area of the pressure side spool Sp.

  Since the annular protrusion 14 of the expansion side spool Se contacts the back surface of the expansion side annular plate 68 and the expansion side annular plate 68 is mounted on the outer periphery of the expansion side spacer 67, the expansion side annular plate 68 is extended to the expansion side. The pressure receiving area to which the pressure of the back pressure chamber Ce acts directly is an area obtained by subtracting the area of the circle having the inner diameter of the annular protrusion 14 from the area of the circle having the outer diameter of the extension side spacer 67 as the diameter. . Therefore, the force obtained by multiplying the area of the circle having the outer diameter of the extension side spool 67 from the area of the circle having the outer diameter of the extension side spool Se by the pressure of the extension side back pressure chamber Ce as the area of the circle having the outer diameter of the extension side spacer 67 as a diameter. As the extension side load, the extension side second leaf valve Ve2 and the extension side first leaf valve Ve1 are urged toward the piston 2 by the extension side load. Note that the extension-side annular plate 68 may be eliminated and the annular protrusion 14 may be brought into direct contact with the back surface of the extension-side second leaf valve Ve2.

  On the other hand, the annular protrusion 18 of the pressure side spool Sp is in contact with the back surface of the pressure side annular plate 63 and the pressure side annular plate 63 is mounted on the outer periphery of the pressure side spacer 62. The pressure receiving area on which the pressure directly acts is an area obtained by subtracting the area of the circle whose diameter is the outer diameter of the compression side spacer 62 from the area of the circle whose diameter is the inner diameter of the annular protrusion 18. Therefore, a force obtained by multiplying the area obtained by subtracting the area of the circle having the outer diameter of the compression side spacer 62 from the area of the circle having the outer diameter of the compression side spool Sp by the pressure of the compression side back pressure chamber Cp as the compression load. The pressure side load causes the pressure side second leaf valve Vp2 and the pressure side first leaf valve Vp1 to be biased toward the piston 2. Alternatively, the pressure side annular plate 63 may be eliminated and the annular protrusion 18 may be brought into direct contact with the back surface of the pressure side second leaf valve Vp2.

  Therefore, when the pressure in the extension side back pressure chamber Ce and the pressure in the compression side back pressure chamber Cp are equal, the extension side second leaf valve Ve2 or the extension side second leaf valve Ve2 is the extension side first leaf valve Ve1. In the state of contact with the pressure side, the expansion side load, which is the load that the expansion side second leaf valve Ve2 and the expansion side first leaf valve Ve1 receive from the expansion side back pressure chamber Ce, is the compression side second leaf valve Vp2 or the compression side second valve. When the leaf valve Vp2 is in contact with the pressure side first leaf valve Vp1, the pressure side second leaf valve Vp2 and the pressure side first leaf valve Vp1 are set to be larger than the pressure side load that is a load received from the pressure side back pressure chamber Cp. ing. If the extension side back pressure chamber Ce is closed by the extension side spool Se and the pressure of the extension side back pressure chamber Ce is not directly applied to the extension side annular plate 68, the extension side load is increased by the extension side spool Se. It is determined only by the pressure receiving area that receives the pressure of the side back pressure chamber Ce. Similarly, the pressure side back pressure chamber Cp is closed by the pressure side spool Sp so that the pressure of the pressure side back pressure chamber Cp does not act directly on the pressure side annular plate 63. In this case, the compression side load is determined only by the pressure receiving area that receives the pressure of the compression side back pressure chamber Cp of the compression side spool Sp. When the pressure in the extension side back pressure chamber Ce and the pressure in the compression side back pressure chamber Cp are equal, the extension side second leaf valve Ve2 or the extension side first leaf valve Ve1 and the extension side second leaf valve Ve2 The extension side load received from the extension side back pressure chamber Ce is larger than the pressure side load received by the compression side second leaf valve Vp2 or the compression side first leaf valve Vp1 and the compression side second leaf valve Vp2 from the compression side back pressure chamber Cp. Therefore, when pressure is not applied directly from the back pressure chambers Ce and Cp to the expansion side annular plate 68 and the compression side annular plate 63, the pressure receiving area of the expansion side spool Se is set to the pressure reception pressure of the compression side spool Sp. It is sufficient to make it larger than the area. When the extension side annular plate 68 and the pressure side annular plate 63 are eliminated as described above, the pressure in the extension side back pressure chamber Ce may be directly applied to the extension side second leaf valve Ve2, or the pressure side back pressure chamber Cp The pressure can be directly applied to the compression side second leaf valve Vp2, and in the structure in which the extension side back pressure chamber Ce is closed by the extension side spool Se, the extension side spool Se is brought into contact with the extension side second leaf valve Ve2. In the structure in which the pressure side back pressure chamber Cp is closed by the pressure side spool Sp, the pressure side spool Sp can be brought into contact with the pressure side second leaf valve Vp2. Whether or not the extension-side back pressure chamber Ce and the compression-side back pressure chamber Cp are closed with a spool can be arbitrarily selected. In the present invention, since the expansion side spool Se and the pressure side spool Sp are used, the pressure-receiving area where the pressure of the expansion side back pressure chamber Ce is applied to the expansion side second leaf valve Ve2 is set to the expansion side second leaf valve Ve2. Can be set larger than the pressure receiving area only, and the pressure receiving area difference between the pressure side spool Sp and the expansion side spool Se can also be set large, so that a large difference can be provided between the expansion side load and the compression side load. A very high degree of freedom can be given to the set width of the side load and the compression side load.

Then, the extension side second leaf valve Ve2 is bent by the extension side load and brought into contact with the extension side first leaf valve Ve1, and the extension side first leaf valve Ve1 is bent until it comes into contact with the extension side valve seat 2d. The extension side first leaf valve Ve1 closes the extension side passage 3, but the extension side load at which the extension side first leaf valve Ve1 closes the extension side passage 3 at a certain piston speed is equal to the pressure receiving area, the extension side first. And it can set by the bending rigidity etc. of 2nd leaf valve Ve1, Ve2 . Similarly to the extension side first leaf valve Ve1, the compression side first leaf valve Vp1 is bent by the pressure side load and abuts against the pressure side valve seat 2c to close the pressure side passage 4. However, the compression side first leaf valve is closed at a certain piston speed. The pressure side load at which Vp1 closes the pressure side passage 4 can be set by the pressure receiving area, the bending rigidity of the pressure side first and second leaf valves Vp1, Vp2 , and the like.

  Subsequently, the extension-side back pressure chamber Ce and the pressure-side back pressure chamber Cp are upstream, the extension-side discharge passage Ee and the pressure-side discharge passage Ep are downstream, and these are communicated with each other through an adjustment passage Pc. In the middle of the adjustment passage Pc, the pressure in the upstream extension side back pressure chamber Ce and the pressure side back pressure chamber Cp can be controlled. Therefore, when the pressure in the extension side back pressure chamber Ce and the pressure side back pressure chamber Cp is controlled by the electromagnetic pressure control valve 6, the extension side load is made larger than the compression side load. Even when it is desired to increase the damping force on the extension side, the maximum pressure to be controlled by the electromagnetic pressure control valve 6 can be lowered.

  In the present embodiment, the expansion-side spool Se is not in sliding contact with the outer periphery of the mounting portion 12a of the expansion-side chamber 12, and the pressure in the expansion-side back pressure chamber Ce is the back surface of the expansion-side annular plate 68. Since the second side leaf valve Ve2 acts on the inner side of the contact portion of the annular protrusion 14 and urges the extension side second leaf valve Ve2, the extension side second pressure valve Ce is set by the pressure of the extension side back pressure chamber Ce. It may be set in consideration of a load for directly energizing the two-leaf valve Ve2. The inner circumference of the pressure side spool Sp is not in sliding contact with the outer periphery of the mounting portion 11a of the pressure side chamber 11, and the pressure in the pressure side back pressure chamber Cp is on the back side of the pressure side annular plate 63 and inside the contact portion of the annular protrusion 18 Since the pressure side second leaf valve Vp2 is urged by acting on the pressure side, the pressure side load is set by taking into account the load that directly urges the pressure side second leaf valve Vp2 with the pressure of the pressure side back pressure chamber Cp. Good.

In turn, in this embodiment, the electromagnetic pressure control valve 6 is set so as to close the adjustment passage Pc when not energized and to perform pressure control during energization, and in the middle of the adjustment passage Pc, the electromagnetic pressure control valve 6 is set. A fail valve FV that bypasses the valve is provided.

  As shown in FIGS. 1 and 2, the electromagnetic pressure control valve 6 includes a valve seat member 30 having a valve housing cylinder 30a and a control valve valve seat 30d, and an electromagnetic valve valve body that is attached to and detached from the control valve valve seat 30d. 31 and a solenoid Sol that applies thrust to the solenoid valve body 31 and drives it in the axial direction.

  Then, the valve seat member 30 is fitted into the socket 8c of the piston holding member 8, and the valve housing cylinder 30a is inserted into the inner periphery of the annular valve housing 32 stacked on the upper end of the flange 8b in FIG. And is accommodated in the accommodating portion L while being positioned in the radial direction.

  As shown in FIG. 2, the valve housing 32 has an annular shape, an annular window 32a provided at the upper end in FIG. 2, a port 32b that opens from the annular window 32a and communicates with the lower end in FIG. 2, and an upper end in FIG. A notch groove 32c that opens from the inner periphery and communicates with the port 32b, a groove 32d that is provided on the outer periphery along the axial direction, and an annular fail valve valve seat 32e that surrounds the outer periphery of the annular window 32a are provided. It is configured.

  When this valve housing 32 is inserted into the socket 8c and laminated on the upper end of the flange 8b in FIG. Further, the groove 32d is communicated with the groove 8j opposite to the groove 8j provided in the flange 8b.

  Therefore, the port 32b and the cutout groove 32c are communicated with the communication path 24 through the annular groove 8e, the port 8f, and the lateral hole 8g, and further extended through the communication path 24, the expansion side pilot orifice Pe, and the compression side pilot orifice Pp. The side back pressure chamber Ce and the pressure side back pressure chamber Cp communicate with each other. Further, the groove 32d communicates with the pressure side chamber R2 in the separator 23 through the groove 8j and through the expansion side discharge passage Ee formed by the check valve 25, and also has a through hole 9c, a recess 8k, a through hole 8m, and a check valve. 22 is communicated with the expansion side chamber R1 through the pressure side discharge passage Ep formed by the line 22.

  In the valve housing 32, the valve accommodating cylinder 30a in the cylindrical valve seat member 30 is accommodated. The valve seat member 30 has a bottomed cylindrical shape, and a valve housing cylinder 30a having a flange 30b on the outer periphery of the upper end in FIG. An annular control valve seat 30d that protrudes in the axial direction is provided at the upper end in FIG. 2 of the valve housing cylinder 30a.

  Further, a fail valve valve body 33, which is an annular leaf valve, is mounted on the outer periphery of the valve housing cylinder 30a of the valve seat member 30, and the valve seat cylinder 30a is inserted into the valve housing 32 so that the valve seat member 30 is inserted. When assembled to the valve housing 32, the fail valve body 33 is fixed by being sandwiched between the flange 30b of the valve seat member 30 and the inner periphery of the upper end of the valve housing 32 in FIG. The provided annular fail valve valve seat 32e is seated with initial deflection, and the annular window 32a is closed. The fail valve body 33 bends when the pressure acting in the annular window 32a through the port 32b reaches the valve opening pressure, opens the annular window 32a, and connects the port 32b to the extension side discharge passage Ee and the pressure side discharge passage Ep. The fail valve body 33 and the fail valve valve seat 32e form a fail valve FV.

  When the valve housing cylinder 30a is inserted into the valve housing 32 and the valve seat member 30 is assembled to the valve housing 32, the notch groove 32c provided in the valve housing 32 is opposed to the through hole 30c provided in the valve housing cylinder 30a. The extension-side back pressure chamber Ce and the compression-side back pressure chamber Cp are communicated with each other in the valve housing cylinder 30a through the port 32b.

  A valve fixing member 35 that is annular and contacts the upper end of the flange 30b in FIG. 1 is stacked above the valve seat member 30 in FIG. A solenoid Sol accommodated in the valve accommodating cylinder 9 is arranged, and when the piston holding member 8 is screwed and integrated with the electromagnetic valve accommodating cylinder 9, the valve housing 32, the fail valve valve body 33, the valve seat The member 30, the valve fixing member 35, and the solenoid Sol are sandwiched and fixed between the electromagnetic valve housing cylinder 9 and the piston holding member 8. Note that the valve fixing member 35 has a notch groove 35 a so that the inner circumferential space of the valve fixing member 35 can communicate with the outer circumferential space of the valve seat member 30 even when abutting against the flange 30 b of the valve seat member 30. Is provided. This communication may be performed not by the notch groove 35a but by a hole such as a port.

  The solenoid Sol is a top-cylindrical molded stator 36 in which a winding 37 and a harness H that energizes the winding 37 are integrated with a mold resin, and a top-cylindrical cylindrical stator that is fitted to the inner periphery of the mold stator 36. The first fixed iron core 38, the annular second fixed iron core 39 stacked on the lower end in FIG. 1 of the molded stator 36, and the first fixed iron core 38 and the second fixed iron core 39 are interposed between the magnets. Filler ring 40 that forms a general gap, a cylindrical movable core 41 that is axially movable on the inner peripheral side of the first fixed core 38 and the second fixed core 39, and an inner periphery of the movable core 41. 1 and is configured to include a fixed shaft 42. By energizing the winding 37, the movable iron core 41 can be sucked to apply a downward thrust to the shaft 42 in FIG. .

  Further, an electromagnetic valve body 31 is slidably inserted into the valve seat member 30. Specifically, the solenoid valve body 31 is provided on the side of the valve seat member 30 that is slidably inserted into the valve housing cylinder 30a of the valve seat member 30 and the counter valve seat member side that is the upper side of the small diameter portion 31a in FIG. A large-diameter portion 31b that is provided and is not inserted into the valve housing cylinder 30a, an annular recess 31c provided between the small-diameter portion 31a and the large-diameter portion 31b, and an outer periphery of the counter-valve seat member side end of the large-diameter portion 31b 31d, a connecting passage 31e penetrating from the front end to the rear end of the solenoid valve body 31, and an orifice 31f provided in the middle of the connecting passage 31e.

  Further, in the electromagnetic valve body 31, as described above, the large-diameter portion 31b is formed with the outer diameter on the counter-valve seat member side being larger than the small-diameter portion 31a with the recess 31c as a boundary. The lower end of the large-diameter portion 31b in FIG. 2 is provided with a seating portion 31g facing the control valve valve seat 30d, and the seating portion 31g is controlled by the solenoid valve body 31 moving in the axial direction with respect to the valve seat member 30. The valve seat 30d is separated from the seat. That is, the electromagnetic pressure control valve 6 is configured to include the electromagnetic valve body 31 and the valve seat member 30, and the electromagnetic pressure control valve 6 is closed when the seating portion 31g is seated on the control valve valve seat 30d. It has become.

  Further, a coil spring 34 is interposed between the flange 30b of the valve seat member 30 and the spring receiving portion 31d to bias the electromagnetic valve valve body 31 in a direction away from the valve seat member 30. A solenoid Sol that exerts a thrust force against the urging force of the spring 34 is provided. Therefore, the electromagnetic valve body 31 is always urged in the direction away from the valve seat member 30 by the coil spring 34, and if a thrust force against the coil spring 34 from the solenoid Sol does not act, It is positioned at the most distant position. In this case, the coil spring 34 is used to urge the solenoid valve valve body 31 in the direction away from the valve seat member 30, but the urging force can be exerted in addition to the coil spring 34. An elastic body that can be used can be used.

  When the solenoid valve body 31 is farthest away from the valve seat member 30, the small diameter portion 31a is opposed to the through hole 30c to close the through hole 30c, and the solenoid Sol is energized to the valve seat member 30. When a predetermined amount is moved from the most distant position to the valve seat member side, the through hole 30c is always opened with the recess 31c opposed to the through hole 30c.

When the solenoid valve body 31 opens the through hole 30c and the seating portion 31g is separated from the control valve valve seat 30d, the through hole 30c passes through the recess 31c of the solenoid valve valve body 31 and the notch groove 35a provided in the valve fixing member 35. It communicates with the expansion side discharge passage Ee and the pressure side discharge passage Ep, and controls the force that biases the solenoid valve body 31 toward the valve seat member 30 by adjusting the thrust of the solenoid Sol. If the action of the pressure upstream of the electromagnetic pressure control valve 6 and the force that pushes up the electromagnetic valve body 31 by the coil spring 34 in FIG. 2 exceeds the force that pushes down the electromagnetic valve body 31 by the solenoid Sol, the electromagnetic pressure control valve 6 is opened, the pressure on the upstream side of the electrostatic 磁圧 force control valve 6 can be controlled in accordance with the thrust of the solenoid Sol. Since the upstream side of the electromagnetic pressure control valve 6 communicates with the expansion side back pressure chamber Ce and the pressure side back pressure chamber Cp via the adjustment passage Pc, the electromagnetic pressure control valve 6 causes the expansion side back pressure chamber Ce and the pressure side to communicate with each other. The pressure in the back pressure chamber Cp can be controlled. Also, downstream of the solenoid pressure control valve 6 is in communication with expansion side discharge passage Ee and pressure side discharge passage Ep, the electromagnetic pressure control valve 6 liquid that has passed through the gentle衝器pressure side chamber of the low pressure side at the time extending action of D to R2, and is discharged into the expansion side chamber R1 of the low-pressure side at the time of contraction operation of the slow衝器D. Therefore, the adjustment passage Pc is formed by the annular groove 8e, the port 8f, the lateral hole 8g, the port 32b, the notch groove 32c, a part of the accommodating portion L, and the groove 32d.

  Further, the electromagnetic pressure control valve 6 includes a blocking position for closing the through hole 30c in the valve seat member 30 with the small diameter portion 31a in the electromagnetic valve valve body 31 at the time of failure in which the solenoid Sol cannot be energized. It also functions as an on-off valve. The fail valve FV opens and closes an annular window 32a that communicates with the port 32b, and the valve opening pressure is set to a pressure that exceeds the upper limit pressure that can be controlled by the electromagnetic pressure control valve 6. The electromagnetic pressure control valve When the pressure on the upstream side of the electromagnetic pressure control valve 6 exceeds the control upper limit pressure because the port 32b can be communicated with the expansion side discharge passage Ee and the pressure side discharge passage Ep by bypassing the pressure control passage 6. The fail valve FV is opened so that the pressure in the extension side back pressure chamber Ce and the pressure side back pressure chamber Cp can be controlled to the valve opening pressure of the fail valve FV. Therefore, for example, when the electromagnetic pressure control valve 6 is in the cutoff position at the time of failure, the pressures in the extension side back pressure chamber Ce and the pressure side back pressure chamber Cp are controlled by the fail valve FV.

  Further, when the electromagnetic valve body 31 is inserted into the valve housing cylinder 30a of the valve seat member 30, a space K is formed in the valve housing cylinder 30a and on the tip side from the through hole 30c. The space K communicates with the outside of the solenoid valve valve body through a communication path 31e provided in the solenoid valve valve body 31 and an orifice 31f. Thereby, when the solenoid valve valve body 31 moves in the axial direction which is the vertical direction in FIG. 2 with respect to the valve seat member 30, the space K functions as a dashpot, and the solenoid valve valve body 31 is suddenly displaced. And the vibrational movement of the solenoid valve body 31 can be suppressed.

  Next, the operation of the shock absorber D will be described. First, the damping force characteristic of the damping force of the shock absorber D is softened, that is, the urging force for urging the expansion side second leaf valve Ve2 and the pressure side second leaf valve Vp2 by the urging means is reduced, and the damping coefficient is set. The case of lowering will be described. In order to soften the damping force characteristic, the solenoid Sol is energized to reduce the resistance given to the passing liquid by the electromagnetic pressure control valve 6, and the urging means gives the extension side second leaf valve Ve2 and the pressure side second leaf valve Vp2. Reduce the force.

  Specifically, even if the expansion side second leaf valve Ve2 is bent by the urging force of the urging means, the expansion side second leaf valve Ve2 does not contact the expansion side first leaf valve Ve1, or even if it contacts By controlling the urging force so that the extension side first leaf valve Ve1 does not sit on the extension side valve seat 2d, the extension side first leaf valve Ve1 and the extension side valve seat 2d are positioned between the extension side first leaf valve Ve1 and the extension side valve seat 2d. A gap is formed. Similarly, the pressure side second leaf valve Vp2 does not come into contact with the pressure side first leaf valve Vp1 even if the pressure side second leaf valve Vp2 is bent by the urging force of the urging means. The pressure side first gap is formed between the pressure side first leaf valve Vp1 and the pressure side valve seat 2c by controlling the biasing force so that the one leaf valve Vp1 does not sit on the pressure side valve seat 2c. And

  In this state, when the shock absorber D is extended and the piston 2 is moved upward in FIG. 1, the liquid pushes the extension side first leaf valve Ve1 and bends it from the extension side chamber R1 to be compressed to the pressure side chamber R2. It moves through the extension side passage 3. An extension side first gap is formed between the extension side first leaf valve Ve1 and the extension side valve seat 2d, and the fluid passes through the extension side first gap. Compared to the conventional case where the leaf valve of the shock absorber is seated on the valve seat and the orifice provided by stamping on the notch or valve seat on the leaf valve is allowed to pass through the fluid, However, the channel area is secured larger than that of the orifice. Therefore, as shown in FIG. 4, the shock absorber D reduces the damping force when the piston speed is in the low speed range as shown by the line B with respect to the damping force generated by the conventional shock absorber shown by the line A. be able to.

  The expansion-side first leaf valve Ve1 bends due to the pressure in the expansion-side chamber R1 that rises with respect to the expansion of the shock absorber D. Bending is performed so that the force to bend one leaf valve Ve1 and the force to return to the expansion valve seat 2d side are balanced by the spring reaction force of the expansion side first leaf valve Ve1 itself according to the amount of bending. Thus, the extension side passage 3 is opened.

  When the speed of the piston when the shock absorber D extends increases and the pressure in the expansion side chamber R1 increases, the expansion side first leaf valve Ve1 is greatly bent and the outer periphery is displaced more than the expansion side second gap. The bending of the extension side first leaf valve Ve1 is suppressed by coming into contact with the second leaf valve Ve2, and the damping force characteristic of the shock absorber D gradually tilts as the piston speed increases as shown in FIG. Becomes larger.

  Further, when the piston speed when the shock absorber D is extended increases, the pressure in the expansion side chamber R1 increases, so that the force for bending the expansion side first leaf valve Ve1 increases, and the expansion by the expansion side back pressure chamber Ce increases. When the force to push down the second side leaf valve Ve2 is exceeded, the extension side second leaf valve Ve2 is bent together with the extension side first leaf valve Ve1 in a direction away from the piston 2, and the extension side valve seat 2d and the extension side first leaf valve Since the gap amount of the extension-side first gap with Ve1 increases, the damping force characteristic of the shock absorber D gradually decreases from the middle as shown in FIG.

  Further, the liquid in the extension side chamber R1 pushes open the extension side check valve Te, passes through the extension side pressure introduction passage Ie, and flows into the adjustment passage Pc. The liquid that has passed through the adjustment passage Pc pushes the check valve 25 open and is discharged to the low pressure side pressure side chamber R2 through the extension side discharge passage Ee. The expansion side pilot orifice Pe gives resistance when the liquid passes and causes a pressure loss. Since the pressure is lower than the expansion side chamber R1 downstream of the adjustment passage Pc in the state where the liquid flows, the pressure side discharge passage The check valve 22 provided on Ep remains closed without opening.

  The expansion-side pressure introduction passage Ie not only communicates with the compression-side back pressure chamber Cp but also communicates with the expansion-side back pressure chamber Ce through the communication passage 24. However, the compression-side pressure introduction passage Ip is blocked by the compression-side check valve Tp. Therefore, the pressure in the extension side back pressure chamber Ce can be made higher than that of the compression side chamber R2 when the shock absorber D is extended. The pressure in the pressure side back pressure chamber Cp is higher than that in the pressure side chamber R2 on the low pressure side, but it is inconvenient because it only energizes the pressure side second leaf valve Vp2 that closes the pressure side passage 4 where no liquid flows. There is no.

  The adjustment passage Pc is provided with the electromagnetic pressure control valve 6 as described above. If the solenoid Sol of the electromagnetic pressure control valve 6 is energized to control the pressure upstream of the adjustment passage Pc, the extension side back pressure is increased. The extension side load can be controlled to a desired load by adjusting the pressure in the chamber Ce. As described above, by controlling the extension side load that presses the extension side second leaf valve Ve2 by the electromagnetic pressure control valve 6, the extension after the extension side first leaf valve Ve1 contacts the extension side second leaf valve Ve2 is increased. It is possible to control the gap amount (the opening degree of the extension side first leaf valve Ve1) of the extension side first gap between the side first leaf valve Ve1 and the extension side valve seat 2d. The extension side damping force when performing the extension operation can be controlled.

  Conversely, when the shock absorber D contracts and the piston 2 moves downward in FIG. 1, the liquid pushes the pressure side first leaf valve Vp1 and bends from the compressed pressure side chamber R2 to the expanded side chamber R1 to be compressed. Move past 4 A pressure-side first gap is formed between the pressure-side first leaf valve Vp1 and the pressure-side valve seat 2c, and the fluid passes through the pressure-side first gap. Compared to the case where a conventional leaf valve of a shock absorber is seated on the valve seat and the orifice provided by passing through the notch or the valve seat provided in the leaf valve is allowed to pass through the fluid, the pressure side first clearance is more A flow path area is ensured larger than the orifice. Therefore, as shown in FIG. 4, the shock absorber D reduces the damping force when the piston speed is in the low speed range as shown by the line D with respect to the damping force generated by the conventional shock absorber shown by the line C. be able to.

  The pressure-side first leaf valve Vp1 bends due to the pressure in the pressure-side chamber R2 that rises with respect to the contraction of the shock absorber D. The amount of bending is determined by the pressure of the pressure-side chamber R2 received from the pressure-side passage 4 side. The pressure side passage 4 is bent so that the force to bend Vp1 and the force to return to the pressure side valve seat 2c side are balanced by the spring reaction force of the pressure side first leaf valve Vp1 itself according to the amount of bending. Will be released.

  When the speed of the piston when the shock absorber D contracts increases and the pressure in the pressure side chamber R2 increases, the pressure side first leaf valve Vp1 is greatly bent and the outer periphery is displaced by more than the pressure side second gap. The bending of the pressure side first leaf valve Vp1 comes into contact with the valve Vp2, and the damping force characteristic of the shock absorber D gradually increases as the piston speed increases, as shown in FIG.

  Further, when the piston speed when the shock absorber D is extended increases, the pressure in the compression side chamber R2 increases, so that the force that deflects the compression side first leaf valve Vp1 increases, and the compression side back pressure chamber Cp causes the compression side second pressure. When the force for pushing down the leaf valve Vp2 is exceeded, the pressure side second leaf valve Vp2 is bent together with the pressure side first leaf valve Vp1 in a direction away from the piston 2, and the pressure side second leaf valve Vp1 between the pressure side valve seat 2c and the pressure side first leaf valve Vp1. Since the gap amount of one gap is increased, the damping force characteristic of the shock absorber D is gradually reduced from the middle as shown in FIG.

  Further, the liquid in the pressure side chamber R2 pushes and opens the pressure side check valve Tp, passes through the pressure side pressure introduction passage Ip, and flows to the adjustment passage Pc. The liquid that has passed through the adjustment passage Pc pushes the check valve 22 open and is discharged to the low-pressure side extension side chamber R1 through the pressure side discharge passage Ep. Note that the pressure side pilot orifice Pp provides resistance when the liquid passes and causes a pressure loss. In the state where the liquid flows, the pressure side pilot orifice Pp has a pressure lower than the pressure side chamber R2 downstream of the adjustment passage Pc. The check valve 25 provided at Ee is not opened and remains closed.

  The pressure side pressure introduction passage Ip not only communicates with the expansion side back pressure chamber Ce, but also communicates with the pressure side back pressure chamber Cp via the communication passage 24. However, the expansion side pressure introduction passage Ie is connected to the expansion side check valve Te. Since it is blocked, the pressure in the compression side back pressure chamber Cp can be made higher than that in the expansion side chamber R1 when the shock absorber D is contracted. The pressure in the extension side back pressure chamber Ce is higher than that in the extension side chamber R1 on the low pressure side, but only by energizing the extension side second leaf valve Ve2 that closes the extension side passage 3 where no liquid flows. There is no inconvenience.

  The adjustment passage Pc is provided with the electromagnetic pressure control valve 6 as described above. If the solenoid Sol of the electromagnetic pressure control valve 6 is energized to control the pressure upstream of the adjustment passage Pc, the pressure side back pressure chamber It is possible to control the pressure side load to a desired load by adjusting the pressure in Cp. The pressure side first leaf valve after the pressure side first leaf valve Vp1 contacts the pressure side second leaf valve Vp2 by controlling the pressure side load that presses the pressure side second leaf valve Vp2 by the electromagnetic pressure control valve 6 as described above. The gap amount of the pressure side first gap between the Vp1 and the pressure side valve seat 2c (the opening degree of the pressure side first leaf valve Vp1) can be controlled, whereby the pressure side attenuation when the shock absorber D is contracted. The power can be controlled.

  Subsequently, the damping force characteristic of the damping force of the shock absorber D is made hard, that is, the urging force for urging the expansion side second leaf valve Ve2 and the pressure side second leaf valve Vp2 by the urging means is increased, and the damping coefficient A case where the height is increased will be described. In order to make the damping force characteristic hard, the resistance applied to the passing liquid by energizing the solenoid Sol is increased, and the expansion side second leaf valve Ve2 and the pressure side second leaf are increased by the urging force provided by the urging means. The valve Vp2 is bent and brought into contact with the corresponding extension-side first leaf valve Ve1 and the compression-side first leaf valve Vp1, and the extension-side first leaf valve Ve1 and the compression-side first leaf valve Vp1 are bent to respectively correspond to the extension. The side valve seat 2d and the pressure side valve seat 2c are seated.

  In this state, the extension side second leaf valve Ve2 contacts the extension side first leaf valve Ve1, and the extension side first leaf valve Ve1 is seated on the extension side valve seat 2d, and the extension side second gap and extension side second No gap is formed, and the pressure side second leaf valve Vp2 contacts the pressure side first leaf valve Vp1 and the pressure side first leaf valve Vp1 is seated on the pressure side valve seat 2c. The two gaps and the pressure side first gap are not formed.

  When the shock absorber D extends to move the piston 2 upward in FIG. 1 and the piston speed is low, the extension side first leaf valve Ve1 receives the pressure of the extension side chamber R1 from the extension side passage 3. Even if it bends, the gap amount of the extension side first gap formed between the extension side valve seat 2d is small. Then, the shock absorber D exhibits a large damping force as compared with the case where the damping force characteristic is soft because the liquid passing through the extension side passage 3 passes through the extension side first gap with a small gap amount. can do.

  On the other hand, the piston speed increases and the pressure of the expansion side chamber R1 acting on the expansion side first leaf valve Ve1 via the expansion side passage 3 rises, and the expansion side first leaf valve Ve1 is extended by the pressure of the expansion side chamber R1. When the force in the direction of separating from the side valve seat 2d increases, the extension side first leaf valve Ve1 and extension side second leaf valve Ve2 are greatly bent, and the extension side annular plate 68 and the extension side spool Se are moved downward in FIG. Press down. Then, the gap amount of the extension side first gap between the extension side first leaf valve Ve1 and the extension side valve seat 2d increases. However, since the urging force by the urging means is greater than the situation where the damping force characteristic is soft, the amount of bending of the expansion side first leaf valve Ve1 is small, and the amount of expansion side first clearance is also the same. Therefore, even if the piston speed is the same as shown by the line E in FIG. 4, the shock absorber D exhibits a higher damping force when it is hard than when it is soft.

  The liquid in the extension side chamber R1 pushes open the extension side check valve Te to pass through the extension side pressure introduction passage Ie and also flows into the adjustment passage Pc, as in the case of making the damping force characteristic and soft. By controlling the pressure on the upstream side of the adjustment passage Pc with the electromagnetic pressure control valve 6 provided in the adjustment passage Pc, the pressure in the extension-side back pressure chamber Ce is adjusted and the extension-side load is desired as in the soft case. The opening of the extension side first leaf valve Ve1 can be controlled, thereby controlling the extension side damping force when the shock absorber D is extended even in hardware. be able to.

  Next, when the shock absorber D contracts and the piston 2 moves downward in FIG. 1 and the piston speed is low, the pressure side first leaf valve Vp1 receives the pressure of the pressure side chamber R2 from the pressure side passage 4 and bends. However, the gap amount of the pressure side first gap formed between the pressure side valve seat 2c is small. Then, the buffer D exhibits a large damping force as compared with the case where the damping force characteristic is soft because the liquid passing through the pressure side passage 4 passes through the pressure side first gap with a small gap amount. Can do.

  On the other hand, the piston speed increases, the pressure in the pressure side chamber R2 acting on the pressure side first leaf valve Vp1 via the pressure side passage 4 rises, and the pressure side first leaf valve Vp1 due to the pressure in the pressure side chamber R2 is changed to the pressure side valve seat 2c. When the force in the direction of separating from the pressure increases, the pressure-side first leaf valve Vp1 and the pressure-side second leaf valve Vp2 are greatly bent to push up the pressure-side annular plate 63 and the pressure-side spool Sp upward in FIG. Then, the gap amount of the pressure side first gap between the pressure side first leaf valve Vp1 and the pressure side valve seat 2c increases. However, since the urging force by the urging means is larger than the situation where the damping force characteristic is soft, the amount of bending of the pressure side first leaf valve Vp1 is reduced, and the amount of clearance of the pressure side first gap is also reduced. Therefore, as shown by the line F in FIG. 4, the shock absorber D exhibits a higher damping force when it is hard than when it is soft even when the piston speed is the same.

  The liquid in the pressure side chamber R2 pushes open the pressure side check valve Tp and passes through the pressure side pressure introduction passage Ip and also flows into the adjustment passage Pc, as in the case of making the damping force characteristic and soft. By controlling the pressure on the upstream side of the adjustment passage Pc with the electromagnetic pressure control valve 6 provided in the adjustment passage Pc, the pressure in the compression side back pressure chamber Cp is adjusted and the pressure side load is set to a desired load as in the case of software. It is possible to control the opening degree of the compression side first leaf valve Vp1, and thereby it is possible to control the compression side damping force when performing the contraction operation of the shock absorber D even in hardware.

  Thus, in the damping valve and the shock absorber D of the present invention, the expansion side and the compression side first leaf valves Ve1, Vp1 and the corresponding expansion side and compression side valve seats 2d, 2c A first clearance on the compression side is formed, and a second clearance on the expansion side and the compression side is provided between the expansion-side and compression-side first leaf valves Ve1, Vp1 and the corresponding expansion-side and compression-side second leaf valves Ve2, Vp2. Therefore, when softening the damping force characteristics, the flow area can be increased compared to conventional damping valves and shock absorbers using a fixed orifice, and the piston speed is in the low speed range. The damping force can be greatly reduced. Further, since a second gap on the expansion side and the pressure side is formed between the expansion side and pressure side first leaf valves Ve1, Vp1 and the corresponding expansion side and pressure side second leaf valves Ve2, Vp2, Even if the bending rigidity of the compression-side first leaf valves Ve1 and Vp1 is lowered, the expansion-side and compression-side first leaf valves Ve1 and Vp1 are bent and contact the corresponding expansion-side and compression-side second leaf valves Ve2 and Vp2. Then, the overall bending rigidity of the extension side and compression side second leaf valves Ve2 and Vp2 corresponding to the extension side and compression side first leaf valves Ve1 and Vp1 increases, so that the damping force can be increased when the piston speed is high. At the same time, by reducing the bending rigidity of the first leaf valves Ve1 and Vp1 on the expansion side and the compression side, the damping force when the piston speed is low can be further reduced.

  Therefore, according to the damping valve and the shock absorber of the present invention, it is possible to reduce the damping force when the piston speed is in the low speed range, and it is possible to expand the damping force adjustment range.

  Further, since the rigidity of the first leaf valves Ve1 and Vp1 on the expansion side and the compression side can be lowered, in the expansion side first leaf valve Ve1, the pressure side is changed in the switching from the expansion operation to the contraction operation of the shock absorber D. The pressure side first leaf valve Vp1 can be quickly seated on the expansion side valve seat 2d under the pressure of the chamber R2, and in the compression side first leaf valve Vp1, the shock absorber D is switched from the contraction operation to the expansion operation. The pressure side valve seat 2c can be quickly seated by receiving pressure, and the expansion side first leaf valve Ve1 and the pressure side first leaf valve Vp1 can quickly function as check valves to eliminate the closing delay. Improves.

  Further, when the damping force characteristic of the shock absorber D of the present embodiment is switched from soft to hard, at the time of extension operation, due to the pressure increase in the extension side back pressure chamber Ce, the extension side first leaf valve Ve1 and the extension side valve seat 2d The first extension leaf valve Ve1 is gradually seated on the extension side valve seat 2d, and the pressure side first pressure is increased by the pressure increase in the compression side back pressure chamber Cp during the contraction operation. The pressure-side first gap between the leaf valve Vp1 and the pressure-side valve seat 2c is gradually reduced so that the pressure-side first leaf valve Vp1 is seated on the pressure-side valve seat 2c. On the contrary, when the damping force characteristic of the shock absorber D according to the present embodiment is switched from hardware to soft, the extension side first leaf valve Ve1 and the extension side valve seat 2d are caused by the pressure reduction in the extension side back pressure chamber Ce during the extension operation. The expansion side first clearance between the pressure side first pressure valve Cp1 and the pressure side valve seat 2c is reduced by the pressure reduction in the compression side back pressure chamber Cp during the contraction operation. Gradually increases. Therefore, when the damping force characteristic of the shock absorber D is switched from software to hardware, or from hardware to software, a sudden change in the damping force characteristic of the shock absorber D is alleviated. When this shock absorber D is applied to the vehicle, sudden changes in the damping force characteristic are alleviated, so that the rider does not perceive a shock when switching the damping force characteristic and the riding comfort in the vehicle can be improved.

  Then, when the electromagnetic force control valve 6 provided in the adjustment passage Pc is closed by shifting the damping force from soft to hard, the pressures in the extension-side back pressure chamber Ce and the pressure-side back pressure chamber Cp increase instantaneously. Even if a surge occurs, a second gap on the expansion side and the pressure side is provided between the expansion side and pressure side first leaf valves Ve1, Vp1 and the corresponding expansion side and pressure side second leaf valves Ve2, Vp2, respectively. Therefore, the second leaf valves Ve2 and Vp2 on the expansion side and the pressure side do not suddenly come into contact with the corresponding first leaf valves Ve1 and Vp1 on the expansion side and the pressure side, and the first leaf valve Ve1 on the expansion side and the pressure side suddenly. , Vp1 is not pressed against the corresponding expansion side valve seat 2d and compression side valve seat 2c to close the expansion side passage 3 and the compression side passage 4, so that the damping force suddenly changes and a spike occurs in the damping force waveform. Without any, there is no worry about worsen the ride comfort in the vehicle.

  An extension-side annular plate 68 that is slidably mounted on the outer periphery of the extension-side spacer 67 is laminated on the back surface of the extension-side second leaf valve Ve2, and is arranged on the outer surface of the compression-side spacer 62 on the back surface of the compression-side second leaf valve Vp2. Since the pressure-side annular plate 63 that is slidably mounted is laminated, the rigidity of the expansion-side annular plate 68 is made higher than that of the expansion-side second leaf valve Ve2, and the pressure-side annular plate 63 is higher than the pressure-side second leaf valve Vp2. By increasing the rigidity of the first and second leaf valves Ve1, Ve2 on the expansion side and the second leaf valve on the expansion side by receiving the urging force by the urging means on the expansion side annular plate 68 and the compression side annular plate 63, the compression side first. And the deformation of the pressure side second leaf valves Vp1, Vp2 can be suppressed, and the deterioration of the leaf valves Ve1, Ve2, Vp1, Vp2 can be suppressed.

  Further, the expansion side annular plate 68 slidably mounted on the outer periphery of the expansion side spacer 67 stacked on the back surface of the expansion side second leaf valve Ve2 and the pressure side stacked on the back surface of the compression side second leaf valve Vp2. A compression-side annular plate 63 that is slidably mounted on the outer periphery of the seat 62 is provided, and the inner diameter of the expansion-side annular plate 68 is made smaller than the outer diameter of the inner peripheral seat portion 2h of the piston 2, and the outer diameter is increased. Since the inner diameter of the pressure side annular plate 63 is made smaller than the outer diameter of the inner peripheral seat portion 2f of the piston 2 and the outer diameter is larger than the inner diameter of the pressure side valve seat 2c, The pressure on the back side of the second leaf valve Ve2 and the pressure side second leaf valve Vp2 can be received by the expansion side annular plate 68 and the pressure side annular plate 63. Therefore, by providing the expansion side annular plate 68 and the pressure side annular plate 63, it is possible to prevent overload from acting on the expansion side first and second leaf valves Ve1, Ve2 and the compression side first and second leaf valves Vp1, Vp2. In addition, the rigidity of the extension side first leaf valve Ve1 and the pressure side first leaf valve Vp1 can be further reduced, and a leaf valve with lower bending rigidity can be adopted, and the damper D reduces the damping. You can show your power.

  Further, since the urging means urges the expansion side second and pressure side second leaf valves Ve2 and Vp2 using the pressure of one or both of the expansion side chamber R1 and the compression side chamber R2 in the shock absorber D. Even without using the generation source, the expansion-side second and compression-side second leaf valves Ve2 and Vp2 can be energized, and the energizing force can be changed by controlling the pressure.

  In general, a shock absorber for a vehicle that suppresses vibration in the vertical direction of the vehicle body needs to increase the extension side damping force during the extension operation compared to the compression side damping force during the contraction operation. In the shock absorber D set in the mold, the pressure receiving area that receives the pressure of the expansion side chamber R1 may be an area obtained by subtracting the cross-sectional area of the rod member 10 from the cross-sectional area of the piston 2, so The pressure needs to be very large compared to the pressure in the compression side chamber R2 during the contraction operation.

  On the other hand, in the shock absorber D of the present invention, when the expansion side back pressure chamber Ce and the compression side back pressure chamber Cp are at the same pressure, the expansion side load that urges the expansion side second leaf valve Ve1. Is larger than the pressure side load for energizing the pressure side second leaf valve Vp2. Further, in the present invention, by using the expansion side spool Se, it is compared with a structure in which the pressure of the expansion side back pressure chamber Ce acts on the back side of the expansion side second leaf valve Ve2 without using the expansion side spool Se. Thus, the pressure receiving area that receives the pressure of the expansion side back pressure chamber Ce of the expansion side spool Se can be made larger than the back surface area of the expansion side second leaf valve Ve2, which is larger than the expansion side second leaf valve Ve2. An extension load can be applied. Furthermore, the degree of freedom in designing the extension side load and the compression side load is improved by using the extension side spool Se and the compression side spool Sp.

  Therefore, in the shock absorber D of the present invention, the pressure in the extension side back pressure chamber Ce is small when it is necessary to increase the extension side load very much in order to adjust the extension side damping force during the extension operation. Both of them can be set so as to output a large extension load, and the control range of the extension damping force can be ensured without using a large solenoid Sol.

  In addition, pressure control of the extension side back pressure chamber Ce and the pressure side back pressure chamber Cp is not performed by driving independent valve bodies, but by increasing the extension side load relative to the compression side load, the extension side back pressure is increased. Even if the pressures in the chamber Ce and the pressure side back pressure chamber Cp are communicated and controlled, the control range of the extension side damping force can be secured, so the electromagnetic pressure control valve 6 can be provided with one electromagnetic valve valve body 31. All that is required is a very simple structure and reduced costs.

  As described above, the solenoid Sol in the electromagnetic pressure control valve 6 can be reduced in size, and the structure of the electromagnetic pressure control valve 6 is simplified, and the shock absorber D is not enlarged even when applied to the piston portion of the shock absorber D. . Therefore, according to the shock absorber D of the present invention, the structure of the shock absorber D can be simplified and downsized, and the solenoid Sol can increase the extension side damping force without deteriorating the mountability on the vehicle. Therefore, since it is not necessary to exert a large thrust, the power consumption when the damping force is reduced can be reduced to save power.

  Since the pressure receiving area that receives the pressure of the expansion side back pressure chamber Ce of the expansion side spool Se is larger than the pressure receiving area that receives the pressure of the compression side back pressure chamber Cp of the compression side spool Sp, the expansion side load is easily compared with the compression side load. Can be enlarged.

Further, Yes so as to communicate with the communication passage 24 through the expansion side back pressure chamber Ce and pressure side resistive element the compression side back pressure chamber Cp respectively and the extension side resistor element, the compression side pressure introduction passage Ip is little resistance extension side Since the liquid is introduced into the back pressure chamber Ce from the pressure side chamber R2, the pressure in the pressure side chamber R2 is quickly introduced into the extension side back pressure chamber Ce when the shock absorber D switches from the expansion operation to the contraction operation. The extension side spool Se presses the extension side second leaf valve Ve2 by the pressure in the extension side back pressure chamber Ce and the bias of the spring member 16 to quickly seat the extension side first leaf valve Ve1 on the extension side valve seat 2d. Thus, the extension side passage 3 can be closed. The expansion side pressure introduction passage Ie also introduces liquid from the expansion side chamber R1 into the compression side back pressure chamber Cp with almost no resistance. Conversely, when the shock absorber D switches from the contraction operation to the expansion operation, the inside of the compression side back pressure chamber Cp The pressure in the extension-side chamber R1 is quickly introduced, and the compression-side spool Sp presses the compression-side second leaf valve Vp2 by the pressure in the compression-side back pressure chamber Cp and the bias of the spring member 20, thereby The pressure side passage 4 can be closed by promptly seating on the pressure side valve seat 2c.

  The annular plate 15 which is a check valve body in the extension side check valve Te and the annular plate 19 which is a check valve valve body in the pressure side check valve Tp are deteriorated over time, and the corresponding pressure side chamber 11 and extension side chamber 12 Even if a gap is generated between them, the extension side pressure introduction passage Ie and the pressure side pressure introduction passage Ip are not provided with the extension side pressure introduction passage Ie and the pressure side pressure introduction passage Ip. Since there is no change in the passing flow rate, there is no influence on the damping force control and the valve closing operation at the time of expansion / contraction switching.

  A piston 2 having an extension side passage 3 and a pressure side passage 4 on the outer peripheral side of the piston rod 7, an extension side first leaf valve Ve1, an extension side second leaf valve Ve2, and a pressure side first leaf laminated on the piston 2. A valve Vp1 and a pressure side second leaf valve Vp2, a cylinder-shaped extension side chamber 12 in which an extension side spool Se is slidably inserted on the inner periphery and forms an extension side back pressure chamber Ce; A pressure side spool Sp is slidably inserted in the inner periphery, and a pressure side chamber 11 forming a pressure side back pressure chamber Cp is mounted, and a pressure side pressure introduction passage Ip is provided in the extension side chamber 12 to provide a pressure side chamber. Since the extension-side pressure introduction passage Ie is provided in 11, the members required for adjusting the damping force can be centrally arranged in the piston portion of the shock absorber D.

  Further, the urging of the expansion side spool Se to the expansion side second leaf valve Ve2 and the urging of the annular plate 15 as a check valve valve body in the pressure side check valve Tp that opens and closes the pressure side pressure introduction passage Ip are made one. Energizing the pressure side spool Sp to the pressure side second leaf valve Vp2 and energizing the annular plate 19 as a check valve body in the extension side check valve Te that opens and closes the extension side pressure introduction passage Ie. Is performed by one spring member 20, so that the check valves Te, Tp and the spool Se, Sp can be restored to the return side by one spring member 16, 20 and the number of parts is reduced. can do.

The shock absorber D is provided at the tip of the piston rod 7 and is provided with a piston 2, an extension side first leaf valve Ve1 , an extension side second leaf valve Ve2, a pressure side first leaf valve Vp1, a pressure side second leaf valve Vp2, A holding shaft 8a on which the extension side chamber 12 and the pressure side chamber 11 are mounted on the outer periphery, a vertical hole 8d opened from the tip of the holding shaft 8a, and a communication path 24 provided in the holding shaft 8a and provided in the vertical hole 8d The expansion side pilot orifice Pe as the expansion side resistance element that communicates with the pressure side pilot orifice Pp of the compression side resistance element, the accommodating portion L that is provided inside and accommodates the electromagnetic pressure control valve 6 through the vertical hole 8d, and the communication path 24 Is provided with an adjustment passage Pc that communicates with the housing portion L, and a pressure-side discharge passage Ep that communicates the housing portion L with the expansion side chamber R1, and is inserted into the longitudinal hole 8d and provided with an annular groove 23a provided on the outer periphery. 8d is provided with the separator 23 that forms the communication passage 24 that communicates the expansion-side back pressure chamber Ce and the compression-side back pressure chamber Cp, and that forms the expansion-side discharge passage Ee on the inner periphery. The electromagnetic pressure control valve 6 can be accommodated, and the expansion side back pressure chamber Ce and the pressure side back pressure chamber Cp can be provided on the outer periphery of the piston rod 7 while being shifted in the axial direction from the electromagnetic pressure control valve 6.

Further, the electromagnetic pressure control valve 6 is set to close the adjustment passage Pc when not energized and to perform pressure control when energized, and includes a fail valve FV provided in the middle of the adjustment passage Pc to bypass the electromagnetic pressure control valve. Since the opening pressure of the valve FV is larger than the maximum control pressure by the electromagnetic pressure control valve 6, the extension side pressure and the compression side load become maximum at the time of failure, and the shock absorber D exhibits the largest damping force, and at the time of failure Even if there is, the body posture can be stabilized.

  In addition, when the electromagnetic pressure control valve 6 takes the cutoff position, the small diameter portion 31a of the electromagnetic valve valve body 31 is opposed to the through hole 30c and the through hole 30c is closed to close the valve. In addition, it is possible to function as a throttle valve by closing the through hole 30c and slightly reducing the recess 31c at the blocking position so as to face the through hole 30c. In this way, in the damping characteristic of the shock absorber D at the time of failure, the characteristic of the throttle valve can be added to the cutoff position in the electromagnetic pressure control valve 6 in the region where the piston speed is low. Riding comfort in the vehicle can be improved.

  Further, the electromagnetic pressure control valve 6 is provided at the end of the valve housing cylinder 30a and the valve housing cylinder 30a which has a cylindrical shape and has a through hole 30c which communicates the inside and the outside and forms a part of the adjustment passage Pc. A valve seat member 30 provided with an annular control valve valve seat 30d, a small diameter portion 31a slidably inserted into the valve housing cylinder 30a, a large diameter portion 31b, the small diameter portion 31a, and the large diameter portion A recess 31c that is provided between the control valve valve seat 30d and an end portion of the large-diameter portion 31b. The adjustment passage Pc is blocked by making the portion 31a face each other. Therefore, the pressure receiving area on which the pressure acts in the direction in which the solenoid valve body 31 is removed from the valve seat member 30 is a circle having the outer diameter of the small diameter portion 31a as the diameter from the area of the circle having the inner diameter of the control valve valve seat 30d as the diameter. Therefore, the pressure receiving area can be made extremely small and the flow path area at the time of valve opening can be made large, so that the movement of the solenoid valve valve 31 is stabilized. Further, since the outer periphery of the small diameter portion 31a is opposed to the through hole 30c to close the through hole 30c, the valve is kept closed even when pressure is applied from the upstream side in the blocking position, and only the fail valve FV is effective. can do.

  The configuration of the urging means is an example, and the configuration of the urging means is not limited to the present embodiment. Further, in the above description, the present invention has been described using an example in which the present invention is embodied in both the expansion side damping valve and the pressure side damping valve. The present invention can also be applied to only one of the compression side damping valves, and although not shown, it can also be applied to a damping valve provided in the base valve instead of the damping valve provided in the piston portion of the shock absorber.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

DESCRIPTION OF SYMBOLS 1 ... Cylinder, 2 ... Piston as valve disc, 2c ... Pressure side valve seat as valve seat, 2d ... Extension side valve seat as valve seat, 2h, 2f ... Inner peripheral seat 3... Extension side passage as a passage, 4... Pressure side passage as a passage, 6... Electromagnetic pressure control valve, 7... Piston rod, 24. Pressure side first annular spacer as a first annular spacer, 61 ... Pressure side second annular spacer as a second annular spacer, 62 ... Pressure side spacer as a spacer, 63 ... Pressure side annular as an annular plate Plate, 65... Extension side first annular spacer as first annular spacer, 66... Extension side second annular spacer as second annular spacer, 67... Extension side spacer as spacer, 68. Stretch-side annular plate as an annular plate, Ce ... Extension side back pressure chamber, Cp: Pressure side back pressure chamber, D: Shock absorber, Ee ... Extension side discharge passage, Ep ... Pressure side discharge passage, Ie ... Extension side pressure introduction passage, Ip ... pressure side pressure introduction passage, Pc ... adjustment passage, Pe ... extension side pilot orifice as extension side resistance element, Pp ... pressure side pilot orifice as pressure side resistance element, R1 ... extension side chamber, R2 ... pressure side chamber, Se ... extension side spool, Sp ... pressure side spool, Ve1 ... extension side first leaf valve as the first leaf valve, Ve2 ... extension as the second leaf valve Side second leaf valve, Vp1... Pressure side first leaf valve as first leaf valve, Vp2... Pressure side second leaf valve as second leaf valve

Claims (9)

A valve disc comprising a passage and a valve seat surrounding the outlet end of the passage;
An annular first leaf valve that is stacked on the valve disc with a first gap between the valve seat, and that opens and closes the passage by being attached to and detached from the valve seat;
A second leaf valve stacked on the opposite valve disc side of the first leaf valve via a second gap;
A damping valve, comprising: an urging means for applying a variable urging force toward the valve disc side of the second leaf valve. A spacer having an outer diameter smaller than that of the second leaf valve and stacked on the opposite valve disc side of the second leaf valve;
2. The damping valve according to claim 1, further comprising: an annular plate that is laminated on a side opposite to the valve disc of the second leaf valve and is slidably mounted on the outer periphery of the spacer in the axial direction. The said urging means can contact the said 2nd leaf valve to the said 1st leaf valve, and can press it, and can make the said 1st leaf valve seat to the said valve seat. Damping valve as described in The inner diameter of the annular plate is smaller than the outer diameter of the inner peripheral seat portion that is provided inside the passage of the valve disc and supports the inner periphery of the first leaf valve,
4. The damping valve according to claim 2, wherein the outer diameter of the annular plate is larger than the inner diameter of the valve seat. One or more first annular spacers interposed between an inner peripheral seat portion provided on the inner side of the passage of the valve disc and the first leaf valve to adjust the height of the first gap;
2. One or more second annular spacers interposed between the first leaf valve and the second leaf valve for adjusting the height of the second gap are provided. 5. The damping valve according to any one of 4. A cylinder,
The damping valve according to any one of claims 1 to 5, housed in the cylinder,
An extension side chamber and a pressure side chamber partitioned in the cylinder by the valve disc;
A piston rod movably inserted into the cylinder and coupled to the valve disc;
The shock absorber, wherein the extension side chamber and the pressure side chamber communicate with each other through the passage.   The shock absorber according to claim 6, wherein the urging means urges the second leaf valve by using a pressure of one or both of the extension side chamber and the pressure side chamber. The valve disc includes an extension side passage and a pressure side passage communicating the extension side chamber and the pressure side chamber as the passage, and an extension side valve seat surrounding the outlet end of the extension side passage as the valve seat and an outlet end of the pressure side passage. With a surrounding pressure side valve seat,
The first leaf valve includes an extension side first leaf valve for opening and closing the extension side passage and a pressure side first leaf valve for opening and closing the pressure side passage,
The second leaf valve includes an extension-side second leaf valve arranged on the anti-valve disk side of the extension-side first leaf valve and a pressure-side second leaf valve arranged on the counter-valve disk side of the pressure-side first leaf valve. And
The urging means includes an expansion side spool that urges the expansion side second leaf valve, an expansion side back pressure chamber that presses the expansion side spool with internal pressure, and a pressure side that urges the compression side second leaf valve. a spool, and the compression side back pressure chamber for pressing the pressure side spool inside pressure via the expansion side resistive elements giving resistance to the flow of liquid through the liquid passing through both when communicated with the pressure side back pressure chamber A communication passage that communicates with the extension- side back pressure chamber via a pressure-side resistance element that provides resistance to the flow; an extension-side pressure introduction passage that allows only a flow of liquid from the extension-side chamber to the compression-side back pressure chamber; The pressure side pressure introduction passage that allows only the flow of liquid from the pressure side chamber to the extension side back pressure chamber, the adjustment passage connected to the communication passage, and the downstream of the adjustment passage communicate with the extension side chamber and From the adjustment passage to the extension side chamber A pressure-side discharge passage that allows only a body flow, an extension-side discharge passage that communicates downstream of the adjustment passage to the pressure-side chamber and allows only a liquid flow from the adjustment passage toward the pressure-side chamber, and the adjustment passage And an electromagnetic pressure control valve for controlling the upstream pressure of the adjustment passage, and when the pressure in the extension side back pressure chamber and the pressure side back pressure chamber is equal, the pressure in the extension side back pressure chamber 8. The buffer according to claim 7, wherein an extension side load for energizing the extension side second leaf valve is made larger than a compression side load for energizing the compression side second leaf valve by a pressure in the compression side back pressure chamber. vessel. 9. The shock absorber according to claim 8, wherein a pressure receiving area of the extension side spool that receives the pressure of the extension side back pressure chamber is larger than a pressure receiving area of the pressure side spool that receives the pressure of the pressure side back pressure chamber. .

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