JP2007253653A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device compactly constituted by integrating a hydraulic control valve for the supply and discharge of hydraulic fluid to a part of a housing of a power cylinder for steering assistance. <P>SOLUTION: This power steering device is provided with a torque sensor 8 for detecting steering torque added to a steering wheel 30 together with a steering direction, the power cylinder 5 for applying steering assist force to a rack shaft 1, and the hydraulic control valve 6 operated based on the detected torque of the torque sensor 8 to perform supply and discharge control of the hydraulic fluid of the power cylinder 5. The hydraulic control valve 6 is constituted in a valve housing 60 attached to a part of the cylinder housing 50 of the power cylinder 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power steering device configured to detect a steering torque applied to a steering member, and to control supply and discharge of the hydraulic pressure of a steering assist power cylinder by a hydraulic control valve that operates based on the detection result.

  In recent automobiles, power steering devices are widely used for the purpose of reducing the labor burden required for steering by applying a steering assist force to the steering mechanism according to the operation of a steering member such as a steering wheel, and obtaining a comfortable steering feeling. Equipped. This power steering device is roughly classified into a hydraulic power steering device that uses a backward-acting hydraulic cylinder (power cylinder) as a source of steering assist force, and an electric power steering device that also uses an electric motor.

  The hydraulic power steering device has the advantage that the generated force of the power cylinder for assisting steering is large and sufficient steering assisting force can be obtained with a compact configuration, while the hydraulic oil to the power cylinder according to the operation of the steering member. Is controlled by the mechanical operation of a hydraulic control valve that uses torsion of a steering shaft that connects the steering member and the steering mechanism, and corresponds to the traveling state such as the vehicle speed and the steering angle. There is a problem that it is difficult to cope with the change control of the auxiliary force characteristics.

  On the other hand, an electric power steering device detects a steering torque applied to a steering member by a torque sensor disposed in the middle of a transmission system to a steering mechanism, and an electric motor for assisting steering is detected based on the detected torque of the torque sensor. It is configured to assist the steering by adding the rotational force generated by this motor to the steering mechanism, and the correspondence relationship between the detected torque and the generated force of the electric motor can be freely changed, and the assist according to the running state While there is an advantage that change control of the force characteristic is easy, there is a problem that when a sufficient steering assist force is obtained, the motor for steering assist and the transmission means from the motor to the steering mechanism are enlarged. is there.

  Under such circumstances, a power steering device configured to combine a hydraulic power steering device and an electric power steering device and take advantage of both has been proposed (see, for example, Patent Document 1).

  This power steering device uses a power cylinder as a source of steering assist force, detects a steering torque applied to the steering member by a torque sensor, operates a hydraulic control valve based on the detected torque, and supplies the power cylinder to the power cylinder. It is the structure which controls supply / discharge of the hydraulic oil.

The hydraulic control valve includes a cylindrical valve body, a valve spool fitted and held in the valve body so as to be movable in the axial length direction, and a solenoid disposed facing both ends of the valve spool. A known solenoid valve is used to excite the corresponding solenoid based on the direction and magnitude of the steering torque detected by the torque sensor, and press the valve spool to move in the axial direction. As a result, the throttle area of the throttle portion provided in parallel with the fitting portion with the valve body is increased or decreased to control the supply and discharge of hydraulic oil to and from the power cylinder.
Japanese Patent Laid-Open No. 11-180332

  In the power steering device configured as described above, a power cylinder is used as a source of steering assist force, and sufficient steering assist force can be obtained with a compact configuration, and torque detected by a torque sensor and a hydraulic control valve can be obtained. By changing the correspondence relationship with the excitation current of the solenoid, it is possible to respond to changes in auxiliary force characteristics according to the running state, and it is an excellent device that combines the advantages of hydraulic power steering devices with the advantages of electric power steering devices is there.

  However, since a hydraulic control valve for supplying and discharging hydraulic oil to and from the power cylinder is provided independently from the transmission system from the steering member to the steering mechanism, a space for arranging the hydraulic control valve is secured. There is a problem that it is necessary to secure a space for the hydraulic piping connecting the hydraulic control valve, the hydraulic pump as the hydraulic power source, and the power cylinder, and it is difficult to configure in a limited space around the steering mechanism.

  The present invention has been made in view of such circumstances, and a hydraulic control valve is formed in a part of the housing of the power cylinder, and a hydraulic pump is arranged in parallel with the housing, so that a large space is not required. An object is to provide a configurable power steering device.

  A power steering apparatus according to a first aspect of the present invention includes a torque sensor that detects a steering torque applied to a steering member together with a steering direction, a power cylinder that applies a steering assist force to a steering shaft in a steering mechanism, and the torque sensor. A hydraulic control valve that operates based on the detected torque of the hydraulic cylinder and controls the supply and discharge of hydraulic oil of the power cylinder, wherein the hydraulic control valve is attached to a part of the housing of the power cylinder, It is characterized by comprising a valve chamber provided in communication with both oil chambers of the power cylinder, and a valve spool that moves in the axial direction in the valve chamber.

  According to a second aspect of the present invention, there is provided a power steering apparatus including an electric pump that is externally fixed to a housing of the power cylinder and generates the hydraulic oil.

  Furthermore, a power steering device according to a third aspect of the invention is characterized in that the power cylinder in the first or second aspect of the invention is externally fixed to the housing of the steering shaft.

  In the power steering device according to the first aspect of the present invention, the hydraulic control valve for supplying and discharging the hydraulic oil is attached to a part of the housing of the power cylinder for assisting the steering, so that the space for arranging the hydraulic control valve becomes unnecessary. In addition, it is not necessary to arrange the hydraulic piping connecting the hydraulic control valve and the power cylinder, and the configuration can be made compact in a limited space around the steering mechanism.

  In the power steering apparatus according to the second aspect of the invention, since the electric pump that is the source of hydraulic oil is externally fixed to the housing of the power cylinder provided with the hydraulic control valve, the electric pump and the hydraulic control valve are communicated with each other. It is not necessary to handle hydraulic piping, and further downsizing can be achieved.

  Furthermore, in the power steering device according to the third aspect of the invention, the power cylinder in which the hydraulic control valve is integrated or the power cylinder in which the hydraulic control valve and the electric pump are integrated is fixed to the housing of the steering shaft. The present invention has an excellent effect, such as being able to be configured compactly and being able to easily configure a power steering device that can cope with changes in assisting force characteristics.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a diagram showing the overall configuration of a power steering apparatus according to the present invention. This power steering apparatus is movable in the axial direction in a rack housing 10 that extends in the left-right direction of a vehicle body (not shown). And a rack and pinion type steering mechanism including a pinion shaft 2 rotatably supported inside a pinion housing 20 that crosses in the vicinity of one end of the rack housing 10.

  Both ends of the rack shaft 1 projecting outward from both sides of the rack housing 10 are connected to left and right front wheels 12 and 12 as steering wheels via respective tie rods 11 and 11, and projecting to the outside of the pinion housing 20. The upper end of the pinion shaft 2 is connected to a steering wheel 30 as a steering member via a steering shaft 3. A pinion (not shown) is formed at the lower part of the pinion shaft 2 extending into the pinion housing 20, and the pinion is formed on the outer surface of the rack shaft 1 at an appropriate length at the intersection with the rack housing 10. Meshed with the rack teeth.

  The steering shaft 3 is rotatably supported inside a cylindrical column housing 31, and is fixed to the inside of a vehicle compartment (not shown) while maintaining a tilted posture with the front facing down through the column housing 31. . A steering wheel 30 is fixed to the upward protruding end of the column housing 31 of the steering shaft 3 and the downward protruding end is connected to the pinion shaft 2 via an intermediate shaft 4 having universal joints at both ends. It is connected.

  With the above configuration, when the steering wheel 30 is rotated for steering, this rotation is transmitted to the pinion shaft 2 via the steering shaft 3 and the intermediate shaft 4, and further at the meshing portion between the pinion and the rack teeth. The movement of the rack shaft 1 is converted into the movement in the axial length direction, and by such movement of the rack shaft 1, the left and right front wheels 12, 12 are pushed and pulled through the respective tie rods 11, 11 to be steered. The

  The other half of the rack housing 10 that supports the rack shaft 1 is provided with a cylinder housing 50 over a predetermined length range, and inside the cylinder housing 50 assists the steering performed as described above. A power cylinder 5 (see FIG. 2) is configured. In addition, a valve housing 60 is attached to the outside of the cylinder housing 50 at an appropriate position in the axial direction at one place in the circumferential direction, and hydraulic oil for the power cylinder 5 is placed inside the valve housing 60. A hydraulic control valve 6 (see FIG. 2) for supply / discharge control is configured.

  Further, a pump bracket 70 is attached to the cylinder housing 50 at a circumferential position adjacent to the valve housing 60. The pump bracket 70 includes an electric pump 7 that generates hydraulic oil for the power cylinder 5, and the electric pump. The motor 71 serving as the drive source 7 is fixed to the both sides in the axial direction in a coaxial manner.

  The electric pump 7 includes a pump bracket 70 and a motor 71, and has a known configuration disclosed in, for example, Japanese Patent Application Laid-Open No. 10-82377 by the applicant of the present application, and protrudes inside the pump bracket 70. The output end of the motor 71 is connected to the input end of the electric pump 7 and is driven by transmission from the motor 71. A discharge path 72 (see FIGS. 2 and 3) of the electric pump 7 is extended to the valve housing 60 through the inside of the pump bracket 70, and hydraulic oil whose pressure has been increased by the operation of the electric pump 7 is discharged from the discharge path 72. Then, the hydraulic control valve 6 in the valve housing 60 is supplied with oil.

  On the other hand, in the middle of the pinion housing 20 that supports the pinion shaft 2, a torque sensor 8 that detects a steering torque applied to the pinion shaft 2 via the steering shaft 3 and the intermediate shaft 4 by a rotation operation of the steering wheel 30 is provided. is there. The torque sensor 8 divides the pinion shaft 2 to be detected into two upper and lower shafts, and these two shafts are connected coaxially by a torsion bar having a known torsion characteristic, and the torsion bar is twisted by the action of the steering torque. With this, there is a known configuration for detecting the relative angular displacement generated between the two axes by an appropriate means.

  FIG. 2 is a longitudinal sectional view schematically showing components of the power cylinder 5 and the hydraulic control valve 6. As shown in the figure, the power cylinder 5 is liquid-tightly sealed inside the cylinder housing 50 between an end wall 51 on the connection side with the rack housing 10 and a seal cylinder 52 fitted in the opening on the other side. The piston 5a, which is coaxially fitted and fixed in the middle of the rack shaft 1, is inserted between the sealing portions, and left and right oil chambers 5L and 5R are provided on both sides of the piston 5a. .

  The hydraulic control valve 6 includes a valve spool 62 that is fitted and held in a valve chamber 61 having a circular cross section provided in the valve housing 60 so as to be movable in the axial direction. Neutral springs 63 and 64 are interposed between both end faces of the valve spool 62 and both end faces of the valve chamber 61 facing each other. The valve spool 62 is caused by the spring force of the neutral springs 63 and 64. The valve chamber 61 is held in a neutral position in the center in the axial direction.

  Three oil grooves are provided around the inner peripheral surface of the valve chamber 61 at a predetermined interval in the axial direction. The central oil groove communicates with the discharge path 72 of the electric pump 7 described above, and serves as an oil supply groove 65 to which high-pressure hydraulic oil discharged from the electric pump 7 is supplied. Further, the two oil grooves on both sides are communicated with an oil tank (not shown) and are drained oil grooves 66 and 66 maintained at a low pressure equivalent to that of the oil tank.

  On the other hand, two oil grooves are provided around the outer periphery of the valve spool 62 at a predetermined interval in the axial direction. These oil grooves are respectively connected to the left and right oil chambers 5L, 5R of the power cylinder 5 by separate oil supply holes 53, 54 formed in the partition wall between the power cylinder 5 and the oil supply grooves 67, When the valve spool 62 is in the neutral position, these oil feeding grooves 67 and 68 are throttle portions having a throttle area substantially equal to the oil supply groove 65 and the oil discharge grooves 66 and 66 on both sides. It is positioned so as to communicate with each other.

  FIG. 3 is an explanatory diagram of a mode of forming the discharge passage 72 along the line III-III in FIG. As described above, the discharge path 72 of the electric pump 7 is provided in the pump bracket 70 that fixes and supports the electric pump 7 together with the driving motor 71. As shown in the figure, the pump bracket 70 is a cylindrical body integrally connected to the outside of the cylinder housing 50 adjacent to the valve housing 60, and the discharge path 72 is radially directed toward the connecting portion with the valve housing 60. 2 and communicates with the oil supply groove 65 of the valve chamber 61 as shown in FIG.

Solenoids S _L and S _R are attached to the outside of the left and right sides of the valve housing 60, and the output ends of both solenoids S _L and S _R extending into the valve chamber 61 are on the same side of the valve spool 62. It is made to contact | abut to the center part of an end surface. The solenoids S _L and S _R operate to project the output end in accordance with the respective excitation, and this operation causes the valve spool 62 to move in the right or left direction against the spring force of the other neutral springs 64 and 63. Accordingly, the throttle area of the throttle portion between the oil feed grooves 67 and 68 on the outer periphery of the valve spool 62 and the oil supply grooves 65 and the oil drain grooves 66 and 66 on both sides of the valve spool 62 changes.

Figure 4 is an explanatory view of the operation of the hydraulic control valve 6, in FIG. 4 (a), the state in which the valve spool 62 by the excitation of the solenoid S _R has moved to the leftward, FIG. 4 (b), the solenoid S _L The state in which the valve spool 62 has moved to the right by the excitation is shown.

  When the valve spool 62 moves, the throttle areas of the throttle portions on both sides of the oil feed grooves 67 and 68 change as described above. This area change occurs in opposite directions in the left and right oil supply grooves 67, 68. When the valve spool 62 moves to the left as shown in FIG. 4A, the oil supply groove 65 in the left oil supply groove 67. In the right oil feed groove 68, the throttle area between the oil supply groove 65 increases and the oil drain groove increases. The aperture area between 66 and 66 is reduced. Conversely, when the valve spool 62 moves to the right as shown in FIG. 4B, the throttle area between the oil supply groove 67 and the oil supply groove 65 increases in the left oil supply groove 67, and between the oil supply groove 66 and the oil supply groove 66. While the throttle area decreases, in the right oil feed groove 68, the throttle area between the oil supply groove 65 decreases and the throttle area between the oil drain groove 66 increases.

  As shown in FIG. 2, when the valve spool 62 is in the neutral position, the pressure oil supplied from the electric pump 7 to the oil supply groove 65 is distributed to the left and right oil supply grooves 67 and 68 through the left and right throttle parts, Further, the oil is introduced into the oil drain grooves 66 and 66 through the throttle portions on the other side of the oil feed grooves 67 and 68. At this time, the left and right throttle portions through which the pressure oil passes have the same throttling area, so the pressure oil is evenly distributed to the left and right sides, and the left and right oil feed grooves 67, 68 and the power cylinder 5 communicated therewith. No pressure difference occurs between the left and right oil chambers 5L, 5R, and the power cylinder 5 does not generate any force.

  When the valve spool 62 moves to the left and is in the position shown in FIG. 4A, the pressure oil supplied to the oil supply groove 65 is mainly introduced into the right oil supply groove 68 through the throttle portion with an increased throttle area. Become so. At this time, the pressure in the right oil supply groove 68 and the right oil chamber 5R communicated with the oil supply groove 68 increases, and as a result of a pressure difference with the left oil chamber 5L, the power cylinder 5 An oil pressure corresponding to the pressure difference is generated, and a leftward steering assist force is applied to the rack shaft 1 as indicated by an arrow in the figure.

  On the other hand, when the valve spool 62 moves to the right and is in the position shown in FIG. 4B, the pressure oil supplied to the oil supply groove 65 is mainly introduced into the oil supply groove 67 on the left side through the throttle portion having an increased throttle area. As a result, the pressure in the left oil chamber 5L communicated with the oil feed groove 67 increases, and the power cylinder 5 generates a steering assist force in the right direction as indicated by an arrow in the figure, and this steering assist A force is applied to the rack shaft 1.

  The hydraulic oil is pushed out from the other oil chamber 5L or 5R by the operation of the power cylinder 5 as described above, and this hydraulic oil returns to the oil feed groove 67 or 68 communicated with the hydraulic chamber 5L or 5R. The oil flows into the oil discharge chambers 66 and 66 through a throttle portion having an increased throttle area on the side, and is discharged to an oil tank T communicated therewith.

Thus, the direction of the steering assist force generated by the power cylinder 5 corresponds to the moving direction of the valve spool 62, and the magnitude of the steering assist force is that of the throttle portion generated as described above according to the movement of the valve spool 62. This corresponds to the increase or decrease of the aperture area. Since the valve spool 62 moves in response to the excitation of the left and right solenoids S _L and S _R , the direction and magnitude of the steering assist force generated by the power cylinder 5 by controlling the excitation current of these solenoids S _L and S _R. Can be controlled.

As shown in FIG. 1, the left and right solenoids S _L and S _R of the hydraulic control valve 6 are configured to be excited in accordance with control commands given from the assist control unit 9. The assist control unit 9 is given a detected value of the steering torque by the torque sensor 8, and from the running state sensor 90 arranged in each part of the vehicle, various running conditions that affect the steering, such as a running speed and a steering angle. The detection result is given.

The assist control unit 9 stores the correspondence relationship between the steering assist force and the steering torque, for example, in the form of a control map, and the assist control unit 9 detects the steering torque applied from the torque sensor 8. A value is applied to the control map to sequentially obtain the direction and magnitude of the necessary steering assist force, and a control operation is performed to issue a control command to the solenoids S _L and S _R to generate the steering assist force. The detection result of the traveling state given from the traveling state sensor 90 is used for correcting the steering assist force obtained as described above. This correction is performed, for example, in order to increase the steering assist force during low-speed traveling and realize lighter steering while reducing the steering assist force during high-speed traveling to increase neutral rigidity.

  By the operation of the steering control unit 9 described above, the valve spool 62 of the hydraulic control valve 6 is moved as described above, and the hydraulic pressure generated by the power cylinder 5 is applied to the rack shaft 1 in accordance with this movement to assist the steering. The As described above, in the power steering apparatus according to the present invention, the power cylinder 5 configured in the middle of the rack shaft 1 is a source of the steering assist force, so that a sufficient steering assist force can be obtained with a compact configuration. Since the hydraulic oil of the power cylinder 5 is supplied and discharged by the hydraulic control valve 6 configured as a solenoid valve, it is possible to flexibly cope with the change control of the assist force characteristic based on the detection result of the steering torque and the running state. .

  In addition, a hydraulic control valve 6 for supplying and discharging hydraulic oil is provided in a valve housing 60 provided integrally with a part of the cylinder housing 50 so as to communicate with the left and right oil chambers 5L and 5R of the power cylinder 5. Since the valve spool 62 is arranged in the 61, hydraulic piping for connecting the hydraulic control valve 6 and the power cylinder 5 is unnecessary, and a compact space is not required around the steering mechanism. Can be configured.

  Further, in the above embodiment, since the electric pump 7 that is a source of hydraulic oil is externally fixed to the cylinder housing 50 that forms a part of the rack housing 10, the electric pump 7 and the hydraulic control valve 6 are fixed. No hydraulic piping between the two is required, and further downsizing can be achieved. Since the electric pump 7 is bulky as shown in the figure, it can be provided separately when the excess space around the rack housing 10 is limited. In this case, the power cylinder 5 is also provided. Needless to say, the above-described integration with the hydraulic control valve 6 can achieve the space saving effect.

  FIG. 5 is a diagram showing an overall configuration of a power steering apparatus according to another embodiment of the present invention. In this embodiment, the steering assist power cylinder 5 is configured separately from the rack housing 10 that supports the rack shaft 1. The power cylinder 5 includes an output rod 54 that protrudes to one side (tip side). The tip of the output rod 54 is connected to a ball joint 14 that connects the rack shaft 1 and the tie rod 11 on one side, A base portion is connected to a fixed bracket 13 projecting outward in the vicinity of a portion where the rack housing 10 and the pinion housing 20 are connected to each other, and is externally attached to the outside of the rack housing 1 along the axial length direction as shown in the figure. It is fixed.

  A valve housing 60 is attached to the outside of the cylinder housing 50 of the power cylinder 5 over an appropriate length in the axial length direction. A pump bracket 70 integrally attached to a circumferential position adjacent to the valve housing 60 is attached to the valve housing 60. The electric pump 7 is fixed together with a driving motor 71. The configuration of other parts is the same as that of the first embodiment shown in FIG. 1 including the configuration of the hydraulic control valve 6 inside the valve housing 60, and the corresponding reference numerals are the same as those of FIG. The description of the configuration and operation is omitted.

  In this embodiment, the same effect as in the first embodiment can be obtained, and a power cylinder 5 in which the hydraulic control valve 6 and the electric pump 7 are integrally attached is externally attached to the rack housing 1. Thus, a power steering device can be configured. In this embodiment as well, it goes without saying that the electric pump 7 can be provided separately.

It is a figure showing the whole power steering device composition concerning the present invention. It is a longitudinal cross-sectional view which briefly shows the structural part of a power cylinder and a hydraulic control valve. It is a cross-sectional view by the III-III line of FIG. It is operation | movement explanatory drawing of a hydraulic control valve. It is a figure which shows the whole structure of the power steering apparatus which concerns on other embodiment of this invention.

Explanation of symbols

1 rack shaft (steering shaft), 5 power cylinder, 5L, 5R oil chamber, 6 hydraulic control valve,
7 Electric pump, 8 Torque sensor, 10 Rack housing (steering shaft housing),
30 Steering wheel (steering member), 50 Cylinder housing (Power cylinder housing), 61 Valve chamber, 62 Valve spool

Claims (3)

A torque sensor for detecting a steering torque applied to the steering member together with a steering direction, a power cylinder for applying a steering assist force to a steering shaft in the steering mechanism, and an operation based on the detected torque of the torque sensor, In a power steering device comprising a hydraulic control valve that controls supply and discharge of hydraulic oil,
The hydraulic control valve is attached to a part of the housing of the power cylinder, and is provided with a valve chamber that communicates with both oil chambers of the power cylinder, and a valve spool that moves in the axial direction within the valve chamber. A power steering device comprising:   The power steering apparatus according to claim 1, further comprising an electric pump that is externally fixed to a housing of the power cylinder and generates the hydraulic oil.   The power steering apparatus according to claim 1 or 2, wherein the power cylinder is externally fixed to a housing of the steering shaft.

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