JP2010053877A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner capable of changing over damper force and excellent in change over response. <P>SOLUTION: The automatic tensioner 4 dividing an inside of a cylinder 7 into a pressure chamber 12 and a reservoir chamber 13 by slidably inserting the plunger 11 in a sleeve 8, and providing communication between the pressure chamber 12 and the reservoir chamber 13 through a leak gap 16 between sliding surfaces of the plunger 11 and the sleeve 8, is provided with a bypass passage 32 providing communication between the reservoir chamber 13 and a valve hole 22 passing through a bottom 9 of the sleeve 8, a spherical valve element 23 opening and closing the valve hole 22, an iron flat plate armature 24 supporting the valve element 23, an iron flat plate yoke 26 provided to oppose to the flat plate armature 24, a compression coil spring 30 energizing the flat plate yoke 26 and the flat plate armature 24 in directions that both of the same mutually separate, and an electromagnetic coil 28 magnetizing the flat plate yoke 26 by excitation. A tube part 27 integrally formed on the flat plate toke 26 is inserted and fixed in the electromagnetic coil 28. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an auto tensioner used to maintain tension of a belt that drives a cam shaft of an engine.

  The engine camshaft is connected to the crankshaft by a belt, and is driven to rotate through the belt. In order to keep the tension of this belt within an appropriate range, generally, a pulley arm that is swingable about a fulcrum shaft, a tension pulley that is rotatably attached to the pulley arm, and a direction in which the tension pulley is pressed against the belt. A tension adjusting device comprising an auto tensioner that urges the pulley arm is used.

  As an auto tensioner incorporated in this tension adjusting device, a bottomed sleeve is fitted into a bottomed cylinder, hydraulic oil is accumulated in the cylinder, and a plunger is slidably inserted into the sleeve to move inside the cylinder. A rod that is divided into a pressure chamber and a reservoir chamber, is provided with a rod that moves integrally with the plunger in the axial direction, and the rod is urged by a return spring in a direction protruding from the cylinder (Patent Document 1).

  In this auto tensioner, the rod moves to a position where the urging force of the return spring balances with the belt tension, thereby absorbing the belt tension fluctuation and keeping the belt tension within an appropriate range.

  The pressure chamber and the reservoir chamber communicate with each other via a leak gap formed between the sliding surfaces of the sleeve and the plunger. When the rod moves in a direction to be pushed into the cylinder, the hydraulic oil in the pressure chamber is leaked into the leak gap. Spill through. At this time, the flow rate of the hydraulic oil flowing through the leak gap is limited, and the damper force acts on the rod, so that the rod moves slowly and keeps the belt in a stable state.

Further, in this auto tensioner, the plunger is provided with an oil passage communicating the pressure chamber and the reservoir chamber, and only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side is provided at the end of the oil passage on the pressure chamber side. When a rod moves in a direction protruding from the cylinder, the check valve opens and hydraulic oil flows from the reservoir chamber side to the pressure chamber side. Therefore, the rod quickly moves in the direction protruding from the cylinder.
JP-A-8-35546

  By the way, since the damper force acting on the rod is constant in the auto tensioner, when the engine speed is in the resonance point region, the rod cannot follow the belt tension fluctuation, and the belt may be over-tensioned. Also, in cold regions and in low temperatures in winter, the viscosity of the hydraulic oil flowing through the leak gap increases, so that the damper force acting on the rod becomes excessive and the belt may become over tension.

  In order to prevent this over-tension, the inventors of the present invention have studied an auto tensioner capable of switching the magnitude of the damper force acting on the rod, and penetrates the bottom of the sleeve as such an auto tensioner. A valve for providing a valve hole, providing a bypass passage communicating the valve hole and the reservoir chamber between the sleeve and the fitting surface of the cylinder, and opening and closing the end of the valve hole opposite to the pressure chamber side Body, an iron flat armature integrally formed with the valve body, an electromagnetic coil provided facing the surface of the flat plate armature opposite to the valve body, and a rod-like shape inserted into the electromagnetic coil An iron core and an elastic member that urges the electromagnetic coil and the flat plate armature in directions away from each other have been devised.

  In the auto tensioner, when the electromagnetic coil is energized, the flat plate armature is attracted to the iron core to open the valve hole and allow the flow of hydraulic oil in the bypass passage, so that the damper force acting on the rod is reduced. Further, when the energization of the electromagnetic coil is interrupted, the flat plate armature is moved by the force of the elastic member to close the valve hole and prohibit the flow of hydraulic oil in the bypass passage, so that the damper force acting on the rod is increased.

  However, since this auto tensioner has a small facing area of the iron core to the flat armature, the force with which the iron core attracts the flat armature is weak, and the responsiveness of the operation of the valve body is low. Therefore, in order to increase the responsiveness of the operation of the valve body, it is conceivable to increase the energization amount to the electromagnetic coil.

  The problem to be solved by the present invention is to provide an auto tensioner capable of switching the magnitude of the damper force and excellent in the response of the switching.

  In order to solve the above problems, a valve hole that penetrates the bottom of the sleeve is provided, and a bypass passage that communicates the valve hole and the reservoir chamber is provided between the fitting surface of the sleeve and the cylinder, and the valve hole A spherical valve body that opens and closes the end opposite to the pressure chamber side, an iron flat armature that supports the valve body, and a surface of the flat armature opposite to the valve body An iron flat plate yoke, an elastic member that urges the flat plate yoke and the flat plate armature in directions away from each other, and an electromagnetic coil that magnetizes the flat plate yoke when energized are provided integrally with the flat plate yoke. The tube portion was inserted into the electromagnetic coil and fixed.

  In this way, when the electromagnetic coil is energized, the flat plate armature is attracted to the flat plate yoke, so that the valve element opens the valve hole to allow the flow of hydraulic oil in the bypass passage, and the damper force acting on the rod is reduced. Get smaller. At this time, since the flat area of the flat plate yoke is large with respect to the flat plate armature, the flat plate armature is attracted with a strong force. On the other hand, when the energization to the electromagnetic coil is interrupted, the flat plate armature moves by the force of the elastic member, so the valve body closes the valve hole and prohibits the flow of hydraulic oil in the bypass passage, and the damper force acting on the rod Becomes larger.

  When the elastic member is accommodated in the cylindrical portion, it is possible to use an elastic member having a long free length, and the elastic member can be prevented from sag. As an elastic member accommodated in a cylinder part, a compression coil spring is mentioned, for example.

  Further, a circumferential groove may be formed on a surface of the flat plate armature facing the flat plate yoke or a surface of the flat plate yoke facing the flat plate armature, and the elastic member may be accommodated in the circumferential groove. If it does in this way, since an elastic member will support a flat plate armature with sufficient balance, the posture of a flat plate armature can be stabilized. Examples of the elastic member accommodated in the circumferential groove include a wave spring in which an annular metal plate is corrugated.

  If the size of the gap between the opposed surfaces of the flat plate armature and the flat plate yoke when the electromagnetic coil is not energized is set to 0.3 mm or less, the magnetic force acting on the flat plate armature from the flat plate yoke becomes large. Responsiveness of switching the magnitude of force can be ensured.

  By the way, when the flat plate yoke sucks the flat plate armature, the hydraulic oil existing between the opposed surfaces of the flat plate yoke and the flat plate armature becomes an obstacle, and the moving speed of the flat plate armature may be lowered. Therefore, when an oil discharge groove is provided on the surface facing the flat plate armature of the flat plate armature or the surface facing the flat plate armature of the flat plate yoke, when the flat plate yoke sucks the flat plate armature, The hydraulic oil present in the cylinder escapes into the oil discharge groove, so that the moving speed of the flat plate armature is difficult to decrease.

  The auto tensioner of the present invention can switch the magnitude of the damper force by switching between energization and de-energization of the electromagnetic coil. Further, this auto tensioner sucks the flat plate armature with a flat plate yoke having a large area facing the flat plate armature, so that the force to suck the flat plate armature is strong and the response of switching the magnitude of the damper force is high.

  FIG. 1 shows a belt tension adjusting device for driving a camshaft of an engine. This tension adjusting device has a pulley arm 2 supported so as to be swingable about a fulcrum shaft 1, a tension pulley 3 rotatably attached to the pulley arm 2, and an auto tensioner 4 according to an embodiment of the present invention. The auto tensioner 4 urges the pulley arm 2 to press the tension pulley 3 against the belt 5.

  The auto tensioner 4 has a cylinder 7 having a bottom 6 at a lower portion, and hydraulic oil is stored in the cylinder 7. A bottomed sleeve 8 is inserted into the cylinder 7 with the bottom 9 facing downward, and a lower portion of the sleeve 8 is fitted into a sleeve fitting recess 10 formed in the bottom 6 of the cylinder 7. A plunger 11 is slidably inserted in the sleeve 8 in the axial direction, and the cylinder 7 is partitioned into a pressure chamber 12 and a reservoir chamber 13 by the sleeve 8 and the plunger 11.

  The pressure chamber 12 and the reservoir chamber 13 communicate with each other via an oil passage 14 provided in the plunger 11, and the end of the oil passage 14 on the pressure chamber 12 side extends from the reservoir chamber 13 side to the pressure chamber 12 side. A check valve 15 that allows only the flow of hydraulic oil to the engine is provided. A leak gap 16 that communicates the pressure chamber 12 and the reservoir chamber 13 is formed between the sliding surfaces of the sleeve 8 and the plunger 11.

  A rod 17 extending upward from the plunger 11 and protruding from the cylinder 7 is connected to the plunger 11. The plunger 11 is urged by a plunger spring 18 incorporated in the pressure chamber 12 and pressed against the rod 17, so that the rod 17 moves in the axial direction integrally with the plunger 11 by the pressing. It has become.

  The rod 17 includes a large-diameter shaft portion 17A and a small-diameter shaft portion 17B connected to the lower end of the large-diameter shaft portion 17A. A wear ring 19 slidable in the axial direction on the inner periphery of the cylinder 7 is fitted to the outer periphery of the small diameter shaft portion 17B, and the lower end of the large diameter shaft portion 17A is supported by the wear ring 19. The wear ring 19 is pressed upward by a return spring 20 incorporated in the reservoir chamber 13, and the rod 17 is biased through the wear ring 19 in a direction protruding from the cylinder 7.

  An oil seal 21 that prevents leakage of hydraulic oil in the cylinder 7 is attached to the upper portion of the cylinder 7. The oil seal 21 is formed in an annular shape, and the large-diameter shaft portion 17A of the rod 17 is slidably penetrated.

  As shown in FIG. 2, a valve hole 22 is provided in the bottom 9 of the sleeve 8. The valve hole 22 penetrates the bottom 9 up and down, and its upper end communicates with the pressure chamber 12. Further, the end of the valve hole 22 opposite to the pressure chamber 12 side is closed by a spherical valve body 23.

  The valve body 23 is supported by an iron flat armature 24 provided so as to be movable in the axial direction. In the flat armature 24, the support surface 25 of the valve body 23 is formed in a concave shape as shown in FIG. 4 in order to stabilize the support of the valve body 23.

  As shown in FIG. 2, an iron flat plate yoke 26 is provided to face the surface of the flat plate armature 24 opposite to the valve body 23. A cylindrical portion 27 is integrally formed at the center of the flat yoke 26, and the cylindrical portion 27 is inserted and fixed in the electromagnetic coil 28. When the electromagnetic coil 28 is energized, the flat yoke 26 is magnetized. ing. The cylindrical portion 27 is fixed, for example, by press-fitting the cylindrical portion 27 into the inner periphery of a case 29 that accommodates the electromagnetic coil 28. As shown in FIG. 1, the cylindrical portion 27 has a bottom and accommodates a compression coil spring 30 that urges the flat yoke 26 and the flat armature 24 in directions away from each other. In a state where the electromagnetic coil 28 is not energized, the size of the gap between the opposing surfaces of the flat plate armature 24 and the flat plate yoke 26 is set to 0.3 mm or less.

  As shown in FIG. 3, an oil discharge groove 31 is formed on a surface of the flat plate armature 24 facing the flat plate yoke 26. In the drawing, the oil discharge grooves 31 are formed in a radial shape, but may be formed in a lattice shape.

  As shown in FIG. 2, a bypass passage 32 that connects the valve hole 22 and the reservoir chamber 13 is formed between the fitting surfaces of the sleeve 8 and the cylinder 7. The bypass passage 32 has a diameter formed between the axial passage 33 formed between the outer periphery of the sleeve 8 and the inner periphery of the sleeve fitting recess 10, and the bottom 9 of the sleeve 8 and the bottom 6 of the cylinder 7. A directional passage 34.

  Next, an operation example of the auto tensioner 4 will be described.

  When the tension of the belt 5 increases, the tension is transmitted to the rod 17 via the tension pulley 3 and the pulley arm 2, and the pressure in the pressure chamber 12 increases. When the pressure in the pressure chamber 12 becomes higher than the pressure in the reservoir chamber 13, as shown in FIG. 2, the hydraulic oil flows through the leak gap 16 from the pressure chamber 12 side to the reservoir chamber 13 side. At this time, since the check valve 15 is closed, the hydraulic oil does not flow through the oil passage 14.

  In this way, when the hydraulic oil flows through the leak gap 16, the rod 17 moves downward, and the tension pulley 3 moves to a position where the tension of the belt 5 and the biasing force of the return spring 20 are balanced. At this time, since the flow rate of the hydraulic oil flowing through the leak gap 16 is limited and a damper action occurs, the tension pulley 3 moves slowly and keeps the belt 5 in a stable state.

  When the electromagnetic coil 28 is energized, the flat plate armature 24 is attracted to the magnetized flat plate yoke 26 as shown in FIG. Therefore, the hydraulic oil in the pressure chamber 12 flows into the reservoir chamber 13 via the bypass passage 32, and the damper force acting on the rod 17 is reduced. When the energization of the electromagnetic coil 28 is interrupted, the flat armature 24 is separated from the flat yoke 26 by the force of the compression coil spring 30 and presses the valve element 23 in the direction of closing the valve hole 22 as shown in FIG. . Therefore, the hydraulic oil in the pressure chamber 12 does not flow through the bypass passage 32, and the damper force that acts on the rod 17 increases.

  On the other hand, when the tension of the belt 5 is reduced, the rod 17 is moved upward by the urging force of the return spring 20 and the volume of the pressure chamber 12 is increased, so that the pressure in the pressure chamber 12 is lowered. When the pressure in the pressure chamber 12 becomes lower than the pressure in the reservoir chamber 13, the check valve 15 is opened, and hydraulic oil flows through the oil passage 14 from the reservoir chamber 13 side to the pressure chamber 12 side. At this time, the tension pulley 3 quickly moves to a position where the tension of the belt 5 and the biasing force of the return spring 20 are balanced, and quickly absorbs the slack of the belt 5.

  As described above, the auto tensioner 4 can switch the magnitude of the damper force acting on the rod 17 even during engine operation by switching between energization and de-energization of the electromagnetic coil 28.

  For example, when the auto tensioner 4 is used, a resonance determination unit that determines whether or not the engine speed is in the resonance point region is provided, and the resonance determination unit determines that the engine rotation number is in the resonance point region. Thus, it is possible to perform control to reduce the damper force by energizing the electromagnetic coil 28. In this way, even when the engine resonates, the rod 17 reliably follows the fluctuation in the tension of the belt 5, and the belt 5 is unlikely to be over-tensioned.

  Further, a low temperature determination means for determining whether or not the engine temperature is in a low temperature range is provided, and when the engine temperature is determined to be in the low temperature range by the low temperature determination means, the electromagnetic coil 28 is energized to reduce the damper force. It is also possible to perform control. In this way, the damper force acting on the rod 17 is unlikely to be excessive and the belt 5 is unlikely to be overtensioned even in a cold region or in a low temperature environment in winter.

  Since the auto tensioner 4 attracts the flat plate armature 24 with the flat plate yoke 26 having a large facing area with respect to the flat plate armature 24, the auto tensioner 4 attracts the flat plate armature 24 with the rod-shaped iron core provided in the electromagnetic coil 28. The force for sucking the flat plate armature 24 is strong, and the response of switching the magnitude of the damper force is high.

  Further, since the auto tensioner 4 accommodates the compression coil spring 30 in the cylindrical portion 27 inserted into the electromagnetic coil 28, the compression coil spring 30 is stretched by using the compression coil spring 30 having a long free length. Can be prevented.

  In the auto tensioner 4, the size of the gap between the opposed surfaces of the flat armature 24 and the flat yoke 26 is set to 0.3 mm or less. Therefore, when the electromagnetic coil 28 is energized, the flat armature 26 extends from the flat armature 26. The magnetic force acting on 24 is large, and the response of switching the magnitude of the damper force is high.

  Further, since the auto tensioner 4 has the oil discharge groove 31 on the surface facing the flat plate yoke 26 of the flat plate armature 24, when the flat plate yoke 26 sucks the flat plate armature 24, the facing surface of the flat plate arm 26 and the flat plate armature 24. The hydraulic oil present between them escapes to the oil discharge groove 31. Therefore, the resistance of the hydraulic oil existing between the opposed surfaces of the flat plate yoke 26 and the flat plate armature 24 is small, and the moving speed of the flat plate armature 24 is unlikely to decrease. As shown in FIG. 6, the oil discharge groove 31 may be formed on the surface of the flat plate yoke 26 facing the flat plate armature 24.

  In the above embodiment, the compression coil spring 30 is employed as an elastic member that urges the flat plate yoke 26 and the flat plate armature 24 in directions away from each other. However, as shown in FIG. The wave spring 35 may be used. In this way, the wave spring 35 supports the flat plate armature 24 in a well-balanced manner, so that the posture of the flat plate armature 24 when the energization to the electromagnetic coil 28 is interrupted can be stabilized.

  When the wave spring 35 is employed as an elastic member that biases the flat plate arm 26 and the flat plate armature 24 away from each other, the wave spring 35 is provided in a circumferential groove 36 formed on the surface of the flat plate armature 24 facing the flat plate yoke 26. When accommodated, the wave spring 35 having a large thickness can be used to prevent the wave spring 35 from sagging. Further, the circumferential groove 36 for accommodating the wave spring 35 may be formed on the surface of the flat plate yoke 26 facing the flat plate armature 24.

Sectional drawing which shows the tension adjusting apparatus incorporating the auto tensioner of this embodiment of this invention FIG. 1 is an enlarged sectional view showing a process in which the rod shown in FIG. 1 moves in the pushing direction. Sectional view along line III-III in FIG. FIG. 2 is an enlarged sectional view in the vicinity of a flat plate armature showing a state in which the electromagnetic coil shown in FIG. FIG. 2 is an enlarged cross-sectional view in the vicinity of a flat plate armature showing a modification in which the compression coil spring shown in FIG. 2 is replaced with a wave spring. FIG. 2 is an enlarged sectional view of the vicinity of a flat plate armature showing a modification in which the oil discharge groove shown in FIG. 2 is formed in a flat plate yoke.

Explanation of symbols

4 Auto-tensioner 7 Cylinder 8 Sleeve 9 Bottom 11 Plunger 12 Pressure chamber 13 Reservoir chamber 14 Oil passage 15 Check valve 16 Leak gap 17 Rod 20 Return spring 22 Valve hole 23 Valve body 24 Flat armature 26 Flat yoke 27 Cylindrical portion 28 Electromagnetic coil 30 Compression coil spring 31 Oil discharge groove 32 Bypass passage 35 Wave spring 36 Circumferential groove

Claims (8)

The bottomed sleeve (8) is fitted into the bottomed cylinder (7), the hydraulic oil is stored in the cylinder (7), and the plunger (11) is slidably inserted into the sleeve (8). The cylinder (7) is partitioned into a pressure chamber (12) and a reservoir chamber (13), and the leak chamber (16) formed between the sliding surfaces of the plunger (11) and the sleeve (8) A pressure chamber (12) and a reservoir chamber (13) communicate with each other, a rod (17) that moves integrally with the plunger (11) in the axial direction is provided, and the rod (17) protrudes from the cylinder (7). An urging return spring (20) is provided, an oil passage (14) communicating the pressure chamber (12) and the reservoir chamber (13) is formed in the plunger (11), and a reservoir chamber (14) is formed in the oil passage (14). 13) From side to pressure chamber (12) side Autotensioner provided a check valve (15) which allows only the flow of a working fluid (4),
A valve hole (22) penetrating the bottom (9) of the sleeve (8) is provided, and a bypass passage (32) communicating the valve hole (22) and the reservoir chamber (13) is formed with the sleeve (8). A spherical valve body (23) provided between the fitting surfaces of the cylinder (7) and opening and closing the end of the valve hole (22) opposite to the pressure chamber (12) side, and the valve body (23 ) Supporting an iron flat plate armature (24), an iron flat plate yoke (26) provided facing the surface of the flat plate armature (24) opposite to the valve body (23), and the flat plate yoke An elastic member (30) for urging the flat armature (26) and the flat plate armature (24) away from each other; and an electromagnetic coil (28) for magnetizing the flat plate yoke (26) when energized. The cylindrical part (27) formed integrally with (26) Auto-tensioner being fixed by inserting in the coil (28).   The auto tensioner according to claim 1, wherein the elastic member (30) is accommodated in the cylindrical portion (27).   The auto tensioner according to claim 2, wherein the elastic member is a compression coil spring (30).   A circumferential groove (36) is formed on a surface of the flat plate armature (24) facing the flat plate yoke (26) or a surface of the flat plate yoke (26) facing the flat plate armature (24), and the circumferential groove (36). The auto tensioner according to claim 1, wherein the elastic member (35) is housed in a casing.   The auto tensioner according to claim 4, wherein the elastic member is a wave spring (35) having a corrugated metal plate.   The size of the gap between the opposing surfaces of the flat plate armature (24) and the flat plate yoke (26) when the electromagnetic coil (28) is not energized is set to 0.3 mm or less. The auto tensioner described in Crab.   The oil discharge groove (31) is provided on an opposing surface of the flat armature (24) to the flat plate yoke (26) or an opposing surface of the flat plate yoke (26) to the flat plate armature (24). The auto tensioner described in 1.   The auto tensioner according to claim 7, wherein the oil discharge groove (31) is a radial or lattice-like groove.

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