JP5118001B2 - Auto tensioner - Google Patents

Description

  The present invention relates to an auto tensioner used for maintaining the tension of a belt for driving an automobile auxiliary machine such as an alternator.

  An auxiliary machine of an automobile, such as an alternator, a car air conditioner, or a water pump, has a rotating shaft connected to a crankshaft of an engine with a belt, and is driven via 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 including an auto tensioner that biases the pulley arm is used.

  As an auto tensioner incorporated in this tension adjustment device, hydraulic oil is stored in a cylinder having a bottom at the bottom, and the outer periphery of the lower portion of the sleeve is fitted into a sleeve fitting recess formed at the bottom of the cylinder, and a rod is placed in the sleeve. The cylinder is slidably inserted in the axial direction to divide the inside of the cylinder into a pressure chamber and a reservoir chamber, a spring seat is fixed to the upper end of the rod, and the spring seat is urged in the direction in which the volume of the pressure chamber increases. A device provided with a return spring is known (Patent Document 1).

  This auto tensioner absorbs fluctuations in belt tension as the spring seat moves to a position where the biasing force of the return spring balances with the belt tension.

  The upper part of the pressure chamber and the upper part of the reservoir chamber communicate with each other through a leak gap formed between the sliding surfaces of the rod and the sleeve, and when the belt tension increases, the volume of the pressure chamber increases. The rod moves in the shrinking direction, and the hydraulic oil in the pressure chamber flows out into the reservoir chamber through the leak gap. At this time, since the damper force is generated by the viscous resistance of the hydraulic oil flowing through the leak gap, the rod moves slowly.

  The lower part of the pressure chamber and the lower part of the reservoir chamber communicate with each other via an oil passage provided between the sleeve fitting recess and the fitting surface of the sleeve, and the end of the oil passage on the pressure chamber side A check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side is incorporated. Therefore, when the belt tension decreases, the rod moves in the direction in which the volume of the pressure chamber increases, the check valve opens, and the hydraulic oil in the reservoir chamber flows into the pressure chamber through the oil passage. Move quickly.

  By the way, in this auto tensioner, the magnitude of the damper force generated when the rod moves in the direction in which the volume of the pressure chamber is reduced increases substantially in proportion to the moving speed of the rod. In addition, the rod cannot follow the fluctuation in tension, and the belt may be over tensioned.

  In order to prevent over tension of the belt, a relief passage that communicates the lower portion of the pressure chamber and the lower portion of the reservoir chamber is provided, and the pressure in the pressure chamber is set in advance at the end of the relief passage on the pressure chamber side. An auto tensioner has been proposed that incorporates a relief valve that opens when it becomes larger (Patent Document 2).

  In this auto tensioner, when the pressure in the pressure chamber increases, the relief valve opens and the hydraulic oil in the pressure chamber flows out through the relief passage to release the pressure chamber pressure. The rod easily follows the tension fluctuation, and the belt is less likely to become over tension.

However, even if the relief valve is opened, the followability of the rod may not be ensured due to the damper force generated by the viscous resistance of the hydraulic oil flowing through the relief passage.
Special Table 2000-504395 JP 2005-214232 A

  The problem to be solved by the present invention is to provide an auto tensioner in which the rod reliably follows the tension fluctuation when the belt is abruptly tensioned.

  In order to solve the above problems, a piston sliding hole that opens to the lower surface of the rod and communicates with the pressure chamber is provided, the piston is slidably inserted into the piston sliding hole, and the piston is attached downward. An urging piston spring was provided in the piston sliding hole. In this way, when the pressure in the pressure chamber increases, the piston rises and expands the volume of the pressure chamber, thereby releasing the pressure chamber pressure. The rod is sure to follow.

  Further, it is preferable that a range of downward movement of the piston is regulated by a retaining ring attached to the inner periphery of the piston sliding hole, and the piston spring is held in a state where a load is applied in advance by the regulation. If it does in this way, unless the pressure of a pressure chamber becomes larger than the pressure corresponding to the load previously applied to the piston spring, a piston will not raise. Therefore, when the belt tension fluctuation is small, the position of the piston is fixed to secure the damper force, and only when the belt tension fluctuation becomes large, the piston can move to release the pressure in the pressure chamber. .

  In addition, it is preferable to provide a communication path that communicates with the reservoir chamber from the region above the piston in the piston sliding hole through the inside of the rod. In this way, when the piston moves up, the pressure above the piston in the piston sliding hole is maintained at the same pressure as the reservoir chamber, so that the followability of the piston can be improved.

  The piston sliding hole and the sliding surface of the piston can be sealed with a seal member. In this case, if a rubber O-ring is used as the seal member, the cost is low, but a metal or resin seal ring in which a part of the circumference is divided may be used. If it does in this way, durability of a sealing member can be secured.

  Further, an annular gap may be provided between the piston sliding hole and the sliding surface of the piston so as to communicate the region above the piston and the region below the piston in the piston sliding hole. In this way, a damper force can be generated by the viscous resistance of the hydraulic oil flowing through the annular gap.

  If the piston is made of ceramic, the piston can be reduced in weight and the followability of the piston can be improved as compared with the case where the piston is made of iron.

  A step portion that receives the upper end of the piston and restricts the upward movement range of the piston can be provided on the inner periphery of the piston sliding hole. If it does in this way, it can prevent that a piston spring carries out a permanent deformation by the raise of a piston.

  When a coil spring is used as the piston spring, the upward movement range of the piston may be regulated by the contact height of the coil spring.

  In the auto tensioner according to the present invention, the piston rises to increase the volume of the pressure chamber, thereby releasing the pressure in the pressure chamber. Therefore, when the pressure in the pressure chamber is released, a damper force due to the viscous resistance of the hydraulic oil is hardly generated. For this reason, when the belt is suddenly tensioned, the rod reliably follows the tension fluctuation.

  FIG. 1 shows a tension adjusting device for a belt 1 for driving an automobile auxiliary machine. This tension adjusting device has a pulley arm 4 supported so as to be swingable around a fulcrum shaft 3 fixed to an engine block 2 (see FIG. 2), and a tension pulley 5 attached to the pulley arm 4 so as to be rotatable.

  One end of an auto tensioner 6 according to an embodiment of the present invention is rotatably connected to the pulley arm 4 via a connecting shaft 7, and the other end of the auto tensioner 6 is supported by a fulcrum shaft 8 fixed to the engine block 2. Has been. The auto tensioner 6 urges the pulley arm 4 in the direction in which the tension pulley 5 is pressed against the belt 1.

  As shown in FIG. 2, the auto tensioner 6 includes a cylinder 10 having a bottom 9 at a lower portion, and hydraulic oil is stored in the cylinder 10. Further, a sleeve 11 is inserted into the cylinder 10 coaxially with the cylinder 10, and a lower outer periphery of the sleeve 11 is fitted into a sleeve fitting recess 12 formed in the bottom 9 of the cylinder 10. A rod 13 is inserted into the sleeve 11 so as to be slidable in the axial direction, and the cylinder 10 is partitioned into a pressure chamber 14 and a reservoir chamber 15 by the rod 13 and the sleeve 11.

  A spring seat 16 is fixed to the upper end of the rod 13. An annular opening between the cylinder 10 and the spring seat 16 includes an annular oil seal 17 mounted on the inner periphery of the cylinder 10 and a cylindrical skirt 18 that extends downward from the spring seat 16 and is in sliding contact with the inner periphery of the oil seal 17. And closed.

  A return spring 19 is incorporated between the spring seat 16 and the bottom 9 of the cylinder 10. The lower end of the return spring 19 is supported by the bottom 9 of the cylinder 10, and the upper end presses the spring seat 16, which urges the spring seat 16 in the direction in which the volume of the pressure chamber 14 increases. Yes.

  As shown in FIG. 3, an oil passage 20 that connects the lower portion of the pressure chamber 14 and the lower portion of the reservoir chamber 15 is formed between the fitting surfaces of the sleeve fitting recess 12 and the sleeve 11. A check valve 21 that allows only the flow of hydraulic oil from the reservoir chamber 15 side to the pressure chamber 14 side is incorporated at the end of the oil passage 20 on the pressure chamber 14 side.

  The check valve 21 includes a valve seat 22 fitted in the lower inner periphery of the sleeve 11, a check ball 23 that opens and closes an upper end opening of a valve hole that vertically penetrates the valve seat 22, and a movement range of the check ball 23. It consists of a valve retainer 24 to be regulated and a valve spring 25 that urges the check ball 23 toward the valve seat 22.

  Between the sliding surfaces of the sleeve 11 and the rod 13, a leak gap 26 that communicates the pressure chamber 14 and the reservoir chamber 15 is formed. Here, the leak gap 26 is very small and functions as a throttle that restricts the flow rate of the hydraulic oil.

  The rod 13 is provided with a piston sliding hole 27 that opens on the lower surface thereof and communicates with the pressure chamber 14. A piston 28 is slidably inserted into the piston sliding hole 27 in the vertical direction. The piston 28 is urged downward by a piston spring 29 incorporated in the piston sliding hole 27. Further, the piston 28 is restricted in its downward movement range by a retaining ring 30 attached to the inner periphery of the piston sliding hole 27, and the piston spring 29 is held in a state where a compression load is applied in advance by the restriction. Has been. The sectional area of the piston 28 is 1/3 or more of the sectional area of the rod 13.

  The piston spring 29 is a coil spring, and the upward movement range of the piston 28 is restricted by the contact height of the coil spring (that is, the height of the coil spring when adjacent coils are in close contact).

  The rod 13 is provided with a communication passage 31 that communicates with the reservoir chamber 15 from the region above the piston 28 in the piston sliding hole 27 through the inside of the rod 13. The communication path 31 includes two holes intersecting inside the rod 13, the end on the piston sliding hole 27 side opens at the upper end surface in the piston sliding hole 27, and the end on the reservoir chamber 15 side is the rod. 13 is open to the outer periphery. The sliding surface between the piston sliding hole 27 and the piston 28 is sealed with a rubber O-ring 32.

  Next, an operation example of the auto tensioner 6 will be described.

  When the tension of the belt 1 decreases, the rod 13 moves in the direction in which the volume of the pressure chamber 14 increases due to the urging force of the return spring 19, and absorbs the slack of the belt 1. At this time, the check valve 21 is opened, and the hydraulic oil in the reservoir chamber 15 flows into the pressure chamber 14 through the oil passage 20, so that the rod 13 moves quickly.

  On the other hand, when the tension of the belt 1 increases, the rod 13 moves in the direction in which the volume of the pressure chamber 14 decreases due to the tension of the belt 1, and absorbs the tension of the belt 1. At this time, the hydraulic oil in the pressure chamber 14 flows out into the reservoir chamber 15 through the leak gap 26, and a damper force is generated by the viscous resistance of the hydraulic oil, so that the rod 13 moves slowly.

  Here, when the belt 1 is abruptly tensioned, such as when the load torque of the auxiliary machine driven by the belt 1 suddenly fluctuates, the pressure in the pressure chamber 14 increases due to the tension of the belt 1. When the pressure of 14 becomes larger than the pressure corresponding to the load previously applied to the piston spring 29, as shown in FIG. 3, the piston 28 rises to expand the volume of the pressure chamber 14, and the pressure of the pressure chamber 14 is increased. Let it go. Therefore, the rod 13 reliably follows the tension fluctuation of the belt 1 and the belt 1 does not become over tension.

  As described above, the auto tensioner 6 releases the pressure in the pressure chamber 14 by raising the piston 28 and expanding the volume of the pressure chamber 14. Therefore, when the pressure in the pressure chamber 14 is released, the viscosity of the hydraulic oil is increased. Damper force due to resistance is unlikely to occur. Therefore, when the belt 1 is abruptly tensioned, the rod 13 reliably follows the tension fluctuation.

  Further, in the auto tensioner 6, the piston 28 does not rise unless the pressure in the pressure chamber 14 becomes larger than the pressure corresponding to the load previously applied to the piston spring 29. Therefore, when the tension fluctuation of the belt 1 is small, the position of the piston 28 is fixed to secure a damper force. Only when the tension fluctuation of the belt 1 becomes large, the piston 28 moves and the pressure in the pressure chamber 14 is increased. Can escape.

  Further, the auto tensioner 6 has a region above the piston 28 in the piston sliding hole 27 that communicates with the reservoir chamber 15 via the communication path 31, so that when the piston 28 moves up, the piston slides. The pressure above the piston 28 in the hole 27 is maintained at the same pressure as the reservoir chamber 15. Therefore, the followability of the piston 28 with respect to the fluctuation in the tension of the belt 1 when the belt 1 is abruptly tensioned is high.

  As shown in the above embodiment, the seal member that seals between the sliding surfaces of the piston sliding hole 27 and the piston 28 is inexpensive when a rubber O-ring 32 is used. As shown in FIG. 4, the sliding surfaces 28 may be sealed with a metal or resin seal ring 33 in which a part of the circumference is divided. If it does in this way, durability of a sealing member can be secured.

  In the above embodiment, the sliding surface between the piston sliding hole 27 and the piston 28 is sealed by the O-ring 32. However, as shown in FIG. An annular gap 34 that communicates the region above the piston 28 and the region below the piston 28 in the piston sliding hole 27 may be provided. In this way, a damper force can be generated by the viscous resistance of the hydraulic oil flowing through the annular gap 34.

  As shown in FIG. 6, the piston 28 may be made of ceramic. If it does in this way, compared with the case where piston 28 is made from iron, piston 28 can be reduced in weight and followability of piston 28 can be improved.

  In the above embodiment, the range of upward movement of the piston 28 is regulated by the contact height of the piston spring 29. However, as shown in FIG. The upper end of the piston 28 may be received by the step portion 35 to restrict the upward movement range of the piston 28. In this way, it is possible to prevent the piston spring 29 from being permanently deformed by raising the piston 28.

The front view which shows the tension adjustment apparatus incorporating the auto tensioner of embodiment of this invention Sectional view along the line II-II in FIG. 2 is an enlarged cross-sectional view in the vicinity of the pressure chamber showing a state in which the piston shown in FIG. FIG. 2 is an enlarged sectional view in the vicinity of a piston showing a modification of the auto tensioner shown in FIG. FIG. 2 is an enlarged sectional view in the vicinity of a piston showing another modification of the auto tensioner shown in FIG. FIG. 2 is an enlarged sectional view in the vicinity of a piston showing still another modification of the auto tensioner shown in FIG. Fig. 2 is an enlarged section near the piston showing still another modification of the auto tensioner.

Explanation of symbols

6 Auto-tensioner 9 Bottom 10 Cylinder 12 Sleeve fitting recess 13 Rod 14 Pressure chamber 15 Reservoir chamber 16 Spring seat 19 Return spring 20 Oil passage 21 Check valve 27 Piston sliding hole 28 Piston 29 Piston spring 30 Retaining ring 31 Communication passage 32 O Ring 33 Seal ring 34 Annular gap 35 Step

Claims (4)

Hydraulic oil is stored in a cylinder (10) having a bottom (9) at the bottom, and the lower outer periphery of the sleeve (11) is fitted into a sleeve fitting recess (12) formed on the bottom (9) of the cylinder (10). The rod (13) is slidably inserted in the sleeve (11) in the axial direction to divide the cylinder (10) into a pressure chamber (14) and a reservoir chamber (15), and the pressure chamber (14) An oil passage (20) communicating with the lower portion of the reservoir chamber (15) is provided between the fitting surfaces of the sleeve fitting recess (12) and the sleeve (11), and a pressure chamber ( A check valve (21) that allows only the flow of hydraulic oil from the reservoir chamber (15) side to the pressure chamber (14) side is incorporated in the end portion on the 14) side, and a spring seat (16) is installed on the upper end of the rod (13). ) And the spring seat (16) is connected to the pressure chamber (14). In the auto tensioner having a return spring (19) the volume of is biased in a direction to expand,
A piston sliding hole (27) that opens to the lower surface of the rod (13) and communicates with the pressure chamber (14) is provided, and the piston (28) is slidably inserted into the piston sliding hole (27). A piston spring (29) for biasing the piston (28) downward is provided in the piston sliding hole (27);
A range of downward movement of the piston (28) is regulated by a retaining ring (30) on the inner periphery of the piston sliding hole (27), and a load is applied to the piston spring (29) in advance by the regulation. Hold on
Providing a communication path (31) communicating with the reservoir chamber (15) from the region above the piston (28) in the piston sliding hole (27) through the inside of the rod (13);
A seal member (32) seals between the sliding surfaces of the piston sliding hole (27) and the piston (28),
A rubber O-ring (32) is used as the sealing member, and the upper region and the lower region of the piston (28) with the piston (28) raised in the piston sliding hole (27). The auto tensioner is characterized in that it is kept in a non-communication state . The auto tensioner according to claim 1 , wherein the piston (28) is made of ceramic. 3. A step portion (35) is provided on the inner periphery of the piston sliding hole (27) for receiving the upper end of the piston (28) and restricting the upward movement range of the piston (28). The described auto tensioner. The auto tensioner according to claim 1 or 2 , wherein the piston spring (29) is a coil spring, and a range of upward movement of the piston (28) is regulated by a contact height of the coil spring.

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