JP5006299B2 - 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 lower portion of the pressure chamber and the lower portion of the reservoir chamber communicate with each other via a first passage formed between the sleeve fitting recess and the fitting surface of the sleeve, and the reservoir chamber is connected to the lower portion of the sleeve from the pressure chamber side. A check valve for preventing the flow of hydraulic oil in the first passage to the side is incorporated, and when the rod moves in the direction in which the volume of the pressure chamber increases, the check valve opens and passes through the first passage to reach the reservoir chamber Hydraulic fluid flows from the side to the pressure chamber side. Therefore, the rod moves quickly in the direction in which the volume of the pressure chamber increases.

  Here, the check valve is a valve seat that is fitted to the lower inner periphery of the sleeve, a check ball that opens and closes the upper end opening of the valve hole that vertically penetrates the valve seat, and a valve that regulates the movement range of the check ball It consists of a retainer.

The upper part of the pressure chamber and the upper part of the reservoir chamber communicate with each other via a second passage having a throttle. When the rod moves in a direction in which the volume of the pressure chamber is reduced, the hydraulic oil in the pressure chamber is passed through the second passage. Spill through. At this time, since the flow rate of the hydraulic oil flowing through the second passage is limited by the throttle and a damper action occurs, the rod moves slowly.
JP 2007-10128 A

  By the way, in the auto tensioner, when the belt is attached to the engine or when the belt tension is excessive, the rod may move excessively in the direction in which the volume of the pressure chamber is reduced. The step formed on the sleeve is received by the snap ring attached to the circumferential groove on the inner periphery of the upper portion of the sleeve, so that the range of movement of the rod in the direction in which the volume of the pressure chamber is reduced is regulated. Yes.

  However, in the auto tensioner, when the stepped portion of the rod is received by the snap ring, an excessive load may be applied to the snap ring, and the snap ring may fall off from the circumferential groove. There is a possibility that the rod further moves in the direction of reducing the volume, and the lower end of the rod comes into contact with the valve retainer below the sleeve. In this case, the valve retainer may be deformed by the contact of the rod, and the function of the check valve may be deteriorated.

  The problem to be solved by the present invention is to reliably prevent the lower end of the rod from coming into contact with the valve retainer below the sleeve.

  In order to solve the above problems, a stopper projection for receiving the lower end of the rod and restricting the movement range of the rod in the direction in which the volume of the pressure chamber is reduced is formed integrally with the sleeve on the inner periphery of the sleeve, The stopper protrusion prevented the rod from contacting the valve retainer. In this way, when the lower end of the rod is received by the stopper protrusion, even if an excessive load is applied to the stopper protrusion, the stopper protrusion is formed integrally with the sleeve, so the strength is high and the rod is securely attached. Take it. Therefore, it is possible to reliably prevent the lower end of the rod from coming into contact with the valve retainer below the sleeve.

  The valve retainer can employ a configuration including a cylindrical portion that accommodates the check ball, an end plate that closes an upper end of the cylindrical portion, and an outward flange portion that is formed at the lower end of the cylindrical portion. In this case, the flange portion can be fixed by sandwiching it vertically between the stopper projection and the valve seat. In this way, the upward movement of the valve retainer is blocked by the stopper projection, so that the contact between the valve retainer and the rod can be more reliably prevented.

  Further, it is preferable to round the upper corner of the base of the stopper projection. In this way, when the lower end of the rod is received by the stopper projection, the stress concentration can be mitigated from occurring at the upper corner of the base of the stopper projection, thereby preventing the occurrence of cracks. In this case, if the chamfered portion is provided on the outer periphery of the lower end of the rod, it is possible to prevent the outer periphery of the lower end of the rod from locally contacting the upper corner of the base of the stopper projection.

  The stopper protrusions may be formed so as to continue without interruption throughout the entire circumference, but are preferably formed by being divided in the circumferential direction. In this way, it is possible to suppress a reduction in the flow area of the hydraulic fluid in the pressure chamber due to the formation of the stopper protrusion, and it is possible to suppress the flow resistance in the vicinity of the check valve in the pressure chamber. Therefore, the rod moves smoothly in the direction in which the volume of the pressure chamber increases, and the responsiveness of the rod when the belt tension becomes small can be ensured.

  When the stopper protrusion is formed by pressing the outer periphery of the sleeve, the processing cost is lower than when the stopper protrusion is formed by cutting the inner periphery of the sleeve. In this case, a press recess corresponding to the stopper protrusion is formed on the outer periphery of the sleeve.

  An annular passage formed between the sliding surfaces of the rod and the sleeve, and an oil passage communicating with the reservoir chamber through the passage through the inside of the rod and the inside of the spring seat. The electromagnetic on-off valve of the second passage can be incorporated in the spring seat. If it does in this way, the movement of the spring seat to the direction which the volume of a pressure chamber reduces can be prevented by closing an electromagnetic on-off valve. Therefore, when this auto tensioner is adopted for an engine that is driven by an alternator connected to the auxiliary belt, the auxiliary belt at the time of starting the engine is started by starting the engine with the electromagnetic on-off valve closed. It is possible to prevent slipping.

  Since the auto tensioner of the present invention receives the lower end of the rod with the stopper protrusion formed integrally with the sleeve, the lower end of the rod can be prevented from coming into contact with the valve retainer at the lower part of the sleeve, and the valve retainer due to the contact of the rod Can be reliably prevented.

  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 3 supported so as to be swingable about a fulcrum shaft 2 fixed to an engine block (not shown), and a tension pulley 4 rotatably attached to the pulley arm 3. One end of an auto tensioner 5 according to an embodiment of the present invention is rotatably connected to the pulley arm 3 via a connecting shaft 6, and the other end of the auto tensioner 5 is supported by a fulcrum shaft 7 fixed to the engine block. Yes. The auto tensioner 5 urges the pulley arm 3 in a direction in which the tension pulley 4 is pressed against the belt 1.

  As shown in FIG. 2, the auto tensioner 5 has a cylinder 9 having a bottom 8 at a lower portion, and hydraulic oil is stored in the cylinder 9. A sleeve 10 is inserted into the cylinder 9 coaxially with the cylinder 9, and a lower outer periphery of the sleeve 10 is fitted into a sleeve fitting recess 11 formed on the bottom 8 of the cylinder 9. A rod 12 is inserted into the sleeve 10 so as to be slidable in the axial direction, and the cylinder 9 is partitioned into a pressure chamber 13 and a reservoir chamber 14 by the rod 12 and the sleeve 10.

  A spring seat 15 is fixed to the upper end of the rod 12. An annular opening between the spring seat 15 and the cylinder 9 is closed by a cylindrical rubber bellows 16 that can be expanded and contracted vertically. The upper inner circumference of the bellows 16 is fitted to the outer circumference of the spring seat 15, and the lower inner circumference of the bellows 16 is fitted to the outer circumference of the cylinder 9.

  A return spring 17 is incorporated between the spring seat 15 and the bottom 8 of the cylinder 9. The return spring 17 has a lower end supported by the bottom 8 of the cylinder 9 via an annular spring receiver 18, and an upper end pressing the spring seat 15. The direction in which the volume of the pressure chamber 13 is expanded by the pressing. The spring seat 15 is biased.

  As shown in FIG. 3, the spring receiver 18 is engaged with a circumferential groove 19 formed on the outer periphery of the sleeve 10, and a downward attachment acting on the sleeve 10 from the return spring 17 via the spring receiver 18. The sleeve 10 is prevented from coming out of the sleeve fitting recess 11 by the force.

  A first passage 20 that communicates the lower portion of the pressure chamber 13 and the lower portion of the reservoir chamber 14 is formed between the fitting surface of the sleeve fitting recess 11 and the sleeve 10. A check valve 21 that prevents the flow of hydraulic oil in the first passage 20 from the pressure chamber 13 side to the reservoir chamber 14 side is incorporated in the lower portion of the sleeve 10.

  The check valve 21 includes a valve seat 22 fitted in the lower inner periphery of the sleeve 10, 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. And a valve retainer 24 to be regulated. Further, a valve spring 25 that urges the check ball 23 toward the valve retainer 24 is incorporated between the check ball 23 and the valve retainer 24.

  The valve retainer 24 includes a cylindrical portion 24B that accommodates the check ball 23, an end plate 24A that closes the upper end of the cylindrical portion 24B, and an outward flange portion 24C that is formed at the lower end of the cylindrical portion 24B. The tube portion 24B is formed with a notch communicating between the inside and the outside. The flange portion 24 </ b> C is fixed between the stopper protrusion 26 formed on the inner periphery of the sleeve 10 and the valve seat 22 fitted on the lower inner periphery of the sleeve 10.

  As shown in FIG. 4, the stopper protrusion 26 is formed integrally with the sleeve 10, and as shown in FIG. 5, the stopper protrusion 26 is divided at intervals in the circumferential direction. As shown in FIG. 3, the stopper protrusion 26 is positioned below the lower end of the rod 12, and when the rod 12 moves in the direction in which the volume of the pressure chamber 13 decreases, the lower end of the rod 12 is moved. The rod 12 is received to regulate the movement range of the rod 12 and prevent the rod 12 from contacting the valve retainer 24.

  As shown in FIG. 4, the stopper protrusion 26 has a rounded upper corner portion 27 at the base thereof. Therefore, as shown in FIG. 3, when the lower end of the rod 12 is received by the stopper projection 26, stress concentration is unlikely to occur in the upper corner portion 27 at the base of the stopper projection 26, and cracks are unlikely to occur. Further, a chamfered portion 28 is provided on the outer periphery of the lower end of the rod 12, thereby preventing the outer periphery of the lower end of the rod 12 from locally contacting the upper corner portion 27 at the base of the stopper projection 26.

  As shown in FIG. 2, the upper portion of the pressure chamber 13 and the upper portion of the reservoir chamber 14 communicate with each other via the second passage 29. The second passage 29 has an annular throttle gap 30 formed between the sliding surfaces of the sleeve 10 and the rod 12, and passes through the inside of the rod 12 and the spring seat 15 from the throttle gap 30 to the reservoir chamber 14. The oil passage 31 communicates with the oil passage 31. Here, the throttle gap 30 constitutes a throttle that limits the flow rate of the hydraulic oil in the second passage 29. The spring seat 15 has a second check valve 32 for preventing the flow of hydraulic oil in the second passage 29 from the reservoir chamber 14 side to the pressure chamber 13 side, and the second passage 29 by switching between energization and de-energization. An electromagnetic on-off valve 33 that opens and closes is incorporated.

  An oil guide 34 that receives hydraulic oil flowing out from the second passage 29 and guides it to the outer periphery of the rod 12 is provided at the end of the second passage 29 on the reservoir chamber 14 side. The oil guide 34 is formed in a cylindrical shape inserted between the rod 12 and the return spring 17, and a flange formed at the upper end thereof is sandwiched between the spring seat 15 and the return spring 17. The end of the second passage 29 on the reservoir chamber 14 side is open between the oil guide 34 and the rod 12.

  Next, an operation example of the auto tensioner 5 will be described.

  When the tension of the belt 1 becomes small, the spring seat 15 moves with respect to the cylinder 9 to a position where the tension of the belt 1 and the biasing force of the return spring 17 are balanced, and the slack of the belt 1 is absorbed. At this time, since the volume of the pressure chamber 13 increases, the hydraulic oil flows from the reservoir chamber 14 to the pressure chamber 13 through the first passage 20 and the spring seat 15 moves quickly.

  On the other hand, when the tension of the belt 1 increases, the spring seat 15 moves relative to the cylinder 9 to a position where the tension of the belt 1 and the biasing force of the return spring 17 are balanced, and absorbs the tension of the belt 1. At this time, since the volume of the pressure chamber 13 is reduced, the hydraulic oil flows from the pressure chamber 13 side to the reservoir chamber 14 side through the second passage 29, and the flow rate of the hydraulic oil is limited by the throttle gap 30 to act as a damper. Therefore, the spring seat 15 moves slowly.

  When the electromagnetic opening / closing valve 33 is closed, the hydraulic oil does not flow through the second passage 29, and therefore the movement of the spring seat 15 in the direction in which the volume of the pressure chamber 13 is reduced can be prevented. Therefore, when this auto tensioner 5 is employed in an engine that is driven and started by an alternator (not shown) connected to the belt 1, the engine is started by starting the engine with the electromagnetic on-off valve 33 closed. It becomes possible to prevent slip of the auxiliary machine belt 1 at the time.

  Even when an excessive load is applied to the stopper projection 26 when the lower end of the rod 12 is received by the stopper projection 26, the auto tensioner 5 is formed integrally with the sleeve 10, so that the strength is high. It is high and reliably receives the rod 12. Therefore, the lower end of the rod 12 can be prevented from coming into contact with the valve retainer 24 at the lower part of the sleeve 10, and deformation of the valve retainer 24 due to contact with the rod 12 can be reliably prevented.

  Further, since the auto tensioner 5 prevents the valve retainer 24 from moving upward by the stopper projection 26, the contact between the valve retainer 24 and the rod 12 can be reliably prevented.

  The stopper protrusions 26 can be continuous without interruption throughout the entire circumference, but as shown in the above embodiment, it is preferable to divide and form the stopper protrusions 26 in the circumferential direction. By doing so, it is possible to suppress a reduction in the flow area of the hydraulic oil in the pressure chamber 13 due to the formation of the stopper protrusion 26, and it is possible to suppress the flow path resistance in the vicinity of the check valve 21 in the pressure chamber 13. . Therefore, the movement of the rod in the direction in which the volume of the pressure chamber increases is smooth, and the responsiveness of the rod 12 when the tension of the belt 1 becomes small can be ensured.

  The stopper protrusion 26 can be formed by, for example, cutting, but it is preferable to form the outer periphery of the sleeve 10 by pressing as shown in FIGS. In this case, the processing cost can be reduced as compared with the case where the stopper protrusion 26 is formed by cutting the inner periphery of the sleeve 10. In this case, a press recessed portion 35 corresponding to the stopper protrusion 26 is formed on the outer periphery of the sleeve 10.

The front view which shows the tension adjustment apparatus incorporating the auto tensioner of embodiment of this invention 1 is an enlarged cross-sectional view near the auto tensioner shown in FIG. FIG. 2 is an enlarged cross-sectional view of the vicinity of the stopper protrusion showing a state where the lower end of the rod shown in FIG. 2 is received by the stopper protrusion. Sectional view of the sleeve shown in FIG. Sectional view along line VV in FIG. Sectional drawing which shows the modification of the sleeve shown in FIG. Sectional drawing along the VII-VII line of FIG.

Explanation of symbols

5 Auto tensioner 8 Bottom 9 Cylinder 10 Sleeve 11 Sleeve fitting recess 12 Rod 13 Pressure chamber 14 Reservoir chamber 15 Spring seat 17 Return spring 20 First passage 21 Check valve 22 Valve seat 23 Check ball 24 Valve retainer 24A End plate 24B Tube 24C Flange portion 26 Stopper projection 27 Upper corner portion 28 Chamfered portion 29 Second passage 30 Throttle gap 31 Oil passage 33 Electromagnetic switching valve 35 Press recess

Claims (6)

The hydraulic oil is stored in a cylinder (9) having a bottom (8) at the bottom, and the lower outer periphery of the sleeve (10) is fitted into a sleeve fitting recess (11) formed on the bottom (8) of the cylinder (9). The rod (12) is slidably inserted in the sleeve (10) in the axial direction to divide the cylinder (9) into a pressure chamber (13) and a reservoir chamber (14), and the rod (12) A spring seat (15) is fixed to the upper end, and a return spring (17) for urging the spring seat (15) in a direction in which the volume of the pressure chamber (13) is enlarged is provided, and the sleeve fitting recess (11) The lower portion of the pressure chamber (13) and the lower portion of the reservoir chamber (14) communicate with each other via a first passage (20) formed between the fitting surfaces of the sleeve (10) and the lower portion of the sleeve (10). First communication from the pressure chamber (13) side to the reservoir chamber (14) side A check valve (21) for preventing the flow of hydraulic oil (20) is incorporated, and the pressure chamber (13) and the reservoir chamber (14) are communicated with each other via a second passage (29) having a throttle (30). The check valve (21) includes a valve seat (22) fitted into the lower inner periphery of the sleeve (10), and a check ball for opening and closing an upper end opening of a valve hole penetrating the valve seat (22) vertically. 23) and an auto tensioner having a valve retainer (24) for restricting the movement range of the check ball (23).
A stopper projection (26) for receiving the lower end of the rod (12) and restricting the movement range of the rod (12) in the direction in which the volume of the pressure chamber (13) is reduced is provided on the inner periphery of the sleeve (10). The auto tensioner is formed integrally with (10), and the stopper projection (26) prevents the rod (12) from contacting the valve retainer (24).   The valve retainer (24) is formed on a cylindrical portion (24B) for accommodating the check ball (23), an end plate (24A) for closing the upper end of the cylindrical portion (24B), and a lower end of the cylindrical portion (24B). The auto flange according to claim 1, wherein the flange portion (24C) is fixed by sandwiching the flange portion (24C) vertically between the stopper projection (26) and the valve seat (22). Tensioner.   The upper corner (27) at the base of the stopper projection (26) is rounded, and the chamfered portion is formed on the outer periphery of the lower end of the rod (12) so that the lower corner of the rod (12) does not contact the upper corner (27). The auto tensioner according to claim 1 or 2, wherein (28) is provided.   The auto tensioner according to any one of claims 1 to 3, wherein the stopper protrusion (26) is formed by being divided in the circumferential direction.   The stopper projection (26) is formed by pressing the outer periphery of the sleeve (10), and the press recess (35) corresponding to the stopper projection (26) is formed on the outer periphery of the sleeve (10). The auto tensioner according to any one of claims 1 to 4.   The second passage (29) is connected to the annular throttle gap (30) formed between the sliding surfaces of the rod (12) and the sleeve (10), and the inside of the rod (12) from the throttle gap (30). And an oil passage (31) that sequentially passes through the interior of the spring seat (15) and communicates with the reservoir chamber (14), and the electromagnetic on-off valve (33) of the second passage (29) serves as the spring seat ( The auto tensioner according to any one of claims 1 to 5, incorporated in 15).

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