JP2010276152A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner preventing excessive tension of a belt even when the belt is rapidly tensioned and having superior reliability in damper performance. <P>SOLUTION: In this automatic tensioner 6, a lower outer periphery of a sleeve 11 is fitted in a sleeve fitting recessed part 12 formed on the bottom 9 of a cylinder 10, a rod 13 is slidably inserted in the sleeve 11 and the inside of the cylinder 10 is partitioned into a pressure chamber 14 and a reserver chamber 15, and a return spring 20 for urging a spring seat 16 at an upper end of the rod 13 is provided. A piston 25 is vertically movably inserted in a piston storage hole 24 opened at a lower face of the rod 13. A piston spring 27 is provided for urging the piston 25 downward. A back pressure relief passage 29 is provided passing from the piston storage hole 24 through the inside of the rod 13 and communicated with the reserver chamber 15. A male screw member 30 is press-fitted in the back pressure relief passage 29. <P>COPYRIGHT: (C)2011,JPO&INPIT

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, a damper load is generated by the viscous resistance of the hydraulic oil flowing through the leak gap, so that 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 load that occurs when the rod moves in the direction in which the volume of the pressure chamber shrinks 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 the auto tensioner, when the pressure in the pressure chamber increases, the relief valve is opened, and hydraulic oil in the pressure chamber is introduced into the reservoir chamber through the relief passage, thereby releasing the pressure in the pressure chamber. Therefore, when the belt is abruptly tensioned, the rod easily follows the tension fluctuation, and the belt is less likely to be over-tensioned.

  However, in this auto tensioner, if a foreign object is caught between the valve body of the relief valve and the valve seat, the pressure chamber and the reservoir chamber remain in communication with each other via the relief passage. In this case, since the hydraulic oil that should flow through the leak gap flows out through the relief passage, a damper load due to the viscous resistance of the hydraulic oil cannot be secured.

Special Table 2000-504395 JP 2005-214232 A

  Accordingly, the inventor of the present invention has studied an auto tensioner that can prevent over tension of the belt even when the belt is suddenly tensioned and has excellent damper performance, and such an auto tensioner. As described above, a piston accommodating hole that opens to the lower surface of the rod and communicates with the pressure chamber is provided, and a piston spring is inserted into the piston accommodating hole so as to be movable up and down, and a piston spring that biases the piston downward is accommodated in the piston accommodating An auto-tensioner provided with a back pressure relief passage provided in the hole and communicating with the reservoir chamber from the piston accommodation hole through the inside of the rod has been devised.

  In this auto tensioner, when the pressure in the pressure chamber increases, the piston rises and expands the volume of the pressure chamber, thereby releasing the pressure in the pressure chamber. The rod will follow the belt securely and the belt will not be over tensioned. Also, even if the piston does not move due to foreign matter being caught, the flow path area between the pressure chamber and the reservoir chamber does not increase, so the damper load does not decrease and the damper performance is reliable. Excellent.

  However, this auto tensioner temporarily reduces the flow rate of hydraulic oil flowing through the leak gap as the piston rises and the volume of the pressure chamber expands as the piston rises to release the pressure in the pressure chamber. Damper performance could be lost.

  The problem to be solved by the present invention is to provide an auto tensioner that can prevent over tension of the belt even when the belt is suddenly tensioned and has excellent damper performance reliability.

  In order to solve the above-described problem, a piston accommodation hole that opens on the lower surface of the rod and communicates with the pressure chamber is provided, and the piston is inserted into the piston accommodation hole so as to be movable up and down, and the piston is biased downward. A piston spring is provided in the piston accommodation hole, a back pressure relief passage is provided that communicates with the reservoir chamber from the region above the piston in the piston accommodation hole through the inside of the rod, and the back pressure relief passage is provided in the back pressure relief passage. A fluid throttle was provided.

  In this way, since a fluid throttle is provided in the back pressure relief passage, a damper load is generated due to the viscous resistance of the hydraulic fluid flowing through the back pressure relief passage, and the damper rises while the piston rises and releases the pressure in the pressure chamber. Performance can be ensured.

  As the fluid throttle, a spiral gap formed between the cylindrical surface formed on the inner periphery of the back pressure relief passage and the thread surface of the male screw member press-fitted into the back pressure relief passage is adopted. can do. In this case, compared with the case where the small-diameter hole constituting the fluid restrictor is directly formed in the rod, the diameter of the hole processed into the rod is large, so that the hole processing is easy and the cost is low.

  The fluid restrictor is formed between the thread surface of the female screw formed on the inner periphery of the back pressure relief passage and the cylindrical surface of the outer periphery of the columnar member press-fitted into the back pressure relief passage. A spiral gap can also be employed. Even if it does in this way, since the diameter of the hole processed into a rod is large compared with the case where the small diameter hole which comprises a fluid constriction is directly formed in a rod, hole processing is easy and it is low-cost.

  Further, a porous member press-fitted into the back pressure relief passage can be employed as the fluid throttle. Even if it does in this way, since the diameter of the hole processed into a rod is large compared with the case where the small diameter hole which comprises a fluid constriction is directly formed in a rod, hole processing is easy and it is low-cost.

  Further, as the fluid throttle, a small-diameter straight hole provided in the middle of the back pressure relief passage may be employed.

  Further, the back pressure relief passage includes an axial hole extending upward from the inner bottom surface of the piston housing hole to the inside of the rod, and a radial hole that intersects the axial hole and opens to the outer periphery of the rod. In this case, a cylindrical ring that covers the opening on the outer periphery of the rod in the radial hole is fitted to the outer periphery of the rod with a minute gap, and the minute gap between the outer periphery of the rod and the inner periphery of the ring is connected to the fluid throttle. can do. In this way, the hydraulic oil that has flowed out of the radial hole is guided along the inner circumference of the ring and flows down along the outer circumference of the rod, so that it is difficult for the hydraulic oil to splash in the cylinder, and the hydraulic oil leaks from the cylinder. Is unlikely to occur.

  When fitting the ring to the outer periphery of the rod, if a plurality of protrusions that contact the outer periphery of the rod are formed at intervals in the circumferential direction on the inner periphery of the ring, the ring is positioned in the radial direction by the contact of the protrusions. Therefore, the shape accuracy of the minute gap between the outer periphery of the rod and the inner periphery of the ring can be increased.

  Moreover, when fitting the said ring to the outer periphery of a rod, if the upper end of the said ring is embedded in the said spring seat and it fixes, the fixation strength of a ring is securable.

  When the pressure in the pressure chamber increases, the auto tensioner of the present invention releases the pressure in the pressure chamber by raising the piston and expanding the volume of the pressure chamber. The rod reliably follows the tension fluctuation and the belt does not become over tension. Further, since the fluid throttle is provided in the back pressure relief passage, it is possible to prevent the loss of the damper performance while the piston is raised and the pressure in the pressure chamber is released. Furthermore, even if the piston does not move due to foreign matter being caught, the flow path area between the pressure chamber and the reservoir chamber does not increase, so the damper load does not decrease and the damper performance is reliable. Excellent.

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. FIG. 2 is an enlarged sectional view in the vicinity of the pressure chamber showing a state in which the pressure in the pressure chamber shown in FIG. 2 has risen above a predetermined pressure. FIG. 3 is an enlarged sectional view in the vicinity of a back pressure relief passage showing another example of the auto tensioner shown in FIG. FIG. 3 is an enlarged sectional view of the vicinity of a back pressure relief passage showing still another example of the auto tensioner shown in FIG. FIG. 3 is an enlarged sectional view of the vicinity of a back pressure relief passage showing still another example of the auto tensioner shown in FIG. FIG. 3 is an enlarged sectional view of the vicinity of a back pressure relief passage showing still another example of the auto tensioner shown in FIG. Sectional view along line VIII-VIII in FIG.

  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. The spring seat 16 is formed by aluminum die casting. 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.

  The skirt 18 is fixed to the spring seat 16 by molding (insert molding) the spring seat 16 in a state where the skirt 18 is set in a molding die of the spring seat 16. The spring seat 16 is integrally provided with a cylindrical cover 19 that faces the outer periphery of the cylinder 10.

  A return spring 20 is incorporated between the spring seat 16 and the bottom 9 of the cylinder 10. The return spring 20 has a lower end supported by the bottom 9 of the cylinder 10 and an upper end pressing the spring seat 16, and the pressing presses the spring seat 16 in a direction in which the volume of the pressure chamber 14 increases. Yes.

  An oil passage 21 that communicates the lower portion of the pressure chamber 14 and the lower portion of the reservoir chamber 15 is formed between the fitting surface of the sleeve fitting recess 12 and the sleeve 11. A check valve 22 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 21 on the pressure chamber 14 side.

  Between the sliding surfaces of the sleeve 11 and the rod 13, a leak gap 23 that connects the pressure chamber 14 and the reservoir chamber 15 is formed. Here, the leak gap 23 is very small and functions as a throttle that restricts the flow rate of the hydraulic oil.

  As shown in FIG. 3, the rod 13 is provided with a piston accommodation hole 24 that opens on the lower surface thereof and communicates with the pressure chamber 14. The piston 25 is inserted into the piston accommodation hole 24 so as to be movable up and down. Yes. Here, the outer periphery of the piston 25 is guided so as to be slidable up and down by a cylindrical cap 26 which is press-fitted and fixed to the lower end of the piston accommodation hole 24.

  The piston 25 is urged downward by a piston spring 27 incorporated in the piston accommodation hole 24. In addition, the piston 25 is restricted in its downward movement range by a stopper projection 28 formed on the inner periphery of the lower end of the cap 26, and the piston spring 27 is held in a state where a compression load is applied in advance by the restriction. ing.

  The piston spring 27 is a coil spring, and the upward movement range of the piston 25 is regulated 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 back pressure relief passage 29 that communicates with the reservoir chamber 15 from the region above the piston 25 in the piston accommodation hole 24 through the inside of the rod 13. The back pressure relief passage 29 includes an axial hole 29A that extends upward from the inner bottom surface of the piston accommodation hole 24 through the inside of the rod 13, and a radial hole 29B that intersects the axial hole 29A and opens to the outer periphery of the rod 13. Consists of. The back pressure relief passage 29 causes the hydraulic oil in the region above the piston 25 in the piston accommodation hole 24 to flow out into the reservoir chamber 15 when the piston 25 moves up, so that the pressure in the piston accommodation hole 24 is increased. Absorb changes.

  A male screw member 30 is press-fitted into the axial hole 29A. Here, a spiral gap 31 is formed between the cylindrical surface on the inner periphery of the axial hole 29 </ b> A and the screw face of the male screw member 30, and this gap 31 is a hydraulic oil that flows through the back pressure relief passage 29. It functions as a fluid restrictor that restricts the flow rate of the fluid.

  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 20 and absorbs the slack of the belt 1. At this time, the check valve 22 is opened, and the hydraulic oil in the reservoir chamber 15 flows into the pressure chamber 14 through the oil passage 21, 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 to the reservoir chamber 15 through the leak gap 23, and a damper load 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 27, as shown in FIG. 3, the piston 25 rises to increase 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.

  Further, when the piston 25 rises to release the pressure in the pressure chamber 14, the flow rate of the hydraulic oil flowing through the back pressure relief passage 29 is limited by the gap 31, so the viscosity of the hydraulic oil flowing through the back pressure relief passage 29 is limited. A damper load is generated by the resistance.

  As described above, when the pressure in the pressure chamber 14 increases, the auto tensioner 6 releases the pressure in the pressure chamber 14 by raising the piston 25 and expanding the volume of the pressure chamber 14. When the belt 1 is abruptly tensioned, the rod 13 reliably follows the tension fluctuation, and the belt 1 does not become over tension.

  In addition, since the flow rate of the hydraulic oil flowing through the back pressure relief passage 29 is limited by the gap 31, the auto tensioner 6 has a loss of damper performance while the piston 25 is lifted and the pressure in the pressure chamber 14 is released. Can be prevented.

  In addition, the auto tensioner 6 can secure the flow rate of the hydraulic oil flowing through the leak gap 23 even if the piston 25 stops moving due to the inclusion of foreign matter such as contamination or a suit. The damper performance is excellent and the damper performance is excellent.

  Further, since the auto tensioner 6 uses the gap 31 between the male screw member 30 and the axial hole 29A as a fluid throttle, it is compared with a case where a small-diameter hole constituting the fluid throttle is directly formed in the rod 13. The diameter of the hole processed into the rod 13 is large. Therefore, the hole processing of the rod 13 is easy and the cost is low.

  In the above embodiment, the auto tensioner 6 that employs the spiral gap 31 as a fluid restrictor for restricting the flow rate of the hydraulic oil flowing through the back pressure relief passage 29 has been described as an example. However, as illustrated in FIG. A spiral gap 33 formed between the thread surface of the female screw formed on the inner periphery of the directional hole 29A and the outer cylindrical surface of the columnar member 32 press-fitted into the axial hole 29A is used as a fluid throttle. May be. Even in this case, since the diameter of the hole to be processed in the rod 13 is larger than that in the case where the small diameter hole constituting the fluid throttle is directly formed in the rod 13, the hole processing of the rod 13 is easy and the cost is low. It is.

  Further, as shown in FIG. 5, a porous member 34 press-fitted into the axial hole 29A may be employed. Even if it does in this way, since the diameter of the hole processed into the rod 13 is large compared with the case where the small diameter hole which comprises a fluid aperture | diaphragm is directly formed in the rod 13, hole processing is easy and it is low-cost. Such a porous member 34 can be formed of, for example, a sintered metal or a sintered resin.

  Moreover, as shown in FIG. 6, you may employ | adopt the small diameter straight hole 35 provided in the middle of the axial direction hole 29A.

  Further, as shown in FIGS. 7 and 8, a cylindrical ring 36 covering the opening of the outer periphery of the rod 13 in the radial hole 29B is fitted to the outer periphery of the rod 13 with a minute gap, and the outer periphery of the rod 13 and the ring The flow rate of the hydraulic oil flowing through the back pressure relief passage 29 may be limited by the minute gap 37 between the inner circumferences of 36.

  In FIG. 7, the upper end of the ring 36 is fixed in a state of being embedded in the spring seat 16 by molding the spring seat 16 with the ring 36 set in a molding die of the spring seat 16 (insert molding). Yes.

  As described above, when the minute gap 37 between the outer periphery of the rod 13 and the inner periphery of the ring 36 is employed as a fluid throttle, the hydraulic oil flowing out from the radial hole 29B is guided on the inner periphery of the ring 36, and the rod 13 Therefore, it is difficult for the hydraulic oil to splash in the cylinder 10 and hydraulic oil leakage from the cylinder 10 hardly occurs.

  When the center of the ring 36 is deviated from the center of the rod 13, the size of the minute gap 37 between the outer periphery of the rod 13 and the inner periphery of the ring 36 is not uniform in the circumferential direction. May become unstable.

  Therefore, as shown in FIG. 8, when a plurality of protrusions 38 that contact the outer periphery of the rod 13 are formed on the inner periphery of the ring 36, the ring 36 can be positioned in the radial direction by the contact of the protrusions 38. By positioning, the shape accuracy of the minute gap 37 between the outer periphery of the rod 13 and the inner periphery of the ring 36 can be increased.

6 Auto tensioner 9 Bottom 10 Cylinder 11 Sleeve 12 Sleeve fitting recess 13 Rod 14 Pressure chamber 15 Reservoir chamber 16 Spring seat 20 Return spring 21 Oil passage 22 Check valve 24 Piston receiving hole 25 Piston 27 Piston spring 29 Back pressure relief passage 29A Shaft Directional hole 29B Radial direction hole 30 Male thread member 31 Clearance 32 Cylindrical member 33 Clearance 34 Porous member 35 Straight hole 36 Ring 37 Micro gap 38 Projection

Claims (8)

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 (21) communicating between the lower portion of the reservoir chamber (15) and 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 (22) 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 14) side, and a spring seat (16) is installed at 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 (20) the volume of is biased in a direction to expand,
A piston receiving hole (24) that opens to the lower surface of the rod (13) and communicates with the pressure chamber (14) is provided, and the piston (25) is inserted into the piston receiving hole (24) so as to be movable up and down. A piston spring (27) for urging the piston (25) downward is provided in the piston accommodation hole (24), and the rod (from the region above the piston (25) in the piston accommodation hole (24) is provided. 13) An auto-tensioner characterized in that a back pressure relief passage (29) communicating with the reservoir chamber (15) through the inside of 13) is provided, and a fluid throttle is provided in the back pressure relief passage (29).   The fluid throttle is formed between a cylindrical surface formed on the inner periphery of the back pressure relief passage (29) and a thread surface of the male screw member (30) press-fitted into the back pressure relief passage (29). The auto tensioner according to claim 1, wherein the auto tensioner is a spiral gap (31).   The fluid throttle includes a thread surface of an internal thread formed on the inner periphery of the back pressure relief passage (29), and a cylindrical surface on the outer periphery of a columnar member (32) press-fitted into the back pressure relief passage (29). The autotensioner according to claim 1, wherein the autotensioner is a spiral gap (33) formed between the two.   The auto tensioner according to claim 1, wherein the fluid throttle is a porous member (34) press-fitted into the back pressure relief passage (29).   The auto tensioner according to claim 1, wherein the fluid throttle is a small-diameter straight hole (35) provided in the middle of the back pressure relief passage (29).   The back pressure relief passage (29) intersects the axial hole (29A) extending upward from the inner bottom surface of the piston receiving hole (24) to the inside of the rod (13), and the axial hole (29A). The cylindrical ring (36) which covers the opening on the outer periphery of the rod (13) of the radial hole (29B) is formed of a radial hole (29B) opened on the outer periphery of the rod (13). 2) with a minute gap (37) on the outer periphery of the rod (13), and the fluid throttle is a minute gap (37) between the outer periphery of the rod (13) and the inner periphery of the ring (36). Auto tensioner.   The auto tensioner according to claim 6, wherein a plurality of protrusions (38) contacting the outer periphery of the rod are formed on the inner periphery of the ring (36) at intervals in the circumferential direction.   The auto tensioner according to claim 7, wherein the upper end of the ring (36) is fixed in a state of being embedded in the spring seat (16).

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