JP3927794B2 - Damping force optimization method of hydraulic auto tensioner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic auto tensioner for automatically applying an appropriate tension to a transmission member such as an endless annular flat belt, a V belt, a toothed belt, or a chain.
[0002]
[Prior art]
The present applicant has previously proposed a hydraulic auto tensioner 60 as shown in FIGS. 7, 8, and 9 (Japanese Patent Laid-Open Nos. 10-141453 and 10-325448). The hydraulic auto tensioner 60 is used, for example, as shown in FIG. 9 , and a plunger 65 urged in the retraction direction from the inner cylinder 64 by the elastic force of the return spring 74 is attached to the shaft portion 5 so as to be swingable. The arm 1 is swung to the belt 1 side, and the belt 1 wound around the pulley 2 and the idler pulley 3 is given an appropriate tension by the idler pulley 3 pivotally supported at the tip of the arm 4. .
Further, when overloaded, the belt 1 tries to cause the plunger 65 to enter the inner cylinder 64 through the idler pulley 3 and the arm 4 in this order. At this time, the check valve 71 formed on the bottom wall 64 a of the inner cylinder 64 blocks the inflow from the high pressure oil chamber 68 to the low pressure oil chamber 69, but the cylinder portion 64 b of the inner cylinder 64 and the piston portion 65 a of the plunger 65. The clearance C between them causes the oil 76 in the high-pressure oil chamber 68 to leak into the low-pressure oil chamber 69, so that the piston portion 65a enters the cylinder portion 64b while receiving a damping force determined by the clearance C. At this time, the tension of the belt 1 is reduced, and at the same time, the change in the length of the belt 1 can be absorbed (automatic adjustment).
[0003]
[Problems to be solved by the invention]
In the hydraulic auto tensioner 60, as shown in FIG. 8 , since the outer surface of the piston portion 65a and the inner surface of the cylinder portion 64b are both straight, the clearance C that determines the damping force is fixed. In consideration of the balance between the high load and the low load, C was determined to be one point with less trouble at both loads. As a result, the damping force becomes insufficient when the load is high, causing belt squealing due to slipping of the belt 1 due to insufficient follow-up, or conversely, the damping force becomes excessive when the load is low, and the tension applied to the belt 1 becomes too large. There is room for study regarding the design of the clearance C, for example, the influence on the lifetime of 1 may not be negligible.
[0004]
An object of the present invention is to provide a damping force optimizing method for a hydraulic auto tensioner that can solve the above problems and obtain an optimum damping force as required in any state from a high load to a low load. It is to provide.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a damping force optimization method for a hydraulic auto tensioner according to the present invention includes an inner cylinder, a high pressure oil chamber inside the inner cylinder, a low pressure oil chamber outside the inner cylinder, and an inner cylinder. In a hydraulic auto tensioner that includes a plunger having a piston portion that enters in the axial direction with a clearance, and a return spring that biases the plunger in the retreating direction, and applies an appropriate tension to the belt as a transmission member from the plunger.
As clearance decreases when the piston unit is displaced in the exit direction in the axial direction, it changes at least one of the outer diameter of the portion determining the clearance of the inner diameter or the piston section of the site to determine the clearance of the inner cylinder in the axial direction Let me know
When the belt extension is small at low load, the piston part enters the inner cylinder deeply and the clearance increases. When the piston part attempts to enter the inner cylinder further deeply from this state, the clearance is large and the damping is attenuated. The force is reduced, so oil is likely to leak from the high-pressure oil chamber to the low-pressure oil chamber via the clearance, and the piston part is likely to enter the inner cylinder,
When the belt extension is large and the belt squeezes easily under high load, the piston part slides out of the inner cylinder to reduce the clearance, and when the piston part tries to enter the inner cylinder from this state Because the clearance is small, the damping force increases, so oil does not leak from the high-pressure oil chamber to the low-pressure oil chamber via the clearance, and the piston part does not easily enter the inner cylinder. It does not occur, and belt squeal does not occur.
[0006]
Here, as "the part for determining the clearance of the inner cylinder" and "the part for determining the clearance of the piston part", when the plunger enters the inner cylinder, it covers the entire range where the inner cylinder and the plunger overlap, A case where the length range is a part of the overlapping range or a case where one part is the overlapping range and the other part is the partial length range can be exemplified.
[0007]
A specific aspect of changing the “inner diameter of the part that determines the clearance of the inner cylinder” or “the outer diameter of the part that determines the clearance of the piston portion” in the axial direction is not particularly limited, but the following aspects can be exemplified.
(1) A mode in which the inner diameter of the portion that determines the clearance of the inner cylinder is constant in the axial direction, and the outer diameter of the portion that determines the clearance of the piston portion is enlarged toward the entrance direction to form a substantially conical surface.
(2) A mode in which the inner diameter of the portion that determines the clearance of the inner cylinder is reduced toward the retreat direction side of the piston portion to form a substantially conical hole surface, and the outer diameter of the portion that determines the clearance of the piston portion is constant in the axial direction.
(3) The inner diameter of the portion that determines the clearance of the inner cylinder is reduced toward the retraction direction side of the piston portion so as to be a substantially conical hole surface, and the outer diameter of the portion that determines the clearance of the piston portion is increased toward the entry direction side. A mode.
[0008]
In these embodiments, “substantially conical surface” or “substantially conical hole surface” means not only a strict conical surface or conical hole surface whose diameter changes linearly in the axial direction, but also a diameter that changes curvedly in the axial direction. It also includes a bell-shaped conical surface or a conical hole surface. The inclination angle (taper angle) with respect to the axis of the “substantially conical surface” or “substantially conical hole surface” is not particularly limited, but is preferably 0.05 to 0.5 degrees, more preferably 0.1 to 0.3 degrees. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments embodying the hydraulic auto-tensioner of the present invention will be described with reference to FIGS. These hydraulic auto tensioners 10 are general-purpose products for automatically applying an appropriate tension to transmission members such as an endless annular flat belt, a V belt, a toothed belt, and a chain. The structure between the hydraulic auto tensioner and the transmission member is not particularly limited.
[0010]
First, the hydraulic auto tensioner 10 of the first embodiment shown in FIGS . 1 to 3 includes a bottomed cylindrical casing 14, and an attachment collar 15 integrally formed on the lower surface of the casing 14 has an annular collar 16. Is rotatably provided via a dry bearing 17. A press-fit portion 18 with a reduced diameter is provided at the inner peripheral lower portion of the casing 14, and an oil groove 19 is recessed in the inner peripheral surface of the press-fit portion 18 and the inner bottom surface of the casing 14.
[0011]
A bottomed cylindrical inner cylinder 30 having an outer diameter slightly smaller than the inner diameter of the casing 14 is inserted into the casing 14, and a lower end portion thereof is press-fitted and fixed to the press-fit portion 18. The rod-like piston portion 21 at the lower end portion of the plunger 12 enters the cylinder portion 32 of the inner cylinder 30 from the opening end portion of the casing 14 (described later) with a clearance C so as to be slidable up and down. . An annular collar 16 is rotatably provided on the attachment portion 22 at the upper end of the plunger 12 via a dry bearing 17.
[0012]
A long outer cylinder 37 a that has entered the opening of the casing 14, a short inner cylinder that is press-fitted into the outer periphery of the plunger 12, and the upper ends of both cylinders are closed above the mounting portion 22 and above the plunger 12. A spring cover 37 integrally formed with the ceiling portion is press-fitted and fixed. A return spring 38 is mounted in a compressed state between the lower surface of the ceiling portion of the spring cover 37 and the spring seat 36 installed on the bottom surface of the casing 14 to urge the plunger 12 in the retracting direction (upward in the figure). is doing.
[0013]
A seal ring 23 that is slidably contacted with the outer cylinder 37a of the spring cover 37 is attached to the stepped portion on the inner periphery of the opening end of the casing 14 together with the ring fitting 24, and the seal ring 23 is fitted in a groove on the inner periphery of the opening end. The stopper ring 25 is locked from below so as not to come off.
[0014]
The inner diameter of the portion A1 that determines the clearance C of the inner cylinder 30 so that the clearance C becomes smaller when the piston 21 is displaced in the retracting direction in the axial direction as the belt 1 as the transmission member extends at the time of high load. Is constant in the axial direction, and the outer diameter of the portion A2 that determines the clearance C of the piston portion 21 is a conical surface that is enlarged toward the approaching direction side.
[0015]
That is, the cylinder portion 32 of the inner cylinder 30 has a constant inner diameter in the axial direction, a body 32a serving as an entrance for the piston portion, a midway portion 32c having a slightly larger inner diameter than the body 32a, and a body 32a and a midway portion 32c. The piston portion 21 is formed with a conical surface 21a whose outer diameter is enlarged toward the approaching direction side. Accordingly, the length range from the boundary portion 32b to the upper end of the body 32a is a portion A1 that determines the clearance C of the inner cylinder 30, and the length range that overlaps when the piston portion 21 slides in the length range is the piston portion 21. This is a portion A2 that determines the clearance C.
[0016]
Further, the upper part of the plunger 12 and the lower part of the attachment part 22 are covered with the opening end part (especially the spring cover 37 and the seal ring 23) of the casing 14 from the plunger 12 and are disposed on the outer periphery of the casing 14. The dust cover 33 is attached, and the dust cover 33 moves up and down together with the plunger 12.
[0017]
The dust cover 33 is formed integrally with a cylindrical portion 34 disposed on the outer periphery of the casing 14 and a plate-like lid portion 35 that closes the upper end of the cylindrical portion 34. The inner peripheral edge of the lid portion 35 is sandwiched between the flange portion 13 formed integrally with the upper portion of the plunger 12 and the upper surface of the ceiling portion of the spring cover 37 with a tightening margin.
[0018]
A high-pressure oil chamber 26 is formed between the inner peripheral surface of the inner cylinder 30 and the lower end surface of the piston portion 21. Further, a low pressure oil chamber 27 is formed between the outer peripheral surface of the inner cylinder 30, the inner peripheral surface of the casing 14, and the spring cover 37, so that the oil 11 is stored. The high pressure oil chamber 26 and the low pressure oil chamber 27 can communicate in one direction from the low pressure oil chamber 27 to the high pressure oil chamber 26 by a check valve 28 provided on the bottom wall 31 of the inner cylinder 30. Further, the high pressure oil chamber 26 and the low pressure oil chamber 27 communicate with each other via the clearance C between the inner cylinder 30 and the piston portion 21, and the oil 11 leaks from the high pressure oil chamber 26 to the low pressure oil chamber 27 via the clearance C. It has come to be able to do.
[0019]
The check valve 28 includes a communication hole 29 opened in the bottom wall 31 of the inner cylinder 30, an annular ball sheet 28a formed by rounding the upper edge of the communication hole 29, and a check ball received by the annular ball sheet 28a. 28b, a retainer 28c fitted so as to surround the check ball 28b just above the annular ball seat 28a, and a spring 28d mounted between the retainer 28c and the check ball 28b.
[0020]
That is, the piston portion 21 of the plunger 12 slides in the retracting direction from the inner cylinder 30 when the belt 1 as a transmission member extends and loosens, and conversely when the belt 1 contracts, the piston portion 21 of the plunger 12 contracts. The oil 11 leaks from the high-pressure oil chamber 26 to the low-pressure oil chamber 27 through the clearance C and slides in the entering direction with respect to the inner cylinder 30 to apply an appropriate tension to the belt 1.
[0021]
The hydraulic auto tensioner configured as described above operates as follows.
As shown in FIG. 2A, when the belt 1 has a small extension under a low load, the idler pulley 3 receives the tension of the belt 1 and is pressed downward, and the plunger 12 enters the inner cylinder 30 deeply. At this time, as shown in FIG. 2B, the clearance C between the inner cylinder 30 and the plunger 12 is minimized between the piston portion 21 and the boundary portion 32b.
When the load fluctuates from this state and the load is slightly lowered, the extension of the belt 1 is further reduced, and the plunger 12 tends to enter the inner cylinder 30 more deeply. At this time, since the clearance C between the inner cylinder 30 and the plunger 12 is large, the damping force is small. Therefore, the oil 11 easily leaks from the high pressure oil chamber 26 to the low pressure oil chamber 27 through the clearance C, and the plunger 12 easily enters the inner cylinder 30.
[0022]
Next, as shown in FIG. 3A, when the belt 1 is extended at a high load, the plunger 12 urged by the return spring 38 slides in the retracting direction from the inner cylinder 30, and the arm 4, The belt 1 is pressed through the pulley 3 to maintain an appropriate tension. At this time, as the plunger 12 slides in the retreating direction from the inner cylinder 30, the clearance C between the cylinder portion 32 and the piston portion 21 is as shown in FIG. It becomes smaller than b).
When the load fluctuates from this state and the load is slightly lowered, the extension of the belt 1 becomes small and the plunger 12 tends to enter the inner cylinder 30. At this time, since the clearance C between the cylinder portion 32 and the piston portion 21 is smaller than that in FIG. 2B when the load is low, the damping force is increased. Accordingly, the oil 11 is less likely to leak through the clearance C, and the plunger 12 is less likely to enter the inner cylinder 30.
[0023]
That is, the damping force of the plunger 12 increases as the load becomes higher, and the damping force of the plunger 12 increases as the belt 1 is slackened and the belt 1 is inclined to a higher load state where the belt squeezes easily. Then, since the follow-up of the plunger 12 to the belt 1 is optimized, there is no shortage of follow-up and belt squeal does not occur.
[0024]
Next, a second embodiment of the hydraulic auto tensioner embodying the present invention will be described with reference to FIG. 4, FIG. 5, and FIG. This embodiment is different from the first embodiment only in the shape of the cylinder part.
[0025]
That is, the inner diameter of the portion that determines the clearance C of the inner cylinder 30 of the present embodiment is reduced toward the retraction direction side of the piston portion 21 to form the conical hole surface 32d, and the outer diameter of the portion that determines the clearance C of the piston portion 21 is the entry direction. The conical surface 21a is enlarged toward the side.
[0026]
The body 32a of the cylinder portion 32 of the present embodiment has a conical hole surface 32d whose inner diameter is enlarged toward the approach direction side. Further, the conical surface 21a of the piston portion 21 and the conical hole surface 32d of the cylinder portion 32 may be formed at different angles with respect to the axis (taper angle), but they are equally formed in the illustrated example. At this time, the length range from the upper end of the body 32a to the boundary portion 32b becomes a portion A5 that determines the clearance C of the inner cylinder 30, and when the piston portion 21 slides to the maximum in the entering direction and the leaving direction, The length range that overlaps the portion A5 that determines the clearance C is the portion A6 that determines the clearance C of the piston portion 21.
[0027]
The hydraulic auto tensioner according to the second embodiment configured as described above operates as follows.
As shown in FIG. 5A, when the belt 1 has a small extension under a low load, the idler pulley 3 receives the tension of the belt 1 and is pressed downward, and the plunger 12 enters the inner cylinder 30 deeply. At this time, as shown in FIG. 5B, the clearance C between the cylinder portion 32 and the piston portion 21 is the distance between the conical hole surface 32d and the conical surface 21a.
When the load fluctuates from this state and the load is slightly lowered, the extension of the belt 1 is further reduced, and the plunger 12 tends to enter the inner cylinder 30 more deeply. At this time, since the clearance C between the inner cylinder 30 and the plunger 12 is large, the oil 11 leaks from the high pressure oil chamber 26 to the low pressure oil chamber 27 through the clearance C, and the piston portion 21 enters the cylinder portion 32. be able to.
[0028]
Next, as shown in FIG. 6 (a), when the belt 1 is extended at a high load, the plunger 12 biased by the return spring 38 slides in the retreating direction from the inner cylinder 30, and the arm 4, The belt 1 is pressed through the pulley 3 to maintain an appropriate tension. At this time, as the plunger 12 slides in the retracting direction from the inner cylinder 30, the clearance C between the cylinder portion 32 and the piston portion 21 is as shown in FIG. smaller than b).
When the load fluctuates from this state and the load is slightly lowered, the extension of the belt 1 becomes small and the plunger 12 tends to enter the inner cylinder 30. At this time, since the clearance C between the cylinder portion 32 and the piston portion 21 is smaller than that in FIG. 5B when the load is low, the oil 11 leaks through the clearance C, and the piston portion 21 is a cylinder. It becomes difficult to enter the portion 32.
[0029]
The hydraulic auto tensioner of this embodiment is basically the same as that of the first embodiment. And according to this embodiment, the same effect as a first embodiment is acquired.
[0030]
In addition, this invention is not limited to the structure of the said embodiment, For example, as follows, it can also change and actualize in the range which does not deviate from the meaning of invention.
(1) Keep the same shape as the part that determines the clearance other than the part that determines the clearance.
(2) Change to a shape different from the part that determines the clearance, except for the part that determines the clearance.
[0031]
【The invention's effect】
Since the damping force optimization method of the hydraulic auto tensioner according to the present invention is configured as described above, it is possible to obtain the optimum damping force as required in any state from high load to low load. There is an excellent effect of being able to.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a hydraulic auto tensioner according to a first embodiment of the present invention.
2A is a schematic view showing a usage state of the hydraulic auto-tensioner, and FIG. 2B is an enlarged cross-sectional view of a main part of FIG. 2A.
3A is a schematic view showing a state different from FIG. 2A, and FIG. 3B is an enlarged cross-sectional view of a main part of FIG. 3A.
FIG. 4 is a longitudinal sectional view of a hydraulic auto tensioner according to a second embodiment of the present invention.
5A is a schematic view showing a usage state of the hydraulic auto tensioner, and FIG. 5B is an enlarged cross-sectional view of a main part of FIG. 5A.
6A is a schematic view showing a state different from FIG. 5A, and FIG. 6B is an enlarged cross-sectional view of a main part of FIG. 6A.
FIG. 7 is a longitudinal sectional view of a conventional hydraulic auto tensioner.
FIG. 8 is an enlarged sectional view of a main part of the hydraulic auto tensioner. .
FIG. 9 is a schematic view showing an example of use of a hydraulic auto tensioner.
[Explanation of symbols]
1 Belt 12 Plunger 21 Piston part 30 Inner cylinder 38 Return spring A1 Part A2 Part C Clearance

Claims (1)

The inner cylinder (30), the high-pressure oil chamber (26) inside the inner cylinder (30), the low-pressure oil chamber (27) outside the inner cylinder (30), and the clearance ( C) includes a plunger (12) having a piston portion (21) that enters in the axial direction and a return spring (38) that urges the plunger (12) in the retreating direction, and serves as a transmission member from the plunger. In the hydraulic auto tensioner that gives a moderate tension to the belt (1) ,
Wherein such clearance (C) is small, the inner diameter of the part which determines the clearance (C) of the inner tube (30) or the piston when the previous SL piston (21) is displaced in the exit direction in the axial direction Changing at least one of the outer diameters of the portion that determines the clearance (C) of the portion (21) in the axial direction ;
When the extension of the belt (1) is small at a low load, the piston part (21) enters deeply into the inner cylinder (30) and the clearance (C) becomes large. From this state, the piston part (21) Is going to enter the inner cylinder (30) more deeply, the damping force is reduced because the clearance (C) is large, and therefore, from the high pressure oil chamber (26) via the clearance (C). Oil (11) is likely to leak into the low pressure oil chamber (27), and the piston portion (21) is likely to enter the inner cylinder (30).
When the extension of the belt (1) is large and the belt squeezes easily under a high load, the piston (21) slides in the retracting direction from the inner cylinder (30), and the clearance (C) becomes small. When the piston portion (21) is about to enter the inner cylinder (30) from the state, the damping force is increased because the clearance (C) is small, and therefore the high-pressure oil is passed through the clearance (C). The oil (11) is less likely to leak from the chamber (26) to the low pressure oil chamber (27), and the piston portion (21) is less likely to enter the inner cylinder (30), and thus the belt of the plunger (12). (1) A dampening force optimization method for a hydraulic auto tensioner, characterized in that insufficient follow-up to (1) does not occur and belt squeal does not occur.

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