JP2008115926A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner without causing slippage in a belt at starting, and without causing a pump-up phenomenon by an increase and a decrease in the tension of the belt. <P>SOLUTION: In this automatic tensioner, a sleeve 11 is arranged in a cylinder 9 storing a hydraulic fluid, and partitioned into a pressure chamber 14 and a reservoir chamber 15 by inserting a rod 13 into the sleeve 11, and a leak clearance 32 for making the pressure chamber 14 communicate with the reservoir chamber 15 is formed between sliding surfaces of the rod 13 and the sleeve 11, and a return spring 18 is arranged for energizing the rod 13, and a check valve 29 allowing only a flow of the hydraulic fluid to the pressure chamber side from the reservoir chamber side is arranged in a passage 26 for making the pressure chamber 14 communicate with the reservoir chamber 15. First and second sliding surfaces 24 and 25 are formed at an interval on the rod 13. The rod 13 is made movable up to a position for forming the leak clearance 32 between both of the sliding surfaces 24 and 25 and the sleeve 11 from a position for forming the leak clearance 32 between only the first sliding surface 24 and the sleeve 11. <P>COPYRIGHT: (C)2008,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, for example, an alternator, a car air conditioner, a water pump, or the like has a rotating shaft connected to a crankshaft of an engine by a belt, and is driven by the engine through the belt. In order to keep the tension of this belt within an appropriate range, generally, a pulley arm that is swingable about a fulcrum shaft, a tension pulley that is rotatably attached to the pulley arm, and a direction in which the tension pulley is pressed against the belt. A tension adjusting device including an auto tensioner that biases the pulley arm is used.

  As an auto tensioner incorporated in this tension adjusting device, hydraulic oil is stored in a bottomed cylinder, and a plunger is slidably inserted in a sleeve provided coaxially with the cylinder in the cylinder, and the plunger and sleeve The cylinder is divided into a pressure chamber and a reservoir chamber, and a rod that moves integrally with the plunger is provided, and the rod is urged by a return spring in the direction of expanding the volume of the pressure chamber ( Patent Documents 1 and 2).

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

  A leak gap is formed between the sliding surfaces of the plunger and the sleeve so that the pressure chamber communicates with the reservoir chamber. When the rod moves in a direction in which the volume of the pressure chamber is reduced, the hydraulic oil in the pressure chamber has a leak gap. Spill through. At this time, since the damper action is generated by the resistance of the hydraulic oil flowing through the leak gap, the rod moves slowly and absorbs the tension while keeping the belt in a stable state.

In addition, the auto tensioner is provided with a passage that allows the pressure chamber and the reservoir chamber to communicate with each other, and the passage is provided with a check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side. When the rod moves in the direction in which the volume of the oil increases, hydraulic oil flows from the reservoir chamber side to the pressure chamber side through the check valve. Therefore, the rod quickly moves in the direction in which the volume of the pressure chamber expands, and absorbs the slack of the belt quickly.
JP-A-10-19099 JP-A-10-306860

  However, in this auto tensioner, the moving speed of the rod in the direction of increasing the volume of the pressure chamber is larger than the moving speed of the rod in the direction of reducing the volume of the pressure chamber. When this occurs, a phenomenon (pump-up phenomenon) in which the position of the rod gradually moves in the direction of expanding the volume of the pressure chamber occurs, and the belt tension may become excessive.

  In order to prevent this pump-up phenomenon, it is conceivable to increase the rod moving speed in the direction to reduce the volume of the pressure chamber by setting a large leak gap. Since the resistance flowing through the gap is reduced, the damping resistance of the rod is insufficient, and when the tension of the belt at the time of starting the engine temporarily increases, the amount of movement of the rod may be excessive and the belt may slip. .

  The problem to be solved by the present invention is to provide an auto tensioner in which the pump-up phenomenon is unlikely to occur when the belt tension is periodically increased or decreased, and the belt is less likely to slip when the engine is started.

  In order to solve the above-mentioned problem, a first sliding surface and a second sliding surface are formed on the outer periphery of the rod at an interval in the axial direction, and the rod is connected to the first sliding surface and the first sliding surface. From the position where the leak gap is formed between only the first sliding surface of the two sliding surfaces and the sleeve, both the first sliding surface and the second sliding surface and the sleeve It was made possible to move to a position where the leak gap was formed between.

  In this auto tensioner, the passage is formed in an outward flange portion provided in the sleeve, and the check valve is provided in a ring-shaped valve body slidably provided on the pressure chamber side surface of the flange portion. The valve body is preferably composed of a valve spring that urges the flange toward the flange portion, and the check valve is preferably arranged so as to overlap the rod in a direction perpendicular to the axis.

  In the auto tensioner according to the present invention, since the sliding surface on the outer periphery of the rod is divided into the first sliding surface and the second sliding surface, the first sliding surface out of the first sliding surface and the second sliding surface. The resistance that hydraulic oil flows through the leak gap with the rod in the position where the leak gap is formed only between the moving surface and the sleeve, and the gap between both the first sliding surface and the second sliding surface and the sleeve The resistance at which the hydraulic oil flows through the leak gap in a state where the rod is at the position where the leak gap is formed can be set individually. Therefore, by setting the resistance in a state where there is a rod at a position where a leak gap is formed between only the first sliding surface of the first sliding surface and the second sliding surface and the sleeve, A pump-up phenomenon can be prevented when the belt tension periodically increases or decreases, and a leak gap is formed between both the first sliding surface and the second sliding surface and the sleeve. By setting a large resistance in the state where the rod is present, it is possible to prevent the belt from slipping when the engine is started.

  In addition, when the check valve is arranged so as to overlap in the direction perpendicular to the axis with respect to the rod, the check valve and the rod are arranged in the direction perpendicular to the axis than when the check valve is arranged in the axis direction with respect to the rod. Because of the overlap, the axial length can be kept short, making it easy to install in tight spaces.

  1 and 2 show a tension adjusting device for a belt 1 for driving an automobile auxiliary machine. This tension adjusting device has a tension pulley 2 that contacts the belt 1 and a pulley arm 3 that rotatably supports the tension pulley 2, and the pulley arm 3 is attached to a fulcrum shaft 5 that is fixed to the engine block 4 shown in FIG. It is supported so that it can swing.

  One end of an auto tensioner 6 according to an embodiment of the present invention is rotatably connected to the pulley arm 3 around a connecting shaft 7, and the other end of the auto tensioner 6 is rotatable to a connecting shaft 8 fixed to the engine block 4. It is connected to. The auto tensioner 6 biases the pulley arm 3 to press the tension pulley 2 against the belt 1.

  As shown in FIG. 2, the auto tensioner 6 has a bottomed cylinder 9 in which hydraulic oil is stored. Further, a sleeve 11 having an outward flange portion 10 at the lower end is provided in the cylinder 9, and the flange portion 10 is a step portion 12 having a small diameter on the bottom side of the cylinder 9 formed on the inner periphery of the cylinder 9. It is put on. A rod 13 is inserted into the sleeve 11 so as to be slidable in the axial direction, and the inside of the cylinder 9 is partitioned into a pressure chamber 14 and a reservoir chamber 15 by the rod 13 and the sleeve 11.

  A connecting piece 16 connected to the pulley arm 3 is fixed to the upper end of the rod 13. A return spring 18 is incorporated between the connecting piece 16 and the flange portion 10 via a spring seat 17 fitted to the outer periphery of the rod 13, and the return spring 18 extends the rod 13 in the direction of expanding the volume of the pressure chamber 14. Energized.

  The spring seat 17 is provided with a cylindrical skirt portion 19 that faces the outer periphery of the cylinder 9. An O-ring 20 that contacts the inner periphery of the skirt portion 19 is provided on the outer periphery of the upper portion of the cylinder 9, and this O-ring 20 prevents foreign matter from entering the cylinder 9.

  A protrusion 21 is formed on the outer periphery of the cylinder 9 below the O-ring 20, and the inner periphery of the skirt portion 19 is locked below the contact position with the O-ring 20 and protrudes toward the inner diameter side. A nail 22 is formed. The protrusion 21 locks the locking claw 22 and prevents the skirt portion 19 from coming off the cylinder 9.

  As shown in FIG. 3, a first sliding surface 24 and a second sliding surface 25 are formed on the outer periphery of the rod with an interval in the axial direction with a circumferentially continuous groove 23 interposed therebetween. Yes. The first sliding surface 24 and the second sliding surface 25 are both cylindrical surfaces having a constant outer diameter.

  In the flange portion 10 of the sleeve 11, a passage 26 for communicating the pressure chamber 14 and the reservoir chamber 15 is formed at intervals in the circumferential direction as shown in FIG. As shown in FIG. 3, the passage 26 is provided with a ring-shaped valve body 27 that is detachably provided on the surface of the flange portion 10 on the pressure chamber 14 side, and the valve body 27 is biased toward the flange portion 10. A check valve 29 including a valve spring 28 is provided. The check valve 29 allows the flow of hydraulic oil from the reservoir chamber 15 side to the pressure chamber 14 side, but prohibits the flow of hydraulic oil from the pressure chamber 14 side to the reservoir chamber 15 side.

  As shown in FIG. 3, the check valve 29 has an inner diameter of the valve body 27 larger than the outer diameter of the rod 13 and does not overlap the rod 13 when viewed in the axial direction. The valve spring 28 includes a cylindrical portion 30 that is press-fitted into the inner periphery of the cylinder 9, and a claw portion 31 that is bent toward the inner diameter side along the lower end of the cylindrical portion 30. The claw portion 31 is illustrated in FIG. As shown, a plurality are formed at regular intervals in the circumferential direction.

  As shown by a two-dot chain line in FIG. 3, the check valve 29 is arranged so as to overlap the rod 13 in a direction perpendicular to the axis in a state where the rod 13 is at the stroke end on the side of reducing the volume of the pressure chamber 14. ing.

  As shown by the solid line in FIG. 5, the first sliding surface 24 and the second sliding surface 25 on the outer periphery of the rod 13 are in the state where the rod 13 is at the stroke end on the side where the volume of the pressure chamber 14 is enlarged. In the state where only one sliding surface 24 forms a leak gap 32 with the sleeve 11 and the rod 13 is at the stroke end on the side where the volume of the pressure chamber 14 is reduced as shown by a two-dot chain line in FIG. Both the first sliding surface 24 and the second sliding surface 25 form a leak gap 32 with the sleeve 11. At this time, the size of the leak gap 32 (for example, 50 μm) is smaller than the size of the gap formed between the inner surface of the groove 23 and the sleeve 11 (for example, 100 μm).

  Therefore, when the rod 13 is pushed and moved in the axial direction, the damping resistance acting on the rod 13 due to the hydraulic oil flowing through the leak gap 32 is the first sliding of the rod 13 as shown in FIGS. The lower end of the rod 13 is located between the position where only the surface 24 forms the leak gap 32 with the sleeve 11 (the point a shown in FIG. 6A and the position b shown in FIG. 6B). At a certain position), the resistance generated between the first sliding surface 24 and the sleeve 11 is dominant, and becomes a substantially constant magnitude. Further, the position at which the first sliding surface 24 and the second sliding surface 25 of the rod 13 form the leak gap 32 between the sleeve 11 (the position of the point b shown in FIG. 6B) and FIG. When the rod 13 moves in the direction of reducing the volume of the pressure chamber 14, the second sliding surface 25 and the sleeve are located. 11 increases and the damping resistance acting on the rod 13 increases. Further, the position of the leak gap 32 formed between the entire surface of the second sliding surface 25 and the sleeve 11 (the position of point c shown in FIG. 6 (C) and the position of point d shown in FIG. 6 (D)). When the rod 13 is at a position where the lower end of the rod 13 is in between), the damping resistance acting on the rod 13 is substantially constant.

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

  When the tension of the belt 1 increases, the tension is transmitted to the rod 13 through the pulley arm 3 and the connecting piece 16 in order, and the pressure in the pressure chamber 14 is increased. When the pressure in the pressure chamber 14 becomes higher than the pressure in the reservoir chamber 15, the hydraulic oil in the pressure chamber 14 flows into the reservoir chamber 15 through the leak gap 32 as shown in FIG. 3. At this time, since the check valve 29 is closed, the hydraulic oil does not flow through the passage 26 of the flange portion 10. Thus, the hydraulic oil flows through the leak gap 32, so that the rod 13 moves, and the tension pulley 2 moves to a position where the tension of the belt 1 and the urging force of the return spring 18 are balanced. At this time, a damper action is generated by the resistance of the hydraulic oil flowing through the leak gap 32, so that the tension pulley 2 moves slowly and absorbs the tension while keeping the belt 1 in a stable state.

  On the other hand, when the tension of the belt 1 decreases, the pressure in the pressure chamber 14 decreases due to the urging force of the return spring 18. When the pressure in the pressure chamber 14 becomes lower than the pressure in the reservoir chamber 15, the check valve 29 opens, and the hydraulic oil in the reservoir chamber 15 flows into the pressure chamber 14 through the passage 26 of the flange portion 10 as shown in FIG. . The rod 13 is moved by the flow of the hydraulic oil, and the tension pulley 2 is moved to a position where the tension of the belt 1 and the urging force of the return spring 18 are balanced. At this time, the tension pulley 2 moves quickly and absorbs the slack of the belt 1 quickly.

  In the auto tensioner 6, the sliding surface on the outer periphery of the rod 13 is divided into a first sliding surface 24 and a second sliding surface 25. Damping resistance in a state where the rod 13 is in a position where the leak gap 32 is formed between only the first sliding surface 24 and the sleeve 11, and both the first sliding surface 24 and the second sliding surface 25 The damping resistance in the state where the rod 13 is in the position where the leak gap 32 is formed between the sleeve 11 and the sleeve 11 can be set individually. Therefore, the damping resistance in a state where the rod 13 is in a position where the leak gap 32 is formed between only the first sliding surface 24 of the first sliding surface 24 and the second sliding surface 25 and the sleeve 11. Is set to be small, the pump-up phenomenon when the tension of the belt 1 is periodically increased or decreased can be prevented, and both the first sliding surface 24 and the second sliding surface 25, the sleeve 11, By setting a large damping resistance in a state where the rod 13 is at a position where the leak gap 32 is formed between them, the belt 1 can be prevented from slipping when the engine is started.

  In addition, since the auto tensioner 6 forms a circumferentially continuous groove 23 on the outer periphery of the rod 13 and divides the sliding surface of the outer periphery of the rod 13, the groove that is continuous in the circumferential direction on the inner periphery of the sleeve 11 is formed. Compared to the case where the sliding surface on the inner periphery of the sleeve 11 is formed and formed, the processing of the sliding surface is simple and the cost is low.

  In the auto tensioner 6, the check valve 29 is disposed so as to overlap the rod 13 in the direction perpendicular to the axis in a state where the rod 13 is at the stroke end on the side of reducing the volume of the pressure chamber 14. Since the check valve 29 and the rod 13 overlap each other in the direction perpendicular to the axis, the axial length can be kept short, and it is easy to install in a narrow space.

  In the above embodiment, the check valve 29 is arranged so as to overlap the rod 13 in the direction perpendicular to the axis only when the rod 13 is at the stroke end on the side of reducing the volume of the pressure chamber 14. 29, the rod 13 always overlaps the rod 13 in the direction perpendicular to the axis in the process from the stroke end on the side of reducing the volume of the pressure chamber 14 to the stroke end on the side of increasing the volume of the pressure chamber 14. You may arrange in. In short, it is only necessary that the check valve overlaps the rod in the direction perpendicular to the axis in a state where the rod is at the stroke end on the side of reducing the volume of the pressure chamber.

  In the above-described embodiment, the urging force of the valve spring 28 acts on the valve body 27 more uniformly by urging the valve body 27 with the claw portions 31 arranged at regular intervals in the circumferential direction. However, other types of valve springs may be used. For example, a coil spring is incorporated between the pressure chamber 14 side surface of the valve body 27 and the bottom surface of the cylinder 9, and the valve spring is used as the valve spring. The body 27 may be biased toward the flange portion 10.

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 of the vicinity of the sleeve of the auto tensioner shown in Fig. 2 Sectional view along line IV-IV in FIG. FIG. 3 is an enlarged cross-sectional view showing a process in which the rod of FIG. 3 moves in the direction of enlarging the volume of the pressure chamber. FIG. 3 is an enlarged sectional view showing the position of the rod of the auto tensioner shown in FIG. The figure which shows the correspondence of the position of the rod shown in FIG. 6, and the damping resistance which acts on the rod of the position

Explanation of symbols

9 Cylinder 10 Flange 11 Sleeve 13 Rod 14 Pressure chamber 15 Reservoir chamber 18 Return spring 24 First sliding surface 25 Second sliding surface 26 Passage 27 Valve element 28 Valve spring 29 Check valve 32 Leak gap

Claims (2)

  Hydraulic oil is stored in a bottomed cylinder (9), and a sleeve (11) is provided coaxially with the cylinder (9) in the cylinder (9), and a rod (13) is axially disposed in the sleeve (11). The cylinder (9) is partitioned by the rod (13) and the sleeve (11) into a pressure chamber (14) and a reservoir chamber (15), and the rod (13) and the sleeve are inserted. A leak gap (32) for communicating the pressure chamber (14) and the reservoir chamber (15) is formed between the sliding surfaces of (11), and the rod ( 13) is provided with a return spring (18), and a passage (26) for communicating the pressure chamber (14) and the reservoir chamber (15) is provided. The passage (26) is connected to the reservoir chamber (15) side. Of hydraulic oil from the pressure chamber to the pressure chamber (14) side In the auto tensioner provided with the check valve (29) that allows only the first sliding surface (24) and the second sliding surface (25) on the outer periphery of the rod (13), an axial interval is provided. Forming the rod (13) between only the first sliding surface (24) of the first sliding surface (24) and the second sliding surface (25) and the sleeve (11); From the position where the leak gap (32) is formed between the first slide surface (24), the second slide surface (25) and the sleeve (11), the leak gap ( 32) An auto tensioner characterized in that it can move to a position where it is formed.   The passage (26) is formed in an outward flange portion (10) provided in the sleeve (11), and the check valve (29) is disposed on the pressure chamber (14) side surface of the flange portion (10). A ring-shaped valve body (27) provided so as to be capable of contacting and separating, and a valve spring (28) for urging the valve body (27) toward the flange portion (10). The auto tensioner according to claim 1, wherein 29) is arranged so as to overlap with the rod (13) in a direction perpendicular to the axis.

Images