JP2008111460A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner with a short axial length, suppressing leaks of hydraulic fluid in a cylinder, and providing smooth movement of a rod. <P>SOLUTION: In a composition adopted in the automatic tensioner, the hydraulic fluid is filled in the bottomed cylinder 9, a sleeve 11 having an outward facing flange part 10 is provided in the cylinder 9, the rod 13 is inserted in the sleeve 11 such that it can axially slide, a cylinder 9 interior is divided into a pressure chamber 14 and a reservoir chamber 15 by the rod 13 and the sleeve 11, a leak gap 25 communicating the pressure chamber 14 with the reservoir chamber 15 is formed between sliding faces of the rod 13 and the sleeve 11, a return spring 17 is provided for energizing the rod 13 in a direction enlarging the volume of the pressure chamber 14, a passage 26 communicating the pressure chamber 14 with the reservoir chamber 15 is formed in the flange part 10, a check valve 29 allowing only a flow of the hydraulic fluid from a reservoir chamber side to a pressure chamber side is provided in the passage 26, and the hydraulic fluid in the cylinder 9 is sealed by an oil seal 18. <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, a sleeve is inserted into a bottomed cylinder, a plunger is slidably inserted in the sleeve in the axial direction, and the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, It is known that the plunger is provided with a rod that moves integrally with the plunger, and is provided with a return spring that urges the rod in a direction in which the volume of the pressure chamber increases. 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. Flows through to the reservoir chamber. At this time, since the flow rate of the hydraulic oil flowing through the leak gap is limited and a damper action occurs, the rod moves slowly and absorbs the tension while keeping the belt in a stable state.

The plunger has a through hole that connects the pressure chamber and the reservoir chamber, and the opening on the pressure chamber side of the through hole allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side. When the valve is provided and the rod moves in the direction in which the volume of the pressure chamber increases, the 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, this auto tensioner has a long axial length because the plunger and the check valve are arranged side by side in the axial direction, and it is difficult to install in a narrow space.

  In order to shorten the axial length of the auto tensioner, the inventor of the present invention provides hydraulic oil in a bottomed cylinder and a sleeve having an outward flange at the lower end is provided in the cylinder. A rod is inserted into the sleeve so as to be slidable in the axial direction, and the cylinder is divided into a pressure chamber and a reservoir chamber by the rod and the sleeve, and the pressure is slid between the sliding surface of the rod and the sleeve. A passage that connects the pressure chamber and the reservoir chamber to the flange portion by providing a return spring that urges the rod in a direction that enlarges the volume of the pressure chamber, forming a leak gap that communicates the chamber with the reservoir chamber And a check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side is provided in the passage, and the check valve is perpendicular to the rod. It was devised an auto-tensioner which is arranged so as to overlap in the direction.

  In this auto tensioner, the check valve is arranged so that it overlaps in the direction perpendicular to the axis with respect to the rod, so that the check valve and the rod overlap in the direction perpendicular to the axis than when the check valve is arranged in the axis direction with respect to the rod. The length in the axial direction can be kept short, making it easy to install in tight spaces.

  However, in order to seal the hydraulic oil in the cylinder, this auto tensioner fixes a cylindrical dust cover facing the outer periphery of the rod to the protruding portion of the rod from the cylinder, and slides with the inner periphery of the dust cover. The O-ring can be installed on the outer periphery of the cylinder. However, when the auto tensioner is tilted, the hydraulic oil tends to accumulate between the outer periphery of the cylinder and the inner periphery of the dust cover. The accumulated hydraulic oil may leak from between the sliding surfaces of the O-ring and the cylinder. Further, since the circumference of the sliding surface of the O-ring is long, the sliding resistance when the rod moves in the axial direction is large, and the rod is difficult to move smoothly.

  The problem to be solved by the present invention is to provide an auto tensioner that has a short axial length, is hard to leak hydraulic oil in a cylinder, and has a smooth rod movement.

  In order to solve the above problems, an annular oil seal that slidably penetrates the rod is fitted to the inner periphery of the cylinder, and the hydraulic oil in the cylinder is sealed with the oil seal.

  In the auto tensioner of the present invention, since the sliding surface of the oil seal is on the inner diameter side of the inner periphery of the cylinder, when the auto tensioner is tilted, the hydraulic oil in the cylinder is placed between the sliding surface of the rod and the oil seal. It is hard to collect and hydraulic oil is hard to leak. Further, since the circumference of the sliding surface of the oil seal is short, the sliding resistance when the rod moves in the axial direction is small, and the rod is likely to move smoothly.

  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.

  The rod 13 includes a large-diameter shaft portion 13A and a small-diameter shaft portion 13B connected to the lower end of the large-diameter shaft portion 13A, and a wear ring 16 is fitted on the outer periphery of the small-diameter shaft portion 13B. The rod 13 is urged in the direction of expanding the volume of the pressure chamber 14 by a return spring 17 incorporated between the wear ring 16 and the flange portion 10.

  An annular oil seal 18 that slidably penetrates the large-diameter shaft portion 13 </ b> A of the rod 13 is fitted to the inner periphery of the open end of the cylinder 9. The oil seal 18 is a chrysanthemum that is locked to the inner periphery of the cylinder 9. The retaining ring 19 prevents the cylinder 9 from coming off. As shown in FIG. 3, the oil seal 18 is formed by covering an annular cored bar 20 having an L-shaped cross section with a rubber material 21, and is fastened to the outer periphery of the large-diameter shaft portion 13 </ b> A by a garter spring 22.

  As shown in FIG. 2, a connecting piece 23 connected to the pulley arm 3 via the connecting shaft 7 is fixed to the protruding portion of the rod 13 from the cylinder 9, and the connecting piece 23 faces the outer periphery of the cylinder 9. A cylindrical dust cover 24 is fixed.

  As shown in FIG. 4, a leak gap 25 is formed between the sliding surfaces of the rod 13 and the sleeve 11 to allow the pressure chamber 14 and the reservoir chamber 15 to communicate with each other. The leak gap 25 is very small and restricts the flow rate of the hydraulic oil flowing from the pressure chamber 14 to the reservoir chamber 15.

  In the flange portion 10, 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. 4, the passage 26 is provided with a ring-shaped valve body 27 slidably 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. 4, the check valve 29 has an inner diameter of the valve element 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.

  Further, as shown by a two-dot chain line in FIG. 4, the check valve 29 overlaps 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 where the volume of the pressure chamber 14 is reduced. Has been placed.

  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 23 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 25 as shown in FIG. 4. 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 25, 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 17 are balanced. At this time, since the flow rate of the hydraulic oil flowing through the leak gap 25 is limited, 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 is reduced, the rod 13 is moved by the urging force of the return spring 17 and the volume of the pressure chamber 14 is increased, so that the pressure in the pressure chamber 14 is reduced. When the pressure in the pressure chamber 14 becomes lower than the pressure in the reservoir chamber 15, the check valve 29 is opened, 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. . At this time, the tension pulley 2 quickly moves 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 quickly absorbed.

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

  Further, since the sliding surface of the oil seal 18 with the rod 13 is closer to the inner diameter side than the inner periphery of the cylinder 9, when the auto tensioner 6 is tilted, the hydraulic oil in the cylinder 9 is transferred to the rod. 13 and the oil seal 18 are less likely to accumulate between the sliding surfaces, and hydraulic oil is less likely to leak.

  Further, since the circumferential length of the sliding surface of the oil seal 18 is short, compared to the case where an O-ring that slides with the inner circumference of the dust cover 24 is provided on the outer circumference of the cylinder 9 in order to seal the hydraulic oil in the cylinder 9. Thus, the sliding resistance when the rod 13 moves in the axial direction is small, and the rod 13 moves easily.

  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.

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 cross-sectional view near the oil seal of the auto tensioner shown in Fig. 2. 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 VV in FIG. 4 is an enlarged cross-sectional view showing a process in which the rod of FIG. 4 moves in the direction of enlarging the volume of the pressure chamber.

Explanation of symbols

9 Cylinder 10 Flange 11 Sleeve 13 Rod 14 Pressure chamber 15 Reservoir chamber 17 Return spring 18 Oil seal 25 Leak gap 26 Passage 29 Check valve

Claims (1)

  A hydraulic oil is stored in a bottomed cylinder (9), a sleeve (11) having an outward flange portion (10) is provided in the cylinder (9), and a rod (13) is provided in the sleeve (11). The rod (13) and the sleeve (11) divide the cylinder (9) into a pressure chamber (14) and a reservoir chamber (15), and the rod (13) And a leak gap (25) for communicating the pressure chamber (14) and the reservoir chamber (15) between the sliding surfaces of the sleeve (11) and increasing the volume of the pressure chamber (14). A return spring (17) for urging the rod (13) is provided, and a passage (26) for communicating the pressure chamber (14) and the reservoir chamber (15) is formed in the flange portion (10). (26), the reservoir chamber (15 A check valve (29) that allows only the flow of hydraulic oil from the side to the pressure chamber (14) side is provided, and the check valve (29) is arranged so as to overlap the rod (13) in a direction perpendicular to the axis. An annular oil seal (18) that slidably penetrates the rod (13) is fitted to the inner periphery of the cylinder (9), and the hydraulic oil in the cylinder (9) is discharged by the oil seal (18). Sealed auto tensioner.

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