JP2008175224A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner of low manufacturing cost. <P>SOLUTION: The automatic tensioner is so constructed that hydraulic oil is stored in a cylinder 10, a sleeve 11 is provided in the cylinder 10, a rod 12 is slidably inserted in the sleeve 11 to compart the interior of the cylinder 10 into a pressure chamber 13 and a reservoir chamber 14, the pressure chamber 13 and the reservoir chamber 14 are brought into communication through a leak clearance 15 formed between sliding surfaces of the sleeve 11 and the rod 12, a passage 24 is provided for bringing a lower part of the pressure chamber 13 and a lower part of the reservoir chamber 14 into communication, a check valve 26 is provided in the lower part of the pressure chamber 13, a spring seat 16 is fixed to an upper part of the rod 12, and a return spring 17 is provide between the spring seat 16 and a bottom 9 of the cylinder 10. A cylinder member 22 is fixed to the bottom 9 of the cylinder 10 by molding the cylinder 10 in a state that the cylinder member 22 is placed in a molding die for the cylinder 10, the passage 24 and the check valve 26 are provided on the cylinder member 22, and the sleeve 11 is fitted on an outer periphery of the cylinder member 22 with tight fit and fixed. <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 shown in FIG. 5, as an auto tensioner incorporated in the tension adjusting device, hydraulic oil is accumulated in a cylinder 42 having a bottom 41 at the lower portion, and a sleeve 43 is provided coaxially with the cylinder 42 in the cylinder 42. The rod 44 is slidably inserted in the axial direction into the cylinder 43, the inside of the cylinder 42 is partitioned into a pressure chamber 45 and a reservoir chamber 46, and a spring seat (not shown) is fixed to the upper portion of the rod 44. And a bottom 41 of the cylinder 42 are provided with a return spring 47 that urges the rod 44 in the direction of expanding the volume of the pressure chamber 45 (Patent Document 1).

  In this auto tensioner, the rod moves to a position where the urging force of the return spring 47 balances with the tension of the belt (not shown), thereby absorbing the belt tension fluctuation and keeping the belt tension within an appropriate range.

  Further, the pressure chamber 45 and the reservoir chamber 46 communicate with each other via a leak gap 48 formed between the sliding surfaces of the sleeve 43 and the rod 44, and the rod 44 moves in a direction in which the volume of the pressure chamber 45 is reduced. Then, the hydraulic oil in the pressure chamber 45 flows out through the leak gap 48. At this time, since the flow rate of the hydraulic oil flowing through the leak gap 48 is limited, the rod 44 moves slowly and absorbs the tension while keeping the belt in a stable state.

  In this auto tensioner, the lower portion of the sleeve 43 is press-fitted into a sleeve fitting recess 49 formed in the bottom 41 of the cylinder 42. Between the fitting surface of the sleeve fitting recess 49 and the sleeve 43, a passage 50 is provided for communicating the lower portion of the pressure chamber 45 and the lower portion of the reservoir chamber 46, and the passage 50 is moved from the reservoir chamber 46 side to the pressure chamber 45 side. A check valve 51 that allows only the flow of the hydraulic oil is provided in the lower part of the pressure chamber 45, and when the rod 44 moves in a direction in which the volume of the pressure chamber 45 increases, the reservoir chamber 46 side passes through the passage 50. The hydraulic oil flows to the pressure chamber 45 side. For this reason, in the auto tensioner, the rod 44 quickly moves in the direction in which the volume of the pressure chamber 45 increases, and the slack of the belt is quickly absorbed.

Further, this auto tensioner has a retaining ring 52 mounted on the outer periphery of the lower portion of the rod 44, and a step formed on the inner periphery of the sleeve 43 when the rod 44 moves in the direction in which the volume of the pressure chamber 45 increases. A retaining ring 52 is engaged with the portion 53, and the rod 44 is prevented from coming off the sleeve 43 by the engagement.
JP 2006-125448 A

  However, in this auto tensioner, when the retaining ring 52 is locked to the stepped portion 53 of the sleeve 43, the urging force of the return spring 47 acts between the sleeve fitting concave portion 49 and the fitting surface of the sleeve 43, and the sleeve fitting. There is a possibility that the sleeve 43 may come out of the joint recess 49. For this reason, it is necessary to manage the tightening margin of the sleeve fitting recess 49 with respect to the sleeve 43 with high accuracy, and it is necessary to process the sleeve fitting recess 49 with high accuracy. Since it is located at the bottom 41, processing is difficult and the manufacturing cost is high.

  The problem to be solved by the present invention is to provide an auto tensioner having a low manufacturing cost.

  In order to solve the above problem, the cylinder member is fixed to the bottom of the cylinder coaxially with the cylinder by molding the cylinder in a state where the cylinder member is disposed in the molding die of the cylinder, and the cylinder member The passage and the check valve are provided, and the sleeve is fitted and fixed to the outer periphery of the cylindrical member with an interference fit.

  In this auto tensioner, it is preferable that an outward flange portion is formed at the lower end of the sleeve, and the lower end of the return spring is supported by the flange portion.

  In the autotensioner according to the present invention, the columnar member separate from the cylinder is fixed to the bottom of the cylinder. Therefore, after processing the outer periphery of the columnar member with high accuracy, the columnar member can be fixed to the bottom of the cylinder. Therefore, compared with the case where the sleeve fitting recess is directly processed at the bottom of the cylinder, the processing is simple and the manufacturing cost is low.

  Further, in the case where an outward flange portion is formed at the lower end of the sleeve and the lower end of the return spring is supported by the flange portion, the urging force of the return spring is between the fitting surface of the sleeve and the cylindrical member. Since it does not act, it is difficult for the sleeve to come off from the cylindrical member, and the reliability of fixing the sleeve to the cylindrical member is excellent.

  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, in the auto tensioner 6, hydraulic oil is stored in a cylinder 10 having a bottom 9 at the bottom. A sleeve 11 is provided coaxially with the cylinder 10 in the cylinder 10, and a rod 12 is inserted into the sleeve 11 so as to be slidable in the axial direction. The sleeve 11 and the rod 12 divide the inside of the cylinder 10 into a pressure chamber 13 and a reservoir chamber 14.

  Between the sliding surfaces of the sleeve 11 and the rod 12, a leak gap 15 that connects the pressure chamber 13 and the reservoir chamber 14 is formed.

  A spring seat 16 is fixed to the upper portion of the rod 12. A return spring 17 is incorporated between the spring seat 16 and the bottom 9 of the cylinder 10, and the return spring 17 urges the rod 12 in the direction of expanding the volume of the pressure chamber 13.

  An annular opening formed between the spring seat 16 and the cylinder 10 is closed by a cylindrical bellows 18, whereby the hydraulic oil in the cylinder 10 is sealed.

  A groove 19 that is continuous in the circumferential direction is formed on the lower outer periphery of the rod 12, and a C-shaped ring-shaped retaining ring 20 is fitted into the groove 19. Further, a step portion 21 having a small diameter on the reservoir chamber 14 side is formed on the inner periphery of the sleeve 11, and the retaining ring 20 is stepped when the rod 12 moves in the direction of expanding the volume of the pressure chamber 13. 21 and the rod 12 is prevented from coming off the sleeve 11 by the locking.

  The lower portion of the sleeve 11 is fitted to the outer periphery of a columnar member 22 provided coaxially with the cylinder 10 on the bottom 9 of the cylinder 10 by an interference fit. By the fitting, the sleeve 11 is fitted to the columnar member 22. It is fixed. The cylindrical member 22 is fixed to the bottom 9 of the cylinder 10 by molding the cylinder 10 in a state where the cylindrical member 22 is disposed in the molding die of the cylinder 10. The cylinder 10 can be molded by, for example, aluminum die casting or resin molding.

  As shown in FIG. 3, a circumferentially continuous groove 23 is formed on the lower outer periphery of the cylindrical member 22, and the cylinder 10 is molded so that the position of the groove 23 is embedded in the bottom 9 of the cylinder 10. The coupling strength between the cylindrical member 22 and the cylinder 10 is improved.

  Further, the cylindrical member 22 is formed with a passage 24 extending from the upper surface of the cylindrical member 22 to the outer periphery, and through the passage 24 and a groove 25 formed in the bottom 9 of the cylinder 10, The lower part of the pressure chamber 13 and the lower part of the reservoir chamber 14 communicate with each other.

  The cylindrical member 22 has a check valve 26 at the end of the passage 24 on the pressure chamber 13 side. The check valve 26 includes a check ball 27, a retainer 29 that holds the check ball 27 detachably on a tapered seat surface 28 whose diameter increases toward the pressure chamber 13, and the check ball 27 toward the seat surface 28. The valve spring 30 is urged to permit the flow of hydraulic oil from the reservoir chamber 14 side to the pressure chamber 13 side of the passage 24, but the flow of hydraulic oil from the pressure chamber 13 side to the reservoir chamber 14 side is allowed. Ban.

  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 12 via the tension pulley 2, the pulley arm 3, and the spring seat 16, and the pressure in the pressure chamber 13 increases. When the pressure in the pressure chamber 13 becomes higher than the pressure in the reservoir chamber 14, the hydraulic oil flows through the leak gap 15 from the pressure chamber 13 side to the reservoir chamber 14 side. At this time, since the check valve 26 is closed, the hydraulic oil does not flow through the passage 24. As the hydraulic oil flows through the leak gap 15 in this way, the rod 12 moves downward, 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 working oil flowing through the leak gap 15 is limited and a damper action is generated, 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 12 is moved upward by the urging force of the return spring 17 and the volume of the pressure chamber 13 is increased, so that the pressure in the pressure chamber 13 is reduced. When the pressure in the pressure chamber 13 becomes lower than the pressure in the reservoir chamber 14, the check valve 26 is opened, and hydraulic oil flows from the reservoir chamber 14 side to the pressure chamber 13 side through the passage 24. At this time, the tension pulley 2 quickly moves to a position where the tension of the belt 1 and the urging force of the return spring 17 are balanced, and quickly absorbs the slack of the belt 1.

  Since the auto tensioner 6 fixes a cylindrical member 22 separate from the cylinder 10 to the bottom 9 of the cylinder 10, after processing the outer periphery of the cylindrical member 22 with high accuracy, the cylindrical member 22 is attached to the bottom 9 of the cylinder 10. Can be fixed. Therefore, as shown in FIG. 5, the processing is simpler and the manufacturing cost is lower than the case where the sleeve fitting recess 49 is directly processed in the bottom 41 of the cylinder.

  Both the sleeve 11 and the cylindrical member 22 are preferably made of an iron-based material. In this way, when the sleeve 11 and the columnar member 22 are thermally expanded due to temperature changes, a difference in thermal expansion between the sleeve 11 and the columnar member 22 is unlikely to occur. It is difficult and the coupling strength between the cylindrical member 22 and the sleeve 11 is more stable.

  The lower end of the return spring 17 may be supported by the bottom 9 of the cylinder 10 as shown in FIG. 3, but an outward flange portion 32 is formed at the lower end of the sleeve 31 as shown in FIG. The lower end of the return spring 17 is preferably supported by the flange portion 32. In this way, when the rod 12 moves in the direction of enlarging the volume of the pressure chamber 13 and the retaining ring 20 is locked to the step portion 21, the urging force of the return spring causes the sleeve 31 and the cylindrical member 22 to be fitted. Since it does not act between the mating surfaces, it is difficult for the sleeve 31 to come off from the cylindrical member 22, and the reliability of fixing the sleeve 31 to the cylindrical member 22 is improved.

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 near the lower end of the sleeve of FIG. FIG. 2 is an enlarged sectional view near the lower end of the sleeve showing a modification of the sleeve of FIG. Enlarged cross section near the sleeve of a conventional auto tensioner

Explanation of symbols

9 Bottom 10 Cylinder 11 Sleeve 12 Rod 13 Pressure chamber 14 Reservoir chamber 15 Leakage gap 16 Spring seat 17 Return spring 22 Cylindrical member 24 Passage 26 Check valve 31 Sleeve 32 Flange

Claims (2)

  The hydraulic oil is stored in a cylinder (10) having a bottom (9) at the bottom, a sleeve (11) is provided in the cylinder (10) coaxially with the cylinder (10), and a rod (12 in the sleeve (11) is provided. ) Is slidably inserted in the axial direction to divide the inside of the cylinder (10) into a pressure chamber (13) and a reservoir chamber (14), and between the sliding surfaces of the sleeve (11) and the rod (12). A passage (communication between the lower portion of the pressure chamber (13) and the lower portion of the reservoir chamber (14) is established through communication between the pressure chamber (13) and the reservoir chamber (14) through a leak gap (15) formed. 24), and a check valve (26) that allows only the flow of hydraulic oil from the reservoir chamber (14) side to the pressure chamber (13) side of the passage (24) is provided in the lower portion of the pressure chamber (13). , A spring seat (16 A return spring that urges the rod (12) between the spring seat (16) and the bottom (9) of the cylinder (10) in the direction of expanding the volume of the pressure chamber (13). In the autotensioner provided with (17), the cylindrical member (22) is molded into the cylinder (10) by molding the cylinder (10) in a state where the cylindrical member (22) is disposed in the molding die of the cylinder (10). 10) is fixed coaxially to the cylinder (10) at the bottom (9), and the cylindrical member (22) is provided with the passage (24) and the check valve (26). An auto-tensioner characterized in that the sleeve (11) is fitted and fixed with an interference fit.   The auto tensioner according to claim 1, wherein an outward flange portion (32) is formed at a lower end of the sleeve (31), and the lower end of the return spring (17) is supported by the flange portion (32).

Images