JP2008014341A - Hydraulic auto-tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the structure of a hydraulic auto-tensioner by press-fitting a rod into a plunger over a stable press-fit strength. <P>SOLUTION: A hydraulic oil is reserved in a cylinder 7 in which a sleeve 6 is secured. The inside of the cylinder 7 is divided into a pressure chamber 9 and a reservoir chamber 10 by the plunger 8 slidably inserted into the sleeve 6. The pressure chamber 9 is allowed to communicate with the reservoir chamber 10 through a leak clearance 22. The pressure chamber 9 is allowed to communicate with the reservoir chamber 10 through a passage 27 in which a check valve 25 allowing only the flow of the hydraulic oil from the reservoir chamber side to the pressure chamber side is installed. The tensioner has a rod 11 moving when the plunger 8 is moved and a return spring 15 biasing the rod 11 in the direction of enlarging the volume of the pressure chamber 9. A blind hole 12 is formed in the reservoir chamber side end surface of the plunger 8. The rod 11 is fixed to the plunger 8 by press-fitting the lower end 11A of the rod into the blind hole 12. An air reservoir 16 is formed in the blind hole 12 into which the lower end 11A of the rod is press-fitted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic auto tensioner used for maintaining tension of a belt that drives an 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 a hydraulic auto tensioner that urges a pulley arm is used.

  As a hydraulic auto tensioner built into this tension adjustment device, hydraulic oil is stored in a cylinder in which a sleeve is inserted, and the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber by a plunger that is slidably inserted into the sleeve, and is integrated with the plunger. Known is a rod that is urged by a return spring in a direction in which the volume of a pressure chamber expands (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.

  In addition, the pressure chamber and the reservoir chamber communicate with each other through a first passage that forms a throttle. When the rod moves in a direction in which the volume of the pressure chamber decreases, the hydraulic oil in the pressure chamber passes through the first passage. Flows into reservoir chamber. At this time, since the flow rate of the hydraulic oil flowing through the first passage is limited, the rod moves slowly, and the belt tension is kept stable.

  Furthermore, the pressure chamber and the reservoir chamber communicate with each other via a second passage provided with a check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side, and the pressure chamber volume increases. When the rod moves, 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 increases, and absorbs the slack of the belt quickly.

In this hydraulic auto tensioner, in order to move the rod and the plunger together, the plunger is urged toward the rod by a plunger spring incorporated in the pressure chamber.
JP-A-10-19099 JP-A-10-306860

  However, if a plunger spring is incorporated in order to move the rod and plunger together, the number of parts increases, resulting in high costs. Accordingly, the inventors of the present invention have devised that a bottomed hole is formed in the plunger and the rod is fixed to the plunger by press-fitting the end of the rod into the bottomed hole. However, when the end of the rod is press-fitted into the bottomed hole, the press-fit length of the rod tends to become unstable due to the repulsive force of the air compressed in the bottomed hole.

  An object of the present invention is to enable the rod to be press-fitted into the plunger with a stable press-fitting length, thereby simplifying the structure of the hydraulic auto tensioner.

  In order to solve the above problems, hydraulic oil is stored in a cylinder having a sleeve fixed therein, and the cylinder is partitioned into a pressure chamber and a reservoir chamber by a plunger slidably inserted into the sleeve to form a throttle. The pressure chamber is connected to the pressure chamber via a first passage, and the pressure chamber is connected to the reservoir chamber via a second passage provided with a check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side. A hydraulic auto-tensioner provided with a return spring that urges the rod in a direction in which the volume of the pressure chamber expands. A bottomed hole is formed in the chamber-side end surface, and the rod is fixed to the plunger by press-fitting the end of the rod into the bottomed hole. And so that the air reservoir is formed in the state where press-fitting the end of the de-bottomed hole.

  In this hydraulic auto tensioner, the rod has a large-diameter portion that is continuous with the end portion, and the end surface of the large-diameter portion is the bottomed hole in a state where the end portion of the rod is press-fitted into the bottomed hole. It is more preferable to contact the edge.

  In the hydraulic auto tensioner according to the present invention, the air reservoir formed in the bottomed hole with the end of the rod being press-fitted into the bottomed hole alleviates the compression of the air in the bottomed hole. Therefore, the repulsive force of the air in the bottomed hole is suppressed, and the press-fit length of the rod is easy to be stabilized. Further, it is not necessary to incorporate a plunger spring for biasing the plunger toward the rod, and the structure is simple.

  Further, the rod has a large-diameter portion that is continuous with the end portion, and the end surface of the large-diameter portion is in contact with an edge of the bottomed hole in a state where the end portion is press-fitted into the bottomed hole. When the rod end is press-fitted into the bottomed hole, the end face of the large-diameter part abuts against the edge of the bottomed hole, and the rod position relative to the plunger is positioned in the press-fitting direction. Is more stable.

  FIG. 1 shows 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 supported so as to be swingable about a fulcrum shaft 4. . The pulley arm 3 is connected to a hydraulic auto tensioner 5 according to an embodiment of the present invention. The hydraulic auto tensioner 5 urges the pulley arm 3 to press the tension pulley 2 against the belt 1.

  As shown in FIG. 2, the hydraulic auto tensioner 5 has a cylinder 7 in which a sleeve 6 is inserted, and hydraulic oil is stored inside the cylinder 7. A plunger 8 is slidably inserted into the sleeve 6, and the inside of the cylinder 7 is partitioned into a pressure chamber 9 and a reservoir chamber 10 by the plunger 8.

  Further, a rod 11 is inserted into the cylinder 7, and a lower end portion 11 </ b> A of the rod 11 is press-fitted into a bottomed hole 12 formed on an end surface of the plunger 8 on the reservoir chamber 10 side. A spring seat 13 is fixed to the upper end portion 11B of the rod 11, and the rod 11 is urged between the spring seat 13 and the flange 14 formed on the outer periphery of the cylinder 7 in the direction of increasing the volume of the pressure chamber 9. A return spring 15 is incorporated.

  As shown in FIG. 3, the rod 11 has a large-diameter portion 11C that is continuous with the lower end portion 11A, and the large-diameter portion 11C has an outer diameter larger than that of the lower end portion 11A. Further, the lower end portion 11 </ b> A is formed shorter than the depth of the bottomed hole 12. Therefore, the lower end surface of the large-diameter portion 11C abuts against the edge of the bottomed hole 12 in a state where the lower end portion 11A is press-fitted into the bottomed hole 12, and an air reservoir 16 is formed in the bottomed hole 12.

  As shown in FIGS. 3 and 4, a cylindrical spacer 18 that presses the sleeve 6 from above with a flange 17 cut and raised to the inner diameter side is fitted into the upper inner periphery of the cylinder 7. As shown in FIG. 2, a wear ring 19 that slidably supports the rod 11 is fitted on the upper side of the spacer 18, and an annular shape that allows the rod 11 to slide slidably on the upper side of the wear ring 19. An oil seal 20 is fitted.

  The oil seal 20 is retained by a chrysanthemum retaining ring 21 that engages with the inner periphery of the cylinder 7, whereby the sleeve 6, the spacer 18, the wear ring 19, and the oil seal 20 are held in the cylinder 7. The rod 11 is retained from the wear ring 19 by a retaining ring 22 attached to the outer periphery of the large diameter portion 11C.

  The pressure chamber 9 and the reservoir chamber 10 communicate with each other via a leak gap 23 formed between the sliding surfaces of the sleeve 6 and the plunger 8. The leak gap 23 is very small, and the flow rate of the hydraulic oil flowing through the leak gap 23 is limited.

  As shown in FIGS. 3 and 5, a communication groove 24 extending from the position of the upper end of the sleeve 6 to the inner bottom of the cylinder 7 is formed on the inner periphery of the cylinder 7, and the communication groove 24 is formed on the inner bottom of the cylinder 7. A communication groove 26 is formed which reaches the position of the check valve 25 press-fitted into the lower end of the sleeve 6. The communication grooves 24 and 26 form a passage 27 that allows the pressure chamber 9 and the reservoir chamber 10 to communicate with each other when the sleeve 6 is inserted into the cylinder 7.

  As shown in FIG. 6, the check valve 25 includes an annular valve seat 28, a hemispherical valve body 29 having a spherical seat surface, and a retainer 30 that faces the valve seat 28 with the valve body 29 interposed therebetween. Consists of. The retainer 30 is formed with an opening 31 through which hydraulic oil passes and a claw 32 that urges the valve body 29 toward the valve seat 28. The check valve 25 allows the flow of hydraulic oil in a direction that separates the valve body 29 from the valve seat 28, but prohibits the flow of hydraulic oil in a direction that presses the valve body 29 against the valve seat 28.

  Next, an operation example of the hydraulic auto tensioner 5 will be described.

  When the load on the auxiliary machine fluctuates and the tension of the belt 1 increases, the tension is transmitted to the hydraulic auto tensioner 5 via the pulley arm 3 and the pressure in the pressure chamber 9 increases. When the pressure in the pressure chamber 9 becomes higher than the pressure in the reservoir chamber 10, the hydraulic oil in the pressure chamber 9 flows into the reservoir chamber 10 through the leak gap 23. At this time, since the check valve 25 is closed, the hydraulic oil does not flow through the passage 27. As the hydraulic oil flows through the leak gap 23 in this way, the plunger 8 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 15 are balanced. At this time, since the flow rate of the hydraulic oil flowing through the leak gap 23 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 load of the auxiliary machine fluctuates and the tension of the belt 1 decreases, the pressure of the pressure chamber 9 decreases due to the urging force of the return spring 15. When the pressure in the pressure chamber 9 becomes lower than the pressure in the reservoir chamber 10, the check valve 25 is opened, and the hydraulic oil in the reservoir chamber 10 flows into the pressure chamber 9 through the passage 27. The plunger 8 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 biasing force of the return spring 15 are balanced. Therefore, the tension pulley 2 moves quickly and absorbs the slack of the belt 1 quickly.

  In this hydraulic auto tensioner 5, the lower end portion 11 </ b> A of the rod is press-fitted into the bottomed hole 12 of the plunger 8 so that the rod 11 and the plunger 8 move together. Therefore, there is no need to incorporate a plunger spring that biases the pressure chamber 9 into the pressure chamber 9, and the number of parts is small. Therefore, the structure is simple and the cost is low.

  Further, the air reservoir 16 formed in the bottomed hole 12 when the lower end portion 11 </ b> A of the rod is press-fitted into the bottomed hole 12 relaxes the compression of the air in the bottomed hole 12. Therefore, when the lower end portion 11A of the rod is press-fitted into the bottomed hole 12, the repulsive force due to the air in the bottomed hole 12 is suppressed, and the press-fitted length of the rod 11 is easily stabilized. Moreover, productivity can be improved by increasing the press-fitting speed of the rod 11.

  Further, when the lower end portion 11A of the rod is press-fitted into the bottomed hole 12, the lower end surface of the large-diameter portion 11C comes into contact with the edge of the bottomed hole 12, and the position of the rod 11 with respect to the plunger 8 is press-fitted by the contact. Since it is positioned in the direction, the press-fitting length of the rod 11 is more stable.

  In the above embodiment, the leak gap 23 is used as a passage for forming a throttle between the pressure chamber 9 and the reservoir chamber 10, but the passage for forming the throttle may be provided by another method. For example, a through hole may be formed in the plunger 8 so that the pressure chamber 9 and the reservoir chamber 10 communicate with each other, and an orifice throttle or a choke throttle may be provided in the through hole.

The front view which shows the tension adjustment apparatus incorporating the hydraulic type auto tensioner of embodiment of this invention 1 is a sectional view of the hydraulic auto tensioner of FIG. Fig. 2 is an enlarged sectional view of the vicinity of the upper part of the sleeve of the hydraulic auto tensioner. Sectional view along line IV-IV in FIG. Sectional drawing along the VV line of FIG. Fig. 2 is an enlarged cross-sectional view of the hydraulic auto tensioner near the check valve.

Explanation of symbols

6 Sleeve 7 Cylinder 8 Plunger 9 Pressure chamber 10 Reservoir chamber 11 Rod 11A Lower end 11C Large diameter portion 12 Bottomed hole 15 Return spring 16 Air reservoir 23 Leak gap 25 Check valve 27 Passage

Claims (2)

  Hydraulic oil is stored in a cylinder (7) in which a sleeve (6) is fixed, and a pressure chamber (9) and a reservoir are stored in the cylinder (7) by a plunger (8) slidably inserted into the sleeve (6). The pressure chamber (9) and the reservoir chamber (10) communicate with each other through a first passage (23) that is partitioned into a chamber (10) and forms a throttle, and operates from the reservoir chamber side to the pressure chamber side. The pressure chamber (9) and the reservoir chamber (10) are communicated with each other via the second passage (27) provided with a check valve (25) that allows only the flow of oil, and moved integrally with the plunger (8). A hydraulic auto tensioner provided with a return spring (15) for urging the rod (11) in a direction in which the volume of the pressure chamber (9) is increased. Reservoir chamber end A bottomed hole (12) is formed in the bottomed hole (12), and the end (11A) of the rod (11) is press-fitted into the bottomed hole (12) to fix the rod (11) to the plunger (8), A hydraulic auto-tensioner characterized in that an air reservoir (16) is formed in the bottomed hole (12) in a state where the end (11A) of the rod (11) is press-fitted.   The rod (11) has a large diameter portion (11C) continuous with the end portion (11A), and the end portion (11A) of the rod (11) is press-fitted into the bottomed hole (12). The hydraulic auto tensioner according to claim 1, wherein an end surface of the large diameter portion (11C) is brought into contact with an edge of the bottomed hole (12).

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