JP2008180243A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic automatic tensioner improved in follow-up performance with respect to a change in tensile force of a belt and having a reduced axial length. <P>SOLUTION: A sleeve 13 is installed into a cylinder 11 filled with hydraulic oil, and a flange 14 provided at the lower end of the sleeve is supported by a step part 15 formed at a lower part of the inner periphery of the cylinder. A rod 16 is inserted in the sleeve to partition the inside of the cylinder into a pressure chamber 17 and a reservoir chamber 18. The rod is applied with elastic force of a return spring 21. A plurality of passages 27 serving for communication between the pressure chamber and the reservoir chamber are formed in the flange. A valve disc 29 that closes each passage when the pressure of the pressure chamber becomes higher than that of the reservoir chamber is provided at an opening end part of the passage on the side of the pressure chamber. The valve disc is in a spherical shape so that it can easily separate from the opening end of the passage, thereby enhancing the responsiveness of opening/closing of the valve element to pressure change of the pressure chamber and improving the follow-up performance of the rod with respect to the change in tensile force of the belt. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic auto tensioner used for maintaining tension of a belt for driving an automobile auxiliary machine such as an alternator, a water pump, and an air conditioner compressor.

  In a belt transmission that transmits the rotation of the crankshaft of an engine to various automotive accessories, a swingable pulley arm that supports a tension pulley is provided on the slack side of the accessory driving belt, and a hydraulic auto tensioner is installed on the pulley arm. An adjustment force is applied to urge the pulley arm in a direction in which the tension pulley presses the belt, so that the belt tension is kept constant.

  As a hydraulic auto tensioner used in the belt transmission device as described above, those described in Patent Document 1 and Patent Document 2 are conventionally known. In this hydraulic auto tensioner, an oil seal that prevents leakage of hydraulic oil filled in the cylinder is incorporated in the upper opening of the cylinder in which the sleeve is built, and slidably penetrates the oil seal. A spring seat is provided at the upper end of the rod, and a return spring is built in between the spring seat and the flange provided at the lower outer periphery of the cylinder to give the rod an outward projecting force. The force is buffered by a hydraulic damper provided inside the sleeve.

  Here, the hydraulic damper is provided with a plunger slidable in the sleeve at the lower end portion of the rod, the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, and a passage communicating the pressure chamber and the reservoir chamber with the plunger is provided. The check ball is provided at the pressure chamber side opening of the passage, and when the rod is pushed in and the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, the check ball closes the passage and the hydraulic oil in the pressure chamber closes the rod. The pushing force applied to the is buffered.

JP-A-10-19099 JP-A-10-306860

  By the way, the conventional hydraulic auto tensioner has a long passage in the axial direction because the plunger is formed with a passage communicating with the pressure chamber and the reservoir chamber, and the passage is opened and closed by a check ball. It was necessary to secure a large space for the assembly of the auto tensioner, and there were still points to be improved in order to make the axial length compact.

  The passage formed in the plunger is a single passage. When the inner diameter of the passage is reduced, the flow resistance of the hydraulic oil increases and the hydraulic oil does not flow smoothly from the reservoir chamber to the pressure chamber, and the belt tension changes. The followability of the rod with respect to becomes worse. Therefore, it is necessary to form a relatively large passage in the plunger, and accordingly, it is necessary to adopt a check ball having a large sphere diameter, which increases the weight of the check ball and the response of the check ball with high frequency vibration. However, there is still a point to be improved in order to improve the response.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a compact hydraulic auto tensioner having an axial length that has good followability to changes in belt tension.

  In order to solve the above problems, in the present invention, a sleeve is incorporated into a bottomed cylinder filled with hydraulic oil, and the outer peripheral portion of the lower surface of the outward flange formed at the lower end of the sleeve is provided. The lower end of the rod is slidably inserted into the sleeve, and the cylinder is divided into a pressure chamber and a reservoir chamber. A return spring is attached to the rod. The elastic force is applied to urge the rod in a direction in which the volume of the pressure chamber formed below the flange increases, and the flange communicates with the reservoir chamber provided above the flange. And a spherical valve element that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber is employed at the opening on the pressure chamber side of each passage.

  As described above, a flange is provided at the lower end portion of the sleeve into which the lower end portion of the rod is slidably inserted, and a passage communicating the pressure chamber and the reservoir chamber is formed in the flange, and the passage is opened and closed by the valve body. As a result, the axial length can be made compact compared to a hydraulic auto tensioner in which a passage is formed in the plunger below the rod and the passage is opened and closed by a check ball.

  Also, if the valve body is a plate-like one that comes into surface contact with the lower surface of the flange and closes the passage, the resistance at the time of separation increases due to the adsorption action of the oil film intervening on the contact surface, so that the valve body is Although it is difficult to separate, the use of a spherical valve body closes the passage while the valve body is in line contact with the open end of the passage, so the resistance when the valve body is separated is small, and the pressure fluctuation in the pressure chamber Accordingly, the valve body smoothly opens and closes, and a hydraulic auto tensioner with good followability of the rod against changes in belt tension can be obtained.

  In addition, since a plurality of passages are provided in the flange at the lower end of the sleeve, and a valve body is provided for each passage, the hydraulic oil in the reservoir chamber flows from each of the plurality of passages to the pressure chamber when the pressure in the pressure chamber drops. Therefore, the passage diameter can be reduced as compared with the case where the hydraulic oil in the reservoir chamber flows to the pressure chamber through a single passage. As the diameter of the passage is reduced, a light valve having a small sphere diameter can be adopted, so that the responsiveness of the passage opening / closing valve body with high-frequency vibration can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a belt tension adjusting device. As shown in the figure, the pulley arm 1 is supported so as to be swingable about a fulcrum shaft 2, and a tension pulley 4 that applies tension to the belt 3 is rotatably supported at the end of the swing side.

  Further, a hydraulic auto tensioner 10 according to the present invention is connected to the pulley arm 1, and the pulley arm 1 is urged by the hydraulic auto tensioner 10 in a direction in which the tension pulley 4 presses the belt 3.

  As shown in FIG. 2, the hydraulic auto tensioner 10 has a bottomed cylindrical cylinder 11 whose upper end is open, and the cylinder 11 is filled with hydraulic oil. A connecting piece 12 connected to the engine block A is provided on the lower surface of the cylinder 11.

  A sleeve 13 is incorporated in the cylinder 11. The sleeve 13 has an outward flange 14 at its lower end, and the outer periphery of the lower surface of the flange 14 is supported by a step portion 15 formed at the lower inner periphery of the cylinder 11.

  A lower end portion of a rod 16 is slidably inserted into the sleeve 13, and the inside of the cylinder 11 is partitioned into a pressure chamber 17 and a reservoir chamber 18 by the rod 16 and the sleeve 13.

  A connecting piece 19 that is connected to the pulley arm 1 is connected to an upper end portion of the rod 16 that is located outside the upper end opening of the cylinder 11. Further, a cylindrical dust cover 20 whose upper end is closed is attached to the upper end of the rod 16 at a position below the connecting piece 19 by means of press fitting, and the dust cover 20 covers the upper outer periphery of the cylinder 11. It has been broken.

  A return spring 21 is incorporated between the upper closed end of the dust cover 20 and the flange 14 of the sleeve 13. The return spring 21 urges the rod 16 in the direction in which the volume of the pressure chamber 17 provided below the flange 14 increases.

  An annular seal groove 23 is formed in the upper outer periphery of the cylinder 11, and the elastic seal ring 24 incorporated in the seal groove 23 is in elastic contact with the inner periphery of the dust cover 20, The hydraulic oil is prevented from leaking to the outside from between the opposing surfaces of the cylinder 11 and the dust cover 20.

  An annular protrusion 25 is formed on the upper outer periphery of the cylinder 11 below the seal groove 23, while a retaining claw 26 is provided on the lower inner periphery of the dust cover 20. The abutment of the retaining claw 26 against the rod 16 prevents the rod 16 from coming out of the cylinder 11.

  As shown in FIGS. 3 to 5, the flange 14 of the sleeve 13 is formed with a plurality of passages 27 communicating with the pressure chamber 17 and the reservoir chamber 18 on the same circle, and the openings on the pressure chamber 17 side of each passage 27. A tapered seat surface 28 is formed at the end, and a spherical valve element 29 is provided on each seat surface 28 so as to be able to contact and separate.

  When the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18, the valve body 29 comes into contact with the seat surface 28 to close the passage 27, and each valve body 29 is provided on the lower surface side of the flange 14. The open / close amount is limited by the retainer 30.

  The belt tension adjusting device shown in the embodiment has the above-described structure, and the tension of the belt 3 changes due to the load fluctuation of the auxiliary machine driven by the belt 3 and the change of the angular velocity of the crankshaft, and the belt 3 is slack. When it occurs, the rod 16 moves outward by the pressing of the return spring 21 and absorbs the slack of the belt 3.

  At this time, when the volume of the pressure chamber 17 increases and the pressure decreases and the pressure becomes lower than the pressure of the reservoir chamber 18, the valve element 29 moves away from the seat surface 28 as shown in FIG. In order to open, the hydraulic oil in the reservoir chamber 18 flows into the pressure chamber 17 from the passage 27 and the minute leak gap 31 formed between the sliding surface of the rod 16 and the sleeve 13, and the rod 16 rapidly moves outward. It moves and absorbs the slack of the belt 3 immediately.

  On the other hand, when the tension of the belt 3 increases, a pushing force is applied from the belt 3 to the rod 16. At this time, since the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18, the valve body 29 comes into contact with the seat surface 28 to close the passage 27 and is enclosed in the pressure chamber 17 as shown in FIG. The pushing force applied to the rod 16 is buffered by the hydraulic oil.

  When the pushing force is larger than the elastic force of the return spring 21, the hydraulic oil in the pressure chamber 17 flows into the reservoir chamber 18 from a minute leak gap 31 formed between the sliding surfaces of the sleeve 13 and the rod 16, and the pushing force The rod 16 is slowly retracted to a position where the elastic force of the return spring 21 is balanced, and the tension of the belt 3 is kept constant.

  As shown in the embodiment, a flange 14 is provided at the lower end of the sleeve 13 into which the lower end of the rod 16 is slidably inserted, and a passage 27 for communicating the pressure chamber 17 and the reservoir chamber 18 is formed in the flange 14. Then, by opening and closing the passage 27 with the valve body 29, the plunger of the hydraulic auto tensioner shown in Patent Document 1 and Patent Document 2 described above can be omitted, and the axial direction of the hydraulic auto tensioner is correspondingly reduced. The length can be made compact.

  Here, if the valve element 29 that opens and closes the passage 27 is a plate-like member that comes into surface contact with the lower surface of the flange 14 to close the passage, the resistance at the time of separation is large due to the adsorption action of the oil film interposed on the contact surface. Thus, the valve body 29 is difficult to separate from the lower surface of the flange 14. In the embodiment, the valve body 29 is formed in a spherical shape, and the passage 27 is closed in a state where the spherical valve body 29 is in line contact with the tapered seat surface 28 formed at the opening end of the passage 27. The resistance when the valve body 29 is separated is small. For this reason, the valve element 29 opens and closes smoothly according to the pressure fluctuation of the pressure chamber 17, and a hydraulic auto tensioner with good followability of the rod 16 against the tension change of the belt 3 can be obtained.

  In addition, since the plurality of passages 27 are provided in the flange 14 at the lower end of the sleeve 13 and the valve body 29 is provided for each passage 27, the hydraulic oil in the reservoir chamber 18 is supplied to the passages when the pressure in the pressure chamber 17 decreases. 27 flows from each of the pressure chambers 17 to the pressure chamber 17. Therefore, the inner diameter of the passage 27 can be reduced compared with the case where the hydraulic oil in the reservoir chamber is caused to flow into the pressure chamber by a single passage, and the valve element 29 also corresponds to the reduction in the diameter of the passage 27. Since a light bulb having a small sphere diameter can be employed, the response of the passage opening / closing valve element 29 with high-frequency vibration can be improved.

Front view showing a belt tension adjusting device using a hydraulic auto tensioner according to the present invention. Sectional view along the line II-II in FIG. Sectional drawing which expands and shows the cylinder lower end part of the hydraulic auto tensioner shown in FIG. Sectional view along line IV-IV in FIG. Sectional drawing which expands and shows the valve body incorporation part of FIG. Sectional view showing the open state of the valve

Explanation of symbols

11 Cylinder 13 Sleeve 14 Flange 15 Step 16 Rod 17 Pressure chamber 18 Reservoir chamber 21 Return spring 27 Passage 29 Valve body

Claims (1)

  A sleeve is built into a bottomed cylinder filled with hydraulic oil inside, and the outer periphery of the lower surface of the outward flange formed at the lower end of the sleeve is supported by a step provided at the lower inner periphery of the cylinder. The lower end of the rod is slidably inserted into the sleeve, the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, and the elastic force of a return spring is applied to the rod, so that it is formed below the flange. The rod is urged in the direction in which the volume of the pressure chamber expands, and a plurality of passages are formed in the flange for communicating the pressure chamber and a reservoir chamber provided above the flange. A hydraulic auto tensioner provided with a spherical valve body that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber.

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