JP2008180242A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the axial length of a hydraulic automatic tensioner and prevent a deficiency in supply of hydraulic oil by facilitating opening of a valve disc in a high-frequency region so as to prevent a reduction in load of a hydraulic damper. <P>SOLUTION: A sleeve 13 is installed into a cylinder 11 filled with the 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. An arcuate passage 27 serving for communication between the pressure chamber and the reservoir chamber is formed in the flange. The passage is adapted to be opened and closed by the ring-like valve element 28 provided at a lower part of the flange, thereby reducing the axial length of the hydraulic automatic tensioner. The valve disc is adapted to move to an opening position by its own weight when the pressure in the pressure chamber is decreased, so as to prevent a delay in opening of the valve disc in the high-frequency region and also to prevent a reduction in load of the hydraulic damper by the hydraulic oil in the pressure chamber. <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. If the rod is pushed in and the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, the passage is closed by the valve body of the check valve, and the operation in the pressure chamber is The pushing force applied to the rod by the oil is buffered.

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

  By the way, the conventional hydraulic auto tensioner forms a passage communicating with the pressure chamber and the reservoir chamber in the plunger provided at the lower portion of the rod, and the passage is opened and closed by the valve body of the check valve. Since the axial length is long, it is necessary to secure a large space for assembling the hydraulic auto tensioner, and there are still points to be improved in order to make the axial length compact.

  An object of the present invention is to provide a hydraulic auto-tensioner that opens and closes a passage that connects a pressure chamber and a reservoir chamber by a valve body, and buffers a pushing force applied to a rod by hydraulic oil sealed in the pressure chamber. And reducing the hydraulic damper load by improving the opening of the valve body in the high frequency region to prevent insufficient supply of hydraulic oil to the pressure chamber.

  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 inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber. Applying elastic force to urge the rod in a direction in which the volume of the pressure chamber formed below the flange expands, the flange is provided with a passage communicating the pressure chamber and the reservoir chamber provided above the flange, A configuration in which a ring-shaped valve body is provided below the flange so as to be in contact with and away from the lower surface of the flange and closes the passage upon contact is adopted.

  Here, by providing a regulating step for restricting the opening amount of the valve body on the inner periphery of the pressure chamber so that the opening / closing amount of the valve body is 0.2 mm or less, the valve body is immediately closed as the pressure in the pressure chamber rises. Returning to the position, it is possible to prevent delay in closing the valve body in the high frequency region.

  As described above, a flange is provided at the lower end of the sleeve into which the lower end 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 formed as a ring-shaped valve body. It is possible to reduce the axial length compared to a hydraulic auto tensioner in which a passage is formed in the plunger provided at the lower part of the rod and the passage is opened and closed by a valve body. it can.

  Here, when the valve body is configured to be biased toward the closed position by the valve spring, the valve body is difficult to open, the valve body is delayed in the high frequency region, and the supply of hydraulic oil to the pressure chamber is insufficient. The hydraulic damper load is reduced and the valve body is maintained in a closed state only by the pressure of the hydraulic oil in the pressure chamber, and when the pressure in the pressure chamber decreases, the valve body moves to the open position by its own weight. In the high frequency region, the valve body is easy to open, and there is no possibility of delaying the opening. Therefore, even if the belt vibrates at a high frequency, there is no inconvenience of insufficient supply of hydraulic oil into the pressure chamber, and a decrease in the hydraulic damper load can be suppressed.

  Further, since the opening / closing amount of the valve body is set to 0.2 mm or less, the valve body can be prevented from being delayed in closing, and the valve body can be opened / closed smoothly with respect to the pressure change in the pressure chamber. The effect of suppressing the decrease in load can be further enhanced.

  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.

  Further, an annular protrusion 25 is formed on the upper outer periphery of the cylinder 11 below the seal groove 23, while a retaining protrusion 26 is provided on the lower inner periphery of the dust cover 20. The contact of the retaining projection 26 with respect to 25 prevents the rod 16 from coming out of the cylinder 11.

  As shown in FIGS. 3 to 5, a plurality of arc-shaped passages 27 communicating with the pressure chamber 17 and the reservoir chamber 18 are formed on the same circle in the flange 14 of the sleeve 13. An opening / closing valve element 28 for the passage 27 is provided below the flange 14.

  The valve body 28 has a ring shape, and an annular groove 29 is formed on the upper surface facing the lower surface of the flange 14. Further, the valve body 28 can be brought into contact with and separated from the lower surface of the flange 14. When the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18, the flange 14 is in contact with and guided by the inner diameter surface of the pressure chamber 17. The upper surface of the inner annular wall 29a formed on the inner periphery of the annular groove 29 and the upper surface of the outer annular wall 29b formed on the outer side of the annular groove 29 are in contact with the lower surface of the flange 14, and a plurality of passages 27 is closed at the same time.

  The opening amount of the valve body 28 is limited by a regulation step portion 30 formed on the inner periphery of the pressure chamber 17. Here, when the opening / closing amount S of the valve body 28 exceeds 0.2 mm, the closing delay occurs with respect to the vibration in the high frequency region of the belt 3, and the hydraulic damper load due to the hydraulic oil in the pressure chamber 17 is reduced. Become. In order to suppress the decrease in the hydraulic damper load, the opening / closing amount S of the valve body 28 is restricted to 0.2 mm or less.

  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 28 is separated from the lower surface of the flange 14 as shown in FIG. Therefore, the hydraulic oil in the reservoir chamber 18 flows into the pressure chamber 17 through the passage 27 and a minute leak gap 31 formed between the sliding surface of the sleeve 13 and the rod 16, and the rod 16 rapidly moves outward. The slack of the belt 3 is immediately absorbed.

  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 28 contacts the lower surface of the flange 14 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 operating 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 ring-shaped valve body 28, the plunger of the hydraulic auto tensioner shown in the above-mentioned Patent Document 1 and Patent Document 2 can be omitted, and the hydraulic auto tensioner correspondingly. The axial length can be made compact.

  Further, the valve body 28 is closed by the pressure of the hydraulic oil in the pressure chamber 17, and when the pressure in the pressure chamber 17 decreases, the valve body 28 moves to the open position by its own weight. There will be no delay. For this reason, even if the belt vibrates at a high frequency, there is no inconvenience that insufficient supply of hydraulic oil to the pressure chamber occurs, and a decrease in the hydraulic damper load is suppressed. Can be reliably absorbed.

  Furthermore, by setting the opening / closing amount of the valve body 28 to 0.2 mm or less, it is possible to prevent the valve body 28 from being delayed in closing, and to smoothly open / close the valve body 28 against the pressure change in the pressure chamber 17. This can further enhance the effect of suppressing the decrease in the hydraulic damper load.

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 28 Valve element 30 Regulating step

Claims (2)

  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 to divide the inside of the cylinder into a pressure chamber and a reservoir chamber. The flange is urged in the direction in which the volume increases, and the flange is provided with a passage communicating with the pressure chamber and the reservoir chamber provided above the flange, and below the flange with respect to the lower surface of the flange A hydraulic auto-tensioner provided with a ring-shaped valve element that can be contacted and separated and closes the passage when contacted.   2. The hydraulic auto tensioner according to claim 1, wherein a regulation step portion for restricting an opening amount of the valve body is provided on an inner periphery of the pressure chamber so that an opening / closing amount of the valve body is set to 0.2 mm or less.

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