JP2008180269A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the axial length of a hydraulic automatic tensioner and prevent deficiency in supply of hydraulic oil to a pressure chamber 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 passage 26 serving for communication between the pressure chamber 17 and a reservoir chamber 18 is formed in a flange 14. The passage 26 is adapted to be opened and closed by a valve disc 27 provided below the flange 14, thereby reducing the axial length of the hydraulic automatic tensioner. The valve disc 27 is urged by a resilient member 29 in a direction that the valve disc 27 is separated from a lower face of the flange 14. The valve disc 27 is immediately released when the pressure in the pressure chamber 17 is decreased so as to prevent a delay in opening of the valve element 27 in the region where a belt vibrates at high frequency and also prevent a reduction in load of the hydraulic damper by the hydraulic oil in the pressure chamber 17. <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. The axial length of the cylinder is made compact and the opening of the valve body in the high frequency range is improved to prevent insufficient supply of hydraulic oil to the pressure chamber, reducing the hydraulic damper load when the rod is pushed in It is to suppress.

  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. A rod is urged in a direction in which the volume of the pressure chamber formed below the flange is increased by applying an elastic force, and the flange has a plurality of passages communicating the pressure chamber and the reservoir chamber provided above the flange. A valve body is provided below the flange to move toward the lower surface of the flange to close the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, and the elastic force of the elastic member is applied to the valve body. Given to it had adopted a configuration in which urges the valve body in the opening direction.

  In the hydraulic auto tensioner having the above-described configuration, a rod is connected to a pulley arm that is swingably supported, and the tension pulley that is rotatably supported by the pulley arm biases the pulley arm toward the direction in which the belt is pressed. To do.

  In the state where the hydraulic auto tensioner is incorporated as described above, when the belt vibrates due to a load change and the belt tension increases and the rod is pushed in, the pressure in the pressure chamber rises. When the pressure becomes higher than the pressure in the reservoir chamber, the valve body moves toward the lower surface of the flange to close the passage, and the pushing force applied to the rod is buffered by the hydraulic oil sealed in the pressure chamber.

  On the other hand, when slack occurs in the belt, the rod moves in the direction in which the volume of the pressure chamber increases, and absorbs the slack in the belt. At this time, since the pressure in the pressure chamber decreases, the valve element moves away from the lower surface of the flange to open the passage, and the hydraulic oil in the reservoir chamber flows from the passage into the pressure chamber. At this time, since the valve body is urged away from the lower surface of the flange by the elastic member, the valve body is released at the same time as the pressure in the pressure chamber is reduced, and there is no delay in opening.

  For this reason, in the region where the belt vibrates at high frequency, there is no inconvenience of insufficient supply of hydraulic oil to the pressure chamber, and it is possible to suppress a decrease in the hydraulic damper load due to the hydraulic oil in the pressure chamber when the rod is pushed in. Can do.

  Here, the valve body that opens and closes the passage may be made of an annular plate that can be brought into contact with and separated from the lower surface of the flange and simultaneously closes the plurality of passages at the time of contact, or made of a ball. It may be.

  When a valve body made of an annular plate is employed, the passage may be an arc-shaped long hole arranged on the same circle, or a circular hole. On the other hand, in the case of a valve body made of a ball, the passage is a circular hole, and a valve body made of a ball is provided so as to face each of the passages made of the circular hole.

  In the case of adopting a valve body made of an annular plate, if an annular groove is formed on the upper surface facing the lower surface of the flange of the valve body, the contact area with the lower surface of the flange can be reduced. The adsorption force of the oil film interposed between the contact surfaces of the valve body and the flange can be reduced, and the delay in opening the valve body can be further improved.

  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 plurality of passages are formed in the flange to communicate the pressure chamber and the reservoir chamber. By opening and closing, a passage is formed in the plunger provided at the lower part of the rod, and the axial length can be made compact compared to a hydraulic auto tensioner in which the passage is opened and closed by a valve body. .

  In addition, when the valve body is urged toward the opening direction by the elastic member, the valve body is opened simultaneously with the pressure drop of the pressure chamber, and the valve body is delayed in the region where the belt vibrates at high frequency. There is no. Therefore, there is no inconvenience of insufficient supply of hydraulic oil into the pressure chamber in the region where the belt vibrates at high frequency, and it is possible to suppress a decrease in the hydraulic damper load due to the hydraulic oil in the pressure chamber when the rod is pushed in. it can.

  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 22 is formed on the outer periphery of the upper portion of the cylinder 11, and the elastic seal ring 23 incorporated in the seal groove 22 is in elastic contact with the inner periphery of the dust cover 20, so The hydraulic oil is prevented from leaking to the outside from between the opposing surfaces of the cylinder 11 and the dust cover 20.

  In addition, an annular protrusion 24 is formed on the lower outer periphery of the seal groove 22 on the upper outer periphery of the cylinder 11, while a retaining protrusion 25 is provided on the lower inner periphery of the dust cover 20. The contact of the retaining projection 25 with respect to 24 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 26 formed of circular stepped holes having a large diameter at the lower portion on the same circle, and the pressure chamber 17 is passed through the passages 26. And the reservoir chamber 18 are communicated with each other. An opening / closing valve element 27 for the passage 26 is provided below the flange 14.

  The valve body 27 is formed of an annular plate, and an annular groove 28 is formed on the upper surface facing the lower surface of the flange 14. The valve body 27 can be brought into contact with and separated from the lower surface of the flange 14 and is guided by the inner diameter surface of the pressure chamber 17 during movement. The valve body 27 is closed in a closed state in which the upper surface of the inner annular wall 28 a formed on the inner periphery of the annular groove 28 and the upper surface of the outer annular wall 28 b formed outside the annular groove 28 are in contact with the lower surface of the flange 14. These passages 26 are closed simultaneously.

  An elastic member 29 made of a spring is incorporated in each of the plurality of passages 26, and the valve element 27 is urged by the elastic member 29 in a direction away from the lower surface of the flange 14 (opening direction).

  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 tension of the belt 3 becomes large. Then, a pushing force is applied from the belt 3 to the rod 16.

  At this time, the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18, and when the pressure in the pressure chamber 17 exceeds the sum of the elastic forces of the plurality of elastic members 29, the valve element 27 faces the lower surface of the flange 14. Moving. As shown in FIG. 3, when the upper surfaces of the inner annular wall 28 a and the outer annular wall 28 b of the valve body 27 come into contact with the lower surface of the flange 14, the plurality of passages 26 are simultaneously closed by the valve body 27. The pushing force applied to the rod 16 is buffered by the hydraulic oil sealed in the cylinder 17.

  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 30 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.

  On the other hand, when slack occurs in the belt 3, the rod 16 moves in a direction in which the volume of the pressure chamber 17 increases due to the pressure of the return spring 21, and absorbs slack in the belt 3. At this time, since the pressure in the pressure chamber 17 decreases, the valve element 27 moves in a direction away from the lower surface of the flange 14 to open the passage 26 as shown in FIG.

  For this reason, the hydraulic oil in the reservoir chamber 18 flows into the pressure chamber 17 from the minute leak gap 30 formed between the sliding surface of the passage 26 and the sleeve 13 and the rod 16, and the rod 16 moves rapidly outward. Then, the slack of the belt 3 is immediately absorbed.

  Here, since the valve body 27 is urged in a direction away from the lower surface of the flange 14 by the elastic member 29, the valve body 27 is instantaneously opened simultaneously with the pressure drop in the pressure chamber 17, causing a delay in opening. There is no such thing.

  Therefore, even in the region where the belt 3 vibrates at a high frequency, there is no inconvenience that insufficient supply of hydraulic oil to the pressure chamber 17 occurs, and the hydraulic damper load due to the hydraulic oil in the pressure chamber 17 when the rod 16 is pushed in. Therefore, the change in the belt tension can be reliably absorbed by the hydraulic oil in the pressure chamber 17.

  Like the hydraulic auto tensioner shown in FIGS. 2 and 3, 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 pressure chamber 17 and a reservoir chamber 18 are provided in the flange 14. Is formed by opening and closing the passage 26 with the valve body 27, so that the plunger of the hydraulic auto tensioner shown in Patent Document 1 and Patent Document 2 can be omitted. The axial length of the hydraulic auto tensioner can be made compact.

  In FIG. 3, the passage 26 is formed of a circular stepped hole, but is not limited thereto, and may be, for example, an arc-shaped long hole arranged on the same circle. Good.

  3 and 4 show the valve body 27 made of an annular plate, but as shown in FIGS. 7 and 8, a valve body 27 made of a ball may be adopted. When the valve body 27 made of a ball is employed, the valve body 27 is provided to face each of the plurality of passages 26. Further, the retainer 31 is press-fitted into the inner diameter surface of the pressure chamber 17 to regulate the opening / closing amount of the valve element 27.

  The material of the valve body 27 is arbitrary, and examples thereof include steel, aluminum, titanium, magnesium, ceramic, resin, and rubber.

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 Sectional drawing which shows other embodiment of the hydraulic auto tensioner which concerns on this invention Sectional drawing which expands and shows a part of FIG.

Explanation of symbols

11 Cylinder 13 Sleeve 14 Flange 15 Step 16 Rod 17 Pressure chamber 18 Reservoir chamber 21 Return spring 26 Passage 27 Valve element 28 Annular groove 29 Elastic member

Claims (4)

  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, and the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, and a resilient force of a return spring is applied to the rod to form a pressure chamber formed below the flange. The flange is urged in the direction in which the volume increases, and the flange is provided with a plurality of passages communicating with the pressure chamber and the reservoir chamber provided above the flange, and the pressure in the pressure chamber is below the flange. When the pressure in the reservoir chamber becomes higher, a hydraulic valve is provided that moves toward the lower surface of the flange and closes the passage, and applies the elastic force of the elastic member to the valve body to urge the valve body in the opening direction. Oh Tensioner.   2. The hydraulic auto tensioner according to claim 1, wherein the valve body is formed of an annular plate that can be contacted and separated from a lower surface of the flange and simultaneously closes a plurality of passages at the time of contact.   The hydraulic auto tensioner according to claim 2, wherein an annular groove is formed on an upper surface of the valve body facing a lower surface of the flange.   2. The hydraulic auto tensioner according to claim 1, wherein the passage is a circular hole, and a valve body that opens and closes the passage includes a ball provided to face each of the plurality of passages.

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