JP2008045692A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compact the axial length of a hydraulic automatic tensioner opening/closing a passage serving for communication between a pressure chamber and a reservoir chamber by a check valve to buffer press-in force loaded to a rod by a hydraulic oil sealed in the pressure chamber. <P>SOLUTION: A sleeve 13 is assembled into a cylinder 11 filled with the hydraulic oil, and a flange 14 provided at the lower end of the sleeve 13 is supported by a step part 15 formed at a lower part of the inner periphery of the cylinder 11. A rod 16 is inserted in the sleeve 13 to partition the inside of the cylinder 11 into the pressure chamber 17 and the reservoir chamber 18. The rod 16 is biased by a return spring 21. A arcuate passage 27 serving for communication between the pressure chamber 17 and the reservoir chamber 18 is formed in the flange 14. A valve element 32 of the check valve 30 opening/closing the arcuate passage 27 is provided to freely get into contact with and separate from a seat surface 31 formed at the lower face of the flange 14, and the valve element 32 is biased by a valve spring 33. <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 that communicates the pressure chamber and the reservoir chamber with the plunger is provided. The check valve is provided in the opening on the pressure chamber side of the passage, and when the rod is pushed and the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, the passage is closed by the check valve 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, in the conventional hydraulic auto tensioner, a passage communicating the pressure chamber and the reservoir chamber is formed in the plunger provided at the lower portion of the rod, and the passage is opened and closed by the check valve. The length was long, and it was necessary to secure a large space for the assembly of the hydraulic auto tensioner, and there were 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 check valve so as to buffer a pushing force applied to a rod by hydraulic oil sealed in the pressure chamber. The axial length of the hydraulic chamber is reduced, and the inertia of the check valve is reduced in the use situation in the high-amplitude high-frequency region where the belt vibrates at high frequency. It is to be able to prevent a shortage of return oil.

  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 rod is urged in the direction in which the volume of the pressure chamber formed below the flange expands, and the flange has a passage communicating the pressure chamber and the reservoir chamber provided above the flange. A check valve is provided at the opening on the pressure chamber side of the passage to close the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, and the check valve is formed on the bottom surface of the flange. A ring-shaped valve body that closes the passage when in contact, and a valve spring that biases the valve body toward the seat surface. A configuration made of a small material was adopted.

  Here, a synthetic resin or ceramics can be mentioned as a material having a specific gravity smaller than that of a metal.

  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 that connects the pressure chamber and the reservoir chamber is formed in the flange, and the passage is opened and closed by the check valve. As a result, the axial length can be reduced compared to a hydraulic auto tensioner in which a passage is formed in a plunger provided at the lower portion of the rod and the passage is opened and closed by a check valve.

  In addition, because the valve body of the check valve is made of a material having a specific gravity smaller than that of metal such as synthetic resin or ceramics, the mass of the valve body is smaller than that of a metal valve body. The check valve can be opened and closed sensitively in response to changes in pressure in the pressure chamber.

  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 the belt tension change can be reliably absorbed by the hydraulic fluid in the pressure chamber.

  In addition, the valve body can be enlarged and the cross-sectional area of the passage can be increased because the mass of the valve body is small, and the hydraulic oil in the reservoir chamber can smoothly flow into the pressure chamber when the belt has a large amplitude. Can do.

  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 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. A spring seat 20 is fixed to the lower end of the connecting piece 19 at the upper end of the rod 16, and a return spring 21 is incorporated between the spring seat 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.

  The spring seat 20 has a cylindrical portion 22 covering the upper outer periphery of the cylinder 11 on the outer periphery. On the other hand, an annular seal groove 23 is formed on the outer periphery of the upper portion of the cylinder 11, and an elastic seal ring 24 incorporated in the seal groove 23 comes into elastic contact with the inner periphery of the cylindrical portion 22, so that the reservoir chamber 18. The inside hydraulic oil is prevented from leaking to the outside from between the fitting surfaces of the cylinder 11 and the cylindrical portion 22.

  Further, an annular protrusion 25 is formed on the lower outer periphery of the seal groove 23 on the upper outer periphery of the cylinder 11. On the other hand, a retaining claw 26 is provided on the inner peripheral lower portion of the cylindrical part 22. 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 and 4, 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. A check valve 30 that closes the passage 27 when the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18 is provided in the opening on the side.

  The check valve 30 has a lower surface of the flange 14 as a seat surface 31, and a ring-shaped valve body 32 having a square cross section is provided in contact with and separated from the seat surface 31. The valve body 32 is seated by a valve spring 33. When the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18 by urging toward the surface 31, the valve body 32 is brought into contact with the seat surface 31 to close the passage 27.

  Here, the valve body 32 is formed of a material having a specific gravity smaller than that of metal. Examples of such materials include synthetic resins and ceramics.

  Further, as the valve spring 33, here, a thin metal plate press in which a plurality of inward elastic pieces 33b are formed at equal intervals in the circumferential direction at the lower end edge of the annular portion 33a press-fitted into the inner periphery of the pressure chamber 17 is used. A molded product is used and the valve element 32 is urged toward the seat surface 31 by the elastic piece 33b. However, a disc spring or a coil spring may be used.

  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 is increased and the pressure is decreased and the pressure is lower than the pressure of the reservoir chamber 18, the valve body 32 of the check valve 30 is separated from the seat surface 31 as shown in FIG. In order to open the passage 27, the hydraulic oil in the reservoir chamber 18 flows from the passage 27 to the pressure chamber 17, and the rod 16 rapidly moves outward to absorb 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 32 of the check valve 30 contacts the seat surface 31 to close the passage 27, and the hydraulic oil sealed in the pressure chamber 17 The pushing force applied to the rod 16 is buffered.

  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 through a minute leak gap b 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 check valve 30, 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 correspondingly. The length can be made compact.

  Further, since the valve body 32 of the check valve 30 is formed of a material having a specific gravity smaller than that of a metal such as synthetic resin or ceramics, the mass of the valve body 32 is smaller than that of a metal valve body. The check valve 30 can be opened and closed in a sensitive manner according to the pressure change in the pressure chamber 17 while smoothly following the pressure change in the pressure chamber 17 and less influenced by the inertia of the behavior of the valve element 32.

  For this reason, even if the belt 3 vibrates at high frequency, there is no inconvenience of insufficient supply of hydraulic oil into the pressure chamber 17, and the change in belt tension is reliably absorbed by the hydraulic oil in the pressure chamber 17. Can do.

  Further, since the mass of the valve body 32 is small, the valve body 32 can be enlarged, and the cross-sectional area of the passage 27 can be increased, so that the hydraulic oil in the reservoir chamber 18 is supplied to the pressure chamber when the belt 3 has a large amplitude. 17 can flow smoothly.

  FIG. 6 shows another example of the check valve 30. In this example, a ring groove 34 communicating with each passage 27 is formed on the lower surface of the flange 14 in which a plurality of arc-shaped passages 27 are formed on the same circle, and the inside of the opening on the pressure chamber 17 side of the ring groove 34 is formed. A ring-shaped valve body 32 made of synthetic resin or ceramics is provided in contact with and separated from a pair of annular seat surfaces 35 formed on the periphery and the outer periphery, and the valve body 32 is seated by a valve spring 33 on the seat surface 35. When the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18, the valve body 32 is brought into contact with the seat surface 35 to close the passage 27.

  Here, the seat surface 35 is arc-shaped in cross section, while the upper surface 32a of the valve body 32 facing the seat surface 35 is also arc-shaped, and the arc-shaped upper surface 32a is brought into line contact with the arc-shaped sheet surface 35. The passage 27 is closed.

  As described above, the seat surface 35 has an arcuate cross section, the arcuate upper surface 32a of the valve body 32 is brought into contact with the arcuate sheet surface 35, and the contact between the seat surface 35 and the valve body 32 is made a line contact. As a result, the valve body 32 is easily separated from the seat surface 35, and the valve body 32 opens and closes smoothly according to the pressure fluctuation in the pressure chamber 17, and the hydraulic auto tensioner with good followability of the rod 16 against the tension change of the belt 3 is achieved. Can be obtained.

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. Enlarged cross-sectional view of the check valve section of the hydraulic auto tensioner shown in FIG. Sectional view along line IV-IV in FIG. Sectional view showing the open state of the check valve Sectional view showing another example of check 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 30 Check valve 31 Seat surface 32 Valve element 33 Valve spring

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, the inside of the cylinder is divided into a pressure chamber and a reservoir chamber, and the elastic force of a return spring is applied to the rod to form the lower part of the flange. The rod is urged in the direction in which the volume of the pressure chamber expands, and a passage is provided in the flange for communicating the pressure chamber and a reservoir chamber provided above the flange, and the pressure chamber has an opening on the pressure chamber side. When the pressure in the chamber becomes higher than the pressure in the reservoir chamber, a check valve that closes the passage is provided, and the check valve can be brought into contact with and separated from the seat surface formed on the lower surface of the flange. A ring-shaped valve element for closing the road consists of a valve spring for urging the valve element on the seat surface, hydraulic auto-tensioner of the valve body is formed with a material having a small specific gravity than metal.   The hydraulic auto tensioner according to claim 1, wherein the valve body is made of synthetic resin or ceramics.

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