JP2008175271A - Hydraulic auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axially compact hydraulic auto tensioner preventing the leakage of operating oil to the outside. <P>SOLUTION: The axially compact hydraulic auto tensioner comprises a flange 14 having a passage 27 for communicating a pressure chamber 17 with a reservoir chamber 18, the passage 27 being opened/closed with a check valve 30. An O-ring 23 is incorporated between the opposed faces of a dust cover 20 and a cylinder 11 for sealing. A return passage 24 is formed ranging from a position of incorporating the O-ring 23 to a one-sided position at the upper side opening end of a cylinder 11. Thereby, the operating oil leaking from the upper side opening end of the cylinder 11 to the outside is returned from the return passage 24 to the inside of the cylinder 11 to improve the reliability on the leakage of the operating oil. <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 compact hydraulic auto tensioner having an axial length which can prevent leakage of hydraulic oil to the outside.

  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 cylinder 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 cylinder is partitioned into a pressure chamber and a reservoir chamber, and the cylinder of the rod A cylindrical dust cover whose upper part is closed is attached to the upper end part located outside from the upper opening of the cylinder to cover the upper outer periphery of the cylinder, and a return spring is incorporated between the closed end of the dust cover and the flange of the sleeve. The rod is urged in the direction of increasing the volume of the pressure chamber formed below, a seal groove is formed in the upper periphery of the cylinder, and an O-ring is incorporated in the seal groove. A seal is provided between the inner diameter surface of the cover and the outer diameter surface of the cylinder, and a return passage is provided to communicate the inside and outside of the cylinder at a position offset from the O ring assembly position on the upper opening end side of the cylinder. A passage that connects the pressure chamber and the reservoir chamber provided above the flange is provided, and a check valve that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber is provided in the opening on the pressure chamber side of the passage. The configuration was adopted.

  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 check valve closes the passage, and the pushing force applied to the rod by the hydraulic oil sealed in the pressure chamber is buffered.

  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 check valve opens the passage, and the hydraulic oil in the reservoir chamber flows into the pressure chamber from the passage. For this reason, the rod moves rapidly in the direction in which the volume of the pressure chamber increases to absorb the slack of the belt immediately, and keeps the belt tension constant.

  As described above, in the hydraulic auto tensioner according to the present invention, 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 to the flange is provided. Formed and opened and closed with a check valve, compared to a hydraulic auto tensioner in which a passage is formed in the plunger provided at the bottom of the rod and the passage is opened and closed with a check valve. The direction length can be made compact.

  In addition, a dust cover with the top closed is attached to the upper end of the rod to cover the upper outer periphery of the cylinder, and the space between the inner diameter surface of the dust cover and the outer diameter surface of the cylinder is sealed by incorporating an O-ring. Intrusion of foreign matter can be prevented.

  Furthermore, by providing a return passage that communicates the inside and outside of the cylinder at a position that is offset from the position where the O-ring is installed on the upper opening end side of the cylinder, the hydraulic oil that has leaked from the upper opening end of the cylinder to the outside is returned. It can be returned to the inside of the cylinder from the passage. For this reason, it is possible to prevent the hydraulic oil leaked to the outside of the cylinder from leaking to the outside from the sliding portion of the O-ring and the dust cover, and to improve the reliability against the hydraulic oil leakage.

  In addition, since hydraulic oil leaked to the outside from the upper opening of the cylinder can be returned from the return passage to the inside of the cylinder, it can be used even in a mounting posture in which the cylinder is slightly inclined from the vertical state so that the return passage is at the bottom. 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 the lower end, and the outer periphery of the lower surface of the flange 14 is supported by a step portion 15 provided 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.

  As shown in FIG. 3, an annular seal groove 22 is formed on the upper outer periphery of the cylinder 11, and the elastic O-ring 23 incorporated in the seal groove 22 is in elastic contact with the inner periphery of the dust cover 20. A plurality of return passages 24 communicating the inside and the outside of the cylinder 11 are formed at intervals in the circumferential direction at a position slightly offset on the upper opening end side of the cylinder from the assembly position of the O-ring 23.

  The return passage 24 is positioned higher than the oil level of the hydraulic oil filled in the cylinder 11 so that the hydraulic oil leaked to the outside from the upper opening of the cylinder 11 and accumulated on the O-ring 23 is returned to the inside of the cylinder 11. It has become.

  Further, as shown in FIG. 2, an annular protrusion 25 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 26 is formed on the lower inner periphery of the dust cover 20. The rod 16 is prevented from coming out of the cylinder 11 by the contact of the retaining projection 26 with the annular projection 25 provided.

  As shown in FIGS. 5 and 6, a plurality of arc-shaped passages 27 communicating with the pressure chamber 17 and the reservoir chamber 18 are formed on the flange 14 of the sleeve 13 on the same circle, and the pressure chamber 17 of the passage 27 is formed. 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, as the valve spring 33, a press-formed product of a thin metal plate 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 The valve body 32 is urged toward the seat surface 31 by the elastic piece 33b, but 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 increases and the pressure decreases, and the pressure becomes lower than the pressure of the reservoir chamber 18, the valve body 32 of the check valve 30 separates from the seat surface 31 as shown in FIG. 7. 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.

  In the hydraulic auto tensioner shown in the embodiment, a flange 14 is provided at the lower end portion of the sleeve 13 into which the lower end portion of the rod 16 is slidably inserted, and the pressure chamber 17 and the reservoir chamber 18 are communicated with the flange 14. Since the passage 27 is formed and the passage 27 is opened and closed by the check valve 30, the plunger of the hydraulic auto tensioner shown in the above-mentioned Patent Document 1 and Patent Document 2 can be omitted. The axial length of the hydraulic auto tensioner can be made compact.

  Further, a dust cover 20 whose upper portion is closed is attached to the upper end portion of the rod 16 to cover the outer peripheral upper portion of the cylinder 11, and the space between the inner diameter surface of the dust cover 20 and the outer diameter surface of the cylinder 11 is sealed by incorporating an O-ring 23. This prevents foreign matter from entering the cylinder 11.

  Here, since the upper part of the cylinder 11 filled with the hydraulic oil is open, the hydraulic oil may leak to the outside from the opening of the cylinder 11 due to vibration or the like when the automobile is running. If the leaked hydraulic oil is accumulated on the O-ring 23, there is a possibility that the dust cover 20 leaks from between the sliding surfaces of the dust cover 20 and the O-ring 23 when the dust cover 20 slides.

  However, since the cylinder 11 is provided with a return passage 24 that communicates the inside and the outside of the cylinder 11 at a position closer to the upper opening end side of the cylinder than the position where the O-ring 23 is assembled, It will return to the inside of the cylinder 11 from the return path 24, and the leakage to the outside is prevented.

  As described above, since the hydraulic oil leaked to the outside from the upper opening of the cylinder 11 can be returned to the inside of the cylinder 11 from the return passage 24, the improvement in the reliability against the hydraulic oil leakage can be improved, and FIG. As shown, the cylinder 11 can be used in an installation posture in which the cylinder 11 is slightly tilted from the vertical state so that one of the plurality of return passages 24 is located below.

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 upper part of the cylinder of the hydraulic auto tensioner shown in FIG. Sectional view showing other assembled state of hydraulic auto tensioner FIG. 2 is an enlarged cross-sectional view showing a check valve portion of the hydraulic auto tensioner shown in FIG. Sectional view along line VI-VI in FIG. Sectional view showing the open state of the check valve

Explanation of symbols

11 Cylinder 13 Sleeve 14 Flange 15 Step 16 Rod 17 Pressure chamber 18 Reservoir chamber 21 Return spring 22 Seal groove 23 O-ring 24 Return passage 27 Passage 30 Check valve

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 to divide the cylinder into a pressure chamber and a reservoir chamber, and the upper portion of the rod is closed from the upper opening of the cylinder to the outside. A cylindrical dust cover is attached to cover the upper outer periphery of the cylinder, and a return spring is assembled between the closed end of the dust cover and the flange of the sleeve so that the volume of the pressure chamber formed below the flange increases. The rod is energized to form a seal groove in the upper part of the outer periphery of the cylinder, and an O-ring is incorporated in the seal groove to seal between the inner diameter surface of the dust cover and the outer diameter surface of the cylinder. A return passage that communicates the inside and the outside of the cylinder is provided at a position offset from the position where the O-ring is assembled on the upper opening end side of the cylinder, and the flange communicates with a pressure chamber and a reservoir chamber provided above the flange. And a check valve that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber at the opening on the pressure chamber side of the passage.

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