JP2007071310A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic automatic tensioner capable of obtaining stable hydraulic damper force. <P>SOLUTION: A piston 16 of a rod 15 is slidably inserted into a valve sleeve 14 on an inside bottom face of a cylinder 11 to form a pressure chamber 17. A return spring 20 is assembled between a spring seat 19 in an upper part of the rod 15 and the cylinder 11. An opening in an upper part of the cylinder 11 is blocked by bellows 23 fixing its one end to the spring seat 19 and its other end to an upper end part of the cylinder 11 to form a reservoir chamber 24. A check valve 26 is provided in a first passage 25 communicating the reservoir chamber 24 with the pressure chamber 17. A second passage 37 communicating the pressure chamber 17 with the reservoir chamber 24 is formed in the rod 15, and an annular minute leak clearance 40 is provided in a lower end part of the second passage 37. Hydraulic damper force is generated by flow resistance when hydraulic fluid circulates in the leak clearance 40 to buffer pressing-in force of the rod 15 and prevent the leak clearance 40 from being affected even if the cylinder 11 and the rod 15 are inclined. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydraulic auto tensioner that maintains a constant tension of a timing belt for driving a camshaft and a belt for driving an auxiliary machine.

  As a hydraulic auto-tensioner that keeps the tension of an auxiliary machine driving belt for driving an auxiliary machine such as an alternator, an air conditioner compressor, or a water pump constant, the one described in Patent Document 1 has been conventionally known. Yes.

  In the above hydraulic auto tensioner, a valve sleeve rising from the inner bottom surface is provided inside the cylinder closed at the lower part, and the lower end of the rod is slidably inserted into the valve sleeve, and the pressure chamber is inserted into the valve sleeve. And a return spring is incorporated between a spring seat provided on the upper portion of the rod and the inner bottom surface of the cylinder to urge the rod and the cylinder in a relatively extending direction. Further, one end portion is fitted to the outer periphery of the spring seat, and the other end portion is closed to the upper outer periphery of the cylinder to close the upper opening of the cylinder to form a reservoir chamber between the cylinder and the valve sleeve, A check valve is provided in a first passage communicating the reservoir chamber and the pressure chamber.

  In the hydraulic auto tensioner, the connecting piece provided at the lower end of the cylinder is connected to the engine block so as to be rotatable, and the connecting piece provided on the spring seat is connected to the swingable pulley arm so as to be rotatable. The adjustment force of the hydraulic auto tensioner is applied to the pulley arm, and the tension pulley supported by the pulley arm is pressed against the belt.

When the pushing force is applied to the rod from the belt via the tension pulley and the pulley arm, the first passage is closed by the check valve, and the hydraulic oil in the pressure chamber is formed between the sliding surface of the valve sleeve and the rod. A hydraulic damper force is generated by a flow resistance when flowing from a small leak clearance into the reservoir chamber to absorb a change in belt tension.
US Pat. No. 4,790,801

  By the way, in the conventional hydraulic auto tensioner, when the pulley arm swings due to a change in belt tension, the hydraulic auto tensioner itself swings, and a moment load is generated in the connecting piece of the cylinder and the connecting piece of the spring seat. The moment load is received by the valve sleeve and the rod. At this time, since the valve sleeve and the rod are relatively inclined, the size of the leak clearance formed between the sliding surfaces of the valve sleeve and the rod becomes uneven in the circumferential direction, and the flow of hydraulic oil flowing through the leak clearance The resistance changes, and a stable hydraulic damper force cannot be obtained.

  Further, when an excessive pushing force is applied to the rod and the pressure in the pressure chamber suddenly increases, the valve sleeve may expand and deform. At this time, since the leak clearance formed between the sliding surfaces of the valve sleeve and the rod changes, a stable hydraulic damper force cannot be obtained as described above.

  An object of the present invention is to provide a hydraulic auto tensioner that can always obtain a stable hydraulic damper force.

  In order to solve the above problems, in the present invention, a valve sleeve rising from the inner bottom surface is provided in a cylinder having a closed end at the lower portion, and the lower end portion of the rod is slidably inserted into the valve sleeve. A pressure chamber is formed in the valve sleeve, and a return spring that urges the cylinder and the rod in a relatively extending direction is installed between the spring seat provided on the upper portion of the rod and the inner bottom surface of the cylinder, and the spring seat A reservoir chamber is formed between the cylinder and the valve sleeve by closing an upper opening of the cylinder with an extendable bellows having one end fitted to the outer circumference of the cylinder and the other end fitted to the upper circumference of the cylinder. A check valve that closes the first passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, in a first passage communicating the lower portion of the chamber and the lower portion of the pressure chamber. In the first hydraulic auto tensioner, the lower end of the rod and the sliding surface of the valve sleeve are sealed with a seal member, and the rod is provided with a second passage communicating the pressure chamber and the reservoir chamber. A configuration is adopted in which an annular minute leak gap is formed at the lower end of the passage on the pressure chamber side.

  Here, a fitting recess is formed in the lower end portion of the second passage on the pressure chamber side, and the upper portion of the stepped columnar body whose lower side is a small diameter portion is press-fitted into the fitting recess, and the stepped columnar shape The leak gap is formed between the outer diameter surface of the lower small-diameter portion of the body and the inner diameter surface of the fitting recess, and the outer periphery of the upper large-diameter portion of the stepped columnar body extends from the lower end of the upper large-diameter portion to the upper surface. By forming the groove-shaped communication path that reaches the center, an annular minute leak gap can be easily formed by press-fitting the stepped columnar body into the fitting recess.

  The leak gap generates a hydraulic damper force due to the flow resistance of the hydraulic fluid that flows inside. Therefore, if the size of the leak gap becomes too small, the flow resistance of the hydraulic oil increases and the hydraulic damper force becomes too large. If the belt becomes over-tensioned and the leak gap becomes too large, the flow of hydraulic oil becomes smooth, the hydraulic damper force becomes small, and the belt tension change cannot be absorbed. For this reason, the size of the leak gap is preferably in the range of 0.01 to 0.03 mm.

  As described above, the second passage for communicating the pressure chamber and the reservoir chamber is provided in the rod, and the annular minute leak gap is provided at the lower end portion of the second passage on the pressure chamber side, so that the hydraulic oil in the pressure chamber is provided. The hydraulic damper force can be generated by the flow resistance when flowing through the leak gap. In this way, by forming a leak gap in the rod that generates hydraulic damper force, the cylinder and rod are relatively inclined due to moment load or the like, or the pressure in the pressure chamber suddenly increases and the valve sleeve expands and deforms. However, the leak gap that generates the hydraulic damper force is not affected at all. As a result, a stable hydraulic damper effect can be obtained at all times.

  Hereinafter, embodiments of the present invention will be described 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 3 is rotatably supported at the end of the swing side. A hydraulic auto tensioner 10 is connected to the pulley arm 1 between the fulcrum shaft 2 and the tension pulley 3.

  The pulley arm 1 is urged in a direction in which the tension pulley 3 presses the belt 4 by an adjustment force applied from the hydraulic auto tensioner 10.

  As shown in FIG. 2, the hydraulic auto tensioner 10 has a cylinder 11 made of an aluminum alloy. The cylinder 11 has a closed end at a lower portion, and a connecting piece 12 that is rotatably attached to the engine block is provided at the closed end.

  A sleeve fitting hole 13 is formed in the inner bottom surface of the cylinder 11, and a lower end portion of a steel valve sleeve 14 is press-fitted into the sleeve fitting hole 13. The rod 15 having the lower end inserted into the valve sleeve 14 has a piston 16 slidable in the valve sleeve 14 at the lower portion, and the pressure chamber 17 is formed in the valve sleeve 14 by incorporating the piston 16. Yes.

  A large-diameter shaft portion 18 is formed at the upper end portion of the rod 15, and a return spring 20 is assembled between the spring seat 19 attached to the large-diameter shaft portion 18 and the inner bottom surface of the cylinder 11. The return spring 20 presses the cylinder 11 and the rod 15 in opposite directions so as to move relative to each other in the direction in which the cylinder 11 and the rod 15 extend.

  A connecting piece 21 is provided at the upper end of the spring seat 19 so as to be rotatably connected to the pulley arm 1. Further, a cylindrical body 22 that covers the upper portion of the return spring 20 is provided on the outer peripheral portion of the lower surface of the spring seat 19, and one end of an extendable bellows 23 made of an elastic body such as rubber is fitted to the outside of the cylindrical body 22. It has been fixed. Further, the other end of the bellows 23 is fitted and fixed to the upper outer periphery of the cylinder 11, and the upper opening of the cylinder 11 is closed by the attachment of the bellows 23, so that the inner diameter surface of the cylinder 11 and the outer diameter surface of the valve sleeve 14 are closed. A reservoir chamber 24 is formed therebetween.

  A first passage 25 that connects the pressure chamber 17 and the reservoir chamber 24 is formed between the sleeve fitting hole 13 of the cylinder 11 and the fitting surface of the lower end portion of the valve sleeve 14, and a check for opening and closing the first passage 25 is performed. A valve 26 is incorporated in the lower end of the valve sleeve 14.

  The check valve 26 includes a valve seat 27 having a valve hole 28, a spherical valve body 29 that opens and closes the valve hole 28 of the valve seat 27, and a retainer 30 that limits the opening and closing amount of the valve body 29.

  The retainer 30 has a cap shape, and a flange 31 is formed outwardly at the opening end. The flange 31 abuts on the upper surface of the valve seat 27 by press-fitting the retainer 30 with respect to the protrusion 32 formed on the upper surface of the valve seat 27. Further, the check valve 26 is made an assembly by press-fitting the retainer 30. The check valve 26 is attached by press-fitting into a valve fitting recess 33 formed at the lower end portion of the valve sleeve 14, and the flange 31 of the retainer 30 is formed on the inner periphery of the lower end portion of the valve sleeve 14 by the valve seat 27 by the attachment. Pressed against the shoulder 34.

  The check valve 26 closes the first passage 25 when the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 24.

  As shown in FIG. 3, a seal groove 35 is formed on the outer periphery of the piston 16, and a seal member 36 composed of an O-ring incorporated in the seal groove 35 is brought into elastic contact with the inner diameter surface of the valve sleeve 14, so that the piston 16 Between the sliding surfaces of the valve sleeve 14.

  As shown in FIGS. 2 and 3, a second passage 37 that connects the pressure chamber 17 and the reservoir chamber 24 is formed at the lower end of the rod 15. A fitting recess 38 is formed at the end of the second passage 37 on the pressure chamber 17 side, and a columnar body 39 is incorporated in the fitting recess 38.

  As shown in FIGS. 3 and 4, the columnar body 39 has a large diameter portion 39 a on the upper side. The large diameter portion 39 a is press-fitted into the fitting recess 38, and an annular minute leak gap 40 is provided between the outer diameter surface of the lower small diameter portion 39 b and the inner diameter surface of the fitting recess 38. In addition, a plurality of groove-shaped communication passages 41 extending from the lower end to the center of the upper surface are formed on the outer periphery of the large diameter portion 39a.

  Since the annular leak gap 40 generates a hydraulic damper force due to the flow resistance when the hydraulic oil in the pressure chamber 17 flows, if the size δ of the leak gap 40 is less than 0.01 mm, The flow resistance becomes too large and the relative movement in the direction in which the cylinder 11 and the rod 15 contract is hindered, and the belt 4 becomes over-tensioned. On the other hand, if it exceeds 0.03 mm, the hydraulic oil in the pressure chamber 17 smoothly flows into the reservoir chamber 24 and it becomes impossible to obtain a hydraulic damper force. For this reason, the size δ of the leak gap 40 is in the range of 0.01 to 0.03 mm.

  The columnar body 39 may be made of a synthetic resin, or may be made of a metal.

  As shown in FIG. 2, in the upper opening of the valve sleeve 14, the relative movement in the extending direction of the rod 15 and the valve sleeve 14 is restricted to prevent the lower end of the rod 15 from coming out of the valve sleeve 14. Stop means 42 is provided.

  The retaining means 42 is formed with an engaging groove 43 in the upper end opening of the valve sleeve 14, and a retaining ring 44 that is elastically deformed in the radial direction by cutting a part in the circumferential direction is attached to the engaging groove 43. The rod 15 is prevented from coming off by contact of the upper surface of the piston 16 with the retaining ring 44.

  The belt tension adjusting device shown in the embodiment has the above-described structure, and when the auxiliary machine is driven by the movement of the belt 4, the tension of the belt 4 changes due to the load fluctuation of the auxiliary machine, and the tension of the belt 4 is changed. When it becomes weaker, the cylinder 11 and the rod 15 move relative to each other in the extending direction due to the pressing force of the return spring 20, and the pulley arm 1 swings due to the relative movement, and the tension pulley 3 is pressed against the belt 4 to loosen the belt 4. Absorb.

  When the cylinder 11 and the rod 15 move relative to each other in the extending direction, the pressure in the pressure chamber 17 is lower than the pressure in the reservoir chamber 24, so the check valve 26 opens the first passage 25. For this reason, the hydraulic oil in the reservoir chamber 24 flows smoothly from the first passage 25 into the pressure chamber 17, and the cylinder 11 and the rod 15 smoothly move relative to each other in the extending direction to immediately absorb the slack of the belt 4.

  On the other hand, when the tension of the belt 4 is increased, a pushing force is applied to the rod 15 via the tension pulley 3 and the pulley arm 1. At this time, since the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 24, the check valve 26 closes the first passage 25. The hydraulic oil in the pressure chamber 17 flows through the leak gap 40, the communication path 41 and the second path 37 and flows into the reservoir chamber 24, and the hydraulic damper force is generated by the flow resistance of the hydraulic oil flowing through the leak gap 40. appear. The pushing force applied to the rod 15 is buffered by the hydraulic damper force, and the cylinder 11 and the rod 15 are contracted to a position where the pushing force applied to the rod 15 and the pushing force of the return spring 20 are balanced. Slowly move relative.

  When the cylinder 11 and the rod 15 move relative to each other in the contracting direction, the hydraulic auto tensioner 10 swings around the connecting piece 12 connected to the engine block. At the time of the swing, even if a moment load is applied to the connecting pieces 12 and 21 of the spring seat 19 provided on the cylinder 11 and the rod 15 and the cylinder 11 and the rod 15 are inclined relatively, a hydraulic damper force is generated. Since the leak gap 40 is provided at the lower end portion of the rod 15, nothing is affected. Further, even if the pressure in the pressure chamber 17 increases and the valve sleeve 14 expands and deforms, the leak gap 40 is not affected at all. For this reason, a stable hydraulic damper effect can be obtained at all times, and the belt 4 can always be maintained at an appropriate tension.

  Further, by setting the size δ of the leak gap 40 in the range of 0.01 to 0.03 mm, an optimal hydraulic damper force can be generated.

Front view of a belt tension adjusting device employing a hydraulic auto tensioner according to the present invention. 1 is a longitudinal front view of the hydraulic auto tensioner shown in FIG. Sectional drawing which expands and shows the fitting part of the valve sleeve and rod of FIG. Sectional view along line IV-IV in FIG.

Explanation of symbols

11 Cylinder 14 Valve sleeve 15 Rod 17 Pressure chamber 19 Spring seat 20 Return spring 23 Bellows 24 Reservoir chamber 25 First passage 26 Check valve 36 Seal member 37 Second passage 38 Fitting recess 39 Columnar body 39a Large diameter portion 39b Small diameter portion 40 Leakage gap 41 Communication path

Claims (3)

A valve sleeve rising from the inner bottom surface is provided in a cylinder having a closed end at the bottom, and the lower end of the rod is slidably inserted into the valve sleeve to form a pressure chamber in the valve sleeve. A return spring that urges the cylinder and the rod in a relatively extending direction is incorporated between the spring seat provided on the top and the inner bottom surface of the cylinder, and one end is fitted to the outer periphery of the spring seat, and the upper outer periphery of the cylinder The upper end of the cylinder is closed by an extendable bellows fitted at the other end thereof to form a reservoir chamber between the cylinder and the valve sleeve, and the lower portion of the reservoir chamber and the lower portion of the pressure chamber communicate with each other. In a hydraulic auto tensioner provided with a check valve for closing the first passage when the pressure in the pressure chamber is higher than the pressure in the reservoir chamber in one passage,
The lower end portion of the rod and the sliding surface of the valve sleeve are sealed with a seal member, and the rod is provided with a second passage communicating the pressure chamber and the reservoir chamber, and the lower end of the second passage on the pressure chamber side A hydraulic auto-tensioner characterized in that an annular minute leak gap is formed in the part.   A fitting recess is formed in the lower end portion of the second passage on the pressure chamber side, and the upper portion of the stepped columnar body whose lower side is a small diameter portion is press-fitted into the fitting recess, and the bottom of the stepped columnar body is pressed. The leak gap is formed between the outer diameter surface of the side small diameter portion and the inner diameter surface of the fitting recess, and the outer periphery of the upper large diameter portion of the stepped columnar body extends from the lower end of the upper large diameter portion to the center of the upper surface. The hydraulic auto tensioner according to claim 1, wherein a groove-shaped communication path is formed.   The hydraulic auto tensioner according to claim 1 or 2, wherein a size of the leak gap is in a range of 0.01 to 0.03 mm.

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