JP2009191863A - Hydraulic auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic auto tensioner for preventing the excessive tension of a belt. <P>SOLUTION: A sleeve 4 is provided in a cylinder 1 in which operating oil is filled, a rod 5 is slidably inserted at its lower end into the sleeve to form a pressure chamber 6 in the sleeve, and a return spring 8 is incorporated between a spring seat 7 provided at the upper part of the rod and the inner bottom face of the cylinder for energizing the cylinder and the rod in their elongating direction. A check valve 15 is provided in a passage 14 which communicates a reservoir chamber 13 formed between the cylinder and the sleeve with the pressure chamber for closing the passage so that the operating oil in the pressure chamber reduces pushing force on the cylinder and the rod when pushed in their contracting direction. A communication passage 16 is formed in the rod for communicating the pressure chamber with the reservoir chamber, and a relief valve 18 is incorporated in the communication passage. The relief valve keeps fluctuation pressure in the pressure chamber at a constant upper limit value to prevent the excessive tension of the belt whose tension is adjusted with the thrust of the rod. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a hydraulic auto-tensioner used for adjusting the tension of a belt for driving an automobile auxiliary machine such as an alternator, a water pump, and an air conditioner compressor.

  As shown in FIG. 4, a belt transmission device for transmitting the rotation of the crankshaft of an engine to various automobile accessories is provided with a swingable pulley arm 43 that supports a tension pulley 42 on the slack side of the belt 41. The adjustment force of the hydraulic auto tensioner A is applied to 43, and the pulley arm 43 is urged in the direction in which the tension pulley 42 presses the belt 41, so that the tension of the belt 41 is kept constant.

  As a hydraulic auto tensioner A used for the belt transmission as described above, one described in Patent Document 1 has been conventionally known. In this hydraulic auto tensioner, the lower part of the rod is slidably inserted into the sleeve rising from the inner bottom surface of the bottomed cylinder filled with hydraulic oil to form a pressure chamber in the sleeve, which is provided at the upper part of the rod. A return spring is incorporated between the spring seat and the bottom surface of the cylinder to urge the rod and the cylinder in the extending direction.

  Further, both ends of an elastic bellows are fitted to the outer periphery of the spring seat and the upper outer periphery of the cylinder to form a reservoir chamber sealed between the cylinder and the sleeve, and the lower portion of the reservoir chamber and the pressure chamber are connected by a passage. A check valve is provided in the passage, and the check valve is closed when a pushing force is applied from the belt 41 to the hydraulic auto tensioner A via the tension pulley 42 and the pulley arm 43 in the direction of contracting the cylinder and the rod. The hydraulic oil sealed in the pressure chamber is caused to flow through a minute gap formed between the inner diameter surface of the sleeve and the outer diameter surface of the rod, and a hydraulic damper force is generated in the pressure chamber due to the viscous resistance of the hydraulic oil during the flow. Thus, the pushing force is buffered.

Special Table 2000-504395

  By the way, in the conventional hydraulic auto tensioner, as described above, the working oil sealed in the pressure chamber is formed between the inner diameter surface of the sleeve and the outer diameter surface of the rod by the pushing force applied from the belt 41 to the rod. The pressure force is buffered by the hydraulic damper force generated in the pressure chamber by the flow, and the hydraulic damper force and the push force are substantially proportional to each other, so the push force increases. As a result, the hydraulic damper force also increases.

  For this reason, the belt cannot be prevented from being over-tensioned, and there is a problem that the durability of the belt is lowered.

  An object of the present invention is to provide a hydraulic auto tensioner capable of preventing a belt from becoming over-tensioned.

  In order to solve the above-mentioned problems, in the present invention, a sleeve rising from the inner bottom surface is provided in a cylinder having a closed end at the lower part and filled with hydraulic oil, and the lower end of the rod is provided in the sleeve. A pressure spring is formed in the sleeve by slidably inserting the part, and a return spring that urges the cylinder and rod in the extending direction is incorporated between the spring seat provided on the top of the rod and the inner bottom surface of the cylinder. A check valve that closes the upper opening of the reservoir chamber formed between the cylinder and the sleeve and closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber in the passage that communicates the reservoir chamber and the pressure chamber. In the provided hydraulic auto tensioner, a communication passage that connects the pressure chamber and the reservoir chamber is formed in the rod, and the pressure of the pressure chamber exceeds the set pressure in the communication passage. Than is adopted a structure incorporating a relief valve to open the communicating passage when.

  As described above, by forming a communication path that connects the pressure chamber and the reservoir chamber to the rod, and by incorporating a relief valve in the communication path, a pushing force is applied from the belt to the rod, and the pressure in the pressure chamber rises. When the pressure exceeds the set pressure of the relief valve, the relief valve opens, the hydraulic oil in the pressure chamber flows into the reservoir chamber from the communication path, and the upper limit value of the hydraulic damper force generated in the pressure chamber becomes the set pressure of the relief valve. It will be suppressed.

  For this reason, the belt is not over-tensioned, and a decrease in the durability of the belt can be suppressed.

  Here, as a relief valve, one end is closed and the other end opening of the cylinder having a small hole formed at the closed end is closed by attaching a valve seat having a valve hole, and the valve is placed inside the cylinder. A valve fitting formed at the end of the communication passage on the pressure chamber side is an assembly product including a spherical valve body for opening and closing the hole and a valve spring for biasing the valve body toward the valve hole. By fitting the relief valve into the hole, the relief valve can be assembled, and the ease of assembling the relief valve can be improved.

  When the relief valve is assembled to the valve fitting hole, the relief valve is prevented from being pulled out while being fitted to the valve fitting hole.

  When retaining the relief valve, a method is adopted in which a retainer having a cylindrical portion formed on the outer periphery of a disc portion having a central hole is press-fitted into the opening end of the valve fitting hole, thereby removing the relief valve from the cylinder body. Since it is not necessary to finish the diameter with high accuracy, the manufacturing cost can be reduced.

  In this case, the inner diameter of the central hole formed in the retainer is set larger than the inner diameter of the valve hole formed in the valve seat of the relief valve so that the hydraulic oil in the pressure chamber flows smoothly into the valve hole.

  In addition, when retaining the relief valve, a method of press-fitting the cylinder of the relief valve into the valve fitting hole can be used to simplify the structure of the hydraulic auto tensioner and reduce the axial length by eliminating the retainer. This makes it possible to achieve a more compact size.

  In the hydraulic auto tensioner according to the present invention, the valve body of the relief valve repeatedly opens and closes while a load exceeding the set pressure of the relief valve is applied to the rod, so that the contact portion between the valve body and the valve seat is easily worn. .

  Therefore, the seat surface on which the valve body of the valve seat is seated is hardened to increase the hardness, or the valve body is made of ceramic to reduce the impact force when the valve body collides with the seat surface. Surface wear can be suppressed and durability can be improved.

  Here, as the surface hardening treatment, a method of shot peening or a method of forming a diamond-like carbon film can be employed.

  As described above, in the present invention, when the pushing force is applied from the belt to the rod and the pressure in the pressure chamber rises and the pressure exceeds the set pressure of the relief valve, the relief valve is opened and the pressure chamber The hydraulic oil flows into the reservoir chamber from the communication path, and the upper limit value of the hydraulic damper force generated in the pressure chamber can be suppressed to the relief valve setting value, so that the belt is over tensioned and the durability is reduced. can do.

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the cylinder 1 is closed at the lower portion, and a connecting piece 2 that is rotatably connected to the engine block is provided at the closed end.

  A sleeve fitting hole 3 is provided on the inner bottom surface of the cylinder 1, and a lower end portion of the sleeve 4 is press-fitted into the sleeve fitting hole 3. The lower part of the rod 5 is slidably inserted into the sleeve 4, and the pressure chamber 6 is provided in the sleeve 4 by the insertion of the rod 5.

  A spring seat 7 is fixed to an upper end portion of the rod 5 located outside the cylinder 1, and a return spring 8 incorporated between the spring seat 7 and the bottom surface of the cylinder 1 extends relative to the cylinder 1 and the rod 5. It is energizing in the direction to do.

  A connecting piece 9 connected to the pulley arm 43 shown in FIG. 4 is provided at the upper end of the spring seat 7. Further, the spring seat 7 is provided with an inner cylinder portion 10 that covers the upper portion of the return spring 8 and an outer cylinder portion 11 that covers the outer periphery of the upper portion of the cylinder 1 on the same axis.

  An elastic seal 12 such as an oil seal is attached in the upper opening of the cylinder 1, and the inner periphery of the elastic seal 12 is in elastic contact with the outer peripheral surface of the inner cylinder 10 to close the upper opening of the cylinder 1. Leakage of hydraulic oil filled in 1 to the outside is prevented.

  By attaching the elastic seal 12, the reservoir chamber 13 sealed between the cylinder 1 and the sleeve 4 is formed. The reservoir chamber 13 and the pressure chamber 6 communicate with each other through a passage 14 formed between the fitting surfaces of the sleeve fitting hole 3 and the sleeve 4, and a check valve 15 provided at the end of the passage 14 on the pressure chamber 6 side. When the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 13, the passage 14 is closed.

  The rod 5 is formed with a communication passage 16 that allows the pressure chamber 6 and the reservoir chamber 13 to communicate with each other. A valve fitting hole 17 is provided at the end of the communication passage 16 on the pressure chamber 6 side, and a relief valve 18 is incorporated in the valve fitting hole 17.

  As shown in FIG. 2, the relief valve 18 is closed at one end and closed at the other end of the cylinder body 19 in which a small hole 20 is formed at the closed end by attaching a valve seat 21. It consists of an assembly in which a spherical valve body 23 for opening and closing the valve hole 22 formed in the valve seat 21 and a valve spring 24 for biasing the valve body 23 toward the valve hole 22 are incorporated. Yes.

  The outer diameter of the cylinder 19 is smaller than the inner diameter of the valve fitting hole 17 and is inserted into the valve fitting hole 17 with a slight margin. The relief valve 18 incorporated in the valve fitting hole 17 is prevented from coming off by a retainer 25 attached in the open end of the valve fitting hole 17.

  The retainer 25 has a cup shape in which a cylindrical portion 27 is formed on the outer periphery of the disc portion 26, and is attached by press-fitting the cylindrical portion 27 into the valve fitting hole 17. Here, a center hole 28 is formed in the disc portion 26, and the inner diameter of the center hole 28 is larger than the inner diameter of the valve hole 22 formed in the valve seat 21.

  The hydraulic auto tensioner shown in the embodiment has the above-described configuration. When adjusting the tension of the accessory drive belt 41 shown in FIG. 4, the connecting piece 2 provided at the closed end of the cylinder 1 is connected to the engine block. In addition, the connecting piece 9 of the spring seat 7 is connected to the pulley arm 43, and an adjusting force is applied to the pulley arm 43.

  In the tension adjustment state of the belt 41 as described above, when the tension of the belt 41 changes due to a load variation of the auxiliary machine and the tension of the belt 41 becomes weak, the cylinder 1 and the rod 5 are expanded by the pressing of the return spring 8. The slack of the belt 41 is absorbed by relative movement in the direction.

  Here, when the cylinder 1 and the rod 5 move relative to each other in the extending direction, the pressure in the pressure chamber 6 becomes lower than the pressure in the reservoir chamber 13, so the check valve 15 opens the passage 14. For this reason, the hydraulic oil in the reservoir chamber 13 flows smoothly from the passage 14 into the pressure chamber 6, and the cylinder 1 and the rod 5 smoothly move relative to each other in the extending direction to immediately absorb the slack of the belt 41.

  On the other hand, when the tension of the belt 41 is increased, a pushing force in a direction of contracting the cylinder 1 and the rod 5 of the hydraulic auto tensioner from the belt 41 is applied. At this time, since the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 13, the check valve 15 closes the passage 14.

  Further, the hydraulic oil in the pressure chamber 6 flows into the minute clearance 29 formed between the inner diameter surface of the sleeve 4 and the outer diameter surface of the rod 5, flows into the reservoir chamber 13, and the hydraulic oil flowing into the minute clearance 29. The hydraulic damper generates a hydraulic damper force in the pressure chamber 6 due to the viscous resistance, and the hydraulic damper force buffers the pushing force applied to the hydraulic auto tensioner, and the cylinder 1 and the rod 5 have a pushing force and a return spring. Relatively moves slowly in the direction of contraction to the position where the elastic force of 8 is balanced.

  Here, when the tension of the belt 41 is strong and the pressure in the pressure chamber 6 exceeds the set pressure of the relief valve 18, the relief valve 18 is opened, and the hydraulic oil in the pressure chamber 6 flows into the reservoir chamber 13 from the communication path 16. The hydraulic damper force generated in the pressure chamber 6 is suppressed to a constant value as shown in a graph showing the relationship between the rod displacement and the hydraulic damper force in FIG.

  Thus, by incorporating the relief valve 18 that opens and closes the communication passage 16 into the valve fitting hole 17 formed in the rod 5, the upper limit value of the pressure in the pressure chamber 6 where the pressure fluctuates is set to the set pressure of the relief valve 18. Since the belt 41 can be held, the belt 41 is not over-tensioned, and a decrease in durability of the belt 41 can be suppressed.

  Here, when the pushing force exceeding the set pressure of the relief valve 18 is continuously applied to the rod 5, the valve body 23 of the relief valve 18 repeatedly opens and closes, and the contact portion between the valve body 23 and the valve seat 21 is worn. However, there is a possibility of deformation.

  Therefore, in the embodiment, the seat surface 30 on which the valve body 23 of the valve seat 21 is seated is subjected to a surface hardening process to increase the hardness. Examples of the surface hardening treatment include a method of shot peening and a method of forming a diamond-like carbon film.

  As described above, the sheet surface 30 is subjected to surface hardening treatment to increase the hardness, thereby preventing wear and deformation of the sheet surface 30 and improving the durability.

  Here, by forming the valve body 23 from ceramic, it is possible to reduce the impact force at the time of the collision of the valve body 23 against the seat surface 30 and to increase the effect of preventing the seat surface 30 from being worn and deformed. .

  In the embodiment, the relief valve 18 is prevented from being pulled out by attaching the retainer 25 to the inside of the opening end of the valve fitting hole 17. However, the cylinder 19 of the relief valve 18 is press-fitted into the valve fitting hole 17, and the relief valve is inserted. 18 may be retained. In this case, since the retainer 25 shown in FIG. 2 can be omitted, the configuration of the hydraulic auto tensioner can be simplified and the axial length can be made compact.

A longitudinal front view showing an embodiment of a hydraulic auto tensioner according to the present invention FIG. 1 is an enlarged cross-sectional view showing a portion where the relief valve of FIG. Graph showing the relationship between rod displacement and hydraulic damper force Front view showing a tension adjusting device for an auxiliary machine driving belt

Explanation of symbols

1 Cylinder 4 Sleeve 5 Rod 6 Pressure chamber 7 Spring seat 8 Return spring 13 Reservoir chamber 14 Passage 15 Check valve 16 Communication passage 17 Valve fitting hole 18 Relief valve 19 Tubular body 20 Small hole 21 Valve seat 22 Valve hole 23 Valve body 24 Valve spring 25 Retainer 26 Disk portion 27 Cylindrical portion 28 Center hole 30 Seat surface

Claims (9)

A cylinder that has a closed end at the bottom and is filled with hydraulic oil inside is provided with a sleeve that rises from its inner bottom surface. The lower end of the rod is slidably inserted into the sleeve, and the pressure chamber is inserted into the sleeve. A return spring that urges the cylinder and the rod in a direction to extend is incorporated between a spring seat provided at the upper portion of the rod and the inner bottom surface of the cylinder, and an upper portion of the reservoir chamber formed between the cylinder and the sleeve. In a hydraulic auto tensioner provided with a check valve that closes the opening and closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber in the passage communicating the reservoir chamber and the pressure chamber.
The hydraulic pressure is characterized in that a communication passage that connects the pressure chamber and the reservoir chamber is formed in the rod, and a relief valve that opens the communication passage when the pressure in the pressure chamber exceeds a set pressure is incorporated in the communication passage. Auto tensioner.   The relief valve is closed at one end and closed at the other end of the cylinder having a small hole at the closed end by attaching a valve seat having a valve hole, and the valve hole is opened and closed inside the cylinder. And a valve fitting formed at the end of the communication passage on the pressure chamber side. The relief valve is formed of an assembly that incorporates a spherical valve body for use and a valve spring that biases the valve body toward the valve hole. 2. The hydraulic auto tensioner according to claim 1, wherein the hydraulic auto tensioner is fitted and fitted in a hole.   3. The hydraulic auto tensioner according to claim 2, wherein the relief valve is retained by press-fitting the retainer having a cylindrical portion formed on the outer periphery of a disc portion having a center hole into the opening end portion of the valve fitting hole.   The hydraulic auto tensioner according to claim 3, wherein an inner diameter of a central hole formed in the retainer is larger than an inner diameter of a valve hole of the relief valve.   The hydraulic auto tensioner according to claim 2, wherein the relief valve is prevented from being pulled out by press-fitting the cylindrical body into the valve fitting hole.   The hydraulic auto tensioner according to any one of claims 1 to 5, wherein a surface hardening treatment is performed on a seat surface on which a valve body of the valve seat is seated.   The hydraulic auto tensioner according to claim 6, wherein the surface hardening treatment is performed by shot peening.   The hydraulic auto tensioner according to claim 6, wherein the surface hardening treatment is performed by forming a diamond-like carbon film.   The hydraulic auto tensioner according to any one of claims 1 to 8, wherein a valve body of the relief valve is made of ceramic.

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