JP2008157382A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner which is simple in processing of a cylinder, and light in weight. <P>SOLUTION: A minor diameter hole 11 and a major diameter hole 12 continuing to the minor diameter hole 11 are coaxially provided in the cylinder 10 made of light metal. The cylinder 10 is filled with a working fluid. A cylinder space 14 is formed between the inner periphery of the major diameter hole 12 and the outer periphery of a sleeve 13 by fitting the sleeve 13 in the minor diameter hole 11. A plunger 16 is slidably inserted in the sleeve 13 to partition the sleeve 13 inside into a pressure chamber 17 and a reservoir chamber 18. A chain pressing rod 19 integrally moving with the plunger 16 is provided. A return spring 21 is provided to urge the rod 19 in the projecting direction. A leak gap 32 is formed in the sliding surfaces between the plunger 16 and the sleeve 13. An auxiliary reservoir chamber 27 is formed in the cylinder 10 to communicate with the reservoir chamber 18 via the cylinder space 14. Air and the working fluid are stored in the auxiliary reservoir chamber 27. A relief valve 34 is provided in a release passage 33. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention mainly relates to a chain tensioner used for maintaining tension of a timing chain that drives a camshaft of an engine.

  In general, an engine transmits rotation of a crankshaft to a camshaft through a timing chain housed in an engine room in an engine cover, and the rotation of the camshaft opens and closes a valve in a combustion chamber. Here, in order to keep the chain tension within an appropriate range, a tension adjusting device composed of a chain guide provided so as to be able to swing around a fulcrum shaft and a chain tensioner that presses the chain via the chain guide is often used. It is done.

  As a chain tensioner incorporated in this tension adjusting device, a plunger is slidably inserted into a cylinder filled with hydraulic oil, the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, and moves integrally with the plunger in the axial direction. A chain pressing rod is provided, and a return spring that biases the rod in a direction protruding from the cylinder is known (Patent Document 1).

  In this chain tensioner, the rod moves to a position where the urging force of the return spring balances with the tension of the chain, thereby absorbing fluctuations in the tension of the chain and keeping the tension of the chain within an appropriate range.

  In addition, a leak gap is formed between the plunger and the sliding surface of the cylinder so that the pressure chamber and the reservoir chamber communicate with each other. When the rod moves in the direction of being pushed into the cylinder, the hydraulic oil in the pressure chamber is leaked. Flows through the reservoir chamber. At this time, since the flow rate of the hydraulic oil flowing through the leak gap is limited, the rod moves slowly, and the belt tension is kept stable.

  The plunger has a communication passage that connects the pressure chamber and the reservoir chamber. The communication passage is provided with a check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side. When the rod moves in a direction protruding from the cylinder, the check valve is opened, and hydraulic oil flows from the reservoir chamber side to the pressure chamber side through the communication path. Therefore, the rod quickly moves in the direction protruding from the cylinder and absorbs the slack of the belt quickly.

Further, in this chain tensioner, a sub-reservoir chamber containing air and hydraulic oil is formed in the cylinder, and the sub-reservoir chamber communicates with the pressure chamber through a relief passage provided with a relief valve. When the pressure becomes larger than a preset pressure, the relief valve is opened to release hydraulic oil from the pressure chamber to the sub reservoir chamber, thereby preventing the chain tension from becoming excessive.
JP 2001-165251 A

  However, in this chain tensioner, it is difficult to form a long escape passage in the cylinder along the axial direction, and the machining cost of the cylinder is high.

  In addition, this chain tensioner needs to form a cylinder using a material whose linear expansion coefficient is the same as that of the plunger material in order to prevent a change in the leak gap between the sliding surface of the plunger and the cylinder due to a temperature change. Therefore, a light alloy cannot be used as the material of the cylinder, and there is a problem that the weight of the chain tensioner becomes heavy.

  The problem to be solved by the present invention is to provide a chain tensioner that is easy to process and lightweight.

  In order to solve the above problems, a light alloy cylinder with one end opened is provided with a small-diameter hole and a large-diameter hole connected to the cylinder opening side coaxially with the small-diameter hole, and hydraulic oil is provided in the cylinder. The bottomed sleeve is fitted into the small-diameter hole portion of the cylinder to form a cylindrical space between the inner periphery of the large-diameter hole portion and the outer periphery of the sleeve, and the plunger can slide within the sleeve The sleeve is divided into a pressure chamber and a reservoir chamber, and a rod for pressing the chain that moves integrally with the plunger in the axial direction is provided, and a return spring that biases the rod in a direction protruding from the cylinder is provided. Forming a leak gap communicating the pressure chamber and the reservoir chamber between the sliding surfaces of the plunger and the sleeve, and providing a sub reservoir chamber communicating with the reservoir chamber via the cylindrical space. The secondary reservoir chamber contains air and hydraulic oil, and communicates with the secondary reservoir chamber and the pressure chamber via an opening formed in the bottom of the sleeve, and the secondary reservoir is connected to the bottom of the sleeve. Providing a check valve that allows only the flow of hydraulic oil from the chamber side to the pressure chamber side, providing an escape passage that allows the pressure chamber and the reservoir chamber to communicate with each other through the inside of the plunger and the rod in order, A structure in which a relief valve that opens when the pressure in the pressure chamber becomes higher than a preset pressure is provided in the relief passage in the chain tensioner.

The chain tensioner is preferably added with the following configuration.
1) Insert the end of the rod into the fitting recess formed on the end surface of the plunger on the reservoir chamber side with a loose fit, and absorb the misalignment between the rod and the plunger shaft by the fit. To do.
2) A resistance ring that penetrates the rod so as to be movable in the axial direction is provided so as to be movable in the axial direction within a certain range relative to the cylinder, and a plurality of resistance claws extending from the resistance ring toward the inner diameter side are provided at the tip of the rod When the tip of the resistance claw is brought into contact with the outer periphery of the rod and the rod moves in a direction to be pushed into the cylinder and slides with the resistance claw. The sliding resistance is set to be larger than the sliding resistance when the rod moves in the direction protruding from the cylinder and slides with the resistance claws.

  In the chain tensioner of the present invention, a cylindrical space that communicates the reservoir chamber and the sub-reservoir chamber is formed by providing a radial gap between the cylinder and the sleeve, and an escape passage that communicates the pressure chamber and the reservoir chamber is formed. Since the plunger and the rod are formed, there is no need to machine a long passage along the axial direction into the cylinder, and the machining of the cylinder is simple.

  Moreover, since a light alloy is used as the material of the cylinder, the weight is light.

  Moreover, since the sleeve is separate from the cylinder, the sleeve can be formed of a material different from the light alloy forming the cylinder. Therefore, a material having the same linear expansion coefficient as that of the plunger can be used as the material of the sleeve, and the change of the leak gap due to the temperature change can be prevented.

  In addition, when the end of the rod is inserted into a fitting recess formed on the end surface of the plunger on the reservoir chamber side with a clearance fit, a force in a direction perpendicular to the axis acts on the tip of the rod. When the is tilted, the displacement between the rod and the plunger is absorbed by the fit of the clearance fit, so that the plunger is difficult to tilt and the leak gap is difficult to change.

  Further, a resistance ring that penetrates the rod so as to be movable in the axial direction is provided so as to be movable in the axial direction within a certain range with respect to the cylinder, and the tip of the resistance claw of the resistance ring is brought into contact with the outer periphery of the rod When the engine is stopped, even if the chain tension increases due to fluctuations in the rotational resistance of the camshaft, the plunger sliding resistance against the resistance claw of the resistance ring limits the movement of the plunger in the direction of being pushed into the cylinder. . Therefore, when the engine is restarted, the slack of the chain can be quickly absorbed, and the chain tension is easily stabilized.

  FIG. 1 shows a chain transmission device incorporating a chain tensioner 1 according to a first embodiment of the present invention. In this chain transmission device, a sprocket 3 fixed to the crankshaft 2 of the engine and a sprocket 5 fixed to the camshaft 4 are connected via a chain 6, and the chain 6 rotates the crankshaft 2. This is transmitted to the camshaft 4 and the valve (not shown) of the combustion chamber is opened and closed by the rotation of the camshaft 4.

  The chain 6 is pressed by the chain tensioner 1 via a chain guide 8 supported so as to be swingable about a fulcrum shaft 7. The chain tensioner 1 is fixed to an engine block (not shown) with bolts 9.

  2 and 3, the chain tensioner 1 has a light alloy cylinder 10 that is open at one end. The cylinder 10 has a small-diameter hole 11 and a small-diameter hole 11 with respect to the small-diameter hole 11. A large-diameter hole 12 that is continuous with the open side is formed coaxially. A bottomed sleeve 13 is fitted into the small diameter hole portion 11, and a cylindrical space 14 is formed between the inner periphery of the large diameter hole portion 12 and the outer periphery of the sleeve 13. As shown in FIG. 2, the cylinder 10 is sealed at its open end by a seal member 15 and filled with hydraulic oil.

  A plunger 16 is inserted into the sleeve 13 so as to be slidable in the axial direction, and the inside of the sleeve 13 is partitioned into a pressure chamber 17 and a reservoir chamber 18 by the plunger 16. A rod 19 slidably penetrating the seal member 15 is connected to the plunger 16, and the tip of the rod 19 is in contact with the chain guide 8.

  On the outer periphery of the rod 19, a wear ring 20 that can slide in the axial direction on the inner periphery of the cylinder 10 is mounted. The wear ring 20 is urged toward the open side of the cylinder 10 by a return spring 21 incorporated in the cylindrical space 14, and the rod 19 is urged through the wear ring 20 in a direction protruding from the cylinder 10.

  As shown in FIG. 3, the rear end of the rod 19 is inserted into a fitting recess 23 formed on the end surface 22 of the plunger 16 on the reservoir chamber 18 side with a clearance fit. Both the inner bottom surface of the fitting recess 23 and the rear end surface of the rod 19 are formed in a spherical shape.

  The plunger 16 is urged toward the rod 19 by a plunger spring 24 incorporated in the pressure chamber 17, and when the rod 19 moves in a direction protruding from the cylinder 10, the urging force of the plunger spring 24 causes It moves integrally with the rod 19 in the axial direction. A space between the inner periphery of the fitting recess 23 of the plunger 16 and the outer periphery of the end of the rod 19 is sealed with a rubber O-ring 25.

  As shown in FIG. 2, the cylinder 10 is formed with a sub-reservoir chamber 27 in which an opening penetrating from the outer periphery to the inner periphery of the cylinder 10 is sealed with a seal cap 26, and air and hydraulic oil are contained in the sub-reservoir chamber 27. Contained. The auxiliary reservoir chamber 27 communicates with the reservoir chamber 18 via the cylindrical space 14, and changes in the temperature of the hydraulic oil and pressure changes in the reservoir chamber 18 due to the axial movement of the rod 19 are contained in the auxiliary reservoir chamber 27. Absorbs by changing the volume of air.

  As shown in FIGS. 2 and 3, the cylinder 10 is formed with a communication passage 30 that communicates the pressure chamber 17 and the auxiliary reservoir chamber 27 through an opening 29 formed in the bottom 28 of the sleeve 13. Further, a check valve 31 is provided at the bottom 28 of the sleeve 13 to allow only the flow of hydraulic oil from the sub reservoir chamber 27 side to the pressure chamber 17 side.

  As shown in FIG. 3, a leak gap 32 that connects the pressure chamber 17 and the reservoir chamber 18 is formed between the sliding surfaces of the plunger 16 and the sleeve 13, and the pressure in the pressure chamber 17 is the pressure in the reservoir chamber 18. The hydraulic oil in the pressure chamber 17 leaks into the reservoir chamber 18 through the leak gap 32 when the pressure becomes larger.

  2 and 3, the plunger 16 and the rod 19 are formed with a relief passage 33 that sequentially passes through the inside of the plunger 16 and the inside of the rod 19 to communicate the pressure chamber 17 and the reservoir chamber 18. 33 is provided with a relief valve 34 that opens when the pressure in the pressure chamber 17 becomes higher than a preset pressure.

  As shown in FIG. 2, a pair of retaining rings 35, 35 facing each other in the axial direction are provided on the inner periphery of the open end of the cylinder 10. Between the retaining rings 35, 35, a resistance ring 36 that penetrates the rod 19 so as to be movable in the axial direction is incorporated, and the resistance ring 36 is within the range of the gap formed between the retaining rings 35, 35. It can move in the axial direction.

  As shown in FIG. 4, a plurality of resistance claws 37 extending toward the inner diameter side are formed in the resistance ring 36, and the tips of the resistance claws 37 are in contact with the outer periphery of the rod 19. As shown in FIG. 2, each resistance claw 37 is inclined in a taper shape with a diameter decreasing toward the opening side of the cylinder 10, and moves in a direction in which the rod 19 is pushed into the cylinder 10 to slide with each resistance claw 37. The sliding resistance when the rod 19 moves in the direction protruding from the cylinder 10 and becomes larger than the sliding resistance when sliding with the respective resistance claws 37.

  A through-hole 38 in the radial direction is formed at the tip of the rod 19, and the through-hole of the rod 19 is moved to the stroke end in the direction in which the rod 19 is pushed into the cylinder 10 as shown in FIG. 6. The rod 19 can be held in a state where it is pushed into the cylinder 10 by inserting a pin 40 through 38 and a radial through hole 39 formed at the open end of the cylinder 10.

  Therefore, the chain tensioner 1 is shipped with the rod 19 pushed to the end of the stroke, and the chain tensioner 1 is assembled in the chain transmission device of the shipping destination, and then the pin 40 is pulled out to project the rod 19 from the cylinder 10 and the chain. 6 tension can be applied.

  Next, an operation example of the chain tensioner 1 will be described.

  When the tension of the chain 6 increases during the operation of the engine, the tension is transmitted to the rod 19 through the chain guide 8, and the rod 19 moves in a direction to be pushed into the cylinder 10 to absorb the tension of the chain 6. At this time, the check valve 31 is closed and the hydraulic oil in the pressure chamber 17 flows to the reservoir chamber 18 through the leak gap 32. However, since the flow rate of the hydraulic oil flowing through the leak gap 32 is limited, the rod 19 is slowly Move and keep the tension of the chain 6 stable.

  On the other hand, when the tension of the chain 6 is reduced during engine operation, the urging force of the return spring 21 and the plunger spring 24 causes the rod 19 to move in a direction protruding from the cylinder 10, pushing the chain guide 8 and moving the chain 6. Absorbs slack. At this time, the check valve 31 is opened, and the hydraulic oil in the auxiliary reservoir chamber 27 flows into the pressure chamber 17 through the opening 29 in the bottom 28 of the sleeve 13, so that the rod 19 moves quickly and the chain 6 is quickly loosened. To absorb.

  Further, when the chain 6 is extended with the passage of time and the rod 19 is moved in a direction protruding from the cylinder 10 due to the extension, the resistance ring 36 is held in contact with the retaining ring 35 on the open side of the cylinder 10. Is extended, the rod 19 slides relative to the resistance claw 37 and moves in a direction protruding from the cylinder 10. At this time, since the resistance claw 37 is inclined in a tapered shape, the sliding resistance of the rod 19 with respect to the resistance claw 37 is small, and the rod 19 moves smoothly without being restricted by the resistance claw 37.

  Further, when the tension of the chain 6 increases due to fluctuations in the rotational resistance of the camshaft 4 when the engine is stopped, the rod 19 moves in the direction in which it is pushed into the cylinder 10, and as shown in FIG. Is held in contact with the retaining ring 35 on the closing side. At this time, since the resistance claw 37 is inclined in a tapered shape, the sliding resistance of the rod 19 with respect to the resistance claw 37 is large, and the movement of the rod 19 in the direction in which it is pushed into the cylinder 10 is limited by the sliding resistance. . Therefore, when the engine is restarted, the slack of the chain 6 can be quickly absorbed, and the tension of the chain 6 is easily stabilized.

  Further, when the tension in the chain 6 increases, if the pressure in the pressure chamber 17 exceeds the set pressure of the relief valve 34, the relief valve 34 is opened. This prevents the hydraulic oil in the pressure chamber 17 from escaping and escaping to the reservoir chamber 18 through the passage 33 and preventing the tension of the chain 6 from becoming excessive.

  In this chain tensioner 1, a cylindrical space 14 that communicates the reservoir chamber and the sub-reservoir chamber 27 is formed by providing a radial gap between the cylinder 10 and the sleeve 13, and the pressure chamber 17 and the reservoir chamber 18 communicate with each other. Since the escape passage 33 is formed in the plunger 16 and the rod 19, it is not necessary to process a long passage in the axial direction in the cylinder 10, and the processing of the cylinder 10 is simple.

  Further, since the chain tensioner 1 uses a light alloy as the material of the cylinder 10, it is light in weight.

  Further, since the sleeve 13 is separate from the cylinder 10, the sleeve 13 can be formed of a material different from the material of the cylinder 10. Therefore, by using a material having the same linear expansion coefficient as the material of the plunger 16 as the material of the sleeve 13, it is possible to prevent a change in the leak gap 32 between the sliding surfaces of the sleeve 13 and the plunger 16 due to a temperature change. .

  Further, since the fitting between the rear end of the rod 19 and the fitting recess 23 of the plunger 16 is a loose fitting fitting, when the rod 19 tilts when a force in a direction perpendicular to the axis acts on the tip of the rod 19, The displacement of the axis of the rod 19 and the plunger 16 is absorbed, and the plunger 16 is difficult to tilt. Therefore, even if the tension of the chain 6 increases and the chain guide 8 swings and the swinging causes a displacement between the contact surfaces of the chain guide 8 and the rod 19, the sliding surface of the sleeve 13 and the plunger 16. The leak gap 32 between them is difficult to change.

  As shown in FIG. 7, the seal cap 26 is preferably provided with an air breather 41 that vents in accordance with the pressure change in the sub reservoir chamber 27. In this way, when the pressure in the reservoir chamber 18 changes due to the temperature change of the hydraulic oil or the axial movement of the rod 19, the pressure change is absorbed by the ventilation of the air breather 41, and the oil leakage from the seal member 15 is further reduced. It becomes difficult to occur.

  The resistance ring 36 may be designed according to the sliding resistance applied to the rod 19, but it is economical to use a commercially available push nut shaft or CS type retaining ring (both manufactured by Ochiai Co., Ltd.).

The front view which shows the chain transmission apparatus incorporating the chain tensioner of 1st Embodiment of this invention Front sectional view of the chain tensioner shown in FIG. Enlarged cross-sectional view along line III-III in FIG. Sectional view along line IV-IV in FIG. 2 is a cross-sectional view of the vicinity of the resistance ring showing the state in which the rod shown in FIG. Sectional drawing of the cylinder open end vicinity which shows the state hold | maintained in the state which pushed the rod shown in FIG. 2 in the cylinder The expanded sectional view of the seal cap vicinity which shows the state which provided the air breather in the seal cap of the subreservoir chamber shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cylinder 11 Small diameter hole part 12 Large diameter hole part 13 Sleeve 14 Cylindrical space 16 Plunger 17 Pressure chamber 18 Reservoir chamber 19 Rod 21 Return spring 23 Fitting recessed part 27 Subreservoir chamber 28 Bottom 29 Opening 31 Check valve 32 Leakage clearance 33 Escape passage 34 Relief valve 36 Resistance ring 37 Resistance claw

Claims (3)

  A light alloy cylinder (10) with one open end is provided with a small diameter hole (11) and a large diameter hole (12) connected to the cylinder open side with respect to the small diameter hole (11). (10) The inside of the large-diameter hole (12) and the sleeve (13) are filled with hydraulic oil, and a bottomed sleeve (13) is fitted into the small-diameter hole (11) of the cylinder (10). A cylindrical space (14) is formed between the outer peripheries of 13), a plunger (16) is slidably inserted into the sleeve (13), and the pressure chamber (17) and the reservoir chamber ( 18), a return spring that is provided with a chain pressing rod (19) that moves integrally with the plunger (16) in the axial direction and urges the rod (19) in a direction protruding from the cylinder (10). (21) and the plunger ( 6) and a leakage gap (32) communicating the pressure chamber (17) and the reservoir chamber (18) between the sliding surfaces of the sleeve (13), and the reservoir through the cylindrical space (14). A sub-reservoir chamber (27) communicating with the chamber (18) is formed in the cylinder (10), air and hydraulic oil are accommodated in the sub-reservoir chamber (27), and the bottom (28) of the sleeve (13) is accommodated. The auxiliary reservoir chamber (27) and the pressure chamber (17) are communicated with each other through the formed opening (29), and the pressure from the auxiliary reservoir chamber (27) side to the bottom (28) of the sleeve (13). A check valve (31) that allows only the flow of hydraulic oil to the chamber (17) side is provided, and passes through the inside of the plunger (16) and the inside of the rod (19) in order, and the pressure chamber (17) and the Relief connecting the reservoir chamber (18) A chain tensioner provided with a relief valve (34) that is opened when the pressure in the pressure chamber (17) becomes higher than a preset pressure. .   The end of the rod (19) is inserted into the fitting recess (23) formed on the end surface of the plunger (16) on the reservoir chamber (18) side by a loose fit, and the rod ( 19. The chain tensioner according to claim 1, wherein the shift of the shaft between the plunger 19 and the plunger 16 is absorbed.   A resistance ring (36) that penetrates the rod (19) so as to be movable in the axial direction is provided so as to be movable in the axial direction within a certain range with respect to the cylinder (10), and from the resistance ring (36) to the inner diameter side. A plurality of extending resistance claws (37) are formed to be inclined in a tapered shape with a reduced diameter toward the tip end side of the rod (19), and the tip ends of the resistance claws (37) are brought into contact with the outer periphery of the rod (19), When the rod (19) moves in the direction to be pushed into the cylinder (10) and slides with the resistance claws (37), the sliding resistance of the rod (19) protrudes from the cylinder (10). The chain tensioner according to claim 1 or 2, wherein the chain tensioner is larger than a sliding resistance when moving in the direction of sliding and sliding with each of the resistance claws (37).

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