JP4927638B2 - Chain tensioner - Google Patents

Description

  The present invention mainly relates to a chain tensioner that keeps the tension of a chain driving a camshaft or a toothed belt constant.

  In general, in a chain transmission for driving a camshaft that spans a chain between a sprocket attached to the end of the crankshaft and a sprocket attached to the end of the camshaft, the chain can be swung on the slack side of the chain. The chain guide is contacted, and the chain tensioner adjustment force is applied to the chain guide to keep the chain tension constant.

  As a chain tensioner employed in the chain transmission device, one described in Patent Document 1 has been conventionally known. In this chain tensioner, a nut member having a rod at the tip is slidably inserted into the body, and a serrated male screw formed on the outer periphery of the bolt member is formed on a serrated female screw formed on the inner periphery of the nut member. The above-mentioned nut member is projected outward by a return spring built into the body, and the pushing force applied to the rod of the nut member from the chain through the chain guide is serrated. When the thrust force is received by the pressure side flank of the screw to prevent the nut member from moving backward, and the pushing force is greater than the pushing force of the return spring, the nut member is rotated to a position where the pushing force and the spring force of the return spring are balanced. While moving backward, the chain tension is kept constant.

  Further, when the chain is slack, the nut member is moved forward by the pressing force of the return spring to absorb the slack of the chain.

Japanese Utility Model Publication No. 64-41755

  By the way, in the conventional chain tensioner, since the tip of the rod provided on the nut member is brought into contact with the swingable supported chain guide, the nut member is inclined when the chain guide swings. A rotational moment in the direction to be applied is applied, and the rotational moment acts directly on the screw engaging portion of the female screw and the male screw.

  Further, if the eccentric position with respect to the center of the rod tip is in contact with the chain guide due to an error during assembly or the like, a rotational force is applied to the nut member by the swinging of the chain guide.

  Here, if the rotational moment applied to the nut member directly acts on the saw-toothed screw, there is a possibility that the saw-toothed screw portion is bitten and the nut member does not move.

  In addition, when a rotational force is applied to the nut member, the nut member moves in the axial direction while rotating, and when the chain is tensioned, the resistance force that suppresses the vibration of the chain is reduced, and the saw-tooth screw operates. The characteristics cannot be exhibited effectively, and the chain tension cannot be kept constant.

  An object of the present invention is to ensure that even when a rotational moment or rotational force is applied from a swingable chain guide, the rotational force or rotational moment is not applied to the saw-toothed thread portion so that stable operation is always obtained. Is to provide a chain tensioner.

In order to solve the above-described problems, in the present invention, lubricating oil is filled in a cylindrical housing having one end opened and the other end closed, and a female screw is provided on the inner periphery of the opening end of the housing, The flank angle of the pressure side flank that receives the pushing force applied to the screw rod by engaging the male screw formed on the outer periphery of the screw rod with the female screw, A large serrated screw is connected to the distal end of the screw rod located outside from the open end of the housing, and the closed end of the distal end of the cylindrical plunger that can slide along the outer diameter surface of the housing is rotatably connected. a return spring provided outside of the plunger, the closed end of the plunger is provided with a flange for receiving the end of the return spring, the Li Than is employing the configuration urged in the direction of extending said plunger over down spring.

  In the chain tensioner having the above configuration, when the chain guide is tensioned by the plunger biased in the direction of extension by the return spring to apply tension to the chain, and the chain is slackened. Further, the plunger is moved in the extending direction by pressing the return spring to absorb the slack of the chain.

  At this time, since the female screw of the housing and the male screw of the screw rod are in a state where the play side flank is in contact and the frictional resistance of the screw portion is small, the screw rod rotates in the direction of extension while moving in the direction of extension of the plunger. Move smoothly.

  On the other hand, when the chain is tensioned, the pushing force applied to the plunger from the chain through the chain guide is received by the pressure side flank of the female screw of the housing and the male screw of the screw rod to prevent the plunger from moving backward.

  When the pushing force is stronger than the pushing force of the return spring, the chain rod is moved in a contracting direction while rotating the screw rod to a position where the pushing force and the elastic force of the return spring are balanced, and the chain tension is kept constant.

  Here, since the chain guide is a swingable support, when a pushing force is applied from the chain guide to the plunger, a rotational moment to be inclined to the plunger is loaded by the swing of the chain guide. At this time, since the plunger is slidably fitted to the outer diameter surface of the housing, the rotational moment is received by the fitting surface of the housing and the plunger, and the rotational moment is applied to the screw rod. There is nothing.

  Even if a rotational force is applied from the chain guide to the closed end face of the plunger, the plunger and the screw rod are rotatably connected, so that the rotational force is not applied to the screw rod.

In the chain tensioner according to the present invention, since the be provided a return spring outside the plunger, as compared with the case where the inside of the plunger providing the return spring is possible to achieve an axial length compactness of the chain tensioner it can.

In the chain tensioner according to the present invention, a ring groove is formed on the outer periphery of the opening end of the housing, and an elastic retaining ring partially cut into the ring groove is incorporated in a reduced diameter state, while the plunger If a retaining groove extending in the circumferential direction is provided on the inner periphery of the rear end, the plunger can be retained by the engagement of the retaining ring with the retaining groove, and the screw is removed when the chain tensioner is removed for maintenance or the like. It is possible to prevent the rod and plunger from falling off the housing.

  As described above, in the present invention, the closed end portion of the distal end of the plunger that can slide along the outer diameter surface of the housing is rotatably connected to the distal end portion of the screw rod that is screw-engaged with the female screw of the housing. Even when a rotational moment or rotational force is applied to the plunger from the chain guide, the rotational moment or rotational force can be prevented from being transmitted to the screw rod. Therefore, the operability of the sawtooth screw by the female screw of the nut member and the female screw of the screw rod is not hindered, and a stable operation can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a tension adjusting device for a camshaft drive chain. As shown in the figure, a chain 5 is spanned between a sprocket 2 attached to the end of the crankshaft 1 and a sprocket 4 attached to the end of the camshaft 3, and a chain guide is connected to the slack side of the chain 5. 6 is provided.

  The chain guide 6 can swing around a shaft 7 provided at the lower end thereof. The chain guide 6 is pressed against the chain 5 with an adjustment force applied from a chain tensioner 10 fixed to the chain cover 7.

  As shown in FIG. 2, the chain tensioner 10 has a housing 11 that is inserted into a tensioner mounting hole 9 formed in the chain cover 8. The housing 11 has a cylindrical shape with one end opened and the other end closed, and a mounting flange 12 that is bolted to the chain cover 8 is provided at the closed end.

  A female screw 13 is formed on the inner periphery of the opening end of the housing 11, and a male screw 15 formed on the outer periphery of the screw rod 14 is threadedly engaged with the female screw 13.

  Here, the thread of the female screw 13 and the male screw 15 has a sawtooth shape in which the flank angle of the pressure side flank 16 that receives the pushing force when the pushing force is applied to the screw rod 14 is larger than the flank angle of the play side flank 17. The sawtooth thread is provided with a lead angle that moves in a direction in which the screw rod 14 extends while rotating by a press of a return spring 22 (to be described later) (a direction to exit the housing 11).

  The screw engaging portions of the female screw 13 and the male screw 15 are lubricated by a lubricating oil filled in the housing 11.

  A cylindrical plunger 18 is slidably fitted to the outside of the housing 11. The plunger 18 is closed at the tip, and the closed end surface serves as a pressing portion of the chain guide 6.

  A stepped hole 19 is formed in the center of the closed end of the plunger 18, and a small diameter shaft portion 14 a formed at the tip of the screw rod 14 is inserted into the small diameter hole of the stepped hole 19. Is sealed by attachment of an O-ring 20. In addition, a rolling bearing 21 is press-fitted into the large-diameter hole of the stepped hole 19, and the screw rod 14 and the plunger 18 are rotatably connected by the rolling bearing 21.

  A return spring 22 is provided outside the plunger 18. Both ends of the return spring 22 are supported by the mounting flange 12 of the housing 11 and a flange 23 provided at the closed end of the plunger 18, and the plunger 18 is urged by the return spring 22 in a direction to extend with respect to the housing 11. The chain guide 6 is pressed.

  A seal groove 24 is formed on the outer periphery of the opening end portion of the housing 11, and the O-ring 25 incorporated in the seal groove 24 is in elastic contact with the inner diameter surface of the plunger 18, and between the sliding surfaces of the housing 11 and the plunger 18. To prevent the lubricating oil filled in the housing 11 from leaking to the outside.

  In addition, a ring groove 26 is formed on the outer periphery of the opening end of the housing 11 at a position slightly offset from the seal groove 24 toward the rear end. The retaining ring 27 is assembled in a reduced diameter state.

On the other hand, a retaining groove 28 is formed on the inner periphery of the rear end of the plunger 18, and the plunger 18 is retained by the engagement of the retaining ring 27 with the retaining groove 28.
It is prevented from falling off from the open end of the housing 11.

  The chain tension adjusting device shown in the embodiment has the above-described structure. In the assembled state of the chain tensioner 10 as shown in FIGS. 1 and 2, the engine is driven, and torque fluctuation due to rotation of the cam shaft 3 is caused. When the chain 5 vibrates and the slack side chain of the chain 5 becomes slack, the plunger 18 moves in the direction in which the return spring 22 is pressed to absorb the slack of the chain 5.

  At this time, the female screw 13 of the housing 11 and the male screw 15 of the screw rod 14 are in a state where the play-side flank 17 is in contact and the frictional resistance of the screw engaging portion is small. Therefore, when the plunger 18 moves in the extending direction, The rod 14 moves smoothly in the extending direction while rotating.

  On the other hand, when the chain 5 is tensioned, a pushing force is applied from the chain 5 to the plunger 18 via the chain guide 6, and the pressure side flank 16 of the female screw 13 of the housing 11 and the male screw 15 of the screw rod 14 is in close contact with each other. The pressing force is received by the pressure side flank 16 in close contact therewith.

  When the pushing force is stronger than the pushing force of the return spring 22, slip occurs on the contact surface of the pressure side flank 16 that is in close contact with each other, and the screw rod 14 rotates to a position where the pushing force and the elastic force of the return spring 22 are balanced. While moving in the contracting direction, the plunger 18 also moves in the contracting direction together with the screw rod 14 to keep the tension of the chain 5 constant.

  In the chain tension adjusting device shown in FIG. 1, since the chain guide 6 is a swingable support, when a pushing force is applied from the chain guide 6 to the plunger 18, the chain guide 6 is swung to the plunger 18. A rotational moment that causes an inclination is applied.

  At this time, since the plunger 18 is slidably fitted along the outer diameter surface of the housing 11, the rotational moment is received by the fitting surface between the plunger 18 and the housing 11. Therefore, no rotational moment is applied to the screw rod 14 connected to the plunger 18, and there is no inconvenience that the screw engaging portion of the female screw 13 and the male screw 15 is bitten.

  Here, when the chain tensioner 10 is assembled, an eccentric position with respect to the center of the closed end surface of the plunger 18 may be assembled so as to contact the chain guide 6 due to an attachment error or the like.

  At this time, the rotation of the chain guide 6 causes a rotational force centered on its axis to be applied to the plunger 18, but the plunger 18 and the screw rod 14 are rotatably connected. No rotational force is applied to 14.

  For this reason, there is no inconvenience that the screw rod 14 rotates and moves in the axial direction, and at the time of tension of the chain 5, it is possible to prevent a decrease in the frictional resistance force at the serrated screw portion that suppresses vibration of the chain 5. The operating characteristics of the serrated screw can be effectively exhibited.

  Here, when the chain tensioner 10 is removed for maintenance or the like, the plunger 18 moves in a direction in which the plunger 18 extends due to the pressing of the return spring 22. When the retaining groove 28 formed on the inner periphery of the rear end portion of the plunger 18 moves in a direction in which the plunger 18 extends to a position facing the retaining ring 27, the retaining ring 27 expands in diameter by its own restoring elasticity. The plunger 18 and the screw rod 14 are retained by the engagement with the retaining groove 28.

  Thus, since the plunger 18 and the screw rod 14 are prevented from being pulled out by the engagement of the retaining ring 27 with the retaining groove 28, the plunger 18 and the screw rod 14 are not dropped from the housing 11, and the chain tensioner. 10 reassembly can be easily performed.

  As shown in the embodiment, when the return spring 22 is provided outside the plunger 18, the axial length of the chain tensioner 10 can be made compact compared to the case where the return spring 22 is provided inside the plunger 18. it can.

Schematic of a chain tension adjusting device employing a chain tensioner according to the present invention Longitudinal front view of the chain tensioner according to the present invention

Explanation of symbols

11 Housing 13 Female screw 14 Screw rod 15 Male screw 16 Pressure side flank 17 Play side flank 18 Plunger 22 Return spring 23 Flange 26 Ring groove 27 Retaining ring 28 Retaining groove

Claims (2)

A cylindrical housing with one end open and the other end closed is filled with lubricating oil. A female screw is provided on the inner periphery of the open end of the housing, and a male screw formed on the outer periphery of the screw rod is screwed into the female screw. Engage the screw threads of the male screw and female screw with a serrated screw whose flank angle of the pressure side flank receiving the pushing force applied to the screw rod is larger than the flank angle of the play side flank. A closed end of a cylindrical plunger that is slidable along the outer diameter surface of the housing is rotatably connected to a distal end of the screw rod that is positioned, and a return spring is provided outside the plunger , and the plunger is closed. the end provided with a flange for receiving the end of the return spring, in the direction of extending said plunger in said return spring It energized the chain tensioner. A ring groove is formed on the outer periphery of the open end of the housing, and an elastic retaining ring partially cut into the ring groove is assembled in a reduced diameter, and the above-mentioned pull-out is formed on the inner periphery of the rear end of the plunger. The chain tensioner according to claim 1, wherein the retaining ring is engageable, and a retaining groove for retaining the plunger by the engagement is formed.

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