JP2009063155A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of abnormal sound due to collision of a plunger against a chain guide and to inhibit abrasion at a contact part of the plunger and the chain guide. <P>SOLUTION: A plunger 13 and a return spring 14 are built in within a cylinder chamber 12 formed in a housing 11, wherein, when pushing force is applied to the plunger 13, the pushing force is damped by oil within a hydraulic damper chamber 15 formed behind the plunger 13. A cap-like pressing member 22 made of an elastic synthetic resin is attached to a small diameter shaft section 13a at a tip of the plunger 13, a semi-spherical projection section 6a formed in a chain guide 6 is pressed by the pressing member 22, the chain guide 6 is energized in the direction a chain 5 is stretched, generation of abnormal sound is inhibited as the contact of the chain guide 6 and the plunger 13 is made the contact of a metal and a synthetic resin, and surface pressure is reduced as the contact area against the projection section 6a is increased by elastic deformation of the pressing member 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a chain tensioner that maintains a constant tension of a timing chain that drives a camshaft.

  Generally, in a chain transmission that uses a timing chain (hereinafter simply referred to as the chain) to transmit the rotation of the crankshaft to the camshaft, the chain tensioner adjustment force is applied to the slack side of the chain to keep the chain tension constant. I am doing so.

  As the chain tensioner, one described in Patent Document 1 is known. In this chain tensioner, a plunger and a return spring that imparts outward protrusion to the plunger are incorporated in a cylinder chamber formed in the housing, and the housing has a hydraulic pressure formed on the back of the plunger. An oil supply passage that communicates with the damper chamber is formed, a check valve is provided at the oil outlet of the oil supply passage, and the protrusion provided on the chain guide that can be swung by the plunger is pressed so that the chain is tensioned. The chain guide is energized, and the pushing force applied to the plunger from the chain through the chain guide is buffered by the hydraulic damper action by the engine oil in the hydraulic damper chamber so that the chain tension is kept constant.

Japanese Patent No. 3670911

  By the way, in the conventional chain tensioner, since the plunger and the chain guide are in contact with metal, the tip of the plunger collides with the protruding portion of the chain guide when the chain loosens suddenly and the follow-up of the plunger is delayed. Then, there was a possibility that abnormal noise was generated.

  In addition, the surface of the protruding portion provided on the chain guide is a spherical surface or a cylindrical surface so that the chain guide swings smoothly, and the flat tip surface of the plunger is brought into contact with the spherical surface or the cylindrical surface. Since the contact is a point contact or a line contact with a small contact area, there is a problem that the surface pressure at the contact portion is high and the contact portion is easily worn.

  An object of the present invention is to provide a chain tensioner capable of preventing abnormal noise from being generated due to a collision of a plunger with a chain guide and suppressing wear at a contact portion between the plunger and the chain guide. It is to be.

  In order to solve the above problems, in the present invention, a plunger slidable in a cylinder chamber formed in a housing and a return spring for imparting outward protrusion to the plunger are incorporated, and the housing is assembled. Is provided with an oil supply passage communicating with the hydraulic damper chamber formed on the back of the plunger, and a check is made to close the oil supply passage when the pressure in the hydraulic damper chamber is higher than the supply pressure of oil sent to the oil supply passage at the oil outlet of the oil supply passage. A chain tensioner provided with a valve and pressing a spherical surface or a cylindrical surface of a protrusion provided on a chain guide swingable by the plunger to urge the chain guide in a direction in which the chain is tensioned. A configuration is adopted in which a pressing member made of synthetic resin having elasticity is attached to the tip.

  As described above, by attaching an elastic synthetic resin pressing member to the tip of the plunger and making the contact between the plunger and the protruding portion of the chain guide be a contact between the metal and the synthetic resin, the chain suddenly relaxes. When the plunger has a follow-up delay and the plunger collides with the protruding portion, the pressing member is elastically deformed to absorb the collision force, and the generation of abnormal noise can be suppressed.

  Further, when a pressing force is applied from the chain guide to the plunger, the pressing member is elastically deformed to increase the contact area, and conversely, the surface pressure decreases, so that wear at the contact portion can be suppressed.

  Here, if the concave surface along the surface shape of the protruding portion is formed on the pressing member, the contact area between the pressing member and the protruding portion can be further increased, so that wear at the contacting portion can be more effectively prevented. it can.

  The pressing member may be a flat plate, or may be a cap having a cylindrical portion that is fitted to the tip of the plunger. In a flat pressing member, it adheres to the front end surface of a plunger through the means by adhesion | attachment. In this case, the adhesive member may be peeled off due to vibration or the like, and may fall off. Therefore, in order to stabilize the attachment, the pressing member is preferably a cap having a cylindrical portion.

  In the cap-shaped pressing member, the cylindrical portion is press-fitted into the distal end portion of the plunger, or the female screw formed on the inner periphery of the cylindrical portion is engaged with the male screw formed on the outer periphery of the distal end portion of the plunger. A tightening attachment method can be adopted, and an attachment method integrated with the plunger by injection molding can be adopted, and an extremely stable attachment state can be obtained.

  As described above, in the present invention, by attaching an elastic synthetic resin pressing member to the tip of the plunger, the plunger is delayed in response to a change in chain tension, and the plunger is connected to the chain guide. When it collides with the protruding portion, the pressing member is elastically deformed to absorb the collision force, so that an effect can be obtained in preventing the generation of abnormal noise.

  In addition, when a pushing force is applied from the chain guide to the plunger, the pressing member is elastically deformed to increase the contact area, and conversely, the surface pressure is reduced, thereby preventing wear at the contact portion. And a decrease in durability can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, 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.

  A chain guide 6 is provided on one side of the slack side chain 5 a of the chain 5. The chain guide 6 is swingable about a shaft 7, and a chain tensioner 10 that loads an adjustment force to the chain 5 via the chain guide 6 is provided on one side thereof.

  As shown in FIG. 2, the chain tensioner 10 has a housing 11 attached to the chain cover 8. A cylinder chamber 12 having a closed end is formed in the housing 11, and a plunger 13 and a return spring 14 are incorporated in the cylinder chamber 12.

  The return spring 14 biases the plunger 13 outward, and the plunger 13 presses the protruding portion 6 a formed on the chain guide 6 by the biasing to apply tension to the chain 5. Here, the protrusion 6a is hemispherical as shown in FIG. 5, but may be semicylindrical as shown in FIG.

  As shown in FIG. 2, the housing 11 is provided with an oil supply passage 16 communicating with a hydraulic damper chamber 15 formed at the back of the plunger 13, and a check valve 17 is provided at an oil outlet portion of the oil supply passage 16. . The check valve 17 closes the oil supply passage 16 when the pressure of the oil in the hydraulic damper chamber 15 becomes higher than the supply pressure of the oil sent to the oil supply passage 16.

  The plunger 13 is provided with a spring accommodating recess 18 that opens at the rear end face located in the cylinder chamber 12 and forms a part of the hydraulic damper chamber 15, and the tip of the return spring 14 is located inside the spring accommodating recess 18. Contained.

  A ring accommodating groove 19 is formed in the inner periphery of the opening of the cylinder chamber 12, and a register ring 20 that is elastically deformable in the radial direction is accommodated in the ring accommodating groove 19. On the other hand, a plurality of circumferential grooves 21 to be tightened by the register ring 20 are provided on the outer periphery of the plunger 13 at equal intervals in the axial direction.

  The inner circumference of the circumferential groove 21 has a small diameter toward the tip of the plunger 13, a tapered surface 21 a that expands the register ring 20 when the plunger 13 moves forward, and a radial direction continuously to the small diameter end of the tapered surface 21 a. An engaging surface 21b extending outward is provided.

  A small-diameter shaft portion 13a is formed at the tip of the plunger 13, and a pressing member 22 is attached to the small-diameter shaft portion 13a. The pressing member 22 has a cap shape in which a cylindrical portion 22b is provided on the outer periphery of the circular end plate 22a, and is fixed to the small diameter shaft portion 13a by press-fitting the cylindrical portion 22b to the outer periphery of the small diameter shaft portion 13a. This pressing member 22 is made of an elastic synthetic resin and is formed by injection molding.

  The chain tension adjusting device shown in the embodiment has the above-described structure, and the chain 5 vibrates due to a change in the angular velocity during one rotation of the crankshaft 1 or a torque fluctuation of the camshaft 3, and the slack side chain of the chain 5 is shown. When the slack of 5a occurs, the plunger 13 moves outward (forward movement) by the pressing of the return spring 14, and absorbs the slack of the chain 5.

  When the plunger 13 moves forward, the register ring 20 is pushed by the taper surface 21a to expand the diameter, so that the forward movement of the plunger 13 is not hindered. When the movement amount of the plunger 13 becomes larger than the pitch of the circumferential groove 21, the next circumferential groove 21 corresponds to the register ring 20, and the circumferential groove 21 is tightened by the register ring 20.

  On the other hand, when the chain 5 is tensioned, a pushing force is applied to the plunger 13 via the chain guide 6. At this time, when the pressure in the hydraulic damper chamber 15 rises and the pressure becomes higher than the supply pressure of the oil supplied from the oil pump to the oil supply passage 16, the check valve 17 closes the oil supply passage 16 and the hydraulic damper chamber 15 The pushing force applied to the plunger 13 is buffered by the hydraulic damper action of the oil enclosed in the.

  When the engine is stopped, the slack side chain 5a may be held in a tension state depending on the relationship of the stop position of the cam. At this time, since the pushing force is applied to the plunger 13 via the chain 5 and the chain guide 6, the plunger 13 moves backward.

  When the plunger 13 is slightly retracted, the register ring 20 abuts against the rear end surface of the spring accommodating groove 19 and is held in a stopped state, and the engaging surface 21b of the circumferential groove 21 is engaged with the register ring 20 in the stopped state. The plunger 13 is prevented from retreating greatly.

  For this reason, even if the engine is restarted, the chain 5 does not loosen greatly, and the plunger 13 does not move greatly outward, so that air does not enter the hydraulic damper chamber 15. .

  Here, in the chain tensioner 10, the plunger 13 is biased toward the chain guide 6 by pressing the return spring 14, and the protruding portion 6 a of the chain guide 6 is pressed by the plunger 13. When the slack side chain 5a is loosened suddenly, the plunger 13 does not follow the slack of the chain 5a, so that a delay occurs and the plunger 13 may collide with the protruding portion 6a.

  At this time, the pressing member 22 is attached to the distal end portion of the plunger 13, and the pressing member 22 is formed of elastic synthetic resin. Therefore, the pressing member 22 is elastic due to the collision of the pressing member 22 with the protruding portion 6a. The impact force is buffered by the elastic deformation. For this reason, no abnormal noise is generated.

  Further, since the pressing member 22 attached to the small-diameter shaft portion 13a at the tip of the plunger 13 has elasticity, when the pressing force is applied from the chain 5 to the plunger 13 through the chain guide 6, the pressing member 22 is elastically deformed. As a result, the contact area with the protrusion 6a increases. At this time, when the protrusion 6a is hemispherical, as shown by a chain line a in FIG. 5, the protrusion 6a and the pressing member 22 are in contact with each other by a spherical surface, and when the protrusion 6a is cylindrical, the chain line in FIG. As shown by B, the contact is made on the narrow surface.

  As described above, since the contact area increases due to elastic deformation of the pressing member 22, the surface pressure of the contact portion decreases on the contrary, so that wear at the contact portion can be suppressed, and the chain has excellent durability. A tensioner can be provided.

  Here, as shown in FIGS. 2 and 3, if a concave surface 23 along the surface of the protruding portion 6 a is provided on the surface of the end plate 22 a of the pressing member 22, the contact area is further increased by elastic deformation of the pressing member 22. Therefore, it is possible to further increase the effect of suppressing wear at the contact portion.

  In the example shown in FIG. 2, the cap-shaped pressing member 22 is fixed to the small-diameter shaft portion 13a of the plunger 13 by press-fitting. However, the pressing member 22 is fixed to the small-diameter shaft portion 13a by means of adhesion. Also good. Alternatively, as shown in FIG. 4, a male screw 24 is formed on the outer periphery of the small-diameter shaft portion 13 a, a female screw 25 is provided on the inner periphery of the cylindrical portion 22 b of the pressing member 22, and tightening by screwing the female screw 25 and the male screw 24 is performed. The pressing member 22 may be fixed.

The front view which shows the tension adjustment apparatus of the chain using the chain tensioner which concerns on this invention 1 is a longitudinal front view of the chain tensioner shown in FIG. Exploded perspective view showing the tip of the plunger and the pressing member Exploded perspective view showing another example of attachment of pressing member The perspective view which shows the protrusion part of a chain guide The perspective view which shows the other example of the protrusion part of a chain guide

Explanation of symbols

5 Chain 6 Chain guide 6a Protruding portion 11 Housing 12 Cylinder chamber 13 Plunger 13a Small-diameter shaft portion 14 Return spring 15 Hydraulic damper chamber 16 Oil supply passage 17 Check valve 22 Pressing member 22b Cylindrical portion 23 Concave surface 24 Male screw 25 Female screw

Claims (6)

A plunger slidable in a cylinder chamber formed in the housing and a return spring that imparts outward protrusion to the plunger are incorporated, and the housing communicates with a hydraulic damper chamber formed on the back of the plunger. An oil supply passage is provided, and a check valve is provided at the oil outlet of the oil supply passage to close the oil supply passage when the pressure in the hydraulic damper chamber becomes higher than the supply pressure of oil sent to the oil supply passage. In the chain tensioner that presses the spherical surface or cylindrical surface of the provided protrusion and urges the chain guide in the direction in which the chain is tensioned,
A chain tensioner characterized in that an elastic synthetic resin pressing member is attached to the tip of the plunger.   The chain tensioner according to claim 1, wherein the pressing member is formed with a concave surface along a surface shape of the protruding portion.   The chain tensioner according to claim 1 or 2, wherein the pressing member is formed in a cap shape having a cylindrical portion fitted on a distal end portion of a plunger on an outer periphery.   The chain tensioner according to claim 3, wherein the cap-shaped pressing member is fixed to the plunger by press-fitting a cylindrical portion.   The chain tensioner according to claim 3, wherein the cap-shaped pressing member is fixed to the plunger by tightening by screw engagement of a female screw formed on the inner periphery of the cylindrical portion and a male screw formed on the outer periphery of the distal end portion of the plunger.   The chain tensioner according to claim 3, wherein the cap-shaped pressing member is integrated with the plunger by injection molding.

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