JP2008014337A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner capable of obtaining a stable movement in a sawtooth shape thread portion even when a turning effort or an angular moment is loaded from a chain guide able to be oscillated in the chain tensioner employing the sawtooth shape thread portion. <P>SOLUTION: The chain tensioner is characterized in that a nut member 13 is put in a cylinder room 12 of housing 11, and a male thread 20 formed in a rear end outer periphery of rod member 15 is engaged in thread to a sawtooth shape female thread 14 of inner periphery of the nut member 13, in that the rod member 15 is divided into a push rod 15a contacted to a chain guide 6 and an adjust screw 15b with a sawtooth shape male thread 20, in that a spring holding concave 21 opening at rear end face is formed in the adjust screw 15b, in that a spring 22 is put in a space between a blocking end of the spring holding concave 21 and blocking end face of the cylinder room 12, in that a ball 23 is put in a space between an end of the spring 22 and the blocking end face of the spring holding concave 21, and in that a rotational resistance of the adjust screw 15b is reduced by the above-mentioned method. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 rotated 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, the conventional chain tensioner is an assembly in which the tip of the rod provided on the nut member is brought into contact with a swingable supported chain guide. When the deviation occurs, a rotational force is applied to the nut member.

  In addition, the chain guide is a swingable support, and in order to absorb the vibration of the chain by the swinging of the chain guide, a rotational moment is applied to the nut member with which the rod at the end abuts the chain guide. The rotational moment acts directly on the screw engaging portions of the nut member and the bolt member.

  Here, 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 sawtooth screw The operating characteristics cannot be exhibited effectively, and the chain tension cannot be kept constant.

  Further, 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.

  An object of the present invention is to provide a chain tensioner in which the chain tension is kept constant by means of serrated screws, even if a rotational force or rotational moment is applied by contact with a swingable chain guide, It is to ensure that a stable operation is always obtained by preventing the rotational moment from being applied to the serrated screw portion.

  In order to solve the above problems, in the present invention, a housing in which a cylinder chamber having one end opened is formed, a nut member incorporated in the cylinder chamber of the housing, and a female screw on the inner periphery of the nut member. The rod member includes an engaging male screw on the outer periphery of the rear end portion, and a return spring that imparts outward protrusion to the rod member, and the rod member is loaded with the spring force of the return spring. A push rod that can move in the axial direction and an adjustment screw having an external thread on the outer periphery are divided into a spring housing recess that opens at the rear end surface of the adjustment screw. The closed end of the spring housing recess and the cylinder chamber A spring that urges the adjusting screw toward the push rod is installed between the closed end faces, and the screw A ball is assembled between the ring end and the closed end face of the spring accommodating recess, and the flank angle of the pressure side flank that receives the pushing force applied to the adjustment screw between the female screw of the nut member and the male screw of the adjustment screw is the play side flank. A configuration with serrated screws larger than the flank angle was adopted.

  The chain tensioner configured as described above is assembled so that the tip of the push rod comes into contact with the swingable chain guide. If slack occurs in the chain in the assembled state, the push rod moves forward by pressing the return spring, and the chain guide is pressed against the chain to absorb the slack in the chain.

  Further, when the chain is tensioned and a pushing force is applied from the chain to the push rod via the chain guide, the pushing force is supported by the pressure side flank of the serrated screw, and the push rod does not move backward. When the pushing force is larger than the spring force of the return spring, the adjusting screw moves backward to a position where the pushing force and the spring force are balanced to keep the chain tension constant.

  When adjusting the chain tension as described above, if the chain guide swings, the contact portion between the chain guide and the push rod is displaced, and a rotational moment is applied to the push rod. At this time, since the push rod and the adjusting screw are separated from each other at the opposed end faces, no rotation moment is applied to the adjusting screw, and the screw engaging portion of the female screw and the male screw is engaged. There is no inconvenience.

  Here, a slide member that can slide along the inner diameter surface of the cylinder chamber is provided at the rear end portion of the push rod located in the cylinder chamber, and a guide member that slidably supports the push rod is provided at the opening of the cylinder chamber. And the rotational moment loaded on the push rod can be received at two locations, the slide member and the mating surface of the cylinder chamber and the mating surface of the guide member and the push rod. The chain tensioner can be moved smoothly in the axial direction and has excellent responsiveness.

  When the chain tensioner as described above is assembled, an eccentric position with respect to the center of the tip surface of the push rod may contact the chain guide due to an assembly error or the like. At this time, a rotational force is applied to the push rod by the swing of the chain guide, but the push rod and the adjusting screw are separated and arranged on the same axis, so that the adjusting screw is not loaded with the rotational force. . For this reason, there is no inconvenience that the adjusting screw rotates and moves in the axial direction. When the chain is tensioned, the resistance force that suppresses the vibration of the chain is prevented from decreasing, and the operating characteristics of the sawtooth screw are effectively exhibited. Can be made.

  Here, if at least one of the rear end surface of the push rod and the front end surface of the adjusting screw is a spherical surface, it is possible to more reliably prevent the rotational force from being transmitted from the push rod to the adjusting screw.

  In the chain tensioner according to the present invention, when a diamond-like carbon film is formed on at least one of the female screw of the nut member and the male screw of the adjusting screw, the wear resistance of the screw engaging portion can be improved.

  In order to make the chain tensioner having the above-described configuration function smoothly, the thread engagement portion of the female screw and the male screw and the space between the cylinder chamber and the sliding surface of the slide member are lubricated with lubricating oil. In order to prevent leakage of the lubricating oil to the outside, a seal member such as an oil seal is provided at the opening end of the cylinder chamber. At this time, by providing a guide member on the opening end side of the cylinder chamber from the assembly position of the seal member, the guide member can prevent the seal member from coming off. Incorporation of members can be eliminated.

  As described above, the rod member that applies adjustment force to the chain guide is divided into the push rod and adjustment screw, so that even if rotational force or rotational moment is applied from the chain guide to the push rod, these rotational forces are applied. And the rotation moment is not transmitted to the adjusting screw, and when the chain is tensioned, the resistance force that suppresses the vibration of the chain is reduced, and the occurrence of inconvenience such as the biting of the serrated screw part is prevented, The chain tension can always be kept constant.

  Here, if the end of the spring that urges the adjusting screw toward the push rod is in contact with the closed end face of the spring accommodating recess, the rotational resistance of the adjusting screw increases, and the fluctuation in the tension of the chain The adjustment screw cannot be smoothly moved in the axial direction while rotating.

  However, by incorporating the ball between the end of the spring and the closed end face of the spring receiving recess formed in the adjustment screw, the rotation resistance of the adjustment screw is extremely small, and it moves smoothly in the axial direction while rotating the adjustment screw. Can be made.

  For this reason, it is possible to absorb a change in the tension of the chain smoothly, and it is possible to employ an easily available ball incorporated in the ball bearing as the ball, so that the cost of the chain tensioner is not significantly increased. .

  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 by an adjustment force applied from the chain tensioner 10.

  As shown in FIG. 2, the chain tensioner 10 has a housing 11, and a cylinder chamber 12 having one end opened is formed in the housing 11.

  A nut member 13 is incorporated in the cylinder chamber 12, and a female screw 14 is formed on the inner periphery of the nut member 13. In addition, a rod member 15 and a return spring 16 that imparts outward protrusion to the rod member 15 are incorporated in the cylinder chamber 12.

  The rod member 15 is divided into a push rod 15a and an adjusting screw 15b. The push rod 15a slidably passes through a seal member 17 such as an oil seal that seals the opening of the cylinder chamber 12, and the cylinder A slide member 18 slidable along the inner diameter surface of the cylinder chamber 12 is provided at the rear end located in the chamber 12, and the pressing force of the return spring 16 is loaded on the slide member 18.

  On the other hand, a ring-shaped guide member 19 is provided in the opening of the cylinder chamber 12 from the seal member 17 to the opening end side of the cylinder chamber 12, and the push rod 15 a is slidably supported by the inner diameter surface of the guide member 19. Has been.

  The adjusting screw 15 b has a male screw 20 on the outer periphery, and the male screw 20 is engaged with the female screw 14 of the nut member 13. The screw engaging portion of the male screw 20 and the female screw 14 and the sliding surface between the slide member 18 and the cylinder chamber 12 are lubricated by the lubricating oil sealed in the cylinder chamber 12.

  The adjusting screw 15b is formed with a spring accommodating recess 21 that opens at its rear end surface. A spring 22 between the closed end surface of the spring accommodating recess 21 and the closed end surface of the cylinder chamber 12 and a ball having a diameter larger than the inner diameter of the spring 22 are formed. 23, and the ball 23 is pressed against the closed end face of the spring accommodating recess 21.

  The spring 22 biases the adjusting screw 15b toward the push rod 15a via the ball 23, and the spherical surface 24a at the tip of the projecting shaft portion 24 provided on the tip surface of the adjusting screw 15b is pushed by the biasing. It is pressed against the rear end face of 15a.

  The thread of the internal thread 14 formed on the inner periphery of the nut member 13 and the external thread 20 formed on the outer periphery of the adjusting screw 15b has a flank angle of the pressure side flank 25 that receives the pressing force when the adjusting screw 15b is pressed. A serrated shape larger than the flank angle of the play side flank 26 is provided, and a lead angle is provided on the serrated screw thread so that the adjusting screw 15b rotates in the axial direction by the pressing force of the spring 22.

  The chain tension adjusting device shown in the embodiment has the above-described structure, and when the engine is driven, the chain 5 vibrates due to torque fluctuations caused by the rotation of the cam shaft 3, and the slack side chain of the chain 5 is slackened. Then, the push rod 15a moves outward by the pressing force of the return spring 16 to press the chain guide 6, and the slack of the chain 5 is absorbed by the pressing.

  When the push rod 15a moves outward, the adjusting screw 15b is rotated toward the push rod 15a side by the pressing force of the spring 22, and the spherical surface 24a at the tip of the projecting shaft portion 24 is the rear end surface of the push rod 15a. Abut.

  On the other hand, when the tension on the slack side chain of the chain 5 increases and a pushing force is applied from the chain 5 to the push rod 15a via the chain guide 6, the pushing force is also applied to the adjusting screw 15b. For this reason, the pressure side flank 25 of the female screw 14 of the nut member 13 and the male screw 20 of the adjusting screw 15b are in close contact with each other, and the pressing force is received by the pressure side flank 25 in close contact.

  When the pressing force is stronger than the pressing force of the return spring 16, slip occurs on the contact surface of the pressure side flank 25 that is in close contact with each other, and the adjusting screw 15 b slowly moves to a position where the pressing force and the pressing force of the return spring 16 are balanced. The chain 5 moves backward while rotating to keep the tension of the chain 5 constant.

  Here, since the spring 22 that biases the adjusting screw 15b toward the push rod 15a presses the adjusting screw 15b via the ball 23, the rotational resistance of the adjusting screw 15b is extremely small.

  For this reason, the adjusting screw 15b is hardly disturbed in rotation, and smoothly rotates and moves in the axial direction. Therefore, the tension change of the chain 5 can be absorbed very smoothly and easily available balls used for ball bearings can be used for the balls 23, which greatly increases the cost of the chain tensioner. There is nothing.

  By the way, since the chain guide 6 to which the adjusting force of the chain tensioner 10 is loaded is supported so as to be swingable about the shaft 7, when the pushing force is applied from the chain guide 6 to the push rod 15a, the push rod 15a. A rotational moment is applied to the.

  At this time, the slide member 18 provided at the rear end of the push rod 15a is slidable along the inner diameter surface of the cylinder chamber 12, and the guide member 19 provided at the opening of the cylinder chamber 12 is a push rod. Since the slide rod 15a is slidably supported, the rotational moment applied to the push rod 15a is supported at two locations: the fitting surface of the cylinder chamber 12 and the slide member 18 and the fitting surface of the push rod 15a and the guide member 19. Will be.

  Therefore, no rotational moment is applied to the adjusting screw 15b, and there is no inconvenience that the screw engaging portion of the female screw 14 and the male screw 20 is caught.

  When the chain tensioner 10 is assembled, an eccentric position with respect to the center of the front end surface of the push rod 15a may be assembled to abut against the chain guide 6 due to an attachment error or the like.

  At this time, a rotational force is applied to the push rod 15a by the swinging of the chain guide 6. However, the push rod 15a and the adjusting screw 15b are arranged coaxially, and the protruding shaft portion 24 of the adjusting screw 15b. Since the tip spherical surface 24a is in point contact with the rear end surface of the push rod 15a, the rotational force is not applied to the adjusting screw 15b.

  For this reason, there is no inconvenience that the adjusting screw 15b 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 thread portion that suppresses the vibration of the chain 5, The operating characteristics of the serrated screw can be effectively exhibited.

  In the example shown in FIG. 2, the rear end surface of the push rod 15 a is a flat surface, and the spherical surface 24 a at the tip of the protruding shaft portion 24 of the adjusting screw 15 b is brought into contact with the rear end surface. A spherical surface may be provided at the rear end of the push rod 15a.

  In the chain tensioner shown in the embodiment, when the internal thread 14 of the nut member 13 and the external thread 20 of the adjusting screw 15b are subjected to heat treatment such as carburizing, quenching and tempering to increase the hardness, the wear resistance of the internal thread 14 and the external thread 20 is improved. Can be made.

  Further, by performing shot peening on at least one of the female screw 14 and the male screw 20 to form irregularities, it is possible to obtain a stable frictional force over a long period of time at the screw engaging portion of the female screw 14 and the male screw 20.

  In order to improve the wear resistance of the female screw 14 and the male screw 20, it is effective to increase the hardness as described above. As a method for increasing the hardness, in addition to the above, a diamond-like carbon coating is applied to the surfaces of the female screw 14 and the male screw 20. There is a method of forming.

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 12 Cylinder chamber 13 Nut member 14 Female screw 15 Rod member 15a Push rod 15b Adjust screw 16 Return spring 18 Slide member 19 Guide member 20 Male screw 21 Spring accommodating recess 22 Spring 23 Ball 24a Spherical surface 25 Pressure side flank 26 Play side flank 26

Claims (6)

  A rod having a cylinder chamber in which one end is opened, a nut member incorporated in the cylinder chamber of the housing, and a rod having a male screw on the outer periphery of the rear end portion that is engaged with a female screw on the inner periphery of the nut member A member, and a return spring that imparts outward protrusion to the rod member, and a push rod that can move the rod member in the axial direction to which the spring force of the return spring is loaded, and a male screw on the outer periphery This spring is divided into an adjusting screw, and a spring accommodating recess that opens at the rear end surface is formed in the adjusting screw, and the adjusting screw is urged toward the push rod between the closed end of the spring accommodating recess and the closed end surface of the cylinder chamber. Between the end of the spring and the closed end face of the spring accommodating recess. Incorporate Lumpur, chain tensioner the external thread of the internal thread and the adjusting screw of the nut member, pressure flank for receiving a pushing force exerted on the adjusting screw has a large serrated screw from flank angle of clearance flanks.   A slide member that is slidable along an inner diameter surface of the cylinder chamber is provided at a rear end portion of the push rod located in the cylinder chamber, and a guide member that slidably supports the push rod is provided in the opening of the cylinder chamber. Item 2. The chain tensioner according to Item 1.   The chain tensioner according to claim 1 or 2, wherein one of the rear end surface of the push rod and the front end surface of the adjusting screw is a spherical surface.   The chain tensioner according to any one of claims 1 to 3, wherein a diamond-like carbon film is formed on at least one of the female screw of the nut member and the male screw of the adjusting screw.   The chain tensioner according to any one of claims 1 to 4, wherein a seal member for preventing leakage of lubricating oil for sliding portion lubrication to the outside is provided at an opening end portion of the cylinder chamber.   The chain tensioner according to claim 5, wherein the guide member is provided closer to the opening end of the cylinder chamber than the seal member.

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