JP2007100781A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner employing a saw-tooth screw which prevents rotational force and rotational moment from acting thereon even if the rotational force and the rotational moment are loaded from an abutted part with a swingable chain guide so as to provide stable operation. <P>SOLUTION: A saw-tooth male screw 21 of a rod member 16 is threadedly engaged with a saw-tooth female screw 15 of a nut member 14 incorporated in a cylinder chamber 13 of a housing 11. The rod member 16 is divided into an adjust screw 16b and a push rod 16a provided with the outward projecting property by a return spring 17. Even if the rotational force is loaded on the push rod 16a from a chain guide 6, the rotational force is prevented from being transmitted to the adjust screw 16b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention mainly relates to an auto tensioner that maintains a constant tension of a chain or a toothed belt that drives a camshaft.

  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 tension of the auto tensioner is applied to the chain guide to keep the chain tension constant.

  As an auto tensioner employed in the chain transmission device, one described in Patent Document 1 has been conventionally known. In this auto 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 from the chain to the rod of the nut member via the chain guide is sawtooth-shaped. The nut member is received by the pressure flank of the screw to prevent the nut member from moving backward, and when 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.1-4755

  By the way, the conventional auto tensioner is an assembly in which a tip of a rod provided on a nut member is brought into contact with a chain guide supported so as to be swingable. 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.

  In the auto tensioner as described above, the nut member is urged by the return spring so that the rod protrudes greatly to the outside, and the nut member is pressed by the return spring during maintenance around the engine for removing the chain. Since it rotates and moves in the axial direction, it is in an extended state. For initial assembly of the auto tensioner to the engine block and reassembly after maintenance, the nut member is mounted on the body by applying rotational force to the rod of the nut member. It is necessary to perform initial assembly and reassembly while maintaining the retracted state, and it takes a lot of time to assemble and should be improved in order to facilitate the assembly. Is left.

  An object of the present invention is to provide an automatic tensioner that maintains a constant chain tension with a serrated screw, even if a rotational force or rotational moment is applied by contact with a swingable chain guide. It is to make it possible to always obtain a stable operation by preventing the rotational moment from being applied to the serrated thread portion, and to facilitate the assembly.

  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. The push rod is movable in the axial direction, and is divided into an adjustment screw having an external thread on the outer periphery, and this adjustment screw is provided with a spring accommodation hole that opens at the rear end surface. The adjustment screw is inserted into the spring accommodation hole as a push rod. The coil spring that is biased toward the coil spring is pressed into the end of the coil spring and integrated. A spherical seat formed on the head is incorporated with a spring seat that makes point contact with a pressing surface pressed by a coil spring, and the female screw of the nut member and the male screw of the adjusting screw receive a pushing force applied to the adjusting screw. A serrated screw with a flank angle on the pressure side flank larger than the flank angle on the play side flank is formed, and a screw hole that is closed by screwing a plug is formed in the closed end wall of the cylinder chamber. The diameter is larger than the outer diameter, and the adjusting screw is provided with an engaging portion that can be engaged with a turning tool inserted from the screw hole.

  The auto 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. An auto tensioner that can move smoothly in the axial direction and has excellent responsiveness can be obtained.

  In the auto tensioner that guides the movement of the push rod by the slide member and the guide member, the guide member is provided closer to the opening end of the cylinder chamber than the sealing member for sealing the lubricating oil provided in the opening of the cylinder chamber. Since the sealing member can be prevented from being removed by the guide member, it is not necessary to incorporate a retaining member such as a retaining ring for retaining the sealing member.

  When the auto tensioner as described above is assembled, the eccentric position with respect to the center of the tip surface of the push rod may come into contact with 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 above auto tensioner, when the chain is removed due to maintenance around the engine, or when the auto tensioner is removed, the push rod moves outward by pressing the return spring, and the adjustment screw rotates by pressing the coil spring. While moving toward the push rod, the auto tensioner is extended. When reassembling the auto tensioner, remove the plug, take out the coil spring and spring seat from the screw hole, insert the turning tool, engage the turning tool with the engaging part, and load the turning tool. Rotate the adjusting screw with the rotational force to rotate, push the push rod in, and after installing the coil spring and spring seat, close the screw hole by screwing in the plug and shrink the auto tensioner. Do the attachment.

  In this case, a set hole penetrating in the radial direction is formed at the opening end of the housing, a pin hole penetrating in the radial direction is provided at the tip of the push rod, and a set pin is inserted into the pin hole from the set hole. By holding the push rod in the pushed-in state, the auto tensioner can be held in the contracted state by the set pin, so that the reassembly can be easily performed and the initial assembly is also facilitated. be able to.

  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.

  Also, by removing the plug, turning the screw hole from the inside and inserting the tool into engagement with the engaging portion, the adjustment screw can be moved backward by the rotation applied to the turning tool. Since the auto tensioner can be brought into the contracted state by pushing the push rod, the auto tensioner can be easily reassembled.

  Furthermore, the spring seat is press-fitted into the coil spring that presses the adjusting screw, and the spherical surface formed on the head of the spring seat is brought into point contact with the pressing surface of the coil spring. The screw can be rotated smoothly. For this reason, an adjustment screw can be made to follow favorably with respect to the tension change of a chain.

  In addition, since the coil spring and the spring seat are integrated by press-fitting, the spring seat is also incorporated at the same time by inserting the coil spring into the screw hole after the adjustment screw is moved backward. Forgetting can be prevented.

  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 adjusting force loaded from the auto tensioner 10.

  As shown in FIG. 2, the auto tensioner 10 has a housing 11, and a plurality of mounting pieces 12 that are bolted to the engine block are provided on the outer periphery of the housing 11. The housing 11 is formed with a cylinder chamber 13 having one end opened.

  A nut member 14 is incorporated in the cylinder chamber 13, and a female screw 15 is formed on the inner periphery of the nut member 14. Further, a rod member 16 and a return spring 17 for imparting outward protrusion to the rod member 16 are incorporated in the cylinder chamber 13.

  The rod member 16 is divided into a push rod 16a and an adjustment screw 16b. The push rod 16a slidably passes through a seal member 18 such as an oil seal that seals the opening of the cylinder chamber 13, and the cylinder A slide member 19 slidable along the inner diameter surface of the cylinder chamber 13 is provided at the rear end located in the chamber 13, and the pressing force of the return spring 17 is loaded on the slide member 19.

  On the other hand, a ring-shaped guide member 20 is provided in the opening of the cylinder chamber 13 from the seal member 18 to the opening end side of the cylinder chamber 13, and the push rod 16 a is slidably supported by the inner diameter surface of the guide member 20. Has been.

  The adjusting screw 16 b has a male screw 21 on the outer periphery, and the male screw 21 is engaged with the female screw 15 of the nut member 14. The screw engaging portions of the male screw 21 and the female screw 15 and the sliding surfaces of the slide member 19 and the cylinder chamber 13 are lubricated by the lubricating oil sealed in the cylinder chamber 13.

  The adjustment screw 16b is formed with a spring accommodating hole 22 that opens at the rear end face thereof, and a female screw 23 as an engaging portion is formed on the inner periphery of the opening end of the spring accommodating hole 22. On the other hand, the housing 11 is provided with a screw hole 24 in the closed end wall of the cylinder chamber 13, and the screw hole 24 is closed by screwing a plug 25.

  A coil spring 26 and a spring seat 27 made up of a pin are assembled between the plug 25 and the closed end face of the spring accommodating hole 22. The spring seat 27 has a head portion 27a, and a spherical surface 27b formed on the head portion 27a is pressed against the closed end of the spring accommodating hole 22 to make point contact.

  The coil spring 26 urges the adjusting screw 16b toward the push rod 16a, and a spherical surface 28a at the distal end of the protruding shaft portion 28 provided on the distal end surface of the adjusting screw 16b is applied to the rear end surface of the push rod 16a. It is pressed.

  The end of the coil spring 26 on the spring seat 27 side has a small diameter, and the spring seat 27 is press-fitted into the end to be integrated.

  As shown in FIG. 3, the threads of the female screw 15 formed on the inner periphery of the nut member 14 and the male screw 21 formed on the outer periphery of the adjusting screw 16b are pressures that receive a pressing force when the adjusting screw 16b is pressed. The flank angle of the side flank 29 is greater than the flank angle of the play side flank 30, and a lead angle that moves in the axial direction while the adjusting screw 16 b is rotated by the pressing force of the coil spring 26 is provided in the serrated thread. It has been.

  As shown in FIG. 5, a set hole 31 penetrating in the radial direction is formed at the open end of the housing 11, while the set hole is formed at the tip of the push rod 16a when the push rod 16a is pushed in. A pin hole 32 corresponding to 31 is provided.

  The push rod 16a and the adjusting screw 16b are held in a pushed state by a set pin 33 inserted from the set hole 31 into the pin hole 32.

  The chain tension adjusting device shown in the embodiment has the above-described structure. When the auto tensioner 10 is assembled, the set pin 33 is inserted into the set hole 31 and the pin hole 32, and the push rod 16a and the adjusting screw 16b are pushed in. The mounting piece 12 of the housing 11 is bolted to the engine block in a contracted state of the auto tensioner 10 held in the state.

  At this time, the housing 11 is attached so that the tip of the push rod 16a faces the chain guide 6. When the set pin 33 is pulled out after the housing 11 is fixed, the push rod 16a moves outward by the pressing of the return spring 17. Then, the chain guide 6 is pressed, and the adjusting screw 16b advances while rotating by the pressing of the coil spring 26 so that the spherical surface 28a at the tip of the projecting shaft portion 28 contacts the rear end surface of the push rod 16a. The tension is adjusted.

  As described above, since the auto tensioner 10 can be held in the contracted state by inserting the set pin 33 into the set hole 31 and the pin hole 32, the initial assembly of the auto tensioner 10 can be easily performed. .

  FIG. 2 shows the assembled state of the auto tensioner 10. In this assembled state, when 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, the return is returned. The push rod 16a moves outward by the pressing force of the spring 17 to press the chain guide 6, and the slack of the chain 5 is absorbed by the pressing.

  When the push rod 16a moves outward, the adjusting screw 16b is rotated toward the push rod 16a side by the pressing force of the coil spring 26, and the spherical surface 28a at the tip of the projecting shaft portion 28 is moved to the rear of the push rod 16a. Abuts against the end face.

  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 16a via the chain guide 6, the pushing force is also applied to the adjusting screw 16b. For this reason, the pressure-side flank 29 of the female screw 15 of the nut member 14 and the male screw 21 of the adjusting screw 16b are in close contact with each other, and the pressing force is received by the pressure-side flank 29 that is in close contact.

  When the pressing force is stronger than the pressing force of the return spring 17, slip occurs on the contact surface of the pressure side flank 29 that closely contacts each other, and the adjusting screw 16 b slowly reaches a position where the pressing force and the pressing force of the return spring 17 are balanced. The chain 5 moves backward while rotating to keep the tension of the chain 5 constant.

At this time, the adjustment screw 16b and the spring seat 27 are in point contact,
The rotational resistance of the adjusting screw 16b is small, the adjusting screw 16b rotates smoothly, and smoothly follows changes in the tension of the chain 5.

  Here, since the chain guide 6 to which the adjusting force of the auto 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 16 a, the push rod A rotational moment is applied to 16a.

  At this time, the slide member 19 provided at the rear end portion of the push rod 16a is slidable along the inner diameter surface of the cylinder chamber 13, and the guide member 20 provided at the opening portion of the cylinder chamber 13 is the push rod. Since 16a is slidably supported, the rotational moment applied to the push rod 16a is supported at two locations: the fitting surface between the cylinder chamber 13 and the slide member 19 and the fitting surface between the push rod 16a and the guide member 20. Will be.

  Therefore, no rotational moment is applied to the adjusting screw 16b, and there is no inconvenience that the screw engaging portion of the female screw 15 and the male screw 21 is bitten.

  When the auto tensioner 10 is assembled, the eccentric position of the push rod 16a with respect to the center of the tip surface may be abutted 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 16a by the swinging of the chain guide 6. However, the push rod 16a and the adjusting screw 16b are arranged coaxially, and the protruding shaft portion 28 of the adjusting screw 16b. Since the tip spherical surface 28a is in point contact with the rear end surface of the push rod 16a, the rotational force is not applied to the adjusting screw 16b.

  For this reason, there is no inconvenience that the adjusting screw 16b 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 the vibration of the chain 5, The operating characteristics of the serrated screw can be effectively exhibited.

  When the chain 5 and the auto tensioner 10 are removed during maintenance around the engine, the push rod 16a moves outward by pressing the return spring 17, and the push screw 16b rotates while the adjustment screw 16b rotates by pressing the coil spring 26. As shown in FIG. 5, the auto tensioner 10 is moved to the extended state.

  For this reason, when reassembling the auto tensioner 10 after maintenance, the auto tensioner 10 needs to be assembled in a contracted state.

  When the auto tensioner 10 is contracted, the plug 25 is removed, the coil spring 26 and the spring seat 27 are taken out from the screw hole 24, and then the bolt A as a tool is inserted into the screw hole 24 as shown in FIG. Then, it engages with a female screw 23 as an engaging portion on the inner periphery of the spring accommodating hole 22 and applies a rotational force to the bolt A so that the adjusting screw 16b is located inside the nut member 14 as indicated by a chain line in FIG. Retreat to a position that fits in

  After the adjustment screw 16b is retracted, the push rod 16a is pushed against the elasticity of the return spring 17, and the push rod 16a is pushed until the pin hole 32 matches the set hole 31, and then set to the set hole 31 and the pin hole 32. The pin 33 is inserted to hold the auto tensioner 10 in the contracted state.

  After the set pin 33 is inserted, the bolt A is disengaged from the adjusting screw 16b, and then the bolt A is pulled out, and as shown in FIG. 6, the coil spring 26 and the spring seat 27 are inserted into the screw hole 24, After the plug 25 is screw-engaged with the screw hole 24 to close the screw hole 24, the auto tensioner 10 is reassembled. At this time, since the coil spring 26 and the spring seat 27 are integrated by press-fitting, the spring seat 27 is also incorporated together with the incorporation of the coil spring 26, and there is no inconvenience of forgetting to incorporate the spring seat 27.

  As described above, the bolt A is inserted into the screw hole 24, and the bolt A is engaged with the female screw 23 and rotated, whereby the adjustment screw 16b can be moved backward, and the push rod 16a is moved after the backward movement. Since the auto tensioner 10 can be brought into a contracted state by being pushed in, the auto tensioner 10 can be easily reassembled.

  In the example shown in FIG. 3, the rear end surface of the push rod 16a is a flat surface, and the spherical surface 28a of the projecting shaft portion 28 of the adjusting screw 16b is brought into contact with the rear end surface. However, as shown in FIG. The front end surface of 28 may be a flat surface and a spherical surface 34 may be provided at the rear end of the push rod 16a.

  In the embodiment, the female screw 23 formed on the inner periphery of the spring accommodating hole 22 is used as an engaging portion, and a bolt A as a turning tool is screw-engaged with the female screw 23 to move the adjusting screw 16b backward. A square hole may be formed at the closed end of the accommodation hole 22, a wrench inserted from the screw hole 24 may be engaged with the square hole, and the wrench may be rotated to move the adjustment screw 16b backward.

Schematic of a chain tension adjusting device employing an auto tensioner according to the present invention Longitudinal front view of the auto tensioner according to the present invention Sectional view showing the adjustment screw assembly Sectional drawing which shows other examples of adjustment screw Longitudinal front view with bolts engaged with adjusting screw Longitudinal front view showing the contraction state of the auto tensioner

Explanation of symbols

11 Housing 13 Cylinder chamber 14 Nut member 15 Female screw 16 Rod member 16a Push rod 16b Adjust screw 17 Return spring 19 Slide member 20 Guide member 21 Male screw 22 Spring accommodating hole 23 Female screw (engagement portion)
24 Screw hole 27 Spring seat 27a Head 27b Spherical surface 28a Spherical surface 29 Pressure side flank 30 Play side flank 31 Set hole 32 Pin hole 33 Set pin 34 Spherical surface

Claims (5)

  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 The adjustment screw is provided with a spring accommodating hole that opens at the rear end surface thereof, and a coil spring that biases the adjusting screw toward the push rod in the spring accommodating hole, and an end of the coil spring The spherical surface formed on the head is integrated into the coil spring. A spring seat that makes point contact with the pressing surface to be pressed is incorporated, and the flank angle of the pressure side flank that receives the pushing force applied to the adjusting screw is used for the female screw of the nut member and the male screw of the adjusting screw. A serrated screw larger than the corner is formed, and a screw hole that is closed by screwing a plug is formed in the closed end wall of the cylinder chamber. The inner diameter of the screw hole is larger than the outer diameter of the coil spring. An auto tensioner provided with an engaging portion with which a turning tool inserted from a screw hole can be engaged.   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 auto tensioner according to Item 1.   The auto tensioner according to claim 2, wherein the guide member is provided on an opening end side of the cylinder chamber from a sealing member for sealing a lubricant provided in an opening of the cylinder chamber.   The auto tensioner according to any one of claims 1 to 3, wherein one of a rear end surface of the push rod and a front end surface of the adjusting screw is a spherical surface.   A set hole penetrating in the radial direction is formed at the opening end of the housing, a pin hole penetrating in the radial direction is provided at the tip of the push rod, and a set pin is inserted into the pin hole from the set hole and pushed. The auto tensioner according to any one of claims 1 to 4, wherein the rod is held in a pushed state.

Images