JP2007120536A - Auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize motion and to facilitate assembling by preventing a rotating force or rotating moment from a portion abutting on a chain guide from operating on a sawtooth-shaped screw. <P>SOLUTION: A male screw 24 of a rod member 17 is engaged with a sawtooth-shaped female screw 16 of a nut member 15 in a cylinder chamber 13 of a housing 11. The rod member 17 is divided into a push rod 17a to be protruded by a return spring 18 and an adjusting screw 17b for preventing a rotating force or rotating moment from the chain guide 6 from being transmitted to the adjusting screw 17b. A peripheral engaging groove 21 is formed at the front-end outer periphery of the push rod 17a, and a pin hole 22 is formed at one end of the housing 11 in the tangential direction of the engaging groove 21. A set pin 23 inserted through the pin hole 22 is engaged with the engaging groove 21 to hold the push rod 17a in a pushed-in state. Then, the auto tensioner is assembled in a contracted state. <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.

  Also, the chain guide is a swingable support, and in order to absorb the vibration of the chain due to the swing of the chain guide, there is a rotational moment to tilt the nut member with the rod at the tip contacting the chain guide. When the load is applied, 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.

  Furthermore, in the conventional tensioner described above, the nut member is urged by the return spring and is in an extended state in which the rod protrudes greatly to the outside. Therefore, when the auto tensioner is initially installed in the engine block, the nut member rod Since it is necessary to apply a rotational force to retract the nut member into the body and maintain the retracted state for assembly, there is an inconvenience that assembly is very troublesome.

  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 ensure that a stable operation is always obtained by preventing the rotational moment from being applied to the serrated screw portion, and to facilitate initial 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. The rod member is loaded with the pressing force of the return spring. A push rod that is movable in the axial direction and an adjustment screw that has a male screw on its outer periphery, and an engagement groove that extends in the circumferential direction is provided on the outer periphery of the tip of the push rod. A pin hole extending in the tangential direction of the engaging groove is formed on the side of the push rod when the push rod is pushed in, and the set inserted in the pin hole is detachable. A pin is engaged with the engagement groove to hold the push rod in a pushed state, and a coil spring for urging the adjustment screw toward the push rod is incorporated in the nut member, and the female screw of the nut member and the adjustment screw are incorporated. The male screw is a saw-toothed screw whose flank angle of the pressure flank receiving the pushing force applied to the adjusting screw is larger than the flank angle of the play flank.

  In the auto tensioner having the above-described configuration, the housing is attached to the engine block in a push-in state of the push rod in which the set pin inserted into the pin hole engages with the engagement groove. In this case, the push rod is attached so as to face the chain guide contacting the chain. After the attachment, the set pin is pulled out, and the chain guide is pressed by the push rod that moves outward by pressing the return spring to tension the chain.

  In the chain tension adjustment state as described above, if slack occurs in the chain, the push rod advances 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 tilt the push rod. At this time, the push rod and the adjusting screw are separated from each other at the opposed end faces, so that no rotating moment is applied to the adjusting screw. For this reason, there is no inconvenience that the screw engaging portion of the female screw and the male screw bites.

  Here, when a slide member slidable along the inner diameter surface of the cylinder chamber is provided at the rear end portion of the push rod, and a wear ring that slidably supports the push rod is provided at the opening of the cylinder chamber, Since the rotational moment loaded on the rod is supported at two locations of the fitting surface of the slide member and the cylinder chamber and the fitting surface of the push rod and the wear ring, the rotational moment is loaded on the adjusting screw. Can be more reliably prevented.

  When the auto tensioner is assembled, the eccentric position with respect to the center of the end surface of the push rod may come into contact with the chain guide due to assembly errors. 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.

  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 inserting the set pin into the pin hole and engaging the set pin with the engagement groove formed at the tip of the push rod, the auto tensioner is held in the contracted state where the push rod is pushed, The auto tensioner can be easily assembled.

  Here, the push rod can be held in the pushed-in state by forming a through-hole penetrating in the radial direction at the tip of the push rod and inserting the set pin inserted into the pin hole into the through-hole. In this case, it is necessary to insert the set pin into the pin hole after phase alignment of the pin hole and the through hole in the axial direction and the circumferential direction, and it takes much time to insert the set pin.

  However, in the present invention, since the engaging groove extending in the circumferential direction is formed in the push rod and the pin hole extending in the tangential direction of the engaging groove is provided in the housing, the push rod is inserted when the set pin is inserted. It is only necessary to align the pin hole and the engaging groove in the axial direction by pushing in, the set pin can be easily inserted, and the engaging groove can be formed by turning, so the outer diameter of the push rod Processing can be performed in the same process as processing, and formation is easy.

  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. An auto tensioner 10 that presses the chain guide 6 toward the chain 5 is provided on one side of the chain guide 6.

  As shown in FIG. 2, the auto tensioner 10 has a cylindrical housing 11, and the housing 11 is provided with a plurality of attachment pieces 12 that are bolted to the engine block.

  The housing 11 is formed with a cylinder chamber 13 that opens at one end surface facing the chain guide 6, and the seal member 14 incorporated in the open end of the cylinder chamber 13 is lubricated in the cylinder chamber 13. Prevents leakage of oil to the outside.

  Further, a nut member 15 is incorporated in the cylinder chamber 13, and a female screw 16 is formed on the inner periphery of the nut member 15. Further, a rod member 17 and a return spring 18 that imparts outward projecting properties to the rod member 17 are incorporated in the cylinder chamber 13.

  The rod member 17 is divided into a push rod 17a and an adjusting screw 17b. The push rod 17a slidably penetrates the seal member 14, and a slide member 19 slidable along the inner diameter surface of the cylinder chamber 13 is provided at a rear end portion located in the cylinder chamber 13. The slide member The pressing force of the return spring 18 is applied to 19.

  On the other hand, a wear ring 20 that pressably supports the push rod 17 a is slid into the opening of the cylinder chamber 13 on the outer end side of the seal member 14.

  As shown in FIGS. 2 and 5, an engagement groove 21 extending in the circumferential direction is formed on the outer periphery of the distal end portion of the push rod 17 a, while a pin facing the tangential direction of the engagement groove 21 is formed at one end portion of the housing 11. A hole 22 is provided, and the push rod 17 a is held in a pushed state by the engagement of the set pin 23 inserted into the pin hole 22 and the engagement groove 21.

  As shown in FIGS. 2 and 3, the adjustment screw 17 b has a male screw 24 on the outer periphery, and the male screw 24 is screw-engaged with the female screw 16 of the nut member 15. The screw engaging portions of the male screw 24 and the female screw 16 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 adjusting screw 17b is formed with a spring accommodating hole 25 that opens at the rear end face, and a female screw 26 is formed on the inner periphery of the opening end of the spring accommodating hole 25. On the other hand, the housing 11 is provided with a screw hole 27 in the closed end wall of the cylinder chamber 13, and the screw hole 27 is closed by screwing a plug 28.

  A coil spring 29 and a spring seat 30 composed of pins are incorporated between the plug 28 and the closed end face of the spring accommodating hole 25. The spring seat 30 has a head portion 30a, and a spherical surface 30b formed on the head portion 30a is pressed against the closed end of the spring accommodating hole 25 to make point contact.

  The coil spring 29 urges the adjustment screw 17b toward the push rod 17a, and the sphere 31a at the tip of the protruding shaft portion 31 provided on the tip surface of the adjustment screw 17b is applied to the rear end surface of the push rod 17a. It is pressed.

  As shown in FIG. 3, the threads of the female screw 16 formed on the inner periphery of the nut member 15 and the male screw 24 formed on the outer periphery of the adjusting screw 17b are pressures that receive a pressing force when the adjusting screw 17b is pressed. The flank angle of the side flank 32 has a sawtooth shape larger than the flank angle of the play side flank 33, and a lead angle that moves in the axial direction while the adjusting screw 17b is rotated by the pressing force of the coil spring 29 is provided in the sawtooth thread. It has been.

  The chain tension adjusting device shown in the embodiment has the above-described structure. FIGS. 2 and 3 show a state where the engaging groove 21 is engaged with the set pin 23 inserted into the pin hole 22 and the push rod 17a is pushed. The auto-tensioner 10 is held in the contracted state, and the auto-tensioner 10 is assembled to the engine block in the contracted state.

  When the set pin 23 is pulled out after the auto tensioner 10 is assembled, the push rod 17a moves forward by the pressing of the return spring 18 to press the chain guide 6 and the coil spring 29 as shown in FIG. The adjustment screw 17b advances while being rotated by the pressure, contacts the rear end of the push rod 17a, and the chain 5 is held in a tension-adjusted state.

  In the tension adjustment state of the chain 5 shown in FIG. 6, when the chain 5 vibrates due to torque fluctuation caused by the rotation of the cam shaft 3 and the slack side chain of the chain 5 is loosened, the push rod is pushed by the pressing force of the return spring 18. 17a moves outward to press the chain guide 6, and loosening of the chain 5 is absorbed by the pressing.

  When the push rod 17a moves outward, the adjusting screw 17b is rotated toward the push rod 17a by the pressing force of the coil spring 29, and the spherical surface 31a at the tip of the projecting shaft portion 31 is moved to the rear of the push rod 17a. Abuts against the end face.

  On the other hand, when the tension of the slack side chain of the chain 5 increases and a pushing force is applied from the chain 5 to the push rod 17a via the chain guide 6, the pushing force is also applied to the adjusting screw 17b. Therefore, the pressure-side flank 32 of the female screw 16 of the nut member 15 and the male screw 24 of the adjusting screw 17b are in close contact with each other, and the pressing force is received by the pressure-side flank 32 that is in close contact.

  When the pressing force is stronger than the pressing force of the return spring 18, slip occurs on the contact surface of the pressure side flank 32 that closely contacts each other, and the adjusting screw 17 b slowly reaches a position where the pressing force and the pressing force of the return spring 18 are balanced. The chain 5 moves backward while rotating to keep the tension of the chain 5 constant.

  At this time, since the adjustment screw 17b and the spring seat 30 and the adjustment screw 17b and the push rod 17a are in point contact, the rotation resistance of the adjustment screw 17b is small, the adjustment screw 17b rotates smoothly, and the tension of the chain 5 changes. Follow smoothly.

  Here, since the chain guide 6 to which the adjustment force of the auto tensioner 10 is loaded is supported so as to be swingable about the shaft 7, when the pushing force is loaded from the chain guide 6 to the push rod 17a, the push rod A rotational moment to be tilted to 17a is loaded.

  At this time, the slide member 19 provided at the rear end of the push rod 17a is slidable along the inner diameter surface of the cylinder chamber 13, and the wear ring 20 provided at the opening of the cylinder chamber 13 is pushed. Since the rod 17a is slidably supported, the rotational moment applied to the push rod 17a is two places on the fitting surface of the cylinder chamber 13 and the slide member 19 and the fitting surface of the push rod 17a and the wear ring 20. Will be supported.

  Therefore, no rotational moment is applied to the adjusting screw 17b, and there is no inconvenience that the screw engaging portion of the female screw 16 and the male screw 24 is bitten.

  When the auto tensioner 10 is assembled, the eccentric position of the push rod 17a 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 17a by the swinging of the chain guide 6. However, the push rod 17a and the adjusting screw 17b are arranged coaxially, and the protruding shaft portion 31 of the adjusting screw 17b. Since the spherical surface 31a at the tip of this is in point contact with the rear end surface of the push rod 17a, the adjusting screw 17b is not loaded with the rotational force.

  For this reason, there is no inconvenience that the adjusting screw 17b 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 17a moves outward by the pressing of the return spring 18, and the push screw 17b rotates while the adjusting screw 17b rotates by the pressing of the coil spring 29. Moving toward 17a, the auto tensioner 10 is in 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 28 is removed, the coil spring 29 and the spring seat 30 are taken out from the screw hole 27, a bolt is inserted into the screw hole 27, and the female screw 26 on the inner periphery of the spring accommodation hole 25. The screw is engaged with the bolt, and a rotational force is applied to the bolt to retract the adjusting screw 17b to a position where it is inside the nut member 15.

  After the adjustment screw 17b is retracted, the push rod 17a is pushed against the elasticity of the return spring 18, and the push rod 17a is pushed to a position where the engagement groove 21 faces the pin hole 22, and then the set pin is inserted into the pin hole 22. 23 is inserted.

  At this time, since the pin hole 22 extends in the tangential direction of the engagement groove 21, the set pin 23 is inserted into the engagement groove 21 by the insertion of the set pin 23 into the pin hole 22, and the engagement groove 21. The push rod 17a is held in the pushed state by the engagement. The auto tensioner 10 is reassembled in the contracted state where the push rod 17a is held in the pushed state.

  Note that after the auto tensioner 10 is assembled, the set pin 23 is pulled out to release the set state in the same manner as described above.

  As described above, the engaging groove 21 extending in the circumferential direction is formed in the push rod 17a, and the pin hole 22 extending in the tangential direction of the engaging groove 21 is provided in the housing 11, so that when the set pin 23 is inserted, It is only necessary to push the push rod 17a and align the engaging groove 21 with respect to the pin hole 22 in the axial direction. For this reason, the set pin 23 can be easily inserted, and the engagement groove 21 can be formed by turning, so that it can be processed in the same process as the outer diameter processing of the push rod 17a. is there.

  In the example shown in FIG. 3, the rear end surface of the push rod 17a is a flat surface, and the spherical surface 31a of the projecting shaft portion 31 of the adjusting screw 17b is brought into contact with the rear end surface. However, as shown in FIG. The front end surface of the shaft portion 31 may be a flat surface, and the spherical surface 34 may be provided at the rear end of the push rod 17a.

Schematic of a chain tension adjusting device employing an auto tensioner according to the present invention Longitudinal front view showing the contracted state 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 Sectional drawing along the VV line of FIG. Longitudinal front view showing the tension adjustment state of the auto tensioner

Explanation of symbols

11 Housing 13 Cylinder chamber 15 Nut member 16 Female thread 17 Rod member 17a Push rod 17b Adjust screw 18 Return spring 19 Slide member 20 Wear ring 21 Engaging groove 22 Pin hole 23 Set pin 31a Spherical surface 32 Pressure side flank 33 Play side flank 34 Spherical surface

Claims (3)

  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 And a return spring that imparts outward protrusion to the rod member. The rod member is movable in the axial direction to which the pressing force of the return spring is loaded, and an external thread is provided on the outer periphery of the male screw. And an engaging groove extending in the circumferential direction is provided on the outer periphery of the front end of the push rod, and the housing has a tangent to the engaging groove when the push rod is pushed into the open end of the cylinder chamber. A pin hole extending in the direction is formed, and a push pin is pushed in by engaging a set pin removably inserted into the pin hole with the engagement groove A coil spring that urges the adjusting screw toward the push rod inside the nut member, and the pressure of the female screw of the nut member and the male screw of the adjusting screw that receives the pushing force applied to the adjusting screw. An auto tensioner with serrated screws whose side flank angle is larger than the play side flank angle.   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 wear ring 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 1 or 2, wherein one of the rear end surface of the push rod and the front end surface of the adjustment screw is a spherical surface.

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