JP2007120537A - Auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain stable motion by preventing a rotating force or rotating moment, when loaded by a portion abutting on a chain guide, from operating on a screw portion. <P>SOLUTION: A cylinder chamber 13 is formed in a housing 11, and a sawtooth-shaped male screw 21 of a rod member 17 is engaged with a sawtooth-shaped female screw 16 of a nut member 15 incorporated in the cylinder chamber 13. The rod member 17 is divided into a push rod 17a to which an outward protruding property is imparted by a return spring 18 and an adjusting screw 17b for preventing a rotating force or rotating moment from the chain guide 6 to the push rod 17a from being transmitted to the adjusting screw 17b. A coil spring 26 for thrusting the adjusting screw 17b toward the push rod 17a and a spring seat 27 having a head 27a whose surface is a spherical face 27b are incorporated in the nut member 15. <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 to the rod of the nut member from the chain through the chain guide is serrated. When the thrust force is received by the pressure side flank of the screw to prevent the nut member from moving backward, and the pushing force is greater than the pushing force of the return spring, the nut member is rotated to a position where the pushing force and the spring force of the return spring are balanced. While moving backward, the chain tension is kept constant.

Further, when the chain is slack, the nut member is moved forward by the pressing force of the return spring to absorb the slack of the chain.
Japanese Utility Model Publication No.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 around the shaft center by the swing of the chain guide.

  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.

  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 acting on the saw-toothed screw portion, and to facilitate maintenance.

  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 having an external thread on the outer periphery, a coil spring that urges the adjustment screw toward the push rod inside the nut member, and a closed end of the cylinder chamber A spring seat having a spherical head surface is incorporated on the side, and the female thread of the nut member and the adjustment screw The screw is a serrated screw whose flank angle of the pressure side flank receiving the pushing force applied to the adjusting screw is larger than the flank angle of the play side flank, and the closed end wall of the cylinder chamber has a diameter larger than the outer diameter of the coil spring. The screw hole is engaged with a plug that receives the spherical surface of the spring seat, and the adjustment screw is provided with an engaging portion that can be engaged with a rotary tool inserted through the screw hole. is doing.

  In the auto tensioner configured as described above, the push rod is assembled to face the chain guide contacting the chain. In the assembled state, when 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.

  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 spring seat and coil spring from the screw hole, insert the rotary tool into the inside from the screw hole, engage the engaging part, and load the rotary tool. The auto tensioner is assembled in a state in which the adjusting screw is moved backward by rotating the rotating force and the push rod is pushed in and the auto tensioner is contracted.

  In the maintenance as described above, the spring seat is pressed against the plug by the coil spring, so that when the plug is removed, the spring seat is pushed out of the screw hole and the end of the coil spring is externally connected from the screw hole. Will jump out.

  For this reason, the spring seat can be removed at the same time by removing the plug even in the lateral orientation of the housing in which the screw holes are arranged on the side, or in the vertical orientation of the housing in which the screw holes are arranged on the upper side. The end of the coil spring can be ejected to the outside. Therefore, the spring seat and the coil spring can be removed to the outside in a state that prevents the lubricating oil sealed in the cylinder from leaking to the outside, and the maintenance work can be facilitated.

  Here, by forming a recess in which the head of the spring seat is fitted on the tip surface of the plug, it is possible to prevent the plug and the spring seat from moving in the radial direction relatively. There is no inconvenience that the spring seat is caught when the plug is removed, and the spring seat can be removed more reliably.

  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.

  In addition, the lubricating oil is sealed in the cylinder chamber by removing the plug in the lateral orientation of the housing in which the screw hole is arranged on the side or in the vertical orientation of the housing in which the screw hole is arranged on the upper side. Since the spring seat can be removed, maintenance work can be easily performed.

  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 3, the adjustment screw 17 b has a male screw 21 on the outer periphery, and the male screw 21 is screw-engaged with the female screw 16 of the nut member 15. The screw engaging portions of the male screw 21 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 22 that opens at the rear end surface 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.

  Between the plug 25 and the closed end face of the spring accommodating hole 22, a coil spring 26 and a spring seat 27 including a pin are incorporated between the coil spring 26 and the plug 25. The spring seat 27 has a head portion 27 a to which the spring force of the coil spring 26 is loaded. The head portion 27a is fitted into a recess 25a formed on the distal end surface of the plug 25, and a spherical surface 27b formed on the surface of the head portion 27a is pressed against the closed end of the recess 25a to make point contact.

  The coil spring 26 urges the adjusting screw 17b toward the push rod 17a, and a spherical surface 28a at the front end of the protruding shaft portion 28 provided on the front end surface of the adjusting 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 21 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 29 has a sawtooth shape larger than the flank angle of the play side flank 30, and a lead angle that moves in the axial direction while the adjusting screw 17 b is rotated by the pressing force of the coil spring 26 is provided in the sawtooth thread. It has been.

  The chain tension adjusting device shown in the embodiment has the above-described structure, and FIG. 2 shows a tension adjusting state of the chain 5 in which the push rod 17a of the chain tensioner 10 presses the chain guide 6 to apply tension to the chain 5. Show.

  In the tension adjustment state of the chain 5 as described above, 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 pressed 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 moved toward the push rod 17a while rotating by the pressing force of the coil spring 26, and the spherical surface 28a at the tip of the projecting shaft portion 28 is behind the push rod 17a. 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 17a via the chain guide 6, the pushing force is also applied to the adjusting screw 17b. Therefore, the internal thread 16 of the nut member 15 and the pressure side flank 29 of the external thread 21 of the adjusting screw 17b are in close contact with each other, and the pressing force is received by the intimate pressure side flank 29.

  When the pushing force is stronger than the pushing force of the return spring 18, slip occurs on the contact surface of the pressure side flank 29 in close contact with each other, and the adjusting screw 17 b slowly reaches a position where the pushing force and the pushing 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 plug 25 and the spring seat 27, 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 21 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 28 of the adjusting screw 17b. Since the tip spherical surface 28a is in point contact with the rear end surface of the push rod 17a, the rotational force is not applied to the adjusting screw 17b.

  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 is moved outward by the pressing of the return spring 18, and the push screw 17b is rotated while the adjustment screw 17b is rotated by the pressing of the coil spring 26. As shown in FIG. 5, the auto tensioner 10 moves 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 a bolt as a rotary tool is inserted into the screw hole 24 so that the inside of the spring accommodating hole 22. The screw is engaged with the peripheral female screw 23, and a rotational force is applied to the bolt to retract the adjustment screw 17 b to a position where it fits inside the nut member 15.

  After the adjustment screw 17b is retracted, the push rod 17a is pushed in and reassembled in the contracted state of the auto tensioner 10.

  In the maintenance work as described above, since the spring seat 27 is incorporated between the plug 25 and the coil spring 26, the spring seat 27 is pressed against the coil spring 26 by the removal of the plug 25 as shown by a chain line in FIG. As a result, the coil spring 26 protrudes outward from the screw hole 24, and the end of the coil spring 26 also protrudes outward from the screw hole 24.

  For this reason, it is sealed in the cylinder chamber 13 by removing the plug 25 in the horizontal orientation of the housing 11 in which the screw hole 24 is located on the side or in the vertical orientation of the housing 11 in which the screw hole 24 is located on the upper side. The spring seat 27 and the coil spring 26 can be removed without leaking the lubricated oil to the outside. Therefore, maintenance work can be easily performed.

  In the example shown in FIG. 3, the rear end surface of the push rod 17a is a flat surface, and the spherical surface 28a of the projecting shaft portion 28 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 28 may be a flat surface, and the spherical surface 31 may be provided at the rear end of the push rod 17a.

  In FIG. 3, a female screw 23 is shown as an engaging portion, and a bolt as a rotating tool is screw-engaged with the female screw 23 to rotate the adjusting screw 17 b. A hole may be formed, and a wrench inserted from the screw hole 24 may be engaged with the square hole to rotate the adjustment screw 17b, and the engaging portion is not limited to the screw hole.

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 showing the contraction state of the auto tensioner

Explanation of symbols

11 Housing 13 Cylinder chamber 15 Nut member 16 Female screw 17 Rod member 17a Push rod 17b Adjust screw 18 Return spring 19 Slide member 20 Wear ring 21 Male screw 23 Female screw 24 Screw hole 25 Plug 25a Recess 26 Coil spring 27 Spring seat 27a Head portion 27b Spherical surface 28a Spherical surface 29 Pressure side flank 30 Play side flank 31 Spherical surface

Claims (4)

  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. A coil spring that urges the adjustment screw toward the push rod inside the nut member, and a spring seat having a spherical head surface on the closed end side of the cylinder chamber. Built-in force for pushing the female screw of the nut member and the male screw of the adjusting screw to the adjusting screw The pressure side flank to be received has a serrated screw whose flank angle is larger than the flank angle of the play side flank, and a closed end wall of the cylinder chamber is provided with a screw hole having a diameter larger than the outer diameter of the coil spring, and a spring seat is provided in the screw hole. An auto-tensioner in which a plug that receives the spherical surface is screw-engaged, and the adjusting screw is provided with an engaging portion into which a rotary 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 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 at least one of the rear end surface of the push rod and the front end surface of the adjustment screw is a spherical surface.   The auto tensioner according to any one of claims 1 to 3, wherein a concave portion into which a head portion of a spring seat is fitted is formed on a front end surface of the plug.

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