JP2007100783A - 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 28 of a rod member 17 is threadedly engaged with a saw-tooth female screw 16 of a nut member 15 incorporated in a cylinder chamber 13 of a housing 11. The rod member 17 is divided into an adjust screw 17b and a push rod 17a provided with the outward projecting property by a return spring 18. Even if the rotational force and rotational moment are loaded on the push rod 17a from a chain guide 6, the rotational force and rotational moment are prevented from being transmitted to the adjust screw 17b. <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.

  Further, in the conventional tensioner, the nut member is urged by the return spring and the rod is in an extended state in which the rod largely protrudes to the outside. Therefore, when the chain 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, the assembly is extremely 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. To ensure that stable operation can be obtained at all times by preventing rotational moment from acting on the sawtooth thread, to facilitate initial assembly, and to automatically cancel the initial set state. It is to be.

  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. The wear ring that slidably supports the push rod is press-fitted into the opening end of the cylinder chamber, and the wear ring is press-fitted into the opening end of the cylinder chamber. Penetrates the ring housing groove from the open end of the cylinder chamber to the inner surface of the tip located outside and the outer surface to the ring housing groove A notched part, a snap ring that is elastically deformable in the radial direction in the ring receiving groove is incorporated in a reduced diameter state, and a pair of operation pieces provided at both ends of the stopper ring are inserted into the notched part, A stopper groove that can be engaged with the stopper ring is provided on the outer periphery of the tip of the push rod, and a reduced diameter state in which the stopper ring is engaged with the stopper groove on the front side of the ring housing groove on the cylinder chamber opening end side. A holding spring is provided, a coil spring for urging the adjusting screw toward the push rod is incorporated inside the nut member, and the pushing force applied to the adjusting screw by the female screw of the nut member and the male screw of the adjusting screw is loaded. Adopted a serrated screw with a flank angle of the pressure side flank that is larger than the flank angle of the play side flank To have.

  In the autotensioner according to the present invention, the holding portion that holds the stopper ring engaged with the stopper groove in a reduced diameter state may be formed of a small-diameter groove or a tapered surface. .

  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. At the time of the assembly, the stopper ring engages with the stopper groove, the diameter of the stopper ring is prevented by the holding portion, and the housing is attached in the initial set state of the auto tensioner in which the push rod is pushed and held.

  When the engine is cranked after the auto tensioner is installed, the chain is tensioned.When the push rod is pushed in a little by the tensioned chain and the stopper ring is removed from the holding part, the stopper ring expands and the engagement with the stopper groove is increased. The auto tensioner's initial set is released. By releasing the initial set, the push rod advances by pressing the return spring to press the chain guide, and the adjustment screw rotates by the pressing of the coil spring to make contact with the rear end surface of the push rod. The tension is adjusted.

  When the chain is slackened when the chain tension is adjusted, 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, 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, if a slide member slidable along the inner diameter surface of the cylinder chamber is provided at the rear end portion of the push rod, the rotational moment applied to the push rod is the fitting surface between the slide member and the cylinder chamber, And since it will be supported by two places of the fitting surface of a push rod and a wear ring, it can prevent more reliably that a rotation moment is loaded to an adjustment screw.

  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.

  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, by engaging the stopper ring with the stopper groove provided at the tip of the push rod and holding the stopper ring in a reduced diameter state by the holding portion, the auto tensioner is an initial set in which the push rod and the adjusting screw are pushed in. Since the state is maintained, the initial assembly of the auto tensioner can be easily performed.

  Furthermore, when the engine is cranked after the auto tensioner is assembled, the push rod is pushed in by the chain that is tensioned, the stopper ring expands in the ring receiving groove due to its own elasticity, and the engagement with the stopper groove is released. Since the push rod moves forward by pressing the return spring and the adjustment screw moves forward by pressing the coil spring, the initial set state of the auto tensioner can be automatically released.

  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, and the seal member 14 incorporated in the open end of the cylinder chamber 13 prevents leakage of the lubricating oil sealed in the cylinder chamber to the outside. ing.

  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. A slide member 20 slidable along the inner diameter surface of the cylinder chamber 13 is provided at the rear end portion of the push rod 17a located in the cylinder chamber 13, and the pressing force of the return spring 18 is loaded on the slide member 20. ing.

  On the other hand, a wear ring 21 that press-fits the push rod 17 a is slidably inserted into the opening of the cylinder chamber 13 on the outer end side of the seal member 14. Between the wear ring 21 and the push rod 17a, there is provided setting means 22 for holding the push rod 17a in the initial set state in which the push rod 17a is pushed into the cylinder chamber 13.

  As shown in FIGS. 2 to 4, the setting means 22 includes a ring receiving groove 23 on the inner diameter surface of the tip portion located outside the opening end of the cylinder chamber 13 of the wear ring 21, and the ring receiving groove from the outer diameter surface. And a pair of operations formed at both ends of the stopper ring 25. A stopper ring 25 that is elastically deformable in the radial direction is incorporated in the ring receiving groove 23 in a reduced diameter state. A piece 25 a is inserted into the notch 24, a stopper groove 26 is provided on the outer periphery of the tip of the push rod 17 a, and the stopper ring 25 in a reduced diameter engaging with the stopper groove 26 is inserted into the ring receiving groove 23. The push rod 17a is held in a pushed state by being held by a holding portion 27 provided on the opening end side of the cylinder chamber 13.

  Here, the holding portion 27 is composed of a small-diameter groove, and the stopper ring 25 has an inner diameter smaller than the outer diameter of the push rod 17a in a state where the stopper ring 25 is in elastic contact with the inner diameter surface of the holding portion 27 made of the small-diameter groove. It is said that.

  As shown in FIGS. 2 and 5, the adjustment screw 17 b has a male screw 28 on the outer periphery, and the male screw 28 is screw-engaged with the female screw 16 of the nut member 15. The screw engaging portions of the male screw 28 and the female screw 16 and the sliding surfaces of the slide member 20 and the cylinder chamber 13 are lubricated by the lubricating oil sealed in the cylinder chamber 13.

  The adjustment screw 17 b is formed with a spring accommodating hole 29 that opens at the rear end face, and a female screw 30 is formed on the inner periphery of the opening end of the spring accommodating hole 29. On the other hand, the housing 11 is provided with a screw hole 31 in the closed end wall of the cylinder chamber 13, and the screw hole 31 is closed by screwing a plug 32.

  Between the plug 32 and the closed end face of the spring accommodating hole 29, a coil spring 33 and a spring seat 34 composed of a pin are incorporated. The spring seat 34 has a head portion 34a, and a spherical surface 34b formed on the head portion 34a is pressed against the closed end of the spring accommodating hole 29 to make point contact.

  The coil spring 33 urges the adjusting screw 17b toward the push rod 17a, and the sphere 35a at the tip of the protruding shaft portion 35 provided on the tip 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. 5, the threads of the internal thread 16 formed on the inner periphery of the nut member 15 and the external thread 28 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 36 has a sawtooth shape larger than the flank angle of the play side flank 37, 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 33 is provided in the sawtooth thread. It has been.

  The chain tension adjusting device shown in the embodiment has the above-described structure. FIG. 2 shows that the stopper ring 25 is engaged with the stopper groove 26, and the stopper ring 25 is held in the engaged state by the holding portion 27. The initial set state of the auto tensioner 10 is shown. In the initial set state, the push rod 17a and the adjusting screw 17b are held in the pushed state, and the auto tensioner 10 is in the contracted state. Therefore, the auto tensioner 10 can be easily incorporated into the engine block.

  When the engine is cranked in the state in which the auto tensioner 10 is assembled, the chain 5 is tensioned, the push rod 17a is pushed in via the chain guide 6 by the tensioned chain 5, and the stopper ring 25 is separated from the holding portion 27. To do. When the stopper ring 25 opposes the ring receiving groove 23, the stopper ring 25 expands due to its own elasticity, and the engagement with the stopper groove 26 is released as shown in FIG.

  When the stopper ring 25 and the stopper groove 26 are disengaged, the push rod 17a moves forward by pressing the return spring 18 to press the chain guide 6, and the coil spring 33 presses to advance the adjusting screw 17b while rotating. As shown in FIG. 9, the chain 5 is held in a tension-adjusted state by contacting the rear end of the push rod 17a.

  As described above, after the auto tensioner 10 is attached, the push rod 17a is pushed in by cranking the engine, and the engagement of the stopper ring 25 with the stopper groove 26 is released. Therefore, the initial setting of the auto tensioner 10 is automatically performed. There is no inconvenience that the user can forcibly cancel and forget to cancel.

  In the tension adjustment state of the chain 5 shown in FIG. 9, 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 33, and the spherical surface 35a at the tip of the projecting shaft portion 35 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. For this reason, the pressure-side flank 36 of the female screw 16 of the nut member 15 and the male screw 28 of the adjusting screw 17b are in close contact with each other, and the pressing force is received by the pressure-side flank 36 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 36 that is in close contact with 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 34, and the adjustment screw 17b and the push rod 17a are in point contact, the rotational 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 is applied to 17a.

  At this time, the slide member 20 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 21 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: the fitting surface between the cylinder chamber 13 and the slide member 20 and the fitting surface between the push rod 17a and the wear ring 21. Will be supported.

  For this reason, no rotational moment is applied to the adjusting screw 17b, and there is no inconvenience that the screw engaging portion between the female screw 16 and the male screw 28 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 35 of the adjusting screw 17b. Since the tip spherical surface 35a 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 press of the return spring 18, and the push screw 17b is rotated while the adjustment screw 17b is rotated by the press of the coil spring 33. 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 32 is removed, the coil spring 33 and the spring seat 34 are taken out from the screw hole 31, and then a bolt is inserted into the screw hole 31 so that the female screw 30 on the inner periphery of the spring accommodation hole 29 is inserted. 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. When the push rod 17a is pushed in until the stopper groove 26 faces the ring receiving groove 23, the pair of operation pieces 25a of the stopper ring 25 are gripped to reduce the diameter of the stopper ring 25, and the stopper ring 25 is engaged with the stopper groove 26. Combine. Then, the push rod 17a is moved forward by pressing the return spring 18, and the stopper ring 25 is held in the engaged state by the engagement of the stopper ring 25 with the holding portion 27. In the set state in which the auto tensioner 10 is contracted and held, The auto tensioner 10 is reassembled.

  Note that after the auto tensioner 10 is assembled, the set state is released by cranking the engine as described above.

  In the example shown in FIG. 5, the rear end surface of the push rod 17a is a flat surface, and the spherical surface 35a of the projecting shaft portion 35 of the adjusting screw 17b is brought into contact with the rear end surface, but as shown in FIG. The tip surface of 35 may be a flat surface and a spherical surface 38 may be provided at the rear end of the push rod 17a.

  In FIG. 4, the holding portion 27 is formed of a small-diameter groove, but the holding portion 27 is not limited to this. For example, as shown in FIG. 10, the side surface of the ring housing groove 23 on the opening end side of the cylinder chamber 13 may be a tapered surface 40 and the tapered surface 40 may be the holding portion. In the holding portion made of the tapered surface 40, the engagement of the stopper ring 25 can be immediately released by slightly pushing the push rod 17a.

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 along line III-III in FIG. Enlarged sectional view showing the stopper ring holding part Sectional view showing the adjustment screw assembly Sectional drawing which shows other examples of adjustment screw Sectional drawing which shows the state before the engagement of a stopper ring Sectional view showing the stopper ring disengaged state Cross-sectional view showing tension adjustment of chain Sectional drawing which shows the other example of a holding | maintenance part

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 20 Slide member 21 Wear ring 23 Ring receiving groove 24 Notch portion 27 Holding portion 35a Spherical surface 36 Pressure side flank 37 Play side flank 38 Spherical surface 40 Tapered surface (holding part)

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 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. The wear ring for slidably supporting the push rod is press-fitted into the opening end of the cylinder chamber, and the wear ring has a tip portion positioned outside from the opening end of the cylinder chamber. A ring housing groove is provided on the inner diameter surface, and a notch passing through the ring housing groove from the outer diameter surface is provided. An elastically deformable stop ring is incorporated in a reduced diameter state, a pair of operating pieces provided at both ends of the stopper ring are inserted into the notch, and the stopper ring can be engaged with the outer periphery of the tip of the push rod. A stopper groove is provided, and a holding portion for holding the stopper ring in a reduced diameter state engaging with the stopper groove is provided at a front side portion of the ring receiving groove on the cylinder chamber opening end side, and an adjustment screw is provided inside the nut member. A coil spring that urges toward the push rod is incorporated, and the flank angle of the pressure side flank that receives the pushing force applied to the adjustment screw is larger than the flank angle of the play side flank. Auto tensioner with serrated screw.   The auto tensioner according to claim 1, 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 auto tensioner according to claim 1 or 2, wherein a slide member 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.   The auto tensioner according to any one of claims 1 to 3, wherein the holding portion is formed of a small-diameter groove.   The auto tensioner according to any one of claims 1 to 3, wherein the holding portion is formed of a tapered surface.

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