JP2010209970A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner with superior assembly workability to an engine, capable of retaining a screw rod in a screwed state into a female screw member. <P>SOLUTION: The automatic tension includes the female screw member 10 having a female screw 15 on an inner circumference, the screw rod 11 having a male screw 16 engaging with the female screw 15 on an outer circumference, and a return spring 12 energizing the screw rod 11 in a direction protruding from the female screw member 10. The slackness of a chain 6 is absorbed by protrusion of the screw rod 11 from the female screw member 10. A head 17 with an outer diameter larger than the inner diameter of the female screw member 10 is formed in a protruding portion of the screw rod 11 from the female screw member 10, and the rotation of the screw rod 11 is prevented through a rotary frictional resistance generated in the head 17 when the screw rod 11 is screwed into the female screw member 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an auto tensioner used for maintaining tension of a chain or a toothed belt that drives a camshaft of an automobile engine.

  In general, the engine of an automobile transmits rotation of a crankshaft to a camshaft via a chain or a toothed belt (hereinafter, a chain will be described as an example), and the rotation of the camshaft opens and closes a valve of a combustion chamber. To do. Here, in order to keep the chain tension within an appropriate range, a tension adjusting device consisting of a chain guide that can swing around a fulcrum shaft and an auto tensioner that presses the chain via the chain guide is often used. It is done.

  As an autotensioner incorporated in this tension adjusting device, a female screw member having a female screw on the inner periphery, a screw rod having a male screw on the outer periphery that engages with the female screw, and a biasing force in a direction in which the screw rod protrudes from the female screw member There is a known return spring that absorbs the slack of the chain by protruding the screw rod from the female screw member (see, for example, Patent Documents 1 to 3).

  Here, in the autotensioners described in Patent Documents 1 and 2, the female screw member is placed in a cylindrical housing whose one end is open and the other end is closed, and the protruding side of the screw rod from the female screw member is the housing. It is fixed in the direction to be the open end side, and the chain is pressed with a screw rod.

  Further, in the auto tensioner described in Patent Document 3, the female screw member is placed in a cylindrical housing with one end opened and the other end closed, and the protruding side of the screw rod from the female screw member is the closed end of the housing. The screw rod is slidably inserted in the direction toward the side, and the protruding end of the screw rod from the female screw member is brought into contact with a rod sheet provided in the housing, and the chain is pressed by the female screw member.

  When the chain tension decreases during engine operation, these auto tensioners move in the direction in which the screw rod protrudes from the female thread member (hereinafter referred to as the “projection direction”) due to the biasing force of the return spring, and the chain is slackened. Absorb.

  On the other hand, when the chain tension increases during engine operation, the chain rod moves in the direction in which the screw rod is pushed into the female screw member (hereinafter referred to as “push-in direction”), and absorbs the chain tension. At this time, the screw rod rotates with respect to the female screw member while repeating forward and backward movement within the gap between the female screw and the male screw due to the vibration of the chain.

  Also, when the engine is stopped, the chain tension may increase depending on the stop position of the camshaft.In this case, the chain does not vibrate, so the male screw of the screw rod is received by the female screw of the female screw member, and the position of the screw rod is Fixed. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.

JP-A-9-280330 JP 2008-267560 A JP 2007-218371 A

  By the way, when each auto tensioner is detached from the engine, the screw rod protrudes from the female screw member due to the urging force of the return spring, but even if the auto tensioner in this state is assembled to the engine, the chain is stretched, The auto tensioner cannot be assembled.

  Therefore, before assembling the auto tensioner to the engine, it is necessary to screw the screw rod into the female screw member in advance and hold the screw rod so that it does not protrude from the female screw member, but holding the screw rod is complicated. It is.

  Therefore, in the auto tensioner described in Patent Document 2, a plug that supports one end of the return spring is detachably provided at the closed end of the housing, and one end of the return spring can be released by removing the plug. It is like that. When one end of the return spring is released, the urging force of the return spring is lost, so the screw rod does not protrude from the female screw member, and it is not necessary to hold down the screw rod when assembling the auto tensioner to the engine.

  However, this auto tensioner needs to be attached to the closed end of the housing after being assembled to the engine, and this attachment work is complicated.

  The problem to be solved by the present invention is to provide an auto tensioner that can hold the screw rod in a state of being screwed into the female screw member and is excellent in assembling workability to the engine.

  In order to solve the above-described problem, a head portion having an outer diameter larger than the inner diameter of the female screw member is formed in a protruding portion of the screw rod from the female screw member, and when the screw rod is screwed into the female screw member, The screw rod is prevented from rotating by the rotational frictional resistance generated in the head. In this way, before the auto tensioner is assembled to the engine, the screw rod is screwed into the female screw member in advance, and the screw rod is screwed into the female screw member by the rotational frictional resistance generated at the head of the screw rod at this time. (Hereinafter referred to as “initial set”). Further, after the auto tensioner is assembled to the engine, the initial set can be released by cranking the engine and applying vibration to the screw rod.

  The screw rod head and the female screw member may be in direct contact with each other when the screw rod is screwed into the female screw member, but an elastic member is incorporated between the screw rod head and the female screw member, It is preferable that the head of the screw rod compresses the elastic member when the screw rod is screwed into the female screw member. In this way, the magnitude of the rotational friction resistance generated at the head of the screw rod changes according to the compression amount of the elastic member, and the compression amount of the elastic member can be easily adjusted by the screwing torque of the screw rod. Therefore, the magnitude of the rotational frictional resistance of the screw rod head can be managed with high accuracy.

  As the elastic member, for example, a rubber O-ring or a resin ring can be used. Here, since the O-ring is a widely distributed member, the use of the O-ring is low cost.

  A compression coil spring can be used as the elastic member. At this time, the compression coil spring can be provided with a knob extending radially outward from one end thereof. In this way, the initial set can be released by moving the knob and causing slippage between the head of the screw rod and the compression coil spring. The set can be released.

  Also, a disc spring or a wave spring can be used as the elastic member. In this way, the disc spring and the wave spring generate a large elastic restoring force with a small compression stroke, so that a large rotational frictional resistance is generated at the head of the screw rod, and the screw rod can be reliably prevented from rotating. .

  The elastic member includes a pair of arm portions arranged in parallel with the screw rod in between, and a connecting portion for connecting one end of the arm portion, and the arm portion is a head of the screw rod. A bifurcated member formed to be elastically compressible between the portion and the female screw member can be used. If it does in this way, initial set can be canceled by operation which pulls out a forked member from between the head of a screw rod and a female screw member, and it is possible to cancel initial set surely without cranking an engine.

  The present invention can be applied to an auto tensioner that uses, as the return spring, a compression coil spring that applies an axial force in a direction protruding from the female screw member to the screw rod. In this case, the male screw and the female screw are It is possible to employ a saw-tooth screw in which the flank angle of the pressure flank that receives pressure when an axial load in the direction of pushing the screw rod into the female screw member is applied is larger than the flank angle of the play flank.

  In addition, the present invention can be applied to an auto tensioner that uses a torsion spring that applies a rotational force in a direction protruding from the female screw member to the screw rod as the return spring. In this case, the male screw and the female screw are sawtooth. Screws, trapezoidal screws or triangular screws can be employed. Examples of the torsion spring include a torsion coil spring, a spring, and a bamboo spring.

The present invention can be applied to, for example, the following auto tensioner.
1) Insert the female screw member into a cylindrical housing with one end open and the other end closed such that the protruding side of the screw rod from the female screw member is the closed end side of the housing. An auto tensioner in which a protruding end from the female screw member is brought into contact with a rod sheet provided in the housing and the chain or belt is pressed by the female screw member.
2) fixing the female screw member in a cylindrical housing with one end open and the other end closed such that the protruding side of the screw rod from the female screw member is the open end side of the housing; Auto tensioner that presses the chain or belt.

  In the auto tensioner of the present invention, before assembling to the engine, the screw rod is screwed into the female screw member in advance, and the screw rod is held in a state of being screwed into the female screw member by the rotational frictional resistance generated at the head of the screw rod at this time. be able to. Therefore, this auto tensioner does not need to hold down the screw rod when assembled to the engine, and is excellent in assembling workability to the engine.

The front view which shows the chain transmission device incorporating the auto tensioner of 1st Embodiment of this invention Expanded sectional view along the line II-II in FIG. FIG. 2 is an enlarged sectional view showing a state where the screw rod shown in FIG. 2 is initially set. FIG. 3 is an enlarged cross-sectional view of the vicinity of the screw rod head of FIG. The expanded sectional view which shows the modification of the head of the screw rod shown in FIG. The expanded sectional view which shows the other modification of the head of the screw rod shown in FIG. The expanded sectional view which shows the auto tensioner of 2nd Embodiment of this invention 7 is a side view of the auto tensioner shown in FIG. 7 as viewed from the head side of the screw rod. Front view showing a chain transmission apparatus incorporating an auto tensioner according to a third embodiment of the present invention. Enlarged cross-sectional view along line XX in FIG. The expanded sectional view which shows the state which initially set the screw rod shown in FIG. FIG. 10 is an enlarged sectional view of the vicinity of the screw rod head showing a modification in which a compression coil spring is employed instead of the O-ring shown in FIG. The expanded sectional view which shows the state which initially set the screw rod shown in FIG. FIG. 10 is an enlarged cross-sectional view of the vicinity of the screw rod head showing a modification in which a disc spring is employed instead of the O-ring shown in FIG. FIG. 10 is an enlarged cross-sectional view showing a modification in which a torsion coil spring is employed as the return spring shown in FIG. FIG. 10 is an enlarged cross-sectional view showing a modification in which a spring is adopted as the return spring shown in FIG. FIG. 16 is an enlarged sectional view taken along line XVII-XVII. FIG. 10 is an enlarged cross-sectional view showing a modification in which a bamboo spring is adopted as the return spring shown in FIG.

  FIG. 1 shows a chain transmission incorporating an auto tensioner 1 according to an embodiment of the present invention. In this chain transmission device, a sprocket 3 fixed to an engine crankshaft 2 and a sprocket 5 fixed to a camshaft 4 are connected via a chain 6, and the chain 6 rotates the crankshaft 2. This is transmitted to the camshaft 4, and the valve (not shown) of the combustion chamber is opened and closed by the rotation of the camshaft 4.

  The chain 6 is in contact with a chain guide 8 that is swingably supported about the fulcrum shaft 7, and the auto tensioner 1 presses the chain 6 through the chain guide 8.

  As shown in FIG. 2, the auto tensioner 1 includes a cylindrical housing 9 that is open at one end and closed at the other end, a female screw member 10 that is slidably inserted in the housing 9 in the axial direction, and a female screw member. And a return spring 12 that biases the screw rod 11. As shown in FIG. 1, the housing 9 is fixed to the engine block 13 with bolts 14 so that the open end faces the chain guide 8.

  As shown in FIG. 2, the female screw member 10 is formed in a bottomed cylindrical shape whose one end is open, and the female screw 15 formed on the inner periphery thereof is connected to the male screw 16 and the screw formed on the outer periphery of the screw rod 11. Is engaged. One end of the screw rod 11 protrudes from the female screw member 10, and a head portion 17 having an outer diameter larger than the inner diameter of the female screw member 10 is formed at the protruding portion. The head 17 has a seating surface 17 a perpendicular to the axial direction of the screw rod 11, and when the screw rod 11 is screwed into the female screw member 10, the seating surface 17 a of the head 17 is directly on the end surface 10 a of the female screw member 10. It comes to contact. The female screw member 10 is inserted into the housing 9 such that the protruding side of the screw rod 11 from the female screw member 10 is the closed end side of the housing 9.

  The male screw 16 and the female screw 15 have a sawtooth shape in which the flank angle of the pressure-side flank 18 that receives pressure when a load in the direction of pushing the screw rod 11 into the female screw member 10 is applied is larger than the flank angle of the play-side flank 19. Is formed.

  The flank angle of the pressure side flank 18 is determined by the rotational friction resistance between the pressure side flank 18, 18 of the male screw 16 and the female screw 15 when a load in the direction of pushing the screw rod 11 into the female screw member 10 is statically applied. It is set to a size that prevents the screw rod 11 from rotating. Further, the flank angle of the play side flank 19 is determined by sliding between the play side flank 19 and 19 of the male screw 16 and the female screw 15 when a load in a direction in which the screw rod 11 protrudes from the female screw member 10 is statically applied. The screw rod 11 is set to a size that allows the rotation.

  The return spring 12 is a compression coil spring. One end of the return spring 12 is supported by the female screw member 10 via the spring seat 20, and an axial force in a direction in which the other end protrudes from the female screw member 10 is applied to the screw rod 11. Due to the axial force, the screw rod 11 is biased in a direction protruding from the female screw member 10. The protruding end of the screw rod 11 from the female screw member 10 is in contact with a rod sheet 21 that is press-fitted into the housing 9 and fixed.

  Here, the female screw member 10 is urged in a direction protruding from the housing 9 by the reaction force of the return spring 12. The female screw member 10 has a protruding end from the housing 9 in contact with the chain guide 8 and presses the chain 6 through the chain guide 8.

  The housing 9 is formed with an oil supply passage 23 for introducing hydraulic oil into a pressure chamber 22 surrounded by the housing 9 and the female screw member 10. The oil supply passage 23 communicates with an oil hole 24 formed in the engine block 13 so that hydraulic oil supplied from an oil pump (not shown) through the oil hole 24 is introduced into the pressure chamber 22. It has become. A check valve 25 that allows only the flow of hydraulic oil from the oil supply passage 23 side to the pressure chamber 22 side is provided at the outlet of the oil supply passage 23.

  A minute leak gap 26 is formed between the sliding surfaces of the female screw member 10 and the housing 9, and hydraulic oil in the pressure chamber 22 leaks through the leak gap 26.

  The above-described assembly of the auto tensioner 1 to the engine block 13 is performed as follows, for example.

  First, the screw rod 11 is screwed into the female screw member 10 in a state of being extracted from the housing 9, and the head 17 of the screw rod 11 is brought into direct contact with the female screw member 10 as shown in FIG. At this time, the screw rod 11 is prevented from rotating by the rotational frictional resistance generated in the head 17, and as a result, the screw rod 11 is held (initially set) in a state of being screwed into the female screw member 10. Here, the torsional torque applied to the screw rod 11 may be a small torque that can be twisted by hand. Moreover, the screw rod 11 and the female screw member 10 can be initialized more reliably if the oil on the surface is removed by performing a degreasing process in advance. Next, the female screw member 10 is inserted into the housing 9, and the housing 9 is fixed to the engine block 13.

  When the crankshaft 2 is rotated by engine cranking after the autotensioner 1 is assembled to the engine block 13 in this manner, the vibration transmitted from the chain 6 to the screw rod 11 causes slippage between the head 17 and the female screw member 10. And the initial set of the screw rod 11 is released. As a result, the screw rod 11 protrudes from the female screw member 10 while rotating, and the female screw member 10 protrudes from the housing 9 to a position where the urging force of the return spring 12 and the tension of the chain 6 are balanced.

  Thereafter, when the tension of the chain 6 is reduced during the operation of the engine, the screw rod 11 moves in a direction protruding from the female screw member 10 due to the urging force of the return spring 12, so that the protruding amount of the female screw member 10 from the housing 9 increases. Thus, the slack of the chain 6 is absorbed. At this time, the check valve 25 is opened, and hydraulic oil flows into the pressure chamber 22 through the oil supply passage 23, so that the female screw member 10 moves quickly.

  On the other hand, if the tension of the chain 6 increases during engine operation, the screw rod 11 moves in the direction of being pushed into the female screw member 10 due to the tension of the chain 6, so that the protruding amount of the female screw member 10 from the housing 9 is small. Thus, the tension of the chain 6 is absorbed. At this time, the screw rod 11 rotates with respect to the female screw member 10 while repeating the forward and backward movements within the range of the axial gap between the female screw 15 and the male screw 16 due to the vibration of the chain 6. Further, since the hydraulic oil in the pressure chamber 22 flows out through the leak gap 26 between the female screw member 10 and the sliding surface of the housing 9, a damper action is generated by the viscous resistance of the hydraulic oil, so that the female screw member 10 is slowly And move.

  When the engine is stopped, the tension of the chain 6 may increase depending on the stop position of the camshaft 4. In this case, the chain 6 does not vibrate, so the male screw 16 of the screw rod 11 is received by the female screw 15 of the female screw member 10, The position of the screw rod 11 is fixed. Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  The auto tensioner 1 can hold the screw rod 11 in a state of being screwed into the female screw member 10 in advance before being assembled to the engine block 13. Therefore, the auto tensioner 1 does not need to hold down the screw rod 11 when assembled to the engine block 13, and is excellent in assembling workability to the engine block 13.

  Further, since the auto tensioner 1 can automatically release the initial set of the screw rod 11 by vibration applied to the screw rod 11 when the engine is cranked, there is a concern that the initial set may be forgotten to be released. Absent.

  In addition, the auto tensioner 1 causes the head 17 of the screw rod 11 to be moved when excessive slip occurs between the screw rod 11 and the female screw member 10 during engine operation, and the screw rod 11 moves greatly in the pushing direction. Since it is received by the female screw member 10 and the movement of the screw rod 11 is restricted, it is possible to prevent the return spring 12 from being excessively compressed and broken.

  The seating surface 17a of the head 17 of the screw rod 11 and the end surface 10a of the female screw member 10 contacting the seating surface 17a may be a plane perpendicular to the axial direction of the screw rod 11, as shown in FIG. As shown in FIG. 5, it is good also as a taper surface which carries out surface contact mutually. In this way, a large rotational frictional resistance is generated by the wedge action of the tapered surface, so that the initial setting can be performed more reliably. Moreover, as shown in FIG. 6, it is good also as R surface which mutually surface-contacts.

  7 and 8 show an auto tensioner 31 according to a second embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The female screw member 10 is formed in a cylindrical shape whose both ends are open, and is press-fitted into the housing 9 and fixed. The female screw member 10 is fixed in the housing 9 such that the protruding side of the screw rod 11 from the female screw member 10 is the open end side of the housing 9.

  One end of the return spring 12 is supported by the closed end of the housing 9, and the other end applies an axial force to the screw rod 11 in a direction protruding from the female screw member 10 via the spring seat 32. Due to the axial force, the screw rod 11 is biased in a direction protruding from the female screw member 10. The protruding end of the screw rod 11 from the female screw member 10 is in contact with the chain guide 8.

  Between the head 17 and the female screw member 10, there are a pair of arm portions 33, 33 arranged in parallel with the screw rod 11 in between, and a connecting portion 34 for connecting one ends of the arm portions 33, 33 to each other. A bifurcated member 35 is incorporated.

  Each arm portion 33 is formed in an arch shape that is curved so that the center of the portion sandwiched between the head portion 17 of the screw rod 11 and the female screw member 10 protrudes toward the head portion 17 side. Thus, the arm portion 33 can be elastically compressed between the head portion 17 and the female screw member 10.

  A jig insertion hole 36 is formed in the connecting portion 34, and a jig (not shown) is inserted into the jig insertion hole 36 so as to be bifurcated from between the head 17 of the screw rod 11 and the female screw member 10. The member 35 can be pulled out. Such a bifurcated member 35 can be formed by press forming a metal plate.

  A circumferential groove 37 is formed under the head 17 of the screw rod 11, and a part of the arm portion 33 is passed through the circumferential groove 37, thereby reducing the width of the arm portion 33 with the head 17. It is wider than the outer diameter difference of the male screw 16. Thereby, the arm part 33 has ensured the magnitude | size of the elastic restoring force produced when it pinches | interposes between the head 17 and the internal thread member 10. FIG.

  In the auto tensioner 31, when the screw rod 11 is screwed into the female screw member 10 to the end and the head portion 17 of the screw rod 11 is brought into contact with the arm portion 33 of the bifurcated member 35, the arm portion 33 is axially moved by the head portion 17. At this time, the screw rod 11 can be initially set by the rotational frictional resistance generated in the head 17.

  Similar to the first embodiment, the auto tensioner 31 can hold the screw rod 11 in a state of being screwed into the female screw member 10 in advance before being assembled to the engine block 13. Therefore, the auto tensioner 31 does not need to hold down the screw rod 11 when assembled to the engine block 13, and is excellent in assembling workability to the engine block 13.

  Further, the auto tensioner 31 can release the initial set by an operation of pulling out the bifurcated member 35 from between the head 17 of the screw rod 11 and the female screw member 10, and the initial set can be reliably released.

  Further, in the auto tensioner 31, the magnitude of the rotational frictional resistance generated in the head 17 of the screw rod 11 changes according to the compression amount of the arm portion 33, and the compression amount of the arm portion 33 is determined by screwing of the screw rod 11. Can be easily adjusted with torque. Therefore, the magnitude of the rotational frictional resistance of the head 17 of the screw rod 11 can be managed with high accuracy.

  9 and 10 show an auto tensioner 41 according to a third embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 10, the auto tensioner 41 includes a cylindrical housing 42 that is open at one end and closed at the other end, a female screw member 10 that is press-fitted into the housing 42, and an inner periphery of the female screw member 10. A screw rod 11 having a male screw 16 on the outer periphery thereof, and a return spring 12 for biasing the screw rod 11.

  The housing 42 is inserted into the tensioner mounting hole 44 of the engine cover 43 with the opening end facing the inside of the engine cover 43. As shown in FIG. 9, the housing 42 has a flange 45 integrally formed on the outer periphery thereof and is fixed to the engine cover 43 with bolts 46.

  As shown in FIG. 10, the female screw member 10 is formed in a cylindrical shape whose both ends are open. One end of the screw rod 11 protrudes from the female screw member 10, and a head portion 17 having an outer diameter larger than the inner diameter of the female screw member 10 is formed at the protruding portion. The female screw member 10 is fixed in the housing 42 such that the protruding side of the screw rod 11 from the female screw member 10 is the open end side of the housing 42.

  One end of the return spring 12 is supported by the closed end of the housing 42, and the other end applies an axial force to the screw rod 11 in a direction protruding from the female screw member 10 via the spring seat 47. Due to the axial force, the screw rod 11 is biased in a direction protruding from the female screw member 10. The protruding end of the screw rod 11 from the female screw member 10 is in contact with the chain guide 8.

  A rubber O-ring 48 is incorporated between the head 17 and the female screw member 10. The O-ring 48 is formed in a size having a portion that overlaps the head 17 of the screw rod 11 when viewed in the axial direction, and when the screw rod 11 is screwed into the female screw member 10, the head 17 and the female screw member 10. An O-ring 48 is sandwiched between the two.

  The auto tensioner 41 is assembled to the engine cover 43 as follows, for example.

  As shown in FIG. 11, the screw rod 11 is screwed into the female screw member 10 to the end, the head 17 of the screw rod 11 is brought into contact with the O-ring 48, and the O-ring 48 is compressed in the axial direction by the head 17. At this time, the screw rod 11 is initially set by the rotational frictional resistance generated in the head 17. Next, with the initial set state, the housing 42 is inserted into the tensioner mounting hole 44 and the flange 45 is fixed with the bolt 46.

  After the autotensioner 41 is assembled to the engine cover 43 in this way, when the crankshaft 2 is rotated by engine cranking, slippage between the head 17 and the O-ring 48 is caused by vibration transmitted from the chain 6 to the screw rod 11. As a result, the initial setting of the screw rod 11 is released, and the screw rod 11 protrudes from the female screw member 10 while rotating.

  When the chain 6 is removed when the engine is overhauled, the screw rod 11 protrudes from the female screw member 10 by the urging force of the return spring 12. In this case, the screw rod 11 is again screwed into the female screw member 10 by the operation of screwing the screw rod 11 into the female screw member 10. 11 can be initially set.

  The auto tensioner 41 can hold the screw rod 11 in a state of being screwed into the female screw member 10 in advance before being assembled to the engine cover 43. Therefore, the auto tensioner 41 does not need to hold down the screw rod 11 when assembled to the engine cover 43, and is excellent in assembling workability to the engine cover 43.

  Further, since the auto tensioner 41 can automatically cancel the initial set by vibration applied to the screw rod 11 when the engine is cranked, there is no fear of forgetting to cancel the initial set.

  Further, in the auto tensioner 41, the magnitude of the rotational friction resistance generated in the head 17 of the screw rod 11 changes according to the compression amount of the O-ring 48, and the compression amount of the O-ring 48 is determined by screwing of the screw rod 11. Can be easily adjusted with torque. Therefore, the magnitude of the rotational frictional resistance of the head 17 of the screw rod 11 can be managed with high accuracy.

  Further, the auto tensioner 41 causes the head 17 of the screw rod 11 to move when the screw rod 11 moves greatly in the pushing direction due to excessive slippage between the screw rod 11 and the female screw member 10 during engine operation. Since it is received by the female screw member 10 and the movement of the screw rod 11 is restricted, it is possible to prevent the return spring 12 from being excessively compressed and broken.

  Since the O-ring 48 is a widely distributed member, it is inexpensive to use the O-ring 48 as an elastic member incorporated between the head 17 of the screw rod 11 and the female screw member 10. A ring made of a ring (not shown) may be used.

  Moreover, as shown in FIGS. 12 and 13, a compression coil spring 49 may be used as an elastic member incorporated between the head 17 of the screw rod 11 and the female screw member 10. Even in this case, the magnitude of the rotational friction resistance generated at the head 17 of the screw rod 11 changes in accordance with the compression amount of the compression coil spring 49, and the compression amount of the compression coil spring 49 depends on the screwing of the screw rod 11. Since the torque can be easily adjusted, the magnitude of the rotational frictional resistance of the head 17 of the screw rod 11 can be managed with high accuracy.

  Thus, when the compression coil spring 49 is incorporated between the head 17 of the screw rod 11 and the female screw member 10, the compression coil spring 49 can be provided with a knob 50 extending radially outward from one end thereof. In this way, the initial set can be released by moving the knob 50 and causing a slip between the head 17 of the screw rod 11 and the compression coil spring 49, and the initial set can be reliably released. Become.

  As shown in FIG. 14, a disc spring 51 may be used as an elastic member incorporated between the head 17 of the screw rod 11 and the female screw member 10. Here, the disc spring 51 is an annular metal spring formed in a conical cylinder shape, and its large-diameter end is supported by the female screw member 10 and its small-diameter end comes into contact with the head 17 of the screw rod 11. Yes. When the disc spring 51 is used, the disc spring 51 generates a large elastic restoring force with a small compression stroke, so that a large rotational frictional resistance is generated in the head 17 of the screw rod 11 and the screw rod 11 is reliably prevented from rotating. Is possible. The same applies when a wave spring (not shown) is used instead of the disc spring 51. Here, the wave spring is an annular metal spring formed so that the waveform is repeated in the circumferential direction.

  In the above embodiment, the O-ring 48 is incorporated between the head 17 of the screw rod 11 and the female screw member 10, but the O-ring 48 is incorporated between the head 17 of the screw rod 11 and the housing 42, and the screw rod 11 is incorporated. When screwed into the female screw member 10, the O-ring 48 may be sandwiched between the head 17 and the housing 42 and compressed. The same applies when an elastic member other than the O-ring 48 is used.

  Further, in each of the above embodiments, the compression coil spring is employed as the return spring 12 that urges the screw rod 11 in the direction protruding from the female thread member 10, but a torsion coil spring may be employed as shown in FIG. Good.

  In FIG. 15, the return spring 12 has one end locked in a locking hole 52 formed in the closed end of the housing 42 and the other end locked in a locking hole 53 formed in the screw rod 11. The screw rod 11 is given a rotational force in a direction protruding from the female screw member 10 by the torsional deformation.

  Moreover, as the return spring 12, as shown in FIGS. 16-18, you may employ | adopt torsion springs other than a torsion coil spring.

  16 and 17, the return spring 12 is a spring that is obtained by winding a thin plate material into a spiral shape. The return spring 12 has a large-diameter end that is prevented from rotating around the closed end of the housing 42, and a small-diameter end that is inserted into a slit formed in the projection 54 at the insertion end of the screw rod 11 into the female screw member 10. A rotational force in a direction protruding from the female screw member 10 is applied to the screw rod 11 by torsional deformation. The external thread 16 on the outer periphery of the screw rod 11 and the internal thread 15 on the inner periphery of the female screw member 10 are vertically symmetrical triangular screws.

  In FIG. 18, the return spring 12 is a bamboo child spring in which a thin plate material is spirally wound. The return spring 12 has a large-diameter end that is prevented from rotating around the closed end of the housing 42, and a small-diameter end that is inserted into a slit formed in the protrusion 55 at the insertion end of the screw rod 11 into the female screw member 10. Due to the torsional deformation, a rotational force in a direction protruding from the female screw member 10 is applied to the screw rod 11. The male screw 16 on the outer periphery of the screw rod 11 and the female screw 15 on the inner periphery of the female screw member 10 are vertically symmetrical trapezoidal screws.

DESCRIPTION OF SYMBOLS 1 Auto tensioner 6 Chain 9 Housing 10 Female thread member 11 Screw rod 12 Return spring 15 Female thread 16 Male thread 17 Head 18 Pressure side flank 19 Play side flank 21 Rod seat 31 Auto tensioner 33 Arm part 34 Connecting part 35 Bifurcated member 41 Auto tensioner 42 Housing 48 O-ring 49 Compression coil spring 50 Knob 51 Belleville spring

Claims (13)

A female screw member (10) having a female screw (15) on the inner periphery, a screw rod (11) having a male screw (16) threadedly engaged with the female screw (15) on the outer periphery, and the screw rod (11) as a female screw member An auto-tensioner having a return spring (12) urging in a direction protruding from (10) and absorbing slack of the chain (6) or belt by the protrusion of the screw rod (11) from the female screw member (10) In
A head (17) having an outer diameter larger than the inner diameter of the female screw member (10) is formed at a protruding portion of the screw rod (11) from the female screw member (10), and the screw rod (11) is connected to the female screw member (10). An auto tensioner characterized in that the screw rod (11) is prevented from rotating by rotational frictional resistance generated in the head (17) of the screw rod (11) when screwed into 10).   The auto tensioner according to claim 1, wherein when the screw rod (11) is screwed into the female screw member (10), the head (17) of the screw rod (11) and the female screw member (10) are in direct contact.   An elastic member (35, 48, 49, 51) was assembled between the head (17) of the screw rod (11) and the female screw member (10), and the screw rod (11) was screwed into the female screw member (10). 2. The auto tensioner according to claim 1, wherein the head (17) of the screw rod (11) sometimes compresses the elastic member (35, 48, 49, 51).   The auto tensioner according to claim 3, wherein the elastic member is a rubber O-ring (48) or a resin ring.   The auto tensioner according to claim 3, wherein the elastic member is a compression coil spring (49).   The auto tensioner according to claim 5, wherein the compression coil spring (49) is provided with a knob (50) extending radially outward from one end thereof.   The auto tensioner according to claim 3, wherein the elastic member is a disc spring (51) or a wave spring.   The elastic member has a pair of arm portions (33, 33) arranged in parallel with the screw rod (11) in between, and a connecting portion (34) for connecting one ends of the arm portions (33, 33) to each other. The arm part (33) is formed to be elastically compressible between the head (17) of the screw rod (11) and the female screw member (10). The auto tensioner according to claim 3.   The return spring (12) is a compression coil spring that applies an axial force in a direction protruding from the female screw member (10) to the screw rod (11). The male screw (16) and the female screw (15) The flank angle of the pressure flank (18) that receives pressure when an axial load in the direction of pushing the screw rod (11) into the female screw member (10) is applied is larger than the flank angle of the play flank (19). The auto tensioner according to any one of claims 1 to 8, wherein the auto tensioner is a large sawtooth screw.   The return spring (12) is a torsion spring that applies a rotational force in a direction protruding from the female screw member (10) to the screw rod (11). The male screw (16) and the female screw (15) are sawtooth screws, The auto tensioner according to any one of claims 1 to 8, which is a trapezoidal screw or a triangular screw.   The auto tensioner according to claim 10, wherein the torsion spring is any one of a torsion coil spring, a spring, and a bamboo spring.   In the cylindrical housing (9) with one end open and the other end closed, the female screw member (10) is placed on the protruding side of the screw rod (11) from the female screw member (10) of the housing (9). Slidably inserted in the direction of the closed end side, the projecting end of the screw rod (11) from the female screw member (10) is brought into contact with the rod sheet (21) provided in the housing (9), The auto tensioner according to any one of claims 1 to 11, wherein the female screw member (10) presses the chain (6) or the belt.   The female screw member (10) is placed in a cylindrical housing (42) having one end opened and the other end closed, and the protruding side of the screw rod (11) from the female screw member (10) is the housing (42). The auto tensioner according to any one of claims 1 to 11, wherein the auto tensioner is fixed in a direction to be an open end side, and the chain (6) or the belt is pressed by the screw rod (11).

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