JP2008051216A - Automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic tensioner which is stably operated even if a force perpendicular to the axis acts on an end part protruded from a housing of a rod. <P>SOLUTION: The automatic tensioner comprises: a wear ring 11 inserted into a housing 10; a rod 14 integrally moving with the wear ring 11, which is provided so as to protrude from an open end 13 of the housing 10; a wear ring 17 for slidably inserting the rod 14 therethrough, which is provided between the wear ring 11 and the open end 13 of the housing; an oil seal 18 incorporated between the wear ring 17 and the wear ring 11, the oil seal sealing oil in the housing 10; a sleeve 21 incorporated between the wear ring 11 and the bottom 19 of the housing; a return spring 23 energizing the sleeve 21 and the wear ring 11 in mutually separating directions; a screw rod 23 screwed to and engaged with the sleeve 21; a spring 27 energizing the screw rod 23 toward the rod 14, which is provided so that an end surface 30 of the screw rod 23 abuts on the rod 14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention mainly relates to an auto tensioner used to maintain tension of a timing chain or timing belt that drives a camshaft of an engine.

  In general, an engine transmits rotation of a crankshaft to a camshaft via a timing chain or a timing belt (which will be described by taking a timing chain as an example) housed in an engine room in an engine cover. The combustion chamber valve is opened and closed by rotating the shaft. Here, in order to keep the tension of the chain in an appropriate range, a tension adjusting device comprising a chain guide provided so as to be swingable around a fulcrum shaft and an auto tensioner that urges the chain guide in a direction to press the chain guide against the chain. Is often used.

  As an auto tensioner incorporated in this tension adjusting device, a rod is slidably inserted in a bottomed cylindrical housing with one end open, and an oil seal incorporated into the open end of the housing is used to oil in the housing. The screw rod is formed in the housing with a male screw formed on the outer periphery that is urged by a return spring provided in the housing in a direction to project the rod from the housing and engages with a female screw formed on the inner periphery of the end of the rod. It is known that the screw rod is urged in a direction away from the rod by a spring incorporated between the screw rod and the rod (Patent Document 1).

  In this auto tensioner, when the chain is vibrated while the camshaft is driven and the chain is vibrated, the rod repeatedly advances and retreats within the gap between the female screw and the male screw, and the screw rod rotates little by little. As a result, the rod moves to a position where the urging force of the return spring balances the tension of the chain, and absorbs the tension of the chain.

  On the other hand, when the chain tension decreases, the rod moves away from the bottom of the housing, and moves to a position where the urging force of the return spring balances with the chain tension. At this time, if the amount of movement of the rod increases, the screw rod moves away from the bottom of the housing. Thereafter, the screw rod moves in the axial direction while rotating with respect to the rod by the urging force of the spring and hits the bottom of the housing. Touch.

When the engine is stopped, the screw rod is kept in contact with the bottom of the housing. At this time, the tension of the chain may be larger than the urging force of the return spring. However, since the chain does not vibrate, the screw rod does not rotate and the rod does not move in the direction close to the bottom of the housing. Therefore, when the engine is restarted, the slack of the chain can be quickly absorbed, and the chain tension is easily stabilized.
Japanese Utility Model Publication No.1-4755

  However, in this auto tensioner, a female screw that is screw-engaged with the male screw of the screw rod is directly formed on the rod, so that when a force perpendicular to the axis acts on the end protruding from the housing of the rod, the male screw and the female screw Increases rotational resistance. For this reason, when the chain tension increases and the chain guide swings and the contact between the chain guide and the rod shifts due to the swing, the force perpendicular to the axis is applied to the end protruding from the rod housing. When it acted, there existed a problem that a screw rod became difficult to rotate with respect to a rod.

  The problem to be solved by the present invention is to provide an auto tensioner that operates stably even when a force in a direction perpendicular to the axis acts on an end portion protruding from the housing of the rod.

  In order to solve the above problems, a moving wear ring is slidably inserted into a bottomed cylindrical housing with one open end, and a rod that moves in the axial direction integrally with the moving wear ring is provided. A fixed wear ring that protrudes from the open end of the housing and slidably passes through the rod is provided between the movable wear ring and the open end of the housing, and the fixed wear ring and the move side Oil is sealed in the housing with an oil seal incorporated between wear rings, and a sleeve having an internal thread formed on the inner periphery is incorporated between the moving wear ring and the bottom of the housing, and the sleeve and the moving wear A return spring that urges the ring in the direction away from the ring is provided, and a screw rod with an external thread formed on the outer periphery is engaged with the sleeve. A spring for biasing the screw rod to the rod provided, employing the configuration is brought into contact with the end face of the rod side of the screw rod to the rod auto tensioner.

  In this auto tensioner, it is preferable that a ring-shaped seal member is incorporated in the outer periphery of the moving wear ring so that sliding resistance is generated between the outer periphery of the seal member and the inner periphery of the housing.

  In the auto tensioner according to the present invention, the screw rod and the sleeve engaged with the screw are both separate from the rod, and the end surface of the screw rod is brought into contact with the rod. Even when a force in a perpendicular direction is applied, the rotational resistance of the male screw and the female screw is unlikely to increase, and the operation is stable.

  In addition, a ring-shaped seal member is incorporated on the outer periphery of the moving wear ring, and a sliding resistance is generated between the outer periphery of the seal member and the inner periphery of the housing. Acts to suppress vibration of the rod.

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

  A chain guide 7 that is swingably supported by a fulcrum shaft 6 fixed to an engine block (not shown) is in contact with the chain 5. The chain guide 7 is pressed against the chain 5 by an auto tensioner 8. Is biased in the direction.

  The auto tensioner 8 has a housing 10 fixed to the engine block with a bolt 9, and the housing 10 is formed in a bottomed cylindrical shape with one end opened as shown in FIG. 2. A movable wear ring 11 is slidably inserted in the housing 10 in the axial direction. The axial through hole 12 formed in the center of the movable wear ring 11 projects from the open end 13 of the housing 10. The rod 14 provided is press-fitted and fixed.

  A ring-shaped seal member 15 is incorporated in the outer periphery of the moving-side wear ring 11, and the outer periphery of the seal member 15 comes into contact with the inner periphery of the housing 10 to generate sliding resistance. The moving side wear ring 11 is formed with an oil passage 16 penetrating in the axial direction at intervals in the circumferential direction.

  Between the moving side wear ring 11 and the open end 13 of the housing, there is provided a fixed side wear ring 17 through which the rod 14 is slidably passed. The stationary wear ring 17 is fixed by being press-fitted into the inner periphery of the housing 10 and supports the outer periphery of the rod 14 so as to be slidable.

  A ring-shaped oil seal 18 that slidably penetrates the rod 14 is incorporated between the movable wear ring 11 and the fixed wear ring 17, and the oil is sealed in the housing 10 by the oil seal 18. Has been.

  Between the moving wear ring 11 and the bottom 19 of the housing 10, a sleeve 21 having a female thread 20 formed on the inner periphery is incorporated coaxially with the housing 10, and the sleeve 21 has a screw rod 23 having a male thread 22 formed on the outer periphery. The screw is engaged. A return spring 24 that urges the sleeve 21 and the moving-side wear ring 11 in the axial direction is incorporated in the housing 10.

  The female screw 20 and the male screw 22 are engaged with each other with play in the axial direction. Further, the female screw 20 and the male screw 22 are formed in a sawtooth shape having an asymmetric cross section along the axis, and a pressure side flank that receives pressure in a state where a force in a direction approaching the bottom 19 of the housing acts on the screw rod 23. The flank angle of 25 is formed to be larger than the flank angle of the play side flank 26.

  A spring seat 28 biased toward the screw rod 23 by a spring 27 is incorporated between the bottom 19 of the housing and the screw rod 23, and a spherical end surface 29 on the screw rod 23 side of the spring seat 28 is a screw rod. 23 abuts. As a result, the urging force of the spring 27 is transmitted to the screw rod 23 via the spring seat 28, and the screw rod 23 is urged toward the rod 14. Further, the spherical end surface 30 of the screw rod 23 on the rod 14 side is in contact with the rod 14.

  Next, an operation example of the auto tensioner 8 will be described.

  When the chain 5 is vibrated by driving the camshaft 3 and the tension of the chain 5 is increased, the screw rod 23 repeatedly moves forward and backward within the gap between the female screw 20 and the male screw 22, and the screw rod 23 is moved to the sleeve 21. Rotate little by little. As a result, the rod 14 moves in the axial direction to a position where the urging force of the return spring 24 is balanced with the tension of the chain 5, and absorbs the tension of the chain 5.

  On the other hand, when the tension of the chain 5 decreases, the rod 14 moves away from the screw rod 23 and moves to a position where the urging force of the return spring 24 is balanced with the tension of the chain 5. At this time, when the amount of movement of the rod 14 becomes larger than the range of the gap between the female screw 20 and the male screw 22, the rod 14 moves away from the end surface 30 of the screw rod 23. Thereafter, the screw rod 23 is moved into the sleeve by the urging force of the spring 27. While rotating with respect to 21, it moves in the axial direction and comes into contact with the rod 14.

  Further, when the engine is stopped, the rod 14 is kept in contact with the end face 30 of the screw rod 23. At this time, the tension of the chain 5 may be larger than the urging force of the return spring 24. However, since the chain 5 does not vibrate, the screw rod 23 does not rotate with respect to the sleeve 21, and the rod 14 does not contact the bottom 19 of the housing. It does not move in the close direction. Therefore, when the engine is restarted, the looseness of the chain 5 can be quickly absorbed, and the tension of the chain 5 is easily stabilized.

  In the auto tensioner 8, the screw rod 23 and the sleeve 21 that are screw-engaged are both separate from the rod 14, and the end surface of the screw rod 23 is brought into contact with the rod 14. When a force in the direction perpendicular to the axis acts on the protruding end, the force is not easily transmitted to the screw rod 23. Therefore, when the tension of the chain 5 is increased and the chain guide 7 is swung, and the contact between the chain guide 7 and the rod 14 is displaced due to the swinging, the end of the rod 14 protruding from the housing 10 is Even when a force in a direction perpendicular to the axis is applied, the rotational resistance of the female screw 20 and the male screw 22 does not easily increase and operates stably.

  Further, in this auto tensioner 8, the sliding resistance generated between the outer periphery of the seal member 15 and the inner periphery of the housing 10 acts as a damper, so that the rod 14 hardly vibrates and the vibration of the chain 5 is suppressed.

  As the sealing member 15, an X-ring having an X-shaped section may be used as shown in FIG. 3A, an O-ring may be used as shown in FIG. 3B, and FIG. As shown, a square ring with a square cross section may be used.

The front view which shows the chain transmission apparatus incorporating the auto tensioner of embodiment of this invention 1 is an enlarged sectional view of the auto tensioner of FIG. 2A is an enlarged cross-sectional view showing an example using an X-ring as a seal member in FIG. 2, FIG. 2B is an enlarged cross-sectional view showing an example using an O-ring as a seal member in FIG. 2, and FIG. The expanded sectional view which shows the example which used the square ring as a sealing member of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Housing 11 Moving side wear ring 13 Open end 14 Rod 15 Seal member 17 Fixed side wear ring 18 Oil seal 19 Bottom 20 Female thread 21 Sleeve 22 Male thread 23 Screw rod 24 Return spring 27 Spring 30 End face

Claims (2)

  A moving wear ring (11) is slidably inserted in an axial direction into a bottomed cylindrical housing (10) whose one end is open, and the rod moves in the axial direction integrally with the moving wear ring (11). (14) is provided so as to protrude from the open end (13) of the housing (10), and a fixed wear ring (17) for slidably penetrating the rod (14) is connected to the movable wear ring (11). Oil is provided in the housing (10) by an oil seal (18) provided between the open end (13) of the housing and incorporated between the fixed wear ring (17) and the movable wear ring (11). A sleeve (21) which is hermetically sealed and formed with an internal thread (20) is assembled between the movable wear ring (11) and the bottom (19) of the housing, and the sleeve (21) and the movable side are assembled. A return spring (24) for urging the air ring (11) in a direction away from the air ring (11) is provided, and a screw rod (23) having a male screw (22) formed on the outer periphery is screw-engaged with the sleeve (21). A spring (27) for urging (23) toward the rod (14) is provided, and the end surface (30) of the screw rod (23) on the rod (14) side is brought into contact with the rod (14). Auto tensioner.   A ring-shaped seal member (15) is incorporated on the outer periphery of the movable wear ring (11) so that sliding resistance is generated between the outer periphery of the seal member (15) and the inner periphery of the housing (10). The auto tensioner according to claim 1.

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