JP2008138774A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner making it hard for a chain to be loosened when an engine is re-started and capable of absorbing the tension of the chain while the engine is running. <P>SOLUTION: A rod 12 for pressing the chain 12 is inserted into a housing 10. A wear ring 11 on the outer periphery of the rod 12 is biased in the direction separating from the bottom 17 of the housing 10 by a return spring 24 in the housing 10. A nut member 19 is installed between the wear ring 11 and the bottom 17 of the housing 10. The nut member 19 is biased in the direction separating from the bottom 17 of the housing by a waveform ring-shaped wave washer 25 between the nut member 19 and the housing 10. A screw rod 21 screwed with the nut member 19 is installed between the rod 12 and the bottom 17 of the housing 10. The screw rod 21 is biased in the direction separating from the bottom 17 of the housing by a spring 27 between the screw rod 21 and the bottom 17 of the housing 10 until the end surface 30 of the screw rod 21 is brought into contact with the rod 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention mainly relates to a chain tensioner used for maintaining tension of a timing chain that drives a camshaft of an engine.

  In general, an engine transmits rotation of a crankshaft to a camshaft through a timing chain housed in an engine room in an engine cover, and the rotation of the camshaft opens and closes a valve in a combustion chamber. Here, in order to keep the chain tension within an appropriate range, a tension adjusting device composed of a chain guide provided so as to be able to swing around a fulcrum shaft and a chain tensioner that presses the chain via the chain guide is often used. It is done.

  As a chain tensioner incorporated in this tension adjusting device, a male screw formed on the outer periphery of a chain pressing rod is thread-engaged with a female screw formed on the inner periphery of a bottomed cylindrical housing, and the rod and the bottom of the housing are There is known a spring in which a rod is urged in a direction away from the bottom of a housing (Patent Document 1).

  In this chain tensioner, when the tension of the chain changes with the engine running, the rod repeatedly rotates forward and backward within the gap between the female screw and the male screw due to the vibration of the chain. The rod moves in the axial direction to the position where is balanced with the chain tension.

Further, when the engine is stopped, the tension of the chain may become larger than the urging force of the spring. However, since the chain does not vibrate, the rod does not rotate and does not move in the axial direction. Therefore, the chain is less likely to be slack when the engine is restarted, and the engine can be started smoothly.
Japanese Utility Model Publication No. 64-41756

  However, this chain tensioner does not rotate if the chain does not vibrate even if the chain tension increases, so when the engine resonates, fluctuations in crankshaft torque or camshaft rotation resistance When is large, the tension of the chain cannot be sufficiently absorbed, and the chain tension may be excessive.

  The problem to be solved by the present invention is to provide a chain tensioner that is less likely to loosen the chain when the engine is restarted, and that can effectively absorb chain tension during engine operation. .

  In order to solve the above-mentioned problem, a rod for pressing a chain is inserted into a bottomed cylindrical housing so as to be movable in the axial direction, and a wear spring provided on the outer periphery of the rod is a return spring provided in the housing. Energized in a direction away from the bottom of the housing, a nut member coaxial with the housing is provided between the wear ring and the bottom of the housing so as to be movable in the axial direction, and provided between the nut member and the bottom of the housing. A wave rod-shaped wave washer urges the nut member in a direction away from the bottom of the housing, and a screw rod that engages with the nut member is provided between the rod and the bottom of the housing. The screw rod and the housing The end of the screw rod is urged by a spring provided between the bottom of the screw in the direction away from the bottom of the housing. Employing the configuration is brought into contact with the rod to the chain tensioner.

  In this chain tensioner, when the chain is vibrated and the chain tension increases, the screw rod repeatedly moves forward and backward within the gap between the screw rod and the nut member, and the screw rod rotates little by little with respect to the nut member. To do. As a result, the rod moves in the axial direction to a position where the urging force of the return spring balances with the tension of the chain, and absorbs the tension of the chain.

  In addition, the chain tension may suddenly increase when the engine resonates, or when the crankshaft rotational force fluctuation or camshaft rotational resistance fluctuation is large. By compressing, the screw rod moves in the axial direction integrally with the nut member, and quickly absorbs the tension of the chain.

  Further, when the engine is stopped, 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 does not move in the axial direction.

The chain tensioner described above can have the following configuration.
1) A plurality of the wave washers are provided adjacent to each other in the axial direction between the nut member and the bottom of the housing, and a flat washer is provided between the adjacent wave washers.
2) The flange portion of the stopper composed of a cylindrical portion and a flange portion formed on the outer periphery of the cylindrical portion is sandwiched between the wave washer and the nut member, and when the wave washer is compressed in the axial direction, The cylindrical portion is brought into contact with the bottom of the housing.

  In the chain tensioner, when the engine stops and the chain does not vibrate, the screw rod does not rotate and does not move in the axial direction even if the chain tension increases. Therefore, the chain is less likely to be slack when the engine is restarted, and the engine can be started smoothly.

  On the other hand, in this chain tensioner, when the chain tension increases with the engine running, the screw rod gradually rotates relative to the nut member to absorb the chain tension, and the chain tension suddenly increases. When this happens, the wave washer compresses to quickly absorb the chain tension. Therefore, the tension of the chain can be effectively absorbed while the engine is operating, and the life of the chain can be prevented from being reduced due to excessive tension.

  FIG. 1 shows a chain transmission device incorporating a chain 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.

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

  The chain tensioner 8 has a housing 10 fixed to the engine block with bolts 9. As shown in FIG. 2, the housing 10 is formed in a bottomed cylindrical shape with one end open, and a moving wear ring 11 is inserted into the housing 10 so as to be slidable in the axial direction. The movement-side wear ring 11 is fitted on the outer periphery of a rod 12 provided coaxially with the housing 10 so that the movement-side wear ring 11 and the rod 12 can move integrally in the axial direction.

  The housing 10 is filled with hydraulic oil, and the hydraulic oil in the housing 10 is sealed with a ring-shaped oil seal 13 that slidably penetrates the rod 12. An oil passage 14 penetrating in the axial direction is formed in the moving-side wear ring 11 at intervals in the circumferential direction.

  Between the moving side wear ring 11 and the open end 15 of the housing 10, a fixed side wear ring 16 that slidably penetrates the rod 12 is provided. The stationary wear ring 16 is press-fitted and fixed to the inner periphery of the housing 10 and supports the outer periphery of the rod 12.

  A nut member 19 having an internal thread 18 formed on the inner periphery is incorporated between the moving wear ring 11 and the bottom 17 of the housing 10 so as to be axially movable in the axial direction. The nut member 19 is disposed on the outer periphery. The screw rod 21 formed with the male screw 20 is screw-engaged.

  The female screw 18 and the male screw 20 are screw-engaged with play in the axial direction. Further, the female screw 18 and the male screw 20 are formed in a sawtooth shape having an asymmetrical 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 17 of the housing acts on the screw rod 21. The flank angle 22 is formed to be larger than the flank angle of the play side flank 23.

  A return spring 24 is incorporated in the housing 10 between the nut member 19 and the moving wear ring 11, and the moving wear ring 11 is urged by the return spring 24 in a direction away from the bottom 17 of the housing 10. ing.

  Between the nut member 19 and the bottom 17 of the housing 10, corrugated ring-shaped wave washers 25, 25 are provided adjacent to each other in the axial direction, and between the adjacent wave washers 25, 25, a disc ring-shaped flat washer. A washer 26 is incorporated. Each wave washer 25 urges the nut member 19 in a direction away from the bottom 17 of the housing 10.

  A spring seat 28 urged toward the screw rod 21 by a spring 27 is incorporated between the bottom 17 of the housing 10 and the screw rod 21, and a spherical end surface 29 on the screw rod 21 side of the spring seat 28 is a screw end 21. It is in contact with the rod 21. As a result, the urging force of the spring 27 is transmitted to the screw rod 21 via the spring seat 28, and the screw rod 21 is urged away from the bottom 17 of the housing 10. Further, the screw rod 21 has a spherical end face 30 on the rod 12 side in contact with the rod 12.

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

  When the tension of the chain 5 increases in the state where the camshaft 3 is driven and the chain 5 vibrates, the screw rod 21 repeatedly advances and retreats within the gap between the female screw 18 and the male screw 20, and the screw rod 21 becomes the nut member. Rotate 19 little by little. As a result, the rod 12 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.

  In addition, the tension of the chain 5 may suddenly increase when resonance occurs in the engine or when the fluctuation of the rotational force of the crankshaft 1 or the fluctuation of the rotational resistance of the camshaft 3 is large. As shown in FIG. 3, the compression of each wave washer 25 causes the screw rod 21 to move integrally with the nut member 19 in the axial direction, thereby quickly absorbing the tension of the chain 5.

  On the other hand, when the tension of the chain 5 decreases, the rod 12 moves in a direction away from the bottom 17 of the housing 10 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 12 becomes larger than the range of the gap between the female screw 18 and the male screw 20, the rod 12 moves away from the end surface 30 of the screw rod 21. While rotating with respect to the member 19, it moves in the axial direction and contacts the rod 12.

  When the engine is stopped, the tension of the chain 5 when the engine is stopped may be larger than the urging force of the return spring 24 due to fluctuations in the rotational resistance of the camshaft 3, but the chain 5 does not vibrate. 21 does not rotate with respect to the nut member 19, and the rod 12 does not move in the axial direction.

  As described above, when the engine is stopped and the chain 5 does not vibrate, the chain tensioner 8 does not rotate and does not move in the axial direction even if the tension of the chain 5 increases. Therefore, the chain 5 is less likely to be slack when the engine is restarted, and the engine can be started smoothly.

  Further, the chain tensioner 8 absorbs the tension of the chain 5 by rotating the screw rod 21 little by little with respect to the nut member 19 when the tension of the chain 5 becomes large with the engine operated. When the tension suddenly increases, the wave washer 25 compresses to quickly absorb the tension of the chain 5. Therefore, the tension of the chain 5 can be effectively absorbed while the engine is operating, and the life of the chain 5 can be prevented from being reduced due to excessive tension.

  In the chain tensioner 8, the screw rod 21 and the nut member 19 that are screw-engaged are both separate from the rod 12, and the end surface 30 of the screw rod 21 is brought into contact with the rod 12. When a force perpendicular to the axis acts on the projecting end of the housing 10, the force is not easily transmitted to the screw rod 21. Therefore, when the tension of the chain 5 increases and the chain guide 7 swings, and the swing causes a shift between the contact surfaces of the chain guide 7 and the rod 12, the rod 12 has a protruding end from the housing 10. Even when a force in a direction perpendicular to the axis is applied, the rotational resistance of the screw rod 21 with respect to the nut member 19 does not easily increase and operates stably.

  As shown in FIG. 4, the chain tensioner 8 sandwiches the flange portion 32 of the stopper 33 including the cylindrical portion 31 and the flange portion 32 formed on the outer periphery of the cylindrical portion 31 between the wave washer 25 and the nut member 19. The cylindrical portion 31 can be brought into contact with the bottom 17 of the housing 10 when the wave washer 25 is compressed in the axial direction. If it does in this way, it will become possible to adjust the movement stroke of nut member 19 by wave washer 25 compressing by changing the length of cylinder part 31 of stopper 33. FIG.

  In the above embodiment, a plurality of wave washers 25 are provided adjacent to each other in the axial direction between the nut member 19 and the bottom 17 of the housing 10, and a flat washer 26 is provided between the adjacent wave washers 25, 25. Although the movement stroke of the nut member 19 due to the compression of the nut 25 is lengthened, only one wave washer 25 may be incorporated between the nut member 19 and the bottom 17 of the housing 10.

The front view which shows the chain transmission apparatus incorporating the chain tensioner of embodiment of this invention 1 is an enlarged cross-sectional view of the chain tensioner shown in FIG. The expanded sectional view of the nut member vicinity which shows the state which the wave washer of FIG. 2 compressed FIG. 2 is an enlarged sectional view of the vicinity of a nut member showing a chain tensioner in which a stopper is incorporated between the wave washer and the nut member shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Housing 11 Moving side wear ring 12 Rod 17 Bottom 19 Nut member 21 Screw rod 24 Return spring 25 Wave washer 26 Flat washer 27 Spring 30 End surface 31 Cylindrical part 32 Flange part 33 Stopper

Claims (3)

  A chain pressing rod (12) is inserted into the bottomed cylindrical housing (10) so as to be movable in the axial direction, and a wear ring (11) provided on the outer periphery of the rod (12) is inserted into the housing (10). The return spring (24) provided on the housing (10) is urged away from the bottom (17) of the housing (10), and the housing (10 ) And a coaxial nut member (19) are provided so as to be movable in the axial direction, and a corrugated ring-shaped wave washer (25) provided between the nut member (19) and the bottom (17) of the housing (10). The member (19) is urged in the direction away from the bottom (17) of the housing (10), and the screw rod (21) engaged with the nut member (19) is screwed into the rod (12) and the housing. The screw rod (21) is provided between the bottom (17) of (10) and the spring rod (27) provided between the screw rod (21) and the bottom (17) of the housing (10). A chain tensioner which is urged in a direction away from the bottom (17) and has an end face (30) of the screw rod (21) in contact with the rod (12).   A plurality of the wave washers (25) are provided adjacent to each other in the axial direction between the nut member (19) and the bottom (17) of the housing (10), and a flat washer is provided between the adjacent wave washers (25, 25). The chain tensioner according to claim 1, wherein (26) is provided.   The wave washer (25) and the nut member (19) of the stopper (33) comprising a tube portion (31) and a flange portion (32) formed on the outer periphery of the tube portion (31). The cylindrical portion (31) of the stopper (33) is brought into contact with the bottom (17) of the housing (10) when the wave washer (25) is compressed in the axial direction. Or the chain tensioner of 2.

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