JP2008138777A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner capable of effectively absorbing the tension of a chain when a variation in the tension of the chain is large and making it hard for the chain to be vibrated when a variation in the tension of the chain is small. <P>SOLUTION: A rod 12 for pressing the chain is axially movably inserted into a bottomed cylindrical housing 10. A wear ring 11 installed on the outer periphery of the rod is biased by a return spring 24 installed in the housing. A nut member 19 is axially movably installed between the wear ring and the bottom of the housing. A spring member 27 and a spring holder 28 are installed between the nut member and the bottom of the housing. The nut member is supported by the spring member held by the spring holder. A screw rod 21 screwed with the nut member is installed between the rod and the bottom of the housing. The screw rod is biased in the direction separating from the bottom of the housing by a spring 34 installed between the screw rod and the bottom of the housing. The end surface 36 of the screw rod is brought into contact with the rod. <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 is slow in the axial movement of the rod even when the chain tension increases, so when the engine resonates, the crankshaft torque or camshaft resistance changes When the chain tension fluctuation during operation of the engine is large, such as when the engine is large, the chain tension cannot be sufficiently absorbed, and the chain tension may be excessive during engine operation.

  Therefore, the inventor of the present invention inserts a chain pressing rod into the bottomed cylindrical housing so as to be movable in the axial direction in order to prevent excessive tension of the chain during engine operation. A wear ring provided on the outer periphery of the rod is urged away from the bottom of the housing by a return spring provided in the housing, and a nut member coaxial with the housing is axially interposed between the wear ring and the bottom of the housing. A screw rod provided between the rod and the bottom of the housing is provided between the rod and the housing so that the nut member is supported by a spring member provided between the nut member and the bottom of the housing. A spring provided between the screw rod and the bottom of the housing urges the screw rod away from the bottom of the housing, and the screw The end face of the head devised a chain tensioner is brought into contact with the rod.

  When the tension of the chain suddenly increases during engine operation, the chain tensioner quickly absorbs the tension of the chain by compressing the spring member, and prevents the tension of the chain from becoming excessive.

  However, when the chain tensioner supports the nut member with the spring member in a free length, the spring member expands and contracts in accordance with the chain tension even when the chain tension fluctuation is small. The chain may vibrate due to the expansion and contraction of the member, which may cause abnormal noise. If the spring constant of the spring member is increased to prevent the noise, the amount of compression of the spring member is insufficient when the chain tension suddenly increases during engine operation, and the chain tension is sufficiently absorbed. There is a risk that it will not be possible.

  The problem to be solved by the present invention is to provide a chain tensioner that effectively absorbs chain tension when the chain tension fluctuation is large, and is less likely to vibrate when the chain tension fluctuation is small.

  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 a ring shape is formed between the nut member and the bottom of the housing. And a spring holder that holds the spring member in a compressed state in the axial direction, supports the nut member with the spring member held by the spring holder, and screw-engages with the nut member. A rod is provided between the rod and the bottom of the housing, and a sprocket provided between the screw rod and the bottom of the housing. The screw rod biased in a direction away from the bottom of the housing ring, employing the configuration is brought into contact with the end face of the screw rod to 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, when the tension of the chain during engine operation is large and the tension of the chain becomes larger than the load (preload) applied to the spring member in advance by the spring holder, the spring rod is compressed, so that the screw rod Moves axially together with the nut member and quickly absorbs chain tension.

  Further, when the tension of the chain during engine operation fluctuates in a range smaller than the preload of the spring member by the spring holder, the spring member does not expand and contract.

  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 stopper member is provided between the nut member and the bottom of the housing to restrict a movement stroke of the nut member in a direction in which the spring member is compressed.
2) The spring holder includes a cylindrical portion that houses the spring member, a bottom portion formed at one end of the cylindrical portion, and an inward flange portion formed by caulking the other end of the cylindrical portion. The spring member is held in the axially compressed state with the orientation flange portion.

  In this chain tensioner, the spring member that receives the tension of the chain is held in a state compressed by the spring holder, and therefore, if the tension of the chain does not become larger than the load previously applied to the spring member by the spring holder, The member does not compress. Therefore, when the chain tension fluctuation is large and the chain tension suddenly increases, the spring member compresses the chain tension quickly, but when the chain tension fluctuation is small, the spring member The chain does not expand and contract and the chain does not vibrate easily.

  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 fixed-side 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.

  As shown in FIG. 3, between the nut member 19 and the bottom 17 of the housing 10, the corrugated ring-shaped wave washers 25 and 25 provided adjacent to each other in the axial direction and the adjacent wave washers 25 and 25 are provided. A spring member 27 comprising a ring-shaped flat washer 26 is incorporated.

  A spring holder 28 is incorporated between the nut member 19 and the bottom 17 of the housing 10 to hold the spring member 27 in an axially compressed state. The spring holder 28 includes a cylindrical portion 29 that houses the spring member 27, a bottom portion 30 formed at one end of the cylindrical portion 29, and an inward flange portion 31 formed by caulking the other end of the cylindrical portion 29. The inward flange portion 31 holds the spring member 27 in an axially compressed state, whereby a load is applied to the spring member 27 in advance.

  A cylindrical stopper member 32 is provided between the nut member 19 and the bottom 17 of the housing 10. In the stopper member 32, a flange portion 33 formed on the outer periphery of the stopper member 32 is sandwiched between the spring member 27 and the inward flange portion 31, so that the spring member 27 is inserted into the nut via the stopper member 32. The member 19 is supported. When the nut member 19 moves in the direction in which the spring member 27 is compressed, the stopper member 32 moves in the axial direction integrally with the nut member 19, abuts against the bottom 30 of the spring holder 28, and the movement stroke of the nut member 19. To regulate.

  As shown in FIG. 2, a spring seat 35 biased toward the screw rod 21 by a spring 34 is incorporated between the bottom 17 of the housing 10 and the screw rod 21, and one end of the spring seat 35 is connected to the screw rod 21. Abut. Thereby, the urging force of the spring 34 is transmitted to the screw rod 21 via the spring seat 35, and the screw rod 21 is urged in a direction away from the bottom 17 of the housing 10. Further, the screw rod 21 has a spherical end surface 36 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.

  Further, 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. At this time, when the tension of the chain 5 becomes larger than the load (preload) previously applied to the spring member 27 by the spring holder 28, the flange portion 33 is separated from the inward flange portion 31 as shown in FIG. The spring member 27 is compressed. Therefore, the screw rod 21 moves in the axial direction integrally with the nut member 19, and the tension of the chain 5 is quickly absorbed.

  Further, when the tension of the chain 5 during operation of the engine fluctuates in a range smaller than the preload of the spring member 27 by the spring holder 28, the spring member 27 does not expand and contract.

  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, if 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 36 of the screw rod 21. While rotating with respect to the member 19, it moves in the axial direction and comes into contact with 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, in this chain tensioner 8, the spring member 27 is not compressed unless the tension of the chain 5 becomes larger than the load previously applied to the spring member 27 by the spring holder 28. Therefore, when the tension variation of the chain 5 is large and the tension of the chain 5 suddenly increases, the tension of the chain 5 is quickly absorbed by the compression of the spring member 27, but when the tension variation of the chain 5 is small The spring member 27 does not expand and contract, and the chain 5 hardly vibrates.

  In the chain tensioner 8, the screw rod 21 and the nut member 19 that are engaged with each other are separate from the rod 12, and the end surface 36 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.

  Further, the chain tensioner 8 can adjust the moving stroke of the nut member 19 by the compression of the spring member 27 by changing the axial length of the stopper member 32.

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. FIG. 2 is an enlarged sectional view in the vicinity of the spring member The expanded sectional view which shows the state which the spring member shown in FIG. 3 compressed to the axial direction

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 27 Spring member 28 Spring holder 29 Tube part 30 Bottom part 31 Inward flange part 32 Stopper member 34 Spring 36 End surface

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) is interposed between the wear ring (11) and the bottom (17) of the housing (10). ) And a coaxial nut member (19) are provided so as to be movable in the axial direction. Between the nut member (19) and the bottom (17) of the housing (10), a ring-shaped spring member (27) and the spring member ( 27) and a spring holder (28) for holding the axially compressed state in the axial direction, and the nut member (19) by the spring member (27) held by the spring holder (28). Is provided between the rod (12) and the bottom (17) of the housing (10), and the screw rod (21) and the housing are screw-engaged with the nut member (19). A spring (34) provided between the bottom (17) of (10) urges the screw rod (21) away from the bottom (17) of the housing (10), and the end face of the screw rod (21). A chain tensioner in which (36) is brought into contact with the rod (12).   Between the nut member (19) and the bottom (17) of the housing (10), a stopper member (32) for restricting the movement stroke of the nut member (19) in the direction of compressing the spring member (27). The chain tensioner according to claim 1 provided.   The spring holder (28) includes a cylindrical part (29) for accommodating the spring member (27), a bottom part (30) formed at one end of the cylindrical part (29), and the other end of the cylindrical part (29). The inward flange portion (31) formed by caulking is formed, and the spring member (27) is held in an axially compressed state by the bottom portion (30) and the inward flange portion (31). Item 3. The chain tensioner according to Item 1 or 2.

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