JP2011021643A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner excelling in the maintainability of an engine. <P>SOLUTION: The chain tensioner 1 includes a plunger 10 inserted in an axially slidable manner into a cylindrical cylinder 9 opened at one end and closed at the other end. The plunger 10 is formed in a bottomed cylinder shape opened at the insertion end into the cylinder 9. The chain tensioner includes a screw rod 18 having, at its outer periphery, an external thread 17 engaged with an internal thread 15 formed at the inner periphery of the plunger 10. A part, projecting from the plunger 10 of the screw rod 18 is made to abut on a rod seat 23 provided in the cylinder 9, and the plunger 10 is energized in a direction to project from the cylinder 9 by a return spring 21 built in between the screw rod 18 and the plunger 10. The open side end of the cylinder 9 has a threaded hole 28 penetrating inner and outer peripheries of the cylinder 9. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  In general, an engine of an automobile transmits rotation of a crankshaft to a camshaft through a timing chain, and opens and closes a valve of a combustion chamber by the rotation of the camshaft. Here, in order to keep the chain tension within an appropriate range, a tension adjusting device consisting of a chain guide that can be swung around a fulcrum shaft and a chain tensioner that presses the chain guide toward the chain is often used. It is done.

  As a chain tensioner incorporated in this tension adjusting device, a plunger is slidably inserted in a cylindrical cylinder having one end opened and the other end closed, and the plunger is inserted into the cylinder at an open end. A rod having a screw rod formed on the outer periphery thereof, which has a male screw threadedly engaged with a female screw formed on the inner periphery of the plunger, and a protruding portion from the plunger of the screw rod provided in the cylinder It is known that the plunger is urged in a direction protruding from a cylinder by a return spring that is brought into contact with a seat and is incorporated between the screw rod and the plunger (Patent Document 1).

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

  On the other hand, when the tension of the chain is reduced during engine operation, the plunger moves in a direction protruding from the cylinder (hereinafter referred to as “protruding direction”) by the urging force of the return spring, and absorbs the slackness of the chain.

  When the engine is stopped, the chain does not vibrate even if the chain force increases due to the cam stop position, so that the internal thread of the plunger is received by the external thread of the screw rod, and the position of the plunger is fixed. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.

JP 10-1332039 A

  By the way, the above-mentioned chain tensioner releases the load in the pushing direction applied to the plunger when the engine is maintained (for example, when the chain guide is replaced), so that the plunger is released from the cylinder by the urging force of the return spring. Protruding.

  Then, since the protruding amount of the plunger from the cylinder is too large as it is, it is necessary to remove the chain tensioner from the engine once and push the plunger into the cylinder, and then attach the chain tensioner to the engine again. However, removing the chain tensioner from the engine is cumbersome.

  The problem to be solved by the present invention is to provide a chain tensioner having excellent engine maintainability.

  In order to solve the above-described problems, a screw hole penetrating the inner and outer circumferences of the cylinder is provided at the open end of the cylinder.

  If it does in this way, the position of a plunger can be arbitrarily fixed by fastening a small screw in the screw hole, and pressing the tip of a small screw against the perimeter of a plunger. Therefore, when maintaining the engine, it is possible to prevent the plunger from protruding from the cylinder by the biasing force of the return spring, and it is not necessary to remove the chain tensioner from the engine.

  An inner diameter enlarged portion larger in diameter than the sliding surface with the cylinder plunger is provided on the inner circumference of the cylinder on the open side, and the inner end of the screw hole is opened in the inner diameter enlarged portion. Can be made. In this way, since the size of the radial gap between the plunger and the cylinder becomes large at the position of the inner diameter enlarged portion, even if a burr occurs when machining the screw hole at the end portion on the open side of the cylinder. The burr can be prevented from interfering with the outer periphery of the plunger.

  Further, an axial groove may be formed on the inner periphery of the open end of the cylinder, and an end of the screw hole on the inner peripheral side of the screw hole may be opened in the axial groove. Even in this case, since the size of the radial gap between the plunger and the cylinder becomes large at the position of the axial groove, the burr generated when machining the screw hole at the end portion on the open side of the cylinder is Interference with the outer periphery of the plunger can be prevented.

  When the seat surface supported by the engine block is formed on the outer periphery of the cylinder, the screw hole can be disposed on the side opposite to the seat surface in the radial direction. This is convenient because the operation of tightening the machine screw in the screw hole can be performed through the small window provided in the chain cover.

  A hexagon socket head machine screw, a hexagon head machine screw, a slot machine machine screw, or a cross machine machine screw can be screwed into the screw hole in advance. In this case, when a nut is attached to the protruding portion of the small screw from the screw hole, the small screw can be prevented from loosening by tightening the nut.

  In the chain tensioner according to the present invention, the position of the plunger can be arbitrarily fixed by tightening a machine screw in the screw hole at the open end of the cylinder. There is no need to remove the tensioner.

Front view showing a chain transmission apparatus incorporating a chain tensioner according to an embodiment of the present invention Expanded sectional view along the line II-II in FIG. Enlarged cross-sectional view along line III-III in FIG. The figure which shows the state which tightened the machine screw in the screw hole shown in FIG. The figure which shows the state which initially set the plunger shown in FIG. (A) is a diagram showing an example using a hexagon socket head screw as the machine screw shown in FIG. 5, (b) is a diagram showing an example using a hexagon head screw machine as the machine screw shown in FIG. (C) is a diagram showing an example in which a slotted screw is used as the machine screw shown in FIG. 5, and (d) is a diagram showing an example in which a machine screw with a cross hole is used as the machine screw shown in FIG. The figure which shows the example which replaced with the internal diameter expansion part shown in FIG. 2, and formed the axial groove | channel in the edge part inner periphery of the open side of a cylinder. FIG. 7 is an enlarged sectional view taken along line VIII-VIII in FIG.

  FIG. 1 shows a chain transmission device incorporating a chain 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 around the fulcrum shaft 7, and the chain tensioner 1 presses the chain 6 through the chain guide 8.

  As shown in FIG. 2, the chain tensioner 1 includes a cylindrical cylinder 9 that is open at one end and closed at the other end, and a plunger 10 that is slidably inserted in the cylinder 9 in the axial direction. The cylinder 9 is fixed to the side surface of the engine block 13 by tightening bolts 12 into a plurality of mounting pieces 11 (see FIG. 1) integrally formed on the outer periphery of the cylinder 9.

  A seat surface 14 that is supported by the side surface of the engine block 13 is formed on the outer periphery of the cylinder 9. A chain cover (not shown) that faces the side surface of the engine block 13 with the chain tensioner 1 in between is attached to the engine block 13.

  The plunger 10 is formed in a bottomed cylindrical shape having an insertion end into the cylinder 9, and a female screw 15 is formed on the inner periphery thereof. In the pressure chamber 16 surrounded by the cylinder 9 and the plunger 10, a screw rod 18 having a male screw 17 that engages with the female screw 15 on the outer periphery is incorporated.

  The male screw 17 and the female screw 15 are formed in a sawtooth shape in which the flank angle of the pressure side flank 19 that receives pressure when a load in the direction of pushing the plunger 10 into the cylinder 9 is applied is larger than the flank angle of the play side flank 20. Has been.

  Here, the flank angle of the pressure side flank 19 is the friction resistance between the pressure side flank 19 and 19 of the male screw 17 and the female screw 15 when a load in a direction of pushing the screw rod 18 into the plunger 10 is statically applied. Therefore, the screw rod 18 is prevented from rotating. Further, the flank angle of the play side flank 20 is determined by the sliding between the play side flank 20, 20 of the male screw 17 and the female screw 15 when a load in a direction in which the screw rod 18 protrudes from the plunger 10 is statically applied. The size is set such that the rod 18 is allowed to rotate.

  A return spring 21 is incorporated between the plunger 10 and the screw rod 18. One end of the return spring 21 is supported by the plunger 10 via the spring seat 22, and the other end presses the screw rod 18 in a direction protruding from the plunger 10. A protruding portion of the screw rod 18 from the plunger 10 is in contact with a rod seat 23 that is press-fitted into the cylinder 9 and fixed.

  Here, the plunger 10 is urged in a direction protruding from the cylinder 9 by the reaction force of the return spring 21. The plunger 10 has a protruding end from the cylinder 9 in contact with the chain guide 8 and presses the chain 6 via the chain guide 8.

  An oil supply passage 24 that communicates with the pressure chamber 16 surrounded by the cylinder 9 and the plunger 10 is formed at the closed end of the cylinder 9. The oil supply passage 24 communicates with an oil hole 25 formed in the engine block 13 so that hydraulic oil supplied from an oil pump (not shown) through the oil hole 25 is introduced into the pressure chamber 16. It has become. At the end of the oil supply passage 24 on the pressure chamber 16 side, a check valve 26 that allows only the flow of hydraulic oil from the oil supply passage 24 side to the pressure chamber 16 side is provided.

  A minute leak gap 27 is formed between the sliding surfaces of the plunger 10 and the cylinder 9, and hydraulic oil in the pressure chamber 16 flows out through the leak gap 27.

  A screw hole 28 penetrating the inner and outer circumferences of the cylinder 9 is provided at the end of the cylinder 9 on the open side. An inner diameter enlarged portion 29 having a larger diameter than the sliding surface of the cylinder 9 with respect to the plunger 10 is provided on the inner periphery of the open end of the cylinder 9, and the cylinder of the screw hole 28 is provided in the inner diameter enlarged portion 29. 9 The end on the inner peripheral side is open. As shown in FIG. 3, the screw hole 28 is disposed on the side opposite to the seat surface 14 in the radial direction.

  Next, an operation example of the chain tensioner 1 will be described.

  When the tension of the chain 6 becomes smaller during the operation of the engine, the plunger 10 moves in the protruding direction by the urging force of the return spring 21 and absorbs the slack of the chain 6. At this time, since the hydraulic oil supplied from the oil pump flows into the pressure chamber 16 through the oil supply passage 24, the plunger 10 moves quickly.

  On the other hand, when the tension of the chain 6 increases during engine operation, the plunger 10 moves in the pushing direction by the tension of the chain 6 and absorbs the tension of the chain 6. At this time, the screw rod 18 is gradually rotated with respect to the plunger 10 while being repeatedly advanced and retracted within the range of the axial gap between the male screw 17 and the female screw 15 due to the vibration of the chain 6. Further, since the hydraulic oil in the pressure chamber 16 flows out through the leak gap 27 between the sliding surfaces of the plunger 10 and the cylinder 9 and a damper action is generated by the viscous resistance of the hydraulic oil, the plunger 10 moves slowly. To do.

  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, since the chain 6 does not vibrate, the plunger is brought about by contact between the pressure side flank 19, 19 of the male screw 17 and the female screw 15. 10 is received by the screw rod 18, and the plunger 10 does not move in the pushing direction. Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  Incidentally, in the chain tensioner 1, the plunger 10 is urged in the protruding direction by the return spring 21 even when the engine is stopped. Therefore, when the engine is maintained (for example, when the chain guide 8 is replaced), when the load in the pushing direction applied to the plunger 10 is released, the plunger 10 protrudes from the cylinder 9 by the urging force of the return spring 21. there's a possibility that.

  If the plunger 10 protrudes in this way, the amount of protrusion of the plunger 10 from the cylinder 9 is too large as it is, so that the operation of temporarily removing the chain tensioner 1 from the engine block 13 and pushing the plunger 10 into the cylinder 9 is performed. Then, it is necessary to attach the chain tensioner 1 to the engine block 13 again.

  However, as shown in FIG. 4, the chain tensioner 1 fixes the plunger 10 at an arbitrary position by tightening a small screw 30 in the screw hole 28 and pressing the tip of the small screw 30 against the outer periphery of the plunger 10. can do. Therefore, when maintaining the engine, it is possible to prevent the plunger 10 from protruding from the cylinder 9 due to the urging force of the return spring 21, and it is not necessary to remove the chain tensioner 1 from the engine block 13.

  Further, as shown in FIG. 5, the chain tensioner 1 can be held (initially set) in a state where the plunger 10 is previously pushed into the cylinder 9 before being assembled to the engine block 13. Therefore, the chain tensioner 1 does not need to hold the plunger 10 when assembled to the engine block 13, and is excellent in assembling workability to the engine block 13.

  Here, as shown in FIG. 5, when a nut 31 is attached to the protruding portion of the small screw 30 from the screw hole 28 and the nut 31 is tightened, the nut 31 is small due to vibration or impact when the chain tensioner 1 is transported. It is possible to prevent the screw 30 from loosening.

  As the machine screw 30, one with a hexagonal hole (see FIG. 6A), one with a hexagon head (see FIG. 6B), one with a slot (see FIG. 6C), A thing with a cross hole (refer to Drawing 6 (d)) can be used.

  The screw hole 28 on the outer periphery of the cylinder 9 can be arranged so as to be located on the upper side of the cylinder 9 in FIG. 1 by changing the circumferential position thereof from the above embodiment, for example, as shown in the above embodiment, It is preferable to arrange on the side opposite to the seat surface 14 in the radial direction. This is convenient because the operation of tightening the machine screw 30 in the screw hole 28 can be performed through a small window (not shown) provided in the chain cover.

  By the way, when machining the screw hole 28, a burr may be generated at the end of the screw hole 28 on the inner peripheral side of the cylinder 9, and this burr interferes with the outer periphery of the plunger 10 to slide the plunger 10. May interfere.

  However, this chain tensioner 1 is provided with an inner diameter enlarged portion 29 on the inner periphery of the open end of the cylinder 9, and the size of the radial gap between the plunger 10 and the cylinder 9 is the position of the inner diameter enlarged portion 29. It is getting bigger. Since the end of the screw hole 28 on the inner peripheral side of the cylinder 9 is opened in the inner diameter enlarged portion 29, even if a burr occurs at the end of the screw hole 28 on the inner peripheral side of the cylinder 9, the plunger 10 It is possible to prevent the burr from interfering with the outer periphery.

  As shown in FIGS. 7 and 8, instead of the inner diameter enlarged portion 29, an axial groove 32 is formed in the inner periphery of the open end of the cylinder 9, and the cylinder 9 of the screw hole 28 is formed in the axial groove 32. The end on the inner peripheral side may be opened. Even in this case, since the size of the radial gap between the plunger 10 and the cylinder 9 is increased at the position of the axial groove 32, when the screw hole 28 is processed in the end portion on the open side of the cylinder 9. It is possible to prevent the generated burr from interfering with the outer periphery of the plunger 10.

DESCRIPTION OF SYMBOLS 1 Chain tensioner 9 Cylinder 10 Plunger 13 Engine block 14 Seat surface 15 Female thread 17 Male thread 18 Screw rod 21 Return spring 23 Rod seat 28 Screw hole 29 Inner diameter expansion part 30 Machine screw 31 Nut 32 Axial groove

Claims (9)

A plunger (10) is slidably inserted in a cylindrical cylinder (9) having one end opened and the other end closed, and the plunger (10) is inserted into the cylinder (9). A screw rod (18) having a male screw (17) on the outer periphery, which is formed in an open bottomed cylindrical shape and is engaged with a female screw (15) formed on the inner periphery of the plunger (10), is provided. 18) a return spring (18) incorporated between the screw rod (18) and the plunger (10) by bringing the protruding portion from the plunger (10) into contact with a rod seat (23) provided in the cylinder (9). 21) In the chain tensioner in which the plunger (10) is urged in a direction protruding from the cylinder (9).
A chain tensioner characterized in that a screw hole (28) penetrating the inner and outer circumferences of the cylinder (9) is provided at the open end of the cylinder (9).   An inner diameter enlarged portion (29) having a diameter larger than that of the sliding surface of the cylinder (9) with the plunger (10) is provided on the inner periphery of the open end of the cylinder (9), and the inner diameter enlarged portion (29) The chain tensioner according to claim 1, wherein an end of the screw hole (28) on the inner peripheral side of the cylinder (9) is opened.   An axial groove (32) is formed on the inner periphery of the open end of the cylinder (9), and the end of the screw hole (28) on the inner peripheral side of the screw hole (28) is formed in the axial groove (32). The chain tensioner according to claim 1, wherein the opening is opened.   A seat surface (14) supported by the engine block (13) is formed on the outer periphery of the cylinder (9), and the screw hole (28) is disposed on a side opposite to the seat surface (14) in the radial direction. Item 4. The chain tensioner according to any one of Items 1 to 3.   The chain tensioner according to claim 4, wherein a screw (30) having a hexagonal hole is screwed into the screw hole (28).   The chain tensioner according to claim 4, wherein a screw (30) having a hexagon head is screwed into the screw hole (28).   The chain tensioner according to claim 4, wherein a screw (30) with a slot is screwed into the screw hole (28).   The chain tensioner according to claim 4, wherein a machine screw (30) with a cross hole is screwed into the screw hole (28).   The chain tensioner according to any one of claims 5 to 8, wherein a nut (31) for preventing loosening of the small screw (30) is attached to a protruding portion of the small screw (30) from the screw hole (28).

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