JP2011117530A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner in which the accidental release of initial setting is less likely to be caused due to vibration and shock during transportation and in which the release of the initial setting is less likely to be forgotten after the chain tensioner has been mounted to an engine. <P>SOLUTION: A chain tensioner 1 includes a cylinder 2, a plunger 3 slidably inserted in the cylinder 2 and a return spring 12 energizing the plunger 3, and absorbs the change in the tension of a chain by the axial movement of the plunger 3, wherein a setting groove 17 and a cutout 18 are provided at the open end of the cylinder 2, and there is provided on the outer circumference of the plunger 3 a step portion 26 which restricts the movement of the plunger 3 in the projecting direction by being locked to the leading ends of arm portions 28 of a furcate set pin 27 which are inserted from the cutout 18 in the gap between the setting groove 17 and the outer circumference of the plunger 3. <P>COPYRIGHT: (C)2011,JPO&amp;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 cylinder having one end opened and the other end closed, a plunger inserted in the cylinder so as to be slidable in the axial direction, and a direction in which the plunger protrudes from the cylinder One having a return spring for biasing is known (Patent Documents 1 and 2).

  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. 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.

Japanese Patent Laid-Open No. 10-19095 Japanese Patent No. 3670911

  By the way, when each chain tensioner is detached from the engine, the plunger protrudes from the cylinder by the urging force of the return spring. If the chain tensioner is attached to the engine in this state, the chain will be stretched and the chain tensioner cannot be attached.

  Therefore, before attaching the chain tensioner to the engine, it is necessary to push the plunger into the cylinder in advance and hold the plunger so as not to protrude from the cylinder. However, holding down the plunger is complicated.

  Therefore, in the chain tensioner described in Patent Document 1, one set pin is commonly inserted into the set hole formed in the cylinder and the pin hole formed in the plunger while the plunger is pushed into the cylinder. Thus, the plunger can be held in a state of being pushed into the cylinder (hereinafter referred to as “initial setting”).

  Here, when the plunger is initially set, the set pin holds the inserted state into the set hole and the pin hole by utilizing the biasing force of the return spring. That is, the insertion state of the set hole and the pin hole is maintained by the resistance generated between the outer periphery of the set pin and the inner surface of the set hole and the pin hole by the urging force in the protruding direction acting on the plunger from the return spring. The initial setting is released by pulling out the set pin from the set hole and the pin hole.

  However, this chain tensioner loses its resistance because the outer periphery of the set pin momentarily leaves the set hole and the inner surface of the pin hole when a load in the pushing direction is unexpectedly applied to the plunger due to vibration or impact during transportation. At that moment, the set pin may fall off from the set hole and the pin hole, and the initial set may be erroneously released.

  Moreover, in the chain tensioner described in Patent Document 2, a C-shaped groove is provided in which an opening end of the cylinder is provided with a set groove extending in the circumferential direction on the inner periphery of the cylinder and the outer periphery of the plunger is elastically tightened in the set groove. The register clip is accommodated, and the plunger can be initially set by locking the step portion on the outer periphery of the plunger with the register clip. The initial set is released by inserting a tool between a pair of bent pieces provided at both ends of the register clip and widening the interval between the bent pieces with the tool.

  However, since this chain tensioner does not remove the register clip when releasing the initial set, it is difficult to determine at a glance whether or not the initial set has been released. Therefore, after attaching the chain tensioner to the engine, the engine cover may be attached in a state where the initial set is forgotten to be released.

  The problem to be solved by the present invention is to provide a chain tensioner which is unlikely to be erroneously released from the initial set due to vibration or impact during transportation, and which is difficult to forget to release the initial set after being attached to the engine.

  In order to solve the above problems, a set groove extending in the circumferential direction around the inner periphery of the cylinder and a notch penetrating the cylinder to the inner and outer diameters are provided at the opening end of the cylinder. A bifurcated set pin is provided in which the other ends of the arm portions are coupled to each other so that the interval between the tips of the arm portions can be elastically reduced, and the arm portions are spaced from each other toward the tip. In the state that the plunger is pushed into the cylinder, the tip of each arm part is inserted into the gap between the notch and the outer periphery of the set groove and locked to the inserted part. And the latching | locking part which controls the movement to the protrusion direction of a plunger was provided in the outer periphery of the said plunger.

  In this way, with the plunger pushed into the cylinder, the tip of each arm part of the set pin is inserted into the gap between the notch at the opening end of the cylinder and the set groove and the outer periphery of the plunger, and the inserted part The plunger can be initially set by locking the locking portion on the outer periphery of the plunger. At this time, the set pin insertion state is maintained by the elasticity of the set pin itself. The initial setting is released by pulling out the set pin from the gap between the set groove and the outer periphery of the plunger.

  As the locking portion, for example, a step portion having a small diameter on the protruding end side from the cylinder formed on the outer periphery of the plunger, or a groove extending in the circumferential direction formed on the outer periphery of the plunger can be employed. .

  It is preferable that the angle formed between the tips of the arm portions is set in a range of 45 to 75 deg. If it is set to 45 deg or more, the tip of each arm part becomes difficult to come out from the gap between the set groove and the plunger outer periphery, and thus it is possible to more effectively prevent the initial set from being erroneously released. Moreover, if it sets to 75 degrees or less, when inserting the front-end | tip of each arm part in the clearance gap between a set groove and plunger outer periphery, the insertion operation | work will be easy.

  When each arm part is formed so that its tip comes into contact with the inner diameter surface of the set groove when inserted into the gap between the set groove and the outer periphery of the plunger, the allowance for the tip of the arm part is secured, An erroneous release of the initial set can be more effectively prevented.

  The set pin can be formed by combining a plurality of members. However, if the metal wire having a round cross section is bent into a U shape, the cost is low. If a piano wire is used as the metal wire, the elasticity of the set pin can be ensured, and erroneous release of the initial set can be more reliably prevented.

  When the seat surface fixed to the engine block is formed on the outer periphery of the cylinder, the notch is disposed on the opposite side of the seat surface, and the protruding height of the set pin from the notch is 50 mm to 150 mm. It is preferable to set the range. If it is set to 50 mm or more, after attaching the chain tensioner to the engine, if you forget to release the initial set and try to install the engine cover, the set pin will interfere with the engine cover and install the engine cover. So you don't have to worry about forgetting to release the initial set. If it is set to 150 mm or less, it is possible to suppress an increase in the size of the chain tensioner at the time of factory shipment.

The present invention can be applied to, for example, the following chain tensioner.
1) A register ring for elastically tightening the outer periphery of the plunger is accommodated in the set groove, and the register ring is engaged with a circumferential groove formed at a certain interval in the axial direction on the outer periphery of the plunger. In each of the circumferential grooves, when a load in a direction in which the plunger protrudes from the cylinder is loaded, a tapered surface that increases the diameter of the register ring and allows the plunger to move, and the plunger in the cylinder A ring-type chain tensioner provided with a stopper surface that locks the register ring and restricts the movement of the plunger when a load in the pushing direction is applied.
2) The plunger is formed into a bottomed cylindrical shape having an opening at the insertion end into the cylinder, and a screw rod having a male screw on the outer periphery that engages with a female screw formed on the inner periphery of the plunger is provided. The protruding end from the plunger is brought into contact with a rod seat provided in the cylinder, and the male screw and the female screw have a flank angle of the pressure side flank that receives pressure when a load is applied in a direction in which the plunger is pushed into the cylinder. However, the saw-tooth thread type chain tensioner is formed in a sawtooth shape larger than the flank angle of the play side flank.

  Since the chain tensioner of the present invention maintains the set pin insertion state by the elasticity of the set pin itself without using the urging force of the return spring, a load in the direction in which the plunger is unexpectedly pushed into the plunger due to vibration or impact during transportation. Even if it acts, the set pin does not fall off, and the initial set is not erroneously released. Further, since the set pin is pulled out when the initial set is released, it can be determined at a glance whether or not the initial set has been released. For this reason, it is difficult to forget to release the initial set after attaching the chain tensioner to the engine.

The front view which shows the chain tensioner of 1st Embodiment of this invention Expanded sectional view along the line II-II in FIG. Expanded sectional view along line III-III in FIG. Expanded sectional view along line IV-IV in FIG. The enlarged view which shows the state extracted from the set groove | channel of the set pin shown in FIG. Sectional drawing which shows the chain tensioner of 2nd Embodiment of this invention Sectional drawing along the VII-VII line of FIG.

  FIG. 1 shows a chain tensioner 1 according to a first embodiment of the present invention. The chain tensioner 1 has a cylindrical cylinder 2 that is open at one end and closed at the other end, and a plunger 3 that is slidably inserted into the cylinder 2 in the axial direction. The cylinder 2 is fixed to the side surface of the engine block 5 by tightening a bolt (not shown) in the bolt insertion hole 4 of the mounting piece 2 a formed integrally with the cylinder 2.

  As shown in FIG. 2, a seat surface 6 that is supported on a side surface of the engine block 5 is formed on the outer periphery of the cylinder 2. An engine cover 7 is attached to the engine block 5 so as to face the side surface of the engine block 5 with the chain tensioner 1 therebetween. The cylinder 2 is made of aluminum in order to reduce the weight of the engine, and is formed by die casting in order to reduce manufacturing costs.

  The plunger 3 is formed in a bottomed cylindrical shape whose opening end into the cylinder 2 is open. An oil supply passage 9 for introducing hydraulic oil into a pressure chamber 8 surrounded by the cylinder 2 and the plunger 3 is formed at the closed end of the cylinder 2. The inlet of the oil supply passage 9 is open to the seat surface 6, and communicates with an oil hole 10 opened on the side of the engine block 5 when the cylinder 2 is attached to the engine block 5. Hydraulic oil is supplied to the oil hole 10 from an oil pump (not shown). At the outlet of the oil supply passage 9, a check valve 11 that allows only the flow of hydraulic oil from the oil supply passage 9 side to the pressure chamber 8 side is provided.

  A return spring 12 is incorporated in the pressure chamber 8. One end of the return spring 12 is supported by the check valve 11, and the other end presses the plunger 3, and the plunger 3 is urged in a direction protruding from the cylinder 2 by the pressing. The plunger 3 pushes a chain (not shown) through a chain guide 13 at the projecting end from the cylinder 2 and moves in the axial direction according to the tension of the chain, thereby absorbing fluctuations in the chain tension.

  A leak gap 14 is formed between the sliding surfaces of the plunger 3 and the cylinder 2, and hydraulic oil in the pressure chamber 8 flows out through the leak gap 14.

  A screw hole 15 penetrating in the axial direction is formed at a protruding end of the plunger 3 from the cylinder 2, and a cylindrical plug 16 is press-fitted into the screw hole 15. A spiral gap is formed between the plug 16 and the screw hole 15 to discharge air when the air enters the pressure chamber 8.

  The opening end of the cylinder 2 is provided with a set groove 17 that extends in the circumferential direction on the inner periphery of the cylinder 2 and a notch 18 that intersects the set groove 17 and penetrates the cylinder 2 to the inner and outer diameters. A register ring 19 is accommodated in the set groove 17 so as to be movable in the axial direction.

  As shown in FIG. 3, the register ring 19 includes a C-shaped ring portion 19 </ b> A from which a part of the circumference is cut off, and a pair of diameter-expansion operation pieces that extend tangentially from both ends of the ring portion 19 </ b> A and cross each other. 19B, 19B. The diameter increasing operation pieces 19 </ b> B and 19 </ b> B are accommodated in the notch 18 at the opening end of the cylinder 2. In this register ring 19, the C-shaped ring portion 19A elastically tightens the outer periphery of the plunger 3, and the diameter of the C-shaped ring portion 19A can be expanded elastically by the operation of gripping the diameter-expanding operation pieces 19B and 19B. It has become.

  As shown in FIG. 2, a plurality of circumferential grooves 20 that engage with the register ring 19 are formed on the outer periphery of the plunger 3 at regular intervals in the axial direction. In each circumferential groove 20, there are provided a tapered surface 21 rising to the insertion end side of the plunger 3 into the cylinder 2 and a stopper surface 22 rising to the protruding end side of the plunger 3 from the cylinder 2.

  As shown in FIG. 4, the taper surface 21 rises gently, and when the load in the protruding direction is applied to the plunger 3, the diameter of the register ring 19 is expanded to allow the movement of the plunger 3. It has become. On the other hand, the stopper surface 22 has a steep rise, and when the load in the pushing direction is applied to the plunger 3, the register ring 19 is locked to restrict the movement of the plunger 3.

  In the set groove 17, a tapered inner peripheral surface 23 rising to the closed end side of the cylinder 2 and an axis perpendicular end surface 24 rising to the opening end side of the cylinder 2 are formed. The taper inner peripheral surface 23 has a gentle rise, and receives the register ring 19 when the plunger 3 moves in the pushing direction, thereby limiting the diameter expansion of the register ring 19. The axially perpendicular end surface 24 receives the register ring 19 when the plunger 3 moves in the protruding direction and restricts further movement of the register ring 19, but allows the register ring 19 to expand in this state.

  As shown in FIG. 2, a stopper groove 25 is formed on the outer periphery of the plunger 3 on the insertion end side into the cylinder 2 further than the circumferential groove 20 closest to the insertion end into the cylinder 2. The stopper groove 25 engages with the register ring 19 to prevent the plunger 3 from coming off the cylinder 2 when the plunger 3 moves excessively in the protruding direction.

  Further, on the outer periphery of the plunger 3, a step portion 26 having a small diameter on the protruding end side from the cylinder 2 is formed further on the protruding end side from the cylinder 2 than the circumferential groove 20 closest to the protruding end from the cylinder 2. Has been.

  As shown in FIGS. 1 and 2, the set pin 27 is inserted into the set groove 17 in a state where the plunger 3 is pushed into the cylinder 2 until the step portion 26 overlaps the set groove 17 in the radial direction. . As shown in FIG. 3, the set pin 27 is formed by bending a metal wire having a round cross section into a U shape, so that the distance between the ends of the pair of arm portions 28 and 28 is elastically maintained. The arm portions 28 and 28 are coupled to each other at the other ends. If a piano wire (for example, SWPA) is used as the metal wire constituting the set pin 27, the elasticity of the set pin 27 can be ensured. Moreover, the wire diameter of 1.5 mm or less can be adopted.

  As shown in FIG. 5, each arm portion 28 has a bent portion 29 that is bent so that the interval between the arm portions 28, 28 is widened toward the tip, and the angle θ between the tips is 45 to 75 deg. It is formed to be a range. Here, both the arm portions 28 and 28 have a fan shape (tapered shape) that opens to the distal end side of the arm portion 28.

  As shown in FIG. 3, the tip of each arm portion 28 is inserted into the gap between the set groove 17 and the outer periphery of the plunger 3 from the notch 18 at the opening end of the cylinder 2. At this time, the portion into which the arm portion 28 is inserted locks the step portion 26 on the outer periphery of the plunger 3 to restrict the movement of the plunger 3 in the protruding direction. At this time, the set pin 27 is in a state in which the distance between the tips of the arm portions 28 is elastically narrowed, and the tips of the arm portions 28 are caught in the cylinder 2 by the elastic restoring force, and the set groove 17 And the insertion state between the outer periphery of the plunger 3 is maintained.

  Here, if each arm portion 28 is formed so that the tip thereof is in contact with the inner diameter surface of the set groove 17, the allowance for the tip of the arm portion 28 is secured, and it is more effective that the set pin 27 is accidentally pulled out. Can be prevented.

  The notch 18 at the opening end of the cylinder 2 is disposed on the side opposite to the seat surface 6 as shown in FIG. The protruding height of the set pin 27 from the notch 18 is set to a height at which the set pin 27 interferes with the engine cover 7 when the engine cover 7 is attached to the engine block 5. It is set in the range of 50 mm to 150 mm.

  As shown in FIGS. 1 to 3, the chain tensioner 1 is attached to the engine block 5 by inserting the set pin 27 into the gap between the set groove 17 and the outer periphery of the plunger 3 in advance. The cylinder 2 is fixed to the side surface of the engine block 5 with bolts (not shown) while being held in a state of being pushed into (ie, initially set).

  After the chain tensioner 1 is attached in this way, when the set pin 27 is pulled out, the plunger 3 is moved in the protruding direction by the urging force of the return spring 12, and the plunger 3 presses the chain guide 13, and the chain guide 13 is moved. Apply tension to the chain.

  If the user forgets to pull out the set pin 27, the plunger 3 is held in the state of being pushed into the cylinder 2, so that the chain remains loose and the engine cannot be started normally. Therefore, the chain tensioner 1 interferes with the mounting of the engine cover 7 by the interference of the set pin 27 with the engine cover 7 when attempting to mount the engine cover 7 in a state where the forgetting to pull out the set pin 27 is attempted. I have to.

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

  When the chain tension increases during engine operation, the plunger 3 moves in the pushing direction by the chain tension, and absorbs the tension of the chain. At this time, since the damper force is generated by the viscous resistance of the hydraulic fluid flowing out from the pressure chamber 8 through the leak gap 14, the plunger 3 moves slowly.

  When the chain tension is reduced during engine operation, the plunger 3 moves in the protruding direction by the urging force of the return spring 12 to absorb the slack of the chain. At this time, the check valve 11 is opened, and the hydraulic oil flows into the pressure chamber 8 from the oil supply passage 9, so that the plunger 3 moves quickly.

  Here, when the plunger 3 repeats advancing and retreating due to the vibration of the chain, the register ring 19 moves back and forth within the set groove 17. Further, when the movement range of the plunger 3 in the protruding direction exceeds the movable range in the set groove 17 of the register ring 19 due to the slack of the chain, the tapered surface 21 in the circumferential groove 20 causes the register ring 19 to move. The diameter of the plunger 3 is increased to allow the plunger 3 to move. At this time, the register ring 19 engages with the adjacent circumferential groove 20.

  When the engine is stopped, the chain tension may increase depending on the stop position of the camshaft (not shown). In this case, the plunger 3 moves in the pushing direction by the engagement of the register ring 19 and the circumferential groove 20. Is prevented. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.

  The chain tensioner 1 does not use the urging force of the return spring 12 and maintains the insertion state of the set pin 27 by the elasticity of the set pin 27 itself. Even when the load is applied, the set pin 27 does not fall off, and the initial set is not erroneously released. Further, since the set pin 27 is pulled out when the initial set is released, it can be determined at a glance whether or not the initial set has been released. For this reason, it is difficult to forget to release the initial set after the chain tensioner 1 is attached to the engine.

  In addition, after attaching the chain tensioner 1 to the engine block 5, the set pin 27 may interfere with the engine cover 7 in the event that the engine cover 7 is to be attached in a state where the initial set has been forgotten to be released. Since the attachment of the engine cover 7 is obstructed, there is no worry of forgetting to release the initial set.

  Further, in this chain tensioner 1, the angle θ formed between the tips of the arm portions 28 is 45 degrees or more, so that the tips of the arm portions 28 are unlikely to come out from the gap between the set groove 17 and the outer periphery of the plunger 3. It is possible to effectively prevent erroneous release of the set. Further, since the angle θ formed by the tips of the arm portions 28 is set to 75 deg or less, when the tips of the arm portions 28 are inserted into the gap between the set groove 17 and the outer periphery of the plunger 3, Easy to work.

  If the set pin 27 has a bifurcated shape in which the other ends of the arm portions 28 and 28 are coupled so that the distance between the ends of the pair of arm portions 28 and 28 is held elastically, a plurality of members are combined. It can also be formed. For example, as the set pin 27, it is also possible to employ a configuration that includes a pair of arm members and a coupling member that couples one end of each of the arm members to each other. However, as shown in the above-described embodiment, it is preferable to use one formed by bending a single metal wire into a U shape because of low cost.

  The set groove 17 into which the set pin 27 is inserted may be formed separately from the groove that accommodates the register ring 19, but when the groove that accommodates the register ring 19 is also used as the set groove 17 as shown in the above embodiment. The processing cost of the cylinder 2 can be suppressed.

  In the above embodiment, the stepped portion 26 on the outer periphery of the plunger 3 has been described as an example of the locking portion that is locked to the inserted portion when the set pin 27 is inserted, but instead of the stepped portion 26, You may employ | adopt the groove | channel (refer 2nd Embodiment) extended on the outer periphery of the plunger 3 to the circumferential direction.

  FIG. 6 shows a chain 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 plunger 3 is formed in a bottomed cylindrical shape whose opening end into the cylinder 2 is opened, and a female screw 32 is formed on the inner periphery thereof. A screw rod 34 having a male screw 33 that engages with the female screw 32 on the outer periphery is incorporated in the plunger 3. One end of the screw rod 34 protrudes from the plunger 3, and the protruding end is in contact with a rod seat 35 provided in the cylinder 2. Here, the rod seat 35 is a valve seat of the check valve 11.

  One end of the return spring 12 is supported by a screw rod 34, and the other end presses the plunger 3 via a spring seat 36, and the plunger 3 is urged in a direction protruding from the cylinder 2 by the pressing.

  The male screw 33 and the female screw 32 are formed in a sawtooth shape in which the flank angle of the pressure side flank 37 that receives pressure when a load in the direction of pushing the plunger 3 into the cylinder 2 is applied is larger than the flank angle of the play side flank 38. Has been.

  Further, on the outer periphery of the plunger 3, a cylindrical surface 39 that forms a leak gap 14 with the inner periphery of the cylinder 2, and a groove 40 that extends in the circumferential direction on the protruding end side from the cylinder 2 with respect to the cylindrical surface 39. Is formed.

  The chain tensioner 31 can also be initially set as in the first embodiment. That is, with the plunger 3 pushed into the cylinder 2 until the groove 40 overlaps the set groove 17 in the radial direction, the tip of each arm portion 28 of the set pin 27 is moved from the notch 18 at the opening end of the cylinder 2. The plunger is inserted into the gap between the set groove 17 and the outer periphery of the plunger 3, and the plunger 3 is held in the cylinder 2 (ie, initially set).

  In this state, when the cylinder 2 is fixed to the side surface of the engine block 5 and the set pin 27 is pulled out, the plunger 3 is moved in the protruding direction by the urging force of the return spring 12, and the plunger 3 presses the chain guide 13, A tension is applied to the chain via the chain guide 13.

  Thereafter, when the chain tension increases during engine operation, the plunger 3 moves in the pushing direction by the chain tension to absorb the tension of the chain. At this time, the screw rod 34 rotates with respect to the plunger 3 while repeating the forward and backward movements within the range of the axial gap between the female screw 32 and the male screw 33 due to the vibration of the chain. Further, since the damper force is generated by the viscous resistance of the hydraulic oil flowing out from the pressure chamber 8 through the leak gap 14, the plunger 3 moves slowly.

  On the other hand, when the chain tension is reduced during engine operation, the plunger 3 moves in the protruding direction by the urging force of the return spring 12 to absorb the slack of the chain. At this time, since the hydraulic oil flows from the oil supply passage 9 into the pressure chamber 8, the plunger 3 moves quickly.

  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 that the internal thread 32 of the plunger 3 is received by the external thread 33 of the screw rod 34 and the plunger 3 is pushed in. Movement in the direction is prevented. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.

  Since the chain tensioner 31 maintains the insertion state of the set pin 27 by the elasticity of the set pin 27 without using the urging force of the return spring 12 as in the first embodiment, vibration and shock during transportation Therefore, even when a load in the pushing direction is unexpectedly applied to the plunger 3, the set pin 27 does not fall off, and the initial setting is not erroneously released. Further, since the set pin 27 is pulled out when the initial set is released, it can be determined at a glance whether or not the initial set has been released. Therefore, it is difficult to forget to release the initial set after the chain tensioner 31 is attached to the engine.

  In addition, after the chain tensioner 31 is attached to the engine block 5, the set pin 27 may interfere with the engine cover 7 if the engine cover 7 is to be attached in a state where the initial set is forgotten to be released. Since the attachment of the engine cover 7 is obstructed, there is no worry of forgetting to release the initial set. Other effects are the same as those of the first embodiment.

  In this embodiment, the groove 40 extending in the circumferential direction around the outer periphery of the plunger 3 has been described as an example of the locking portion that locks the inserted portion when the set pin 27 is inserted. Instead, a step portion (see the first embodiment) having a small diameter on the protruding end side from the cylinder 2 may be employed.

DESCRIPTION OF SYMBOLS 1 Chain tensioner 2 Cylinder 3 Plunger 5 Engine block 6 Seat surface 12 Return spring 17 Set groove 18 Notch 19 Register ring 20 Circumferential groove 21 Tapered surface 22 Stopper surface 26 Step part 27 Set pin 28 Arm part 31 Chain tensioner 32 Female thread 33 Male thread 34 Screw rod 35 Rod seat 37 Pressure side flank 38 Play side flank 40 Groove θ Angle formed by tips of arm parts

Claims (10)

A cylinder (2) with one end open and the other end closed, a plunger (3) inserted into the cylinder (2) so as to be slidable in the axial direction, and the plunger (3) from the cylinder (2) A chain tensioner having a return spring (12) biasing in a protruding direction and absorbing a change in chain tension by an axial movement of the plunger (3);
At the opening end of the cylinder (2), a set groove (17) extending in the circumferential direction on the inner periphery of the cylinder (2) and intersecting the set groove (17) penetrates the cylinder (2) to the inner and outer diameters. A bifurcated set in which notches (18) are provided, and the other ends of the arm portions (28, 28) are joined together so that the distance between the tips of the pair of arm portions (28, 28) is held elastically. A pin (27) is provided, and each arm portion (28) is bent toward the tip so that the space between the arm portions (28, 28) is widened, and the plunger (3) is pushed into the cylinder (2). In this state, the tip of each arm portion (28) is inserted into the gap between the notch (18) and the outer periphery of the set groove (17) and the plunger (3), and is locked to the inserted portion. To restrict the movement of the plunger (3) in the protruding direction Chain tensioner, characterized in that provided on the outer periphery of that the locking portion and the plunger (3).   The chain tensioner according to claim 1, wherein the locking portion is a step portion (26) having a small diameter on a protruding end side from the cylinder (2) formed on the outer periphery of the plunger (3).   The chain tensioner according to claim 1, wherein the locking portion is a circumferential groove (40) formed on an outer periphery of the plunger (3).   The chain tensioner according to any one of claims 1 to 3, wherein an angle (θ) formed between tips of the arm portions (28) is set in a range of 45 to 75 deg.   Each of the arm portions (28) is formed so that the tip thereof comes into contact with the inner diameter surface of the set groove (17) when inserted into the gap between the set groove (17) and the outer periphery of the plunger (3). The chain tensioner according to any one of claims 1 to 4, wherein the chain tensioner is provided.   The chain tensioner according to any one of claims 1 to 5, wherein the set pin (27) is formed by bending a metal wire having a round cross section into a U shape.   The chain tensioner according to claim 6, wherein the metal wire is a piano wire.   A seat surface (6) fixed to the engine block (5) is formed on the outer periphery of the cylinder (2), and the notch (18) is disposed on the opposite side of the seat surface (6). The chain tensioner according to any one of claims 1 to 7, wherein a protruding height of the set pin (27) from (18) is set in a range of 50 mm to 150 mm.   A register ring (19) for elastically tightening the outer periphery of the plunger (3) is accommodated in the set groove (17), and the register ring (19) is arranged on the outer periphery of the plunger (3) at a constant interval in the axial direction. When a load is applied in the circumferential groove (20) in a direction in which the plunger (3) protrudes from the cylinder (2). In addition, when a load is applied in the direction in which the diameter of the register ring (19) is increased to allow the plunger (3) to move, and the plunger (3) is pushed into the cylinder (2). The chain tensioner according to any one of claims 1 to 8, further comprising a stopper surface (22) for locking the register ring (19) and restricting the movement of the plunger (3).   The plunger (3) is formed into a bottomed cylindrical shape having an opening end into the cylinder (2), and a male screw (33) that engages with a female screw (32) formed on the inner periphery of the plunger (3). A screw rod (34) having an outer periphery is provided, and a projecting end of the screw rod (34) from the plunger (3) is brought into contact with a rod sheet (35) provided in the cylinder (2), so that the male screw (33) and the female thread (32) are such that the flank angle of the pressure side flank (37) that receives pressure when the load in the direction of pushing the plunger (3) into the cylinder (2) is applied is the play side flank (38). The chain tensioner according to any one of claims 1 to 8, wherein the chain tensioner is formed in a sawtooth shape larger than a flank angle.

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