JP3705945B2 - Chain tensioner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a chain tensioner that maintains a constant tension of a camshaft drive chain.
[0002]
[Prior art]
A chain tensioner shown in FIG. 7 is known as a chain tensioner that keeps the tension of the chain for driving the camshaft constant. This chain tensioner incorporates a plunger 42 and a spring 43 in a cylinder chamber 41 formed in the housing 40 so that the chain 44 is pressed by the plunger 42 imparted with a projecting property by the spring 43.
[0003]
Further, an oil supply passage 46 is communicated with a pressure chamber 45 formed on the back portion of the plunger 42, and a check valve 47 is provided in the oil supply passage 46. The plunger 42 moves outward and the pressure in the pressure chamber 45 decreases. At this time, the check valve 47 is opened so that the oil flows from the oil supply passage 46 to the pressure chamber 45 by driving the oil supply pump.
[0004]
By the way, in the camshaft driving chain, when the engine is stopped, the chain 44 may be held in a tension state due to the relationship of the stop position of the cam provided on the camshaft. In this case, since the plunger 42 of the chain tensioner is pushed by the chain 44 in a tension state, the oil in the pressure chamber 45 leaks from the sliding surfaces of the plunger 42 and the cylinder chamber 41, the plunger 42 moves backward, and the chain 44 The elastic force and the tension of the spring 43 are held at a balance position.
[0005]
For this reason, when the chain 44 is slackened due to the restart of the engine, the plunger 42 moves greatly outward. At this time, since the hydraulic pump is immediately after start-up and the discharge amount is small, sufficient oil cannot be supplied to the pressure chamber 45, air enters the pressure chamber 45, the damping characteristic is deteriorated, and abnormal noise is generated. May occur.
[0006]
Further, at the time of starting at low temperature, the oil has a high viscosity and poor fluidity, so that the same problem as described above occurs.
[0007]
In order to solve the above-mentioned problems, a rod insertion hole that opens at the rear end face is formed in the plunger, and a male screw formed on the outer periphery of the screw rod is formed on the female screw provided on the inner periphery of the opening of the rod insertion hole. The present applicant has already developed a chain tensioner that engages with a screw and has a male and female thread threaded in a sawtooth shape, and that incorporates a spring between opposing portions of the plunger and screw rod and presses both members in opposite directions. It has been proposed (Japanese Patent Application No. 9-71947).
[0008]
In the above chain tensioner, when the engine is stopped and the chain is tensioned due to the cam stop position and a pushing force is applied to the plunger, the pushing force is received by the pressure side flank of the serrated thread and the plunger moves backward. To prevent movement. For this reason, even if the engine is restarted and slackening occurs, the amount of slackening is small, so that the plunger does not move greatly outward, and air can be prevented from entering the pressure chamber. doing.
[0009]
[Problems to be solved by the invention]
By the way, in the chain tensioner that has already been proposed, the plunger jumps out of the cylinder chamber due to the elasticity of the spring during maintenance around the engine when the chain is removed, and the parts such as the screw rod and spring are disassembled, so forget to incorporate the parts when reassembling. Or an assembly error may occur, and there are still points to be improved in accurately reassembling the chain tensioner.
[0010]
An object of the present invention is to prevent the components of the chain tensioner already proposed from being disassembled apart during maintenance around the engine such as removing the chain.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, the housing is provided with a cylinder chamber and an oil supply passage that opens at the closed end of the cylinder chamber, and a plunger for pressing the chain is slidable in the cylinder chamber. The screw rod inserted into the back of the plunger is screw-engaged with the plunger, and a spring is inserted between the screw rod and the plunger in a direction opposite to each other. In the middle, an axial engagement means for preventing the plunger from coming off is provided , and the engagement means is formed with a circumferential engagement groove on the outer diameter surface of the plunger. A configuration in which a stopper insertion hole is provided, and a stopper member that can be engaged with the engagement groove is slidably inserted into the stopper insertion hole. It was was.
[0012]
As described above, by providing an engaging means in the axial direction between the plunger and the housing to prevent the plunger from coming off, various parts inserted into the cylinder chamber are disassembled during maintenance around the engine for removing the chain. Can be prevented.
[0014]
In the above engagement means, when the wall surface on the plunger tip side of the engagement groove is a tapered surface inclined toward the plunger outer diameter surface, the engagement groove and the stopper member are engaged by pushing the plunger while rotating. Can be released, and the chain tensioner can be easily reproduced in use.
[0015]
Further, in the above locking means, when a ball is used as a stopper member, if the plunger quickly protrudes outward, the ball does not completely fall into the engagement groove, but the ball is lifted at the edge of the engagement groove and the plunger There is a case where it cannot be prevented from coming off. In order to prevent such inconvenience, the stopper member is preferably formed of a pin or a columnar body having a rectangular cross section. The housing is preferably mounted with the stopper insertion hole positioned above so that the stopper member can be smoothly lowered by its own weight.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0017]
As shown in FIG. 1, a chain 5 is stretched between a sprocket 2 attached to the end of the crankshaft 1 and a sprocket 4 attached to the end of the camshaft 3, and is connected to a slack side chain 5 a of the chain 5. The slipper 6 is in contact. The slipper 6 is supported so as to be swingable about a shaft 7. The slipper 6 is pressed by a chain tensioner 10, and the chain 5 is held at a constant tension by the pressing.
[0018]
2 to 5 show details of the chain tensioner 10. The chain tensioner has a housing 11 that is screwed to the engine block.
[0019]
The housing 11 is provided with a cylinder chamber 12 and an oil supply passage 13 that opens at the closed end of the cylinder chamber 12.
[0020]
A plunger 14 is slidably inserted into the cylinder chamber 12. The plunger 14 is formed with a rod insertion hole 15 that opens at the rear end surface, and a male screw 18 formed on the outer periphery of the screw rod 17 is thread-engaged with a female screw 16 provided on the inner periphery of the opening of the rod insertion hole 15. Yes.
[0021]
The screw rod 17 is formed with a spring accommodating hole 19 extending in the axial direction from the front end and a communication hole 20 penetrating from the rear end to the spring accommodating hole 19. The closed end of the spring accommodating hole 19 and the rod insertion hole 15 is formed. A spring 21 and a spring seat 22 are assembled between them. The spring seat 22 is carburized and quenched, and the spherical surface 23 formed at the tip is in point contact with the closed end of the rod insertion hole 15.
[0022]
The thread of the internal thread 16 formed on the plunger 14 and the external thread 18 provided on the screw rod 17 is such that the flank angle of the pressure side flank 24 that receives the pushing force when the plunger 14 is pushed in the axial direction is the play side flank. The sawtooth is larger than 25 flank angles. The serrated thread is provided with a lead angle that moves toward the closed end of the cylinder chamber 12 while the screw rod 17 is rotated by the pressure of the spring 21.
[0023]
A rod seat 26 that receives the rear end of the screw rod 17 is incorporated in the closed end of the cylinder chamber 12. The rod seat 26 is press-fitted into the cylinder chamber 12 so as to be non-movable in the axial direction, and the rod seat 26 is provided with a passage 27 that allows the oil supply passage 13 and the cylinder chamber 12 to communicate with each other.
[0024]
A check valve 28 and a retainer 29 that limits the opening / closing amount of the check valve 28 are incorporated in the passage 27, and the check valve 28 passes through the passage 27 when the pressure in the cylinder chamber 12 becomes higher than the pressure in the oil supply passage 13. It is supposed to close.
[0025]
An engaging mechanism 30 is provided between the plunger 14 and the housing 11 to prevent the plunger 14 from coming off when the plunger 14 protrudes more than necessary outside.
[0026]
The engagement mechanism 30 has an engagement groove 31 formed at the rear end of the cylindrical outer peripheral surface of the plunger 14, and a stopper insertion hole 32 that opens at the inner peripheral surface of the cylinder chamber 12 at the upper end of the housing 11. The stopper member 33 is slidably inserted into the stopper insertion hole 32, and the plunger 14 is prevented from coming off by the engagement of the stopper member 33 and the engagement groove 31.
[0027]
Here, the wall surface on the plunger distal end side of the engagement groove 31 is a tapered surface 34 that is gently inclined toward the outer peripheral surface of the plunger 14.
[0028]
Any stopper member 33 can be employed. However, when a member composed of a ball is employed, when the plunger 14 rapidly protrudes outward by the pressing of the spring 21, it does not fall into the engagement groove 31 and is engaged. There is a possibility that the plunger 14 cannot be prevented from being pulled out by being pushed up by the edge of the joint groove 31. In order to prevent the occurrence of such inconvenience, the stopper member 33 is a columnar body such as a cylindrical body or a prismatic body.
[0029]
Now, when the engine is started and the slack in the slack side chain 5a of the chain 5 is caused by the rotation of the sprocket 2 attached to the end of the crankshaft 1 in the direction of the arrow, the pressure of the oil fed into the passage 31 from the oil supply passage 13 The plunger 14 and the screw rod 17 move outward, and the screw rod 17 is moved away from the rod seat 26 by the movement, and oil is supplied into the cylinder chamber 12.
[0030]
Further, since the plunger 14 presses the slipper 6 due to the outward movement of the plunger 14, the slack of the chain 5 is absorbed, and the elastic force of the spring 21 causes the screw rod 17 to rotate while rotating the cylinder chamber 12. The chain 5 moves toward the closed end and comes into contact with the rod seat 26, and the chain 5 is held at a predetermined elasticity by stopping the plunger 14 and the screw rod 17.
[0031]
When the temperature of the engine rises and the distance between the centers of the crankshaft 1 and the camshaft 3 increases due to thermal expansion, and the plunger 14 is pressed by increasing the tension of the chain 5, the pressing force is enclosed in the cylinder chamber 12. While being received by oil, it is received by the pressure side flank 24 of the internal thread 16 and the external thread 18, and the plunger 14 does not retract. When the pressing force that presses the plunger 14 becomes stronger than the resultant force of the spring 21 and the hydraulic pressure, the screw rod 17 rotates and the plunger 14 moves backward.
[0032]
At this time, the oil in the cylinder chamber 12 leaks from between the sliding surfaces of the cylinder chamber 12 and the plunger 14, and the plunger 14 slowly reaches a position where the combined force of the pressing force, the elasticity of the spring 21 and the supply oil pressure is balanced. And move backwards.
[0033]
When the engine is stopped, the slack side chain 5a of the chain 5 may be tense due to the relationship of the stop position of the cam provided on the camshaft 3. In this case, the plunger 14 is pressed by the chain 5, and the pressing force is received by the pressure side flank 24 in the screw engaging portion of the female screw 16 and the male screw 18.
[0034]
Here, since the pressing force is a static load without vibration, even when the pressing force is greater than the elasticity of the spring 21, the screw rod 17 does not rotate and the plunger 14 does not move backward.
[0035]
For this reason, even if the engine is restarted and the slack side chain 5a of the chain 5 becomes slack, the slack amount is extremely small and the protruding amount of the plunger 14 is also small. Therefore, since the pressure drop in the cylinder chamber 12 is small, air does not enter the cylinder chamber 12.
[0036]
Note that when the engine is started at a low temperature, the viscosity of the oil sent from the pump to the oil supply passage 13 is high and the oil does not flow into the cylinder chamber 12, but even in this case, the amount of movement of the plunger 14 in the outward direction is small. The air can be prevented from entering the cylinder chamber 12.
[0037]
In the state of use of the chain tensioner 10 as shown in FIG. 2, the plunger 14 is always pressed outward by the spring 21. Therefore, when the chain 15 is removed for maintenance around the engine, the plunger 14 is removed. When the plunger 14 moves to a position where the engagement groove 31 provided on the outer periphery protrudes to the position where the engagement groove 31 faces the stopper insertion hole 32, the stopper member 33 engages with the engagement groove 31 as shown in FIG. The plunger 14 is prevented from coming off.
[0038]
For this reason, parts such as the screw rod 17 and the spring 21 are not disassembled apart and there is no need to reassemble them, so that it is possible to prevent parts from being forgotten or mistakenly assembled.
[0039]
As shown in FIG. 6, when the chain tensioner 10 with the plunger 14 in the protruding state is used again, the plunger 14 is pushed in the axial direction while rotating, and the stopper member 33 is moved upward by the pressing action of the tapered surface 34. Thus, the engagement with the engagement groove 31 is released. By releasing the engagement, the plunger 14 can be retracted, and the spring 21 is contracted by the retraction of the plunger 14 to reproduce the chain tensioner 10 in a use state. This stopper structure is not limited to a chain tensioner using a screw, but can also be applied to a hydraulic tensioner.
[0040]
【The invention's effect】
As described above, in the present invention, when the chain is removed, the plunger moves outward by the elastic force of the spring, but when the predetermined amount is moved, the engaging means is engaged and the plunger is prevented from coming off. It is possible to prevent parts such as screw rods and springs incorporated in the room from being disassembled apart.
[0041]
For this reason, there is no need for reassembly, and it is possible to prevent parts from being forgotten or erroneously assembled.
[0042]
Further, in the engagement means for preventing the plunger from coming off by engaging the stopper member with the engagement groove formed on the outer periphery of the plunger, if the wall surface on the plunger tip side of the engagement groove is a tapered surface, the engagement groove and the stopper By pushing in the axial direction while rotating the plunger that has been prevented from coming off due to the engagement of the member, the stopper member is pushed by the tapered surface and disengages from the engagement groove, so that the chain tensioner can be easily reproduced in use. .
[0043]
Furthermore, by making the stopper member a columnar body, even when the plunger is rapidly moved outward, the stopper member can be engaged with the engaging groove, and the plunger can be reliably prevented from coming off.
[Brief description of the drawings]
FIG. 1 is a front view showing a chain tensioner according to the present invention in use. FIG. 2 is a longitudinal front view of the chain tensioner. FIG. 3 is a sectional view taken along line III-III in FIG. Fig. 5 is a partially cutaway plan view of the chain tensioner. Fig. 6 is a longitudinal front view showing a state in which the plunger of the chain tensioner is retained. Fig. 7 is a conventional chain tensioner. Sectional view shown [Explanation of symbols]
11 Housing 12 Cylinder chamber 13 Oil supply passage 14 Plunger 16 Female screw 17 Screw rod 18 Male screw 21 Spring 30 Engaging mechanism 31 Engaging groove 32 Stopper insertion hole 33 Stopper member 34 Tapered surface

Claims (4)

The housing is provided with a cylinder chamber and an oil supply passage that opens at the closed end of the cylinder chamber. A plunger for pressing the chain is slidably inserted into the cylinder chamber, and a screw rod incorporated in the back of the plunger is inserted. A spring that engages the plunger with a screw and presses both members in opposite directions is incorporated between the screw rod and the plunger, and an axial engagement that prevents the plunger from coming off between the plunger and the housing. Means, and the engaging means forms a circumferential engaging groove on the outer diameter surface of the plunger, and the housing is provided with a stopper insertion hole that opens at the upper inner periphery of the cylinder chamber. A chain tensioner having a structure in which a stopper member engageable with an engaging groove is slidably inserted . The chain tensioner according to claim 1 , wherein a wall surface of the engagement groove on the distal end side of the plunger is a tapered surface inclined toward the outer diameter surface of the plunger. The chain tensioner according to claim 1 or 2 , wherein the stopper member is a columnar body. The chain tensioner according to any one of claims 1 to 3 , wherein the housing is an attachment in which a stopper insertion hole is located above.

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