JP3635192B2 - 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]
The chain tensioner shown in FIG. 4 is known as a chain tensioner for keeping 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 a housing 40, and a slipper 49 supported by the plunger 42, which is provided with a projecting property by the spring 43, so as to be swingable. The chain 44 is pressed.
[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-described problems, a rod insertion hole that opens at the rear end face is formed in the plunger, and a female screw is provided on the inner periphery of the opening of the rod insertion hole, and the male screw formed on the outer periphery of the screw rod is screwed. The applicant has already proposed a chain tensioner that engages and has a male and female thread threaded in a sawtooth shape, and that incorporates a spring between the opposed parts of the plunger and screw rod to press both members in opposite directions. (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 already proposed chain tensioner, the housing is made of aluminum in order to reduce the weight, and the rod is incorporated in the cylinder chamber in order to prevent the housing from being worn or damaged by the contact of the screw rod. The rear end of the screw rod is received by the seat.
[0010]
The rod seat is provided with a passage for communicating the oil supply passage with the cylinder chamber, a check valve for preventing the oil in the cylinder chamber from flowing back into the oil supply passage in the passage, and a retainer for limiting the amount of movement of the check valve; Is built in.
[0011]
Here, the retainer incorporated in the passage of the rod sheet is formed of a press-formed product of a metal thin plate or a metal plate, and the attachment is performed by press-fitting. However, a retainer made of a metal sheet press-molded product requires a certain press-fit length to obtain a stable attachment, and the axial length of the rod seat is increased, and the axial length of the chain tensioner is compact. There are still some points that need to be improved.
[0012]
On the other hand, in a retainer made of a metal plate, since the press-fitting length is short, a stable attachment cannot be obtained, and there are still points to be improved in order to stabilize the attachment.
[0013]
In addition, since any retainer has a small outer diameter and low rigidity, it takes a lot of work to install.
[0014]
The object of the present invention is to improve the already proposed chain tensioner, to make it easier to manage the opening / closing amount of the check valve by eliminating the need for a retainer, and to make the axial length of the chain tensioner more compact and easier to incorporate. It is to plan.
[0015]
[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 communicating with the closed end of the cylinder chamber, and a chain pressing plunger is slidably inserted into the cylinder chamber. The plunger is pressed with a spring to give the plunger outward protrusion, a valve seat is brought into contact with the closed end of the cylinder chamber, and a passage for communicating the oil supply passage with the cylinder chamber is provided in the valve seat. A check valve for preventing the oil in the cylinder chamber from flowing back into the oil supply passage is provided in this passage, and a perforated rod seat for restricting the opening / closing amount of the check valve is abutted against the valve seat, and the rod seat and the valve A configuration in which the sheets are not separated in the abutting state is adopted.
[0016]
Here, the rod seat may be press-fitted into a fitting recess provided on the outlet side of the passage of the valve seat. Alternatively, the rod seat may be press-fitted into the inner diameter surface of the cylinder chamber and the closed end surface of the cylinder chamber and the rod seat. A valve seat may be held.
[0017]
The plunger may be provided with a rod insertion hole that opens at the rear end surface, and the screw rod may be screw-engaged with a female screw formed on the inner periphery of the opening of the rod insertion hole.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.
[0019]
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.
[0020]
FIG. 2 shows details of the chain tensioner 10. The chain tensioner has a housing 11 that is screwed to the engine block.
[0021]
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.
[0022]
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.
[0023]
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, and the plunger 14 and the screw rod 17 are pressed in opposite directions by the spring 21. 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.
[0024]
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.
[0025]
A valve seat 26 is incorporated in the closed end of the cylinder chamber 12 through a press-fitting means. The valve seat 26 has a passage 27 that allows the oil supply passage 13 and the cylinder chamber 12 to communicate with each other, and a fitting recess 28 is formed on the outlet side of the passage 27.
[0026]
Check valve 29 the oil in the cylinder chamber 12 is prevented from flowing back to the oil supply passage 13 side is incorporated in the passage 27, the check valve 29 weight opened and closed by Russia Ddoshito 30 press-fitted into the fitting recess 28 is Limited.
[0027]
The rod sheet 30 has a recess 31 at the tip, and a conical rod sheet surface 32 that receives the rear end of the screw rod 17 is formed at the opening of the recess 31. A hole 33 is provided in the bottom surface of the recess 31.
[0028]
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 27 from the oil supply passage 13 The plunger 14 and the screw rod 17 are moved outward, and the screw rod 17 is separated from the rod seat 30 by the movement, and oil is supplied into the cylinder chamber 12.
[0029]
Further, since the plunger 14 presses the slipper 6 by the outward movement of the plunger 14, the slack of the chain 5 is absorbed and the screw rod 17 is rotated by the elasticity of the spring 21 while the cylinder rod 12 is rotating. The chain 5 moves toward the closed end and comes into contact with the rod sheet 30, and the chain 5 is held at a predetermined elasticity by stopping the plunger 14 and the screw rod 17.
[0030]
When the temperature of the engine rises and the center-to-center distance between 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 check valve 29 closes the passage 27, The applied pressing force is received by the oil sealed in the cylinder chamber 12, and is also received by the pressure side flank 24 of the female screw 16 and the male screw 18, so that the plunger 14 does not move backward. 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.
[0031]
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 moves to a position where the resultant force of the pressing force, the elasticity of the spring 21 and the supply oil pressure is balanced. Move backwards.
[0032]
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.
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
In the chain tensioner shown in FIG. 2, the rod seat 30 is incorporated in the fitting recess 28 formed in the valve seat 26 to limit the opening / closing amount of the check valve 29, so that the retainer in the conventional chain tensioner is unnecessary. It can be. For this reason, the axial length of the chain tensioner can be made compact, and the valve seat 26 and the rod seat 30 are each attached by press fitting, so that assembly is easy.
[0037]
The valve seat 26 and the rod seat 30 are coupled in advance before being assembled into the cylinder chamber 12, and the opening / closing amount of the check valve 29 is measured and managed in the coupled state.
[0038]
FIG. 3 shows another example of the chain tensioner according to the present invention. The chain tensioner and the chain tensioner shown in FIG. 2 are different in the mounting of the valve seat 26 and the rod seat 30. That is, the valve seat 26 is fitted with a gap with respect to the inner diameter surface of the cylinder chamber 12, the rod seat 30 is press-fitted into the inner diameter surface of the cylinder chamber 12, and the valve seat 26 is brought into contact with the closed end surface of the cylinder chamber 12. Therefore, the valve seat 26 is prevented from moving in the axial direction, and the opening and closing amount of the check valve 29 is limited by the rod seat 30.
[0039]
In the chain tensioner in the above embodiment, the rod seat 30 is overlapped with the valve seat 26 to measure and manage the opening / closing amount of the check valve 29, and after that management, each component is incorporated into the cylinder chamber 12.
[0040]
【The invention's effect】
As described above, in the present invention, the rod seat abutted against the valve seat has a function of restricting the opening / closing amount of the check valve, so that a retainer can be made unnecessary, and the axial length of the chain tensioner is reduced. Can be made compact.
[0041]
In addition, the rod seat is press-fitted into the fitting recess formed in the valve seat or the inner diameter surface of the cylinder chamber, so that assembly is easy and a stable mounting state is obtained, and the check valve always functions accurately. be able to.
[Brief description of the drawings]
FIG. 1 is a front view showing a use state of a chain tensioner according to the present invention. FIG. 2 is a sectional view showing a chain tensioner of the same. FIG. 3 is a sectional view showing another example of a chain tensioner. Sectional view showing tensioner 【Explanation of symbols】
11 Housing 12 Cylinder chamber 13 Oil supply passage 14 Plunger 15 Rod insertion hole 16 Female screw 17 Screw rod 18 Male screw 21 Spring 26 Valve seat 27 Passage 28 Fitting recess 29 Check valve 30 Rod seat 33 Hole

Claims (4)

A housing is provided with a cylinder chamber and an oil supply passage communicating with the closed end of the cylinder chamber. A plunger for pressing a chain is slidably inserted into the cylinder chamber, and the plunger is pressed by a spring to be removed from the plunger. The valve seat is in contact with the closed end of the cylinder chamber, and a passage is provided in the valve seat for communicating the oil supply passage with the cylinder chamber. The oil in the cylinder chamber flows back into the oil supply passage in this passage. A chain tensioner provided with a check valve for preventing the contact, a perforated rod seat for restricting the opening and closing amount of the check valve is abutted against the valve seat, and the rod seat and the valve seat are not separated in the abutting state. 2. The chain tensioner according to claim 1, wherein the means for separating the rod seat and the valve seat is provided with a fitting recess on an outlet side of the passage formed in the valve seat, and the rod seat is press-fitted into the fitting recess. . The chain tensioner according to claim 1, wherein the means for separating the rod seat and the valve seat press-fits the rod seat into the inner diameter surface of the cylinder chamber and sandwiches the valve seat between the rod seat and the closed end of the cylinder chamber. . The chain tensioner according to any one of claims 1 to 3, wherein a rod insertion hole that opens at a rear end surface is provided in the plunger, and a screw rod is screw-engaged with a female screw formed on an inner periphery of the opening of the rod insertion hole.

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