JP3602706B2 - Chain tensioner - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a chain tensioner that keeps the tension of a camshaft driving chain constant.
[0002]
[Prior art]
FIG. 5 shows a known chain tensioner that keeps the tension of a camshaft driving chain constant. In this chain tensioner, a plunger 42 and a spring 43 are incorporated in a cylinder chamber 41 formed in a housing 40, and a chain 44 is pressed by the plunger 42 provided with a projecting property by the spring 43.
[0003]
Further, an oil supply passage 46 communicates with a pressure chamber 45 formed at the back 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, and the oil supply pump drives the oil to flow the oil from the oil supply passage 46 to the pressure chamber 45.
[0004]
By the way, in the camshaft driving chain, when the engine is stopped, the chain 44 may be held in a tensioned state due to 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 tensioned chain 44, the oil in the pressure chamber 45 leaks from the sliding surface between the plunger 42 and the cylinder chamber 41, and the plunger 42 retreats, It is held at a position where the elasticity and the tension of the spring 43 are balanced.
[0005]
Therefore, when the chain 44 is loosened due to the restart of the engine, the plunger 42 largely moves outward. At this time, since the hydraulic pump has just been started and the discharge amount is small, it is not possible to supply sufficient oil to the pressure chamber 45, and air enters the pressure chamber 45 to reduce the damping characteristics and noise is generated. May occur.
[0006]
Further, at the time of starting at low temperature, the same problem as described above occurs because the viscosity of the oil is high and the fluidity is poor.
[0007]
In order to solve the above problems, a rod insertion hole is formed in the plunger at the rear end face thereof, and a female screw is provided on the inner periphery of the opening of the rod insertion hole, and a male screw formed on the outer periphery of the screw rod is screwed. The present applicant has already proposed a chain tensioner that engages, makes the threads of the male and female threads serrated, and incorporates a spring between the opposed portions of the plunger and the 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 is retracted. To prevent movement. For this reason, even if the engine is restarted and the slack occurs, the amount of the slack is small, so that the plunger does not largely move outward, thereby preventing the air from entering the pressure chamber. are doing.
[0009]
[Problems to be solved by the invention]
By the way, in the chain tensioner which has been already proposed, the length in the natural state of the spring pressing the plunger and the screw rod in opposite directions is a length that cannot secure the engagement of the screw portion of the plunger and the screw rod. Therefore, it is necessary to insert the screw rod into the cylinder chamber of the housing, and after assembling the spring, the plunger is screwed into the screw rod by screw engagement. At this time, the spring must be housed by pushing the plunger and the plunger must be screw-engaged with the screw rod, so that the threaded portion cannot be smoothly meshed, and it takes time and effort to assemble the assembly. There are still points that need to be improved.
[0010]
In the chain tensioner, the chain may be detached during maintenance such as removing the engine camshaft. At this time, the plunger jumps out of the cylinder chamber due to the elasticity of the spring, and parts such as the screw rod and the spring are disassembled. There are still points to be improved in accurately reassembling the.
[0011]
An object of the present invention is to facilitate the assembly of a chain tensioner that has already been proposed, and to prevent parts constituting the chain tensioner from being disassembled at the time of maintenance around an engine such as removing a chain. .
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the present invention, a cylinder chamber and an oil supply passage that opens at a closed end of the cylinder chamber are provided in a housing, and a plunger for pressing a chain is slidably provided in the cylinder chamber. The screw rod incorporated into the back of the plunger is screwed into the plunger, and a spring is inserted between the screw rod and the plunger to press the two members in opposite directions. A configuration is adopted in which the length is such that engagement between the screw engagement portion of the plunger and the screw rod is ensured.
[0013]
Further, in the present invention, the plunger is provided with a rod insertion hole that opens at the rear end face, and a female screw formed on the inner periphery of the opening of the rod insertion hole is screw-engaged with a male screw provided on the outer circumference of the screw rod, The flank angle of the pressure side flank which receives the axial pushing force applied to the plunger into the female and male thread threads has a sawtooth shape larger than the flank angle of the play side flank, and the screw rod is rotated by the pressing of the spring. While providing a lead angle that moves in the axial direction.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS.
[0015]
As shown in FIG. 1, a chain 5 is stretched between a sprocket 2 attached to an end of a crankshaft 1 and a sprocket 4 attached to an end of a camshaft 3, and is attached to a slack side chain 5 a of the chain 5. The slipper 6 is in contact. The slipper 6 is swingably supported about a shaft 7. The slipper 6 is pressed by the chain tensioner 10, and the chain 5 is held at a constant tension by the pressing.
[0016]
FIG. 2 shows details of the chain tensioner 10. This chain tensioner has a housing 11 which is screwed to an engine block.
[0017]
The housing 11 is provided with a cylinder chamber 12 and an oil supply passage 13 opened at a closed end of the cylinder chamber 12.
[0018]
A plunger 14 is slidably inserted into the cylinder chamber 12. A rod insertion hole 15 is formed in the plunger 14 at the rear end face. A male screw 18 formed on the outer periphery of a screw rod 17 is screwed into a female screw 16 provided on the inner periphery of the opening of the rod insertion hole 15. I have.
[0019]
The screw rod 17 has a spring storage hole 19 extending axially from the distal end, and a communication hole 20 penetrating from the rear end to the spring storage hole 19, and a closed end of the spring storage hole 19 and the rod insertion hole 15. A spring 21 and a spring seat 22 are incorporated 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.
[0020]
The spring 21 presses the plunger 14 and the screw rod 17 in opposite directions, and the length in the natural state is such that the female screw 16 of the plunger 14 and the male screw 18 of the screw rod 17 are engaged with each other, as shown in FIG. Length.
[0021]
The screw thread of the female screw 16 formed on the plunger 14 and the male screw 18 provided on the screw rod 17 is such that the flank angle of the pressure side flank 24 which receives the pushing force when the plunger 14 is pushed in the axial direction is the play side flank. It has a sawtooth shape larger than 25 flank angles. A lead angle at which the screw rod 17 rotates and moves toward the closed end of the cylinder chamber 12 while being pressed by the spring 21 is provided on the serrated thread.
[0022]
A rod sheet 26 for receiving the rear end of the screw rod 17 is incorporated in the closed end of the cylinder chamber 12. The rod sheet 26 is press-fitted into the cylinder chamber 12 and is non-movably mounted in the axial direction. The rod sheet 26 is provided with a passage 27 that connects the oil supply passage 13 and the cylinder chamber 12.
[0023]
In the passage 27, a check valve 28 and a retainer 29 for limiting the opening and closing amount of the check valve 28 are incorporated. The check valve 28 opens the passage 27 when the pressure in the cylinder chamber 12 becomes higher than the pressure in the oil supply passage 13. It is designed to close.
[0024]
Now, when the engine is started and the slack side chain 5a of the chain 5 is slackened 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 from the oil supply passage 13 into the passage 31 causes The plunger 14 and the screw rod 17 move outward, and the screw rod 17 separates from the rod sheet 26 by the movement, and oil is supplied into the cylinder chamber 12.
[0025]
Further, the outward movement of the plunger 14 causes the plunger 14 to press the slipper 6, so that the slack of the chain 5 is absorbed, and the elasticity of the spring 21 causes the screw rod 17 to rotate and the cylinder chamber 12 to rotate. The chain 5 moves toward the closed end and abuts on the rod sheet 26, and the chain 5 is maintained at a predetermined elasticity by stopping the plunger 14 and the screw rod 17.
[0026]
When the temperature of the engine rises, the center distance between the crankshaft 1 and the camshaft 3 increases due to thermal expansion, and the plunger 14 is pressed by the increased tension of the chain 5, the pressing force is sealed in the cylinder chamber 12. It is received by the oil and 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 for pressing the plunger 14 becomes stronger than the combined force of the elasticity of the spring 21 and the hydraulic pressure, the screw rod 17 rotates and the plunger 14 moves backward.
[0027]
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 pressing force, the elasticity of the spring 21, and the resultant force of the supply oil pressure balance. And retreat.
[0028]
When the engine is stopped, the slack side chain 5a of the chain 5 may be tensioned due to 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 engagement portion between the female screw 16 and the male screw 18.
[0029]
Since the pressing force is a static load without vibration, the screw rod 17 does not rotate and the plunger 14 does not retreat even when the pressing force is larger than the elasticity of the spring 21.
[0030]
Therefore, even if the slack side chain 5a of the chain 5 is slackened due to the restart of the engine, the slack amount is extremely small, and the amount of protrusion of the plunger 14 is also small. Therefore, since the pressure drop in the cylinder chamber 12 is small, no air enters the cylinder chamber 12.
[0031]
In addition, 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 badly. In addition, it is possible to prevent air from entering the cylinder chamber 12.
[0032]
When assembling the chain tensioner, the rod sheet 26 is pressed into the cylinder chamber 12 of the housing 11. On the other hand, the plunger 14, the screw rod 17, the spring 21, and the spring seat 22 are assembled outside, and the assembly A is inserted into the cylinder chamber 12, as shown in FIG.
[0033]
When assembling the assembly A, the spring 21 is inserted into the spring accommodating hole 19 of the screw rod 17, the spring seat 22 is inserted into the end of the spring 21, and the female screw 16 of the plunger 14 is connected to the male screw 18 of the screw rod 17. Screw engagement.
[0034]
Here, since the length of the spring 21 in the natural state is such that the engagement between the female screw 16 of the plunger 14 and the male screw 18 of the screw rod 17 is ensured, the spring 21 engages with the female screw 16 and the male screw 18. There is no inconvenience of disturbing, the female screw 16 and the male screw 18 can be smoothly meshed, and the assembly A can be easily assembled.
[0035]
After the assembly A is inserted into the cylinder chamber 12, the plunger 14 is rotated to move the plunger 14 toward the back of the cylinder chamber 12, and is inserted into a radial pin hole 30 formed on the outer periphery of the end of the housing 11. With the engagement grooves 31 provided on the outer periphery of the distal end of the plunger 14 aligned with each other, a set pin (not shown) is inserted into the engagement groove 31 from the pin hole 30 to prevent the plunger 14 from coming off.
[0036]
In the use state of the chain tensioner 10 as shown in FIG. 2, the plunger 14 is constantly pressed outward by the spring 21. Therefore, when the chain 15 is removed for maintenance around the engine, the plunger 14 is removed. However, since the length of the spring 21 is such that the engagement between the female screw 16 of the plunger 14 and the male screw 18 of the screw rod 17 is ensured, the plunger 14 is prevented from falling out of the cylinder chamber 12, Parts are not broken apart.
[0037]
【The invention's effect】
As described above, in the present invention, the length of the spring that presses the plunger outward in the natural state is set to the length that ensures the engagement between the internal thread of the plunger and the external thread of the screw rod, so that the chain tensioner can be easily assembled. It is possible to prevent the components from being disassembled during maintenance for removing the chain.
[Brief description of the drawings]
FIG. 1 is a front view showing an example of use of a chain tensioner according to the present invention. FIG. 2 is a cross-sectional view of the same chain tensioner. FIG. 3 is a cross-sectional view of an assembly including a plunger, a screw rod, a spring and a spring seat. FIG. 4 is a cross-sectional view showing a conventional chain tensioner.
DESCRIPTION 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 19 Spring storage hole 21 Spring 24 Pressure side flank 25 Play side flank

Claims (2)

In the housing, a cylinder chamber and an oil supply passage opening at the closed end of the cylinder chamber are provided, and a plunger for pressing a chain is slidably inserted into the cylinder chamber, and a screw rod incorporated in the back of the plunger is provided. A spring that engages with the plunger and presses both members in opposite directions between the screw rod and the plunger is incorporated, and the length of the spring in the natural state is determined by the length of the screw engagement portion between the plunger and the screw rod. A chain tensioner with a length that ensures engagement. The plunger is provided with a rod insertion hole that opens at the rear end face, and a female screw formed on the inner periphery of the opening of the rod insertion hole is screw-engaged with a male screw provided on the outer periphery of the screw rod. The flank angle of the pressure side flank which receives the axial pushing force applied to the plunger has a sawtooth shape larger than the flank angle of the play side flank, and the screw rod moves in the axial direction while rotating by the pressing of the spring. The chain tensioner according to claim 1, wherein a lead angle is provided.

Images