JP4266803B2 - Chain tensioner - Google Patents

Description

  The present invention relates to a chain tensioner that keeps the tension of a chain such as a camshaft drive chain constant.

  As this type of chain tensioner, a cylinder chamber is formed in a housing attached to an engine block, a plunger and a spring that presses the plunger outward are incorporated in the cylinder chamber, and the housing is formed on the back of the plunger. An oil supply passage communicating with the pressure chamber is provided, the chain is pressed by the plunger, and the pushing force applied to the plunger from the chain is buffered by the hydraulic oil in the pressure chamber to keep the chain tension constant. Things are conventionally known.

  Incidentally, as described above, in the chain tensioner that buffers the pushing force applied to the plunger by the hydraulic oil enclosed in the pressure chamber, the pressure of the hydraulic oil in the pressure chamber may be higher than necessary. In this case, the reaction force by which the plunger presses the chain becomes too large, the chain tension becomes excessively high, and wear of the chain is accelerated or abnormal noise is generated.

  In order to prevent the occurrence of such inconvenience, in the chain tensioner described in Patent Document 1, a relief valve is incorporated in a communication hole that communicates the pressure chamber and the outside, and the pressure of the hydraulic oil in the pressure chamber is reduced by the relief valve. Is prevented from becoming higher than the set pressure of the relief valve.

  Here, if air is mixed in the hydraulic oil supplied to the pressure chamber of the chain tensioner, the air is compressed when the chain tension increases, so that the damping effect is reduced and the chain flutters.

In order to eliminate such inconvenience, in the chain tensioner described in Patent Document 1, an air vent disk having a ventilation passage is incorporated in the plunger, and the air mixed in the hydraulic oil in the pressure chamber is incorporated in the chain tensioner. It is made to discharge outside from the passage for ventilation.
JP 2001-021011 A

  By the way, the chain tensioner described in Patent Document 1 has a configuration in which air is eliminated by incorporating an air vent disk, so that the number of parts increases and the cost is high.

  An object of the present invention is to reduce costs by reducing the number of parts of a chain tensioner with a relief valve having an air evacuation means.

  In order to solve the above-described problems, in the present invention, a plunger that is slidable in a cylinder chamber formed in a housing and a spring that presses the plunger outward are incorporated, and the housing includes a plunger. An oil supply passage communicating with the pressure chamber formed in the back portion is provided, and when the pressure of the hydraulic oil in the pressure chamber exceeds a set pressure, the hydraulic oil in the pressure chamber is opened to the outside through the communication hole communicating with the pressure chamber and the outside. In a chain tensioner incorporating a relief valve that flows into the valve, the relief valve includes a bottomed sleeve having an oil drain hole, a valve seat that closes the opening of the sleeve, and a valve hole formed in the valve seat. It consists of a valve body that opens and closes from the inside of the sleeve, and a spring that presses the valve body toward the valve hole, on which the valve body of the valve seat It had adopted a configuration in which an air discharge groove for communicating the valve bore and the inner sleeve to the sheet surface.

  Here, when the valve seat is formed of a sintered alloy, the air discharge groove can be formed when the valve seat is molded, so that a great effect can be obtained in reducing the cost of the chain tensioner.

  Moreover, since the assembly of the relief valve can be obtained by press-fitting and integrating the valve seat into the opening end of the sleeve, it is possible to improve the incorporation of the relief valve into the chain tensioner.

  Further, a hollow chamber opened at the rear end surface is formed in the plunger, a communication hole comprising a stepped hole is formed at the closed end of the hollow chamber, and a relief valve incorporated in the communication hole is provided with a holed retainer for the communication hole. By fixing by press fitting, the relief valve can be easily assembled, and the retainer can prevent the relief valve from moving in the axial direction, so that a stable assembled state can be obtained.

  As described above, according to the present invention, the air discharge groove is formed on the seat surface on which the valve body of the valve seat is seated, so that when the pressure in the pressure chamber is increased, the plunger is pushed by the chain. The mixed air can be discharged to the outside from the air discharge groove, and a reduction in the damping effect can be suppressed.

  Further, since an air vent disk for eliminating air is unnecessary, the number of parts is reduced, and the cost of the chain tensioner can be reduced.

  Furthermore, by changing the setting of the cross-sectional area of the air discharge groove, it is possible to adjust the amount of hydraulic oil flowing out until the relief valve opens, and change the damping characteristics until the relief valve opens. Is possible.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of a chain tensioner according to the present invention.

  As shown in FIG. 1, a cylinder chamber 2 having a closed end is formed in a housing 1 attached to an attachment target such as an engine block, and a plunger 3 is slidably incorporated in the cylinder chamber 2.

  The plunger 3 has a hollow chamber 4 opened at the rear end surface, and a spring 5 incorporated between the closed end of the hollow chamber 4 and the closed end of the cylinder chamber 2 presses the plunger 3 outward. .

  The housing 1 is provided with an oil supply passage 7 communicating with a pressure chamber 6 formed in the back portion of the plunger 3, and oil is supplied from the engine. A check valve 8 is incorporated on the oil outlet side of the oil supply passage 7. When the pressure of the hydraulic oil in the pressure chamber 6 becomes higher than the pressure in the oil supply passage 7, the check valve 8 closes the oil supply passage 7 to prevent the hydraulic oil in the pressure chamber 6 from flowing back into the oil supply passage 7.

  Between the housing 1 and the plunger 3, there is provided a backward movement regulating mechanism 10 that prevents the plunger 3 from moving backward by a predetermined amount toward the closed end of the cylinder chamber 2.

  As shown in FIGS. 1 and 2, the backward movement restricting mechanism 10 is formed with a ring receiving groove 11 in the inner periphery of the opening of the cylinder chamber 2, and in the radial direction provided in the register ring 12 in the ring receiving groove 11. A ring portion 12 a that can be elastically deformed is accommodated, and a plurality of circumferential grooves 13 that are fastened by the ring portion 12 a are provided at equal intervals in the axial direction on the outer peripheral portion of the plunger 3. 3 is provided with a taper surface 13a having a small diameter toward the tip of 3 and an engagement surface 13b at the small diameter end of the taper surface 13a.

  In the backward movement restricting mechanism 10 configured as described above, the taper surface 13a allows the plunger 3 to move forward by the action of expanding the diameter of the ring portion 12a of the register ring 12, and contacts the rear wall surface 11a of the ring receiving groove 11. The retraction movement of the plunger 3 is restricted by the engagement of the engagement surface 13b with the ring portion 12a of the register ring 12 that stops.

  As shown in FIGS. 1 and 3, a communication hole 20 that communicates between the pressure chamber 6 and the outside is formed at the closed end of the plunger 3. The communication hole 20 is formed of a stepped hole, has a valve fitting hole 20a and a retainer fitting hole 20b, and a relief valve 21 is incorporated in the valve fitting hole 20a. The relief valve 21 is pressed against the step portion 23 of the valve fitting hole 20a by a perforated retainer 22 press-fitted into the retainer fitting hole 20b, and is supported in a non-movable manner in the axial direction.

  As shown in FIG. 3, the relief valve 21 includes a bottomed sleeve 24, a valve seat 25 that closes an opening of the sleeve 24, a valve body 26 that is a ball incorporated in the sleeve 24, and a valve body thereof. A spring 27 that presses the valve 26 toward the valve seat 25, and an oil drain hole 28 is provided at the closed end of the sleeve 24.

  The valve seat 25 is formed of a sintered alloy compact. The valve seat 25 is provided with a protrusion 25a that is press-fitted into the open end of the sleeve 24, and the relief valve is made an assembly by the press-fitting of the protrusion 25a.

  The valve seat 25 is formed with a valve hole 29 communicating with the inside of the pressure chamber 6 and the sleeve 24, and a conical seat surface 30 on which the valve body 26 is seated. And an air discharge groove 31 communicating with the inside of the sleeve 24 is provided.

  The chain tensioner shown in the embodiment has the above-described structure. FIG. 1 shows the shaft 52 around the shaft 52 by the plunger 3 that fixes the housing 1 to the engine block and is given the outward projecting property by the elasticity of the spring 5. A state is shown in which the chain guide 51 supported so as to be swingable is pressed against the camshaft drive chain 53 to hold the chain 53 in a tensioned state.

  In the tension adjustment state of the chain 53 as described above, if the chain 53 vibrates due to a change in the angular velocity during one rotation of the crankshaft or a torque fluctuation of the camshaft, and the chain 53 becomes slack, the plunger 5 is caused by the elasticity of the spring 5. 3 moves outward to absorb the slack of the chain 53.

  Here, when elongation occurs due to wear of the link portion of the chain 53 and the slackness of the chain 53 increases, the ring portion 12a of the register ring 12 is pushed by the tapered surface 13a of the circumferential groove 13 of the plunger 3 that moves forward. Expand the diameter. Therefore, the plunger 3 continues to move forward and absorbs the slack of the chain 53, and the ring portion 12 a of the register ring 12 fits into the next circumferential groove 13.

  On the other hand, when the chain 53 is tensioned, a pushing force is applied to the plunger 3 through the chain guide 51, and the pushing force is buffered by the hydraulic oil in the pressure chamber 6.

  When the pressure in the pressure chamber 6 rises abnormally and the pressure exceeds the set pressure of the relief valve 21, the valve body 26 of the relief valve 21 is separated from the seat surface 30 and the valve hole 29 is opened. The hydraulic fluid inside flows into the sleeve 24 from the valve hole 29 and flows out from the oil drain hole 28 and the communication hole 20 to the outside. For this reason, the tension | tensile_strength of the chain 53 does not become excessive and generation | occurrence | production of the chain 53 and generation | occurrence | production of unusual noise can be suppressed.

  Here, when hydraulic oil is supplied to the pressure chamber 6, air may flow into the pressure chamber 6 together with the hydraulic oil, and when the air stays in the pressure chamber 6, the chain 53 is tensioned. Since the plunger 3 compresses air, the damping effect is reduced, and the chain 53 flutters.

  However, since the air discharge groove 31 is formed in the seat surface 30 on which the valve body 26 of the valve seat 25 is seated, the air mixed in the hydraulic oil in the pressure chamber 6 is contained in the pressure chamber 6 due to the retraction of the plunger 3. When the pressure rises, the air flows from the valve hole 29 to the air discharge groove 31 and flows into the sleeve 24, and flows out from the oil discharge hole 28 and the communication hole 20 to the outside.

  As described above, the air mixed in the hydraulic oil in the pressure chamber 6 is automatically discharged to the outside due to the pressure increase in the pressure chamber 6, so that the damping effect is not reduced and the pushing force from the chain 53 is pressurized. It can be reliably buffered by the hydraulic oil in the chamber 6, and the chain 53 can be prevented from flapping.

  In addition, by forming the air discharge groove 31 for air release in the valve seat 25, it is possible to eliminate the need for incorporating an air vent disk for air release, thereby reducing the number of parts and discharging the air. Since the groove 31 can be formed at the time of molding the valve seat 25 made of a sintered alloy, groove processing is unnecessary, and the cost of the chain tensioner can be reduced.

  When the pressing force from the chain 53 is buffered by the hydraulic oil in the pressure chamber 6, the hydraulic oil in the pressure chamber 6 flows into the air discharge groove 31 and flows out to the outside. Therefore, by appropriately setting the cross-sectional area of the air discharge groove 31, it is possible to adjust the outflow amount of the hydraulic oil, and it is possible to adjust the damping characteristic until the relief valve 21 is opened.

  Further, since the relief valve 21 is an assembly in which the valve seat 25 is press-fitted into the opening end portion of the sleeve 24, the relief valve 21 can be easily assembled into the communication hole 20 of the plunger 3. At the time of assembling, the relief valve 21 can be incorporated very efficiently by adopting assembling in which the perforated retainer 22 is press-fitted into the communication hole 20.

  5 and 6 show a second embodiment of the chain tensioner according to the present invention. In this embodiment, the relief valve 21 is attached to the housing 1. That is, a communication hole 40 that communicates the pressure chamber 6 with the outside is formed in the housing 1, a stepped hole 40 a that extends from the upper surface of the housing 1 to the pressure chamber 6, and a stepped hole from the side surface of the housing 1. Tightening of a set screw 41 formed by a discharge hole 40b extending in the middle of 40a, inserting the relief valve 21 into the stepped hole 40a, and screwing the relief valve 21 into the opening end of the stepped hole 40a. Is pressed against the stepped portion 42.

  Here, the relief valve 21 is different from the relief valve 21 shown in FIG. 3 in that an oil drain hole 28 is provided on the outer periphery of the sleeve 24.

  Since the other configuration is the same as that of the chain tensioner shown in the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  Also in the chain tensioner in the second embodiment, the air mixed in the hydraulic oil in the pressure chamber 6 can be discharged to the outside from the air discharge groove 31 and the communication hole 40 formed in the valve seat 25.

Longitudinal front view showing a first embodiment of a chain tensioner according to the present invention FIG. 1 is an enlarged cross-sectional view showing a backward movement restricting mechanism of the chain tensioner shown in FIG. FIG. 1 is an enlarged cross-sectional view showing a built-in portion of the relief valve of the chain tensioner shown in FIG. Sectional view along line IV-IV in FIG. Longitudinal front view showing a second embodiment of the chain tensioner according to the present invention FIG. 5 is an enlarged cross-sectional view showing the assembly portion of the relief valve of the chain tensioner shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Cylinder chamber 3 Plunger 4 Hollow chamber 5 Spring 6 Pressure chamber 7 Oil supply passage 20 Communication hole 21 Relief valve 22 Perforated retainer 24 Sleeve 25 Valve seat 26 Valve body 27 Spring 28 Oil drain hole 29 Valve hole 30 Seat surface 31 Air Discharge groove 40 communication hole

Claims (4)

  A slidable plunger formed in the cylinder chamber formed in the housing and a spring that presses the plunger outward are incorporated, and an oil supply passage communicating with the pressure chamber formed on the back of the plunger is provided in the housing. A chain tensioner incorporating a relief valve that opens when the pressure of the hydraulic oil in the pressure chamber exceeds a set pressure to the communication hole that communicates the pressure chamber with the outside, and flows the hydraulic oil in the pressure chamber to the outside. A relief valve includes a bottomed sleeve having an oil discharge hole, a valve seat that closes the opening of the sleeve, a valve body that opens and closes a valve hole formed in the valve seat, and a valve body A spring that presses against the valve hole, and communicates the valve hole and the inside of the sleeve with the seat surface on which the valve body of the valve seat is seated. Chain tensioner being characterized in that a groove.   The chain tensioner according to claim 1, wherein the valve seat is formed of a sintered alloy molded product, and an air discharge groove is formed during the molding.   The chain tensioner according to claim 1 or 2, wherein the valve seat is press-fitted into an open end of the sleeve to form a relief valve.   A hollow chamber that opens at the rear end surface is formed in the plunger, a communication hole including a stepped hole is formed at the closed end of the hollow chamber, and a relief valve incorporated in the communication hole is provided with a holed retainer for the communication hole. The chain tensioner according to claim 3, which is fixed by press-fitting.

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