JP5189533B2 - Chain tensioner - Google Patents

Description

  The present invention mainly relates to a chain tensioner that maintains a constant tension of a timing chain for driving a camshaft.

  As a chain tensioner used for tension adjustment of a timing chain, what was described in patent document 1 is conventionally known.

  In the chain tensioner, a plunger for pressing the chain and a return spring that presses the plunger outward are incorporated in a cylinder chamber formed in the housing, and the housing has a pressure formed on the back of the plunger. An oil supply passage communicating with the chamber is provided, a check valve is provided at the oil outlet of the oil supply passage, and when a pushing force is applied from the chain to the plunger, the check valve is closed and a hydraulic damper for the hydraulic oil sealed in the pressure chamber The pushing force is buffered by the action.

  In addition, a valve mounting hole communicating with the pressure chamber from the outer periphery of the housing is formed in the housing, and a relief valve is incorporated into the valve mounting hole. When the pressure in the pressure chamber reaches the set pressure of the relief valve, the relief valve The valve is opened, and the pressure in the pressure chamber is leaked to the outside to prevent the chain from becoming over-tensioned.

JP 2006-17214 A

  By the way, in a chain tensioner having a relief valve, the check ball that opens and closes the valve hole and the spring that urges the check ball toward the valve hole provide flow resistance when the hydraulic oil flows out. When the temperature becomes high, the hydraulic oil cannot be discharged to the outside smoothly, and there is a possibility that the hydraulic damper force becomes high and the chain becomes over-tensioned.

  In addition, air is mixed with the hydraulic oil fed into the oil supply passage, and when the air is fed into the pressure chamber, the air cannot be discharged to the outside when the relief valve is closed. At this time, when the plunger is pushed in, air is compressed, so that there is a problem that the hydraulic damper effect is reduced and the chain cannot be held at an appropriate tension.

  Furthermore, since the relief valve has a large number of parts including a valve seat having a valve hole, a check ball, and a spring, there is a problem that it is disadvantageous in terms of cost.

  An object of the present invention is to provide a chain tensioner having a simple configuration with a small number of parts that can maintain the chain in an appropriate tension adjustment state even at low temperatures.

In order to solve the above problems, in the present invention, a plunger for pressing a chain and a return spring for pressing the plunger outward are incorporated in a cylinder chamber formed in the housing, A chain tensioner provided with an oil supply passage communicating with the pressure chamber formed on the back portion of the plunger, and buffering the pushing force applied to the plunger by the hydraulic oil supplied from the oil supply passage to the pressure chamber via the check valve The housing is made of an exterior that has a flange for attachment to the timing cover on the outer periphery, and a pressure relief passage that communicates the pressure chamber with the outside is formed in the flange, and the pressure relief passage is the flange. Stepped hole from the outer peripheral surface of the cylinder to the pressure chamber and the large diameter of the stepped hole from the side of the flange It consists of a transverse hole leading to the parts, the the large diameter hole portion screwed the plug into the open end of the large diameter portion which is sealed by the plug, has a closed end, the large and the closed end as a trailing side A plate is press-fitted into the open end of the sleeve to be inserted into the diameter hole, and a throttle portion is provided on the plate to communicate the small diameter hole of the stepped hole with the inside of the sleeve. A configuration in which oil drain holes that communicate with the horizontal holes are provided is adopted.

  As described above, the flow resistance of the hydraulic oil is small by providing the throttle portion in a part of the pressure relief passage as compared with the case where the relief valve is provided. For this reason, even at low temperatures when the viscosity of the hydraulic fluid increases, when the plunger is pushed in and the pressure in the pressure chamber rises, the hydraulic fluid in the pressure chamber flows out smoothly and the chain becomes over-tensioned. There is no such thing as.

  In addition, since the pressure relief passage is always in communication with the outside of the pressure chamber, even if hydraulic fluid mixed with air is sent into the pressure chamber, the air is released from the pressure relief passage to the outside when the pressure in the pressure chamber rises. It will be pushed out and discharged. For this reason, there is no stagnation of air in the pressure chamber, and the hydraulic damper effect is not reduced.

As in the chain tensioner according to the present invention, a flange is provided with a pressure relief passage, and the pressure relief passage includes a stepped hole extending from the outer peripheral surface of the flange to the pressure chamber, and a large diameter hole portion of the stepped hole from the side surface of the flange. The plug is screwed into the opening end portion of the large-diameter hole portion, the sleeve is inserted into the large-diameter hole portion closed by the plug, and the throttle portion is inserted into the open end portion of the sleeve. incorporate a plate orifice is formed as a by removal of the plug, by the diameter of the orifice is to be replaced with other different plates, it is possible to easily adjust the hydraulic damper force, replacing the plunger Therefore, the adjustment is easier than the case where the hydraulic damper force is adjusted by changing the size of the leak gap.

Here, if the orifice diameter is too small, the hydraulic oil flow resistance increases, the hydraulic damper force may increase, and the chain may become over-tensioned. If the orifice diameter becomes too large, In order to reduce the damper effect, the hole diameter is preferably in the range of φ0.4 mm to φ1.5 mm.

  Instead of the orifice, the plate may be formed of sintered metal, and the continuous fine holes may be used as the throttle portion.

  As described above, according to the present invention, the flow resistance of the hydraulic oil is smaller than when a relief valve is provided by providing a throttle part in a part of the pressure relief passage communicating with the pressure chamber and the outside. Even at low temperatures when the viscosity of the hydraulic fluid increases, when the plunger is pushed in and the pressure in the pressure chamber rises, the hydraulic fluid in the pressure chamber can flow smoothly to the outside, causing the chain to become over-tensioned. There is no such thing, and the chain can always be held in an appropriate tension adjustment state.

  In addition, the simple structure with the orifice provided in the pressure relief passage is advantageous in terms of cost compared to the case where the relief valve is provided, and the pressure relief passage is always in communication between the pressure chamber and the outside. Therefore, even if hydraulic oil mixed with air is sent into the pressure chamber, the air is pushed out from the pressure relief passage when the pressure in the pressure chamber rises, so there is no stagnation of air in the pressure chamber, and the hydraulic damper The effect is never reduced.

Front view of a chain tension adjusting device using a chain tensioner according to the present invention 1 is a longitudinal front view of the chain tensioner shown in FIG. (I) is a cross-sectional view showing an enlarged portion of the orifice plate shown in FIG. 2, (II) is a cross-sectional view showing another example of the orifice, and (III) is a cross-section showing still another example of the orifice. Figure

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a chain tension adjusting device using a chain tensioner according to the present invention. As shown in the figure, a chain 5 is spanned 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 a chain guide is connected to the chain 5 a on the slack side of the chain 5. 6 is in contact.

  The chain guide 6 is supported so as to be swingable about a shaft 7 provided at the lower end thereof. On one side of the chain guide 6, there is provided a chain tensioner 10 that presses the chain guide 6 against the chain 5 to keep the tension of the chain 5 constant.

  As shown in FIG. 2, the chain tensioner 10 has a housing 11 that is inserted into a tensioner mounting hole 9 formed in the timing cover 8, and is bolted to the outer surface of the timing cover 8 on the outer periphery of the housing 11. A flange 12 is provided.

  The housing 11 is provided with a cylinder chamber 13, and a plunger 14 slidable in the cylinder chamber 13 and a plunger spring 40 for urging the plunger 14 outward are incorporated. The plunger 14 has a cylindrical shape with the front end closed and the rear end opened, and a male screw 17 provided on the outer periphery of the screw rod 16 is thread-engaged with a female screw 15 formed on the inner periphery of the opening. .

  A through hole 18 having a small rear end is formed on the axis of the screw rod 16, and the tip is spherical between the inner peripheral step 18 a of the through hole 18 and the closed end of the plunger 14. A spring seat 19 and a return spring 20 are assembled, and the plunger 14 and the screw rod 16 are urged by the return spring 20 in the extending direction.

  The internal thread 15 of the inner periphery of the plunger 14 and the external thread 17 of the outer periphery of the screw rod 16 have a sawtooth whose flank angle of the pressure flank 21 that receives the axial pushing force applied to the plunger 14 is larger than the flank angle of the play flank 22. The sawtooth screw is provided with a lead angle that moves in a direction in which the plunger 14 and the screw rod 16 are rotated while being relatively rotated by pressing of the return spring 20.

  The housing 11 is formed with an oil supply passage 24 communicating with a pressure chamber 23 formed on the back portion of the plunger 14, and a check valve 25 is provided at an oil outlet portion of the oil supply passage 24 on the pressure chamber 23 side.

  The check valve 25 includes a valve seat 27 press-fitted into a seat fitting hole 26 provided at the closed end of the cylinder chamber 13, a check ball 29 that opens and closes a valve hole 28 formed in the valve seat 27, and The retainer 30 regulates the opening / closing amount of the check ball 29, and the check ball 29 closes the valve hole 28 when the pressure in the pressure chamber 23 becomes higher than the supply pressure of the hydraulic oil supplied to the oil supply passage 24. It has become.

  Here, the valve seat 27 mainly has a function as a rod seat for receiving the rear end of the screw rod 16, and a contact surface between the valve seat 27 and the screw rod 16 is a tapered surface 27a.

  The flange 12 of the housing 11 is formed with a pressure relief passage 31 that communicates the pressure chamber 23 and the inside of the timing cover 8. The pressure relief passage 31 includes a stepped hole 32 extending from the outer peripheral surface of the flange 12 to the pressure chamber 23, and a lateral hole 33 extending from a side surface facing the timing cover 8 of the flange 12 to the large diameter hole portion 32 a of the stepped hole 32. The radial hole 34 communicates with the lateral hole 33 at the outer end, and the end opening of the large diameter hole 32 a is closed by screwing the plug 35.

  As shown in FIG. 3 (I), a sleeve 36 having a closed end is inserted into the large-diameter hole portion 32a with the closed end as a rear side, and is press-fitted into the open end of the sleeve 36. 37 is provided with an orifice 38 as a throttle portion.

  The orifice 38 has a hole diameter in the range of φ0.4 mm to φ1.5 mm. Several kinds of plates 37 having different hole diameters of the orifices 38 are prepared and exchangeable.

  The sleeve 36 is formed with an oil drain hole 39 that communicates the inside with the lateral hole 33.

  The chain tension adjusting device shown in the embodiment has the above structure, and when the engine is driven, the chain 5 moves in the direction indicated by the arrow in FIG. 1 and the camshaft 3 is driven. Further, engine oil (hydraulic oil) is sent into the pressure chamber 23 of the chain tensioner 10 by driving a pump (not shown).

  When the slack side chain 5a of the chain 5 is slackened due to torque fluctuation in the driving state of the camshaft 3, the plunger 14 moves outward, and the hydraulic oil supplied from the oil supply passage 24 to the pressure chamber 23 becomes the pressure chamber. 23 and the through-hole 18 of the screw rod 16.

  Since the plunger 14 presses the chain guide 6 by the outward movement of the plunger 14, the slack of the chain 5a is absorbed, and the screw rod 16 is rotated by the return spring 20 and the check rod 25 side is rotated. The chain 5 is held at a predetermined tension when the plunger 14 and the screw rod 16 are stopped.

  On the other hand, when the chain 5 is tensioned, a pushing force is applied to the plunger 14 via the chain 5 and the chain guide 6. At this time, since the pressure of the hydraulic oil flowing into the through hole 18 of the screw rod 16 and the plunger 14 and the pressure in the pressure chamber 23 increase, the check valve 25 closes the valve hole 28 and enters the housing 11. The pushing force is received by the sealed hydraulic oil and the pressure side flank 21 of the female screw 15 and the male screw 17, and the plunger 14 does not move backward.

  When the pressing force that presses the plunger 14 becomes stronger than the resultant force of the pressing force of the return spring 20 and the plunger spring 40 and the hydraulic pressure of the hydraulic oil in the housing 11, the screw rod 16 rotates and the plunger 14 has a volume of the pressure chamber 23. Move in a smaller direction.

  At this time, the hydraulic oil in the pressure chamber 23 leaks to the outside through a minute leak gap formed between the sliding surfaces of the cylinder chamber 13 and the plunger 14, and the plunger 14 is oiled with the return spring 20 and the plunger spring 40. Slowly retracts to a position where the resultant pressure force and the pushing force are balanced.

  When the chain 5 vibrates, the plunger 14 repeatedly advances and retreats within a screw gap formed in the screw engaging portion of the female screw 15 and the male screw 17, and a hydraulic damper is formed by hydraulic oil sealed in the pressure chamber 23. The vibration is absorbed by the action.

  Here, since the hydraulic oil supplied to the pressure chamber 23 is engine oil, air may be mixed into the hydraulic oil. When air is mixed into the hydraulic oil, the air flows into the pressure relief passage 31 due to the pressure in the pressure chamber 23 and is discharged to the outside.

  For this reason, air does not stay in the pressure chamber 23, and the hydraulic damper effect does not deteriorate.

  When adjusting the tension of the chain 5 as described above, since the pressure chamber 23 communicates with the outside via the pressure relief passage 31, the hydraulic oil in the pressure chamber 23 flows out to the outside. Since the orifice 38 is provided, the pressure chamber 23 is maintained in a substantially constant pressure state. As the pressure in the pressure chamber 23 increases, the amount of hydraulic oil passing through the orifice 38 increases in proportion to the increase in pressure.

  For this reason, even if the plunger 14 is pushed in suddenly and the pressure in the pressure chamber 23 increases rapidly, the hydraulic oil in the pressure chamber 23 is smoothly discharged to the outside. In particular, even when the operating oil has a high viscosity at low temperatures, the operating oil is smoothly discharged to the outside. For this reason, the pressure chamber 23 is always maintained at a substantially constant pressure, and the chain 5 does not become over-tensioned.

  Here, since the pressure in the pressure chamber 23 differs depending on the engine, the pressure in the pressure chamber 23 is adjusted (damper adjustment) corresponding to each engine. In the adjustment, the plug 35 is removed, the sleeve 36 is pulled out, and the plate 37 is replaced with another plate 37 having a different hole diameter of the orifice 38.

  In FIG. 3 (I), a plate 37 having an orifice 38 is press-fitted into the open end of the sleeve 36 secured by the plug 35. However, as shown in FIG. The plate 37 may be press-fitted. Further, the plate 37 may be omitted, and an orifice 38 may be formed in a part of the pressure relief passage 31 as shown in FIG.

  3 (I) and 3 (II), the orifice 38 as the throttle portion is formed in the plate 37. However, the plate 37 may be formed of sintered metal, and the continuous fine holes may be used as the throttle portion. .

11 Housing 12 Flange 13 Cylinder chamber 14 Plunger 20 Return spring 23 Pressure chamber 24 Oil supply passage 25 Check valve 31 Pressure relief passage 32 Stepped hole 32a Large diameter hole portion 33 Horizontal hole 35 Plug 36 Sleeve 37 Plate 38 Orifice 39 Oil discharge hole

Claims (3)

A plunger for pushing a chain and a return spring that pushes the plunger outward are incorporated in a cylinder chamber formed in the housing, and the housing is connected to a pressure chamber formed on the back of the plunger. In the chain tensioner that buffers the pushing force applied to the plunger by the hydraulic oil supplied from the oil supply passage to the pressure chamber via the check valve,
The housing is made of an exterior having a flange for attachment to the timing cover on the outer periphery, and a pressure relief passage communicating with the pressure chamber and the outside is formed in the flange, and the pressure relief passage is formed on the outer periphery of the flange. It consists of a stepped hole from the surface to the pressure chamber and a lateral hole from the side of the flange to the large diameter hole of the stepped hole, and a plug is screwed into the open end of the large diameter hole and sealed by the plug. The plate has a closed end in the large-diameter hole, the plate is press-fitted into the open end of the sleeve inserted into the large-diameter hole with the closed end as the trailing side, and the small-diameter hole of the stepped hole is inserted into the plate. A chain tensioner comprising: a throttle portion that communicates the inside of the sleeve with the inside of the sleeve; and an oil drain hole that communicates the inside of the sleeve with the lateral hole . 2. The chain tensioner according to claim 1 , wherein the throttle portion is made of an orifice, and the orifice has a hole diameter of φ0.4 mm to φ1.5 mm. The chain tensioner according to claim 1 or 2 , wherein the plate is made of a sintered metal and the continuous fine pores are used as a throttle portion.

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