JP4880428B2 - Lubrication type auto tensioner - Google Patents

Description

  The present invention relates to an oil supply type auto tensioner that keeps the tension of a timing belt or timing chain for driving a camshaft constant.

  In general, in a belt transmission that transmits engine rotation to a camshaft by means of a timing belt or timing chain (hereinafter simply referred to as a belt), an adjustment force of an auto tensioner is applied to the belt on the slack side of the belt to increase the belt tension. I try to keep it constant.

  As this type of auto tensioner, a plunger for pressing a belt that is slidable in a cylinder chamber formed in the housing and a return spring that imparts outward protrusion to the plunger are incorporated. An oil supply passage that communicates with the pressure chamber formed in the oil supply passage, a check valve is provided at the hydraulic oil outlet of the oil supply passage, and the pushing force applied to the plunger from the belt by the hydraulic oil supplied from the oil supply passage to the pressure chamber It is known that the belt slack is absorbed by a plunger that moves outward by pressing a return spring.

  By the way, in the oil supply type auto tensioner, when the engine is stopped, if the slack side belt is held in tension due to the relationship of the cam stop position, the plunger is pushed in by the pushing force applied from the slack side belt. The stroke end position is held.

  At this time, when the engine is restarted, the slack side belt of the belt is greatly slackened, so that the plunger is rapidly moved outward by the return spring to absorb the slackness of the belt. At that time, since the stroke amount of the plunger in the outward direction is large, the volume of the pressure chamber is increased and the pressure is suddenly reduced. There was a problem that air was sucked into the pressure chamber and the hydraulic damper function was lowered.

  In order to solve the problem, it is effective to provide a mechanism for preventing the plunger from moving backward as described in Patent Documents 1 to 3. Here, in the oil supply type auto tensioner described in Patent Document 1, the swingable ratchet provided in the housing is engaged with the rack teeth formed on the outer periphery of the plunger so as to prevent the plunger from moving backward. I have to.

  In the oil supply type auto tensioner described in Patent Document 2, a screw hole opened at the rear end face is formed in the plunger, and a male screw formed on the outer periphery of the screw rod is screw-engaged with the screw hole. The female thread formed on the inner periphery of the hole is formed in a sawtooth shape, and the plunger is prevented from retreating by the frictional force acting on the contact surface of the pressure side flank of the sawtooth thread.

  Furthermore, in the oil supply type auto tensioner described in Patent Document 3, a guide groove is provided in the inner periphery of the opening end of the cylinder chamber formed in the housing, a register ring is incorporated in the guide groove, and the outer periphery of the plunger is provided. Forms a plurality of circumferential grooves to be tightened by a register ring, and provides a tapered surface on the inner periphery of each circumferential groove and an engagement surface at the small diameter end of the tapered surface. This prevents the plunger from moving backward.

Utility Model Registration No.251627 Japanese Patent No. 3748656 Japanese Patent No. 3670911

  By the way, in the oil supply type auto tensioner described in Patent Document 1, if the plunger protrudes outward due to excessive vibration of the belt, the return of the plunger cannot be absorbed when the engine is returned to low speed, The belt may be cut due to excessive tension, or the ratchet may be damaged. Moreover, since it is necessary to process rack teeth on the outer peripheral surface of the plunger, there is a disadvantage that the processing cost is increased.

  Further, in the oil supply type auto tensioner described in Patent Document 2, when the belt is over-tensioned, a dynamic load applied to the plunger causes a slip on the contact surface of the pressure side flank, causing the plunger to move backward. Although it is possible to prevent the belt from being over-tensioned, it takes time to process the saw-toothed screw, and there is a disadvantage that the processing cost becomes high as in the case of the auto tensioner described in Patent Document 1.

  Furthermore, in the oil supply type auto tensioner described in Patent Document 3, as with the auto tensioner described in Patent Document 1, since the plunger cannot be retracted, there is a possibility that the belt becomes over-tension, There is an inconvenience that it takes time to form the circumferential groove with respect to the outer periphery of the plunger, and the processing cost increases.

  An object of the present invention is to provide a low-cost oil supply type auto tensioner capable of reliably preventing air from being mixed into hydraulic oil in a pressure chamber.

  In order to solve the above-described problems, the present invention incorporates a plunger for pressing a belt that is slidable in a cylinder chamber formed in a housing, and a return spring that imparts outward protrusion to the plunger. The housing is provided with an oil supply passage that communicates with a pressure chamber formed on the back of the plunger, and in the oil supply type auto tensioner in which a check valve is provided at the hydraulic oil outlet of the oil supply passage, at the opening end of the cylinder chamber A large-diameter hole is formed and inclined toward the protruding direction of the plunger on the inner periphery of a brake retaining ring movable within the large-diameter hole. A plurality of engagement pieces for preventing backward movement are provided, and the amount of movement of the retaining ring for braking in the axial direction is set between the open end of the large diameter hole and the closed end of the large diameter hole. It was adopted a structure in which a stop for the snap ring retaining the limit.

  Here, the stopper may consist of a retaining ring attached to the inner periphery of the large-diameter hole, or from a retaining ring having a cylindrical portion fitted on the outer periphery of the end of the housing on the outer periphery. It may be.

  In the oil supply type auto tensioner configured as described above, when the engine is stopped, the belt is tensioned due to the relationship of the cam stop position, and when a pushing force is applied from the belt to the plunger, the braking retaining ring is pushed together with the plunger. Rarely contacts the closed end of the large-diameter hole, and the braking retaining ring is held in the stopped state by the contact, and the inner diameter edge of the engagement piece of the retaining ring for braking engages the outer peripheral surface of the plunger. Then, the plunger is held in a stopped state.

  For this reason, the slack side belt of the belt is held in a tension state although there is a slight decrease in tension. Therefore, even if the engine is restarted, the slack side belt does not loosen greatly, and since the amount of movement of the plunger in the outward direction is small, the pressure drop in the pressure chamber is small, and dissolved air in the hydraulic oil is deposited. In addition, air is not sucked into the pressure chamber, and air is not mixed into the hydraulic oil in the pressure chamber.

  As described above, in the present invention, when the tension of the belt increases, the braking retaining ring is held in a stopped state by contact with the closed end of the large-diameter hole, and the engagement formed on the braking retaining ring Since the plunger is also held in a stopped state by engagement between the tip inner diameter edge of the piece and the outer peripheral surface of the plunger, the slack side belt can be held in a predetermined tension state when the engine is stopped.

  For this reason, even if the engine is restarted, the slack side belt does not loosen greatly, and since the amount of movement of the plunger in the outward direction is small, the pressure drop in the pressure chamber is small, and the air in the hydraulic oil in the pressure chamber Can be reliably prevented.

  In addition, it has a simple structure in which a retaining ring for braking having an engagement piece is incorporated in the large-diameter hole, and there is no need to perform any processing on the outer peripheral surface of the plunger. Can be provided.

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the housing 1 has a mounting piece 2 on its outer periphery that is bolted to the engine block.
Also, the housing 1 is formed with a cylinder chamber 3 that opens at its end face, and a plunger 4 that can slide in the cylinder chamber 3 and a return spring 5 that urges the plunger 4 outward are incorporated. It is.

  In the housing 1, an oil supply passage 7 communicating with a pressure chamber 6 formed in the back portion of the plunger 4 is formed, and a check valve 8 is incorporated in a hydraulic oil outlet portion of the oil supply passage 7. The check valve 8 closes the oil supply passage 7 when the pressure in the pressure chamber 6 becomes higher than the supply pressure of the hydraulic oil supplied to the oil supply passage 7.

  As shown in FIGS. 2 and 3, a large-diameter hole 9 is formed at the open end of the cylinder chamber 3, and a brake retaining ring 10 is incorporated in the large-diameter hole 9. A retaining ring 11 as a stopper for retaining the retaining ring is attached to the opening end of the large diameter hole 9, and an axial clearance formed between the retaining ring 11 and the closed end surface of the large diameter hole 9. Within the range of δ, the brake retaining ring 10 is movable.

  The brake retaining ring 10 has a plurality of engaging pieces 10a inclined toward the protruding direction of the plunger 4 on the inner periphery, and the distal ends of the engaging pieces 10a are in elastic contact with the outer peripheral surface of the plunger 4, When a load in the pushing direction is applied to the plunger 4, the inner diameter edge at the tip of each engagement piece 10 a is engaged with the outer peripheral surface of the plunger 4.

  The oil supply type auto tensioner shown in the embodiment has the above structure, and when adjusting the tension of the cam shaft driving belt (not shown), the oil supply type auto tensioner is arranged on the slack side belt side of the belt, and the housing 1 is arranged. The slack side belt is pressed by the plunger 4 which is fixed to the engine block and provided with the outward spring by the return spring 5.

  In the belt tension adjustment state as described above, when the belt tension changes due to load fluctuations or changes in the angular velocity of the crankshaft, and the belt is slackened, the plunger 4 moves outward by pressing the return spring 5. Then absorb the slack of the belt.

  On the other hand, when the belt tension increases, a pushing force is applied from the belt to the plunger 4, and the pushing force is buffered by the hydraulic oil in the pressure chamber 6.

  When the pushing force is larger than the elastic force of the return spring 5, the hydraulic oil in the pressure chamber 6 leaks to the outside through a minute leak gap formed between the sliding surfaces of the cylinder chamber 3 and the plunger 4. The plunger 4 is slowly retracted to a position where the elastic force of the return spring 5 is balanced, and the belt tension is kept constant.

  When adjusting the belt tension as described above, the retaining ring 10 for braking moves together with the plunger 4. When elongation occurs in the belt due to secular change, the plunger 4 moves outward by pressing of the return spring 5, and when the braking retaining ring 10 comes into contact with the retaining ring 11 as a stopper and stops, the plunger 4 is engaged. The piece 10a is moved outward while elastically deforming radially outward to absorb the elongation of the belt.

  When the engine is stopped, the belt on the slack side of the belt may be held in tension due to the stop position of the cam. At this time, since the pushing force is applied to the plunger 4 from the slack side belt, the brake retaining ring 10 is pushed together with the plunger 4 and comes into contact with the closed end surface of the large-diameter hole 9 as shown in FIG. The tip end inner diameter edge of the engagement piece 10a of the brake retaining ring 10 is engaged with the outer peripheral surface of the plunger 4, and the plunger 4 is held in a stopped state.

  For this reason, the slack side belt of the belt is held in a tension state although there is a slight decrease in tension. Therefore, even if the engine is restarted, the slack side belt does not loosen greatly, and since the amount of movement of the plunger 4 in the outward direction is small, the pressure drop in the pressure chamber 6 is small, and dissolved air in the hydraulic oil is deposited. Neither the air is sucked into the pressure chamber 6 nor the air is mixed into the hydraulic oil in the pressure chamber 6.

  FIG. 5 shows the direction of axial displacement of the plunger 4 depending on engine conditions, and FIG. 6 is necessary between the retaining ring 10 for braking and the closed end face of the large-diameter hole 9 during operation according to the conditions of FIG. The size of the axial gap δ is shown. FIG. 7 shows the maximum and minimum values of the force acting on the oil supply type auto tensioner during the engine sweep, and FIG. 8 shows the axial displacement of the plunger 4 during the engine sweep.

  5 to 8, as shown in FIG. 7 as an example, the maximum value of the load acting on the oil supply type auto tensioner on the low speed side and the high speed side is substantially equal, but the displacement of the plunger 4 in FIG. When looking at, it is pushed a little on the high speed side than the low speed side. This is because the plunger 4 is pushed by the slack side belt because the belt swells from the initial track due to centrifugal force.

  As for the variable load from the belt, when the camshaft rotates, the valve spring load is applied to the crankshaft one rotation and the variable load is applied twice to the oil supply type auto tensioner. As shown in FIG. 7, the maximum load varies depending on the engine speed. The load increases because the belt vibrates due to resonance, and the plunger 4 protrudes (around 3200 r / min) in order to suppress the vibration.

  The pushing of the plunger 4 due to the temperature change is due to an increase in the distance between the centers of the crankshaft and the camshaft.

  With respect to belt elongation due to aging, the plunger 4 only protrudes.

  FIG. 6 summarizes the range of the displacement of the plunger 4 under the above conditions during the engine operation, and moves in the range of a 'to c. Therefore, by setting the axial gap δ shown in FIG. 2 in the range of a ′ to c, the braking retaining ring 10 moves without being in contact with the closed end face of the large-diameter hole 9 during operation, and FIG. Such a large load does not act on the retaining ring 10 for braking.

  The plunger 4 gradually protrudes due to the pressing of the return spring 5 against the belt elongation due to aging. Since the resistance is small and the amount of movement is very small, the tensioner characteristics are not adversely affected.

  Conversely, when the plunger 4 is pushed beyond a predetermined axial clearance δ due to some disturbance, the retaining ring 10 for braking is not locked, and the plunger 4 is pushed by a force greater than the set load. Rarely, over tension can be prevented.

  When the engine is stopped, when the slack side belt is stretched by the phase of the cam, the force is the force by which the valve spring pushes up the cam. In the case of a four-cylinder engine, since the first and second cylinders are always in the intake stroke, the force acts. The force is halved due to the cam and pulley radius differences. Further, it is further reduced depending on the winding angle of the pulley.

  Further, since the return spring 5 is incorporated in the oil supply type auto tensioner, the difference between the tension and the elastic force of the return spring 5 becomes the force for pushing the plunger 4. In general, the valve spring load of a 4-cylinder engine is about 300 N at maximum, and the return spring 5 is about 100 N as shown by the Min load in FIG. Therefore, the belt tension when the engine is stopped is about 100 to 200 N. When the spring load of the return spring 5 is subtracted, a pushing force of about 100 N acts on the plunger 4, and a generally used retaining ring is attached. By adopting it, it fully functions.

  In the embodiment shown in FIG. 2, the brake retaining ring 10 is secured by the retaining ring 11 attached to the inner periphery of the opening end of the large-diameter hole 9, but as shown in FIG. The cylindrical portion 12a formed on the outer periphery of the retaining ring 12 is fitted to the outer periphery of the retaining portion, and the retaining ring 12 is held in contact with the end surface of the housing 1 by crimping the cylindrical portion 12a. The retaining ring 10 for braking may be retained by the ring 12.

Longitudinal front view showing an embodiment of an oil supply type auto tensioner according to the present invention Cross-sectional view showing the built-in part of the retaining ring for braking Right side view of FIG. Sectional drawing which shows the prevention state of the backward movement of a plunger Graph showing the direction of plunger axial displacement depending on engine conditions Graph showing plunger displacement while the engine is running A graph showing the maximum and minimum values of the force acting on the lubricated auto tensioner during engine sweep Graph showing the axial displacement of the plunger during engine sweep Sectional drawing which shows other embodiment of the oil supply type auto tensioner which concerns on this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 3 Cylinder chamber 4 Plunger 5 Return spring 6 Pressure chamber 7 Oil supply passage 8 Check valve 9 Large diameter hole part 10 Stop ring 10a for engagement 11 Stop ring (stopper)
12 Retaining ring (stopper)

Claims (3)

A plunger for pressing a belt slidable in a cylinder chamber formed in the housing and a return spring for imparting outward protrusion to the plunger are incorporated, and the pressure chamber formed in the back of the plunger in the housing In the oil supply type auto tensioner, which has an oil supply passage communicating with the oil supply passage and a check valve provided in the hydraulic oil outlet of the oil supply passage,
A large-diameter hole is formed at the opening end of the cylinder chamber, and the tip of the plunger with respect to the outer peripheral surface of the plunger is inclined toward the protruding direction of the plunger on the inner periphery of the brake retaining ring movable within the large-diameter hole. A plurality of engagement pieces for preventing the plunger from moving backward by engagement of the inner diameter edge are provided, and the opening end portion of the large diameter hole portion and the closed end of the large diameter hole portion are arranged in the axial direction of the brake retaining ring. A lubrication type auto tensioner provided with a stopper for retaining the retaining ring for limiting the movement amount of the retaining ring.   The oil supply type auto tensioner according to claim 1, wherein the stopper includes a retaining ring attached to the inner periphery of the large-diameter hole.   The oil supply type auto-tensioner according to claim 1, wherein the stopper comprises a retaining ring having a cylindrical portion fitted on the outer periphery of the end portion of the housing on the outer periphery.

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