JP2008128291A - Hydraulic auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic auto tensioner for preventing the mixture of air in operating oil. <P>SOLUTION: At the lower end of a rod 7, a plunger 8 is provided which is slidable while keeping a slight gap between the inner diameter face of a cylinder and itself. The plunger 8 has a passage 11 for communicating a pressure chamber 9 under the plunger with a reservoir chamber 10 thereabove. A check valve 12 is provided in the passage 11 for imparting projecting property to the rod 7 with a return spring 14 in the cylinder 1. To the rod 7, a braking retainer ring 17 is fitted whose inner periphery is provided with a plurality of engaging pieces 17a inclined in the same direction. The braking retainer ring 17 is movable in a case 16 in the cylinder 1. At stopping an engine when the rod 7 is pushed in by a belt, the braking retainer ring 17 is stopped while abutting on a bottom 16b of the case 16. Then, the front end inner diameter edges of the engaging pieces 17a on the inner periphery the braking retainer ring 17 engage with the outer peripheral face of the rod 7 to prevent backward movement of the rod 7, thus preventing great outward movement of the rod 7 at restarting the engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In general, in a belt transmission device 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 slack side of the belt to keep the belt tension constant. Try to keep on.

  As this type of auto tensioner, the one described in Patent Document 1 has been conventionally known. In this auto tensioner, the upper opening of a cylinder filled with hydraulic oil is sealed by incorporating an oil seal, an air reservoir is provided on the hydraulic oil, and the lower end of a rod that slidably penetrates the oil seal is provided at the lower end of the rod. , Provides a slidable plunger that divides the inside of the cylinder into a pressure chamber and a reservoir chamber, provides a passage in the plunger to communicate the pressure chamber and the reservoir chamber, and incorporates a check valve into the opening on the pressure chamber side of the passage, The return spring built into the cylinder gives the rod outward protrusion, and when the slack side belt tension decreases, the rod moves outward to absorb the slack in the belt. When the belt tension increases, the pushing force applied to the rod from the belt is absorbed by the damper action of the hydraulic oil sealed in the pressure chamber. It is to keep the door of the tension constant.

Utility Model Registration No. 2503437

  By the way, in the conventional hydraulic auto tensioner, when the slack side belt is held in tension due to the cam stop position when the engine is stopped, the pushing force applied to the rod from the slack side belt causes The rod is pushed to the lower limit position where the plunger comes into contact with the bottom of the cylinder and held in a stopped state.

  At this time, when the engine is restarted, the slack side belt of the belt is greatly slackened, so that the rod and the plunger are rapidly moved outward by the return spring to absorb the slack of the belt. At that time, since the stroke of the rod is large, the volume of the pressure chamber increases and the pressure drops rapidly, so that air dissolved in the hydraulic oil is deposited or air in the air pool is sucked into the pressure chamber. There was a risk of reducing the hydraulic damper function.

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

  In order to solve the above problems, in the present invention, the upper opening of a cylinder having a closed end at the bottom and filled with hydraulic oil is sealed by incorporating an oil seal, and the oil seal is slidable. A slidable plunger is provided at the lower end of the rod penetrating the cylinder while maintaining a minute leak gap between the cylinder inner surface and the plunger is formed with a pressure chamber provided below the plunger and above the plunger. A passage that communicates with the reservoir chamber is provided, and a check valve that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber is provided in the passage, and is externally attached to the rod by a return spring built into the cylinder. In a hydraulic auto tensioner with a projecting ability in the direction, a brake retaining ring is fitted to the part of the rod located inside the cylinder. A plurality of engagement pieces are provided on the inner periphery of the brake retaining ring so as to be inclined in the protruding direction of the rod and prevent the rod from retreating by engagement of the inner diameter edge of the tip with the outer peripheral surface of the rod. A configuration is adopted in which a stopper that stops and holds the retaining ring for braking until the lower end of the plunger comes into contact with the closed end of the cylinder is employed at a position offset toward the closed end of the cylinder.

  Here, a bottomed case is incorporated in the cylinder in a non-movable manner in the axial direction, the retaining ring for braking can be freely moved in the case, and the bottom of the case may be used as a stopper, or an oil seal may be attached to the cylinder. A pair of retaining rings may be attached to a position offset toward the upper opening end side with an interval in the vertical direction, the braking retaining ring may be movable between the pair of retaining rings, and the lower retaining ring may be used as a stopper.

  In the hydraulic auto tensioner having the above configuration, when the engine is stopped, if the belt is tensioned due to the cam stop position and a pushing force is applied from the belt to the rod, the brake retaining ring is pushed together with the rod. The brake retaining ring is held in a stopped state by the contact with the stopper, and the tip inner diameter edge of the engagement piece of the braking retaining ring is engaged with the outer peripheral surface of the rod. Is held in a stopped state until it is reached.

  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 when the engine is restarted, the slack side belt does not loosen greatly, and the amount of outward movement of the rod is small, so the pressure drop in the pressure chamber is small, and dissolved air in the hydraulic oil precipitates. 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, the amount of movement of the braking retaining ring toward the cylinder closed end is limited by the stopper, and the tip of the engaging piece of the braking retaining ring held in the stopped state by the stopper Since the rod is held in a stopped state until the rod reaches the lower limit position by engagement between the inner diameter edge and the rod outer peripheral surface, 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 rod 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.

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the cylinder 1 is closed at the bottom and opened at the top. The cylinder 1 is made of an aluminum alloy, and a bottomed cylindrical sleeve 2 made of steel is fitted therein.

  The cylinder 1 is filled with hydraulic oil. An oil seal 3 for preventing leakage of hydraulic oil to the outside is incorporated in the upper opening of the cylinder 1, and the oil seal 3 is retained by a retaining ring 4 attached in the opening end of the cylinder 1. An air reservoir 5 is provided between the oil seal 3 and the hydraulic oil surface.

  The oil seal 3 has a rod insertion hole 6, and a rod 7 is slidably inserted into the rod insertion hole 6. A plunger 8 is provided at the lower end of the rod 7 so as to be slidable with a small leak gap between the inner diameter surfaces of the sleeve 2, and the inside of the cylinder 1 is partitioned into a pressure chamber 9 and a reservoir chamber 10 by the plunger 8. Yes.

  The plunger 8 has a passage 11 communicating with the lower pressure chamber 9 and the upper reservoir chamber 10, and a check valve 12 is provided at the opening of the passage 11 on the pressure chamber 9 side. The check valve 12 closes the passage 11 when the pressure in the pressure chamber 9 becomes higher than the pressure in the reservoir chamber 10.

  A wear ring 13 slidable along the inner diameter surface of the cylinder 1 is fitted to a portion of the rod 7 located in the cylinder 1, and a return spring 14 incorporated below the wear ring 13 causes the wear ring 13 to move. The rod 7 is pressed against the lower end of the large-diameter shaft portion 15 formed on the upper portion of the rod 7 to give the rod 7 an outward projecting property.

  A case 16 is assembled between the lower end of the return spring 14 and the upper end of the sleeve 2. The case 16 has a lid 16 a also serving as a spring seat and a bottom 16 b as a stopper, and a retaining ring 17 for braking is fitted on the outer periphery of the rod 7 in the case 16. The brake retaining ring 17 is movable within an axial gap δ formed between the lid 16a and the bottom 16b of the case 16.

  As shown in FIG. 2, the brake retaining ring 17 has a plurality of engaging pieces 17 a inclined toward the protruding direction of the rod 7 on the inner periphery, and the distal end portion of each engaging piece 17 a is the outer periphery of the rod 7. Elastic contact with the surface.

  Further, the brake retaining ring 17 moves together with the rod 7 by elastic contact of the distal end portion of each engagement piece 17a with the outer peripheral surface of the rod 7 in a tension adjustment state of the belt where the rod 7 presses the belt (not shown). The cylinder 16 is held in a stopped state by contact with the bottom 16b of the case 16 to prevent the cylinder 1 from moving in the closed end direction (downward), and a load in the pushing direction is applied to the rod 7 in the stopped state. Then, the tip inner diameter edge of each engagement piece 17 a is engaged with the outer peripheral surface of the rod 7.

  The hydraulic auto tensioner shown in the embodiment has the above-described structure, and when adjusting the tension of a cam shaft driving belt (not shown), the hydraulic auto tensioner is disposed on the slack side belt side of the belt, and the cylinder 1 is arranged. The slack side belt is pressed by the rod 7 which is fixed to the engine block and provided with the outward springiness by the return spring 14.

  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 rod 7 is moved outward by pressing the return spring 14. Then absorb the slack of the belt.

  At this time, since the plunger 8 also moves in the same direction as the rod 7, the volume of the pressure chamber 9 increases and the pressure decreases. When the pressure becomes lower than the pressure in the reservoir chamber 10, the check valve 12 opens the passage 11. Therefore, the hydraulic oil in the reservoir chamber 10 flows from the passage 11 to the pressure chamber 9, and the rod 7 and the plunger 8 rapidly move outward to immediately 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 rod 7. At this time, since the pressure in the pressure chamber 9 becomes higher than the pressure in the reservoir chamber 10, the check valve 12 closes the passage 11, and the pushing force applied to the rod 7 by the hydraulic oil sealed in the pressure chamber 9 is increased. Buffered.

  When the pushing force is larger than the elastic force of the return spring 14, the hydraulic oil in the pressure chamber 9 flows into the reservoir chamber 10 through a minute leak gap formed between the sleeve 2 and the sliding surface of the plunger 8, and the pushing force and The rod 7 slowly retracts to a position where the elastic force of the return spring 14 is balanced, and the belt tension is kept constant.

  When adjusting the tension of the belt as described above, the braking retaining ring 17 fitted to the rod 7 moves together with the rod 7 and a predetermined axial clearance is secured between the case 16 and the bottom 16b. It moves in the case 16.

  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 rod 7 from the slack side belt, the brake retaining ring 17 is pushed together with the rod and comes into contact with a bottom 16b as a stopper of the case 16 as shown in FIG. Due to the contact, the retaining ring 17 for braking is held in a stopped state, and the inner diameter edges of the plurality of engaging pieces 17 a formed on the inner periphery of the retaining ring 17 for braking engage the outer peripheral surface of the rod 7. The rod 7 is held in a stopped state until reaching the lower limit position.

  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 rod 7 in the outward direction is small, the pressure drop in the pressure chamber 9 is small and the dissolved air in the hydraulic oil is deposited. The air is not sucked into the pressure chamber 9 and air is not mixed into the hydraulic oil in the pressure chamber 9.

  FIG. 4 shows the direction of axial displacement of the rod 7 according to engine conditions, and FIG. 5 shows the axial clearance δ required between the retaining ring 17 for braking and the case bottom 16b during operation according to the conditions of FIG. Indicates the size. FIG. 6 shows the maximum and minimum values of the force acting on the hydraulic auto tensioner during the engine sweep, and FIG. 7 shows the axial displacement of the rod 7 during the engine sweep.

  4 to 7, as shown in FIG. 6 as an example, the maximum value of the load acting on the hydraulic auto tensioner on the low speed side and the high speed side is substantially equal, but the displacement of the rod 7 in FIG. When looking at, it is pushed a little on the high speed side than the low speed side. This is because the rod 7 is pushed by the slack side belt because the belt swells from the initial track due to the centrifugal force.

  As for the variable load from the belt, when the camshaft rotates, the valve spring load is applied to the crankshaft for one rotation and the variable load is applied to the hydraulic auto tensioner twice. As shown in FIG. 6, the maximum load varies depending on the engine speed. The load increases because the belt vibrates due to resonance, and the rod 7 protrudes (around 3200 r / min) to suppress the vibration.

  The pushing of the rod 7 due to the temperature change is due to an increase in the distance between the centers of the crankshaft and the camshaft.

  Regarding the belt elongation due to aging, the rod 7 only protrudes.

  FIG. 5 summarizes the range of the displacement of the rod 7 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 to a range of a ′ to c, the braking retaining ring 17 moves without being in contact with the bottom 16b of the case 16 during operation, as shown in FIG. A large load does not act on the brake retaining ring 17.

  The rod 7 gradually protrudes by the pressing of the return spring 14 with respect to the secular change. Since the resistance is small and the amount of movement is very small, the tensioner characteristics are not adversely affected.

  On the contrary, when the rod 7 is pushed beyond a predetermined axial clearance δ due to some disturbance, the brake retaining ring 17 is not locked, so the rod 7 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. Furthermore, it becomes smaller depending on the winding angle of the pulley.

  Further, since the return spring 14 is incorporated in the hydraulic auto tensioner, the difference between the tension and the elastic force of the return spring 14 becomes a force for pushing the rod 7. In general, the valve spring load of a 4-cylinder engine is about 300 N at the maximum, and the return spring 14 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 14 is subtracted, a pushing force of about 100 N acts on the rod 7, and a generally used retaining ring is attached. By adopting it, it fully functions.

  In the embodiment shown in FIG. 1, the brake retaining ring 17 is movable in a case 16 incorporated in the cylinder 1, and the rod 7 is brought into contact with the bottom 16 b of the case 16 by the contact of the braking retaining ring 17. Although the downward movement is prevented, as shown in FIG. 8, a retaining ring 20 is attached to a position offset from the retaining ring 4 for retaining the oil seal 3 to the upper opening end of the cylinder 1. The brake retaining ring 17 is movable within the range of the axial clearance δ formed between the wheel 20 and the oil seal retaining retaining ring 4, and the retaining ring 4 is used with the oil seal retaining retaining ring 4 as a stopper. 4 may prevent the rod 7 from moving downward.

A longitudinal front view showing an embodiment of a hydraulic auto tensioner according to the present invention (I) is an enlarged cross-sectional view of the brake snap ring assembly, (II) is a cross-sectional plan view of (I) Cross-sectional view showing rod holding state Graph showing the direction of axial displacement of the rod according to engine conditions Graph showing rod displacement during engine operation Graph showing the maximum and minimum values of the force acting on the hydraulic auto tensioner during engine sweep Graph showing axial displacement of rod during engine sweep Sectional drawing which shows other embodiment of the hydraulic auto tensioner which concerns on this invention

Explanation of symbols

1 Cylinder 3 Oil seal 4 Retaining ring (stopper)
5 Air reservoir 7 Rod 8 Plunger 9 Pressure chamber 10 Reservoir chamber 11 Passage 12 Check valve 14 Return spring 16 Case 16b Bottom (stopper)
17 Brake retaining ring 17a Engagement piece 20 Retaining ring

Claims (3)

The upper opening of the cylinder with a closed end at the bottom and filled with hydraulic oil is sealed by incorporating an oil seal, and the lower end of a rod that slidably penetrates the oil seal is placed between the cylinder inner surface and the cylinder. The plunger is provided with a slidable plunger while maintaining a minute leak gap, and the plunger is provided with a passage communicating with the pressure chamber provided below the plunger and the reservoir chamber formed above the plunger. In the hydraulic auto tensioner provided with a check valve that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, and the rod is provided with outward protrusion by a return spring built in the cylinder,
A brake retaining ring is fitted to a portion of the rod located inside the cylinder, and the rod is inclined to the inner periphery of the braking retaining ring in the protruding direction of the rod, and the inner diameter edge of the tip is engaged with the outer peripheral surface of the rod. A plurality of engagement pieces for preventing the backward movement of the brake are provided, and the brake retaining ring is provided until the lower end of the plunger comes into contact with the closed end of the cylinder at a position offset from the brake retaining ring toward the closed end of the cylinder. A hydraulic auto tensioner provided with a stopper for stopping and holding the motor.   The hydraulic auto tensioner according to claim 1, wherein a case with a bottom is incorporated in the cylinder in a non-movable manner in the axial direction, a retaining ring for braking is movable in the case, and the bottom of the case is used as a stopper.   A pair of retaining rings are vertically spaced from the oil seal toward the upper opening end of the cylinder, and a braking retaining ring is movable between the pair of retaining rings. The hydraulic auto tensioner according to claim 1, wherein the hydraulic auto tensioner is a stopper.

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