WO2015115555A1

WO2015115555A1 - Hydraulic automatic tensioner

Info

Publication number: WO2015115555A1
Application number: PCT/JP2015/052546
Authority: WO
Inventors: 唯久田中; 前野　栄二; 洋生森本
Original assignee: Ntn株式会社
Priority date: 2014-01-31
Filing date: 2015-01-29
Publication date: 2015-08-06

Abstract

A leak flow passage which allows oil within the pressure chamber (6) of a hydraulic automatic tensioner to leak from the pressure chamber (6) is formed by a first leak gap (21) which has small flow resistance and by a second leak gap (32) which has large flow resistance, the first and second leak gaps (21, 32) connecting the pressure chamber (6) and a reservoir chamber (14) through a communication passage (18) formed in a rod (5). The communication passage (18) is adapted to be opened and closed by a second check valve (22) set at a higher pressure than a first check valve (17). When an engine is operated normally, oil within the pressure chamber (6) is allowed to leak from the first leak gap (21) having small flow resistance, to the reservoir chamber (14), and when starting the engine using a starter-generator, the oil within the pressure chamber (6) is allowed to leak from the second leak gap (32) having large flow resistance, to the reservoir chamber (14), thereby applying appropriate tension to a belt.

Description

Hydraulic auto tensioner

The present invention relates to a hydraulic auto tensioner used for adjusting the tension of a belt that drives an auxiliary machine such as an alternator, a water pump, and a compressor of an air conditioner.

In order to reduce carbon dioxide emissions, an engine equipped with an ISG (Integrated Starter Generator) idle stop mechanism that stops the engine when the vehicle stops and starts the engine instantly when the vehicle starts when the accelerator pedal is depressed. Proposed.

FIGS. 11A and 11B show an engine belt transmission device equipped with an ISG idle stop mechanism that achieves both engine accessory drive and engine start, and a crankshaft pulley P ₁ attached to a crankshaft 71. When, passing over the starter-generator pulley P ₂ attached to a rotating shaft of the ISG of the starter generator 72, the belt 74 between the accessory pulley P ₃ attached to a rotating shaft of the auxiliary machine 73 such as a water pump, during normal operation of the engine, as shown in FIG. 11 (a), to drive the starter-generator 72 and the auxiliary 73 by rotation in the direction indicated by the arrow of the crankshaft pulley P _1, to function starter-generator 72 as a generator I am doing so.

On the other hand, when the engine is started by driving the starter generator 72, as shown in FIG. 11 (b), rotates the crankshaft pulley P ₁ by rotation in the direction indicated by the arrow of the starter-generator pulley P _2, starter The generator 72 is caused to function as a starter.

The belt transmission device as described above, a tension pulley 75 provided on the crankshaft pulley P ₁ and the starter generator belt portion 74a over the pulley P _2, the swingable pulley arm 76 for rotatably supporting the tension pulley 75 The adjustment force of the hydraulic auto tensioner A is applied to urge the pulley arm 76 in the direction in which the tension pulley 75 presses the belt 74, so that the tension change of the belt 74 is absorbed by the hydraulic auto tensioner A.

As the hydraulic auto tensioner A, those described in Patent Document 1 and Patent Document 2 below have been conventionally known. In this hydraulic auto tensioner, a lower end portion of a rod is slidably inserted into a valve sleeve projecting on the bottom surface of the cylinder, a pressure chamber is formed in the valve sleeve, and the upper end portion of the rod is A return spring is incorporated between the provided spring seat and the bottom surface of the cylinder to urge the rod and the valve sleeve in the extending direction.

In addition, a sealed reservoir chamber is provided between the inner periphery of the cylinder and the outer periphery of the valve sleeve, and the lower portion of the reservoir chamber and the lower portion of the pressure chamber communicate with each other through an oil passage formed in the bottom surface of the cylinder. A check valve is installed in the lower end, and when the pushing force is applied to the rod and the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, the check valve is closed to block the communication between the oil passage and the pressure chamber. ing.

In the hydraulic auto tensioner having the above-described configuration, the connecting piece provided on the upper surface of the spring seat is rotatably connected to the engine block E shown in FIG. 11A, and the connecting piece provided on the lower surface of the cylinder is connected. When the pushing force is applied to the rod from the belt 74 via the tension pulley 75 and the pulley arm 76, the check valve is closed and the oil sealed in the pressure chamber is slid between the valve sleeve and the rod. The fluid is caused to flow in a leak gap formed between the surfaces, and a hydraulic damper force is generated in the pressure chamber by the viscous resistance of the oil at the time of flow to buffer the pushing force.

JP 2009-275757 A JP 2012-241794 A

By the way, in the conventional hydraulic auto tensioner, when a pushing force is applied to the rod, the oil in the pressure chamber leaks from a single leak gap formed between the sliding surface of the valve sleeve and the rod. Therefore, an appropriate tension cannot be applied to the belt 74 during normal operation of the engine and when the engine is started by the starter / generator 72.

That is, if the leak gap is set to a size that can absorb the belt tension fluctuation during the normal operation of the engine, the leak gap is large, and therefore, the rod 74 is largely pushed in when the engine is started by driving the starter generator 72, and the belt 74 This may cause slack in the belt, and slippage at the contact portion between the belt 74 and the pulleys P _{1 to} P ₃ , which may reduce the life of the belt and cause engine start failure due to the starter / generator 72.

On the other hand, if the leak gap is set to a size that can absorb fluctuations in the tension of the belt 74 when the engine is started by driving the starter generator 72, the tension of the belt 74 during normal operation of the engine is reduced because the leak gap is small. Since the belt 74 becomes too high and the belt 74 becomes over-tensioned, the belt 74 and the bearings that rotatably support the pulleys P _{1 to} P ₃ are liable to be damaged, resulting in a problem of increased fuel consumption.

An object of the present invention is to provide a hydraulic auto tensioner that can apply an appropriate tension to the belt during normal operation of the engine and when the engine is started with a starter generator.

In order to solve the above problems, in the present invention, a valve sleeve is projected from the bottom of a bottomed cylinder filled with oil, and the lower end of the rod is slidably inserted into the valve sleeve. A pressure spring is provided in the valve sleeve, and a return spring that urges the cylinder and the rod in the extending direction is incorporated between a spring seat provided at the top of the rod and the bottom surface of the cylinder, and the inner circumference of the cylinder and the valve sleeve An oil passage that communicates between the lower part of the reservoir chamber and the lower part of the pressure chamber formed between the outer circumferences of the pressure chambers and closes when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber in the lower end of the valve sleeve. A first check valve that shuts off the communication between the chamber and the oil passage, and closes the first check valve when a pushing force is applied to the rod, In a hydraulic auto tensioner that leaks into a reservoir chamber from a leak channel provided in an upper portion of the pressure chamber so as to buffer a pushing force applied to the rod by a hydraulic damper action by oil in the pressure chamber. The leak passage is connected to the pressure chamber via a communication passage having an axial hole that opens at a lower end surface of the rod and a radial hole that communicates with an upper portion of the axial hole and opens at an outer diameter surface of the rod. A first leak gap that communicates with the reservoir chamber, and a second leak gap that has a larger flow resistance than the first leak gap and that always communicates with the pressure chamber and the reservoir chamber. A configuration is adopted in which opening and closing is possible by a second check valve whose set pressure is higher than that of the first check valve.

In the hydraulic auto tensioner having the above-described structure, when adjusting the belt tension in the belt drive device for driving an auxiliary machine of an engine equipped with an ISG idle stop mechanism, a spring seat at the end of the rod is attached to a tensioner attachment target such as an engine block. The closed end of the cylinder is connected to a pulley arm that supports the tension pulley. Let

In the state where the hydraulic auto tensioner is incorporated in the belt transmission as described above, if the belt tension is increased in the normal operation state of the engine and a pushing force is applied from the belt to the rod, the pressure in the pressure chamber increases. The first check valve is closed, and the oil in the pressure chamber flows through the second check valve in the open state from the communication path, leaks into the reservoir chamber from the first leak gap having a small flow path resistance, and the first leak A hydraulic damper force is generated in the pressure chamber by the viscous resistance of the oil flowing through the gap, and the pushing force is buffered by the hydraulic damper force, and the belt is held at an appropriate tension.

On the other hand, when the engine is started by driving the starter / generator, the belt tension increases rapidly and the pressure in the pressure chamber increases rapidly. At this time, the first check valve is closed and, after the first check valve is closed, the second check valve is closed to block the communication path between the pressure chamber and the first leak gap.

Therefore, the oil in the pressure chamber leaks from the second leak gap into the reservoir chamber. Since the flow resistance of the second leak gap is large, the pressure drop in the pressure chamber is small, and the belt tension required to drive the crankshaft is suppressed because the push of the rod is suppressed by the hydraulic damper action in the pressure chamber. To prevent slippage between the belt and the pulley.

In the hydraulic auto tensioner according to the present invention, when the first leak gap is formed, a pin is fitted into the radial hole in the communication path, and a spiral groove is provided between the fitting surface of the pin and the radial hole. The groove may be the first leak gap. Further, a guide cylinder is provided in the axial hole in the communication path, a radial groove is provided on the upper end surface of the guide cylinder, and a spiral groove communicating with the radial hole is provided on the upper outer periphery, and the spiral groove is used as the first leak gap. It is good.

In any of the first leak gaps described above, an annular leak gap formed between the sliding surfaces of the rod and the valve sleeve is defined as a second leak gap.

As a second check valve for blocking the communication path between the pressure chamber and the first leak gap, a valve seat fitted in the lower end portion of the axial hole in the communication path, and a valve hole formed in the valve seat are connected to the valve seat. A check ball that opens and closes from below, a pusher for pressing the check ball, and a coil spring that urges the check ball in the opening direction via the pusher, and the inner diameter of the coil spring is A diameter larger than the diameter can be employed.

Here, when the second check valve is configured to press the check ball directly by the coil spring and urge it in the opening direction, the check ball is opened by using a coil spring whose inner diameter is smaller than the check ball diameter and weak in elastic force. It is necessary to urge toward the direction. In this case, the second check valve is easily closed during normal operation, leading to unnecessary valve closing, and there is a possibility that the flow rate cannot be regulated by the first leak gap. As a result, the hydraulic damper force cannot be set small, the belt tension during normal operation increases, and fuel consumption increases.

As in the second check valve, a coil spring having a larger elastic force than the diameter of the check ball can be employed by urging the check ball in the opening direction via the pusher. For this reason, there is no inconvenience that the second check valve is unnecessarily closed during normal operation, and the hydraulic damper force can be set small by regulating the flow rate by the first leak gap. As a result, the belt tension during normal operation can be lowered, and the fuel consumption can be improved.

In adopting the second check valve, if a valve retainer having an oil passage hole is incorporated in the lower end portion of the axial hole to restrict the opening / closing amount of the check ball, the tensioner stroke until the second check valve is completely closed is extremely small. Can be set to

In addition, a guide hole having a diameter larger than the diameter of the check ball is provided continuously at the lower end of the valve hole formed in the valve seat, and the check ball for opening and closing the valve hole is freely movable in the guide hole. By installing a valve retainer with an oil passage hole in the lower end to prevent the check ball from being pulled out, the check ball opening / closing stroke can be set to a relatively large range, the starting torque when starting the engine is small, and the pressure when starting the engine The present invention can also be applied to an engine in which the difference between the pressure in the chamber and the pressure in the pressure chamber during normal operation is relatively small.

Further, the pusher has a push rod for squeezing the valve body, which is slidably inserted into the valve hole, and a spring seat which is provided on the push rod and supports the end of the coil spring. Is the outer diameter that is slidably guided on the inner diameter surface of the communication path, and the lower end opening is the upper opening of the valve hole while the spring seat is seated on the upper end surface of the valve seat. By providing an axial groove communicating with the spring, the pusher can be smoothly moved in the axial direction by preventing the pusher from being inclined due to the sliding guide of the spring seat by the inner diameter surface of the communication path. . Moreover, a sufficient oil flow rate can be secured around the spring seat due to the presence of the axial groove.

The first leak gap and the second leak gap are not limited to those described above. For example, it may consist of the following configurations a to c.

Configuration a: Two annular leak gaps with different clearances are provided between the sliding surfaces of the rod and the valve sleeve, with an axial gap provided so that the leak gap with a small clearance is located on the pressure chamber side. A leak gap having a large amount is designated as a first leak gap, and a leak gap having a small gap is designated as a second leak gap.

Configuration b: A cylindrical core is incorporated in the axial hole in the communication path, and an annular leak gap formed between the outer diameter surface of the core and the inner diameter surface of the axial hole is defined as the first leak gap. An annular leak gap formed between the sliding surfaces of the valve sleeve and the rod is used as the second leak gap.

Configuration c: A cylindrical core is incorporated in the axial hole in the communication path, and the spiral groove formed on the outer diameter surface of the core is used as the first leak gap, and is formed between the sliding surface of the rod and the valve sleeve. The annular leak gap formed as a second leak gap.

Further, the second check valve having the following configuration can be adopted.
That is, it consists of a check ball provided so as to be able to contact and separate from the seat surface formed in the axial hole of the communication path, and a coil spring that urges the check ball in a direction away from the seat surface, A valve retainer having an oil passage hole in a lower end portion of the axial hole is used to prevent the check ball from being removed.

In the adoption of the second check valve as described above, if the check ball is made of a material having a specific gravity smaller than that of the check ball in the first check valve, the response of the second check valve can be improved, and the starter generator A relatively large hydraulic damper force can be instantaneously generated when the engine is started. As a result, it is possible to prevent the generation of abnormal noise due to the slip of the belt and to suppress the reduction in the life due to the wear of the belt and the pulley.

Here, when the check ball in the first check valve is made of steel, the check ball of the second check valve is made of ceramic. As the ceramic, silicon carbide, silicon nitride, alumina, or aluminum nitride can be employed.

In the present invention, as described above, when the pressure in the pressure chamber rises, the leak flow path that leaks the oil in the pressure chamber to the reservoir chamber is divided into two leak paths, the first leak gap and the second leak gap. A second check valve, which is formed by a leak gap, opens and closes the first leak gap having a small flow path resistance and communicates with the pressure chamber by pressure fluctuation in the pressure chamber, and the set pressure is higher than that of the first check valve. By enabling the opening and closing, an appropriate tension can be applied to the belt during normal operation of the engine and when the engine is started by the starter / generator.

1 is a longitudinal sectional view showing a first embodiment of a hydraulic auto tensioner according to the present invention. Sectional drawing which expands and shows the formation site of the 1st leak gap of FIG. 1, and the 2nd leak gap Sectional view along line III-III in FIG. Sectional drawing which shows the state which the oil in a pressure chamber has leaked from the 2nd leak clearance Sectional drawing which shows 2nd Embodiment of the hydraulic auto tensioner which concerns on this invention Sectional drawing which shows 3rd Embodiment of the hydraulic auto tensioner which concerns on this invention Sectional drawing which shows the state in which the oil in the pressure chamber of the hydraulic auto tensioner shown in FIG. 6 is leaking from the 1st leak clearance Sectional drawing which shows the state in which the oil in the pressure chamber of the hydraulic auto tensioner shown in FIG. 6 has leaked from the 2nd leak clearance Sectional drawing which shows 4th Embodiment of the hydraulic auto tensioner which concerns on this invention Sectional drawing which shows 5th Embodiment of the hydraulic auto tensioner which concerns on this invention 1 shows a belt transmission device of an engine equipped with an idle stop mechanism, (a) is a front view showing a normal operation state of the engine, and (b) is a front view showing a start state of the engine by a starter generator.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 4 show a first embodiment of a hydraulic auto tensioner according to the present invention. As shown in FIG. 1, the cylinder 1 has a bottom portion, and a connecting piece 2 connected to the pulley arm 76 of FIG. 11A is provided on the bottom surface of the bottom portion.

The connecting piece 2 is provided with a shaft insertion hole 2a penetrating from one side surface to the other side surface, a cylindrical fulcrum shaft 2b in the shaft insertion hole 2a, and a sliding bearing 2c for rotatably supporting the fulcrum shaft 2b. And the fulcrum shaft 2b is fixed by tightening a bolt that is inserted into the fulcrum shaft 2b and threadedly engaged with the pulley arm 76, and the cylinder 1 and the pulley arm 76 are relatively positioned around the fulcrum shaft 2b. It is a rotatable connection.

A sleeve fitting hole 3 is provided on the bottom surface of the cylinder 1, and a lower end portion of a steel valve sleeve 4 is press-fitted into the sleeve fitting hole 3. The lower portion of the rod 5 is slidably inserted into the valve sleeve 4, and a pressure chamber 6 is provided in the valve sleeve 4 below the rod 5 by the insertion of the rod 5.

A spring seat 7 is fixed to an upper end portion of the rod 5 located outside the cylinder 1, and a return spring 8 incorporated between the spring seat 7 and the bottom surface of the cylinder 1 extends relative to the cylinder 1 and the rod 5. It is energizing in the direction to do.

A connecting piece 9 connected to the engine block E shown in FIGS. 11A and 11B is provided on the upper end of the spring seat 7. The connecting piece 9 is formed with a sleeve insertion hole 9a penetrating from one side surface to the other side surface, and a sleeve 9b and a slide bearing 9c for rotatably supporting the sleeve 9b are incorporated in the sleeve insertion hole 9a. The connecting piece 9 is rotatably connected to the engine block E by tightening a bolt that is inserted into the sleeve 9 b and screwed to the engine block E.

The spring seat 7 is formed of a molded product, and a cylindrical dust cover 10 that covers the upper outer periphery of the cylinder 1 and a cylindrical spring cover 11 that covers the upper portion of the return spring 8 are simultaneously molded to form the spring seat 7. It is integrated.

Here, the spring seat 7 may be an aluminum die-cast molded product, or may be a molded product of a resin such as a thermosetting resin.

The entire outer periphery of the spring cover 11 is covered with a cylindrical body 12 that is insert-molded when the spring seat 7 is molded. The cylinder 12 is made of a press-formed product of a steel plate.

An oil seal 13 as a seal member is incorporated in the upper opening of the cylinder 1, and the inner periphery of the oil seal 13 is in elastic contact with the outer peripheral surface of the cylinder 12 to close the upper opening of the cylinder 1. This prevents the oil filled inside the tank from leaking to the outside and prevents dust from entering the inside.

By incorporating the oil seal 13, a sealed reservoir chamber 14 is formed between the cylinder 1 and the valve sleeve 4. The reservoir chamber 14 and the pressure chamber 6 are an oil reservoir comprising an oil passage 15 formed between the fitting surfaces of the sleeve fitting hole 3 and the valve sleeve 4 and a circular recess formed at the center of the bottom surface of the sleeve fitting hole 3. 16 to communicate with each other.

A first check valve 17 is incorporated in the lower end portion of the valve sleeve 4. The first check valve 17 includes a check ball 17c for opening and closing the valve hole 17b of the valve seat 17a press-fitted into the lower end portion of the valve sleeve 4 from the pressure chamber 6 side, and urging the check ball 17c toward the valve hole 17b. And a retainer 17e for restricting the opening / closing amount of the check ball 17c.

In the first check valve 17, when the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 14, the check ball 17c closes the valve hole 17b and the communication between the pressure chamber 6 and the oil passage 15 is cut off. 6 is prevented from flowing into the reservoir chamber 14 through the oil passage 15.

As shown in FIGS. 1 and 2, the rod 5 is provided with a communication path 18 that communicates the pressure chamber 6 and the reservoir chamber 14. The communication path 18 includes an axial hole 18 a that opens at the lower end surface of the rod 5, and a radial hole 18 e that communicates with the upper portion of the axial hole 18 a and opens at the outer diameter surface of the rod 5.

A pin 20 is press-fitted into the radial hole 18e, and a spiral groove 21 that connects the communication path 18 and the reservoir chamber 14 is formed on the outer diameter surface of the pin 20, and the spiral groove 21 serves as a first leak gap. ing. In addition, you may make it provide the 1st leak clearance 21 which consists of a spiral groove in the internal diameter surface of the radial direction hole 18e.

The axial hole 18a is a stepped hole having a large-diameter hole 18b, a medium-diameter hole 18c, and a small-diameter hole 18d in order from the bottom, and a second check is placed in the large-diameter hole 18b of the axial hole 18a. A valve 22 is incorporated.

The second check valve 22 includes a valve seat 23, a check ball 26 for opening / closing a valve hole 24 formed on the axis of the valve seat 23, a pusher 27 for pressing the check ball 26, and the pusher 27. A coil spring 28 that urges the check ball 26 in the opening direction, and a valve retainer 29 that regulates the opening / closing amount of the check ball 26.

The valve seat 23 is press-fitted into the large-diameter hole portion 18a, and is positioned in the axial direction by contact with the upper end wall of the large-diameter hole portion 18a, and tapers at the lower end of the valve hole 24 formed on the shaft center. A sheet surface 25 is provided. In addition, a tapered large-diameter hole portion 24 a is provided in the upper portion of the valve hole 24. The check ball 26 can be separated from the seat surface 25 and closes the valve hole 24 by contact.

The pusher 27 has a push rod 27a inserted into the valve hole 24 in the lower part, a spring seat 27b is provided on the push rod 27a, and a protruding shaft 27c is provided on the upper surface of the spring seat 27b. ing.

The spring seat 27b is slidable along the inner diameter surface of the medium-diameter hole 18b, and a plurality of axial grooves 30 are spaced apart in the circumferential direction on the outer diameter surface, as shown in FIGS. Formed.

The lower end opening of each of the plurality of axial grooves 30 faces the large-diameter hole portion 24 a of the valve hole 24 in the vertical direction, and the lower surface of the spring seat 27 b is axially lowered when the pusher 27 is seated on the upper end surface of the valve seat 23. The lower end opening of the groove 30 communicates with the large diameter hole portion 24 a of the valve hole 24.

The inner diameter of the coil spring 28 is larger than the diameter of the check ball 26, and the lower end thereof is supported by the spring seat 27 b of the pusher 27 to urge the pusher 27 downward. As a result, the spring seat 27b is supported on the upper surface of the valve seat 23, and the check ball 26 is held by the push rod 27a to open the valve hole 24.

The valve retainer 29 has a cup shape in which a cylindrical portion 29b is provided on the outer periphery of the circular end plate 29a, and an oil passage hole 31 is formed in the cylindrical portion 29b. The valve retainer 29 is mounted to press-fit the cylindrical portion 29b into the large-diameter hole portion 18a, and restricts the opening / closing stroke of the check ball 26 to a small range.

The set pressure of the second check valve 22 is higher than the set pressure of the first check valve 17, and after the first check valve 17 is closed, when the pressure in the pressure chamber 6 further rises, it operates to close the communication path 18.

As shown in FIG. 2, a small-diameter hole portion 4a is provided in the upper part of the inner periphery of the valve sleeve 4, and the rod 5 is slidable along the inner diameter surface of the small-diameter hole portion 4a. An annular leak gap 32 is provided. The leak gap 32 is a second leak gap, and the flow resistance of the second leak gap 32 is larger than that of the first leak gap 21 formed of the spiral groove described above.

Each of the first leak gap 21 and the second leak gap 32 causes a hydraulic damper action in the pressure chamber 6 due to viscous resistance when oil in the pressure chamber 6 leaks along the

leak gaps

21 and 32. It is like that.

The first leak gap 21 is set to a size capable of absorbing fluctuations in the tension of the belt 74 during normal operation of the engine shown in FIG. 11A due to a hydraulic damper action caused by oil leak. On the other hand, the second leak gap 32 is set to such a size that the rod 5 is not pushed suddenly when the engine is started by driving the starter generator 72 shown in FIG.

An annular tapered groove 33 having a small diameter at the top is formed on the outer periphery of the lower end of the rod 5, and a retaining ring 34 is incorporated in the tapered groove 33. The outer peripheral portion of the retaining ring 34 is exposed to the outside from the tapered groove 33 and faces the step portion 35 formed on the inner peripheral upper portion of the valve sleeve 4 in the vertical direction, and the rod 5 is prevented from being pulled out by contact with the step portion 35. .

The hydraulic auto-tensioner shown in the first embodiment has the above-described configuration. When the engine is installed in the belt drive device for driving an accessory equipped with the idle stop mechanism shown in FIG. The connecting piece 9 is connected to the engine block, and the connecting piece 2 provided at the closed end of the cylinder 1 is connected to the pulley arm 76 to apply an adjusting force to the pulley arm 76.

In the tension adjustment state of the belt 74 as described above, when the tension of the belt 74 changes due to the load fluctuation of the auxiliary machine 73 in the normal operation state of the engine, and the tension of the belt 74 becomes weak, the cylinder is pressed by the return spring 8 and pressed. The slack of the belt 74 is absorbed by relative movement in the direction in which 1 and the rod 5 extend.

Here, when the cylinder 1 and the rod 5 move relative to each other in the extending direction, the pressure in the pressure chamber 6 becomes lower than the pressure in the reservoir chamber 14, so the first check valve 17 is opened. For this reason, the oil in the reservoir chamber 14 smoothly flows from the oil passage 15 through the oil reservoir 16 into the pressure chamber 6, and the cylinder 1 and the rod 5 smoothly move relative to each other in the extending direction to thereby loosen the belt 74. Absorb immediately.

On the other hand, when the tension of the belt 74 is increased, a pushing force in a direction in which the cylinder 1 and the rod 5 are contracted is applied from the belt 74 to the hydraulic auto tensioner. Since the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 14 due to the load of the pushing force, the first check valve 17 is closed.

At this time, since the check ball 26 of the second check valve 22 is in an open state as shown in FIG. 2, the oil in the pressure chamber 6 is axially directed from the valve hole 24 as shown by the arrow in FIG. The oil flows into the groove 30, flows into the first leak gap 21 from the medium diameter hole 18 c and the small diameter hole 18 d of the communication passage 18, leaks into the reservoir chamber 14, and is pressurized by the oil flowing through the first leak gap 21. A hydraulic damper force is generated in the chamber 6. The pushing force applied to the hydraulic auto tensioner is buffered by the hydraulic damper force.

Here, since the first leak gap 21 is set to a size that can absorb fluctuations in the tension of the belt 74 during normal operation of the engine, the tension of the belt 74 during normal operation of the engine will not be too high. And is maintained at an appropriate tension.

On the other hand, when the engine is started by driving the starter generator 72, the tension of the belt 74 increases rapidly, the pushing force against the rod 5 increases, and the pressure in the pressure chamber 6 increases rapidly. At this time, the first check valve 17 is closed, and the check ball 26 of the second check valve 22 rises against the elasticity of the coil spring 28 to come into contact with the seat surface 25 as shown in FIG. Closed state.

As the second check valve 22 is closed, the communication path 18 is in a state of blocking the communication between the pressure chamber 6 and the first leak gap 21, so that the oil in the pressure chamber 6 is changed as shown by an arrow in FIG. 2 It flows into the leak gap 32 and leaks into the reservoir chamber 14.

At this time, since the flow resistance of the second leak gap 32 is larger than that of the first leak gap 21, the oil in the pressure chamber 6 slowly flows in the second leak gap 32. For this reason, there is no sudden pressure drop in the pressure chamber 6, the push of the rod 5 is suppressed by the action of the hydraulic damper in the pressure chamber 6, and the belt 74 is held at the belt tension necessary to drive the crankshaft 71. Thus, slip between the belt 74 and the pulleys P _{1 to} P ₃ is prevented.

As described above, when the tension of the belt 74 increases during normal operation of the engine, the oil in the pressure chamber 6 leaks into the reservoir chamber 14 from the first leak gap 21 having a small flow path resistance. When the tension of the belt 74 increases when the engine is started by the generator, the oil in the pressure chamber 6 leaks into the reservoir chamber 14 from the second leak gap 32 having a large flow path resistance. Appropriate tension can be applied to the belt at each engine start with the generator.

As shown in FIG. 2, when the check ball 26 in the second check valve 22 is urged in the opening direction by the coil spring 28, it is biased in the opening direction via a pusher 27 having a spring seat 27b. As the spring 28, a spring having a larger elastic force than the diameter of the check ball 26 can be employed.

Therefore, during normal operation, there is no inconvenience that the second check valve 22 is unnecessarily closed due to pressure fluctuations in the pressure chamber 6, and the second check valve 22 can function reliably, and the first leak gap 21 The hydraulic damper force can be set to be small by regulating the flow rate by the above, and the belt tension during normal operation can be lowered.

Further, the pusher 27 is provided with a spring seat 27b that is slidably guided on the inner diameter surface of the medium diameter hole 18c, and the axial groove 30 is provided on the outer diameter surface of the spring seat 27b, thereby suppressing the inclination of the pusher 27. A sufficient oil flow rate can be ensured in the state.

FIG. 5 shows a second embodiment of the hydraulic auto tensioner according to the present invention. In this embodiment, the axial hole 18a of the communication passage 18 formed in the rod 5 is a stepped hole in which a small diameter hole 18d is formed in the upper part of the large diameter hole 18b, and the small diameter hole 18d is in the small diameter hole 18d. A guide cylinder 40 for slidingly guiding the spring seat 27b of the pusher 27 is provided, and the rod 5 is in a contracted state that most penetrates into the valve sleeve 4 and is located outside the inner diameter surface in a portion positioned higher than the upper end of the valve sleeve 4. A radial hole 18e penetrating the radial surface is provided, and the guide tube 40 is provided with a radial groove 42 on the upper end surface and a spiral groove 43 communicating with the radial groove 42 and the radial hole 18e on the upper outer periphery. The spiral groove 43 serves as a first leak gap.

Further, a guide hole 44 is provided below the valve hole 24 formed in the valve seat 23 to guide the check ball 26 so that the check ball 26 can move by a fixed stroke.

Since the other configuration is the same as that of the hydraulic auto tensioner shown in FIG. 1, the same parts are denoted by the same reference numerals and the description thereof is omitted.

In the hydraulic auto tensioner shown in FIG. 5, in the normal operation state of the engine, when the pressure in the pressure chamber 6 is increased by the pressing force applied from the belt 74, the check ball 26 is in an open state. Flows from the gap between the check ball 26 and the guide hole 44 through the valve hole 24 to the axial groove 30 formed on the outer diameter surface of the valve seat 27b, and from the inside of the guide cylinder 40 to the radial groove 42, Flows into the first leak gap 43, leaks from the radial hole 18 e to the reservoir chamber 14, and hydraulic damper force is generated in the pressure chamber 6 by the oil flowing through the first leak gap 43. The pushing force applied to the hydraulic auto tensioner is buffered by the hydraulic damper force.

On the other hand, when the engine is started by driving the starter / generator 72, the pressure in the pressure chamber 6 rapidly increases due to the pushing force applied to the rod 5 from the belt 74, and the check ball 26 of the second check valve 22 moves to the coil spring 28. As shown by the chain line in FIG. 5, it rises against elasticity and comes into contact with the seat surface 25 to be in a closed state.

By closing the second check valve 22, the communication passage 18 is in a state of blocking the communication between the pressure chamber 6 and the first leak gap 43, so that the oil in the pressure chamber 6 flows between the sliding surfaces of the valve sleeve 4 and the rod 5. It flows into the second leak gap 32 formed therebetween and leaks into the reservoir chamber 14.

Therefore, also in the hydraulic auto tensioner shown in this embodiment, an appropriate tension can be applied to the belt 74 during normal operation of the engine and when the engine is started by the starter / generator.

Further, by providing a guide hole 44 for guiding the check ball 26 so that the check ball 26 can move by a fixed stroke in the valve seat 23, the tensioner needs to be contracted to some extent until the check valve 26 is completely closed. The present invention can also be applied to an engine having a small torque and having a relatively small difference between the pressure in the pressure chamber 6 at the start of the engine and the pressure in the pressure chamber 6 at the normal operation.

FIG. 6 shows a third embodiment of the hydraulic auto tensioner according to the present invention. In this embodiment, two large-

diameter portions

5a and 5b are vertically provided at the lower end portion of the rod 5 inserted in the cylindrical inner surface of the valve sleeve 4 at intervals in the axial direction. The portion 5a is made smaller than the outer diameter of the lower large diameter portion 5b, and an annular leak gap 45 formed between the outer diameter surface of the upper large diameter portion 5a and the inner diameter surface of the valve sleeve 4 is defined as the first leak gap.

Further, an annular leak gap 46 formed between the sliding surface of the lower large diameter portion 5b and the valve sleeve 4 is used as the second leak gap.

Furthermore, a communication passage 47 that communicates the pressure chamber 6 and the first leak gap 45 is provided at the lower end of the rod 5. The communication passage 47 includes an axial hole 47a that extends in the axial direction from the lower end surface of the rod 5, and a radial hole 47b that intersects the axial hole 47a and opens at the lower outer diameter surface of the upper large-diameter portion 5a. The second check valve 48 is incorporated in the axial hole 47a.

The second check valve 48 has a check ball 50 that can be brought into and out of contact with a tapered seat surface 49 formed in the axial hole 47 a, and a direction in which the check ball 50 is separated from the seat surface 49. The ring-shaped valve retainer 52 that holds the check ball 50 in an open state is press-fitted into the lower end portion of the axial hole 47a.

The set pressure of the second check valve 48 is higher than the set pressure of the first check valve 17 incorporated in the lower end portion of the valve sleeve 4, and after the first check valve 17 is closed, when the pressure in the pressure chamber 6 further increases, the shaft The direction hole 47a is closed to block communication between the communication passage 47 and the first leak gap 45.

The check ball 50 of the second check valve 48 is formed of a ceramic having a specific gravity smaller than that of the check ball 17c made of steel of the first check valve 17 incorporated in the lower end portion of the valve sleeve 4. Examples of the ceramic include silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), aluminum nitride (AlN), and any ceramic may be employed.

Further, an annular groove 53 is formed in the upper end portion of the inner diameter surface of the valve sleeve 4, and a retaining ring 54 is incorporated in the annular groove 53, and the upper end surface of the upper large diameter portion 5 a with respect to the inner peripheral portion of the retaining ring 54 is The rod 5 is prevented from coming out of the valve sleeve 4 by the contact. Since the other structure is the same as that of the hydraulic auto tensioner shown in FIG.

When the tension of the belt 74 is increased in the normal operation state of the engine in the tension adjustment state of the belt in which the hydraulic auto tensioner is incorporated in the belt transmission device shown in FIGS. 11 (a) and 11 (b) as shown in FIG. In addition, the check ball 17c of the first check valve 17 closes the valve hole 17b.

Further, the check ball 50 of the second check valve 48 moves upward due to the pressure increase in the pressure chamber 6 after the first check valve 17 is completely closed, and is separated from the valve retainer 52, as shown in FIG. In addition, it does not move up to a position where it contacts the seat surface 24 and is kept open.

Therefore, the oil in the pressure chamber 6 flows into the communication passage 47 as shown by the arrow in FIG. 7, flows through the first leak gap 45, leaks into the reservoir chamber 14, and flows through the first leak gap 45. A hydraulic damper force is generated in the pressure chamber 6 due to the viscous resistance. The pushing force applied to the hydraulic auto tensioner is buffered by the hydraulic damper force, and the belt 74 is held at an appropriate tension.

On the other hand, when the engine is started by driving the starter generator 72, the tension of the belt 74 increases rapidly, the pushing force against the rod 5 increases, and the pressure in the pressure chamber 6 increases rapidly. At this time, the first check valve 17 is closed, and after the closing, the check ball 50 of the second check valve 48 is lifted and comes into contact with the seat surface 49 as shown in FIG.

As the second check valve 48 is closed, the communication passage 47 is in a state where the communication between the pressure chamber 6 and the first leak gap 45 is blocked, so that the oil in the pressure chamber 6 is second as shown by the arrow in FIG. It flows from the leak gap 46 into the first leak gap 45 and leaks into the reservoir chamber 14.

At this time, since the flow resistance of the second leak gap 46 is larger than that of the first leak gap 45, the oil in the pressure chamber 6 slowly flows in the second leak gap 46. For this reason, there is no sudden pressure drop in the pressure chamber 6, the push of the rod 5 is suppressed by the action of the hydraulic damper in the pressure chamber 6, and the belt 74 is held at the belt tension necessary to drive the crankshaft 71. Thus, slip between the belt 74 and the pulleys P _{1 to} P ₃ is prevented.

As described above, when the engine is started by driving the starter / generator 72, the tension of the belt 74 rapidly increases, so it is necessary to instantly generate a large pressure in the pressure chamber 6.

Here, the time required to generate pressure varies depending on the engine performance. For this reason, if the check ball 50 in the second check valve 48 is made of steel, which is generally employed and has a large specific gravity, it takes time to close the second check valve 48 and applies an appropriate tension to the belt. The belt 74 may slip and generate abnormal noise, or the engine cannot be restarted.

However, since the check ball 50 in the second check valve 48 is made of ceramic having a small specific gravity, the second check valve 50 has good responsiveness to pressure fluctuations in the pressure chamber 6, and when the belt tension suddenly increases, 2 The check ball 50 of the check valve 48 is instantly seated on the seat surface 49 and immediately closes the communication passage 47. For this reason, the above problems do not occur.

FIG. 9 shows a fourth embodiment of the hydraulic auto tensioner according to the present invention. In this embodiment, the communication path 18 formed in the rod 5 has the same configuration as the communication path 18 shown in FIG. 2, and a cylindrical core 55 is incorporated in the medium diameter hole portion 18 c. An annular leak gap 56 formed between the outer diameter face and the inner diameter face of the medium diameter hole 18 c is defined as a first leak gap, and the first leak gap 56 is formed in a radial groove formed in the upper end face of the core 55. The small diameter hole 18d communicates with 55a.

Further, a second check valve 57 for opening and closing the large diameter hole 18b is incorporated in the large diameter hole 18b of the axial hole 18a. The second check valve 57 has a valve seat 59 formed on the shaft center and a valve seat 58 provided with a radial groove 60 on the upper end surface, and a tapered seat surface 61 formed on the lower end of the valve hole 59. The check ball 62 is provided so as to be freely contacted to and separated from each other, and a coil spring 63 that urges the check ball 62 in a direction away from the seat surface 61. The cap-shaped retainer 29 having an oil passage hole 31 press-fitted into the diameter hole portion 18b is held in an open state.

Here, the check ball 38 in the second check valve 25 is made of ceramic in the same manner as the check ball 26 shown in FIG.

Since the other configuration is the same as that of the hydraulic auto tensioner shown in FIG. 2, only the relationship between the valve sleeve 4 and the rod 5 is shown here.

In the hydraulic auto tensioner shown in FIG. 9, in the normal operation state of the engine shown in FIG. 11 (a), when a pushing force is applied from the belt 74 to the rod 5, the oil in the pressure chamber 6 is reduced in flow path resistance. A hydraulic damper force is generated in the pressure chamber 6 by the viscous resistance of oil flowing through the first leak gap 56 from the small first leak gap 56 and the pushing force is buffered by the hydraulic damper force. The belt 74 is held at an appropriate tension.

When the engine is started by driving the starter / generator 72 shown in FIG. 11B, the second check valve 57 is closed by a large pushing force applied to the rod 5 from the belt 74, and the oil in the pressure chamber 6 is closed. Is leaked from the second leak gap 32 having a large flow path resistance to the reservoir chamber 14, and a sudden pressure drop in the pressure chamber 6 is suppressed by the viscous resistance of oil flowing through the second leak gap 32, and the rod 5 is pushed in greatly. The belt 74 is held at the belt tension necessary to drive the crankshaft 71.

Also in the example shown in FIG. 9, since the check ball 62 in the second check valve 57 is made of ceramic, the response of the second check valve 57 to the pressure fluctuation in the pressure chamber 6 is good, and when the belt tension suddenly increases, 2 The check ball 62 of the check valve 57 is instantly seated on the seat surface 61 and immediately closes the lower large-diameter hole portion 18b of the communication passage 18 to securely hold the belt 74 at an appropriate tension.

In FIG. 9, the annular leak gap formed between the outer diameter surface of the core 55 and the inner diameter surface of the medium diameter hole 18c is defined as the first leak gap 56, but in the fifth embodiment shown in FIG. Thus, the spiral groove 65 may be formed on the outer diameter surface of the core 64, and the spiral groove 65 may be used as the first leak gap.

1 cylinder 4 valve sleeve 5 rod 6 pressure chamber 7 spring seat 8 return spring 14 reservoir chamber 15 oil passage 17 first check valve 18 communication passage 18a axial hole 18e radial hole 20 pin 21 spiral groove (first leak gap)
22 Second check valve 23 Valve seat 24 Valve hole 26 Check ball 27 Pusher

27a Push rod

27b Spring seat

27c Projection shaft 28 Coil spring 29 Valve retainer 30 Axial groove 31 Oil passage hole 32 Second leak gap 40 Guide cylinder 42 Radial groove 43 Spiral groove (first leak gap)
44 Guide hole 45 Annular leak gap (first leak gap)
46 Annular leak gap (second leak gap)
47 Communication passage 47a Axial hole 47b Radial hole 48 Second check valve 49 Seat surface 50 Check ball 51 Coil spring 52 Valve retainer 55 Core 56 Annular leak gap (first leak gap)
57 Second check valve 58 Valve seat 59 Valve hole 60 Radial groove 62 Check ball 63 Coil spring 64 Core 65 Spiral groove

Claims

A valve sleeve protrudes from the bottom of the bottomed cylinder containing oil, and the lower end of the rod is slidably inserted into the valve sleeve to provide a pressure chamber in the valve sleeve. A return spring that urges the cylinder and the rod in the extending direction is incorporated between the spring seat provided in the cylinder and the bottom surface of the cylinder, and the lower part of the reservoir chamber formed between the inner periphery of the cylinder and the outer periphery of the valve sleeve and the pressure An oil passage that communicates with the lower portion of the chamber, and a first check valve that closes when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber and shuts off the communication between the pressure chamber and the oil passage in the lower end portion of the valve sleeve. When the pushing force is applied to the rod, the first check valve is closed, and the oil in the pressure chamber is supplied to the leak passage provided in the upper portion of the pressure chamber. In hydraulic auto-tensioner which is adapted to buffer the pushing force to be loaded into the rod by a hydraulic damping action by the oil in the pressure chamber by leakage into the reservoir chamber,
The leak passage is connected to the pressure chamber via a communication passage having an axial hole that opens at a lower end surface of the rod and a radial hole that communicates with an upper portion of the axial hole and opens at an outer diameter surface of the rod. A first leak gap that communicates with the reservoir chamber, and a second leak gap that has a larger flow resistance than the first leak gap and that always communicates with the pressure chamber and the reservoir chamber. A hydraulic auto tensioner characterized in that it can be opened and closed by a second check valve whose set pressure is higher than that of the first check valve.
A pin is fitted into the radial hole in the communication path, a spiral groove is provided between the fitting surface of the pin and the radial hole, the spiral groove is used as a first leak gap, and the sliding surface of the rod and the valve sleeve The hydraulic auto tensioner according to claim 1, wherein an annular leak gap formed therebetween is a second leak gap.
A guide cylinder is provided in the axial hole in the communication passage, a radial groove is provided on the upper end surface of the guide cylinder, and a spiral groove communicating with the radial hole is provided on the outer periphery of the guide cylinder. The spiral groove is defined as a first leak gap. 2. The hydraulic auto tensioner according to claim 1, wherein an annular leak gap formed between the sliding surfaces of the rod and the valve sleeve is used as a second leak gap.
The second check valve is a valve seat fitted in the lower end portion of the axial hole, a check ball for opening and closing a valve hole formed in the valve seat from below the valve seat, and for pressing the check ball And a coil spring for urging the check ball in the opening direction via the pusher, wherein the inner diameter of the coil spring is larger than the diameter of the check ball. The hydraulic auto tensioner according to claim 1.
The hydraulic auto tensioner according to any one of claims 1 to 4, wherein a valve retainer having an oil passage hole is incorporated in a lower end portion of the axial hole to regulate an opening / closing amount of the check ball.
5. A guide hole having a diameter larger than the diameter of the check ball is provided continuously at the lower end of the valve hole formed in the valve seat, and the check ball for opening and closing the valve hole is movable in the guide hole. Hydraulic auto tensioner as described in 1.
The pusher includes a push rod for pressing a valve body that is slidably inserted into the valve hole, and a spring seat that is provided on an upper portion of the push rod and supports an end of the coil spring. The seat has an outer diameter that is slidably guided on the inner diameter surface of the communication passage, and the opening at the lower end is formed on the outer diameter surface of the spring seat while the spring seat is seated on the upper end surface of the valve seat. The hydraulic auto-tensioner according to any one of claims 4 to 6, wherein an axial groove communicating with the upper opening is provided.
Two annular leak gaps with different gaps are provided between the sliding surfaces of the rod and the valve sleeve so that the leak gap with a small gap is located on the pressure chamber side and spaced in the axial direction. The hydraulic auto tensioner according to claim 1, wherein the large leak gap is defined as a first leak gap, and the small leak gap is defined as a second leak gap.
A cylindrical core is incorporated in the axial hole portion of the communication passage, and an annular leak gap formed between the outer diameter surface of the core and the inner diameter surface of the axial hole portion is defined as a first leak gap, and the valve sleeve The hydraulic auto tensioner according to claim 1, wherein an annular leak gap formed between the sliding surfaces of the rod and the rod is the second leak gap.
A cylindrical core is incorporated into the axial hole in the communication path, and a spiral groove formed on the outer diameter surface of the core is used as the first leak gap, and is formed between the sliding surface of the rod and the valve sleeve. The hydraulic auto tensioner according to claim 1, wherein the annular leak gap is a second leak gap.
The second check valve urges the check ball in a direction away from the seat surface, and a check ball provided so as to be able to contact and separate from a seat surface formed in the axial hole of the communication path. The check ball is made of a material having a specific gravity smaller than that of the check ball in the first check valve, which is made up of a coil spring and incorporates a valve retainer having an oil passage hole in the lower end portion of the axial hole. The hydraulic auto tensioner according to any one of claims 8 to 10.
The hydraulic auto tensioner according to claim 11, wherein the check ball of the first check valve is made of steel, and the check ball of the second check valve is ceramic.
The hydraulic auto tensioner according to claim 12, wherein the ceramic is made of any one of silicon carbide, silicon nitride, alumina, and aluminum nitride.