JP6257950B2 - Hydraulic auto tensioner - Google Patents

Description

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

  An engine equipped with an ISG (Integrated Starter Generator) idle stop mechanism that stops the engine when the vehicle is stopped and instantly starts the engine when the vehicle is started by depressing the accelerator pedal to reduce carbon dioxide emissions Has been proposed.

FIG. 7 shows an engine belt transmission equipped with an ISG idle stop mechanism that achieves both engine auxiliary drive and engine start, and includes a crankshaft pulley P ₁ attached to a crankshaft 51 and an ISG starter generator. 52 and the starter-generator pulley P ₂ which is attached to the rotation shaft of, passing over the belt 54 between the accessory pulley P ₃ attached to a rotating shaft of the auxiliary machine 53 such as a water pump, during normal operation of the engine, the as shown in FIG. (a), to drive the starter-generator 52 and the auxiliary 53 by rotation in the direction indicated by the arrow of the crankshaft pulley P _1, and so as to function the starter-generator 52 as a generator.

On the other hand, when the engine is started by driving the starter generator 52, as shown in FIG. (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 52 is caused to function as a starter.

The belt transmission device as described above, a tension pulley 55 provided on the crankshaft pulley P ₁ and the starter generator belt portion 54a over the pulley P _2, the swingable pulley arm 56 for rotatably supporting the tension pulley 55 The adjustment force of the hydraulic auto tensioner A is applied to urge the pulley arm 56 in the direction in which the tension pulley 55 presses the belt 54, and the tension change of the belt 54 is absorbed by the hydraulic auto tensioner A.

  As hydraulic autotensioner A, what was described in patent document 1 and patent document 2 is 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.

The hydraulic auto tensioner configured as described above connects the connecting piece provided on the lower surface of the cylinder to the pulley arm 56 shown in FIG. 7A, and rotates the connecting piece provided on the upper surface of the spring seat to the engine block. When the pushing force is applied to the rod from the belt 54 via the tension pulley 55 and the pulley arm 56, the check valve is closed and the oil sealed in the pressure chamber is removed from the sliding surface of the valve sleeve and the rod. The fluid is caused to flow through a leak gap formed therebetween, 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 54 during normal operation of the engine and when the starter / generator 52 starts the engine.

In other words, if the leak gap is set to a size that can absorb fluctuations in belt tension during normal operation of the engine, the leak gap is large, so that the rod is pushed in greatly when the engine is started by driving the starter generator 52, and the belt 54 There is a possibility that a slack occurs in the belt 54 and slippage occurs at the contact portion between the belt 54 and the pulleys P _{1 to} P ₃ , and the life of the belt may be shortened or the starter / generator 52 may fail to start the engine.

On the other hand, if the leak gap is set to a size that can absorb fluctuations in the tension of the belt 54 when the engine is started by driving the starter / generator 52, the tension of the belt 54 during normal operation of the engine is reduced because the leak gap is small. The belt 54 becomes excessively high and the belt 54 becomes over-tensioned, and the bearings that rotatably support the belt 54 and the pulleys P _{1 to} P ₃ are easily damaged, resulting in a problem that fuel consumption increases.

  An object of the present invention is to provide a hydraulic auto tensioner that can apply an appropriate tension to a belt during normal operation of the engine and when the engine is started by 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 A reservoir chamber is provided between the outer periphery of the cylinder, and an oil passage is formed in the bottom of the cylinder to connect the lower portion of the reservoir chamber and the lower portion of the pressure chamber. The pressure in the pressure chamber is stored in the lower end of the valve sleeve. A first check valve is provided for closing the communication between the pressure chamber and the oil passage when the pressure in the chamber becomes higher than the pressure in the chamber, and when the pushing force is applied to the rod, the first check valve is provided. In the hydraulic auto tensioner that closes the pressure valve and leaks oil in the pressure chamber from the minute leak flow path to the reservoir chamber to buffer the pushing force applied to the rod by the hydraulic damper action of the oil in the pressure chamber. The flow path is composed of a first leak gap and a second leak gap having a larger flow path resistance than the first leak gap, and the rod is provided with a communication path that communicates the first leak gap and the pressure chamber. A configuration is adopted in which the communication path is opened and closed 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 configuration, 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 cylinder is connected to a tensioner mounting target such as an engine block, The spring seat at the tip of the rod is connected to a pulley arm that supports a tension pulley, and the tension pulley urges the pulley arm in a direction to press the belt portion between the crankshaft pulley and the motor / generator pulley, thereby tensioning the belt.

  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. Thus, the first check valve is closed, and the oil in the pressure chamber leaks from the first leak clearance with a small flow path resistance to the reservoir chamber, and the hydraulic damper force is generated in the pressure chamber by the viscous resistance of the oil flowing through the first leak clearance. Is generated, 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 rapidly increases and the pressure in the pressure chamber rapidly increases. At this time, the first check valve is closed, and after the first check valve is closed, the second check valve closes the communication path to block the communication between the pressure chamber and the first leak clearance.

  For this reason, the oil in the pressure chamber leaks from the second leak gap into the reservoir chamber. Since the flow resistance of the second leak clearance is large, there is little pressure drop in the pressure chamber, and the belt tension required for driving the crankshaft is suppressed by the rod being pushed by the hydraulic damper action in the pressure chamber. To prevent slippage between the belt and the pulley.

  Here, two annular leak gaps with different clearances are provided between the sliding surfaces of the rod and the valve sleeve so that the leak gap with a small clearance is located on the pressure chamber side, and the clearance is set in the axial direction. A large leak gap may be used as the first leak gap, and a small leak gap may be used as the second leak gap. In this case, the rod is provided with a communication path that communicates the first leak clearance and the pressure chamber, and the second check valve is incorporated in the communication path.

  The rod is provided with a leak passage having an axial hole opening at its lower end surface and a radial hole opening at the outer diameter surface of the rod in communication with the upper end of the axial hole, and a pressure chamber. A cylindrical core is incorporated in the axial hole portion of the leak passage in communication with the reservoir chamber, and the annular leak gap formed between the outer diameter surface of the core and the inner diameter surface of the axial hole portion is One leak gap may be used, and an annular leak gap formed between the sliding surfaces of the valve sleeve and the rod may be used as the second leak gap. In this case, the lower part of the axial hole portion is used as a communication path, and the second check valve is incorporated in the communication path.

  Furthermore, the rod is provided with a leak passage having an axial hole opening at its lower end surface and a radial hole opening at the outer diameter surface of the rod in communication with the upper end of the axial hole, and a pressure chamber. A cylindrical core is incorporated into the axial hole portion of the leak passage in communication with the reservoir chamber, a spiral orifice formed on the outer diameter surface of the core is used as the first leak clearance, and the valve sleeve and rod An annular leak gap formed between the sliding surfaces may be used as the second leak gap. In this case, as described above, the lower part of the axial hole portion is used as a communication path, and the second check valve is incorporated in the communication path.

  In the present invention, as described above, when the pressure in the pressure chamber rises, the leak flow path for leaking the oil in the pressure chamber to the reservoir chamber is formed up to the first and second leak clearances having different flow path resistances. Since one of the first leak gaps with a small flow path resistance is opened and closed by the pressure fluctuation of the pressure chamber and can be opened and closed by the second check valve whose set pressure is higher than that of the first check valve, Appropriate tension can be applied to the belt during operation and when the engine is started with the starter generator.

1 is a longitudinal sectional view showing an embodiment of a hydraulic auto tensioner according to the present invention. Sectional drawing which expands and shows the formation site of the 1st leak clearance of FIG. 1, and the 2nd leak clearance Sectional drawing which shows the state in which the oil in a pressure chamber has leaked from the 1st leak clearance Sectional drawing which shows the state in which the oil in a pressure chamber has leaked from the 2nd leak clearance Sectional drawing which shows other embodiment of the hydraulic auto tensioner which concerns on this invention Partial sectional view showing still another embodiment of the hydraulic auto tensioner according to the present 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. As shown in FIG. 1, the cylinder 1 has a bottom portion, and a connecting piece 2 connected to the pulley arm 56 of FIG. 7 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, and a cylindrical fulcrum shaft 2b and a sliding bearing 2c for rotatably supporting the fulcrum shaft 2b in the shaft insertion hole 2a. 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 56 , and the connecting piece 2 is attached to the pulley arm 56 so as to be rotatable .

  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 is provided at 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 by a bolt inserted into the sleeve 9b.

  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 molded at the same time to form the spring seat 7. 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 is closed when the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 14, and the communication between the pressure chamber 6 and the oil passage 15 is cut off. It is prevented from flowing through the reservoir chamber 14.

  As shown in FIGS. 1 and 2, two large-diameter portions 5a and 5b are provided at the lower end portion of the rod 5 positioned in the valve sleeve 4, and the outer diameter of the upper large-diameter portion 5a is lower. The outer diameter of the large diameter portion 5b is smaller.

  As shown in FIG. 2, an annular leak gap 21 is formed between the outer diameter surface of the upper large-diameter portion 5 a and the inner diameter surface of the valve sleeve 4, and the leak gap 21 is the first leak gap. On the other hand, an annular leak gap 22 is formed between the sliding surface of the lower large diameter portion 5b and the valve sleeve 4, and the leak gap 22 is a second leak gap.

  The first leak gap 21 and the second leak gap 22 are different in the amount of gap, so that the flow path resistance of the first leak gap 21 is smaller than the flow path resistance of the second leak gap 22. Each of the first leak gap 21 and the second leak gap 22 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 22. It is like that.

  The first leak gap 21 is set to a size that can absorb the tension fluctuation of the belt 54 during the normal operation of the engine shown in FIG. 7A due to the hydraulic damper action caused by the oil leak. On the other hand, the second leak gap 22 is set to such a size that the rod 5 is not pushed suddenly when the engine is started by driving the starter / generator 52 shown in FIG.

  A communication passage 23 that communicates the pressure chamber 6 and the first leak gap 21 is formed at the lower end of the rod 5. The communication path 23 includes an axial hole 23a that extends in the axial direction from the lower end surface of the rod 5, and a radial hole 23b that intersects the axial hole 23a and opens at the lower outer diameter surface of the upper large-diameter portion 5a. The second check valve 25 is incorporated in the axial hole 23a.

  The second check valve 25 has a check ball 26 that can be freely contacted and separated from a tapered seat surface 24 formed in the axial hole 23a, and directs the check ball 26 away from the seat surface 24. A stopper ring 28 that presses the check ball 26 in an open state is press-fitted into the lower end portion of the axial hole 23a.

  The second check valve 25 is configured such that when the pressure in the pressure chamber 6 becomes high, the check ball 26 comes into contact with the seat surface 24 to close the communication path 23 and block the communication between the pressure chamber 6 and the first leak gap 21. It has become. The set pressure of the second check valve 25 is higher than the set pressure of the first check valve 17 and is activated when the pressure in the pressure chamber 6 further increases after the first check valve 17 is closed.

  An annular groove 29 is formed at the upper end of the inner diameter surface of the valve sleeve 4, and a retaining ring 30 is incorporated in the annular groove 29. The inner peripheral portion of the retaining ring 30 is positioned inward from the inner diameter surface of the valve sleeve 4, and the rod 5 comes out of the valve sleeve 4 by contact of the upper end surface of the upper large diameter portion 5 a with the inner peripheral portion of the retaining ring 30. Is prevented.

The hydraulic auto-tensioner shown in the embodiment has the above-described configuration, and when the engine equipped with the idle stop mechanism shown in FIG. The connecting piece 2 provided on the connecting portion 2 is connected to the pulley arm 56 , and the connecting piece 9 of the spring seat 7 is connected to the engine block to apply an adjusting force to the pulley arm 56.

  In the tension adjustment state of the belt 54 as described above, in the normal operation state of the engine, the tension of the belt 54 changes due to the load fluctuation of the auxiliary machine 53, and when the tension of the belt 54 becomes weak, the return spring 8 is pressed. The cylinder 1 and the rod 5 move relative to each other in the extending direction, and the slack of the belt 54 is absorbed.

  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 loosen the belt 54. Absorb immediately.

  On the other hand, when the tension of the belt 54 is increased, a pushing force in a direction of contracting the cylinder 1 and the rod 5 of the hydraulic auto tensioner is applied from the belt 54. At this time, since the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 14, the first check valve 17 is closed.

  In addition, the check ball 26 of the second check valve 25 moves upward due to the pressure increase in the pressure chamber 6 after the first check valve 17 is completely closed, and separates from the stopper ring 28. It does not move up to the contact position and is kept open.

  By the movement of the check ball 26 with respect to the stopper ring 28, the oil in the pressure chamber 6 flows into the communication path 23, flows through the first leak gap 21, leaks into the reservoir chamber 14, and flows through the first leak gap 21. As a result, a hydraulic damper force is generated in the pressure chamber 6. The pushing force applied to the hydraulic auto tensioner is buffered by the hydraulic damper force.

  At this time, since the first leak clearance 21 is set to a size that can absorb the tension fluctuation of the belt 54 during the normal operation of the engine, the tension of the belt 54 during the normal operation of the engine will not be too high. Without being held at the proper tension

  On the other hand, when the engine is started by driving the starter / generator 52, the tension of the belt 54 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 25 is raised to come into contact with the seat surface 24 as shown in FIG.

  By closing the second check valve 25, the communication passage 23 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 second as shown by the arrow in FIG. It flows from the leak gap 22 into the first leak gap 21 and leaks into the reservoir chamber 14.

At this time, since the flow resistance of the second leak gap 22 is larger than that of the first leak gap 21, the oil in the pressure chamber 6 slowly flows in the second leak gap 22. For this reason, there is no sudden pressure drop in the pressure chamber 6, and the pushing of the rod 5 is suppressed by the hydraulic damper action in the pressure chamber 6, and the belt 54 is held at the belt tension necessary to drive the crankshaft 51. the slip between the belt 54 and the pulleys _{P 1} to _{P 3} is prevented.

  FIG. 5 shows another embodiment of the hydraulic auto tensioner according to the present invention. In this embodiment, the rod 5 is provided with a leak passage 31 that allows the pressure chamber 6 and the reservoir chamber 14 to communicate with each other. The leak passage 31 includes an axial hole portion 32 formed of a stepped hole and an axial hole portion 32 thereof. The cylindrical core 34 is incorporated in the intermediate hole 32 a of the axial hole 32, and communicates with the upper end of the rod 5. An annular leak gap 21 formed between the radial face and the inner face of the intermediate hole portion 32a is defined as a first leak gap.

  Further, the second check valve 25 is incorporated in the lower large-diameter hole portion 32b as the communication passage of the axial hole portion 32, and the second check valve 25 is formed in a cylindrical shape with a valve hole 36 formed on the shaft center. Of the valve seat 35, a check ball 38 which is provided so as to be in contact with and away from the tapered seat surface 37 formed at the lower end of the valve hole 36, and the check ball 38 in a direction away from the seat surface 37. The check ball 38 is held in an open state by a cap-like retainer 40 having a communication hole 41 press-fitted into the lower large-diameter hole portion 32b of the rod 5.

  Furthermore, the rod 5 is formed into a cylindrical shape having the same outer diameter over the entire length in the axial direction, and the cylindrical rod 5 is slidably inserted into a small diameter hole portion 4a formed at the inner peripheral upper end portion of the valve sleeve 4, An annular leak gap 22 formed between the sliding surfaces is defined as a second leak gap.

  Further, an annular groove 42 is provided on the outer periphery of the lower end portion of the rod 5, and a retaining ring 43 is attached to the annular groove 42. ing.

  Since the other structure is the same as that of the hydraulic auto tensioner shown in FIG. 1, only the relationship between the valve sleeve 4 and the rod 5 is shown here.

  In the hydraulic auto tensioner shown in FIG. 5, when a pushing force is applied from the belt 54 to the rod 5 in the normal operation state of the engine shown in FIG. The first leak clearance 21 having a small flow path resistance leaks into the reservoir chamber 14, and a hydraulic damper force is generated in the pressure chamber 6 by the viscous resistance of the oil flowing through the first leak clearance 21, and the above-described pushing is performed by the hydraulic damper force. The force is buffered so that the belt 54 is held at an appropriate tension.

  Further, when the engine is started by driving the starter / generator 52 shown in FIG. 7B, the second check valve 25 is closed by a large pushing force applied to the rod 5 from the belt 54, so that the oil in the pressure chamber 6 is closed. Is leaked from the second leak gap 22 having a large flow path resistance to the reservoir chamber 14, the viscosity resistance of the oil flowing through the second leak gap 22 is suppressed, and a sudden pressure drop in the pressure chamber 6 is suppressed, and the rod 5 is pushed in greatly. The belt 54 is held at the belt tension necessary to drive the crankshaft 51.

  In FIG. 5, the annular leak gap 21 formed between the outer diameter surface of the core 34 and the inner diameter surface of the intermediate hole portion 32 a is used as the first leak gap. However, as shown in FIG. A spiral orifice 21 may be formed on the surface, and the orifice 21 may be used as the first leak clearance.

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 21 First Leakage Clearance 22 Second Leakage Clearance 23 Communication Passage 25 Second Check Valve 31 Leakage Passage 32 Shaft Direction hole 33 Radial hole 34 Core

Claims (1)

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 rod in the extending direction is incorporated between the spring seat provided on the cylinder and the bottom surface of the cylinder, and a reservoir chamber is provided between the inner circumference of the cylinder and the outer circumference of the valve sleeve. Forms an oil passage communicating the lower portion of the reservoir chamber and the lower portion of the pressure chamber, and closes in the lower end portion of the valve sleeve when the pressure of the pressure chamber becomes higher than the pressure in the reservoir chamber. Provided with a first check valve that shuts off the communication of the pressure chamber, and when the pushing force is applied to the rod, the first check valve is closed to allow the oil in the pressure chamber to flow in a minute amount. In hydraulic auto-tensioner which is adapted to buffer the pushing force exerted on the rod by a hydraulic damper effect of the pressure chamber of the oil by leakage into the reservoir chamber from the flow path,
The leak flow path includes a first leak gap and a second leak gap having a larger flow path resistance than the first leak gap, and the rod has a communication path that connects the first leak gap and the pressure chamber. And the communication path can be opened and closed by a second check valve whose set pressure is higher than that of the first check valve .
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 large leak gap is the first leak gap, the small leak gap is the second leak gap, and the rod is provided with a communication path that connects the first leak gap and the pressure chamber. A hydraulic auto tensioner incorporating the second check valve.

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