JP2009257412A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic automatic tensioner capable of preventing intrusion of a foreign material from an open part of a vent. <P>SOLUTION: A sleeve 13 is provided in a cylinder 11, and a lower end of a rod 14 is slidably inserted into the sleeve 13 to form a pressure chamber 15 inside the sleeve 13, and pushing force of a return spring 19 is applied to a spring seat 18 provided in an upper part of the rod. A bellows 22 is installed between the periphery of the spring seat and an upper part of the cylinder to form a reservoir chamber 23 between the cylinder and the sleeve. A first check valve 25 is provided in a first oil passage 24 communicating the reservoir chamber and the pressure chamber with each other, and when the cylinder is loaded with pushing force, a hydraulic fluid inside the pressure chamber buffers the pushing force. A vent fitting hole 42 and a ventilation passage 43 are provided in the spring seat, and a vent 44 is incorporated in the vent fitting hole. The pressure inside the reservoir chamber is changed to make the outside air flow into the reservoir chamber or to make the air inside the reservoir chamber flow out. A labyrinth 49 is formed in the ventilation passage to prevent a flow of foreign materials into the reservoir chamber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In belt transmissions that transmit engine crankshaft rotation to various automotive accessories, a swingable pulley arm that supports a tension pulley is provided on the slack side of the belt, and the adjustment force of a hydraulic auto tensioner is applied to the pulley arm. The tension pulley urges the pulley arm in the direction in which the belt is pressed, so that the belt tension is kept constant.

  As a hydraulic auto tensioner used in the belt transmission device as described above, the one described in Patent Document 1 has been conventionally known. In this hydraulic auto tensioner, the lower part of the rod is slidably inserted into the sleeve rising from the inner bottom surface of the bottomed cylinder filled with hydraulic oil to form a pressure chamber in the sleeve, which is provided at the upper part of the rod. A return spring is incorporated between the spring seat and the bottom surface of the cylinder to urge the rod and the cylinder in the extending direction.

  Further, both ends of the bellows having elasticity are fitted to the outer periphery of the spring seat and the upper outer periphery of the cylinder to form a reservoir chamber sealed between the cylinder and the sleeve, and a passage between the lower portion of the reservoir chamber and the pressure chamber is formed. The check valve is closed when the pushing force in the direction of contraction from the belt to the cylinder and rod is applied via the tension pulley and pulley arm, and the check valve is closed and sealed in the pressure chamber. The pushing force is buffered by an oil damper action.

  By the way, in the above hydraulic auto tensioner, when the cylinder and the rod are relatively expanded, the volume of the reservoir chamber is increased and the pressure is decreased, and conversely, the cylinder and the rod are relatively contracted. Because the volume of the reservoir chamber decreases and the pressure increases, the bellows contracts or expands due to pressure fluctuations in the reservoir chamber, and a pulling force is applied to the bellows during the contraction, and the bellows contracts or expands. There is a possibility that a gap is formed and the internal hydraulic fluid is ejected.

  In order to eliminate such inconvenience, in the hydraulic auto tensioner described in Patent Document 2, an air passage that communicates the reservoir chamber with the outside is provided in the spring seat, a vent is incorporated in the air passage, The vent is opened when the pressure decreases due to the volume decrease or when the pressure increases due to the volume increase, so that the pressure in the reservoir chamber is kept constant to prevent the bellows from coming off or the hydraulic oil from being ejected.

Special Table 2000-504395 JP 2007-315562 A

  By the way, in the conventional hydraulic auto tensioner described in Patent Document 2, when external air is inhaled by opening the vent, foreign matter such as dust and water enters and mixes with the hydraulic oil in the reservoir chamber. there is a possibility.

  Here, if foreign matter enters the hydraulic fluid, the check valve will not close due to the foreign matter being caught, or the relative expansion and contraction of the cylinder and rod will be hindered and the function of the hydraulic auto tensioner will not be able to be exerted. The problem occurs.

  An object of the present invention is to provide a hydraulic auto tensioner capable of preventing foreign matter from entering a reservoir chamber from an opening portion of a vent.

  In order to solve the above-mentioned problems, in the present invention, a sleeve rising from the inner bottom surface is provided in a cylinder having a closed end at the lower part and filled with hydraulic oil, and the lower end of the rod is provided in the sleeve. A pressure chamber is formed in the sleeve by slidably inserting the portion, and an elastic force of a return spring is applied to a spring seat provided on the upper portion of the rod to bias the cylinder and the rod, The outer periphery of the spring seat and the upper outer periphery of the cylinder are fitted with elastic elastic bellows at both ends to form a reservoir chamber sealed between the cylinder and the sleeve. A first oil passage that communicates with the chamber, and a check valve that closes the first oil passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber is provided in the first oil passage; A second oil passage communicating with the server chamber is provided, and the spring seat has a vent attachment hole that opens on the outer peripheral surface thereof, a closed end of the vent attachment hole, and air formed on the hydraulic oil surface of the reservoir chamber A vent passage that communicates with the reservoir is provided, and a vent that communicates between the reservoir chamber and the outside is built in the vent mounting hole when the pressure in the reservoir chamber drops below the set pressure or exceeds the set pressure. In the hydraulic auto tensioner, a configuration in which a labyrinth is provided in the air passage is adopted.

  In the hydraulic auto tensioner configured as described above, when the cylinder and the rod are relatively stretched and the pressure is reduced due to the increase in the volume of the reservoir chamber, the vent is opened, and external air flows from the vent mounting hole to the ventilation path. It flows into the reservoir chamber. For this reason, the pressure in the reservoir chamber is kept constant, and the bellows is prevented from coming off.

  Here, even when foreign matter such as dust enters the air passage along with the external air when the external air is inhaled into the reservoir chamber, the foreign matter is stored in the reservoir by the labyrinth because the labyrinth is provided in the air passage. Intrusion into the room is prevented. As a result, it is possible to suppress a decrease in function due to the entry of foreign matter.

Here, the labyrinth may consist of a small-diameter hole, but if the small-diameter hole is formed in the spring seat itself by drilling, the machining is difficult and the cost is increased. When the labyrinth is formed, if the following configuration is adopted, the labyrinth can be easily formed, and the processing cost can be reduced.
(I) A female screw is formed on the inner periphery of the air passage, a screw member is screw-engaged with the female screw, and a screw gap formed in the screw engaging portion is defined as a labyrinth.
(II) A porous body is press-fitted into an air passage, and the open cells of the porous body are used as a labyrinth.
(III) A screw member is press-fitted into the air passage, and the screw groove of the screw member is used as a labyrinth.
(IV) A female thread is formed in the air passage, a cylindrical member is press-fitted into the inner diameter of the female thread, and the thread groove of the female thread is used as a labyrinth.

  Here, in a belt transmission device that drives an auxiliary machine by driving an engine, a motor / generator is mounted, and when the vehicle is stopped, the engine is stopped and the motor / generator is switched to a driving operation to drive the auxiliary machine. There is one for idle stop compatible cars.

  In the belt transmission for an idle stop compatible vehicle as described above, a tension pulley is provided on the tension side of the belt driven by the motor / generator (the slack side of the belt driven by the engine), and a hydraulic auto tensioner is provided on the tension pulley. The tension of the belt is applied to keep the belt tension constant.

  In this case, the spring seat is provided with a valve mounting hole that opens at the outer peripheral surface thereof, and a third oil passage that communicates the second oil passage and the reservoir chamber via the valve mounting hole. When the pressure in the chamber becomes higher than the pressure in the pressure chamber, the third oil passage is closed, and a second check valve that is locked in a closed state by a solenoid supported on the outer periphery of the spring seat is provided. 2. By holding the check valve in the closed state, relative expansion and contraction of the cylinder and the rod can be prevented, and the tension pulley can be held in a fixed position.

  For this reason, when the engine is driven by the motor / generator, the tension pulley is held at a fixed position by the operation of the solenoid, so that the belt can be prevented from slipping and the engine can be started stably.

  Also, by arranging the vent mounting hole at a position opposite to the valve mounting hole, it is possible to ensure a space for forming the vent mounting hole on the outer periphery of the spring seat, and when the hydraulic auto tensioner is stored sideways. The labyrinth can prevent the hydraulic oil in the reservoir chamber from flowing into the vent mounting hole, and can prevent the hydraulic oil from leaking to the outside.

  As described above, in the present invention, by providing a labyrinth in the ventilation path that communicates the outside and the reservoir chamber via the vent attachment hole, the vent incorporated in the vent attachment hole is opened and the external When the air flows into the reservoir chamber, foreign substances such as dust can be prevented from entering the reservoir chamber together with the external air, and a hydraulic auto tensioner with little deterioration in function can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a belt transmission device for an idle stop-compatible vehicle in which an auxiliary machine is driven by a motor / generator when the engine is stopped. In this belt transmission, a belt 7 is stretched over a pulley 2 attached to a crankshaft 1 of an engine, a pulley 4 attached to a rotating shaft 3 of a motor / generator, and a pulley 6 attached to a rotating shaft 5 of an auxiliary machine, The motor / generator and auxiliary machine switched to the power generation operation by the engine are driven, and the engine and auxiliary machine are driven by the motor / generator switched to the starting operation.

  A tension pulley 8 is brought into contact with a belt that is on the slack side when the engine is driven, and a pulley arm 9 that supports the tension pulley 8 is supported so as to be swingable about a shaft 10. A hydraulic auto-tensioner is supported on the pulley arm 9. The tension pulley 8 is pressed against the belt 7 by the adjustment force A.

  FIG. 2 shows a hydraulic auto tensioner A. This hydraulic auto tensioner A has a cylinder 11 whose lower portion is closed, and a lower end portion of a sleeve 13 is press-fitted into a sleeve fitting hole 12 formed on the inner bottom surface of the cylinder 11. A lower portion of the rod 14 is slidably inserted into the sleeve 13, and a pressure chamber 15 is provided in the sleeve 13 by the insertion of the rod 14.

  The lower end portion of the rod 14 is a small-diameter portion 14 a, and a diaphragm 16 having a minute gap is formed between the outer diameter surface of the small-diameter portion 14 a and the inner diameter surface of the sleeve 13. Further, the rod 14 is formed with a ring groove 17 at a position slightly offset from the small diameter portion 14 a, and the O-ring 17 a fitted in the ring groove 17 is in elastic contact with the inner diameter surface of the sleeve 13.

  A spring seat 18 is fixed to an upper end portion of the rod 14 located outside the cylinder 11, and a return spring 19 assembled between the spring seat 18 and the inner bottom surface of the cylinder 11 causes the cylinder 11 and the rod 14 to be relatively relative to each other. It is energized in the extending direction.

  A connecting piece 20 connected to the engine block shown in FIG. 1 is provided at the upper end of the spring seat 18. The spring seat 18 is integrally provided with a cylindrical portion 21 that covers the upper portion of the return spring 19, and a bellows 22 is mounted between the cylindrical portion 21 and the upper portion of the cylinder 11.

  The bellows 22 is formed with an upward reversing portion 22a at the center in the length direction and a downward reversing portion 22b outside the upward reversing portion 22a, and a small-diameter cylindrical portion 22c continuously connected to the upward reversing portion 22a. It is fitted and secured to the portion 21.

  Further, the end portion of the large-diameter cylindrical portion 22d connected to the downward inversion portion 22b is fitted to the upper outer periphery of the cylinder 11 and is prevented from being removed.

  By mounting the bellows 22, the upper opening of the cylinder 11 is closed to prevent leakage of hydraulic oil filled therein. In addition, when the bellows 22 is attached, a sealed reservoir chamber 23 is formed between the cylinder 11 and the sleeve 13, and an air reservoir 23 a is provided on the hydraulic oil surface of the reservoir chamber 23.

  The reservoir chamber 23 and the pressure chamber 15 communicate with each other through a first oil passage 24 formed between the fitting surfaces of the sleeve fitting hole 12 and the sleeve 13, and the end of the first oil passage 24 on the pressure chamber 15 side. The provided first check valve 25 closes the first oil passage 24 when the pressure in the pressure chamber 15 becomes higher than the pressure in the reservoir chamber 23.

  A second oil passage 26 is formed in the rod 14. The lower end of the second oil passage 26 opens at a position opposite to the outer periphery of the small diameter portion 14 a and communicates with the pressure chamber 15 through the throttle 16, and the upper end opens at the upper surface of the rod 14.

  The spring seat 18 has a valve mounting hole 27 that opens on the outer peripheral surface thereof, and a third oil passage 28 that communicates the second oil passage 26 and the air reservoir 23a of the reservoir chamber 23 via the valve mounting hole 27. Is formed.

  As shown in FIGS. 2 and 3, a solenoid valve unit 30 is connected to the valve mounting hole 27. The solenoid valve unit 30 has a housing 31, and the housing 31 is provided with a connecting cylinder 32 that is fitted into the valve mounting hole 27.

  Two seal rings 33 are attached to the outer periphery of the connection tube 32 at intervals in the axial direction, and each seal ring 33 is in elastic contact with the inner diameter surface of the valve attachment hole 27 so that the valve attachment hole 27 and the connection tube 32 are in contact with each other. Seals between mating surfaces.

  An oil passage hole 34 that communicates the inside of the connection cylinder 32 with the third oil passage 28 is formed at the tip of the connection cylinder 32. The oil passage hole 34 includes an annular groove 34 a formed between the two seal rings 33, and a plurality of radial holes 34 b that penetrate from the groove bottom surface of the annular groove 34 a to the inner diameter surface of the connection cylinder 32.

  A second check valve 35 and a solenoid 36 that locks the second check valve 35 in a closed state are incorporated in the housing 31. The second check valve 35 includes a valve seat 37 that is press-fitted into the distal end portion of the connection cylinder 32, a rod 39 that is provided so as to be movable back and forth with respect to a valve hole 38 formed in the valve seat 37, A hemispherical valve body 40 held at the tip and a spring 41 that urges the rod 39 in a direction in which the valve body 40 closes the valve hole 38, and the outer diameter surface of the rod 39 and the connecting cylinder A gap is provided between the 32 inner diameter surfaces.

When the pressure in the second oil passage 26 becomes higher than the pressure in the reservoir chamber 23 by a set pressure determined by the pressing force of the spring 41, the second check valve 35 closes the valve hole 38. ing.
When the solenoid 36 is energized, the rod 39 is locked while the valve body 40 closes the valve hole 38.

  As shown in FIG. 3, the spring seat 18 has a vent mounting hole 42 that is disposed at a position opposed to the valve mounting hole 27 and opens on the outer periphery of the spring seat 18, and a closed end portion of the vent mounting hole 42 is connected to the reservoir chamber. A vent passage 43 communicating with the air reservoir 23a is formed, and a vent 44 called an automatic air valve is incorporated in the vent attachment hole 42.

  As shown in FIG. 4, the vent 44 has a cap shape in which a valve plate 46 is provided at one end of a cylindrical portion 45 fitted in the vent mounting hole 42, and a bulge formed at the center of the valve plate 46. The slit 46 is provided in the portion 46 a, and the whole is formed of a rubber material, and the outer periphery of the cylindrical portion 45 and the valve plate 46 is reinforced by a metal ring 48.

  Here, examples of the rubber material include nitrilo rubber, nitrilo rubber to which hydrogen is added, acrylic rubber, and fluorine rubber.

  In the vent 44 having the above-described configuration, the set pressure can be adjusted by changing the hardness of the rubber material, the thickness of the bulging portion 46a, and the width of the slit 47, and the reservoir chamber 23 When the internal pressure becomes higher or lower than the set pressure, the slit 47 is opened.

  As shown in FIG. 3, a labyrinth 49 is provided in the air passage 43. In forming the labyrinth 49, in FIG. 3, a female screw 50 is formed on the inner periphery of the air passage 43, a screw member 51 is screw-engaged with the female screw 50, and the female screw 50 and the screw engaging portion of the screw member 51 are formed. The labyrinth is a screw gap.

  5 (I) to (III) show other examples of the labyrinth 49. In FIG. 5I, a porous body 52 such as a sintered metal is press-fitted into the inner periphery of the air passage 43, and the open cell of the porous body 52 is used as a labyrinth 49.

  In FIG. 5 (II), the screw member 53 is press-fitted into the air passage 43, and the screw groove of the screw member 53 is a labyrinth. 5 (III), a female screw 54 is formed on the inner periphery of the air passage 43, a cylindrical member 55 is press-fitted into the inner diameter of the female screw 54, and the thread groove of the female screw 54 is used as a labyrinth.

  The hydraulic auto tensioner shown in the embodiment has the above-described configuration. When adjusting the tension of the accessory driving belt 7 shown in FIG. 1, the connecting piece 11 a provided at the closed end of the cylinder 11 is connected to the pulley arm 9. In addition, the connecting piece 20 of the spring seat 18 is connected to the engine block, and an adjustment force is applied to the pulley arm 9.

  Here, when the engine and the auxiliary machine are driven by the motor / generator, the solenoid 36 shown in FIG. 2 is energized. On the other hand, the energization of the solenoid 36 is cut off during normal driving by driving the engine.

  Now, when the solenoid 36 is energized, the valve body 40 of the second check valve 35 is locked at the closed position where the valve hole 38 is closed.

  For this reason, even if the engine is driven by the motor / generator to increase the tension of the belt 7 and the pushing force is applied from the belt 7 to the cylinder 11 through the pulley arm 9 and the pressure in the pressure chamber 15 is increased, The second oil passage 26 is in a state where communication with the reservoir chamber 23 is blocked by the second check valve 35, and the first oil passage 24 is closed by the first check valve 25, so that the operation in the pressure chamber 15 is performed. The oil does not flow toward the reservoir chamber 23, and the hydraulic oil enclosed in the pressure chamber 15 prevents the cylinder 11 and the rod 14 from moving in the direction of relative contraction, and the tension pulley 8 is in a fixed position. Fixed.

  Thus, since the tension pulley 8 can be fixed at a fixed position by energizing the solenoid 36, the belt 7 can be prevented from slipping and the engine can be started stably.

  After the engine is started by the motor / generator, when the solenoid 36 is de-energized during normal running by driving the engine, the second check valve 35 is unlocked and exhibits a check function.

  In the unlocked state of the second check valve 35, when the tension of the belt 7 changes due to load fluctuation of the auxiliary machine and the tension of the belt 7 becomes weak, the cylinder 11 and the rod 14 are extended by the pressing of the return spring 19 And the slack of the belt 7 is absorbed.

  Here, when the cylinder 11 and the rod 14 move relative to each other in the extending direction, the pressure in the pressure chamber 15 becomes lower than the pressure in the reservoir chamber 23, so the first check valve 25 opens the first oil passage 24. . Therefore, the hydraulic oil in the reservoir chamber 23 flows smoothly from the first oil passage 24 into the pressure chamber 15, and the cylinder 11 and the rod 14 smoothly move relative to each other in the extending direction to immediately absorb the slack of the belt 7. .

  On the other hand, when the tension of the belt 7 is increased, a pushing force in a direction of contracting the cylinder 11 and the rod 14 of the hydraulic auto tensioner is applied from the belt 7. At this time, since the pressure in the pressure chamber 15 becomes higher than the pressure in the reservoir chamber 23, the first check valve 25 closes the first oil passage 24.

  Further, the hydraulic oil in the pressure chamber 15 flows from the throttle 16 to the second oil passage 26 and flows into the reservoir chamber 23, and a hydraulic damper force is generated by the flow resistance when flowing in the throttle 16, and the hydraulic pressure is increased. The above-mentioned pushing force applied to the hydraulic auto tensioner A is buffered by the damper force, and the cylinder 11 and the rod 14 are slowly moved relative to each other in a direction in which the pushing force and the elastic force of the return spring 19 are contracted. Moving.

  Here, the belt 7 whose tension is adjusted by the hydraulic auto tensioner A is largely slackened when the engine is started. At that time, the cylinder 11 and the rod 14 of the hydraulic auto tensioner A rapidly move relative to each other in the extending direction, the volume of the reservoir chamber 23 increases, and conversely, the pressure rapidly decreases.

  At this time, as shown in FIG. 2, the slit 47 of the vent 44 is opened, and external air flows into the air reservoir 23a of the reservoir chamber 23, and the pressure in the reservoir chamber 23 is kept constant by the inflow of the air. Will be retained.

  For this reason, a tensile force is not applied to the bellows 22, and there is no inconvenience that the bellows 22 comes off. Here, when external air flows into the reservoir chamber 23, foreign matter such as dust may enter the air passage 43 together with the external air. At this time, since the labyrinth 49 is provided in the ventilation path 43, the flow of foreign matter is inhibited by the labyrinth 49 and is prevented from flowing into the reservoir chamber 23.

  Further, the tension of the belt 7 increases when the engine and the auxiliary machine are driven by the motor / generator switched to the operation. At that time, the cylinder 11 and the rod 14 of the hydraulic auto tensioner A rapidly move relative to each other in the contracting direction, the volume of the reservoir chamber 23 decreases, and conversely, the pressure rapidly increases.

  At this time, as shown in FIG. 2, the slit 47 of the vent 44 is opened, and the air in the air reservoir 23 a of the reservoir chamber 23 flows from the labyrinth 49 to the ventilation path 43 and flows out from the opened slit 47 to the outside. The pressure in the reservoir chamber 23 is kept constant by the outflow of the air.

  Thus, the slit 47 of the vent 44 is opened when the pressure rises due to the volume reduction of the reservoir chamber 23, the air in the air reservoir 23a flows out, and the pressure in the reservoir chamber 23 is kept constant. There is no inconvenience that the bellows 22 expands and a gap is formed in the fitting portion, and it is possible to reliably prevent the hydraulic oil from being ejected.

Schematic of a belt transmission device incorporating a hydraulic auto tensioner according to the present invention 1 is a longitudinal front view of the hydraulic auto tensioner shown in FIG. Sectional drawing which expands and shows the spring seat part of FIG. Partially cutaway perspective view of vent (I) thru | or (III) is sectional drawing which shows the other example of a labyrinth

Explanation of symbols

11 Cylinder 13 Sleeve 14 Rod 15 Pressure chamber 18 Spring seat 19 Return spring 22 Bellows 23 Reservoir chamber 23a Air reservoir 24 First oil passage 25 First check valve 26 Second oil passage 27 Valve mounting hole 28 Third oil passage 35 Second Check valve 36 Solenoid 42 Vent mounting hole 43 Ventilation path 44 Vent 49 Labyrinth 50 Female screw 51 Screw member 52 Porous body 53 Screw member 54 Female screw 55 Cylindrical member

Claims (6)

A cylinder that has a closed end at the bottom and is filled with hydraulic oil inside is provided with a sleeve that rises from its inner bottom surface. The lower end of the rod is slidably inserted into the sleeve, and the pressure chamber is inserted into the sleeve. Forming an elastic force of a return spring to a spring seat provided on the upper part of the rod, and urging the cylinder and the rod in an extending direction,
A reservoir chamber sealed between the cylinder and the sleeve is formed by fitting both ends of an elastic bellows having elasticity to the outer periphery of the spring seat and the upper outer periphery of the cylinder, and at the bottom of the cylinder, the reservoir chamber and A first oil passage that communicates with the pressure chamber is provided, and a check valve that closes the first oil passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber is provided in the first oil passage, and the pressure chamber and the reservoir chamber are provided on the rod. A second oil passage that communicates is provided, and the spring seat has a vent mounting hole that opens on the outer peripheral surface thereof, a closed end of the vent mounting hole, and an air reservoir formed on the hydraulic oil surface of the reservoir chamber. A hydraulic system that incorporates a vent that communicates with the outside of the reservoir chamber when the pressure in the reservoir chamber drops below the set pressure or exceeds the set pressure. Oh In the tensioner,
A hydraulic auto tensioner, wherein a labyrinth is provided in the air passage.   The hydraulic auto tensioner according to claim 1, wherein a female screw is formed on an inner periphery of the air passage, a screw member is screw-engaged with the female screw, and a screw gap formed in the screw engaging portion is a labyrinth.   The hydraulic auto tensioner according to claim 1, wherein a porous body is press-fitted into the air passage, and open cells of the porous body are used as a labyrinth.   The hydraulic auto tensioner according to claim 1, wherein a screw member is press-fitted into the air passage, and a screw groove of the screw member is used as a labyrinth.   The hydraulic auto tensioner according to claim 1, wherein a female screw is formed in the air passage, a cylindrical member is press-fitted into an inner diameter of the female screw, and a thread groove of the female screw is used as a labyrinth.   The spring seat is provided with a valve mounting hole that opens on the outer peripheral surface thereof, and a third oil passage that communicates the second oil passage with the reservoir chamber via the valve mounting hole. When the pressure is higher than the pressure in the pressure chamber, a second check valve is provided that closes the third oil passage and is locked in a closed state by a solenoid supported on the outer periphery of the spring seat. The hydraulic auto tensioner according to any one of claims 1 to 5, wherein a hole is disposed.

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