WO2017043642A1

WO2017043642A1 - Hydraulic auto tensioner

Info

Publication number: WO2017043642A1
Application number: PCT/JP2016/076662
Authority: WO
Inventors: 愛作里村; 北野　聡; 雄太望月; 洋生森本
Original assignee: Ntn株式会社
Priority date: 2015-09-10
Filing date: 2016-09-09
Publication date: 2017-03-16
Also published as: JP6537415B2; JP2017053447A

Abstract

During normal engine operations, oil inside a pressurized chamber (15) is leaked from a first leak gap (31) to a reservoir chamber (24) when a pressing force from a belt is applied to a cylinder (10) and a spring seat (16) in the contracting direction. When starting an engine with a starter generator, a plunger (28) is raised by pressure inside the pressurized chamber (15), the first leak gap (31) is closed by a second check valve (35) provided between the plunger (28) and a rod (14), and oil inside the pressurized chamber (15) leaks to the reservoir chamber (24) from a second leak gap (32) with a large flow resistance. A valve sheet (35a) and a sheet face (35b) of the second check valve (35) have different surface hardness, thereby ensuring the second check valve (35) to be completely closed.

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.

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 to reduce carbon dioxide emissions and fuel consumption. Engine has been proposed.

FIGS. 9A and 9B show an engine belt transmission equipped with an ISG idle stop mechanism that achieves both engine auxiliary drive and engine start. The crankshaft pulley P ₁ attached to the crankshaft 51 and the ISG a starter-generator pulley P ₂ attached to a rotating shaft of the starter generator 52, 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, the normal operation of the engine when, as shown in FIG. 9A, drives 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. 9B, it rotates the crankshaft pulley P ₁ by rotation in the direction indicated by the arrow of the starter-generator pulley P _2, the starter generator 52 I try 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 the hydraulic auto tensioner A, one described in Patent Document 1 below has been conventionally known. In this hydraulic auto tensioner, a lower end portion of a rod is slidably inserted into a valve sleeve erected 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 has a connecting piece provided on the upper surface of the spring seat rotatably connected to the engine block E shown in FIG. 9A, and a connecting piece provided on the lower surface of the cylinder is connected to the pulley arm 56. 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 placed between the sliding surface of the valve sleeve and the rod. The fluid is caused to flow through the formed leak gap, and a hydraulic damper force is generated in the pressure chamber by the viscous resistance of the oil at the time of the flow to buffer the pushing force.

JP 2009-275757 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 an appropriate tension to the belt during normal operation of the engine and when starting the engine with the starter generator, and to ensure slip of the belt when starting the engine with the starter generator. It is an object of the present invention to provide a hydraulic auto tensioner that can be prevented.

In order to solve the above-described problems, in the present invention, a valve sleeve is erected on the bottom surface of the bottomed cylinder, and the lower end of the rod is slidably inserted into the valve sleeve to be inserted into the valve sleeve. A pressure chamber is provided, and a return spring that urges the spring seat and the cylinder in the direction of extension is incorporated between the spring seat provided on the top of the rod and the bottom surface of the cylinder, and between the inner circumference of the cylinder and the outer circumference of the valve sleeve. An oil passage that communicates the lower portion of the formed reservoir chamber and the lower portion of the pressure chamber is formed, and the pressure chamber and the oil passage are closed when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber in the lower end portion of the valve sleeve. Provided with a first check valve that shuts off the communication, and when a pushing force is applied to the rod through the spring seat, the first check valve is closed and oil in the pressure chamber is discharged. In a hydraulic auto tensioner that leaks into the server chamber and damps the pushing force applied to the rod by the hydraulic damper action of the oil in the pressure chamber, it slides between the outer diameter surface of the rod and the inner diameter surface of the valve sleeve. A movable cylindrical plunger is fitted, a first leak gap is provided between the plunger and the sliding surface of the rod, and the first leak gap flows between the plunger and the sliding surface of the valve sleeve. A second leak gap having a large path resistance is provided, and a second check valve is provided between the rod and the plunger to close the first leak gap when the plunger rises due to a pressure rise in the pressure chamber. A valve spring that urges the rod toward a stopper for stopper provided at the lower end of the rod, and a valve seat of the second check valve And it had adopted a configuration in which with a difference in the surface hardness of the seat surface.

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 lower end of the cylinder is connected to the pulley arm, and the tension pulley supported by the pulley arm urges the pulley arm in the direction to press the belt between the crankshaft pulley and the starter / generator pulley, and tensions the belt. 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. Thus, the first check valve is closed, and the oil in the pressure chamber leaks from the first leak gap having 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 gap. 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 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 plunger is raised, the second check valve is closed, and the first leak gap is closed.

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 larger than the flow resistance of the first leak gap, the pressure drop in the pressure chamber is small, and the push of the rod is suppressed by the hydraulic damper action in the pressure chamber, so that the belt is connected to the crankshaft. The belt tension required to drive the belt is maintained, and slippage between the belt and the pulley is prevented.

Here, if the second check valve is not completely closed, the oil leaks from the first leak gap having a small flow path resistance, so that the damper force becomes small and belt slip may occur.

However, in the present invention, since the surface hardness of the valve seat and the seat surface of the second check valve is different, the second check valve is caused by the elastic deformation of the contact portion in the initial use of the product (hydraulic auto tensioner). The closure can be complete. On the other hand, when the second check valve is repeatedly opened and closed, a plastic deformation occurs at the contact portion between the valve seat and the seat surface, and a conforming effect is obtained, and the second check valve is completely closed. can do. Therefore, the belt does not slip when the engine is started by driving the starter generator.

Here, as the second check valve, a valve seat is formed at the lower end of the large-diameter shaft portion located outside from the upper end of the plunger of the rod, and a seat surface that can be seated on the valve seat is provided on the upper inner diameter surface of the plunger. It is possible to adopt a configuration consisting of different configurations.

If either the valve seat or the seat surface of the second check valve is a convex curved surface and the other is a tapered flat surface, the contact between the valve seat and the seat surface can be a line contact. Plastic deformation is likely to occur, and a good conforming effect can be obtained.

Further, by making the member on the side of the convex curved surface high in hardness, the member on the low hardness side can easily follow the convex surface of high hardness, and a better conforming effect can be obtained.

In increasing the hardness of the convex member, it can be achieved by performing a surface hardening treatment. As the surface hardening treatment, diamond-like carbon treatment (DLC treatment), hard film coating treatment, shot peening, or WPC treatment can be employed.

In the hydraulic auto tensioner according to the present invention, a coil spring, a disc spring, a wave washer, and a wave spring may be employed as a valve spring that biases the plunger toward a retaining stopper provided at the lower end of the rod. it can.

In the present invention, as described above, during normal operation of the engine, oil in the pressure chamber leaks into the reservoir chamber from the first leak gap having a small flow path resistance, while at the start of the engine with the starter generator, Since the oil leaks from the second leak gap having a large flow path resistance into the reservoir chamber, 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.

In addition, since the surface hardness of the valve seat and the seat surface of the second check valve is made different, the second check valve should be completely closed by the elastic deformation of the contact portion at the initial stage of use of the product. In addition, when used, the second check valve can be completely closed by repeating the opening and closing of the second check valve, and the closing of the second check valve can be completed. It is possible to reliably prevent belt slip when starting the engine.

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 gap of FIG. 1, and the 2nd leak gap Sectional drawing which shows the leak state of the oil from the 2nd leak clearance Sectional drawing which expands and shows the 2nd check valve part of FIG. Sectional view showing the familiarity of the seat surface Sectional view showing another example of valve spring Sectional view showing still another example of valve spring Sectional view showing still another example of valve spring The graph which shows the measurement example of the reaction force characteristic of embodiment and the conventional hydraulic auto tensioner Front view showing the engine's belt drive equipped with an idle stop mechanism and showing the engine's normal operating condition Front view showing the starter / generator starting state of the engine with the idle stop mechanism.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the cylinder 10 has a bottom portion, and a connecting piece 11 connected to the pulley arm 56 of FIGS. 9A and 9B is provided on the bottom surface of the bottom portion.

The connecting piece 11 is provided with a shaft insertion hole 11a penetrating from one side surface to the other side surface, a cylindrical fulcrum shaft 11b and a slide bearing 11c for rotatably supporting the fulcrum shaft 11b in the shaft insertion hole 11a. The fulcrum shaft 11b is fixed by tightening a bolt that is inserted into the fulcrum shaft 11b and screw-engaged with the pulley arm 56, and the connecting piece 11 is rotatably attached to the pulley arm 56.

A valve sleeve fitting hole 12 is provided on the bottom surface of the cylinder 10, and a lower end portion of a steel valve sleeve 13 is press-fitted into the valve sleeve fitting hole 12. The lower portion of the rod 14 is slidably inserted into the valve sleeve 13, and a pressure chamber 15 is provided in the valve sleeve 13 below the rod 14 by the insertion of the rod 14.

A spring seat 16 is provided at an upper end portion of the rod 14 located outside the cylinder 10, and a return spring 17 incorporated between the spring seat 16 and the bottom surface of the cylinder 10 extends relative to the cylinder 10 and the rod 14. It is energizing in the direction to do.

A connecting piece 18 connected to the engine block is provided at the upper end of the spring seat 16. The connecting piece 18 is formed with a sleeve insertion hole 18a penetrating from one side surface to the other side surface, and a sleeve 18b and a slide bearing 18c for rotatably supporting the sleeve 18b are incorporated in the sleeve insertion hole 18a. The connecting piece 18 is rotatably connected to the engine block by a bolt inserted into the sleeve 18b.

The spring seat 16 is formed of a molded product, and a cylindrical dust cover 20 that covers the upper outer periphery of the cylinder 10 and a cylindrical spring cover 21 that covers the upper part of the return spring 17 are molded at the same time.

Here, the spring seat 16 may be an aluminum die-cast molded product or a resin molded product such as a thermosetting resin.

The entire outer periphery of the spring cover 21 is covered with a cylindrical body 22 that is insert-molded when the spring seat 16 is molded. The cylinder 22 is made of a press-formed product of a steel plate.

An oil seal 23 as a seal member is incorporated in the upper opening of the cylinder 10, and the inner periphery of the oil seal 23 is in elastic contact with the outer peripheral surface of the cylinder 22 to close the upper opening of the cylinder 10. 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 23, a sealed reservoir chamber 24 is formed between the cylinder 10 and the valve sleeve 13. The reservoir chamber 24 and the pressure chamber 15 are composed of an oil passage 25 formed between the fitting surfaces of the valve sleeve fitting hole 12 and the valve sleeve 13 and a circular recess formed in the center of the bottom surface of the valve sleeve fitting hole 12. Communication is made through an oil sump 26.

A first check valve 27 is incorporated in the lower end portion of the valve sleeve 13. The first check valve 27 includes a steel check ball 27c that opens and closes the valve hole 27b of the valve seat 27a press-fitted into the lower end portion of the valve sleeve 13 from the pressure chamber 15, and the check ball 27c faces the valve hole 27b. And a retainer 27e for restricting the opening / closing amount of the check ball 27c.

In the first check valve 27, when the pressure in the pressure chamber 15 becomes higher than the pressure in the reservoir chamber 24, the check ball 27c closes the valve hole 27b, and the communication between the pressure chamber 15 and the oil passage 25 is cut off. The oil in 15 is prevented from flowing into the reservoir chamber 24 through the oil passage 25.

1 and 2, a cylindrical plunger 28 is fitted to the rod 14. The plunger 28 is slidable along the outer diameter surface of the rod 14 and a small inner diameter surface 13 a formed on the inner periphery of the valve sleeve 13, and is cylindrical between the sliding surface of the rod 14 and the plunger 28. A first leak gap 31 is formed. A cylindrical second leak gap 32 is provided between the sliding surfaces of the plunger 28 and the valve sleeve 13.

The gap amount of the second leak gap 32 is smaller than the gap amount of the first leak gap 31, and the flow path resistance of the second leak gap 32 is larger than the flow path resistance of the first leak gap 31 due to the difference in the gap amount. Yes.

Each of the first leak gap 31 and the second leak gap 32 causes a hydraulic damper action in the pressure chamber 15 due to viscous resistance when oil in the pressure chamber 15 leaks along the

leak gaps

31 and 32. It is like that.

The first leak gap 31 is set to a size capable of absorbing fluctuations in the tension of the belt 54 during normal operation of the engine shown in FIG. 9A 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 14 is not pushed suddenly when the engine is started by driving the starter generator 52 shown in FIG. 9B.

As shown in FIG. 2, a stopper 34 for preventing the plunger 28 is provided at the lower end of the rod 14. Here, a retaining ring is employed as the stopper 34 and is attached to a ring groove 33 provided at the lower end of the rod 14.

Here, the stopper 34 formed of a retaining ring has a separation part 34a in a part in the circumferential direction, and the pressure chamber 15 and the first leak gap 31 are always in communication with each other via the separation part 34a.

Between the rod 14 and the plunger 28, there is provided a second check valve 35 that closes the first leak gap 31 when the pressure at the start of the engine is increased by driving the starter generator 52 (see FIGS. 9A and 9B). Yes.

The second check valve 35 is provided with a large-diameter shaft portion 14a at an upper portion located outside from the upper end of the plunger 28 of the rod 14, and a convex-curved valve seat 35a is provided at the lower end portion of the large-diameter shaft portion 14a. A seat surface 35b made of a tapered flat surface is formed on the upper inner diameter surface of the plunger 28. When the plunger 28 is raised by the pressure in the pressure chamber 15, the seat surface 35b is formed on the valve seat 35a as shown in FIG. The upper end opening of the first leak gap 31 is closed by being seated.

Here, the valve seat 35a formed on the large-diameter shaft portion 14a is subjected to surface hardening treatment to increase the strength, and the surface hardness thereof is harder than the surface hardness of the seat surface 35b of the plunger 28. Here, the DLC treatment is applied as the surface hardening treatment, but instead of the DLC treatment, a hard coating may be applied or shot peening may be applied.

As described above, when the surface hardness of the convex curved valve seat 35a is harder than the surface hardness of the flat seat surface 35b, as shown in FIG. 4A, the valve seat 35a and the seat surface 35b are initially used. Are brought into line contact, and the second check valve 35 can be completely closed by elastic deformation of the contact portion. On the other hand, when the second check valve 35 is used, the seat surface 35b undergoes plastic deformation due to repeated opening and closing, resulting in familiarity. As shown in FIG. 4B, the second check valve 35 comes into surface contact with the convex curved surface of the valve seat 35a. Thus, the second check valve 35 can be completely closed.

In FIG. 4A, the valve seat 35a has a convex curved surface and is harder than the surface hardness of the flat seat surface 35b. However, the seat surface 35b has a convex curved surface and the valve seat 35a has a tapered flat surface. May be made harder than the surface hardness of the valve seat 35a.

In the embodiment, the second check valve 35 is provided on the upper end side of the plunger 28. However, the second check valve 35 may be provided inside the plunger 28 or on the lower end side of the plunger 28. .

As shown in FIGS. 1 and 2, an outward flange 29 is provided on the upper portion of the plunger 28, and a valve spring 37 is incorporated between opposing surfaces of the flange 29 and the spring seat 16. The valve spring 37 urges the plunger 28 toward the above-described stopper 34 attached to the lower end portion of the rod 14.

As the valve spring 37, a coil spring is adopted in FIG. 2, but it may be a disc spring as shown in FIG. 5, or a wave washer as shown in FIG. Furthermore, as shown in FIG. 7, a wave spring may be used. When the corrugated washer is employed, a plain washer 38 is interposed between the overlapping portions of the plural corrugated washers 37 as shown in FIG.

As shown in FIG. 2, a ring-shaped tapered groove 39 having a large diameter at the lower portion is provided at the lower outer periphery of the plunger 28, and a retaining ring 40 is attached in the tapered groove 39. The retaining ring 40 has an outer diameter in a natural state larger than the outer diameter of the plunger 28, an outer peripheral portion is located outside the outer diameter surface of the plunger 28, and is formed on the inner peripheral upper portion of the valve sleeve 13. The plunger 28 and the rod 14 are prevented from coming out upward from the upper end of the valve sleeve 13 by abutting the lower end of the small-diameter inner diameter surface 13a with the step portion 13b.

The hydraulic auto tensioner shown in the embodiment has the above-described configuration. When the engine is installed in an auxiliary drive belt transmission for an engine equipped with the idle stop mechanism shown in FIGS. 9A and 9B, the closed end of the cylinder 10 is used. The connecting piece 11 provided on the connecting portion 11 is connected to the pulley arm 56, and the connecting piece 18 of the spring seat 16 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 17 is pressed. The cylinder 10 and the spring seat 16 are relatively moved in the extending direction, and the slack of the belt 54 is absorbed.

Here, when the cylinder 10 and the spring seat 16 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 24, so the first check valve 27 is opened. For this reason, the oil in the reservoir chamber 24 smoothly flows from the oil passage 25 through the oil reservoir 26 into the pressure chamber 15, and the cylinder 10 and the spring seat 16 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 to contract the cylinder 10 and the spring seat 16 of the hydraulic auto tensioner from the belt 54 is applied. At this time, since the pressure in the pressure chamber 15 becomes higher than the pressure in the reservoir chamber 24, the check ball 27c of the first check valve 27 closes the valve hole 27b.

Also, the oil in the pressure chamber 15 flows through the first leak gap 31 as shown by the arrow in FIG. 2, leaks from the upper end opening of the first leak gap 31 to the reservoir chamber 24 shown in FIG. A hydraulic damper force is generated in the pressure chamber 15 by the oil flowing through the one leak gap 31. The pushing force applied to the hydraulic auto tensioner is buffered by the hydraulic damper force.

At this time, since the first leak gap 31 is set to a size capable of absorbing the fluctuation in tension of the belt 54 during normal operation of the engine, the tension of the belt 54 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 52, the tension of the belt 54 is suddenly increased, the pushing force against the rod 14 acting via the spring seat 16 is increased, and the pressure in the pressure chamber 15 is rapidly increased. . At this time, the first check valve 27 is closed and the pressure in the pressure chamber 15 rises. When the pressure becomes higher than the elastic force of the valve spring 37, the plunger 28 rises against the elasticity of the valve spring 37. As shown in FIG. 3, the seat surface 35b is seated on the valve seat 35a, and the second check valve 35 is closed.

By closing the second check valve 35, the upper end opening of the first leak gap 31 is closed, and the oil in the pressure chamber 15 flows into the second leak gap 32 as shown by the arrows in FIG. Leak into the reservoir chamber 24.

At this time, since the flow path resistance of the second leak gap 32 is larger than the flow path resistance of the first leak gap 31, the oil in the pressure chamber 15 flows slowly in the second leak gap 32. For this reason, there is no sudden pressure drop in the pressure chamber 15, the pushing of the rod 14 is suppressed by the action of the hydraulic damper in the pressure chamber 15, and the belt 54 is held at the belt tension necessary for driving the crankshaft 51. the slip between the belt 54 and the pulleys _{P 1} to _{P 3} is prevented.

As described above, during normal operation of the engine, oil in the pressure chamber 15 leaks from the first leak gap 31 having a small flow path resistance to the reservoir chamber 24, while at the time of starting the engine by the starter generator 52, the pressure chamber 15 leaks to the reservoir chamber 24 from the second leak gap 32 having a large flow path resistance, so that an appropriate tension is applied to the belt 54 during normal operation of the engine and when the engine is started by the starter / generator. be able to.

Here, when the starter / generator 52 starts the engine, if the second check valve 35 is not completely closed, the oil leaks from the first leak gap 31 having a small flow path resistance. Therefore, belt slip may occur.

However, in the embodiment, since the surface hardness of the valve seat 35a and the seat surface 35b of the second check valve 35 is different, in the initial use of the hydraulic auto tensioner, as shown in FIG. 4A, The second check valve 35 is completely closed by elastic deformation of the contact portion between the seat 35a and the seat surface 35b. On the other hand, when the second check valve 35 is used, the seat surface 35b undergoes plastic deformation due to repeated opening and closing, resulting in familiarity. As shown in FIG. 4B, the second check valve 35 comes into surface contact with the convex curved surface of the valve seat 35a. In this state, the second check valve 35 is completely closed. Therefore, the belt 54 does not slip when the engine is started by driving the starter generator 52 shown in FIG. 9B.

FIG. 8 shows a measurement example comparing the reaction force characteristics of the hydraulic auto tensioner (hereinafter referred to as “implemented product”) of the above embodiment and the reaction force characteristics of a conventional hydraulic auto tensioner (hereinafter referred to as “conventional product”). Indicates. This will be described below.

As the implemented product, the tensioner described in the above embodiment was used. That is, as shown in FIGS. 1 and 2, a bottomed cylindrical cylinder 10, a valve sleeve 13 extending upward from the bottom surface of the cylinder 10, and a plunger inserted into the valve sleeve 13 slidably up and down. 28, a rod 14 slidably inserted into the plunger 28, a pressure chamber 15 surrounded by the valve sleeve 13, the rod 14, and the plunger 28, and a sliding surface between the rod 14 and the plunger 28. The cylindrical first leak gap 31, the cylindrical second leak gap 32 formed between the sliding surfaces of the plunger 28 and the valve sleeve 13, the spring seat 16 fixed to the upper end of the rod 14, and the A return spring 17 that biases the spring seat 16 upward relative to the cylinder 10, a valve spring 37 that biases the plunger 28 downward, and a rod 4 includes a valve seat 35a serving as an upper stopper that restricts the upward movement range of the plunger 28 relative to 4, and a retaining ring serving as a lower stopper 34 that restricts the downward movement range of the plunger 28 relative to the rod 14. The tensioner was used. The spring seat 16 was vibrated up and down with the cylinder 10 fixed, and the change in upward force (tensioner reaction force) acting on the spring seat 16 was measured.

Further, as a conventional product, the tensioner shown in FIG. 1 of JP-A-2009-275757 (a tensioner having no member corresponding to the plunger 28 of the actual product and the rod 14 slides directly on the valve sleeve 13) is used. did.

The excitation conditions are as follows.
・ Control method: Displacement control ・ Excitation waveform: Sine wave ・ Excitation frequency: 10Hz

In the displacement control, the displacement of the spring seat 16 is controlled so that the time change of the position of the spring seat 16 becomes a sine wave regardless of how the force (tensioner reaction force) acting on the spring seat 16 increases or decreases. Control method. The vibration amplitude was set to ± 0.5 mm, which is larger than the general vibration amplitude (for example, about ± 0.1 mm to ± 0.2 mm) applied to the tensioner during normal operation of the engine. Both the practical product and the conventional product use the return spring 17 having a spring coefficient of about 35 N / mm.

FIG. 8 shows the relationship between the tensioner displacement (downward displacement of the spring seat 16) and the tensioner reaction force (upward force acting on the spring seat 16) obtained by the above vibration test.

As shown in FIG. 8, in the process in which the tensioner contracts, the tensioner reaction force changes in three stages of sudden, slow, and sudden. In other words, during the process in which the tensioner contracts, the tensioner reaction force of the product is almost increased in the first stroke (points P1 to P2) that increases relatively rapidly starting from the minimum value of the tensioner reaction force (point P1). Without passing through the second stroke (points P2 to P3) that maintains a substantially constant magnitude and the third stroke (points P3 to P4) that increase relatively abruptly in order, the maximum value of the tensioner reaction force ( Changes to point P4).

After that, in the process of the tensioner, the tensioner reaction force changes in four stages: sudden, slow, sudden and slow. In other words, in the process in which the tensioner is extended, the tensioner reaction force of the product is almost reduced in the first stroke (points P4 to P5) in which the maximum value (point P4) of the tensioner reaction force starts to decrease relatively rapidly. The second stroke (points P5 to P6) that maintains a substantially constant size without any reduction, and the third stroke (points P6 to P7) that decreases relatively suddenly, and a substantially constant size that hardly decreases. It changes to the minimum value (point P1) of the tensioner reaction force through the fourth stroke (point P7 to point P1) for maintaining the height in order.

On the other hand, in the conventional product, the tensioner reaction force generally increases monotonously from the minimum value (point Q1) to the maximum value (point Q2) during the process of contraction of the tensioner. In the conventional product, the tensioner reaction force changes in two steps, abrupt and slow, as the tensioner extends. In other words, in the process of tensioner extension, the tensioner reaction force of the conventional product is almost reduced in the first stroke (points Q2 to Q3) where the tensioner reaction force starts from the maximum value (point Q2). Without going through the second stroke (points Q3 to Q1) maintaining a substantially constant magnitude, the tensioner reaction force changes to the minimum value (point Q1).

That is, in the tensioner of the product, the change point P2 in which the increase rate of the tensioner reaction force changes from sudden to slow and the change point P3 in which the increase rate of the tensioner reaction force changes from slow to sudden in the course of contraction of the tensioner in order. The reaction force characteristic is shown. Further, the tensioner of the practical product has a tension point P5 where the rate of decrease of the tensioner reaction force changes from abrupt to moderate, and a point of change P6 where the rate of decrease of the tensioner reaction force changes suddenly. The reaction force characteristic which has the change point P7 in which the decreasing rate of reaction force changes from sudden to moderate is shown.

The reason why the tensioner of the product exhibits the reaction force characteristic will be described with reference to FIGS. 1, 2, and 8. FIG.

<Point P1 to Point P2>
The rod 14 shown in FIG. 2 starts to descend. At this time, since the plunger 28 is urged downward by the valve spring 37 and pressed by the stopper 34, the plunger 28 is also lowered integrally with the rod 14. When the plunger 28 and the rod 14 are lowered integrally, a part of the oil in the pressure chamber 15 flows out of the pressure chamber 15 through the first leak gap 31, and the oil in the pressure chamber 15 is compressed. When the oil in the pressure chamber 15 is compressed, the pressure of the oil in the pressure chamber 15 increases and the tensioner reaction force increases relatively abruptly (points P1 to P2 in FIG. 8). 8, the upward pressure acting on the plunger 28 from the oil in the pressure chamber 15 and the downward biasing force acting on the plunger 28 from the valve spring 37 are balanced.

<Points P2 to P3>
The rod 14 shown in FIG. At this time, the upward pressure acting on the plunger 28 from the oil in the pressure chamber 15 exceeds the downward urging force acting on the plunger 28 from the valve spring 37, whereby the plunger 28 rises. During this time, as the plunger 28 rises, the pressure rise in the pressure chamber 15 is suppressed, and the tensioner reaction force becomes substantially constant (points P2 to P3 in FIG. 8). That is, since the plunger 28 rises as the rod 14 descends, the volume of the pressure chamber 15 hardly changes and the pressure in the pressure chamber 15 becomes substantially constant. At this time, since the volume of the pressure chamber 15 hardly changes, oil hardly flows into the first leak gap 31 and the second leak gap 32. Then, at point P3 in FIG. 8, as shown in FIG. 3, the seat surface 35b is seated on the valve seat 35a, and the raising of the plunger 28 is stopped.

<Points P3 to P4>
The rod 14 shown in FIG. At this time, as shown in FIG. 3, since the seat surface 35 b is seated on the valve seat 35 a, the plunger 28 is also lowered integrally with the rod 14. When the plunger 28 and the rod 14 are integrally lowered, the oil in the pressure chamber 15 is further compressed, so that the pressure of the oil in the pressure chamber 15 increases again, and the tensioner reaction force suddenly increases again (in FIG. 8). Points P3 to P4). At this time, as shown in FIG. 3, since the seat surface 35b is seated on the valve seat 35a, the oil does not flow into the first leak gap 31, and a part of the oil in the pressure chamber 15 becomes the second leak gap. It flows out of the pressure chamber 15 through 32.

<Points P4 to P5>
The rod 14 shown in FIG. 3 starts to rise. At this time, since the upward pressure acting on the plunger 28 from the oil in the pressure chamber 15 exceeds the downward urging force acting on the plunger 28 from the valve spring 37, the plunger 28 also rises integrally with the rod 14. When the plunger 28 and the rod 14 rise together, the compression of the oil in the pressure chamber 15 is gradually released, so that the pressure of the oil in the pressure chamber 15 decreases and the tensioner reaction force decreases relatively rapidly (see FIG. 8 points P4 to P5). At this time, since the compression of the oil in the pressure chamber 15 is released (that is, the oil in the pressure chamber 15 expands), the volume of the oil in the pressure chamber 15 increases. Hardly flows. Further, as shown in FIG. 3, the seat surface 35 b is seated on the valve seat 35 a, so that no oil flows through the first leak gap 31. 8, the upward pressure acting on the plunger 28 from the oil in the pressure chamber 15 and the downward urging force acting on the plunger 28 from the valve spring 37 are balanced.

<Points P5 to P6>
The rod 14 shown in FIG. At this time, the upward pressure acting on the plunger 28 from the oil in the pressure chamber 15 falls below the downward urging force acting on the plunger 28 from the valve spring 37, whereby the plunger 28 descends. During this time, the plunger 28 is lowered, so that the pressure drop in the pressure chamber 15 is suppressed, and the tensioner reaction force becomes substantially constant (points P5 to P6 in FIG. 8). That is, since the plunger 28 descends as the rod 14 moves up, the volume of the pressure chamber 15 hardly changes and the pressure in the pressure chamber 15 becomes substantially constant. At this time, as in the case of points P4 to P5, the compression of the oil in the pressure chamber 15 is released (that is, the oil in the pressure chamber 15 expands), so that the volume of the oil in the pressure chamber 15 increases. Therefore, almost no oil flows through the first leak gap 31 and the second leak gap 32. Then, at point P6 in FIG. 8, as shown in FIG. 2, the downward movement of the plunger 28 is blocked by the stopper 34, and the lowering of the plunger 28 is stopped.

<Points P6 to P7>
The rod 14 shown in FIG. At this time, as shown in FIG. 2, since the downward relative movement of the plunger 28 with respect to the rod 14 is blocked by the stopper 34, the plunger 28 also rises integrally with the rod 14. When the plunger 28 and the rod 14 rise together, the compression of the oil in the pressure chamber 15 is further released, so that the pressure of the oil in the pressure chamber 15 begins to decrease again, and the tensioner reaction force suddenly decreases again ( Point P6 to point P7 in FIG. At this time, as in the case of points P4 to P5, the compression of the oil in the pressure chamber 15 is released (that is, the oil in the pressure chamber 15 expands), so that the volume of the oil in the pressure chamber 15 increases. Therefore, almost no oil flows through the first leak gap 31 and the second leak gap 32. At point P7 in FIG. 8, the pressure of the oil in the pressure chamber 15 shown in FIG. 1 is reduced to a pressure equivalent to the oil in the reservoir chamber 24, and the compression of the oil in the pressure chamber 15 is completely released. It becomes a state.

<Point P7 to Point P1>
The rod 14 shown in FIG. At this time, since the downward relative movement of the plunger 28 with respect to the rod 14 is blocked by the stopper 34, the plunger 28 also rises integrally with the rod 14. When the plunger 28 and the rod 14 rise together, the first check valve 27 opens when the oil pressure in the pressure chamber 15 falls below the pressure in the reservoir chamber 24, and the oil passes from the reservoir chamber 24 through the oil passage 25. It flows into the pressure chamber 15. For this reason, the pressure of the oil in the pressure chamber 15 hardly changes, and the tensioner reaction force becomes substantially constant (points P7 to P1 in FIG. 8).

As described above, when the tensioner reaction force reaches a predetermined value (value at the point P2 in FIG. 8) in the process in which the tensioner contracts, the plunger 28 rises and the volume of the pressure chamber 15 changes. During the absorption, the tensioner reaction force becomes substantially constant (points P2 to P3 in FIG. 8). For this reason, in the process in which the tensioner contracts, the implemented product has a change point P2 at which the rate of increase in the tensioner reaction force changes from sudden to moderate, and a change point P3 at which the rate of increase in the tensioner reaction force changes from slow to sudden. Shows force characteristics.

Further, when the tensioner reaction force reaches a predetermined value (the value at the point P5 in FIG. 8) during the extension of the tensioner, the plunger 28 descends to absorb the change in the volume of the pressure chamber 15. During this time, the tensioner reaction force becomes substantially constant (points P5 to P6 in FIG. 8). For this reason, in the process in which the tensioner is extended, the implemented product has a change point P5 where the rate of decrease of the tensioner reaction force changes suddenly and slowly and a change point P6 where the rate of decrease of the tensioner reaction force changes suddenly and suddenly. Shows force characteristics.

Since the tensioner of the practical product has the above-described reaction force characteristics, during the normal operation of the engine, the magnitude of the tensioner reaction force is kept small, and the tension applied to the belt 54 by the tension pulley 55 shown in FIG. 9A is kept small. it can, on the other hand, at the time of starting the engine by driving the starter generator 52, to generate a larger tensioner reaction force, it is possible to effectively prevent the slippage between the belt 54 and the pulley P ₂ shown in FIG. 9B.

That is, during normal operation of the engine, the tensioner is displaced with an amplitude smaller than ± 0.5 mm (for example, an amplitude of about ± 0.1 mm to ± 0.2 mm) as indicated by reference numeral S1 in FIG. At this time, the tensioner reaction force increases from the point P1 to the value between the points P2 and P3 in the process where the tensioner contracts, and then increases to the value between the points P2 and P3, and then in the process where the tensioner extends. Starting from the value between point P3 and point P3, it decreases to a value between point P5 and point P6, and further passes through point P6 and point P7 in order and decreases to point P1. As described above, when the tensioner of the actual product is used, the maximum value of the tensioner reaction force can be suppressed to a value between the points P2 and P3 during the normal operation of the engine, and the tension pulley 55 shown in FIG. The tension applied to the engine can be kept small, and the fuel consumption of the engine can be reduced.

On the other hand, when the engine is started by driving the starter / generator 52, the tensioner contracts to or near the maximum value of the amplitude of ± 0.5 mm, as indicated by reference numeral S2 in FIG. At this time, the tensioner reaction force increases to the point P4 or the vicinity thereof. Therefore, when starting the engine by driving the starter generator 52, greater tensioner reaction force can be generated, it is possible to effectively prevent the slippage between the belt 54 and the pulley P ₂ shown in FIG. 9B.

On the other hand, in the conventional tensioner, the tension of the belt 54 tends to be excessive during normal operation of the engine. That is, when the tensioner is displaced with the amplitude indicated by S1 in FIG. 8, in the process in which the tensioner contracts, the tensioner reaction force increases from the point Q1 to a value between the points Q1 and Q2, and then In the process of extending the tensioner, the value between the point Q1 and the point Q2 is set as a starting point, the value is decreased to a value between the point Q3 and the point Q1, and further decreased to the point Q1. Thus, when the conventional tensioner is used, the maximum value of the tensioner reaction force increases to a value between point Q1 and point Q2 during normal operation of the engine, so that the tension pulley 55 shown in FIG. The tension to be applied tends to be excessive, and it is difficult to reduce the fuel consumption of the engine.

Further, it is difficult for the conventional tensioner to generate a large tensioner reaction force when the engine is started by driving the starter generator 52. That is, when the tensioner contracts to the maximum value of the amplitude of ± 0.5 mm indicated by reference numeral S2 in FIG. 8 or the vicinity thereof, the tensioner reaction force increases only to the point Q2 or the vicinity thereof. Therefore, when the engine is started by driving the starter generator 52, a large tensioner it is difficult to generate a reaction force, slip is likely to occur between the belt 54 and the pulley P ₂ shown in FIG. 9B.

10 cylinder 13 valve sleeve 14 rod 15 pressure chamber 16 spring seat 17 return spring 24 reservoir chamber 25 oil passage 27 first check valve 28 plunger 31 first leak gap 32 second leak gap 34 stopper 35 second check valve

35a valve seat

35b Seat surface 37 Valve spring

Claims

A valve sleeve (13) is erected on the bottom surface of the bottomed cylinder (10), and the lower end of the rod (14) is slidably inserted into the valve sleeve (13) so as to be inside the valve sleeve (13). A pressure chamber (15) is provided on the rod (14), and the spring seat (16) and the cylinder (10) are attached between the spring seat (16) and the bottom surface of the cylinder (10) in a direction to extend. A return spring (17) is installed, and the lower part of the reservoir chamber (24) formed between the inner periphery of the cylinder (10) and the outer periphery of the valve sleeve (13) communicates with the lower part of the pressure chamber (15). An oil passage (25) is formed, and when the pressure in the pressure chamber (15) becomes higher than the pressure in the reservoir chamber (24) in the lower end portion of the valve sleeve (13), the pressure chamber (15) and the oil passage are closed. Block communication of (25) The first check valve (27) is provided, and when the pushing force is applied to the rod (14) through the spring seat (16), the first check valve (27) is closed, and the pressure chamber (15) In the hydraulic auto tensioner in which oil is leaked to the reservoir chamber (24) and the pushing force applied to the rod (14) is buffered by the hydraulic damper action by the oil in the pressure chamber (15).
A slidable cylindrical plunger (28) is fitted between the outer diameter surface of the rod (14) and the inner diameter surface of the valve sleeve (13), and the plunger (28) and the rod (14) slide. A first leak gap (31) is provided between the moving surfaces, and a second leak having a larger flow path resistance than the first leak gap (31) between the sliding surfaces of the plunger (28) and the valve sleeve (13). A gap (32) is provided, and the first leak gap (31) is provided between the rod (14) and the plunger (28) when the plunger (28) rises as the pressure in the pressure chamber (15) rises. A second check valve (35) for closing the valve (3), and a valve spring (37) for urging the plunger (28) toward a retaining stopper (34) provided at the lower end of the rod (14). Providing the second check Hydraulic auto-tensioner which is characterized in that with a difference in the surface hardness of the valve the valve seat (35a) and the seat surface of the (35) (35b).
The second check valve (35) is provided with a valve seat (35a) at the lower end of the large-diameter shaft portion (14a) located outside from the upper end of the plunger (28) of the rod (14), and the plunger (28 The hydraulic auto tensioner according to claim 1, further comprising a seat surface (35b) that can be seated on the valve seat (35a) on an upper inner diameter surface of the valve.
The hydraulic auto tensioner according to claim 1 or 2, wherein one of the valve seat (35a) and the seat surface (35b) of the second check valve (35) is a convex curved surface, and the other is a flat surface.
4. The hydraulic auto tensioner according to claim 3, wherein the member on the side having the convex curved surface has high hardness.
The hydraulic auto tensioner according to claim 1, wherein the valve spring (37) is a coil spring, a disc spring, a wave washer, or a wave spring.