JP5820626B2 - Hydraulic auto tensioner - Google Patents

Description

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

  In the belt transmission device for transmitting the rotation of the crankshaft of the engine to various automobile auxiliary machines, as shown in FIG. 9, a pulley arm 43 that can swing around a fulcrum shaft 42 is provided on the slack side of the belt 41. The adjustment force of the hydraulic auto tensioner A is applied to the pulley arm 43, and the pulley arm 43 is urged in the direction in which the rotatable tension pulley 44 supported by the swinging end of the pulley arm 43 presses the belt 41, The tension of the belt 41 is kept constant.

  As a hydraulic auto tensioner A used for the belt transmission as described above, 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 an elastic bellows 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 the lower portion of the reservoir chamber and the pressure chamber are connected by a passage. A check valve is provided in the passage, and the check valve is closed when a pushing force is applied from the belt 41 to the hydraulic auto tensioner A via the tension pulley 44 and the pulley arm 43 in the direction of contracting the cylinder and the rod. The hydraulic oil sealed in the pressure chamber is caused to flow through a minute gap formed between the inner diameter surface of the sleeve and the outer diameter surface of the rod, and a hydraulic damper force is generated in the pressure chamber due to the viscous resistance of the hydraulic oil during the flow. Thus, the pushing force is buffered.

  By the way, in the conventional hydraulic auto tensioner, as described above, the working oil sealed in the pressure chamber is formed between the inner diameter surface of the sleeve and the outer diameter surface of the rod by the pushing force applied from the belt 41 to the rod. The pressure force is buffered by the hydraulic damper force generated in the pressure chamber by the flow, and the hydraulic damper force and the push force are substantially proportional to each other, so the push force increases. As a result, the hydraulic damper force also increases.

  For this reason, the belt cannot be prevented from being over-tensioned, and there is a problem that the durability of the belt is lowered.

  In order to solve such a problem, in Patent Document 2, an oil passage that communicates a pressure chamber and a reservoir chamber is formed in a rod, a relief valve is incorporated in the oil passage, and the pressure in the pressure chamber is set to the relief valve. When the pressure is exceeded, the relief valve is opened, the hydraulic oil in the pressure chamber is released from the oil passage to the reservoir chamber, the upper limit of the pressure in the pressure chamber is defined as the set pressure of the relief valve, and the belt is over-tensioned I try to prevent it.

JP-A-10-133204 JP 2009-191863 A

  By the way, in the hydraulic auto tensioner described in Patent Document 2, when the relief valve is opened, the hydraulic oil in the pressure chamber instantaneously escapes from the oil passage into the reservoir chamber, so that a sudden pressure drop occurs in the pressure chamber. A hydraulic damper failure occurred, and there were still points to be improved.

  An object of the present invention is to provide a hydraulic auto tensioner capable of preventing a hydraulic damper failure from occurring by suppressing a sudden drop in pressure in a pressure chamber when a relief valve is opened. That is.

  In order to solve the above problems, in the present invention, a sleeve fitting hole is provided in the bottom surface of a cylinder filled with hydraulic oil, and the lower end portion is fitted in the sleeve fitting hole. A return that slidably inserts the lower end of the rod to form a pressure chamber in the sleeve, and urges the cylinder and the rod in the extending direction between the spring seat provided on the upper portion of the rod and the inner bottom surface of the cylinder. A spring is incorporated, the upper opening of the reservoir chamber formed between the cylinder and the sleeve is closed, and a passage is provided between the fitting surface of the sleeve and the sleeve fitting hole to communicate the reservoir chamber and the pressure chamber. In addition, a check valve that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber is provided, and the rod has a valve fitting hole opened at a lower end surface thereof and an upper portion of the valve fitting hole. An oil passage communicating with the reservoir chamber is provided, and a relief valve is built in the valve fitting hole to release the pressure chamber pressure from the oil passage to the reservoir chamber when the pressure in the pressure chamber exceeds the set pressure. The relief valve has a valve seat press-fitted into the valve fitting hole, a valve body that opens and closes the valve hole formed in the valve seat from the inside of the valve fitting hole, and the valve body faces the valve hole. In a hydraulic auto tensioner composed of a valve spring that is energized, oil is passed through either the hydraulic oil inflow path from the pressure chamber to the valve body of the relief valve or the hydraulic oil outflow path from the valve body to the oil path. A configuration provided with a throttle part for regulating the amount was adopted.

  As described above, by providing a throttle in either the hydraulic oil inflow path from the pressure chamber to the valve body of the relief valve or the hydraulic oil outflow path from the valve body to the oil path, when the relief valve is opened, The oil flow rate is regulated by the throttle portion. For this reason, a rapid drop in pressure in the pressure chamber is suppressed, and the occurrence of a hydraulic damper failure is prevented.

  Here, the throttle portion may be an orifice formed in the oil inlet portion of the valve hole, or a plate body that is attached to the surface facing the pressure chamber of the valve seat and covers the valve hole and the valve seat facing surface It may be a spiral groove formed on one side of the pressure chamber and communicating with the valve hole. Furthermore, the small hole of the porous body which is attached to the opposing surface with respect to the pressure chamber of a valve seat and covers a valve hole may be sufficient.

  When the orifice is used, the orifice may be provided on the valve seat, or the orifice plate may be attached to the surface of the valve seat facing the pressure chamber and formed on the orifice plate.

  At this time, if the inner diameter of the orifice becomes larger than necessary, the pressure difference between the oil inlet side and the oil outlet side of the relief valve cannot be relaxed, and the pressure in the pressure chamber rapidly decreases, When it becomes smaller than necessary, drilling becomes difficult, and the inner diameter of the orifice is preferably in the range of 0.1 mm to 1.0 mm from the viewpoint of relaxation of the pressure difference and workability.

  The restricting portion is not limited to the orifice, the spiral groove, or the small hole of the porous body as described above. For example, a spring seat with a circular diameter that can slide along the inner diameter surface of the valve fitting hole is installed between the valve body of the relief valve and the valve spring, and between the spring seat and the sliding surface of the valve fitting hole. The minute leak gap formed in the above may be used as the throttle portion.

  Alternatively, a spiral groove may be formed on the outer diameter surface of a spring seat that is slidably incorporated between a valve body of a relief valve and a valve spring, and the spiral groove may be used as a throttle portion.

  Further, a rod disposed in the valve spring is provided on the upper surface of the spring seat, and the upper end surface of the rod is abutted against the closed end surface of the upper portion of the valve fitting hole when the valve body of the relief valve is opened. The length may be an axial length, and a groove may be provided on the upper end surface of the rod, and the groove may be used as a throttle portion.

  In the present invention, as described above, the relief portion is provided by providing the throttle portion in one of the hydraulic oil inflow path from the pressure chamber to the valve body of the relief valve and the hydraulic oil outflow path from the valve body to the oil path. When the valve is opened, the amount of oil can be regulated by the throttle portion. For this reason, there is no sudden drop in pressure in the pressure chamber, and it is possible to prevent the occurrence of a hydraulic damper failure.

A longitudinal front view showing an embodiment of a hydraulic auto tensioner according to the present invention FIG. 1 is an enlarged cross-sectional view showing a built-in portion of the relief valve of FIG. Sectional drawing which shows the other example of formation of an orifice (A) is sectional drawing which shows the other example of an aperture part, (b) is sectional drawing along the IV-IV line of (a). Sectional drawing which shows other examples of an aperture part Sectional drawing which shows other examples of an aperture part Sectional drawing which shows other examples of an aperture part (C) is a cross-sectional view showing still another example of the narrowed portion, and (d) is a cross-sectional view showing a formation state of the narrowed portion. Front view showing a tension adjusting device for an auxiliary machine driving belt

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the cylinder 1 is closed at the lower portion, and a connecting piece 2 that is rotatably connected to the engine block is provided at the closed end portion.

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

  A spring seat 7 is fixed to the upper end portion of the rod 5 located outside the cylinder 1, and the 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 pulley arm 43 shown in FIG. 9 is provided at the upper end of the spring seat 7. Further, the spring seat 7 is provided with an inner cylinder portion 10 that covers the upper portion of the return spring 8 and an outer cylinder portion 11 that covers the outer periphery of the upper portion of the cylinder 1 on the same axis.

  An elastic seal 12 such as an oil seal is attached in the upper opening of the cylinder 1, and the inner periphery of the elastic seal 12 is in elastic contact with the outer peripheral surface of the inner cylinder 10 to close the upper opening of the cylinder 1. Leakage of hydraulic oil filled in 1 to the outside is prevented.

  By attaching the elastic seal 12, the reservoir chamber 13 sealed between the cylinder 1 and the sleeve 4 is formed. The reservoir chamber 13 and the pressure chamber 6 communicate with each other through a passage 14 formed between the fitting surfaces of the sleeve fitting hole 3 and the sleeve 4, and a check valve 15 provided at the end of the passage 14 on the pressure chamber 6 side. When the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 13, the passage 14 is closed.

  The rod 5 is formed with a valve fitting hole 16 that opens at the lower end surface thereof, and a T-shaped oil passage 17 that communicates the upper portion of the valve fitting hole 16 with the reservoir chamber 13. A relief valve 20 is incorporated therein.

  As shown in FIG. 2, the relief valve 20 opens and closes a valve seat 21 press-fitted into the lower end opening of the valve fitting hole 16 and a valve hole 22 formed in the valve seat 21 from within the valve fitting hole 16. A spherical valve body 23, a spring seat 24 provided on the upper side of the valve body 23, and a valve spring 25 that urges the valve body 23 toward the valve hole 22 through the spring seat 24. .

  The relief valve 20 uses the elastic force of the valve spring 25 as a set pressure, and the valve body 23 opens the valve hole 22 when the pressure in the pressure chamber 6 exceeds the set pressure. An orifice 26 as a throttle portion is formed at the lower end of the valve hole 22, and the inner diameter of the orifice 26 is in the range of 0.1 mm to 1.0 mm.

  Here, the spring seat 24 has a circular diameter and can slide along the inner diameter surface of the valve fitting hole 16, and a leak gap 27 is formed between the sliding surface of the spring seat 24 and the valve fitting hole 16. Has been.

  Further, a rod 24a disposed in the valve spring 25 is integrally provided on the upper surface of the spring seat 24, and a conical recess 24b into which the upper portion of the valve body 23 is fitted is formed on the lower surface.

  The hydraulic auto tensioner shown in the embodiment is configured as described above. When adjusting the tension of the accessory drive belt 41 shown in FIG. 9, the connecting piece 2 provided at the closed end of the cylinder 1 is connected to the engine block. In addition, the connecting piece 9 of the spring seat 7 is connected to the pulley arm 43, and an adjusting force is applied to the pulley arm 43.

  In the tension adjustment state of the belt 41 as described above, when the tension of the belt 41 changes due to the load fluctuation of the auxiliary machine and the tension of the belt 41 becomes weak, the cylinder 1 and the rod 5 are extended by the pressing of the return spring 8. Relative movement in the direction absorbs slackness of the belt 41.

  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 13, so the check valve 15 opens the passage 14. For this reason, the hydraulic oil in the reservoir chamber 13 smoothly flows from the passage 14 into the pressure chamber 6, and the cylinder 1 and the rod 5 smoothly move relative to each other in the extending direction to immediately absorb the slack of the belt 41.

  On the other hand, when the tension of the belt 41 is increased, a pushing force in a direction of contracting the cylinder 1 and the rod 5 of the hydraulic auto tensioner from the belt 41 is applied. At this time, since the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 13, the check valve 15 closes the passage 14.

  Further, the hydraulic oil in the pressure chamber 6 flows into the minute gap 28 formed between the inner diameter surface of the sleeve 4 and the outer diameter surface of the rod 5 and flows into the reservoir chamber 13. The hydraulic damper generates a hydraulic damper force in the pressure chamber 6 due to the viscous resistance, and the hydraulic damper force buffers the pushing force applied to the hydraulic auto tensioner, and the cylinder 1 and the rod 5 have a pushing force and a return spring. Relatively moves slowly in the direction of contraction to the position where the elastic force of 8 is balanced.

  When the tension of the belt 41 is strong and the pressure in the pressure chamber 6 exceeds the set pressure of the relief valve 20, the relief valve 20 is opened, and the hydraulic oil in the pressure chamber 6 escapes from the oil passage 17 into the reservoir chamber 13, The pressure in the chamber 6 is maintained at the set pressure of the relief valve 20.

  Here, when the hydraulic oil in the pressure chamber 6 escapes instantaneously into the reservoir chamber 13 due to the relief valve 20 being opened, the pressure in the pressure chamber 6 is suddenly reduced and a hydraulic damper failure occurs. . In the embodiment, since the orifice 26 is formed at the lower end of the valve hole 22, the amount of oil passing through the orifice 26 is restricted when the hydraulic oil in the pressure chamber 6 passes through the orifice 26. The restriction of the oil flow rate suppresses a rapid pressure drop in the pressure chamber 6 and prevents the occurrence of a hydraulic damper failure.

  In FIG. 2, the orifice 26 is provided in the valve seat 21. However, as shown in FIG. 3, the orifice plate 29 is attached to the lower surface of the valve seat 21 facing the pressure chamber 6, and the orifice 26 is attached to the orifice plate 29. You may make it form.

  In FIG. 2 and FIG. 3, the orifice 26 is shown as the throttle portion, but the throttle portion is not limited to the orifice 26. 4 to 9 show other examples of the aperture portion.

  4A and 4B, a plate body 30 that covers the valve hole 22 is attached to the lower surface of the valve seat 21 that faces the pressure chamber 6, and the upper surface of the plate body 30 that abuts the lower surface of the valve seat 21. A spiral groove 31 is provided, and the spiral groove 31 is used as a throttle portion. Instead of the upper surface of the plate body 30, spiral grooves may be formed on the lower surface of the valve seat 21.

  In FIG. 5, a porous body 32 is attached to the lower surface of the valve seat 21 facing the pressure chamber 6, and a small hole of the porous body 32 is used as a throttle portion.

  In FIG. 6, the radial gap amount δ of the leak gap 27 formed between the sliding surfaces of the spring seat 24 and the valve fitting hole 16 of the rod 5 is set in the range of 10 μm to 500 μm. The aperture part.

  In FIG. 7, a spiral groove 33 is formed on the outer diameter surface of a circular spring seat 24 slidable along the inner diameter surface of the valve fitting hole 16, and the spiral groove 33 serves as a throttle portion.

8 (c) and 8 (d), the rod 24a integrally provided on the upper surface of the spring seat 24 is in the open state of the valve body 23 of the relief valve 20 shown in FIG. as the axial length l ₂ in contact with the closed end face of the upper portion of the fitting hole 16, a groove 35 is provided on the upper end surface of the rod 24a, it has the groove 35 and the throttle portion.

  Here, the opening / closing stroke amount of the valve body 23 is in the range of 0.25 mm to 1.00 mm. Moreover, although the radial direction groove | channel is shown here as the groove | channel 35, it is not limited to a radial direction groove | channel. For example, a cross groove may be used.

  In any throttle part of FIGS. 4 to 8, it is possible to suppress a rapid pressure drop in the pressure chamber 6.

1 Cylinder 3 Sleeve fitting hole 4 Sleeve 5 Rod 6 Pressure chamber 7 Spring seat 8 Return spring 13 Reservoir chamber 14 Passage 15 Check valve 16 Valve fitting hole 17 Oil passage 20 Relief valve 21 Valve seat 22 Valve hole 23 Valve body 24 Spring Seat 24a Rod 25 Valve spring 26 Orifice (throttle part)
27 Leakage gap (throttle part)
29 Orifice plate 30 Plate body 31 Spiral groove (throttle part)
32 Porous body 33 Spiral groove (throttle part)
35 groove (diaphragm)

Claims (1)

A sleeve fitting hole is provided in the bottom of the cylinder filled with hydraulic oil, and the lower end of the rod is slidably inserted into the sleeve with the lower end fitted in the sleeve fitting hole. A reservoir formed between the cylinder and the sleeve is formed between the spring seat provided at the upper part of the rod and the inner bottom surface of the cylinder, and a return spring that urges the cylinder and the rod in the extending direction. When the upper opening of the chamber is closed, a passage is provided between the fitting surface of the sleeve and the sleeve fitting hole to connect the reservoir chamber and the pressure chamber, and the pressure in the pressure chamber is higher than the pressure of the reservoir chamber in the passage. A check valve for closing the passage is provided, and the rod is provided with a valve fitting hole that opens at a lower end surface thereof, and an oil passage that communicates an upper portion of the valve fitting hole with the reservoir chamber. A relief valve that opens when the pressure in the pressure chamber exceeds the set pressure and releases the pressure in the pressure chamber from the oil passage to the reservoir chamber is inserted into the joint hole, and the relief valve is press-fitted into the valve fitting hole. In a hydraulic auto tensioner comprising a valve seat, a valve body that opens and closes a valve hole formed in the valve seat from the inside of the valve fitting hole, and a valve spring that biases the valve body toward the valve hole,
A spring seat having a circular diameter that is slidable along the inner diameter surface of the valve fitting hole is incorporated between the valve body of the relief valve and the valve spring, and is disposed in the valve spring on the upper surface of the spring seat. A rod is formed, and the rod has an axial length in which the upper end surface abuts on the closed end surface of the valve fitting hole when the valve body of the relief valve is open, and a groove is formed on the upper end surface of the rod. A hydraulic auto-tensioner characterized in that a throttle portion is provided.

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