JP2007255615A - Hydraulic auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic auto tensioner capable of enhancing extraction force of a bellows blocking an upper opening of a cylinder without increasing an interference. <P>SOLUTION: A valve sleeve 4 is provided in the cylinder 1 filled with operating oil. A lower part of a rod 5 is inserted into the valve sleeve 4, and a pressure chamber 6 is provided in the valve sleeve 4. A return spring 8 is incorporated between a spring seat 7 provided at the upper part of the rod 5 and the bottom face of the cylinder 1. An end of a small diameter cylinder part 11c provided to the bellows 11 is fitted with the spring seat 7, a large diameter cylinder part 11d is fitted on an upper outer periphery of the cylinder 1, and lips 12, 13, and 15 provided to the inner periphery of each of the cylinder parts 11c and 11d are fitted to lip engagement grooves 14 and 16 formed on the outer periphery of the spring seat 7 and the cylinder 1. The extraction force of the bellows 11 is enhanced by making the number of the lips formed on the inner periphery of the small diameter cylinder part 11c a plurality of numbers, and even when pressure in a reserver chamber 17 is lowered, the small diameter cylinder part 11c is prevented from coming off. <P>COPYRIGHT: (C)2008,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.

  As shown in FIG. 4, in a belt transmission device for transmitting the rotation of the crankshaft of an engine to various automobile accessories, a swingable pulley arm 33 for supporting a tension pulley 32 is provided on the slack side of the belt 31, and the pulley arm The adjustment force of the hydraulic auto tensioner A is applied to 33 to urge the pulley arm 33 in the direction in which the tension pulley 32 presses the belt 31 so that the tension of the belt 31 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 valve sleeve rising from the inner bottom surface of the bottomed cylinder filled with hydraulic oil to form a pressure chamber in the valve sleeve. A return spring is incorporated between the provided spring seat and the bottom surface of the cylinder to urge the rod and the cylinder in the extending direction.

  In addition, an elastic bellows is installed between the spring seat and the upper part of the cylinder to close the upper opening of the cylinder, and the lower part of the reservoir chamber formed between the cylinder and the valve sleeve communicates with the pressure chamber through a passage. A check valve is provided in the passage, and when a pushing force is applied from the belt 31 via the tension pulley 32 and the pulley arm 33 to the hydraulic auto tensioner A in a direction to contract the cylinder and the rod, the check valve is closed and the pressure is The pushing force is buffered by a damper action of hydraulic oil sealed in the room.

  Since the hydraulic auto tensioner as described above has a telescopic function of several mm to several tens of mm, the bellows that closes the upper opening of the cylinder is also required to be stretchable. Further, the bellows needs to be airtightly connected to the spring seat and the cylinder in order to prevent leakage of hydraulic oil in the cylinder to the outside.

Therefore, in the hydraulic auto tensioner described in Patent Document 1, an upward reversing portion is provided at the center in the length direction of the bellows, and a downward reversing portion is provided outside the reversing portion to provide elasticity. The small-diameter cylindrical portion connected to the upward inversion portion is fitted to the outside of the spring seat, and the large-diameter cylindrical portion continuous to the downward inversion portion is fitted to the upper outer periphery of the cylinder. Each of the annular lips formed on the inner periphery of the end portion and the inner periphery of the end portion of the large-diameter cylindrical portion is engaged with a lip engaging groove formed on the outer periphery of the spring seat and the cylinder with a tightening margin to maintain airtightness, and The bellows are secured.
Special Table 2000-504395

  By the way, in the conventional hydraulic auto tensioner, since the lip formed on the inner periphery of the small diameter cylindrical portion and the large diameter cylindrical portion of the bellows is a single lip, the cylinder and rod of the hydraulic auto tensioner extend. When the pressure in the reservoir chamber suddenly decreases and the pressure in the reservoir chamber suddenly decreases and a tensile force is applied to the bellows due to the change in pressure, the lip slips out of the lip engaging groove and the bellows may come off.

  In particular, even if the tightening allowance of the small-diameter cylindrical portion and the large-diameter cylindrical portion is the same, the small-diameter cylindrical portion has a small fitting diameter, so that the binding force is small compared to the large-diameter cylindrical portion, and the small-diameter cylindrical portion is likely to come off.

  Therefore, by increasing the binding force, it can be effective in preventing detachment, but when installing the bellows, it is necessary to enlarge the diameter of the small diameter cylinder or large diameter cylinder, making it difficult to install the bellows. Problem arises.

  An object of the present invention is to provide a hydraulic auto tensioner that can increase the pulling force of the bellows without increasing the tightening allowance.

  In order to solve the above-described problems, in the present invention, a valve sleeve rising from the inner bottom surface is provided in a cylinder having a closed end at a lower portion and filled with hydraulic oil inside, and a rod is provided in the valve sleeve. A return that slidably inserts the lower end of the valve to form a pressure chamber in the valve sleeve and urges the cylinder and rod in the direction of extension between the spring seat provided at the top of the rod and the inner bottom surface of the cylinder A spring is incorporated, and lip engaging grooves are provided on the outer periphery of the spring seat and the upper outer periphery of the cylinder, respectively, and annular lips are formed on the inner periphery of both ends to be fitted to each lip engaging groove with a tightening margin. A passage that connects the reservoir chamber and the pressure chamber by closing the upper opening of the cylinder by forming a bellows having elasticity and forming a reservoir chamber between the cylinder and the valve sleeve In a hydraulic auto-tensioner provided with a check valve that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, a small-diameter cylindrical portion fitted in the spring seat of the bellows and a large-diameter cylinder fitted in the cylinder Among the portions, a configuration in which a plurality of lips formed at least on the inner periphery of the small-diameter cylindrical portion is used is adopted.

  Here, among the plurality of lips, the lip engagement groove into which the inner lip located on the reservoir chamber side is fitted is located between the inner lip and the small-diameter cylindrical portion in the axial direction due to the increase in the internal pressure of the reservoir chamber. The pressure in the reservoir chamber is abnormally high by forming a pressure outflow passage that communicates the reservoir chamber with the outside through the minute gap on the inner circumference of the small diameter cylindrical portion. Then, the inner lip is elastically deformed in the axial direction to form a minute gap with the lip engaging groove, and the pressure in the reservoir chamber can be leaked to the outside through the minute gap and the pressure outflow path. .

  In addition, by making the cross-sectional area of the inner lip located on the reservoir chamber side smaller than the cross-sectional area of the lip located on the outer side of the plurality of lips, the inner lip is easily elastically deformed in the axial direction, and more The pressure in the reservoir chamber can be easily leaked to the outside.

  As described above, by using a plurality of lips formed on the inner periphery of at least the small-diameter cylindrical portion of the bellows, it is possible to increase the binding force without increasing the tightening allowance. For this reason, the pulling-out force of the small-diameter cylindrical portion is improved, and an effect can be obtained for preventing the detachment, and the fastening allowance is not increased, so that the bellows can be easily attached.

  In addition, a lip engaging groove into which an inner lip located on the reservoir chamber side of a plurality of lips is fitted is minutely positioned between the inner lip and the small-diameter cylindrical portion due to an increase in internal pressure of the reservoir chamber. Since the size of the gap is formed, when the pressure in the reservoir chamber becomes abnormally high, the inner lip is elastically deformed in the axial direction, and a minute gap is formed between the lip engaging groove, and the minute gap and Since the pressure in the reservoir chamber is leaked to the outside through the pressure outflow path, the small diameter cylindrical portion of the bellows is not deformed in the radial direction, and there is no risk of interference with other members or other portions of the bellows.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. As shown in the drawing, the cylinder 1 is closed at the bottom, and a connecting piece 2 is provided at the closed end of the cylinder 1 so as to be rotatably connected to the engine block.

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

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

  A connecting piece 9 connected to the pulley arm 33 shown in FIG. 4 is provided at the upper end of the spring seat 7. The spring seat 7 is integrally provided with a cylindrical portion 10 that covers the upper portion of the return spring 8, and a bellows 11 is mounted between the cylindrical portion 10 and the upper portion of the cylinder 1.

  As shown in FIG. 2, the bellows 11 is formed with an upward inversion portion 11a at the center in the length direction and a downward inversion portion 11b on the outside of the upward inversion portion 11a, and is connected to the upward inversion portion 11a. The small-diameter cylindrical portion 11 c is fitted to the spring seat 7, and the large-diameter cylindrical portion 11 d connected to the downward inversion portion 11 b is fitted to the upper outer periphery of the cylinder 1.

  The bellows 11 is formed of an elastic member such as rubber and has elasticity, and the small diameter cylindrical portion 11c tightens the cylindrical portion 10 of the spring seat 7 with a predetermined tightening force, and the inner circumference of the small diameter cylindrical portion 11c. The outer lip 12 and the inner lip 13 are formed at an interval in the axial direction.

  Each of the outer lip 12 and the inner lip 13 is fitted in each of a pair of lip engaging grooves 14 formed on the outer periphery of the cylindrical portion 10 of the spring seat 7, and each lip engaging groove 14 is set with a predetermined tightening allowance. Tightened.

  As shown in FIG. 3 (I), the cross-sectional area of the inner lip 13 is smaller than the cross-sectional area of the outer lip 12. The lip engaging groove 14 into which the inner lip 13 is fitted is larger than the cross-sectional area of the inner lip 13, and the inner lip 13 is in elastic contact with the inner peripheral lower portion of the lip engaging groove 14, so When it moves in the axial direction toward the outer lip 12, a minute gap δ is formed between the inner lip 13 and the lip engaging groove 14 as shown in FIG. 3 (II).

  On the other hand, one annular lip 15 is provided on the inner periphery of the large-diameter cylindrical portion 11 d, and the lip 15 is fitted in a lip engaging groove 16 formed on the upper outer periphery of the cylinder 1. The lip 15 also fastens the lip engaging groove 16 with a predetermined tightening allowance.

  As shown in FIG. 1, by mounting the bellows 11, the upper opening of the cylinder 1 is closed to prevent leakage of hydraulic oil filled therein. In addition, a reservoir chamber 17 is formed between the cylinder 1 and the valve sleeve 4 by mounting the bellows 11. The reservoir chamber 17 and the pressure chamber 6 communicate with each other through a passage 18 formed between the fitting surfaces of the sleeve fitting hole 3 and the valve sleeve 4, and a check valve provided at the end of the passage 18 on the pressure chamber 6 side. 19 closes the passage 18 when the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 17.

  A communication passage 20 that connects the pressure chamber 6 and the reservoir chamber 17 is formed at the lower end of the rod 5. A fitting recess 21 is provided at the end of the communication passage 20 on the pressure chamber 6 side, and a throttle 23 is formed in the throttle member 22 press-fitted into the fitting recess 21.

  As shown in FIG. 3 (II), a minute gap δ is formed between the fitting surfaces of the inner lip 13 and the lip engaging groove 14 on the inner periphery of the small diameter cylindrical portion 11c of the bellows 11 as shown in the same figure. In this state, a pressure outflow path 24 that communicates between the reservoir chamber 17 and the outside through the minute gap δ is formed.

  The hydraulic auto tensioner shown in the embodiment has the above-described configuration. When adjusting the tension of the accessory driving belt 31 shown in FIG. 4, 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 33, and an adjusting force is applied to the pulley arm 33.

  In the tension adjustment state of the belt 31 as described above, when the tension of the belt 31 changes due to a load change of the auxiliary machine and the tension of the belt 31 becomes weak, the cylinder 1 and the rod 5 are expanded by the pressing of the return spring 8. The slack of the belt 31 is absorbed by relative movement in the direction.

  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 17, so the check valve 19 opens the passage 18. For this reason, the hydraulic oil in the reservoir chamber 17 smoothly flows from the passage 18 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 31.

  On the other hand, when the tension of the belt 31 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 31 is loaded. At this time, since the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 17, the check valve 19 closes the passage 18.

  The hydraulic oil in the pressure chamber 6 flows from the throttle 23 to the communication path 20 and flows into the reservoir chamber 17, and a hydraulic damper force is generated by the flow resistance when flowing in the throttle 23. As a result, the pushing force applied to the hydraulic auto tensioner is buffered, and the cylinder 1 and the rod 5 slowly move relative to each other in a direction in which the pushing force and the elastic force of the return spring 8 are balanced.

  Here, the belt 31 whose tension is adjusted by the hydraulic auto tensioner is largely slackened when the engine is started. At this time, the cylinder 31 and the rod 5 of the hydraulic auto tensioner are rapidly moved relative to each other in the extending direction. The pressure in the chamber 17 rapidly decreases, and a relatively large tensile force is applied to the small diameter cylindrical portion 11c and the large diameter cylindrical portion 11d of the bellows 11 due to the pressure change.

  At this time, even if the tightening allowance of the small-diameter cylindrical portion 11c and the large-diameter cylindrical portion 11d is the same, the small-diameter cylindrical portion 11c has a small fitting diameter, so that the binding force is small with respect to the large-diameter cylindrical portion 11d. Although detachment is likely to occur, two lips 12 and 13 are provided on the inner periphery of the small-diameter cylindrical portion 11c, and each lip 12 and 13 is engaged with the lip engaging groove 14 with a tightening margin. Is large and does not come off from the cylindrical portion 10 of the spring seat 7.

  In addition, the small diameter cylindrical portion 11c has a structure in which the pulling force is increased as the double lips 12 and 13, and the pulling force is not increased by increasing the tightening force of the small diameter cylindrical portion 11c. Easy.

  Further, in the tension adjustment state of the belt 31, when the pressure in the reservoir chamber 17 rises abnormally due to a temperature rise or the like, the inner lip 13 moves in the axial direction, and as shown in FIG. A minute gap δ is formed between the groove 14 and the pressure in the reservoir chamber 17 flows out through the minute gap δ and the pressure outflow path 24. For this reason, the abnormal deformation | transformation of the bellows 11 can be prevented and the fall of durability can be suppressed.

  In the embodiment, the cross-sectional area of the inner lip 13 is made smaller than the cross-sectional area of the outer lip 12 to facilitate deformation in the axial direction. For example, the connecting portion between the inner lip 13 and the outer lip 12 is made thin. For example, the inner lip 13 may be easily deformed in the axial direction.

  Moreover, although the inner lip of the small diameter cylindrical portion 11c is a double lip, the number of lips is arbitrary. Moreover, although the inner lip of the large diameter cylindrical portion 11d is a single lip, a plurality of lips may be provided.

A longitudinal front view showing an embodiment of a hydraulic auto tensioner according to the present invention Sectional drawing which expands and shows the attachment part of the bellows of FIG. (I) is an enlarged cross-sectional view showing the connection between the bellows and the spring seat shown in FIG. Front view showing tension adjusting device for auxiliary drive belt

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 4 Valve sleeve 5 Rod 6 Pressure chamber 7 Spring seat 8 Return spring 11 Bellows 11c Small diameter cylinder part 11d Large diameter cylinder part 12 Outer lip 13 Inner lip 14 Lip engagement groove 15 Lip 16 Lip engagement groove 17 Reservoir chamber 18 Passage 19 Check valve 24 Pressure outflow path δ Minute gap

Claims (3)

A cylinder that has a closed end at the bottom and is filled with hydraulic oil is provided with a valve sleeve that rises from its inner bottom surface. The lower end of the rod is slidably inserted into the valve sleeve, A return spring is formed between the spring seat provided at the top of the rod and the inner bottom surface of the cylinder to urge the cylinder and the rod in the extending direction, and the outer periphery of the spring seat and the upper outer periphery of the cylinder A lip engagement groove is provided in each of the cylinders, and an annular lip that is fitted to each lip engagement groove with a tightening margin is attached to an elastic bellows formed on the inner periphery of both ends. When a reservoir chamber is formed between the cylinder and the valve sleeve, and the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber in the passage communicating the reservoir chamber and the pressure chamber. In hydraulic auto-tensioner having a check valve for closing the road,
Of the small-diameter cylinder part fitted to the spring seat of the bellows and the large-diameter cylinder part fitted to the cylinder, at least a plurality of lips formed on the inner periphery of the small-diameter cylinder part are provided. Auto tensioner.   Among the plurality of lips, a minute gap is formed between the lip engagement groove into which the inner lip located on the reservoir chamber side is fitted and the inner lip when the small-diameter cylindrical portion is moved in the axial direction due to an increase in internal pressure of the reservoir chamber. 2. The hydraulic auto tensioner according to claim 1, wherein a pressure outflow passage is formed on the inner periphery of the small-diameter cylindrical portion to communicate the reservoir chamber with the outside through the minute gap.   Among the plurality of lips, a cross-sectional area of an inner lip located on the reservoir chamber side is made smaller than a cross-sectional area of a lip located on the outer side, and a lip engaging groove into which the inner lip is fitted is provided in the reservoir chamber A small gap is formed between the small-diameter cylindrical portion and the inner lip when the small-diameter cylindrical portion is moved in the axial direction due to an increase in internal pressure of the small-diameter cylindrical portion. The hydraulic auto tensioner according to claim 1 or 2, wherein a pressure outflow passage is formed.

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