JP2008256120A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic automatic tensioner capable of keeping internal pressure of a bellows substantially constant and preventing permanent set of the bellows. <P>SOLUTION: By engaging a lip 24 formed on the upper end inner circumference of the bellows 23 and having a square cross-section with a lip engagement groove 26 formed on the outer circumference of a spring seat 18 and having a square cross-section, an annular projection 25 formed on the inner circumference of the lip 24 and having a circular arc cross-section is elastically brought into contact with an inner peripheral surface of the lip engagement groove 26. Protrusions 28 are radially formed on a lower face of the lip 24 so as to define air passages 29 between the adjacent protrusions 28. As a result, the inside of the bellows 23 is not sealed by an edge e of the bottom surface inner circumference of the lip engagement groove 26 even when the edge e strongly makes contact with the lower face of the lip 24 due to extension and reduction in diameter of the bellows 23 caused by abrupt pressure decrease in the bellows 23, and air is allowed to flow between the inside and outside of the bellows 23 through the air passages 29. It is thus possible to prevent the bellows 23 from being kept in a deformed state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  In a belt transmission that transmits the rotation of the crankshaft of an engine to various automobile accessories, a swingable pulley arm that supports a tension pulley is provided on the slack side of the accessory drive belt, and a hydraulic auto tensioner is installed on the pulley arm. An adjustment force is applied to urge the pulley arm in a direction in which the tension pulley presses the belt, so that the tension of the belt is kept constant.

  As a hydraulic auto tensioner used in the belt transmission device as described above, the one described in Patent Document 1 has been conventionally known. In this hydraulic auto tensioner, a sleeve is assembled in a cylinder filled with hydraulic oil, and a spring seat is fixed to the upper end of a rod having a lower end slidably inserted into the sleeve. A return spring is incorporated between the bottom surfaces of the cylinders to urge the rods outward, and the pushing force applied to the rods from the belt is buffered by a hydraulic damper.

  Also, the lower end of the bellows is fitted to the outer periphery of the upper end of the cylinder, the annular protrusion formed on the inner periphery of the upper end of the bellows is fitted to the engagement groove formed on the outer periphery of the spring seat, and the rod When the internal pressure of the cylinder rises due to a stroke change or a temperature change, the change in the internal pressure is absorbed by the elastic deformation in the radial direction of the bellows.

  In addition, a notch is formed in the annular protrusion formed on the inner periphery of the upper end of the bellows, and the cylinder internal pressure is abnormal, such as when the rod is pushed to the bottom dead center position and the hydraulic auto tensioner is removed from the engine. When the height of the bellows is increased, the air in the cylinder is discharged from the notch to prevent the bellows from being detached from the spring seat.

Special Table 2000-504395

  By the way, in the conventional hydraulic auto tensioner, when the pressure in the cylinder rises abnormally, the air in the cylinder is discharged from the notch formed in the annular protrusion as described above. However, after the assembly of the hydraulic auto tensioner, if the rod moves in the direction in which the rod suddenly protrudes and the inside of the cylinder becomes negative pressure, the bellows expands and contracts in the radial direction, and is loaded on the annular protrusion. The edge of the inner periphery of the bottom surface of the engagement groove is in strong contact with the lower surface of the annular protrusion due to the tensile load, preventing the entry of air from the outside, and the inside of the bellows may be held in a negative pressure state, causing the bellows to be permanently deformed. There is.

  An object of the present invention is to provide a hydraulic auto tensioner that can keep the internal pressure of the bellows substantially constant and prevent permanent deformation of the bellows.

  In order to solve the above-described problems, in the present invention, a valve sleeve rising from the bottom surface is provided in a cylinder having a closed end at a lower portion and filled with hydraulic oil inside, and a rod sleeve is provided in the valve sleeve. A return spring that slidably inserts the lower end portion 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 on the upper portion of the rod and the inner bottom surface of the cylinder. Lip engagement grooves are provided on the outer periphery of the spring seat and the upper outer periphery of the cylinder, and annular lips are formed on the inner periphery of both ends to be fitted with each lip engagement groove with a tightening margin. By attaching a bellows having high elasticity, the upper opening of the cylinder is closed to form a reservoir chamber between the cylinder and the valve sleeve, and a passage communicating the reservoir chamber and the pressure chamber is formed. 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 lip engagement groove formed in the spring seat and a lip engaged in the lip engagement groove Each of which has a square cross section, a ventilation space is provided between the top surface of the square lip and the top surface of the square lip engagement groove, and a cross-sectional circle that elastically contacts the inner peripheral surface of the square lip engagement groove on the inner peripheral surface of the square lip A configuration in which an arc-shaped annular protrusion is formed and a radial air passage is formed on either the lower surface of the square lip and the bottom surface of the square lip engaging groove opposite to the square lip at intervals in the circumferential direction. Adopted.

  Here, a plurality of ridges may be radially formed on the lower surface of the square lip, and a ventilation path may be provided between adjacent ridges, or a plurality of grooves may be formed radially on the bottom surface of the square lip engaging groove, The groove may be a ventilation path.

  As described above, the annular projection formed on the inner periphery of the lip having a square cross section is in contact with the inner peripheral surface of the lip engagement groove having a square cross section, and the upper surface of the lip and the upper surface of the lip engagement groove are contacted. By providing a ventilation space between the bottom surface of the lip and the bottom surface of the lip engaging groove, the lip expands when the internal volume of the bellows decreases due to the pushing of the rod and the pressure increases. Then, the annular protrusion is separated from the lip engaging groove, and the air inside the bellows flows from the ventilation path to the ventilation space through the annular space formed between the inner peripheral surface of the lip and the inner peripheral surface of the lip engaging groove. To the outside.

  Also, when the rod moves in the protruding direction to the stroke end due to the elasticity of the return spring, the internal volume of the bellows expands, and when the internal pressure of the bellows suddenly drops to a negative pressure state, the bellows is reduced in diameter, A tensile load is applied to the lip due to the extension of the bellows, and the inner peripheral edge of the bottom surface of the lip engaging groove comes into strong contact with the lower surface of the lip, but one of the bottom surface of the lip engaging groove and the lower surface of the lip Since the ventilation path is formed in the bellows, the inside of the bellows is not sealed by the edge.

  For this reason, the diameter of the lip is expanded by the external pressure acting on the ventilation space, and the external air passes through the annular space formed between the inner peripheral surface of the lip and the inner peripheral surface of the lip engaging groove from the ventilation space. It flows into the air passage and flows into the bellows.

  In this way, when the pressure inside the bellows increases, the air inside the bellows flows out, and when the pressure of the bellows decreases and becomes negative, the outside air flows into the bellows. The pressure can always be kept substantially constant, the permanent deformation of the bellows can be prevented, and the lip can be prevented from coming off from the lip engaging groove.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a belt tension adjusting device. As shown in the figure, the pulley arm 1 is supported so as to be swingable about a fulcrum shaft 2, and a tension pulley 4 that applies tension to the belt 3 is rotatably supported at the end of the swing side.

  Further, a hydraulic auto tensioner 10 according to the present invention is connected to the pulley arm 1, and the pulley arm 1 is urged by the hydraulic auto tensioner 10 in a direction in which the tension pulley 4 presses the belt 3.

  As shown in FIG. 2, the hydraulic auto tensioner 10 has a cylinder 11 whose lower portion is closed, and a connecting piece 12 provided on the lower surface of the hydraulic auto tensioner 10 is rotatably connected to the engine block A by tightening bolts 13. Yes.

  A sleeve fitting hole 14 is provided in the bottom surface of the cylinder 11, and a lower end portion of the valve sleeve 15 is press-fitted into the sleeve fitting hole 14. A piston 16a provided under the rod 16 is slidably inserted into the valve sleeve 15, and a pressure chamber 17 is provided in the valve sleeve 15 by the insertion of the piston 16a.

  A spring seat 18 is fixed to an upper end portion of the rod 16 located outside the cylinder 11, and a return spring 19 incorporated between the spring seat 18 and the bottom surface of the cylinder 11 extends relative to the cylinder 11 and the rod 16. It is energizing in the direction to do.

  A connecting piece 20 is provided at the upper end of the spring seat 18. The connecting piece 20 is rotatably connected to the pulley arm 1 by tightening bolts 21. The spring seat 18 is integrally provided with a cylindrical portion 22 that covers the upper portion of the return spring 19, and a bellows 23 is mounted between the cylindrical portion 22 and the upper end portion of the cylinder 11.

  The bellows 23 is formed with an upward inversion portion 23a at the center in the length direction and a downward inversion portion 23b on the outside of the upward inversion portion 23a. A small-diameter cylindrical portion 23c is continuously provided on the upward inversion portion 23a. A large-diameter cylindrical portion 23d is connected to the reversing portion 23b.

  The bellows 23 is formed of an elastic member such as rubber and has elasticity, and the small-diameter cylindrical portion 23c is fitted into the cylindrical portion 22 of the spring seat 18 so that air can flow between the fitting surfaces. Is formed. The small diameter cylindrical portion 23c may be fitted to the cylindrical portion 22 with a predetermined tightening allowance. In this case, an axial groove is provided on the inner peripheral surface of the small diameter cylindrical portion 23c or the outer peripheral surface of the cylindrical portion 22 so that air can flow.

  As shown in FIGS. 3 and 4, an annular lip 24 is formed on the inner periphery of the upper end portion of the small diameter cylindrical portion 23c. The lip 24 has a square cross section, and an annular protrusion 25 having an arc cross section is provided on the inner periphery thereof.

  The lip 24 is fitted into a lip engaging groove 26 having a square cross section formed on the outer periphery of the spring seat 18, and the inner peripheral surface of the lip engaging groove 26 is tightened with a predetermined tightening margin, and the annular protrusion 25. Is in pressure contact with the inner peripheral surface of the lip engaging groove 26.

  The groove width of the lip engaging groove 26 is such that the lip 24 can be fitted with a margin, and the upper surface of the lip 24 and the lip engaging groove with the lower surface of the lip 24 engaged with the bottom surface of the lip engaging groove 26. A ventilation space 27 is formed between the upper surfaces of 26.

  A plurality of ridges 28 extending in the radial direction are formed radially on the lower surface of the lip 24, and a ventilation path 29 is formed between the adjacent ridges 28.

  As shown in FIG. 2, an annular lip 30 is provided on the inner periphery of the large-diameter cylindrical portion 23 d in the bellows 23, and the lip 30 is fitted in a lip engagement groove 31 formed on the upper outer periphery of the cylinder 11. ing. The lip 30 also fastens the lip engaging groove 31 with a predetermined tightening allowance.

  By mounting the bellows 23 between the spring seat 18 and the upper end of the cylinder 11, the upper opening of the cylinder 11 is closed to prevent leakage of hydraulic oil filled therein. In addition, a reservoir chamber 32 is formed between the cylinder 11 and the valve sleeve 15 by mounting the bellows 23. The reservoir chamber 32 and the pressure chamber 17 communicate with each other through a passage 33 formed between the fitting surfaces of the sleeve fitting hole 14 and the valve sleeve 15, and a check valve provided at the end of the passage 33 on the pressure chamber 17 side. 34 closes the passage 33 when the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 32.

  A communication passage 35 that connects the pressure chamber 17 and the reservoir chamber 32 is formed at the lower end of the rod 16. A fitting recess 36 is provided at the end of the communication passage 35 on the pressure chamber 17 side, and a throttle 38 is formed in a throttle member 37 press-fitted into the fitting recess 36.

  A retaining ring 39 is attached to the inner periphery of the upper end of the valve sleeve 15, and the rod 16 is prevented from being pulled out by contact of the upper end of the piston 16 a with the retaining ring 39.

  The belt 3 tension adjusting device shown in the embodiment has the above-described structure. When the tension of the belt 3 changes due to load fluctuation of the auxiliary machine and the tension of the belt 3 becomes weak, the cylinder 11 is pressed by the return spring 19. The rod 16 is relatively moved in the extending direction, and the slack of the belt 3 is absorbed.

  Here, when the cylinder 11 and the rod 16 move relative to each other in the extending direction, the pressure in the pressure chamber 17 becomes lower than the pressure in the reservoir chamber 32, so the check valve 34 opens the passage 33. For this reason, the hydraulic oil in the reservoir chamber 32 smoothly flows from the passage 33 into the pressure chamber 17, and the cylinder 11 and the rod 16 smoothly move relative to each other in the extending direction to immediately absorb the slack of the belt 3.

  On the other hand, when the tension of the belt 3 is increased, a pressing force is applied in a direction in which the cylinder 11 and the rod 16 of the hydraulic auto tensioner 10 are contracted from the belt 3. At this time, since the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 32, the check valve 34 closes the passage 33.

  Further, the hydraulic oil in the pressure chamber 17 flows from the throttle 38 to the communication path 35 and flows into the reservoir chamber 32, and a hydraulic damper force is generated by the flow resistance when flowing in the throttle 38, and the hydraulic damper force As a result, the pushing force applied to the hydraulic auto tensioner is buffered, and the cylinder 11 and the rod 16 slowly move relative to each other in a contracting direction to a position where the pushing force and the elastic force of the return spring 19 are balanced.

  Here, in the hydraulic auto tensioner 10, the rod 16 is pushed into the valve sleeve 15, and the cylinder block 11 and the rod 16 are contracted, so that the engine block A is attached and detached.

  At this time, since the volume inside the bellows 23 is reduced by pushing the rod 16, the pressure inside the bellows 23 rises conversely. Here, when the pressure in the bellows 23 rises, the lip 24 provided in the small-diameter cylindrical portion 23c of the bellows 23 increases in diameter, the annular protrusion 25 moves away from the lip engaging groove 26, and the air inside the bellows 23 The air flows from the air passage 29 through the annular space formed between the inner peripheral surface of the lip 24 and the inner peripheral surface of the lip engaging groove 26 to the vent space 27 and flows out.

  When the push of the rod 16 is released after the hydraulic auto tensioner 10 is attached or removed, the rod 16 is suddenly moved in the protruding direction by the elasticity of the return spring 19, and as shown in FIG. The piston 16 a comes into contact with the retaining ring 39.

  At this time, the volume inside the bellows 23 is expanded, and the pressure inside the bellows 23 is rapidly reduced to a negative pressure state. The bellows 23 is reduced in diameter by the negative pressure, and a tensile load is applied to the lip 24 due to the extension of the bellows 23. As shown in FIG. The lip 24 has a plurality of ridges 28 formed radially on the lower surface of the lip 24, and air passages 29 are provided between the adjacent ridges 28. The inside of the bellows 23 is not sealed.

  For this reason, the lip 24 is expanded in diameter by the external pressure acting on the ventilation space 27, and as shown by the arrows in the figure, the external air flows from the ventilation space 27 to the inner peripheral surface of the lip 24 and the lip engagement groove 26. Flows through the annular space formed between the inner peripheral surfaces of the gas to the ventilation path 29 and flows into the bellows 23.

  As described above, when the pressure inside the bellows 23 increases, the air inside the bellows 23 flows out, and when the pressure in the bellows 23 decreases and becomes negative, the outside air flows into the bellows 23. Therefore, the internal pressure of the bellows 23 can always be kept substantially constant.

  For this reason, since the bellows 23 is not maintained in a deformed state, it is not permanently deformed, and the lip 24 is not detached from the lip engaging groove 26.

  3 and 4, the protrusions 28 extending in the radial direction are radially formed on the lower surface of the lip 24 and the air passages 29 are formed between the adjacent protrusions 28, but are shown in FIGS. 7 and 8. As described above, a radially extending groove may be formed on the bottom surface of the lip engaging groove 26 and the groove may be used as the air passage 29.

Front view showing a belt tension adjusting device employing a hydraulic auto tensioner according to the present invention. Sectional view along the line II-II in FIG. Sectional drawing which expands and shows the connection part of a spring seat and a bellows Sectional view along line IV-IV in FIG. Sectional view showing the rod's retaining state Sectional drawing which expands and shows the connection part of the spring seat and bellows in the state shown in FIG. Sectional drawing which shows the other example of an air passage Sectional view along line VIII-VIII in FIG.

Explanation of symbols

11 cylinder 15 valve sleeve 16 rod 17 pressure chamber 18 spring seat 19 return spring 23 bellows 24 lip 25 annular projection 26 lip engagement groove 27 vent space 28 ridge 29 vent passage 32 reservoir chamber 33 passage 34 check valve

Claims (3)

A cylinder with a closed end at the bottom and filled with hydraulic oil inside is provided with a valve sleeve that rises from its bottom, and the lower end of the rod is slidably inserted into the valve sleeve. A pressure chamber is formed, and a return spring that urges the cylinder and the rod in the extending direction is incorporated between the spring seat provided at the upper part of the rod and the inner bottom surface of the cylinder, and the outer circumference of the spring seat and the upper outer circumference of the cylinder are Each lip engagement groove is provided with an annular lip that is fitted with a tight margin in each lip engagement groove, and the upper opening of the cylinder is closed by mounting elastic bellows formed on the inner periphery of both ends. Thus, a reservoir chamber is formed between the cylinder and the valve sleeve, and is passed through the passage communicating the reservoir chamber and the pressure chamber when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber. In the hydraulic auto-tensioner provided with a closing check valve,
Each of the lip engaging groove formed in the spring seat and the lip engaged with the lip engaging groove has a square cross section, and a ventilation space is provided between the upper surface of the rectangular lip and the upper surface of the rectangular lip engaging groove. An annular protrusion having an arcuate cross-section that elastically contacts the inner peripheral surface of the square lip engaging groove is formed on the inner peripheral surface of the square lip, and the lower surface of the square lip and the square lip engaging groove opposed thereto A hydraulic auto-tensioner characterized in that a radially extending air passage is formed on either one of the bottom surfaces at intervals in the circumferential direction.   The hydraulic auto tensioner according to claim 1, wherein a plurality of protrusions are formed radially on the lower surface of the square lip, and an air passage is formed between adjacent protrusions.   The hydraulic auto tensioner according to claim 1, wherein a plurality of grooves are formed radially on the bottom surface of the square lip engaging groove, and the grooves serve as air passages.

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