JP2008032128A - Hydraulic auto-tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic auto-tensioner in which a bellows is prevented from coming out and a hydraulic oil is prevented from spouting. <P>SOLUTION: A sleeve 4 is installed in a cylinder 1 filled with a hydraulic oil. A pressure chamber 6 is formed in the sleeve 4 by slidably inserting the lower end of a rod 5 into the sleeve 4. A return spring 8 is assembled between a spring seat 7 formed at the upper part of the rod 5 and the inside bottom surface of the cylinder 1 to bias the cylinder 1 and the rod 5 in the extending direction. An extensible bellows 11 is installed between the outer periphery of the spring seat 7 and the upper part of the cylinder 1 to form a reservoir chamber 17 between the cylinder 1 and the sleeve 4. A check valve 19 is installed in a passage 18 allowing the reservoir chamber 17 to communicate with the pressure chamber 6. A through-hole 25 allowing the outside to communicate with the reservoir chamber 17 is formed in the spring seat 7. A plug body 26 is press-fitted into the through-hole 25. The reservoir chamber 17 communicates with the outside through a vent hole 27 formed in the plug body 26. <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 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 31 to the hydraulic auto tensioner A via the tension pulley 32 and the pulley arm 33 in the direction of contracting the cylinder and the rod. The pushing force is buffered by a damper action of the hydraulic oil sealed in the pressure chamber.

  Since the hydraulic auto tensioner as described above has an expansion / contraction function of several mm to several tens of mm, the bellows sealing the reservoir chamber is required to be elastic.

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 cylinder part connected to the upward reversing part is fitted to the outer periphery of the spring seat with a tightening margin, and the large diameter cylindrical part connected to the downward reversing part is fitted to the upper outer periphery of the cylinder with a tightening allowance. ing.
Special Table 2000-504395

  By the way, in the conventional hydraulic auto tensioner, the volume of the reservoir chamber increases and the pressure decreases during expansion, and the volume of the reservoir chamber decreases and increases when contracted. When the bellows contracts or expands, there is a possibility that a pulling force is applied to the bellows when the bellows is contracted, and the bellows is detached, or a gap is formed in the fitting portion when the bellows is expanded, and the internal hydraulic oil may be ejected.

  An object of the present invention is to provide a hydraulic auto tensioner capable of preventing the bellows from being detached and the hydraulic oil from being ejected.

  In order to solve the above-mentioned problems, in the present invention, a sleeve rising from the inner bottom surface is provided in a cylinder having a closed end at the lower part and filled with hydraulic oil, and the lower end of the rod is provided in the sleeve. A pressure spring is formed in the sleeve by slidably inserting the part, and a return spring that urges the cylinder and rod in the extending direction is incorporated between the spring seat provided on the top of the rod and the inner bottom surface of the cylinder. The outer periphery of the spring seat and the upper outer periphery of the cylinder are fitted with elastic elastic bellows to form a reservoir chamber sealed between the cylinder and the sleeve, and the reservoir chamber communicates with the pressure chamber. 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. Part forming a through hole communicating, it had adopted a structure in which press-fitting the cylindrical plug body vent holes are formed in a small diameter that penetrates from one end to the other end in the through hole.

  As described above, the spring seat is formed with a through-hole communicating with the reservoir chamber and the outside, the plug is press-fitted into the through-hole, and the reservoir chamber and the outside are connected through the small-diameter vent formed in the plug. Since the cylinder and rod are relatively stretched to increase the volume of the reservoir chamber and the pressure decreases, external air flows into the reservoir chamber from the vent hole of the plug, and the cylinder When the rod contracts relatively and the volume of the reservoir chamber decreases and the pressure increases, the air in the reservoir chamber flows out from the vent hole to the outside. Since the pressure in the reservoir chamber can always be kept constant by the air flow, the bellows is not greatly expanded or contracted, and it is possible to reliably prevent the bellows from coming off or the hydraulic oil from being ejected. .

  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.

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

  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.

  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 a small diameter cylindrical portion 11c connected to the upward inversion portion 11a. The portion 10 is fitted with a tightening margin, and is secured by engagement of a lip 12 formed on the inner periphery of the end of the small-diameter cylindrical portion 11 c and a lip engaging groove 13 provided on the outer periphery of the cylindrical portion 10.

  Further, the end of the large-diameter cylindrical portion 11d connected to the downward reversing portion 11b is fitted to the upper outer periphery of the cylinder 1 with an allowance, and the lip 14 formed on the inner periphery of the end of the large-diameter cylindrical portion 11d The cylinder 1 is prevented from being pulled out by engagement of a lip engagement groove 15 provided on the upper outer periphery of the cylinder 1.

  By mounting the bellows 11, the upper opening of the cylinder 1 is closed to prevent leakage of hydraulic oil filled therein. Further, a sealed reservoir chamber 17 is formed between the cylinder 1 and the 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 sleeve 4, and a check valve 19 provided at the end of the passage 18 on the pressure chamber 6 side. When the pressure in the pressure chamber 6 becomes higher than the pressure in the reservoir chamber 17, the passage 18 is closed.

  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 FIGS. 1 and 2, the spring seat 7 is formed with a stepped through hole 25 having a large diameter at the top and communicating with the outside and the reservoir chamber 17. A cylindrical plug body 26 is press-fitted into the 25 large-diameter holes 25a.

  As shown in FIGS. 2 and 3, the plug body 26 has a plurality of small-diameter vent holes 27 penetrating from one end to the other end, and the reservoir chamber 17 communicates with the outside through the vent holes 27. . The size of the cross-sectional area of the vent hole 27 is such that when the hydraulic auto tensioner is in the lateral direction with the plug body 26 as the lower part or the spring seat 7 is in the downward direction, the hydraulic oil is naturally exposed to the outside by its surface tension. It is the size which does not leak.

  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 that is tension-adjusted by the hydraulic auto tensioner has a large slack when the engine is started. At that time, the cylinder 1 and the rod 5 of the hydraulic auto tensioner rapidly move relative to each other in the extending direction to increase the volume of the reservoir chamber 17 and conversely, the pressure rapidly decreases.

  At this time, external air flows into the reservoir chamber 17 from the vent hole 27 of the plug 26, and the pressure in the reservoir chamber 17 is kept constant by the inflow of the air. Further, when the cylinder 1 and the rod 5 of the hydraulic auto tensioner rapidly move relative to each other in the contracting direction, the volume of the reservoir chamber 17 decreases, and conversely, the pressure rapidly increases. At this time, the air in the reservoir chamber 17 is discharged to the outside from the vent hole 27, and the pressure in the reservoir chamber 17 is kept constant by the discharge of the air.

  In this manner, air flows between the reservoir chamber 17 and the outside through the vent hole 27 formed in the plug body 26 in accordance with the pressure change in the reservoir chamber 17, and the pressure in the reservoir chamber 17 is kept constant. Therefore, the bellows 11 does not expand or contract greatly, and it is possible to reliably prevent the bellows 11 from coming off and the hydraulic oil from being ejected.

A longitudinal front view showing an embodiment of a hydraulic auto tensioner according to the present invention Enlarged sectional view of the through-hole part formed in the spring seat Perspective view showing plug Front view showing tension adjusting device for auxiliary drive belt

Explanation of symbols

1 Cylinder 4 Sleeve 5 Rod 6 Pressure chamber 7 Spring seat 8 Return spring 11 Bellows 17 Reservoir chamber 18 Passage 19 Check valve 25 Through hole 26 Plug body 27 Ventilation hole

Claims (1)

A cylinder that has a closed end at the bottom and is filled with hydraulic oil inside is provided with a sleeve that rises from its inner bottom surface. The lower end of the rod is slidably inserted into the sleeve, and the pressure chamber is inserted into the sleeve. A return spring that urges the cylinder and the rod in the extending direction is incorporated between the spring seat provided at the top of the rod and the inner bottom surface of the cylinder, and elasticity is provided to the outer periphery of the spring seat and the upper outer periphery of the cylinder. A telescopic bellows having both ends is fitted to form a sealed reservoir chamber between the cylinder and the sleeve, and the pressure in the pressure chamber is greater than the pressure in the reservoir chamber in a passage communicating the reservoir chamber and the pressure chamber. In the hydraulic auto tensioner with a check valve that closes the passage when it gets higher,
The spring seat is formed with a through-hole that communicates with the reservoir chamber and the outside, and a cylindrical plug body in which a small-diameter vent hole that penetrates from one end to the other end is press-fitted in the through-hole. Hydraulic auto tensioner.

Images