JP2008267456A - Hydraulic auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic auto tensioner having a compact axial length and high reliability on the wear of a sliding portion. <P>SOLUTION: A sleeve 14 is incorporated in a cylinder 11 filled with operating oil and an outward flange 15 formed at the lower end of the sleeve 14 is supported by the bottom face of the cylinder 11 to form a reservoir chamber 17 between the outer diameter face of the sleeve 14 and the inner diameter face of the cylinder 11. A rod 18 is inserted into the sleeve 14 to form a pressure chamber 19 in the cylinder 11. The pressure chamber 19 and the reservoir chamber 17 are communicated with each other via an oil passage 28 formed on the lower face of the flange 15 and a check valve 30 is pressed into the lower end of the sleeve 14. Thus, the hydraulic auto tensioner has a compact axial length. With the rod 18 inserted into the sleeve 14, the capacity of the pressure chamber 19 is reduced and a load per stroke generated by the rod 18 is increased to reduce the amplitude of the auto tensioner, improving the reliability on the wear of the sliding portion. <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 conditioner compressor.

  In a belt transmission that transmits the rotation of the crankshaft of an engine to various automotive accessories, a swingable pulley arm that supports a tension pulley is provided on the slack side of the accessory driving 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 belt tension 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, an oil seal that prevents leakage of hydraulic oil filled in the cylinder is incorporated in the upper opening of the cylinder in which the sleeve is built, and slidably penetrates the oil seal. A spring seat is provided at the upper end of the rod, and a return spring is built in between the spring seat and the flange provided at the lower outer periphery of the cylinder to give the rod an outward projecting force. The force is buffered by a hydraulic damper provided inside the sleeve.

  Here, the hydraulic damper is provided with a plunger slidable in the sleeve at the lower end portion of the rod, the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, and a passage that communicates the pressure chamber and the reservoir chamber with the plunger is provided. The check valve is provided in the opening on the pressure chamber side of the passage, and when the rod is pushed and the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, the passage is closed by the check valve and the hydraulic oil in the pressure chamber closes the rod. The pushing force applied to the is buffered.

JP-A-10-306860

  By the way, in the conventional hydraulic auto tensioner, a lower passage of the rod and a plunger provided in the lower portion of the rod are formed with a passage communicating the pressure chamber and the reservoir chamber, and the passage is provided on the lower surface side of the plunger. Since it is opened and closed by a check valve, the length in the axial direction is long, and it is necessary to secure a wide space for incorporating the hydraulic auto tensioner, so it should be improved in order to make the axial length compact The point was left.

  In addition, since a plunger having a larger outer diameter than the rod is slidably incorporated in the sleeve and a pressure chamber is formed in the sleeve, the volume of the pressure chamber becomes relatively large. Here, when the volume of the pressure chamber is large, the generated load per stroke of the rod becomes small, and when applied to an engine with a large load, the amplitude of the hydraulic auto tensioner becomes large, which is disadvantageous for wear of the sliding part. become. Therefore, the point which should be improved also in improving the reliability with respect to abrasion of a sliding part remains.

  An object of the present invention is to provide a hydraulic auto tensioner having a compact axial length and high reliability with respect to wear of a sliding portion.

  In order to solve the above-described problems, in the present invention, a sleeve is supported in a bottomed cylinder filled with hydraulic oil, and an outward flange formed at the lower end thereof is supported on the bottom surface of the cylinder. The reservoir chamber is provided between the outer diameter surface of the sleeve and the inner diameter surface of the cylinder, and the lower end of the rod is slidably inserted into the sleeve to form a pressure chamber in the sleeve. A cylindrical dust cover whose upper end is closed is attached to the upper end of the rod located outside from the upper opening to cover the upper outer periphery of the cylinder, and a return spring incorporated between the closed end of the dust cover and the flange of the sleeve. The rod is urged in the direction in which the volume of the pressure chamber increases, and the dust cover comes into elastic contact with the inner diameter surface of the dust cover in the seal groove formed in the upper outer periphery of the cylinder. A seal member that seals between the mating surfaces of the cylinder is incorporated, and an oil passage that communicates the lower end of the reservoir chamber and the lower end of the pressure chamber is formed between the bottom surface of the cylinder and the abutting surface of the flange of the sleeve. The pressure chamber is closed when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, and a check valve is used to press-fit the hydraulic fluid in the pressure chamber from flowing out of the oil passage into the reservoir chamber.

  In the hydraulic auto tensioner having the above-described configuration, the tensioner is connected to a pulley arm supported so as to be swingable, and the pulley arm is urged toward the direction in which the tension pulley supported rotatably on the pulley arm presses the belt. To do.

  In the state where the hydraulic auto tensioner is incorporated as described above, when the belt vibrates due to a load change and the belt tension increases and the rod is pushed in, the pressure in the pressure chamber rises. When the pressure becomes higher than the pressure in the reservoir chamber, the check valve is closed to prevent the hydraulic oil in the pressure chamber from flowing out from the oil passage into the reservoir chamber, and is loaded on the rod by the hydraulic oil sealed in the pressure chamber. The pushing force is buffered.

  When the pushing force is larger than the elastic force of the return spring, the hydraulic oil in the pressure chamber flows into the reservoir chamber through a minute leak gap formed between the sleeve and the sliding surface of the rod, and the pushing force and the elastic force of the return spring The rod moves slowly in the direction in which the volume of the pressure chamber is reduced to a position where the pressure balances, thereby keeping the belt tension constant.

  On the other hand, when slack occurs in the belt, the rod moves in the direction in which the volume of the pressure chamber increases, and absorbs the slack in the belt. At this time, since the pressure in the pressure chamber decreases, the check valve is opened, and the hydraulic oil in the reservoir chamber flows from the oil passage into the pressure chamber. For this reason, the rod moves rapidly in the direction in which the volume of the pressure chamber increases to absorb the slack of the belt immediately, and keeps the belt tension constant.

  Here, if the sleeve is unstable support with play in the radial direction, or if the coaxiality with respect to the cylinder is poorly assembled, the slide resistance of the rod increases, and the sleeve wear increases.

  Such inconvenience can be eliminated by making the outer diameter of the flange substantially equal to the inner diameter of the cylinder, but increasing the accuracy of the coaxiality of the entire cylinder surface increases the cost.

  Therefore, by forming a small-diameter flange fitting hole in the lower part of the inner circumference of the cylinder on the same axis as the cylinder to fit the circular flange at the lower end of the sleeve, it is sufficient to ensure the accuracy of coaxiality within a small range. Cost can be reduced.

  In addition, the sleeve can be held coaxially with the cylinder by fitting the flange into the flange fitting hole, and the sleeve can be prevented from moving in the radial direction. It can slide smoothly.

  As described above, in the hydraulic auto tensioner in which the flange fitting hole is formed in the inner peripheral lower portion of the cylinder, as an oil passage communicating the reservoir chamber and the pressure chamber, in the circumferential direction formed on the inner diameter surface of the flange fitting hole. By adopting a plurality of long concave portions and radial grooves formed on the lower surface of the flange, the thickness of the bottom of the cylinder can be reduced, so that the weight of the cylinder can be reduced, By simply fitting the flange of the sleeve into the flange fitting hole, the concave portion and the radial groove are surely communicated with each other. Therefore, it is not necessary to align the sleeve, and the assembly can be facilitated. it can.

  The oil passage includes a plurality of axial grooves formed at equal intervals on the inner diameter surface of the flange fitting hole, and a radial groove formed on the bottom surface of the flange fitting hole and communicating with the lower end of each axial groove. By adopting such a configuration, since it is not necessary to perform any processing on the sleeve side, the sleeve can be easily manufactured by forging or the like, and the sleeve can be easily assembled.

  As described above, in the hydraulic auto tensioner according to the present invention, the rod is slidably inserted into the sleeve incorporated in the cylinder, a pressure chamber is formed in the sleeve, and the inside of the lower end of the sleeve is formed. Since the check valve is press-fitted into the sleeve, a plunger provided at the lower end of the rod is slidably inserted into the sleeve to form a pressure chamber, and a check valve is provided on the lower surface side of the plunger. Compared to a hydraulic auto tensioner, the axial length of the hydraulic auto tensioner can be made compact.

  In addition, since the pressure chamber is formed by slidably inserting the rod into the sleeve, compared to the case where the plunger provided at the lower portion of the rod is slidably inserted into the sleeve to form the pressure chamber. The volume of the pressure chamber is reduced and the generated load per stroke of the rod is increased, so that the amplitude of the hydraulic auto tensioner is reduced and the reliability of the sliding portion against wear can be improved.

  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 bottomed cylindrical cylinder 11 whose upper end is open, and the cylinder 11 is filled with hydraulic oil. A connecting piece 12 is provided on the lower surface of the cylinder 11, and the connecting piece 12 is rotatably connected to the engine block A by tightening bolts 13.

  A sleeve 14 is incorporated in the cylinder 11. The sleeve 14 has an outward flange 15 at the lower end, and the flange 15 is fitted into a small-diameter flange fitting hole 16 provided at the lower inner periphery of the cylinder 11 and supported by the bottom surface of the cylinder 11. The sleeve 14 is held coaxially with the cylinder 11 by the fitting of the flange fitting hole 16 and the flange 15.

  In addition, by incorporating the sleeve 14 into the cylinder 11, a reservoir chamber 17 is formed between the inner diameter surface of the cylinder 11 and the outer diameter surface of the sleeve 14.

  A lower end portion of a rod 18 is slidably inserted into the sleeve 14, and a pressure chamber 19 is formed in the sleeve 14 by incorporating the rod 18.

  A connecting piece 20 is connected to an upper end portion of the rod 18 which is located outside the upper end opening of the cylinder 11, and the connecting piece 20 is connected to the pulley arm 1 by tightening a bolt 21. A cylindrical dust cover 22 whose upper end is closed is attached to the upper end portion of the rod 18 at a position below the connecting piece 20 by means of press-fitting. The dust cover 22 covers the upper outer periphery of the cylinder 11. It has been broken.

  A return spring 23 is incorporated between the upper closed end of the dust cover 22 and the flange 15 of the sleeve 14. The return spring 23 urges the rod 18 in the direction in which the volume of the pressure chamber 19 increases.

  An annular seal groove 24 is formed on the outer periphery of the upper portion of the cylinder 11, and the elastic seal member 25 incorporated in the seal groove 24 is in elastic contact with the inner periphery of the dust cover 22. The space between the fitting surfaces of the cylinder 11 is sealed.

  An annular protrusion 26 is formed on the lower outer periphery of the seal groove 24 on the upper outer periphery of the cylinder 11. On the other hand, a retaining protrusion 27 is provided on the lower inner periphery of the dust cover 22. The rod 18 is prevented from coming out of the cylinder 11 by the abutment of the retaining projection 27 with respect to 26.

  As shown in FIGS. 3 and 4, an oil passage 28 that communicates the reservoir chamber 17 and the pressure chamber 19 is formed between the fitting surfaces of the flange fitting hole 16 and the flange 15 of the sleeve 14. The oil passage 28 includes a plurality of circumferentially long recesses 28 a formed on the inner diameter surface of the flange fitting hole 16 and radial grooves 28 b formed on the lower surface of the flange 15.

  As described above, when the plurality of recesses 28a that are long in the circumferential direction are formed on the inner diameter surface of the flange fitting hole 16, the recesses 28a and the radial grooves are simply fitted into the flange fitting hole 16 by the flange 15 of the sleeve 14. 28b is surely communicated with each other, so that it is not necessary to align the position of the sleeve 14, and the assembly of the sleeve 14 can be facilitated.

  A check valve 30 is incorporated in the lower end portion of the sleeve 14. The check valve 30 includes a valve seat 31 that is press-fitted into the sleeve 14, a valve body 33 that is a ball that opens and closes a valve hole 32 formed in the valve seat 31, and a circular protrusion provided on the upper surface of the valve seat 31. The retainer 34 is pressed into the valve body 33 to regulate the opening / closing amount of the valve element 33. In the check valve 30, when the pressure in the pressure chamber 19 becomes higher than the pressure in the reservoir chamber 17, the valve body 33 closes the valve hole 32, and the hydraulic oil in the pressure chamber 19 flows out from the oil passage 28 into the reservoir chamber 17. To prevent it.

  The belt tension adjusting device shown in the embodiment has the above-described structure, and the tension of the belt 3 changes due to the load fluctuation of the auxiliary machine driven by the belt 3 and the change of the angular velocity of the crankshaft, and the belt 3 is slack. When this occurs, the rod 18 moves in a direction (outward direction) in which the volume of the pressure chamber 19 expands due to the pressure of the return spring 23 and absorbs the slackness of the belt 3.

  At this time, when the volume of the pressure chamber 19 increases and the pressure decreases, and the pressure becomes lower than the pressure of the reservoir chamber 17, the valve element 33 of the check valve 30 is separated from the opening end of the valve hole 32 and the valve hole 32. Therefore, the hydraulic oil in the reservoir chamber 17 flows from the oil passage 28 to the pressure chamber 19, and the rod 18 rapidly moves outward to absorb the slack of the belt 3 immediately.

  On the other hand, when the tension of the belt 3 increases, a pushing force is applied from the belt 3 to the rod 18. At this time, since the pressure in the pressure chamber 19 becomes higher than the pressure in the reservoir chamber 17, the valve body 33 of the check valve 30 closes the valve hole 32 and is loaded on the rod 18 by the hydraulic oil sealed in the pressure chamber 19. The pushing force is buffered.

  When the pushing force is larger than the elastic force of the return spring 23, the hydraulic oil in the pressure chamber 19 flows into the reservoir chamber 17 from a minute leak gap a formed between the sliding surfaces of the sleeve 14 and the rod 18, and the pushing is performed. The rod 18 moves slowly in the direction in which the volume of the pressure chamber 19 decreases (inward) until the force and the elastic force of the return spring 23 are balanced, and the tension of the belt 3 is kept constant.

  In the tension adjustment of the belt 3 as described above, when the volume of the pressure chamber 19 is large, the generated load per stroke of the rod 18 is small, and the amplitude of the hydraulic auto tensioner is large when applied to an engine having a large load. This is disadvantageous for the wear of the sliding part.

  However, in the hydraulic auto tensioner 10 shown in the embodiment, since the rod 18 is slidably inserted into the sleeve 14 to form the pressure chamber 19, the plunger provided at the lower portion of the rod is placed in the sleeve. As compared with the case where the pressure chamber is formed by being slidably inserted into the pressure chamber 19, the volume of the pressure chamber 19 is small, and the generated load per stroke of the rod 18 can be large. As a result, the amplitude of the hydraulic auto tensioner is reduced, and the reliability of the sliding portion against wear can be improved.

  In the hydraulic auto tensioner shown in the embodiment, a rod 18 is slidably inserted into a sleeve 14 incorporated in the cylinder 11, and a pressure chamber 19 is formed in the sleeve 14. Since the check valve 30 is press-fitted into the lower end portion of the rod 14, a plunger provided at the lower end portion of the rod is slidably inserted into the sleeve to form a pressure chamber, and a check valve is formed on the lower surface side of the plunger. The axial length of the hydraulic auto tensioner can be made smaller than that of the hydraulic auto tensioner provided with.

  5 and 6 show another example of the oil passage 28 communicating with the reservoir chamber 17 and the pressure chamber 19. The oil passage 28 shown in this example includes a plurality of axial grooves 28c formed at equal intervals on the inner diameter surface of the flange fitting hole 16, and a lower end of each axial groove 28c formed on the bottom surface of the flange fitting hole 16. And a radial groove 28d communicating with the.

  As described above, since the oil passage 28 is formed on the flange fitting hole 16 side, it is not necessary to perform any processing on the flange 15 of the sleeve 14, so that the sleeve 14 can be easily manufactured by forging or the like. In addition, the sleeve 14 can be easily assembled.

Front view showing a belt tension adjusting device using 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 lower end part of the cylinder of the hydraulic auto tensioner shown in FIG. Sectional view along line IV-IV in FIG. Sectional drawing which shows the other example of the oil path which connects a reservoir chamber and a pressure chamber Sectional view along line VI-VI in FIG.

Explanation of symbols

11 Cylinder 14 Sleeve 15 Flange 16 Flange fitting hole 17 Reservoir chamber 18 Rod 19 Pressure chamber 22 Dust cover 23 Return spring 24 Seal groove 25 Seal member 28 Oil passage 28a Recess 28b Groove 28c Axial groove 28d Radial groove 30 Check valve

Claims (4)

  The sleeve is installed in a bottomed cylinder filled with hydraulic oil, and the outer flange formed on the lower end of the sleeve is supported by the bottom surface of the cylinder. A reservoir chamber is provided in between, the lower end of the rod is slidably inserted into the sleeve, a pressure chamber is formed in the sleeve, and the upper end of the upper end of the rod located outside the upper opening of the cylinder is A closed cylindrical dust cover is attached to cover the upper outer periphery of the cylinder, and the return spring incorporated between the closed end of the dust cover and the flange of the sleeve urges the rod in a direction that increases the volume of the pressure chamber. Incorporates a seal member that elastically contacts the inner diameter surface of the dust cover and seals between the dust cover and the mating surface of the cylinder in a seal groove formed on the outer periphery of the cylinder An oil passage that communicates the lower end of the reservoir chamber and the lower end of the pressure chamber is formed between the bottom surface of the cylinder and the abutting surface of the sleeve flange, and the pressure in the pressure chamber is higher than the pressure in the reservoir chamber in the lower end portion of the sleeve. This is a hydraulic auto tensioner that is closed and press-fitted with a check valve that prevents hydraulic oil in the pressure chamber from flowing out of the oil passage into the reservoir chamber.   The hydraulic auto tensioner according to claim 1, wherein a small-diameter flange fitting hole into which a circular flange at a lower end of the sleeve is fitted is formed coaxially with the cylinder at a lower inner periphery of the cylinder.   3. The hydraulic auto tensioner according to claim 2, wherein the oil passage includes a plurality of circumferentially long recesses formed on an inner diameter surface of the flange fitting hole and a radial groove formed on a lower surface of the flange.   The oil passage includes a plurality of axial grooves formed at equal intervals on the inner diameter surface of the flange fitting hole, and a radial groove formed on the bottom surface of the flange fitting hole and communicating with the lower end of each axial groove. The hydraulic auto tensioner according to claim 2.

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