JP4964041B2 - Hydraulic auto tensioner - Google Patents

Description

  The present invention relates to a hydraulic auto tensioner used for adjusting the tension of a belt that drives an auxiliary vehicle such as a timing belt or an alternator that drives a cam.

  As this type of hydraulic auto tensioner, one described in Patent Document 1 has been conventionally known. In this auto tensioner, the upper opening of the oil chamber formed in the cylinder is sealed by incorporating an oil seal, and a rod that slides slidably through the oil seal is protruded outward by a return spring incorporated in the oil chamber. And the belt is pressed by the rod to apply tension to the belt.

  Also, a plunger slidable along the inner diameter surface of the oil chamber is provided at the lower end portion located in the oil chamber of the rod, and a pressure chamber formed on the plunger lower side and a reservoir chamber provided on the plunger upper side on the plunger. Is formed, a seat surface is provided at the lower end opening of the passage, the check ball can be freely contacted and separated from the seat surface, and when the pushing force is applied from the belt to the rod, the check ball is The passage is closed by making contact with the seat surface, and the hydraulic oil in the pressure chamber is loaded on the rod by the hydraulic damper action of the hydraulic oil that leaks into the reservoir chamber through a minute leak gap formed between the oil chamber and the sliding surface of the plunger. The pushing force is buffered.

Japanese Utility Model Publication No. 8-35546

  By the way, in the hydraulic auto tensioner as described above, the check ball repeatedly opens and closes due to pressure fluctuations in the pressure chamber due to the vibration of the timing belt and the accessory driving belt, and comes into contact with the seat surface every time it is closed. Wear easily occurs at the contact portion of the check ball. In particular, since the seat surface is always in contact with the check ball at the same site, the seat surface is easily worn. As a countermeasure against wear, the hardness of the seat surface is increased by heat treatment, but the wear of the seat surface cannot be avoided, and the contact area between the check ball and the seat surface increases due to the wear of the seat surface. The check ball is attracted to the seat surface due to the surface tension of the hydraulic oil intervening in the section, and the check ball detachability deteriorates, causing a problem that the performance of the hydraulic auto tensioner is lowered.

  An object of the present invention is to improve the detachability of a check ball.

In order to solve the above problems, in the present invention, the upper opening of the oil chamber formed inside the cylinder is sealed with an oil seal, and the elastic force of the return spring is applied to a rod that slidably passes through the oil seal. Providing outward protrusion and providing a plunger slidable along the inner surface of the oil chamber at the end of the rod located in the oil chamber, and forming a protrusion on the lower surface of the plunger. The seat surface is provided at the lower end opening of the passage that penetrates from the lower surface of the protruding portion to the upper surface of the plunger and communicates with the pressure chamber formed below the plunger and the reservoir chamber provided above. The check ball can be freely contacted and separated, and a cylindrical retainer is fitted to the outer periphery of the protruding portion provided on the lower surface of the plunger to limit the opening / closing amount of the check ball. Was the hydraulic auto-tensioner, the check ball of the sheet surface is lower than the central opening portion of the passage formed with roundness to the plunger of the site of contact and non-uniform radial thickness in the circumferential direction A configuration in which the roundness of the sheet surface is lowered by the strain after the heat treatment of the protrusion is adopted.

Here, the plunger is subjected to heat treatment after forging and the hardness is increased. Therefore, as described above , a cylindrical surface and a flat surface are formed on the outer periphery of the protruding portion, and heat treatment is performed in a state in which the radial thickness of the protruding portion is not uniform in the circumferential direction. The roundness of the surface can be intentionally lowered, and the roundness of the sheet surface can be reduced very easily.

  In this case, the number of flat surfaces formed on the outer periphery of the protruding portion is arbitrary, and when forming a plurality of flat surfaces, it is preferable to form them at equal intervals. In the heat treatment, it is preferable to employ carburizing quenching or carbonitriding quenching (carbonitriding treatment) in order to increase the hardness of the sheet surface. By subjecting the sheet surface to shot peening after the quenching, the hardness of the sheet surface is increased, and the effect of preventing abrasion of the sheet surface can be obtained.

  As described above, even if the seat surface is worn by making the roundness of the portion of the seat surface that contacts the check ball lower than the roundness of the central through hole portion of the passage formed in the plunger, the wear Since the amount is non-uniform in the circumferential direction, the surface tension of the working oil intervening in the contact portion with the check ball is also non-uniform, and the detachability of the check ball 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.

  The pulley arm 1 is urged toward the direction in which the tension pulley 4 presses the belt 3 by the adjusting force applied from the hydraulic auto tensioner 10.

  As shown in FIG. 2, the hydraulic auto tensioner 10 has a bottomed cylindrical cylinder 11 whose upper end is open. The cylinder 11 is made of an aluminum alloy, and a steel bottomed cylindrical sleeve 12 is fitted therein.

  The inside of the cylinder 11 and the sleeve 12 is an oil chamber 13, and the upper end opening of the oil chamber 13 is sealed by incorporating an oil seal 14, and between the oil seal 14 and the oil surface of the hydraulic oil filled in the oil chamber 13. An air pocket is formed on the surface.

  The oil seal 14 is secured by a retaining ring 15 attached in the opening of the cylinder 11, and the retaining ring 15 and a rod 16 that slidably penetrates the oil seal 14 are stepped to have a small diameter rod portion 16a. The wear ring 17 slidable along the inner diameter surface of the cylinder 11 is fitted to the small diameter rod portion 16a.

  A return spring 18 is incorporated between the wear ring 17 and the upper end surface of the sleeve 12. The return spring 18 presses the wear ring 17 against a stepped portion 16b formed at the base of the small-diameter rod portion 16a to urge the rod 16 outward.

  A plunger 19 slidable along the inner diameter surface of the sleeve 12 is provided at the lower end portion of the rod 16. The plunger 19 has a rod insertion hole 20 on its upper surface, and the lower end portion of the rod 16 is fitted into the rod insertion hole 20, and the plunger 19 and the rod 16 are pressed by a plunger spring 21 provided below the plunger 19. It is held in a fitted state.

  The oil chamber 13 is partitioned into a pressure chamber 22 and a reservoir chamber 23 by incorporating the plunger 19 into the sleeve 12, and a passage 24 is formed in the plunger 19 to communicate the lower pressure chamber 22 with the upper reservoir chamber 23. ing.

  The passage 24 opens at the lower surface of the projecting portion 25 formed on the lower surface of the plunger 19, and a seat surface 26 formed of a tapered surface or a rounded surface is formed at the lower end opening of the passage 24. The passage 24 is opened and closed by a check valve 27.

  As shown in FIG. 3, the check valve 27 includes a check ball 28 provided so as to be able to come into contact with and away from the seat surface 26, and a retainer 29 that regulates the opening / closing amount of the check ball 28. The retainer 29 is cylindrical and has an oil passage hole. The retainer 29 is fitted to the protrusion 25 on the lower surface of the plunger 19, and the flange 30 formed outward from the fitting end is pressed against the lower surface of the plunger 19 by the pressing of the plunger spring 21 and held in the fitted state. Has been.

  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 16 moves outward due to the pressure of the return spring 18 and absorbs the slack of the belt 3.

  At this time, since the pressure in the pressure chamber 22 becomes lower than the pressure in the reservoir chamber 23, the check ball 28 is separated from the seat surface 26 and the passage 24 is opened, and the hydraulic oil in the reservoir chamber 23 is discharged from the passage 24 to the pressure chamber. The rod 16 and the plunger 19 rapidly move outward and immediately absorb the slack of the belt 3.

  On the other hand, when the tension of the belt 3 increases, a pushing force is applied from the belt 3 to the rod 16. At this time, since the pressure in the pressure chamber 22 becomes higher than the pressure in the reservoir chamber 23, the check ball 28 contacts the seat surface 26, the passage 24 is closed, and the hydraulic oil sealed in the pressure chamber 22 The pushing force applied to 16 is buffered.

  When the pushing force is larger than the elastic force of the return spring 18, the hydraulic oil in the pressure chamber 22 flows into the reservoir chamber 23 from a minute leak gap a formed between the sliding surface of the sleeve 12 and the plunger 19, and the pushing force The rod 16 is slowly retracted to a position where the elastic force of the return spring 18 is balanced, and the tension of the belt 3 is kept constant.

  In the hydraulic auto tensioner 10, as described above, the check ball 28 repeatedly opens and closes due to pressure fluctuations in the pressure chamber 22 due to vibration of the belt 3, and contacts the seat surface 26 every time it is closed. Easy to do. When the seat surface 26 wears, the contact area between the check ball 28 and the seat surface 26 increases, and the check ball 28 is attracted to the seat surface 26 due to the surface tension of the hydraulic oil interposed in the contact portion, and the check ball 28 can be detached. It will worsen and the performance of the hydraulic auto tensioner will decrease.

In order to improve the detachability of the check ball 28, here, as shown in FIG. 4 (I), when the plunger 19 is forged, a cylindrical surface 31 and a flat surface 32 are formed on the outer periphery of the protruding portion 25, and the plunger 19 was subjected to heat treatment, and due to strain after the heat treatment,
The roundness of the portion of the seat surface 26 where the check ball 28 contacts is lower than the roundness of the central through hole 24 a of the passage 24 formed in the plunger 19.

  As described above, by intentionally reducing the roundness of the portion of the seat surface 26 where the check ball 28 contacts, even if the seat surface 26 is worn, the amount of wear is uneven in the circumferential direction. Further, the surface tension of the hydraulic oil interposed in the contact portion with the check ball 28 becomes non-uniform, and the detachability of the check ball 28 can be improved.

  Here, in FIG. 4I, the number of flat surfaces 32 is one, but the number of flat surfaces is arbitrary. FIG. 4 (II) shows an example in which two flat surfaces 32 are provided at opposing positions, and FIG. 4 (III) shows an example in which three flat surfaces 32 are provided at an interval of 120 °. Show.

  In the heat treatment, it is preferable to employ carburizing quenching or carbonitriding quenching in order to increase the hardness of the sheet surface 26. When shot peening is performed on the sheet surface 26 after the quenching, the hardness of the sheet surface 26 is increased.

Front view of belt tension adjusting device using hydraulic auto tensioner according to the present invention 1 is a longitudinal front view of the hydraulic auto tensioner shown in FIG. Sectional drawing which expands and shows the check valve part of the hydraulic auto tensioner shown in FIG. (I) thru | or (III) is a perspective view which shows each example of a plunger

Explanation of symbols

11 Cylinder 13 Oil chamber 14 Oil seal 16 Rod 18 Return spring 19 Plunger 22 Pressure chamber 23 Reservoir chamber 24 Passage 25 Projection portion 26 Seat surface 28 Check ball 29 Retainer 31 Cylindrical surface 32 Flat surface

Claims (5)

The upper opening of the oil chamber formed inside the cylinder is sealed with an oil seal, and an elastic force of a return spring is applied to a rod that slidably passes through the oil seal to give outward protrusion, A plunger slidable along the inner diameter surface of the oil chamber is provided at the end located in the oil chamber of the rod, a protrusion is formed on the lower surface of the plunger, and the lower surface of the protrusion penetrates the upper surface of the plunger. A seat surface is provided at a lower end opening of a passage communicating with a pressure chamber formed below the plunger and a reservoir chamber provided above, and a check ball is freely contacted and separated from the seat surface. In a hydraulic auto tensioner that is fitted with a cylindrical retainer on the outer periphery of the protruding portion provided on the lower surface so as to limit the opening / closing amount of the check ball,
Means for lowering the roundness of the portion of the seat surface that comes into contact with the check ball than the central through-hole portion of the passage formed in the plunger and lowering the roundness of the seat surface has a radial thickness in the circumferential direction. Hydraulic auto-tensioner, characterized by strain after heat treatment of protrusions that are uneven in thickness. The hydraulic auto tensioner according to claim 1 , wherein the heat treatment comprises carburizing quenching or carbonitriding quenching. The hydraulic auto tensioner according to claim 1 or 2 , wherein the protrusion has a cylindrical surface and a flat surface on the outer periphery. The hydraulic auto tensioner according to claim 3 , wherein a plurality of the flat surfaces are provided at equal intervals in the circumferential direction. The hydraulic auto tensioner according to any one of claims 1 to 4 , wherein the sheet surface is shot peened.

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