JP2007211853A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic automatic tensioner for surely preventing slipping-out of a rod, even when the tension adjusting rod of a belt moves in the full stroke outside direction. <P>SOLUTION: An oil seal 13 is incorporated into an upper opening of a cylinder 11 filled with a hydraulic fluid, and a hydraulic damper 30 is arranged in a lower part of the rod 16 penetrating through its oil seal 13. A return spring 19 is arranged on the rod 16 on the outside of a cylinder 11. A wear ring 37 is fitted to the rod 16. The rod 16 is attached with a snap ring 39 for preventing slipping-out of the wear ring 37, by arranging a cross-sectional circular arc-shaped engaging groove 38 in a position opposed to an under surface of its wear ring 37 in a state of allowing the wear ring 37 to abut on a step part arranged in an intermediate part in the longitudinal direction of its rod 16. When the belt is cut and the rod 16 moves in the outward direction, the snap ring 39 is made to bite in the edge and the engaging groove 38 of the under surface of the wear ring 37 stopping by abutting on the oil seal 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydraulic auto tensioner used for adjusting the tension of a belt for driving an auxiliary machine such as an alternator.

  As this type of hydraulic auto tensioner, one described in Patent Document 1 has been conventionally known. This auto tensioner seals the opening of the cylinder fitted with a steel bottom sleeve with an oil seal to prevent leakage of the hydraulic oil filled inside, and the oil seal can slide freely. An elastic force of a return spring is imparted to the rod penetrating the rod to impart an outward projecting property, and the pushing force applied from the belt to the rod is buffered by a hydraulic damper incorporated in the sleeve.

  In addition, a wear ring that is slidable along the inner diameter surface of the cylinder is attached to a portion of the rod located inside the cylinder, and the wear ring prevents deformation such as bending of the rod.

  Here, the oil seal is prevented from moving downward by a step formed on the inner periphery of the cylinder, and is prevented from being pulled out by a retaining ring attached to the upper side thereof.

The wear ring is secured by a step formed on the outer periphery of the rod and a retaining ring attached to the outer periphery of the rod below the step.
JP-A-10-19099

  By the way, in the conventional hydraulic auto tensioner, a C-shaped retaining ring is adopted as a retaining ring, and the retaining ring is attached to an engaging groove having a square cross section formed on the outer periphery of the rod. When the belt is cut and the rod moves rapidly outward due to the elastic force of the return spring, and the rod is retained by the wear ring contacting the oil seal, a large impact force is applied to the retaining ring or engaging groove. The retaining ring may be deformed by the impact force, or the engaging groove may be damaged and the rod cannot be secured. It was.

  In addition, since the engaging groove for attaching the retaining ring has a square cross section, the strength of the rod is low, and in order to secure the required strength, it is necessary to increase the outer diameter of the rod, and the weight of the hydraulic auto tensioner However, there are still points to be improved in terms of weight reduction.

  The object of the present invention is to provide a lightweight hydraulic auto that is excellent in the retaining effect so that the rod can be securely retained even when the belt tension adjusting rod rapidly moves outward in the full stroke direction. To provide a tensioner.

  In order to solve the above problems, the present invention includes a cylinder filled with hydraulic oil, an oil seal that seals an upper opening of the cylinder in a state where an air layer is formed on the hydraulic oil, and the oil A rod that slidably penetrates the seal, a return spring that imparts outward protrusion to the rod, a hydraulic damper that cushions the pushing force applied to the rod, and a rod that is incorporated into the cylinder A wear ring that supports the end of the wear ring. A retaining ring is attached to the rod below the wear ring, and the rod is retained by contacting the retaining ring with the inner periphery of the lower surface of the wear ring. In the hydraulic auto tensioner, the retaining ring is formed of a circlip having a part cut off of a round wire, The outer periphery of the rod to form the engagement grooves for the circlips fitted, it had adopted a configuration in which a circular arc cross sectional shape along the engagement groove on the inner periphery of the circlip.

  In the hydraulic auto tensioner configured as described above, when the rod rapidly moves outward due to a belt rupture or the like, the circlip bites between the inner circumferential edge of the wear ring and the engagement groove, The rod can be prevented from being pulled out by the biting, and a hydraulic auto tensioner excellent in the retaining effect can be obtained.

  In addition, even when the circlip has a thin wire diameter, the circlip has sufficient damage strength, so that a circlip with a thin wire diameter can be adopted, and the circlip is strong even when the groove depth of the engaging groove is shallow. The outer diameter of the rod can be reduced as much as the engagement effect can be exerted and the depth of the engagement groove can be reduced, and the weight of the hydraulic auto tensioner can be reduced.

  Furthermore, since the engagement groove formed in the rod has an arc-shaped cross section, the rod has a higher breakage strength than the engagement groove having a square cross section, and a rod having excellent durability can be obtained.

  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 for applying tension to the belt 3 is rotatably supported at the end of the swing side. .

  The pulley arm 1 is connected to a hydraulic auto tensioner 10 according to the present invention, 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. 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 is filled with hydraulic oil, and the hydraulic oil is prevented from leaking to the outside by an oil seal 13 that seals the upper opening of the cylinder 11. The oil seal 13 is supported at the outer peripheral portion of the lower surface by a step portion 14 formed at the inner peripheral upper portion of the cylinder 11, and an air pocket is formed between the oil seal 13 and the oil surface of the hydraulic oil. Further, the oil seal 13 is secured by a retaining ring 15 attached to the upper inner periphery of the cylinder 11.

  Here, the retaining ring 15 is formed of a chrysanthemum retaining ring, and the edges of the ends of a plurality of bent pieces 15a formed on the outer periphery engage with the inner periphery of the cylinder 11, and the attachment state is maintained by the engagement. ing.

  A spring seat 17 is attached to an upper end portion of the rod 16 slidably penetrating the chrysanthemum retaining ring 15 and the oil seal 13 and located outside the cylinder 11, and a flange provided on the spring seat 17 and a lower outer periphery of the cylinder 11. A return spring 19 is provided between the rods 18 to give the rod 16 outward projecting properties.

  A connecting piece 20 is formed on the upper surface of the spring seat 17, and the connecting piece 20 is connected to the pulley arm 1 via a bolt 21 screwed into the pulley arm 1. On the other hand, a connecting piece 22 is also provided at the lower end of the cylinder 11, and the connecting piece 22 is connected to the engine block 23 via a bolt 24 screwed into the engine block 23.

  A hydraulic damper 30 is incorporated in the sleeve 12 to buffer the pushing force applied to the rod 16.

  The hydraulic damper 30 connects a plunger 31 slidable along the inner diameter surface of the sleeve 12 to the lower end of the rod 16 to partition the inside of the sleeve 12 into a pressure chamber 32 and a reservoir chamber 33. A passage 34 communicating with the pressure chamber 32 and the upper reservoir chamber 33 is provided, and the passage 34 is closed at the opening of the passage 34 on the pressure chamber 32 side when the pressure in the pressure chamber 32 becomes higher than the pressure in the reservoir chamber 33. The check valve 35 is provided to buffer the pushing force applied to the rod 16 by the hydraulic oil sealed in the pressure chamber 32. Reference numeral 36 denotes a plunger spring that presses the plunger 31 against the lower end of the rod 16.

  The rod 16 has a configuration in which a small-diameter shaft portion 16b is provided at the lower end of the large-diameter shaft portion 16a, and the wear ring 37 fitted to the small-diameter shaft portion 16b is slidable along the inner diameter surface of the cylinder 11. The middle portion of the rod 16 in the length direction is supported by the wear ring 37.

  An engagement groove 38 is formed in the small diameter shaft portion 16b at a position facing the lower surface of the wear ring 37 in a state where the wear ring 37 is in contact with the lower end of the large diameter shaft portion 16a.

  As shown in FIG. 3, the engagement groove 38 has a substantially arc-shaped cross section, and a circlip 39 made of a round wire is cut into the engagement groove 38. The wear ring 37 is supported in a non-movable manner in the axial direction by the lower end surface of the radial shaft portion 16a.

  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 by the pressure of the return spring 19 and absorbs the slack of the belt 3.

  At this time, since the plunger 31 also moves in the same direction as the rod 16, the volume of the pressure chamber 32 increases and the pressure decreases. When the pressure becomes lower than the pressure of the reservoir chamber 33, the check valve 35 opens the passage 34. Therefore, the hydraulic oil in the reservoir chamber 33 flows from the passage 34 to the pressure chamber 32, and the rod 16 and the plunger 31 move rapidly outward to 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 32 becomes higher than the pressure in the reservoir chamber 33, the check valve 35 closes the passage 34, and the pushing force applied to the rod 16 by the hydraulic oil sealed in the pressure chamber 32 is increased. Buffered.

  When the pushing force is larger than the elastic force of the return spring 19, the hydraulic oil in the pressure chamber 32 flows into the reservoir chamber 33 through a minute leak gap formed between the sliding surface of the sleeve 12 and the plunger 31, and the pushing force and The rod 16 is slowly retracted to a position where the elastic force of the return spring 19 is balanced, and the tension of the belt 3 is kept constant.

  When the tension of the belt 3 is adjusted as described above, when the belt 3 is broken, the rod 16 is rapidly moved outward by the pressing of the return spring 19 and the wear ring 37 is brought into contact with the oil seal 13 and stopped. The circlip 39 bites between the edge e on the inner periphery of the lower surface of the wear ring 37 and the engaging groove 38, and the rod 16 is prevented from being pulled out by the biting.

  In this way, the rod 16 is prevented from being pulled out by the circlip 39 being caught between the edge e on the inner periphery of the lower surface of the wear ring 37 and the engaging groove 38. it can.

  Here, even when the circlip 39 has a small wire diameter, the circlip 39 has a sufficient breakage strength. Therefore, the circlip 39 having a thin wire diameter can be adopted, and the groove depth of the engaging groove 38 can be adopted. Even if it is shallow, a strong retaining effect is exhibited, and the outer diameter of the rod 16 can be reduced by the amount that the groove depth of the engaging groove 38 can be reduced, so that the weight of the hydraulic auto tensioner can be reduced. it can.

  Furthermore, since the engaging groove 38 formed in the rod 16 has an arc-shaped cross section, the rod 16 has a higher breakage strength and superior durability compared to a case where the engaging groove having a square cross section is formed. Can be obtained.

  In FIG. 2, a wear ring sliding type hydraulic auto tensioner in which the wear ring 37 moves together with the rod 16 is shown, but the hydraulic auto tensioner is not limited to this. For example, as shown in FIG. 4 (I), a wear ring fixing type hydraulic auto tensioner in which a wear ring 37 is assembled between an oil seal 13 and a stepped portion 14 to support the rod 16 slidably. Also good.

  2 and 4I show the upper suction type auto tensioner in which the hydraulic oil in the reservoir chamber 33 is caused to flow into the pressure chamber 32 from the passage 34 provided in the plunger 31. As shown in FIG. 4 (II), the hydraulic oil in the reservoir chamber 33 is made to flow into the lower part in the pressure chamber 32 from the passage 40 formed between the fitting surfaces of the cylinder 11 and the sleeve 12. An auto tensioner may be used.

  In any of the auto tensioners shown in FIGS. 4I and II, a circlip having an engagement groove 38 having a circular arc cross section formed in the intermediate portion in the longitudinal direction of the rod 16 and attached to the engagement groove 38. 39 is engaged with the edge of the inner peripheral portion of the lower surface of the wear ring 37 and the engaging groove 38 to prevent the rod 16 from being pulled out.

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 view showing the wear ring attachment (I) and (II) are sectional views showing other examples of hydraulic auto tensioners

Explanation of symbols

11 Cylinder 13 Oil seal 16 Rod 19 Return spring 30 Hydraulic damper 37 Wear ring 38 Engaging groove 39 Circlip

Claims (1)

A cylinder filled with hydraulic oil, an oil seal that seals the upper opening of the cylinder with an air layer formed on the hydraulic oil, a rod that slidably penetrates the oil seal, and a rod It consists of a return spring that imparts outward projecting properties, a hydraulic damper that cushions the pushing force applied to the rod, and a wear ring that is built into the cylinder and supports between both ends of the rod, In the hydraulic auto tensioner, a retaining ring is attached to the rod below the wear ring, and the rod is retained by contact of the retaining ring with the inner peripheral portion of the lower surface of the wear ring.
The retaining ring is a circlip made of a round wire and partly cut off. An engagement groove for attaching a circlip is formed on the outer periphery of the rod, and the engagement groove is formed on the inner periphery of the circlip A hydraulic auto tensioner characterized by having a circular arc cross section along the line.

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