JP4485841B2 - Hydraulic tensioner - Google Patents

Description

  The present invention relates to a hydraulic tensioner provided with a pole ratchet mechanism.

  The hydraulic tensioner generally includes a housing, a piston slidably inserted into a piston hole formed in the housing and biased in a protruding direction by a spring, and a fluid chamber defined by the piston hole and the piston in the housing. Is mainly composed of During operation of the tensioner, the pressing force acting on the tip of the piston from the chain or belt balances the elastic repulsive force due to the spring and the drag force due to the hydraulic pressure in the chamber.

  By the way, in the case of a hydraulic tensioner that is applied to a timing system or an auxiliary machine (oil pump, etc.) drive system, especially in an automotive application, a situation where sufficient hydraulic pressure does not act in the chamber, such as when the engine is started. Below, when a pressing force is applied from the chain to the piston tip, the piston is easily pushed into the housing and the piston contracts, resulting in noise and vibration.

  Therefore, in order to prevent such piston degeneration, a hydraulic tensioner having a pole ratchet mechanism as shown in US Pat. No. 5,304,099 has been proposed.

  The ratchet mechanism includes a rack tooth formed on a sleeve disposed on the outer periphery of the piston, a pole having a pointed portion that is received in a pole hole orthogonal to the piston hole and can be engaged with the rack tooth of the sleeve, and a pole. It is comprised from the pole coil spring urged | biased in the engagement direction with a rack tooth.

  In this case, when the piston moves together with the sleeve in the projecting direction with the tip of the pole engaged with the rack teeth of the sleeve, the rack teeth of the sleeve move over the tip of the pole, thereby moving the piston. However, when the piston moves with the sleeve in the retracting direction, the sleeve's rack teeth are kept engaged with the tip of the pole so that the piston moves in the retracting direction. Movement is regulated.

However, the conventional pole ratchet mechanism is not provided with a backlash, while there is a demand for a hydraulic tensioner with a pole ratchet mechanism having a backlash.
US Pat. No. 5,304,099 (see FIG. 2)

  The problem to be solved by the present invention is to provide a backlash in a hydraulic tensioner with a pole ratchet mechanism, and to make the pole coil spring act on the pole with a stable spring force and to reduce the manufacturing cost. Is to make it.

The hydraulic tensioner according to the first aspect of the present invention includes a housing having a piston hole that opens at one end, and is slidably inserted into the piston hole to form a fluid chamber between the piston hole and the rack teeth of the outer periphery. A piston formed at least in part, a piston spring disposed in the piston hole and biasing the piston in the protruding direction, and allowing the piston to move in the protruding direction and restricting the movement in the backward direction It was formed by penetrating the housing in the left-right direction and upward so as to have a pole having a tooth part engaged with the rack teeth on the lower surface and a clearance allowing the movement of the pole in the front-rear direction, between the front and rear end surfaces of the pole. A pole hole for accommodating the pole, a pole spring accommodating portion provided at the top of the housing in communication with the pole hole, and a pole spring Housed in volume unit, together with the wound on elliptic cylindrical shape, the major axis direction of the cross-sectional shape is disposed to direct in the axial direction of the piston, the teeth of the pole rack teeth engage the piston A pole coil spring that presses the upper surface of the pole on the side, and a cover that is detachably provided on the housing and has a holding portion that covers the pole spring housing portion and holds the pole coil spring from both the left and right sides.

  In the first aspect of the present invention, the pole having a tooth portion that engages with the rack tooth of the piston is disposed through the clearance in the front-rear direction between the pole hole, and this clearance acts as a backlash. Yes. Thereby, the hydraulic tensioner provided with the backlash mechanism can be realized with a simple structure.

According to the first aspect of the present invention, the pole coil spring is wound in an elliptical cylindrical shape , and is arranged so that the major axis direction of the cross-sectional shape is oriented in the axial direction of the piston. Thereby, when the pole moves together with the piston, the wire rod portion of the pole coil spring wound in an elliptic cylinder shape can be brought into contact with the upper surface of the pole substantially. The contact area of the pole coil spring with respect to the upper surface of the pole can be made substantially constant. As a result, the pressing force from the pole coil spring to the pole can be made substantially constant, and a stable spring force can be applied to the pole.

Furthermore, according to the invention of claim 1, since the cover that covers the pole spring accommodating portion has the holding portion for holding the pole coil spring from both the left and right sides, the pole coil spring having an elliptical cross section can be stabilized. Can be held. In this case, since the cover is provided separately from the housing, the cover along the outer shape of the pole coil spring can be easily formed, and the manufacturing cost can be reduced. On the other hand, when the pole spring accommodation hole is formed in the housing, it is necessary to make a hole having an elliptical cross section in the housing, which increases the manufacturing cost.

In the invention of claim 2, the cross-sectional shape of the pole coil spring is composed of a pair of straight portions along the long axis direction and facing each other, and semicircular portions disposed at both ends thereof. Each part is in contact with the top surface of the pole.

  In this case, even when the pole moves, the contact area of the pole coil spring with respect to the top surface of the pole can be made substantially constant, and thereby the pressing force from the pole coil spring to the pole can be made substantially constant. As a result, a more stable spring force can be applied to the pole during operation of the tensioner.

  The pole spring may have an elliptical cross section as described in the invention of claim 3.

  In the invention of claim 4, the cover has a pair of shoulder portions that project in the left-right direction from the lower end of the holding portion and cover the upper surface of the pole.

In the invention of claim 5, the clearance between the inner wall surface of the shoulder portion and the upper surface of the pole is C, and the distance between the tip surface of the tooth portion of the pole and the tip surface of the rack tooth of the piston is h _b. , when the distance between the tip surface and the outer circumferential surface of the piston of the teeth and h _d, the relationship of h b _{<C <h d} is satisfied.

In this case, when h _b <C, when the piston extends during operation, when the rack tooth of the piston rides on the tooth portion of the pole and the pole is lifted upward, the upper surface of the pole is the cover shoulder portion. The rack teeth of the piston can get over the teeth of the pole without interfering with the inner wall surface of the piston, and the piston can be smoothly extended. Further, when the piston is rotated from the engaged state between the rack tooth of the piston and the tooth portion of the pole, even if an attempt is made to release this engaged state, the rack tooth is formed due to the relationship of C <h _d. It is not possible to move the outer peripheral surface of the piston not to the pole tooth position. Thereby, it is possible to prevent the engagement state between the rack teeth of the piston and the teeth of the pole from being inadvertently released.

  As described in the invention of claim 6, the cover may have a hanging portion that is hung downward from the front end of the shoulder portion and covers the left and right end surfaces of the pole.

According to the hydraulic tensioner according to the present invention, the pole having the tooth portion that engages with the rack tooth of the piston is provided through the clearance in the front-rear direction between the pole hole and the liquid with the backlash mechanism. A pressure tensioner can be realized with a simple structure. Further, in this case, the pole coil spring is wound in an elliptical cylinder shape and is arranged so that the major axis direction of the cross-sectional shape is oriented in the axial direction of the piston. On the other hand, a stable spring force can be applied. Furthermore, in this case, since the cover having the holding portion for holding the pole coil spring from both the left and right sides is provided separately from the housing, the cover along the outer shape of the pole coil spring can be easily formed. Thereby, the manufacturing cost can be reduced.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 to 5 are views for explaining a hydraulic tensioner according to an embodiment of the present invention. FIG. 1 is an overall perspective view of the hydraulic tensioner, and FIG. 2 is a hydraulic tensioner with a cover removed. FIG. 3 is a partial sectional view taken along the line III-III of FIG. 2 and also shows a cross section of the cover, FIG. 4 is a schematic view taken along arrow IV of FIG. 3, and FIG. It is a top view for demonstrating the positional relationship with these.

  As shown in FIGS. 1 and 2, the hydraulic tensioner 1 includes a housing 2 in which a piston hole 2a extending in the axial direction and having an opening at one end is formed, and in the piston hole 2a of the housing 2 in the axial direction (left and right in FIG. 2). Direction) It is mainly composed of a hollow piston 3 slidably inserted and a piston spring 4 which is disposed in the piston hole 2a of the housing 2 and urges the piston 3 in a direction protruding from the piston hole 2a. .

  The housing 2 has bolt holes 20 and 21 into which mounting bolts for mounting the hydraulic tensioner 1 in, for example, an engine are inserted. In the housing 2, a fluid chamber 30 is formed from an inner space 3a formed in the piston 3 and an inner wall surface of the piston hole 2a. An introduction path 10 for introducing engine oil as a working fluid into the fluid chamber 30 from an external pressurized fluid source (not shown) is formed at the bottom of the housing 2.

  A check valve 7 is provided at the bottom of the piston hole 2 a in the housing 2. The check valve 7 is for allowing the flow of fluid from the introduction path 10 to the fluid chamber 30 while preventing the flow of fluid in the opposite direction. Here, a ball check valve is employed.

  A vent disk 8 is provided on the piston head side in the internal space 3 a of the piston 3. The vent disk 8 is a member for discharging the air mixed in the fluid chamber 30 to the outside of the tensioner and controlling the amount of fluid leaked from the fluid chamber 30, and on the side surface of the piston head side, For example, a spiral groove (not shown) is formed. On the other hand, an axial through hole 31 is formed in the piston head. The air in the fluid chamber 30 is discharged from the through hole 31 to the outside of the tensioner through the spiral groove of the vent disk 8 together with the fluid containing the air. The vent disk 8 has a shaft portion 8a. The piston spring 4 is disposed around the shaft portion 8a of the vent disk 8, and its tip urges the vent disk 8 toward the piston head.

  Rack teeth 3 b are formed on part of the outer peripheral surface of the piston 3. On the other hand, the housing 2 is formed with a pole hole 2b that communicates with the piston hole 2a and penetrates the housing 2 in the left-right direction (the vertical direction in FIG. 2) and upward (upward in the figure). A pole 5 is accommodated in the pole hole 2b. The pole 5 has a tooth portion 5a on the lower surface that engages with the rack teeth 3b of the piston 3 and is formed so as to allow the piston 3 to move in the protruding direction and restrict the movement in the backward direction. In addition, a clearance is formed between the front and rear end faces of the pole 5 and the pole hole 2b (see FIG. 5). That is, when the width in the front-rear direction of the pole 5 is t and the length in the front-rear direction of the pole hole 2b is d, t <d. By this clearance, the pole 5 can move in the pole hole 2b in the front-rear direction (that is, in the piston axial direction).

  In the upper opening portion of the pole hole 2b, the housing 2 is provided with a pair of standing wall portions 25 and 26 spaced apart in the front-rear direction. In the pole spring accommodating portion 24 which is a space sandwiched between the standing wall portions 25 and 26, the upper surface 5b of the pole 5 (see FIG. 3) is formed on the side where the tooth portion 5a of the pole 5 engages with the rack tooth 3b of the piston 3. The pole coil spring 6 is urged in a compressed manner. The pole coil spring 6 is wound in a substantially elliptic cylindrical shape (see FIG. 4).

  The major axis direction (arrow a direction in FIG. 5), which is a substantially elliptical shape that is the cross-sectional shape of the pole coil spring 6, is arranged so as to coincide with the piston axis direction (arrow b direction in the figure). The wire portions 60 and 60 ′ substantially along the long axis direction at the lower end of the pole coil spring 6 are in pressure contact with the upper surface 5 b of the pole 5.

  In the example shown in FIG. 5, the wire portions 60 and 60 'of the pole coil spring 6 extend in a straight line while facing each other, and the semicircular portions 61 are provided at both ends of the wire portions 60 and 60'. , 62 are formed.

  The pole spring accommodating portion 24 opens upward and in the left-right direction, and the housing 2 is provided with a cover 8 that covers these opening portions in a detachable manner (see FIG. 1). The cover 8 is a member mainly for preventing the pole coil spring 6 from falling out of the pole spring accommodating portion 24, and is configured by bending a sheet metal. The upper end of the pole coil spring 6 is in pressure contact with the upper surface of the cover 8. A part of the cover 8 is formed with a plurality of engagement hook portions 80 bent inward. The cover 8 is attached to the housing 2 by the engagement hooks 80 engaging with the recesses 25b and 26b formed in the standing walls 25 and 26 of the housing 2, respectively.

  As shown in FIGS. 3 and 4, the cover 8 has a pair of holding portions 8 a that hold the pole coil spring 6 from both the left and right sides. The cover 8 projects from the lower end of the holding portion 8a in the left-right direction so as to cover the upper surface 5b of the pole 5 and is suspended downward from the tip of the shoulder 8b so that the left-right end surface of the pole 5 is And a hanging portion 8c for covering.

Here, the clearance between the upper surface 5b of the inner wall surface and the pole 5 of the shoulder portion 8b is C, between the front end face 3b ₁ of the rack teeth 3b of the front end surface 5a of the tooth portions 5a ₁ and the piston 3 of the pole 5 the distance between the _{h b,} and the distance between the outer peripheral surface 35 of the front end surface 5a ₁ and the piston 3 of the teeth 5a and _{h d,} the relationship of _h b <C <h _d is satisfied.

  As shown in FIG. 2, a through-hole 23 extending in the left-right direction (in the direction perpendicular to the drawing) is formed near the opening of the piston hole 2a in the housing 2. On the other hand, a locking groove 3 e extending in the width direction is formed in the head of the piston 3. The through hole 23 and the locking groove 3e are for holding the piston 2 in a contracted state when the tensioner is transported. The piston 2 is brought into a retracted state by inserting a shipping pin (not shown) into the through hole 23 and the locking groove 3e from a state where the piston 2 is in the retracted state and the through hole 23 and the locking groove 3e are aligned. It is supposed to be retained.

  In the piston 3, a stopper groove 3d is formed behind the rearmost tooth of the rack tooth 3b. This stopper groove 3d is for preventing further protrusion of the piston 3 by engaging with the tooth portion 5a of the pole 5 when the piston 3 moves in the protrusion direction. Has a retaining function.

  In the hydraulic tensioner configured as described above, the piston 3 protrudes from the housing 2 by the spring force of the piston spring 4 when the chain becomes slack or the chain tension decreases during operation. Move in the direction (ie move forward). At this time, the piston 3 moves in the direction of the arrow b together with the pole 5 while the rack teeth 3b are engaged with the teeth 5a of the pole 5 or the rack teeth 3b get over some of the teeth 5a ( (See solid line position in FIG. 5 → dot-dotted line position)

  When the piston 3 moves in the protruding direction, the pressure in the fluid chamber 30 becomes negative, whereby the check valve 7 is opened, and engine oil is introduced into the fluid chamber 30 from the introduction path 10 through the check valve 7. As a result, the resultant force of the spring force of the piston spring 4 and the hydraulic pressure in the fluid chamber 30 acts on the chain via the tensioner arm (not shown), and the chain tension is maintained.

  Next, when the tension of the chain increases during operation and a pressing force from the chain acts on the piston 3, the piston 3 retracts (that is, retracts) into the housing 2. That is, the piston 3 moves in the arrow b direction together with the pole 5 while the rack tooth 3b is engaged with the tooth portion 5a of the pole 5 (see the dashed line position → the solid line position in FIG. 5). Then, when the rear end surface 5c of the pole 5 comes into contact with the inner wall surface of the pole hole 2b, the movement of the piston 3 stops. At this time, the clearance formed between the rear end surface 5c of the pole 5 and the inner wall surface of the pole hole 2b before the movement of the pole 5 acts as a backlash when the piston 3 moves backward. By this backlash, even when an excessive pressing force is applied from the chain to the piston, the impact on the piston can be reduced.

  In this case, since the pole 5 having the tooth portion 5a that engages with the rack tooth 3b of the piston 3 is disposed between the pole hole 2b and the clearance in the front-rear direction, the liquid having the backlash mechanism is provided. A pressure tensioner can be realized with a simple structure.

  Further, in this case, when the pole 5 moves as the piston 3 moves forward and backward, as shown in FIG. 5, the pole 5 is connected to each wire portion (straight portion) 60, 60 ′ of the pole coil spring 6. Is in constant contact.

  Here, when the contact portions of the pole coil spring 6 before and after the movement of the pole 5 are 6A and 6B, both 6A and 6B have the same contact length and the same contact area. Thereby, it is possible to prevent the pressing force from the pole coil spring 6 against the pole 5 from fluctuating with the movement of the pole 5, and to make the spring force of the pole coil spring 6 against the pole 5 constant. As a result, a stable pressing force can be applied to the pole 5 at all times during operation.

  Next, for comparison with the present invention, FIG. 6 shows a case where the pole coil spring is a cylindrical coil spring generally used conventionally. In the figure, the same reference numerals as those in FIG. 5 denote the same or corresponding parts.

  In the example shown in FIG. 6, the pole coil spring 6 ′ has a circular cross section, so that the contact locations 6 ′ A and 6 ′ B of the pole coil spring 6 are different before and after the pole 5 is moved. It has a length, and each contact area is also different. For this reason, the pressing force from the pole coil spring 6 ′ against the pole 5 may vary as the pole 5 moves.

  Further, according to the present embodiment, the cover 8 covering the pole spring accommodating portion 24 has the holding portion 8a for holding the pole coil spring 6 from both the left and right sides. 6 can be stably held. In this case, since the cover 8 is provided separately from the housing 2, the cover along the outer shape of the pole coil spring 6 can be easily formed, and the manufacturing cost can be reduced. On the other hand, when the hole for accommodating the pole spring 6 is formed in the housing 2, it is necessary to drill a hole having a substantially elliptical cross section in the housing 2, which increases the manufacturing cost.

Furthermore, according to the present embodiment, as described with reference to FIG. 3, the relationship of h _b <C is established, so that when the piston 3 extends during operation, the rack teeth 3b of the piston 3 are extended. When the pole 5 rides on the teeth 5a of the pole 5 and the pole 5 is lifted upward, the extension of the piston 3 is smoothly performed without the pole upper surface 5b interfering with the inner wall surface of the cover shoulder 8b. On the other hand, by making the rack teeth 3b of the piston 3 to rotate the piston 3 engaged with the teeth portion 5a of the pawl 5, attempting to clear this engagement state, the relationship of C <h _d is satisfied Thus, as a result of the pole upper surface 5b interfering with the inner wall surface of the cover shoulder portion 8b, the piston outer peripheral surface 35 (FIG. 3) on which the rack teeth 3b are not formed cannot be moved to the position of the pole tooth portion. Thereby, it can prevent that the engagement state of the rack tooth 3b of the piston 3 and the tooth | gear part 5a of the pole 5 removes carelessly, and the piston 3 falls off.

Next, when the piston 3 protrudes by the maximum length while the shipping pin is removed from the through hole 23 of the housing 2 during transportation of the tensioner or during installation, the stopper groove 3d of the piston 3 (FIG. 2). The rear side wall surface comes into contact with the pole 5, and the pole 5 tries to ride on the front end surface 3d _{1 of the} stopper groove 3d on the rear side wall surface (consisting with the outer peripheral surface 35 of the piston 3 (see FIG. 3)). In such a case, by satisfying the above-mentioned relational expression C <h _d , the pole upper surface 5b interferes with the inner wall surface of the cover shoulder portion 8b. As a result, the pole 5 is formed on the rear side wall surface of the stopper groove 3d. It can not be run on the front end face 3d _1. Thereby, it can prevent that the engagement state of the rack tooth 3b of the piston 3 and the tooth | gear part 5a of the pole 5 remove | deviates, and can prevent the piston 3 from falling off.

  In the above embodiment, as the most preferable mode, the example in which the cross sectional shape of the pole coil spring 6 is composed of a pair of linear portions and semicircular portions has been shown. The present invention can be similarly applied to an elliptical surface shape.

1 is an overall perspective view of a hydraulic tensioner according to an embodiment of the present invention. It is a longitudinal cross-sectional view in the state where the cover was removed in the hydraulic tensioner (FIG. 1). It is the III-III sectional view taken on the line of FIG. 2, and is a figure which also shows the cross section of a cover. FIG. 4 is a schematic view taken along arrow IV in FIG. 3. It is a top view for demonstrating the positional relationship of the elliptical cylindrical pole coil spring and pole in the hydraulic tensioner by this invention. It is a top view which shows the positional relationship of a cylindrical pole coil spring and a pole for contrast with FIG.

1: Hydraulic tensioner

2: Housing 2a: Piston hole 2b: Pole hole 24: Pole spring housing

3: Piston 3b: Rack tooth 30: Fluid chamber

4: Piston spring

5: Paul 5a: Tooth part 5b: Upper surface

6: Pole coil spring 60: Straight part 60 ': Straight part 61: Semicircular part 62: Semicircular part

8: Cover 8a: Holding part 8b: Shoulder part 8c: Hanging part

Claims (6)

A hydraulic tensioner (1) for applying tension to the chain,
A housing (2) having a piston hole (2a) open at one end;
A piston (3) that is slidably inserted into the piston hole (2a), forms a fluid chamber (30) with the piston hole (2a), and has rack teeth (3b) formed on at least a part of the outer periphery. When,
A piston spring (4) disposed in the piston hole (2a) and biasing the piston (3) in a direction protruding from the housing (2);
A pole (5) having a tooth portion (5a) on the lower surface that engages with a rack tooth (3b) of the piston (3) so as to allow movement of the piston (3) in the protruding direction and restrict movement in the backward direction; ,
Accommodates the pole (5) formed by penetrating the housing (2) in the left-right direction and upward so as to have clearance between the front and rear end faces of the pole (5) that allows the pole (5) to move in the front-rear direction. A pole hole (2b),
A pole spring accommodating portion (24) provided in an upper portion of the housing (2) in communication with the pole hole (2b);
It is accommodated in the pole spring accommodating portion (24) and wound in an elliptical cylinder shape , and is arranged so that the major axis direction of the cross-sectional shape is oriented in the axial direction of the piston (3). A pole coil spring (6) for pressing the upper surface (5b) of the pole (5) to the side where the tooth portion (5a) engages with the rack tooth (3b) of the piston (3);
A cover (8) that is detachably provided on the housing (2), has a holding portion (8a) that covers the pole spring accommodating portion (24) and holds the pole coil spring (6) from both the left and right sides;
Hydraulic tensioner with In claim 1,
The cross-sectional shape of the pole coil spring (6) is a pair of straight portions (60, 60 ') along the major axis direction and facing each other, and the semicircular portions (61, 62) disposed at both ends thereof. Each linear portion (60, 60 ') is in contact with the upper surface (5b) of the pole (5),
A hydraulic tensioner characterized by that. In claim 1,
The pole spring (6) has an elliptical cross section,
A hydraulic tensioner characterized by that. In claim 1,
The cover (8) has a pair of shoulder portions (8b) that protrude in the left-right direction from the lower end of the holding portion (8a) and cover the upper surface (5b) of the pole (5).
A hydraulic tensioner characterized by that. In claim 4,
The clearance between the inner wall surface of the shoulder (8b) and the top surface (5b) of the pole (5) is C, and the tip surface (5a ₁ ) of the tooth (5a) of the pole (5) and the piston (3) The distance between the front end surface (3b ₁ ) of the rack tooth (3b) is h _b and the distance between the front end surface (5a ₁ ) of the tooth portion (5a) and the outer peripheral surface (35) of the piston (3). Where h _d
h _b <C <h _d
The relationship is established,
A hydraulic tensioner characterized by that. In claim 4,
The cover (8) has a suspended portion (8c) that is suspended downward from the tip of the shoulder (8b) and covers the left and right end surfaces of the pole (5).
A hydraulic tensioner characterized by that.

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