JP2004286126A - Hydraulic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent overthrust acting on a housing via a pole member in retraction of a piston. <P>SOLUTION: This hydraulic tensioner comprises the housing 2 having a piston hole 2a and a pole hole 2b communicated therewith, the hollow piston 3 slidably inserted into the piston hole 2a to form a fluid chamber 30 between the piston hole 2a and itself and having rack teeth 3b formed on part of the outer periphery, a piston ring 4 for energizing the piston 3 in the projecting direction, the pole member 5 provided in the pole hole 2b of the housing 2 and having a toothed portion 5a for engaging with the rack teeth 3b of the piston 3, and a pole spring 6 provided in the pole hole 2b of the housing 2 for energizing the pole member 5 to the side of the toothed portion 5a of the pole member 5 engaging with the rack teeth 3b. A width 5A of the pole member 5 is greater than a width 3A of a tooth edge portion of each of the rack teeth 3b of the piston 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydraulic tensioner for applying an appropriate tension to a chain or a belt, and more particularly to a hydraulic tensioner having a ratchet mechanism for preventing the piston from retracting when the hydraulic pressure is reduced.
[0002]
[Prior art and its problems]
The hydraulic tensioner is generally defined by a housing, a hollow piston slidably inserted into a hole formed in the housing and urged in a projecting direction by a spring, and a piston and the hollow hole in the hole of the housing. And a fluid chamber. During operation of the tensioner, the pressing force acting on the piston tip from the chain or belt balances the elastic force of the spring and the drag force of the hydraulic pressure in the chamber.
[0003]
By the way, especially in a hydraulic tensioner applied to a timing system for an automobile, when a sufficient hydraulic pressure is not acting in the chamber, such as when starting an engine, a pressing force is applied from the chain to the tip of the piston. When this occurs, the piston is easily pushed into the housing and the piston retracts, which may result in noise and vibration.
[0004]
Therefore, in order to prevent such retraction of the piston, for example, a hydraulic tensioner provided with a ratchet mechanism as disclosed in JP-A-2002-147551 has been proposed.
[0005]
The ratchet mechanism includes a rack tooth formed on an outer periphery of a piston, a toothed pad having teeth provided on a pole hole formed in a housing and capable of engaging with a rack tooth on the outer periphery of the piston, and a toothed pad. And an annular spring biasing in the direction of engagement with the teeth. Further, the axial length of the toothed pad is slightly shorter than the axial length of the pole hole of the housing, whereby the toothed pad is axially moved through the pole hole of the housing in accordance with the axial movement of the piston. It can be moved slightly in the direction.
[0006]
[Patent Document 2]
JP-A-2002-147551 (see FIGS. 3 and 6)
[0007]
In the conventional ratchet mechanism, the width of a pole member such as a toothed pad that engages with the rack teeth of the piston is formed corresponding to the width of the rack teeth, and the width dimension of the pole member is determined by the tooth size of the rack teeth. It is smaller than the width of the tip.
[0008]
For this reason, when excessive tension is applied to the chain and excessive pressing force acts on the tip of the piston from the chain, the narrow pole member moves axially in the pole hole of the housing with the retraction of the piston. Presses against the inner wall surface of the pole hole, resulting in deformation of the inner wall surface of the pole hole, or in extreme cases, locking of the pole member between the rack teeth of the piston and the inner wall surface of the pole hole of the housing. There is fear.
[0009]
SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a hydraulic tensioner including a pole member, where an excessive pressing force acts on the housing via the pole member when the piston is retracted. In order to prevent the user from doing so.
[0010]
[Means for Solving the Problems]
The hydraulic tensioner according to the first aspect of the present invention has a housing having a piston hole opened at one end and a pole hole communicating with the piston hole, and is inserted slidably in the piston hole in the axial direction so as to form a fluid chamber between the piston hole and the housing. A hollow piston having an internal space formed therein and having rack teeth formed on at least a part of the outer periphery; a piston spring disposed in the piston hole, for urging the piston in a protruding direction; and a pole in a pole hole of the housing. A pole member having an axial clearance between the hole and a tooth portion for engaging with the rack teeth of the piston and allowing the piston to move in the protruding direction and preventing the piston from moving in the retreating direction. And a pole spring that is provided in a pole hole of the housing and biases the pole member toward the side where the teeth of the pole member engage with the rack teeth. Eteiru. The width of the pole member is larger than the width of the tip of the rack teeth of the piston.
[0011]
According to the first aspect of the present invention, when the piston moves in the direction in which the piston protrudes from the housing, if the amount of movement of the piston is large, the rack teeth of the piston get over some of the teeth of the pole member. , The piston moves in the protruding direction. Then, when the pressing force acting on the chain from the tip of the piston by the spring force of the piston spring and the liquid pressure in the fluid chamber is balanced with the pressing force acting on the tip of the piston from the chain by the chain tension, the movement of the piston stops.
[0012]
Next, when a pressing force is applied from the chain to the tip of the piston in a state where sufficient fluid pressure is not acting in the fluid chamber, the rack teeth on the outer periphery of the piston are engaged with the teeth of the pole member. Is maintained, the piston retreats together with the pole member, and the rear end face of the pole member presses against the inner wall surface of the pole hole of the housing. This stops the movement of the piston.
[0013]
At this time, the width of the pole member is larger than the width of the tip of the rack teeth of the piston, and the contact area between the rear end surface of the pole member and the inner wall surface of the pole hole of the housing is large. That is, the pressure receiving area on the inner wall surface of the pole hole of the housing is large. Accordingly, it is possible to prevent an excessive pressing pressure from acting on the housing via the pawl member when the piston is retracted.
[0014]
In the invention of claim 2, the pole hole has a surface with which the front end face or the rear end face of the pole member abuts when the pole member advances or retreats.
[0015]
According to the third aspect of the present invention, the width of the pole member is larger than the width of the bottom portion of the rack teeth of the piston. In this case, the pressure receiving area on the inner wall surface of the pole hole of the housing can be further increased, thereby effectively preventing excessive pressing pressure from acting on the housing via the pole member when the piston is retracted. it can.
[0016]
According to the fourth aspect of the invention, the width of the pole member is larger than the outer diameter of the piston. In this case, the pressure receiving area on the inner wall surface of the pole hole of the housing can be further increased, thereby making it possible to more effectively prevent an excessive pressing pressure from acting on the housing via the pole member when the piston is retracted. Can be prevented.
[0017]
According to the fifth aspect of the present invention, the housing is made of a material having a lower hardness than the pole member, such as aluminum. In this case, the pole hole of the housing is easily deformed when a high surface pressure is applied from the pole member. However, as described above, the width dimension of the pole member is set to at least the tip of the rack teeth of the piston. By making the width larger than the width, the surface pressure acting on the pole hole of the housing from the pole member is reduced. Therefore, even if the housing is a low-hardness member, the deformation of the housing can be effectively suppressed. become.
[0018]
According to the invention of claim 6, the pole spring has at least one U-shaped bent portion formed by performing a bending process on the strip-shaped member, and the U-shaped bent portion is formed of the pole member. It is in contact with the back.
[0019]
In the invention of claim 7, the pole spring has two U-shaped bent portions, and each U-shaped bent portion is symmetrically arranged on both the left and right sides of the center axis of the piston. In this case, it is possible to stably maintain the engagement state between the teeth of the pole member and the rack teeth of the piston without the widened pole member tilting to the left or right side.
[0020]
The pole spring may have a substantially W-shaped bent portion, as described in the invention of claim 8.
[0021]
According to the ninth aspect of the present invention, the pole spring has at least one U-shaped bent portion formed by performing a bending process on the strip-shaped member, and the back surface of the pole member has a groove extending in the axial direction. The U-shaped bent portion of the pole spring is engaged with the groove on the back surface of the pole member.
[0022]
In this case, during the movement of the piston, when the pole member moves together with the piston, the movement of the pole member is guided by the U-shaped bent portion of the pole spring, so that the pole member moves in the axial direction. Can be performed more stably. In this case, by forming a groove on the back side of the pole member, the center of the moment of inertia of the pole member moves toward the teeth of the pole member. Thus, when the pole member receives the action of the rotational moment from the piston, the amount of lifting of the pole member can be suppressed, and the pole member can be prevented from jumping out.
[0023]
According to the tenth aspect of the present invention, the pole spring has locking hook portions at both ends, and the housing has a locking concave portion at the opening end of the pole hole where the locking hook portion of the pole spring can lock. ing.
[0024]
According to the eleventh aspect of the present invention, the check valve that allows the flow of the fluid into the fluid chamber and prevents the flow of the fluid in the reverse direction is provided at the bottom of the piston hole of the housing.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall perspective view of a hydraulic tensioner according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the hydraulic tensioner of FIG. 1, FIG. 3 is a view taken in the direction of the arrow III in FIG. 5 is a plan view showing the rack teeth of the plunger, FIG. 5 is a cross-sectional view taken along the line VV of FIG. 2, FIG. 6 is an enlarged perspective view of a pole hole portion of the housing, and FIG. Is a diagram showing a conventional pressure receiving surface. In FIG. 5, hatching is omitted for convenience of illustration.
[0026]
As shown in FIGS. 1 to 3, the hydraulic tensioner 1 includes a housing 2 having a piston hole 2 a extending in the axial direction and having an open end, and a piston 2 a in the housing 2. Direction) It is mainly composed of a hollow piston 3 slidably inserted, and a piston spring 4 arranged in the piston hole 2a of the housing 2 and for urging the piston 3 in a direction protruding from the piston hole 2a. .
[0027]
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 internal space 3a formed in the piston 3 and an inner wall surface of the piston hole 2a. At the bottom of the housing 2, an introduction passage 10 for introducing engine oil as a working fluid into the fluid chamber 30 from an external pressurized fluid source (not shown) is formed.
[0028]
A check valve 7 is provided at the bottom of the piston hole 2 a in the housing 2. The check valve 7 allows the flow of the fluid from the introduction passage 10 to the fluid chamber 30, while preventing the flow of the fluid in the opposite direction. Here, a ball check valve is employed, but another configuration may be employed.
[0029]
A vent disc 8 is provided on the piston head side in the internal space 3a 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 for controlling the amount of leakage of the fluid from the fluid chamber 30. For example, a spiral groove 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 8a. The piston spring 4 is disposed around the shaft portion 8a of the vent disc 8, and its tip urges the vent disc 8 toward the piston head.
[0030]
Rack teeth 3b are formed on a part of the outer peripheral surface of the piston 3 (see FIG. 4). On the other hand, a pole hole 2b communicating with the piston hole 2a is formed in the housing 2. The pole member 5 is disposed in the pole hole 2b. On the lower surface of the pawl member 5, a tooth portion 5a that can engage with the rack teeth 3b of the piston 3 is formed. An axial clearance is formed between the pole hole 2b and the pole member 5 (see FIG. 2).
[0031]
As shown in FIG. 5, the width 5A of the pole member 5 is at least larger than the width 3A of the tip of the rack teeth 3b of the piston 3. Preferably, the width dimension 5A of the pole member 5 is greater than the width dimension 3B of the root portion of the rack teeth 3b of the piston 3, and more preferably, is greater than the outer diameter dimension 3D of the piston 3 (FIG. 4). And FIG. 5). In FIG. 5, reference numeral 50A indicates a width dimension of the conventional pole member.
[0032]
As shown in FIGS. 1 to 3 and 5, the pole member 5 is attached to the opening of the pole hole 2 b of the housing 2 on the side where the teeth 5 a of the pole member 5 engage with the rack teeth 3 of the piston 3. A biasing pole spring 6 is provided.
[0033]
The pole spring 6 has at least one U-shaped bent portion formed by bending a band-shaped member. Here, as shown in FIG. 5, the pole spring 6 has two U-shaped bent portions 6a and 6b. In other words, the pole spring 6 is bent in a substantially W shape. Each U-shaped bent portion 6a, 6b is in contact with the back surface 5b of the pole member 5. Further, it is preferable that the U-shaped bent portions 6a and 6b are symmetrically arranged on both left and right sides of a center axis passing through the center O of the piston 3.
[0034]
The pole spring 6 has locking hook portions 60 and 61 at both ends. On the other hand, locking recesses 22 and 22 'are formed in the housing 2 at the opening of the pole hole 2b, as shown in FIG. The pawl spring 6 is attached to the housing 2 by locking the respective locking hook portions 60 and 61 of the pawl spring 6 into these locking concave portions 22 and 22 ′.
[0035]
In the housing 2, a through hole 23 in the width direction is formed near the opening of the piston hole 2a (see FIGS. 1 and 6). A locking groove 3e extending in the width direction is formed in the head of the plunger 3 (see FIG. 4). The through holes 23 and the locking grooves 3e are for holding the piston 2 in a contracted state at the time of transporting the tensioner or the like. By inserting the retaining pin 9 shown in FIG. 3 into the through hole 23 and the locking groove 3e from the state where the through hole 23 and the locking groove 3e are aligned with the piston 2 in the retracted state, the piston 2 is It is kept in a degenerated state.
[0036]
As shown in FIG. 4, a stopper groove 3d is formed in the piston 3 behind the rearmost tooth portion of the rack teeth 3b. The stopper groove 3 d is for preventing the piston 3 from further projecting by engaging with the tooth portion 5 a of the pawl member 5 when the piston 3 moves in the projecting direction. It has the function of retaining.
[0037]
Next, the operation and effect of this embodiment will be described.
If the chain becomes loose or the tension of the chain decreases during operation of the tensioner, the piston 3 moves in the direction in which the piston 3 projects from the housing 2 by the spring force of the piston spring 4.
[0038]
At this time, when a clearance is formed between the front end face 5c (FIG. 4) of the pole member 5 and the inner wall surface of the pole hole 2b of the housing 2, the piston 3 causes the rack teeth 3b to It moves together with the pawl member 5 in a state of being engaged with the tooth portion 5a. If the required movement amount of the piston 3 is large and the piston 3 moves further in a state where the front end face 5c of the pole member 5 is in contact with the inner wall surface of the pole hole 2b of the housing 2, the rack teeth of the piston 3 3b moves over some teeth of the tooth portion 5b of the pole member 5.
[0039]
When the piston 3 moves in the protruding direction, the inside of the fluid chamber 30 becomes negative pressure, so that 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 liquid pressure in the fluid chamber 30 acts on the chain via the tensioner arm, and the tension of the chain is maintained.
[0040]
Next, when a pressing force is applied from the chain to the piston tip 3c in a state where sufficient fluid pressure is not acting in the fluid chamber 30, such as when starting the engine, the rack teeth 3b on the outer periphery of the piston are removed. The piston 3 retreats together with the pole member 5 while maintaining the state of engagement with the tooth portion 5a of the pole member 5, and the rear end face 5d (FIG. 4) of the pole member 5 is pressed against the inner wall surface of the pole hole 2b of the housing 2. I do. As a result, the backward movement of the piston 5 is stopped.
[0041]
At this time, the contact surface of the rear end surface 5d of the pole member 5 with the inner wall surface 25 (FIG. 6) of the pole hole 2b of the housing 2 is a hatched area a as shown in FIG. On the other hand, the contact surface of the conventional pole member is a hatched area b in FIG. That is, in this case, the pressure receiving area on the inner wall surface 25 of the pole hole 2b of the housing 2 is large. This prevents an excessive pressing pressure from acting on the housing 2 via the pawl member 5 when the piston 3 moves backward.
[0042]
As a result, even when the housing 2 is made of a relatively soft material such as aluminum and the hardness of the pole member 5 is higher than the hardness of the housing 2, the contact area of the pole member 5 with the housing 2 increases. Thereby, the surface pressure on the pressure receiving surface of the housing 2 can be reduced, thereby preventing deformation of the housing surface.
[0043]
Furthermore, in this case, the U-shaped bent portions 6a and 6b of the pole spring 6 are symmetrically arranged on both left and right sides of the center axis of the piston 3, so that the wide pole member 5 can be moved to either the left or right. The engagement between the teeth 5a of the pawl member 5 and the rack teeth 3a of the piston 3 can be stably maintained without tilting to the side.
[0044]
( Other embodiments )
FIG. 8 shows another embodiment of the pole member and the pole spring. In the figure, the same reference numerals as those of the above-described embodiment indicate the same or corresponding parts.
[0045]
As shown in FIG. 8, in this embodiment, the pole member 5 has an axially extending groove 5e on the back surface 5b. On the other hand, a U-shaped bent portion 6c is formed at the center of the pole spring 6, and the U-shaped bent portion 6c is engaged with the groove 5e of the pole member 5.
[0046]
In this case, when the piston 3 moves, when the pole member 5 moves together with the piston 3, the movement of the pole member 5 is guided by the U-shaped bent portion 6 c of the pole spring 6. 5 can be more stably moved in the axial direction. In this case, the center of the moment of inertia of the pole member 5 is moved toward the tooth portion 5a of the pole member 5 by forming a groove on the back side of the pole member 5. Accordingly, when the pole member 5 receives the action of the rotational moment from the piston 3, the amount of lifting of the pole member 5 can be suppressed, and the pole member 5 can be prevented from protruding from the pole hole 2b of the housing 2.
[0047]
In each of the above-described embodiments, the example in which the width 5A of the pole member 5 is larger than the outer diameter 3D of the piston 3 has been described, but the width 5A of the pole member 5 is at least the rack tooth 3b of the piston 3. By making the tip size 3A larger, it is possible to increase the pressure receiving area of the pole hole of the housing as compared with a conventional pole member.
[0048]
【The invention's effect】
As described in detail above, according to the hydraulic tensioner of the present invention, the pole member engaging with the rack teeth on the outer periphery of the housing is provided in the pole hole of the housing, and the width dimension of the pole member is set to the teeth of the rack teeth of the piston. Since the width is larger than the width of the front portion, there is an effect that it is possible to prevent an excessive pressing pressure from acting on the housing via the pawl member when the piston is retracted.
[Brief description of the drawings]
FIG. 1 is an overall perspective view of a hydraulic tensioner according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a hydraulic tensioner (FIG. 1).
FIG. 3 is a view taken in the direction of arrow III in FIG. 2;
FIG. 4 is a plan view showing rack teeth of a piston in the hydraulic tensioner.
FIG. 5 is a schematic sectional view taken along line VV of FIG. 2;
FIG. 6 is an enlarged perspective view of a pole hole portion of a housing in the hydraulic tensioner.
FIG. 7 is a diagram showing a pressure receiving surface on the housing side by a pole member of the present embodiment together with a conventional pressure receiving surface.
FIG. 8 is a cross-sectional view of a hydraulic tensioner according to another embodiment of the present invention, corresponding to FIG. 5 of the embodiment.
[Explanation of symbols]
1: hydraulic tensioner 2: housing 2a: piston hole 2b: pole hole 22: locking recess 22 ': locking recess 25: inner wall surface 3: piston 3a: internal space 3b: rack teeth 3c: tip 30: fluid chamber 3A : Width 3B of the tip of the rack tooth 3B: Width 3D of the root of the rack tooth: Piston outer diameter 4: Piston spring 5: Pole member 5a: Teeth 5b: Back face 5c: Front end face 5d: Rear end face 5e: Groove 5A: Width of pole member 50A: Width of conventional pole member 6: Pole spring 6a: U-shaped bent portion 6b: U-shaped bent portion 6c: U-shaped bent portion 60: Hook portion 61: Hook part 7: Check valve

Claims (11)

A hydraulic tensioner for applying tension to the chain,
A housing having a piston hole extending in the axial direction and having one end opened, and a pole hole communicating with the piston hole;
A hollow piston axially slidably inserted into the piston hole and having an internal space forming a fluid chamber between the piston hole and a rack tooth formed on at least a part of the outer periphery;
A piston spring disposed in the piston hole and biasing the piston in a protruding direction;
In the pole hole of the housing, an axial clearance is arranged between the pole hole and the pole hole, the piston hole engages with the rack teeth of the piston, and allows the piston to move in a protruding direction and is set in a retreating direction. A pole member having teeth for preventing the movement of
A pole spring that is provided in the pole hole of the housing and biases the pole member to a side where the teeth of the pole member engage with the rack teeth;
The width dimension of the pawl member is larger than the width dimension of the tip of the rack teeth of the piston,
A hydraulic tensioner characterized in that: In claim 1,
The pole hole has a surface with which the front end face or the rear end face of the pole member abuts when the pole member advances or retreats,
A hydraulic tensioner characterized in that: In claim 1 or 2,
The width dimension of the pawl member is larger than the width dimension of the bottom portion of the rack teeth of the piston,
A hydraulic tensioner characterized in that: In claim 3,
The width dimension of the pawl member is larger than the outer diameter dimension of the piston,
A hydraulic tensioner characterized in that: In any one of claims 1 to 4,
The said housing is comprised from the member whose hardness is lower than the said pole member, The hydraulic tensioner characterized by the above-mentioned. In any one of claims 1 to 4,
The pole spring has at least one U-shaped bent portion formed by performing a bending process on a strip-shaped member, and the U-shaped bent portion is in contact with a back surface of the pole member. Yes,
A hydraulic tensioner characterized in that: In claim 6,
The pole spring has two U-shaped bent portions, and each of the U-shaped bent portions is symmetrically disposed on both left and right sides of a center axis of the piston.
A hydraulic tensioner characterized in that: In claim 7,
The pole spring has a substantially W-shaped bent portion,
A hydraulic tensioner characterized in that: In any one of claims 1 to 4,
The pole spring has at least one U-shaped bent portion formed by performing a bending process on a band-shaped member, and the back surface of the pole member has a groove extending in an axial direction, The U-shaped bent portion of the pole spring is engaged with the groove,
A hydraulic tensioner characterized in that: In any one of claims 6 to 9,
The pole spring has a locking hook portion at both ends, and the housing has a locking recess at the opening end of the pole hole where the locking hook portion of the pole spring can lock. ,
A hydraulic tensioner characterized in that: In claim 1,
A check valve is provided at the bottom of the piston hole of the housing to allow fluid flow into the fluid chamber and block fluid flow in the opposite direction.
A hydraulic tensioner characterized in that:

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