JPH0882353A - Hydraulic tensioner - Google Patents

Abstract

PURPOSE: To provide an hydraulic tensioner which is constituted to prevent a plunger from backward movement through simple structure and besides decrease a friction loss by arranging a support member with a small inside diameter in the opening part of a housing provided at its inside with an oil chamber. CONSTITUTION: A hydraulic tensioner 10 to exert proper pressing force on a chain and a belt by which the cam shaft of an engine is driven is provided with a piston rod (a plunger) 12 inserted in the hole 11a of a housing 11 and pressing force is exerted on a belt through a tensioner arm by a contact part 12a at the tip thereof. In this case, a support member 15 is pressed in the hole opening part of a body 11 and the inside diameter D of the inner peripheral surface 15a of the support member 15 is set to a value lower than the inside diameter D' of the hole 11a of the body 11. A recessed part 15c is formed between the inner and outer peripheral surfaces 15a and 15b and a part of a soil spring 13 is contained therein, and an oil reservoir 25 is formed in the upper part of the body 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic tensioner for applying an appropriate pressing force to a chain or a belt that drives a cam shaft of an engine.

[0002]

2. Description of the Related Art A hydraulic tensioner has been conventionally used in order to suppress fluttering of a chain or a belt due to torque fluctuation of an engine and reduce noise, vibration and guide wear.

This hydraulic tensioner generally has a housing having a hole having an opening at one end, a hollow plunger slidably supported in the hole of the housing and having an opening at the rear end side, and a housing. Is mainly provided with a spring that is contracted in the hole and has one end pressed against the hole side wall of the housing and the other end pressed against the hole side wall of the hollow plunger to urge the plunger in the protruding direction. An oil chamber is formed by the hole of the housing and the plunger, and external hydraulic pressure acts on the oil chamber. The tip of the plunger is in contact with a tensioner arm arranged on the loose side of the chain and belt.

During operation of such a hydraulic tensioner,
The hydraulic pressure acts on the rear end side of the plunger in the oil chamber, and the pressing force resulting from the combination of the hydraulic pressure and the spring force causes the plunger to push the chain and the belt via the tensioner arm.

On the other hand, during operation of the engine, the chain,
As the belt tension increases, the plunger experiences a backward force. At this time, if sufficient oil is not supplied to the oil chamber immediately after the engine is started, or if the oil temperature and engine speed are low and the oil pressure is not sufficiently working in the oil chamber, the plunger can easily retract. Then, there arises a problem that an appropriate pressing force cannot be applied to the chain and the belt.

Therefore, even in such a case, in order to prevent the plunger from retracting and maintain an appropriate pressing force against the chain and the belt, it is necessary to set the spring force to a somewhat high value.

However, in the above-mentioned conventional hydraulic tensioner, due to the structure in which the spring is mounted in the hole of the hollow plunger,
The diameter of the plunger is large to some extent, and the pressure receiving area of the plunger is large. Therefore, as mentioned above,
When the spring force is set higher, the pressing force due to the combination of hydraulic pressure and spring force becomes larger than necessary in the engine's normal rotation range, and friction loss increases, resulting in wear of the tensioner arm, guide, etc. The problem arises that

Therefore, in the conventional hydraulic tensioner, the spring force is consequently weakened to reduce the friction loss, and a ratchet mechanism is newly provided to prevent the plunger from retracting. As a result,
The structure is complicated and the cost is increasing.

The present invention has been made in view of such conventional circumstances, and an object thereof is to provide a hydraulic tensioner capable of preventing the plunger from retracting with a simple structure and reducing friction loss.

[0010]

A hydraulic tensioner according to a first aspect of the present invention is provided with a housing having an oil chamber inside and having an opening communicating with the oil chamber at one end, and the opening. A support member having an inner diameter smaller than the inner diameter of the oil chamber, and a contact portion whose rear end is inserted into the oil chamber and slidably supported by the support member and capable of contacting a tensioner arm is a tip. And a biasing member that is disposed on the outer circumference of the plunger between the support member and the contact portion and that biases the plunger in the protruding direction.

A hydraulic tensioner according to a second aspect of the present invention is
An oil reservoir for storing oil is provided in the housing so as to be connected to the oil chamber.

The hydraulic tensioner according to the invention of claim 3 is
A check valve is provided between the oil reservoir and the oil chamber.

[0013]

According to the first aspect of the present invention, since the support member having a small inner diameter is provided in the opening of the housing and the plunger is supported by the support member, the diameter of the plunger can be made smaller than the inner diameter of the oil chamber. As a result, the pressure receiving area of the plunger can be reduced, and the pressing force of the hydraulic pressure acting on the plunger can be reduced. Therefore, even when the spring force is set to be high, the pressing force due to the combination of the hydraulic pressure and the spring force can be suppressed to a certain limit or less in the normal rotation range of the engine.

This will be described with reference to FIG. FIG. 5 shows changes in the pressing force due to the composition of the hydraulic pressure and the spring force together with the engine speed. In the figure, the broken line shows the conventional product, the solid line shows the present invention, and K
And K'represent the spring force at the time of initial setting of the product of the present invention and the conventional product, respectively.

As described above, according to the present invention, the pressing force by the hydraulic pressure is reduced by reducing the plunger diameter. Therefore, the curve of the pressing force in FIG. The degree of increase in the pressing force with respect to the increase (i.e., increase in hydraulic pressure) is small. Therefore, even when the spring force K, which is the initial pressing force, is set to be larger than the spring force K ′ of the conventional product, the pressing force can be made smaller than that of the conventional product in the engine normal rotation range N, and the pressing force can be applied over each rotation range. Can be the minimum required size.

As a result, while suppressing the friction loss, it is possible to increase the spring force and increase the pressing force in the rotation range S below idling as compared with the conventional product, and as a result, without providing the ratchet mechanism. The simple structure can prevent the plunger from retracting.

In the prior art, when the engine was stopped, the oil in the oil chamber leaked from the plunger sliding surface of the housing opening. However, in the present invention, the housing opening is provided with a support member having a small inner diameter. As a result, a space for storing oil can be formed below the plunger, and a part of the oil in the oil chamber can be stored in the space even after the engine is stopped.

Thus, when the engine is restarted, the oil chamber is filled with oil in a short time, and the hydraulic pressure can be immediately applied to the plunger, so that the response characteristic of the hydraulic tensioner can be improved.

Further, since the urging member is arranged on the outer circumference of the plunger between the support member and the contact portion, it is not necessary to form the plunger as a hollow member as in the conventional case, and the capacity of the oil chamber is reduced. Can be made smaller.

As a result, when the engine is restarted, the oil chamber can be filled with oil in a short time, and the hydraulic pressure can be immediately applied to the plunger, and in combination with the effect of forming the oil reservoir, the response characteristic can be improved. Can be further improved.

According to the second aspect of the present invention, since the oil reservoir connected to the oil chamber is provided, the oil can be stored, and the oil reservoir is appropriately replenished with oil to suppress a decrease in oil pressure in the oil chamber. Therefore, it is possible to suppress a decrease in the pressing force of the plunger.

Further, particularly immediately after the engine is started, the oil from the oil reservoir fills the oil chamber in a short time, so that the hydraulic pressure can be immediately applied to the plunger. This makes it possible to prevent the plunger from retracting with a simple structure without providing a ratchet mechanism.

According to the third aspect of the present invention, since the check valve is provided between the oil reservoir and the oil chamber, when the backward force is applied to the plunger, the oil in the oil chamber is prevented from leaking to the oil reservoir side. It is possible to prevent the plunger from retracting. Further, when the engine is started, the oil from the oil reservoir can be appropriately supplied into the oil chamber via the check valve.

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 6 are views for explaining a hydraulic tensioner according to an embodiment of the present invention, FIG. 1 is a diagram showing an example of a timing system of an engine in which the hydraulic tensioner is adopted, and FIG. 2 is the hydraulic tensioner. Side view, FIG. 3 is a sectional view thereof, FIG. 4 is a partially enlarged view of FIG.
FIG. 6 is a diagram showing the correlation between the pressing force of the hydraulic tensioner and the engine speed in comparison with the conventional example, and FIG. 6 is a diagram for explaining the action and effect of the embodiment.

FIG. 1 shows a timing system of a DOHC engine. The timing system 1 has a drive sprocket 3 fixed to a crankshaft 2.
A driven chain sprocket 6 and 7 fixed to the two camshafts 4 and 5, respectively, and a timing chain 8 wound between the sprockets. The arrow a indicates the rotation direction of the crankshaft 2.

A hydraulic tensioner 10 for applying a pressing force to the timing chain 8 via a tensioner arm 9 is arranged on the loose side of the timing chain 8.

As shown in FIGS. 2 and 3, the hydraulic tensioner 10 includes a tensioner body (housing) 11 having a hole 11a having an opening at one end, and a hole 11a.
It has a piston rod (plunger) 12 that is inserted into the inside thereof and has a contact portion 12a that comes into contact with the tensioner arm 9 at the tip thereof, and a coil spring 13 that biases the piston rod 12 in the protruding direction. .

A support member 15 is press-fitted into the hole opening of the body 11. The support member 15, as shown in FIG.
It has a shape in which two cylinders having different diameters are concentrically arranged and one end of each is connected, and the inner diameter D of the inner peripheral surface 15a is smaller than the inner diameter D'of the hole 11a of the body 11.
The piston rod 12 is slidably supported by the inner peripheral surface 15a having the length L. Inner surface 1
A recess 15c for accommodating a part of the coil spring 13 is formed between 5a and the outer peripheral surface 15b. One end of the coil spring 13 is on the side wall of the recess, and the other end is on the contact portion 12a.
Abutting on the side walls of each.

Inside the hole 11a of the body 11, the hole 11a
An oil chamber 20 defined by the inner wall of the piston, the piston rod 12, and the holding member 15 is formed. The oil chamber 20 is supplied with hydraulic pressure from an external hydraulic circuit (not shown) including an oil pump.

Further, the piston rod 12 is attached to the support member 15
By supporting the oil via the valve, a space for storing oil is formed below the piston rod 12 in the oil chamber 20. After the engine is stopped, a part of the oil in the oil chamber 20 can be stored in the space (see FIG. 6).

An oil reservoir 25 for collecting and storing splash oil in the engine is provided on the upper portion of the body 11. The oil reservoir 25 is composed of an opening recess 25 a formed in the upper part of the body 11.
An oil passage 26 is formed between the oil chamber 20 and the oil reservoir 25, and the oil passage 26 is connected to the oil reservoir 25 via a check valve 30. Check valve 3
0 is composed of a ball 31 and a spring 32 for urging the ball 31 toward the seat surface (upper side in FIG. 3). A pin 28 is attached to the rear end of the piston rod 12 to prevent it from coming off.

Next, the function and effect of this embodiment will be described. During operation of the engine, the hydraulic pressure from the external hydraulic circuit is supplied into the oil chamber 20, and the pressing force resulting from the combination of the hydraulic pressure and the repulsive force of the coil spring 13 is applied from the abutting portion 12a of the piston rod 12. It acts on the chain 8 via the tensioner arm 9. Further, the splash oil during operation of the timing system 1 is stored in the oil reservoir 25 (see FIG. 6).

At this time, since the piston rod 12 is supported by the support member 15 as described above, the diameter (≈D) of the piston rod 12 is smaller than the hole diameter D ′. Therefore, the pressure receiving area of the piston rod 12 is small, and the pressing force by the hydraulic pressure acting on the piston rod 12 is also small.

Therefore, as described with reference to FIG. 5, the degree of increase in the pressing force with respect to the increase in the engine speed (that is, the increase in hydraulic pressure) is small. Therefore, even when the spring force K is set to be high, the pressing force due to the combination of the hydraulic pressure and the spring force is suppressed to a certain limit or less in the normal engine rotation range N, and the pressing force is maintained over each rotation range. It is the minimum size required.

This makes it possible to increase the spring force while suppressing friction loss. As a result, even if the tension of the chain increases, the piston rod 12 can be prevented from retreating with a simple structure without providing a ratchet mechanism.

After the engine is stopped, a part of the oil in the oil chamber 20 is stored in the oil storage space below the piston rod 12 (see FIG. 6). As a result, when the engine is restarted, the oil chamber 20 is filled with oil in a short time, and the oil pressure can be immediately applied to the piston rod 12. As a result, the piston rod 12 can be prevented from retreating with a simple structure without providing a ratchet mechanism.

Immediately after the engine is started (that is, immediately after the chain 8 is driven), the chain 8 is pulled by the drive sprocket 3, and as a result, slackness occurs on the slack side of the chain 8 and the piston rod 12 of the hydraulic tensioner 10 is removed. The spring force of the coil spring 13 causes the coil spring 13 to slightly project.

Then, the pressure in the oil chamber 20 becomes negative, and the oil in the oil reservoir 25 flows into the oil chamber 20 via the check valve 30. The oil that has flowed into the oil chamber 20 is mixed with the oil that has been stored in the oil reservoir space.
The inside will soon be filled with oil.

Further, the coil spring 13 is connected to the piston rod 12
Since it is attached to the outer circumference of the oil chamber, it is not necessary to use a hollow member as in the prior art as the piston rod.
The capacity within 0 is small.

As a result, when the engine is restarted, the oil chamber 20 is filled with oil in a short time, and the piston rod 1
The hydraulic pressure can be immediately applied to the hydraulic pressure regulator 2, and the response characteristic of the hydraulic tensioner 10 can be further improved in combination with the effect of the space for storing the oil.

Further, since the check valve 30 is provided, when the tension of the chain 8 increases and a backward force acts on the piston rod 12, the oil in the oil chamber 20 leaks to the oil reservoir 25 side. It is possible to prevent the piston rod 12 from moving backward.

Further, the piston rod 12 is attached to the support member 15
By supporting the piston rod 12, the contact member 12a, the coil spring 13, and the support member 15 as a sub-assembly (sub-assembly), they can be integrated.

As a result, when the hydraulic tensioner 10 is assembled, the hole opening of the body of the conventional hydraulic tensioner is preliminarily subjected to additional work for press-fitting the support member 15, and then the sub-assembly is attached to the opening. Just enough. This facilitates assembly and reduces assembly cost.

Further, in the prior art, high processing accuracy was required over the entire plunger sliding portion of the tensioner body, whereas in the present embodiment, the tensioner body 11 is used.
For, it is only necessary to process the press-fitted portion of the support member 15,
Moreover, the press-fitting portion is sufficient with rough processing accuracy. This can reduce the processing cost.

Further, in the prior art, since the tensioner body 11 itself is required to have a high working accuracy as described above, cast iron or the like having good workability and wear resistance is generally used as the material of the body 11. On the other hand, in the present embodiment, it is not necessary to use such a heavy material, and the weight can be reduced as a whole by using, for example, lightweight aluminum die casting.

Further, conventionally, it was necessary to control the oil leakage time (leak down time) over the entire plunger sliding portion of the tensioner body, whereas in the present embodiment, the length L and the inner diameter of the support member 15 are controlled. Since it becomes possible to control with D, control becomes easy.

In the above embodiment, the oil reservoir 2
Although an example in which 5 is provided separately from the external hydraulic circuit is shown, this oil reservoir 25 may be connected to the external hydraulic circuit.

Further, in the above-mentioned embodiment, the hydraulic tensioner is of the type mounted from the side of the engine. However, the hydraulic tensioner according to the present invention can be applied to the type of mounting from the front of the engine. Also in this case, the same effect as that of the above-mentioned embodiment is obtained.

FIG. 7 shows a hydraulic tensioner of this type, and FIG. 8 shows a hydraulic tensioner in which the hydraulic tensioner is adopted.
1 shows a timing system of an OHC engine. Note that, in FIG. 8, the same reference numerals as those in the above-mentioned embodiment indicate the same or corresponding portions.

In FIG. 7, the hydraulic tensioner 50 includes a tensioner body 51 and a contact portion 52 which is inserted into a hole of the body 51 and abuts on the tensioner arm 9 (FIG. 8).
Has a piston rod (not shown) attached to its tip, and a coil spring 53 for urging the piston rod in the protruding direction. The piston rod is slidably supported by a supporting member (not shown) as in the case of the above-described embodiment. Further, at the upper and lower parts of the body 51, leg members 54 having holes for inserting bolts for attaching the hydraulic tensioner 50 to the side wall of the cylinder block of the engine are provided.

[0051]

As described above, according to the hydraulic tensioner of the present invention, since the plunger is supported by the supporting member having a small inner diameter, the pressure receiving area of the plunger can be reduced and the pressing force by the hydraulic pressure acting on the plunger can be reduced. Can be made smaller. As a result, it is possible to increase the spring force while suppressing friction loss, and as a result, it is possible to prevent the plunger from retracting with a simple structure without providing a ratchet mechanism.

[Brief description of drawings]

FIG. 1 is a diagram showing a timing system of a DOHC engine adopting a hydraulic tensioner according to an embodiment of the present invention.

FIG. 2 is a side view of the hydraulic tensioner.

FIG. 3 is a sectional view of the hydraulic tensioner.

FIG. 4 is a partially enlarged view of FIG. 3 (enlarged cross-sectional view of a supporting member).

FIG. 5 is a view showing a correlation between a pressing force of the hydraulic tensioner and an engine speed in comparison with a conventional example.

6A and 6B are views for explaining the function and effect of the embodiment.

FIG. 7 is a side view of a hydraulic tensioner according to another embodiment of the present invention.

FIG. 8 is a diagram showing an example in which the hydraulic tensioner (FIG. 7) is adopted in the timing system.

[Explanation of symbols]

 9 Tensioner arm 10 Hydraulic tensioner 11 Tensioner body (housing) 12 Piston rod (plunger) 12a Abutting part 13 Coil spring (biasing member) 15 Supporting member 20 Oil chamber 25 Oil reservoir 30 Check valve D Inner diameter of supporting member D'Oil Chamber inner diameter

Claims (3)

[Claims] 1. A housing having an oil chamber therein and having an opening communicating with the oil chamber at one end, and a support member provided in the opening and having an inner diameter smaller than an inner diameter of the oil chamber. Between the support member and the contact portion, a plunger having a rear end inserted into the oil chamber, slidably supported by the support member, and having a contact portion capable of contacting the tensioner arm, And a biasing member that is disposed on the outer circumference of the plunger and biases the plunger in the protruding direction. 2. The hydraulic tensioner according to claim 1, wherein the housing is provided with an oil reservoir for storing oil, the oil reservoir being connected to the oil chamber. 3. Between the oil reservoir and the oil chamber,
The hydraulic tensioner according to claim 2, wherein a check valve is provided.