JPH08247237A - Hydraulic tensioner - Google Patents

Abstract

PURPOSE: To provide a hydraulic tensioner capable of reducing the number of parts and simplifying the structure. CONSTITUTION: A hydraulic tensioner 10 is provided with a housing 11 having a hole 11a to be communicated with an oil chamber 16 formed inside thereof, and an advancing/retracting plunger 13. A supporting part 14 to slidably support the plunger 13 is provided on an opening part of the hole 11a, a female screw part 11b is formed on the inner circumference of the opening part, and a male screw part 14b to be engaged with the female screw part 11b is formed on the outer circumference of the supporting part 14. In addition, the outer diameter of the male screw part 14b is formed small than the prescribed value (the normal dimension corresponding to the inner diameter of the female screw part).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic tensioner, and more particularly to a so-called air bleeding mechanism for discharging air mixed in an oil chamber of a housing to the outside of the housing.

[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 engine torque fluctuation and to reduce noise and vibration. Generally, a hydraulic tensioner includes a housing having a hole having an opening at one end, a plunger that is retractably inserted into the hole and that abuts on a tensioner arm that is disposed on a loose side of a chain or a belt. And a spring that biases the plunger in the protruding direction. An oil chamber is formed by the inner wall surface of the hole of the housing and the outer peripheral surface of the plunger, and external oil pressure acts on the oil chamber.

In such a hydraulic tensioner, air may be mixed into the hydraulic oil in the oil chamber. In such a case, since the air is a compressible fluid, tension is applied to the chain or belt. When this happens, the mixed air is compressed and the plunger retracts, resulting in vibration of the chain and belt.

For this reason, various air venting mechanisms have been proposed for exhausting the mixed air in the oil chamber to the outside of the housing. As a conventional air venting mechanism, for example, Japanese Patent Publication No.
There is one using a sintered filter made of a sintered alloy as shown in Japanese Patent Publication No. 28575-85, but in the one using this sintered filter, in a dust or a hydraulic oil in the atmosphere during the use of the hydraulic tensioner. The sludge may fill the pores of the sintered filter, and the air discharge performance is not stable.

Therefore, in order to solve such a problem, there has been proposed an air venting mechanism as shown in Japanese Utility Model Publication No. 60-30507, which discharges air by extraction gas having a screw groove formed on the outer circumference.

However, in this case, since it is necessary to separately prepare a part called extraction gas for removing air, the number of parts increases and the structure becomes complicated.

The present invention has been made in view of such conventional circumstances, and an object of the present invention is to provide a hydraulic tensioner capable of reducing the number of parts and simplifying the structure.

[0008]

A hydraulic tensioner according to the invention of claim 1 comprises a housing having a hole communicating with an oil chamber formed therein, and a retractable plunger inserted in the hole. In the hydraulic tensioner, a support portion that slidably supports the plunger is provided in the opening portion of the hole, a female thread portion is formed on the inner periphery of the opening portion, and an outer peripheral surface of the support portion is formed. It is characterized in that a male screw portion that is screwed with the female screw portion is formed.

A hydraulic tensioner according to a second aspect of the present invention is
In claim 1, at least one of the outer diameter and the diameter of the valley of the male thread portion is formed smaller than a specified dimension.

The hydraulic tensioner according to the invention of claim 3 is
In claim 1 or 2, at least one of the inner diameter of the female screw portion and the diameter of the valley is formed to be larger than a specified dimension.

[0011]

According to the present invention, the air mixed in the oil chamber passes through the gap between the male screw portion on the outer periphery of the support portion and the female screw portion on the inner periphery of the hole opening portion that is screwed into the outer peripheral portion of the support portion. Is guided to the side,
It is discharged from the open end to the outside of the housing.

That is, in this case, since the support portion that slidably supports the plunger is used as the extraction gas for air discharge, it is not necessary to separately provide a component for air discharge, and thus, the component can be The number of points can be reduced and the structure can be simplified.

According to the second aspect of the invention, at least one of the outer diameter and the root diameter of the male screw portion formed on the outer periphery of the supporting portion is smaller than the specified dimension. Between the top of the thread of the male thread and the root of the female thread, or between the root of the male thread and the thread of the female thread when the A larger gap is formed between the top portion and the top portion than when the male screw portion is formed to have a specified size. As a result, a spiral groove having a large cross-sectional area is formed over the entire threaded portion, and the air mixed in the oil chamber is
It is discharged to the outside of the housing through this spiral groove. As a result, the air mixed in the oil chamber can be easily discharged to the outside of the housing, and the air discharging performance can be improved.

According to the third aspect of the invention, at least one of the inner diameter of the screw portion and the diameter of the valley is larger than the specified dimension because it is formed on the inner circumference of the hole opening portion. When the male thread of the support section is screwed onto the support, it is between the top of the thread of the female thread and the root of the male thread, or between the root of the female thread and the top of the thread of the male thread. A gap larger than that in the case where the female screw portion is formed to have a specified size is formed between the two. As a result, as in the case of the second aspect of the invention, a spiral groove having a large cross-sectional area is formed over the entire threaded portion, and the air mixed in the oil chamber passes through the spiral groove. It is discharged to the outside of the housing. As a result, the air mixed in the oil chamber can be easily discharged to the outside of the housing, and the air discharging performance can be improved.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4 are views for explaining a hydraulic tensioner according to an embodiment of the present invention, FIG. 1 is a view showing an example of an engine timing system in which the present hydraulic tensioner is adopted, and FIG. 2 is a present hydraulic tensioner. Is a front view, FIG. 3 is a sectional view thereof, and FIG. 4 is an enlarged view of a portion A of FIG.

FIG. 1 shows a timing system of a vehicle DOHC engine.
Includes a drive sprocket 3 fixed to the crankshaft 2, a driven sprocket 6 and 7 fixed to two camshafts 4 and 5, respectively, and a timing chain 8 wound between the sprockets. . 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 is inserted into the housing 11 and a housing 11 having a hole 11a having an opening at one end thereof.
A plunger 13 having an abutting portion 12 that abuts the tensioner arm 9 is attached to the tip, a supporting portion 14 that slidably supports the plunger 13, and a coil spring 15 that biases the plunger 13 in the protruding direction. ing.

An oil chamber 16 defined by the inner wall surface of the hole, the outer peripheral surface of the plunger 13, and the end surface of the support member 14 is formed in the hole 11a. Oil pressure from an external hydraulic circuit (not shown) including an oil pump is supplied to the oil chamber 16 via a check valve 17. The tip of the coil spring 15 is in pressure contact with the back surface of the contact portion 12, and the rear end thereof is in pressure contact with the end surface 14 a of the support portion 14.

A female screw portion 11b is formed on the inner circumference of the hole opening of the housing 11. On the outer periphery of the support member 14, a male screw portion 14b that is screwed into the female screw portion 11b is formed.

As shown in FIG. 4, the top portion 20 of each thread of the male thread portion 14b has a prescribed dimension (here, the female thread portion 11).
It is formed to be slightly lower than each thread crest upper portion 20 'in the case of a regular dimension corresponding to the inner diameter of b). That is, the outer diameter do of the male screw portion 14b is slightly smaller than the specified dimension.

Therefore, the outer diameter of the male thread portion 14b is formed between the respective thread crest upper portions 20 of the male thread portion 14b and the corresponding valley bottom portions 21 of the female thread portion 11b in a prescribed dimension. A gap 22 larger than the case is formed,
A spiral groove having a large cross-sectional area is formed over the entire threaded portions 11b and 14b.

With this structure, the air mixed as bubbles in the oil chamber 16 is guided to the opening end side of the hole 11a through the spiral groove and is discharged to the outside of the housing from the opening end. As a result, the vibration of the plunger and the vibration of the chain due to the mixed air can be prevented.

As described above, according to this embodiment, since the support portion 14 which slidably supports the plunger 13 is used as the extraction gas for discharging air, it is not necessary to separately provide a component for discharging air. As a result, the number of parts can be reduced and the structure can be simplified. Further, since air is evacuated by using the spiral groove formed over the whole of each screw part, the air mixed in the oil chamber can be easily discharged to the outside of the housing, and the air discharging performance can be improved.

Furthermore, since the mounting of the support portion into the hole is performed by screwing the respective screw portions together, the processing accuracy required for press-fitting the support portion into the hole is not required, and the processing cost can be reduced. In the case of press-fitting, if the pressure of the internal oil chamber rises, the support part may slip out to the hole opening end side, but in the case of this embodiment, because of the screw-threaded mounting, This fear can be eliminated.

[ First Modification ] In the above embodiment, the outer diameter do of the male screw portion 14b is formed to be smaller than the specified dimension to form the spiral groove having a large cross-sectional area.
The application of the present invention is not limited to this, and as shown in FIG.
The diameter di of the valley of the external thread 14b may be formed smaller than the specified dimension.

In FIG. 5, the roots 23 of the threads of the male thread 14b are the roots in the case of a specified dimension (a regular dimension corresponding to the inner diameter of the female thread 11b as in the above embodiment). It is formed slightly lower than the portion 23 ′, and is formed between the respective bottom portions 23 of the male screw portion 14 b and the corresponding thread crests 24 of the female screw portion 11 b corresponding thereto.
A larger gap 25 is formed than in the case where the diameter of the valley of b is formed to the specified size.

As a result, as in the case of the above embodiment,
A spiral groove having a large cross-sectional area is formed over the entire threaded portions 11b and 14b, and the air mixed in the oil chamber 16 is easily discharged to the outside of the housing through the spiral groove.

[ Second and Third Modifications ] In the above-described embodiments and the first modification, the outer diameter do of the male screw portion 14b or the diameter di of the valley is formed smaller than the specified dimension.
The application of the present invention is not limited to this, and as shown in FIG. 6 and FIG. 7, the inner diameter Do of the female threaded portion 11b or the diameter Di of the valley Di.
May be changed.

Second Modification FIG. 6 shows each screw when the top 26 of each thread of the female threaded portion 11b has a prescribed dimension (here, a regular dimension corresponding to the outer diameter of the male threaded portion 14b). An example is shown in which it is formed slightly lower than the top 26 'of the summit, that is, the inner diameter Do of the female screw portion 11b is slightly larger than the specified dimension. Thereby, each thread crest top part 26 of the female thread part 11b and each trough bottom part 2 of the male thread part 14b corresponding to this.
7, there is formed a gap 28 larger than that in the case where the inner diameter of the female threaded portion 11b is formed to have a specified dimension, and as in the case of the first modification, each of the threaded portions 11b and 14b is formed. A spiral groove having a large cross-sectional area is formed over the entire area.

Third Modified Example In FIG. 7, each valley bottom portion 29 of the female threaded portion 11b has a specified dimension (a regular dimension corresponding to the outer diameter of the threaded portion 14b as in the case of the second modified example). In this case, it is formed to be slightly lower than each valley bottom portion 29 ', that is, the diameter Di of the valley of the female screw portion 11b is slightly larger than the specified dimension. As a result, the diameter of the root of the female threaded portion 11b is formed between the bottoms 29 of the female threaded portion 11b and the tops 30 of the thread crests of the male threaded portion 14b corresponding to the valley bottoms 29 to a prescribed size. A larger gap 31 is formed than in the case, and the screw portions 11b and 14 are formed in the same manner as in the above embodiment.
A spiral groove having a large cross-sectional area is formed over the entire area of b.

[ Fourth Modification ] Further, the embodiments and the respective modifications may not be used individually, but may be used in an arbitrary combination. For example, the first modification may be combined with the above-described embodiment, or the second modification and the third modification may be combined. Further, at least one of the second and third modified examples may be combined with the above-described embodiment, or at least one of the second and third modified examples may be combined with the first modified example. You may make it combine. Further, all of the first to third modified examples may be combined with the above embodiment.

[ Fifth Modification ] Although the diameter of the female threaded portion 11b or the male threaded portion 15b is changed in the embodiment and the first to fourth modified examples, the present invention is not limited to this. ,
The present invention can be applied to the case where each threaded portion is formed to have a specified dimension without changing the diameter of each threaded portion. Also in this case, the spiral groove formed between the screw parts is used as the air vent.

[ Other Application Examples ] Although the hydraulic tensioner applied to the timing system for the automobile engine has been shown in the above-mentioned embodiment and each modification, the present invention is also applied to the timing system for the motorcycle engine. it can.

FIG. 8 shows an example of such a hydraulic tensioner. In FIG. 8, the same reference numerals as in FIG. 3 indicate the same or corresponding parts. Here, check valve 17
Is arranged on the end side of the housing 11, which is different from the above-mentioned embodiment. With this configuration, the oil passage 40 from the outside of the engine can be easily connected.

[0035]

As described above, according to the hydraulic tensioner of the present invention, since the supporting portion for slidably supporting the plunger is used as the extraction gas for discharging the air, the number of parts can be reduced. This has the effect of simplifying the structure.

[Brief description of drawings]

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

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

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

FIG. 4 is an enlarged view of portion A of FIG.

FIG. 5 is a diagram showing a modified example (first modified example) of FIG. 4;

FIG. 6 is a diagram showing a modified example (second modified example) of FIG. 4;

FIG. 7 is a diagram showing a modification (third modification) of FIG. 4;

FIG. 8 is a diagram showing another application example of the present invention.

[Explanation of symbols]

 10 Hydraulic tensioner 11 Housing 11a Hole 11b Female thread 13 Plunger 14 Support 14b Male thread do Male thread outer diameter di Male thread trough diameter Do Female thread inner diameter Di Female thread trough diameter

Claims (3)

[Claims] 1. A hydraulic tensioner comprising a housing having a hole formed therein and communicating with an oil chamber, and a retractable plunger inserted into the hole, wherein the opening of the hole has the plunger. And a female screw portion is formed on the inner circumference of the opening, and a male screw portion that is screwed into the female screw portion is formed on the outer circumference of the support portion. The hydraulic tensioner is characterized by 2. The hydraulic tensioner according to claim 1, wherein at least one of an outer diameter of the male thread portion and a diameter of a valley is formed smaller than a specified dimension. 3. The hydraulic tensioner according to claim 1, wherein at least one of an inner diameter of the female screw portion and a diameter of a valley is formed larger than a specified dimension.