JPH03260445A - Belt tensioner - Google Patents

Abstract

PURPOSE:To prevent leak of lubricant due to external factors such as temp. change, vibration, and inclination by forming an air bleeder hole over the lubricant level by means of communicating of a minor hole part with major hole part. CONSTITUTION:In the upper part of the drum part of a casing 20 an air bleeder hole 70 is formed which has a minor hole part 71 and a major hole part 72 so as to have communication with the outside. The major hole part 72 shall have a good greater dia. than the minor hole part 71, and a guide surface 75 is provided inclining from the former part 72 toward the latter 71. A cap 73 is fitted to the cylindrical part 25 removably, and therewith the over part of the major hole part 72 is enclosed, and also an air hole 74 is opened to generate communication of inside and outside of the casing 20. Thereby the lubricant can be prevented from leaking even though it reaches the major hole part 72 because of temp. change, vibration, and inclination.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a belt tensioner that applies a constant tension to a timing belt that drives a camshaft of an engine of a two-wheel vehicle or a four-wheel vehicle.

[Prior Art] A belt tensioner directly or indirectly presses a timing belt (hereinafter referred to as a belt), and even if the belt stretches or wears out during use and becomes loose, the belt tensioner maintains a certain level of pressure on the belt. Used to maintain tension. By the way, since the above-mentioned belt in an automobile is used in a dry environment, the belt tensioner itself needs to have lubricating performance, and the belt tensioner itself is filled with lubricating oil. In order to prevent leakage of this lubricating oil and intrusion of dust from the outside, the belt tensioner is in a sealed state, and the internal pressure is likely to change due to fluctuations in stroke due to pressure on the belt and fluctuations in environmental temperature. This results in
This causes the following inconveniences. In other words, when the internal pressure is high, lubricating oil moves smoothly toward the belt, but lubricating oil tends to leak out.On the other hand, when the internal pressure is low, lubricating oil is difficult to advance toward the belt, resulting in poor responsiveness. Missing.

A belt tensioner that prevents such internal pressure changes is disclosed in Japanese Utility Model Application No. 19015/1983. FIG. 5 shows a conventional belt tensioner shown in this publication. This belt tensioner includes a cylindrical casing 1 that is installed substantially vertically through a fixing bolt hole 1a, a rotating body 2 on a shaft that is rotatably inserted into the casing 1, and a rotating body 2 formed at the tip of the rotating body 2. A pressing body 3 that is screwed onto the male threaded portion 2a and propelled by the rotation of the rotating body 2; a spring (torsion spring) 4 that is fitted onto the rotating body 2 and imparting rotational force to the rotating body 2; The main part is constituted by a bearing 5 which has a non-circular bearing hole passing through it, is fixed to the casing 1, and restricts the rotation of the pressing body 3.

In such a configuration, the rotating body 2 is rotated and the spring 4 is
When the pressing body 3 is brought into contact with the belt while storing rotational energy, the rotating body 2 is rotated by the spring 4, and this rotational force is transmitted to the pressing body 3. However, since the rotation of the pressing body 3 is restricted by the bearing 5, the rotational force of the rotating body 2 is converted into propulsive force to press the belt. This results in
A constant tension can be maintained without the belt loosening.

In such a belt tensioner, as described above, it is necessary to seal the inside of the casing 1 in order to prevent dust from entering into the casing 1 and to prevent lubricating oil filled inside from leaking out. Therefore, the proximal end of the casing 1 (
A seal bolt 7 is screwed into the lower end of the casing 1, and a telescopic bellows 6 is covered between the tip (upper end) of the casing 1 and the pushing body 3 which is propelled. The lower end is attached to the pressing body 3 by a spring band 8, and the lower end is connected to a cylindrical body 9 press-fitted into the casing 1, thereby sealing the space between the pressing body 3 and the casing 1. A figure 7-shaped air vent hole 11 is formed in the pressing body 3 located above the bellows 6. The air vent hole 11 is located at the level of the lubricating oil inside the casing 1 (
It is formed at a position higher than the oil level (oil level level) and communicates the inside of the casing l with the outside. This air vent hole 11 serves to prevent negative pressure from occurring due to a change in volume inside the casing as the pressing body 3 is propelled, thereby ensuring that the pressing body 3 is propelled.

In addition, 10 in the figure is a stopper that locks the propulsion of the pressing body 3, and is designed to be removed as appropriate after the belt tensioner is attached.

[Problems to be Solved by the Invention] In the conventional belt tensioner, an air vent hole 11 is formed to prevent negative pressure inside the casing 1.
Lubricating oil leaks from this air vent hole 11. In other words, the air bleed hole 11 is formed above the oil level surface, but this oil level surface is likely to fluctuate due to expansion and vibration due to temperature rise, or the inclination of the vehicle when driving on a slope, and these fluctuations cause the lubricating oil to deteriorate. Because it leaks from the air bleed hole 11. - Once the lubricating oil has leaked out, it cannot be recovered into the casing 1, causing a problem that the lubricating oil is insufficient during operation and proper operation cannot be achieved. Moreover, this leakage of lubricating oil causes the lubricating oil to adhere to the belt and cause the belt to slip, causing a problem that proper operation of the belt cannot be ensured.

The present invention was made in consideration of such circumstances, and an object of the present invention is to provide a belt tensioner that does not leak lubricating oil.

[Means for Solving the Problems] In order to achieve the above object, the belt tensioner of the present invention includes a rotating body which is urged to rotate by a spring and a pressing body whose rotation is restrained by a bearing, which are screwed together in a casing. When inserted, the casing is filled with lubricating oil, and in a device that converts the rotational force of the rotary body into an axial propulsive force of the pressing body, a small hole communicating with the inside of the casing and the outside of the casing puffer are inserted. The casing is characterized in that an air vent hole, which is formed in communication with a communicating large hole portion, is formed at a predetermined portion of the casing so as to be located above the oil level surface of the lubricating oil.

In this case, a guide surface that slopes toward the small hole may be formed in the large hole of the air vent hole.

Further, a cap with a small hole that covers the large diameter portion may be removably attached to the large hole portion of the air vent hole.

[Function] Even if the lubricating oil reaches the small hole of the air vent hole due to temperature rise, vibration, etc., the lubricating oil is prevented from leaking because the large hole communicating with the small hole stalls.

In addition, if a guide surface is formed in the large hole, even if lubricating oil passes through the small hole and flows into the large hole, it will be guided by the guide surface of the large hole and enter the casing from the small hole. will be collected.

Furthermore, the cap covering the large hole more effectively prevents lubricating oil from leaking out.

[Examples] Hereinafter, the present invention will be specifically explained with reference to Examples shown in the drawings. Note that in each embodiment, the same elements are designated by the same reference numerals, thereby omitting redundant explanation.

FIG. 1 shows the overall configuration of a first embodiment of the present invention. This first embodiment is used in a horizontal layout so that the pressing body advances in the horizontal direction.

The belt tensioner includes a casing 20 in which an axial cavity 21 is formed, a rotating body 30 and a pressing body 40 that are screwed into the cavity 21 of the casing 20, and applies rotational force to the rotating body 30. A spring (torsion spring) 50 to be applied,
The bearing 60 is attached to the tip of the casing 20 (the right end in FIG. 1) and restrains the rotation of the pressing body 40.

The casing 20 is attached to a device (not shown) such as an engine, and the inside thereof is filled with lubricating oil (not shown). A seal bolt 84 is screwed into the base end (left end in FIG. 1) via a packing 83 to maintain airtightness on the base end side. Furthermore, casing 2
0 has a small diameter small hole part 71 and a large diameter large hole part 7 in the upper part of the body part.
An air vent hole 70 having 2 is formed to communicate with the outside. This air vent hole 70 prevents negative pressure inside the casing 20, as will be described later.

The rotating body 30 is rotatably supported within the casing 20. The rotating body 30 is formed by connecting a male threaded portion 31 on the distal end side and a shaft portion 32 on the proximal end side. A pressing body 40 is screwed onto the portion 31 to transmit rotational force, and the shaft portion 32 is supported within the support recess 23 of the casing 20 for rotational support. In this case, a bottomed cylindrical support member 82 is provided between the shaft portion 32 and the support recess 23 of the casing. The support member 82 is inserted between the rotating body 30 and the casing 20 to provide rotational support for the rotating body 30. By inserting the supporting member 82 in this way, the rotational support of the rotating body 30 is smoothly supported. In addition, since the process is performed reliably, it is not necessary to process the support recess 23 of the casing 20 with high precision, and the rotating body 30
This makes it possible to prevent wear of the casing 20. Note that the shaft portion 32 of this rotating body 30 has an axial split slit 3.
3 is formed and, as will be described later, is engaged with a spring 50 and biased to rotate.

The pressing body 40 includes a pipe portion 42 having a male threaded portion 41 formed on its inner surface, and a bushing shaft 43 fitted to the tip of the pipe portion 42 .

The pipe portion 42 is screwed into the male threaded portion 31 of the rotating body 30 to transmit the rotational force of the rotating body 30, and is inserted into the bearing 60 in a rotationally restrained state to convert the rotational force of the rotating body 30 into propulsive force. It is something. On the other hand, the tip of the bush shaft 43 extends outward from the casing 20, and the tip surface contacts the belt of the device directly or via a roller that presses the belt. This maintains the belt tension.

The spring 50 is connected to such a pressing body 40 and the rotating body 30.
has been extrapolated to This spring 50 is fitted onto the pressing body 40 and the rotating body 30 when they are in a screwed state, and the extrapolated portion extends from the inside to the outside of the rotating body 30.
．． It has a triple structure of a pressing body 40 and a spring 50.

Such a triple structure has the advantage that a sufficient stroke of the pressing body 40 can be ensured even if the length of the pressing body 40 in the advancing and retreating direction is shortened. Here, one end 51 of the spring 50 is folded back into an oval shape and inserted into the slit 24 formed in the axial direction of the casing 20.
The other end 52 is secured to the casing 20, and the other end 52 is connected to the rotating body 3.
It is inserted into the 0 split slit 33 and engaged with the rotating body 30. Therefore, when a driver or the like is inserted into the split slit 33 from the outside of the casing 20 with the seal bolt 84 removed and the rotating body 30 is rotated, the spring 5
It is possible to store rotational energy at zero.

The bearing 60 restricts the rotation of the pressing body 40, and is prevented from being pulled out by the circlip 61 so that the casing 20
Attached to the tip of the The bearing 60 has a bearing hole 62 formed in its central portion, and engagement pieces 63 formed at 90 degree intervals in its outer portion. The bearing hole 62 is formed into a substantially oval shape in which both sides of a circle are cut parallel to each other, and the vibration part 4 of the pressing body 40 has the same external shape.
2 is inserted into the bearing hole 62, thereby restricting the rotation of the pressing body 40. On the other hand, the retaining piece 63 performs rotation restraint against the rotational force of the rotating body 30. For this reason, engagement grooves are formed at 90 degree intervals on the front end surface of the casing 20 in correspondence with the retention pieces 63, and the rotational restraint is performed by fitting the engagement pieces 63 into the engagement grooves. It has become.

In the figure, 80 is a bellows that extends between the bush shaft 43 of the pressing body 40 and the casing 20, and covers the space between them.

By attaching the bellows 80, the tip side of the casing 20 has a sealed structure, and the lubricating oil filled inside is prevented from leaking.

40a is a circulation path opened in the vibrator portion 42 of the pressing body 40, and by forming this circulation path, the lubricating oil sealed in the casing 20 is evenly circulated.

The air vent hole 70 communicates the inside of the casing 20 with the outside, and includes a small diameter hole 71 formed on the upper surface of the body of the casing 20 and a large diameter hole communicating with the small hole 71. 72. In this case, a cylindrical portion 25 extending in the radial direction of the casing 20 is formed in the body corresponding to the periphery of the small hole 71 of the casing 20, and the large hole 72 is formed by drilling this cylindrical portion 25. It is formed. The diameter of the large hole 72 is formed to be much larger than that of the small hole 71.

Further, a cap 73 is removably attached to the cylindrical portion 25, and the upper portion of the large hole portion 72 is covered by the attachment of the cap 73. Note that air holes 74 are appropriately opened in the cap 73. In such an air vent hole 70, the small hole 71 communicates with the inside of the casing 20, while the large hole 7
2 communicates with the outside of the casing 20, and the pressing body 40
As the bellows 80 expands as the casing 20 moves forward, the internal volume of the casing 20 increases, and the casing 2
When the pressure inside the casing 20 decreases, external air is introduced to maintain a constant pressure inside the casing 20. This allows the pushing body 40 to advance smoothly. In addition to this effect, the air vent hole 70 is formed in the upper part of the casing 20 in the installed state, and the air vent hole 70 is
Since the air vent hole 70 is located above the oil level surface of the lubricating oil in the air hole 70, it acts to prevent the lubricating oil from leaking. Therefore, this leakage can be more effectively prevented.

In other words, even if lubricating oil passes through the small hole 71 due to temperature rise, vibration, or inclination, its speed is significantly reduced in the large hole 72, so it will not flow out beyond the large hole 72. , which can effectively prevent leakage. Therefore, leaked lubricating oil does not adhere to the belt, and malfunction of the belt can be prevented. In particular, the large hole 72 is covered by a cap 73, and this cap 73 prevents the lubricating oil from flowing out above the large hole 73. In addition to the stalling effect of the large hole 72, the cap 73
Measures are also taken to prevent leakage. Note that the cap 73 also functions to prevent dust from entering. In addition to such an effect, in this embodiment, the bottom surface of the large hole portion 72 is formed into a conical shape, and serves as a guide surface 75 for circulating lubricating oil into the casing 20. This guide surface 75 is inclined in a curved manner toward the small hole 71, and the casing 2
The lubricating oil flowing from the 0 yen into the large hole 72 flows in the direction of the small hole 71. Therefore, even if the lubricating oil flows into the large hole 72, the guide surface 75 promotes the flow down toward the small hole 71, so that the flow back to the casing 20 is smoothly performed, and the air bleed hole 70 This further prevents leakage from occurring.

In the figure, 76 is a bottle that is fitted into the air hole 74 of the cap 73, and is used during transportation, storage, etc., and is removed after being attached to the device.

FIG. 2 shows a second embodiment of the present invention, in which an insertion hole of a stopper bin 85 is used as the air vent hole 70. This second embodiment is also used in a horizontal layout, similar to the first embodiment. The lower end of the stopper bin 85 is inserted into the split slit 33 of the rotating body 30, and this insertion locks the rotation of the rotating body 30 against the bias of the spring 50.

This stopper bin 85 is pulled out after being attached to the device. In this case, since there is no need to newly form a dedicated air vent hole, there is an advantage that processing of the casing 20 is facilitated. Note that after the stopper bin 85 is pulled out, the air bleed hole 70 has a small hole 71 and a large hole 7.
2, the inside and outside of the casing 20 are communicated with each other to prevent lubricating oil from leaking as in the previous embodiment. In this case, the large hole 72 may be covered with a removable cap as in the first embodiment.

FIG. 3 shows a third embodiment of the invention. This embodiment is used by being mounted upright on a device with the seal bolt 84 positioned upward and the bush shaft 43 of the pressing body 40 positioned downward. In such embodiments,
Air vent hole 70 is formed at the upper end of casing 20. The air vent hole 70 has a small hole part 71 and a large hole part 72, but in this embodiment, the small hole part 71 is connected to the seal bolt 83.
A screw-sized gap portion where the casing 20 is screwed into the casing 20 is utilized. On the other hand, the large hole 7 communicating with this small hole 71
2 is formed on the upper end surface of the casing 20. The bottom of the large hole 72 is a guide surface 75 that is linearly inclined toward the small hole 7 and serves as a guide surface 75 for the lubricating oil casing 20.
reflux is being promoted. In this case, the packing 83 inserted between the casing 20 and the seal bolt 83 covers the large hole 72 and performs the same function as the cap in the first embodiment. Reference numeral 83a denotes an air hole formed in the packing 83, which is appropriately closed by inserting the bottle 76.

FIG. 4 shows a modification of the third embodiment, in which the seal bolt 83
A slit 27 is formed along the screw hole into which the slit 27 is screwed. By forming this slit 27, the casing 20
Since the large hole 72 of the air bleed hole 70 communicates smoothly with the large hole 72 of the air bleed hole 70, positive air bleed can be ensured.

[Effects of the Invention] As explained above, in the present invention, the air vent hole provided above the oil level surface of the lubricating oil is formed by communicating with the small hole portion and the large hole portion, which prevents temperature changes.

This has the effect of preventing leakage of lubricating oil due to external factors such as vibration and tilt.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the overall configuration of the first embodiment of the present invention;
FIG. 2 is a sectional view showing the second embodiment, FIG. 3 is a sectional view of main parts showing the third embodiment, FIG. 4 is a sectional view along the rV-TV line of FIG. FIG. 5 is a sectional view showing a conventional example. 20...Casing, 30...Rotating body, 40...
Pressing body, 50... Spring, 6o... Bearing, 70...
Air vent hole, 71...Small hole portion, 72...Large hole portion. Patent applicant NHK Spring Co., Ltd.

Claims (3)

[Claims] (1) A rotating body urged to rotate by a spring and a pressing body whose rotation is restrained by a bearing are inserted into a casing in a screwed state, and the casing is filled with lubricating oil, and the rotating body In the device for converting the rotational force of the casing into the axial propulsion force of the pressing body, an air vent hole formed by communicating a small hole communicating inside the casing and a large hole communicating outside the casing is used for the lubrication. A belt tensioner characterized in that it is formed at a predetermined part of a casing so as to be located above an oil level surface. (2) The belt tensioner according to claim 1, wherein the large hole portion of the air vent hole is formed with a guide surface that slopes toward the small hole portion. (3) The belt tensioner according to claim (1), wherein a cap with a small hole that covers the large diameter portion is removably attached to the large hole portion of the air vent hole.