JPH03260446A - Belt tenstioner - Google Patents

Abstract

PURPOSE:To prevent leakage of lubricant due to a change in the internal pressure or temperature, vibration, and inclination by incorporating a sealed structure with the lubricant encapsulated in a casing, and furnishing a pressure adjusting chamber over the oil level so as to have communication with inside of the casing. CONSTITUTION:Lubricant is encapsulated in the cavity 21 of a casing 20 in a sealed structure, and a pressure adjusting chamber 70 is installed at the top of the casing 20. This is formed by covering a screw hole in a seal bolt with a bellows member which is capable of expanding and contracting. Installation of the pressure adjusting chamber 70 is made in such a manner that its inside is in communication with inside the casing 20 through screw hole for seal bolt, and if the internal capacity of the casing 20 has increased or decreased with advance/retreat of a pressing element 40, the chamber operates so as to follow the pressure change caused thereby. Thus pressure change in the casing 20 is prevented, and the tensioner is ensured with proper operation, and also leakage of lubricant due to external factor will be prevented such as 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 suppressor 3 that is screwed onto the male threaded portion 2a and is propelled by the rotation of the rotating body 2; a spring (torsion spring) 4 that is fitted onto the rotating body 2 and applies 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 casing 1 (lower end), and a telescopic bellows 6 is covered between the tip (upper end) of the casing 1 and the pushing body 3 that is propelled. The upper end of the bellows 6 is attached to the suppressor 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 presser 3 and the casing 1. A T-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 level (oil level level) and communicates the inside of the casing 1 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 suppressor 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. It leaks from the air vent 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, creating a fatal problem in which 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.

C Means for Solving the Problem] 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. In the device that is inserted and converts the rotational force of the rotating body into the axial propulsive force of the pressing body, the casing has a sealed structure in which lubricating oil is sealed inside the casing, and the oil level of the lubricating oil is above the oil level surface. It is characterized in that a pressure air adjustment chamber communicating with the inside of the casing is provided at a predetermined portion of the casing.

The pressure adjustment chamber may be an air chamber formed by covering a communication hole into the casing with a flexible member so that the internal volume increases or decreases as the pressure inside the casing increases or decreases.

[Function] The pressure adjustment chamber prevents changes in internal pressure due to the advancement of the pressing body, but since this pressure adjustment chamber is provided in a sealed manner above the oil level surface, lubrication is maintained even if there are temperature changes, vibrations, or tilts. Designed to prevent oil leakage.

[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 given the same reference numerals to correspond to each other, thereby omitting redundant explanation.

FIG. 1 shows the overall structure of a first embodiment of the present invention. This first embodiment is used by arranging the pressing body vertically so that it extends downward.

The belt tensioner applies rotational force to 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 a rotating body 3o. A spring (torsion spring) 50 and a pressing body 40 attached to the lower end of the casing 20
The casing 20 includes a bearing 60 that restricts the rotation of the casing 20, and a pressure adjustment chamber 70 provided at the upper end of the casing 20.

In this embodiment, the casing 20 is placed vertically so that the pressing body 40 is located on the lower side, and is installed in equipment such as an engine (not shown), and the pressure adjustment chamber 7o is located at the upper part of the casing 20. It is located in This casing 20
Lubricating oil (not shown) is sealed in the cavity 21,
It has its own lubrication performance. In this case, a seal bolt (not shown) is attached to the upper end of the casing 20 before the belt tensioner is attached to the device, and the pressure adjustment chamber 70 is attached to the upper end of the casing after this seal bolt is removed. .

The rotary body 30 is rotatably supported within the casing 20. The rotary body 30 has a male threaded portion 31 on the distal end (lower end) side and a shaft portion 32 on the proximal end (upper end) side connected to each other. The pressing body 40 is screwed into the male threaded portion 31 to transmit rotational force, and the shaft portion 32 is connected to the casing 2.
It is inserted into the support recess 23 of No. 0 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 rotating body 30
Since rotation support is performed smoothly and reliably, it is not necessary to process the support recess 23 of the casing 20 with high accuracy, and wear of the rotating body 30 and the casing 20 can be prevented. Note that an axial split slit 33 is formed in the shaft portion 32 of this rotating body 30, and as described later,
It is designed to be engaged with the spring 50 and biased to rotate.

The pressing body 40 includes a vibrator 42 having a female thread 41 formed on its inner surface, and a bushing shaft 43 fitted into the tip (lower end) of the vibrator 42 . Vibrator part 4
2 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. be. On the other hand, the front end portion (lower end portion) of the bush shaft 43 extends outward from the casing 20, and the front end 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 5o.

Such a triple structure has the advantage that a sufficient stroke of the pressing body 4o 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 a slit 24 formed in the axial direction of the casing 2o to engage with the casing 20, and the other end 52 is rotated. body 30
It is inserted into the split slit 33 of the rotary body 30 and is secured to the rotating body 30.

Therefore, when a driver or the like is inserted into the split slit 33 from the upper part of the casing 20 and the rotating body 30 is rotated, rotational energy can be stored in the spring 50.

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 lower end 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 pipe portion 4 of the pressing body 40 is formed to have the same outer 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 outer surface of the lower end of the casing 20 to correspond to the engagement pieces 63.
The rotational restraint is performed by fitting into the engagement groove.

In the figure, 80 is a bellows that is passed between the bush shaft 43 of the pressing body 40 and the casing 20 to cover the space between them. This bellows 80 has protrusions 81 formed on the inner surfaces of both upper and lower ends, and each protrusion 81
is fitted into the grooves formed on the outer surface of the casing 20 and the outer surface of the bush shaft 43 of the pressing body 40, and expands as the pressing body 40 moves forward, so that there is a gap between the casing 2o and the pressing body 40. is always covered.

By attaching the bellows 80, the lower end 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 pressure adjustment chamber 70 is attached to the upper end of the casing 20. This pressure adjustment chamber 70 is formed by covering the threaded hole of the seal bolt with a telescopic bellows member such as a rubber boot. The pressure adjustment chamber 70 is attached to the casing 20 by forming an engagement protrusion 71 on the inner side of the lower end of the pressure regulation chamber, and forming an engagement groove 25 on the outer surface of the upper end of the casing 20. This is done by fitting the engagement grooves 25 into each other, but by adhesion,
This pressure adjustment chamber 70 may be welded or may be used in combination.The pressure adjustment chamber 70 is installed so that the inside thereof communicates with the inside of the casing 20 through a screw hole for a seal bolt, and the pressure adjustment chamber 70 is attached so that the inside thereof communicates with the inside of the casing 20 through a screw hole for a seal bolt. When the internal volume of the casing 20 increases or decreases accordingly, the expansion and contraction operation follows the pressure change within the casing 20 accompanying this volume change and compensates for this change. This eliminates pressure changes within the casing 20, allowing the pressing body 40 to operate smoothly. When the pressure inside the casing 20 becomes negative, this pressure adjustment chamber 70 is contracted as shown by the two-dot chain line in FIG. 11 to prevent the pressure from becoming negative. Such a pressure adjustment chamber 70 is attached to the upper end of the casing 20 and
The top end is sealed. This prevents the lubricating oil filled in the casing 20 from leaking out, but by being attached to the upper end of the casing, sealing is performed above the oil level surface of the lubricating oil.

Therefore, even if the oil level of the lubricating oil increases due to temperature rise, vibration, or tilt, it is possible to reliably prevent lubricating oil from leaking, eliminating belt malfunctions caused by lubricating oil leakage. play.

FIG. 2 shows a modification of the first embodiment, in which the casing 2
The upper end portion of the pressure adjustment chamber 70 is recessed in an arc shape to form a recess 26, and an upper portion corresponding to the recess 26 is covered with a flexible cover 72 to form a pressure adjustment chamber 70.

FIG. 3 shows a second embodiment of the invention. This embodiment is used so that the bush shaft 43 of the pressing body 40 is positioned above, and a pressing force is applied to the belt of the device from below. In the figure, 84 is a seal bolt screwed into the lower end of the casing 20, and by inserting the seal 83 between the seal bolt 84 and the lower end surface of the casing 20, the lower end of the casing 20 is sealed. There is. In this embodiment, a bellows 80 is hooked between the casing 20 and the bushing shaft 43 of the pressing body 40 to seal the upper end of the casing 20. It is expanded in a zigzag pattern.

By expanding the lower portion of the bellows 80, a pressure adjustment chamber 7o, in which air is sealed, is formed in the expanded portion. That is, the air adjustment chamber 7o is formed by extending the lower part of the bellows 80 in the axial direction of the casing 20, and by bending this extended portion in multiple stages. Thereby, the pressure adjustment chamber 70 is in communication with the inside of the casing 20, and expands and contracts following the forward and backward movement of the pressing body 40, thereby preventing pressure fluctuations within the casing 20. By being connected to the bellows 80, the pressure adjustment chamber 70 is located above the oil level surface of the lubricating oil filled in the casing 20, and as a result, as in the first embodiment,
Prevents lubricating oil from leaking due to temperature changes, vibrations or tilting.

FIG. 4 shows a third embodiment of the invention. This embodiment is used so that the casing 20 and the pressing body 40 are positioned horizontally, and press against the belt of the device from the lateral direction. In this embodiment, a radial communication hole 27 is formed in the upper surface of the body of the casing 20.

A cylindrical portion 28 is formed outside the communication hole 27, and a bellows member is attached to the cylindrical portion 28 to form a pressure adjustment chamber 70. Also in this example,
A pressure adjustment chamber 70 is provided in the upper part of the casing 20,
Since it is located above the oil level surface of the lubricating oil in the casing 20, leakage of the lubricating oil can be prevented.

[Effects of the Invention] As explained above, the present invention provides a pressure regulating chamber that communicates with the inside of the casing so as to be located above the oil level surface of the lubricating oil in the casing. This has the effect of not only ensuring proper operation of the tensioner by preventing pressure build-up, but also preventing lubricating oil from leaking due to external factors such as temperature changes, vibrations, or tilting.

[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 partial sectional view showing a modification thereof, FIG. 3 is a sectional view showing the second embodiment, and FIG. 4 is a sectional view showing the third embodiment.
FIG. 5 is a sectional view showing a conventional example. 20...Casing, 30...Rotating body, 4o...
Pressing body, 50... Spring, 60... Bearing, 70...
Pressure adjustment chamber. 4:! 1 Patent applicant NHK Spring Co., Ltd. 84 Ko 4

Claims (2)

[Claims] (1) A rotating body that is rotationally biased 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 rotational force of the rotating body is converted into an axial propulsive force of the pressing body. The converting device has a sealed structure in which lubricating oil is sealed inside the casing, and a pressure adjustment chamber communicating with the inside of the casing is provided at a predetermined part of the casing located above the oil level surface of the lubricating oil. A belt tensioner characterized by: (2) The pressure adjustment chamber is an air chamber formed so that the communication hole into the casing is covered with a flexible member so that the internal volume increases or decreases as the pressure inside the casing increases or decreases. belt tensioner.