JPH01126460A - Tension device for chain, belt and the like - Google Patents

Abstract

PURPOSE:To reduce the length of the device in the axial direction and to reduce the device in size by forming the outline shape of a screw portion of a male screw member for adjusting tension corresponding to the shape of a bearing hole for restricting the rotation of the above member. CONSTITUTION:A male screw member 20 and a female screw member 30 are disposed in the engagement state in a casing 11. The female screw member 20 is rotated by the force of a spring 40, whereby the male screw member 20 is advanced in the axial direction. The outline shape of a screw portion 21 of the male screw member 20 is formed corresponding to the shape of a bearing hole 51 for restricting the rotation of the male screw member. Thus, the length of the device can be reduced in the axial direction so as to achieve reduction in size of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tensioning device that applies a constant tension to a chain or timing belt that drives a camshaft of an engine of an automobile or the like.

[Prior Art] A tensioning device is generally used in an engine as a chain tensioner or a belt tensioner. This tensioning device acts to maintain a constant tension by directly or indirectly pushing the chain or belt in one direction when it becomes loose due to stretching or wear. be.

FIG. 8 shows a conventional example of such a tensioning device.

As shown in the figure, a male threaded member 2 and a female threaded member 3 are screwed together and inserted into a casing l. The male threaded member 2 and the female threaded member 3 are screwed together in the first half of the male threaded member 2, and the coil spring 4 is inserted into the second half of the threaded member 2. This coil spring 4 has one end 4a inserted into a long groove 18 formed in the casing 1, and the other end 4b inserted into a slit in the male threaded member 2, whereby the male threaded member 2 applies rotational force. are doing. - way,
The female screw member 3 passes through a bearing 5 attached to the open end (left end) of the casing 1, and a cap 6 is placed on the tip (left end) of the bearing 5. The hole of the bearing 5 through which the female threaded member 3 passes is formed in a non-circular shape, such as an oval shape with opposing faces cut out in parallel, and the outer shape of the female threaded member 3 is also formed in the same shape. In such a structure, the rotation of the female threaded member 3 is restrained by the bearing 5, and the rotational force from the male threaded member 2 is converted into the propulsive force of the female threaded member 3, and the female threaded member 3 is pulled out from the casing l (leftward direction). ) Go straight ahead. Therefore, the cap 6 at the tip of the female thread member 3 constantly presses the belt, chain, etc., and these act to maintain a constant tension. It is an extendable boot for covering, and 8 is a seal bolt screwed into the base end (right side) of the casing 1. These boots 7 and seal bolts 8 are installed to prevent dust from entering the casing 2 from inside and outside the engine, and to prevent lubricating oil inside the casing 1 from leaking outside. It is.

However, such a structure requires a first half where the male threaded member 2 is screwed with the female threaded member 3 and a second half where the coil spring 4 is inserted, and the dimensions of this male threaded member determine the device dimensions. The entire device is axially elongated.

Moreover, this direction is the direction in which the tension of chains, belts, etc. is adjusted, and when considering installation in extremely narrow spaces such as engines, short dimensions are preferable, and longer dimensions are a fatal problem in terms of installation space. It has become.

In order to reduce such dimensions, a device has been proposed in which three members, a male threaded member, a female threaded member, and a coil spring, are combined so as to overlap in the radial direction (Utility Model Application No. 62-11555
However, with this structure, the stroke of the straight-moving member is sacrificed, and even if it is possible to shorten the entire device, the tension adjustment length of the chain, belt, etc. will become smaller. . For this reason, the adjustable range is narrow, making it impractical.

[Problems to be solved by the invention] As described above, in the conventional technology, when the device is long, it is difficult to attach it to an engine, etc. On the other hand, when the device is shortened, the stroke becomes short and the tension There is a problem that the adjustment range becomes narrower.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tensioning device such as a chain or belt that satisfies both the miniaturization of the device and the securing of a sufficient tension adjustment range.

[Means for Solving the Problems] A tensioning device for a chain, a belt, etc. according to the present invention is provided in a casing with a male threaded member and a female threaded member in a screwed state, and the male threaded member is rotated by a spring force. In the tensioning device in which the male threaded member advances in the axial direction, the outer shape of the threaded portion of the male threaded member is formed to correspond to the shape of a bearing hole that restrains rotation of the member.

[Function] Since the present invention is configured as described above, the threaded portion of the male threaded member is also restrained from rotating and can slide in the bearing hole, which makes it possible to slide in the tension adjustment direction of the device. Despite the shorter dimensions, a sufficient stroke length of the male threaded member can be ensured.

[Example] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of an embodiment in which the present invention is applied to a belt tensioner, FIGS. 2 and 3 are left and right side views thereof, and FIGS. 4 to 6 are parts diagrams. An axial cavity 12 is formed in the casing 11, which has an engine mounting hole 11a formed on the outside, and a male threaded member 2°, a female threaded member 30, and a coil spring 40 are assembled in this cavity 12. The male threaded member 20 is screwed into the female threaded member 30, as shown in FIGS. 1 and 4.
A threaded portion 21 in which a screw 21a that is screwed into the female threaded member 30 is carved, and a head portion 22 that is extracted outward from the casing 11 are integrally formed in the axial direction.

On the other hand, the female thread member 30 is formed into a cylindrical body with a bottom,
A bottom portion 31 on the base side thereof is inserted into a stepped portion formed in the casing 11 together with the washer 15, and is rotatably supported. A threaded portion 33 is partially formed on the inner surface of the cylindrical portion 32 connected to the bottom portion 31, and the male threaded member 2
The threaded portions 21 of 0 are screwed together. Further, a bearing member 50 is attached to the tip portion (left end portion) of the casing. As shown in FIG. 6, the bearing member 50 is formed into a generally triangular star shape as a whole, with a bearing hole 51 opened in the center, and a portion extending outward from the bearing hole 51 bent rearward. This forms a fitting piece 52. This fitting piece 5
The bearing member 2 is fitted onto the tip of the casing 11 to fix the bearing member 50 to the casing 11. For this reason, each fitting piece 52 is provided at the tip of the casing 11 as shown in Figure 5.
A fitting groove 13 into which is inserted is formed. On the other hand, the male threaded member 2o is inserted into the bearing hole 51 while being rotationally restricted. In this embodiment, the bearing hole 51 has two parallel lines,
It consists of a circular arc line connecting both ends of this parallel line. The threaded portion 21 of the male threaded member 20 is inserted into this bearing hole 51 and its rotation is restricted. Therefore, the screw 2 of the male threaded member 2o
The outer shape of the threaded portion 21 with 1a carved therein is the bearing hole 51.
It is molded into a shape that corresponds to the Therefore, Fig. 4 (C
), the outer shape of the threaded portion 21 is circular, and the opposing surfaces are cut in parallel to form a shape that fits into the bearing hole 51. In such a structure, the rotation of the female threaded member 30 is transmitted from the threaded portion of the threaded portion 21.31 to the male threaded member 2o, but since the rotation of the male threaded member 20 is restrained by the bearing hole 51, it is not propelled in the linear direction. This is converted into force, and the male threaded member 20 moves straight. ! This allows the head portion 22 of the male threaded member 20 to directly or indirectly press against the belt to maintain them under a predetermined tension. In this case, the stroke length of the male threaded member 20 is determined by the threaded portion 21 that engages with the female threaded member 30, but the entire length of the external shape of this threaded portion 21 is formed into a shape corresponding to the bearing hole 51, so that the threaded portion 21 Since the entire length can be inserted into the bearing hole 51, a sufficient stroke length of the male threaded member 20 can be ensured even if the axial length of the device is shortened.

The coil spring 40 has a coil portion inserted into the female screw member 30, and one end 41 of the coil spring 40 is bent in the axial direction of the casing 11 and inserted into the long groove 14 formed in the cavity 12 of the casing 11. There is. On the other hand, the coil spring 40
The other end 42 is inserted into a slit 34 formed in the bottom 31 of the female threaded member 30. As a result, the female threaded member 30 is rotated by the coil spring 40, and the male threaded member 20 is driven in a straight line. In this structure in which the male threaded member 20 is inserted into the female threaded member 30 and the female threaded member 30 is inserted into the coil spring 40, it is possible to shorten the length of the device in the axial direction, that is, the length in the tension adjustment direction. can.

In FIG. 1, 60 is a snap ring fitted to the front end surface of the casing 11, and serves to prevent the bearing member 50 from coming off; 61 is a cover that covers the front end of the casing 11;
62 is a male screw member 2 whose base is glued to this cover 61.
This is a boot that covers the head portion 22 of the o and the tip opening of the casing 11. 63 is a garter spring for preventing the boot 62 from coming off. Further, a seal bolt 67 is screwed onto the base side of the casing 11 via a seal plate 64 and a washer 65 to seal the base side. Furthermore, 68 is a stopper bin that is inserted into and removed from the casing 11 from the outside, and its tip reaches into the slit 34 of the female screw member 30.

When the stopper pin 68 is inserted, the rotation of the female screw member 30 is locked. Note that since this embodiment is used as a belt tensioner in air, lubricating oil is sealed inside the device. In order to allow this lubricating oil to flow smoothly, an oil reservoir 69 is appropriately formed in the female thread member 30 and the bearing member 50. Further, in this embodiment, the head portion 22 of the male threaded member 20 is formed with an air vent hole 23 that communicates with the outside, so that it can accommodate changes in the internal volume of the boot 62 and the casing 11. The device of this embodiment is used with the head portion 22 of the male threaded member 20 facing upward to prevent lubricating oil from leaking from the air vent hole 23.

The assembly of this embodiment as described above involves inserting the female threaded member 30 into which the male threaded member 20 is screwed into the coil spring 40, hooking the other end 42 of this coil spring 40 into the slit 34 of the female thread member 30, and The bearing member 50 is attached to the threaded portion 21 of the male threaded member 20 to form a subarashi. Next, this subarashi is inserted into the casing 11, and the bottom portion 31 of the female threaded member 30 is inserted into the casing 11 together with the washer 15 to support it. and snap ring 60
This snap ring 60, which prevents the subarashi from coming off, is fitted into a groove 11b formed at the tip of the casing 11. Then, a cover ring 61 to which one end of the boot 62 is fixed is attached by caulking or adhesive, and then the other end of the boot 62 is attached to the head portion 22 of the male threaded member 20 using a garter spring 63 to seal the tip portion of the casing 11. After that, insert a tool such as a screwdriver into the slit 3 of the female screw member 30 from the base side of the casing 11.
4 and rotate the female screw member 30 to wind up the coil spring 40 to accumulate energy. In this state, insert the stopper pin 68 to lock the rotation. Furthermore, after injecting lubricating oil into the casing 11, the seal It is sealed with bolts 67. This completes the assembly of the device, fixes it at the place of use, etc., and removes the stopper pin 68. When the coil spring 40 rotates the female threaded member 30, the male threaded member 20 advances and presses the belt.

Fig. 7 shows a modification of the threaded portion of the male threaded member 2o in which the threads 21a are cut. It is shaped into a roughly square shape with mountains. Also, the same figure (
In C), threads are formed in three directions, and in FIG. In either modification, the outer peripheral shape of the threaded portion is non-circular, and the rotation of the male threaded member is restricted by forming the bearing hole of the bearing member into the same shape.

In the above embodiment, lubricating oil is sealed inside the casing, but when used as a chain tensioner in a motorcycle engine, etc., the lubricating oil is not necessary because it is installed while being immersed in engine oil. In this case, since the boot is not required, the head member 2 of the male threaded member 20 for attaching the boot is
2 can also be shortened in the axial direction, allowing the length of the device in the adjustment direction to be shorter.

[Effects of the Invention] As explained above, in the present invention, the threaded portion of the male threaded member that adjusts the tension is formed in a shape corresponding to the shape of the bearing hole that restricts its rotation, so that the stroke length of the male threaded member can be adjusted. The effect is that the length of the device can be shortened in the axial direction without sacrifice, and the device can be made smaller.

[Brief explanation of the drawing]

1, 2, and 3 are cross-sectional views of an embodiment of the present invention,
Left side view, right side view, Figures 4(a), (b), and (c) are sectional views of the male threaded member, left side view, right side view, Figure 5 is a side view of the casing, Figure 6( a) and (b) are a front view and a side view of the bearing member, FIGS. 7(a) to (d) are side views of a modification of the male threaded member, and FIG. 8 is a sectional view of a conventional device. DESCRIPTION OF SYMBOLS 11...Casing, 20...Male thread member, 21.
... Threaded portion, 30... Female thread member, 40... Spring (coil spring), 50... Bearing member, 51... Bearing hole. Patent applicant: NHK Spring Co., Ltd. Agent: Patent attorney: Hideaki SatoFigure 7

Claims (1)

[Scope of Claims] A tensioning device in which a male threaded member and a female threaded member are provided in a casing in a screwed state, and in which the male threaded member advances in the axial direction when the female threaded member rotates by a spring force, the male threaded member 1. A tensioning device for a chain, belt, etc., characterized in that the outer shape of the threaded portion is formed to correspond to the shape of a bearing hole that restrains rotation of the member.