JPH0425553Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automatic belt tension adjustment device, and particularly to an automatic belt tension adjustment device that changes the position of a pulley shaft in accordance with changes in belt tension.

[Conventional technology]

The internal combustion engine of an automobile is provided with a belt power transmission mechanism that uses part of its output to drive a valve train that opens and closes intake and exhaust valves. Here, the toothed belt that is wound around the driving pulley and the driven pulley must be maintained at a predetermined tension to prevent slips and skipped stitches, so the belt power transmission mechanism has automatic belt tension adjustment. Equipment is being installed. For example, Utsukai 58-
As shown in No. 50343, the automatic belt tension adjustment device includes a pulley 1 supported so as to be in contact with the back side of the belt, as shown in FIG. A bolt 3 is inserted into the shaft 2 of the pulley 1 off-center, and the shaft 2 swings about the bolt 3 as an axis. Here, the tips 6a, 6 of the torsion coil spring 6 are inserted between the engine body side and the shaft 2 side so as to fit inside the shaft 2.
b are hooked into the respective engagement holes 4 and 5. Due to the force of this torsion coil spring 6,
A moment is generated to rotate the shaft 2 using the bolt 3 as a fulcrum, the pulley 1 presses the belt, and tension is set. In addition, when the distance between the axes of the pulley 1 increases due to thermal expansion or the belt itself stretches, and the belt tension changes, the shaft 2 rotates and the pulley 1 changes its position, causing the belt to tighten. The tension is prevented from becoming too large or too small.

[Problem that the invention attempts to solve]

By the way, in the above automatic belt tension adjustment device,
As schematically shown in FIG.
When the shaft 2 rotates around the center and the pulley 1 changes its position to the position drawn by the two-dot chain line, the engagement hole 4 formed on the engine body side moves into a circle forming the outer shape of the torsion coil spring 6. Since the tip 6a of the torsion coil spring 6 is twisted unevenly due to deviation from the circumference, the tip 6a may easily come off from the engagement hole 4, or it may be difficult to apply a predetermined tension to the timing belt. There's a problem.

Therefore, the technical problem of the present invention is to displace the tip of the torsion coil spring that fits into the engagement hole on the engine body side so that it is always on the circumference of the torsion coil spring. The objective is to reduce the torsional force applied to the tip of the torsion coil spring.

[Means for solving problems]

According to the belt tension automatic adjustment device of the present invention, the measures taken to solve the above technical problems are as follows:
A bottom wall is provided on the fixed member side of the shaft, and a guide hole into which the tip of the torsion coil spring is inserted is provided on the bottom wall to form a partial arc shape that matches the outer shape of the torsion coil spring. The fixing member is provided with an engagement hole into which the tip end of the torsion coil spring is caught, forming a long hole extending radially from the fixing shaft.

[Effect]

According to this means, the tip of the torsion coil spring receives force from the wall surface of the guide hole whose position changes with the pulley, and moves along the engagement hole until the guide hole and the engagement hole intersect.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

A belt power transmission mechanism is used to drive a valve train of an internal combustion engine, as shown in FIG. Here, a timing pulley 10 fixed to one end of a crankshaft (not shown) is shown.
A toothed timing belt 12 is wound around a cam pulley 11 fixed to one end of a camshaft. This timing belt 12 is also wound around a pulley 13 that drives an oil pump. Idler pulleys 14 and 15 without teeth are arranged on the back side of the timing belt 12. Of these, idler pulley 14
is the timing belt 12 and each pulley 10,1
The idler pulley 15 is provided to set the winding angle between the timing belt 1 and the timing belt 3, and the idler pulley 15 is also used to set the tension of the timing belt 3.

As shown in FIGS. 1 and 2, the idler pulley 15 is part of an automatic belt tension adjustment device, and is connected to the shaft 17 via a ball bearing 16.
It is rotatably mounted around the The shaft 17 is formed in a hollow shape and includes a bottom wall portion 18 that covers about half of one end on the side of the engine main body. This bottom wall portion 18 has resin 1 as a friction material.
9 is attached to close one end of the shaft 17 so as to sandwich the entire both sides of the bottom wall portion 18.
As can be seen from FIG. 3, the resin 19 is provided with a through hole 21 into which a mounting bolt 20 is inserted. The through hole 21 is located outside the bottom wall 18 and eccentrically from the center of the shaft 17. In this way, the shaft 17
It can swing freely using the fulcrum.

Further, a torsion coil spring 22 is housed inside the shaft 17 as an elastic member.
This torsion coil spring 22 is connected to an engagement hole 24 formed in a cylinder block 23 on the side of the engine body.
The tip 22a is hooked to the shaft 17, and the other tip is hooked to a groove 30 provided in the shaft 17. Here, as can be seen from FIG. 3, the guide hole 27 through which the tip end 22a of the torsion coil spring 22 passes is formed, together with the through hole 21, in the resin 19 attached to the bottom wall portion 18. The shape of the guide hole 27 is determined to be a partially arcuate shape, and the outline drawn by the torsion coil spring 22 in the state of being accommodated in the shaft 17 matches the outer curve of the guide hole 27. . Note that the guide hole 27
The width corresponds to the thickness of the torsion coil spring 22. Furthermore, as can be seen from FIG.
The hole is shaped like a long hole that extends in the radial direction so as to pass through the center of the hole.

Next, a guide 29 is formed on the peripheral wall of the retainer 25 and protrudes from the wall to guide the shaft 1.
A groove 30 into which the guide 29 fits is formed in the inner circumferential surface of the groove 7 . This groove 30 is located farthest from the bolt 20, which is the pivot axis of the shaft 17, and is cut parallel to the center line of the shaft 17 halfway toward the bottom wall portion 18. Incidentally, the retainer 25 is also provided with a through hole 31 into which the bolt 20 is inserted, and the head of the bolt 20 comes into contact with the resin washer 32. In this way, due to the tightening force of the bolt 20, the torsion coil spring 22 spirally wound around the bolt 20 is compressed and twisted.

Hereinafter, the functions and effects of this embodiment will be explained based on the drawings.

The retainer 25 is a torsion coil spring 22
This torsional force is applied to the groove 3.
0 is transmitted from the guide 29 to the shaft 17 as a moment M ₁ (shown in FIG. 2). In this case, the shaft 17 causes the timing belt 4 to press the pulley 15, and the moment _M1 is
The pulley 15 receiving the belt reaction force balances the moment transmitted to the shaft 17.

By the way, when the tension of the timing belt 12 changes, as shown in FIG.
7 rotates around the bolt 20 and the pulley 15 changes its position, thereby suppressing changes in tension as small as possible. At this time, shaft 17
As the guide hole 27 rotates, the position of the guide hole 27 changes to the position indicated by the two-dot chain line in the figure. Guide hole 2
By changing the position of 7, the tip 22a of the torsion coil spring 22 is directed toward the bolt 20 along the shape of the engagement hole 24 until the guide hole 27 and the engagement hole 24 intersect. Once moved. Therefore, even if the pulley 15 changes its position to the position indicated by the two-dot chain line in the figure, the tip of the torsion coil spring 22 is always located on the circumference of the torsion coil spring 22. do.

In addition, by the torsion coil spring 22,
The force that presses the bottom wall portion 18 side of the shaft 17 against the engine body appears as a frictional force when the resin 19 comes into sliding contact. Therefore, the vibration of the timing belt 12 causes the shaft 17 to tighten the bolt 20.
Even if vibrations occur around the shaft 17, the vibrations of the shaft 17 are kept small and quickly damped.

[Effect of idea]

In this way, according to the means taken by the present invention, the tip of the torsion coil spring, which receives force from the wall surface of the guide hole whose position changes together with the pulley, is engaged to the point where the guide hole and the engagement hole intersect. Since it is moved along the matching hole, the tip of the torsion coil spring can always be positioned on the circumference that forms the outer shape of the torsion coil spring.
By coming off the circumference, it is possible to reduce the uneven torsional force that the tip of the torsion coil spring has been subjected to.

Furthermore, according to the measures taken by the present invention, the torsion coil spring is housed inside the shaft in a state eccentric to the fixed shaft, so the torsion coil spring can be placed concentrically to the fixed shaft. The diameter of the torsion coil spring can be selected from a wider range than when the torsion coil spring is installed, and the degree of freedom in design can be expanded.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an automatic belt tension adjustment device according to an embodiment of the present invention, FIG. 2 is a plan view of an automatic belt tension adjustment device according to an embodiment of the invention, and FIG. FIG. 4 is a sectional view taken along line - in FIG. 1, and FIG. 5 is a belt power transmission mechanism for an internal combustion engine using an automatic belt tension adjustment device according to an embodiment of the present invention. The layout shown in FIG. 6 shows the operation and operation of the embodiment of the present invention.
FIG. 7, which is a diagram used to explain the effect, is a sectional view showing a conventional belt tension automatic adjustment device, and FIG. 8 is a diagram used to explain the problems of the conventional device. 12...Timing belt (toothed belt), 1
5... Pulley, 17... Shaft, 18... Bottom wall, 20... Bolt (fixed shaft), 22... Torsion coil spring, 22a... Tip, 23...
Cylinder block (fixing member), 24...engaging hole,
27...Guide hole.

Claims (1)

[Scope of utility model registration request] A fixed shaft on which a pulley shift swings in contact with the back side of the toothed belt is installed at a location off the center of the shaft, and a torsion coil spring with one end hooked to the fixed member is installed inside the shaft. In the automatic belt tension adjustment device, the automatic belt tension adjustment device is arranged to press the pulley against the belt by the torsional force of the torsion coil spring, and a bottom wall portion is provided on the side of the fixing member of the shaft; A guide hole into which the tip of the torsion coil spring is inserted is provided on the bottom wall side to form a partial arc shape that matches the outer shape of the torsion coil spring;
An automatic belt tension adjustment device characterized in that an engagement hole into which a tip end of the torsion coil spring is caught is provided in the fixing member to form a long hole extending in a radial direction from the fixing shaft.