JPH0721945Y2 - Belt tension adjustment device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a belt tension adjusting device for keeping the tension of a timing belt of an engine or the like constant, and in particular, it absorbs slack of the belt due to aging and The present invention relates to a belt tensioner that prevents deterioration.

[Conventional technology]

In a small engine or the like, a fixed belt tensioner has been conventionally used to maintain the belt tension. The fixed belt tensioner does not have the function of keeping the tension of the belt constant by following the slack of the belt.Therefore, in a vehicle equipped with such an engine, if the mileage reaches tens of thousands of km, it may change with time. In order to remove the slack, it is necessary to adjust the belt tension at repair shops.

In order to eliminate such maintenance, it has been proposed to use a belt tensioner having a one-way clutch and a ratchet mechanism in place of the fixed tensioner (Japanese Utility Model Publication No. 64-15851 and Japanese Utility Model Publication No. 64-7940).

[Problems to be solved by the device]

However, a belt tensioner equipped with a one-way clutch and a ratchet mechanism always has play in the axial direction and the circumferential direction. Since the force acting on the tension pulley from the belt is always a fluctuating load, the rattling as described above easily causes abrasion and damage, resulting in lack of durability.

Therefore, an object of the present invention is to provide a belt tension adjusting device capable of smoothly following the slack of the belt due to aging and the like, and preventing a decrease in belt tension.

[Means for Solving the Problems]

To achieve the above object, a first means of the present invention is to insert a fixing bolt into an eccentric position of a pulley shaft, rotatably support the pulley shaft with the fixing bolt, and to the pulley shaft in a belt tension direction. Attach one end of a tension adjustment spring that urges the pulley to the pulley pedestal, which is integral with the pulley fixing member, and forms an inclined cam surface facing the pulley shaft. The inclined cam surface swings when the pulley tensions the belt. It is formed so that it has a tendency to gradually separate from the pulley shaft in the direction of rotation, and a male screw parallel to the fixing bolt is screwed into the pulley shaft and its tip is brought into contact with the above-mentioned inclined cam surface. The configuration is one in which one end of a torsion coil spring for giving is attached.

The second means is the belt tension adjusting device of the first means, wherein the tension adjusting spring is omitted and the other end of the torsion coil spring is locked to the outer diameter surface of the pulley shaft. is there.

A third means is to insert a fixing bolt into an eccentric position of the pulley shaft, rotatably support the pulley shaft by the fixing bolt, and form an inclined cam surface on a surface of the pulley shaft facing the pulley pedestal. The cam surface is formed so as to have an inclination to gradually move away from the pulley base in the direction in which the pulley swings when the belt is strained. It is configured such that one end of a torsion coil spring that applies a rotational torque in the screwing direction is attached to the male screw by contacting the inclined cam surface.

[Action]

In the belt tension adjusting device of the above-mentioned first means, in a normal state, the minimum value of the belt tension fluctuation, the spring force of the tension adjusting spring and the force of the male screw pressing the inclined cam surface against the pulley swing. Stops when the sum of the component forces in the directions is balanced.

When the belt is loosened, the above balance is lost, and the pulley follows the looseness of the belt and swings to maintain the tension constant. Simultaneously with the swing of the pulley, the male screw is rotated in the screwing direction by the rotating torque of the torsion coil spring, and the tip of the male screw swings downward on the inclined cam surface and stops at the above-mentioned force balance point.

The second means is the first means except that the spring force of the tension adjusting spring in the first means does not contribute to the operation of the pulley.
It is the same as the operation of the means. However, in this case, as the torsion coil spring that applies the rotation torque to the male screw, one having a relatively large spring force as compared with that of the first means is used.

Also in the case of the third means, the tension of the belt and the component of the force of the male screw pressing the inclined cam surface in the pulley swinging direction are balanced. In this case, the male screw side receives a reaction force, and the pulley shaft having the inclined cam surface and the pulley integrated with the pulley shaft swing.

In each of the above first to third means, when the tension of the belt increases, the male and female threads are locked by the mutual contact of the flank surfaces, so that the pulley moves in the opposite direction (belt slack direction). It is not rocked.

〔Example〕

1 to 5 show an embodiment of the above-mentioned first means (hereinafter referred to as the first embodiment), in which the pulley 1 includes an inner ring 3 and a rolling element 4 fixed around a pulley shaft 2. The outer ring 5 is rotatably held by the outer ring 5.

A bolt insertion hole 6 and a stepped hole 7 are formed in the pulley shaft 2 at its eccentric position (see FIG. 5). The small diameter portion of the stepped hole 7 is a female screw 8 (see FIG. 1).

On the rear end surface of the pulley shaft 2, as shown in FIG. 5, a plate 9 is positioned by a knock pin 10 and fixed by a screw 11. The plate 9 has an oval hole 12 having a size that surrounds the two holes 6 and 7, and an arm 13 is projectingly provided on an outer diameter portion of the plate 9, and one end of a tension adjusting spring 14 is locked to this. .

A pulley pedestal 16 is provided on the pulley mounting base 15. Half of the surface of the pulley base 16 on the pulley shaft 2 side is an inclined cam surface 17 (see FIG. 5), and a fixing bolt insertion hole 18 is provided in the other half. The inclined cam surface 17 is the pulley 1
Is formed so as to gradually move away from the pulley shaft 2 in the swinging direction when the belt 19 is tensioned (see arrow A in FIG. 2). The pulley base 16 is positioned by a knock pin 20 as shown in FIG.
Fixed by 21.

The fixing bolt 21 is inserted into the bolt insertion hole 6 of the pulley shaft 2 via the sleeve 22 and the slide bearing 23, and the slide bearing 23
Press the collar 24 against the pulley base 16. As a result, the pulley shaft 2 rotates eccentrically around the fixing bolt 21 while sliding on the surface of the pulley base 16.

On the other hand, a male screw 26 is inserted into the stepped hole 7 and screwed into the female screw 8. The tip of the male screw 26 is the pulley shaft 2.
It is projected from the rear end face and is inserted into the recess 28 of the cap member 27. An inclined surface corresponding to the inclined cam surface 17 is formed on the rear surface of the cap member 27. In the large diameter portion of the stepped hole 7, a torsion coil spring 29 is fitted around the male screw 26, one end of which is locked to the male screw 26, and the other end of which is projectingly provided on the front end face of the pulley shaft 2. Locked to 30, male thread
Applying rotation torque in the screwing direction to 26.

The first embodiment has the above-described configuration, and the outer ring 5 is used with the belt 19 hung on the outer peripheral surface thereof. Belt 19 has its tension
The clockwise rotation torque of FIG. 2 is applied to the pulley ₁ by F ₁ , and the tension adjusting spring 14 is caused by its spring force F ₂ .
Provides counterclockwise rotation torque. Also, torsion coil spring
Reference numeral 29 gives a rotation torque in the screwing direction to the male screw 26, and imparts a counterclockwise rotation torque to the pulley 1 by the horizontal component force F ₃ of the force pressing the inclined cam surface 17 via the cap member 27. . Therefore, pulley 1 has a minimum value of F ₁ and F ₂ +
It stops at the balance point of the rotational torque by F _{3, and} the tension of the belt 19 is kept constant.

When the belt 19 is loosened from this state, F ₁ <F ₂ + F _3, and therefore the pulley 1 swings in the counterclockwise direction, and at the same time, the male screw 26 is screwed in by the rotational torque of the torsion coil spring 29, and the cap member 27. At the same time, the inclined cam surface 17 is moved to the downward slope side, and stops when the rotational torques of F ₁ and F ₂ + F ₃ are balanced again.

Contrary to the above, when the tension of the belt 19 is increased, the inclined cam surface 17 exerts a force on the male screw 26 in the direction of coming out of the female screw 8. This force causes the flank surface of the male screw 26 to flank the female screw 8. It acts to press against the male screw 26
To the female screw 8. This prevents the male screw 26 from coming out.

The second embodiment shown in FIGS. 6 and 7 is another embodiment of the above-mentioned first means, and has basically the same configuration as that of the first embodiment. Differences are that the flank angle of the male screw 26 is a sawtooth shape having a high flank on the entry side and a low flank on the retreat side, and that the torsion coil spring 29 is locked to the fixing bolt 21. In this case, the male screw 26 has a small resistance at the time of entry, but a large resistance at the time of retreat.
The locking of the male screw 26 when the tension of the male screw 26 is increased becomes more reliable.

Next, a third embodiment shown in FIGS. 8 and 9 is an embodiment of the above-mentioned second means. In this case, the tension adjusting spring 14 used in the first and second embodiments is omitted, and the torsion coil spring 31 has a large diameter to be fitted around the pulley shaft 2 and has a large spring force. I am using a strong one. One end of this torsion coil spring 31 is a male screw
26, and the other end is locked to a pin 32 on the outer diameter surface of the pulley shaft 2. Other configurations are similar to those of the second embodiment.

In the case of the third embodiment described above, the tension of the belt 19 is kept constant by the balance of the rotational torque by the forces F ₁ and F ₃ shown in FIGS. 3 and 4.

Next, a fourth embodiment shown in FIGS. 10 to 12 is an embodiment of the above-mentioned third means. In this case, an inclined cam surface 17 'is formed on the rear end surface of the pulley shaft 2. Further, a radial protrusion 33 is provided on the pulley pedestal 16, and a male screw 26 'is screwed into a female screw 8'provided on the protrusion 33 in a direction opposite to the screwing direction of the fixing bolt 21, and the tip of the male screw 26' is inclined. ′
Apply to. A torsion coil spring 31 'is fitted around the pulley pedestal 16, one end of which is locked to the male screw 26', and the other end of which is screwed into the outer diameter surface of the pulley pedestal 16.
Is locked to.

In the case of the fourth embodiment described above, the tension of the belt 19 is kept constant by the balance of the rotational torque by the tension F _{1 of the} belt 19 and the component force F ₃ of the force with which the male screw 26 'pushes the inclined cam surface 17'. It If the belt 19 becomes loose, the above balance is lost,
When the male screw 26 receives the reaction force of the component force F ₃ , the pulley 1 is swung and stopped again at the above-mentioned balance point.

[Effect of device]

As described above, according to the first to third means of the present invention, the tip of the male screw, which is given the rotational torque by the torsion coil spring, is pressed against the inclined cam surface to follow the swing of the pulley, and the male screw is moved. It is moved in the screwing direction, and is locked by the thread flank surface to increase the belt tension. Therefore, the pulley smoothly oscillates with respect to the slack of the belt due to aging, and the tension thereof is kept constant. Moreover, since the torque of the torsion coil spring does not cause looseness in the fitting portion between the male screw and the female screw, the durability is excellent.

[Brief description of drawings]

1 is a vertical side view of the first embodiment, FIG. 2 is a front view of the same, FIG. 3 is a sectional view taken along the line III-III of FIG. 2, and FIG. FIG. 5 is an exploded perspective view of the above, FIG.
FIG. 7 is a vertical side view of the second embodiment, FIG. 7 is a front view of the same,
FIG. 8 is a vertical side view of the third embodiment, FIG. 9 is a front view of the same as above, FIG. 10 is a vertical side view of the fourth embodiment, FIG. 11 is a front view of the same, and FIG. It is explanatory drawing of a force relationship. 1 ... Pulley, 2 ... Pulley shaft, 3 ... Inner ring, 4 ... Rolling element, 5 ... Outer ring, 6 ... Bolt insertion hole, 7 ... Stepped hole, 8,8 '... Female thread, 9 ...... Plate, 10 ...... knock pin, 11 ...... screw, 12 ...... hole, 13 ...... arm, 14 ...... tension adjusting spring, 15 ...... plate mounting base, 16 ...... pulley pedestal, 17, 17 '... … Inclined cam surface, 18 …… fixing bolt insertion hole, 19 …… belt, 20 …… knock pin, 21 …… fixing bolt, 22 …… sleeve, 23 …… sliding bearing, 24 …… collar,
26, 26 '... Male screw, 27 ... Cap member, 28 ... Recess, 29 Torsion coil spring, 30 ... Pin, 31, 31' ... Torsion coil spring, 32 ... Pin, 33 ... Projection, 34 ……Screw.

Claims (3)

[Scope of utility model registration request] 1. A fixing bolt is inserted into an eccentric position of a pulley shaft, the pulley shaft is rotatably supported by the fixing bolt, and one end of a tension adjusting spring for urging the pulley in the belt tension direction is attached to the pulley shaft. , Forming an inclined cam surface facing the pulley shaft on the pulley pedestal integrated with the pulley fixing member,
The inclined cam surface is formed so as to have an inclination that it gradually separates from the pulley shaft in the direction in which the pulley swings when the belt is tensioned, and a male screw parallel to the fixing bolt is screwed into the pulley shaft, and the tip of the inclined cam surface is formed as described above. A belt tension adjusting device in which one end of a torsion coil spring for applying a rotating torque to the male screw is attached to the inclined cam surface to apply rotational torque to the male screw. 2. The belt tension adjusting device according to claim 1, wherein the tension adjusting spring is omitted, and the other end of the torsion coil spring is locked to the outer diameter surface of the pulley shaft. 3. A fixing bolt is inserted into an eccentric position of the pulley shaft, the pulley shaft is rotatably supported by the fixing bolt, and an inclined cam surface is formed on a surface of the pulley shaft facing the pulley pedestal. The surface is formed so that it has a tendency to gradually move away from the pulley base in the direction in which the pulley swings when the belt is tensioned. A belt tension adjusting device in which one end of a torsion coil spring for applying a rotating torque to the male screw is attached to the inclined cam surface to apply rotational torque to the male screw.