JP2000230612A - Belt transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend a life of a belt by controlling occurrence of shear torsion in a rib part of a V-ribbed belt regardless of an alternator load when the belt driven with the V-ribbed belt wound between a crank pulley of an engine and an auxiliary pulley around an alternator rotary shaft of an alternator. SOLUTION: Pressure is elastically applied to a span 12a in a tension side and a span 12b in a slack side of a belt 12 by tension pulleys 28 in auto tensioners 17 and 18. When a crankshaft 2 is accelerated, force transmission from a core wire 13 of a specific part of the belt 12 on a crank pulley 3 and the span 12a in the tension side to a core wire on a pulley 5 is softened by elastic displacement of the pulley 28. When the crankshaft 2 is decelerated, force transmission from the core wire 13 of a specific part of the belt 12 on a pulley 3 and the span 12b in the slack side to the core wire 13 on a pulley 5 is also softened by elastic displacement of the pulley 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt transmission device in which a rotational force of a drive rotary shaft accompanied by a minute variation (rotational variation) of an angular velocity is transmitted to a driven rotary shaft having rotary inertia via a belt. And, more particularly, to the technical field of extending the life of a belt.

[0002]

2. Description of the Related Art In general, in an engine (internal combustion engine), drive energy is generated only in the explosion stroke, and rotational torque is not generated in other strokes. Therefore, when transmitting the rotation torque of this engine to another driven rotation shaft by a belt,
There is a problem that as the load on the driven rotary shaft increases, the influence of the angular velocity fluctuation becomes more apparent.

That is, in a belt transmission using an engine as a drive source, the circumferential speed of the belt also changes at the same time due to the change in the angular speed. Therefore, when the rotational inertia of the driven rotary shaft is large, the shear strain (deformation) applied to the bottom rubber of the belt between the pulley and the belt on the driven rotary shaft due to the fluctuation of the peripheral speed increases. As a result, the service life of the belt is significantly shortened due to wear and the like.

For example, in an automobile, when an alternator as a generator, which is one of the auxiliary machines, is driven by belt transmission using an engine as a drive source, the alternator rotating shaft has a large rotational inertia, and thus the angular velocity fluctuation peculiar to the engine causes the alternation. The shear strain applied to the bottom rubber of the belt on the pulley of the alternator rotating shaft increases. Moreover, since the alternator generally has a speed increase relationship with respect to the crankshaft of the engine with a large pulley diameter, the above-mentioned problem becomes more remarkable.

[0005] In particular, when the belt is a V-ribbed belt that is employed for the purpose of reducing the space occupied, the wear of the belt surface directly causes the service life of the V-ribbed belt to be significantly shortened. Controlling shear strain is a non-negligible problem.

[0006] In order to solve such a problem, a method of providing a flywheel on a crankshaft to increase the inertia of the flywheel so as to approach a smooth running is adopted in a normal engine. However, due to the torsional strength of the crankshaft, there is a limit in increasing the inertia force. The gasoline engine has a crankshaft angular velocity fluctuation of about 1.5 to 2.0 ° at the maximum, and the diesel engine has a maximum of 6 to 6 °.
It is unavoidable that the angular speed fluctuation of the crankshaft by about 8 ° occurs.

Conventionally, various attempts have been made to improve the structural or strength of the belt, and some effects have been obtained. However, as described above, fluctuations in the angular velocity of the drive rotary shaft cannot be completely avoided, and the reduction of belt wear and generation of abnormal noise is only a matter of degree.

In view of the above, the present applicant has previously proposed a belt transmission with a variation in the angular velocity of the drive rotary shaft in which a one-way clutch is interposed between the drive rotary shaft and the pulley. . According to this, the transmission of only the forward rotation direction of the drive rotary shaft is performed by the engagement operation of the one-way clutch, and the rotational force in the relatively reverse direction is reduced by the engagement release operation of the one-way clutch. Further, excessive stress is prevented from acting on the belt, and the life of the belt is extended and the noise is reduced (see JP-A-61-228153).

[0009]

However, the above-mentioned conventional device is not without problems. That is, considering the deceleration state among the rotation fluctuations of the drive rotary shaft, first, after the drive rotary shaft has been decelerated, the belt on the drive pulley (the pulley winding portion) and the loose side between the drive and driven pulleys Each core with the span is decelerated, and then the core of the belt on the driven pulley of the driven rotary shaft is decelerated.However, since the rotational inertia of the driven rotary shaft is large and it is difficult to decelerate, it engages with the driven pulley. Shear distortion occurs in the bottom rubber of the running belt. In the above proposal, the transmission of force between the driven pulley of the driven rotation shaft and the core of the belt on the pulley is reduced, thereby reducing the shear distortion of the bottom rubber of the belt. , When the load on the driven rotary shaft is large,
The effect of alleviating the transmission of force between the driven pulley of the driven rotation shaft and the core of the belt is insufficient, making it difficult to reduce the shear distortion of the bottom rubber of the belt, and may not provide an effective effect. There is.

The present invention has been made in view of the above points, and an object of the present invention is to improve the structure of the above-described belt transmission so that the transmission can be performed even when the load on the driven rotary shaft is large. An object of the present invention is to suppress the occurrence of shear strain in the bottom rubber of the belt and to prolong the life of the transmission belt.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, the tension side and slackness of a transmission belt which is stretched between a driving pulley on a driving rotary shaft and a driven pulley on a driven rotary shaft. Both of the side spans are elastically pressed by an elastic pressing means comprising an auto tensioner or an idler pulley with a variable pulley, and the transmission of the force is reduced by the displacement of the pulley of the elastic pressing means.

More specifically, according to the first aspect of the present invention, the drive pulley is provided on a drive rotary shaft that rotates while the angular velocity changes slightly, while the driven pulley is provided on a driven rotary shaft having rotational inertia. In addition, a belt transmission device in which a transmission belt is wound around at least the driving pulley and the driven pulley is assumed.

Further, there is provided an elastic pressing means for elastically pressing the tension side span and the loose side span between the driving pulley and the driven pulley by means of elastically displaceable pulleys.

That is, when considering the acceleration state among the rotation fluctuations of the drive rotary shaft, first, (1) after the drive rotary shaft is accelerated, (2) a portion of the belt on the drive pulley (a pulley winding portion) (3) The core of the belt on the driven pulley of the driven rotary shaft is accelerated.However, the rotational inertia of the driven rotary shaft is so large that it is difficult to accelerate. Shear distortion is about to occur in the bottom rubber of the belt on the pulley. On the other hand, in the deceleration state, as described above,
(1 ′) After the drive rotation shaft is decelerated, (2 ′) the core wire between the portion on the drive pulley and the loose side span in the belt is decelerated,
Next, (3 ') the core wire of the belt on the driven pulley of the driven rotary shaft is decelerated, but since the rotational inertia of the driven rotary shaft is large and it is difficult to decelerate, the shear strain is applied to the bottom rubber of the belt on the driven pulley. About to happen.

However, according to the configuration of the first aspect of the present invention, the tension side span and the loose side span of the belt are each elastically pressed by the pulleys of the elastic pressing means. Between the time when the core wire between the portion on the drive pulley and the tension side span accelerates and the time when the core wire of the belt on the driven pulley of the driven rotary shaft accelerates (between (2) and (3) above) Is reduced by the elastic displacement of the pulley in the elastic pressing means. on the other hand,
In the deceleration state, the period from when the core of the belt on the drive pulley to the loose side span is reduced until the core of the belt on the driven pulley of the driven rotary shaft is decelerated (see (2 ′) above)
And (3 ')) is similarly mitigated by the elastic displacement of the pulley of the elastic pressing means. With this,
Even when the load on the driven rotary shaft is large, only the elastic displacement of the pulley in the elastic pressing means occurs, which absorbs and reduces the deformation of the bottom rubber of the belt,
The deformation of the bottom rubber can be suppressed to extend the life of the belt.

According to the second aspect of the present invention, the elastic pressing means is an auto tensioner. According to the third aspect of the present invention, the elastic pressing means is an idler pulley having a variable pulley diameter. In this case, a desirable elastic pressing means can be easily obtained.

According to a fourth aspect of the present invention, the driving rotary shaft is a crankshaft of an engine (internal combustion engine), and the driven rotary shaft is an accessory shaft provided in an auxiliary device driven by the engine. According to this configuration, when the driving force of the crankshaft of the engine is transmitted to the auxiliary machine through the belt transmission and driven, even if there is an angular velocity fluctuation in the crankshaft, the angular velocity fluctuation is detected by the pulley displacement of the elastic pressing means. This suppresses an increase in the shear strain acting on the bottom rubber of the belt by absorbing the rubber, thereby prolonging the life of the belt.

In the invention according to claim 5, the auxiliary machine is an alternator. In this way, an effective effect can be obtained.

In the invention according to claim 6, the transmission belt is a V-ribbed belt. In the invention according to claim 7, the transmission belt is a V-belt. This results in the desired transmission belt.

[0020]

FIG. 1 shows a belt transmission A according to an embodiment of the present invention. Reference numeral 1 denotes a diesel engine mounted on an automobile. This engine 1 is used as a drive shaft with a small variation in angular velocity. A crank pulley 3 composed of a V-ribbed pulley having a predetermined pulley diameter is rotatably attached to an end of the crankshaft 2 protruding toward the front side of the engine 1.

On the front side of the engine 1, an alternator rotating shaft 4, a pump rotating shaft 6, and a compressor rotating shaft 8 are arranged in parallel with the crankshaft 2 and rotatably supported. The alternator rotating shaft 4 is provided on an alternator (not shown) as an auxiliary machine, and the alternator rotating shaft 4 is a driven rotating shaft having a rotational inertia due to a load generated by the alternator. Similarly, although not shown, the pump rotating shaft 6 is used as a hydraulic pump as another accessory constituting the power steering device, and the compressor rotating shaft 8 is used as a compressor as another accessory constituting the vehicle air conditioner. Each is provided.

The alternator rotating shaft 4 has V
An alternator pulley 5 consisting of a ribbed pulley, a similar pump pulley 7 on a pump rotating shaft 6, and a similar compressor pulley 9 on a compressor rotating shaft 8 are integrally and rotationally attached, respectively. 5, 7, 9 and V mounted and supported on top of engine 1
Between the idler pulley 10, which is a ribbed pulley, and the tension pulleys 28, 28 of the tension-side and loose-side auto-tensioners 17, 18, which will be described later, a V as a transmission belt is provided.
The ribbed belt 12 includes the crank pulley 3, the tension pulley 28 of the loose-side auto-tensioner 18, the alternator pulley 5, the pump pulley 7, the idler pulley 10, the compressor pulley 9, and the tension-side auto tensioner 17.
Are wound in a so-called serpentine layout so as to travel in the order of the tension pulley 28. still,
The belt 12 includes a crank pulley 3 including the V-ribbed pulley, a pulley 5 for an alternator, a pulley 7 for a pump,
The pulley 9 for the compressor and the idler pulley 10 are on the inner circumferential side (bottom side) of the belt, and the other pulleys 18 and
18 is wound around the outer peripheral side (back side) of the belt.

As shown in FIG. 2, the V-ribbed belt 12 is provided on a belt body 14 in which a core wire 13 spirally wound in the belt length direction is embedded, and on the bottom side of the belt body 14. , And a canvas layer 16 provided on the back side of the belt main body 14. The rotation of the crankshaft 2 of the engine 1 is rotated by the rotation of each of the auxiliary machines via the V-ribbed belt 12. It is transmitted to the shafts 4, 6, 8 to drive these accessories.

As a feature of the present invention, as shown in FIG.
Between the crank pulley 3 and the compressor pulley 9, a tension auto tensioner 17 that elastically presses a tension span 12 a of the belt 12 between the crank pulley 3 and the alternator pulley 5, and a crank pulley 3. Between the crank pulley 3 and the alternator pulley 5, a loose side auto-tensioner 18 that elastically presses the loose side span 12 b of the belt 12 between the crank pulley 3 and the alternator pulley 5 is disposed. The tension-side and loose-side auto-tensioners 17 and 18 both constitute elastic pressing means, and have basically the same structure, and include the torsion torque of the torsion coil spring 30 and the coefficient of friction of the damping member, which will be described later. The damping force is different, and the damping force of the tension side auto-tensioner 17 is larger than that of the loose side auto-tensioner 18 (in addition, the tension side and the loose side auto-tensioner 1).
7 and 18 may be the same). Also,
Tension pulley 2 of the tension side auto tensioner 17
The maximum displacement of 8 is set to a value corresponding to, for example, the angular displacement (crank angular displacement) of the crank pulley 3 during idling operation of the engine.

The auto tensioners 17 and 18 will be described in detail.
8 includes a fixing member 19 that is fixed to the engine 1 as shown in FIGS. The fixing member 19 is made of a metal such as an aluminum alloy, and has one side (the engine 1).
Has a bottomed cylindrical cup portion 19a which is open on the front side of the cup portion 19a. A plurality of mounting pieces 19b, 19b,... 19b, 19b,...
9 is fixed to the engine 1 side. Cup part 1
The peripheral wall 9a is provided with a locking portion 19c penetrating the peripheral wall. At the center of the bottom wall inside the cup portion 19a, a hollow cylindrical shaft portion 20 having an axis P is protruded toward the opening side of the cup portion 19a, and the outer peripheral surface of the shaft portion 20 faces the tip end side. Is formed on a tapered surface having a gradually decreasing diameter. A keyway (not shown) extending in the axial direction is provided on the outer peripheral surface of the shaft portion 20.

A rotating member 22 made of a metal such as an aluminum alloy is rotatably supported on the shaft portion 20 of the fixing member 19. That is, the rotating member 22 has a bottomed cylindrical cup portion 22a that opens to one side (the rear side of the engine 1).
A hollow cylindrical boss portion 23 that can be externally fitted to the shaft portion 20 of the fixing member 19 is provided so as to protrude toward the opening side of the cup portion 22a, and the boss portion 23 is fixed to the shaft portion 20 of the fixing member 19. The rotation member 22 is rotatably fitted to the fixed member 19 through an insert bearing 33 to be described later. Are rotatably supported in a state where the openings face each other.

At the tip of the shaft 20 of the fixing member 19,
A disk-shaped metal plate member 24 that is located on the bottom surface side of the rotating member 22 outside the cup portion 22a and that prevents the boss portion 23 of the rotating member 22 from coming off the shaft portion 20 is fixed. A resin thrust washer 25 as a damping member is interposed between the thrust washer 25 and the outer bottom surface of the cup portion 22a.

The cup portion 22a of the rotating member 22
Is provided with a locking hole 22b penetrating through the peripheral wall. An arm 26 extending radially outward from the outer periphery of the cup portion 22a is provided integrally with the cup portion 22a, and a tip of the arm 26 is provided at the center of the boss portion 23 (the shaft A pulley shaft 27 having an axis Q parallel to the center P) is protruded, and a tension pulley 28 that rotates around the axis P integrally with the arm 26 has a bearing (not shown) on the pulley shaft 27. It is rotatably mounted and supported through the intermediary.

On the outer periphery of the boss 23 of the rotating member 22,
A torsion coil spring 30 biases the rotating member 22 against the fixing member 19 so that the tension pulley 28 presses each of the spans 12 a and 12 b of the belt 12.
The torsion coil spring 30 is externally fitted to a sliding contact portion 31a of a spring support 31 to be described later. The coil portion of the torsion coil spring 30 has a cylindrical shape and is, for example, right-handed, and one of the tongues is a fixed tongue 30a.
And the other tongue, the rotating tongue 30b, projects radially outward from the coil portion, and the fixed tongue 30a radially penetrates the locking portion 19c with respect to the fixing member 19, The rotating tongue 30b is locked to the rotating member 22 in a state of penetrating the locking hole 22b in the radial direction, and the fixed tongue locked to the locking portion 19c of the fixing member 19. The rotation side tongue 30b of the torsion coil spring 30 applies a torsion torque in the direction in which the coil portion expands in the locking hole 22b to the rotation member 22 with the rotation point 30a as a fulcrum. The member 22 is urged to rotate about the axis P in the direction in which the tension pulley 28 presses the belt 12 (the counterclockwise direction in FIG. 3) with respect to the fixing member 19.

Around the boss 23 of the rotating member 22,
Resin spring support 3 as damping member
1 is arranged. This spring support 31
A sliding contact portion 31a is provided between the boss portion 23 and the coil portion of the torsion coil spring 30 so as to extend in the circumferential direction. The sliding contact portion 31a fixes the torsional torque of the torsion coil spring 30. Under the reaction force with the side tongue 30a as a fulcrum, it is pressed inward in the radial direction and pressed against the outer peripheral surface of the boss portion 23. An end (the lower end in FIG. 4) corresponding to the base end of the shaft portion 20 in the sliding contact portion 31a is integrally formed with a flange portion 31b extending radially outward from the outer periphery thereof. Is axially pressed by the torsion coil spring 30 to attach the spring support 31 to the fixing member 1.
9 so that it cannot rotate. The reaction force of the torsion coil spring 30 with the tongue 30a as a fulcrum of the torsion torque of the torsion coil spring 30 causes the sliding contact portion 31 of the spring support 31 to rotate.
As a is pressed and pressed against the boss 23 of the rotating member 22, the boss 23 is also pressed and pressed against the insert bearing 33 described later.

The shaft portion 20 of the fixing member 19 and the rotating member 2
2 between the boss 23 and the spring support 3.
An insert bearing 33 which is a damping member different from 1 is interposed. This insert bearing 33
Is made of a cylindrical resin, and its inner and outer peripheral surfaces are
The insert bearing 33 is formed by engaging a key portion (not shown) on the inner peripheral surface with a key groove on the outer peripheral surface of the shaft portion 2. The outer peripheral surface is slidably in contact with the inner peripheral surface of the boss 23.

Therefore, in the above-described embodiment, when the diesel engine 1 is operated, the rotational driving force of the crankshaft 2 of the engine 1 is supplied via the V-ribbed belt 12 to the compressor for an air conditioner as an auxiliary machine and the hydraulic pump for a power steering device. And an alternator to drive them.

In this case, when the transmission between the crank pulley 3 and the alternator pulley 5 is considered, if the crankshaft 2 is in an acceleration state of the rotation fluctuation, first,
After the crankshaft 2 is accelerated, the cores 13 of the portion (the pulley winding portion) of the belt 12 on the crank pulley 3 and the tension side span 12a are accelerated, and then the belt on the alternator pulley 5 Although the core wire 13 of the alternator 12 accelerates, since the rotational inertia of the alternator rotating shaft 4 is large and it is difficult to accelerate, the belt 12 on the alternator pulley 5
(Bottom rubber) of the rib portions 15, 15,... On the other hand, in the deceleration state, after the crankshaft 2 decelerates, the cores 13 of the belt 12 on the crank pulley 3 and the loose side span 12b decelerate, and then the belt 12 on the alternator pulley 5 Core 13
Are decelerated, but the rotational inertia of the alternator rotating shaft 4 is so large that it is difficult to decelerate. Therefore, the ribs 15, 15,... Of the belt 12 on the alternator pulley 5 tend to be sheared.

However, in this embodiment, the tension side span 12a of the V-ribbed belt 12 has elasticity by the tension pulley 28 of the tension side automatic tensioner 17, and the loose side span 12b has elasticity by the tension pulley 28 of the loose side automatic tensioner 18. In the accelerated state, each core 13 between the belt 12 on the crank pulley 3 and the tension side span 12a is pressed.
The belt 12 on the alternator pulley 5
The transmission of the force until the core wire 13 is accelerated is alleviated by the displacement of the tension pulley 28 in the tension side auto tensioner 17. On the other hand, in the deceleration state, the portion of the belt 12 on the crank pulley 3 and the loose side span 12b
The transmission of the force between the time when the core 13 of the belt 12 on the alternator pulley 5 is decelerated and the time when the core 13 of the belt 12 on the alternator pulley 5 is decelerated is reduced by the tension pulley 2 of the automatic tensioner 18 on the loose side.
8 is mitigated by the displacement. Therefore, even if the load on the alternator rotating shaft 4 is large due to an increase in the electric load of the alternator, each of the auto tensioners 17 and 18 can be used.
Of the tension pulley 28, the deformation of the ribs 15, 15,... Of the belt 12 is absorbed and reduced, and the deformation of the ribs 15, 15,. Life can be extended.

In the above embodiment, the crank pulley 3
The tension-side auto tensioner 17 is disposed between the compressor pulley 9 and the tension-side auto tensioner 17. For example, the tension-side auto tensioner 17 may be disposed between the compressor pulley 9 and the pump pulley 7. What is necessary is just to press the tension side span 12a from the pulley 3 to the alternator pulley 5.

Although the above embodiment is applied to the case where the alternator is driven by the diesel engine 1, the present invention is applicable to the case where the alternator is driven by the gasoline engine, or other auxiliary devices other than the alternator, and other components. The present invention can also be applied to the case of driving a device on the axis of. In short, any belt transmission device may be used as long as it transmits the rotational force of the drive rotary shaft accompanied by minute fluctuations in angular velocity to the driven rotary shaft having rotational inertia via a transmission belt.

Further, in the above embodiment, the elastic pressing means for pressing the tension side and the loose side spans 12a, 12b of the belt 12 with elasticity are both auto tensioners 17, 18, but one or both of them are used. For example, it may be changed to a known idler pulley with a variable pulley diameter, and the same operation and effect as the above embodiment can be obtained.

A V-ribbed belt 1 is used as a transmission belt.
The same effect can be obtained by using a V-belt or another type of transmission belt in place of 2.

[0039]

As described above, according to the first aspect of the present invention, the drive pulley is attached to the drive rotary shaft with minute fluctuation of the angular velocity, and the driven pulley is attached to the driven rotary shaft having rotational inertia. For a belt transmission device in which a transmission belt is wound between both pulleys, an elastic pressing means for elastically pressing the tension side and the loose side span of the belt between the driving pulley and the driven pulley with elastically displaceable pulleys is provided. In the accelerated state, the transmission of force between the core of the belt on the driven pulley and the core of the belt on the driven pulley accelerates after acceleration in the belt in the accelerated state, In the state,
The transmission of the force from the time when the core of the belt on the drive pulley to the loose side span is decelerated to the time when the core of the belt on the driven pulley is decelerated is reduced by the displacement of the pulley of the elastic pressing means. Therefore, even when the load on the driven rotary shaft is large, only the pulley displacement of the elastic pressing means is caused to absorb and reduce the deformation of the bottom rubber of the belt, and the life of the belt can be extended.

In the invention of claim 2, the elastic pressing means is an auto tensioner. In the invention of claim 3, the elastic pressing means is an idler pulley having a variable pulley diameter. According to these inventions, desirable elastic pressing means can be easily obtained.

According to the fourth aspect of the present invention, the driving rotary shaft is the crankshaft of the engine, and the driven rotary shaft is the shaft of an auxiliary machine driven by the engine, so that the driving force of the crankshaft of the engine is transmitted to the belt. When it is transmitted to and driven through the auxiliary machine, the increase in the shear strain acting on the bottom rubber of the belt by absorbing the angular velocity fluctuation of the crankshaft is suppressed,
The service life of the belt can be extended.

According to the fifth aspect of the present invention, an effective effect can be obtained by using the alternator as the auxiliary machine.

In the invention according to claim 6, the transmission belt is a V-ribbed belt. In the invention of claim 7, the transmission belt is a V-belt. According to these inventions, a desirable transmission belt can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing a belt transmission according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a part of a V-ribbed belt.

FIG. 3 is an enlarged front view of the auto tensioner.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

[Explanation of symbols]

 A Belt transmission device 1 Engine 2 Crank shaft (drive rotation shaft) 3 Crank pulley (drive pulley) 4 Alternator rotation shaft (driven rotation shaft, accessory shaft) 5 Alternator pulley (driven pulley) 12 V ribbed belt (transmission belt) 13 core Wire 15 Rib (bottom rubber) 17 Tension side auto tensioner 18 Loose side auto tensioner 28 Tension pulley 30 Torsion coil spring

Continued on the front page (72) Inventor Shoji Fujimaru 3-2-15 Meiwadori, Hyogo-ku, Kobe-shi, Hyogo F-term (reference) in Bando Chemical Co., Ltd. 3J049 AA02 AA04 BB05 BB15 BC03 CA03

Claims (7)

[Claims] 1. A drive pulley is provided on a drive rotary shaft that rotates while the angular velocity changes slightly, while a driven pulley is provided on a driven rotary shaft having rotational inertia, and at least the drive pulley and the driven pulley In a belt transmission device in which a transmission belt is wound between the driving pulley and the driven pulley, elastic pressing means for elastically pressing a tension side and a loose side span of the belt between the driving pulley and the driven pulley with respective elastically displaceable pulleys is provided. A belt transmission characterized by being carried out. 2. The belt transmission according to claim 1, wherein the elastic pressing means is an auto tensioner. 3. The belt transmission according to claim 1, wherein the elastic pressing means is an idler pulley having a variable pulley diameter. 4. The belt transmission according to claim 1, wherein the driving rotary shaft is an engine crankshaft, and the driven rotary shaft is an auxiliary shaft provided on an auxiliary device driven by the engine. A belt transmission device, characterized in that: 5. The belt transmission according to claim 4, wherein the auxiliary device is an alternator. 6. The belt transmission according to claim 1, wherein the transmission belt is a V-ribbed belt. 7. The belt transmission according to claim 1, wherein the transmission belt is a V-belt.