JPH0248726B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a belt transmission device in an internal combustion engine. (Prior Art) Generally, in an internal combustion engine, explosive force within a cylinder is converted into rotation of a crankshaft, so the rotational force changes significantly during one rotation. Furthermore, as the crankshaft, flywheel, etc. are made lighter (lower rigidity), the rotation of the crankshaft tends to become less smooth and the angular velocity changes significantly. Therefore, a forced angular velocity fluctuation is induced in a drive pulley fixed to the crankshaft (output shaft), for example, a pulley on which a timing belt for driving a camshaft is hung, or a pulley on which a V-belt or multi-ribbed belt for driving auxiliary equipment is hung. The angular velocity fluctuation of this crankshaft drive pulley is
It acts to forcibly move the driven pulley via the transmission belt. At this time, on the driven side, rotational resistance is generated by an inertial force corresponding to the variation, which is added or subtracted from the original driven load, and the belt tension is also subject to variation due to this load variation on the driven side. The fluctuation in the belt tension increases the belt stress and shortens the belt life, and if the stress exceeds the allowable stress, it causes belt slip or skipped stitches in the toothed belt, leading to premature failure of the belt. Therefore, in order to withstand this variation, it is necessary to increase the belt width to improve the transmission capacity. In particular, the angular velocity fluctuation of the crankshaft is large in a diesel engine, and a belt width several times larger than that in a gasoline engine may be required. However, in vehicles with narrow engine spaces, such as automobiles, it is difficult to increase the belt width, which poses an obstacle in belt design. To solve the above problem, as shown in Utility Model Application No. 113996/1987, periodic torque fluctuations are applied to the toothed belt that connects the driving gear and the driven gear to reduce the tension fluctuations acting on the belt. A technique has been proposed to eliminate belt skipping by arranging an eccentric rotating body that rotates while contacting the toothed belt in a belt transmission device where this phenomenon occurs, and by absorbing belt tension fluctuations with this eccentric rotating body. ing. (Problem to be Solved by the Invention) However, although the above proposed technique is effective for toothed belts, it cannot achieve the same effect for V-belts with slips or multi-ribbed belts, and instead promotes fluctuations. There are cases where
Furthermore, since the dominant order of engine rotational speed fluctuations (vibrations) changes depending on the rotational range in which it is used, and the range of fluctuation increases or decreases, this proposed technique has a problem in that it does not function effectively in the entire rotational range. Therefore, the present invention has been made in view of this point, and aims to eliminate the above-mentioned drawbacks of the conventional belt by effectively absorbing fluctuations in belt tension over the entire rotation range without aggravating them. (Means for Solving the Problems) In order to achieve the above object, the first invention of the present application includes a drive pulley fixed to an output shaft of an internal combustion engine, and a drive pulley driven by the drive pulley via a transmission belt. In a belt transmission device having two or more driven pulleys, the belt transmission device includes a pulley that moves in contact with the belt in response to fluctuations in belt tension at a maximum tension span of the belt tension on the tension side of the drive pulley; It is assumed that tension adjustment means is provided to regulate the maximum value of tension to a predetermined value or less. Furthermore, in the second invention of the present application, in addition to the configuration of the first invention, a known tensioner for absorbing belt slack is added to the minimum tension caspan of the belt tension on the slack side of the drive pulley. (Function) As a result, in the first and second inventions, when there is a large angular velocity fluctuation in the output shaft of the internal combustion engine, in order to prevent it from being transmitted to the belt as a shock,
By disposing the tension adjustment means at the maximum tension span of the belt tension, the maximum value of the belt tension is regulated to a predetermined value or less, and tension fluctuations are absorbed and alleviated. Incidentally, a belt tensioning device (belt tensioner) has conventionally been used in a belt transmission device to apply the necessary transmission tension to the belt. This belt tensioner maintains a constant belt tension so that the belt and pulley can rotate in operational correlation with each other without slipping due to tension reduction due to belt elongation. It is. This type of belt tensioner has a pulley that presses the belt at the location where the tension is least between the pulleys, that is, the position on the slack side of the drive pulley, so that the difference in belt tension before and after the drive pulley is kept at a constant value. The tension adjustment means of the present invention is different from the tension adjustment means of the present invention in its basic idea. (Example) Examples of the present invention will be described below with reference to the drawings. In a belt transmission device 1 for an internal combustion engine shown in FIG. 1, 2 is a crankshaft as the output shaft of the internal combustion engine, 3 is a drive pulley fixed to the crankshaft 2, and 4 and 5 are driven wheels for driving auxiliary equipment. This is a pulley, and the auxiliary equipment includes an alternator, water pump, air pump, air compressor, hydraulic pump for power steering, or camshaft. Reference numeral 6 denotes a transmission belt wound around the drive pulley 3 and driven pulleys 4 and 5, and the transmission belt 6 may be a V-belt, a multi-ribbed belt, a toothed belt, or the like. In addition, the above-mentioned transmission belt 6
If the belt is a V-belt, V-groove pulleys are used for each pulley 3 to 5, and if it is a multi-rib belt, a multi-rib groove pulley or flat pulley is used, and if it is a toothed belt, a toothed belt is used. A pulley is used. When winding the transmission belt 6, the drive pulley 3 rotates in the direction of the arrow R in the figure, where 6A is the maximum tension span on the tension side of the drive pulley 3, and 6B is the slack side of the drive pulley 3. The lowest tension span 6C is the second tension span between the driven pulleys 4 and 5. For the maximum tension span 6A, the tension adjustment means 7
is installed. This tension adjustment means 7 is connected to an idler pulley 8 from the outside with respect to the back surface of the transmission belt 6.
The idler pulley 8 is pressed against the transmission belt 6 with a predetermined biasing force by an elastic body 9 such as a spring, and the elastic body 9 deforms according to fluctuations in belt tension, thereby causing the idler pulley 8 to move. moves, regulates the maximum value of tension at the maximum tension span 6A, and is configured to absorb tension fluctuations. In addition, the tensioner 10 is used for the lowest tension span 6B.
The tensioner 10 includes a movable idler pulley 11 that contacts the back surface of the transmission belt 6 from the outside, and a spring 12 that biases the idler pulley 11. The tension adjusting means 7, as shown in FIG.
The idler pulley 8 is connected to the transmission belt 6 so as to urge the transmission belt 6 from the inside to the outside of the transmission belt 6.
The tensioner 10 may also be arranged so as to be in contact with the inner surface of the tensioner 10, and the tensioner 10 may also be arranged so as to be biased from the inside like the tension adjusting means 7. On the other hand, the tensioner 10 is provided as required, and may be omitted as shown in FIG. 3. In FIG. 2 and FIG. 3, the same reference numerals are given to the same structural parts as in FIG. 1, and the explanation thereof will be omitted. Furthermore, the number of driven pulleys 4 and 5 installed can be increased or decreased depending on the number of auxiliary machines to be driven, and depending on the arrangement of these auxiliary machines, the tension adjustment means 7 can be positioned outside the belt 6 or outside the belt 6 as described above. It is placed inward. Specific structural examples of the tension adjusting means 7 are shown in FIGS. 4 to 6. The tension adjustment means 7A in FIG.
An arm 13 that supports an idler pulley 8 that contacts the transmission belt 6 is pivotably mounted, and a tension spring 14 is connected to this arm 13 to constitute an elastic body 9A that presses the arm 13 against the transmission belt 6. It will be done. The tension adjustment means 7B in FIG. 5 swingably supports an arm 13 supporting the idler pulley 8 via an elastic body 9B having a built-in torsion spring or spiral spring, and connects the idler pulley 8 to the transmission belt 6. It is something that energizes.
In addition, the tension adjustment means 7C in FIG. This biases the idler pulley 8 against the transmission belt 6. Next, the operation of the above embodiment will be explained. In the rotation of the crankshaft 2 of the internal combustion engine, fluctuations in the angular velocity ω as shown in FIG. 7A occur. In general, in the low-speed range where displacement is large, this vibration order mainly fluctuates in the (number of cylinders/2) order component, but at high speeds, it resonates near the natural frequency of the crankshaft 2, and the vibration order becomes dominant. Things change. In the case where the tension adjustment means 7 is not provided, the variation in the belt tension at the maximum tension span 6A corresponding to the angular velocity variation of the crankshaft 2 is as shown in FIG. 7B, and the variation in the angular velocity ω in FIG. 7A. is changing at the same frequency. In other words, the tension increases due to the inertial force of the driven pulley 4 that follows the fluctuation of the crankshaft 2, and when the fluctuation is small or the tension is within the transmission capacity of the transmission belt 6 due to the action of the tensioner 10, the transmission belt 6 follows the fluctuations of the drive pulley 3 without causing slips or skipped stitches. On the other hand, if the fluctuation in the drive pulley 3 increases and the tension exceeds the belt transmission capacity, the transmission belt 6 will slip or skip stitches, as shown in part a, as shown in FIG. 7C. If this state continues, the transmission belt 6 will break at an early stage. The above tension fluctuation is caused by the tensioner 10
It cannot be absorbed by some people. In other words, when the tension increases at the maximum tension span 6A, the tension decreases at the minimum tension span 6B, and the tensioner 10 acts to increase this decrease in tension. It is not possible to absorb the increase in tension at tension span 6A. When the tension adjusting means 7 is provided at the maximum tension span 6A, the width of the tension fluctuation becomes smaller as shown in FIG. 7D in response to fluctuations in the angular velocity ω of the crankshaft 2. In other words, as the transmission belt 6 follows the fluctuation of the crankshaft 2, the driven pulley 4
In response to the inertial force of the (auxiliary machine), the belt tension at the maximum tension span of 6A tries to increase first. However,
This increase in tension is caused by the tension adjustment means 7, which causes the idler pulley 8 to move against the elastic body 9, absorbing and relaxing the increase in tension and suppressing the increase, and at the same time, when the tension decreases, the deformation of the elastic body 9 is restored. The elastic force urges the power transmission belt 6 to increase its tension and reduce the range of tension fluctuation. Therefore, fluctuations in the angular velocity of the crankshaft 2 are adjusted by the tension adjusting means 7, and the fluctuations transmitted to the driven pulley 4 are reduced. In addition, due to the action of the tension adjustment means 7, when the tension increases abnormally, the movement of the idler pulley 8 becomes large, so that the belt length absorbed by the tension adjustment means 7 increases with respect to the slack side of the belt 6, that is, the minimum tension span 6B. If the tension is significantly reduced due to the addition of a stress, slip will occur in the drive pulley 3, but the tensioner 10 installed at the lowest tension span 6B absorbs the slack and increases the tension, thereby preventing slip. Since this can be prevented from occurring, it is preferable to provide the tension adjustment means 7 and the tensioner 10 together. However, if the fluctuation of the crankshaft 2 is relatively small, provision of the tension adjustment means 7 is sufficient. Here, a test example will be shown in which the effect of the tension adjusting means 7 was confirmed. In this test, a multi-rib belt (3PK990) was used as an accessory drive belt in an automobile diesel engine (displacement 1800c.c.).
The weight wear rate of the belt with respect to the running distance was measured with and without the tension adjustment means 7. In addition, for the drive pulley 3 (diameter 140 mm) fixed to the crankshaft 2, the driven pulley 4 (diameter 60 mm) of the alternator is the first auxiliary device, and the driven pulley connected to the water pump and fan is the second auxiliary device. 5 (diameter 130mm) is installed,
In this configuration, a tension adjustment means 7 is provided at the maximum tension span 6A, and a tensioner 10 is provided at the minimum tension span 6B. The above multi-rib belt has 3 ribs, a rib width of 3.56mm, and a belt thickness of 5.8mm.
The belt length is 990mm. Furthermore, the car is equipped with an automatic transmission, and the mileage is the actual city mileage of the car. The results of the above tests are shown in the table below, comparing the results of a gasoline engine (displacement 1800 c.c.) as a reference example.

[Table] As is clear from the above table, the belt of the present invention, which has the tension adjustment means 7, has less wear and the occurrence of slips is prevented, whereas the conventional example, which does not have the tension adjustment means 7, has a large amount of wear. and are reaching the end of their lifespan early. (Effects of the Invention) As explained above, according to the first and second inventions of the present application, the tension adjusting means disposed at the maximum tension span of the belt tension adjusts the angular velocity fluctuation at the output shaft of the internal combustion engine. The belt tension can be effectively absorbed and relaxed over the entire rotation range without aggravating fluctuations in belt tension, and the maximum value can be regulated below a predetermined value, so the belt life can be improved.
Furthermore, it has the advantage that the belt width can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of the belt transmission device of the present invention, FIG. 2 is a schematic configuration diagram showing another example of the belt transmission device, and FIG. 3 is a schematic configuration diagram showing another example of the belt transmission device. 4 is a front view of the main part showing an example of the tension adjustment means, FIG. 5 is a perspective view of the main part showing another example of the tension adjustment means, and FIG. 6 is a main part perspective view of another example of the tension adjustment means. Main part front view showing example, No. 7
Figures A to D are explanatory diagrams for explaining the action of the tension adjusting means. 1...Belt transmission device, 2...Crankshaft, 3
... Drive pulley, 4, 5 ... Driven pulley, 6 ...
Transmission belt, 6A... Maximum tension span, 6B...
Minimum tension span, 6C...Second tension span, 7...
...Tension adjustment means, 8...Idler pulley, 9...
Elastic body, 10... tensioner.

Claims (1)

[Scope of Claims] 1. A belt transmission device having a drive pulley fixed to the output shaft of an internal combustion engine and one or more driven pulleys driven by the drive pulley via a transmission belt. At the maximum tension span of the belt tension on the tension side, a tension adjustment means is provided, which has a pulley that moves in contact with the belt in response to fluctuations in belt tension, and regulates the maximum value of the belt tension to a predetermined value or less. A belt transmission device characterized by: 2. In a belt transmission device having a drive pulley fixed to the output shaft of an internal combustion engine and one or more driven pulleys driven by the drive pulley via a transmission belt, the belt tension on the tension side of the drive pulley is A tension adjustment means is disposed at the maximum tension span, and has a pulley that moves in contact with the belt in response to fluctuations in belt tension, and is provided with a tension adjustment means for regulating the maximum value of the belt tension to a predetermined value or less, and the drive pulley A belt transmission device characterized in that a tensioner for absorbing belt slack is provided at the lowest tension span of the belt tension on the slack side of the belt.