JPS624760Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an internal air circulation type cooling structure for a belt power transmission device.

(Prior art) In motorcycles, as a means of transmitting the rotation of the engine crankshaft to the drive wheels, the pitch of the pulley on the crankshaft side is automatically adjusted by utilizing centrifugal force that accompanies the increase in engine rotation speed. JP-A-55-155951 discloses a belt power transmission device that automatically changes the rotation ratio by changing the pitch of the pulley on the driving wheel side accordingly.

(Problem that the invention aims to solve) The driven pulley, which directly affects power transmission, generates a large amount of heat, and the two parts that make up the driven pulley move toward and away from each other in response to changes in rotational speed. Since it is necessary to take cooling measures according to the phenomenon described above, there has been a problem in that the conventional method of providing cooling by simply stirring the inside air by installing a fan on the pulley is not sufficient.

(Means for solving the problem) The purpose is to provide an internal air circulation type cooling structure for a belt power transmission device that is capable of cooling according to the rotational speed of the pulleys. In a power transmission mechanism in which a power transmission mechanism is housed in a power transmission chamber, the pulley is provided with a circulation fan, and a partition plate forming an opening facing the pulley separates the power transmission chamber from the pulley. The rotating surface is divided into left and right halves, and each of the movable faces that constitute the pulley together with the fixed face is provided with a ventilation hole that faces each other when the pulley is at its maximum pitch diameter, and is further provided with ventilation holes that face each other when the pulley's maximum pitch diameter is at its minimum pitch diameter. When the pitch diameter is changed toward , the ventilation holes are arranged in a staggered manner.

(Function) When airflow circulates through a pulley through two chambers separated by a partition plate, if the pulley is rotating at high speed, the movable face moves away from the fixed face, so the airflow is sent to that space. The pulley is cooled from the inside, and the ventilation holes formed on both faces are arranged in a staggered manner, so the airflow sent from the outside of the pulley to the space between the faces is reduced over the distance traveled. becomes longer, allowing for sufficient heat exchange. On the other hand, when the pulley is rotating at a low speed, the movable face approaches the fixed face so that the positions of the ventilation holes formed at predetermined intervals on the circumference at the center of both faces coincide. Therefore, the airflow concentrates and passes through this ventilation hole, thereby cooling the pulley and, by extension, cooling the power transmission chamber.

(Embodiment) An embodiment of the present invention will be described below with reference to the accompanying drawings.

As an example of a motorcycle is shown in FIG. The rear wheel 4 as the driving wheel
There is a power transmission mechanism built into the engine that changes speed and transmits the transmission.

2 and 3 show details of the inside of the power transmission chamber 3, and the crankshaft 6 of the engine 2 has a drive pulley 7 with a centrifugal variable pitch structure.
A driven pulley 10 with a variable pitch structure is supported on a driven shaft 9 which transmits rotation to a final shaft 8, which is the axle of the rear wheel 4. A drive belt 11 having a V-belt structure formed as a main body is wound around.

The drive pulley 7 is connected to the crankshaft 6
The drive-side movable face 12 is movable in the axial direction of the crankshaft 6, and the drive-side fixed face 13 is fixed in the axial direction of the crankshaft 6 and is made of, for example, aluminum and has good thermal conductivity.

On the other hand, the driven pulley 10 includes a driven side fixed face 14 rotatably fixed to the driven shaft 9 and a driven side movable face 15 movable in the axial direction of the driven shaft 9.

As shown in detail in FIG. 4, the driven side movable face 15 of the driven pulley 10 has a cam groove 17 formed at a predetermined angle (approximately 45 degrees) with respect to the axial direction of the boss portion 16. , this cam groove 1
7, a pin 1 is implanted in a driven face boss 18 that is rotatable around the axis of the driven shaft 9.
9 is inserted, and the driven side movable face 1
It is designed to rotate by itself according to the advance and retreat of 5.

On the other hand, a drive side fan 22 is attached to the back of the drive side fixed face 13 of the drive pulley 7, and on the driven pulley 10 side, driven side fans 23 are provided radially on the back of the driven side fixed face 14. .

On the other hand, as shown in FIGS. 5 to 7, a plurality of ventilation holes 24, 24, . A movable face 1 on the driven side arranged in an annular shape and facing oppositely thereto.
In the flat surface portion 26 of the drive side fixed face 14, ventilation holes 27, 27, .

Here, each ventilation hole 24 in the driven side fixed face 14 and the driven side movable face 15,
27, when the driven side movable face 15 rotates and comes closest to the driven side fixed face 14 due to the relationship between the cam groove 17 and the pin 19,
In other words, when the pitch diameter of the driven pulley 10 is maximum (see Fig. 6), the ventilation holes 24, 27 of both
conversely, as both faces 14 and 15 separate, ventilation holes 24 and 27
The positions of the vent holes 24 and the vent holes 27 are gradually shifted as shown in FIG. 7, so that the vent holes 24 on one side and the vent holes 27 on the other side are arranged in a staggered manner.

Incidentally, at the shaft end of the driven shaft 9, there is a centrifugal clutch 21 which is covered by a clutch outer 20 having a substantially U-shaped cross section and having a ventilation hole 20a.
A centrifugal clutch 21 is connected to the clutch outer 20 to transmit the rotation to the driven shaft 9 when the boss portion 18 reaches a predetermined rotation speed or higher.

Furthermore, the power transmission chamber 3 has a sealed structure, and its configuration consists of a case 28 that is connected to the crankcase of the engine 2, and a cover 29 that is joined to the case 28 in the middle. A partition plate 30 is inserted between the joint surfaces of the case 28 and the cover 29, and the partition plate 30 also serves as a seal. The first chamber A on the crankcase side and the second chamber B on the cover 29 side are divided into two. The drive pulley 7 and the driven pulley 10 are arranged so as to straddle the first chamber A and the second chamber B, and the partition plate 30 of this part has a hole 31 for allowing both the pulleys 7 and 10 to fit therein. 32 are drilled.

Note that an air communication passage 33 is provided in the drive pulley 7 portion, extending between the first chamber A and the center portion of the drive face 16 corresponding to the shaft end portion of the drive shaft 9 in the second chamber B. However, in FIG. 3, for convenience, the communicating passage 33 portion of FIG. 2 is shown expanded to the left.

Next, the operation of the above embodiment will be explained.

The heat generated between the drive pulley 7 and the drive belt 11 exchanges heat with the airflow in the second chamber B, and is sent to the rear of the power transmission chamber 3 by the rotation of the fan 22, while being exchanged with the cover 29. . When the driven pulley 10 is rotating at a low speed, the airflow that has reached the rear is caused by the driven side movable face 15
When the clutch outer 20 and the movable face 15 are in close proximity to the fixed face 14 (see FIG. 6), the air flows into the first chamber A through the respective ventilation holes 24 and 27 that are substantially coincident with each other through the clutch outer 20 and the movable face 15. It's blown out.

On the other hand, when the driven pulley 10 is rotating at high speed, the driven side movable face 15 is separated from the fixed face 14 and both faces 14, 1
5 (see FIG. 7), the following two modes of cooling can be considered.

First of all, a part of the airflow from the front of the second chamber B is transferred to both faces 14 and 15 of the driven pulley 10.
The heat flows into the space between the two faces 14, 15, sufficiently touching the inner surfaces (ie, the belt surfaces) of both faces 14, 15, and cooling the faces 14, 15 from the inside while exchanging heat. Most of this cooling airflow is sucked out into the first chamber A through the ventilation hole 24 of the fixed face 14 by the suction force of the driven side fan 23 attached to the back surface of the fixed face 14.

Second, another part of the airflow from the front of the second chamber B passes through the ventilation hole 27 of the movable face 15 and flows into the space between the two faces 14 and 15, and this airflow flows into the fan. Vent hole 2 due to suction power of 23
The air flows toward the ventilation holes 24 that are staggered with respect to the airflow hole 7, and heat exchange occurs while the airflow moves from one ventilation hole 27 to the other ventilation hole 24. In this case, since the ventilation holes 24 and 27 are arranged in a staggered manner, the distance that the airflow passes between the faces 14 and 15 becomes longer, and the distance between the faces 14 and 15 becomes longer. Sufficient heat exchange with the high heat in the space takes place.

Incidentally, at this time, the internal pressure of the first chamber A is negative with respect to the internal pressure of the second chamber B due to the circulation fan 22 attached to the drive pulley 7, so the airflow flowing into the driven pulley 10 is not driven. The air is blown out from the ventilation hole 24 of the side fixed face 14 into the first chamber A with almost no resistance.

Furthermore, the airflow from the second chamber B to the first chamber A is promoted by the fan 23, and the airflow that has entered the first chamber A exchanges heat with the case 28 and passes through the communication passage 33 to the pulley 22 of the second chamber B. It is sucked out to the center of the shaft. This is repeated to cool the pulleys 7 and 10.

(Effects of the invention) As explained above, according to the invention, the power transmission chamber is divided into two with the pulley as the boundary, and in the communication passage between the two chambers, ventilation holes are provided in the fixed face and the movable face so as to penetrate the rotating surface. Since the configuration is such that separate pulleys are arranged, the airflow from the direction perpendicular to the rotating surface of the pulley is concentrated in the ventilation hole during low rotations when the flow velocity is slow, thereby cooling the pulley and increasing the flow velocity. At high rotation speeds, airflow from inside the pulley is used to cool the pulley.Furthermore, the ventilation holes formed on both faces of the pulley are arranged in a staggered manner, so that the airflow passing between both faces is effectively cooled. The longer passage distance allows for sufficient heat exchange, and the pulley can be cooled by effectively circulating internal air according to the rotational speed.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an example of a motorcycle to which the present invention is applied, FIG. 2 is a partially cutaway side view of a power transmission chamber equipped with a cooling structure according to the present invention, and FIG. 3 is a horizontal sectional view of the same. Figure 4 is a side view of the driven pulley seen from the direction along the rotating surface, Figure 5 is a side view of the driven pulley seen from the direction perpendicular to the rotating surface, and Figure 6 shows the state of the driven pulley when rotating at low speed. FIG. 7 is a partially cutaway perspective view showing the state at the same high speed rotation. 3...Power transmission chamber, 7...Drive pulley, 1
0... Driven pulley, 11... Drive belt, 14... Driven side fixed face, 15...
Driven side movable face, 29...Cover, 30
...Inner partition plate, 22...Drive side fan, 23
...Driver side fan, 24, 27...Vent hole.

Claims (1)

[Scope of utility model registration request] A power transmission mechanism in which a belt is wound around two variable pitch pulleys is housed in a power transmission chamber, in which a circulation fan is provided on the pulleys, and a partition plate forming an opening facing the pulleys is used. The power transmission chamber is divided into left and right halves with respect to the rotating surface of the pulley, and each of the movable faces constituting the pulley together with the fixed face is provided with ventilation holes that face each other when the pulley has its maximum pitch diameter. An internal air circulation type cooling structure for a belt power transmission device, characterized in that the ventilation holes are arranged in a staggered manner when the pitch diameter is changed from the maximum pitch diameter to the minimum pitch diameter.