Variable diameter pulley of high-power continuously variable transmission and continuously variable transmission system

Field of the invention

Variable diameter pulley of high-power continuously variable transmission and continuously variable transmission system relate to continuously variable transmission (CVT for short) for vehicle.

Background of the invention

Vehicles with mechanical CVT can achieve less fuel consumption and good acceleration, but most CVTs for vehicles transmit the power by friction force, and the main driving components such as belt or chain, variable diameter pulleys and so on, are limited by the coefficient of friction and stress endurance, so they can't transmit high power, and the efficiency and reliability can't meet the vehicle performance requirements. As a result, CVTs are only used in some small ears.

Reducing and avoiding the relative slip between the driving components of CVT is the effective way for improving the efficiency, increasing the power transmitted, and prolonging the life-span of CVT.

Summary of the invention

It is an object of the invention to provide a kind of variable diameter pulley used in CVT of belt or chain, which can achieve high efficiency, long life-span and can be used to transmit high power, and also provide a high-power continuously variable transmission system.

These and other advantages of the invention have been achieved with a variable diameter pulley of high-power continuously variable transmission and a continuously variable transmission system the characteristic properties of which have been given in the claims.

The said variable diameter pulley of the high-power continuously variable transmission, is a kind of pulley which is cone-shaped, and there are several sector shaped curved surfaces and conical surfaces distributed alternately on the cone surface, wherein the generators of the said sector shaped curved surfaces are in parallel with the generators of the adjacent conical surfaces; and the angles between any generator of the said sector shaped curved surfaces and the center line of the said cone pulley are same; the said sector shaped curved surface is a kind of concave or convex shaped curved surface which has a different shape from the said conical surfaces. And areas of the said sector shaped curved surfaces and the said conical surfaces are different.

"Generator" in this application is used in the meaning of the top or bottom line of each of the said sector shaped curved surfaces and of the conical surfaces. In this sense the lines are seen from the side. The generator may thus be the apex line of the concave or convex shaped surface or the segment line of the same.

The said continuously variable transmission system, comprising:

- four variable diameter pulleys, input shaft, output shaft and transmitting belt, wherein: - said variable diameter pulleys are all cone-shaped, and there are several sector shaped curved surfaces and conical surfaces distributed alternately on the cone surface, wherein:

- the generators of the said sector shaped curved surfaces are in parallel with the generators of the adjacent conical surfaces; - and the angles between any generator of the said sector shaped curved surfaces and the centre line of the said cone pulley are same;

- and the said sector shaped curved surface is a kind of concave or convex shaped curved surface which has a different shape from the said conical surfaces;

- input shaft and output shaft, when every two of the said variable diameter pulleys are assembled on the same input shaft or output shaft in such a way that the sector shaped curved surfaces and conical surfaces of the two pulleys are set respectively face to face, a continuously variable transmission system is composed of the said four variable diameter pulleys, input shaft, output shaft and

the transmitting belt encircling around the wrapping angles of the said four variable diameter pulleys.

As is proved by the test, it can achieve the prospective object. The belt whose original torque rapacity is 180 Nm is used in the test rig, but the torque actually transmitted without slip between belt and pulleys can reach 470 Nm, which is higher than all CVTs for vehicles. It proves that it is feasible to transmit high torque with this kind of variable diameter pulley.

Brief description of the drawings

Figs. 1a and 1b show a longitudinal section of the said continuously variable transmission system;

Fig. 1 a, is a view showing the status before speed-changing; Fig. 1 b, is a view showing the status after speed-changing;

Figs. 2a is a front view of the said continuously variable transmission system; Fig. 2b is a sectional view on the line A-A in Fig. 2a;

Figs.3a and 3b show the principle drawing of the said variable diameter pulley: Fig. 3a is a longitudinal section of the variable diameter pulley; C and D are the enlarged view showing that generators of sector shaped curved surface are in parallel with the conical surfaces; Fig. 3b shows that angles between any generator of the sector shaped curved surfaces and the center line of the cone pulley are same;

Figs 4a and 4b show a sketch map showing the connecting relation between the said variable diameter pulley and the transmitting belt; Fig. 4a is a platform; Fig. 4b is a sectional view on the line B-B in Fig. 4a;

Figs.5a and 5b are the other sketch map showing the connecting relation between the said variable diameter pulley and the transmitting belt; Fig. 5a is a front view of the connecting relation;

Fig. 5b is a side view of the belt 4; and

Fig. 5c is a front view of the wedge metal block 2.

Detailed description of the embodiments

Transmitting means of the invention is the same as traditional continuously variable transmission with belt or chain. By axial movement of variable diameter pulleys 11 - 14, the metal belt or chain 21 , 214, 22 or 215 stays at different contacting points of the pulleys, and the working radii are different, so the speed ratio can be varied in a continuous manner

In the embodiment test, the metal belt used is the transmitting belt produced by VDT from Holland. This belt is made of hundreds of wedge metal blocks 2 and two groups of metal rings 7 as described in Fig.5, and the metal rings 7 are set in the cut-outs on both sides of the block 2, so that hundreds of blocks are connected together, forming a flexible transmitting belt 4. Traditional continuously variable transmission transmits power by friction force between the wedge surface of the belt and the conical surface of the pulleys.

The difference between the invention and the traditional continuously variable transmission with belt or chain is that, this invention is an innovation in the contacting means between belt 4 or chain and variable diameter pulley 11 - 14, and the invention achieves the power transmitting by the wedging force generated between belt 4 or chain and the pulleys 11 - 14. The key technology of the invention is that: there are several sector shaped curved surfaces 61 , 62 and conical surfaces 51, 52 distributed alternately on the cone surface, the shape of the variable diameter pulley 1 is cone-shaped, and the sector shaped curved surfaces 61, 62 and conical surfaces 51 , 52 have characters as follows:

1. Generators of the said sector shaped curved surfaces are in parallel with the corresponding generators of which the conical surfaces 51 , 52 is composed. Reference is made to the enlarged view C, D shown in Fig. 3a, wherein the continuous line is the generator of the conical surface, while the dash line is the

generator of sector shaped curved surface, and the distances between the two lines at different radius points are equal and the two lines are parallel;

2. The angles between any generator of the said sector shaped curved surfaces, dash line shown in Fig. 3b, and the centre line of the cone pulley are same;

3. The sector shaped curved surface which has the two above characters can be formed by concave or convex shaped curved surface which has a different shape from the conical surfaces;

4. The cone-shaped variable diameter pulley composed of conical surfaces and sector shaped curved surfaces is suitable for different kinds of metal belts and metal chains specially used in continuously variable transmission.

Its working principle is that: the shaft hole of the pulley is machined in spline-shaped shown e.g. in Fig. 2b. Two variable diameter pulleys 11 , 12 are assembled on the same spline shaft 3, and the sector shaped curved surfaces 61 , 62 and the conical surfaces 51 , 52 of the two pulleys are set respectively face to face. The belt 4 or chain encircles around the wrapping angle θ as shown in Fig. 4b, the belt or chain in the arc area, of the two variable diameter pulleys, and within the wrapping angle θ , its working radius on different curved surfaces self adaptively changes because of the effect of tension force F1 , F2 (Refer to Fig 4) existing in belt or chain itself. Because the axial projection size of the two sector shaped curved surfaces 61 , 62 is larger than that of the two conical surfaces 51 , 52 (Refer to Fig. 2a ), the working radius of the metal blocks 2 of transmitting belt 4 (or the chain links) in sector shaped curved surfaces 61 , 62 area is defined as R2, while the working radius of the metal blocks 2 of transmitting belt 4 or the chain links in the conical surfaces 51 , 52 area is defined as R1, and R2 is smaller than R1 as shown in Fig. 4b. As a result, both wedge contacting surfaces of the metal blocks 2 of the transmitting belt 4 or the chain links in the sector shaped curved surfaces 61 , 62 (As shown in Fig. 4b, take the blocks or chain links in the sector shaped curved surfaces for example) are exposed to two forces: the first force is the circumferential resistance F3, F4 from the axial convex curved

surfaces of the two adjacent conical surfaces; the second force is the tension force F1, F2 existing in belt or chain, which can prevent the belt or chain from moving to the outside of the said working radius and moving over the adjacent axial convex curved surfaces which can avoid the circumferential slip of the belt or chain. As a result, the circumferential force between the transmitting belt 4 or chain and the variable diameter pulleys 1 serve as the self wedging force, and this can make the belt and pulley run at the same speed and in the same direction, so the power can be transmitted effectively.

It's proved that: this self wedging force can avoid the circumferential relative slip between the belt or chain and the two variable diameter pulleys which is a common phenomenon during the work, so high torque can be transmitted by belt or chain and pulleys.

As shown in Figs. 1-5, variable diameter pulley with sector shaped curved surfaces and conical surfaces has the performance of circumferential self wedging, and the connecting relation between the pulleys and other transmitting components has been explained before. The whole transmission system is composed of traditional symmetrical governor CVT with two shafts and four conical pulleys. The power is input through input shaft, namely spline shaft 3, and then transmitted from two driving pulleys 11 , 12 to two driven pulleys 13, 14 via the transmitting belt 4 or chain. By this, the speed is changed, and power is output through output shaft 8.

There are a fixed variable diameter pulley and an axially movable variable diameter pulley on both the input shaft and the output shaft, and the movement of the axially movable pulleys on the two shafts can be controlled by the current electric-hydraulic control system widely used in ECVT. As this control method has been developed and well-known, here don't explain in detail.