Continuously variable V-belt transmission

Abstract

A continuously variable V-belt transmission basically has a driving pulley, a driven pulley and a V-belt wound around the pulleys. The frictional engagement between the pulleys and the V-belt is controlled by regulating pulley axial thrusts to the pulleys. The V-belt has a plurality of torque transmitting connected by an annular ring. A boundary-detection arrangement is provided to detect a boundary position between a first region, in which the elements are arranged without any gap therebetween, and a second region, in which the elements are arranged with a gap therebetween, along a portion of the driving pulley when torque is being transmitted. The detected boundary position is used to estimate the pulley axial thrust applied by the driving pulley against the V-belt, and to control the pulley axial thrust to a lower limit which ensures that the V-belt will not slip upon application of the maximum torque.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of this original disclosure:

FIG. 1 is a cross sectional view of a continuously variable V-belt transmission that is configured in accordance with one preferred embodiment of the present invention;

FIG. 2 is a simplified diagrammatic view of the V-belt and the pulleys of the continuously variable V-belt transmission illustrated in FIG. 1 that shows the transmission of torque by the V-belt from the driving pulley to the driven pulley;

FIG. 3 is a simplified diagrammatic view of the V-belt and the driving pulley of the continuously variable V-belt transmission illustrated in FIG. 1 that shows the relationship between the active arc region and the pulley axial thrust;

FIG. 4 is another simplified diagrammatic view of the V-belt and the driving pulley of the continuously variable V-belt transmission illustrated in FIG. 1 that shows the relationship between the active arc region and the pulley axial thrust;

FIG. 5 is a graph showing the relationship between the tensile force on the ring and the pulley axial thrust;

FIG. 6 is a diagram view showing the relationship between the stress on the ring and the pulley axial thrust;

FIG. 7 is a graph showing the relationship between the force to push element and the pulley axial thrust;

FIG. 8 is a graph showing the relationship between the difference in tensile force and the pulley axial thrust;

FIG. 9 is diagram showing the relationship between the stress on element and the pulley axial thrust;

FIG. 10 is a simplified diagrammatic view of the V-belt and the driving pulley of the continuously variable V-belt transmission illustrated in FIG. 1 that shows one example of an arrangement of sensors; and

FIG. 11 is a diagram showing the state of the elements of the V-belt within the active arc region and the state of the elements of the V-belt within the idle arc region.

Claims

1. A continuously variable V-belt transmission comprising: a driving pulley including a fixed driving sheave half and a moveable driving sheave half;a driven pulley including a fixed driven sheave half and a moveable driven sheave half;a V-belt wound around the driving pulley and the driven pulley, the V-belt including a plurality of elements and an annular ring consecutively connecting the elements together;a boundary-detection arrangement configured and arranged relative to the V-belt to detect a boundary position between a first region, in which the elements are arranged without any gap therebetween, and a second region, in which the elements are arranged with a gap therebetween, along a portion of the driving pulley, when torque is transmitted from the driving pulley to the driven pulley via the V-belt; anda thrust-estimation section configured to estimate a pulley axial thrust with which the driving pulley engages the V-belt, based on the boundary position that was detected.

2. The continuously variable V-belt transmission as recited in claim 1, wherein the boundary-detection arrangement includes at least two sensors that are configured and arranged that are arranged at a predetermined interval in a direction of the circumference of the driving pulley to detect presence of a gap between the elements in order to detect the boundary position between the first region and the second region.

3. The continuously variable V-belt transmission as recited in claim 2, wherein the driving pulley is configured and arranged such that the boundary position between the first and the second regions varies with different magnitudes of the pulley axial thrust being applied to the driving pulley; andthe sensors are arranged in an area of the driving pulley to detect the boundary position between the first and the second regions that corresponds to a lower limit value of the pulley axial thrust which prevents the V-belt from slipping.

4. The continuously variable V-belt transmission as recited in claim 1, wherein the driving pulley is configured and arranged such that when the pulley axial thrust is large, the first region is small and the second region is large, and when the pulley axial thrust is small, the first region is large and the second region is small.

5. The continuously variable V-belt transmission as recited in claim 1, further comprising: a controller configured to control an actual pulley axial thrust, with which the driving pulley engages the V-belt, such that the boundary position is located at a target position.

6. The continuously variable V-belt transmission as recited in claim 1, wherein the thrust-estimation section include an interface permitting access to the estimated pulley axial thrust.

7. The continuously variable V-belt transmission as recited in claim 5, wherein the boundary-detection arrangement includes at least two sensors that are configured and arranged that are arranged at a predetermined interval in a direction of the circumference of the driving pulley to detect presence of a gap between the elements in order to detect the boundary position between the first region and the second region.

8. The continuously variable V-belt transmission as recited in claim 7, wherein the driving pulley is configured and arranged such that the boundary position between the first and the second regions varies with different magnitudes of the pulley axial thrust being applied to the driving pulley; andthe sensors are arranged in an area of the driving pulley to detect the boundary position between the first and the second regions that corresponds to a lower limit value of the pulley axial thrust which prevents the V-belt from slipping.

9. The continuously variable V-belt transmission as recited in claim 8, wherein the driving pulley is configured and arranged such that when the pulley axial thrust is large, the first region is small and the second region is large, and when the pulley axial thrust is small, the first region is large and the second region is small.

10. The continuously variable V-belt transmission as recited in claim 6, wherein the boundary-detection arrangement includes at least two sensors that are configured and arranged that are arranged at a predetermined interval in a direction of the circumference of the driving pulley to detect presence of a gap between the elements in order to detect the boundary position between the first region and the second region.

11. The continuously variable V-belt transmission as recited in claim 10, wherein the driving pulley is configured and arranged such that the boundary position between the first and the second regions varies with different magnitudes of the pulley axial thrust being applied to the driving pulley; andthe sensors are arranged in an area of the driving pulley to detect the boundary position between the first and the second regions that corresponds to a lower limit value of the pulley axial thrust which prevents the V-belt from slipping.

12. The continuously variable V-belt transmission as recited in claim 11, wherein the driving pulley is configured and arranged such that when the pulley axial thrust is large, the first region is small and the second region is large, and when the pulley axial thrust is small, the first region is large and the second region is small.

13. A continuously variable V-belt transmission comprising: driving pulley means for transmitting a torque;driven pulley means for receiving the torque from the driving pulley means;V-belt means for transmitting the torque from the driving pulley means to the driven pulley means, the V-belt including a plurality of elements and an annular ring consecutively connecting the elements together;boundary-detection means for detecting a boundary position between a compression region and a tension region, along a portion of the driving pulley means, when the torque is transmitted from the driving pulley means to the driven pulley means via the V-belt means; andthrust-estimation section means for estimating a pulley axial thrust with which the driving pulley means engages the V-belt means, based on the boundary position that was detected.

14. A method for a continuously variable V-belt transmission, the method comprising: inputting an input torque to a driving pulley including a fixed driving sheave half and a moveable driving sheave half to drive a driven pulley including a fixed driven sheave half and a moveable driven sheave half by a V-belt wound around the driving pulley and the driven pulley;detecting a boundary position between a first region, in which the elements are arranged without any gap therebetween, and a second region, in which the elements are arranged with a gap therebetween, along a portion of the driving pulley when torque is transmitted from the driving pulley to the driven pulley via the V-belt; andestimating a pulley axial thrust with which the driving pulley engages the V-belt, based on the boundary position that was detected.

15. The method as recited in claim 13, further comprising controlling an actual pulley axial thrust, with which the driving pulley engages the V-belt such that the boundary position is located at a target position.