This application is a national stage entry of PCT/US01/27656 filed on Sep. 6, 2001 which claims the benefit of U.S. Provisional Application No. 60/231,115 filed on Sep. 8, 2000.
Most speed changers in use today utilize gears to produce an output speed different than the input speed. Gears require the manufacture of precise shapes for the teeth to satisfy the fundamental law of gearing which insures a constant speed ratio for the system. If the gears are to be used in a transmission, special provision must be made so the speed ratio can be changed without causing gear teeth on one gear to clash with those on the mating gear.
There are, however, other types of speed changers in use including traction drive speed changers. These depend on friction between rolling elements to transmit torque from the input member to the output member. The rolling elements are held together with a prescribed normal force to generate the required friction force based on the power to be transmitted by the device. However, these devices are not self-actuating. Further, these devices often require a separate clutch to allow the output to be disengaged from the input.
It is therefore a principal object of this invention to provide a traction drive speed changer which is self-actuating.
It is a further object of this invention to provide a traction drive speed reducer that does not require a clutch.
A further object of this invention is to provide a self-actuating traction drive speed changer wherein the normal force on the roller members is only present when needed to permit the rolling elements to be operationally disengaged.
A still further object of this invention is to provide a self-actuating traction drive speed changer which can be easily engaged and disengaged in response to changing speed requirements.
These and other objects will be apparent to those skilled in the art.
A self-actuating traction drive speed changer has a movable force input element having a planar drive surface, and a movable force output element having a planar drive surface which is connectable to an output load. One or more movable roller elements has a planar drive surface operatively connected for movement to the input element, and are in frictional engagement with the planar drive surface of the output element so that movement of the input element will cause the planar drive surface of the roller element to engage and frictionally move the output element.
A modified form of the invention mounts the input and output elements on one each of a pair of spaced support elements. An elongated link having a center and opposite ends is pivotally secured at its center to one of the support elements. One each of first and second roller elements are secured to the ends of the link with each roller element having a planar drive surface. The planar drive surface of the first roller element is in friction driving engagement with the planar surface of the input element. Rotation of the input element will rotate the first roller to pivot the link so that the planar drive surface of the second roller will engage the planar drive surface of the output element to rotate the output element.
With reference to
Slots J on the outer ends of link H receive the pins 22 of outer rollers G. Slots J (
In
As the input shaft D and roller E rotate counterclockwise, the links H and rollers F and G rotate clockwise and the pins I move radially outwardly in their respective slots 19. Because of the inclined orientation angle of the intermediate roller assemblies (inks H and rollers F and G), the clockwise torque generated on the output roll K by the output load produces the necessary normal forces to press the rolling members against one another. This in turn creates sufficient friction between rolling elements to prevent slip. Furthermore, the angle of inclination is designed for the expected coefficients of friction to ensure that slip will not occur no matter what the output load. Hence, the traction effect is automatically achieved at just the right level to transmit the instantaneous torque required for the unit.
The geometry of the device is designed so that, given a specific coefficient of friction between the various contacting surfaces, the appropriate normal force will be induced, which will allow the required tractive force to be generated. Thus, the device will not slip, no matter how much load is applied to the output member. Parts will fracture before slippage occurs.
The A set of rollers is shown engaged while the B set of rollers is disengaged. The general idea is that the diameters of the A set of rollers are designed to be different than the B set of rollers. This produces different speed ratios for the two sets of rollers. Thus, the device is shifted from one speed to another by disengaging by any convenient means (not shown) the A set of rollers and engaging the B set of rollers. More than two sets of rollers can be included in the device, allowing for more than two speed ratios.
It should be noted that for this configuration, the output member rotates in the same direction as the input member. It should also be noted that for the configuration shown in
If the input member rotates counterclockwise driving the output member counterclockwise, and the output member speeds up in a counterclockwise direction, it will simply overrun the input and coast along at the higher speed.
The “sun gear” 2 can be held in a stationary position with the receiving structure to rotate therearound.
The distances along horizontal and vertical directions were considered to obtain:
By squaring and adding these two equations to eliminate ρ, χ1, and χ2 and solve for φ:
Similarly, β and φ were eliminated to solve for (α1+α2):
By rearranging the same scalar equations so that when squared and added, β and φ, were eliminated.
This provides a solution for α1:
Where R is:
R={(r2+r3)2+r32+2r3(r2+r3)cos φ}1/2
Thus, φ, α1 and α2 are calculated once the values are set for the radii of all the members.
Summation of forces and torques in
where F=F3=F4
To prevent slip between the input member E and the inner roller F (3) as well as between the outer roller G (4) and the output member K (i.e., FIG. 1):
f≦μ3F3
f≦μ4F4
where μ3 is the coefficient of friction between the input member E and the inner roller F and μ4 is the coefficient of friction between the outer roller G and the output member K.
By combining these inequalities with both of the above equations, the minimum requirements for the coefficients of friction to avoid slip are
Similarly, to ensure that slip does not occur between inner and outer rollers F and G:
where μ34 is the coefficient of friction between the inner and outer rollers 3 and 4.
It should be understood that the input and output can be linear in nature and not just rotational. Further, this invention can use various combinations of linear input or output with rotational input or output. Two types of the linear concepts are shown in
In
Since there is no slip, points on the periphery of roll 3 that contact 1 at the initial and final times are separated by an arc length equal to d. Hence, the member compound roller consisting of rolls 3 and 4 rotates
Then, if rolls 4 and 5 roll without slippage relative to one another, the compound roller consisting of rolls 5 and 6 rotates clockwise
Roll 6 then rolls without slip relative to linear member 7 for a distance s given by
s=r6θ56
When the first two above equations are substituted into the foregoing equation, the value of s is
Finally, the distance member 7 moves relative to member 1 is
If the product
r4r6<r3r5
then member 7 will move upwardly for a distance less than arm 2. If, however, the product
r4r6>r3r5
then member 7 moves down while member 2 moves upwardly. If the two products are equal, then member 7 remains stationary while member 2 moves upwardly.
The work input and work output are reflected in:
Fd=Py (8)
When equation (5) is substituted into (8), F has a value of:
The arrangement shown in
In
The arrangement in
The geometry of the device is designed so that, given a specific coefficient of friction between the various contacting surfaces, the appropriate normal force will be induced, which will allow the required tractive force to be generated. Thus, the device will not slip, no matter how much load is applied to the output member. Parts will fracture before slippage occurs. Also, the device can be configured to operate in one direction only, and it will “overrun” in the opposite direction. Or, if one or more intermediate roller pairs are oriented in the opposing direction, the device can be operated in both directions.
From the foregoing, it is seen that this invention in its several embodiments will accomplish at least all of its stated objectives.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US01/27656 | 9/6/2001 | WO | 00 | 3/7/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO02/21017 | 3/14/2002 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3254546 | Nasvytis | Jun 1966 | A |
3367214 | Nasvytis | Feb 1968 | A |
3433099 | Nasvytis | Mar 1969 | A |
3475993 | Hewko | Nov 1969 | A |
4128016 | Nasvytis | Dec 1978 | A |
4487090 | Burnham | Dec 1984 | A |
4617838 | Anderson | Oct 1986 | A |
4813303 | Beezer et al. | Mar 1989 | A |
4950110 | Suzuki | Aug 1990 | A |
5021035 | Zhou | Jun 1991 | A |
5238459 | Andre | Aug 1993 | A |
5688201 | Zhou | Nov 1997 | A |
5851163 | Kawase et al. | Dec 1998 | A |
5873786 | Hosoya et al. | Feb 1999 | A |
5876298 | Kato et al. | Mar 1999 | A |
5893813 | Yamamoto | Apr 1999 | A |
5896774 | Funahashi et al. | Apr 1999 | A |
5901802 | Sunohara et al. | May 1999 | A |
5947854 | Kopko | Sep 1999 | A |
6076413 | Verot et al. | Jun 2000 | A |
6095940 | Ai et al. | Aug 2000 | A |
6125717 | Phillips | Oct 2000 | A |
6148605 | Lardellier | Nov 2000 | A |
6162145 | Wang | Dec 2000 | A |
6202507 | Phillips | Mar 2001 | B1 |
6225265 | Shibuya et al. | May 2001 | B1 |
6436000 | Minegishi et al. | Aug 2002 | B1 |
20020111243 | Minegishi et al. | Aug 2002 | A1 |
20040162175 | Ai | Aug 2004 | A1 |
Number | Date | Country |
---|---|---|
58-180868 | Oct 1983 | JP |
Number | Date | Country | |
---|---|---|---|
20040023754 A1 | Feb 2004 | US |