GB2164719A

GB2164719A - A recirculating rolling ball transmission

Info

Publication number: GB2164719A
Application number: GB08423494A
Authority: GB
Inventors: Paul Clifford Green
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-09-18
Filing date: 1984-09-18
Publication date: 1986-03-26
Also published as: GB8423494D0

Abstract

Power is transmitted from a drive shaft (1) to a driven shaft (2) by recirculating loose spherical balls (4) rolling in a spiral raceway formed between the shafts by spiral tracks provided in the circumference of gear members integral with the shafts. As shown, when the drive shaft 1 rotates it causes the loose spherical balls 4 to roll along the spiral track 1C in the outside of the drive shaft gear member and through the raceway formed by this track and a similar spiral track in circumference of the driven shaft gear member, and therefore, as the spherical balls progress along the spiral raceway the driven shaft is forced to rotate. To loose spherical balls are recirculated via passageway means 8, 9, 1D. <IMAGE>

Description

SPECIFICATION A recirculating rolling ball transmission I PAUL CLIFFORD GREEN a citizen of the UN ITED KINGDOM OF GREAT BRITAIN, and resident of 61 St Leonards View, Polesworth, in the county of North Warwickshire, B78 1JZ, do hereby declare an invention for which I pray a patent may be granted to me, and to the method by which it is to be performed, to be described in and by the following statement.

This invention relates to the transmission of power by rotary motion between a drive shaft connected by means of mechanical engagement with a driven shaft.

One of the most popular methods of constructing a rotary drive between two shafts is by the use of gear teeth equally spaced on a pitch circle diameter around the circumference of two separate wheels one of which is integral with the drive shaft and the other is integral with the driven shaft and commonly referred to as gear wheels.

Most gear wheel teeth take the form of an involute shape which is a geometrical profile derived or generated by tracing out a point on a straight line rolling without slippage around a base circle diameter.

The engagement characteristics of involute gear teeth meshing together is a combination of a rolling and sliding motion along the line of contact with each other.

The sliding component of this motion is detrimental to the efficiency because it produces friction and in the case where lubricants are used in the drive, shearing of the oil film across the contact area. In many applications using gear teeth, special materials and lubricants prove necessary to provide an acceptable service live.

According to the present invention, the power flow from a drive shaft to a driven shaft is accomplished by a substantially rolling contact motion along the line of contact between the said shafts and so produces a numerically high mechanical efficiency. Furthermore, because there is little or no sliding motion present, the boundary temperature and surface fatigue properties at the contact zone are of a low enough order as to enable popular materials to be used.

In one construction of the invention, the gear teeth previously referred to are replaced by loose spherical balls which can roll and move relative to but in contact with the drive and driven shaft of the transmission, and thus maintain a direct mechanical engagement between the said shafts.

A spiral roller track conforming to the circumferential profile of the spherical balls is formed in and aound the circumference of two separate wheels one of which is integral with the drive shaft and the other is integral with the driven shaft. Both roller tracks have similer shape, spiral. angle and pitch, along the common pitch plane of contact, such that when they rotate into proximity with each other, the said spiral roller tracks produce an enclosed spiral roller raceway through which the said spherical balls can travel whilst still maintaining contact with each of the said wheels.

When the drive shaft rotates under power, the contact pressure between the drive wheel, spherical balls and driven wheel, cause the spherical balls to roll along the roller raceway and thus produce rotary motion of the driven shaft.

When the spherical balls are not moving through the raceway between the said wheels, they are caused to continue rolling along the spiral roller track in one of the wheels, and are kept in contact with the said spiral roller track by a retaining cylinder mounted concentric with the said wheel and having running clearance over the path traced by the said spherical balls. At the position where the drive and driven wheels converge together towards the contact zone, an aperture is formed in the retaining cylinder conforming to the outer profiles of the said wheels but with sufficient clearance to allow them to pass into engagement with the spherical balls. The passageway formed by the said retaining cylinder and the raceway between the said wheels is a continuous uninterrupted chamber through which the spherical balls can travel.

At each end of the spiral roller track in the said wheel is positioned a cylinderical section tube through which the said spherical balls can leave or return to the said spiral roller track. The tubes connect with a transfer hole of similar cross section to that of the tubes.

The said transfer hole passes through the central section of the said wheel at a position below the said spiral roller track.

The path formed by the said spiral roller track, the raceway between the wheels, the tubes and the transfer hole, is a continuous circuit around which the said spherical balls can recirculate whilst the said wheel rotates.

Although the foregone describes a single start spiral roller track formed in the drive and driven wheels, the invention can readily be constructed for multi-start spiral tracks.

The speed ratio between the drive and driven shaft is obtained by the selection of the number of tracks in the wheels carried by the shafts.

The invention can be put into practice for shafts rotating in the same or different planes of rotation to each other.

The drive system can equally function in a clockwise or anticlockwise direction of rota tion and in a drive or overrun condition.

The invention may be carried into practice in various ways, but one specific embodiment will be described by way of example only and with reference to the accompanying drawings, in which: Figure 1, is a sectional view of a drive axle for a land driven vehicle, such as an automobile, in the setting corresponding to a rear wheel drive with the prime mover connecting with the drive shaft and the driven shaft having two co-axial output shafts connecting with the the road wheels.

Figure 2, is a sectional view through the shafts and shows the relative position and profiles of the drive and driven wheel integral with their respective shaft.

The illustrated drive axle comprises a casing 3 in which are journalled a drive shaft 1 which connects with the prime mover, and a driven shaft 2 with two co-axial output shafts 2B and 2C which connect with the road wheels of the vehicle.

The drive shaft 1 carries an integral wheel 1A with a spiral roller track 1C formed along its central length. The driven shaft 2 carries an integral wheel 2D in which a spiral roller track 2A is formed having a similar shape, spiral angle and pitch, along the common pitch plane to that with the wheel 1 A. At the point of proximity between the spiral roller tracks carried in the wheels 1A and 2D a spiral roller raceway is formed having a cross section of similar cross section to that of the loose spherical balls 4 which are carried in the spiral roller track of the wheel 1 A.

The retaining cylinder 5 is mounted concentric to the spiral roller track 1C and with running clearance over the path traced by the spherical balls 4 so that it guides and retains the said spherical balls as the move along the said spiral roller track. At the central length of the retaining cylinder 5 an aperture is formed which has a profile conforming to the outer profile of the driven wheel 2D such that the said spherical balls can pass smoothly from the retaining cylinder to the spiral raceway formed between the said wheels.

Tubes 8 and 9 which are positioned at each end of the spiral roller track 1C transfer the spherical balls 4 to and from the said spiral roller track via a hole 1D passing through the central section of the wheel 1 A and connecting with the said tubes.

When the prime mover turns the drive shaft 1 the frictional contact between the spiral roller track 1C, the spherical balls 4 and the spiral roller track 2A cause the said spherical balls to roll and progress axially relative to the drive shaft 1 and hence produce a rotary motion of the output shaft 2.

When the spherical balls 4 leave their engagement with the spiral track in the wheel 2A, they pass into the retaining cylinder 5 and driven by the preceeding spherical ball they continue to roll along the spiral roller track 1C.

At one end of the spiral roller track 1C the spherical balls 4 enter the tube 8 which transfers the said spherical balls via the hole 1D to the tube 9 through which they transfer to the opposite end of the spiral roller track from which they had previously departed. Thus the said spherical balls can repeatedly recirculate around a circuit comprising the said raceway formed by the said spiral roller tracks, the said tubes, the said hole and the said retaining cylinder concentric with the said spiral roller track.

When the vehicle is moving in an overrun mode, that is then the road wheels are driving back to the prime mover, the rolling ball drive continues to operate as described but with the power flowing from the previously stated driven shaft 2 to the previously stated drive shaft 1.

Claims

1. A RECIRCULATING ROLLING BALL TRANSMISSION of numerically high mechanical efficiency which provides a positive rotary power motion from a drive shaft to a driven shaft each having mechanical engagement with each other by the action of loose spherical balls which are caused by friction to substantially roll through a spiral roller raceway formed by the proximity of spiral roller tracks carried in the circumference of each of the said shafts, one of which has a passageway through which the said loose spherical balls can leave, return or continue to recirculate around the spiral roller track formed in the said shaft's circumference whilst the shaft rotates, thus giving a continuous rolling contact motion between the said shafts.

2. A transmission as claimed in Claim 1, having the drive shaft(s) and driven shaft(s) positioned in the same or different planes of rotation to each other.

3. A transmission as claimed in Claims 1 and 2, which can change the speed ratio between the drive and driven shafts by matching the number of spiral roller tracks in each of the shafts.

4. A transmission as claimed in any of the preceeding claims which can operate in both a clockwise and anti-clockwise direction of rotation.

5. A transmission as claimed in any of the preceding claims which can operate in an overrun condition with power being transfered back to the prime mover.