Title: Differential with continuous variable power distribution

Technical Field

The invention relates to a hydraulic differential distributing the power of an input shaft to two output shafts.

The invention is intended for use as differential with continuous variable power distribution in vehicles, at which the part "Best Mode for Carrying Out the Invention" is aimed.

The invention can also function as continuous variable transmission, by fixating the input shaft, and using one of the output shafts as input.

The invention can function as clutch, because it can be set in such a way that the input shaft drives only one of both output shafts, or both output shafts simultaneously.

If the in- and output shafts are swapped, the invention can transmit the power of two input shafts to one output shaft, for example in order to drive one gear system with two variable power engines, like in a helicopter.

The invention can be applied in machines, vehicles, boats, airplanes and tools.

Background Art: A conventional differential distributes the power of an input shaft to two output shafts according to a set value. Development of anti-slipping-devices, anti-brakelock-systems and/or systems to assist in vehicle or boat steering, could require a differential with continuous variable power distribution. Patent applications have been made, intended to cope with this requirement (FR 1 074 474, DE 39 26 487, SE 460 552, EP 0 384 759 en DE 40 10 764), but they involve very complex constructions.

The object of this invention is to distribute the power of an input shaft continuously variable to two output shafts using a simple construction.

Disclosure of Invention

The invention involves two output shafts, that are each connected to one of the rotatably mounted gears of two gearpumps/motors with adjustable yield (GPMA's), whose housings are connected to the input shaft, and whose in- and outlets are connected by a hydraulic system in such way, that, if the input shaft is fixed and one output shaft turns, the other output shaft will turn in the opposite direction.

The power from the input shaft is transmitted by both GPMA's to the output shafts. The fluid pressure that is built in a GPMA by the reaction torque of its output shaft, is inversely proportional to its fluid displacement per revolution, or yield. The GPMA that builds the highest pressure will pump the fluid in the hydraulic system, and thereby reduce the power applied to its output shaft. The other GPMA, receiving that power via the hydraulic system, will act as a hydraulic motor, adding power to its output shaft.

This will continue until the fluid pressures are equal.

In this way the power distribution to the output shafts can be regulated by adjusting the yields of the GPMA's.

The yield adjustment system for the GPMA's is preferably a mechanical and/or hydraulic system, in which the yields are complementary adjusted.

In the extreme settings of the yield adjustment the hydraulic system connecting the in- and outlets of the GPMA's preferably blocks the GPMA with the largest yield, and short-circuits the other.

The GPMA's are preferably adjustable by axially shifting the gears in relation to each other, like for example those described in European patent application EP 0 221 256.

The yield adjustment of the GPMA's is preferably limited in such a way, that the gears will not slide out of mesh.

Brief Description of Drawings The next part is illustrated by the drawings, in which the figures have the following meaning. Figure 1 is a schematic top view of the invention. Figure 2 is a schematic side view of the invention.

Figure 3 is a cross-section by plane A-A' of figure 1. Figure 4 is a cross-section by plane B-B' of figure 1. Figure 5 is a cross-section by plane C-C of figure 1. Figure 6 is a cross-section by plane D-D' of figure 1. Figure 7 is a cross-section by plane E-E' of figure 1.

Figure 8 is a schematic side view of the invention, in which the displacements of the GPMA's per revolution are different. Figure 9 is a schematic side view of the invention, in which one GPMA is blocked, and the other is short-circuited.

Best Mode for Carrying Out the Invention

In the following example for carrying out the invention, the GPMA based on axially shifting the gears of a geromotor (or Eaton pump) is used. The numbers refer to the drawings. The input shaft 18 drives housing 1 by gear 17. Two axial adjustable gerotor GPMA's 3+4 and 5+6, whose in- and outlets are connected by a hydraulic system 9 and 10, are located in the housing. The spur gears of the GPMA's are rotatably mounted on shaft 7. The internal gears of the GPMA's are connected by extensions 13 and 14 to the output shafts 15 and 16. The pistons 11 and 12, that are formed like a spur gear to fit exactly into the internal gear of the GPMA's, are rotatably mounted at the end of shaft 7. The assembly of shaft 7, plate 2 and spur gears 3 and 5 shifts together with pistons -11 and 12. The adjustment system for the pistons is a hydraulic servosystem 19. Pistons 11 and 12 serve simultaneously to confine the hydraulic fluid in the GPMA's and the hydraulic channels 9 and 10.

Shifting the pistons (fig. 8) changes the overlap of gears 3 and 4, and complementary changes the overlap of gears 5 and 6. This is equivalent with the adjustment of the fluid displacement of the GPMA's per revolution, or yield.

The shifting of shaft 7 is limited by the plate 2 (fig. 9) to prevent the gears sliding out of mesh. In this situation the GPMA with the highest yield is blocked by plate 2 so that its output shaft is directly connected to the input shaft. The other GPMA is simultaneously short-circuited by groove 8 so that the other output shaft can rotate freely.