BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a hydraulic module with swashplate drive units in section in the plane of the drive shafts;
FIG. 2 shows the hydraulic module from FIG. 1 viewed in the direction of the pivot axis;
FIG. 3 shows the double swashplate according to the exemplary embodiment in FIGS. 1 and 2;
FIG. 4 shows a hydraulic module with oblique axis drive units viewed in the direction of the pivot axis;
FIG. 5 is an overall view of the hydraulic module with oblique axis drive units;
FIG. 6 shows the double yoke of the hydraulic module viewed from the direction of the drive shafts;
FIG. 7 shows an example of the angular relationships between the drive units and the double yoke;
FIG. 8 shows an example of the angular relationships between the drive units when volume flow compensation occurs;
FIG. 9 shows the double yoke in a front view with scavenging port feed and pressure protector;
FIG. 10 shows the hydraulic connection for feeding or scavenging;
FIG. 11 shows a further configuration of the hydraulic connection for feeding and scavenging; and
FIG. 12 shows the servo control for adjusting the pivot angle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a hydraulic module 1 according to the invention which is used in hydrostatic mechanical gearboxes. It comprises two drive units of a swashplate design specifically a pump 2a and a hydraulic motor 3a which are mounted with parallel drive shafts 12 in a common housing 25, 29.
FIG. 1 shows here a section in the plane extending through the parallel drive shafts 12. The two drive units 2a, 3a each have a cylinder block 2.1, 3.1 which rotates with the shaft 12 and has expeller pistons 26 which are displaceable in the cylinders and are supported on a common swashplate 22 by means of sliding shoes 23. The swashplate 22 can be rotated about the pivot axis 24 by means of a servo system (not illustrated) and has a bearing face for the pump 2a and one for the hydraulic motor 3a, each with different oblique positions which are however not shown in the section along the central plane of the drive units.
FIG. 2 shows the same arrangement from the side viewed in the direction of the pivot axis 24. Pump 2a and motor 3a are located one behind the other here. The expeller pistons 26 of the pump cylinder block 2.1 are supported on the swashplate 22 which is at the pivot angle zero, i.e., in the neutral position for the pump in the illustration in FIG. 2. For the hydraulic motor which lies behind it and is concealed by the pump, the bearing face has in contrast, an angle of inclination which corresponds to the maximum pivot angle and is indicated by the double arrow in the figure. The swashplate 22 is pivoted in such a way that the pump is adjusted from the neutral position to a maximum pivot angle, i.e., a maximum value of the volume flow. At the same time the motor adjusts from the maximum initial value of its swept volume to zero. The minimum pivot angle for the pump can, for reasons of compensation, lie slightly below or above zero as will be explained in more detail below with respect to FIG. 8.
FIG. 3 shows the double swashplate 22 of the swashplate unit. The double swashplate 22 can be adjusted about the pivot axis 24 by means of a servo system and has in each case a bearing face 27, 28 for the expeller pistons of the pump and hydraulic motor. The two bearing faces 27, 28 have different angles of inclination. This means that in the neutral position the pump is at the pivot angle 0°, while at the same time the hydraulic motor has an adjustment corresponding to its maximum swept volume. When the pivot angle of the double swashplate 22 changes, the pump adjusts from its home position to its maximum adjustment angle at which it delivers the maximum volume flow, while at the same time the hydraulic motor is positively and synchronously adjusted from the maximum to the minimum pivot angle.
FIG. 4 shows the principle of a hydraulic module according to the invention with oblique axis drive units in the direction of the pivot axis. Therefore, of the two coaxial drive shafts 12 only that of the hydraulic motor 3 can be seen. In this illustration the motor 3 and the pump 2 are again located one behind the other in their respective home position, i.e., the pump 2 is located with its cylinder block 2.1 in the 0° position, that is to say in the state which is virtually without delivery, while the hydraulic motor 3 and its cylinder block assume the maximum pivot angle of approximately 45° with respect to the axis of the drive shaft 12 at which angle the hydraulic motor has its maximum swept volume. The pistons 14 of the hydraulic motor 3 which are mounted with the piston head 15 in the drive flange 16 of the shaft 12 reach the maximum travel in the cylinders 13 here. The cylinder block 3.1 bears against a valve plate 5 in a known fashion here.
The pump 2 and hydraulic motor 3 are embraced by the double yoke 4 and are positively pivoted together with it. At the same time the hydraulic motor 3 moves over the pivoting range SM between a maximum and a minimum angle. In the illustrated example the pivot angle is 45° at maximum and 0° at minimum. At the same time the pump 2 pivots with its cylinder block 2.1 and its valve plate 6 which are illustrated by dashed lines in the figure over the angular range SP from 0° to 45°, i.e., it adjusts from zero to maximum volume flow.
FIG. 5 is an overall view of the hydraulic module with oblique axis drive units. The fixed part of the hydraulic module 1 contains the parallel drive shafts 12 on whose flanges the respective expellers are pivotably mounted. The respective cylinder blocks of the pump and hydraulic motor are embraced by the double yoke 4 which can be adjusted about the pivot axis 10 by means of a servo system. The yoke has a journal 11 on each side on which journal 11 the ports for the feeding 17 and scavenging 18 are also provided. The connecting ducts between the pump and the motor are formed in the yoke as a result of which long connecting ducts, bushings and seals which are difficult to cope with such as are necessary in the case of separate drive units, which can be controlled independently of one another, are dispensed with.
The pump 2 and motor 3 are positively adjusted together with the yoke 4. This is in turn carried out in such a way that the pump 2 which is in the region of the pivot angle 0° in the home position is adjusted in the direction of its maximum pivot angle while at the same time the motor 3 which is at its maximum pivot angle in its home position is adjusted in the direction of pivoting towards 0° up to a minimum value.
FIG. 6 shows the removed double yoke 4 from the direction of the drive shafts. The bearing journals 11 which are located on each side and at which the double yoke 4 can be pivoted about the pivot axis 10 and at which the ports for the feeding 17 and scavenging are formed are illustrated. Furthermore, the support faces 5a, 6a which are offset with respect to one another at an angle can be seen in the common yoke 4 for the valve plates 5, 6 of the motor and of the pump.
The described angular relationship is illustrated in FIG. 7. It is conditioned by the mechanical positive coupling of the two drive units in the common double yoke while in the illustrated case the pump pivots between 0° and 45° and the hydraulic motor between 45° and 0°.
FIG. 8 shows that the adjustment range does not necessarily have to extend in each case from 0° to 45° but rather can be predefined separately for each drive unit. This fact can be used to compensate for volumetric losses, and for example, to provide active stationary state control. This may be necessary in order to avoid a creeping movement of the vehicle in the neutral position of the hydraulic module in an off road situation on an incline and means that the minimum pivot angle of the pump can differ slightly from 0°. For example, FIG. 8 shows a pump adjustment from −2.5° to 42.5°, while the hydraulic motor pivots synchronously from 45° to 0°. In the same way the adjustment range of the hydraulic motor can also be displaced, for example, slightly towards positive values.
FIG. 9 shows the double yoke 4 in a front view with the devices for scavenging and for feeding in and for pressure protection. The connecting ducts 7 which run in the interior of the yoke between the valve plate 5 of the hydraulic motor and the valve plate 6 of the pump as well as fluid lines for feeding in and scavenging the ports of which are led outwards for example, at a journal like projection 11 of the yoke 4 at a pivoting connection are shown. Valves 8 are provided in each case between the port and the valve plates 5, 6 in the line for feeding 17 said valves 8 functioning on the one hand as high pressure limiting valves and on the other hand, also assuming the function of the feed valves. In the lines which lead to the scavenging port 18 a scavenging slide 9 is provided which, like the high pressure valves, is also integrated in the double yoke 4.
FIGS. 10 and 11 show possible ways of implementing the connection in the feed port 17 and the scavenging port 18. The connection is formed according to FIG. 10 by a pipe element 20 which is fitted with play 19 with a length which is sufficient for the sealing effect into the journal 11 of the yoke 4 in the coaxial direction with respect to the pivot axis 10. The seal is thus provided by metallic means over the sealing length for which approximately 5 mm is sufficient, for example. This makes it possible for the connecting piece to turn. This principle is further developed in FIG. 11. The pipe element 20 which is surrounded coaxially by the pipe element 21 for scavenging 18 is used for feeding 17. Both pipe elements are in turn fitted with sufficient length into the journal of the yoke 4 with play 19.
FIG. 12 shows the hydraulic module 1 with the drive shafts 12 and the double yoke 4 with which the pump and hydraulic motor are positively coupled in a mechanical fashion such that when the pump pivots from 0° to 45°, the hydraulic motor is adjusted at the same time from 45° to 0°. The adjustment is carried out by a servo system whose servo pistons 31 rotate the double yoke 4 about the pivot bearing 11.
The invention thus provides a compact unit for a hydrostatic drive with which the expenditure on the two drive units which are usually separate is considerably reduced which is much more cost effective and is significantly more reliable during operation.
Patent Application
20070277520
