Sauer-danfoss Inc.

Danfoss Power Solutions Inc.

Sauer-sundstrand Company

Axel Widemann

The invention relates to a drive train () for a hydraulic drive where a friction coupling () is arranged between a hydraulic machine () and a consumer (). The coupling () has two parts (A,B) which are displaceable towards each other in the axial direction () and are connected to the hydraulic machine () or to the consumer (). Hydraulic fluid is introduced by means of a pressure line () into a pressure chamber () formed between the parts (A,B), as a result of which the complementarily formed friction surfaces (A,B) become frictionally locked together and a torque is able to be transmitted between the hydraulic machine () and the consumer (). The friction surfaces (A,B) are each fixedly connected at least radially to the shaft of the hydraulic machine () or of the consumer ().

Axial coupling with compensated forces

A hydraulic motor ( ), has an output shaft ( ), a block cylinder ( ), and high-pressure pistons ( ) guided therein, and a block cylinder spring ( ) and a valve plate ( ). The block cylinder ( ) exerts a contact-pressure force on the valve plate ( ) by way of the charging pressure of the hydraulic oil in the block cylinder ( ) and of the spring force of the block-cylinder spring ( ). The contact-pressure force is counter-acted, when the hydraulic motor ( ) is at a standstill, by a hydraulic pressure field which is built up on a surface ( ) between the block cylinder ( ) and the valve plate ( ) via a valve device ( ).

Hydraulic motor with shift transmission

A hydraulic motor ( ) with a braking device ( ), is acted upon by means of a control fluid via a brake release line ( ). The brake release line ( ) is used to allow a continuous flushing flow of control fluid through the hydraulic motor at the same time as the release of the brake. The braking device ( ) is connected to the casing of the hydraulic motor ( ). An outlet opening ( ) of the hydraulic motor ( ) leads via a leakage-oil line ( ) to the tank for the control fluid. In a hydraulic travel drive with a closed hydraulic circuit, the brake release line ( ) can be connected to the shut-off device ( ) for the servo adjustment system of the variable-displacement pump ( ), and the leakage-oil line ( ) of the hydraulic motor ( ) can lead to the tank for the entire hydraulic fluid in the system. Since the control fluid coming from the tank for the hydraulic fluid is always cooler than the hydraulic fluid used to drive the hydraulic motor ( ) and circulating in the closed circuit, a cooling effect on the hydraulic motor ( ) is obtained.

Method for flushing the casing of a hydraulic motor

In a hydraulic vehicle drive which has a hydraulic circuit consisting of a variable displacement pump ( ) and a hydraulic motor ( ), the variable displacement pump ( ) is driven by a diesel engine ( ). During the braking or overrunning operation of the vehicle, the hydraulic motor becomes the pump and drives the variable displacement pump ( ) which acts as a motor on the diesel engine ( ) and attempts to accelerate the latter. The braking effect which is intended and obtained thereby involves the risk of the diesel engine ( ) reaching impermissibly high rotational speeds. The braking therefore takes place in a controlled manner by a sequence valve ( ) being arranged in the line ( ) between the hydraulic motor ( ) and the variable displacement pump ( ). The sequence valve acts on the pivot angle of the variable displacement pump ( ) via the pump bypass line ( B). The control takes place in such a manner that the product of the displacement volume of the variable displacement pump ( ) and of the pressure of the hydraulic fluid in the line ( ) upstream of the variable displacement pump ( ) remains approximately constant. In addition, flow control valves ( ) may also be present.

System for controlling a hydraulic vehicle drive

A hydrostatic system includes a variable displacement hydraulic motor whose absorption volume is adjusted by a pressure regulator, depending on the rpms generated by the power source driving the system. The apparatus enables the variable displacement motor to fully utilize the drive power avaiable from the power source over a range of operating speeds.

Growing community of inventors

Neumunster, Germany

Axel Widemann