Hydrostatic vehicle transmission

Claim 2

Hydrostatic vehicle transmission having a closed, symmetrical circuit, a variable displacement hydraulic pump with a reversible direction of delivery, a fixed displacement hydrostatic motor and having an anti-pressure build-up device, by means of which the pressure in the lIne carrying short-circuit fluid from the hydraulic motor to the pump is released when, under particular travel conditions, especially during deceleration of the vehicle, the motor acts as a pump and vice versa, comprising a first control valve in the main line between the high pressure outlet of the pump and the high pressure inlet of the motor, a second control valve between the low pressure outlet of the motor and the low pressure inlet of the pump, said valves connected in such a manner that the control valves will, in their rest position and in the neutral position of the pump, short-circuit the pump from the motor via a connection line between the two control valves, means in each of said valves for interrupting the short circuit when the pump is moved a certain amount out of its neutral position and pressure is built up as a result thereof and for reconnecting the short circuit as soon as the pressure sides have been reversed or the pressure on the pressure side has been released.

Claim 3

Vehicle transmission according to claim 1 in which each of said control valves is provided with a control plunger which, in its spring adjusted rest position, opens a port connected to the connection line and which closes this port when the pump is moved out of the neutral position and a certain pressure is built up as a result thereof.

Claim 4

Vehicle transmission according to claim 2 having a feed pump driven together with the hydraulic pump, which delivers pressure fluid into the main lines between the motor and the control valves via check valves, the feed pressure acting upon a pressure chamber of the control valves which coacts with that side of the control plungers which is opposite to the side of the control plunger that is acted upon by the pressure fluid coming from the pump.

Claim 5

Hydrostatic vehicle transmission having a closed, symmetrical circuit and a variable displacement hydraulic pump with a reversible direction of delivery, and having an anti-pressure build-up device, by means of which the pressure in the line carrying pressure fluid from the hydraulic motor to the pump is released when, under particular travel conditions, especially during deceleration of the vehicle, the motor acts as a pump and vice versa, comprising a control valve in each main line between the pump and the motor connected in such a manner that the control valves will, in their rest position and in the neutral position of the pump, short-circuit both the pump and the motor via a connection line between the two control valves so that, if the pump is moved a certain amount out of its neutral position and pressure is built up as a result thereof, the control valve on the pressure side will interrupt the short circuit and deliver the pressure fluid from the pump to the motor and from there to the other control valve and return to the rest position as soon as the pressure sides have been reversed or the pressure on the pressure side has been released, each of said control valves being provided with a control plunger which in its spring adjusted rest position opens a port connected to said connection line and which closes said port when the pump is moved out of the neutral position and a certain pressure is built up as a result thereof, each of said plungers being acted upon by pressure fluid coming from the pump, each control plunger having a line of a small sectional area through which a small amount of pressure fluid can pass to the short circuit via said ports and the said connection line without the control plunger being moved out of its rest position when a small deviation of the pump from the neutral position occurs.

Claim 6

Hydrostatic vehicle transmission having a closed, symmetrical circuit and a variable displacement hydraulic pump with a reversible direction of delivery, and having an anti-pressure build-up device, by means of which the pressure in the line carrying pressure fluid from the hydraulic motor to the pump is released when, under particular travel conditions, especially during deceleration of the vehicle, the motor acts as a pump and vice versa, comprising a control valve in each main line between the pump and the motor connected in such a manner that the control valves will, in their rest position and in the neutral position of the pump, short-circuit both the pump and the motor via a connection line between the two control valves so that, if the pump is moved a certain amount out of its neutral position and pressure is built up as a result thereof, the control valve on the pressure side will interrupt the short circuit and deliver the pressure fluid from the pump to the motor and from there to the other control valve and return to the rest position as soon as the pressure sides have been reversed or the pressure on the pressure side has been released, each of said control valves being provided with a control plunger which in its spring adjusted rest position opens a port connected to said connection line and which closes said port when the pump is moved out of the neutral position and a certain pressure is built up as a result thereof, each of said plungers being acted upon by pressure fluid coming from the pump, each control plunger having a line of a small sectional area through which a small amount of pressure fluid can pass to the short circuit via said ports and the said connection line without the control plunger being moved out of its rest position when a small deviation of the pump from the neutral position occurs.

Claim 7

Hydrostatic vehicle transmission having a closed, symmetrical circuit and a variable displacement hydraulic pump with a reversible direction of delivery, and having an anti-pressure build-up device, by means of which the pressure in the line carrying pressure fluid from the hydraulic motor to the pump is released when, under particular travel conditions, especially during deceleration of the vehicle, the motor acts as a pump and vice versa, comprising a control valve in each main line between the pump and the motor connected in such a manner that the control valves will, in their rest position and in the neutral position of the pump, short-circuit both the pump and the motor via a connection line between the two control valves so that, if the pump is moved a certain amount out of its neutral position and pressure is built up as a result thereof, the control valve on the pressure side will interrupt the short circuit and deliver the pressure fluid from the pump to the motor and from there to the other control valve and return to the rest position as soon as the pressure sides have been reversed or the pressure on the pressure side has been released, each of said control valves being provided with a control plunger which in its spring adjusted rest position opens a port connected to said connection line and which closes said port when the pump is moved out of the neutral position and a certain pressure is built up as a result thereof, each of said plungers being acted upon by pressure fluid coming from the pump, the administration of pressure to the control plunger being effected via a pilot line branching off from the line that comes from the pump through which pilot line as well as through a check valve in the control plunger, fluid pressure returning from the motor to the pump when the control valve is in its rest position.

Claim 8

Hydrostatic vehicle transmission having a closed, symmetrical circuit and a variable displacement hydraulic pump with a reversible direction of delivery, and having an anti-pressure build-up device, by means of which the pressure in the line carrying pressure fluid from the hydraulic motor to the pump is released when, under particular travel conditions, especially during deceleration of the vehicle, the motor acts as a pump and vice versa, comprising a control valve in each main line between the pump and the motor connected in such a manner that the control valves will, in their rest position and in the neutral position of the pump, short-circuit both the pump and the motor via a connection line between the two control valves so that, if the pump is moved a certain amount out of its neutral position and pressure is built up as a result thereof, the control valve on the pressure side will interrupt the short circuit and deliver the pressure fluid from the pump to the motor and from there to the other control valve and return to the rest position as soon as the pressure sides have been reversed or the pressure on the pressure side has been released, each of said control valves being provided with a control plunger which in its spring adjusted rest position opens a port connected to said connection line and which closes said port when the pump is moved out of the neutral position and a certain pressure is built up as a result thereof, each of said plungers being acted upon by pressure fluid coming from the pump, the administration of pressure to the control plunger being effected via a pilot line branching off from the line that comes from the pump through which pilot line as well as through a check valve in the control plunger, fluid pressure returning from the motor to the pump when the control valve is in its rest position.