Servohydraulic Drive

• US 20200132091A1
• Filed: 10/22/2019
• Published: 04/30/2020
• Est. Priority Date: 10/24/2018
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Gellner, Thomas, Hendrix, Gottfried, Goldbach, Michael
• Granted Patent: US 11,015,620 B2
• Time in Patent Office: Days
• CPC Class Codes: F15B 1/033 with electrical control means
• CPC Class Codes: F15B 11/022 in which a rapid approach stroke is followed by a slower, high-force working stroke F15B11/0325 takes precedence
• CPC Class Codes: F15B 11/04 for controlling the speed F15B11/024 takes precedence
• CPC Class Codes: F15B 11/0423 by controlling pump output or bypass, other than to maintain constant speed
• CPC Class Codes: F15B 15/18 Combined units comprising both motor and pump
• CPC Class Codes: F15B 2211/20515 Electric motor
• CPC Class Codes: F15B 2211/20553 with pilot circuit, e.g. for controlling a swash plate
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/20569 capable of working as pump and motor
• CPC Class Codes: F15B 2211/27 Directional control by means of the pressure source
• CPC Class Codes: F15B 2211/30565 having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
• CPC Class Codes: F15B 2211/323 the biasing means being adjustable
• CPC Class Codes: F15B 2211/613 Feeding circuits
• CPC Class Codes: F15B 2211/615 Filtering means
• CPC Class Codes: F15B 2211/62 Cooling or heating means
• CPC Class Codes: F15B 2211/625 Accumulators
• CPC Class Codes: F15B 2211/6306 representing a pressure
• CPC Class Codes: F15B 2211/6309 the pressure being a pressure source supply pressure
• CPC Class Codes: F15B 2211/6313 the pressure being a load pressure
• CPC Class Codes: F15B 2211/6336 representing a state of the output member, e.g. position, speed or acceleration
• CPC Class Codes: F15B 2211/6355 : having valve means
• CPC Class Codes: F15B 2211/6651 : Control of the prime mover, e.g. control of the output torque or rotational speed
• CPC Class Codes: F15B 2211/6652 : Control of the pressure source, e.g. control of the swash plate angle
• CPC Class Codes: F15B 2211/7053 : Double-acting output members
• CPC Class Codes: F15B 2211/775 : Combined control, e.g. control of speed and force for providing a high speed approach stroke with low force followed by a low speed working stroke with high force, e.g. for a hydraulic press
• CPC Class Codes: F15B 7/006 : Rotary pump input

Abstract

A servohydraulic drive includes a hydrostatic displacement machine, an electric machine that is mechanically speed-coupled with the displacement machine, a hydraulic cylinder that is fluidically connected to the displacement machine via first and second working lines, a hydraulic accumulator, and a supply unit. The displacement machine has a stroke that is adjustable via a hydraulic adjustment device. The cylinder is configured to be activated by reversal of the fluid flow through the displacement machine in opposite directions. The accumulator is preset to a low pressure and is fluidically connected via a valve assembly in each case to the lower pressure working line. The supply unit is configured to supply the adjustment device with pressurized fluid under the necessary pressure for the adjustment regardless of the present pressure in the working lines such that the displacement machine is configured for an active and load pressure-independent adjustment of its stroke volume.

Claims

1. A servohydraulic drive, comprising:

a hydrostatic displacement machine having a stroke volume configured to be adjusted by a hydraulic adjustment device;

an electric machine that is mechanically speed-coupled with the displacement machine;

a hydraulic cylinder that is fluidically connected to the displacement machine via a first working line and a second working line, the hydraulic cylinder configured to be activated by reversal of the fluid flow through the displacement machine in opposite directions;

a low-pressure hydraulic accumulator that is preset to a low pressure and fluidically connected via a valve assembly in each case to one of the first and second working lines in which the lower pressure prevails; and

a supply unit configured to supply the adjustment device with pressurized fluid under the necessary actuating pressure for the adjustment regardless of the present pressure in the first and second working lines.

2. The servohydraulic drive according to claim 1, further comprising a switching valve that has (i) a first switching position in which the hydraulic adjustment device is subjected to actuating pressure and (ii) a second switching position in which the hydraulic adjustment device is relieved of pressure to a pressure that is less than a minimum actuating pressure.

3. The servohydraulic drive according claim 2, wherein, in the second switching position, a first port of the switching valve connected to the hydraulic adjustment device is open to a second port of the switching valve connected to a relief fluid path leading to the low-pressure hydraulic accumulator.

4. The servohydraulic drive according to claim 3, wherein the relief fluid path leads to the low-pressure hydraulic accumulator while bypassing a leakage port of the displacement machine.

5. The servohydraulic drive according to claim 2, wherein the switching valve is integrated in the supply unit.

6. The servohydraulic drive according to claim 1, wherein the supply unit includes an auxiliary pump and an electric motor configured to drive the auxiliary pump, the auxiliary pump having (i) a pressure port by which the hydraulic adjustment device is configured to be supplied with pressurized fluid and (ii) a suction port that is connected to the low-pressure hydraulic accumulator.

7. The servohydraulic drive according to claim 6, wherein the pressure port of the auxiliary pump is configured to be connected to a relief fluid path leading to the low-pressure hydraulic accumulator.

8. The servohydraulic drive according to claim 7, wherein one or more of a filter device and a cooling device configured for the pressurized fluid is situated in the relief fluid path.

9. The servohydraulic drive according to claim 7, wherein the pressure port of the auxiliary pump is connected directly to the hydraulic adjustment device and is configured to be connected via the switching valve to the relief fluid path.

10. The servohydraulic drive according to claim 3, wherein the supply unit includes an actuating pressure hydraulic accumulator, wherein the switching valve has a third port that is connected to the actuating pressure hydraulic accumulator, and wherein the first port of the switching valve is connected to (i) the third port in the first switching position and (ii) the second port in the second switching position.

11. The servohydraulic drive according to claim 6, further comprising a switching valve that has (i) a first switching position in which the hydraulic adjustment device is subjected to actuating pressure and (ii) a second switching position in which the hydraulic adjustment device is relieved of pressure to a pressure that is less than a minimum actuating pressure,

wherein, in the second switching position, a first port of the switching valve connected to the hydraulic adjustment device is open to a second port of the switching valve connected to a relief fluid path leading to the low-pressure hydraulic accumulator,

wherein the supply unit includes an actuating pressure hydraulic accumulator,

wherein the switching valve has a third port that is connected to the actuating pressure hydraulic accumulator,

wherein the first port of the switching valve is connected to (i) the third port in the first switching position and (ii) to the second port in the second switching position, and

wherein the actuating pressure hydraulic accumulator is configured to be charged by the auxiliary pump.

12. The servohydraulic drive according to claim 11, further comprising a second switching valve that has (i) a third switching position in which the auxiliary pump is connected to the actuating pressure hydraulic accumulator via the second switching valve of the pressure port and (ii) a fourth switching position in which the auxiliary pump is connected to the relief fluid path leading to the low-pressure hydraulic accumulator via the second switching valve of the pressure port.

13. The servohydraulic drive according to claim 10, wherein the actuating pressure hydraulic accumulator is configured to be charged from one of the first and second working lines in which the higher pressure is conducted.

14. The servohydraulic drive according to claim 10, wherein the actuating pressure hydraulic accumulator is configured as a pressure booster having (i) a large piston face that is adjacent to a low-pressure chamber and (ii) a small piston face that is adjacent to a high-pressure chamber and mechanically connected to the large piston face, and wherein the low-pressure chamber is connected to the low-pressure hydraulic accumulator and the high-pressure chamber is connected to the third port of the switching valve.