Hydrostatic drive

Patent metadata

Field	Value
Publication number	US-10161372-B2
Application number	US-201515507633-A
Country	US
Kind code	B2
Filing date	Aug 4, 2015
Priority date	Sep 15, 2014
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

A hydrostatic drive includes a hydraulic machine, a hydraulic adjusting device, a high-pressure accumulator, an accumulator-closing valve, and an electronic control unit. The hydraulic machine has a swept volume that is adjustable via the hydraulic adjusting device from a maximum positive swept volume to a maximum negative swept volume via a zero swept volume. The hydraulic machine is operated as a pump with positive swept volume and as a motor with negative swept volume. The high-pressure accumulator supplies the hydraulic machine with pressure medium for operation as a motor via a pressure line. The accumulator-closing valve has a first position and a second position and is arranged in the pressure line. A fluidic connection from the high-pressure accumulator to the hydraulic machine is open in the first position and closed in the second position. The accumulator-closing valve is actuated in accordance with signals from the electronic control unit.

First claim

What is claimed is:

1. A hydrostatic drive, comprising:
a hydraulic machine with an adjustable swept volume;
a hydraulic adjustment device configured to adjust the swept volume of the hydraulic machine from a maximum positive swept volume via a swept volume of zero to a maximum negative swept volume, the hydraulic machine is operable with positive swept volume as a pump and with negative swept volume as a motor;
at least one high-pressure accumulator from which the hydraulic machine is configured to be supplied with pressure medium via a pressure line for operation as a motor, the pressure line running between a pressure port of the hydraulic machine and the high-pressure accumulator;
an accumulator shut-off valve arranged in the pressure line and having a first position and a second position, a fluidic connection from the high-pressure accumulator to the hydraulic machine is open in the first position of the accumulator shut-off valve and is shut off in the second position of the accumulator shut-off valve; and
an electronic control unit, the accumulator shut-off valve actuable as a function of signals of the electronic control unit,
wherein, in the event of an adjustment of the hydraulic machine from a negative swept volume to a positive swept volume, the electronic control unit transmits a signal for switching the accumulator shut-off valve from the first position into the second position at such a time that the accumulator shut-off valve switches into the second position only in the presence of a swept volume of zero or a positive swept volume of the hydraulic machine.

2. The hydrostatic drive as claimed in claim 1 , wherein the adjustment device comprises a first adjustment chamber, which adjoins an adjustment piston and for which an inflow, which effects an adjustment in the direction of maximum negative swept volume, and an outflow of pressure medium are controllable by a valve arrangement, a second adjustment chamber, which adjoins an adjustment piston and which is permanently fluidically connected to the pressure port and which is decreased in size in the event of an adjustment in the direction of maximum negative swept volume and is increased in size in the event of an adjustment in the direction of maximum positive swept volume, and a restoring spring, which acts in the direction of maximum positive swept volume.

3. The hydrostatic drive as claimed in claim 2 , wherein the valve arrangement comprises a control valve by which, for an adjustment to negative swept volume, the first adjustment chamber is configured to be supplied with pressure medium from a pressure medium source independently of the pressure port of the hydraulic machine.

4. The hydrostatic drive as claimed in claim 3 , wherein:
the valve arrangement comprises, for the operation of the hydraulic machine as a pump, a hydraulic regulating unit with a port,
the control valve is a 3/2-way valve with a first port, which is fluidically connected to the port of the hydraulic regulating unit, with a second port, which is fluidically connected to the pressure medium source, and with a third port, which is connected to the first adjustment chamber, and
the control valve has a first position, in which the third port is fluidically connected to the first port and the second port is shut off, and a second position, in which the third port is connected to the second port and the first port is shut off.

5. The hydrostatic drive as claimed in claim 4 , wherein the hydraulic regulating unit comprises a load sensing regulating valve which is acted on, in the sense of a pressure medium inflow into the first adjustment chamber of the adjustment device, by the pressure at the pressure port, and in the sense of a pressure medium outflow out of the first adjustment chamber ( 30 ), by a regulating spring and an LS control pressure which prevails at an LS port, and wherein an LS control pressure is transmitted to the LS port of the load sensing regulating valve when the swept volume of the hydraulic machine is still negative.

6. The hydrostatic drive as claimed in claim 5 , wherein the load sensing regulating valve is acted on with an LS control pressure already while the control valve is still situated in its second position.

7. The hydrostatic drive as claimed in claim 5 , wherein the LS control pressure transmitted to the LS port is lower, approximately by the pressure equivalent of the regulating spring, than the pressure at the pressure port when the hydraulic machine reaches the swept volume of zero when pivoting back from the maximum negative swept volume, such that the hydraulic machine is adjusted beyond the swept volume of zero but not as far as the maximum positive swept volume.

8. The hydrostatic drive as claimed in claim 5 , wherein:
an LS control pressure is transmitted to the LS port of the load sensing regulating valve when the control valve is still situated in its second position,
the LS control pressure initially follows the falling accumulator pressure with a fixed pressure difference below the pressure in the high-pressure accumulator, and
the LS control pressure is held constant when the control valve is switched from its second position into its first position.

9. The hydrostatic drive as claimed in claim 8 , wherein the fixed pressure difference is approximately 1.6 times the pressure equivalent of the regulating spring of the load sensing regulating valve.

10. The hydrostatic drive as claimed in claim 1 , wherein the hydraulic machine includes a sensor for the swept volume, and wherein, after the switching of the control valve from the second position into the first position, the level of an LS control pressure is determined in a manner dependent on the magnitude of the negative swept volume or of the change in the negative swept volume.

11. The hydrostatic drive as claimed in claim 1 , wherein the hydraulic machine includes a sensor for the swept volume and wherein, after the switching of the control valve from the second position into the first position, the accumulator shut-off valve is switched from the first position into the second position in a manner dependent on the magnitude of the detected swept volume.

12. The hydrostatic drive as claimed in claim 1 , wherein the hydrostatic drive is configured to start an internal combustion engine.

Assignees

• Bosch Gmbh Robert

Inventors

• Mast Michael
• Hernandez Ladera Paul Luis

Classifications

• F15B1/033

  with electrical control means · CPC title

• F15B2211/6306

  representing a pressure · CPC title

• B60K2006/126

  the hydraulic accumulator starts the engine · CPC title

• F15B2211/212

  the pressure sources being accumulators · CPC title

• F15B2211/20523

  Internal combustion engine · CPC title