EP2069640A1

EP2069640A1 - Hydrostatic drive unit

Info

Publication number: EP2069640A1
Application number: EP07785899A
Authority: EP
Inventors: Jörg Dantlgraber
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-09-26
Filing date: 2007-07-05
Publication date: 2009-06-17
Anticipated expiration: 2027-07-05
Also published as: CN101517243A; WO2008037306A1; ATE537366T1; CN101517243B; EP2069640B1; DE102006045442A1

Abstract

A hydrostatic drive unit is disclosed for supplying pressure medium to a hydraulic consumer having two pressure spaces. According to the invention, the hydrostatic drive unit has an adjusting motor and two hydrostatic units which can be driven via the adjusting motor. Pressure medium is conveyed directly from one of the pressure spaces into the other pressure space via one of the hydrostatic units. The further hydrostatic unit conveys pressure medium from a tank into the lastmentioned pressure space or, depending on the drive direction, from the latter into the tank.

Description

description

Hydrostatic drive unit

The invention relates to a hydrostatic drive unit according to the preamble of claim 1.

Such hydrostatic drive units are used, for example, for actuating hydraulic cylinders and have a secondary controlled subsystem, which consists essentially of a hydraulic transformer which is connected to a system with impressed pressure. In principle, a hydraulic transformer is mechanically coupled hydrostatic units, one of which is connected to the system with the impressed operating pressure, and the other is connected to the consumer, for example a hydraulic cylinder. For extending the hydraulic cylinder against load, the unit connected to the cylinder operates as a pump which is driven by the motor fed by the system with impressed operating pressure. When the hydraulic cylinder is retracted under load, the functions of the hydrotransformer reverse and the unit that previously operated as a motor now in turn travels the secondary system. The basic structure of such hydrotransformers, for example, in the book "The Hydraulic Trainer", Volume 6, "Hydrostatic drives with secondary control", Chapter 6; Vogel book publisher Würzburg described.

In EP 0 851 121 a hydraulic transformer with two axial piston machines is disclosed which operate as motor and pump or in reverse function. The pistons of the two axial piston machines are supported on a common swash plate. In EP 1 100 670 Bl a hydrostatic drive unit is shown, in which a differential cylinder is actuated by means of a hydraulic transformer. The hydrotransformer is designed with a tank connection, a pressure connection and a working connection, with pressure applied to the pressure connection, for example via a hydraulic accumulator. This pressure also acts in the annulus of the differential cylinder. The bottom-side cylinder chamber is connected to the working port of the hydrotransformer. Although such a drive system has a comparatively simple structure. However, it has been found that the cylinder must be sized larger compared to a drive unit with conventional valve control, because the pressure in the annulus B can not be reduced below the applied pressure.

In principle, there is also the possibility of carrying out the hydrostatic drive system with an additional hydrotransformer whose working connection is connected to the annular space and at whose pressure connection the pressure applied via a hydraulic accumulator is present. In such an embodiment, although the cylinder may be made of the same size as in systems with a conventional valve control, it is disadvantageous, however, that due to the second hydraulic transformer, a considerable device complexity is required.

In contrast, the invention has for its object to provide a hydrostatic drive unit which allows a control of a consumer, in particular a hydraulic cylinder with low device complexity. This object is achieved by a hydrostatic drive unit with the features of claim 1.

According to the invention, a hydrotransformer used in such a hydrostatic drive unit is in principle made of three hydrostatic units, two hydrostatic units, which are preferably designed as constant units, being drivable by an adjustable hydraulic machine. The two ports of a hydrostatic unit with the two pressure chambers of the consumer, for example, the differential cylinder are connected, while a working port of the second hydrostatic unit with the larger of the pressure chambers and a tank port of this hydrostatic unit is connected to a tank. These two hydrostatic units are driven by the adjustable hydromachine, whose pressure connection is connected to a pressure line carrying the impressed pressure and whose tank connection is connected to a tank line leading to the tank. By the first-mentioned hydrostatic unit pressure medium from the shrinking annulus is promoted in the expanding bottom-side cylinder chamber, for example, when extending a differential cylinder. The further hydrostatic unit conveys pressure fluid from the tank into the increasing pressure chamber. To retract the differential cylinder, the direction of rotation of the adjustable hydraulic machine is reversed and promoted by the first hydrostatic unit pressure medium from the cylinder chamber into the annulus. The second unit conveys pressure medium back from the cylinder chamber to the tank.

In a particularly preferred embodiment, the two hydrostatic units are designed as constant units, which are drivable by the adjustable hydraulic machine. The pressure chambers of the hydraulic consumer preferably have different volumes, wherein the delivery port of the first-mentioned hydrostatic unit with the larger and the delivery port of the second hydrostatic unit is connected to the smaller pressure chamber.

In such a construction, it is preferred if a second delivery port of the second hydrostatic unit is also connected to the larger of the pressure chambers.

The displacement volumes of the two constant units behave according to an advantageous development of each other as the ratio of the piston rod surface to the piston bottom surface.

In an advantageous embodiment of the invention, the impressing of the system pressure via. one

Hydraulic cylinder which is chargeable by a storage loading pump.

The dynamic behavior of the hydrostatic drive unit can be improved by a bias of the hydraulic cylinder.

The hydrostatic drive unit can be made particularly compact, if the hydrotransformer is formed by a Doppelaxialkolbenmaschine, with a double unit both constant units and the other unit forms the hydraulic adjustable machine.

Preferred embodiments of the invention are explained in more detail below with reference to schematic drawings. Show it: Figure 1 is a schematic diagram of a hydrostatic drive unit according to the invention;

FIG. 2 shows a longitudinal section through a hydrotransformer usable in a hydrostatic drive unit according to the invention in FIG

Double axial piston construction and

3 shows an embodiment of a bias voltage for the hydraulic cylinder according to FIG. 1

1 shows a circuit diagram of a hydrostatic drive unit 1 for a differential cylinder 2, which has a bottom-side cylinder chamber 4 and a piston rod side annular space 6. The hydrostatic drive unit 1 essentially has a dot-dash line. indicated hydrotransformer 8, consisting of a hydraulic adjusting motor 10, the two constant units, in the present case two constant-displacement pumps 12, 14 drives. A pressure port P of the adjusting motor 10 is connected to a pressure line 16, which is impressed on a hydraulic accumulator 18, a system pressure. The hydraulic accumulator 18 is charged by means of a storage loading pump 20. A tank connection of the variable displacement motor 10 is connected to a tank T via a tank line 22.

A delivery port P of the fixed displacement pump 12 opens into a working line 24 leading to the cylinder chamber 4 of the differential cylinder 2. The suction port T of this constant displacement pump 12 is connected to the tank line 22.

A delivery port P of the further constant pump 14 opens into the working line 24, while the other delivery port T - called here for simplicity suction port - is connected via a second working line 26 to the annular space 6. Both constant-displacement pumps 12, 14 and the adjusting motor 10 are designed with a reversible conveying direction, so that correspondingly the connections P of the fixed-displacement pumps designated as conveying connection in FIG. 1 can also act as suction connections. The direction of rotation of the adjustment motor 10 is effected by appropriate adjustment of the pivot angle.

This is set to extend the differential cylinder 2 so that the constant displacement pump 12 draws pressure medium from the tank T via the tank line 22 and promotes via the delivery port P and the working line 24 in the bottom-side cylinder chamber 4. The displaced from the annular space 6 pressure fluid is summed over the second constant pump 14 to the funded by the constant pump 12 pressure medium flow in the working line 24, so that the differential cylinder 2 extends.

The displacement volumes V1 and V2 of the two constant-displacement pumps 12 and 14, respectively, relate to the cylinder surfaces A, B (see FIG. 1) as follows:

V1 / V2 = (A - B) / B

wherein the area difference A - B corresponds to the piston rod area C.

Figure 2 shows a concrete embodiment of such a hydraulic transformer 8, in which the three hydrostatic units are summarized as an axial piston machine in a compact housing. The basic structure of such a "floating-cup axial piston machine" is known for example from the post-published application 10 2005 056 631.1, so that only the components required for understanding the invention are described here. Such a hydraulic transformer 8 in Axial piston construction has a housing with a central part 28 which is closed at the end by two connection covers 30, 32. In the housing, a shaft 34 is mounted, which has approximately centrally a radially projecting drive flange 36, in the axis parallel to the shaft axis 38 a plurality of double piston 40 are used, the remote from the drive flange 36, spherical end sections each dipping into a cylinder sleeve 42 and limit each with a working space 60 with this. The ZyIinderhülsen 42 arranged in Figure 2 right of the drive flange 36 are biased by a spring against a cylinder drum 44, which in turn is supported on the front side of a swash plate 46 which is pivotally mounted with its convex back in a corresponding bearing recess 47. In this kidneys 48, 50 are formed, which are hydraulically connected to a pressure channel 54 and a tank channel 52, which lead to the pressure port P and the tank port T of the adjustment motor 10. The cylinder drum 44 is rotatably connected via a driver 64 with a bearing portion of the shaft 34. This driver 64 is designed so that the cylinder drum 44 can perform a wobbling motion.

In order to allow the hydraulic connection between the kidneys 48, 50 and the associated channels 52 and 54 at different pivot angles, 46 control pockets 56, 58 are formed on the convexly executed back of the swash plate. The limited by a respective cylinder sleeve 42 and an end portion of the double piston 40 working spaces 60 of the axial piston unit are connected by one connecting channel 62 - depending on the angle of rotation of the cylinder drum 44 with one of the control kidneys 48 and 50, so that pressure medium via the pressure channel 52 in Working spaces 60 flow or can be displaced from these via the tank channel 54 to the tank port T. The arranged in Figure 2 left of the drive flange 36 end portions of the double piston 40 dive accordingly in cylinder sleeves 42, which are sealingly guided on a further cylinder drum 66. Also, this cylinder drum 66 is connected via a further driver 68 with another bearing portion of the shaft 34 such that they perform a tumbling motion. can. The left in Figure 2 end face of the cylinder drum 66 is biased against a swash plate 70, on which two radially inner control kidneys 72, 74 and two radially outer control kidneys 76, 78 are formed. The control kidneys 72, 74 are assigned to the constant displacement pump 12 and the outer control kidneys 76, 78 of the constant displacement pump 14. The trained in the swash plate 70 control kidneys 74 and 76 are connected via working channels 80 and 82 with the first working line 24, which in turn opens into the cylinder chamber 4 of the differential cylinder 2. The radially inner control kidney 72 is connected via a further working channel 86 to the further working line 26 and the control kidneys 78 via a tank channel 84 to the tank line 22, so that form the pressure fluid flow paths shown in Figure 1.

As further shown in Figure 2, each second of the left end portions of the double piston 40 and the respective associated cylinder sleeve 42 limited work spaces 88 via a slant channel 90 in the cylinder drum 66 with the control kidney 76 or via another inclined channel 92 with the control kidney 78th connectable. The intervening work spaces 68 can be connected via the dashed lines indicated channels 94, 96 with the control kidneys 74 and 72, respectively. That is, each second end portion of the double piston 40 to the left of the drive flange 36 is thus a piston of the fixed displacement pump 12, while the intermediate end portions piston of the further constant pump 14 are. Such a design principle is known as a so-called "split flow double pump".

The above-described double axial piston machine is characterized by an extremely simple and compact design. For further details, in particular the sealing guidance of the cylinder sleeves 42 on the associated cylinder drum 44 and 66, reference is made to the aforementioned subsequently published application, which shows a so-called "floating cup pump".

The dynamic behavior of the hydrostatic drive unit can be improved by biasing the differential cylinder 2. FIG. 3 shows a possibility for such a bias voltage. Accordingly, branch from the two working lines 24, 26 bias lines 98 and 100 from. The bias line 100 leads to a storage line 102, in which a first aperture 104 is formed with a comparatively large diameter ^•. The biasing line 102 is connected on the one hand with a hydraulic accumulator 106 and on the other hand via a second orifice 108 with a comparatively small diameter to the tank T. In the region between the first diaphragm 104 and the hydraulic accumulator 106, a branch line 110 branches off from the preload line, in which a third diaphragm 112 and a fourth diaphragm 114 are arranged and which opens into the tank T beyond the fourth diaphragm 114. The biasing line 98 is connected to the region between the two apertures 112, 114. In other words, via the two bias lines 98, 100 is tapped between the respective associated apertures 104, 108 and 112, 114, a biasing pressure for the differential cylinder 2, wherein the low pressure medium losses through the small apertures 108, 114 to the tank T out in Purchase can be taken.

In the basic position, the adjusting motor 10 is pivoted back to 0, ie the swash plate 46 according to FIG. 2 is set transversely to the shaft axis 38 with its face facing the cylinder drum 44. To extend the differential cylinder 2, the control disk 46 (Figure 2) is pivoted so that the constant displacement pump 12 pressure medium from the tank T in the working line 24 and from there into the bottom-side cylinder chamber 4 promotes. To retract the cylinder, the conveying direction of the constant displacement pumps 12, 14 is reversed by opposing pivoting of the control disk 46, so that corresponding pressure medium from the cylinder chamber 4 via the working line 24 and the constant displacement pump 12 is conveyed into the tank line 22 and from there into the tank T. At the same time promotes the constant-displacement pump 14 pressure medium directly from the pressure line 24 via the second working line 26 in the increasing annular space. 6

In contrast to conventional drive systems, the tilt angle of the adjustment motor is no longer associated with a precisely defined drive speed, but with impressed system pressure a specific torque.

Constant pumps 12, 14 were used in the embodiments described above. In principle, however, variable displacement pumps could also be used.

Disclosed is a hydrostatic drive unit for supplying pressure medium to a hydraulic consumer with two pressure chambers. The hydrostatic drive unit has. According to the invention, an adjusting motor and two hydrostatic units which can be driven via the adjusting motor. Via one of the hydrostatic units, pressure medium is conveyed directly from one of the pressure chambers into the other pressure chamber. The further hydrostatic unit conveys pressure fluid from a tank in the latter pressure chamber or depending on the drive direction of this in the tank.

Claims

12Patentansprüche

1. Hydrostatic drive unit for supplying pressure medium of a hydraulic consumer (2) with two pressure chambers (4, 6), for example a differential cylinder, with a hydrostatic unit (12, 14) which is driven by an adjustable hydraulic machine (10) and one with a The delivery port (P) connected to the pressure chambers (4), wherein a suction port (T) of the hydraulic machine (10) is connected to a tank (T) and a pressure port (P) of the hydraulic machine (10) is connected to a pressure line (16) by a further, by the hydraulic machine (10) drivable hydrostatic unit (14) whose delivery port (B) is connected to the further pressure chamber (6).

2. Hydrostatic drive unit according to claim 1, wherein the hydrostatic units as constant units

(12, 14) are executed.

3. Hydrostatic drive unit according to claim 1 or 2, wherein the pressure chambers (4, 6) have different volumes and the delivery port (P) of the first hydrostatic unit (12) with the larger and the delivery port (B) of the second hydrostatic unit (14). is connected to the smaller pressure chamber (6).

4. Hydrostatic drive unit according to claim 3, wherein a further delivery port (A) of the second hydrostatic unit (14) is also connected to the larger pressure chamber (4).

5. Hydrostatic drive unit according to one of the preceding claims, wherein the displacement volumes of the two hydrostatic units

(12, 14) behave as follows to the active surfaces of the pressure chambers (4, 6): 13

V1 / V2 = (A - B) / B with A bottom side cylindrical surface, with B ringraumseitige cylinder surface.

6. Hydrostatic drive unit according to one of the preceding claims, wherein the pressure line (16) a pressure is impressed.

7. Hydrostatic drive unit according to one of the preceding claims, wherein the impingement of the pressure by means of a hydraulic accumulator (18), which is chargeable by a Speieherladepumpe (20).

8. Hydrostatic drive unit according to one of the preceding claims, wherein the pressure chambers (4, 6) of the consumer are biased.

9. Hydrostatic drive unit with a Doppelaxialkolbenmaschine with two units, wherein a dual unit both constant units (12, 14) and the other unit forms the adjustable hydraulic machine (10).