WO2011069597A1

WO2011069597A1 - Hydrostatic drive

Info

Publication number: WO2011069597A1
Application number: PCT/EP2010/007041
Authority: WO
Inventors: Rüdiger HONSBEIN
Original assignee: Hydac System Gmbh
Priority date: 2009-12-11
Filing date: 2010-11-19
Publication date: 2011-06-16
Also published as: EP2510261A1; EP2510261B8; DE102009058005B4; DE102009058005A1; EP2510261B1

Abstract

The invention relates to a hydrostatic drive having a closed circulation system (2). The hydrostatic drive comprises an adjustable hydraulic pump (4) driven by an internal combustion engine (3) and a hydraulic motor (5) as well as a first working line (6) and a second working line (7). The first working line (6) and second working line (7) each connect the hydraulic pump (4) and the hydraulic motor (5) to one another. The hydrostatic drive is characterised in that a first hydraulically pilot-controlled valve (8) regulates the fluid flow in the first working line (6), which in a forward driving operation forms the return line for fluid from the hydraulic motor (5) to the hydraulic pump (4), the hydraulic pilot control of the valve (8) is effected by a pressure control valve (9), which detects the fluid pressure in the first working line (6), and depending on the fluid pressure in the first working line (6) and in the second working line (7), and when a pressure set in the pressure control valve (9) exceeds the fluid pressure in the first working line (6), during a braking operation, the valve (8) switches to a position in which the fluid flow is conducted to a further load (10).

Description

Hydrostatic drive

The invention relates to a hydrostatic drive with a closed loop, which has an adjustable, driven by an internal combustion engine hydraulic pump and a hydraulic motor, and a first working line and a second working line, wherein the first and the second working line in each case the hydraulic pump and the hydraulic motor fluid connect with each other.

Hydrostatic drives, as used for example in mobile machines, often consist of a closed circuit management, which is formed by a hydraulic pump, a hydraulic motor and two connecting them each working lines. The two working lines convey pressure medium or fluids in opposite directions. The hydraulic pump is driven by a drive shaft through an internal combustion engine. The internal combustion engine is often designed as a diesel engine.

In certain driving situations, in particular in the so-called push operation of a commercial vehicle or a working machine equipped accordingly with such a hydrostatic drive, it happens that the hydraulic motor promotes pressure medium through the closed circuit and the hydraulic pump is pressurized. The hydraulic pump then works as a hydraulic motor and then supports itself on the working machine. There is also the danger in this operating state of the working machine that the corresponding speed of the drive motor or the internal combustion engine available brake load is exceeded. If this is the case, then the speed of the internal combustion engine increases and then appropriate measures have to be taken to prevent an overload damaging the internal combustion engine by overspeeding.

From DE 102 41 950 A1 it is known to provide a throttle valve in the working line arranged downstream of the hydraulic motor. With the help of this valve throttling of the flow in the working line can be realized. The throttle valve is for this purpose influenced by an actuating piston in terms of its position. The position of the actuating piston is in turn dependent on the working line pressure arranged downstream of the throttle valve and a pressure which can be predetermined by the rotational speed of the drive motor. The fact that the entire delivery volume must be promoted by the Drosselstele, resulting in significant temperature increases for the pressure medium. The control of the throttle valve is also expensive.

From JP 2002-01 3636 A, a hydrostatic drive is known, in which an adjustable pump is connected in a closed circulation with a constant motor as a hydraulic motor. The two working lines, which connect the hydraulic pump with the hydraulic motor, are throttled connected via a switching valve. To bring the switching valve into its connecting position, it must be supplied with a feed pressure of a feed pressure pump. The connection and thus the throttled short-circuiting of the two working spaces thus takes place only in dependence on a feed pressure generated by the feed pump. This has the disadvantage that an actuation of the switching valve does not depend on the rotational speed of a drive machine connected to the feed pump. The pressure generated by the feed pump can therefore no measure of represent exceeding a critical for the engine speed.

In practice, hydrostatic drives are also known in whose working lines are circuits, consisting of valve units, with a bleed valve, a differential pressure valve and non-return valves, the pressure fluid under power losses, which could lead to over-rotation of the drive machine with appropriate shift operation derive a pressure medium tank. In addition, such circuits can also control an actuator for the hydraulic motor and change its displacement volume.

The known hydrostatic drives and their controls are regularly not able to achieve a maximum possible braking power or to effect an energy return into a hydraulic overall system of which the hydrostatic drive is part.

In view of this state of the art, the object of the invention is to provide a hydrostatic drive which, in a simple manner, enables maximum braking power with high utilization of the recirculated energy within a hydraulic overall system.

According to the invention this object is achieved by a hydrostatic drive with the features of claim 1 in its entirety.

In the hydrostatic drive according to the invention with an adjustable, driven by an internal combustion engine hydraulic pump and a hydraulic motor, which are connected to a first working line and a second working line with each other, to protect against overspeeding the internal combustion engine during coasting each valve as a switching valve or proportional valve in the first and second Inserted working line and piloted by the fluid pressure in the working lines. A first valve in the first working line is precontrolled by the pressure in the first working line and ensures an adaptive discharge of pressure medium when a predeterminable pressure level is exceeded during pushing operation, ie when the pressure is exchanged in the first working line. Thus, the flow direction is maintained; otherwise it would come to reversing the direction of rotation of the engine. The pressure medium is forwarded to a consumer and thus enables energy recovery. The second valve in the second working line can be used in the same way to dissipate at inverse flow direction ratios excess pressure medium to at least one consumer and then supply a pressure medium container.

With the solution according to the invention, the hydraulic pilot control of the valve by a, the fluid pressure in the first working line detected pressure control valve and in response to the fluid pressure in the first working line and in the second working line. The hydraulic pilot control is thus independent or adjustable in dependence on the characteristic of the internal combustion engine and is available as an electrical signal or is predefined fixed.

It can also be provided in an advantageous manner to provide different modes of operation with respect to the pilot control of the valves such that the pilot pressure of the valves in the first and second working lines is determined by a pressure regulating valve. This will be the

Pressure medium flow through the hydraulic pump so reduced that an impermissible increase in the speed of the internal combustion engine is prevented. The pilot control of the valves for the discharge of pressure medium to the consumer also allows an adaptation of the derived pressure medium flow to the respective characteristic of the consumer. The consumer may for example be a cooling fan. The valves are expediently bridged by a bypass line, which are locked during coasting, ie at pressure interchange, from the hydraulic motor to the hydraulic pump by a check valve, and otherwise open load operation with a flow direction of the pressure medium from the hydraulic pump to the hydraulic motor, so that the valves at This mode can also be operated in a closed position, in which they may require no energy. About the illustrated valve control, the consumer can be fed by pressure medium from the first working line and from the second working line.

In a particularly preferred embodiment, the valves may be so controlled or interconnected that the valve in the first working line, which forms the return line for fluid from the hydraulic motor to the hydraulic pump in the usual load mode, is in a partially or completely blocked switching position in the pressure medium the consumer is discharged through the open check valve in the bypass line, which bridges each valve. In this sliding mode of the hydrostatic drive, the second valve is open in the second working line and allows a transport of fluid from the hydraulic pump to the hydraulic motor. Pressure medium can thus be derived from the respective bypass line or bypass line of each valve, depending on the prevailing in the working lines pressure interchanging. It is recommended that a differential pressure control of the pilot operated valves in accordance with the prevailing in the respective working pressures.

In a supply line to the consumer, a pressure relief valve and a flow control valve is preferably integrated. The flow control valve is preferably designed as a 3-way flow control valve, so that overall a fluid flow adapted to the operating behavior of the respective consumer is provided. is adjustable. The 3-way flow control valve can divide the fluid flow to the consumer and another consumer, such as a pressure fluid cooler or accumulator. It may also be expedient for energy recovery in the overrun operation of the hydraulic motor, to charge a pressure fluid reservoir by pressure medium, which is guided by the valves or by the bypass lines üm the valves around. For this purpose, it may be advantageous to fluidly connect the accumulator with both bypass outlets to the respective valves via a 3/3-way valve. The 3/3

Directional control valve, which preferably blocks in a spring-centered position, may be precontrolled by signals of a flow direction indicator introduced into the second or first working line. Thus, depending on the detected flow direction in the first and second working lines, the pressure medium accumulator can optionally supply pressure medium to the first working line or the second working line.

The accumulator can still be connected to the supply line for the first consumer and charge via a suitable switching valve in the supply line with pressure medium. The switching valve may be pilot-controlled, for example by a differential pressure between the first pressure relief valve and a downstream second pressure relief valve in the supply line. A particularly simple protection against overspeeding of the internal combustion engine can be achieved by the fact that the valves are designed as 2/2-way valves.

The invention is explained in detail below with reference to the drawing. 1 shows a schematic circuit diagram of a hydrostatic drive according to the invention, with one in a flow direction. tion of the fluid from the hydraulic motor to the hydraulic pump acting overspeed protection in a working line;

a schematic circuit diagram of a hydrostatic drive according to the invention, with an acting in both flow directions of the fluid from the hydraulic motor to the hydraulic pump overspeed protection in both working lines; a schematic circuit diagram of a hydrostatic drive according to the invention, with an acting in both flow directions of the fluid overspeed protection in both working lines of the hydrostatic drive in load operation; a schematic circuit diagram of a hydrostatic drive according to the invention, with an acting in the two flow directions of the fluid overspeed protection in braking or pushing operation;

a schematic circuit diagram of a hydrostatic drive according to the invention, with an acting in a flow direction of the fluid from the hydraulic motor to the hydraulic pump overspeed protection with return of the fluid in a pressure fluid reservoir;

a schematic circuit diagram of a hydrostatic drive according to the invention, with an acting in both flow directions of the fluid overspeed protection with return of the fluid in a pressure fluid reservoir;

the hydrostatic drive of Figure 6 in load operation. and possible energetic recovery from a pressure fluid reservoir;

the hydrostatic drive of FIG. 6 in a braking or pushing operation with outfeed of the fluid in a pressure fluid reservoir. FIG. 1 shows a first exemplary embodiment of the hydrostatic drive according to the invention. The hydrostatic drive 1 has an internal combustion engine 3, which is designed as a diesel internal combustion engine. The internal combustion engine 3 drives an adjustable in its delivery volume and variable hydraulic pump 4. The hydraulic pump 4 may be for example a radial piston pump or a vane pump or a two-way pivotable hydrostatic axial piston machine. The hydraulic pump 4 can promote fluid under pressure either in a first working line 6 or in a second working line 7. The funded by the hydraulic pump 4 fluid drives a hydraulic motor 5, which drives an unillustrated vehicle via an output shaft. In the usual driving operation under load, the first working line 6 forms a return line, the second working line 7 a delivery line for fluid to the hydraulic motor 5. Overall, a closed circuit 2 is formed. The fluid is conveyed from the connection pump of the hydraulic pump 4 to the connection ΑΜΟΙΟΓ of the hydraulic motor 5 and is returned from the connection Β ΟΜΓ of the hydraulic motor 5 to the connection Bpum e of the hydraulic pump 4.

In the first working line 6 as a 2/2-Wegeventi I formed with direct hydraulic control first valve 8 is turned on. The valve 8 is bypassed by a first bypass line 1 1. In the bypass line 1 1, a check valve 12 is installed, which acts blocking in the flow direction of the fluid set forth. To the bypass line 1 2, a branch B 1 for a further hydrostatic circuit, which is shown in the lower half of Fig. 1, is present. The second working line 7 also has a branch AI for fluid to this further hydraulic circuit.

The valve 8 is driven by a pressure control valve 9 and is shown in Fig. 1 in its open switching position. The pressure control valve 9 thus controls the pressure medium pressure in the first working line 6, which represents the return line to the hydraulic pump 4. When critical pressures occur in the first working line 6, approximately in coasting when the traction motor or the hydraulic motor 5 are operated without load, and much more pressure medium or pressure via the first working line 6 is conveyed to the hydraulic pump 4, the valve 8 is spent at least in a partially closed switching position , This prevents that the hydraulic pump 4, in particular the internal combustion engine 3 undergoes an overspeed or overspeeding.

The pressure medium flow in the first working line 6 is then partly conveyed by the branch B1 and the branch A1 into the further hydraulic circuit, namely to a consumer 10. The consumer 10 is a cooling fan 13 in the embodiments shown in FIGS. 1 to 8 for the return oil, eg for the internal combustion engine 3, or for self-cooling.

A supply line 14 for the consumer 10 is connected with a shuttle valve 22 to the two branches AI, B1. Downstream of the shuttle valve 22 is a first pressure relief valve 15 and this in turn downstream of a flow control valve 16. The flow control valve 16 is designed as a 3-way flow regulator 1 7 and is capable of diverting the fluid flow to the load 10 divided into partial flows to the load 10 or to a cooler K, wherein a further pressure control valve D a fluidfüh-rende connection from the supply line 14th to the cooling fan 13 and to the radiator K is capable of bridging. The fluid flow divided by the 3-way flow regulator 1 7 is in turn combined downstream of the cooling fan 13 and upstream of the cooler K and cooled to a pressure low side 23. The fluid can be conveyed back from a feed pump SP to the hydraulic pump 4 afterwards. FIG. 2 shows a further exemplary embodiment of a hydrostatic drive 1, in which, in addition to the second working line 7, a second tes valve 8 'is turned on. The valve 8 'is as 2/2-way valve with the same type of control, as the valve 8 shown in Fig. 1, driven, via the pressure regulating valve 9. The second valve 8' is also handled by a bypass line 1 1 ', the is connected in the second working line 7. A check valve 12 'is arranged in the bypass line 1 V such that it is in the open position during normal load operation. Both valves 8, 8 'can be actuated directly and in the sense of an override of the pressure control valve 9 via a remote control connection F. If F is pressurized, so is the entire

Protective circuit has been disabled (machine dies with the load). Moreover, the same reference numerals as shown in FIG. 1 are shown for the same components and the explanations so far taken so far also apply to the following embodiments.

FIG. 3 shows the hydraulic circuit 2 in FIG. 2 in a normal operating phase. In this case, pressure medium from the hydraulic pump 4 coming via the second working line 7 is pumped with locked switching position of the second valve 8 'via the bypass line 1 1' to the hydraulic motor 5. Pressure medium is thereby returned via the first working line 6 through the valve 8 located in the open switching position to the hydraulic pump 4.

In Fig. 4, the hydraulic circuit 2 in Fig. 2 in a reverse operation as shown in Fig. 3 is shown. It is shown a sliding operation without load on the hydraulic motor 5, wherein the hydraulic motor 5 promotes pressure medium. The first valve 8 in the first working line 6 is in a partially closed state, the second valve 8 'in an open switching position. Pressure medium is conveyed via the second working line 7 without pressure to the hydraulic motor 5 and conveyed under high pressure in the first working line 6 from the hydraulic motor 5 to the first valve 8. In whose Bypass line 1 1 results in a rise back to the branch AI, so that in the locked switching position of the check valve 12 pressure medium directed to the load 10 and the hydropneumatic 5 is relieved. 5 to 8 further embodiment of a hydrostatic drive 1 are shown, wherein a flow direction indicator 1 9 is connected in the second working line 7. The flow direction indicator 19 controls the switching position of a hydraulically piloted switching valve 20, which is shown as 3/3-Wegeventi I with spring centering in a neutral locked position. The check valve above the main control valve 20 controls the discharge of pressure medium in a pressure fluid accumulator 18 as a high-pressure accumulator for fluid with, with a return feed is not provided. Another hydraulic accumulator 18 'is used as a low pressure accumulator (Figure 5). Further, the 3/3-way valve controls the fluid flow from the pressure accumulator 18 back into the hydraulic circuit 2, in the sense of traction or relief for the traction motor or the hydraulic motor 5 (see also Fig. 7). In addition to the main control valve 20, a pilot valve 20 'is provided which cooperates with the main control valve, in particular via the locks A, B.

As shown in FIG. 5 also shows, an alternative charging phase of the accumulator 18 may also be effected in that the charging of the accumulator 18 from one, the change-over valve 22 downstream switching valve 24, takes place from. The switching valve 24 can be hydraulically pre-controlled by taking into account differential pressures of the supply line 14 between the first pressure limiting valve 15 and the second pressure limiting valve 21. If, for example, the pressure medium pressure rises sharply during a very large increase in pressure in the overrun mode in the first working line 6, then pressure medium from the supply line 14 can be guided into the pressure medium reservoir 18. The 3/2-way valve for controlling the operation of the accumulator 1 8 can of pressure medium press, which are tapped at the first check valve 1 2 and the second check valve 12 ', be pre-controlled n.

6 shows a further embodiment of a hydrostatic drive 1, in which, in contrast to the solution shown in FIG. 5, a valve 8, 8 'is switched on in both working lines 6, 7, the functional integration of which is shown in principle with reference to the above-described figures , Fig. 7 shows the hydraulic circuit 2 in Fig. 6 in a feed phase from the accumulator 1 8 in a normal operating situation, i n the pressure fluid from the hydraulic pump 4 to the hydraulic motor 5 via the second working line 7 is promoted. The second valve 8 'is in a locked position, so that pressure medium is conveyed via the bypass line 1 V via the flow direction indicator 1 9 to the hydraulic motor 5. At the branch Bi pressure medium can be diverted to the supply line 101 and the memory 1 8 '(low-pressure accumulator). It can thereby also the accumulator 1 8 charge. The first Venti l 8 is an open Schaltstel lungs tion in the pressure medium in the first working line 6 back promoted from the hydraulic motor 5 to the hydraulic pump 4 wi rd. Between the supply line 101 and the other supply line 1 02 a change-over valve 103 is connected.

FIG. 8 shows the same hydraulic circuit as shown in FIG. 7 in a mode of operation in sliding operation, that is to say under pressure rise in the first working line 6 due to accelerations of the traction motor and the hydraulic motor 5, for example during a descent of the vehicle.

The first Venti l 8 in the return line or first working line 6 is in a tei lweise locked position, so that by the pressure increase in front of the venti l 8 and due to the locked position of the Rückschlagventi ls 12, pressure medium from the branch B1 to the supply line 14 is guided. The second valve 8 'is in a locked switching position, ie pressure medium can reach the hydraulic motor 5 without pressure via 12' in the second working line 7 from the hydraulic pump 4.

Claims

P a t e n t a n s r ü c h e

Hydrostatic drive with a closed circuit

(2), which is an adjustable, of an internal combustion engine

(3) driven hydraulic pump

(4) and a hydraulic motor

(5) as well as an initial work manager

(6) and a second working line (7), the first and second working lines (6,

7) each connect the hydraulic pump (4) and the hydraulic motor (5) to one another, characterized in that a first hydraulically pilot-controlled valve (8) regulates the fluid flow in the first working line (6), which in a forward driving mode is the return line for fluid from the The hydraulic motor (5) to the hydraulic pump (4) forms the hydraulic pilot control of the valve

(8) by a pressure control valve (9) which detects the fluid pressure in the first working line (6) and depending on the fluid pressure in the first working line (6) and in the second working line (7), and that when the fluid pressure in the first working line (6) from one in the pressure control valve

(9) set pressure during a braking process, the valve (8) changes to a switching position in which the fluid flow is guided to another consumer (10).

Hydrostatic drive according to claim 1, characterized in that the first valve (8) is bridged via a bypass line (1 1) in the first working line (6), and that the bypass line (1 1) has a check valve (12), which is blocking acts on the fluid flow during a braking process and the bypass line (1 1) is connected to the other consumer (10) in a fluid-carrying manner.

Hydrostatic drive according to claim 1 or 2, characterized in that the further consumer (10) is a hydraulic drive for a cooling fan (13). Hydrostatic drive according to one of claims 1 to 3, characterized in that the further consumer (10) is operated by a fluid flow from the first working line (6) or from the second working line (7).

Hydrostatic drive according to one of claims 1 to 4, characterized in that a first pressure relief valve (1 5) and a flow valve (16) are arranged in a supply line (Ί 4) for the further consumer (10).

Hydrostatic drive according to claim 5, characterized in that the flow valve (16) is a 3-way flow regulator (1 7) which divides the fluid flow between the further consumer (10) and a cooling circuit (K).

Hydrostatic drive according to one of claims 1 to 6, characterized in that it comprises a pressure accumulator (18) which can be charged or hydraulically pilot-controlled depending on signals from a flow direction indicator (19) inserted in the second working line (7). can be switched on.

Hydrostatic drive according to claim 7, characterized in that the pressure accumulator (18) can be charged with fluid from the first working line (6) or from the second working line (7) or from the supply line (14) for the further consumer (10), whereby the main control valve (20) has the task of supplying energy to the system depending on the pressure level, taking into account the flow direction.

Hydrostatic drive according to claim 8, characterized in that the switching valve (24) is dependent on a fluid pressure between the Most pressure relief valve (1 5) and a second pressure relief valve (21) following this is controlled.

10. Hydrostatic drive according to one of claims 7 to 9, characterized in that the switching valve (24) which regulates the charging process of the pressure accumulator (18) is a 2/2-way valve which locks it in its rest position.

1 1 . Hydrostatic drive according to one of claims 1 to 10, characterized in that a second hydraulically pilot-controlled valve (8 ') regulates the fluid flow in the second working line (7), which in forward driving mode supplies the inlet line for fluid from the hydraulic motor (5). the hydraulic pump (4) and that the hydraulic pilot control of the second valve (8') is carried out by the pressure control valve (9) which detects the fluid pressure in the second working line (7) and depending on the fluid pressure in the first working line (6 ) and in the second work line (7) to achieve bidirectional operation.

12. Hydrostatic drive according to one of claims 1 to 1 1, characterized in that the first and the second valve (8, 8 ') are a 2/2-

Directional valve is.

1 3. Hydrostatic drive according to claim 1 1 or 12, characterized in that the second valve (8 ') is bridged with a bypass line (1 1 ') in the second working line (7), the bypass line (1 1 '). Check valve (12 '), which opens in forward driving mode and connects the bypass line (1 1 ') to the other consumer (10) in a fluid-carrying manner.

14. Hydrostatic drive according to one of claims 1 to 13, characterized in that the fluid flow to the further consumer (10) and is pilot-controlled to the cooling circuit (K) by a pressure valve.