DE102018207945A1 - Mobile work machine with hydrostatic working and traction drive - Google Patents

Abstract

Disclosed is a mobile machine with a mechanical drive train and at least one hydrostatic driving consumers coupled thereto, and with at least one hydrostatic working consumer and a hydraulic machine to the pressure medium supply, which is fluidly connected to a pressure medium reservoir of the working machine and the at least one working consumer.

Description

The invention relates to a mobile work machine according to the preamble of patent claim 1.

A mobile work machine usually has a mechanical drive train and one or more hydraulic working consumers. To support the mechanical drive train, especially in difficult ground conditions, a hydraulic drive can be switched on. This is done especially at slow speeds. Such a hydraulic auxiliary traction drive attacks, for example, on an axle, usually the front axle, and is conventionally designed in a closed hydraulic circuit. Thus, in the closed hydraulic circuit, a hydrostatic transmission is formed, wherein the hydraulic machine acting as a pump is often electrically proportional, in particular volume flow controlled. In order to transfer an additional torque to the axle, a flow of the hydraulic motor relative to the mechanically driven axle must be controlled via the volume flow control.

Deviating from the volume flow control concepts are known in which the operated in a closed circuit hydraulic pump is pressure-controlled. In this way, a defined torque in direct dependence on a driver's request can be provided on the axle.

A solution with hydrostatic auxiliary drive, which provides an additional torque on a mechanically driven axle, shows the document US 2018 006 54 79 A1 , Two hydraulic machines are arranged in the closed hydraulic circuit. To control the activation of the auxiliary drive an auxiliary or "booster" pump is provided, via which one of the working lines of the circuit is pressurized, whereby the two hydraulic machines of the hydraulic circuit are coupled to transmit torque with a respective axis.

For pressure medium supply of the hydrostatic working load - such as a fan drive, a concrete mixing drive or a hydraulic cylinder of a hoist or slewing the mobile machine - a hydraulic pump is provided in the open circuit conventionally. For the permanent or shiftable hydrostatic drive, however, as stated above, a hydraulic pump is installed in a closed circuit. Therefore, two separate hydraulic circuits with a plurality of multiple existing hydraulic components and two hydraulic pumps are provided. This represents a high device complexity and associated costs.

In contrast, the present invention seeks to provide a mobile machine with hydrostatic working load and traction drive, which is simplified in terms of device technology.

This object is achieved by a mobile work machine having the features of patent claim 1.

Advantageous developments of the mobile machine are described in the claims 2 to 9.

A mobile work machine, in particular a truck, has a mechanical drive train for a high-speed driving operation. For a low-speed driving operation and in particular for working drives under difficult ground conditions, it also has at least one hydrostatic drive consumer which can be coupled to the drive train, in particular a hydraulic machine which can be operated as a hydraulic motor. For performing work, the working machine has at least one hydrostatic working consumer, which can be supplied with pressure medium via a hydraulic machine, in particular with an adjustable displacement volume. The hydraulic machine is arranged in the open hydraulic circuit or it is fluid-connectable on its low-pressure side with an open to the atmosphere or with a pressurized pressure medium reservoir or tank of the machine, in particular - connected. According to the invention, the hydraulic machine is also provided for supplying pressure medium to the at least one driving consumer.

In contrast to working machines of the prior art, in which the working consumers and the driving consumers are each supplied by hydraulic pumps - one in the open and the other in a closed circuit - supplied with pressure medium, only one hydraulic pump is provided according to the invention. In addition, with the reduction of a number of hydraulic components can be saved. In total, this results in a lower technical device complexity and lower costs.

In a development, the working machine has a drive machine, in particular a diesel engine, via which the mechanical drive train and advantageously also the hydraulic machine can be driven or are.

In a further development, the working machine has a control unit, via which, depending on a load pressure of the consumer, a working pressure of the Hydraulic machine, in particular by a pressure difference above a highest of the load pressures, is adjustable.

Alternatively or additionally, the control unit is designed in such a way that it can regulate a pressure medium volume flow demanded by the consumers as a function of a load pressure of the consumer.

For detecting and reporting the load or the load pressures to the controller and / or to a pump controller, the machine has in one development, one or more pressure detection units, via which a load pressure or a respective highest load pressure of the consumer can be detected.

The working machine proves to be directly and easily operable for the operator by a further development in which the control unit is designed in such a way that a respective torque and / or torque can be transmitted to it as a function of a speed and / or acceleration request of a setpoint generator which can be operated in particular by the driver a respective speed of the or the driving consumer is controllable.

In a further development for improving cornering, the control unit is configured in such a way that it can be used to adjust the speed requirement with a steering angle and a curve inside of the driving load can be controlled at a lower speed than a curve outside. Thus, a high traction can be achieved even in tight cornering and in principle an active, hydraulic differential can be provided.

In a further development, the working machine has an inlet, via which the hydraulic machine can be fluid-connected with a hydraulic control device, from which a working consumer inlet for supplying pressure to the at least one working consumer and a driving consumer inlet to the pressure medium supply of the at least one driving consumer extend.

In the simplest case, this control device is a simple T or Y piece, thus allowing no controlling intervention, but divides the pressure fluid flow.

In a preferred embodiment, this control device can be controlling, for example, designed as a directional control valve, so that one of the inlets (working or driving consumers) can be throttled and / or shut off.

In a further development, a driving consumer return is provided which extends directly or indirectly from the at least one driving consumer back to the hydraulic control device.

In a further development, the driving consumer return, in particular via the hydraulic control device, with the pressure medium reservoir, in particular throttled, fluidly connected.

In particular, with respect to a small space required a training proves to be advantageous in which the at least one driving consumer is designed as a radial piston machine.

Particularly preferably, the driving consumer is free-running, in order to deactivate the hydrostatic auxiliary drive at a higher speed, for example above 15kmh, and to avoid damage.

The required free-wheeling capability is another reason for the use of a radial piston engine as a driving consumer. This is due to the fact that with this type of device relatively simple means of lifting the working pistons from a working stroke defining control surface (lifting curve or lifting surface) and thus the powerless switching of the hydrostatic driving consumer (freewheeling) is made possible.

In a further development, the working machine has a valve, via which the driving consumer return can be throttled, so that a housing or leak oil pressure can be set or regulated to a value above a pressure of the driving consumer intake on at least one driving consumer. In this way, the said lifting of the working piston of the lift curve and the required "free wheeling", in particular above about 15kmh, can be effected.

In a further development, the working machine has a hydraulic accumulator which can be fluid-connected to the inlet. Thus, it can be filled with pressure medium via the hydraulic machine, in particular with pressure medium overcapacity of the hydraulic machine, whereby pressure medium energy can be stored.

If necessary, in particular for starting a prime mover of the working machine, this pressure medium energy can be recuperated in a preferred development by the hydraulic machine from the control unit in the engine operation is controlled and pressure fluid from the hydraulic accumulator on the hydraulic machine is relaxed.

An embodiment of a mobile working machine according to the invention is shown in a drawing. With reference to the figure of this drawing, the invention will now be explained in more detail.

1 shows a hydraulic circuit diagram of a mobile working machine according to the invention 1 ,

The mobile work machine 1 is, for example, designed as a truck suitable for high speed travel ("on highway"). The truck 1 has an engine designed as a diesel engine 2 to which a switchable multi-speed transmission (not shown) is coupled. The multi-speed gear acts on a drive axle 4 that have two wheels 6 having. The mechanical connection of the gearbox with the axle 4 via a cardan shaft and a differential gear is not shown.

Torque-resistant with the drive machine 2 is a variable in their displacement hydraulic machine 8th connected. This is configured in the embodiment shown as an axial piston machine in swash plate design with swivel plate swivel. The hydraulic machine 8th is arranged in the open hydraulic circuit. A suction connection 10 is for this purpose connected to a designed as a tank T pressure medium reservoir on fluid. With a pressure connection 12 the hydraulic machine 8th is a feed 14 fluidly connected, on the one hand a work consumer unit 16 and on the other hand, a hydrostatic auxiliary drive in the form of a driving consumer unit 18 (HTA) can be supplied with pressure medium.

The working consumer unit 16 has several working consumers, of which 1 only an attachment designed as a loading crane 20 is shown. Furthermore, the work consumer unit 16 a valve control block 22 with several valve sections or discs. Each work consumer is assigned a valve section. The valve section has in a known manner for each consumer an orifice and an associated individual pressure compensator for load pressure independent pressure medium distribution.

Each of the valve sections is via an inlet 24 and a return 26 with the associated hydrostatic working consumer 20 fluid-connected.

The valve control block 22 is via a low pressure line to the tank T pressure medium connected and via a working consumer inflow 28 and a distribution control block 30 with the feed 14 pressure medium connected and supplied with pressure medium.

Each of the wheels 6 is equipped with a designed as a radial piston engine hydraulic machine 32 torque connected. The hydraulic machines 32 have a common feed 34 for supplying pressure medium of high pressure and a common return 36 for removing the pressure medium which has been relieved via it. Intake 34 and return 36 are connected to a valve control block 38 connected. The latter is about a driving consumer inflow 40 and a driver's return 42 with the distributor control block 30 fluidly connected.

In addition, the driving consumer unit has 18 a counter-valve 44 on, via which a respective pressure medium connection of the valve control block 38 with the distributor control block 30 over the inlet 40 and the return 42 controllable, in particular connectable and separable.

For storing hydrostatic pressure medium energy has the mobile machine 1 a hydraulic accumulator 46 that has a control valve 48 with the feed 14 pressure medium is connectable. The hydraulic accumulator 46 can from the hydraulic machine 8th be filled with pressure medium. The pressure medium energy stored in this way can be used to start the engine 2 be used by the pressure medium from the hydraulic accumulator 46 in the hydraulic machine 8th is relaxed during engine operation. As a result, the crankshaft of the prime mover 2 driven and the diesel engine started. In this way, an electric starter can be relieved. In addition, via the hydraulic accumulator 46 the inlet 14 before commissioning of the hydraulic machine or hydraulic pump 8th be placed under working pressure, so that the or the working consumer 20 and the driving consumers 32 without lead time, are immediately ready for use.

The mobile work machine 1 has a load-sensing system through which the hydraulic pump 8th as a function of a load pressure, in particular a highest load pressure of the working consumer or consumers 20 and the driving consumer 32 , is controllable. To tap the highest of the load pressures of the working consumers, the valve control block 22 an electronic pressure detection unit 48 , This detects the one in the valve control block 22 arranged Wechselventilkaskade determined highest of the load pressures of the working consumer and converts it into an electronic signal. The electronic pressure detection unit 48 is via a signal line with a bus system 50 signal-connected. To the bus system 50 is an electronic control unit 52 connected.

Also the hydraulic accumulator 46 has a pressure detection unit 54 that in the hydraulic accumulator 46 prevailing pressure and electronically to the bus system 50 and then the controller 52 reports. Furthermore, the distributor control block has 30 a pressure detection unit 56 as well with the bus system 50 is signal-connected.

To control the or the working consumer 20 the mobile work machine has one or more joysticks 58 , the or the to the bus system 50 is connected or are. To specify a driving speed has the mobile machine 1 an accelerator pedal 60 that to the bus system 50 connected. About this a speed and / or acceleration request of an operator or driver can be specified.

Another sensor is a swivel angle sensor 62 provided via the swivel angle of the hydraulic machine 8th , and thus indirectly their displacement volume, is detectable. Also this registration unit 62 is to the bus system 50 connected.

First, a description of a stand operation, in which only working consumers, such as the loading crane 20 , are operated. Accordingly, via the distributor control block 30 the driving consumer inflow 40 and the driver's consumer return 42 shut off. The pressure medium supply via the hydraulic pump 8th via the inlet 14 , to the distributor control block 30 and about the labor consumer inflow 28 towards the valve control block 22 , About the operation of the joystick or joysticks 58 the operator can the desired working movement, such as the loading crane 20 , pretend electronically. This will be the loading crane 20 in the valve control block 22 assigned metering orifice adjusted in its cross section. Permanent is via the pressure detection unit 48 the highest of the load pressures of the consumers supplied by the valve control block with pressure medium. In the example described, it is assumed that the loading crane 20 the highest pressure is the working load.

In the control unit 52 This electronic signal of the load pressure can be further processed, in particular modified, according to a control strategy stored there for execution. In the embodiment shown is done in the control unit 52 depending on the speed of the loading crane 20 , and thus its pressure medium volume flow, an impact of a differential pressure on the reported load pressure signal. The thus increased, resulting electronic signal is transmitted via a signal line 64 to the control valve 48 reported. Based on this electronic signal, the pressure in the control line 66 set so that a pump regulator (not shown) located on the pump, the displacement volume of the hydraulic pump 8th adjusted by an adjustment such that the pressure in the inlet 14 is controlled to the load pressure plus the corresponding differential pressure.

In a low speed operation mode, both the work consumer unit 16 , as well as the driving consumer unit 18 active, that is via the hydraulic pump 8th supplied with pressure medium. In addition to setpoint specifications for the working consumers of the working consumer unit 16 about the joystick (s) 58 now takes place via the accelerator pedal 60 also a setpoint specification for an acceleration or speed of the wheels 6 , This is done via a signal line 66 depending on the position of a direction switch (not shown) the information which direction is desired. Accordingly, the distribution control block controls 30 the pressurization of the pressure medium lines 40 . 42 , with working pressure or low pressure, as a result of which the assignment as inlet and return can change depending on the direction of travel. A the inflow 40 and return 42 associated spool of the distributor control block 30 is completely open, only his position determines the direction of travel.

Via the valve control block 38 and the inflow 34 the pressure medium flows with the approximately in the inlet 14 Pending working pressure to the radial piston motors 32 ,

About the accelerator pedal 60 the operator is given a desired acceleration. From the control unit 52 a corresponding torque is determined as a function of the accelerator pedal position. From this is via the control unit from the displacement volume of the radial piston 32 dependent, necessary working pressure in the inflow 14 determined. Accordingly, the controller sends 52 over the signal line 64 an electronic signal to the control valve 48 which is the hydraulic pump 8th to the desired pressure, and thus the torque at the radial piston engines 32 , regulates.

In a driving operation, the mobile work machine 1 from the hydrostatic drive unit 18 be driven alone or with the support of said mechanical drive train or by the mechanical drive train alone.

The 1 shows a "One Fits All" solution where different hydraulic units 16 . 18 - the one of the working consumers 16 and the one of the driving consumers 18 - by a common hydraulic pump 8th be supplied with pressure medium.

The hydraulic pump 8th is arranged in the open hydraulic circuit and can be operated pressure-controlled and / or volume flow controlled.

In particular, the mobile work machine 1 a commercial vehicle, the working consumers represent a body hydraulics.

Due to the realization of the hydrostatic drive shown, more precisely, the pressure medium supply of the driving consumer unit 18 by a hydraulic pump arranged in an open hydraulic circuit 8th , offer new ones Possibilities of extending the hydraulic actuators of the working consumer with the known behavior of a hydrostatic auxiliary drive in a closed circuit.

With the solution shown is a torque control for the hydrostatic drive consumer unit 18 or realized the hydrostatic auxiliary drive in the open hydraulic circuit.

Until now, hydrostatic auxiliary drives, for example in construction machines or excavators, have been operated in an open circuit, as a rule by means of hydraulic load sensing. Thus, the hydraulic pump could only react to a hydraulically tapped from the drive and hydraulically reported load pressure and provide the requested by the metering orifices volume flow. This corresponded to a volume flow control.

With the invention of the electronic control unit 52 controlled hydraulic pump 8th in the open hydraulic circuit is now an electronic load-sensing, so that in the inlet 14 provided working pressure can be adjusted individually and thus in the case of active, hydrostatic drive 18 a torque on the axle 4 can be actively made.

Disclosed is a mobile machine with a hydrostatic working load or attachment and a hydrostatic drive consumer or hydraulic motor, both consumers of the same, operated in an open hydraulic circuit, hydraulic pump can be supplied with pressure medium.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 20180065479 A1 [0004]

Claims (9)

Mobile working machine with a mechanical drive train and at least one hydrostatic driving consumer (32) coupled thereto, and with at least one hydrostatic working consumer (20) and a hydraulic machine (8) for supplying pressure medium to a pressure medium reservoir (T) of the working machine (1) and the at least one working consumer (20) is fluid-connectable, characterized in that the hydraulic machine (8) is also fluid-communicable with the at least one driving consumer (32) to the pressure medium supply. Working machine after Claim 1 with a control unit (52), via which a working pressure of the hydraulic machine (8) can be regulated as a function of a load pressure of the load (20, 32), and / or wherein a pressure medium volume flow of the hydraulic machine (20, 32) is dependent on a load pressure of the load (20, 32) 8) is adjustable. Working machine after Claim 1 or 2 with a control unit (52) via which a respective torque and / or a respective speed of the driving consumer (32) or of the plurality of driving consumers (32) can be regulated as a function of a speed and / or acceleration request of a setpoint generator (60). Work machine according to one of the preceding claims with an inlet (14), via which the hydraulic machine (8) with a hydraulic control device (30) is fluid-connected, of which a Arbeitsverbraucherzulauf (28) for supplying pressure to the at least one working consumer (20) and a Fahrverbraucherzulauf (40) for pressure medium supply of the at least one driving consumer (32) extend. Working machine after Claim 4 with a driver return (42), which extends directly or indirectly from the at least one driving consumer (32) to the hydraulic control device (30). Working machine after Claim 5 , wherein the driving consumer return (42), in particular via the hydraulic control device (30), with the pressure medium reservoir (T) is fluid-connectable. Work machine according to one of the preceding claims, wherein the at least one driving consumer is a radial piston machine (32). Working machine at least after Claim 5 or 6 with a valve (44), via which the driving consumer return (42) can be throttled, so that at least one driving consumer (32) a leakage oil pressure to a value above a pressure of the driving consumer inlet (40) is adjustable or adjustable. Work machine according to one of the preceding claims with a hydraulic accumulator (46) which is fluid-connectable to the inlet (14) and can be stored via the hydraulic energy and, if necessary, in particular for starting a drive machine (2) of the working machine (1), recuperatable ,

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