WO2019170345A1

WO2019170345A1 - Drive for a machine

Info

Publication number: WO2019170345A1
Application number: PCT/EP2019/052823
Authority: WO
Inventors: Jürgen LEGNER
Original assignee: Zf Friedrichshafen Ag
Priority date: 2018-03-09
Filing date: 2019-02-06
Publication date: 2019-09-12
Also published as: CN111836933A; DE102018203624A1; CN111836933B

Abstract

A drive for a wheel loader has a first electric motor (3) for driving the vehicle wheels (5) and a second electric motor (4) for driving a pump (6) for the work attachment (7). The first electric motor (3) and the second electric motor (4) are controlled depending on a signal relating to the position of an accelerator pedal, the torque of the first electric motor (3) being directly dependent on the position of the accelerator pedal when the vehicle is at a standstill.

Description

Drive for a working machine

The invention relates to a drive of a working machine such as a wheel loader according to the closer defined in the preamble of claim 1.

Generic drives have an electric motor which drives the vehicle wheels.

US 2015/0197239 A1 and EP 31 30 708 A1 disclose a wheel loader with an electric motor for driving the vehicle wheels.

The present invention has for its object to further improve the drive for a work machine with an electric motor for driving the vehicle wheels.

The problem is solved by a generic drive having the characterizing features of the main claim.

According to the invention, the drive has a computing unit which can receive signals from an accelerator pedal and which drives a first electric motor for driving the vehicle wheels. Furthermore, the arithmetic unit controls a further motor, which is suitable for driving a working equipment, for example by the drive of a hydraulic pump. There is the possibility that this further motor is a second electric motor. However, there is also the possibility that this further engine is a different type of engine. In the following, however, only the term second electric motor will be used for the sake of simplicity.

By means of the arithmetic unit, the first electric motor for driving the vehicle wheels and the second electric motor for driving the working equipment can be controlled separately from one another. This makes it possible to control a work machine such as a wheel loader so that it has a similar ride as today's diesel engine-driven wheel loader. This makes it possible to use a purely electric machine, without the driver of a diesel engine driven working machine has to get used.

The working machine can draw the energy from a battery. However, there is also the possibility that the work machine has a fuel cell or other electrical energy sources such as a connection to a network by means of a cable. This makes it possible to operate the machine purely electrically.

In the driver's cab of the wheel loader, an accelerator pedal is arranged, which outputs a signal to the arithmetic unit. When the accelerator pedal is not actuated, it is possible to output a signal with 0%; with the accelerator pedal fully depressed it is possible to output a signal with 100%. Furthermore, a brake pedal is arranged to brake the vehicle. The brake pedal also outputs a signal to the arithmetic unit. In the first pedal stroke of the brake pedal, the brake pedal outputs a signal in order not to brake the vehicle by means of the service brake, but a so-called inching operation is to be activated. In inching mode, the speed of the motor for driving the work equipment should be increased and the torque on the vehicle wheels should be reduced. Furthermore, the wheel loader on a multi-function lever, by means of which the operation of the working equipment, such as the Hub ... and the bucket is possible and the direction of travel can be set and a driving range, for example, a fast driving range and a slow driving range is selectable. The vehicle further includes a neutral switch and a parking brake operation.

In order to design the electric work machine in behavior as a diesel engine work machine, the first electric motor should be controllable in response to the signal of the position of the accelerator pedal. For this purpose, the accelerator pedal to an analog sensor, which detects the position of the accelerator pedal and used as a default for the speed and torque of the first electric motor becomes. In this case, an additional memory unit is present, in which a map is stored with characteristics in which the torque of the first electric motor and the rotational speed of the first electric motor are stored to a plurality of pedal positions of the accelerator pedal. The characteristics are designed so that when the first electric motor is stopped, the torque varies depending on the pedal position. This is possible, for example, in that the maximum torque corresponds to the maximum actuated accelerator pedal and no torque corresponds to a non-actuated accelerator pedal. Now, the torque can be linearly associated with the change of the accelerator pedal.

This makes it possible to allow the wheel loader a driving behavior in which the wheel loader can be brought to fill the blade to its traction limit of the wheels by changing the position of the accelerator pedal.

Likewise, it is necessary for the characteristic curve to which an accelerator pedal position is assigned to have a defined maximum speed which can not be reached with any torque. As a result, it is possible to keep the speed by means of the accelerator pedal even when the vehicle is moving in such a terrain in which the vehicle requires no torque.

If the vehicle is in overrun mode, advantageously a limited torque is predetermined in order to map the driver to a known coasting or braking behavior. Since in today's internal combustion engine drives, the braking torque is significantly smaller than the drive torque, the drive and thus the first electric machine should always be transferred to overrun when the maximum speed at torque 0 is exceeded with the appropriate pedal position of the accelerator pedal. The braking torque should increase with increasing speed in a gradient up to a defined level and remain almost constant even with further increasing speed. The maximum braking torque is preferably predetermined independently of the pedal position of the accelerator pedal. There is also the possibility to increase the braking torque with less pedal operation of the accelerator pedal and specify the brake torque lower with strong pedal operation of the accelerator pedal. If the vehicle has a selector switch for a fast driving range and a slow driving range, then in the fast driving range the maximum rotational speed of the first electric motor is only limited at very high, namely the technically meaningful maximum rotational speed. When selecting the slow driving range, the speed is limited significantly earlier depending on the position of the accelerator pedal. For this purpose, the accelerator pedal position is divided 0 to 100% to a speed range of the first electric motor, wherein the maximum speed in the slow driving range, for example, one third of the maximum speed of the fast driving range can correspond.

To optimally use the vehicle in inching mode, the vehicle has a brake pedal next to the accelerator pedal. In inching mode, the power from the first electric motor is reduced and the power of the second electric motor is increased. The brake pedal has an analog sensor which outputs a signal depending on the position of the brake pedal. This signal is used as a default for reducing the speed and torque of the first electric motor for ferry operation. In the first part of the brake pedal operation, the service brake is not activated. The sensor signal is thus used in this part for the inching operation, the reduction of the speed and the torque of the first electric motor and the increase of the power of the second electric motor.

If the brake pedal is pressed further, the service brake is additionally actuated.

In a further embodiment, the second electric motor, which drives the actuation of the working equipment, is controlled in dependence on the signal of the accelerator pedal. It is possible to control the second electric motor not only as a function of the accelerator pedal signal, but also as a function of the rotational speed of the first electric motor. The working equipment may be, for example, the lifting and bucket movement, which can be activated with a multi-function lever. It is possible to use the second electric motor to drive hydraulic pumps which act on cylinders of the working equipment. These hydraulic pumps can be designed as constant pumps, thus pumps with constant displacement volume, but it is also possible to use pumps with adjustable displacement. When using pumps with a constant displacement volume, the speed of the second electric motor determines the delivery volume. The second electric motor should be controlled so that without actuation of the accelerator pedal, the second electric motor has a minimum speed, whereby a minimum volume flow can be conveyed in order to perform steering movements even when the vehicle is stationary. The pump, which is connected to the second electric motor, in this case promotes pressure medium to a steering valve, which acts on actuators for the steering with pressure medium.

If the accelerator pedal is actuated, a speed specification for the first electric motor is output via a characteristic which is stored in a memory unit. The more the accelerator pedal is actuated, the higher the speed of the first electric motor should be. The speed of the second electric motor is limited depending on the speed of the first electric motor. At low speed of the first electric motor, the speed of the second electric motor must be possible up to the maximum speed. At higher speed of the first electric motor, the speed of the second electric motor can be reduced, since in this case the vehicle has a higher speed and thus the work equipment, such as the lifting or blade hydraulics, does not have to be moved quickly. However, a minimum speed for the steering of the vehicle must be maintained, so the speed of the second electric motor must not fall below a minimum speed. By limiting the speed of the second electric motor, the efficiency is improved.

Preferably, constant displacement pumps driven by the second electric motor are used for lower power work machines. Heavy duty machines use adjustable pumps, which are preferably used in combination with a Loud Sensing System. In the case of the Loud Sensing System, several consumers The highest load pressure and the pump pressure of a pressure layer are used to adjust the pump. The pump only delivers as much as the driven consumers need in total. The pump pressure always corresponds to the highest load consumer. If no consumer is activated, the pump only delivers the leakage oil flow.

In another embodiment, this pump, which can be adjusted in its stroke volume, has a sensor by means of which the current delivery volume of the pump can be detected. This signal is used for the speed specification of the second electric motor. Here, the sensor signal is calibrated and interpreted. The signal can take values between 0% and 100%. The speed of the second electric motor can now be adjusted depending on the signal of the sensor to the corresponding needs. If no work function is actuated, for example, the cylinders of the hoist not controlled, the sensor signal of the adjustable pump is almost 0. In this state, the speed specification for the second electric motor is controlled to a lower limit. Now, if the consumer is controlled, for example, actuates the hoist, so reports the Loud Sensing System of the work pump a funding requirement and the work pump will increase its flow and the sensor signal will increase. The term working pump is hereby referred to as the adjustable pump, which is connected to the second electric motor. If the available flow rate of the working pump increases beyond the required level, this is detected by a falling sensor signal from the working pump. Another speed increase does not make sense. Therefore, the second electric motor is driven so that it no longer increases its speed. When the threshold value is not reached, the speed specification for the second electric motor is reduced to the lower limit value by means of a control algorithm. The lower limit is defined by a minimum volume flow, for example for the steering. In order to stabilize the speed specification for the second electric motor, a hysteresis between increasing and decreasing sensor signal is present. In addition, the change of the sensor signal over time can be used for the speed specification of the second electric motor. A strongly rising or falling signal can influence the dynamics of the speed specification.

In another embodiment, there are sensors on the work equipment, such as the hoist and the bucket. It is also possible, by one or more sensors in the multi-function lever, by means of which the hoist is controlled to detect an actuation of the hoist or the blade. Depending on the operation of the hoist, the speed of the second electric motor will be adjusted as needed.

Here, the dependence of the speed specification of the second electric motor to the accelerator pedal position and the speed of the first electric motor remain. This dependence is superimposed on the sensor information which detects an actuation of the hoist and the bucket thus the work equipment.

The sensors in the multi-function lever or in the hoist and the bucket generate a proportional signal according to the operation of the hoist and the bucket. These sensor signals are calibrated and interpreted. Both signals can take values between -100% and + 100%. For the lifting movement, the sensor signal is calibrated for maximum lowering to -100% and for maximum lifting to + 100%. For the blade movement, a sensor signal of -100% means a maximum tilting of the blade and + 100% a maximum tip-in of the blade. If the multi-function lever is not actuated, ie no movement is requested for the hub and the bucket, then the sensors each deliver a signal of 0%. The speed specification for the second electric motor should each use the largest amount of the two sensor signals. If the signal from the sensors is 0%, no actuation of the work function is provided, whereby the speed specification for the second electric motor is controlled to a lower limit. If the sensor detects that the hoist is to be moved, the speed of the second electric motor is increased as a function of the signal of the sensor. In order to drive the first electric motor and the second electric motor, the first electric motor and the second electric motor each have power electronics, which is arranged immediately adjacent to the first electric motor and the second electric motor. The power electronics of the first electric motor and the power electronics of the second electric motor are connected via a CAN bus system with a vehicle computer, also called arithmetic unit. There is the possibility that additionally a display is connected via the CAN. The vehicle computer receives signals from a brake pedal, an accelerator pedal, a parking brake switch, and a travel direction switch, a vehicle speed switch between a fast and a slow vehicle speed, and a neutral position switch. When using adjustable working pumps, which are connected to the second electric motor, the vehicle computer can also receive a signal from a sensor on the position of the stroke volume of the working pump.

The power supply is via a battery. However, it is also possible to form the power supply via an internal combustion engine which drives a generator, and it is possible to supply the vehicle with energy by means of a connection to a stationary power grid. There is also the possibility that a combination of these power supplies exists.

The arithmetic unit is according to the operating strategy setpoints for the speed and the maximum torque to the power electronics of the first electric motor and to the power electronics of the second electric motor. The power electronics themselves regulate the two electric motors according to the specifications. The actual values of the rotational speed and of the torque as well as the operating states of the two electric motors are reported back to the arithmetic unit. As a result, standard power electronics can be used, which only have so much computing power that they can operate the electric motors. The arithmetic unit needs no additional outputs, but only inputs and communication via the CAN. This is very inexpensive. Further features can be found in the description of the figures.

Show it:

Fig. 1 is a wheel loader

2 is a diagram of the drive of the wheel loader,

3 shows a characteristic diagram for controlling the first electric motor for a fast driving range,

4 is a map for driving the first electric motor for a slow driving range,

5 shows a characteristic curve when the brake pedal is actuated,

Fig. 6 is a characteristic for controlling the speed of the second electrical

Motors,

7 shows a characteristic curve for controlling the second electric motor,

Fig. 8 is a characteristic for driving the second electric motor and

Fig. 9 is a characteristic for controlling the second electric motor in response to the signal of the accelerator pedal and the multi-function lever.

Fig. 1:

A wheel loader 1 has a battery 2, which provides the energy for the first electric motor 3 and the second electric motor 4. The first electric motor 3 drives the vehicle wheels 5. It is possible to use a plurality of electric motors instead of a first electric motor 3. The second electric motor 4 drives a pump 6, which is also called a work pump and the cylinders of the lifting mechanism 7 and the steering of the wheel loader 1 supplied with pressure medium. The pump 6 may be designed for vehicles with lower power than pump with constant displacement, in this case, more constant pumps can be used. For vehicles with greater power, it is also possible to form the pump 6 as one or more pumps with adjustable delivery. These variable displacement pumps are often designed as Loud Sensing pumps.

Fig. 2:

The energy of the battery 2 is supplied via the power electronics 8 to the first electric motor 3. The energy of the battery 2 is supplied via the power electronics 9 to the second electric motor 4. The second electric motor 4 drives the pump 6, which is designed to be adjustable in its stroke volume. The first motor 3 drives not shown vehicle wheels. About valves 10 actuators 1 1 of the work equipment or the steering can be controlled. In order to detect the current displacement of the pump 6, a sensor 12 is connected to the pump 6.

Via lines 13, for example by means of CAN, the battery 2, the power electronics 8, the power electronics 9, the sensor 12 and a display 14, on which the direction of travel, the speed, the driving range and other vehicle states are displayed, with a computing unit 15, which is also called vehicle computer connected. The arithmetic unit 15 receives signals from a sensor of the brake pedal 16, a sensor of the accelerator pedal 17, a switch for the parking brake 18 and multiple switches and / or sensors in a multi-function lever 19, by means of which the speed range of a neutral function and other functions, such as the operation the actuators 1 1 of the working equipment, such as the bucket or the hoist, are controllable. It is possible to form the functions of the multi-function lever 19 in a lever. However, it is also possible to form the individual sensors and switches in several switches and levers.

If, for example, the accelerator pedal 17 is actuated, then the arithmetic unit 15 generates a signal for the first electric motor 3. In the arithmetic unit 15 is also a Store memory unit within which the characteristics, which are described in the other figures, are stored. On the basis of the signals which the arithmetic unit 15 receives and the stored characteristic curves, the arithmetic unit 15 calculates a pre-signal which the arithmetic unit 15 outputs via the line 13. This makes it possible to form the power electronics 8 and the power electronics 9 so that they must be able to control only the first electric motor 3 and the second electric motor 4.

When using the pump 6 as a load sensing pump, it is possible to determine by means of a sensor, the Vestellung the stroke volume of the pump 6.

With a load sensing system, the highest load pressure and the pump pressure of a pressure compensator are used to adjust the pump for several consumers. The pump only delivers as much as the driven consumers need in total. The pump pressure always corresponds to the highest load consumer. If no consumer is activated, the pump 6 promotes only the leakage oil flow.

With the sensor on the adjustment of the pump 6, the current delivery volume of the pump can be detected. This signal is now used for the speed specification of the second electric motor 3. The sensor signal is calibrated and interpreted. The signal can take values between 0% to 100%. By using this sensor to the adjustment of the pump 6, the speed of the second electric motor 4 and thus the speed of the pump 6 can be adjusted according to the needs and thus make more efficient.

If no operation of the working equipment 1 1 takes place, the sensor signal of the adjustment of the pump 6 will be almost 0%. In this state, the speed command for the second electric motor 4 is controlled to a lower limit. Now, if a consumer, thus the work equipment 11 is controlled, the load sensing system of the pump 6 reports a delivery requirement and the pump 6 will increase its delivery and the sensor signal will increase. For the speed specification of the second electric motor 4, a threshold value for the sensor signal is defined. niert, in which the pump 6 is almost completely swung out, for example, 95%. If this threshold is exceeded, this is interpreted as insufficient flow and therefore increases the speed specification for the working drive to the maximum value.

If the available flow rate increases beyond the required level, this is detected by a falling sensor signal from the working pump. Another speed increase does not make sense. When the threshold is undershot, the speed specification for the second electric motor 4 is reduced to the lower limit value by means of a control algorithm.

In addition, a hysteresis is used to stabilize the speed command by this threshold.

It is also possible to use the change of the sensor signal over time for the speed specification of the second electric motor 4. A strongly rising or falling signal can influence the dynamics of the speed specification.

3:

In the arithmetic unit 15 of FIG. 2 characteristic curves are stored, which map a fast driving range and a slow driving range. The diagram shown in FIG. 3 depicts the fast driving range. In order for the driver of the wheel loader to be able to control the torque at the vehicle wheels when entering the pile until the vehicle is stationary when the vehicle is stationary, it is necessary to limit the torque of the first electric motor as a function of the position of the accelerator pedal. This makes it possible to generate a defined torque for each position of the accelerator pedal when the vehicle is stationary at the vehicle wheels, whereby the driver can steer the vehicle to the traction limit via the accelerator pedal. For this purpose, the position of the accelerator pedal is determined by means of a sensor, wherein, when the accelerator pedal is not actuated, the sensor outputs a signal which corresponds to the accelerator pedal signal 20 of 0%, and when fully accelerated. tigtem accelerator pedal, the sensor outputs a signal corresponding to the accelerator pedal signal 20 of 100%. The characteristics of FIG. 3 are entered in a Cartesian coordinate system, wherein the coordinate depicts the torque 21 of the first electric motor and the abscissa represents the rotational speed 22 of the first electric motor. By forming points of intersection of individual characteristic curves, which may for example be uniformly distributed, once at the speed 0 from the torque 0 23 to the maximum torque 24 above the accelerator pedal signal 20 = 100%, intersections 25 are generated which are associated with a defined pedal position of the accelerator pedal. For example, it is possible to generate these intersections with a certain number of characteristics, for example 0%, 25%, 50%, 75% and 100%. The linear distribution is only an example, it is also possible to create a non-linear distribution. The intermediate values between the characteristic curves are then interpolated. Thus, it is possible to generate a torque at the vehicle wheels at standstill of the vehicle to each accelerator pedal position. At the speed 22 of the first electric motor is moved in the same way, which also points of intersection with the abscissa at 0 torque are generated. So that the vehicle does not come above the maximum permissible speed, the speed 22 of the first electric motor is limited to a maximum speed 26. This makes it possible to regulate the speed of the vehicle by means of the accelerator pedal with very little or no torque. Subsequently, the diagram is created so that first the maximum possible power as a function of the accelerator pedal position is plotted. The maximum power is shown in line 27. In the other lines, the intersections of the ordinate are connected to the intersections of the abscissa.

The diagram shown shows only one quadrant of possible operation of the first electric motor. In this quadrant the train area and the direction of rotation are shown forward. A similar or mirrored characteristic curve can also be used backwards in the opposite direction of rotation. In overrun advantageous a limited torque is given to represent a usual coasting or braking behavior. In today's internal combustion engine drives, the braking torque is significantly smaller than the drive torque. The drive should only go into push mode when the intersection of the speed is exceeded at 0 torque and corresponding pedal position. The generated braking torque should rise with increasing speed in a gradient up to a defined level and remain almost constant even with further increasing speed. The maximum braking torque can be set constant and independent of the pedal position or be set higher with low pedal operation and lower with strong pedal operation.

It is also possible to design the vehicle with only one driving range, in which case the diagram is used for the fast driving range. When using an additionally slow driving range, an additional diagram corresponding to FIG. 4 is formed.

4:

The slow driving range shown in Fig. 4 is required for positioning maneuvers, such as working with a fork, with a fine accelerator pedal resolution. The term fine accelerator pedal resolution means here that the final speed in the slow driving range is reached only when the accelerator pedal is fully actuated and not in the first third of the actuation of the accelerator pedal, as in the fast driving range. The points of intersection 25 of the respective maximum torque at the speed 0 are identical to the points of intersection 25 of the fast driving range of FIG. 3. The maximum speed 26, however, is significantly reduced compared to the maximum speed 26 of FIG. However, the maximum speed 26 of FIG. 4 is also reached only at 100% of the accelerator pedal signal 20. As a result, the interfaces of the respective maximum rotational speed of the first traction motor are scaled at torque 0 to lower rotational speeds.

Fig. 5:

In order to also be able to represent an inching function, the signal of the brake pedal is processed in addition to the signal of the accelerator pedal. This makes it possible to operate the vehicle in inching mode, that is, the power and thus the torque and reduce the speed of the first electric motor and the power, thus the speed and the torque, for the second electric motor and thus the pump 6 of Figure 2 for the work equipment, thus the steering and / or lifting and rotating of the blade, to increase. For this purpose, the brake pedal position via a sensor, preferably an analog sensor, detected and used as a default for the reduction of the speed and torque, thus the power of the first electric motor for the travel drive.

For this purpose, the current value of the signal 20 of the accelerator pedal between 0 and 100% is listed on the ordinate of FIG. 5 and on the abscissa is the signal of

Brake Pedal 28 listed from 0 to 100%. If the brake pedal is not actuated, the signal of the accelerator pedal is not reduced. When fully depressed accelerator pedal, thus at 100%, and not actuated brake pedal the signal of the accelerator pedal 20 thus remains the same. The more the brake pedal is pressed, the more the signal of the accelerator pedal is reduced. In the first part 29 of the brake operation, the service brake is not activated, but reduces the power for the first electric motor by using the characteristic curve 30, the signal of the accelerator pedal is reduced, and thus the first electric motor is driven with a lower target signal. Thus, the speed specification for the first electric motor with constantly depressed accelerator pedal and increasing depressed brake pedal is always reduced. The characteristic curve 30 is designed in such a way that when the accelerator pedal is fully depressed, the signal of the accelerator pedal is already greatly reduced when the brake pedal is pressed only slightly. If the accelerator pedal is only slightly activated, the brake pedal must be pressed very far in order to reduce the signal of the accelerator pedal. From a previously defined actuation path of the accelerator pedal, the service brake is additionally activated. At point 31, the characteristic 30 intersects the abscissa, which means that the accelerator pedal is not actuated, this point 31 either being coincident with the actuation travel at which the service brake is actuated, or shortly after this actuation travel of the brake pedal to ensure appropriate overlap. By the characteristic curve 30, the accelerator pedal signal is reduced in accordance with the operation of the brake pedal, there is a change in the control of the first electric motor with respect to its speed and its torque. Fig. 6:

However, in order not only to control the first electric motor in response to the operation of the brake pedal, it is necessary to also control the second electric motor. For this purpose, the vehicle has a multi-function lever in the driver's cab, by means of which the working equipment, for example, the lifting and blade movement is controllable. The characteristic shown in Fig. 6 is used for the second electric motor with one or more pumps with constant displacement. In this embodiment, the delivery volume is determined solely by the speed of the second electric motor. When using multiple pumps, for example, a pump for the articulation of the wheel loader and a second pump for the work equipment may be present. The direct control of the second electric motor allows by controlling the speed of the second electric motor to adjust the flow rate to the required work situation. In conventional wheel loaders with an internal combustion engine, the pump is directly connected to the internal combustion engine, whereby a free control of the pump is not possible.

The control of the rotational speed of the second electric motor should be effected in dependence on the accelerator pedal signal and in dependence on the rotational speed of the first electric motor. On the ordinate in Fig. 6, therefore, the speed of the second electric motor is shown and in the abscissa, the operation of the accelerator pedal or the accelerator pedal signal is shown. In point 32, the accelerator pedal is not actuated, causing the vehicle is at a standstill. However, since steering movements must be possible in this standstill, the second electric motor is driven at a minimum speed as shown in point 32. As the accelerator pedal signal increases, the speed specification for the second electric motor is increased up to the maximum speed 34 via the characteristic curve 33. To limit the maximum speed 34 of the second electric motor, a second dependence on the speed of the first electric motor is used. If the first electric motor is at low speed, thus the vehicle is moving at low speed, the speed of the first electric motor must be able to reach the maximum speed his. At higher speed of the first electric motor and thus higher driving speed of the vehicle, it is possible to reduce the speed of the second electric motor. This is because hydraulics for the bucket and hoist do not have to be moved quickly at higher speeds. It is essential, however, that a minimum speed for the steering is maintained. By lowering the rotational speed of the second electric motor as a function of the rotational speed of the first electric motor and thus as a function of the driving speed, the efficiency of the system is increased. The reduction in the rotational speed of the second electric motor as a function of the rotational speed of the first electric motor is shown in FIG. 7.

Fig. 7:

The speed of the second electric motor is plotted on the ordinate and the speed of the first electric motor is indicated on the abscissa. Up to point 35, the vehicle is still at low driving speeds and the maximum possible speed of the second electric motor, which is represented by the characteristic curve 36, is not reduced. The line 37 shows the maximum speed of the first electric motor or the maximum driving speed in the slow driving range and the line 38 shows the maximum possible speed of the first electric motor or the maximum driving speed of the vehicle in the fast driving range. The speed of the second electric motor is reduced to the point 39 to ensure a sufficient flow rate for the steering.

Fig. 8:

When using additional sensors either directly on the hoist or the blade or on the multi-function lever, by means of which the hoist and the blade can be controlled, the speed of the second electric motor can be further adjusted according to demand. Here, the dependencies of the speed specification for the second electric motor for accelerator pedal position and the speed of the first electric motor remain. additionally However, the information of the sensors of the operation of the hoist and the blade is used. These sensors provide a signal according to the operation, which may be, for example, a proportional signal. These sensor signals are calibrated and interpreted. Both signals can take values from -100% to + 100%, for which the sensor signal for maximum lowering can be calibrated, for example, to -100% and calibrated to 100% for the maximum lifting of the lifting movement. For the blade movement, a sensor signal of -100% means a maximum tilting of the blade and a sensor signal of + 100% a maximum tip-in of the blade. If the multi-function lever is not actuated, thus no movement of the working equipment or the hoist and the bucket is requested, the sensors each deliver a signal of 0%. For the speed specification of the second electric motor in each case the largest amount of the two sensor signals should be used. Fig. 8 shows the dependence of the speed command for the second electric motor on the speed of the first electric motor and the signal of the sensors of the work equipment. On the ordinate here the speed of the second electric motor is plotted and on the abscissa the speed of the first electric motor is plotted. Line 40 shows an increase in the speed of the second electric motor while reducing the speed of the first electric motor. The line 37 here is the maximum achievable speed of the first electric motor in the slow driving range and the line 38 is in this case the maximum achievable speed of the first electric motor in the fast driving range. The characteristic 36 with the points 35 and 39 corresponds to the characteristic curve 36 of FIG. 7. This speed is now reduced depending on the sensor signal of the lifting equipment to the line 40. This is shown by the arrow 41.

Fig. 9:

In Fig. 9, the reduction of the rotational speed of the second electric motor in response to the sensors of the working equipment is shown as described in Fig. 7. The diagram corresponds to the diagram of FIG. 6 and the arrow 42 shows that the speed of the second electric motor in dependence the signals of the sensors of the working equipment reduced. It is only possible to reduce the speed of the second electric motor to line 43.

Wheel loader reference

battery

first electric motor

second electric motor

vehicle wheels

pump

hoist

power electronics

valves

actuators

sensor

management

display

computer unit

brake pedal

accelerator

parking brake

Multi-function lever

Accelerator pedal signal

torque

number of revolutions

Torque 0

maximum torque

intersection

Maximum speed

line

Brake pedal signal

first part

curve

Point Point

curve

Maximum speed

Point

curve

line

Point

line

arrow

line

Claims

claims

1. drive for a work machine, wherein the drive has a computing unit, by means of which a first electric motor (3) for driving the vehicle wheels (5) and a second electric motor (4) for driving a working equipment (1 1) is controllable, wherein the arithmetic unit processes a signal which corresponds to a position of an accelerator pedal (17) and the first electric motor (3) and the second electric motor (4) can be controlled separately from one another and the first electric motor (3) as a function of the signal of the position of the Accelerator pedal (11) is controllable.

2. Drive according to claim 1, characterized in that stored in a memory unit characteristics for a fast driving range from standstill of the working machine to the maximum speed of the machine, each characteristic of a position of the accelerator pedal (11) and images of each characteristic a speed for the first electric motor (3) as a function of the torque of the first electric motor (3) can be derived.

3. Drive according to claim 2, characterized in that each characteristic is formed so that at standstill of the first electric motor (3) each characteristic is associated with a torque, wherein the fully actuated accelerator pedal (1 1) stored at standstill of the first electrical Engine (3) outputs the maximum achievable torque and with less actuated accelerator pedal (1 1) stored characteristic at standstill of the first electric motor (3) outputs a lower torque, each with a low accelerator pedal and the output torque is reduced.

4. Drive according to claim 2, characterized in that each characteristic is formed so that in a state in which the first electric motor (3) no torque outputs, each characteristic outputs a rotational speed of the first electric motor (3), wherein the with fully actuated accelerator pedal (1 1) stored characteristic outputting the maximum achievable speed and the stored at less actuated accelerator pedal outputs a lower speed.

5. Drive according to claim 1, characterized in that stored in a memory unit characteristics for a slow driving range from standstill of the working machine to a speed which is less than the maximum speed of the working machine, each characteristic a position of the accelerator pedal (1 1 ) and thereby from each characteristic a speed for the first electric motor (3) in dependence of a torque of the first electric motor can be derived.

6. Drive according to claim 5, characterized in that each characteristic is formed so that at standstill of the first electric motor (3) each characteristic is associated with a torque, wherein the fully actuated accelerator pedal (1 1) stored characteristic at standstill of the first electric Engine (3) outputs the maximum achievable torque and with less actuated accelerator pedal (1 1) stored characteristic at standstill of the first electric motor (3) outputs a lower torque, each with a low actuated accelerator pedal (1 1) and the output torque itself reduced.

7. Drive according to claim 5, characterized in that each characteristic is formed so that in a state in which the first electric motor (3) outputs no torque, each characteristic outputs a speed of the first electric motor, wherein the fully actuated accelerator pedal (1 1) stored characteristic curve outputs a speed which is smaller than the maximum achievable speed in the fast driving range and the characteristic stored at less actuated accelerator pedal outputs an even lower speed.

8. Drive according to claim 1, characterized in that the arithmetic unit processes a signal of a position of a brake pedal (16), wherein in dependence of the signal of the position of the brake pedal (16) the signal of the position of the accelerator pedal (1 1) is changed so that when the brake pedal (16) is pressed, the signal of the accelerator pedal (1 1) corresponds to a position of the accelerator pedal (1 1) which is smaller than the position of the accelerator pedal (1 1) when the brake pedal (16) is not actuated.

9. Drive according to claim 1, characterized in that the rotational speed of the second electric motor (4) in dependence on the rotational speed of the first electric motor (3) is controllable.

10. Drive according to claim 1, characterized in that the rotational speed of the second electric motor (4) in dependence of the position of the accelerator pedal (1 1) is controllable.

1 1. Drive according to claim 10, characterized in that the rotational speed of the second electric motor (4) at nichtbetätigtem accelerator pedal (1 1) is greater than 0.

12. Drive according to claim 10, characterized in that the rotational speed of the second electric motor (4) at a rotational speed of the first electric motor (3) between greater than 0 and the maximum achievable speed of the first electric motor (3) is driven so that the maximum speed of the second electric motor (4) is not reached.

13. Drive according to claim 10, characterized in that the rotational speed of the second electric motor (4) at a rotational speed of the first electric motor (3) between 0 and a speed below the maximum achievable speed of the first electric motor (3) is so controlled in that the maximum speed of the second electric motor is reached.

14. Wheel loader with a first electric motor (3) and a second electric motor (4) and a drive train according to claim 1.