Work machine, in particular dump truck or truck, having an electric drive

Abstract

The present invention relates to a work machine, in particular in the form of a dump truck or truck, comprising a traction drive unit and/or main work unit which can be driven by a drive apparatus comprising at least one electric motor. The invention further relates to a method for operating such a work machine, in accordance with the invention, the drive apparatus comprises at least one hydraulic motor supporting the electric motor, the hydraulic motor being switched in for starting the drive apparatus and being decoupled on an exceeding of a predefined speed.

Claims

1. A work machine having a traction drive unit and/or a main work unit which is driven via a drive apparatus comprising at least one electric motor, wherein the drive apparatus has at least one hydraulic motor supporting the electric motor, wherein the hydraulic motor is switched in and decoupled with a clutch, wherein the electric motor is arranged between the hydraulic motor and an element of the traction drive unit and/or main work unit to be driven by the drive apparatus, wherein torque of the hydraulic motor is transferred via the electric motor to the element of the traction drive unit and/or main work unit to be driven, and wherein a control apparatus is provided and includes a control device for an automatic decoupling of the hydraulic motor on an exceeding of a predefined speed and/or on a falling below of a predefined drive torque.

2. The work machine in accordance with claim 1, wherein the clutch is configured as a dog clutch or as a multi-disk clutch.

3. The work machine in accordance with claim 1, wherein the electric motor and the hydraulic motor are connected to a common drive train which is connected at an output side to an element of the traction drive unit and/or main work unit to be driven.

4. The work machine in accordance with claim 3, wherein the common drive train forms a wheel chassis drive or tracked chassis drive of the traction drive unit of the work machine.

5. The work machine in accordance with claim 3, wherein a transmission is provided between the electric motor and the element to be driven by the drive train.

6. The work machine in accordance with claim 1, wherein the hydraulic motor is arranged coaxially to the electric motor.

7. The work machine in accordance with claim 1, wherein a transmission is provided between the hydraulic motor and the electric motor.

8. The work machine in accordance with claim 1, wherein the control apparatus is provided for controlling a switching in and out of the hydraulic motor in dependence on a speed and/or on a required drive torque of the traction drive unit and/or main work unit.

9. The work machine in accordance with claim 1, wherein the electric motor has a maximum starting torque and/or a maximum drive torque which is smaller than the maximum starting torque required by the drive apparatus and/or the required maximum drive torque, wherein a sum of the maximum starting torques and/or drive torques of the electric motor and of the switched in hydraulic motor is at least as large as the required maximum starting torque and/or drive torque of the drive apparatus.

10. The work machine in accordance with claim 1, wherein the work machine is configured as a dump truck and the drive apparatus is configured as a wheel drive for driving at least one wheel of a chassis of the dump truck.

11. The work machine in accordance with claim 10, wherein the hydraulic motor is supplied by a pump of a tilting mechanism for tilting up a dump body of the dump truck.

12. The work machine in accordance with claim 1, wherein the main work unit is configured as a hoisting drum drive, wherein the work machine is configured as a crane or of a piece of lifting gear and a hoisting drum is provided for adjusting a hoist rope or a guying rope.

13. The work machine in accordance with claim 1, wherein the work machine is a truck.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 shows a schematic side view of a self-propelled work machine in the form of a dump truck in accordance with an advantageous embodiment of the invention in which the traction drive for at least one drivable wheel comprises an electric motor and a hydraulic motor which can be switched in.

(2) FIG. 2 shows a schematic representation of the drive train for a wheel of the dump truck of FIG. 1, wherein the connection of the hydraulic motor which can be switched in via a clutch to the electric motor of the drive train and the connection of the couplable drive motors to the wheel via a transmission are shown.

(3) FIG. 3 shows a tractive force diagram of the electric motor and of the hydraulic motor which can be switched in.

DETAILED DESCRIPTION

(4) As FIG. 1 shows, the work machine can be configured, for example, as a dump truck 1 which comprises a dump body 2 supported on a chassis 3 for the transport of bulk material such as excavated material from mines, earth from construction sites, gravel or the like. The named dump body 2 can be rocked up and down or tilted about a horizontal axis 21 relative to the chassis 3 in order to be able to unload the transport material loaded in the dump body 2 by rocking up the dump body 2. The tilting mechanism 22 provided for tilting the dump body 2 can comprise an adjustment actuator not shown in more detail, for example in the form of a hydraulic cylinder which is fed from a pressure source or pump.

(5) As FIG. 1 shows, the dump truck 1 can comprise a chassis 4 having a plurality of chassis axles at which wheels 5 are respectively supported. For example, the dump truck 1 can comprise a front axle 6 and a rear axle 7 at which wheels 5a and 5b are respectively provided.

(6) The wheels 5 of the chassis 4 can be driven via a drive apparatus 8, with the drive apparatus 8 being able to drive only one chassis axle or also a plurality of chassis axles, in particular both the front axle 6 and the rear axle 7. In this respect, a one-wheel drive can be provided for each wheel 5 with which a single electric motor and a hydraulic motor are provided for each wheel. Alternatively, an axial drive can also be provided by means of which the wheels of one axle or also of a plurality of axles can be driven together, optionally via a differential.

(7) As FIG. 2 shows, the drive train 9 of the chive apparatus 8 for a wheel 5 can comprise an electric motor 10 which is connected to the named wheel 5 via a transmission 11 so that the torque of the drive of the electric motor 10 can be transmitted to the wheel 5.

(8) The drive apparatus 8 furthermore comprises a hydraulic motor 12 which can be coupled via a clutch 13 to the named drive train 9 and can be decoupled therefrom. As FIG. 2 shows, the named hydraulic motor 12 can be directly connected to the electric motor 10 via the clutch 13 so that the hydraulic motor 12 and the clutch 13 are connected in series, i.e. the torque of the hydraulic motor 12 is conducted via the electric motor 10 to the output of the drive train 9 with a closed clutch 13.

(9) The named coupling 13 can be a dog clutch or also a multi-disk clutch, with the advantage of a dog clutch being that it works without loss in the open state, while the hydraulic motor 12 can be simply switched in with a multi-disk clutch, even with a rolling dump truck 1.

(10) The switching in of the hydraulic motor 12 can in this respect be controlled via a control apparatus 14 which can control the coupling 13 in order to selectively close or open it, with the control apparatus 14 being able to be manually actuated or activated by means of a control or adjustment element 15 in the operator's cabin 20. Alternatively or additionally to such a manual actuation, the control apparatus 14 can, however, also comprise control means for an automatic or semiautomatic switching in or switching off of the hydraulic motor 12 and can for this purpose take account of different operating parameters of the dump truck 1, in particular the travel speed, for example in the form of the speed of the wheel 5 to be driven and/or the speed of the electric motor 10 which is detected via a suitable sensor 16 and which can be reported to the control apparatus 14. Alternatively or additionally, on the switching off or switching in of the hydraulic motor 12, the control apparatus 14 can take account of the drive torque which is required by the wheel 5, with here, for example, the power take-up or the torque of the electric motor 10 being able to be detected as an indicator via a suitable power take-up sensor 17 or by a torque sensor and being able to be reported to the control apparatus 14.

(11) The additional drive torque of the hydraulic motor 12 is typically only required on starting and this in turn only when an extremely high starting torque is required, for example when the dump truck 1 has to start in the loaded state on an incline with poor ground. For this purpose, the hydraulic motor 12 can be coupled in via the clutch 13 on a standstill of the vehicle. This can be triggered via the named control apparatus 14, for example by the driver pressing a button in the operator's cabin 24, or it can also be done automatically by the control apparatus 14 when a travel speed still in the region of zero is detected via the sensors 16 and 17 and it is determined that the electric motor 10 reaches its maximum torque without the vehicle starting.

(12) On reaching a predefined speed, for example a speed of approximately 5 k.p.h., the control apparatus 14 can switch off the hydraulic motor 12 again in that the clutch 13 is released since the drive torque of the electric motor 10 alone is sufficient from this point onward. The switching off or decoupling of the electric motor 10 can take place either automatically during travel or can be triggered manually by the machine operator. Provision can alternatively be made that the vehicle first has to be brought to a standstill on a better ground on which the vehicle can then start again without the support of the hydraulic motor 12. When the vehicle is stationary, the decoupling can be triggered, for example, by a manual actuation of the control element 15 in the operator's cabin 24. The control apparatus 14 can in this respect, for example, be configured such that inadmissibly high speeds of the hydraulic motor 12 are suppressed by a corresponding control of the electric motor 10 and/or of the hydraulic motor 12 as long as the hydraulic motor 12 is coupled to the drive train 9.

(13) As FIG. 3 shows, the hydraulic motor 12 can in particular be switched in with the electric motor 10 in a range of low speed and the tractive force of the electric motor 10 can be harmoniously increased beyond its maximum torque limit. The solid line in FIG. 3 in this respect shows the tractive force curve of the electric motor 10 alone, while the dashed line shows the tractive force curve supplemented by the hydraulic motor 12, i.e. the tractive force which can be generated by switching the electric motor 10 and the hydraulic motor 12 together. As FIG. 3 shows, the switching in of the hydraulic motor 12 can take place, for example, in a speed range of the drive apparatus 8 which starts at the speed zero, i.e. on the starting, and extends over less than 25%, optionally also less than 10%, of the total possible speed range.

(14) If the hydraulic motor 12 is required and switched in, the hydraulic motor 12 can advantageously be fed by the pump which feeds and actuates the tilting mechanism 22 of the dump body 2 since the tilting mechanism 22 is typically not required in drive operation and thus also at the starting of the dump truck 1.

(15) In particular the following advantages can be utilized in the electric motor 10 by means of the shown mechatronic system: The electric motor 10 can be dimensioned smaller since it can have a smaller maximum torque. The electric motor 10 hereby becomes less expensive. Weight can be saved at the electric motor 10.