Drive system for a mobile work machine

Abstract

The invention relates to a drive system (100) for a mobile work machine, the drive system (100) comprising a hydrostatic displacement module including at least one hydrostatic pump (101) connected to at least one hydrostatic motor (102), the hydrostatic motor (102) being coupled to at least one drive wheel (5a) of the mobile work machine to drive the rotation of at least one drive wheel (5a), and at least two electric motors (105, 106) to drive the hydrostatic pump (101), the two electric motors (105, 106) and the hydrostatic pump (101) being mounted in series on a common main shaft (104) to be driven in synchronous rotation. Figure for the abstract: Fig. 2

Description

Title of the invention: Drive system for a mobile work machine technical field

[0001] The invention relates to the field of drive systems for electrically powered mobile work machines. Technological background

[0002] Mobile work machines are generally equipped with a drive system that includes an electric motor to limit pollutant emissions. The drive system may include a mechanical coupling between the motor and the drive wheels. In this case, it is necessary to stop and reverse the direction of rotation of the electric motor to reverse the direction of movement of the work machine.

[0003] However, a hydrostatic drive system, comprising at least one hydrostatic pump and one hydrostatic wheel motor, makes it possible to generate a better traction force in the case where the speed of movement of the working machine is low.

[0004] US 10578211 discloses a personnel-lifting utility vehicle comprising a hydrostatic drive system for the axles, the vehicle having four wheels and capable of forward and reverse movement. The described drive system includes an electric motor driving two pumps, one for vehicle movement and the other for actuating a lifting device, the electric motor and the two pumps being mounted in series on a common drive shaft.

[0005] However, such a device has limitations. Indeed, the electric motor provides a limited amount of power and must drive both pumps. Thus, the effort produced by the drive system is necessarily limited. Summary

[0006] One idea underlying the invention is to provide a mobile, electrically powered work machine that makes it possible to increase the amount of power available for moving and possibly actuation of a lifting device.

[0007] According to one embodiment, the invention provides a drive system for a mobile work machine, the drive system comprising: - a hydrostatic displacement module comprising at least one hydrostatic pump connected to at least one hydrostatic motor, the hydrostatic motor being coupled to at least one drive wheel of the working machine to drive a rotation of at least one drive wheel; - and at least two electric motors to drive the hydrostatic pump, the two electric motors and the hydrostatic pump being mounted in series on a common main shaft to be driven in synchronous rotation.

[0008] Thanks to these characteristics, the drive system provides significant hydrostatic traction. Furthermore, combining at least two electric motors allows for the addition of their torques and power outputs. Thus, without increasing the electric current, the total available torque and power are higher. Maintaining a moderate current prevents harmful overheating of the drive system components and therefore extends their service life.

[0009] According to embodiments, such a drive system may include one or more of the following characteristics.

[0010] According to one embodiment, the two electric motors are located on either side of the hydrostatic pump.

[0011] Thus, forces on the common main shaft are better distributed so as to limit the force applied on each portion of the shaft and not to exceed acceptable mechanical stresses, thus avoiding wear and the risk of malfunction of the drive system.

[0012] According to one embodiment, the drive system further comprises a hydraulic actuation pump connected to at least one hydraulic actuator, said at least one hydraulic actuator being arranged to actuate a lifting arm of the work machine; the hydraulic actuation pump being mounted in series on said common main shaft to be driven by a synchronous rotation with the hydrostatic pump.

[0013] Thus, said electric motor can drive both the hydraulic actuation pump and the hydrostatic pump while optimizing a distribution of the resisting torques generated by the two pumps, which limits the torques to be transmitted by each portion of the common main shaft.

[0014] Thus, since the driving power for movement of the lifting arm and the driving power for movement of the mobile work machine are both generated by the rotation of the common main shaft, the opportunities to stop the rotation of the common main shaft during machine operation are reduced. This arrangement therefore contributes to smoother operation of the electric motor(s). Consequently, it is possible to reduce the number of stops and restarts of the electric motor(s) and the resulting drawbacks: high starting current, overheating, and intensive use that reduces the lifespan of the electrical components.

[0015] According to one embodiment, the hydraulic actuation pump is mounted directly in series with the hydrostatic pump.

[0016] According to one embodiment, two electric motors are located on either side of an assembly consisting of the hydrostatic pump and the hydraulic actuation pump mounted directly in series with the hydrostatic pump.

[0017] According to one embodiment, an electric motor is mounted between the hydraulic actuation pump and the hydrostatic pump.

[0018] According to one embodiment, the hydraulic actuation pump is a variable volume pump.

[0019] Thus, a flow produced by the hydraulic actuation pump can vary according to a required speed of movement of the lifting arm.

[0020] According to one embodiment, the hydraulic actuation pump comprises a variable tilt plate.

[0021] According to another embodiment, the hydraulic actuation pump is a fixed-displacement pump, the drive system further comprising means for diverting flow generated by the hydraulic actuation pump to a receiving reservoir in response to non-consumption of the generated flow, for example, when the flow generated by the hydraulic actuation pump exceeds the flow requirement due to an electric motor speed exceeding the requirement of the hydraulic actuation pump. The electric motor speed may be caused by a demand from other elements for other needs, such as the hydrostatic displacement pump connected to the same main drive shaft. The excess flow, not used by hydraulic movements, can be directed to the reservoir by a hydraulic distributor.Thus, when the flow from the hydraulic actuation pump is not in use, it can be diverted to the receiving tank.

[0022] According to one embodiment, the drive system further comprises a control unit, the control unit comprising an operator interface, the control unit being configured to start a rotation of the common main shaft in response to the receipt of a request to lift the arm or a request to move the work machine by the operator interface.

[0023] Thus, an operator will be able to control the drive system by transmitting a signal to raise the arm, a signal to lower the arm or a signal to move the mobile work machine.

[0024] According to one embodiment, the rotation of the common main shaft stops after a latency period during which no request to lift the lifting arm or request to move the mobile working machine is received by the operator interface.

[0025] Thus, the number of electric motor starts is reduced, thereby preserving the inertia of the drive system. Furthermore, reducing the number of electric motor starts optimizes the service life of both the electric motors and the inverters, as these deteriorate when subjected too frequently to high starting currents.

[0026] According to one embodiment, the electric motors are capable of generating total drive power, and the control unit allows for varying the distribution of this total drive power between a partial drive power allocated to moving the mobile work machine and a partial drive power allocated to actuating the lifting arm. The control unit can be factory-set or user-configured. For user configuration, a suitable human-machine interface can be provided in the control station and can take various forms: for example, a dedicated menu in a graphical interface, a button with at least two positions, a potentiometer-type button, and more generally, any other type of control made available to the user to adjust the power distribution.

[0027] Thus, the power generated by the hydrostatic pump and the hydraulic actuation pump will be adjusted by the control unit according to the pressure and flow requirements.

[0028] According to one embodiment, the control unit varies said distribution of total motive power in response to a distribution request received by the operator interface.

[0029] Thus, according to one mode of operation, the operator can himself vary the use of the available motive power by influencing the distribution between the power allocated to the movement of the lifting machine and the power allocated to the actuation of the lifting arm.

[0030] According to one embodiment, the drive system further comprises a third electric motor mounted in series on said common main shaft.

[0031] Thus, the amount of available power can be increased and / or lower currents can be used to generate power of the same intensity.

[0032] According to one embodiment, at least two of said electric motors are mounted directly in series.

[0033] According to one embodiment, the common main shaft is formed by shaft segments coupled in rotation to each other by coupling devices.

[0034] Thus, a common main shaft length can accommodate additional pumps and motors that can be added to the drive system. Furthermore, various components of the drive system are subject to synchronous rotation.

[0035] According to one embodiment, a said coupling device is a grooved device.

[0036] According to one embodiment, the hydrostatic pump and / or said electric motor comprises a through shaft forming said shaft segment, said through shaft comprising two ends respectively provided with coupling devices.

[0037] Thus, the various constituent elements of the drive system can be mounted in series to form the common main shaft.

[0038] According to one embodiment, the hydrostatic pump comprises a main mounting flange and an auxiliary mounting flange, the main mounting flange being disposed on a first side of the hydrostatic pump through which the common main shaft passes, and the auxiliary mounting flange being disposed on a second side of the hydrostatic pump, the second side of the hydrostatic pump being opposite to the first side and also through which the common main shaft passes.

[0039] Thus, the electric motors can be easily mounted on either side of the hydrostatic pump.

[0040] According to one embodiment, the hydrostatic pump is a reversible circulation pump comprising a control element that can be acted upon to reverse the direction of fluid circulation between the hydrostatic pump and the hydrostatic motor without changing the direction of rotation of the common main shaft.

[0041] Thus, the direction of fluid flow can be reversed, allowing the direction of movement of the mobile working machine to be reversed as well.

[0042] Thus, it is not necessary to change the direction of rotation of the common main shaft and / or the electric motors.

[0043] Thus, an inertia of the drive system is conserved in changing the direction of movement of the mobile working machine.

[0044] According to one embodiment, the hydrostatic pump is a variable volume pump.

[0045] Thus, a hydraulic power output of the hydrostatic pump can vary according to the need for effort and speed of movement of the mobile work machine.

[0046] According to one embodiment, the hydrostatic pump comprises a plate with variable inclination.

[0047] According to one embodiment, the control unit is configured to regulate a volumetric flow rate of the hydrostatic pump and / or a volumetric flow rate of the hydraulic actuation pump.

[0048] According to one embodiment, the drive system further comprises a hydraulic actuating pump connected to at least one hydraulic actuator, said at least one hydraulic actuator being arranged to actuate a lifting arm of the work machine, the hydraulic actuation pump not being mounted in series on said common main shaft, and a secondary electric motor to drive the hydraulic actuation pump independently of the hydrostatic pump.

[0049] Thus, the hydraulic actuation pump and the hydrostatic pump can be decoupled.

[0050] According to one embodiment, the drive system further comprises a flywheel coupled to the common main shaft.

[0051] Thus, the flywheel makes it possible to store energy produced during the latency period and to release it afterwards. Brief description of the figures

[0052] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings.

[0053] [Fig-1] The [Fig. 1] is a side view representation of an electric handling trolley equipped with a lifting arm.

[0054] [Fig.2] The [Fig.2] is a schematic representation of a drive system for the electric handling trolley of the [Fig.1] according to a first embodiment.

[0055] [Fig.3] The [Fig.3] is a cross-sectional representation of an electric motor that can be used within the drive system according to a preferred embodiment.

[0056] [Fig.4] The [Fig.4] is a cross-sectional representation of a hydrostatic pump that can be used within the drive according to the preferred embodiment.

[0057] [Fig.5] The [Fig.5] is a schematic representation of the drive system according to a second embodiment.

[0058] [Fig.6] Fig.6 is a perspective view of the drive system according to a third embodiment.

[0059] [Fig.7] The [Fig.7] is a schematic representation of the drive system according to the third embodiment.

[0060] [Fig.8] The [Fig.8] is a schematic representation of the drive system according to a fourth embodiment.

[0061] [Fig.9] The [Fig.9] is a schematic representation of the drive system according to a fifth embodiment.

[0062] [Fig. 10] The [Fig. 10] is a schematic representation of the drive system according to a sixth embodiment. Description of the implementation methods

[0063] Figure 1 represents an electrically powered handling trolley 1 comprising a main body 2 mounted to roll on a front axle 15 having two front wheels 5a and a rear axle 16 having two rear wheels 5b. A lifting arm 4, shown here in the raised position, is mounted to pivot about a horizontal axis arranged at the rear of the main body 2. The main body 2 is surmounted by a driver's cab 3 inside which an operator can be seated to drive the handling trolley 1 and control the actuation of the lifting arm 4.

[0064] The lifting arm 4 can be a telescopic arm with an adjustable length between a retracted and an extended position. The lifting arm allows loads to be carried. A rotational degree of freedom between the main body 2 and the lifting arm 4 allows the lifting arm 4 to be raised or lowered by means of a lifting cylinder (not shown). A tool 21 can be attached to a tool holder 25 on the lifting arm 4. In a preferred embodiment, the tool holder 25 can be designed to removably mount various handling tools such as forks, a jib, a bucket, or others. A digging cylinder 22 allows the tool 21 to be oriented relative to the lifting arm 4. A telescoping cylinder (not shown) allows the length of the telescopic arm to be adjusted.

[0065] The handling trolley 1 is moved by rotating the front wheels 5a in contact with the ground using a hydrostatic transmission system. A hydraulic drive device actuates the lifting arm 4. The hydrostatic transmission system and the hydraulic drive device form part of a drive system that will be described with reference to Figures 2 to 10.

[0066] With reference to figures 2 to 10, the structure and operation of a drive system will be described, enabling the handling trolley 1 to move and the lifting arm to move.

[0067] With reference to Figures 2 to 4, a main drive shaft 104 is common to two electric motors 105 and 106, a main hydrostatic pump 101, and a secondary hydraulic pump 103. The two electric motors 105 and 106 consist of an end electric motor 105 and an intermediate position electric motor 106. The figure 100 more precisely identifies the components of the hydrostatic transmission system.

[0068] The main transmission shaft 104 can be formed by joining the segments consisting of the shaft specific to each component: the end electric motor 105, the main hydrostatic pump 101, the intermediate position electric motor 106, and the secondary hydraulic pump 103. These segments can be connected between They are connected by splined couplings. Multiple dimensions are possible for the splined couplings of the main transmission shaft 104 in order to increase compatibility between different parts.

[0069] The end electric motor 105, the intermediate position electric motor 106, the main hydrostatic pump 101, and the secondary hydraulic pump 103 each have a transmission shaft section, the ends of the transmission shaft section being able to be provided with hollow (female) or solid (male) splined connections, to facilitate interlocking with another transmission shaft section. The main transmission shaft 104 is composed of the interlocking transmission shaft sections.

[0070] With reference to [Fig. 3], the intermediate position electric motor 106 is shown. The shaft 80 of the intermediate position electric motor 106 has two hollow splined joints 81 and 82.

[0071] With reference to [Fig.2], the intermediate position electric motor 106 is mounted in series between the main hydrostatic pump 101 and the secondary hydraulic pump 103.

[0072] With reference to [Fig.4], the main hydrostatic pump 101 has a main mounting flange 91 and a secondary mounting flange 92, the main mounting flange 91 and the secondary mounting flange 92 being placed on two opposite sides of the shaft 90 of the main hydrostatic pump 101. The main mounting flange 91 is here a male splined connection and the secondary mounting flange 92 a female splined connection.

[0073] The main mounting flange 91 and the secondary mounting flange 92 allow the intermediate position electric motor 106 to be mounted on one side and the end electric motor 105 on the other side respectively, the end electric motor and the intermediate position electric motor 106 driving the main hydrostatic pump 101.

[0074] The main hydrostatic pump 101 has an adjustable tilting plate 66, which allows the volume of the pump to be varied.

[0075] With reference to [Fig. 2], the main hydrostatic pump 101 exchanges an incompressible fluid with at least one hydrostatic motor 102, which drives the drive wheels of the handling trolley 1 in rotation. The drive wheels are, for example, the front wheels 5a and 5b (i.e., two drive wheels), or the front wheels 5a and the rear wheels 5b (i.e., four drive wheels). Several hydrostatic motors can be provided for this purpose. In this respect, [Fig. 2] is schematic.

[0076] The secondary hydraulic pump 103 supplies the actuators of the lifting arm 4.

[0077] With reference to [Fig. 5], a drive system 200 is described according to a second embodiment. An end electric motor 205 is mounted in series with an intermediate position electric motor 206. A main hydrostatic pump 201 is mounted in series with the intermediate position electric motor 206 and a secondary hydraulic pump 203, the main hydrostatic pump 201 exchanging a fluid with at least one hydrostatic motor 202 driving the front wheels 5a of the handling trolley 1 via a reduction gearbox 65. Here a transmission shaft 64 couples the reduction gearbox 65 also to the rear axle to provide four-wheel drive.

[0078] The secondary hydraulic pump 203 supplies the actuators of the lifting arm 4.

[0079] With reference to Figures 6 and 7, a drive system 300 is described according to a third embodiment. An end electric motor 305 is mounted in series with a first intermediate position electric motor 306 on a main transmission shaft.

[0080] The first intermediate position electric motor 306 is mounted in series with a main hydrostatic pump 301, the main hydrostatic pump 301 being further mounted in series with a second intermediate position electric motor 307. The second intermediate position motor 307 is mounted in series with a secondary hydraulic pump 303.

[0081] With reference to [Fig. 8], a drive system 400 is described according to a fourth embodiment. An end electric motor 405 is connected in series with a first intermediate position electric motor 406, the first intermediate position electric motor 406 being connected in series with the main hydrostatic pump 401. The main hydrostatic pump 401 is further connected in series with a second intermediate position electric motor 407.

[0082] The second intermediate position motor 407 is coupled to a third intermediate position electric motor 408, the third intermediate position motor 408 being further mounted in series with a secondary hydraulic pump 403.

[0083] With reference to [Fig. 9], a drive system 500 is described according to a fifth embodiment. A first end electric motor 505 is mounted in series with an intermediate position electric motor 506, the intermediate position electric motor 506 being mounted in series with a main hydrostatic pump 501.

[0084] The main hydrostatic pump 501 is mounted directly in series with a secondary hydraulic pump 503, the secondary hydraulic pump 503 being further mounted in series with a second end electric motor 507.

[0085] With reference to [Fig. 10], a hydrostatic transmission system 600 is described according to a sixth embodiment. A first end electric motor 605 is mounted in series with a main hydrostatic pump 601, the main hydrostatic pump 601 also being mounted in series with a second motor electric end 606. The first electric end motor 605, the main hydrostatic pump 601 and the second electric end motor 606 are mounted on a main drive shaft.

[0086] The drive system further comprises a third motor 607 mounted in series with a secondary hydraulic pump 603 and which are independent of the hydrostatic transmission system 600.

[0087] It is clear that other embodiments not explicitly described may be envisaged. In particular, the number of electric motors and their position within the hydrostatic transmission system may vary. Furthermore, additional secondary hydraulic pumps with fixed or variable displacement and / or secondary hydrostatic pumps may be added.

[0088] In addition, compressors and speed reducers can be included in the hydrostatic transmission system.

[0089] With reference to figures 2 to 10, the operation of the systems shown will now be described.

[0090] Within the main transmission shaft, at least two electric motors drive in rotation at least one main hydrostatic pump, and possibly a secondary hydraulic pump.

[0091] With reference to [Fig.2], the main hydrostatic pump 101 is driven in rotation synchronously by the first end electric motor 105 and the intermediate position electric motor 106. The secondary hydraulic pump 103 is also driven in rotation synchronously by the first end electric motor 105 and the intermediate position electric motor 106 around the main transmission shaft 104.

[0092] In other words, the main hydrostatic pump 101 is driven in rotation by electric motors 105 and 106 mounted in series on either side of the main hydrostatic pump 101, the electric motors having a synchronous rotation due to the coupling of the shaft segments between them.

[0093] With reference to [Fig.5], the hydrostatic pump 201 is driven in rotation by an assembly consisting of the end electric motor 205 and the intermediate position electric motor 206. The secondary hydraulic pump 203 is mounted in series with the main hydrostatic pump 201 around the main transmission shaft (not shown) and is driven in rotation synchronously with the main hydrostatic pump 201.

[0094] With reference to Figures 6 and 7, the main hydrostatic pump 301 is driven in rotation on the one hand by an assembly consisting of the end electric motor 305 and the first intermediate position electric motor 306, and on the other hand by the second intermediate position motor 307, the end electric motor 305, the first intermediate position electric motor 306 and the second intermediate position motor 307 having synchronous rotation due to the coupling of the shaft segments together.

[0095] With reference to [Fig.8], the main hydrostatic pump 401 is driven in rotation on the one hand by a first assembly consisting of the end electric motor 405 and the first intermediate position electric motor 406, and on the other hand by a second assembly consisting of the second intermediate position electric motor 407 and the third intermediate position electric motor 408.

[0096] With reference to [Fig.9], a set of motors consisting of the first end electric motor 505 and the intermediate position electric motor 506 is in synchronous rotation with the second end electric motor 507, and the main hydrostatic pump 501 and the secondary hydraulic pump 503 are driven synchronously by the set of motors and the second end electric motor 507.

[0097] With reference to [Fig. 10], the secondary transmission shaft and the main transmission shaft are separate and do not rotate synchronously. Thus, electric motors 605 and 606 located on the main transmission shaft may have a different rotational speed than the electric motor 607 located on the secondary transmission shaft.

[0098] With reference to figures 6 and 7, a control unit 70 communicates with the transmission system to transmit a command 71, the command being a command to move the handling trolley 1 or a command to move the lifting arm.

[0099] In addition, the control unit varies a quantity of power produced by the main hydrostatic pump 101-601 and another quantity of power produced by the secondary hydraulic pump 103-603. In particular, an operator interface can be used by an operator driving the handling trolley 1 to select the quantity of power produced by the main hydrostatic pump 101-601 and the other quantity of power produced by the secondary hydraulic pump 103-603.

[0100] The amount of power produced by the main hydrostatic pump 101-601 is adjusted by modifying the volume of the main hydrostatic pump 101-601. According to a preferred embodiment, the amount of power produced by the main hydrostatic pump 101-601 is adjusted by modifying the angle of inclination of a swashplate of the main hydrostatic pump 101-601.

[0101] The other quantity of power produced by the secondary hydraulic pump 103-603 is adjusted by modifying the volume of the secondary hydraulic pump 103-603. According to a preferred embodiment, the quantity of power produced by the secondary hydraulic pump 103-603 is adjusted through a modification of the tilt angle of a swashplate of the secondary hydraulic pump.

[0102] In particular, a certain amount of available power can be entirely allocated to the secondary hydraulic pump 103-603. Indeed, if the handling trolley 1 is stationary and the lifting arm is moving, the swashplate of the main hydrostatic pump 101-601 can be set to its minimum or zero displacement, so that the amount of torque produced by the main hydrostatic pump 101-601 is zero. Similarly, the amount of available torque can be entirely allocated to the main hydrostatic pump 101-601 by setting the swashplate of the secondary hydraulic pump 103-603 to its minimum or zero displacement.

[0103] The tilt of the swashplate of the main hydrostatic pump 101-601 and the tilt of the swashplate of the secondary hydraulic pump 103-603 can be changed by the control unit, either automatically or by the operator via the operator interface.

[0104] Thus, the main transmission shaft continues to rotate in the case where the handling trolley 1 is not moving or in the case where the lifting arm 4 is stationary.

[0105] If the main drive shaft 104 is stationary, the control unit can transmit a start signal to the hydrostatic transmission system 100-600. The start signal is generated when either a request to move the handling trolley 1 or a request to move the lifting arm 4 is transmitted through the operator interface. The start signal initiates rotation of the main drive shaft 104.

[0106] In a case where the handling trolley 1 is stopped and the lifting arm 4 is stationary, a standby mode is introduced. The standby mode consists of the main transmission shaft 104 continuing to rotate for a predefined latency period, which may be thirty seconds according to a preferred embodiment.

[0107] If the latency period elapses without a new request to move the lifting arm 4 or a new request to move the handling trolley 1 being transmitted to the hydrostatic transmission system 100-600, the main transmission shaft 104 then stops rotating.

[0108] The latency period prevents the electric motors from stopping unexpectedly, thus preserving the inertia of the 100-600 hydrostatic transmission system. However, the motors may stop if the operator requests a stop command or if a specific action is detected. For example, unfastening a seatbelt may result in the motors stopping automatically.

[0109] According to one embodiment, the hydrostatic transmission system includes a Flywheel, which can have fixed or variable inertia. During the lag time, the power output of the main hydrostatic pump 101-601 and the power output of the secondary hydraulic pump 103-603 are zero, but the main drive shaft continues to rotate. Thus, the flywheel charges and stores kinetic energy generated by the electric motors.

[0110] When the latency period is interrupted and the movement of the lifting arm or the movement of the handling trolley 1 resumes, the flywheel can then release stored energy.

[0111] The inertia of the hydrostatic transmission system 100-600 can also be preserved when the handling trolley 1 changes direction of movement and goes from forward to reverse or from reverse to forward.

[0112] According to a preferred embodiment, the electric motors can only rotate in one direction. Thus, the main transmission shaft 104 also has a single direction of rotation.

[0113] In such a configuration, a change in the direction of movement of the handling trolley 1 is achieved through a change in the direction of fluid flow in the main hydrostatic pump 101-601 and in the hydrostatic motor 102-602. The fluid flowing in the opposite direction causes the wheels 5 to rotate in the opposite direction.

[0114] According to one embodiment, adjusting the tilt of the oscillating plate allows the direction of fluid flow to be reversed.

[0115] The travel speed of the handling trolley 1 is preferably between 0 and 35 km / h.

[0116] Rotation of the main transmission shaft 104 is preferably carried out at a rotational speed corresponding to a nominal operating speed of the electric motors.

[0117] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0118] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0119] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Drive system (100-600) for a mobile work machine (1), the drive system comprising: - a hydrostatic displacement module comprising at least one hydrostatic pump (101-601) connected to at least one hydrostatic motor (102-602), the hydrostatic motor being coupled to at least one drive wheel (5a) of the mobile work machine (1) to drive a rotation of at least one drive wheel (5a); - and at least two electric motors (105-605, 106-606) to drive the hydrostatic pump (101-601), characterized in that the two electric motors (105-605, 106-606) and the hydrostatic pump (101-601) are mounted in series on a common main shaft (104) to be driven by a synchronous rotation, in which the two electric motors (105-605, 106-606) are located on either side of the hydrostatic pump (101-601).

2. A drive system (100-600) according to claim 1, further comprising a hydraulic actuation pump (103-603) connected to at least one hydraulic actuator, said at least one hydraulic actuator being arranged to actuate a lifting arm (4) of the mobile work machine (1); the hydraulic actuation pump being mounted in series on said common main shaft (104) to be driven in synchronous rotation with the hydrostatic pump (101-601).

3. Drive system (100-600) according to claim 2, wherein the hydraulic actuation pump (103-603) is mounted directly in series with the hydrostatic pump (101-601).

4. Drive system (500) according to claim 3, wherein two said electric motors (506, 507) are located on either side of an assembly consisting of the hydrostatic pump (501) and the hydraulic actuation pump (503) mounted directly in series with the hydrostatic pump (501).

5. Drive system (300) according to claim 2, wherein said electric motor (307) is mounted between the hydraulic actuation pump (303) and the hydrostatic pump (301).

6. A drive system according to any one of claims 2 to 5, wherein the hydraulic actuation pump (103-603) is a variable volume pump.

7. A drive system according to any one of claims 2 to 5, wherein the hydraulic actuation pump (103-603) is a fixed displacement pump, the drive system further comprising means for diverting a flow generated by the hydraulic actuation pump (103-603) to a receiving reservoir in response to a non-consumption of the generated flow.

8. A drive system (100-600) according to any one of claims 2 to 7, further comprising a control unit, the control unit comprising an operator interface, the control unit being configured to start a rotation of the common main shaft (104) in response to receiving a request to lift the lifting arm (4) or a request to move the mobile work machine (1) by the operator interface.

9. Drive system (100-600) according to claim 8, wherein the rotation of the common main shaft (104) stops after a latency period during which no request to lift the lifting arm (4) or request to move the mobile working machine (1) is received by the operator interface.

10. A drive system (100-600) according to any one of the preceding claims, wherein the common main shaft (104) is formed by shaft segments rotationally coupled to each other by coupling devices.

11. Drive system (100-600) according to claim 10, wherein a said coupling device is a splined device.

12. Drive system (100-600) according to claim 10 or 11, wherein the hydrostatic pump (101-601) and / or said electric motor (105-605, 106-606) comprises a through shaft forming said shaft segment, said through shaft comprising two ends respectively provided with coupling devices.

13. Drive system (100-600) according to any one of the preceding claims, wherein the hydrostatic pump (101-601) is a reversible circulation pump having an actuable control element to reverse one direction of fluid circulation between the hydrostatic pump (101-601) and the hydrostatic motor (102-602) without changing one direction of rotation of the common main shaft (104).

14. Drive system (100-600) according to any one of the preceding claims, wherein the hydrostatic pump (101-601) is a variable volume pump.

15. Drive system (100-600) according to any one of the preceding claims, further comprising a flywheel coupled to the common main shaft (104).

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