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 comprising 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 in order to rotate the at least one drive wheel (5a), and at least two electric motors (105, 106) for driving 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) for the synchronous rotation thereof.

Description

Drive system for a mobile working machine

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

[0002] Mobile work machines are usually equipped with a travel system comprising an electric motor to limit pollutant emissions. The travel 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 travel of the work machine.

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

[0004] US10578211 discloses a utility vehicle for lifting people having a hydrostatic displacement system driving the axles, the vehicle having four wheels and capable of moving forward and backward. The drive system described includes an electric motor driving two pumps, one for moving the vehicle 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 force produced by the drive system is necessarily limited. Summary

[0006] An idea underlying the invention is to provide an electrically powered mobile working machine which makes it possible to increase the amount of power available for moving and possibly actuating a lifting device.

[0007] According to one embodiment, the invention provides a drive system for a mobile working 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 rotation of the 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 a significant hydrostatic tractive effort. In addition, a combination of at least two electric motors allows the torques and powers of the electric motors to be combined. Thus, without increasing the intensity of the electric current, a higher total available torque and total available power are achieved. This maintenance of a moderate intensity value prevents harmful heating of the drive system components and therefore extends the service life of the components.

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

[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 to each portion of the shaft and not exceed acceptable mechanical constraints, thus avoiding wear and a risk of malfunction of the drive system.

[0012] 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 working machine; the hydraulic actuating pump being mounted in series on said common main shaft to be driven in synchronous rotation with the hydrostatic pump.

[0013] Thus, said electric motor can drive both the hydraulic actuating pump and the hydrostatic pump while optimizing a distribution of the resistive 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 a movement of the lifting arm and the driving power for a movement of the mobile working machine are both generated by the rotation of the common main shaft, the opportunities to stop the rotation of the common main shaft during operation of the machine are reduced. This arrangement therefore contributes to smoothing the operation of the electric motor(s). Thus, it is possible to reduce the number of stops and restarts of the electric motor(s) and the resulting disadvantages: high starting current, heating, intensive use reducing the service life of the electrical components.

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

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

[0017] According to one embodiment, a said electric motor is mounted between the hydraulic actuating pump and the hydrostatic pump.

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

[0019] Thus, a flow rate produced by the hydraulic actuating pump can vary depending on a need for speed of movement of the lifting arm.

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

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

[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 receiving 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 an arm lifting signal, an arm lowering signal or a signal to move the mobile work machine.

[0024] According to one embodiment, 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 work machine is received by the operator interface.

[0025] This reduces the number of electric motor starts, preserving the inertia of the drive system. Furthermore, reducing the number of electric motor starts helps to optimize the service life of electric motors and inverters, as electric motors and inverters deteriorate when subjected to high starting currents too frequently.

[0026] According to one embodiment, the electric motors are capable of generating a total driving power and the control unit makes it possible to vary a distribution of the total driving power between a partial driving power allocated to the movement of the mobile working machine and a partial driving power allocated to the actuation of the lifting arm. The control unit can be factory-configured, or configured by the user. For configuration by the user, an appropriate human-machine interface can be provided in the control station and can take different forms: for example a dedicated menu of a graphical interface, a button with at least two positions, a potentiometer-type button, and more generally by any other type of control made available to the user to act on the distribution of the power.

[0027] Thus, the power generated by the hydrostatic pump and the hydraulic actuating 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 the total engine power in response to a distribution request received by the operator interface.

[0029] Thus, depending on the operating mode, the operator can himself vary the use of the available driving power by influencing the distribution between the power allocated to moving the lifting machine and the power allocated to operating 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, an amount of available power can increase and / or lower currents can be used to generate power of the same intensity.

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

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

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

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

[0036] According to one embodiment, the hydrostatic pump and / or a said electric motor comprises a through shaft forming a 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 connected 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 traversed by the common main shaft and the auxiliary mounting flange being disposed on a second side of the hydrostatic pump, the second side of the hydrostatic pump being opposite the first side and also being traversed by the common main shaft.

[0039] This means that 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 member operable to reverse a direction of circulation of the fluid between the hydrostatic pump and the hydrostatic motor without changing a direction of rotation of the common main shaft.

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

[0042] Thus, there is no need to change the direction of rotation of the common main shaft and / or electric motors.

[0043] Thus, an inertia of the drive system is maintained when 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, hydraulic power output from the hydrostatic pump can vary depending on the effort required and the travel speed of the mobile working machine.

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

[0047] According to one embodiment, the control unit is configured to adjust a volume of the hydrostatic pump and / or a volume of the hydraulic actuating 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 working machine, the hydraulic actuating pump not being mounted in series on said common main shaft, and a secondary electric motor for driving the hydraulic actuating pump independently of the hydrostatic pump.

[0049] This allows the hydraulic actuating pump and the hydrostatic pump to be decoupled.

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

[0051] Thus, the flywheel allows energy produced during the latency period to be stored and released later.

[0052] According to one embodiment, the hydrostatic displacement module comprises several hydrostatic pumps, for example two or four hydrostatic pumps, mounted in series on the common main shaft to be driven by synchronous rotation. According to embodiments, the characteristics indicated above in relation to the hydrostatic pump can be applied to one or each of said hydrostatic pumps. Brief description of the figures

[0053] The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings.

[0054] This is a side view of an electric forklift truck with a lifting arm.

[0055] This is a schematic representation of a drive system for the electric handling trolley according to a first embodiment.

[0056] This is a cross-sectional representation of an electric motor that may be used within the drive system according to a preferred embodiment.

[0057] This is a cross-sectional representation of a hydrostatic pump that can be used within the drive according to the preferred embodiment.

[0058] This is a schematic representation of the drive system according to a second embodiment.

[0059] This is a perspective view of the drive system according to a third embodiment.

[0060] This is a schematic representation of the drive system according to the third embodiment.

[0061] This is a schematic representation of the drive system according to a fourth embodiment.

[0062] This is a schematic representation of the drive system according to a fifth embodiment.

[0063] This is a schematic representation of the drive system according to a sixth embodiment.

[0064] The invention represents an electrically powered handling trolley 1 comprising a main body 2 mounted to roll on a front axle 15 comprising two front wheels 5a and a rear axle 16 comprising two rear wheels 5b. A lifting arm 4, shown here in the raised position, is pivotally mounted about a horizontal axis arranged at the rear of the main body 2. The main body 2 is surmounted by a driving cabin 3 inside which an operator can sit to drive the handling trolley 1 and control actuation of the lifting arm 4.

[0065] The lifting arm 4 may be a telescopic arm with an adjustable length between a retracted position and an extended position. The lifting arm can carry loads. A degree of freedom in rotation between the main body 2 and the lifting arm 4 makes it possible to raise or lower the lifting arm 4 by means of a lifting cylinder (not shown). A tool 21 can be attached to a tool holder 25 of the lifting arm 4. According to a preferred embodiment, the tool holder 25 can be designed to removably mount different handling tools such as forks, a jib, a bucket or the like. A digging cylinder 22 makes it possible to orient the tool 21 relative to the lifting arm 4. A telescoping cylinder (not shown) makes it possible to adjust the length of the telescopic arm.

[0066] A movement drive of the handling trolley 1 is enabled by rotating the front wheels 5a in contact with the ground by means of a hydrostatic transmission system. A hydraulic movement drive device enables the lifting arm 4 to be actuated. The hydrostatic transmission system and the hydraulic movement drive device are part of a drive system which will be described with reference to Figures 2 to 10.

[0067] With reference to figures 2 to 10, the structure and operation of a drive system for driving the handling trolley 1 in movement and for causing movement of the lifting arm will be described.

[0068] With reference to Figures 2 to 4, a main transmission shaft 104 is common to two electric motors 105 and 106, to a main hydrostatic pump 101 and to a secondary hydraulic pump 103. The two electric motors 105 and 106 are composed of an end electric motor 105 and an intermediate position electric motor 106. The number 100 more precisely identifies the elements constituting the hydrostatic transmission system

[0069] The main drive shaft 104 may 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 may be connected to each other by spline couplings. Multiple dimensions are possible for the spline couplings of the main drive shaft 104 so as to increase compatibility between different parts.

[0070] The end electric motor 105, the intermediate position electric motor 106, the main hydrostatic pump 101, and the secondary hydraulic pump 103 each comprise a drive shaft section, the ends of the drive shaft section being able to be provided with hollow (female) or solid (male) splined connections, to facilitate interlocking with another drive shaft section. The main drive shaft 104 is composed of the interlocked drive shaft sections.

[0071] Referring to the, the intermediate position electric motor 106 is shown. The shaft 80 of the intermediate position electric motor 106 has two hollow splined connections 81 and 82.

[0072] With reference to the, the intermediate position electric motor 106 is connected in series between the main hydrostatic pump 101 and the secondary hydraulic pump 103.

[0073] Referring to the, 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 is a female splined connection.

[0074] The main mounting flange 91 and the secondary mounting flange 92 respectively allow the intermediate position electric motor 106 to be mounted on one side and the end electric motor 105 on the other side, the end electric motor and the intermediate position electric motor 106 driving the main hydrostatic pump 101.

[0075] The main hydrostatic pump 101 has an adjustable tilt plate 66, which allows the pump volume to be varied.

[0076] With reference to the, 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 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 the is schematic.

[0077] The secondary hydraulic pump 103 powers the actuators of the lifting arm 4.

[0078] With reference to the, a drive system 200 is described according to a second embodiment. An end electric motor 205 is connected in series with an intermediate position electric motor 206. A main hydrostatic pump 201 is connected 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 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.

[0079] The secondary hydraulic pump 203 powers the actuators of the lifting arm 4.

[0080] Referring to Figures 6 and 7, a drive system 300 is described according to a third embodiment. An end electric motor 305 is connected in series with a first intermediate position electric motor 306 on a main transmission shaft.

[0081] The first intermediate position electric motor 306 is connected in series with a main hydrostatic pump 301, the main hydrostatic pump 301 being further connected in series with a second intermediate position electric motor 307. The second intermediate position motor 307 is connected in series with a secondary hydraulic pump 303.

[0082] With reference to the, 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.

[0083] The second intermediate position motor 407 is coupled to a third intermediate position electric motor 408, the third intermediate position motor 408 being further connected in series with a secondary hydraulic pump 403.

[0084] With reference to the, a drive system 500 is described according to a fifth embodiment. A first end electric motor 505 is connected in series with an intermediate position electric motor 506, the intermediate position electric motor 506 being connected in series with a main hydrostatic pump 501.

[0085] The main hydrostatic pump 501 is connected directly in series with a secondary hydraulic pump 503, the secondary hydraulic pump 503 being further connected in series with a second end electric motor 507.

[0086] With reference to the, a hydrostatic transmission system 600 is described according to a sixth embodiment. A first end electric motor 605 is connected in series with a main hydrostatic pump 601, the main hydrostatic pump 601 also being connected in series with a second end electric motor 606. The first end electric motor 605, the main hydrostatic pump 601 and the second end electric motor 606 are mounted on a main transmission shaft.

[0087] The drive system further comprises a third motor 607 connected in series to a secondary hydraulic pump 603 and which are independent of the hydrostatic transmission system 600.

[0088] It is clear that other embodiments not explicitly described may be envisaged. In particular, a number of electric motors and a position of said electric motors within the hydrostatic transmission system may be varied. In addition, other secondary hydraulic pumps with fixed or variable displacement and / or secondary hydrostatic pumps may be added.

[0089] Additionally, compressors and speed reducers can be included in the hydrostatic transmission system.

[0090] With reference to Figures 2 to 10, the operation of the systems shown will now be described.

[0091] Within the main drive shaft, at least two electric motors rotate at least one main hydrostatic pump, and possibly a secondary hydraulic pump.

[0092] With reference to the, the main hydrostatic pump 101 is rotated synchronously by the first end electric motor 105 and the intermediate position electric motor 106. The secondary hydraulic pump 103 is also rotated synchronously by the first end electric motor 105 and the intermediate position electric motor 106 around the main transmission shaft 104.

[0093] 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.

[0094] With reference to the, the hydrostatic pump 201 is rotated 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 rotated synchronously with the main hydrostatic pump 201.

[0095] With reference to Figures 6 and 7, the main hydrostatic pump 301 is driven in rotation on the one hand by an assembly composed 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 a synchronous rotation due to the coupling of the shaft segments together.

[0096] With reference to the, the main hydrostatic pump 401 is driven in rotation on the one hand by a first assembly composed of the end electric motor 405 and the first intermediate position electric motor 406, and on the other hand by a second assembly composed of the second intermediate position electric motor 407 and the third intermediate position electric motor 408.

[0097] Referring to the, a motor assembly composed of the first end electric motor 505 and the intermediate position electric motor 506 is synchronously rotated with the second end electric motor 507, and the main hydrostatic pump 501 and the secondary hydraulic pump 503 are synchronously driven by the motor assembly and the second end electric motor 507.

[0098] With reference to the, the secondary drive shaft and the main drive shaft are separate and do not rotate synchronously. Thus, electric motors 605 and 606 located on the main drive shaft may have a different rotational speed than the electric motor 607 located on the secondary drive shaft.

[0099] With reference to figures 6 and 7, a control unit 70 communicates with the transmission system to transmit an instruction 71, the instruction possibly being an instruction for moving the handling trolley 1 or an instruction for moving the lifting arm.

[0100] In addition, the control unit varies one amount of power produced by the main hydrostatic pump 101-601 and another amount of power produced by the secondary hydraulic pump 103-603. In particular, an operator interface may be used by an operator driving the handling truck 1 to select the amount of power produced by the main hydrostatic pump 101-601 and the other amount of power produced by the secondary hydraulic pump 103-603.

[0101] The amount of power produced by the main hydrostatic pump 101-601 is adjusted through a change in a 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 through a change in a tilt angle of a swash plate of the main hydrostatic pump 101-601.

[0102] The other amount of power produced by the secondary hydraulic pump 103-603 is adjusted through a change in a volume of the secondary hydraulic pump 103-603. According to a preferred embodiment, the amount of power produced by the secondary hydraulic pump 103-603 is adjusted through a change in a tilt angle of a swash plate of the secondary hydraulic pump.

[0103] In particular, an amount of available power can be fully allocated to the secondary hydraulic pump 103-603. Indeed, if the handling truck 1 is stationary and the lifting arm is in motion, the swash plate of the main hydrostatic pump 101-601 can be set to the minimum displacement or zero, so that the amount of torque produced by the main hydrostatic pump 101-601 is zero. Similarly, the amount of available torque can be fully allocated to the main hydrostatic pump 101-601, by setting the swash plate of the secondary hydraulic pump 103-603 to the minimum displacement or zero.

[0104] The inclination of the swash plate of the main hydrostatic pump 101-601 and the inclination of the swash plate of the secondary hydraulic pump 103-603 can be changed by the control unit, either automatically or by the operator via the operator interface.

[0105] 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.

[0106] If the main drive shaft 104 is stationary, the control unit may transmit a start signal to the hydrostatic transmission system 100-600. The start signal is generated when one of a movement request from the handling truck 1 or a movement request from the lifting arm 4 is transmitted by the operator interface. The start signal initiates a rotation of the main drive shaft 104.

[0107] In a case where the handling trolley 1 is stationary and the lifting arm 4 is stationary, a waiting regime is introduced. The waiting regime 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.

[0108] If the latency period elapses without a new movement request for the lifting arm 4 or a new movement request for the handling trolley 1 being transmitted to the hydrostatic transmission system 100-600, the main transmission shaft 104 then stops rotating.

[0109] The latency period prevents the electric motors from stopping unexpectedly and thus preserves the inertia of the 100-600 hydrostatic transmission system. However, the motors can stop in the event of a stop request transmitted by the operator or the detection of a specific action. For example, opening a seat belt can result in an automatic stop of the motors.

[0110] According to one embodiment, the hydrostatic transmission system includes a flywheel, which may be of fixed or variable inertia. During the lag period, the amount of power produced by the main hydrostatic pump 101-601 and the amount of power produced by the secondary hydraulic pump 103-603 are zero but the main transmission shaft continues to rotate. Thus, the flywheel charges and stores kinetic energy produced by the electric motors.

[0111] 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.

[0112] The inertia of the hydrostatic transmission system 100-600 can further be preserved when the handling trolley 1 changes direction of travel and changes from forward to reverse or from reverse to forward.

[0113] 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.

[0114] In such a configuration, a change in the direction of movement of the handling trolley 1 is made through a change in a direction of circulation of the fluid in the main hydrostatic pump 101-601 and in the hydrostatic motor 102-602. The fluid circulating in an opposite direction causes a rotation in the opposite direction of the wheels 5.

[0115] According to one embodiment, adjusting the inclination of the oscillating plate makes it possible to reverse the direction of circulation of the fluid.

[0116] A movement speed of the handling trolley 1 is preferably between 0 and 35 km / h.

[0117] A rotation of the main transmission shaft 104 is preferably carried out at a rotation speed corresponding to a nominal speed of the electric motors.

[0118] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto 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.

[0119] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim. The use of the indefinite article "un" or "une" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

[0120] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Drive system (100-600) for a mobile work machine (1), the drive system comprising: - a hydrostatic displacement module including a 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 two electric motors (105-605, 106-606) to drive the hydrostatic pump (101-601), the two electric motors (105-605, 106-606) and the hydrostatic pump (101-601) being mounted in series on a common main shaft (104) to be driven in synchronous rotation. Drive system (100-600) according to claim 1, wherein the two electric motors (105-605, 106-606) are located on either side of the hydrostatic pump (101-601). Drive system (100-600) according to claim 1 or 2, 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). Drive system (100-600) according to claim 3, wherein the hydraulic actuation pump (103-603) is mounted directly in series with the hydrostatic pump (101-601). Drive system (500) according to claim 4, in which 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). Drive system (300) according to claim 3, wherein said electric motor (307) is mounted between the hydraulic actuation pump (303) and the hydrostatic pump (301). Drive system according to any one of claims 3 to 6, wherein the hydraulic actuation pump (103-603) is a variable volume pump. Drive system according to any one of claims 3 to 6, wherein the hydraulic actuating pump (103-603) is a fixed displacement pump, the drive system further comprising means for diverting a flow generated by the hydraulic actuating pump (103-603) to a receiving reservoir in response to a non-consumption of the generated flow. Drive system (100-600) according to any one of claims 3 to 8, 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 the receipt of a request to lift the lifting arm (4) or a request to move the mobile work machine (1) by the operator interface. Drive system (100-600) according to claim 9, 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. Drive system (100-600) according to any one of the preceding claims, wherein the common main shaft (104) is formed by shaft segments coupled in rotation to each other by coupling devices. Drive system (100-600) according to claim 11, wherein a said coupling device is a splined device. Drive system (100-600) according to claim 11 or 12, 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. 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). Drive system (100-600) according to any one of the preceding claims, wherein the hydrostatic pump (101-601) is a variable volume pump. 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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