WO2020245544A1

WO2020245544A1 - Method for adding a hydraulic machine to a machine comprising a primary transmission

Info

Publication number: WO2020245544A1
Application number: PCT/FR2020/050951
Authority: WO
Inventors: François-Xavier LELAY; Cyril LE MOING
Original assignee: Poclain Hydraulics Industrie
Priority date: 2019-06-04
Filing date: 2020-06-03
Publication date: 2020-12-10
Also published as: FR3096935B1; FR3096935A1

Abstract

Method for integrating a hydraulic machine in a machine, in which (E1) the gearbox (30), the primary motor (10) and the oil pan (20) are separated, (E2) the bearing surface of the oil pan (20) is machined, (E3) a fastening segment (70) is positioned in bearing contact with the oil pan (20), said segment comprising a primary portion (72) filling the machined volume of the oil pan (20), and a secondary portion (74) projecting from the oil pan (20), (E4) the gearbox (30) is secured to the primary motor (10) and to the oil pan (20), the fastening segment (70) being interposed between the oil pan (20) and the gearbox (30), (E5) a hydraulic machine is positioned with respect to the secondary portion (74), a shaft of the hydraulic machine being centred with respect to a drilling (76) of the secondary portion (74).

Description

Title of the invention: Method of adding a hydraulic machine to a machine comprising a primary transmission

Technical area

This presentation relates to hydraulic machines and their integration into a machine comprising a gearbox.

Prior art

[0002] The integration of hydraulic assistance on a machine requires coupling a hydraulic pump to an existing system of the machine.

[0003] Figure 1 shows schematically a propulsion system of a

machine, comprising a primary motor 10 provided with an oil pan 20, a gearbox 30 coupled to a differential 40, the differential here being connected to two wheels 50 and 60 via shafts 52 and 62 respectively provided with cardans 54 and 64 respectively. The gearbox 30 includes a gearbox housing. The primary motor 10 includes a motor housing. In general, the gearbox 30 and the primary motor 10 will be designated by their respective housings. The gearbox 30 is coupled to a clutch 35 positioned in the extension of the gearbox 30, the clutch being positioned in a housing

clutch produced as an extension of the gearbox casing 30. The gearbox casing 30 thus comprises a first sealed internal volume in which the gearbox 30 is positioned, and a second internal volume, typically non-sealed , in which the clutch 35 is positioned.

The gearbox 30 is coupled to the primary motor 10 and to the oil pan 20 so that the clutch 35 is positioned between the gearbox 30 and the primary motor 10 via support planes or support planes fitted out on these different elements. More precisely, the gearbox housing 30 has a gearbox support plane 32, against which are positioned a primary motor housing 10 support plane, and an oil pan 20 support plane, the support planes ensuring structural cohesion between the gearbox 30 on the one hand, and the primary motor 10 on the other hand. In order to achieve the integration of a hydraulic transmission in such a system, the known solutions require modifying the gearbox housing 30 of the machine, the power take-off on the differential body and the fixings pump, which is particularly restrictive, and goes so far as to require the modification of existing foundry molds.

[0006] We therefore seek to propose a solution simplifying the installation of a

hydraulic assistance on a vehicle already fitted with a primary transmission.

Disclosure of the invention

[0007] The present disclosure thus aims to respond at least partially to these

problematic, and proposes a method for integrating a hydraulic machine on a machine comprising a gearbox coupled to a clutch, a differential, a primary motor and an oil pan associated with the primary motor, the gearbox being secured to the primary engine and to the oil pan according to a bearing plane formed between a bearing surface of a gearbox housing on the one hand, and a bearing surface of a primary engine housing and a secondly, the oil pan bearing surface, in which the following steps are carried out successively:

a- we separate the oil pan from the gearbox and the primary engine, b- we machine the bearing surface of the oil pan, so as to define a machined volume,

c- the gearbox is secured to the primary motor, and a fixing segment is positioned resting on the gearbox, said fixing segment comprising a primary portion positioned so as to occupy the location of the machined volume of the surface of support of the oil pan and a secondary portion dimensioned so as to protrude from the oil pan and having a bore,

d- the oil pan is secured to the gearbox and to the primary motor, the fixing segment being interposed between the oil pan and the gearbox and occupying the machined volume of the casing bearing surface d 'oil,

e- a hydraulic machine is positioned relative to the secondary portion of the fixing segment, a shaft of the hydraulic machine being centered relative to the drilling of the secondary portion of the fixing segment. [0008] According to one example, the machining of the bearing surface of the oil pan is carried out so that the primary portion of the fixing segment forms a flat support with the gearbox on the one hand, and with the oil pan on the other hand.

[0009] According to one example, the primary portion of the fixing segment reproduces the

volume machined into the oil pan bearing surface.

[0010] According to one example, the fixing segment comprises a housing adapted to cooperate with a centering pin so as to allow centering of the fixing segment relative to the gearbox and primary motor when positioning the fixing segment. When positioning the fixing segment, the housing of the fixing segment then cooperates, for example, with a centering pin extending from the gearbox or from the primary motor.

According to one example, during the positioning of the hydraulic machine relative to the secondary portion of the fixing segment, a centering sleeve is positioned in a bore of the fixing segment, said centering sleeve protruding from both sides. another from the fixing segment, and a differential case and a hydraulic machine case are fitted on the centering sleeve on either side of the fixing segment.

A segment is then typically positioned in the centering sleeve, said segment being configured so as to couple in rotation a cage of the differential, and a shaft of the hydraulic machine.

[0013] According to one example, when positioning the hydraulic machine relative to the secondary portion of the fixing segment, said machine

hydraulic is secured to the secondary portion of the fixing segment.

According to one example, during the positioning of the hydraulic machine relative to the secondary portion of the fixing segment, a shaft of the hydraulic machine is aligned with an output shaft of the differential or with an output shaft of the gearbox. speed.

This presentation also relates to a vehicle comprising a gearbox coupled to a clutch, a differential, a primary motor and an oil sump, in which the gearbox is secured to the primary motor and to the oil pan,

said vehicle being characterized in that it further comprises

- a fixing segment, the fixing segment comprising a primary portion interposed between the oil pan and the gearbox, and a secondary portion projecting from the oil pan and having a bore

a hydraulic machine having a shaft centered relative to the drilling of the fixing segment, the hydraulic machine being secured to the fixing segment.

[0016] According to one example, the bore of the fixing segment is dimensioned so as to be aligned with an output shaft of the differential or with an output shaft of the gearbox.

[0017] According to one example, the primary motor drives in rotation a primary axle of the vehicle, in which the hydraulic machine is a hydraulic pump with radial pistons, the vehicle further comprising at least one hydraulic motor supplied by the hydraulic pump and suitable for rotating a secondary axle of the vehicle.

[0018] According to one example, the fixing segment comprises a housing adapted to cooperate with a centering pin so as to allow centering of the fixing segment relative to the gearbox and to the oil sump during positioning of the segment of fixation.

[0019] According to one example, the fixing segment comprises a second housing adapted to cooperate with a centering pin inserted in a housing of the gearbox or of the primary motor, so as to allow an angular orientation of the fixing segment with respect to the gearbox and the primary motor when positioning the fixing segment.

[0020] According to one example, the fixing segment has a section forming a support plane adapted to cooperate with a support plane formed by the primary motor on a surface of the primary motor against which the machined volume of the casing bears. oil, so as to allow angular orientation of the fixing segment relative to the gearbox and the primary engine. Brief description of the drawings

[0021] The invention and its advantages will be better understood on reading the

detailed description given below of various embodiments of the invention given by way of non-limiting examples. This description refers to the pages of figures appended and listed below.

[0022] [Fig. 1] FIG. 1 described above schematically represents a pre-existing transmission on a vehicle.

[0023] [Fig. 2] Figure 2 schematically illustrates a first step of a method according to one aspect of the invention.

[0024] [Fig. 3] Figure 3 is a view of the support plane between the primary engine, the oil pan and the gearbox shown in Figure 2.

[0025] [Fig. 4] Figure 4 illustrates another step of a method according to one aspect of the invention.

[0026] [Fig. 5] Figure 5 shows a view of an example of a fastener segment according to one aspect of the invention.

[0027] [Fig. 6] Figure 6 is a schematic view of a primary transmission to which has been added a securing segment via a method according to one aspect of the invention.

[0028] [Fig. 7] Figure 7 shows an example of a pre-existing transmission to which a hydraulic machine has been added by means of a method according to one aspect of the invention.

[0029] [Fig. 8] Figure 8 schematically illustrates the steps of a method according to one aspect of the invention.

[0030] [Fig. 9] FIG. 9 illustrates an example of centering a hydraulic machine on a fixing segment according to one aspect of the invention.

In the various figures, the elements in common are identified by identical numerical references. Description of embodiments

A method for adding such a transmission is now described.

hydraulic with reference to Figures 2 to 7 which illustrate the various steps of the process, and Figure 8 which schematically shows the process.

During a first step E1 shown schematically in Figure 2, the oil pan 20 is separated from the gearbox 30 and from the primary motor 10, for example by removing the connecting elements such as the bolts ensuring a tight assembly at the level of the support surfaces (or support surfaces) of the gearbox 30, the primary motor 10 and the oil sump 20. The gearbox 30 and the primary motor 10 can be kept assembled to each other or separated to simplify the removal of the oil pan 20.

Figure 3 shows a view of the support planes of the primary motor 10 and the oil pan 20. It is seen that the primary motor casing 10 and the oil pan 20 define an opening allowing in particular the passage of 'an output shaft 12 of the primary motor 10 in order to couple it to the gearbox 30. In the example illustrated, the opening has a generally circular shape, the bearing planes of the primary motor 10 and of the casing. oil 20 each having the general shape of a ring segment around this opening and provided with housings for pins and / or fixing screws. The various support planes are typically each in a plane perpendicular to an axis of rotation of a primary motor shaft 10.

The method as proposed consists in coming to machine the bearing plane of the oil pan 20 during a machining step E2, so as to define a machined volume in which a fixing segment 70 will be inserted. .

[0036] Figure 4 schematically illustrates such a machining operation of the support plane of the oil pan 20, and Figure 5 shows an example of fixing segment 70.

As shown schematically in Figure 4 the oil pan 20 is machined so as to define a machined volume. This machined volume extends from the bearing plane of the oil pan 20, and has a thickness E corresponding to the thickness of material removed by machining. The fixing segment 70 is typically a plate having a primary portion 72 and a secondary portion 74. The primary portion 72 reproduces the volume machined in the oil pan 20. Thus, the primary portion 72 typically has a thickness E corresponding to the thickness of the volume machined in the oil pan 20, and fills the volume machined in the oil pan 20. The primary portion 72 can also extend beyond the volume machined in the casing. oil 20, in particular in an external radial direction, in particular in order to improve its mechanical properties and to integrate therein indexing means such as additional bores for pins or indexes.

The secondary portion 74 of the fixing segment 70 extends from the primary portion 72, and is dimensioned so as to extend beyond the volume machined in the oil pan 20. The secondary portion 74 of the segment fixing 70 has a bore 76 adapted to allow the insertion of a hydraulic machine shaft and thus achieve centering of a hydraulic machine, as will be seen below. The secondary portion 74 of the fixing segment 70 also has housings 78 for fixing or indexing means such as pins, screws or bolts. The shape of the secondary portion 74 as shown is purely illustrative. It is understood that the shape of the secondary portion 74 is determined as a function of the required mechanical properties, and as a function of the dimensions and fixings required for the hydraulic machine that is to be integrated.

[0040] The gearbox 30 is also modified. The gearbox housing 30 can be replaced, or its outlet port can be machined. The differential 40 coupled to the gearbox 30 is typically replaced by a differential having a cage with a splined outlet in particular in order to allow its connection with a hydraulic machine as will be seen below.

Thus, during a step E3 of positioning the fixing segment 70, place the fixing segment 70 and the primary motor 10 against the gearbox 30. The primary motor 10 is returned to its initial position resting against the gearbox 30. The fixing segment 70 is positioned so that its primary portion 72 comes to take the place previously occupied by the volume machined in the oil pan 20 relative to the

initial configuration shown in figure 1. Positioning can be performed in particular by means of pawns. It is understood that in the case where only the oil pan 20 has been removed in step E1, the gearbox 30 and the primary motor 10 are then already assembled to each other, and step E3 then consists

only to come to position and assemble indexing segment 70 to gearbox 30 and primary motor 10.

[0042] The indexing of the fixing segment 70 relative to the assembly comprising the primary motor 10 and the gearbox 30 can be achieved by means of a first centering element, for example a pin or centering pin. The centering means may pass through the fixing segment 70 and also connect the primary motor 10 and the gearbox 30. The connection between the first centering element and the fixing segment 70 may have a clearance of less than 5 mm, or else again. less than 3 mm.

[0043] The indexing of the fixing segment 70 is typically completed by means of angular orientation. This angular orientation means can be achieved by a second pin interposed for example between the fixing segment 70 and the gearbox 30 or between the fixing segment 70 and the primary motor 10, which ensures the angular orientation of the segment of fixing 70. The connection between the angular orientation means and the fixing segment 70 may have a clearance of less than 5 mm, or even less than 3 mm.

[0044] According to one example, the angular indexing means can be produced at

by means of two flat supports, for example between a section of the fixing segment 7 and a support plane on the engine. The connection between the angular orientation means and the fixing segment 70 can then have a play of less than 5 mm, or even less than 3 mm.

[0045] According to one embodiment, the fixing segment 7 comprises

through holes intended to pass screws. Such bores are typically not part of the angular centering and indexing means, and may have a greater clearance than the latter.

Following step E3; during a step E4 illustrated schematically in FIG. 6, the oil pan 20 is fixed to the primary motor 10 and to the gearbox 30 with which the fixing segment 70 is associated. As seen in Figure 6, we thus find the original configuration of Figure 1, with the difference that the fixing segment 70 has been inserted. The realization of the connection between the gearbox 30 and the primary motor 10 is therefore modified. A bearing plane is formed between the gearbox casing 30 and the primary motor casing 10 as was the case initially. A bearing plane is also formed between the gearbox housing 30 and the fixing segment 20, and between the fixing segment and the oil pan 20.

The oil pan 20 is typically mounted to slide relative to the primary motor casing 10 in an axial direction, typically perpendicular to the various bearing planes between the gearbox casing 30, the primary motor casing 10 and the oil pan 20. FIG. 6 shows the direction of the bearing planes by the Z axis, and the axial direction of sliding of the oil pan 20 relative to the primary motor casing 10 by the. X axis perpendicular to the Z axis. The authorized sliding is typically limited, so as to allow a clearance for example less than 1 mm, for example equal or substantially equal to 0.4 mm in the direction defined by the X axis. This sliding assembly is for example produced by means of screws or bolts mounted in oblong housings, or by any other suitable means. Such a sliding assembly makes it possible to ensure alignment of the various bearing planes between the gearbox housing 30, the primary motor housing 10 and the oil sump 20. The tight fitting of the oil sump 20 fitted of the fixing segment 70 on the gearbox housing 30 will cause an alignment of a bearing plane between the oil sump 20 and the primary motor housing 10.

[0049] Following step E4, we come to a step E5 to position a machine

hydraulic 80, for example a hydraulic pump with radial pistons and multilobe cam, which is then centered by means of the fixing segment 70. More precisely, a hydraulic machine 80 is centered by inserting a shaft of the hydraulic machine 80 in the bore 76 of the secondary portion 74 of the fixing segment 70, the shaft then typically being provided with a sleeve. The fixing segment 70 is dimensioned so that once centered with respect to the primary motor 10 and the gearbox 30, the bore 76 is aligned with an output shaft of the differential 40 or with an output shaft of the gearbox 30 adapted to carry out a drive of the machine

hydraulic 80.

A housing of the hydraulic machine 80 is fixed to the fixing segment via the housings 78. FIG. 7 schematically shows a system thus assembled. A shaft 82 of the hydraulic machine 80 is then coupled to a drive shaft of the machine, for example via the differential 40 or more precisely by connecting the shaft of the hydraulic machine 80 to an output shaft of the differential 40 or with an output shaft of the gearbox 30 adapted to drive the hydraulic machine 80. The centering of the hydraulic machine 80 by means of the fixing segment 70 ensures good positioning, that is to say precise, repeatable and without excessive play of the hydraulic machine 80 (and more precisely of its shaft 82) relative to a drive shaft of the machine, or a shaft output of the gearbox.

The fixing segment 70 is sized to withstand the forces and stresses resulting from the addition of the hydraulic machine 80 and its operation.

FIG. 8 summarizes the various steps described above as well as their sequence.

An exemplary embodiment of the centering of a machine is described below

hydraulic 80 relative to the fixing segment 70. With reference to Figure 9.

[0054] FIG. 9 shows the fixing segment 70 which is interposed between the differential 40 at the output of the gearbox 30 on the one hand, and a hydraulic machine 80 on the other hand.

A centering sleeve 90 is positioned in the bore 76 of the fixing segment 70. This centering sleeve 90 forms bearing surfaces on either side of the fixing segment 70 for the differential 40 (or typically a differential housing 40) on the one hand, and for the hydraulic machine 80 (or typically a housing of the hydraulic machine 80) on the other hand. The sealing of the connections between the centering sleeve 90 with the differential 40 and the hydraulic machine 80 is ensured by means of seals 94 and 98 respectively, typically O-rings. A segment 100, typically a splined sleeve, is inserted into the centering sleeve 90. A cage 42 of the differential 40 is inserted into the segment 100 via its end near the differential 40; the cage 42 has splines adapted to engage the splines of the segment 100, and thus be integral in rotation with the segment 100. An internal shaft 82 of the hydraulic machine 80 is also inserted into the segment 100 via its end close to the hydraulic machine 80 , and has splines adapted to engage the splines of the segment 100, and thus be integral in rotation with the segment 100. The sleeve 100 thus ensures the transmission of the rotational movement between the cage 42 of the differential 40 and the internal shaft 82 of the hydraulic machine 80. The seal around the internal shaft 82 of the hydraulic machine 80 is typically provided by means of a dynamic seal 84 of the lip ring type.

A central shaft 48, typically linked to a satellite of the differential 40, passes through the cage 42 of the differential 40 and the internal shaft 82 of the hydraulic machine, for example to transmit a torque to a wheel of a vehicle, such as initially shown in Figure 1.

So we find in the bore 76, arranged concentrically from the inside to the outside: the central shaft 48, the cage 42 of the differential 40 and the internal shaft 82 of the hydraulic machine 80, the segment 100 then the centering sleeve 90. The insertion of these various elements into the bore 76 will ensure angular locking of the fixing segment 70, eliminating any degree of rotational freedom which may remain following the mounting of the fixing segment 70. on the gearbox 30.

As a variant, the centering sleeve 90 may be initially mounted on the housing of the differential 40 or on the housing of the hydraulic machine 80, then inserted into the bore 76 of the fixing segment 70 when the differential 40 or the hydraulic machine 80 is positioned relative to the fixing segment.

[0060] As a variant, the centering sleeve 90 can be integrated into the housing of the

hydraulic machine 80 or to the differential housing 40. The use of a sleeve independent centering 90 is advantageous in order to allow the use of pre-existing components.

The precise positioning of the hydraulic machine 80 in the bore 76 of the fixing segment 70 is typically provided by a sliding adjustment which has, for example, a play of less than 0.1 mm.

The precise positioning of the hydraulic machine 80 relative to the central shaft 48 (that is to say relative to an output shaft of the gearbox 30), or relative to the assembly comprising the primary motor 10 and the gearbox 30 is ensured by the reduced play in the positioning of the fixing segment 70, by its centering and angular orientation means, and by the reduced play in the centering of the hydraulic machine 80 on the segment fixing 70.

According to one example, the centering of the hydraulic machine 80 is achieved by a centering nose or sleeve which cooperates with the bore 76. The hydraulic machine 80 then typically comprises fastening means comprising a support plane for tightening , and a centering nose. The centering nose is then typically concentric with one of the output shafts of the gearbox 30 or of the differential 40.

[0064] Alternatively, the precise positioning of the machine

hydraulic 80 in the fixing segment 70 can be produced without a centering sleeve or nose, for example by means of two centering pins, possibly performing the function of a screw, and having a clearance of less than 0.1 mm. In this case, the hydraulic machine 80 typically has a support plane without a nose or centering sleeve, and pins. The tightening function can then be provided by additional screws, or by a screw function carried by the pins.

The method as presented thus makes it possible to facilitate the addition of a

hydraulic transmission on a machine having a pre-existing transmission, and makes it possible in particular to avoid modifying the gearbox casing 30 and of the differential 40, such a modification being in fact highly restrictive. The method as proposed moreover makes it possible to ensure good positioning and to take up the mechanical forces associated with the hydraulic machine 80. The method as presented can in particular make it possible to add a hydraulic transmission to a pre-existing vehicle, for example in order to allow the modification of a vehicle of the traction or propulsion type so that it can have an all-wheel drive which can be selectively engaged via the addition of a hydraulic transmission.

Claims

[Claim 1] A method of integrating a hydraulic machine (80) on a machine comprising a gearbox (30) coupled to a clutch (35), a differential (40), a primary motor (10) and a housing oil (20) associated with the primary motor (10), the gearbox (30) being secured to the primary motor (10) and to the oil pan (20) according to a bearing plane formed between a surface of support of a gearbox housing (30) on the one hand, and a bearing surface of a primary motor housing (10) and a bearing surface of the oil pan (20) on the other part, in which the following steps are carried out successively:

a- (El) the oil sump (20) is separated from the gearbox (30) and from the primary motor (10),

b- (E2) the bearing surface of the oil pan (20) is machined, so as to define a machined volume,

c- (E3) the gearbox (10) is secured to the primary motor (20), and a fixing segment (70) is positioned resting on the gearbox (30), said fixing segment (70) comprising a primary portion (72) positioned so as to occupy the location of the machined volume of the bearing surface of the oil pan (20) and a secondary portion (74) dimensioned so as to protrude from the oil pan ( 20) and having a bore (76),

d- (E4) the oil sump (20) is secured to the gearbox (10) and to the primary motor (20), the fixing segment (70) being interposed between the oil sump (20) and the gearbox (10) and occupying the machined volume of the bearing surface of the oil pan (20),

e- (E5) a hydraulic machine (80) is positioned relative to the secondary portion (74) of the fixing segment (70), a shaft of the hydraulic machine being centered relative to the bore (76) of the secondary portion ( 74) of the fixing segment (70).

[Claim 2] The method of claim 1, wherein the machining (E2) of the bearing surface of the oil pan (20) is carried out so that the primary portion (72) of the fixing segment ( 70) forms a flat support with the gearbox (30) on the one hand, and with the oil pan (20) on the other hand.

[Claim 3] Method according to one of claims 1 or 2, in

wherein the primary portion (72) of the fixing segment (70) reproduces the volume machined in the bearing surface of the oil pan (20).

[Claim 4] The method according to one of claims 1 to 3, wherein the fixing segment (70) comprises a housing (78) adapted to cooperate with a centering pin so as to allow centering of the fixing segment (70 ) relative to the gearbox (30) and to the oil sump (20) when positioning (E3) the fixing segment (70).

[Claim 5] A method according to claim 4, wherein upon

positioning (E3) of the fixing segment (70), the housing (78) of the fixing segment (70) cooperates with a centering pin extending from the gearbox (30) or from the oil pan (20 ).

[Claim 6] Method according to one of claims 1 to 5, wherein during positioning (E5) of the hydraulic machine (80) relative to the secondary portion (74) of the fixing segment (70), a centering sleeve (90) in a bore (76) in the fixing segment (70), said centering sleeve (90) projecting on either side of the fixing segment (70), and a differential housing is fitted (40) and a casing of the hydraulic machine (80) on the centering sleeve (90) on either side of the fixing segment (70).

[Claim 7] The method of claim 6, wherein

positions a segment (100) in the centering sleeve (90), said segment (100) being configured to rotatably couple a cage of the differential (40), and a shaft (82) of the hydraulic machine (80).

[Claim 8] A vehicle comprising a gearbox (30) coupled to a clutch (35), a differential (40), a primary motor (10) and an oil pan (20), in which the gearbox ( 30) and secured to the primary motor (10) and to the oil pan (20),

said vehicle being characterized in that it further comprises

- a fixing segment (70), the fixing segment (70) comprising a primary portion (72) interposed between the oil pan (20) and the gearbox (30), and a secondary portion (74) projecting from the oil pan (20) and having a bore (76)

- a hydraulic machine (80) having a shaft (82) centered relative to the bore (76) of the fixing segment (70), the hydraulic machine being secured to the fixing segment (70).

[Claim 9] A vehicle according to claim 8, wherein the bore (76) in the fixing segment (70) is dimensioned to be aligned with an output shaft of the differential (40) or with an output shaft of the gearbox. speed (30).

[Claim 10] Vehicle according to one of claims 8 and 9, in

wherein the primary motor (10) rotates a primary axle of the vehicle, wherein the hydraulic machine (80) is a radial piston hydraulic pump, the vehicle further comprising at least one hydraulic motor powered by the hydraulic pump and suitable for rotating a secondary axle of the vehicle.