HYBRID TRANSMISSION WITH OFFSET ELECTRIC MACHINE

Description

[0001] The present invention relates to the field of hybrid transmissions for motor vehicles, comprising on the one hand a thermal drive engine, and on the other hand an electric machine.

[0002] More specifically, the present invention relates to a hybrid transmission for a motor vehicle equipped with a thermal engine and an electric traction machine located on the same line, comprising two concentric primary shafts connected respectively to the thermal engine and to the electric machine without a cut-off clutch, a secondary shaft connected to the wheels of the vehicle by a differential, and a shaft for transferring movement from a primary shaft to the secondary shaft, and for coupling the primary shafts.

[0003] Publication FR 3 022 495 discloses a hybrid transmission with a remote electric machine comprising two concentric primary shafts, one of which is a solid primary shaft connected to a thermal engine.ICE and a hollow primary shaft connected to an electric machine ME offset to the opposite end of the transmission. The transmission has a secondary shaft carrying a differential drive pinion. It also has a transfer shaft, permanently connected to the solid primary shaft. The transfer shaft returns the motion of the primary to the secondary shaft in certain transmission ratios, but does not directly drive the differential.

[0004] In reference to the figure 1 , there " structure de traction électrique » of this first transmission, is composed of two electric ratios EV1 And EV2, ensured by the meshing of two " pignons fixes électriques » of the hollow primary shaft with two " pignons fous électriques » rotating on the secondary shaft.

[0005] His " structure de traction thermique » is composed of four thermal ratios ICE1, ICE2, ICE3 And ICE4, associated with two idle gears of the thermal primary shaft, and two idle gears of the transfer shaft. The ratios ICE2 And ICE4 descend directly from the primary line onto two fixed gears of the secondary shaft. The ratios ICE1 And ICE3 take the transfer shaft, to go back down to the secondary via the gears of the reports EV2 Or ICE4. Finally, the transmission receives torque from a second electric machine HSG, descending on the transfer shaft by a connecting gear.

[0006] The transmission has two electric gears EV1 And EV2, and four thermal ratios ICE1, ICE2, ICE3 And ICE4.

[0007] These ratios, and their hybrid combinations, allow the traction motors to be adapted to optimize overall energy performance.

[0008] However, the change between the two electrical ratios EV1 And EV2 Acceleration involves a break in torque, which is unpleasantly felt by some users, particularly those accustomed to the usual comfort of automatic transmissions without a break in torque, such as dual-clutch gearboxes, or infinitely variable transmissions (CVT), or even single-speed electric vehicles.

[0009] A similar hybrid transmission is known from document EP 3 309 031 A1.

[0010] The present invention aims to take advantage of the increase in the electrical storage capacities of batteries, and the improvement in the performance of electric machines, to overcome the drawbacks of the known transmission. It allows the transmission to escape the reproach of discomfort mentioned above, linked mainly to poor quality of certain gear changes.

[0011] For this purpose, the proposed transmission includes the features of claim 1. Thus, it comprises only three primary idler gears associated with the heat engine, the first two gears of which rotate around the primary shaft linked to the heat engine, and the third gear rotates around the transfer shaft, and at least one primary gear fixed on the primary shaft, linked to the electric traction machine.

[0012] In one embodiment, the third idler gear meshes with a fixed gear of the primary shaft, linked to the traction machine.

[0013] Thanks to these modifications, it becomes possible to benefit from the increased capacity of electric machines, to improve, on the one hand, the performance in terms of efficiency and mass of the transmission, and on the other hand, the quality of gear changes. Thanks to the invention, it is also possible to limit the number of gear changes, by eliminating a short thermal gear, and the second electric gear.

[0014] The present invention will be better understood upon reading the following description of a non-limiting embodiment thereof, with reference to the appended drawings, in which: there figure 1 illustrates a previously known transmission, the figure 2 illustrates a first embodiment of the invention, the figure 3 shows its transverse arrangement, the figure 4 is a matrix of its parallel, thermal, electric hybrid kinematic modes, the figure 5 illustrates its serial hybrid mode, the figure 6 shows its electrical-thermal bond structure, the figure 7 shows its electrical connection structure, the figure 8 shows its hybrid traction structure, the figure 9 illustrates the use of the transmission on a plug-in hybrid vehicle, the figure 10 illustrates its use on a non-rechargeable hybrid vehicle, the figure 11 illustrates an embodiment of a transmission not covered by the claimed invention, the figure 12 relates to its electrical-thermal connection structure thereof not covered by the claimed invention, the figure 13 , to its electrical connection structure, the figure 14 , to its bridge descent structure, and the figure 15 and the figure 16 , illustrate its use on a plug-in hybrid vehicle (PHEV) or not (HEV).

[0015] The hybrid transmission of the figure 1 for a motor vehicle equipped with a heat engine 1 and an electric drive machine 2, comprises two concentric primary shafts 3, 4, connected to the crankshaft of the heat engine 1 ( ICE ) (not shown) and to the main electric traction machine 2 ME, without cut-off clutch. It comprises a secondary shaft 5 connected to the wheels of the vehicle by a differential 7, and a transfer shaft 6 for movement of the solid primary shaft 3 on the secondary shaft 5, and for coupling the primary shafts 3, 4. The solid primary shaft 3 is connected via a filtration system 21 (damper hub, " damper » , double damping flywheel DVA or other), at the nose of the crankshaft 1a of the thermal engine ICE. The transmission is also coupled to a second electric machine 16 HSG, connected to the transfer shaft 6 by a return pinion 19a.

[0016] This transmission has three couplers: a first coupler C2-4Th allows you to engage the second and fourth thermal gears on the primary line ICE2, ICE4, a second coupler C1-2EV, allows two electric gears to be engaged on the secondary line EV1, EV2, and a third coupler C1-3Th allows a first and third thermal ratio to be engaged on the transfer shaft ICE1, ICE3.

[0017] On the figure 2 , we find in part the same arrangement. It is also a hybrid transmission for a motor vehicle equipped with a thermal engine 1 and an electric traction machine 2 offset on the same line, comprising two concentric primary shafts 3, 4 linked respectively to the thermal engine and to the electric machine 2 without a cut-off clutch, a secondary shaft 5 connected to the wheels of the vehicle by a differential 7, and a transfer shaft 6 for movement from a primary shaft 3 to the secondary shaft 5 and for coupling the primary shafts 3, 4.

[0018] However, the drivetrain has evolved considerably. The new transmission has only three primary idler gears 8, 9, 10, associated with the thermal engine 1. The first two 8, 9 rotate around the primary shaft 3 linked to the thermal engine 1 ICE. They each allow a thermal report to be established ICE2, ICE4, " hybridable » by combination with an electrical report EV1. The third idler gear 10 rotates around the transfer shaft 6. Two primary gears 11, 14 are fixed on the hollow shaft 4 connected to the machine ME. Only the fixed primary gear 14, meshing with a secondary idle gear 12, is dedicated to a purely electric mode, on the ratio EV1. The second idler gear 13 of the secondary shaft 5, facing the first, is only dedicated to a hybrid mode Hyb3.

[0019] In the two non-limiting embodiments of the invention described, the transmission can be connected to a secondary electric machine 16 HSG, whose output shaft 18 descends on the transfer shaft 6, so as to be able to combine its torque with that of the thermal engine. The second electric machine 16 makes it possible to have a series hybrid mode, in which the thermal engine 1 drives the secondary machine 16 as a generator, in order to produce electrical energy usable by the electric traction machine ME, to move the vehicle.

[0020] On the figure 2 , the third idler gear 10, dedicated to thermal ratios, meshes with a fixed gear 11 of the primary shaft 4 linked to the traction machine 8. It makes it possible to establish hybrid modes on two different thermal ratios ICE1 And IC3, and in particular the mode " Hyb3 ", which benefits from the multiplication of the thermal ratio ICE3. The transfer shaft 6 carries a fixed pinion 20 meshing with the primary fixed pinion 3a.

[0021] The two idle gears 12, 13 of the secondary shaft 5 mesh with two fixed gears 11, 14 of the hollow primary shaft 4 to establish the electrical ratio EV1 and the thermal ratio ICE1, or hybrid mode Hyb3. When the third idler gear 10 is engaged, the thermal torque descends onto the hollow primary shaft 4. If the gear 12 is engaged at the same time as the gear 10, the reduction of the thermal torque corresponds to that of a first thermal ratio ICE1. This ratio can be hybridized by combination with the electrical ratio EV1. If, on the contrary, pinion 13 is clutched on its shaft, Hyb3 mode is engaged, with a third thermal reduction ratio ICE3.

[0022] The cross-sectional view of the figure 3 shows the spatial arrangement of the shaft and pinion lines of the figure 2 From left to right, we see the differential line 7, the secondary line 5, then the primary line whose largest diameter is that of the thermal idler gear 9, of the thermal ratio ICE4 ; above this, on the left the transfer line 6 and on the right the intermediate gear line 9 towards the line 18 of electric machine 16 HSG.

[0023] The new hybrid transmission offered has eight traction modes: an electric traction mode on the electric report EV1, two thermal traction modes on the reports ICE2 And ICE4, and five hybrid modes: a first parallel mode « Hyb11 » combining the torque of the thermal engine on the ICE1 ratio, and that of the electric ratio EV1 ; a second parallel mode " Hyb3 » grouping on the gable Hyb3, the machine torque ME and that of the thermal pinion ICE1-3 ; a third parallel mode " Hyb21 » combining the torque of the second thermal ratio and that of the electric ratio; a fourth parallel mode « Hyb41 » combining the torque of the fourth thermal gear and the electric gear; finally a series hybrid mode « e-drive1 » in which the thermal engine provides the energy supply to the traction machine ME, by running the second machine HSG in generator. In the four parallel hybrid modes, the power of the secondary machine HSG 16 can be combined with that of the thermal engine.

[0024] The torque flows established on each of these modes are detailed on the figure 4 : top left, the report EV1 is engaged: coupler C1-2EV on the left, couplers C2-4Th And C1-3Th in neutral, on the first line, three hybrid gears: mode EV1 + ICE1-3 with coupler C1-2EV left and coupler C1-3Th3 engaged; fashion EV1 + ICE2 with coupler C2-4Th left; fashion EV1 + ICE4 with coupler C2-4Th on the right, on the second line the coupler C1-2EV is in neutral: two gears in thermal mode, IC2 And ICE4, according to the position of C2-4Th, on the third line, hybrid mode Hyb3 : coupler C2-4Th in neutral, coupler C1-2EV right and coupler C1-3Th engaged.

[0025] There figure 5 illustrates a series hybrid mode, where the thermal engine runs the machine HSG in generator, while the machine ME alone ensures the vehicle's traction.

[0026] There " structure de liaison électrique-thermique » ( HSG-ICE ) of the transmission is highlighted on the figure 6 It is composed of three lines of shafts kinematically connecting the secondary electric machine HSG to the thermal engine ICE : the input shaft 18 of the HSG machine, the connecting shaft 17, and the solid primary shaft 3 on which the fixed pinion 3a is attached.

[0027] The solid primary shaft 3 also supports the DVA 21 , as well as the coupling system C2-4Th idle gears I8 And 9. The linking structure HSG-ICE is also engaged with the transfer shaft 6 by the primary pinion 3a, meshing with the pinion 17a of the connecting shaft 17, coupled to the pinion 18a, to ensure the functions of synchronization, assistance with disengagement, and " boost » with the idler gear ICE1-3 thanks to the coupling system C1-3Th.

[0028] This structure ensures the following functions: launching the thermal engine ICE by the HSG electric motor through a triple gear (" triplette ») 18a, 17a, 3a (instead of a quadruple gear in the previous architecture), synchronization of the rotation speeds of the thermal engine ICE using the HSG on the rotation speeds of the idler gears to be engaged in each gear, assistance in disengaging the gears thanks to the cancellation of the inertial torque by the secondary machine HSG, contribution of additional torque to the gear engaged by the secondary engine HSG, providing a function boost » driving pleasure, by the immediate contribution of acceleration of the vehicle when quickly pressing the accelerator pedal, recharging of the battery by using the available torque of the thermal engine not needed for traction of the vehicle, to turn the machine HSG in generator; the power in this case passes through shafts 3, 17, 18, through a triple gear (which improves the efficiency of the transmission compared to the quadruple gear of the previous transmission), and limitation of the impact torque levels during sudden blockages of the kinematic chain thanks to the clipping of the torque, by the DVA 21 .

[0029] There " structure de traction électrique » of the transmission is highlighted on the figure 7 . The hollow primary shaft 4 connected to the machine ME, and concentric to the solid shaft 3, carries two fixed pinions: the fixed pinion 14 of the electric report EV1, engaged with the first idler gear 12 of the secondary shaft 5, and the fixed gear 11 of the triple gear 10, 11, 13 allowing the engagement of two hybrid modes Hyb11 And Hyb3.

[0030] The two idler gears 12 and 13 are " crabotables » on their shaft 5, using the coupling system C1EV-H3. A total gear reduction of approximately 10 on the report EV1 helps ensure good performance for the " décollage » from a standstill, with an acceleration of 1m / s 2< on a 12% slope, and a maximum travel speed Vmax ≥ 130km / h at 12000 revolutions per minute (rpm) of the machine ME. The electric traction structure provides the following functions: the vehicle's take-off from a standstill, in all reasonably foreseeable situations of slope, grip and vehicle load, the vehicle's traction up to approximately 130 km / h in pure electric or hybrid mode (with the contribution of the thermal engine's torque) depending on the energy available in the battery and the pressure on the accelerator pedal.

[0031] In reference to the figure 8 , there " hybrid traction structure » of the transmission is as follows: the first hybrid mode Hyb1-1is obtained by clutching the pinion ICE1-3 with the Walkman C1-3Th, and by clutching the pinion EV1 by the walkman CEV1-H3, and hybrid mode Hyb3 is achieved by engaging pinion 10 with the sliding gear C1-3Th, and by turning the pinion 13 with the sliding gear CEV1-H3.

[0032] In hybrid mode Hyb3, the torque of the thermal engine descends from the transfer shaft 6 onto the secondary shaft 5 in the second thermal gear ICE3, by a triple gear consisting of the third idler gear 10, a fixed gear 11 of the primary shaft 4 linked to the electric traction machine 2, and an idler gear 13 of the secondary shaft 5. The realization of the third thermal ratio in place of the second electric ratio of the known transmission, makes it possible to release the reductions achievable in third and fourth thermal ratio ICE3 And ICE4,to adapt them more flexibly to the dynamic performance and consumption constraints of each vehicle. The " hybrid structure » of the transmission provides the following functions: the vehicle's traction on a steep slope, in mode Hyb11, and the maximum travel speed of the vehicle in the mode Hyb3, by adding the electric and thermal torques to ensure the strongest acceleration of the vehicle and reach its maximum power Pmax.

[0033] The combination of these structures within the transmission allows for gear changes without torque interruption, for example in the following two gear change sequences: Hyb21-> Hyb3 : Hyb21->ICE2->Hyb22 -> ZEV2 -> Hyb3, Or ICE4 -> Hyb3 : ICE4 -> Hyb42 ->ZEV2 -> Hyb3.

[0034] There figure 9offers, in a non-limiting manner, preferred areas of use, for the different transmission modes, depending on the depressing of the accelerator butterfly and the speed of travel. This with the gear change zones on a rechargeable vehicle PHEV, depending on the vehicle speed and the pressure on the accelerator pedal: EV1 (electrical report), Hyb21 (Hybrid ICE2 + EV1 on the second thermal report), and Hyb41 on the fourth, with or without the addition of the second electric machine HSG. The Hyb3 report can also benefit from the support of the second electric machine HSG.

[0035] There figure 10 gives similar indications in the case of a non-rechargeable hybrid vehicle HEV.

[0036] THE figures 11 to 16 illustrate an embodiment of a transmission not covered by the claimed invention, devoid of its " first thermal report » ICE1.The structures of " electrical-thermal connection, of " electrical connection ", and the bridge structure, are not identical to the first embodiment.

[0037] The hollow shaft 4, connected to the electric traction machine 2, carries a single fixed pinion 14, meshing with an idler pinion 12 of the secondary shaft. The third idler pinion 10 meshes with the pinion 9 of the ratio ICE4, meshing itself with the fixed pinion 15 of the secondary shaft 5 to establish a thermal relationship.

[0038] The gear ratio is adapted to take advantage of the maximum torque of the electric machine at the rotation speed allowing the ignition of the thermal engine. As indicated on the figure 12 , there " electrical-thermal connection structure ", is composed of four lines of shafts kinematically connecting the machine HSG to the thermal engine ICE: the input shaft 18 of the HSG 16, the connecting shaft 19, the transfer shaft 6 coupling with its fixed gear 20, and the coupling system of the idler gear 10 (thermal ratio ICE3 ) , and the solid primary shaft 3, supporting the damping system ( DVA ) 21, as well as the coupling system of idler gears 8 and 9 (thermal ratios ICE2 And ICE4 ) .

[0039] This structure performs the following functions: the start of the ICE thermal engine by the HSG electric machine, the synchronization of the rotation speed of the thermal engine ICE using the HSG on the rotation speed of the idle gears to be engaged, assistance in disengaging the gears to be disengaged, thanks to the cancellation of the inertial torque by the HSG, the contribution by the HSG,additional torque in the gear engaged, and recharging the battery by using the available torque from the thermal engine not needed for traction of the vehicle, when the HSG works as a generator, filtering the a-cycling of the thermal engine ICE speak DVA 21, and the limitation of impact torques, in the event of sudden blocking of the drive train.

[0040] With reference to Fig. 13, the “ electrical connection structure » of the transmission is as follows. The electrical report EV1 is obtained by the fixed gear 14 of the hollow shaft 4 and the idle gear 12 of the secondary shaft 5; it is " dog-friendly » using the coupling system C1EV. A total gear ratio of approximately 10 on this ratio ensures good take-off performance of the vehicle with an acceleration of 1m / s 2< under load on a 12% slope, and a maximum speed greater than 130km / h at 12,000 revolutions per minute (rpm).

[0041] The connecting structure provides the following functions: the vehicle's take-off in all reasonably foreseeable situations of slope, grip, and vehicle load, the vehicle's traction up to approximately 130 km / h in pure electric mode, or in hybrid mode (with the contribution of the thermal engine's torque), depending on the energy available in the battery and the pressure on the accelerator pedal.

[0042] The "structure of bridge descent » corresponding, isolated on the figure 14 is as follows: transmission of thermal torque to the transmission shafts from thermal idle gears 8, 9, 10, transmission of torque from the electric traction machine to idle gear 12 of the ratio EV1, transmission of thermal and electrical torque to the wheels by the secondary shaft 5 and its drive pinion 22, the secondary shaft 5 supporting the fixed pinions 23, 15 of the ratios ICE4 And ICE2, as well as the coupling system C1EV of the report EV1 ; the secondary shaft 5 also provides guidance for the idler gear 12 of the EV1 ratio.

[0043] THE figures 15 and 16 offer simplified (non-limiting) usage matrices, ratios based on accelerator pedal pressure and vehicle speed, for a plug-in hybrid vehicle PHEV for the figure 15 Or HEV, on the figure 16 .

[0044] In the two non-limiting embodiments of the invention described, the transmission has three idler gears associated with the thermal engine and a main ratio multiplying the power of the electric machine. In the first embodiment, the second electric ratio of the transmission is only used in hybrid mode.

[0045] The thermal idler gear 10, arranged on the transfer shaft 6, connects the thermal and electrical primary lines. It allows parallel hybridization directly at the output of the two traction sources (thermal engine ICE and electric machine ME ) . Its combination with the gear ratios of the electric primary shaft (hollow shaft 4) creates gear ratios corresponding to a first and third gear ratio in a thermal powertrain.

[0046] The separate production of third-year reports ICE3 and fourth ICE4 allows perfect adaptation of the gearbox opening by adjusting the fourth gear for optimal consumption on the highway, while the third gear can be dedicated to the dynamic performance of the vehicle (maximum acceleration and maximum travel speed).

[0047] In the embodiment not covered by the claimed invention and described within the figures 11 to 16 , the transmission has no second electric gear, and no idler gear connecting the primary electric and thermal lines. The third thermal gear is achieved by a triplet gear passing over the idler gear of the fourth gear. This arrangement reduces the axial size of the transmission and its mass, while allowing a gain in efficiency. This embodiment is of great interest, since the power of the thermal engine is transformed into electrical energy for electric traction in EV1 is sufficient to do without hybrid mode Hyb11.

[0048] In both embodiments described, the serial hybrid mode “ E-drive » allows the mechanical efficiency of the transmission to be optimized, by using the surplus thermal torque to recharge the battery.

[0049] In the first ( figures 2 to 8 ), the power passes in both directions between the thermal engine ICE and the secondary electric machine HSG 16 by a triple gear 18a, 17a, 3a, between the solid primary shaft 3, an intermediate shaft 17 (radially offset from the transfer shaft 6) and the shaft 18 of the secondary machine 16. This arrangement simplifies the kinematic chain between the heat engine and the secondary electric machine HSG, because the gear ratio between the two motors is the result of two gears instead of three, without going through the transfer shaft.

[0050] In the second ( figures 11 to 14 ), this transit is carried out in a similar manner to the figure 1 , through a quadruple gear. In this respect the architecture of the first embodiment of the transmission is more efficient than that of the second.

[0051] Finally, the developments in the powertrain do not degrade the dynamic performance of the vehicle, as for the " takeoff » , to hill traction and maximum speed in electric mode. These modifications mainly consist of removing the second electric gear EV2 and the first thermal report ICE1. They allow you to optimize: the transmission efficiency through gains in tooth friction and friction of the idler gears on their shafts, the mass involved, therefore the cost of the component and also the vehicle's autonomy, the overall quality of gear changes, thanks to the elimination of gear changes EV1-EV2 and of his “couple hole”, very appreciable suppression in urban and semi-urban driving on the new electric mode " without changing gears”.

Claims

1. Hybrid transmission for a motor vehicle equipped with a heat engine (1) and an electric traction machine (2) offset on the same line, comprising two concentric primary shafts (3, 4) connected respectively to the heat engine and to the electric machine (2) without a disconnect clutch, a secondary shaft (5) connected to the vehicle wheels by a differential (7), and a shaft (6) for transferring motion from a primary shaft (3) to the secondary shaft (5) and for coupling the primary shafts (3, 4), the hybrid transmission comprising only three idle gears (8, 9, 10) associated with the heat engine, the first two (8, 9) of which rotate around the primary shaft (3) connected to the heat engine and the third (10) of which rotates around the transfer shaft (6), and at least one fixed primary gear (14) on the primary shaft (4) connected to the electric traction machine (2), the transmission comprising a secondary electric machine (16) of which the output shaft (18) descends to the transfer shaft (6) so as to be able to combine its torque with that of the heat engine and the power traveling from the heat engine (1) to the secondary electric machine (16) in both directions,via a triple gear set (18a, 17a, 3a) between the primary shaft (3) connected to the heat engine, an intermediate shaft (17) radially offset from the transfer shaft (6) and the shaft (18) of the secondary machine (16), the triple gear set (18a, 171, 3a) comprising a fixed primary gear (3a) fitted on the primary shaft (3) connected to the heat engine (1), the fixed primary gear (3a) meshing with a gear (17a) on the intermediate shaft (17), which is coupled to a gear (18a) on the shaft (18) of the secondary machine (16).

2. Hybrid transmission according to claim 1, characterized in that the third idle gear associated with the heat engine (10) meshes with a fixed gear (11) of the primary shaft (4) connected to the traction machine (8).

3. Hybrid transmission according to either of the preceding claims, characterized in that the first two idle gears (8, 9) associated with the heat engine each make it possible to establish a heat ratio (ICE2), (ICE4), which can be hybridized by being combined with an electric ratio (EV1).

4. Hybrid transmission according to claims 2 and 3, characterized in that the third idle gear associated with the heat engine (10) makes it possible to establish hybrid modes in two different heat ratios (ICE1) and (ICE3).

5. Hybrid transmission according to claim 4, characterized in that the secondary shaft (5) carries two idle gears (12, 13) meshing with two fixed gears (14, 11) of the primary shaft (4) connected to the traction machine, these two idle gears making it possible to establish, for one of the gears, the electric ratio (EV1), and for the other gear the first heat ratio (ICE1) or the hybrid mode (Hyb3).

6. Hybrid transmission according to claim 5, characterized in that in hybrid mode (Hyb3) the torque of the heat engine (1) descends from the transfer shaft (6) to the secondary shaft (5) in the second heat ratio (ICE3) via a triple gear set consisting of the third idle gear associated with the heat engine (10), a fixed gear (11) of the primary shaft (4) connected to the electric traction machine (2), and an idle gear (13) of the secondary shaft (5).

7. Hybrid transmission according to any of the preceding claims, characterized in that it has a series hybrid mode, in which the heat engine (1) drives the secondary electric machine (16) as a generator in order to produce electrical energy that can be used by the electric traction machine (2) to move the vehicle.