METHOD AND DEVICE FOR IMMOBILIZING A ROAD VEHICLE AT A STATION

Description

[0001] The present invention relates to the control of hybrid powertrains, and their immobilization when stationary. More specifically, it relates to a method and a device for immobilizing a road vehicle when stationary, by pressing its mass on the compressive strength of its thermal engine. On hybrid vehicles having an electric machine linked to the thermal engine, it may be necessary to keep the vehicle stopped, on the compressive strength of its thermal engine, particularly in very cold weather. In these circumstances, the engine crankshaft must be kept mechanically connected to the vehicle's wheels. To do this, the transmission must be "closed" with a gear engaged.

[0002] With a manual transmission, the driver who wants to benefit from the compression resistance of the thermal engine to immobilize his vehicle, particularly on a slope, has the reflex to engage a gear, after having switched off the engine, and possibly having applied the brakes.

[0003] If the brakes are then released, the vehicle tends to lurch uncontrollably forward or backward. This lurch results from the difference between two adjacent compression positions of the crankshaft. Its amplitude depends on the gear ratio between the engine and the wheels, and the radius of the wheels. It allows the vehicle to adjust its position, based on the compression of a cylinder.

[0004] The vehicle's jump can reach several tens of centimeters. This distance is determined by the crankshaft's rotation angle between two compressions. It corresponds to the product of the crankshaft's rotation angle α,by the gear ratio to the wheel r, by the radius of the wheel R, and by 2 Π / 360.

[0005] Generally speaking, if the driver has the option of voluntarily leaving the vehicle with the engine stopped, "in gear" in a gear engaged, whether on a thermal or hybrid vehicle, the vehicle risks reacting by jerking, to place its engine in a compression position, when the brakes are released.

[0006] WO 2019 / 219294 A1 presents a hybrid transmission for a motor vehicle equipped with a heat engine and an electric traction machine located on the same line, comprising two concentric primary shafts connected respectively to the heat 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 coupling the primary shafts, characterized in that it comprises only three primary idler gears associated with the heat engine, the first two of which rotate around the primary shaft connected to the heat engine and the third of which rotates around the transfer shaft, and at least one primary gear fixed on the primary shaft connected to the electric traction machine.

[0007] DE 10 2010 004711 A1 discloses a hybrid drivetrain and a method for controlling the same. The invention relates to a hybrid drivetrain for a motor vehicle, comprising a first drive unit, a dual-clutch transmission and an electric machine, the dual-clutch transmission comprising a first and a second friction clutch and a first and a second sub-transmission, the first sub-transmission being assigned odd gears and the second sub-transmission being assigned even gears, and the electric machine being assigned one of the sub-transmissions. A third friction clutch is arranged between the two friction clutches and the first drive unit.

[0008] EP 3309031 A1 presents a mode transition control device for a hybrid vehicle, said hybrid vehicle comprising an internal combustion engine (ICE) arranged to be mechanically connected to a drive wheel via a first clutch (C1) engaged by a clutch stroke from a disengaged position; a first electric motor (MG1) arranged to be mechanically connected to the drive wheel via a third clutch (C3) engaged by a clutch stroke from a disengaged position; a second electric motor (MG2) mechanically connected to the internal combustion engine, and a battery electrically connected to the first electric motor and the second electric motor.When a battery (SOC) is at a power generation demand threshold value A or lower, the vehicle travels in a “series HEV mode,” in which the first electric motor (first motor / generator MG1), to which the electric power generated by the second motor / generator (MG2) and the battery power are supplied, is used as a drive source. The hybrid vehicle is equipped with a transmission control unit for performing control so that the travel mode switches to a “parallel HEV mode” when the vehicle speed (VSP) has reached a switching speed during travel in the “series HEV mode.”When an increase in temperature of the second power generation system, including the second motor-generator (MG2), is expected during travel in "series HEV mode," the transmission control unit changes the vehicle shift speed to a second vehicle shift speed (VSP2) that is slower than the first vehicle shift speed (VSP1) used before the temperature increase was determined.

[0009] DE 11 2014 000581 T5 presents a hybrid vehicle (1A), which comprises a dual-clutch transmission having six forward gears. Arranged in the hybrid vehicle (1A) between a first input shaft and a first output shaft of the transmission are: a first gear train (G1) corresponding to one speed; a third gear train (G3) corresponding to three speeds; a fifth gear train (G5) corresponding to five speeds; and a sixth gear train (G6) corresponding to six speeds. A second gear train (G2) corresponding to two speeds and a fourth gear train (G4) corresponding to four speeds are arranged between a second input shaft and a second output shaft.A first liner is disposed between the first gear train (G1) and the third gear train (G3); a second liner is disposed between the fifth gear train (G5) and the sixth gear train (G6); and a third liner is disposed between the second gear train (G2) and the fourth gear train (G4). A second Motor / Generator MG is used in order to be able to output motive force to the second input shaft. The present invention aims to eliminate any risk of reaction of the vehicle when closing its powertrain, with the engine off.

[0010] To this end, it proposes to carry out the following operations: immobilization of the vehicle by its wheel brakes, switching off the engine, opening the vehicle's transmission so as to decouple the thermal engine from the wheels, angular adjustment of the engine's crankshaft on the compression of at least one cylinder, carried out by an electrical machine connected to the crankshaft, and closing the vehicle's transmission.

[0011] Preferably, the assembly consisting of the heat engine and the first electric machine is not mechanically connected to the wheels of the vehicle during adjustment of the crankshaft.

[0012] The proposed device for immobilizing a road vehicle when stationary by applying its mass to the compressive strength of its thermal engine comprises a first coupling means capable of connecting the assembly consisting of the engine and an electrical machine to the transmission, or of disconnecting them to allow angular adjustment of the crankshaft.

[0013] This invention finds a preferred, but not limiting, application on a vehicle having a hybrid powertrain.

[0014] Using one or more electric machines to place the thermal engine on compression just before closing the transmission, allows the vehicle to be completely immobilized when stationary.

[0015] Other characteristics and advantages of the present invention will appear clearly on reading the following description of a non-limiting embodiment thereof, with reference to the attached drawings. [ Fig. 1 ] is a hybrid GMP kinematic diagram. [ Fig. 2 ] isolates a part of it. [ Fig. 3A ] graphically translates the adjustment of the crankshaft. [ Fig. 3B ] also. [ Fig. 4 ] illustrates the process.

[0016] The device for immobilizing a road vehicle when stationary by pressing on the compressive strength of its thermal engine is illustrated in a non-limiting manner by the figure 1 This diagram corresponds to the kinematic architecture of a hybrid powertrain (GMP) such as that described in detail in publication FR 3 022 495, to which reference may be made.

[0017] This GMP is composed of a stepped ratio transmission 1, combining the torque of a thermal engine 2, and an electric traction machine 3, in the direction of the wheels of a vehicle. The engine 2, and the machine, 3 are placed on a line of concentric primary shafts 4, 5. Their torques are grouped on a secondary shaft 6 driving a differential 7 which distributes the torque between the two wheels of an axle. The thermal engine 2 is connected to another electric machine 8, such as a starter, or an auxiliary machine, by a gear descent 9a, 9b, 9c.

[0018] The proposed immobilization device includes: a first coupling means C3 capable of connecting the assembly consisting of the engine and an electric machine 8 to the transmission, or of disconnecting them to allow the angular adjustment of the crankshaft, a second coupling means C2 capable of connecting an electric traction machine 3 to the transmission to vary the position of the shafts thereof during the angular adjustment of the crankshaft, and a third coupling means C1, which serves to directly couple the engine 2 and the traction machine 3.

[0019] The combined closure of the two coupling means C3, C2 ensures the engagement of a transmission ratio in which the thermal engine is connected to the wheels. In this ratio, the electric traction machine 3 is also connected to the wheels.

[0020] Transmission 1 allows the compressive resistance of the thermal engine 2 to be transferred to the wheels when stationary, to immobilize the vehicle if the two couplers C3 and C2 are tightened when the vehicle brakes are released. The cumulative closure of these two couplers allows the transmission to be closed, and the vehicle to be immobilized when stationary by engaging a gear in which the thermal engine 2 is connected to the wheels, as well as the electric traction machine 3.

[0021] In this state, the transmission is capable of limiting, and even completely eliminating the slight movement of the vehicle resulting from its jump, which is normally necessary to find support on the compression of a cylinder of the thermal engine 2, once the vehicle is stopped and its engine is switched off. This result is obtained thanks to the intervention on the thermal engine, of an electric machine 8 or 3. The intervention consists of actuating an electric machine 8 or 3, to carry out an angular adjustment of the crankshaft on a compression position of the engine 2 while the vehicle is held at a standstill by its wheel brakes, engine switched off with its transmission open, before closing it.

[0022] In a first embodiment, the angular adjustment of the crankshaft is carried out by the electric machine 8, which is connected to it by the gear descent 9a, 9b, 9c. As an alternative to the gear descent 9a, 9b, 9c, the descent of the movement of the electric machine 8 on the heat engine 2 can be ensured by a belt, or any other transfer means.

[0023] Machine 8 is an electrical machine that can be controlled in terms of force and / or position, for example a starter, or a simple auxiliary machine. During adjustment of the crankshaft by machine 8, the assembly consisting of the heat engine 2 and machine 8, which is isolated on the figure 2 , is not mechanically connected to the vehicle's wheels, because all the transmission couplers are open.

[0024] The vehicle is brought to a standstill as follows. The driver brakes until the vehicle stops. The thermal engine 2 is then switched off at the driver's request. The engine is disconnected from the wheels by opening the couplers C3 and C2. The thermal engine 2 - first electric machine 8 assembly is then independent of the wheels. Initially, the angular position of the crankshaft is random, as in the figure 3A . The thermal engine 2 is then rotated using the electric machine 8, to adjust the crankshaft to the compression of a cylinder. This movement continues until the position illustrated by the figure 3B From this, the electric machine 8 holds the crankshaft in position.

[0025] The following operation concerns the vehicle's transmission 1. Engaging a gear, for example a first forward gear, is carried out by closing the couplers C3 and C2 on the figure 4 Their closure allows the movement of the thermal engine 2 and the electric machine 8 to descend on the differential 7, towards the wheels. The thermal engine 2 is then linked to the wheels on the first thermal ratio, and the mass of the vehicle is supported by the compression of a cylinder.

[0026] In summary, the process of immobilizing a stationary vehicle, by applying its mass to the compressive strength of the thermal engine, essentially involves the following steps: immobilization of the vehicle by its wheel brakes, switching off the engine 2, opening the transmission 1 of the vehicle so as to decouple the engine 2 from the wheels, angular adjustment of the crankshaft of the engine 2 on the compression of at least one cylinder carried out by an electrical machine connected to the crankshaft, and closing the transmission 1 of the vehicle.

[0027] Alternatively, the position of the crankshaft can be varied slightly, using the electric traction machine 3, and the internal shafts of the gearbox. Their position is then controlled by the electric traction machine 3. The previous method remains applicable.

[0028] The transmission described from the figures does not limit the application of the proposed method to a particular hybrid architecture. This method can be implemented on any type of powertrain with a thermal engine, a transmission capable of temporarily disconnecting the engine from the wheels, and an electric machine with a connection to the engine crankshaft. Its main advantage is to control the movement of the vehicle when it is stopped by "pressing" on an engine compression.

[0029] In the example described, the gear engaged is a first forward gear, which is engaged by closing the couplers C3 and C2 of the transmission in accordance with the figure 4 . However, without departing from the scope of the invention, the method can be applied by engaging another forward gear or a reverse gear, depending on the direction of the vehicle relative to the slope.

Claims

1. Method of immobilizing a road vehicle at a standstill by pressing on the compressive strength of its internal combustion (2) engine, characterized in that it comprises the following steps: - immobilization of the vehicle by its wheel brakes, - engine (2) shutdown, - opening of the vehicle transmission (1) so as to decouple the engine (2) from the wheels, - angular adjustment of the engine (2) crankshaft on the compression of at least one cylinder made by an electric (8, 3) machine connected to the crankshaft, and - closing the vehicle transmission (1).

2. Method for immobilising a road vehicle at a standstill according to claim 1, characterized in that the assembly consisting of the heat engine and the electric (8) machine is not mechanically connected to the wheels of the vehicle, during the angular adjustment of the crankshaft.

3. Method for immobilising a road vehicle at a standstill according to claim 1 or 2, characterised in that the electric (8) machine is controllable in terms of force and / or position.

4. Method for immobilising a road vehicle at standstill according to claim 1, characterized in that the angular adjustment of the crankshaft is also carried out by the internal shafts of the transmission (1).

5. Method for immobilising a road vehicle at standstill according to claim 4, characterized in that the angular adjustment of the crankshaft by the internal shafts of the transmission is controlled by an electric traction (3) machine6. Device for immobilising a road vehicle at a standstill by pressing the compressive strength of its combustion (2) engine, characterized in that it comprises means for implementing the method according to one of the preceding claims and a first coupling means (C3) capable of connecting the assembly consisting of the engine and an electric (8) machine to the transmission, to allow the angular adjustment of the crankshaft.

7. Device for immobilising a road vehicle at a standstill according to claim 6, characterized in that it comprises a second coupling means (C2) capable of connecting an electric traction machine (3) to the transmission to vary the position of the shafts thereof during the angular adjustment of the crankshaft.

8. Device for immobilising a road vehicle at a standstill according to claims 6 and 7, characterized in that the cumulative closure of the two coupling means (C3, C2) ensures the engagement of a transmission ratio on which the combustion engine is connected to the wheels.

9. Device for immobilising at a standstill according to claim 8, characterized in that, in this ratio, the electric traction (3) machine is also connected to the wheels.