Method for locking or unlocking a transmission element

Abstract

Method for locking or unlocking a transmission element. Method for locking or unlocking a transmission element (4) arranged between at least one drive wheel (2) of a motor vehicle (1) and an engine (3) of the vehicle, by means of a parking locking device (5), the locking device comprising a toothed wheel (6) and a locking member (7), the toothed wheel being fixed to the transmission element, the locking member being movable between a locking position and an unlocking position, a locking finger (10) of the locking member (7) being positioned between two adjacent teeth (8) of the toothed wheel when it is in the locking position to lock the transmission element, the locking member being disengaged from the toothed wheel when it is in the unlocking position to release the transmission element. Figure for the abbreviation: Figure 1

Description

Title of the invention: Method for locking or unlocking a transmission element. Technical field of the invention

[0001] The invention relates to a method for locking or unlocking a transmission element arranged between at least one drive wheel of a motor vehicle and an engine of the vehicle, by means of a parking lock device. The invention also relates to a parking lock device configured to implement such a method. The invention further relates to a motor vehicle comprising such a locking device. Prior art

[0002] To secure the parking of a motor vehicle, vehicles are generally equipped with a handbrake. A handbrake comprises a lever connected by a cable to a wheel braking system for the vehicle, particularly the rear wheels. Parking locking devices are also known, designed to act on a transmission means between an engine and the drive wheels of the vehicle. Such locking devices are configured to reversibly lock a transmission element belonging to the drive train established between the engine and the drive wheels. Such a locking device generally comprises a toothed wheel and a locking member. The toothed wheel is fixed to the transmission element. The locking member is movable between a locked position and an unlocked position.A locking finger of the locking mechanism is positioned between two adjacent teeth of the gear when it is in the locking position to lock the transmission element, and it is moved away from the gear when it is in the unlocking position to release the transmission element. The locking mechanism can be moved between its two positions by means of a mechanism operated by a vehicle user or by an electrical actuator, such as an electric motor, controlled by an electronic control unit.

[0003] The force exerted by the locking member on the toothed wheel can, under certain circumstances, become very high. For example, very high forces appear when the locking member is moved into its locked position while the vehicle speed is not zero, particularly greater than or equal to 1 km / h. Such a situation occurs relatively frequently with modern vehicles in which comfort is very important. Indeed, in these vehicles, the user does not necessarily perceive that the vehicle is not completely stationary when the locking device. He may then feel a shock between the locking mechanism and the toothed wheel.

[0004] According to another example, such forces occur when the vehicle is parked on a slope (downhill or uphill). In particular, when parking on a slope, the user first immobilizes the vehicle by pressing the brake pedal, then actuates the locking device so as to move the locking member into the locked position. It sometimes happens that the locking member initially positions itself in a so-called "tooth-on-tooth" position, that is, the locking finger is not positioned between two adjacent teeth of the gear but on the crest of a tooth of the gear. In this position, the transmission element is not locked. When the user releases the brake pedal, the vehicle moves due to the slope (forward or backward depending on the direction of the slope).The vehicle's movement causes the gear wheel to rotate, so that the locking pin eventually engages between two adjacent teeth. If the incline is steep enough, the vehicle can reach a considerable speed when the locking pin engages between two adjacent teeth of the gear wheel, creating a significant impact between the locking pin and a radial face of a gear tooth. A vehicle speed of 1 km / h or more can already be considered a significant speed. Such a speed risks damaging the locking mechanism.

[0005] According to yet another example, the force exerted by the locking member on the toothed wheel can also become detrimental during the unlocking operation of the locking device, particularly when the vehicle is parked on a slope. Indeed, when the vehicle is parked on a slope, the vehicle's weight can generate a significant force at the interface between the locking member and a tooth of the toothed wheel. This force generates frictional forces that make it more difficult to move the locking member from its locked position to its unlocked position.

[0006] The criticality of these different situations is further increased when the kinematic chain between the motor and the drive wheels is very rigid, which is increasingly common on compact vehicles, and / or when said motor is an electric motor because such a motor includes a very significant inertia.

[0007] To overcome these drawbacks, it is known to oversize the elements of the locking device, in particular by using a large-diameter gear cooperating with a locking member that is also very robust, and therefore also very bulky. Coatings and / or surface treatments of the gear and / or the locking member can also be provided to increase the strength of these components. The means for moving the locking member between its locked and unlocked positions must also be reinforced. The locking devices known from the prior art are therefore particularly heavy, bulky, and complex to manufacture. Presentation of the invention

[0008] The object of the invention is to provide a parking locking device intended to lock or unlock a transmission element arranged between at least one drive wheel of a motor vehicle and an engine of the vehicle and a locking or unlocking method remedying the above disadvantages and improving the devices and methods known in the prior art.

[0009] More specifically, a first object of the invention is a solution for reducing the forces exerted at the interface between the toothed wheel and the locking member of the parking lock device. Summary of the invention

[0010] The invention relates to a method for locking or unlocking a transmission element arranged between at least one drive wheel of a motor vehicle and an engine of the vehicle, by means of a parking locking device, the locking device comprising a toothed wheel and a locking member, the toothed wheel being fixed to the transmission element, the locking member being movable between a locking position and an unlocking position, a locking finger of the locking member being positioned between two adjacent teeth of the toothed wheel when it is in the locking position to lock the transmission element, the locking member being disengaged from the toothed wheel when it is in the unlocking position to release the transmission element, the locking or unlocking method comprising: - a first step involving the receipt of a request to block or unblock the transmission element, then - a second stage comprising the generation of torque by the motor, said torque being configured to act on the transmission element so as to limit the force exerted at the interface between the toothed wheel and the locking member, then - a third step involving a movement of the locking mechanism.

[0011] The locking device may include an actuator, in particular an actuator comprising an electric motor, configured to move the locking member between its locking position and its unlocking position, the third step comprising moving the locking member by means of the actuator.

[0012] The locking device may include a return means configured to move the locking member between its locking position and its unlocking position, the third step comprising moving the locking member by means of the return means.

[0013] The locking device may include: - a control means intended to be operated by a user, - a means for detecting the operation of the control means, the first step comprising the detection of the operation of the control means by the detection means.

[0014] The first step may include receiving a request to lock the transmission element. The second step may include the generation of a resistive torque by the motor to limit the vehicle's speed to a predefined maximum value. And the third step may include moving the locking member to its locked position.

[0015] The second step may include a comparison of the vehicle speed with a predefined speed threshold, then if the vehicle speed is greater than or equal to the predefined threshold, and the second step may include the generation of a resistive torque by the motor until the vehicle speed becomes strictly less than the predefined threshold.

[0016] The first step may include receiving a request to lock or unlock the transmission element, then moving the locking member from its unlocked position to an intermediate position in which the locking finger is in contact with a crest of a tooth of the gear, then the second step may include generating a resistive torque by the motor to limit the speed of the vehicle to a predefined maximum value, then the third step may include moving the locking member from its intermediate position to its locking position.

[0017] The third step may include moving the locking member from its unlocked position to its locked position.

[0018] The first step may include receiving a request to unlock the transmission element, then the second step may include generating a motor torque by the motor to move the transmission element so as to reduce a force exerted by the locking finger on a tooth of the gear, then the third step may include moving the locking member from its locking position to its unlocking position.

[0019] The invention also relates to a parking locking device configured to lock or unlock a transmission element arranged between at least one drive wheel of a motor vehicle and an engine of the vehicle, the locking device comprising a toothed wheel and a locking member, the toothed wheel being intended to be mounted integrally with the transmission element, the locking member being movable between a locked position and an unlocked position, the locking member comprising a locking finger positioned between two adjacent teeth of the gear when it is in the locking position to lock the transmission element, the locking member being disengaged from the gear when it is in the unlocking position to release the transmission element, the locking device comprising hardware and software means configured to implement the locking or unlocking process as defined above.

[0020] The invention also relates to a motor vehicle comprising at least one drive wheel, an engine, a transmission element arranged between at least one drive wheel and the engine, and a parking locking device as defined above. Presentation of the figures

[0021] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0022] Fig. 1 is a schematic view of a motor vehicle according to one embodiment of the invention.

[0023] Fig. 2 is a schematic view of a vehicle locking device according to one embodiment of the invention.

[0024] The [Fig.3] is a synoptic diagram of a process according to a first embodiment of the invention.

[0025] The [Fig.4] is a synoptic diagram of a process according to a second embodiment of the invention.

[0026] The [Fig.5] is a synoptic diagram of a process according to a third embodiment of the invention.

[0027] Fig. 6 is a diagram illustrating the evolution of the speed of a vehicle as a function of time.

[0028] The [Fig.7] is a synoptic diagram of a process according to a fourth embodiment of the invention. Detailed description

[0029] Figure 1 schematically illustrates a motor vehicle 1 according to an embodiment of the invention. The vehicle 1 may, in particular, be a passenger car, a commercial vehicle, a truck, or even a bus. The vehicle 1 comprises at least one drive wheel 2, in particular two drive wheels, and a motor 3 configured to drive the at least one drive wheel 2 in rotation. A mechanical transmission system is arranged between a rotor of the motor 3 and the at least one drive wheel 2. The transmission system comprises a kinematic chain adapted to transmit torque supplied between the motor 3 and the at least one drive wheel 2. The transmission system may, for example, comprise a gearbox and / or shafts transmission. The transmission system includes, in particular, a transmission element 4, for example a drive shaft, arranged between at least one drive wheel 2 and the motor 3. The transmission element 4 belongs to the kinematic chain of the transmission system: a rotation of the rotor of the motor 3 causes a rotation of the transmission element 4, which in turn causes a rotation of at least one drive wheel 2. Conversely, a rotation of at least one drive wheel 2 causes a rotation of the transmission element 4, which in turn causes a rotation of the rotor of the motor 3. Where appropriate, the transmission element can be positioned upstream or downstream of the gearbox.

[0030] The motor 3 is preferably an electric motor, for example a wound-rotor synchronous motor. An electric motor has the advantage of being very responsive. An electric motor can therefore very quickly provide motor torque or resistive torque.

[0031] The vehicle 1 also includes a parking locking device 5 configured to lock or unlock the transmission element 4. When the locking device 5 locks the transmission element 4, it also blocks the rotation of at least one drive wheel 2 and the rotation of the motor rotor 3. When the locking device 5 unlocks the transmission element, it releases the rotation of at least one drive wheel and the rotation of the motor rotor 3. The motor 3 can then freely drive at least one drive wheel 2, and vice versa.

[0032] The locking device 5 includes a toothed wheel 6 and a locking member 7. The toothed wheel 6 is mounted integrally with the transmission element 4. For example, the toothed wheel 6 may include a central opening provided with internal splines, the internal splines cooperating with teeth formed on the periphery of the transmission element 4. The toothed wheel 6 includes a set of teeth 8, projecting radially and distributed on its outer contour.

[0033] The locking member 7 is a movable member between a locked position and an unlocked position. The locking member 7 can, for example, be mounted to rotate relative to a vehicle chassis by means of a pivot joint 9.

[0034] The locking position of the locking member 7 is illustrated by a solid line in [Fig. 1]. In its locked position, a locking finger 10 of the locking member 7 is positioned between two adjacent teeth 8 of the gear 6. When the locking member 7 is in the locked position, it prevents the gear 6 from rotating and thus locks the transmission element 4. Note that, depending on the precise dimensions of the locking finger 10 and the space separating two adjacent teeth 8, some play may remain, allowing the gear 6 to pivot slightly, for example, by a few degrees. Thus, "locking the transmission element 4" also includes a configuration in in which the rotation of the transmission element 4 is simply limited, in particular by a few degrees, for example to a maximum of 5°, or even to a maximum of 10°.

[0035] The unlocked position of the locking member 7 is illustrated by a dotted line in [Fig. 1]. In its unlocked position, the locking finger 10 of the locking member 7 is positioned at a distance from the gear 6, and is therefore not in contact with it. When the locking member 7 is in the unlocked position, it does not prevent the gear 6 from rotating. The transmission element 4 is then free to rotate, and torque can be transmitted between the motor 3 and at least one drive wheel 2.

[0036] The locking device 5 also includes an actuator 11 configured to move the locking member between its locked position and its unlocked position. Specifically, the actuator 11 is configured to move the locking member from its locked position to its unlocked position and from its unlocked position back to its locked position. The actuator 11 may, for example, include an electric motor and a mechanical linkage between a rotating shaft of the electric motor and the locking member 7. The electric motor may be configured to move the locking member 7 from its unlocked position to its locked position. Alternatively or in addition, the actuator 11 may include a return means, for example, a spring. The return means may be configured to move the locking member from its locked position to its unlocked position.

[0037] Figure 2 illustrates more precisely one embodiment of the device Locking device 5. The actuator 11 comprises an electric motor 12 equipped with a shaft oriented perpendicular to the axis in which the transmission element 4 extends. Alternatively, the shaft could be oriented differently. A rod 13 is fixed by a pivot joint to a plate 14, which is itself fixed to the shaft of the electric motor 12. A pivot point of the pivot joint between the rod 13 and the plate 14 is offset from the axis of rotation of the shaft of the electric motor 12. The rod 13 is advantageously guided in translation parallel to the direction in which it extends. The locking device 5 is thus configured so that a rotation of the shaft of the electric motor causes a translational movement of the rod 13. The rod 13 is equipped with a cam 15 configured to bear against the locking member 7.The support of the cam 15 on the locking member 7 tends to rotate the locking member 7 in the direction of the toothed wheel 6, so that the locking finger 10 is positioned between two adjacent teeth 8 of the toothed wheel 6.

[0038] Advantageously, the cam 15 can be fixed to the rod 13 by means of a sliding connection, and a return means 16, in particular a spring, can be arranged between the cam 15 and a stop formed on the rod 13. When the electric motor 12 is activated to move the locking member 7 into its locked position, it can happen If the locking finger 10 accidentally comes into contact with the tip of a tooth 8, the cam 15 slides along the rod, and the return means 16 is then tensioned. In this "tooth-on-tooth" configuration, the transmission element 4 is not yet locked. However, a subsequent rotation of the transmission element 4 allows the locking finger 10 to position itself between two adjacent teeth 8, thanks to the action of the return means 16, thus achieving the desired locking position. This subsequent rotation must have a sufficient amplitude, taking into account the shape and dimensions of the teeth 8. The thinner the teeth 8, the smaller the amplitude of the subsequent rotation required for the locking finger 10 to move down between two adjacent teeth 8. Conversely, each tooth 8 must also be sufficiently thick to withstand the forces to which it is subjected.

[0039] As a side note, other embodiments of the locking device could be considered. In particular, the invention can also be implemented with a motor vehicle comprising a completely mechanical locking device, i.e., one without an electric motor. In this case, the user's force moves the locking element between its locked and unlocked positions. A transmission mechanism is then provided between a control means accessible in the vehicle's passenger compartment and the locking element.

[0040] The force exerted by the locking finger 10 on a tooth 8 is represented by an arrow F in [Fig. 2]. The force F is oriented perpendicularly to the contact surface between the tooth 8 and the locking finger 10. When the vehicle 1 is parked on level ground, the static force between the tooth 8 and the locking finger 10 may be zero. When the vehicle 1 is parked on an incline, the static force between the tooth 8 and the locking finger 10 may depend on the slope and the weight of the vehicle. The interface between the tooth 8 and the locking finger 10 must also withstand a dynamic force, caused by an impact between these two elements when the locking member moves into its locked position. For example, when the locking finger 10 makes contact with a tooth 8 while the vehicle is moving at 1.3 km / h, the dynamic torque borne by the gear can reach more than 700 NmAs we will see later, the invention proposes a method for locking or unlocking the transmission element 4 which makes it possible to reduce the maximum dynamic torque supported by the gear. In particular, the invention makes it possible to limit the dynamic torque supported by the gear to a maximum of 600 Nm, or even to a maximum of 500 Nm.

[0041] In relation to [Fig. 1], the vehicle 1 also includes a control means 17 intended to be operated by a user. The control means 17 may, for example, include a button accessible to the driver of the vehicle. The control means 17 includes a detection means 18 configured to detect user interaction with the control means 17. The detection means 18 may include an electrical contactor, in particular integrated into the button. The control means 17 is electrically connected to an electronic control system 19, which is itself electrically connected to the actuator 11 and the motor 3. In particular, the electronic control system 19 is configured to issue control commands to the actuator 11 and the motor 3. The electronic control system 19 is specifically configured to issue a motor torque command or a resistive torque command to the motor 3, as well as to issue an activation command to the actuator 11 to move the locking element into its locked or unlocked position.

[0042] A vehicle speed sensor 20 is also electrically connected to the electronic control system 19.

[0043] The electronic control system 19 comprises a microprocessor 21, a memory 22, and an electronic communication interface 23. The electronic control system 19 is connected to the motor 3, the actuator 11, the control means 17 and the speed sensor 20 by means of its electronic communication interface 23.

[0044] The memory 22 of the electronic control system 19 is a data storage medium on which is stored a computer program comprising program code instructions for implementing a method of locking or unlocking the transmission element 4 according to an embodiment of the invention. The microprocessor 21 is capable of executing this computer program.

[0045] Different embodiments of the method for locking or unlocking the transmission element 4 are now described, each embodiment being able to be carried out in a particular situation of the vehicle 1.

[0046] Figure 3 shows a block diagram of a first embodiment of a method for locking the transmission element 4 according to the invention. In this first embodiment, it is assumed that a vehicle user activates the locking device while the vehicle 1 is not completely stopped and is on a horizontal surface.

[0047] In step 11, the vehicle has a non-zero speed. The locking member 7 is then in the unlocked position. The user presses a brake pedal of the vehicle, which has the effect of slowing the vehicle down. While the vehicle's speed is still non-zero, the user actuates the control means 17. The actuation of the control means 17 is detected by the detection means 18, which causes the control means to send a request to lock the transmission element 4. 17 to the electronic control system 19. Receiving this request does not systematically lead to activation of the actuator 11.

[0048] Next, in a step E2, the vehicle speed Vv provided by the speed sensor 20 is compared in E21 with a predefined speed threshold Vs. The predefined speed threshold Vs can, for example, be between 0.5 km / h and 1 km / h inclusive. Then, if the vehicle speed Vv is greater than or equal to the predefined speed threshold Vs, the motor 3 is controlled in E22 so that it generates a resistive torque to reduce the vehicle speed until the vehicle reaches a speed strictly below the predefined speed threshold Vs.

[0049] A step E3 is then initiated as soon as the vehicle speed falls strictly below the predefined speed threshold Vs. Step E3 can therefore be executed immediately after the actuation of the control means 17 if the speed of vehicle 1 is already strictly below the predefined speed threshold Vs when the control means 17 is actuation, or after a time necessary for the vehicle to slow down, if the speed of vehicle 17 is greater than or equal to the predefined threshold when the control means 17 is actuation. Advantageously, when the motor 3 is an electric motor, it can provide a fairly high resistive torque very responsively. This makes it possible to reduce the vehicle speed very quickly. Thus, the duration of step E2 can remain very short. Step E2 can be imperceptible or virtually imperceptible to the vehicle's users.The procedure does not involve any activation of the vehicle's braking system, in particular no activation of an ESP system.

[0050] As a note, step E2 may also include comparing the vehicle speed provided by the speed sensor 20 with a second predefined speed threshold. The second predefined speed threshold may, for example, be 10 km / h. If the vehicle speed is greater than or equal to the second predefined speed threshold, the actuation of the control means 17 can simply be ignored, and no control of the motor 3 is performed. This prevents disruption to the vehicle's operation if the control means 17 is accidentally activated, for example, while the vehicle is traveling at high speed, such as on a motorway.

[0051] In step E3, the actuator 11 is activated. For this purpose, the electronic control system 19 sends an electrical current to control the electric motor 12. The rotation of the shaft of the electric motor 12 moves the locking member from its unlocked position to its locked position. If the vehicle speed is non-zero, the locking finger 10 can come into contact with a radial face of a tooth 8 of the gear 6. This generates an impact between the locking finger and the tooth 8. The dynamic force at the interface between the locking finger and the tooth is moderate because the vehicle's speed is strictly below the predefined threshold. The locking finger 10 can also come into contact with the crest of a tooth 8 of the gear 6. In this case, since the vehicle's speed is not zero, the gear 6 continues to rotate, which allows the locking finger 10 to finally take position between two adjacent teeth 8.

[0052] If the vehicle's speed is zero when the locking member 7 moves from its unlocked position to its locked position, two scenarios are possible. Either the locking finger 10 engages directly between two adjacent teeth, in which case the transmission element 4 is immediately locked. Or the locking finger 10 aligns tooth-on-tooth with the gear. In this case, the transmission element 4 is not immediately locked. However, any subsequent movement of the vehicle, forward or backward, would cause the gear 6 to rotate and the locking finger 10 to align between two adjacent teeth. The vehicle is therefore also secured if the locking finger 10 aligns "tooth-on-tooth" with the gear while the vehicle is on level ground.

[0053] Figure 4 shows a block diagram of a second embodiment of a process of the locking of the transmission element 4 according to the invention. According to this second embodiment, the method first comprises the three steps E1, E2, and E3 previously described. According to this embodiment, the method then comprises a step E4 subsequent to step E3 during which the actuator 11 is activated. This step E4 aims to limit the vehicle's speed by means of a resistive torque generated by the motor 3 in the same way as during step E2.

[0054] Step E4 can be advantageously implemented when the vehicle is on a slope and step E3 has resulted in the locking finger 10 being positioned in the intermediate position known as "tooth on tooth". In such a case, when the user releases the brake pedal, the vehicle, not being completely locked, accelerates again due to the slope until the locking finger 10 is positioned between two adjacent teeth. To limit the dynamic force between the locking finger 10 and the tooth 8, the vehicle speed is therefore limited in the same way as in step E2. In particular: in E41, the vehicle speed Vv provided by the speed sensor 20 is compared with the predefined speed threshold Vs. The predefined speed threshold Vs can, for example, be between 0.5 km / h and 1 km / h.Then, if the vehicle speed Vv becomes greater than or equal to the predefined speed threshold Vs, motor 3 is controlled in E42 so that it generates a resistive torque to keep the vehicle speed strictly below the predefined threshold.

[0055] Then, in a fifth step E5, when the toothed wheel has rotated sufficiently, the locking finger 10 moves from its intermediate position to a position between two adjacent teeth. This movement occurs, for example, under the effect of the return means 16. The locking member thus completes its movement towards its locking position. As the vehicle speed was limited during step E4, the impact between the locking finger 10 and the tooth 8 is moderate. The method therefore prevents excessive dynamic force at the interface between the locking finger 10 and the tooth 8 when the vehicle is parked on a slope. The vehicle speed control implemented during step E4 can be stopped as soon as the vehicle speed is detected as zero and / or after a certain time has elapsed since the vehicle speed was detected as zero. The same algorithm can be executed during steps E2 and E4.

[0056] Figure 5 shows a block diagram of a third embodiment of a method for locking the transmission element 4 according to the invention. The third embodiment is based on the second embodiment and is simplified by omitting step E2 described above. Thus, according to this third embodiment, the locking member 7 is automatically moved during step E3 to its locking position following receipt of the request to lock the transmission element in step E1. Step E4, as described in the second embodiment, is performed in the same way in the third embodiment. This third embodiment therefore serves only to limit the dynamic force at the interface between the locking finger 10 and the tooth 8 when the vehicle is on a slope and the locking finger 10 aligns tooth-on-tooth with the gear during step E3.

[0057] Figure 6 shows a time-domain diagram of the vehicle's speed during the implementation of the second or third embodiment of the invention. Elapsed time is represented on the x-axis. The vehicle's speed is represented on the y-axis. In a first phase P1, the user slows the vehicle by pressing the brake pedal until the vehicle comes to a complete stop. At the end of the first phase P1, the vehicle's speed is zero, and it is assumed that the vehicle is resting on a slope, either forward or backward. In a second phase P2, following the first phase P1, the user keeps their foot pressed on the brake pedal. The vehicle therefore remains stationary. During the second phase P2, the user activates the control means 17 at time T0.Since the vehicle's speed is zero, the actuator 11 is controlled by the electronic control system 19 to move the locking member 7 into the locked position. It is assumed that the locking finger 10 aligns tooth to tooth with the toothed wheel 6. At time T1, the user releases the brake pedal. A third phase P3 then begins, during which the vehicle moves under the effect of gravity. In [Fig. 6], the evolution of this phase is represented by a dashed line L1. The vehicle's speed until the locking finger 10 makes contact with the radial face of a tooth 8 is shown in a diagram of a vehicle in the prior art. During the impact between the locking finger 10 and the radial face of the tooth 8, the vehicle's speed can, for example, reach approximately 1.5 km / h, or even higher if the slope on which the vehicle is resting is steep. The evolution of the vehicle's speed until the locking finger 10 makes contact with the radial face of a tooth 8 is also represented by a solid line L2 in a diagram of a vehicle in an embodiment of the invention. During the impact between the locking finger 10 and the radial face of the tooth 8, the vehicle's speed is limited to the predefined speed threshold Vs, which is advantageously between 0.5 km / h and 1 km / h. The impact is therefore less severe.

[0058] Figure 7 now illustrates a block diagram of a method for unblocking the element of transmission 4 according to an embodiment of the invention. Initially, the vehicle 1 is considered to be stationary and the locking member 7 is in the locked position. The locking finger 10 is positioned between two adjacent teeth 8 of the gear 6. More precisely, it is assumed that the locking finger 10 is bearing against a radial face of a tooth 8 of the gear, for example, because the vehicle is parked on a slope. Indeed, the force of gravity acting on the vehicle is supported by the interface between a tooth of the gear and the locking finger. In other words, it is the reaction force of the locking finger 10 on the gear that locks the vehicle in position. In a step E101, the user actuates the control means to unlock the transmission element 4.

[0059] Next, in a step E102, the electronic control system 19 sends a command to the motor 3 to generate a motor torque directed so as to reduce the force exerted by the tooth 8 on the locking finger 10. If the vehicle is parked on a downward slope, the torque supplied by the motor is a reverse torque. Conversely, if the vehicle is parked on an upward slope, the torque supplied by the motor is a forward torque. Advantageously, the step E102 includes a substep E1021 for determining the direction in which the motor torque should be applied, in particular a step for determining the direction of the slope on which the vehicle is parked. The direction of the slope on which the vehicle is parked can be determined by any means: for example, by means of an accelerometer or by detecting the direction in which the rotation of the transmission element 4 is blocked.Indeed, if the vehicle is parked on a downward slope, the locking finger's stop on the tooth of the gear prevents the transmission element from rotating forward. Conversely, if the vehicle is parked on an upward slope, the locking finger's stop on the tooth of the gear prevents the transmission element from rotating in reverse.

[0060] The execution of step E102 makes it possible to reduce the force exerted by the locking finger on the tooth of the gear and thus to facilitate the movement of the locking member towards its unlocking position.

[0061] As a note, the application of engine torque during step E102 can be conditional upon the absence of activation of the vehicle's brake pedal, such activation being detectable by means of a suitable sensor. However, even if the user maintains pressure on the brake pedal, the application of engine torque already reduces the force at the interface between the tooth 8 and the locking finger 10, it being understood that a very slight rotation of the transmission element is sufficient to reduce the stresses at this interface. Thus, by using the vehicle's suspension, the drive wheels can be kept completely stationary, and the vehicle can be made to pitch forward or downward slightly to release the stress at the interface between the tooth 8 and the locking finger 10, just long enough to move the locking member to its unlocked position. This movement of the vehicle may nevertheless remain imperceptible to its users.

[0062] Then, in a step E103, the locking member 7 is moved from its locked position to its unlocked position, for example by activating the actuator 11 and / or by means of a return means provided for this purpose. Advantageously, since the reaction force between the locking finger 10 and the tooth 8 has become zero or very low at the end of step E102 or during step E102, moving the locking member requires very little effort.

[0063] Finally, thanks to the invention, it is proposed to use a resistive torque or a motor torque supplied by the motor 3 to reduce the mechanical stresses exerted on a parking locking device. The parking locking device 5 is thus more durable and / or can be designed to withstand lower mechanical stresses. It is therefore less bulky, lighter, and less complex to manufacture.

Claims

Demands

1. A method for locking or unlocking a transmission element (4) arranged between at least one drive wheel (2) of a motor vehicle (1) and an engine (3) of the vehicle, by means of a parking locking device (5), the locking device comprising a toothed wheel (6) and a locking member (7), the toothed wheel being fixed to the transmission element, the locking member being movable between a locking position and an unlocking position, a locking finger (10) of the locking member (7) being positioned between two adjacent teeth (8) of the toothed wheel when it is in the locking position to lock the transmission element, the locking member being disengaged from the toothed wheel when it is in the unlocking position to release the transmission element, the locking or unlocking method comprising: - a first step (E1,E101) comprising the reception of a request to lock or unlock the transmission element (4), then - a second step (E2, E4, E102) comprising the generation of a torque by the motor (3), said torque being configured to act on the transmission element so as to limit a force exerted at the interface between the toothed wheel and the locking member, then - a third step (E3, E5, E103) comprising a movement of the locking member.

2. A locking or unlocking method according to the preceding claim, characterized in that the locking device (5) comprises an actuator (11), in particular an actuator comprising an electric motor (12), configured to move the locking member (7) between its locking position and its unlocking position, the third step (E3, E103) comprising the movement of the locking member by means of the actuator.

3. A method of locking or unlocking according to any one of the preceding claims, characterized in that the locking device (5) comprises a return means (16) configured to move the locking member (7) between its locking position and its unlocking position, the third step (E5) comprising the movement of the locking member by means of the return means.

4. A method for locking or unlocking according to any one of the preceding claims, characterized in that the locking device (5) comprises: - a control means (17) intended to be actuated by a user, - a detection means (18) for the actuating of the control means, the first step (11) comprising the detection of the actuating of the control means by the detection means.

5. A locking method according to any one of the preceding claims, characterized in that the first step (E1) includes receiving a request to lock the transmission element (4), in that the second step (E2, E4) includes generating a resistive torque by the motor (3) to limit the speed of the vehicle to a predefined maximum value, and in that the third step (E3, E5) includes moving the locking member (7) to its locking position.

6. A blocking method according to the preceding claim, characterized in that the second step (E2) comprises a comparison (E21) of the vehicle speed (Vv) with a predefined speed threshold (Vs), and then whether the vehicle speed is greater than or equal to the predefined threshold, and in that the second step comprises the generation (E22) of a resistive torque by the motor until the vehicle speed becomes strictly less than the predefined threshold.

7. A locking method according to any one of the preceding claims, characterized in that: - the first step (E1) comprises receiving a request to lock the transmission element (4), then - moving the locking member (7) from its unlocked position to an intermediate position in which the locking finger (10) is in contact with a crest of a tooth (8) of the gear (6), then in that - the second step (E4) comprises generating a resistive torque by the motor (3) to limit the speed of the vehicle to a predefined maximum value, then in that - the third step (E5) comprises moving the locking member from its intermediate position to its locking position.

8. A locking method according to claim 5 or 6, characterized in that the third step (E3) comprises the movement of the locking member (7) from its unlocking position to its locking position.

9. A method for unlocking according to any one of claims 1 to 4, characterized in that: - the first step includes receiving a request to unlock the transmission element (4), then in that - the second step includes generating a motor torque by the motor (3) to move the transmission element so as to reduce a force exerted by the locking finger (10) on a tooth (8) of the gear (6), then in that - the third step includes moving the locking member (7) from its locking position to its unlocking position.

10. A parking locking device (5) configured to lock or unlock a transmission element (4) arranged between at least one drive wheel (2) of a motor vehicle (1) and an engine (3) of the vehicle, the locking device (5) comprising a toothed wheel (6) and a locking member (7), the toothed wheel being intended to be mounted integrally with the transmission element, the locking member being movable between a locking position and an unlocking position, the locking member comprising a locking finger (10) positioned between two adjacent teeth (8) of the toothed wheel when it is in the locking position to lock the transmission element, the locking member (7) being disengaged from the toothed wheel when it is in the unlocking position to release the transmission element, the locking device comprising hardware and software means (19, 21, 22,23) configured to implement the blocking or unlocking method according to one of the preceding claims.

11. Motor vehicle (1) comprising at least one drive wheel (2), an engine (3), a transmission element (4) arranged between the at least one drive wheel and the engine, and a parking locking device (5) according to the preceding claim.

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