Method for rolling an electrically powered vehicle into a stationary position

Description

Technical field

[0001] The invention relates to a method for rolling an electrically driven vehicle provided with a parking lock device into a stationary position of the vehicle from a position in which a pawl is prevented from locking a parking lock wheel. State of the art

[0002] DE 10 2015 217 975 A1 relates to a method for disengaging a parking lock of a dual-clutch transmission of a vehicle. The dual-clutch transmission comprises a parking lock. To disengage the parking lock of a dual-clutch transmission of a vehicle, a torque request is issued upon detection of a road gradient, and a powershift clutch of the dual-clutch transmission is engaged when a gear is engaged in the sub-transmission to which the powershift clutch is assigned. The powershift clutch to be engaged and the requested torque are selected such that the torque counteracts the torque applied to the transmission output side via the drive wheels when the parking lock is engaged, which torque is supported by the pawl, and serves as a load-relieving torque.

[0003] DE 10 2011 079 618 A1 relates to a parking lock comprising a parking lock gear with a toothing and a pawl. The pawl is movable relative to the parking lock gear such that it blocks or releases the parking lock gear. The parking lock gear is movable by a drive operating independently of the adjustment mechanism. Before or during engagement or disengagement of the parking lock by means of the drive, the parking lock gear is repositioned relative to the pawl, with the parking lock gear being subjected to a torque. This reduces the engagement or disengagement forces required by the adjustment mechanism.

[0004] DE 10 2009 030 084 B4 relates to a method for releasing a parking lock of a motor vehicle. First, the parking lock is activated using a control variable to release the parking lock. A drive torque counteracting a downhill torque is set as a function of a control variable. A downhill torque is determined using a characteristic measured variable as a function of the control variable, which acts on the locked wheels via the parking lock. A drive torque counteracting the downhill torque is set as a function of the measured variable.The drive torque is adjusted in the opposite direction to the approach direction if the approach direction and the downhill direction are in the same direction, whereby the downhill torque exceeds the drive torque during release and / or during holding or alternatively the drive torque is adjusted in the approach direction, this and the downhill direction are opposite to each other.

[0005] Parking locks are now used in most automatic transmissions to prevent the vehicle from rolling away unintentionally. In electrically powered vehicles, parking locks are also installed in the transmission downstream of the electric motor. If a vehicle equipped with a parking lock is parked on an uphill or downhill slope, the following situation can arise: The driver brakes the vehicle to a stop and then engages the parking lock. The parking lock actuator then uses a mechanism to operate the pawl to engage a gap in the parking lock gear. This can result in the pawl tooth colliding with the tooth of the parking lock gear, making locking impossible. In this case, a spring is preloaded, pressing the pawl onto the parking lock gear.If the driver now releases the vehicle's brake, it begins to roll forward or backward, depending on whether it is on a downhill or uphill section of the route. The rolling of the vehicle turns the drive wheels, the transmission and thus also the parking lock gear coupled to it. The pressed-in pawl engages into the next gap in the parking lock gear due to the effect of the spring preload. However, this brings the vehicle to an abrupt stop, resulting in vibrations and torques that place mechanical stress on the components in the drive train and can also lead to a reduction in noise and comfort for the driver. To make this abrupt stopping more gentle, DE 10 2017 118 517 A1 and US 2018 / 0042895 A1 propose gradually reducing the applied brake pressure, thereby allowing the vehicle to roll slowly into the parking lock.

[0006] From DE 10 2019 216 848 A1, a generic method for rolling an electrically driven vehicle provided with a parking lock device into a stationary position of the vehicle is known, having the features of the preamble of claim 1. By controlling an electric machine, the parking lock gear is rotated forwards or backwards, depending on how quickly a tooth gap on an external toothing of a parking lock gear can be reached.

[0007] Another method for actuating a parking lock in a vehicle equipped with an electric drive motor is known from DE 10 2019 11 515 A1. In this method, the position of the tooth gap of the parking lock gear relative to a tooth of a parking lock pawl is adjusted by an electric drive motor included in the drive train. Description of the invention

[0008] A method is proposed for rolling an electrically driven vehicle provided with a parking lock device into a stationary position of the vehicle, wherein the parking lock device comprises a pawl and a parking lock gear and is designed, when actuated, to engage with the pawl in an external toothing formed on the circumference of a parking lock gear and to block said toothing. The parking lock device comprises an actuator which actuates the pawl via an actuating mechanism. The actuating mechanism has a slider which is movable in translation along a guide, is actuated by a biasing spring and acts on an actuating surface of the pawl. Upon activation of the parking lock device, a position is present in which the pawl is prevented from locking a parking lock gear, comprising the following method steps: a) Pretensioning of the pretensioning spring by the actuator upon activation of the parking lock device, b) Transmission of a position of the rotationally fixed parking lock gear detected by position detection to a control unit, c) Determination of a twist angle of the rotor shaft of the electric machine to reach the nearest tooth gap of an external toothing of the parking lock gear and d) Control of the electric machine to travel through the twist angle determined according to c) and a controlled approach to the position of the tooth gap determined according to c).

[0009] According to the invention, a direction of rotation of the electric machine for traveling through the angle of rotation determined according to c) is obtained from the information as to whether the electric machine delivered a torque when the electrically driven vehicle reached its standstill position, or whether the electric machine was rotated by the vehicle movement in recuperation mode before the electrically driven vehicle reached its standstill position.

[0010] In the manner described above, a smooth roll-in of the vehicle can be achieved without the need for additional sensors when the electrically powered vehicle is parked on an uphill or downhill section and the parking lock device is in a tooth-on-tooth position. The brake pressure or the brake pressure reduction gradient is not used, and no additional sensors or other components are required. Finally, the advantageous possibility of a cost-effective and simple implementation exists.

[0011] This makes it possible to use existing components to determine both the angle of rotation required to reach the nearest tooth gaps and the direction of rotation in which the electric machine is to be moved, without the need for additional hardware components.

[0012] In an advantageous development of the method proposed according to the invention, the rotational movement of the pawl about a rotational axis is brought about by a translational movement of an actuating mechanism. This advantageously allows for the realization of short travel distances, so that the actuator of the parking lock device can be designed accordingly.

[0013] In a further advantageous embodiment of the method proposed according to the invention, the preload of the preload spring according to a) is transmitted to a translationally movable slider of the actuating mechanism of the parking lock device, so that the slider is positioned against an actuating surface having a wedge-shaped contact surface.

[0014] In a further advantageous embodiment of the method proposed according to the invention, the position of the parking lock gear according to b) is detected by means of a position detection device designed as a resolver. This advantageously ensures reliable signal acquisition.

[0015] In a further advantageous embodiment of the method proposed according to the invention, during the execution of the

[0016] In process steps a) to d), the pawl is held in a position that is aligned with the external toothing of the parking lock gear. This ensures that as soon as the information regarding the angle of rotation and the direction of rotation of the electric motor has been determined in the control unit, the parking lock can be locked immediately in the nearest accessible tooth gap in the external toothing of the parking lock gear, without any further delays in the signal chain.

[0017] In a further advantageous embodiment of the method proposed according to the invention, the pawl, after engaging in the nearest tooth gap of the external toothing according to c), is locked there by the slider of the actuating mechanism, so that the vehicle locked in its parking position remains reliably secured.

[0018] In the method proposed according to the invention, the pawl is unlocked again, i.e. released again, by a translatory movement of the slider after the parking lock device has been activated again after the controlled rolling movement into the parking lock device has been carried out. Advantages of the invention

[0019] In contrast to the known methods, in which the brake pressure can be used to execute a rolling movement and is then slowly reduced during the rolling process, the method proposed according to the invention does not require the use of the brake pressure. In electrically powered vehicles, the driver can bring the vehicle to a standstill using only one-pedal operation, since if the accelerator pedal is not operated, the electrically powered vehicle is braked by the drag torque generated by the electric motor, i.e., the application of the brake is not absolutely necessary for deceleration. In this driving position and in this driving mode, i.e.If, in one-pedal operation, the situation arises that the electrically powered vehicle comes to a standstill on an uphill or downhill gradient and the parking lock is in a tooth-on-tooth position, the method proposed according to the invention can achieve a gentle roll-in of the vehicle. This takes place without additional sensors, in which already known components for detecting the position of the parking lock gear, for example in the form of a resolver, are used. This allows a reliable rotational position of the parking lock gear to be determined on the one hand, and on the other hand, the information on the direction of rotation of the electric machine tells us whether the electric machine supplied a torque before the vehicle came to a standstill, or whether a torque was imposed on it by the vehicle movement in towing mode.From the position detection and the known geometry of the external toothing of the parking lock gear, the nearest tooth gap in the external toothing of the parking lock gear can be determined without the use of additional hardware.

[0020] Based on the now known angle of rotation of the rotor shaft, on whose circumference the parking lock gear is fixed in a rotationally fixed manner, and from the known direction of rotation of the electric machine, a controlled rolling of the electrically driven vehicle into the parking lock can now be achieved.

[0021] A further advantage of the method proposed according to the invention is that, with regard to the software, the method can also be subsequently installed as an update in vehicles that have already been delivered and can thus improve the driving comfort of vehicles that have already been delivered. Short description of the drawings

[0022] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0023] They show: Figure 1 shows the components of the electric drive train of an electrically powered vehicle, Figure 2a shows a parking lock device of an electrically powered vehicle with a tooth-on-tooth position between external teeth and pawl, and Figure 2b shows a pawl of a parking lock device inserted into a tooth gap of the external teeth. Embodiments of the invention

[0024] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0025] Figure 1shows a schematic illustration of an electric drive train 12 of an electrically powered vehicle 10. The electrically powered vehicle 10 includes the electric drive train 12, which includes an electric machine 14 and a transmission 16. A first drive shaft 18 having a first drive gear 22 and a second drive gear 24 is driven via the transmission 16. An axle differential 26 is located within the transmission 16. Flanged to the side of the transmission 16 is a housing 28 in which a stator 30 of the electric machine 14 is received. A rotor 32 of the electric machine, mounted on a rotor shaft 34, rotates in the stator 30.

[0026] As can be seen from the illustration according to Figure 1As further shown, the electric machine 14, in particular its rotor shaft 34, is assigned a position detection device 36, which can be designed, for example, as a resolver mounted on the outside of the housing 28. The position detection device 36 is connected to a control unit 40 in the electric drive train 12 via a signal connection 38.

[0027] Out of Figure 1 It is further apparent that a number of gears 42 are accommodated in the transmission 16, which convert the rotational movement of the rotor 32 of the electric machine 14 into a drive torque in accordance with the respective gear ratio(s).

[0028] Furthermore, the gear 16 is provided with a gear box 18 as shown in Figure 1a parking lock device 44 is assigned. The parking lock device 44 comprises a parking lock gear 46, which is non-rotatably mounted, for example, on the rotor shaft 34 of the electric machine 14. Alternatively, the parking lock gear 46 can also be assigned to a shaft in the transmission 16, to an intermediate shaft, or to the axle differential 26. Furthermore, the parking lock device 44 comprises a pawl 48, which engages with an external toothing 56 formed on the circumference of the parking lock gear 46 and blocks it when actuated. The parking lock device 44 is actuated by an actuator 52, which in turn is controlled via the control unit 40.

[0029] According to the illustration Figure 2aa position of the parking lock device 44 can be seen in which, when an electrically driven vehicle 10 is stationary, whether on a downhill or uphill gradient, a tooth-on-tooth position occurs. In the present context, this means that a pawl tooth 64 of a pawl 48, which is movable about a rotational axis 62, lies on a tooth 58 of the external toothing 56 on the outer circumference of the parking lock gear 46, and thus cannot engage in a tooth gap 60 formed between two adjacent teeth 58 of the external toothing 56, thus blocking the rotational movement of the parking lock gear 46. This state of the parking lock device 44 is in Figure 2ashown. Located above the pawl 48, which can pivot about the rotational axis 62, is an actuating mechanism 50 of the parking lock device 44. In addition to a preload spring 54, this comprises a slide 68 that is translationally movable and guided along a guide 66. The slide 68 acts on a contact surface 70, which can be designed, for example, as a wedge and is located on the upper side of the pawl 48, which can pivot about the rotational axis 62.

[0030] Figure 2b shows a state in which a twisting movement and thus a plunging movement 72 is imposed on the pawl 48, which is movable about the rotational axis 62, via the slide 68 by pre-tensioning the pre-tensioning spring 54. In Figure 2bIn the state shown, the actuating surface 70 is overrun in the form of a wedge due to the translatory movement of the slide 68 along the guide 66, so that the ratchet tooth 64 of the pawl 48 is retracted into the tooth gap 60 and thereby the rotational movement of the parking lock gear 46 remains blocked at the external toothing 56 formed on the outer circumference. As long as the slide 68 is in the Figure 2b shown position, the pawl tooth 64 of the pawl 48 remains retracted into the tooth gap 60 of two adjacent teeth 58 of the external toothing 56 according to the plunging movement 72 and is also locked there.

[0031] The transition from the state in the position according to Figure 2a , which shows a tooth-on-tooth position of the parking lock device 44, into an activated, ie blocked, state of the parking lock device 44, is achieved by applying the method proposed according to the invention.

[0032] The position detection system 36 is connected to the control unit 40 via the signal connection 38. The control unit 40 can be the control unit of the entire electric drive train 12, but a separate control unit 40 can also be used for this purpose.

[0033] The rotor shaft 34 of the electric motor 14 transmits the torque of the electric motor 14 to the transmission 16. There, torque conversion takes place via the gears 42. The torque is transmitted via the axle differential 26 to the drive wheels 22 and 24 via the drive shafts 18, 20. The parking lock device 44 is located in the transmission 16.

[0034] The parking lock gear 46 of the parking lock device 44 is connected, for example, to the rotor shaft 34 or the rotor 32 of the electric machine 14 in such a way that a rotational movement detected by the position detection device 36 in the form of a resolver also leads to a corresponding rotation of the parking lock gear 46. This means that the position of the parking lock gear 46, which can be mounted in a rotationally fixed manner on the rotor shaft 34 or on an intermediate shaft, can be unambiguously assigned to a signal from the position detection device 36. This makes it possible to precisely determine the position of the parking lock gear 46 from the position detection device 36 signal.

[0035] If the electrically driven vehicle 10 comes to a standstill on an uphill or downhill gradient and the parking lock device 44 is actuated by the driver, the control unit 40 controls the parking lock actuator 52 of the parking lock device 44, which in turn actuates the pawl 48 via the actuation mechanism 50. In the case of the Figure 2a In the tooth-on-tooth position shown, the preload spring 54 is preloaded and the pawl 48 is pressed against the external toothing 56 or one of the teeth 58 of the external toothing 56 of the parking lock gear 46. The position detection 36 now transmits the position of the parking lock gear 46 to the control unit 40.

[0036] The control unit 40 calculates the angle of rotation by which the electric machine 14 in the electric drive train 12 must rotate the rotor 32 or the rotor shaft 34 so that the nearest tooth gap 60 of the external toothing 56 of the parking lock gear 46 can engage with the pawl 48 or its pawl tooth 64.

[0037] In the control unit 40, the direction of rotation of the electric motor 14 is known because, in the case of the vehicle being parked on an uphill gradient, the electric motor 14 delivered a torque before coming to a standstill. When passing a downhill section before the vehicle was parked, the vehicle's movement imparted a drag torque to the electric motor 14.

[0038] Since the control unit 40 now knows the direction of rotation of the electric machine 14 and the angle of rotation to reach the nearest tooth gap 60, this position can now be approached in a precisely controlled manner, which corresponds to the state of the Figure 2b corresponds to a position in which a plunging movement 72 of the pawl 48 into the nearest determined tooth gap 60 of the external toothing 56 of the parking lock gear 46 has taken place.

[0039] This process does not require the driver of the electrically powered vehicle 10 to depress the brake pedal. However, if the driver has depressed the brake pedal out of habit and then released it again, the brake actuation or release is transmitted to the control unit 40, for example, via a CAN bus in the electrically powered vehicle 10.

[0040] If the electrically powered vehicle 10 begins to move and a rotational movement is transmitted via the drive wheels 22, 24, the drive shafts 18 and 20 to the transmission 16 and thus to the electric machine 14, this rotational movement is detected by the position detection device 36. The control of the further movement, ie the rolling of the electrically powered vehicle 10 into the parking lock device 44, via a corresponding control of the electric machine 14 in the electric drive train 12 can be carried out as described above.

[0041] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope defined by the claims.

Claims

1. Method for rolling an electrically driven vehicle (10) provided with a parking lock device (44) into a standstill position of the vehicle, wherein the parking lock device (44) comprises a pawl (48) and a parking lock gear (46) and is designed, when activated, to engage by way of the pawl (48) in an external toothing (56) formed on the circumference of a parking lock gear (46) and to block same, wherein the parking lock device (44) comprises an actuator (52), which activates the pawl (48) via an actuating mechanism (50), wherein the actuating mechanism (50) comprises a slider (68) which is translationally movable along a guide, is biased by a biasing spring (54) and acts on an activating surface (70) of the pawl (48), wherein, when the parking lock device (44) is activated, there is a position in which the pawl (48) is prevented from locking a parking lock gear (46), said method comprising the following method steps: a) biasing the biasing spring (54) by way of the actuator (52) when the parking lock device (44) is activated, b) transmitting to a control unit (40) a position of the parking lock gear (46) accommodated in a rotationally fixed manner, said position being identified by a position identification system (36), c) determining an angle of rotation of the rotor shaft (34) of the electric machine (14) to reach the nearest tooth space (60) of an outer toothing (56) of the parking lock gear (46) and d) actuating the electric machine (14) to pass through the angle of rotation determined in accordance with c) and controlling an approach to the position of the tooth space (60) determined in accordance with c), characterized in that a direction of rotation of the electric machine (14) to pass through the angle of rotation determined in accordance with c) is obtained from the information about whether the electric machine (14) has delivered a torque when the standstill position of the electrically driven vehicle (10) is reached or whether the electric machine (14) was rotated by the vehicle movement in recuperation mode before the standstill position of the electrically driven vehicle (10) was reached.

2. Method according to Claim 1, characterized in that a rotational movement of the pawl (48) about an axis of rotation (62) is initiated by a translational movement of the actuating mechanism (50).

3. Method according to Claim 1 or 2, characterized in that the biasing of the biasing spring (54) in accordance with a) adjusts the translationally movable slider (68) against the activating surface (70).

4. Method according to Claim 1, characterized in that the position of the parking lock gear (46) in accordance with b) is detected by means of a position identification system (36) in the form of a resolver.

5. Method according to Claim 1, characterized in that, during the execution of method steps a) to d), the pawl (48) is held in a position set against the outer toothing (56) of the parking lock gear (46).

6. Method according to Claim 1, characterized in that the pawl (48) remains locked there by the slider (68) after latching in the nearest tooth gap (60) of the outer toothing (56) in accordance with c).

7. Method according to Claim 1, characterized in that the pawl (48) is released by a translational movement of the slider (68) after the re-actuation of the parking lock device (44) after the controlled rolling process into the latter.