Vehicle control system

Abstract

The present invention provides a vehicle control device that can suppress the occurrence of shocks caused by torque output from the motor in response to the twisting of the drive shaft when the parking lock is engaged. [Solution] A vehicle control device comprising a drive shaft connected to a wheel, a motor capable of transmitting torque to the drive shaft, and a parking lock mechanism capable of selectively locking the rotation of the drive shaft, wherein when the tilt angle in the pitching direction of the vehicle is at or above a first predetermined angle at the time the parking lock mechanism is locked, and it is determined that the drive shaft has twisted, and when the tilt angle in the pitching direction of the vehicle is at or above a second predetermined angle at the time the parking lock mechanism is released (Yes in step S13), an assist torque opposite to the twisting direction of the drive shaft is output from the motor.

Description

Technical Field

[0001] This invention relates to a vehicle control device capable of locking a drive shaft by a parking lock mechanism.

Background Art

[0002] Patent Document 1 describes a vehicle including a front drive shaft connected to a front wheel, a rear drive shaft connected to a rear wheel, a front motor connected to the front drive shaft, and a rear motor connected to the rear drive shaft. This vehicle is provided with a parking lock mechanism capable of selectively locking the rotation of the front drive shaft. This parking lock mechanism is configured to prohibit the rotation of the front drive shaft by meshing a parking gear and a parking pole interlocked with the front drive shaft, and to allow the front drive shaft to rotate by releasing the meshing.

[0003] Also, Patent Document 1 describes a control device for suppressing the occurrence of shock when releasing the meshing of the front drive shaft by the parking lock mechanism as described above. This control device stores the front phase difference between the rotational phase of the front motor before switching to the locked state in which the rotation of the front drive shaft is prohibited by the parking mechanism and the rotational phase of the front motor after switching the front drive shaft to the locked state, and the rear phase difference between the rotational phase of the rear motor before switching the front drive shaft to the locked state by the parking mechanism and the rotational phase of the rear motor after switching the front drive shaft to the locked state.

[0004] Furthermore, when the parking mechanism makes the front drive shaft rotatable, the control device reads the difference between the front phase difference and the rear phase difference, calculates the amount of torsion of the front drive shaft based on that difference, and outputs a torque from the front motor corresponding to that amount of torsion. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-027134 [Overview of the project] [Problems that the invention aims to solve]

[0006] The control device described in Patent Document 1 is configured to determine the amount of torsion of the front drive shaft based on the rotational phase of each motor at the time the front drive shaft is locked by the parking lock mechanism, and to determine the torque of the front motor when the front drive shaft is allowed to rotate by the parking lock mechanism based on that amount of torsion. In other words, there is a time difference between the time when the amount of torsion of the front drive shaft is determined and the time when the torque of the front motor is set based on that amount of torsion.

[0007] On the other hand, for example, if a parked vehicle is towed, or if the object is crushed while the front wheels are parked on a relatively soft object, the rotation of the front wheels may relieve the twist in the front drive shaft, or the amount of twist may differ from that when the vehicle is parked. Also, if the parked vehicle is towed, the angle or direction of the slope of the road surface on which the vehicle is parked may change between the time the front drive shaft is locked by the parking lock mechanism and the time the front drive shaft is allowed to rotate by the parking lock mechanism.

[0008] As described above, if the amount of torsion of the front drive shaft changes between the time the torsion is calculated and the time the parking lock mechanism is released, or if the gradient angle or direction of the road surface where the vehicle is parked changes, then if the torque of the front motor is determined based on the amount of torsion at the time of parking, the magnitude and direction of that torque will deviate from the magnitude and direction of the torque required to suppress the shock caused by the unwinding of the torsion of the front drive shaft. Therefore, there is a possibility that a shock may occur when the parking lock mechanism is released.

[0009] This invention was made in view of the above-mentioned technical problems, and the object of this invention is to provide a vehicle control device that can suppress the occurrence of shocks caused by torque output from the motor in response to the twisting of the drive shaft when the parking lock is engaged. [Means for solving the problem]

[0010] To achieve the above objective, this invention provides a vehicle control device comprising: a drive shaft with one end connected to a wheel; a motor capable of transmitting torque to the drive shaft; and a parking lock mechanism capable of selectively switching between a locked state in which the rotation of a predetermined rotating member between the motor and the drive shaft is prohibited and an unlocked state in which the predetermined rotating member is rotatable, wherein the device comprises a controller for controlling the motor, the controller comprising: a first tilt angle determination unit that determines whether the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is locked is greater than or equal to a predetermined first angle; and a first tilt angle determination unit that determines whether the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is locked is greater than or equal to a predetermined first angle, and the drive shaft The system is characterized by comprising: a twist determination unit that determines whether the drive shaft is twisted; a second tilt angle determination unit that determines whether the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is released is greater than or equal to a predetermined second angle; and a motor control unit that outputs an assist torque from the motor in the direction opposite to the twisting direction of the drive shaft when the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is locked is greater than or equal to the first predetermined angle, it is determined that the drive shaft is twisted, and the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is released is greater than or equal to the second predetermined angle.

[0011] Furthermore, in this invention, the motor control unit may determine the magnitude of the assist torque output from the motor according to the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is released.

[0012] Furthermore, in this invention, the controller may further include a motor control prohibition unit that prohibits outputting the assist torque from the motor when the difference between the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is locked and the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is released is greater than or equal to a predetermined difference.

[0013] Furthermore, in this invention, the controller may further include a motor control prohibition unit that prohibits outputting the assist torque from the motor when the tilt direction in the pitching direction of the vehicle at the time the parking lock mechanism is locked is different from the tilt direction in the pitching direction of the vehicle at the time the parking lock mechanism is released. [Effects of the Invention]

[0014] The vehicle control device in this invention outputs an assist torque from the motor in opposition to the twisting direction of the drive shaft when the vehicle's pitching angle is greater than or equal to a first predetermined angle at the time the rotation of a predetermined rotating member connected to the drive shaft is locked by the parking lock mechanism, and the drive shaft is twisted, and the vehicle's tilt angle at the time the parking lock mechanism is released is greater than or equal to a second predetermined angle. Therefore, when the vehicle's posture changes, such as when the vehicle is towed, in other words, when the vehicle is towed and placed horizontally and the twisting of the drive shaft is eliminated, the output of assist torque from the motor can be suppressed. As a result, when the drive shaft is released by the parking lock mechanism, vibrations and shocks caused by the output of assist torque from the motor can be suppressed.

[0015] Furthermore, by determining the magnitude of the assist torque output from the motor according to the pitching angle of the vehicle at the time the parking lock mechanism is released, it is possible to suppress fluctuations in the target value of the assist torque based on signals, for example, when the detected value of the sensor that detects the vehicle's tilt angle changes while the motor is outputting assist torque, or when noise is included in the signal output from that sensor. As a result, it is possible to suppress vehicle vibration caused by fluctuations in the motor's assist torque due to factors other than drive shaft twisting.

[0016] Furthermore, the vehicle control device in this invention prohibits the output of assist torque from the motor if the difference between the tilt angle in the pitching direction of the vehicle when the parking lock mechanism is locked and the tilt angle in the pitching direction of the vehicle when the parking lock mechanism is released is greater than or equal to a predetermined difference. In other words, it determines that the vehicle's posture has changed, or in other words, that the amount of torsion of the drive shaft has changed, and in such cases, it prohibits the output of assist torque from the motor. Therefore, it is possible to suppress the occurrence of vehicle vibration caused by the output of assist torque from the motor when the amount of torsion of the drive shaft has changed or the vehicle's posture has changed.

[0017] Furthermore, if the tilt direction in the vehicle's pitching direction when the parking lock mechanism is locked is different from the tilt direction in the vehicle's pitching direction when the parking lock mechanism is released, the motor is prohibited from outputting the assist torque. Therefore, by prohibiting the motor from outputting assist torque when the torsional direction of the drive shaft changes, it is possible to suppress the occurrence of vehicle vibration caused by the output of assist torque from the motor. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic diagram showing an example of a vehicle according to an embodiment of this invention. [Figure 2] Figure 2 is a block diagram illustrating the functional configuration of the controller. [Figure 3] Figure 3 is a flowchart illustrating a control example for setting the torsion detection flag. [Figure 4] Figure 4 is a flowchart illustrating a control example for setting the motor control execution flag. [Figure 5] Figure 5 is a flowchart illustrating an example of control for setting the assist torque. [Figure 6]FIG. 6 is a diagram showing an example of a map for determining a target torque according to the tilt angle of a vehicle. [Figure 7] FIG. 7 is a flowchart for explaining a control example of setting a motor control execution flag based on the tilt angle of the vehicle at the time of twist determination and the current tilt angle of the vehicle. [Figure 8] FIG. 8 is a flowchart for explaining a control example of setting a motor control execution flag based on the tilt direction of the vehicle at the time of twist determination and the current tilt direction of the vehicle. MODE FOR CARRYING OUT THE INVENTION

[0019] This invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of the case where this invention is embodied, and do not limit this invention.

[0020] An example of a vehicle in an embodiment of this invention is schematically shown in FIG. 1. The vehicle Ve shown in FIG. 1 is an electric vehicle equipped with a motor (MG) 1 as a driving force source. The motor 1 can be configured in the same manner as a motor provided as a driving force source in a conventional electric vehicle or hybrid vehicle. That is, in addition to the function as a motor that generates a driving torque by being supplied with electric power from a power storage device (not shown), it has a function as a generator that converts at least a part of the power of the output shaft 2 into electric power when the output shaft 2 is rotated together. Specifically, it is composed of a permanent magnet type synchronous motor, an induction motor, or the like.

[0021] A first drive gear 3 is attached to the output shaft 2 of the motor 1. A first driven gear 4 that meshes with the first drive gear 3 and is formed with a larger diameter than the first drive gear 3 is attached to an intermediate shaft 5 arranged parallel to the output shaft 2 of the motor 1. That is, a reduction gear pair is constituted by the first drive gear 3 and the first driven gear 4.

[0022] A second drive gear 6 is further attached to the intermediate shaft 5. A second driven gear 7, which meshes with the second drive gear 6 and is formed to be larger in diameter than the second drive gear 6, is attached to the output shaft 8 of the motor 1, which is arranged parallel to the output shaft 2 and the intermediate shaft 5. In other words, the second drive gear 6 and the second driven gear 7 constitute a reduction gear pair. One end of a drive shaft 9 is connected to the output shaft 8 so as to be able to rotate as a whole, and a wheel 10 is connected to the other end of the drive shaft 9.

[0023] Furthermore, a parking lock mechanism 11 is provided that can selectively switch between a locked state in which the rotation of the intermediate shaft 5 is prohibited and an unlocked state in which the intermediate shaft 5 is rotatable. This parking lock mechanism 11 can be configured in the same way as parking lock mechanisms provided in conventional vehicles. Specifically, the parking lock mechanism 11 consists of a parking lock gear 12 attached to the intermediate shaft 5, a parking pawl 13 that can selectively engage with the parking lock gear 12, and an actuator (not shown) that operates the parking pawl 13. When a parking range is selected by the shift device 24 described later, the parking pawl 13 is rotated by an actuator (not shown) or the like to engage with the parking lock gear 12. By engaging the parking pawl 13 with the parking lock gear 12 in this way, the rotation of the parking lock gear 12 is prohibited. Therefore, the rotation of the drive shaft 9, which is connected to the parking lock gear 12 via the intermediate shaft 5 or the like in a way that allows torque transmission, is prohibited.

[0024] The vehicle Ve shown in Figure 1 is equipped with a brake system 14 that applies braking torque to the wheels 10 in accordance with the amount of operation of a brake pedal (not shown) operated by the driver. This brake system 14 can be configured in the same way as brake systems installed in conventional vehicles. That is, it can be configured as a disc brake that applies braking torque to the wheels 10 by clamping a brake rotor that rotates integrally with the wheels 10 with brake pads, or as a drum brake that applies braking torque to the wheels 10 by pressing brake shoes from the inside of a drum that rotates integrally with the wheels 10. Furthermore, the clamping force of the brake pads and the pressing force of the brake shoes can be controlled by an actuator (not shown) that generates hydraulic or electromagnetic force in accordance with the amount of operation of the brake pedal.

[0025] Furthermore, the vehicle Ve shown in Figure 1 is equipped with an electric parking brake (hereinafter referred to as EPB) 15. This EPB 15 is configured in the same way as an EPB installed in a conventional vehicle, and when a shift operation is performed to select the parking range, the motor 16 is activated, driving a caliper and brake shoe (not shown) to apply braking torque to the wheel 10, and when a driving range other than the parking range is selected, the braking torque is reduced. From the viewpoint of mounting the motor 16, the motor 16 may be installed on the vehicle body, and a wire or the like that is provided to connect the motor 16 to the caliper and brake shoe, and the caliper and brake shoe may be driven by rotating the motor 16 to wind up the wire.

[0026] In the example shown in Figure 1, the motor 1, the gear train that transmits torque from the motor 1 to the output shaft 8, and the output shaft 8 are housed in a single case 17, which is connected to the vehicle body 19 via a mount 18. The wheels 10 are also held to the vehicle body 19 via a suspension 20.

[0027] In the vehicle Ve shown in Figure 1, when the brake pedal is operated and the driver performs a shift operation to select the parking range, the vehicle is permitted to switch the driving range to the parking range. When switching to the parking range in this manner, the rotation of the intermediate shaft 5 is prohibited by the parking lock mechanism 11, and braking torque is applied to the wheels 10 by the EPB 15.

[0028] As described above, the time from when the shift operation is performed until the rotation of the intermediate shaft 5 is prohibited by the parking lock mechanism 11 may be shorter than the time until braking torque is applied to the wheels 10 by the EPB 15. Therefore, for example, when parking the vehicle Ve on a slope or when the wheels 10 are parked on top of some object, if the driver reduces the amount of brake pedal operation before braking torque is applied to the wheels 10 by the EPB 15, the wheels 10 will rotate (turn) even though the rotation on the input side of the drive shaft 9 is prohibited. Also, if the EPB 15 cannot be activated for some reason, the wheels 10 will rotate (turn) even though the rotation on the input side of the drive shaft 9 is prohibited after the driver reduces the amount of brake pedal operation. As a result, the drive shaft 9 twists. In other words, torque (hereinafter referred to as torsional torque) corresponding to its elastic modulus and the amount of twist accumulates in the drive shaft 9.

[0029] When the drive shaft 9 is twisted in this manner, and the shift is operated to select a driving range other than the parking range, the twist of the drive shaft 9 is released at the same time that the lock on the intermediate shaft 5 by the parking lock mechanism 11 is released. In other words, the torsional torque accumulated in the drive shaft 9 is transmitted to the motor 1, which is the driving force source. When this twist of the drive shaft 9 is released, the torque pulsates according to the elastic modulus of the drive shaft 9. As a result, the transmission of the pulsating torque to the motor 1 may cause the vehicle Ve to vibrate.

[0030] Furthermore, the pulsation of torque in the drive shaft 9 can cause the suspension 20 to vibrate vertically, and this vibration can be transmitted to the vehicle body 19, potentially causing the vehicle Ve to vibrate.

[0031] Therefore, if the drive shaft 9 is twisted, the motor 1 outputs an assist torque to counteract the torsional torque accumulated in the drive shaft 9, thereby suppressing vibration when the parking lock mechanism 11 is released.

[0032] On the other hand, if the vehicle Ve is towed after parking, the amount of torsion of the drive shaft 9 may change due to the change in the frictional force between the wheel 10 and the road surface acting on it. Alternatively, if the vehicle Ve is towed while the braking torque of the EPB 15 is not being applied to the wheel 10 due to some factor, the amount of torsion of the drive shaft 9 may change as the wheel 10 rotates. Or, if the torque acting on the wheel 10 from the road surface during towing is greater than the braking torque of the EPB 15, the wheel 10 may rotate, and the amount of torsion of the drive shaft 9 may change.

[0033] Furthermore, if the vehicle Ve's tilt angle changes while the braking torque of the EPB15 is not being applied to the wheels 10 due to some factor, the rotation (rotation) of the wheels 10 may change the amount of torsion of the drive shaft 9.

[0034] As described above, if the amount of torsion of the drive shaft 9 changes between the time the drive shaft 9 is locked by the parking lock mechanism 11 and the time the drive shaft 9 is released by the parking lock mechanism 11, controlling the assist torque of the motor 1 based on the amount of torsion of the drive shaft 9 at the time the drive shaft 9 is locked may result in excessive or insufficient assist torque, potentially causing a shock when the parking lock mechanism 11 is released.

[0035] Therefore, the vehicle Ve shown in Figure 1 is equipped with an electronic control unit (hereinafter referred to as ECU) 21 that controls the motor 1 to output assist torque when the drive shaft 9 is twisted and the inclination angle in the pitching direction of the vehicle Ve when the parking lock mechanism 11 is released is greater than or equal to a predetermined angle. This ECU 21 is mainly composed of a microcomputer and is configured to control the output torque of the motor 1 based on the input signal and pre-stored calculation formulas. This ECU 21 corresponds to the "controller" in this embodiment of the invention.

[0036] In the example shown in Figure 1, the ECU 21 is connected to an acceleration sensor 22 that detects the longitudinal acceleration of the vehicle Ve, a resolver 23 that detects the rotational speed (rotation angle) of the motor 1, and a shift sensor 25 that detects the driving range selected by the shift device 24, and signals are input from these sensors 22, 23, and 25. In addition, the ECU 21 is connected to an EPB-ECU 26 that controls the EPB 15 and a B-ECU 27 that controls the brake device 14, and signals are input from these ECUs 26 and 27.

[0037] The above-described shift device 24 may be a so-called momentary type shift device in which, for example, operating the shift lever 28 to a shift position corresponding to the driving range turns on a shift sensor 25 corresponding to that shift position, a signal is input to the ECU 21, and releasing the operation of the shift lever 28 returns the shift lever 28 to a predetermined standby position. The shift device 24 may also be provided with a parking button for selecting a parking range, and the shift sensor 25 may include a sensor that is turned on when the parking button is pressed.

[0038] Furthermore, the EPB-ECU26 is connected to, for example, the shift sensor 25, and based on the signal input from the shift sensor 25, it determines whether or not the EPB 15 is operating, and based on the result of that determination, it outputs a command signal to the ECU21 and the motor 16. In addition, the B-ECU27 receives signals such as the amount of brake pedal depression or pedal force or master cylinder pressure, or signals that detect hydraulic pressure or electromagnetic force to generate braking torque for the brake device 14, and based on these signals, it determines the braking torque to be applied to the brake device 14 or the braking torque that is currently applied to the brake device 14. Then it outputs a signal representing the magnitude of that braking torque to the ECU21.

[0039] Figure 2 shows a block diagram illustrating the functional configuration of the ECU 21. The ECU 21 shown in Figure 2 includes a parking detection unit 29, a brake detection unit 30, a first tilt angle detection unit 31, a twist detection unit 32, an abnormality detection unit 33, a second tilt angle detection unit 34, a motor control prohibition unit 35, and a motor control unit 36.

[0040] The parking determination unit 29 determines whether the vehicle is in a parking range where the rotation of the intermediate shaft 5 is prohibited by the parking lock mechanism 11, or in other words, whether it is in a locked state where the rotation of the intermediate shaft 5 is prohibited. Specifically, it determines whether the vehicle is in a parking range based on whether a predetermined time has elapsed since the parking range was selected by a shift operation, or based on a command signal to the actuator that operates the parking pole 13.

[0041] The brake determination unit 30 determines whether the braking torque acting on the wheels 10 is less than or equal to a predetermined torque. Specifically, it determines whether the braking torque acting on the wheels 10 is less than or equal to a predetermined torque based on signals input to the ECU 21 from the EPB-ECU 26 or B-ECU 27. The predetermined torque can be set to a braking torque such that the wheels 10 do not rotate when the vehicle Ve is stopped on a road surface at a predetermined angle as defined in the specifications of the vehicle Ve.

[0042] The first tilt angle determination unit 31 determines whether the tilt angle (absolute value) in the pitching direction of the vehicle Ve at the time the intermediate shaft 5 is locked by the parking lock mechanism 11 is greater than or equal to a predetermined first angle. Specifically, it measures the tilt angle of the vehicle Ve based on the longitudinal acceleration of the vehicle Ve detected by the acceleration sensor 22, and determines whether that tilt angle is greater than or equal to the tilt angle at which the wheels 10 would rotate if no braking torque were applied to the wheels 10.

[0043] The twist detection unit 32 determines that the drive shaft 9 has twisted. For example, if the vehicle Ve is tilted at an angle greater than a predetermined angle, the intermediate shaft 5 (drive shaft 9) is locked by the parking lock mechanism 11, and the braking torque acting on the wheel 10 is less than or equal to a predetermined torque, the unit determines that the drive shaft 9 has twisted. In other words, the unit determines that the drive shaft 9 has twisted within a predetermined time after the drive shaft 9 is locked by the parking lock mechanism 11.

[0044] The abnormality detection unit 33 determines an abnormality if the braking torque applied to the wheel 10 by the brake device 14 or EPB 15 cannot be controlled, or if the ECU 21 cannot receive a signal related to that braking torque. Specifically, it determines whether a signal indicating a malfunction in the brake device 14 or EPB 15 has been input to the ECU 21 from the EPB-ECU 26 or B-ECU 27, or whether there is a problem with communication between the EPB-ECU 26 or B-ECU 27 and the ECU 21. In other words, it determines whether the preconditions for the motor 1 to output assist torque have been met. The result of this determination is then output to the torsion detection unit 32.

[0045] The second tilt angle determination unit 34 determines whether the tilt angle of the vehicle Ve in the pitching direction at the time the parking lock mechanism 11 is released is greater than or equal to a predetermined second predetermined angle. This second predetermined angle may be the same as the first predetermined angle determined by the first tilt angle determination unit 31, and is set to be greater than or equal to the tilt angle at which the wheels 10 rotate if no braking torque is applied to the wheels 10.

[0046] The motor control prohibition unit 35 prohibits the output of assist torque from the motor 1 if the difference between the tilt angle in the pitching direction of the vehicle Ve at the time the parking lock mechanism 11 is locked and the tilt angle in the pitching direction of the vehicle Ve at the time the parking lock mechanism 11 is released is greater than or equal to a predetermined difference. This is because if the vehicle Ve's posture changes from the time it is determined that the drive shaft 9 has twisted, outputting assist torque from the motor 1 could actually cause the vehicle Ve to vibrate.

[0047] Furthermore, if the tilt direction in the pitching direction of the vehicle Ve changes, the twisting direction of the drive shaft 9 also changes. In such cases, if the motor 1 outputs assist torque based on the tilt direction in the pitching direction of the vehicle Ve at the time the parking lock mechanism 11 is locked, the vehicle Ve may actually vibrate. Therefore, the motor control prohibition unit 35 prohibits the output of assist torque from the motor 1 when the tilt direction in the pitching direction of the vehicle Ve at the time the parking lock mechanism 11 is locked is different from the tilt direction in the pitching direction of the vehicle Ve at the time the parking lock mechanism 11 is released.

[0048] When the torsion detection unit 32 determines that the drive shaft 9 is torsion, the motor control unit 36 ​​outputs an assist torque to counteract the torsional torque accumulated in the drive shaft 9 when releasing the parking lock mechanism 11. Specifically, the magnitude of the assist torque of the motor 1 is determined according to the tilt angle in the pitching direction of the vehicle Ve at the time the parking lock mechanism 11 is released.

[0049] As described above, the vehicle control device in this embodiment of the invention determines whether the drive shaft 9 has twisted when the parking lock mechanism 11 is locked, and then outputs an assist torque from the motor 1 when the parking lock mechanism 11 is released. Therefore, first, an example of control that determines whether the drive shaft 9 has twisted when the parking lock mechanism 11 is locked will be described. Figure 3 shows a flowchart illustrating this control example. In the control example shown in Figure 3, first, it is determined whether the parking range is set and whether the abnormality determination flag is off (step S1). Whether the parking range is set in step S1 can be determined by the parking determination unit 29. Specifically, this can be determined based on whether a predetermined time has elapsed since the parking range was selected by a shift operation, or based on a command signal to the actuator that operates the parking pole 13.

[0050] Furthermore, the abnormality determination flag in step S1 is a flag that is set to ON when the braking torque applied to the wheel 10 by the brake device 14 or EPB 15 cannot be controlled, or when the ECU 21 cannot receive a signal related to that braking torque, and this can be determined by the abnormality determination unit 33. In other words, it determines whether the brake device 14 or EPB 15 is operating normally and whether the ECU 21 can receive a signal indicating that it has operated.

[0051] If the parking range is not set or the abnormality detection flag is turned on, and a negative result is determined in step S1, the flag indicating that the drive shaft 9 is twisted (hereinafter referred to as the twist detection flag) is set to off (step S2), that is, it is determined that the drive shaft 9 is not twisted, and this routine is terminated. If the twist detection flag is set to off, the twist detection counter, which will be described later, is set to "0".

[0052] Conversely, if a positive determination is made in step S1 because the parking range is set and the abnormality determination flag is off, then it is determined whether the EPB 15 and the brake device 14 are in a non-braking state (step S3). This step S3 is for determining whether the conditions for twisting of the drive shaft 9 are met. That is, it is determined whether the rotation on the input side of the drive shaft 9 is prohibited, while the wheel 10 is able to rotate, or in other words, whether sufficient braking torque is not acting on the wheel 10. This step S3 can be determined by the brake determination unit 30 described above. Note that the braking torque applied to the wheel 10 by the EPB 15 begins to increase after a predetermined time has elapsed since the motor 16 was energized, but there is no sensor to detect the point in time when that braking torque begins to act. Therefore, it is also possible to determine that the EPB 15 is in a non-braking state if the time elapsed since the motor 16 was energized is less than the predetermined time.

[0053] If a positive determination is made in step S3 because the EPB15 and brake device 14 are not braking, the amount of torsion of the drive shaft 9 may increase. Therefore, if a positive determination is made in step S3, the torsion determination counter for determining whether or not the drive shaft 9 has torn is incremented (step S4). Conversely, if a negative determination is made in step S3 because at least one of the EPB15 and brake device 14 is applying braking torque to the wheel 10, the torsion determination counter is maintained (step S5).

[0054] Following steps S4 and S5, it is determined whether the tilt angle (absolute value) of the vehicle Ve in the pitching direction is greater than or equal to a predetermined first angle, and whether the torsion determination counter is greater than or equal to a predetermined value (step S6). This step S6 can be determined by the first tilt angle determination unit 31 described above. That is, the tilt angle of the vehicle Ve is measured based on the longitudinal acceleration of the vehicle Ve detected by the acceleration sensor 22, and it is determined whether that tilt angle is greater than or equal to the first tilt angle at which the wheels 10 rotate.

[0055] Furthermore, the predetermined value in step S6 is the time required for the drive shaft 9 to twist to the point where the motor 1 needs to output assist torque when releasing the parking lock mechanism 11, and is determined by conducting experiments or simulations. Since the rate of change of the drive shaft 9's twist is thought to differ depending on the vehicle Ve's tilt angle, the predetermined value in step S6 may be a variable number set to decrease as the vehicle Ve's tilt angle increases.

[0056] If the tilt angle of vehicle Ve is greater than or equal to a first predetermined angle, and the twist determination counter is greater than or equal to a predetermined value, a positive determination is made in step S6, the twist determination flag is set to ON (step S7), and this routine is terminated. Conversely, if the tilt angle (absolute value) of vehicle Ve is less than the first predetermined angle, or the twist determination counter is less than a predetermined value, and a negative determination is made in step S6, the twist determination flag is maintained (step S8), and this routine is terminated. Step S7 functions as the "twist determination unit" in this embodiment of the invention.

[0057] Next, an example of control that determines whether or not to output assist torque from the motor 1 at the time of releasing the parking lock mechanism 11 will be explained. Figure 4 shows a flowchart illustrating this control example. In the control example shown in Figure 4, first, it is determined whether or not the condition for ending the output of assist torque from the motor 1 has been met (step S11). Specifically, it is determined whether or not the assist torque has been output continuously for a predetermined time or longer, and more specifically, whether or not the assist execution counter, which will be described later, is above a predetermined value. It is also determined whether or not the lock of the drive shaft 9 by the parking lock mechanism 11 has been released, and more specifically, whether or not a driving range other than the parking range is set. Furthermore, it is determined whether or not the twist of the drive shaft 9 has been resolved, and more specifically, whether or not the absolute value of the rotational speed (rotation angle) of the motor 1 is above a predetermined rotational speed (predetermined rotation angle). In addition, it is determined whether or not any abnormality has occurred while the motor 1 has been outputting assist torque, that is, whether or not the abnormality determination flag is on.

[0058] If at least one of the following conditions is met in step S11, such that the assist execution counter is above a predetermined value, a driving range other than the parking range is set, the absolute value of the rotational speed of motor 1 is above a predetermined rotational speed, or the abnormality judgment flag is on, then the flag for executing control to output assist torque from motor 1 (hereinafter referred to as the motor control execution flag) is set to off (step S12).

[0059] Conversely, if the assist execution counter is less than a predetermined value, the parking range is set, the absolute value of the motor 1's rotational speed is less than a predetermined rotational speed, and the abnormality determination flag is off, and therefore a negative determination is made in step S11, then a shift operation is performed to select a driving range other than the parking range, the twisting determination flag is on, and it is determined whether the pitching angle of the vehicle Ve is greater than or equal to a predetermined second tilt angle (step S13). The determination in step S13 as to whether the pitching angle of the vehicle Ve is greater than or equal to the second tilt angle can be made by the second tilt angle determination unit 34 described above. The second tilt angle may be the same as the first tilt angle in step S6.

[0060] If a shift operation is performed to select a driving range other than the parking range, the torsion detection flag is on, and the pitching angle of the vehicle Ve is greater than or equal to the second tilt angle, and a positive determination is made in step S13, the motor control execution flag is set to on (step S14). Conversely, if a shift operation is not performed to select a driving range other than the parking range, or the torsion detection flag is off, or the pitching angle of the vehicle Ve is less than the second tilt angle, and a negative determination is made in step S13, the motor control execution flag is maintained (step S15).

[0061] Following steps S12, S14, and S15, it is determined whether the motor control execution flag is on (step S16). If the motor control execution flag is on and the determination in step S16 is positive, the assist execution counter is incremented (step S17) and this routine is terminated. Conversely, if the motor control execution flag is off and the determination in step S16 is negative, the assist execution counter is set to "0" (step S18) and this routine is terminated.

[0062] As described above, the motor control execution flag is set to ON if the tilt angle of the vehicle Ve at the time the drive shaft 9 is locked by the parking lock mechanism 11 is greater than or equal to a first predetermined angle, the drive shaft 9 is twisted, and the tilt angle of the vehicle Ve at the time the drive shaft 9 is released by the parking lock mechanism 11 is greater than or equal to a second predetermined angle. In other words, the motor 1 outputs assist torque. Therefore, if the posture of the vehicle Ve changes, such as when the vehicle Ve is towed, in other words, if the vehicle Ve is towed and placed horizontally and the twist of the drive shaft 9 is eliminated, the output of assist torque from the motor 1 can be suppressed. As a result, vibration and shocks in the vehicle Ve caused by the output of assist torque from the motor 1 when the drive shaft 9 is released by the parking lock mechanism 11 can be suppressed.

[0063] Figure 5 shows a flowchart illustrating a control example for determining the assist torque by motor 1. In the control example shown in Figure 5, first, it is determined whether the motor control execution flag is off or not (step S21). If the determination in step S21 is positive because the motor control execution flag is off, the target value of the assist torque by motor 1 (hereinafter simply referred to as target torque) is set to "0" (step S22). Conversely, if the determination in step S21 is negative because the motor control execution flag is on, it is determined whether the motor control execution flag has switched from off to on or not (step S23). This step S23 can be determined depending on whether the determination in step S21 in the previous routine was positive or negative.

[0064] If a positive determination is made in step S23 because the motor control execution flag has switched from off to on, the target torque is determined based on the tilt angle of the vehicle Ve at that time (step S24). Specifically, when the motor control execution flag switches from off to on, the tilt angle of the vehicle Ve is calculated from the acceleration of the vehicle Ve detected by the acceleration sensor 22, and the target torque is determined based on the tilt angle of the vehicle Ve and the map shown in Figure 6, which has been constructed in advance through experiments or simulations. In Figure 6, the tilt angle of the vehicle Ve is plotted on the horizontal axis and the target torque is plotted on the vertical axis. That is, the map is constructed so that the target torque increases as the tilt angle of the vehicle Ve increases.

[0065] On the other hand, if the motor control execution flag has not switched from off to on, that is, if it is determined negatively in step S23 because the target value of the assist torque of motor 1 has been set in a routine prior to the previous one, the target value of the assist torque of motor 1 is maintained at the previous position (step S25).

[0066] Following steps S22, S24, and S25, the rate of decrease of the assist torque output from motor 1 is determined. Specifically, it is first determined whether an abnormality has occurred, such as when the ECU 21 is unable to receive signals related to the braking torque of the brake device 14 or EPB 15 while motor 1 is outputting assist torque. Specifically, it is determined whether the abnormality determination flag is on (step S26).

[0067] If the abnormality detection flag is turned on and a positive determination is made in step S26, the rate at which the assist torque of motor 1 decreases is set to the maximum rate predetermined based on the characteristics of motor 1 (step S27). Conversely, if the abnormality detection flag is turned off and a negative determination is made in step S26, the rate at which the assist torque decreases is set to a rate corresponding to the magnitude of the assist torque (target torque) of motor 1 so that the assist torque decreases over a predetermined time (step S28).

[0068] Following steps S27 and S28, the target value of the assist torque of motor 1 is multiplied by the reduction rate set in steps S27 and S28 and the elapsed time to determine the effective value of the output torque of motor 1 (step S29), and this routine is then terminated.

[0069] As described above, by determining the target value of the assist torque of motor 1 based on the tilt angle of vehicle Ve at the moment the motor control execution flag switches from off to on, it is possible to suppress fluctuations in the target value of the assist torque based on signals, for example, when vehicle Ve vibrates and the detected value of acceleration sensor 22 changes while motor 1 is outputting assist torque, or when noise is included in the signal input from acceleration sensor 22 to ECU 21. As a result, it is possible to suppress vibration of vehicle Ve due to fluctuations in the assist torque of motor 1 caused by factors other than the amount of torsion of drive shaft 9.

[0070] In the control example described above, the motor control execution flag is switched on when the vehicle Ve's tilt angle at the time the parking lock mechanism 11 is locked is greater than or equal to the first tilt angle, and when the vehicle Ve's tilt angle at the time the parking lock mechanism 11 is released is greater than or equal to the second tilt angle. On the other hand, since the amount of torsion of the drive shaft 9 depends on the vehicle Ve's tilt angle, even if the vehicle Ve's tilt angle at the time the parking lock mechanism 11 is released is greater than or equal to the second tilt angle, the amount of change from the vehicle Ve's tilt angle at the time the parking lock mechanism 11 is locked may be large. In such cases, if the motor 1 outputs an assist torque determined based on the vehicle Ve's tilt angle at the time the parking lock mechanism 11 is locked, the assist torque output from the motor 1 may be excessive or insufficient, potentially causing the vehicle Ve to vibrate.

[0071] Therefore, in this embodiment of the invention, the control device may set the motor control execution flag to OFF when there is a large difference between the tilt angle of the vehicle Ve when the parking lock mechanism 11 is locked and the tilt angle of the vehicle Ve when the parking lock mechanism 11 is released. A flowchart illustrating an example of this control is shown in Figure 7. Steps identical to those in the control example shown in Figure 4 are given the same step numbers and their explanations are omitted.

[0072] In the control example shown in Figure 7, if a negative determination is made in step S11 because the assist execution counter is less than a predetermined value, the parking range is set, the absolute value of the rotational speed of motor 1 is less than a predetermined rotational speed, and the abnormality determination flag is off, then it is determined whether the absolute value of the difference between the tilt angle of the vehicle Ve at the time the parking lock mechanism 11 is locked (tilt angle when twisting is determined) and the tilt angle of the vehicle Ve at the time the parking lock mechanism 11 is released (current tilt angle) is greater than or equal to a predetermined difference (step S31). This predetermined difference in step S31 can be set to, for example, a magnitude equivalent to the detection error of the acceleration sensor 22, or a magnitude sufficient to determine that the attitude of the vehicle Ve has changed.

[0073] If the difference between the tilt angle at the time of torsion determination and the current tilt angle is greater than or equal to a predetermined difference, and a positive determination is made in step S31, the amount of torsion of the drive shaft 9 cannot be accurately determined, so the process proceeds to step S12 and the motor control execution flag is set to off. In other words, the output of assist torque from motor 1 is prohibited.

[0074] Conversely, if the difference between the tilt angle at the time of twist determination and the current tilt angle is less than a predetermined difference, and a negative determination is made in step S31, it is considered that the attitude of the vehicle Ve has not changed, and the process proceeds to step S13. In other words, based on the determination result in step S13, it is decided whether to switch the motor control execution flag to ON or to keep the motor control execution flag ON.

[0075] As described above, by determining whether or not to output assist torque from the motor 1 based on the difference between the tilt angle of the vehicle Ve when the parking lock mechanism 11 is locked and the tilt angle of the vehicle Ve when the parking lock mechanism 11 is released, it is possible to determine whether or not the posture of the vehicle Ve has changed. In other words, it is possible to determine whether or not the amount of torsion of the drive shaft 9 has changed. Therefore, by prohibiting the output of assist torque from the motor 1 when the posture of the vehicle Ve changes significantly, it is possible to suppress vibrations of the vehicle Ve caused by the output of assist torque from the motor 1.

[0076] Furthermore, if the tilt direction in the pitching direction of the vehicle Ve when the parking lock mechanism 11 is locked is different from the tilt direction in the pitching direction of the vehicle Ve when the parking lock mechanism 11 is released, the torsional direction of the drive shaft 9 is likely to be reversed. Also, since the assist torque of the motor 1 is output to counteract the torsional torque of the drive shaft 9, if the torsional direction of the drive shaft 9 is reversed as described above, the direction of the assist torque of the motor 1 will also be reversed. Therefore, if the tilt direction of the vehicle Ve is different, outputting an assist torque from the motor 1 corresponding to the tilt direction of the vehicle Ve when the parking lock mechanism 11 is locked may increase the vibration of the vehicle Ve.

[0077] Therefore, in this embodiment of the invention, the control device may set the motor control execution flag to OFF if the tilt direction of the vehicle Ve at the time the parking lock mechanism 11 is locked is different from the tilt direction of the vehicle Ve at the time the parking lock mechanism 11 is released. A flowchart illustrating an example of this control is shown in Figure 8. Steps identical to those in the control example shown in Figure 4 are given the same step numbers, and their explanations are omitted.

[0078] In the control example shown in Figure 8, if a negative determination is made in step S11 because the assist execution counter is less than a predetermined value, the parking range is set, the absolute value of the rotational speed of motor 1 is less than a predetermined rotational speed, and the abnormality determination flag is off, then it is determined whether the tilt direction of the vehicle Ve at the time the parking lock mechanism 11 is locked (tilt direction when twisting is determined) and the tilt direction of the vehicle Ve at the time the parking lock mechanism 11 is released (current tilt direction) are different (step S41). The tilt direction in step S41 can be determined, for example, based on whether the signal detected by the acceleration sensor 22 is a positive or negative value.

[0079] If, when the parking lock mechanism 11 is locked, the front of the vehicle Ve is tilted so that it is vertically higher than the rear, and when the parking lock mechanism 11 is released, the front of the vehicle Ve is tilted so that it is vertically lower than the rear, or if, when the parking lock mechanism 11 is locked, the front of the vehicle Ve is tilted so that it is vertically lower than the rear, and when the parking lock mechanism 11 is released, the front of the vehicle Ve is tilted so that it is vertically higher than the rear, and the tilt direction at the time of torsion determination differs from the current tilt direction, and a positive determination is made in step S41, then the amount of torsion of the drive shaft 9 cannot be accurately determined, or the torsion direction of the drive shaft 9 may be reversed, so the process proceeds to step S12 and the motor control execution flag is set to off. In other words, the output of assist torque from motor 1 is prohibited.

[0080] Conversely, if the tilt direction at the time of twist determination and the current tilt direction are the same, and a negative determination is made in step S41, it is considered that the attitude of the vehicle Ve has not changed, and the process proceeds to step S13. In other words, based on the determination result in step S13, it is decided whether to switch the motor control execution flag to ON or to keep the motor control execution flag ON.

[0081] As described above, by determining whether or not to output assist torque from the motor 1 based on the tilt direction of the vehicle Ve when the parking lock mechanism 11 is locked and the tilt direction of the vehicle Ve when the parking lock mechanism 11 is released, it is possible to determine whether or not the twisting direction of the drive shaft 9 has changed. Therefore, by prohibiting the output of assist torque from the motor 1 when the twisting direction of the drive shaft 9 changes, it is possible to suppress vibrations of the vehicle Ve caused by the output of assist torque from the motor 1.

[0082] Furthermore, the vehicle in this embodiment of the invention is not limited to a vehicle in which a motor is connected to each wheel, but may also be a vehicle configured to transmit torque from a single motor to a pair of front wheels or rear wheels, or to all wheels. In addition, it may be a hybrid vehicle equipped with an engine as a driving force source in addition to the motor.

[0083] Furthermore, the configuration connecting the motor 1 and the drive shaft 9, and the rotating member whose rotation is prohibited by the parking lock mechanism 11, are not limited to those shown in Figure 1. Moreover, the vehicle in this embodiment of the invention does not need to be equipped with an EPB 15. In that case, a torsional determination flag can be set based on whether or not the brake device 14 is applying braking torque to the wheel 10. [Explanation of symbols]

[0084] 1,16 motor 2.8 Output shaft 3.6 drive gear 4.7 Driven gear 5 Intermediate axis 9 Drive shaft 10 wheels 11 Parking lock mechanism 12 Parking lock gear 13 Parking poles 14 Brake system 15. Electric Parking Brake (EPB) 17 cases 18 Mount 19 car bodies 20 Suspension 21 Electronic Control Unit (ECU) 22 Accelerometer 23 resolvers 24 Shift device 25 Shift Sensor 26 EPB-ECU 27 B-ECU 28 Shift lever 29 Parking determination unit 30 Brake detection unit 31 First inclination angle determination section 32. Torsion detection unit 33 Abnormality determination section 34 Second tilt angle determination section 35 Motor control prohibition unit 36 Motor control unit Vehicle

Claims

1. A vehicle control device comprising: a drive shaft with one end connected to a wheel; a motor capable of transmitting torque to the drive shaft; and a parking lock mechanism capable of selectively switching between a locked state in which the rotation of a predetermined rotating member between the motor and the drive shaft is prohibited and an unlocked state in which the predetermined rotating member is rotatable, The motor is equipped with a controller that controls the motor, The aforementioned controller, A first tilt angle determination unit determines whether the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is locked is greater than or equal to a predetermined first angle, A torsion detection unit that determines whether the drive shaft has twisted after the parking lock mechanism has been locked, A second tilt angle determination unit determines whether the tilt angle in the pitching direction of the vehicle at the time the parking lock mechanism is released is greater than or equal to a predetermined second angle, The system is configured as follows: When the vehicle's pitching inclination angle at the time the parking lock mechanism is locked is greater than or equal to the first predetermined angle, it is determined that the drive shaft has twisted, and when the vehicle's pitching inclination angle at the time the parking lock mechanism is released is greater than or equal to the second predetermined angle, the system outputs an assist torque from the motor that is opposite to the twisting direction of the drive shaft. A vehicle control device characterized by the following features.

2. A vehicle control device according to claim 1, The motor control unit determines the magnitude of the assist torque output from the motor according to the pitching angle of the vehicle at the time the parking lock mechanism is released. A vehicle control device characterized by the following features.

3. A vehicle control device according to claim 1 or 2, The aforementioned controller, The system further includes a motor control prohibition unit that prohibits the output of the assist torque from the motor if the difference between the tilt angle in the pitching direction of the vehicle when the parking lock mechanism is locked and the tilt angle in the pitching direction of the vehicle when the parking lock mechanism is released is greater than or equal to a predetermined difference. A vehicle control device characterized by the following features.

4. A vehicle control device according to claim 1 or 2, The aforementioned controller, The system further includes a motor control prohibition unit that prohibits the output of the assist torque from the motor when the tilt direction in the pitching direction of the vehicle at the time the parking lock mechanism is locked is different from the tilt direction in the pitching direction of the vehicle at the time the parking lock mechanism is released. A vehicle control device characterized by the following features.

Images