Vehicle control system
The vehicle control device addresses torsional torque pulsations by using a motor to counteract and manage assist torque based on the drive shaft's natural frequency, effectively damping vibrations and shocks during the release of the parking lock mechanism.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2025-01-10
- Publication Date
- 2026-07-23
AI Technical Summary
Existing vehicle control devices experience vibrations and shocks due to torsional torque pulsations when the parking lock mechanism is released, as the torsional torque is transmitted to the motor and torque transmission members, leading to inefficiencies in torque management.
A vehicle control device that includes a motor to counteract torsional torque during the locked state of the parking lock mechanism, with a controller to manage assist torque reduction based on the natural frequency of the drive shaft, ensuring the assist torque becomes zero before the torsional torque direction reverses, thereby damping the pulsating torque.
The solution effectively suppresses vibrations and shocks by quickly damping the torsional torque fluctuations, improving vehicle stability and reducing vibrations during the transition from the locked to unlocked state of the parking lock mechanism.
Smart Images
Figure 2026121183000001_ABST
Abstract
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 control device provided with a parking lock mechanism configured to prohibit rotation of a drive shaft connected to a wheel by engaging a parking gear interlocked with the wheel and a parking pole, and to allow the drive shaft to rotate by releasing the engagement.
[0003] In the parking lock mechanism described in Patent Document 1, a shift lever operated by a driver and a parking pole are mechanically connected. Therefore, when the load acting on the meshing surface between the parking gear and the parking pole is large, the operating force of the shift lever required to release the meshing increases. Therefore, the control device described in Patent Document 1 is configured to output torque from a motor in a direction in which the meshing load between the parking lock gear and the parking pole decreases. Specifically, the output torque of the motor is gradually increased, and the meshing load between the parking lock gear and the parking pole is reduced by maintaining the torque at the time when the rotation angle of the motor changes. Further, the control device is configured to set the output torque of the motor to "0" when it is determined that the parking lock mechanism has been released.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] The control device described in Patent Document 1 reduces the operating force of the shift lever required to release the parking lock mechanism by outputting torque from the motor until the engagement between the parking lock gear and the parking pawl is disengaged. In other words, it increases the amount of torsion of the drive shaft. Furthermore, when the control device determines that the parking lock mechanism has been released, it sets the output torque of the motor to zero. Therefore, at the moment the output torque of the motor is set to zero, the torsional torque caused by the twisting of the drive shaft is transmitted to the motor and the torque transmission member between the motor and the drive shaft. This torsional torque pulsates according to the elastic modulus of the drive shaft. Therefore, vibrations and shocks may occur due to the pulsation of the torsional torque during the process of reducing the twist of the drive shaft.
[0006] 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 vibrations and shocks when the parking lock mechanism is released while the drive shaft is twisted. [Means for solving the problem]
[0007] 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 when the parking lock mechanism is in the locked state, the vehicle control device outputs an assist torque from the motor to counteract the torsional torque associated with the twisting of the drive shaft, and further comprises a controller for controlling the motor, wherein the controller comprises a switching determination unit for determining when the parking lock mechanism has switched from the locked state to the unlocked state; a rate setting unit for setting the assist torque reduction rate so that the assist torque becomes zero after a predetermined time has elapsed from the time the parking lock mechanism has switched to the unlocked state; and a motor control unit for controlling the motor based on the assist torque, the reduction rate, and the elapsed time from the time the parking lock mechanism has switched to the unlocked state.
[0008] Furthermore, in this invention, the predetermined time may be a time determined based on the natural frequency of the drive shaft.
[0009] Furthermore, in this invention, the predetermined time may be the time of a half-cycle based on the natural frequency of the drive shaft.
[0010] Furthermore, in this invention, the rate setting unit may include a rate obtained by dividing the assist torque at the time the parking lock mechanism switches to the released state by the predetermined time.
[0011] Furthermore, in this invention, the controller further includes an abnormality determination unit that determines an abnormality in which the torque acting on the drive shaft cannot be controlled normally, and the rate setting unit may, when it is determined that the torque acting on the drive shaft cannot be controlled normally, set the assist torque reduction rate so that the assist torque becomes zero in a shorter time than the predetermined time. [Effects of the Invention]
[0012] The vehicle control device in this invention outputs an assist torque from a motor to counteract the torsional torque associated with the twisting of the drive shaft when the parking lock mechanism is in a locked state, prohibiting the rotation of a predetermined rotating member connected to the drive shaft. The assist torque reduction rate is set so that the assist torque becomes zero after a predetermined time has elapsed from the time the parking lock mechanism switches from the locked state to a released state in which the predetermined rotating member can rotate. Therefore, the output of the assist torque can be stopped before the parking lock mechanism is released and the direction of the torsional torque of the drive shaft reverses. In other words, the assist torque can be reduced in accordance with the decrease in the torsional torque of the drive shaft. Therefore, during the process in which the torsional torque of the drive shaft is decreasing, the assist torque that counteracts that torsional torque can be applied to the drive shaft to suppress the generation of vibration. Furthermore, after the direction of the torsional torque of the drive shaft has reversed, the assist torque can be added to that torsional torque to suppress an increase in the amount of twisting of the drive shaft. As a result, the pulsating torsional torque of the driveshaft can be quickly dampened. In other words, the effect of reducing vehicle vibration can be improved. [Brief explanation of the drawing]
[0013] [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 an example of control for setting the torque output from a motor. [Figure 4] Figure 4 is a time chart illustrating the reduction rate corresponding to the assist torque. [Figure 5] Figure 5 is a time chart illustrating an example of changes in the vehicle's tilt angle, shift position, driving range, motor control execution flag, rate processing flag, and assist torque (actual value) when the control example shown in Figure 3 is executed. [Modes for carrying out the invention]
[0014] This invention will be described based on the embodiments shown in the figures. The embodiments described below are merely examples of how this invention can be implemented and do not limit it.
[0015] An example of a vehicle in this embodiment of the present invention is schematically shown in Figure 1. The vehicle Ve shown in Figure 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 way as motors provided as driving force sources in conventional electric vehicles and hybrid vehicles. That is, in addition to functioning as a motor that generates driving torque by being supplied with power from an energy storage device (not shown), it also functions as a generator that converts at least a portion of the power of the output shaft 2 into electricity by being rotated along with the output shaft 2. Specifically, it is configured as a permanent magnet synchronous motor or an induction motor, etc.
[0016] A first drive gear 3 is attached to the output shaft 2 of motor 1. A first driven gear 4, which meshes with the first drive gear 3 and is formed to be larger in diameter than the first drive gear 3, is attached to an intermediate shaft 5 that is positioned parallel to the output shaft 2 of motor 1. In other words, the first drive gear 3 and the first driven gear 4 constitute a reduction gear pair.
[0017] 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.
[0018] 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.
[0019] In the vehicle Ve shown in FIG. 1, a braking device 14 is provided that applies a braking torque corresponding to the operation amount of a brake pedal (not shown) operated by the driver to the wheel 10. This braking device 14 can be configured in the same manner as the braking device provided in a conventional vehicle. That is, it can be configured by a disc brake that applies a braking torque to the wheel 10 by sandwiching a brake rotor that rotates integrally with the wheel 10 with brake pads, or a drum brake that applies a braking torque to the wheel 10 by pressing a brake shoe from the inside of a drum that rotates integrally with the wheel 10, etc. Also, the clamping force of those brake pads and the pressing force of the brake shoes can be controlled by an actuator (not shown) that generates hydraulic pressure or electromagnetic force according to the operation amount of the brake pedal.
[0020] Furthermore, an electric parking brake (hereinafter referred to as EPB) 15 is provided in the vehicle Ve shown in FIG. 1. This EPB 15 is configured in the same manner as the EPB provided in a conventional vehicle. When a shift operation for selecting a parking range is performed, the motor 16 operates, whereby a caliper or a brake shoe (not shown) is driven to apply a braking torque to the wheel 10. When a running range other than the parking range is selected, it is configured to reduce the braking torque. From the perspective of the mounting property of the motor 16, etc., the motor 16 is provided on the vehicle body, and a wire or the like for connecting the motor 16 to the caliper or the brake shoe is provided, and by rotating the motor 16, the wire is wound up or the like to drive the caliper or the brake shoe.
[0021] In the example shown in FIG. 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 one case 17, and the case 17 is connected to the vehicle body 19 via the mount 18. Also, the wheel 10 is held by the vehicle body 19 via the suspension 20.
[0022] 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.
[0023] 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.
[0024] The amount of torsion (i.e., torsional torque) of the drive shaft 9 is proportional to the tilt angle of the vehicle Ve. Specifically, the longitudinal load acting on the vehicle Ve, depending on its tilt angle, acts on the contact surface of the wheel 10 with the road surface, and a torque proportional to this load and the radius of the wheel 10 acts on one end of the drive shaft 9. In contrast, the other end of the drive shaft 9 does not rotate because it is locked by the parking lock mechanism 11. As a result, the drive shaft 9 gradually twists, generating a torsional torque proportional to the amount of torsion and the elastic modulus of the drive shaft 9. The amount of torsion of the drive shaft 9 is maintained when the torque acting on the drive shaft 9 from the wheel 10 balances the torsional torque proportional to the amount of torsion of the drive shaft 9. The direction of torsion of the drive shaft 9 corresponds to the tilt direction in the pitching direction of the vehicle Ve.
[0025] When the drive shaft 9 is twisted in this manner, and a shift operation is performed to select a driving range other than the parking range, the twist of the drive shaft 9 is released at the moment the lock on the intermediate shaft 5 by the parking lock mechanism 11 is released. When this twist of the drive shaft 9 is released, the torque pulsates according to the elastic modulus of the drive shaft 9. Specifically, after the amount of twist of the drive shaft 9 decreases toward "0", the drive shaft 9 twists in the opposite direction, and then the amount of twist of the drive shaft 9 decreases toward "0" again. In this way, the direction of twist of the drive shaft 9 reverses, and the amount of twist (peak value) gradually decreases. As a result, the case 17 vibrates, and this vibration is transmitted to the vehicle body 19 via the mount 18 while being dampened. As a result, the vehicle Ve may vibrate.
[0026] Therefore, when 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 vibrations when the parking lock mechanism 11 is released.
[0027] On the other hand, because there is no sensor to detect the torsional torque of the drive shaft 9, it may not be possible to perfectly match the assist torque output from the motor 1 with the torsional torque of the drive shaft 9. Also, if the motor 1 outputs an assist torque greater than the torsional torque of the drive shaft 9, the amount of twisting of the drive shaft 9 may actually increase. When the assist torque of the motor 1 is reduced, the time it takes for the torque of the motor 1 to decrease will be longer, or vibration may occur when the torque of the motor 1 is reduced and the torsional torque is released.
[0028] Therefore, the assist torque output from motor 1 is controlled to be less than or equal to the estimated torsional torque of the drive shaft 9. In other words, when the parking lock mechanism 11 is released, the rotating member, including motor 1 connected to the drive shaft 9, rotates (moves) due to the torsional torque, and the vehicle Ve vibrates as a result. The rotational speed (or rotational angle) of this rotating member fluctuates due to the pulsation of the torsional torque of the drive shaft 9. Therefore, for example, if motor 1 continues to output assist torque to counteract the torsional torque accumulated in the drive shaft 9, when the parking lock mechanism 11 is released and the direction of the torsional torque of the drive shaft 9 reverses, the assist torque will be added to the reversed torsional torque. This may exacerbate the increase in the rotational speed (or rotational angle) of the rotating member. In other words, it may not be possible to quickly dampen the torsional torque.
[0029] In this embodiment of the invention, the vehicle control device is configured to reduce the assist torque according to a predetermined reduction rate such that the assist torque output from the motor 1 becomes "0" when the direction of the torsional torque of the drive shaft 9 reverses. An electronic control device (hereinafter referred to as ECU) for controlling the motor 1 in this manner is provided in the vehicle Ve. This ECU 21 is mainly composed of a microcomputer and is configured to control the output torque of the motor 1 based on input signals and pre-stored calculation formulas. This ECU 21 corresponds to the "controller" in this embodiment of the invention.
[0030] 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.
[0031] The above-described shift device 24 may be a so-called momentary type shift device in which, for example, when the driver operates the shift lever 28 to a shift position corresponding to the driving range desired by the driver, a shift sensor 25 corresponding to that shift position is turned on, a signal is input to the ECU 21, and when the operation of the shift lever 28 is released, the shift lever 28 returns 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.
[0032] 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.
[0033] Figure 2 shows a block diagram illustrating the functional configuration of the ECU 21. The ECU 21 shown in Figure 2 comprises a switching determination unit 29, a target torque setting unit 30, a rate setting unit 31, a motor control unit 32, and an abnormality determination unit 33.
[0034] The switching determination unit 29 determines that the intermediate shaft 5 has switched from a locked state, in which the rotation of the intermediate shaft 5 is prohibited by the parking lock mechanism 11, to an unlocked state, in which the intermediate shaft 5 is rotatable. Specifically, for example, it stores the rotation speed (or rotation angle) of the motor 1 when the parking lock mechanism 11 is in the locked state, and determines that the parking lock mechanism 11 has switched from the locked state to the unlocked state when the rotation speed (or rotation angle) of the motor 1 changes.
[0035] The target torque setting unit 30 counteracts the torsional torque associated with the twisting of the drive shaft 9 and sets a target value for the assist torque (hereinafter referred to as the target assist torque) that is less than or equal to that torsional torque. Specifically, it estimates the tilt angle of the vehicle Ve based on the acceleration detected by the acceleration sensor 22, and estimates the torsional torque of the drive shaft 9 based on that tilt angle, the elastic modulus of the drive shaft 9, the vehicle weight, etc. Then, it sets a torque less than or equal to the estimated torsional torque as the target assist torque. Note that the amount of twisting (torsional torque) of the drive shaft 9 changes depending on whether the brake device 14 and EPB 15 are operating and the timing of their operation, so the torsional torque may be estimated according to whether the brake device 14 and EPB 15 are operating and the timing of their operation.
[0036] The rate setting unit 31 sets the assist torque reduction rate so that the assist torque of the motor 1 becomes zero after a predetermined time has elapsed from the moment the parking lock mechanism 11 switches from the locked state to the unlocked state. In other words, it sets a rate obtained by dividing the assist torque of the motor 1 at the moment the parking lock mechanism 11 switches from the locked state to the unlocked state by the predetermined time. Specifically, the reduction rate is set so that the assist torque of the motor 1 becomes zero at the moment the direction of the torsional torque of the drive shaft 9 reverses. This torsional torque fluctuates with a period corresponding to the natural frequency of the drive shaft 9. Therefore, the predetermined time can be a half-period time based on the natural frequency corresponding to the shape and elastic modulus of the drive shaft 9.
[0037] Furthermore, if the abnormality detection unit 33, described later, determines that the torque acting on the drive shaft 9 cannot be controlled normally, the rate setting unit 31 sets the reduction rate so that the assist torque becomes zero at the maximum rate determined based on the characteristics of the motor 1. In other words, the reduction rate is set so that the assist torque is reduced to zero in a shorter time than the predetermined time for reducing the assist torque when the torque acting on the drive shaft 9 can be controlled normally.
[0038] The motor control unit 32 controls the effective value of the assist torque based on the assist torque at the time the parking lock mechanism 11 switches from the locked state to the unlocked state, the reduction rate set by the rate setting unit 31, and the elapsed time since the time the parking lock mechanism 11 switched from the unlocked state. In other words, it calculates the instantaneous assist torque of the motor 1 and controls the torque of the motor 1 so that it becomes the calculated assist torque. Specifically, the instantaneous assist torque is calculated by subtracting a value obtained by multiplying the reduction rate and the elapsed time from the assist torque at the time the parking lock mechanism 11 switches from the locked state to the unlocked state.
[0039] The abnormality detection unit 33 determines whether an abnormality has occurred in which the torque acting on the drive shaft 9 cannot be controlled properly. Specifically, for example, 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, it determines that an abnormality has occurred. In other words, 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. The abnormality detection unit 33 sets the abnormality detection flag to ON when an abnormality has occurred in which the torque acting on the drive shaft 9 cannot be controlled properly.
[0040] Figure 3 shows a flowchart illustrating an example of control for setting the torque output from motor 1. In the control example shown in Figure 3, first, it is determined whether the motor control execution flag is off or not (step S1). This motor control execution flag is turned on when the drive shaft 9 is twisted to such an extent that the vehicle Ve vibrates when the parking lock mechanism 11 is released. In other words, the motor control execution flag is turned on based on various conditions that cause the drive shaft 9 to twist, such as the parking lock mechanism 11 being in a locked state, the braking torque applied to the wheel 10 after the parking lock mechanism 11 is locked being less than or equal to a predetermined torque and allowing the wheel 10 to rotate, and the pitching angle (absolute value) of the vehicle Ve being greater than or equal to a predetermined angle.
[0041] If step S1 is determined to be positive because the motor execution control flag is off, the target value of the assist torque by motor 1 (hereinafter simply referred to as the target assist torque) is set to "0" (step S2). Conversely, if step S1 is determined to be negative because the motor control execution flag is on, it is determined whether or not the motor control execution flag has switched from off to on (step S3). This step S3 can be determined depending on whether or not step S1 in the previous routine was determined to be positive.
[0042] If a positive determination is made in step S3 because the motor control execution flag has switched from off to on, a target assist torque is set based on the tilt angle of the vehicle Ve (step S4). This step S4 is performed by the target torque setting unit 30. Specifically, a map is constructed in advance by conducting experiments to define the target assist torque corresponding to the tilt angle of the vehicle Ve, and this map is stored in the ECU 21. The target assist torque is then determined based on the tilt angle of the vehicle Ve corresponding to the acceleration detected by the acceleration sensor 22 and the map. Note that the tilt angle of the vehicle Ve is not limited to the tilt angle detected when the parking lock mechanism 11 is switched from the locked state to the unlocked state, but may also be the tilt angle detected when the parking lock mechanism 11 is locked in order to park.
[0043] On the other hand, if it is determined negatively in step S3 because the motor control execution flag has not yet switched from off to on, that is, because the motor control execution flag has already been switched on and the target assist torque for motor 1 has been set, then the target assist torque for motor 1 is maintained at the previous value (step S5). In other words, the target assist torque for motor 1 is set when the motor control execution flag is switched on, and that value is maintained.
[0044] Following steps S2, S4, and S5, the rate of decrease of the assist torque output from motor 1 is determined. Specifically, first, it is 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, the abnormality determination unit 33 determines whether the abnormality determination flag is set to ON (step S6).
[0045] If the abnormality detection flag is turned on and a positive determination is made in step S6, 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 S7). Conversely, if the abnormality detection flag is turned off and a negative determination is made in step S6, the rate is set to a rate corresponding to the magnitude of the assist torque at that time so that the assist torque decreases over a predetermined time (step S8). Steps S7 and S8 can be performed by the rate setting unit 31.
[0046] Figure 4 shows a time chart illustrating the reduction rate corresponding to the assist torque. The solid line shows the change in assist torque and motor control execution flag when a relatively large target assist torque is set due to a large tilt angle of the vehicle Ve, the dashed line shows the change in assist torque and motor control execution flag when a relatively small target assist torque is set due to a small tilt angle of the vehicle Ve, and the dashed line shows the change in assist torque and motor control execution flag when the parking lock mechanism 11 is released before the assist torque reaches the target assist torque.
[0047] In the examples shown by the solid and dashed lines in Figure 4, the motor control execution flag is switched on at time t0, setting a target assist torque, and the assist torque begins to increase toward that target assist torque. Note that because the assist torque is increased at a predetermined rate, the timing at which the assist torque reaches the target assist torque varies depending on the magnitude of the target assist torque.
[0048] Then, at time t1, the parking lock mechanism 11 switches from the locked state to the unlocked state, which executes step S8 and sets the assist torque reduction rate. Specifically, the reduction rate is set so that the assist torque becomes "0" at time t2 in Figure 4. In other words, regardless of the magnitude of the target assist torque, the reduction rate is set according to the assist torque at the time the parking lock mechanism 11 is released.
[0049] As shown by the dashed line in Figure 4, there are cases where the parking lock mechanism 11 switches from the locked state to the unlocked state immediately after the motor control execution flag is switched on (at time t3), or where the parking lock mechanism 11 switches from the locked state to the unlocked state before the assist torque reaches the target assist torque. In such cases, the reduction rate is set so that the assist torque at the time the parking lock mechanism 11 switches from the locked state to the unlocked state becomes "0" within a predetermined time.
[0050] Then, following steps S7 and S8, the effective value of the assist torque is set (step S9), and this routine is terminated. Specifically, the effective value of the assist torque is set by multiplying the assist torque at the time the parking lock mechanism 11 switches from the locked state to the unlocked state by the reduction rate set in steps S7 and S8 and the elapsed time.
[0051] Figure 5 shows a time chart illustrating an example of the changes in the vehicle Ve's tilt angle, shift position, driving range, motor control execution flag, rate processing flag, and assist torque (actual value) when the control example shown in Figure 3 is executed. Note that Figure 5 also shows an example using a momentary type shift device 24.
[0052] In the example shown in Figure 5, at time t10, the parking range (P) is set, and the tilt angle of the vehicle Ve is greater than or equal to a predetermined angle. Consequently, the twist detection flag is turned on. On the other hand, because the shift lever 28 is in the standby position (Home), switching the driving range is not expected. Therefore, the motor control execution flag is turned off.
[0053] At time t10, the shift operation has begun. Specifically, the shift operation is performed to switch the driving range from the parking range to the drive range (D). In this example, the shift lever 28 is moved to the drive position at time t12 via the neutral position (N). At time t13, the driver releases their hand from the shift lever 28, and the shift position returns to the standby position.
[0054] At t10, a shift operation is initiated, which is expected to switch the driving range from the parking range to another driving range. This is positively judged in step S3 of the control example above. As a result, the motor control execution flag is switched on, and the target assist torque (dashed line) is set based on the tilt angle of the vehicle Ve. Therefore, the assist torque of motor 1 gradually increases from t11 towards the target assist torque, and in the example shown in Figure 5, the actual assist torque of motor 1 increases to the target assist torque at t12.
[0055] In the example shown in Figure 5, the parking lock mechanism 11 is switched to the released state before time t14. As a result, the load bearing the torsional torque caused by the meshing of the parking gear 12 and the parking pawl 13 decreases, and the excess torque obtained by subtracting the assist torque from the torsional torque is transmitted to the motor 1, causing the motor 1 to start rotating, and the motor control execution flag is switched to off. Consequently, the target assist torque (dashed line) is "0" at time t14. Note that the abnormality detection flag remains off at time t14.
[0056] Therefore, a reduction rate is set according to the magnitude of the assist torque at time t14, and the effective value of the assist torque begins to decrease according to that reduction rate. Furthermore, a rate processing flag, which determines whether to control the effective value of the assist torque based on the set reduction rate, is switched on at time t14.
[0057] Then, at t15, the effective value of the assist torque switches to "0", and at t16, the driving range switches to drive range (D).
[0058] As described above, by setting the reduction rate according to the assist torque at the time the parking lock mechanism 11 is switched to the released state, so that the assist torque becomes "0" in a predetermined time, it is possible to stop the output of assist torque before the parking lock mechanism 11 is released and the direction of the torsional torque of the drive shaft 9 reverses. In other words, the assist torque can be reduced in accordance with the decrease in the torsional torque of the drive shaft 9. Therefore, during the process in which the torsional torque of the drive shaft 9 is decreasing, an assist torque that opposes that torsional torque can be applied to the drive shaft 9 to suppress the generation of vibration. Furthermore, after the direction of the torsional torque of the drive shaft 9 has reversed, the assist torque is applied to that torsional torque to suppress an increase in the amount of twist of the drive shaft 9. As a result, the pulsating torsional torque of the drive shaft 9 can be quickly dampened. That is, the effect of reducing the vibration of the vehicle Ve can be improved.
[0059] 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 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. Moreover, 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. Furthermore, the vehicle in this embodiment of the invention may not be equipped with an EPB 15. [Explanation of symbols]
[0060] 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 Switching determination unit 30 Target Torque Setting Section 31 Rate setting section 32 Motor control unit 33 Abnormality determination section 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, wherein when the parking lock mechanism is in the locked state, the motor outputs an assist torque to counteract the torsional torque associated with the twisting of the drive shaft, The motor is equipped with a controller that controls the motor, The aforementioned controller, A switching determination unit that determines whether the parking lock mechanism has switched from the locked state to the unlocked state, A rate setting unit sets the assist torque reduction rate so that the assist torque becomes zero after a predetermined time has elapsed from the time the parking lock mechanism switches to the released state, The system includes a motor control unit that controls the motor based on the assist torque, the reduction rate, and the elapsed time since the parking lock mechanism switched to the released state. A vehicle control device characterized by the following features.
2. A vehicle control device according to claim 1, The predetermined time is determined based on the natural frequency of the drive shaft. A vehicle control device characterized by the following features.
3. A vehicle control device according to claim 2, The predetermined time is the time of half a cycle based on the natural frequency of the drive shaft. A vehicle control device characterized by the following features.
4. A vehicle control device according to claim 1, The rate setting unit includes a rate obtained by dividing the assist torque at the time the parking lock mechanism switches to the released state by the predetermined time. A vehicle control device characterized by the following features.
5. A vehicle control device according to any one of claims 1 to 4, The aforementioned controller, The system further includes an abnormality determination unit that determines an abnormality in which the torque acting on the drive shaft cannot be controlled properly, If the rate setting unit determines that it cannot properly control the torque acting on the drive shaft, it sets the assist torque reduction rate so that the assist torque becomes zero in a shorter time than the predetermined time. A vehicle control device characterized by the following features.