Vehicle control device

Abstract

To improve the control accuracy of friction braking force.SOLUTION: A vehicular control apparatus provided in a vehicle includes: an electric motor coupled to at least one of a first wheel and a second wheel; a brake mechanism for braking at least one of the first wheel and the second wheel; and a control system for controlling the electric motor and the brake mechanism. The control system increases the friction braking force of the brake mechanism while reducing the regenerative braking force of the electric motor, in deceleration traveling in a low vehicle speed range in which accelerator operation and brake operation by a driver are canceled, and a vehicle speed is less than a first threshold. The control system corrects correlation data between a control instruction value provided to the brake mechanism and the friction braking force generated by the control instruction value, when triggered by the change rate of vehicle acceleration exceeding a second threshold in the deceleration traveling in the low vehicle speed range.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device provided in a vehicle. [Background technology]

[0002] BACKGROUND ART Vehicles such as automobiles are provided with not only friction brakes that decelerate using friction braking force, but also regenerative brakes that decelerate using regenerative braking force (see Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-34818 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-127721 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-49368 Summary of the Invention [Problem to be solved by the invention]

[0004] During deceleration when the accelerator and brake pedals are released, regenerative braking may be actively applied to stop the vehicle in order to improve the vehicle's energy efficiency. Even when regenerative braking is applied to stop the vehicle, the rotational speed of the electric motor decreases at low vehicle speeds. Therefore, the regenerative braking force of the regenerative brake is often reduced and the friction braking force of the friction brake is often increased to stop the vehicle. However, because the control accuracy of friction brakes is lower than that of regenerative brakes, there is a risk of shock occurring when the regenerative braking force is reduced and the friction braking force is increased. To suppress the shock that occurs when switching from regenerative braking force to friction braking force, there is a need to improve the control accuracy of the friction braking force.

[0005] An object of the present invention is to improve the accuracy of controlling the friction braking force. [Means for solving the problem]

[0006] One embodiment of a vehicle control device is a vehicle control device provided in a vehicle, and includes an electric motor connected to at least one of a first wheel and a second wheel, a brake mechanism that brakes at least one of the first wheel and the second wheel, and a control system that has a processor and memory that are communicatively connected to each other and controls the electric motor and the brake mechanism, wherein the control system reduces the regenerative braking force of the electric motor while increasing the frictional braking force of the brake mechanism when the driver's accelerator operation and brake operation are released and the vehicle is decelerating in a low vehicle speed range where the vehicle speed is below a first threshold, and the control system corrects correlation data between a control instruction value instructed to the brake mechanism and the frictional braking force generated by the control instruction value when the rate of change of vehicle acceleration exceeds a second threshold during deceleration in the low vehicle speed range. [Effects of the Invention]

[0007] The control system corrects the correlation data between the control command value issued to the brake mechanism and the friction braking force generated by the control command value when the rate of change of the vehicle acceleration exceeds the second threshold value during deceleration driving in a low vehicle speed range, thereby improving the control accuracy of the friction braking force. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of the configuration of a vehicle provided with a vehicle control device according to an embodiment of the present invention; [Figure 2] FIG. 1 is a diagram illustrating an example of the configuration of a vehicle control device. [Figure 3] FIG. 10 is a diagram showing an example of correlation data between friction braking force and brake fluid pressure. [Figure 4] FIG. 2 is a diagram showing an example of the basic structure of each control unit. [Figure 5]FIG. 4 is a diagram showing an example of a driving force map showing a required driving force. [Figure 6] FIG. 6 is an enlarged view of a portion of the driving force map shown in FIG. 5. [Figure 7] 4 is a timing chart showing an example of an execution state of deceleration travel control. [Figure 8] 8 is a timing chart showing an enlarged view of a portion of the timing chart shown in FIG. 7. [Figure 9] 4 is a timing chart showing an example of an execution state of deceleration travel control. [Figure 10] 10 is a flowchart illustrating an example of an execution procedure of a correction flag setting process that constitutes data correction control. [Figure 11] 10 is a flowchart illustrating an example of an execution procedure of a data correction process that constitutes data correction control. [Figure 12] 10 is a flowchart illustrating an example of an execution procedure of a data correction process that constitutes data correction control. [Figure 13] 10 is a timing chart showing an example of an execution status of a data correction process. [Figure 14] FIG. 10 is a diagram illustrating an example of a correction state of correlation data. [Figure 15] 10 is a timing chart showing an example of an execution state of deceleration travel control after correlation data correction. [Figure 16] 10 is a flowchart illustrating an example of an execution procedure of a data verification process that constitutes data correction control. [Figure 17] 10 is a timing chart showing another example of the execution status of the data correction process. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In the following description, identical or substantially identical configurations and elements are designated by the same reference numerals and will not be described repeatedly.

[0010] [Vehicle configuration] FIG. 1 is a diagram showing an example of the configuration of a vehicle 11 provided with a vehicle control device 10 according to one embodiment of the present invention, and FIG. 2 is a diagram showing an example of the configuration of the vehicle control device 10. As shown in FIG. 1, the vehicle 11 is equipped with an electric axle 14 consisting of a motor generator (electric motor) 12 and a differential mechanism 13. As shown in FIG. 2, a drive gear 15 is connected to a rotor 12r of the motor generator 12 that constitutes the electric axle 14, and a driven gear 16 fixed to the differential mechanism 13 is meshed with the drive gear 15. Furthermore, left and right rear wheels 18 are connected to axles 17 extending from the differential mechanism 13. In this manner, the motor generator 12 of the electric axle 14 is connected to the rear wheels (first wheels) 18 of the vehicle 11. Note that in the illustrated example, the motor generator 12 is connected only to the rear wheels 18, but this is not a limitation, and the motor generator 12 may be connected to at least one of the front wheels 19 and the rear wheels 18. For example, the motor generator 12 may be connected only to the front wheels (second wheels) 19, or the motor generator 12 may be connected to both the front wheels 19 and the rear wheels 18.

[0011] As shown in Fig. 2, a battery pack 21 is connected to a stator 12s of the motor generator 12 constituting the electric axle 14 via an inverter 20. The battery pack 21 is provided with a battery module 22 consisting of a plurality of battery cells, and is also provided with a battery control unit CU1 that monitors the charging and discharging of the battery module 22. The battery pack 21 is further provided with a battery sensor 23 that detects charging and discharging current, terminal voltage, etc. The battery control unit CU1 has a function of calculating a State of Charge (SOC) that is the state of charge of the battery module 22 based on the charging and discharging current, terminal voltage, etc. detected by the battery sensor 23. The SOC of the battery module 22 is a ratio that indicates the remaining amount of electricity in the battery module 22, and is the ratio of the amount of stored electricity to the fully charged capacity of the battery module 22.

[0012] A motor control unit CU2 is connected to the inverter 20, which controls the energization state of the motor generator 12. The motor control unit CU2 controls the inverter 20, which is made up of a plurality of switching elements and the like, to control the motor torque (powering torque, regenerative torque) output from the motor generator 12. The motor torque output from the motor generator 12 includes powering torque that is generated on the acceleration side by controlling the motor generator 12 to a powering state, and regenerative torque, or power generation torque, that is generated on the deceleration side by controlling the motor generator 12 to a regenerative state.

[0013] The vehicle 11 is provided with a brake mechanism 30 that brakes the front wheels 19 and rear wheels 18. The brake mechanism 30 includes a master cylinder 32 that outputs brake fluid pressure in conjunction with a brake pedal 31, and calipers 34 that brake disc rotors 33 of the front wheels 19 and rear wheels 18. A brake actuator 35 that controls the brake fluid pressure supplied to each caliper 34 is provided between the master cylinder 32 and the caliper 34. The brake actuator 35 is composed of an electric pump, an accumulator, an electromagnetic valve, etc. (not shown). A brake control unit CU3 that controls the brake fluid pressure by controlling the electromagnetic valve, etc. is connected to the brake actuator 35. The brake mechanism 30 is not limited to the disc brakes shown in the drawings, and may be a drum brake.

[0014] FIG. 3 is a diagram showing an example of correlation data between frictional braking force and brake fluid pressure. As shown in FIG. 3, by controlling the brake fluid pressure with the brake actuator 35, it is possible to control the frictional braking force, which is the sum of the braking forces acting on the disc rotors 33 of the front wheels 19 and the rear wheels 18. For example, as shown by characteristic line Xa in FIG. 3, when the frictional braking force of the brake mechanism 30 is controlled to "Fbk," the brake fluid pressure is adjusted to "Pbk" by the brake actuator 35. That is, the brake control unit CU3 sets a target brake fluid pressure (control command value) Pbk based on the target frictional braking force Fbk and transmits the target brake fluid pressure Pbk to the brake actuator 35. Then, the brake actuator 35 controls the brake fluid pressure to "Pbk," and the frictional braking force of the brake mechanism 30 to "Fbk."

[0015] [Control System] As shown in FIG. 2, the vehicle control device 10 is provided with a control system 40 made up of multiple electronic control units to control the motor generator 12, brake actuator 35, etc. The electronic control units that make up the control system 40 include the battery control unit CU1, motor control unit CU2, and brake control unit CU3 described above. Another electronic control unit that makes up the control system 40 is a vehicle control unit CU4 that outputs control signals to the control units CU1 to CU3. These control units CU1 to CU4 are connected to each other so that they can communicate with each other via an in-vehicle network 41 such as a Controller Area Network (CAN). The vehicle control unit CU4 sets operation targets for the electric axle 14, brake mechanism 30, etc. based on input information from the various control units CU1 to CU3 and various sensors described below. The vehicle control unit CU4 then generates control signals according to the operation targets for the electric axle 14, brake mechanism 30, etc., and outputs these control signals to the various control units CU1 to CU3.

[0016] Sensors connected to the vehicle control unit CU4 include a vehicle speed sensor 50 that detects the vehicle speed, which is the traveling speed of the vehicle 11, an accelerator sensor 51 that detects the amount of accelerator pedal operation (hereinafter referred to as accelerator opening), and a brake sensor 52 that detects the amount of brake pedal operation 31. Sensors connected to the vehicle control unit CU4 also include an acceleration sensor 53 that detects vehicle acceleration acting on the front and rear of the vehicle, and wheel speed sensors 54, 55, 56, and 57 that detect the rotational speeds of the wheels 18 and 19 provided on the front, rear, left, and right sides (hereinafter referred to as wheel speeds). A start switch 58 that is operated by the driver when starting up the control system 40 is also connected to the vehicle control unit. Sensors connected to the motor control unit include a motor rotation sensor 59, such as a resolver, that detects the rotation angle of the rotor 12r (hereinafter referred to as rotor rotation angle).

[0017] Fig. 4 is a diagram showing an example of the basic structure of each of the control units CU1 to CU4. As shown in Fig. 4, each of the control units CU1 to CU4 has a microcontroller 62 incorporating a processor 60 and a main memory (memory) 61. A predetermined program is stored in the main memory 61, and the program is executed by the processor 60. The processor 60 and the main memory 61 are connected to each other so that they can communicate with each other. In the example shown in the figure, one processor 60 and one main memory 61 are incorporated in the microcontroller 62, but this is not limiting, and multiple processors 60 may be incorporated in the microcontroller 62, and multiple main memories 61 may be incorporated in the microcontroller 62.

[0018] Each of the control units CU1 to CU4 is also provided with an input circuit 63, a drive circuit 64, a communication circuit 65, an external memory 66, etc. The input circuit 63 converts signals input from various sensors into signals that can be input to the microcontroller 62. The drive circuit 64 generates drive signals for actuators such as the valve unit 45 described above based on signals output from the microcontroller 62. The communication circuit 65 converts signals output from the microcontroller 62 into communication signals directed to other control units. The communication circuit 65 also converts communication signals received from other control units into signals that can be input to the microcontroller 62. Furthermore, the external memory 66, such as a non-volatile memory, stores programs, various data, etc.

[0019] [Required driving force] Fig. 5 is a diagram showing an example of a driving force map showing the required driving force. As shown in Fig. 5, the driving force map has characteristic lines L1 to L4 set to indicate the required driving force for each accelerator opening Acp. That is, when the accelerator opening Acp is 0%, the vehicle control unit CU4 sets the required driving force for the vehicle 11 along characteristic line L1, and when the accelerator opening Acp is 25%, the vehicle control unit CU4 sets the required driving force for the vehicle 11 along characteristic line L2. When the accelerator opening Acp is 50%, the vehicle control unit CU4 sets the required driving force for the vehicle 11 along characteristic line L3, and when the accelerator opening Acp is 100%, the vehicle control unit CU4 sets the required driving force for the vehicle 11 along characteristic line L4.

[0020] For example, when the vehicle speed is "Va" and the accelerator pedal is depressed so that the accelerator opening Acp is "50%," the vehicle control unit CU4 sets the required driving force to "df." On the other hand, when the vehicle speed is "Va" and the accelerator pedal is released so that the accelerator opening Acp is "0%," the vehicle control unit CU4 sets the required driving force to "-bf." The vehicle control unit CU4 then sets the target motor torque of the motor generator 12 so that the required driving force is "df" or "-bf," and controls the motor generator 12 to a powering state or a regenerative state via the motor control unit CU2.

[0021] That is, when the required driving force is set to "df" on the acceleration side (positive side) by depressing the accelerator pedal, the target motor torque of the motor generator 12 is set to the powering side, and the motor generator 12 is controlled to a powering state. The powering torque of the motor generator 12 is controlled so that the total value of the powering driving force transmitted from the motor generator 12 to the rear wheels 18 reaches the required driving force "df". On the other hand, when the required driving force is set to "-bf" on the deceleration side (negative side) by releasing the accelerator pedal, the target motor torque of the motor generator 12 is set to the regenerative side, and the motor generator 12 is controlled to a regenerative state. The regenerative torque of the motor generator 12 is controlled so that the total value of the regenerative braking force transmitted from the motor generator 12 to the rear wheels 18 reaches the required driving force on the negative side, i.e., the required braking force "-bf". In addition, for ease of explanation, four characteristic lines L1 to L4 are set in the driving force map shown in Figure 5, but this is not limited to this, and it goes without saying that five or more characteristic lines may be set in the driving force map.

[0022] [Regenerative braking force and friction braking force during deceleration] The following describes the regenerative braking force controlled by motor generator 12 and the friction braking force controlled by brake mechanism 30 during deceleration traveling when the driver's accelerator and brake operations are released. In the following description, an increase or decrease in the required braking force, which is the required negative driving force, means an increase or decrease in the absolute value of the required braking force. Note that deceleration traveling when the driver's accelerator and brake operations are released is sometimes called coasting.

[0023] FIG. 6 is an enlarged view of a portion of the driving force map shown in FIG. 5. As shown in FIG. 6, during deceleration when the driver releases the accelerator and brake pedals, the required braking force, which is the negative required driving force, is set along characteristic line L1. That is, when the vehicle speed decreases from "V1" to "0" as indicated by arrow α1 in FIG. 6, the required braking force decreases from "-bf1" to "-bf3" as indicated by arrow α2. During deceleration, motor generator 12 is controlled to a regenerative state. However, because the rotational speed of motor generator 12 decreases at low vehicle speeds, it is necessary to increase the frictional braking force of brake mechanism 30 as the vehicle speed decreases. Therefore, at low vehicle speeds below a predetermined speed threshold (first threshold) Vx, a characteristic line Lx is set that indicates the magnitude of the regenerative braking force provided by motor generator 12. That is, the required braking force, which is the target braking force for the front wheels 19 and the rear wheels 18, is divided into the regenerative braking force obtained by the motor generator 12 and the friction braking force obtained by the brake mechanism 30 based on the characteristic line Lx.

[0024] For example, when the vehicle speed is "V1," the required braking force "-bf1" is entirely obtained by the regenerative braking force x1a of the motor generator 12. When the vehicle speed is "V2" in the low vehicle speed range, the required braking force "-bf2" is entirely obtained by the regenerative braking force x2a of the motor generator 12 and the frictional braking force x2b of the brake mechanism 30. When the vehicle speed is "0," the required braking force "-bf3" is entirely obtained by the frictional braking force x3b of the brake mechanism 30. In this way, when the driver releases the accelerator operation and the brake operation and the vehicle is decelerating in the low vehicle speed range where the vehicle speed is below the speed threshold Vx, the regenerative braking force of the motor generator 12 gradually decreases as the vehicle speed decreases, and the frictional braking force of the brake mechanism 30 gradually increases as the vehicle speed decreases. That is, when the vehicle is decelerating at a low vehicle speed, as the vehicle speed decreases, the regenerative braking that applies braking using the regenerative braking force of the motor generator 12 is switched to the friction braking that applies braking using the friction braking force of the brake mechanism 30.

[0025] [Deceleration control (timing chart)] The following describes deceleration control that is performed when the driver releases the accelerator and brake pedal operation and the vehicle 11 passes through a low vehicle speed range and stops. Fig. 7 is a timing chart showing an example of the execution of deceleration control, and Fig. 8 is a timing chart showing an enlarged view of a portion of the timing chart shown in Fig. 7. Fig. 9 is a timing chart showing an example of the execution of deceleration control. Fig. 9 shows a section similar to the section in the timing chart shown in Fig. 8, and times t2 and t3 shown in Fig. 8 and Fig. 9 are the same timing.

[0026] 7 and 8 show a state in which regenerative braking is smoothly switched to friction braking, while FIG. 9 shows a state in which regenerative braking is shockingly switched to friction braking. Also, in FIGS. 7 to 9, as the braking force of the entire vehicle, the regenerative braking force Rbf of motor generator 12 is shown by a dashed line, the friction braking force Fbf of brake mechanism 30 is shown by a dashed line, and the total braking force Tbf, which is the sum of regenerative braking force Rbf and friction braking force Fbf, is shown by a solid line. In the following description, an increase or decrease in regenerative torque, which is negative motor torque, means an increase or decrease in the absolute value of the regenerative torque.

[0027] As shown at time t1 in FIG. 7, the driver releases the accelerator pedal, and the accelerator opening degree decreases to "0" (symbol a1). At time t1, the driver has released the brake pedal. When the brake pedal and accelerator pedal are released in this manner, the motor torque is switched from powering torque to regenerative torque (symbol b1), and the regenerative braking force Rbf by the motor generator 12 is increased (symbol c1), so that a total braking force Tbf equivalent to the target required braking force is obtained. Thereafter, as shown at time t2, when the vehicle speed decreases and falls below the speed threshold Vx (symbol d1), a switch from regenerative braking to friction braking begins in order to stop the vehicle.

[0028] That is, as shown in Fig. 8, the regenerative torque of the motor-generator 12 is reduced to reduce the regenerative braking force Rbf (symbols b2 and c2), while the brake fluid pressure of the brake mechanism 30 is increased to increase the frictional braking force Fbf (symbols e1 and c3). This allows the total braking force Tbf to be gradually changed toward vehicle stop (symbol c4), enabling a smooth transition from regenerative braking to frictional braking. In other words, the vehicle acceleration Gv can be gradually changed (symbol g1) so that the rate of change in the vehicle acceleration Gv acting on the front and rear of the vehicle (hereinafter referred to as the acceleration jerk Rg) does not exceed a predetermined determination threshold (second threshold) Rx (symbol f1), allowing the vehicle 11 to be stopped without causing any discomfort to the driver.

[0029] Thus, in order to ensure a gradual change in vehicle acceleration Gv when switching from regenerative braking to friction braking, it is necessary to accurately increase the frictional braking force Fbf in accordance with the decrease in the regenerative braking force Rbf. Furthermore, in order to improve the control accuracy of the frictional braking force Fbf, it is necessary to improve the accuracy of the correlation data relating to the frictional braking force and the brake fluid pressure. For example, as shown by the dashed line Xb in Figure 3, if the frictional braking force obtained by the brake fluid pressure commanded to the brake actuator 35 becomes smaller than the original characteristic line Xa due to aging or the like, there is a risk of shock occurring when switching from regenerative braking to friction braking.

[0030] That is, as shown by dashed line Xb in FIG. 3, when the frictional braking force obtained by the brake fluid pressure is smaller than characteristic line Xa, the rise of the frictional braking force Fbf generated in the brake mechanism 30 is delayed relative to the increase in the brake fluid pressure controlled by the brake actuator 35, as shown by reference characters e1 and c5 in FIG. 9. In this case, it is difficult to compensate for the decrease in the regenerative braking force Rbf by increasing the frictional braking force Fbf, and therefore the total braking force Tbf temporarily drops (reference character c6). This may cause excessive fluctuations in the vehicle acceleration Gv (reference character g2) and fluctuations in the jerk Rg exceeding the determination threshold Rx (reference character f2), which may cause the driver to feel uncomfortable. Therefore, the control system 40 executes data correction control to correct the correlation data in order to improve the control accuracy of the frictional braking force Fbf.

[0031] [Data correction control] The data correction control for correcting correlation data will be described below. Fig. 10 is a flowchart showing an example of the execution procedure of the correction flag setting process that constitutes the data correction control. Figs. 11 and 12 are flowcharts showing an example of the execution procedure of the data correction process that constitutes the data correction control. In Figs. 11 and 12, the flowcharts are connected to each other at the location indicated by the symbol A. Note that each step shown in the flowcharts of Figs. 10 to 12 represents a process executed by the processor 60 that constitutes the control system 40. Furthermore, the data correction control is a control that is executed by the control system 40 at predetermined intervals after the driver operates the start switch 58 and the control system 40, which is composed of the vehicle control unit CU4 and the like, is started up.

[0032] <Correction flag setting process> As shown in FIG. 10, in step S10, it is determined whether or not the correction flag FLa is set to "0." Here, the correction flag FLa is a control flag used when determining whether or not correction of correlation data is necessary. If it is determined that correction of correlation data is necessary, the correction flag FLa is set to "1," whereas if it is determined that correction of correlation data is not necessary, the correction flag FLa is set to "0." If it is determined in step S10 that the correction flag FLa is set to "0," the process proceeds to step S11, where it is determined whether or not the vehicle is currently decelerating and the driver's accelerator and brake operations are released.

[0033] If it is determined in step S11 that the vehicle is decelerating, the process proceeds to step S12, where it is determined whether the vehicle speed is in a low-speed range below the speed threshold Vx. If it is determined in step S12 that the vehicle speed is in a low-speed range below the speed threshold Vx, the process proceeds to step S13, where it is determined whether the absolute value of the jerk Rg exceeds the determination threshold Rx. If it is determined in step S13 that the jerk Rg exceeds the determination threshold Rx, the process proceeds to step S14, where the correction flag FLa is set to "1."

[0034] In step S13, the situation in which it is determined that the jerk Rg exceeds the determination threshold Rx is a situation in which a shock occurs when switching from regenerative braking to friction braking during deceleration driving at a low vehicle speed, as described with reference to Fig. 9. In other words, since there is a risk that the control accuracy of the friction braking force Fbf by the brake mechanism 30 has decreased, the control system 40 sets the correction flag FLa to "1" to start a data correction process for correcting the correlation data. In other words, the control system 40 starts the data correction process, which will be described later, when the jerk Rg exceeds the determination threshold Rx.

[0035] <Data correction processing> As shown in FIG. 11, in step S20, it is determined whether the vehicle is stopped. If it is determined in step S20 that the vehicle is stopped, the process proceeds to step S21, where it is determined whether the driver's brake operation has been released. If it is determined in step S21 that the brake pedal 31 is not depressed, that is, if it is determined that the vehicle is stopped without being braked, the process proceeds to step S22, where it is determined whether the correction flag FLa is set to "1." Note that the stopped state without being braked is a state in which the vehicle is kept stopped by the friction braking force x3b of the brake mechanism 30, as shown in FIG. 3.

[0036] In this way, when it is determined in step S22 that the correction flag FLa is set to "1" while the vehicle is held stationary by the frictional braking force x3b of the brake mechanism 30, the relationship between the brake fluid pressure and the resulting frictional braking force is estimated in order to correct the correlation data between the brake fluid pressure and the frictional braking force. That is, in step S23, the current brake fluid pressure is maintained by the brake actuator 35, and in the following step S24, the inverter 20 gradually increases the power running driving force of the motor generator 12. In the following step S25, it is determined whether the rotor rotation angle of the motor generator 12 exceeds a predetermined determination threshold Ax.

[0037] The determination threshold value Ax, which is compared with the rotor rotation angle in step S25, is set to a value that enables detection of rotation of the disc rotor 33 constrained by the caliper 34. That is, in step S25, a situation in which the rotor rotation angle exceeds the determination threshold value Ax is a situation in which the power driving force reaches the friction braking force being generated, causing the disc rotor 33, constrained by the caliper 34, to start rotating at a predetermined angle, i.e., a situation in which the vehicle 11 starts to start moving. Note that in the above explanation, whether or not the vehicle speed has changed is determined based on the rotor rotation angle from the motor rotation sensor, but this is not limiting, and whether or not the vehicle has started moving may also be determined based on the wheel speeds detected by the wheel speed sensors 54 to 57.

[0038] If it is determined in step S25 that the rotor rotation angle exceeds the determination threshold value Ax, the process proceeds to step S26, as shown in FIG. 12, where the current powering driving force is stored as the frictional braking force being generated. Subsequently, in step S27, the frictional braking force is increased and decreased to maintain the vehicle stopped state, and in step S28, correlation data between the brake fluid pressure and the frictional braking force is corrected. That is, in step S28, the correlation data is corrected based on the brake fluid pressure maintained in step S23 and the frictional braking force stored in step S26. After the correlation data has been corrected in this manner, the process proceeds to step S29, where the correction flag FLa is cleared and set to "0," and then to step S30, where the verification flag FLb is set to "1." The verification flag FLb is a control flag used when determining whether or not to execute a data verification process, which will be described later. If it is determined that execution of the data verification process is necessary, the verification flag FLb is set to "1," whereas if it is determined that execution of the data verification process is not necessary, the verification flag FLb is set to "0."

[0039] Here, Fig. 13 is a timing chart showing an example of the execution status of the data correction process, and Fig. 14 is a diagram showing an example of the correction status of the correlation data. As shown at time t11 in Fig. 13, when the vehicle is stopped and the driver is not applying the brakes, the brake fluid pressure output from the brake actuator 35 is maintained at the current "Pbk1" (reference symbol a11), and the power running driving force of the motor generator 12 is gradually increased (reference symbol b11). In other words, the power running driving force of the motor generator 12 is gradually increased while the stopped state is maintained by the brake fluid pressure Pbk1.

[0040] Next, as shown at time t12, when the rotor rotation angle exceeds the determination threshold value Ax (reference symbol c11), the current powering driving force "Dfm1" is stored as the frictional braking force being generated. That is, the control system 40 stores the current frictional braking force "Fbk1" as "Dfm1." Thereafter, in order to maintain the vehicle stopped state, the brake fluid pressure is increased to increase the frictional braking force (reference symbols a12, d11), and the powering driving force of the motor-generator 12 is decreased (reference symbol b13). In this way, once the frictional braking force of the brake mechanism 30 is estimated based on the powering driving force, the control system 40 corrects the correlation data from the previous characteristic line Xc to a new characteristic line Xd, as shown in FIG. 14, so that the frictional braking force Fbk1 is obtained using the brake fluid pressure Pbk1.

[0041] When the correlation data is corrected in this manner, the control system 40 can accurately control the friction braking force of the brake mechanism 30, thereby suppressing shock when switching from regenerative braking to friction braking. Fig. 15 is a timing chart showing an example of the execution status of deceleration driving control after correlation data correction. Fig. 15 shows a section similar to the section in the timing chart shown in Fig. 9, and times t2 and t3 shown in Fig. 15 and Fig. 9 are the same timing.

[0042] When the correlation data has been corrected, as shown by reference symbol e2 in FIG. 15, it is possible to control the brake fluid pressure higher based on the correlation data compared to the example shown by reference symbol e1 in FIG. 9. As a result, as shown by reference symbol c7 in FIG. 15, it is possible to quickly increase the frictional braking force Fbf of the brake mechanism 30 compared to the example shown by reference symbol c5 in FIG. 9. In other words, since the decrease in the regenerative braking force Rbf can be appropriately compensated for by an increase in the frictional braking force Fbf, it is possible to gradually change the total braking force Tbf (reference symbol c8). As a result, it is possible to gradually change the vehicle acceleration Gv (reference symbol g3) so that the jerk Rg does not exceed the determination threshold Rx (reference symbol f3), and it is possible to stop the vehicle 11 without causing any discomfort to the driver.

[0043] <Data verification process> The data verification process for verifying the correction content of the correlation data will be described below. Fig. 16 is a flowchart showing an example of the execution procedure of the data verification process constituting the data correction control. Note that each step shown in the flowchart in Fig. 16 represents a process executed by the processor 60 constituting the control system 40.

[0044] As shown in Fig. 16, in step S40, it is determined whether the vehicle is stopped. If it is determined in step S40 that the vehicle is stopped, the process proceeds to step S41, where it is determined whether the verification flag FLb is set to "1." If it is determined in step S41 that the verification flag FLb is set to "1," the process proceeds to step S42, where it is determined whether a start operation has been performed by the driver. Examples of start operations by the driver include an operation of depressing the accelerator pedal and an operation of releasing the brake pedal 31.

[0045] If it is determined in step S42 that the driver has performed a start operation, the process proceeds to step S43, where the brake fluid pressure is controlled to "Pbk2," which is a control instruction value (confirmation instruction value), and then the process proceeds to step S44, where the motor generator 12 is controlled to a predetermined powering state. Furthermore, "Pbk2" instructed to the brake mechanism 30 in step S43 is the brake fluid pressure that was instructed to the brake mechanism 30 when the jerk Rg exceeded the determination threshold Rx, as shown in FIG. 9. In other words, it is the brake fluid pressure that was instructed to the brake mechanism 30 when the frictional braking force Fbf of the brake mechanism 30 had not yet risen sufficiently during deceleration traveling in a low vehicle speed range.

[0046] As described above, in the data verification process, the vehicle 11 is started by the powering torque of the motor generator 12 while the brake mechanism 30 is activated by the brake fluid pressure Pbk2. Then, in step S45, it is determined whether the vehicle acceleration Gv at the time of vehicle start exceeds a predetermined determination threshold (third threshold) Gx. In step S45, a situation in which the vehicle acceleration Gv exceeds the determination threshold Gx means that the vehicle 11 starts without any hesitation even though the brake mechanism 30 is activated by the brake fluid pressure Pbk2. In other words, the brake fluid pressure Pbk2 instructed to the brake mechanism 30 does not sufficiently generate the frictional braking force of the brake mechanism 30. In this case, since it is assumed that the frictional braking force was insufficient due to a defect in the correlation data, the process proceeds to step S46, where the content of the correction of the correlation data that has already been performed is confirmed. Then, the process proceeds to step S47, where the verification flag FLb is set to "0," and the routine ends.

[0047] On the other hand, in step S45, a situation in which the vehicle acceleration Gv is equal to or less than the determination threshold Gx, i.e., a situation in which the vehicle acceleration Gv falls below the determination threshold Gx, means that the brake mechanism 30 is actuated by the brake hydraulic pressure Pbk2, causing the vehicle 11 to start moving hesitantly. In other words, the brake hydraulic pressure Pbk2 commanded to the brake mechanism 30 is sufficient to generate the frictional braking force of the brake mechanism 30. In this case, it is assumed that the cause of the jerk Rg exceeding the determination threshold Rx is a cause other than a defect in the correlation data, i.e., a change in acceleration due to passing over a bump or the like. Therefore, the process proceeds to step S48, where the correction of the correlation data that has already been made is canceled and the correlation data is restored to the state before the correction. Then, the process proceeds to step S47, where the verification flag FLb is set to "0," and the routine ends.

[0048] [Other embodiments (data correction processing)] In the example shown in FIG. 13, the data correction process is executed when the vehicle is stopped after the jerk Rg exceeds the determination threshold Rx. However, this is not limiting and the data correction process may be executed when the vehicle is traveling at a constant speed after the jerk Rg exceeds the determination threshold Rx. FIG. 17 is a timing chart showing another example of the execution status of the data correction process. As shown at time t21 in FIG. 17, when the vehicle is traveling at a constant speed, the brake fluid pressure of the brake mechanism 30 is increased by a predetermined amount of change ΔPbk (reference symbol a21), and the frictional braking force of the brake mechanism 30 is increased by a predetermined amount of change ΔFbk (reference symbol b21). In other words, the brake fluid pressure is increased in the direction of increasing the frictional braking force. Then, while the increased brake fluid pressure is maintained, the power driving force of the motor generator 12 is gradually increased (reference symbol c21).

[0049] By controlling the brake fluid pressure and the powering driving force in this manner, the vehicle speed temporarily decreases due to the increase in brake fluid pressure, but the decrease in vehicle speed is stopped by the increase in powering driving force. That is, although the absolute value of the vehicle speed change rate increases due to the increase in brake fluid pressure (symbol d21), the absolute value of the vehicle speed change rate decreases due to the subsequent increase in powering driving force (symbol d22). Then, as shown at time t22, when the absolute value of the vehicle speed change rate falls below a predetermined determination threshold Bx (symbol d23), the current change in powering driving force, "ΔDfm," is stored as the change in frictional braking force ΔFbk that is currently being generated (symbol c22). That is, the control system 40 stores the current change in frictional braking force, "ΔFbk," as "ΔDfm." Thereafter, to restore the vehicle to the most recent constant-speed traveling state, the brake fluid pressure is reduced to reduce the frictional braking force (symbols a22, b22), and the powering driving force of the motor-generator 12 is reduced (symbol c23).

[0050] As described above, the control system 40 estimates the change in powering driving force ΔDfm when the vehicle speed stops decreasing as the change in frictional braking force ΔFbk generated in the brake mechanism 30. The control system 40 then corrects the correlation data based on the change in frictional braking force ΔFbk estimated based on the change in powering driving force ΔDfm and the change in brake hydraulic pressure ΔPbk when the vehicle speed stops decreasing. Even when the correlation data is corrected in this manner, the control system 40 can accurately control the frictional braking force of the brake mechanism 30, thereby suppressing shock when switching from regenerative braking to friction braking. Note that in the example shown in FIG. 17 , the data correction process gradually increases the powering driving force while maintaining the increased brake hydraulic pressure until the vehicle speed stops decreasing. However, the present invention is not limited to this. For example, under constant-speed driving conditions, the brake hydraulic pressure may be gradually increased while maintaining the powering driving force increased by a predetermined amount until the vehicle speed stops increasing.

[0051] [summary] As described above, when the driver releases the accelerator and brake pedal operations and the vehicle is decelerating in a low-speed range where the vehicle speed is below the speed threshold Vx, the control system 40 reduces the regenerative braking force of the motor generator 12 while increasing the frictional braking force of the brake mechanism 30. Furthermore, when the rate of change Rg of the vehicle acceleration Gv exceeds the determination threshold Rx during deceleration in a low-speed range, the control system 40 is triggered to correct the correlation data between the brake fluid pressure (control command value) instructed to the brake mechanism 30 and the frictional braking force generated by the instructed brake fluid pressure. This improves the accuracy of the correlation data and the control accuracy of the frictional braking force.

[0052] The control system 40 corrects the correlation data in a stopped state after the rate of change Rg of the vehicle acceleration Gv exceeds the determination threshold Rx. That is, the control system 40 increases the powered driving force while maintaining the brake fluid pressure in a stopped state in which the brake mechanism 30 is activated, thereby estimating that the powered driving force at the time when the vehicle 11 starts to move is the frictional braking force generated in the brake mechanism 30. The control system 40 then corrects the correlation data based on the frictional braking force estimated based on the powered driving force and the brake fluid pressure at the time when the vehicle 11 starts to move. In the example shown in FIG. 13 , in the data correction process, the powered driving force is gradually increased while maintaining the brake fluid pressure in a stopped state until the vehicle 11 starts to move. However, the present invention is not limited to this. For example, the powered driving force may be increased to a predetermined value and maintained at that value in a stopped state, while gradually decreasing the brake fluid pressure until the vehicle 11 starts to move.

[0053] In order to perform the data verification process, the control system 40 starts the vehicle 11 while operating the brake mechanism 30 when the vehicle starts after correcting the correlation data. Then, when the vehicle acceleration Gv at the time of vehicle start is below the determination threshold Gx, the control system 40 confirms the correction content of the correlation data. On the other hand, when the vehicle acceleration Gv at the time of vehicle start is above the determination threshold Gx, the control system 40 cancels the correction content of the correlation data. Furthermore, in order to perform the data verification process, when the vehicle starts after correcting the correlation data, the control system 40 instructs the brake mechanism 30 to use a brake fluid pressure as a confirmation instruction value. This brake fluid pressure as a confirmation instruction value is the brake fluid pressure that was instructed to the brake mechanism 30 when the rate of change Rg of the vehicle acceleration Gv exceeded the determination threshold Rx during deceleration driving in a low vehicle speed range. This allows the correlation data to be appropriately corrected.

[0054] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present invention. In the above description, the vehicle control device 10 is applied to an electric vehicle (vehicle) equipped with only a motor generator 12 as a power source, but the present invention is not limited to this, and the vehicle control device 10 may also be applied to a hybrid vehicle equipped with a motor generator and an engine as a power source. In the illustrated example, the vehicle 11 is equipped with one motor generator 12, but the present invention is not limited to this, and multiple motor generators 12 may be equipped with the vehicle 11. In addition, so-called in-wheel motors provided on the front wheels 19 or the rear wheels 18 may also be used as the motor generator 12.

[0055] In the above description, the brake mechanism 30 is a hydraulic brake mechanism equipped with a caliper 34 operated by brake fluid pressure. However, this is not limited thereto, and an electric brake mechanism equipped with a caliper operated by an electric motor may also be used. In an electric brake mechanism, frictional braking force can be controlled by controlling the rotation speed, etc., of the electric motor. Therefore, the target rotation speed, etc., transmitted from the brake control unit CU3 to the electric motor serves as a control instruction value. In the illustrated example, the brake mechanism 30 brakes both the front wheels 19 and the rear wheels 18. However, this is not limited thereto, and the brake mechanism 30 may brake at least one of the front wheels 19 and the rear wheels 18. For example, the brake mechanism 30 may brake only the front wheels 19, or only the rear wheels 18. In the above description, the control system 40 is configured by multiple control units CU1 to CU4. However, this is not limited thereto. For example, the control system 40 may be configured by a single control unit.

[0056] In the example shown in FIG. 10 , the correction flag FLa is set to “1” when the jerk Rg exceeds the determination threshold Rx. However, this is not limiting. For example, the correction flag FLa may be set to “1” when the rate of change of the wheel speed or the motor rotation speed exceeds a predetermined determination threshold. That is, it may be determined that the jerk Rg exceeds the determination threshold Rx when the rate of change of the wheel speed or the rate of change of the motor rotation speed exceeds a predetermined determination threshold. Furthermore, in the example shown in FIG. 11 , the relationship between the brake fluid pressure and the resulting frictional braking force is estimated when the vehicle is stopped and the driver is not applying the brakes. However, this is not limiting. The relationship between the brake fluid pressure and the resulting frictional braking force may be estimated when the driver is applying the brakes. In this case, the power driving force of the motor generator 12 is increased more than when the vehicle is stopped and the driver is not applying the brakes. [Explanation of symbols]

[0057] 10 Vehicle control device 11 vehicles 12 Motor generator (electric motor) 18 Rear wheel (1st wheel) 19 Front wheel (2nd wheel) 30 Brake mechanism 40 Control System 60 processors 61 Main memory (memory) Vx velocity threshold (first threshold) Rx judgment threshold (second threshold) Gx judgment threshold (third threshold) Rbf Regenerative braking force Fbf Friction braking force Gv Vehicle acceleration Rg Change rate of acceleration (rate of change)

Claims

1. A vehicle control device provided in a vehicle, an electric motor coupled to at least one of the first wheel and the second wheel; a brake mechanism that brakes at least one of the first wheel and the second wheel; a control system including a processor and a memory communicatively connected to each other, the control system controlling the electric motor and the brake mechanism; and the control system reduces the regenerative braking force of the electric motor while increasing the frictional braking force of the brake mechanism when the driver releases the accelerator operation and the brake operation and the vehicle is decelerating in a low vehicle speed range where the vehicle speed is below a first threshold value; the control system corrects correlation data between a control instruction value instructed to the brake mechanism and the friction braking force generated by the control instruction value, using a change rate of the vehicle acceleration exceeding a second threshold value as a trigger when the vehicle is decelerating in the low vehicle speed range. Vehicle control device.

2. 2. The vehicle control device according to claim 1, the control system corrects the correlation data in a stopped state after the rate of change of the vehicle acceleration exceeds the second threshold. Vehicle control device.

3. 3. The vehicle control device according to claim 2, The control system includes: In a stopped state in which the brake mechanism is activated, gradually increasing the power driving force output from the electric motor while maintaining the control instruction value instructed to the brake mechanism; The power driving force when the vehicle starts to move is estimated to be the friction braking force generated in the brake mechanism, correcting the correlation data based on the friction braking force estimated based on the power driving force and the control instruction value when the vehicle starts to move; Vehicle control device.

4. The vehicle control device according to any one of claims 1 to 3, The control system includes: When the vehicle starts after correcting the correlation data, the vehicle starts while operating the brake mechanism; When the vehicle acceleration at the time of starting the vehicle exceeds a third threshold, the correction content of the correlation data is determined, and If the vehicle acceleration at the time of starting the vehicle is lower than the third threshold value, cancel the correction content of the correlation data. Vehicle control device.

5. 5. The vehicle control device according to claim 4, The control system includes: when the vehicle starts after correcting the correlation data, a confirmation instruction value is instructed to the brake mechanism as the control instruction value; the confirmation instruction value is the control instruction value that is instructed to the brake mechanism when the rate of change of the vehicle acceleration during deceleration traveling in the low vehicle speed range exceeds the second threshold value; Vehicle control device.

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