Vehicle control device

Abstract

To suppress a vehicle from slipping down when returning from creep cut control.SOLUTION: A control part 22 performs creep cut control of decreasing output torque of an MG30 in a state where a vehicle stops and a brake is turned on. When determining that the brake is turned off on the basis of a change rate of brake fluid pressure while decreasing the output torque of the MG30, the control part 22 performs return-time control of making the MG30 output torque above guarantee gradient corresponding torque set so that the vehicle does not slip down on an uphill road with a predetermined road surface gradient.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle control device. [Background technology]

[0002] Patent Document 1 describes a technology that controls the drive source based on a creep drive force that is set to prevent the vehicle from rolling down when stopped on a slope, and reduces the drive force when the braking force generated by the driver's brake operation is greater than the creep drive force.

[0003] Patent document 2 also describes a technology that changes the amount of torque while the vehicle is stopped in accordance with the amount of road surface inclination acquired by a road surface condition acquisition means (G sensor) when a brake operation is detected while the vehicle is stopped. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 019766 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-166053 Summary of the Invention [Problem to be solved by the invention]

[0005] Although Patent Document 1 describes reducing the driving force generated by the motor when a braking force that does not cause the vehicle to roll down is being generated, it does not describe control for restoring the driving force generated by the motor when the brake is released. For this reason, the technology described in Patent Document 1 may cause the vehicle to significantly roll down when the vehicle is stopped on a slope, particularly when the brake is released quickly.

[0006] Furthermore, the technology described in Patent Document 2 leaves creep torque corresponding to the amount of inclination (inclination angle) when a slope is detected, so although it may be possible to prevent the vehicle from rolling downhill even when the brakes are released, it has the disadvantage of increasing the vehicle's electricity consumption. Also, sensors that detect road surface gradients (e.g., G sensors) have variations in detected values, and if the road surface gradient detected by the sensor is smaller than the actual road surface gradient, there is a risk that the vehicle will roll downhill when the brakes are released.

[0007] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a vehicle control device that can suppress the occurrence of a vehicle sliding downhill when returning from creep cut control. [Means for solving the problem]

[0008] A vehicle control device according to a first aspect includes a control unit that performs creep cut control to reduce the output torque of a motor that is a drive source of the vehicle when the vehicle is stopped and the brake is on, and that performs return control to cause the motor to output a torque equal to or greater than a guaranteed gradient torque that is set to prevent the vehicle from rolling downhill on an uphill road with a predetermined road surface gradient when it is determined that the brake has been turned off based on the rate of change in brake fluid pressure while the output torque is being reduced.

[0009] In the first mode, creep cut control is performed to reduce the output torque of the motor, which is the drive source of the vehicle, when the vehicle is stopped and the brake is applied. This can improve the vehicle's electricity consumption. In addition, in the first mode, brake release is determined based on the rate of change in brake fluid pressure while the motor output torque is being reduced. In this way, by using the rate of change in brake fluid pressure, it is possible to quickly determine that the brake is released, even if the brake is released quickly.

[0010] In the first mode, when it is determined that the brake has been released, a return control is performed in which the motor outputs a torque equal to or greater than the torque equivalent to the guaranteed gradient, which is set to prevent the vehicle from rolling downhill on an uphill road with a predetermined road gradient. This makes it possible to suppress the vehicle from rolling downhill when returning from creep cut control with simple control. In particular, when the road on which the vehicle is parked is less than the predetermined road gradient, it is possible to reliably suppress the vehicle from rolling downhill when returning from creep cut control without being affected by variations in the detection value of the gradient detection sensor.

[0011] In a second aspect, in the first aspect, when the control unit determines that the vehicle has rolled over after determining that the brake has been released, the control unit increases the output torque at a higher rate of increase than when it has not determined that the vehicle has rolled over.

[0012] In the second mode, when it is determined that the vehicle has rolled over after it has been determined that the brakes have been released, the motor output torque is increased at a higher rate than when it is not determined that the vehicle has rolled over. This increases the rate at which the motor output torque increases when the vehicle rolls over, thereby reducing the amount of rollover of the vehicle.

[0013] In a third aspect, in the second aspect, the control unit determines the ascending rate so that the ascending rate increases as the road surface gradient detected by a gradient detection sensor that detects the road surface gradient increases.

[0014] In the third aspect, the rate of increase of the output torque is increased as the road surface gradient detected by the gradient detection sensor increases, thereby reducing the amount of vehicle slippage when the road surface gradient is relatively large.

[0015] In a fourth aspect, in the first aspect, the control unit does not perform the creep cut control when the shift position of the vehicle is shifted to the drive range for the first time after the ignition of the vehicle is turned on.

[0016] According to the fourth aspect, when the vehicle is stopped on a slope, there is no risk of the vehicle rolling down when the gears are first shifted into the drive range upon restarting. [Effects of the Invention]

[0017] The present disclosure has an effect of being able to suppress the occurrence of a vehicle rolling downhill when returning from creep cut control. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a schematic configuration of a vehicle control device according to an embodiment; [Figure 2] 4 is a flowchart showing a creep cut / return control process executed by the HEV ECU. [Figure 3] 4 is a timing chart showing the rate of increase in the output torque of the MG, etc. [Figure 4] FIG. 4 is a diagram showing an example of the relationship between the road surface gradient amount and the increase rate of the MG output torque when the vehicle slides downhill. DETAILED DESCRIPTION OF THE INVENTION

[0019] An example of an embodiment of the present disclosure will be described in detail below with reference to the drawings. The vehicle equipped with a vehicle control device 10 shown in Fig. 1 is a hybrid electric vehicle (HEV) equipped with an engine (not shown), a motor / generator (hereinafter referred to as "MG") 30 that operates as a motor for propelling the vehicle and as a generator, and a high-voltage battery (not shown). The vehicle control device 10 includes a brake ECU 18, an HEV Electronic Control Unit (ECU) 20, a power control unit (hereinafter referred to as "PCU") 26 equipped with an MG ECU 28, and the MG 30. The MG 30 is an example of a motor in the present disclosure.

[0020] The MG 30 and the above-mentioned high-voltage battery are connected to the PCU 26. The PCU 26 includes an inverter capable of converting AC power to DC power and DC power to AC power. When the MG 30 operates as a motor, power is supplied to the MG 30 from the high-voltage battery via the PCU 26. When the MG 30 operates as a generator, power generated by the MG 30 is supplied to the high-voltage battery via the PCU 26, thereby charging the high-voltage battery.

[0021] The MG ECU 28 includes a CPU (Central Processing Unit), memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), non-volatile storage units such as a HDD (Hard Disk Drive) and an SSD (Solid State Drive), and an I / F (Interface) unit. When the MG 30 operates as a motor, the MG ECU 28 receives a torque command value from the HEV ECU 20 and controls the operation of the MG 30 so that the output torque from the rotating shaft of the MG 30 matches the received torque command value. The MG ECU 28 also receives a detected value of the rotation speed (rotational speed) of the rotating shaft of the MG 30 from a rotation detection sensor 32 built into the MG 30 and outputs the received detected value of the rotation speed of the MG 30 to the HEV ECU 20.

[0022] On the other hand, the brake ECU 18 includes a CPU, memories such as ROM and RAM, a non-volatile storage unit such as an HDD or SSD, and an I / F unit. The brake ECU 18 is connected to a G sensor 12 mounted on the vehicle and a brake device 14 including a hydraulic pressure sensor 16. The detection value of the G sensor 12 is used to calculate the detection value of the road surface gradient amount θ. The G sensor 12 is an example of a gradient detection sensor in the present disclosure.

[0023] The hydraulic pressure sensor 16 detects the hydraulic pressure P of the brake fluid in the master cylinder of the brake device 14. The brake ECU 18 performs hill-hold control to maintain the brake on state when the brake is released while the vehicle is stopped on an uphill road where the road gradient θ is equal to or greater than a second threshold θth2. The second threshold θth2 has a relationship of θth2>θth1 with respect to a first threshold θth1 (described later), and is, for example, a road gradient of approximately 7%. The brake ECU 18 is connected to the HEV ECU 20 and outputs the detection values ​​of the G sensor 12 and the hydraulic pressure sensor 16 to the HEV ECU 20.

[0024] The HEV ECU 20 includes a CPU, memories such as ROM and RAM, a non-volatile storage unit such as an HDD or SSD, and an I / F unit. A shift position sensor 24 that detects the shift position of the vehicle is connected to the HEV ECU 20. A control program is stored in the storage unit of the HEV ECU 20. The HEV ECU 20 functions as a control unit 22 by reading the control program from the storage unit and loading it into the memory, and then executing the control program loaded into the memory by the CPU. The control unit 22 then performs creep cut / return control processing (described below) while the vehicle ignition is on.

[0025] The control unit 22 performs creep cut control to reduce the output torque of the MG 30 when the vehicle is stopped and the brake is on. When the control unit 22 determines that the brake has been released based on the rate of change in the brake fluid pressure P while the output torque of the MG 30 is being reduced, the control unit 22 performs return control to cause the MG 30 to output a torque equivalent to a guaranteed gradient that is set to prevent the vehicle from sliding down an uphill road with a predetermined road gradient θ. The control unit 22 is an example of a control unit in the present disclosure.

[0026] Next, as an operation of this embodiment, the creep cut / return control process executed by the control unit 22 while the ignition of the vehicle is on will be described with reference to FIG.

[0027] In step 100, the control unit 22 determines whether the current shift position of the vehicle is in the D range based on the shift position signal input from the shift position sensor 24. The D range is an example of a drive range in this disclosure. If the current shift position of the vehicle is in the D range, the control unit 22 also determines whether the shift from a range other than the D range to the D range is the first shift to the D range since the ignition was turned on.

[0028] If the determination in step 100 is affirmative, the process proceeds to step 122, where a torque command value is output to the MG ECU 28 so that the output torque from the MG 30 coincides with the normal creep torque, and the creep cut / return control process is terminated. Note that the normal creep torque is, for example, a torque that causes the vehicle's creep speed to reach a predetermined value (for example, approximately 5 to 10 km / h) when the vehicle is positioned on a flat road. In this way, if the determination in step 100 is affirmative, the creep cut control described below is not performed, and therefore, if the parking lot where the vehicle is stored is on an uphill road, it is possible to prevent the vehicle from rolling down the road in the parking lot.

[0029] If the determination in step 100 is negative, the process proceeds to step 102. In step 102, the control unit 22 determines whether or not the conditions for implementing creep cut control are met. An example of the conditions for implementing creep cut control is when, as shown by arrow A in FIG. 3, the rotation speed of the MG 30 detected by the rotation detection sensor 32 becomes zero, the brake is turned on and the brake flag switches to a value indicating brake on, and the detected value of the road surface gradient θ is less than a first threshold value θth1. The first threshold value θth1 is a road surface gradient corresponding to the maximum value of the detection variation of the road surface gradient θ by the G sensor 12, and is, for example, a road surface gradient of approximately 3.5%.

[0030] If the determination in step 102 is positive, the process proceeds to step 108, where the control unit 22 switches the creep cut control flag (see FIG. 3) to a value indicating that creep cut control is in progress, and performs creep cut control to reduce the output torque of the MG 30. In creep cut control, the output torque of the MG 30 may be set to 0, or may be set to a value that is smaller than the output torque before the creep cut control was started and greater than 0, for example, a value corresponding to the detected value of the road surface gradient amount θ. By performing this creep cut control, the vehicle's electricity consumption can be improved.

[0031] Once creep cut control is performed in step 108, the process proceeds to step 110. In step 110, the control unit 22 determines whether the rate of change of the brake fluid pressure P is equal to or greater than a first predetermined value. If the determination in step 110 is negative, the process proceeds to step 112. In step 112, the control unit 22 determines whether the absolute value of the brake fluid pressure P is less than a second predetermined value. If the determination in step 112 is also negative, the process returns to step 110, and steps 110 and 112 are repeated until the determination in step 110 or step 112 is positive.

[0032] For example, if the brakes are released quickly, the rate of change of the brake fluid pressure P becomes equal to or greater than a first predetermined value, and the determination in step 110 is affirmative. In this case, it is possible to determine early that the brakes have been released. On the other hand, if the brakes are released slowly, the absolute value of the brake fluid pressure P becomes less than a second predetermined value, and the determination in step 112 is affirmative. This makes it possible to appropriately determine that the brakes have been released, even if the brakes are released slowly.

[0033] If the determination in step 110 or step 112 is affirmative, the brake flag is switched to a value indicating brake-off, and the creep cut control flag is switched to a value indicating that creep cut control is not being performed (see also arrow B in FIG. 3), and then the process proceeds to step 114. Then, from step 114 onwards, return control is performed.

[0034] That is, in step 114, the control unit 22 outputs a torque command value to the MG ECU 28 so that the MG 30 outputs a torque equivalent to the guaranteed gradient that is set so as not to cause the vehicle to roll downhill on an uphill road where the road surface gradient amount is the first threshold value θth1. The increase rate of the output torque at this time is the reference torque rate (see FIG. 3).

[0035] This makes it possible to suppress, with simple control, the occurrence of vehicle rolling down when returning from creep cut control. In particular, in this embodiment, the first threshold θth1 is set to a road surface gradient amount corresponding to the maximum value of the detection variation of the road surface gradient amount θ by the G sensor 12, and creep cut control is performed when the detected value of the road surface gradient amount θ is less than the first threshold θth1. This reduces the influence of the variation in the detection value of the G sensor 12, and makes it possible to suppress the occurrence of vehicle rolling down when returning from creep cut control.

[0036] In step 116, the control unit 22 determines whether or not reverse rotation of the rotation shaft of the MG 30 has been detected by the rotation detection sensor 32, i.e., whether or not the vehicle has rolled down. If the determination in step 116 is negative, the process proceeds to step 120. In step 120, the control unit 22 determines whether or not to end the return control by determining whether or not an end condition for the return control, such as the vehicle moving forward, has been met. If the determination in step 120 is negative, the process returns to step 116, and steps 116 and 120 are repeated.

[0037] Furthermore, if the vehicle has skidded, the determination in step 116 is affirmative, and the skid determination flag is switched to a value indicating that skid is occurring (see also arrow C in FIG. 3), after which the process proceeds to step 118. In step 118, control unit 22 outputs a torque command value to MG ECU 28 so that the output torque from MG 30 is increased at an increase rate (slide determination rate: see FIG. 3) that is greater than the reference torque rate and that corresponds to the detected value of road surface gradient amount θ. In this way, by making the increase rate of the output torque from MG 30 greater than the reference torque rate, the amount of skid of the vehicle can be reduced.

[0038] The rate of increase of the output torque according to the detected value of the road surface gradient θ may be determined so that when the detected value of the road surface gradient θ is equal to or greater than a predetermined value, the rate of increase of the output torque is higher than when the detected value of the road surface gradient θ is less than the predetermined value.

[0039] Specifically, for example, as shown in Figure 4(A), the increase rate of the output torque may be determined so that the increase rate of the output torque increases stepwise with an increase in the road surface gradient θ. Alternatively, for example, as shown in Figure 4(B), the increase rate of the output torque may be determined so that the increase rate of the output torque increases linearly with an increase in the road surface gradient θ. Furthermore, for example, as shown in Figure 4(C), the increase rate of the output torque may be determined so that the increase rate of the output torque increases quadratically with an increase in the road surface gradient θ. This makes it possible to reduce the amount of vehicle slippage when the road surface gradient θ is relatively large.

[0040] After the processing of step 118 is performed, the process proceeds to step 120. If the determination of step 120 is affirmative, then in step 122, a process is performed to cause the MG 30 to output normal creep torque, and then the creep cut / return control process is terminated.

[0041] If it is determined in step 102 that the detected value of the road surface gradient amount θ is equal to or greater than the first threshold value θth1, the creep cut / return control process is terminated via step 122.

[0042] As described above, in this embodiment, the control unit 22 performs creep cut control to reduce the output torque of the MG 30 when the vehicle is stopped and the brake is applied. Furthermore, when it is determined that the brake is released based on the rate of change in the brake fluid pressure while the output torque of the MG 30 is being reduced, the control unit 22 performs return control to output from the MG 30 a torque equivalent to the guaranteed gradient that is set so that the vehicle does not roll downhill on an uphill road with a predetermined road surface gradient (first threshold value θth1). This makes it possible to suppress the occurrence of rolling downhill of the vehicle when returning from the creep cut control with simple control.

[0043] Furthermore, in this embodiment, when the control unit 22 determines that the vehicle has rolled over after determining that the brakes have been released, it increases the output torque of the MG 30 at a higher rate than when it has not determined that the vehicle has rolled over, thereby reducing the amount of rollover of the vehicle.

[0044] In this embodiment, the control unit 22 determines the ascending rate so that the ascending rate increases as the road surface gradient detected by the G sensor 12 increases, thereby reducing the amount of vehicle slippage when the road surface gradient is relatively large.

[0045] In this embodiment, the control unit 22 does not perform creep cut control when the vehicle's shift position is shifted to D range for the first time after the vehicle ignition is turned on. This prevents the vehicle from rolling downhill in a parking lot where the vehicle is kept, if the parking lot is on an uphill road.

[0046] In the above embodiment, the vehicle equipped with the vehicle control device 10 is an HEV, but the vehicle equipped with the vehicle control device 10 may be an EV (Electric Vehicle).

[0047] In addition, in the above embodiment, a torque equivalent to the guaranteed gradient is output from MG30 in step 114 of FIG. 2, but the present disclosure is not limited to this, and a torque exceeding the torque equivalent to the guaranteed gradient may be output from MG30.

[0048] In the above embodiment, the vehicle's sliding downhill is detected by the reverse rotation of the rotation shaft of the MG 30. However, the present disclosure is not limited to this, and the vehicle's sliding downhill may be detected by the reverse rotation of the vehicle's wheels. Furthermore, the vehicle's sliding downhill may be detected by a GNSS (Global Navigation Satellite System) sensor or the like.

[0049] The following additional notes are provided regarding the above-described embodiments.

[0050] (Appendix 1) A vehicle control device including a control unit that performs creep cut control to reduce the output torque of a motor that is a drive source of the vehicle when the vehicle is stopped and the brake is on, and performs return control to cause the motor to output a torque equal to or greater than a torque equivalent to a guaranteed gradient that is set to prevent the vehicle from rolling down an uphill road with a predetermined road surface gradient when it is determined that the brake has been released based on the rate of change in brake fluid pressure while the output torque is being reduced.

[0051] (Appendix 2) A vehicle control device as described in Appendix 1, wherein the control unit, when determining that the vehicle has rolled over after determining that the brake has been released, increases the output torque at a higher increase rate than when it is not determined that the vehicle has rolled over.

[0052] (Appendix 3) 3. The vehicle control device according to claim 2, wherein the control unit determines the ascent rate so that the ascent rate increases as a road surface gradient detected by a gradient detection sensor that detects a road surface gradient increases.

[0053] (Appendix 4) 2. The vehicle control device according to claim 1, wherein the control unit does not perform the creep cut control when the shift position of the vehicle is shifted to a drive range for the first time after an ignition of the vehicle is turned on.

[0054] (Appendix 5) 2. The vehicle control device according to claim 1, wherein the predetermined road surface gradient amount is a road surface gradient amount corresponding to a maximum value of detection variation in a gradient detection sensor that detects the road surface gradient amount. According to the aspect described in Supplementary Note 5, even when the detection variation of the gradient detection sensor is relatively large, it is possible to cause the motor to output a torque sufficient to prevent the vehicle from sliding downhill.

[0055] (Appendix 6) 2. A vehicle control device according to claim 1, wherein the control unit does not perform the creep cut control when the road surface gradient detected by a gradient detection sensor that detects the road surface gradient is equal to or greater than the predetermined road surface gradient when the vehicle is stopped and the brake is on. According to the aspect described in Supplementary Note 6, it is possible to reliably prevent the vehicle from sliding downhill in a region where the detected value of the road surface gradient is equal to or greater than a predetermined road surface gradient.

[0056] (Appendix 7) 2. The vehicle control device according to claim 1, wherein the control unit determines that the brakes are released when a rate of change in the brake fluid pressure is equal to or greater than a first predetermined value and when an absolute value of the brake fluid pressure is less than a second predetermined value. According to the aspect described in Supplementary Note 7, even if the brake is slowly released, it can be appropriately determined that the brake has been released. [Explanation of symbols]

[0057] 10 Vehicle control device 12 G sensor (gradient detection sensor) 16. Hydraulic pressure sensor 20 HEV ECU 22 Control Unit 30 MG 32 Rotation detection sensor

Claims

1. A vehicle control device including a control unit that performs creep cut control to reduce the output torque of a motor that is a drive source of the vehicle when the vehicle is stopped and the brake is on, and performs return control to cause the motor to output a torque equal to or greater than a torque equivalent to a guaranteed gradient that is set to prevent the vehicle from rolling down an uphill road with a predetermined road surface gradient when it is determined that the brake has been released based on the rate of change in brake fluid pressure while the output torque is being reduced.

2. 2. The vehicle control device according to claim 1, wherein when it is determined that the vehicle has rolled over after determining that the brake has been released, the control unit increases the output torque at a higher rate than when it is not determined that the vehicle has rolled over.

3. 3. The vehicle control device according to claim 2, wherein the control unit determines the ascending rate so that the ascending rate increases as the road surface gradient detected by a gradient detection sensor that detects the road surface gradient increases.

4. 2. The vehicle control device according to claim 1, wherein the control unit does not perform the creep cut control when the shift position of the vehicle is shifted to the drive range for the first time after the ignition of the vehicle is turned on.

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