JP2018024343A - Braking force control device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow even a vehicle that can perform regenerative braking and hydraulic braking to perform ABS by simple control with good accuracy, without causing interruption of deceleration and making braking force unstable.SOLUTION: The braking force control device of a vehicle, which has a function of an ABS of controlling braking force during braking so that a lock state of a wheel is prevented, detects a road surface state in front of the vehicle and predicts actuation of the ABS on the basis of the road surface state and a travelling state of the vehicle; and when predicting the actuation of the ABS, outputs signals to an inverter 4 and a brake driving portion 7 and actuates the ABS after switching regenerative braking to hydraulic braking, before the vehicle reaches a point at which the actuation of the ABS is predicted.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a braking force control device for a vehicle having a function of an antilock brake control (hereinafter, abbreviated as ABS) capable of regenerative braking and hydraulic braking to prevent a wheel from being locked.

  Conventionally, an ABS that prevents a wheel from being locked is used in many vehicles, and is also used in an electric vehicle and a hybrid vehicle that can perform a regenerative brake and a hydraulic brake. At this time, the regenerative brake is superior in control responsiveness compared to the hydraulic brake, but the regenerative braking force has a different characteristic that it varies depending on the situation and is unstable. For example, JP-A-2015-196474 In the ABS (hereinafter referred to as Patent Document 1), in ABS, when the locking tendency is eliminated and the total braking force is restored, the regenerative brake is increased prior to the hydraulic brake, and the regenerative brake precedes the hydraulic brake. After being increased, a technique of a braking force control device for a vehicle is disclosed in which at least a part of the regenerative brake is replaced with a hydraulic brake by increasing the hydraulic brake while reducing the regenerative brake.

Japanese Patent Laying-Open No. 2015-196474

  By the way, ABS requires precise braking force control (reduction, retention, increase, etc.) for a very short time, and if the regenerative brake and hydraulic brake are simply controlled, the responsiveness and stability are controlled. There is a problem that the deceleration is lost due to the difference between the two, or the braking force is unstable. For this reason, when controlling with brakes having different characteristics such as a regenerative brake and a hydraulic brake, it is necessary to adopt the ABS technique disclosed in the above-mentioned Patent Document 1, and there is a problem that the control becomes complicated. .

  The present invention has been made in view of the above circumstances, and even if the vehicle is capable of regenerative braking and hydraulic braking, deceleration can be lost by simple control of the ABS or braking force can be unstable. An object of the present invention is to provide a braking force control device for a vehicle that can be accurately performed without becoming.

  One aspect of the vehicle braking force control device according to the present invention is a vehicle braking force control device that can be freely braked by a regenerative brake and a hydraulic brake of an electric motor. Anti-lock brake control means for preventing a locked state and anti-lock brake control operation prediction for detecting the front road surface state and predicting the operation of the anti-lock brake control means based on the front road surface state and the running state of the vehicle And a control means for replacing the regenerative brake with a hydraulic brake before the operation of the antilock brake control means when the operation of the antilock brake control means is expected.

  According to the braking force control device for a vehicle according to the present invention, even if the vehicle is capable of regenerative braking and hydraulic braking, the deceleration is lost by simple control of the ABS, or the braking force becomes unstable. It becomes possible to carry out with accuracy without becoming.

1 is a schematic configuration diagram of a regenerative brake system and a hydraulic brake system for a vehicle according to an embodiment of the present invention. It is a flowchart of the braking force control program which concerns on one Embodiment of this invention. It is detection explanatory drawing of the front road surface state change which concerns on one Embodiment of this invention. It is characteristic explanatory drawing of the ABS intervention determination threshold value which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes a vehicle, and a left front wheel 2fl, a right front wheel 2fr, a left rear wheel 2rl, and a right rear wheel 2rr of the vehicle 1 are supported by the vehicle body via suspensions (not shown).

  Inside the left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl, and right rear wheel 2rr are a left front wheel in-wheel motor 3fl, a right front wheel in-wheel motor 3fr, a left rear wheel in-wheel motor 3rl, and a right rear wheel in-wheel. A motor 3rr is incorporated so that power can be transmitted to each wheel.

  In the present embodiment, the driving force described below, which is generated in each wheel 2fl, 2fr, 2rl, 2rr by independently controlling the torque of each in-wheel motor 3fl, 3fr, 3rl, 3rr, and The regenerative braking force (regenerative brake) can be independently controlled.

  Each in-wheel motor 3fl, 3fr, 3rl, 3rr is connected to an inverter 4 provided corresponding to each motor, and converts the direct current power supplied from the battery 5 into alternating current power. Are supplied independently to each in-wheel motor 3fl, 3fr, 3rl, 3rr. Thereby, each in-wheel motor 3fl, 3fr, 3rl, 3rr is drive-controlled, and a driving force is provided with respect to each wheel 2fl, 2fr, 2rl, 2rr.

  Each in-wheel motor 3fl, 3fr, 3rl, 3rr also functions as a generator, generates electric power by the rotational energy of each wheel 2fl, 2fr, 2rl, 2rr, and regenerates the generated power to the battery 5 via the inverter 4. The regenerative energy generated by the power generation of each in-wheel motor 3fl, 3fr, 3rl, 3rr gives regenerative braking force (regenerative braking) to each wheel 2fl, 2fr, 2rl, 2rr. Give.

  On the other hand, each wheel 2fl, 2fr, 2rl, 2rr is provided with a friction brake mechanism 6fl, 6fr, 6rl, 6rr. These friction brake mechanisms 6fl, 6fr, 6rl, 6rr are, for example, disc brakes, This is a known brake device such as a drum brake.

  These friction brake mechanisms 6fl, 6fr, 6rl, 6rr are connected to the brake drive unit 7, and the pistons of the wheel cylinders are actuated by the hydraulic pressure supplied from the brake drive unit 7, and the wheels 2fl, 2fr, 2rl, A braking force (hydraulic brake) is applied to 2rr.

  The brake drive unit 7 includes a hydraulic pressure generator including a booster pump, an accumulator, etc., a pressure adjustment control valve that adjusts the pressure of the brake hydraulic oil and supplies it to the wheel cylinders of the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr, and a friction brake The hydraulic unit includes an open / close control valve that opens and closes a hydraulic circuit that supplies brake hydraulic oil to the mechanisms 6fl, 6fr, 6rl, and 6rr.

  And the above-mentioned inverter 4 and the brake drive part 7 are each connected to the control unit 10. FIG.

  The control unit 10 includes a microcomputer including a CPU, a ROM, a RAM, and the like, and executes various programs to control the in-wheel motors 3fl, 3fr, 3rl, and 3rr, and the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr. Control the operation independently. Therefore, the control unit 10 includes an accelerator sensor 11 that detects the driver's accelerator operation amount, a brake sensor 12 that detects the driver's brake operation amount, and wheel speeds ωfl, ωfr, and ωrl of each wheel 2fl, 2fr, 2rl, and 2rr. , Ωrr for detecting wheel speed sensors 13fl, 13fr, 13rl, 13rr, a road surface state detecting device 14 for detecting a road surface state ahead, and a longitudinal acceleration sensor 15 for detecting a longitudinal acceleration Gx. Further, the control unit 10 controls each in-wheel motor 3fl, 3fr, 3rl, 3rr, such as a signal representing a current value flowing from the inverter 4 to each in-wheel motor 3fl, 3fr, 3rl, 3rr, a signal representing a voltage value, and the like. The sensor signal necessary for this is input from the inverter 4.

  Here, the above-described road surface state detection device 14 is based on image information in front of a traveling road photographed by a camera as disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-127882 and Japanese Patent Application Laid-Open No. 2004-168286. The road surface state (asphalt dry road surface, asphalt wet road surface, snow road, etc.) in a predetermined area is detected, and these road surface states are detected by replacing them with preset road surface friction coefficients. For example, as shown in FIG. 3, based on the image information from the camera, A1, A2, A3, A4, A5,..., An-2, An-1, An The area is divided into areas, and the road surface friction conditions μ1, μ2, μ3, μ4, μ5,. The road surface condition ahead is detected.

  Based on the above-mentioned signals, the control unit 10 requests the required driving force (target driving force) according to the driver's accelerator operation amount or the required braking force (target braking force) according to the driver's brake operation amount, that is, The required braking / driving force required for running or braking the vehicle 1 is calculated with reference to a preset map, table, etc., for each wheel 2fl, 2fr, 2rl, 2rr. The in-wheel motors 3fl, 3fr, 3rl, and 3rr are allotted to each wheel demand braking / driving force generated. When the required braking / driving force value is positive, the driving force is requested, and when the requested braking / driving force is negative, the braking force is requested.

  The control unit 10 generates a control signal (for example, a PWM control signal) so that a current corresponding to the required braking / driving force of each wheel 2fl, 2fr, 2rl, 2rr flows to each in-wheel motor 3fl, 3fr, 3rl, 3rr. And output to the inverter 4. When the required braking / driving force of each wheel 2fl, 2fr, 2rl, 2rr is negative, the control unit 10 sets the required braking / driving force of each wheel 2fl, 2fr, 2rl, 2rr by experiment, calculation or the like in advance. According to the ratio, the regenerative brakes generated by the in-wheel motors 3fl, 3fr, 3rl, and 3rr and the hydraulic brakes generated by the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr are distributed. At this time, the control unit 10 outputs a control signal for generating the regenerative brake to the inverter 4, and outputs a control signal for generating the hydraulic brake to the brake drive unit 7. Thereby, the target regenerative brake is generated in each of the in-wheel motors 3fl, 3fr, 3rl, and 3rr, and the target hydraulic brake is generated in the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr.

  The control unit 10 also has an ABS function that controls the braking force during braking to prevent the wheel from being locked. As described above, the control unit 10 detects the front road surface state and detects the front road surface state and the vehicle running state. When the ABS operation is predicted based on the state, and the ABS operation is predicted, a signal is output to the inverter 4 and the brake drive unit 7 before the vehicle reaches the position where the ABS operation is predicted. Execute ABS after replacing brake with hydraulic brake. Specifically, the ABS of the present embodiment is, for example, when the preset wheel deceleration is reached, the increase of the brake fluid pressure is suppressed, and the brake fluid pressure is maintained. When the slip ratio exceeds a preset value, the brake fluid pressure is reduced, and thereafter, the brake fluid pressure is maintained, the brake fluid pressure is increased, and so on. Thus, the control unit 10 has functions as antilock brake control means, antilock brake control operation prediction means, and control means.

  Next, the braking force control of the present embodiment executed by the control unit 10 will be described with reference to the flowchart of FIG.

  First, in step (hereinafter abbreviated as “S”) 101, it is determined whether or not the host vehicle 1 is being braked. If the vehicle is not being braked, the program is exited, and if it is being braked, the process proceeds to S102.

  In S102, it is determined whether or not the braking being executed includes a regenerative brake (whether or not the regenerative brake and the hydraulic brake are applied). If the regenerative brake is not included, that is, only the hydraulic brake, The process jumps to S112 to continue the braking control as it is, and the ABS is activated as necessary.

  Note that, as described above, the ABS in the present embodiment, for example, when the wheel deceleration that has been set in advance is reached, the increase in the brake fluid pressure is suppressed, and the brake fluid pressure is maintained. When the tire slip ratio exceeds a preset value, the brake fluid pressure is reduced, and thereafter, the brake fluid pressure is maintained, the brake fluid pressure is increased, and so on.

  If it is determined in S102 that the regenerative brake is included (braking by the regenerative brake and the hydraulic brake), the process proceeds to S103, and a change in the road surface state is detected. Specifically, as shown in FIG. 3, road surface friction coefficients μ1, μ2, μ3, μ4, μ5,..., Μn−2, μn detected for each region in front of the traveling road detected by the road surface state detection device 14. −1, μn, in a region adjacent to the front and rear, a difference between (a road surface friction coefficient in a region closer to the host vehicle) and (a road surface friction coefficient in a region far from the host vehicle) is used to obtain a road surface friction coefficient Change amounts Δμ1, Δμ2, Δμ3, Δμ4, Δμ5,..., Δμn−3, Δμn−2, and Δμn−1 are calculated. That is, if the amount of change in the road surface friction coefficient is a positive value, the road is expected to travel on a road surface with a low road surface friction coefficient.

  Next, the process proceeds to S104, and the amount of change in the road surface friction coefficient detected in S103 exceeds a threshold value (positive value) set in advance by experiment, calculation, etc. It is determined whether or not there is a part that varies greatly to a low value (for example, a part that varies from an asphalt dry road surface to a snowy road).

  As a result of the determination in S104, if it is determined that there is no region where the amount of change in the road surface friction coefficient exceeds a threshold value (positive value) set in advance through experiments, calculations, etc., the current running state (deceleration state) Since it can be determined that the ABS will not operate due to a sudden change in the road surface condition (for example, high μ road → low μ road), jump to S112 and continue the braking control, and the ABS operates as necessary. Is done.

  Conversely, if it is determined in S104 that there is a region where the change amount of the road surface friction coefficient exceeds a threshold value (positive value) set in advance through experiments, calculations, etc., the process proceeds to S105, which will be described later. An ABS intervention judgment threshold value DABS is set. When it is determined that there are a plurality of areas where the amount of change in the road surface friction coefficient exceeds a threshold value (positive value) set in advance by experiment, calculation, etc., the nearest area is the following S105 to S111. This is the processing target area.

  The ABS intervention determination threshold value DABS is set, for example, in advance by experiment, calculation, etc. For example, as shown in the characteristic diagram of FIG. 4, the ABS that keeps the wheel slip rate during braking within a predetermined range. It is set in accordance with the deceleration to be operated, and is set to a lower value as the road surface friction coefficient in the far side region of the region adjacent to the front and rear is lower.

  Next, in S106, the longitudinal acceleration Gx of the host vehicle and the ABS intervention determination threshold value DABS are compared.

  As a result of the comparison in S106, when Gx <DABS, it can be determined that the ABS does not operate due to a sudden change in the road surface condition (for example, high μ road → low μ road) in the current running state (deceleration state). Therefore, the process jumps to S112 to continue the braking control as it is, and the ABS is operated as necessary.

  Further, if Gx ≧ DABS, the ABS is predicted to be activated when the road surface state change position (sudden change position) is reached in the current traveling state (deceleration state), so the process proceeds to S107, and the road surface state change position is reached. The distance Lμ is detected.

  Next, the process proceeds to S108, and the time tμ until the road surface state change position is calculated, for example, according to the relationship of the following expression (1).

Lμ = V0 · tμ + (1/2) · Gx · tμ ² (1)
Here, V0 is the current vehicle speed calculated from the wheel speed sensors 13fl, 13fr, 13rl, and 13rr, and the sign of the longitudinal acceleration Gx is negative because it is a deceleration state.

  Next, the process proceeds to S109, and the time tst for substituting the regenerative brake to the hydraulic brake by subtracting the margin time Δt set in advance by experiment, calculation, etc. from the time tμ calculated in S108 until the road surface state change position. Is calculated (tst = tμ−Δt).

  Next, the process proceeds to S110 and waits until the time tst for switching the regenerative brake to the hydraulic brake elapses. When the time tst elapses, the process proceeds to S111, the regenerative brake is replaced with the hydraulic brake, and the process proceeds to S112 to continue the braking control. When the ABS is activated, the ABS is the braking only by the hydraulic brake.

  As described above, according to the embodiment of the present invention, the ABS function of controlling the braking force during braking to prevent the wheel from being locked is detected, and the front road surface state is detected. When the ABS operation is predicted based on the running state of the vehicle and the ABS operation is predicted, a signal is output to the inverter 4 and the brake drive unit 7 before the vehicle reaches the position where the ABS operation is predicted. Then, the ABS is executed after the regenerative brake is replaced with the hydraulic brake. For this reason, even if the vehicle is capable of regenerative braking and hydraulic braking, the ABS is prevented from operating when brakes having different characteristics such as regenerative braking and hydraulic braking are operating. In particular, it is possible to perform the ABS with high accuracy without using a complicated control without causing the deceleration to be lost and the braking force becoming unstable.

  In this embodiment, an electric vehicle having in-wheel motors on four wheels has been described as an example. However, a vehicle that travels with one motor, a vehicle that travels with two motors, and an electric vehicle that travels with three motors. Needless to say, it can also be applied to hybrid vehicles.

DESCRIPTION OF SYMBOLS 1 Vehicle 2fl, 2fr, 2rl, 2rr Wheel 3fl, 3fr, 3rl, 3rr In-wheel motor 4 Inverter 5 Battery 6fl, 6fr, 6rl, 6rr Friction brake mechanism 7 Brake drive part 10 Control unit (Anti-lock brake control means, anti-lock Brake control operation prediction means, control means)
DESCRIPTION OF SYMBOLS 11 Accelerator sensor 12 Brake sensor 13fl, 13fr, 13rl, 13rr Wheel speed sensor 14 Road surface state detection apparatus 15 Longitudinal acceleration sensor

Claims (3)

In a braking force control device for a vehicle that can be freely braked by a regenerative brake and a hydraulic brake of an electric motor,
Anti-lock brake control means for controlling the braking force during braking to prevent the wheel from being locked;
Anti-lock brake control operation predicting means for detecting the front road surface state and predicting the operation of the anti-lock brake control means based on the front road surface state and the running state of the vehicle;
When the operation of the antilock brake control means is expected, a control means for replacing the regenerative brake with a hydraulic brake before the operation of the antilock brake control means;
A braking force control device for a vehicle, comprising:   2. The braking force of the vehicle according to claim 1, wherein the antilock brake control operation predicting means predicts the operation of the antilock brake control means at a position where the front road friction coefficient changes in a direction of decreasing. Control device.   When the operation of the antilock brake control unit is expected, the control unit replaces the regenerative brake with a hydraulic brake before the vehicle reaches a position where the operation of the antilock brake control unit is predicted. The braking force control device for a vehicle according to claim 1 or 2, characterized in that

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