JP2019198179A - Brake control device - Google Patents

Abstract

To provide a brake control device that can increase an amount of regenerative power generation while controlling a drive wheel from being locked.SOLUTION: An ECU estimates a frictional coefficient μ of a road surface on a forward side in a travel direction more than a rear wheel 61 of a vehicle 100 and calculates an upper limit value Fof regenerative brake force based on the frictional coefficient μ.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a brake control device.

  Conventionally, a vehicle including a motor as a driving force source for traveling is known (see, for example, Patent Document 1).

  Such a vehicle is configured to perform cooperative brake control using both the friction braking force by the friction brake device and the regenerative braking force by the motor.

JP 2009-292176 A

  Here, for example, if the upper limit value of the regenerative braking force is set to a low constant value so that the driving wheels do not lock even when the road surface friction coefficient is low, it is difficult to increase the amount of regenerative power generation.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a brake control device capable of increasing the amount of regenerative power generation while suppressing the drive wheels from being locked. Is to provide.

  A brake control device according to the present invention controls a brake for a vehicle, and is based on an estimation unit that estimates a friction coefficient of a road surface ahead of a driving wheel of a vehicle and a friction coefficient estimated by the estimation unit. And a calculating unit for calculating an upper limit value of the regenerative braking force. The upper limit value of the regenerative braking force is an upper limit value of the regenerative braking force within a range where the drive wheels are not locked.

  With this configuration, the drive wheel is locked by lowering the upper limit value of the regenerative braking force when the friction coefficient is low and increasing the upper limit value of the regenerative braking force when the friction coefficient is high. While suppressing, it is possible to increase the amount of regenerative power generation.

  According to the brake control device of the present invention, it is possible to increase the amount of regenerative power generation while suppressing the drive wheels from being locked.

1 is a schematic diagram illustrating an overall configuration of a vehicle including an ECU according to an embodiment of the present invention. It is the block diagram which showed ECU by this embodiment. It is a flowchart for demonstrating the operation example at the time of the regenerative braking in the vehicle of this embodiment.

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

-Mechanical configuration-
First, a mechanical configuration (drive mechanism) of a vehicle 100 including an ECU 9 according to an embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the vehicle 100 is an FR (front engine / rear drive) hybrid vehicle, and includes an engine 1, a motor 2, a generator 3, and a power split mechanism 4. Therefore, the vehicle 100 is configured such that the driving force output from at least one of the engine 1 and the motor 2 is transmitted to the rear wheel 61 via the propeller shaft 51, the differential device 52, and the drive shaft 53. Yes. That is, in the vehicle 100, the rear wheel 61 is a driving wheel, and the front wheel 62 is a driven wheel.

  An engine (internal combustion engine) 1 is, for example, a gasoline engine, and is configured to be able to output a driving force for traveling. The output shaft (crankshaft) of the engine 1 is connected to the propeller shaft 51 and the generator 3 via the power split mechanism 4.

  The motor 2 mainly functions as an electric motor, and also functions as a generator depending on the situation. The motor 2 is, for example, an AC synchronous motor, and is configured to be able to output a driving force for traveling to the propeller shaft 51. The motor 2 is configured to generate a regenerative braking force when functioning as a generator when the vehicle 100 is decelerated. The motor 2 is an example of the “vehicle brake” in the present invention.

  The generator 3 mainly functions as a generator, and also functions as an electric motor depending on the situation. The generator 3 is an AC synchronous generator, for example, and is configured to generate electric power by the driving force of the engine 1. The generator 3 functions as a starter motor when the engine 1 is started.

  The power split mechanism 4 is, for example, a planetary gear mechanism, and an engine 1, a motor 2, and a generator 3 are connected to three rotating elements, respectively. The power split mechanism 4 is configured to distribute the output of the engine 1 to the propeller shaft 51 and the generator 3.

  In addition, the vehicle 100 is provided with a hydraulic friction brake device 7 in the vicinity of the rear wheel 61 and the front wheel 62. The friction brake device 7 includes, for example, a disc rotor 7a and a brake caliper 7b having a brake pad (not shown). The friction brake device 7 is configured to generate a friction braking force when a brake pad driven by the hydraulic control unit 71 sandwiches the disc rotor 7a. The friction brake device 7 is an example of the “vehicle brake” in the present invention.

-Electrical configuration-
Next, the electrical configuration (control system) of the vehicle 100 according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 2, vehicle 100 includes an ECU 9, a battery 82, and inverters 81a and 81b.

  The ECU 9 is configured to control the traveling of the vehicle 100 by executing the vehicle system. For example, the ECU 9 performs operation control of the engine 1, drive control of the motor 2 and the generator 3, cooperative control of the engine 1, the motor 2, and the generator 3. Further, the ECU 9 is configured to execute cooperative brake control using both the friction braking force by the friction brake device 7 and the regenerative braking force by the motor 2.

  The ECU 9 includes a CPU 9a, a ROM 9b, a RAM 9c, a backup RAM 9d, and an input / output interface 9e, which are connected via a bus. The ECU 9 is an example of the “brake control device” of the present invention, and the “estimator” and “calculator” of the present invention are realized by the CPU 9a executing a program stored in the ROM 9b.

  The CPU 9a executes arithmetic processing based on various control programs and maps stored in the ROM 9b. The ROM 9b stores various control programs, maps that are referred to when the various control programs are executed, and the like. The RAM 9c is a memory that temporarily stores the calculation result by the CPU 9a, the detection result of each sensor, and the like. The backup RAM 9d is a non-volatile memory that stores data to be saved when the vehicle system is stopped.

  The input / output interface 9e has a function of inputting a detection result of each sensor and outputting a control signal to each unit. An accelerator pedal position sensor 91, a brake pedal position sensor 92, a wheel speed sensor 93, and the like are connected to the input / output interface 9e.

  The accelerator pedal position sensor 91 is provided for detecting the operation amount (depression amount) of the accelerator pedal, and the brake pedal position sensor 92 is provided for detecting the operation amount (depression amount) of the brake pedal. The wheel speed sensor 93 is provided to detect the wheel speed of the four wheels (the left and right rear wheels 61 and the left and right front wheels 62).

  The input / output interface 9e is connected to the injector 11, the igniter 12, and the throttle motor 13 of the engine 1. The ECU 9 is configured to be able to control the operating state of the engine 1 by controlling the fuel injection amount, the ignition timing, the throttle opening (intake air amount), and the like based on the detection result of each sensor. .

  The input / output interface 9e is connected to a battery 82 and inverters 81a and 81b.

  The battery 82 is a chargeable / dischargeable high-voltage power supply, and is configured to store electric power generated by the motor 2 and the generator 3 while supplying electric power for driving the motor 2 and the generator 3.

  Inverters 81a and 81b are, for example, a three-phase bridge circuit having an IGBT and a diode, and regenerative control or power running control is performed by controlling the on / off state of the IGBT by a drive signal supplied from ECU 9.

  The inverter 81a converts the direct current supplied from the battery 82 into an alternating current to drive the motor 2 (powering control), and converts the alternating current generated by the motor 2 during regenerative braking into a direct current. Output (power generation control). The ECU 9 can control the regenerative power generation amount in the motor 2 using the inverter 81a, and a regenerative braking force corresponding to the regenerative power generation amount is generated in the motor 2.

  The inverter 81b converts the alternating current generated by the generator 3 by the power of the engine 1 into a direct current and outputs it to the battery 82 (power generation control), and converts the direct current supplied from the battery 82 into an alternating current. The generator 3 is driven (power running control).

  A hydraulic control unit 71 is connected to the input / output interface 9e. The hydraulic control unit 71 is provided to control the braking hydraulic pressure supplied to the friction brake device 7. The ECU 9 is configured to adjust the friction brake force in the friction brake device 7 by adjusting the brake oil pressure using the oil pressure control unit 71. For example, the ECU 9 calculates the required braking force for the front wheel 62 and the required braking force for the rear wheel 61 based on the amount of operation of the brake pedal, and controls the hydraulic pressure control unit 71 so that the required braking force for the front wheel 62 is obtained. At the same time, the inverter 81a and the hydraulic control unit 71 are controlled so that the required braking force for the rear wheel 61 is obtained.

Here, the ECU 9 of the present embodiment is configured to calculate the upper limit value F _MAX of the regenerative braking force based on the inertia specifications and the road surface friction coefficient μ. The upper limit value F _MAX of the regenerative braking force is an upper limit value of the regenerative braking force within a range where the rear wheel 61 is not locked. That is, in the present embodiment, since the upper limit value F _MAX of the regenerative braking force is variable, the upper limit value of the regenerative power generation amount is variable. Specifically, when the friction coefficient μ is high, the upper limit value F _MAX of the regenerative braking force is made higher than when the friction coefficient μ is low. In the case of a constant product, the upper limit value F _MAX of the regenerative braking force is made higher than in the case of a light product. Therefore, even when the friction coefficient μ is low and the product is lightly loaded (when the drive wheel is likely to be locked), the upper limit value of the regenerative braking force is set to a low constant value so that the drive wheel is not locked. Compared to the case, it is possible to increase the amount of regenerative power generation. For example, the fixed product is a state in which the vehicle 100 is the heaviest (the number of passengers of the vehicle 100 is a capacity, and a load is loaded on the vehicle 100). This is the lightest state (a state where only the driver is on the vehicle 100).

-Operation example during regenerative braking of a vehicle-
Next, with reference to FIG. 3, an operation example during regenerative braking (an example of cooperative brake control for the rear wheel 61 by the ECU 9) in the vehicle 100 of the present embodiment will be described. The following steps are executed by the ECU 9.

First, in step S1 in FIG. 3, inertia parameters are estimated. This inertia specifications are included centroid height H and the rear wheel load M _R, the center of gravity height H and the rear wheel load M _R is estimated, for example, using known techniques.

  Next, in step S2, the friction coefficient μ between the rear wheel 61 and the road surface is estimated. The friction coefficient μ is estimated based on, for example, the rotational speed of the front wheels 62 and the vehicle speed. That is, since the friction coefficient μ is estimated using the front wheels 62, the friction coefficient μ of the road surface on the front side in the traveling direction with respect to the rear wheels 61 as drive wheels is estimated. That is, the friction coefficient μ of the road surface through which the rear wheel 61 passes thereafter is estimated.

  Next, in step S3, it is determined whether regenerative braking is possible. For example, when the friction coefficient μ estimated in step S2 is 0.1 or more, it is determined that regenerative braking is possible. If it is determined that regenerative braking is possible, the process proceeds to step S4. On the other hand, when it is determined that the regenerative braking is not possible, the process returns. If there is a braking request when regenerative braking is not possible, the hydraulic control unit 71 is controlled so that a friction braking force corresponding to the required braking force is output.

Next, in step S4, an upper limit value F _MAX of the regenerative braking force within a range where the rear wheel 61 is not locked is calculated. The upper limit F _MAX of this regenerative braking force is calculated by the following equation (1), for example.

F _MAX = (μ · M _R · g) / {1+ (H / L) · μ} (1)
In Equation (1), μ is a friction coefficient, M _R is a rear wheel load, g is a gravitational acceleration, H is a height of the center of gravity, and L is a wheel base (front wheel 62 and rear wheel 61 and Distance). The friction coefficient μ is estimated values in step S2, the center of gravity height H and the rear wheel load M _R is the estimated value in step S1. The wheel base L is a preset value.

Therefore, the upper limit value F _MAX of the regenerative braking force becomes larger as the friction coefficient μ increases, the larger wheel load M _R after correlating with the vehicle weight is increased.

  Next, in step S5, it is determined whether there is a braking request. For example, it is determined that there is a braking request when the brake pedal is operated. If it is determined that there is a braking request, the process proceeds to step S6. On the other hand, if it is determined that there is no braking request, the process returns.

Next, in step S6, it is determined whether the required braking force for the rear wheel 61 is equal to or less than the upper limit value F _MAX of the regenerative braking force. The required braking force for the rear wheel 61 is calculated based on, for example, the amount of operation of the brake pedal. If it is determined that the required braking force of the rear wheel 61 is equal to or less than the upper limit value F _MAX , the process proceeds to step S7. On the other hand, when it is determined that the required braking force of the rear wheel 61 is not less than or equal to the upper limit value F _MAX (when the required braking force of the rear wheel 61 exceeds the upper limit value F _MAX ), the process proceeds to step S8.

  In step S7, the required braking force of the rear wheel 61 is covered by the regenerative braking force of the motor 2. For this reason, the inverter 81a is controlled so that the regenerative braking force corresponding to the required braking force of the rear wheel 61 is output. That is, the regenerative braking force by the motor 2 is output, and the friction braking force by the friction brake device 7 is not output.

In step S8, the required braking force of the rear wheel 61 is covered by the regenerative braking force by the motor 2 and the friction braking force by the friction brake device 7. That is, when the required braking force of the rear wheel 61 exceeds the upper limit value F _MAX of the regenerative braking force, the friction braking force is added. Specifically, the upper limit value F _MAX of the regenerative braking force is output from the motor 2, and the remaining braking force obtained by subtracting the upper limit value F _MAX from the required braking force of the rear wheel 61 is output from the friction brake device 7. For this reason, the inverter 81a is controlled so that the regenerative braking force of the upper limit value F _MAX is output, and the hydraulic control unit 71 is controlled so that the remaining friction braking force with respect to the required braking force of the rear wheel 61 is output. Is done.

-Effect-
In the present embodiment, as described above, by calculating the upper limit value F _MAX of the regenerative braking force based on the friction coefficient of inertia specifications and the road surface mu, the upper limit value F _MAX of the regenerative braking force is variable. Therefore, the upper limit value F _MAX of the regenerative braking force is lowered when the friction coefficient μ is low, the upper limit value F _MAX of the regenerative braking force is increased when the friction coefficient μ is high, and the regenerative braking force is obtained in the case of a light product. of the lower limit value F _MAX, by increasing the upper limit value F _MAX of the regenerative braking force in the case of constant volume, while suppressing the wheel 61 after a drive wheel to lock, the increase in regenerative power generation amount Can be planned. Therefore, the fuel consumption can be improved and the load on the friction brake device 7 can be reduced.

  In the present embodiment, the friction coefficient μ of the road surface through which the rear wheel 61 passes can be estimated by estimating the friction coefficient μ using the front wheel 62.

Further, in the present embodiment, by calculating the upper limit F _MAX of the regenerative braking force in advance before the braking request, the motor 2 and the friction brake device 7 can be controlled with high responsiveness when the braking request is made. .

-Other embodiments-
In addition, embodiment disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, the technical scope of the present invention includes all modifications within the meaning and scope equivalent to the scope of the claims.

  For example, in the above-described embodiment, an example in which the present invention is applied to a hybrid vehicle including the engine 1 and the motor 2 as driving power sources for traveling has been described. However, the present invention is not limited thereto, and only a motor is used as a driving power source for traveling. You may make it apply this invention to the electric vehicle provided.

  In the above embodiment, the example in which the present invention is applied to the hybrid vehicle including the power split mechanism 4 has been described. However, the present invention is not limited thereto, and the present invention is applied to a hybrid vehicle in which the power split mechanism is not provided. May be.

  In the above-described embodiment, the example in which the vehicle 100 is the FR method has been described. In this case, the friction coefficient of the road surface ahead of the traveling direction with respect to the front wheels of the vehicle may be estimated using at least one of the camera image, the map information, and the weather information.

In the above embodiment, the example in which the upper limit value F _MAX of the regenerative braking force is calculated using the equation (1) is not limited to this, but the maximum vehicle deceleration set according to the friction coefficient is shown. The upper limit value of the regenerative braking force may be calculated based on the vehicle weight. In this case, the vehicle weight may be included as an inertial specification.

  Moreover, although the engine 1 showed the example which is a gasoline engine in the said embodiment, not only this but an engine may be other engines, such as a diesel engine.

  Moreover, in the said embodiment, ECU9 is comprised by HV (hybrid) ECU, engine ECU, MG (motor generator) ECU, battery ECU, brake EUC, etc., and these ECUs may be connected so that communication is mutually possible. .

  The present invention is applicable to a brake control device that controls a vehicle brake.

2 Motor (vehicle brake)
7 Friction brake device (vehicle brake)
9 ECU (brake control device)
61 Rear wheel (drive wheel)
100 vehicles

Claims (1)

A brake control device for controlling a vehicle brake,
An estimation unit for estimating a friction coefficient of a road surface on the front side in the traveling direction from the driving wheel of the vehicle;
A brake control device comprising: a calculation unit that calculates an upper limit value of the regenerative braking force based on the friction coefficient estimated by the estimation unit.

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