WO2014192120A1

WO2014192120A1 - Braking force control device

Info

Publication number: WO2014192120A1
Application number: PCT/JP2013/065068
Authority: WO
Inventors: 好隆藤田; 加藤　英久
Original assignee: トヨタ自動車株式会社
Priority date: 2013-05-30
Filing date: 2013-05-30
Publication date: 2014-12-04

Abstract

A braking force control device is a braking force control device that controls braking force provided to each wheel of a vehicle and is provided with: a deceleration detection unit that detects deceleration of the vehicle; and a braking force control unit that, when a system failure develops in the vehicle, determines braking force provided to each wheel using a deviation between the deceleration detected by the deceleration detection unit and a target deceleration, and maintains a constant value of braking force for a rear wheel before braking force for the rear wheel exceeds the determined braking force.

Description

Braking force control device

The present invention relates to a braking force control device that controls the braking force applied to each wheel.

When controlling the braking force distribution of the front and rear wheels according to the loading state of the vehicle, control by EBD (Electronic Brake force Distribution) is known as a method for bringing the actual braking force distribution ratio as close as possible to the ideal braking force distribution ratio. . EBD is a technique for optimally allocating braking force to wheels based on the number of rotations of the front and rear wheels and the turning state, and functions by detecting the braking force limit of the rear wheels from the slip difference between the front and rear wheels during braking. To achieve.

Also, JP 2010-284990 A describes a braking force control device including a rear wheel slip determination unit that determines whether or not a slip state has occurred in the rear wheel. In this braking force control device, when the actual rear wheel braking force reaches the rear wheel braking force during light loading in the ideal braking force distribution, the rear wheel braking force is distributed when the rear wheel is not slipping. The ratio is increased. Japanese Patent Laid-Open No. 2001-171502 discloses a technique for calculating a reference value from a measured value of a vehicle speed sensor and limiting the braking force applied to the rear wheel when the deceleration is equal to or higher than the reference value. Has been.

JP 2010-284990 A JP 2001-171502 A

Incidentally, in order to control the braking force by EBD, it is assumed that the state of the wheel can be detected by a wheel speed sensor or the like. Therefore, when it becomes impossible to detect the state of the wheel due to a failure of the wheel speed sensor or the like, there is a problem that the EBD function cannot be realized because the presence or absence of slip cannot be detected.

Therefore, an object of the present invention is to provide a braking force control device that can achieve both vehicle stabilization and securing of braking force and can perform appropriate braking force control even when the system fails.

That is, the braking force control device according to the present invention is a braking force control device that controls the braking force applied to each wheel of the vehicle, and includes a deceleration detection unit that detects vehicle deceleration, and a system failure in the vehicle. If the braking force to be applied to each wheel is determined using the deviation between the deceleration detected by the deceleration detection unit and the target deceleration, the rear wheel braking force exceeds the determined braking force. And a braking force control unit that maintains the braking force of the rear wheels at a constant value.

In the braking force control device according to the present invention, when a system failure occurs in the vehicle, the braking force control unit determines the braking force to be applied to each wheel from the target deceleration and the detected actual deceleration. The braking force of the rear wheel is maintained at a constant value before the braking force of the rear wheel exceeds the determined braking force. Therefore, the limit of the braking force of the rear wheel that can be realized is obtained, and the braking force of the rear wheel can be effectively used by controlling the braking force of the rear wheel so that it does not exceed the above limit. Can be prevented. Further, since the braking force of the rear wheels is controlled so as not to exceed the determined braking force, it is possible to prevent the deterioration of the vehicle stability due to the rear wheel lock. Therefore, appropriate braking force control can be performed even when the system fails, and both vehicle stabilization and securing of the braking force can be achieved.

In the braking force control apparatus according to the present invention, the braking force control unit controls the rear wheel until the braking force of the rear wheel reaches a reference value determined based on a case where the vehicle is in an empty state. The power may be increased. Therefore, since the braking force of the rear wheel is increased until the reference value determined based on the case where the vehicle is in an empty state is reached, the braking force of the rear wheel is effectively used and applied to the wheel. It is possible to control the braking force to be in an optimum state.

In the braking force control apparatus according to the present invention, when the vehicle system has failed, the output of the wheel speed sensor in the vehicle may not be detected. In this case, since the braking force control as described above is performed in a state in which the output of the wheel speed sensor cannot be detected, it is possible to perform the appropriate braking force control at an appropriate timing.

According to the present invention, it is possible to achieve both vehicle stabilization and securing of braking force, and appropriate braking force control can be performed even when the system fails.

1 is a schematic configuration diagram of a braking force control device according to an embodiment of the present invention. It is a graph which shows an ideal braking force distribution diagram. It is a flowchart which shows a braking force control process. It is a graph for demonstrating each threshold value. It is a graph for demonstrating a target distribution line. It is a graph for demonstrating a threshold value. It is a graph for demonstrating control of the braking force by a target distribution line.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 1, the braking force control device 1 is mounted on a vehicle 100 and controls the braking force applied to the left front wheel 11, the right front wheel 12, the left rear wheel 13, and the right rear wheel 14 of the vehicle 100. To do. The left front wheel 11, the right front wheel 12, the left rear wheel 13 and the right rear wheel 14 are provided with

wheel speed sensors

11a, 12a, 13a, 14a, respectively, and the rotational speed of each wheel is determined by the

wheel speed sensors

11a, 12a, 13a and 14a.

Further, the braking force control device 1 includes a deceleration sensor (deceleration detection unit) 15 that detects the deceleration of the vehicle 100. The braking force control device 1 is configured to detect the deceleration detected by the deceleration sensor 15 and the target deceleration when the system fails to detect the slip difference between the front and rear wheels due to a failure of the

wheel speed sensors

11a, 12a, 13a, and 14a. A braking force control unit 22 that determines a braking force to be applied to the left front wheel 11, the right front wheel 12, the left rear wheel 13, and the right rear wheel 14 using a deviation from the speed is provided. The braking force control unit 22 controls the braking force so that the braking force of the

rear wheels

13 and 14 is maintained at a constant value before the braking force of the

rear wheels

13 and 14 exceeds the braking force determined above. The braking force control unit 22 is provided in an ECU (Electronic Control Unit) 20, for example.

The braking force control device 1 electrically controls the distribution of the braking force applied to the

front wheels

11 and 12 and the

rear wheels

13 and 14 according to the loading state of the vehicle 100 when no system failure has occurred. EBD control is performed. In addition, the braking force control device 1 can distribute the braking force to be applied to the

front wheels

11 and 12 and the

rear wheels

13 and 14 using the remaining information even when the system of the vehicle 100 fails. Examples of the vehicle 100 on which the braking force control device 1 is mounted include a truck having a loading platform on which a load is mounted.

The wheel speed value detected by each

wheel speed sensor

11a, 12a, 13a, 14a is output to the ECU 20. The ECU 20 is connected to the deceleration sensor 15 described above and a master cylinder pressure sensor 16 that detects the master cylinder pressure. The deceleration of the vehicle 100 detected by the deceleration sensor 15 and the master cylinder pressure detected by the master cylinder pressure sensor 16 are output to the ECU 20.

ECU20 is provided with the failure detection part 21 which detects failure of the

wheel speed sensors

11a, 12a, 13a, 14a other than the braking force control part 22 mentioned above. The failure detection unit 21 determines whether or not each of the

wheel speed sensors

11a, 12a, 13a, and 14a has failed based on information on the wheel speeds input from the

wheel speed sensors

11a, 12a, 13a, and 14a. .

ECU20 controls the braking force of each wheel by controlling the brake actuator 30 according to the deceleration of the vehicle 100 and the master cylinder pressure. A master cylinder 35 is connected to the brake actuator 30. The brake actuator 30 includes a wheel cylinder (not shown) corresponding to each of the left front wheel 11, the right front wheel 12, the left rear wheel 13 and the right rear wheel 14, and a hydraulic circuit for controlling each wheel cylinder. Various valves and pumps are connected to this hydraulic circuit. In the brake actuator 30, the braking force of the corresponding left front wheel 11, right front wheel 12, left rear wheel 13 and right rear wheel 14 is adjusted by pressurizing or depressurizing each wheel cylinder.

A brake pedal 41 is connected to the piston shaft of the master cylinder 35. For example, a brake pressure sensor that detects an operation state of the brake pedal 41 is connected to the brake pedal 41. Here, when the brake pedal 41 is depressed by the driver, the piston shaft of the master cylinder 35 is pushed, and a hydraulic pressure (master pressure) corresponding to the depression amount of the brake pedal 41 is generated. Then, the hydraulic fluid in the hydraulic circuit of the brake actuator 30 is supplied in parallel to each wheel cylinder through each valve according to the depression amount of the brake pedal 41. Here, the ECU 20 outputs an electrical signal to a valve in the brake actuator 30 to independently control the hydraulic pressure of each wheel cylinder, thereby allowing the left front wheel 11, the right front wheel 12, the left rear wheel 13, and the right rear wheel 14 to be controlled. Control each braking force.

Next, the operation of the braking force control apparatus 1 according to this embodiment will be described with reference to FIGS. As shown in FIG. 2, in a loaded vehicle such as a truck, the ideal braking force distribution line is different in the loaded state. Since the ideal braking force distribution line is determined according to the weight of the vehicle and the distribution of the front and rear wheels, a plurality of ideal distribution lines C1, C2, C3 and equal G lines g (see FIG. 4) are determined according to the loaded weight of the vehicle. . The width of the equal G line g increases as the weight of the vehicle 100 increases, and decreases as the weight of the vehicle 100 decreases.

Hereinafter, description will be made based on the straight line A in the ideal braking force distribution diagram shown in FIG. The straight line A is obtained from the brake specifications of the front and rear wheels set based on the ideal distribution line in the fixed volume state (loading amount as designed) of the vehicle 100. The flowchart shown in FIG. 3 shows the flow of the braking force control process in this embodiment, and is executed by the ECU 20. The braking force control process shown in FIG. 3 is repeatedly executed at regular intervals, for example.

In the braking force control apparatus according to the present embodiment, first, in step S1 (hereinafter referred to as “S1”, the same applies to other steps), the failure detection unit 21 causes each

wheel speed sensor

11a, 12a, 13a, 14a. Is broken and it is determined whether or not the wheel speed is abnormal. Here, the wheel speed abnormality means that the EBD control using the slip difference between the front wheel slip and the rear wheel slip cannot be performed, that is, the ECU 20 cannot detect the outputs of the

wheel speed sensors

11a, 12a, 13a, and 14a. Indicates the state.

If it is determined in S1 that the wheel speed is not abnormal, the EBD control is possible. Therefore, the braking force control process in FIG. 3 is terminated and the normal EBD control is executed. On the other hand, when it is determined in S1 that the wheel speed is abnormal, the process proceeds to S2, and it is determined whether or not the brake pedal 41 is depressed and braking is being performed. If it is determined in S2 that braking is not being performed, the series of processes is terminated, and if it is determined that braking is being performed, the process proceeds to S3. When braking, the braking force of each of the left front wheel 11, the right front wheel 12, the left rear wheel 13 and the right rear wheel 14 is linear so as to follow the straight line A of the graph shown in FIG. Is getting bigger.

In S3, it is determined whether or not the braking force of the left front wheel 11 and the right front wheel 12 is greater than the threshold value TH1. Here, when it is determined that the braking force of the left front wheel 11 and the right front wheel 12 is larger than the threshold value TH1, the process proceeds to S4. In S4, the braking force control unit 22 maintains the hydraulic pressure of each of the

rear wheels

13, 14, so that the braking force of the left rear wheel 13 and the right rear wheel 14 is a constant value as shown by the line segment L1 in FIG. Maintained. The threshold value TH1 indicates, for example, a braking force equivalent to 0.2G in design. On the other hand, when it is determined in S3 that the braking force of the left front wheel 11 and the right front wheel 12 is not greater than the threshold value TH1, the process proceeds to S5.

In S5, it is determined whether or not the braking force of the left front wheel 11 and the right front wheel 12 is greater than the threshold value TH2. Here, the threshold value TH2 indicates, for example, a braking force equivalent to 0.3 G in design. If it is determined in S5 that the braking force of the left front wheel 11 and the right front wheel 12 is greater than the threshold value TH2, the process proceeds to S6. In S6, the braking force of the left rear wheel 13 and the right rear wheel 14 increases as shown by the line segment L2 in FIG. Is done. On the other hand, when it is determined in S5 that the braking force of the left front wheel 11 and the right front wheel 12 is not greater than the threshold value TH2, the process proceeds to S7.

In S7, it is determined whether or not the braking force of the left front wheel 11 and the right front wheel 12 is greater than the threshold value TH3. As shown in FIG. 4, the threshold value TH3 indicates a reference value determined based on the case where the vehicle 100 is in an empty state, and the ideal distribution line C1 when the vehicle 100 is in an empty state. It is the value of the front wheel braking force when slightly lower than the value of the rear wheel braking force at. Here, the threshold value TH3 indicates, for example, a braking force equivalent to 0.5G in design. In S7, when it is determined that the braking force of the left front wheel 11 and the right front wheel 12 is greater than the threshold value TH3, the process proceeds to S8, where it is determined that the braking force of the left front wheel 11 and the right front wheel 12 is not greater than the threshold value TH3. If so, the process proceeds to S9.

In S <b> 8, the target distribution line determination process is executed by the braking force control unit 22. Specifically, as indicated by a line segment L3 in FIG. 5, the braking force of the left rear wheel 13 and the right rear wheel 14 is held at a constant value, and the braking force of the left front wheel 11 and the right front wheel 12 is constant. Increased by the value ΔBrkForce_f_const. Then, a target distribution line is obtained from the deceleration of the vehicle 100 when the braking force of the left front wheel 11 and the right front wheel 12 is increased by a constant value ΔBrkForce_f_const, the braking force of each wheel, and the equal G line g. Specifically, the rear wheel braking force RF of the left rear wheel 13 and the right rear wheel 14, the front wheel braking force FF of the left front wheel 11 and the right front wheel 12 at the start of the processing of S8, and the above-described constant value ΔBrkForce_f_const are reduced. The actual vehicle estimated weight m of the vehicle 100 is calculated from the following equation (1) using the deceleration Gx detected by the speed sensor 15.
(RF + FF + ΔBrkForce_f_const) / Gx = m (1)

Then, the calculated actual vehicle estimated weight m is compared with the weight corresponding to each ideal distribution line C1, C2, C3, and the ideal corresponding to the weight that is heavier than the actual vehicle estimated weight m and closest to the actual vehicle estimated weight m. The distribution line is determined as the target distribution line. In FIG. 5, for example, the ideal distribution line C2 is determined as the target distribution line. After the target distribution line is determined, the braking forces of the left front wheel 11, the right front wheel 12, the left rear wheel 13 and the right rear wheel 14 are increased along the target distribution line, and the process proceeds to S9.

In S9, it is determined whether or not the braking force of the left front wheel 11 and the right front wheel 12 is greater than the threshold value TH4. The threshold value TH4 is a value that is arbitrarily set according to the target distribution line determined in S8, and is a value that is set along the target distribution line C2, for example, as shown in FIG. In S9, when it is determined that the braking force of the left front wheel 11 and the right front wheel 12 is larger than the threshold value TH4, the process proceeds to S10. In S10, the braking force control unit 22 maintains the hydraulic pressure of each of the

rear wheels

13 and 14, whereby the braking force of the left rear wheel 13 and the right rear wheel 14 is maintained at a constant value, and the series of processes is terminated. On the other hand, when it is determined in S9 that the braking force of the left front wheel 11 and the right front wheel 12 is not greater than the threshold value TH4, the series of processing is ended as it is.

As described above, the braking force control apparatus 1 according to the present embodiment is detected by the target deceleration determined based on the equal G line g and the deceleration sensor 15 when a system failure occurs in the vehicle 100. The braking force is determined as a target distribution line from the actual deceleration. As shown in FIG. 7, before the braking force of the

rear wheels

13 and 14 exceeds the braking force on the determined target distribution line, the braking force of the

rear wheels

13 and 14 is maintained at a constant value. Therefore, the limit of the braking force of the

rear wheels

13 and 14 that can be realized is obtained, and the braking force of the

rear wheels

13 and 14 is effectively controlled by controlling the braking force of the

rear wheels

13 and 14 not to exceed the above limit. Therefore, it is possible to prevent a reduction in braking force. Further, since the braking force of the

rear wheels

13 and 14 is controlled so as not to exceed the braking force determined on the target distribution line, the deterioration of the vehicle stability due to the rear wheel lock can be prevented. Therefore, appropriate braking force control can be performed even when the system fails, and both vehicle stabilization and securing of the braking force can be achieved.

Further, the braking force control unit 22 applies the braking force of the rear wheel along the straight line A, for example, until the braking force of the rear wheel reaches a threshold value TH3 determined based on the case where the vehicle 100 is in an empty state. Increase. Therefore, since the braking force of the rear wheel is increased until the threshold value TH3 is reached, the braking force of the rear wheel is effectively used and applied to the left front wheel 11, the right front wheel 12, the left rear wheel 13, and the right rear wheel 14. The braking force applied can be controlled to be in an optimum state.

Furthermore, the braking force control device 1 calculates the actual vehicle estimated weight m using the above-described equation (1), and determines the target distribution line from the calculated actual vehicle estimated weight m. Therefore, it is possible to apply the braking force in consideration of the actual vehicle estimated weight m. Further, in the braking force control device 1, since the braking force is applied without using the

wheel speed sensors

11a, 12a, 13a, and 14a, the braking force control device 1 is used as a backup when the EBD cannot be operated. Thus, it is possible to suppress a decrease in braking performance when the system fails.

In addition, embodiment mentioned above demonstrated embodiment of the braking force control apparatus which concerns on this invention, and the braking force control apparatus which concerns on this invention is not limited to what was described in this embodiment. The braking force control apparatus according to the present invention may be a modification of the braking force control apparatus according to the present embodiment, or may be applied to other ones without changing the gist described in each claim.

For example, in the above embodiment, the brake actuator 30 is connected to the master cylinder 35 and includes a wheel cylinder. However, the configuration of the brake actuator can be changed as appropriate without being limited to the above embodiment.

Further, the deceleration detection unit that detects the deceleration of the vehicle 100 is not limited to the deceleration sensor 15 of the above embodiment, and various sensors can be used. Further, instead of the detection value of the deceleration sensor 15, for example, a differential value of the detection value of the vehicle speed sensor acquired in advance may be used.

Moreover, although the process shown by the flowchart of FIG. 3 was demonstrated as a braking force control process by the braking force control apparatus 1, it is not restricted to the process of the flowchart of FIG. 3, It is possible to delete or add a process suitably. It is.

In addition, as the vehicle 100 on which the braking force control device 1 is mounted, a truck having a loading platform on which a load is mounted is cited, but a bus or the like may be used as long as the vehicle can load the load.

The present invention can be used as a braking force control device that can achieve both vehicle stabilization and securing of braking force and can be operated without any problem even when the system fails.

DESCRIPTION OF SYMBOLS 1 ... Braking force control apparatus, 11 ... Left front wheel (front wheel), 11a, 12a, 13a, 14a ... Wheel speed sensor, 12 ... Right front wheel (front wheel), 13 ... Left rear wheel (rear wheel), 14 ... Right rear wheel (Rear wheel), 15 ... deceleration sensor (deceleration detection unit), 20 ... ECU, 22 ... braking force control unit, 100 ... vehicle, TH3 ... threshold (reference value).

Claims

A braking force control device for controlling a braking force applied to each wheel of a vehicle,
A deceleration detector for detecting the deceleration of the vehicle;
When a system failure of the vehicle occurs, a braking force to be applied to each wheel is determined using a deviation between the deceleration detected by the deceleration detecting unit and the target deceleration, and the braking force of the rear wheel is determined. A braking force control unit for maintaining the braking force of the rear wheel at a constant value before the braking force exceeds the determined braking force;
A braking force control device comprising:
The braking force control unit increases the braking force of the rear wheel until the braking force of the rear wheel reaches a reference value determined based on a case where the vehicle is in an empty state.
The braking force control apparatus according to claim 1.
When the system failure of the vehicle occurs, the output of the wheel speed sensor in the vehicle cannot be detected.
The braking force control apparatus according to claim 1 or 2.