JP2024145544A - Brake Control Device - Google Patents

Abstract

To suppress decline in braking force when an own vehicle comprising two or more braking mechanisms collides with an obstacle.SOLUTION: A brake control device comprises: a determination part which determines on the basis of data acquired during travel of an own vehicle, whether or not at least one of a first condition that collision with an obstacle is inevitable and a time until the collision is within a prescribed time and a second condition that a rate of change in an acceleration of the own vehicle in a longitudinal direction is equal to or more than a threshold for determination of collision, is satisfied; and a control part which performs brake control by using both of a first braking mechanism and a second braking mechanism, which are included in the own vehicle, when the determination part determines that at least one of the first condition and the second condition is satisfied when performing brake control by using the first braking mechanism without using the second braking mechanism.SELECTED DRAWING: Figure 4

Description

The present invention relates to a braking control device.

AEB (Autonomous Emergency Braking) control technology has been developed and used for vehicles (passenger cars, etc.) for a long time. With AEB control, when the vehicle is about to collide with an obstacle in its travel direction, automatic (computer-controlled) braking control is performed to avoid the collision or to reduce damage if a collision does occur.

When this AEB control is performed by a braking system that has an upstream mechanism (mechanism on the master cylinder side) and a downstream mechanism (mechanism on the wheel cylinder side), for example, braking control is performed by controlling only the upstream mechanism.

Publication No. 52-096033 JP 2009-45982 A Special Publication No. 2019-520254

However, with the above-mentioned conventional technology, if the vehicle collides with an obstacle and the upstream mechanism fails, the braking force can be significantly reduced, potentially resulting in greater damage.

Therefore, the present invention has been made in consideration of the above circumstances, and aims to provide a braking control device that can suppress a decrease in braking force when a vehicle equipped with two or more braking mechanisms collides with an obstacle.

The brake control device of the present invention includes a determination unit that determines whether or not at least one of a first condition that a collision with an obstacle is unavoidable and the time until the collision is within a predetermined time and a second condition that a rate of change in acceleration in the longitudinal direction of the vehicle is equal to or greater than a collision determination threshold is satisfied based on data acquired while the vehicle is traveling, and a control unit that performs brake control using both the first and second braking mechanisms when the determination unit determines that at least one of the first and second conditions is satisfied when braking control is performed using the first braking mechanism without using the second braking mechanism among a first braking mechanism and a second braking mechanism provided in the vehicle.

In addition, in the brake control device, the first brake mechanism is an upstream mechanism that controls the hydraulic pressure of the brake fluid based on a braking request, and the second brake mechanism is a downstream mechanism that is connected to the upstream mechanism via a hydraulic circuit and adjusts the hydraulic pressure generated by the upstream mechanism and supplies it to the wheel cylinder.

In addition, in the brake control device, when the control unit is performing brake control using the first brake mechanism without using the second brake mechanism based on a target wheel pressure, which is a target value of the hydraulic pressure in the wheel cylinder of the second brake mechanism, and the judgment unit judges that at least one of the first condition and the second condition is satisfied, the control unit performs brake control using the first brake mechanism to generate hydraulic pressure of the target wheel pressure by the first brake mechanism, and performs brake control using the second brake mechanism to generate hydraulic pressure of the target wheel pressure by the second brake mechanism.

In the brake control device, when the control unit uses the first brake mechanism without using the second brake mechanism to perform brake control based on a target wheel pressure, which is a target value of the hydraulic pressure in the wheel cylinder of the second brake mechanism, and when the judgment unit judges that at least one of the first condition and the second condition is satisfied, the control unit uses the first brake mechanism to perform brake control to generate hydraulic pressure of the target wheel pressure by the first brake mechanism, and when the detected hydraulic pressure detected by a hydraulic pressure sensor that detects the hydraulic pressure of a hydraulic circuit connecting the first brake mechanism and the second brake mechanism is smaller than the target wheel pressure, the control unit uses the second brake mechanism to perform brake control to generate hydraulic pressure of the difference between the target wheel pressure and the detected hydraulic pressure by the second brake mechanism.

In addition, in the brake control device, the second brake mechanism further includes a differential pressure valve provided in a portion adjacent to the first brake mechanism, and when the control unit is performing brake control using the first brake mechanism without using the second brake mechanism based on a target wheel pressure, which is a target value of the hydraulic pressure in the wheel cylinder of the second brake mechanism, and the determination unit determines that at least one of the first condition and the second condition is satisfied, the control unit uses the first brake mechanism to perform brake control to generate hydraulic pressure of the target wheel pressure by the first brake mechanism, and sends an instruction to the differential pressure valve using the second brake mechanism to maintain the differential pressure between the hydraulic pressure on the wheel cylinder side and the lower hydraulic pressure on the first brake mechanism side at the target wheel pressure.

In addition, in the braking control device, after sending the instruction to the differential pressure valve, when the control unit detects a failure in the first braking mechanism or when the detected hydraulic pressure detected by a hydraulic pressure sensor that detects the hydraulic pressure in the hydraulic circuit connecting the first braking mechanism and the second braking mechanism drops, if the control unit sends an instruction to the differential pressure valve to increase the differential pressure, the control unit performs braking control to increase the hydraulic pressure generated by the second braking mechanism by driving a motor in the second braking mechanism.

In the brake control device, the first braking mechanism is an upstream mechanism that controls the hydraulic pressure of the brake fluid based on a braking request, and the second braking mechanism is an electric braking mechanism provided in a downstream mechanism that is connected to the upstream mechanism via a hydraulic circuit and adjusts the hydraulic pressure generated by the upstream mechanism and supplies it to a wheel cylinder, and the electric braking mechanism generates an electric braking force by pressing a braking member against a member to be braked that rotates integrally with the wheel by driving a motor.

FIG. 1 is a schematic diagram of an overall configuration of a brake device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the functional configuration of the brake control device and the like according to the embodiment. FIG. 3 is a diagram showing how the positional relationship between the host vehicle and an obstacle changes over time in the embodiment. FIG. 4 is a flowchart illustrating a first processing example of the embodiment. FIG. 5 is a flowchart illustrating a second processing example of the embodiment. FIG. 6 is a flowchart illustrating a third processing example of the embodiment. FIG. 7 is a flowchart illustrating a fourth processing example of the embodiment.

Embodiments of the brake control device and the like of the present invention will be described below with reference to the drawings. Note that the configurations of the embodiments described below and the actions and effects brought about by said configurations are merely examples, and the present invention is not limited to the contents described below.

First, the brake device to be controlled in this embodiment will be described. FIG. 1 is a schematic diagram of the overall configuration of the brake device in this embodiment. This brake device is installed, for example, in a general four-wheeled vehicle (host vehicle).

As shown in FIG. 1, the brake device includes a hydraulic brake 1 and an electric parking brake 2. The hydraulic brake 1 is capable of generating hydraulic braking force, which is a braking force applied by hydraulic pressure, to the wheels of the vehicle. The hydraulic brake 1 is configured to be capable of applying a braking force (friction braking torque) to both the front wheels 2FL, 2FR and the rear wheels 2RL, 2RR.

The electric parking brake 2 (EPB) is an electric parking brake that can generate a parking braking force separate from the hydraulic braking force by driving the EPB motor 60 (motor). The electric parking brake 2 is configured to apply a braking force only to the rear wheels 2RL and 2RR.

In the following, when it is necessary to distinguish between the braking force generated by the hydraulic brake 1 and the braking force generated by the electric parking brake 2, the former will be referred to as the hydraulic braking force and the latter as the parking braking force.

The hydraulic brake 1 includes a pressure generating unit 32, wheel cylinders 38FL, 38FR, 38RL, and 38RR (hereinafter, also referred to as "wheel cylinders 38" when no distinction is made), pressure adjusting units 34FL, 34FR, 34RL, and 34RR, and a reflux mechanism 37. The pressure generating unit 32 is a mechanism that generates pressure (hydraulic pressure) according to the operation of the brake pedal 31 by the driver of the vehicle. The wheel cylinders 38FL, 38FR, 38RL, and 38RR are mechanisms that apply braking force to the wheels 2FL, 2FR, 2RL, and 2RR by pressurizing friction braking members, respectively.

Pressure adjustment units 34FL, 34FR, 34RL, and 34RR are mechanisms that adjust the hydraulic pressure applied to wheel cylinders 38FL, 38FR, 38RL, and 38RR, respectively. The return mechanism 37 is a mechanism that returns the fluid (working fluid) that serves as the medium for generating hydraulic pressure to the upstream side (the pressure generating unit 32 side).

More specifically, the pressure generating unit 32 includes a master cylinder 32a and a reservoir tank 32b. The master cylinder 32a is pressed in with the operation (depression) of the brake pedal 31, and discharges the fluid refilled from the reservoir tank 32b to two discharge ports. These two discharge ports are connected to the front pressure adjustment unit 34FR and the front pressure adjustment unit 34FL, and the rear pressure adjustment unit 34RL and the rear pressure adjustment unit 34RR, respectively, via solenoid valves 33 (differential pressure valves) that can be electrically switched between an open state and a closed state. The solenoid valves 33 open and close under the control of the brake control device 100 (see FIG. 2), which will be described later. Specifically, the solenoid valves 33 are configured to be able to adjust the differential pressure between the inlet pressure and the outlet pressure, and are provided in the downstream mechanism 90 on the upstream mechanism 80 side.

In addition, pressure adjustment units 34FL, 34FR, 34RL, and 34RR each have solenoid valves 35 and 36 that can be electrically switched between an open state and a closed state. Solenoid valves 35 and 36 are provided between solenoid valve 33 and reservoir 41. Solenoid valve 35 is connected to solenoid valve 33, and solenoid valve 36 is connected to reservoir 41.

The solenoid valves 35 and 36 can be opened and closed under the control of the braking control device 100 (see Figure 2) to increase, maintain, or reduce the pressure generated in the wheel cylinder 38.

The reflux mechanism 37 includes a reservoir 41, a pump 39, and a pump motor 40 that rotates the front and rear pumps 39 to transport the fluid upstream. One reservoir 41 and one pump 39 are provided for each combination of pressure adjustment units 34FR and 34FL, and one for each combination of pressure adjustment units 34RL and 34RR.

The hydraulic brake 1 is also provided with a stroke sensor 51 that can detect the amount of operation (stroke) of the brake pedal 31.

An EPB motor 60 that is driven under the control of the brake control device 100 (see FIG. 2) is connected to each of the rear wheels 2RL and 2RR. The EPB motor 60 is driven to press a braking member toward a member to be braked that rotates integrally with the rear wheels 2RL and 2RR, thereby applying a braking force to the rear wheels 2RL and 2RR. Therefore, in this embodiment, hydraulic braking force by the wheel cylinders 38RL and 38RR and parking braking force by each EPB motor 60 can be generated separately for each of the rear wheels 2RL and 2RR.

Next, referring to FIG. 2, the functional configuration of the brake control device 100 and the like of this embodiment will be described. FIG. 2 is a block diagram showing the functional configuration of the brake control device 100 and the like of this embodiment. In addition to the hydraulic brake 1 and the electric parking brake 2, the vehicle on which the brake control device 100 is mounted is provided with an M/C (master cylinder) pressure sensor 3, a W/C (wheel cylinder) pressure sensor 4, an acceleration sensor 5, a wheel speed sensor 6, a temperature sensor 7, an EPB switch 8, and a surrounding conditions sensor 9, which are not shown in FIG. 1. They are electrically connected to the brake control device 100.

The M/C pressure sensor 3 detects the pressure generated in the master cylinder 32a (Figure 1) and outputs a signal related to the detected pressure. The W/C pressure sensor 4 is provided for each wheel cylinder 38, detects the pressure generated in the wheel cylinder 38, and outputs a signal related to the detected pressure.

The acceleration sensor 5 detects the acceleration in the longitudinal direction of the vehicle body and outputs a signal related to the detected acceleration. The wheel speed sensor 6 is provided for each of the wheels 2FL, 2FR, 2RL, and 2RR, detects the rotational speed of each wheel, and outputs a signal related to the detected rotational speed.

Temperature sensors 7 are provided for each of the wheels 2FL, 2FR, 2RL, and 2RR, detect the temperature of a specific part of each wheel, and output a signal related to the detected temperature. The EPB switch 8 is provided, for example, near the driver's seat, and outputs a signal related to the start of parking brake when operated by the driver, etc.

The surrounding condition sensor 9 detects the surrounding conditions and outputs a signal related to the detected information. The surrounding condition sensor 9 is, for example, a camera, an ultrasonic sensor, an infrared sensor, a radar sensor, etc.

The brake control device 100 controls the hydraulic brake 1 and the electric parking brake 2. The brake control device 100 is realized as part of a brake ECU (Electronic Control Unit) that has hardware similar to that of a normal computer device, such as a processor and memory. The brake control device 100 may be integrated with other parts of the brake ECU, or may be configured separately from the other parts.

As shown in FIG. 1, the upstream mechanism 80 is a collective term for multiple components related to controlling (increasing, maintaining, decreasing) the hydraulic pressure of the brake fluid in the master cylinder 32a. The downstream mechanism 90 is a collective term for multiple components connected to the upstream mechanism 80 via a hydraulic circuit and related to adjusting (increasing, maintaining, decreasing) the hydraulic pressure generated by the upstream mechanism 80 and supplying it to the wheel cylinder 38.

The braking control device 100 is realized, for example, by an ECU corresponding to the upstream mechanism 80 and an ECU corresponding to the downstream mechanism 90.

The braking control device 100 has the following functional components: an acquisition unit 110, a determination unit 120, a control unit 130, and a memory unit 140.

The storage unit 140 is composed of, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, etc. The storage unit 140 stores operation programs, data (maps, tables, functions, etc.) used in various calculations related to control, calculation results (including values during calculation), etc.

The acquisition unit 110 acquires various signals. The acquisition unit 110 acquires a braking request signal related to a braking operation by the driver, such as an operation for generating a hydraulic braking force in the hydraulic brake 1 (hydraulic brake operation) or an operation for setting a state in which a parking braking force can be generated (parking brake operation). This hydraulic brake operation is, for example, an operation (pressing) of the brake pedal 31 by the driver. The acquisition unit 110 detects a braking request signal related to a hydraulic brake operation based on, for example, the detection result of the stroke sensor 51, etc.

The parking brake operation is the operation of the EPB switch 8 located near the driver's seat. The acquisition unit 110 acquires, for example, a signal output in response to the operation of the EPB switch 8 as a braking request signal related to the parking brake operation. The acquisition unit 110 may acquire braking request signals (including electric parking brake drive request signals) from other systems, not limited to the braking operation by the driver as described above. An example of such a system is a control system that transmits a braking request signal based on signals from various sensors (e.g., M/C pressure sensor 3, W/C pressure sensor 4, acceleration sensor 5, wheel speed sensor 6, temperature sensor 7, EPB switch 8, stroke sensor 51, etc.).

The determination unit 120 executes various determinations. For example, during AEB control, the determination unit 120 determines whether or not at least one of the following first and second conditions is satisfied based on data acquired while the host vehicle is traveling (for example, host vehicle speed data, relative distance data between the host vehicle and an obstacle, etc.).
<First condition> A collision with an obstacle is unavoidable, and the time until the collision is within a predetermined time. <Second condition> The rate of change in the acceleration of the vehicle in the forward/rearward direction is equal to or greater than the threshold for collision judgment (a threshold value set in advance for collision judgment).

The first condition is a condition that may be satisfied when the host vehicle is about to collide with an obstacle.
The second condition is a condition that is satisfied when the host vehicle collides with an obstacle.

Specifically, there may be cases where the first condition is not satisfied and the vehicle collides with an obstacle. For example, during AEB control, it may be determined that the vehicle's braking control can avoid a collision with an obstacle until halfway through, but then the friction between the road surface and the vehicle's wheels decreases due to a wet road surface, etc., causing the braking force to decrease. Another example is when an obstacle suddenly appears from a blind spot.

Therefore, by determining whether or not at least one of the first and second conditions is satisfied, if the first condition is satisfied, it is possible to recognize the state immediately before a collision, and even if the first condition is not satisfied, it is possible to recognize the state immediately after a collision if the second condition is satisfied.

The control unit 130 is realized as a result of the CPU (Central Processing Unit) of the braking control device 100 executing various programs stored in the memory unit 140. Note that some or all of this functional configuration may be realized by a dedicated circuit, etc.

The control unit 130 executes various controls. For example, the control unit 130 controls the hydraulic brake 1 and the electric parking brake 2.

In addition, for example, in AEB control, the control unit 130 performs braking control by controlling only the upstream mechanism without controlling the downstream mechanism 90.

However, in this case, if the braking control is continued, for example, if the vehicle collides with an obstacle and the upstream mechanism 80 fails (for example, if an ECU or actuator related to the upstream mechanism 80 fails), the braking force may decrease significantly and the damage may become greater. Therefore, the following describes a technology that can suppress the decrease in braking force when a vehicle equipped with two or more braking mechanisms collides with an obstacle.

When the control unit 130 is performing braking control using the upstream mechanism 80 without using the downstream mechanism 90, if the determination unit 120 determines that at least one of the first condition and the second condition is satisfied, the control unit 130 thereafter performs braking control using both the upstream mechanism 80 and the downstream mechanism 90.

The processing of the determination unit 120 and the control unit 130 will be described with reference to FIG. 3. FIG. 3 is a diagram showing how the positional relationship between the vehicle and an obstacle changes over time in an embodiment.

In (a), the host vehicle C detects an obstacle O (such as another vehicle) ahead based on signals from the surroundings sensor 9, and starts AEB control. In AEB control, the control unit 130 performs braking control using the upstream mechanism 80 without using the downstream mechanism 90.

Next, in (b), it is assumed that the determination unit 120 determines that the first condition is satisfied. If this is the case, the control unit 130 will then perform braking control using both the upstream mechanism 80 and the downstream mechanism 90.

In addition, suppose that in (b) the first condition is not satisfied, and in (c) the determination unit 120 determines that the vehicle C collides with an obstacle O and the second condition is satisfied. In this case, the control unit 130 thereafter performs braking control using both the upstream mechanism 80 and the downstream mechanism 90.

After (b) and (c), in (d), the upstream mechanism 80 fails. However, even in this case, braking control can be continued by the downstream mechanism 90, which is not failing. Therefore, the decrease in braking force can be suppressed. Note that suppression here does not only mean making it zero, but also means making it less than in the case of the conventional technology.

Specific processing examples will be described below with reference to Figures 4 to 7. Figure 4 is a flowchart showing a first processing example of the embodiment. Here, when the control unit 130 uses the upstream mechanism 80 without using the downstream mechanism 90 to perform braking control based on the target wheel pressure, which is the target value of the hydraulic pressure in the wheel cylinder 38, and the determination unit 120 determines that at least one of the first condition and the second condition is satisfied, the control unit 130 uses the upstream mechanism 80 to perform braking control to generate hydraulic pressure of the target wheel pressure by the upstream mechanism 80, and also uses the downstream mechanism 90 to perform braking control to generate hydraulic pressure of the target wheel pressure by the downstream mechanism 90.

First, in step S41, the control unit 130 performs braking control using the upstream mechanism 80 to generate hydraulic pressure equal to the target wheel pressure.

Next, in step S42, the determination unit 120 determines whether a collision with an obstacle is unavoidable and the time until the collision is within a predetermined time, that is, whether the first condition is satisfied. If the answer is Yes, the process proceeds to step S44, and if the answer is No, the process proceeds to step S43.

In step S43, the determination unit 120 determines whether the rate of change in the acceleration in the longitudinal direction of the vehicle is equal to or greater than the collision determination threshold, i.e., whether the second condition is satisfied. If the answer is Yes, the process proceeds to step S44, and if the answer is No, the process returns to step S42.

Next, in step S44, the control unit 130 uses the downstream mechanism 90 to perform braking control to generate hydraulic pressure equal to the target wheel pressure through the downstream mechanism 90.

For example, if the target wheel pressure is 3 MPa (megapascals), in steps S41 and S44, the upstream mechanism 80 and downstream mechanism 90 each generate a hydraulic pressure of 3 MPa, which is the target wheel pressure, so that a total hydraulic pressure of 6 MPa can be generated in the wheel cylinder 38. Therefore, even if the upstream mechanism 80 subsequently fails, the hydraulic pressure of 3 MPa generated by at least the downstream mechanism 90 can be continued, so that a decrease in braking force can be suppressed.

Next, FIG. 5 is a flowchart showing a second processing example of the embodiment. Here, when the control unit 130 uses the upstream mechanism 80 without using the downstream mechanism 90 to perform braking control based on the target wheel pressure, if the determination unit 120 determines that at least one of the first condition and the second condition is satisfied, the control unit 130 uses the upstream mechanism 80 to perform braking control to generate hydraulic pressure of the target wheel pressure by the upstream mechanism 80. Furthermore, when the detected hydraulic pressure detected by the hydraulic pressure sensor that detects the hydraulic pressure of the hydraulic circuit is lower than the target wheel pressure, the control unit 130 uses the downstream mechanism 90 to perform braking control to generate hydraulic pressure of the difference between the target wheel pressure and the detected hydraulic pressure by the downstream mechanism 90.

First, in step S51, the control unit 130 uses the upstream mechanism 80 to perform braking control in which the upstream mechanism 80 generates hydraulic pressure equal to the target wheel pressure. Steps S52 and S53 are the same as steps S42 and S43 in FIG. 4.

Next, in step S54, the control unit 130 determines whether the detected fluid pressure is lower than the target wheel pressure. If the answer is Yes, the control proceeds to step S55, and if the answer is No, the control returns to step S54.

In step S55, the control unit 130 performs braking control using the downstream mechanism 90 to generate a hydraulic pressure that is the difference between the target wheel pressure and the detected hydraulic pressure.

For example, if the target wheel pressure is 3 MPa, first, in step S51, the upstream mechanism 80 generates a hydraulic pressure of 3 MPa, which is the target wheel pressure. If the upstream mechanism 80 subsequently fails and the hydraulic pressure generated by the upstream mechanism 80 becomes smaller, the detected hydraulic pressure becomes smaller than the target wheel pressure (Yes in step S54), and in step S55, the downstream mechanism 90 generates a hydraulic pressure that is the difference between the target wheel pressure and the detected hydraulic pressure. Therefore, the hydraulic pressure of 3 MPa can be maintained in the wheel cylinder 38, and a decrease in braking force can be suppressed.

Next, FIG. 6 is a flowchart showing a third processing example of the embodiment. Here, when the control unit 130 uses the upstream mechanism 80 without using the downstream mechanism 90 to perform braking control based on the target wheel pressure, if the determination unit 120 determines that at least one of the first condition and the second condition is satisfied, the control unit 130 uses the upstream mechanism 80 to perform braking control that generates hydraulic pressure at the target wheel pressure by the upstream mechanism 80. At the same time, the control unit 130 uses the downstream mechanism 90 to send an instruction to the solenoid valve 33 (differential pressure valve) to maintain the differential pressure (the difference between the hydraulic pressure on the wheel cylinder 38 side and the lower hydraulic pressure on the master cylinder 32a side) at the target wheel pressure.

First, in step S61, the control unit 130 uses the upstream mechanism 80 to perform braking control to generate hydraulic pressure equal to the target wheel pressure by the upstream mechanism 80. Steps S62 and S63 are similar to steps S42 and S43 in FIG. 4.

Next, in step S64, the control unit 130 instructs the solenoid valve 33 (differential pressure valve) to maintain the differential pressure at the target wheel pressure.

For example, if the target wheel pressure is 3 MPa, first, in step S61, the upstream mechanism 80 generates a hydraulic pressure of 3 MPa, which is the target wheel pressure. Then, in step S64, an instruction is sent to the solenoid valve 33 (differential pressure valve) to maintain the differential pressure at the target wheel pressure. As a result, even if the upstream mechanism 80 subsequently fails and the hydraulic pressure generated by the upstream mechanism 80 decreases, the hydraulic pressure of 3 MPa can be continued in the wheel cylinder 38 by maintaining the differential pressure by the solenoid valve 33 (differential pressure valve), so that a decrease in braking force can be suppressed.

However, with this method, even if the target wheel pressure is increased from 3 MPa to 4 MPa after a failure of the upstream mechanism 80, the hydraulic pressure in the wheel cylinder 38 remains at 3 MPa. Therefore, this point is improved by the fourth processing example shown in Figure 7.

Figure 7 is a flowchart showing a fourth processing example of the embodiment. Here, assuming the case of Figure 6, after sending an instruction to the solenoid valve 33, when the control unit 130 detects a failure of the upstream mechanism 80 or when the detected hydraulic pressure drops, if it sends an instruction to the solenoid valve 33 to increase the differential pressure, it performs braking control to drive the pump motor 40 (Figure 1) (motor) in the downstream mechanism 90 to increase the hydraulic pressure generated by the downstream mechanism 90. Note that the detection of a failure of the upstream mechanism 80 is realized, for example, by sending the result of the self-failure detection by the upstream mechanism 80 to the downstream mechanism 90 by communication or the like. In addition, when communication from the upstream mechanism 80 is interrupted, it may be determined that the ECU of the upstream mechanism 80 is broken.

First, steps S71 to S74 are the same as steps S61 to S64 in FIG. 6. After step S74, in step S75, the control unit 130 determines whether a failure of the upstream mechanism 80 has been detected. If the result is Yes, the process proceeds to step S77. If the result is No, the process proceeds to step S76.

In step S76, the control unit 130 determines whether the detected fluid pressure has decreased, and if Yes, proceeds to step S77, and if No, returns to step S75.

In step S77, the control unit 130 sends an instruction to the solenoid valve 33 to increase the pressure difference.

In this case, in step S78, the control unit 130 performs braking control to drive the pump motor 40 (Figure 1) in the downstream mechanism 90 to increase the hydraulic pressure generated by the downstream mechanism 90.

For example, if the target wheel pressure is 3 MPa, first, in step S71, the upstream mechanism 80 generates a hydraulic pressure of 3 MPa, which is the target wheel pressure. Then, in step S74, an instruction is sent to the solenoid valve 33 (differential pressure valve) to maintain the differential pressure at the target wheel pressure. As a result, even if the upstream mechanism 80 subsequently fails and the hydraulic pressure generated by the upstream mechanism 80 decreases, the hydraulic pressure of 3 MPa can be continued in the wheel cylinder 38 by maintaining the differential pressure by the solenoid valve 33 (differential pressure valve), so that a decrease in braking force can be suppressed.

Furthermore, if the target wheel pressure is to be increased from 3 MPa to 4 MPa, for example, in step S77, an instruction is sent to the solenoid valve 33 to increase the differential pressure (increase from 3 MPa to 4 MPa), and in step S78, the pump motor 40 (Figure 1) is driven to increase the hydraulic pressure generated by the downstream mechanism 90. This allows the hydraulic pressure in the wheel cylinder 38 to be increased from 3 MPa to 4 MPa.

In this way, according to the brake control device 100 of this embodiment, for example, when braking control is performed using only the upstream mechanism 80 during AEB control, if at least one of the first and second conditions is satisfied, braking control is also performed using the downstream mechanism 90. This makes it possible to suppress a decrease in braking force when a host vehicle equipped with two or more braking mechanisms collides with an obstacle.

More specifically, the actions and effects described above can be achieved using Figures 4 to 7.

(Modification)
Next, a modified example will be described. For example, the first braking mechanism may be the upstream mechanism 80, and the second braking mechanism may be the electric parking brake 2. In that case, during AEB control, the control unit 130 first executes braking control by controlling only the upstream mechanism 80 without controlling the electric parking brake 2.

Then, when the determination unit 120 determines that at least one of the first condition and the second condition is satisfied, the control unit 130 performs braking control using both the upstream mechanism 80 and the electric parking brake 2 thereafter.

The target vehicle may also be an autonomous vehicle. In this case, the conditions for switching from braking control using one braking mechanism to braking control using two or more braking mechanisms are the same as when the target vehicle is not an autonomous vehicle.

Although the embodiments of the present invention have been described above, the above-mentioned embodiments are merely examples and are not intended to limit the scope of the invention. The novel embodiments described above can be implemented in various forms, and various omissions, substitutions, or modifications can be made without departing from the gist of the invention. Furthermore, the above-mentioned embodiments and their modifications are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

For example, the overall configuration in FIG. 1 is an example, and other configurations may be used as long as the present invention can be realized.

1...hydraulic brake, 2...electric parking brake, 3...M/C pressure sensor, 4...W/C pressure sensor, 5...acceleration sensor, 6...wheel speed sensor, 7...temperature sensor, 8...EPB switch, 51...stroke sensor, 60...EPB motor, 100...braking control device, 110...acquisition unit, 120...determination unit, 130...control unit, 140...storage unit

Claims (7)

a determination unit that determines whether or not at least one of a first condition that a collision with an obstacle is unavoidable and the time until the collision is within a predetermined time and a second condition that a rate of change in acceleration in a forward/rearward direction of the host vehicle is equal to or greater than a collision determination threshold is satisfied, based on data acquired during the traveling of the host vehicle;
a control unit that performs braking control using both the first braking mechanism and the second braking mechanism when the judgment unit determines that at least one of the first condition and the second condition is satisfied when braking control is performed using the first braking mechanism without using the second braking mechanism, of a first braking mechanism and a second braking mechanism provided on the vehicle. the first braking mechanism is an upstream mechanism that controls a hydraulic pressure of brake fluid based on a braking request;
2. The brake control device according to claim 1, wherein the second braking mechanism is a downstream mechanism that is connected to the upstream mechanism via a hydraulic circuit and that adjusts the hydraulic pressure generated by the upstream mechanism and supplies the adjusted hydraulic pressure to a wheel cylinder. The control unit is
When the second braking mechanism is not used and the first braking mechanism is used to perform braking control based on a target wheel pressure, which is a target value of the hydraulic pressure in a wheel cylinder of the second braking mechanism, and when the determination unit determines that at least one of the first condition and the second condition is satisfied,
performing braking control by using the first braking mechanism to generate a hydraulic pressure of the target wheel pressure by the first braking mechanism;
3. The brake control device according to claim 1, further comprising: a brake control unit for performing brake control by using the second brake mechanism to generate a hydraulic pressure equal to the target wheel pressure by the second brake mechanism. The control unit is
When the second braking mechanism is not used and the first braking mechanism is used to perform braking control based on a target wheel pressure, which is a target value of the hydraulic pressure in a wheel cylinder of the second braking mechanism, and when the determination unit determines that at least one of the first condition and the second condition is satisfied,
performing braking control by using the first braking mechanism to generate a hydraulic pressure of the target wheel pressure by the first braking mechanism;
When a detected hydraulic pressure detected by a hydraulic pressure sensor that detects a hydraulic pressure in a hydraulic circuit connecting the first braking mechanism and the second braking mechanism is smaller than the target wheel pressure,
3. The brake control device according to claim 1, further comprising: a brake control unit for performing brake control by using the second brake mechanism to generate a hydraulic pressure equal to a difference between the target wheel pressure and the detected hydraulic pressure by the second brake mechanism. the second braking mechanism further includes a differential pressure valve provided in a portion adjacent to the first braking mechanism;
The control unit is
When the second braking mechanism is not used and the first braking mechanism is used to perform braking control based on a target wheel pressure, which is a target value of the hydraulic pressure in a wheel cylinder of the second braking mechanism, and when the determination unit determines that at least one of the first condition and the second condition is satisfied,
performing braking control by using the first braking mechanism to generate a hydraulic pressure of the target wheel pressure by the first braking mechanism;
3. The brake control device according to claim 1, further comprising: a second brake mechanism that outputs a command to the differential pressure valve to maintain a differential pressure between a hydraulic pressure on the wheel cylinder side and a lower hydraulic pressure on the first brake mechanism side at the target wheel pressure. The control unit is
When a failure of the first braking mechanism is detected after the instruction is sent to the differential pressure valve, or when a detected hydraulic pressure detected by a hydraulic pressure sensor that detects a hydraulic pressure in a hydraulic circuit connecting the first braking mechanism and the second braking mechanism is reduced,
6. The brake control device according to claim 5, wherein when an instruction is sent to the differential pressure valve to increase the differential pressure, a brake control is performed in which a motor in the second brake mechanism is driven to increase the hydraulic pressure generated by the second brake mechanism. the first braking mechanism is an upstream mechanism that controls a hydraulic pressure of brake fluid based on a braking request;
2. The brake control device according to claim 1, wherein the second braking mechanism is an electric braking mechanism provided in a downstream mechanism that is connected to the upstream mechanism via a hydraulic circuit and that adjusts the hydraulic pressure generated by the upstream mechanism and supplies it to a wheel cylinder, and the electric braking mechanism generates an electric braking force by pressing a braking member toward a braked member that rotates integrally with the wheel by driving a motor.

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