Braking control device

Abstract

To prevent a free running distance in the event that any of two or more braking mechanisms of a vehicle malfunctions.SOLUTION: A braking control device of the present invention includes: a determination unit that, based on data acquired during traveling of a host vehicle, determines whether at least one of a first condition that a deceleration is equal to or greater than a deceleration threshold value and a second condition that a deceleration gradient is equal to or greater than a deceleration gradient threshold value is satisfied; and a control unit that executes braking control using both a first braking mechanism and a second braking mechanism of the host vehicle if the determination unit determines that at least one of the first condition and the second condition is satisfied when braking control is performed using, of the first braking mechanism and the second braking mechanism, the first braking mechanism without using the second braking mechanism.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a brake control device. [Background technology]

[0002] Conventionally, vehicles (such as passenger cars) often include a plurality of braking mechanisms, such as an upstream mechanism (a mechanism on the master cylinder side) and a downstream mechanism (a mechanism on the wheel cylinder side).

[0003] In such vehicles, whether they are manually driven or automatically driven, braking control may be performed by only one of the multiple braking mechanisms (e.g., an upstream mechanism) for the purpose of, for example, reducing power consumption or suppressing deterioration of the braking mechanism.

[0004] Furthermore, vehicle braking control is generally provided with a fail-safe function. For example, if a failure occurs in the upstream mechanism while braking control is being performed only by the upstream mechanism, the braking control is automatically switched to the downstream mechanism. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Publication No. 52-096033 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above-mentioned conventional technology, the braking force decreases from when the upstream mechanism fails until the downstream mechanism starts to control the brakes. In particular, when the deceleration or deceleration gradient is large, the reduction in braking force increases the free running distance, so there is room for improvement.

[0007] Therefore, the present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a braking control device that can reduce the free running distance in the event of a failure of a braking mechanism for a vehicle equipped with two or more braking mechanisms. [Means for solving the problem]

[0008] The braking control device of the present invention includes a judgment unit that judges whether or not at least one of a first condition, that the deceleration is equal to or greater than a deceleration threshold, and a second condition, that the deceleration gradient is equal to or greater than a deceleration gradient threshold, is satisfied based on data acquired while the host vehicle is traveling, and a control unit that performs braking control using both the first braking mechanism and the second braking mechanism when the judgment unit judges 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 host vehicle.

[0009] In addition, in the braking 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 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.

[0010] In addition, in the braking control device, when the control unit is performing braking control using the first braking mechanism without using the second braking mechanism based on a target wheel pressure, which is a target value of the hydraulic pressure in the wheel cylinder of the second braking mechanism, and the judgment unit determines that at least one of the first condition and the second condition is satisfied, the control unit performs braking control using the first braking mechanism to generate hydraulic pressure of the target wheel pressure by the first braking mechanism, and when the detected hydraulic pressure detected by a hydraulic pressure sensor that detects the hydraulic pressure in a hydraulic circuit connecting the first braking mechanism and the second braking mechanism is smaller than the target wheel pressure, the control unit performs braking control using the second braking mechanism to generate hydraulic pressure that is the difference between the target wheel pressure and the detected hydraulic pressure by the second braking mechanism.

[0011] In addition, in the braking control device, the second braking mechanism further includes a differential pressure valve provided in a portion adjacent to the first braking mechanism, and when the control unit is not using the second braking mechanism but is using the first braking mechanism to perform braking control based on a target wheel pressure, which is a target value of the hydraulic pressure in the wheel cylinder of the second braking mechanism, and when the judgment unit determines that at least one of the first condition and the second condition is satisfied, the control unit uses the first braking mechanism to perform braking control to generate hydraulic pressure of the target wheel pressure by the first braking mechanism, and sends an instruction to the differential pressure valve using the second braking mechanism to maintain the differential pressure between the hydraulic pressure on the wheel cylinder side and the lower hydraulic pressure on the first braking mechanism side at the target wheel pressure.

[0012] Furthermore, in the braking control device, after sending the instruction to the differential pressure valve, when the control unit detects a failure of the first braking mechanism or when the detected hydraulic pressure detected by a hydraulic pressure sensor that detects the hydraulic pressure in a 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 by driving a motor in the second braking mechanism to increase the hydraulic pressure generated by the second braking mechanism.

[0013] In addition, in the braking control device, a third braking mechanism provided on the vehicle is an electric braking mechanism that generates an electric braking force by driving a motor to press a braking member toward a braked member that rotates integrally with the wheel, and when the control unit detects a failure of at least one of the first braking mechanism and the second braking mechanism while performing braking control using both the first braking mechanism and the second braking mechanism, the control unit performs braking control using the third braking mechanism.

[0014] In addition, in the braking control device, a third braking mechanism provided on the vehicle is an electric braking mechanism that generates an electric braking force by driving a motor to press a braking member toward a braked member that rotates integrally with the wheel, and when the control unit performs braking control using both the first braking mechanism and the second braking mechanism, it also performs braking control using the third braking mechanism. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of an overall configuration of a brake device according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing a functional configuration of the brake control device and the like according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing how braking control of the host vehicle changes over time in the embodiment. [Figure 4] FIG. 4 is a flowchart illustrating a first processing example of the embodiment. [Diagram 5] FIG. 5 is a flowchart illustrating a second processing example of the embodiment. [Figure 6] FIG. 6 is a flowchart illustrating a third processing example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the brake control device and the like of the present invention will be described with reference to the drawings. Note that the configurations of the embodiments described below and the actions and effects brought about by the configurations are examples, and the present invention is not limited to the contents described below.

[0017] First, a brake device to be controlled in this embodiment will be described. Fig. 1 is a schematic overall configuration diagram of the brake device of this embodiment. This brake device is provided in, for example, a general four-wheeled vehicle (host vehicle).

[0018] As shown in Fig. 1, the brake device includes a hydraulic brake 1 and an electric parking brake 2 (electric braking mechanism: third braking mechanism). The hydraulic brake 1 is capable of generating hydraulic braking force, which is a braking force by hydraulic pressure, on the wheels of the vehicle. The hydraulic brake 1 is configured to be capable of applying braking force (friction braking torque) to both the wheels 2FL, 2FR, which are the front wheels, and the wheels 2RL, 2RR, which are the rear wheels.

[0019] The electric parking brake 2 (EPB) is an electric parking brake that can generate an electric braking force different from a hydraulic braking force by driving an EPB motor 60 (motor). The electric parking brake 2 is configured to be able to apply a braking force only to the wheels 2RL and 2RR, which are the rear wheels.

[0020] 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 electric braking force.

[0021] 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 forces to the wheels 2FL, 2FR, 2RL, and 2RR by pressurizing friction braking members, respectively.

[0022] The pressure adjustment units 34FL, 34FR, 34RL, and 34RR are mechanisms for adjusting the hydraulic pressure applied to the wheel cylinders 38FL, 38FR, 38RL, and 38RR, respectively. The return mechanism 37 is a mechanism for returning the fluid (working fluid) serving as a medium for generating hydraulic pressure to the upstream side (the pressure generating unit 32 side).

[0023] More specifically, the pressure generating unit 32 includes a master cylinder 32a and a reservoir tank 32b. The master cylinder 32a is pressed in response to 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 adjusting unit 34FR and the front pressure adjusting unit 34FL and the rear pressure adjusting unit 34RL and the rear pressure adjusting unit 34RR 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 a braking control device 100 (see FIG. 2) 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 at a portion on the upstream mechanism 80 side.

[0024] Furthermore, 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.

[0025] The solenoid valves 35 and 36 are capable of increasing, maintaining, or decreasing the pressure generated in the wheel cylinder 38 by opening and closing under the control of the braking control device 100 (see FIG. 2).

[0026] 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 each combination of pressure adjustment units 34RL and 34RR.

[0027] In addition, the hydraulic brake 1 is provided with a stroke sensor 51 capable of detecting the amount of operation (stroke) of the brake pedal 31.

[0028] Further, 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 electric braking force by each EPB motor 60 can be generated separately for each of the rear wheels 2RL and 2RR.

[0029] Next, the functional configuration of the brake control device 100 of this embodiment will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the functional configuration of the brake control device 100 of this embodiment. In addition to a hydraulic brake 1 and an electric parking brake 2, a vehicle equipped with the brake control device 100 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 condition sensor 9, all of which are not shown in Fig. 1. These are electrically connected to the brake control device 100.

[0030] The M / C pressure sensor 3 detects the pressure generated in the master cylinder 32a (FIG. 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.

[0031] 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 rotation speed of each wheel, and outputs a signal related to the detected rotation speed.

[0032] The temperature sensor 7 is provided for each of the wheels 2FL, 2FR, 2RL, and 2RR, detects the temperature of a predetermined part of each wheel, and outputs 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 starting the parking brake when operated by the driver or the like.

[0033] The surrounding condition sensor 9 detects the surrounding condition 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, or the like.

[0034] The braking control device 100 controls a hydraulic brake 1 and an electric parking brake 2. The braking control device 100 is realized as a part of a brake ECU (Electronic Control Unit) equipped with hardware similar to that of a normal computer device, such as a processor and a memory. The braking control device 100 may be integrated with other parts of the brake ECU, or may be configured separately from the other parts.

[0035] 1, the upstream mechanism 80 (first braking mechanism) is a collective term for multiple components related to controlling (increasing, holding, decreasing) the hydraulic pressure of the brake fluid in the master cylinder 32a. The downstream mechanism 90 (second braking mechanism) is a collective term for multiple components connected to the upstream mechanism 80 via a hydraulic circuit and related to adjusting (increasing, holding, decreasing) the hydraulic pressure generated by the upstream mechanism 80 and supplying it to the wheel cylinder 38.

[0036] The braking control device 100 is realized by, for example, an ECU corresponding to the upstream mechanism 80 and an ECU corresponding to the downstream mechanism 90.

[0037] The braking control device 100 includes, as its functional components, an acquisition unit 110, a determination unit 120, a control unit 130, and a storage unit 140.

[0038] 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.

[0039] 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 an electric 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 the braking request signal related to the hydraulic brake operation based on, for example, a detection result of the stroke sensor 51 or the like.

[0040] The parking brake operation is the operation of the EPB switch 8 provided 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 a braking request signal (including an electric parking brake drive request signal) from another system, not limited to the braking operation by the driver as described above. An example of such a system may be a control system that transmits a braking request signal based on signals from various sensors (e.g., the M / C pressure sensor 3, the W / C pressure sensor 4, the acceleration sensor 5, the wheel speed sensor 6, the temperature sensor 7, the EPB switch 8, the stroke sensor 51, etc.).

[0041] The determination unit 120 executes various determinations. For example, during braking control in autonomous driving, 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, acceleration data, wheel speed data, etc.). <Condition 1> Deceleration is equal to or greater than the deceleration threshold <Second condition> The deceleration gradient is equal to or greater than the deceleration gradient threshold.

[0042] The control unit 130 is realized as a result of a CPU (Central Processing Unit) of the braking control device 100 executing various programs stored in the storage unit 140. Note that a part or all of the functional configuration may be realized by a dedicated circuit or the like.

[0043] The control unit 130 executes various controls. For example, the control unit 130 controls the hydraulic brake 1 and the electric parking brake 2.

[0044] Furthermore, for example, in braking control during automatic driving, the control unit 130 executes braking control by controlling only the upstream mechanism 80 without controlling the downstream mechanism 90.

[0045] However, if the braking control is continued as in the conventional technology, when a failure (failure of the actuator or ECU) occurs in the upstream mechanism 80, the braking force will decrease from the time the failure occurs in the upstream mechanism 80 to the start of braking control in the downstream mechanism 90 when the control is automatically switched to that in the downstream mechanism 90. In particular, when the deceleration or deceleration gradient is large, the reduction in braking force increases the free running distance, so there is room for improvement. Therefore, hereinafter, a technology capable of suppressing the free running distance when a braking mechanism fails for a vehicle equipped with two or more braking mechanisms will be described.

[0046] When the control unit 130 is performing braking control using the upstream mechanism 80 without using the downstream mechanism 90, if the judgment 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.

[0047] 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 braking control of the host vehicle changes over time in the embodiment.

[0048] In (a), the host vehicle C satisfies at least one of the first condition and the second condition, and the control unit 130 uses both the upstream mechanism 80 and the downstream mechanism 90 to perform braking control.

[0049] Next, in (b), it is assumed that the upstream mechanism 80 fails. However, even in this case, braking control can be continued by the downstream mechanism 90 that is not failing. Therefore, it is possible to suppress the decrease in braking force. Note that suppression here does not only mean making it zero, but also includes the meaning of making it less than in the case of the conventional technology.

[0050] A specific processing example will be described below with reference to FIGS.

[0051] (First processing example) 4 is a flowchart showing a first processing example of the embodiment. Here, when the control unit 130 performs braking control based on the target wheel pressure 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 performs braking control using the upstream mechanism 80 to generate hydraulic pressure of the target wheel pressure by the upstream mechanism 80. Furthermore, when the detected hydraulic pressure detected by a hydraulic pressure sensor that detects the hydraulic pressure of the hydraulic circuit is lower than the target wheel pressure, the control unit 130 performs braking control using the downstream mechanism 90 to generate hydraulic pressure of the difference between the target wheel pressure and the detected hydraulic pressure by the downstream mechanism 90.

[0052] First, in step S41, the control unit 130 uses the upstream mechanism 80 to perform braking control in which the upstream mechanism 80 generates a hydraulic pressure equal to a target wheel pressure.

[0053] Next, in step S42, the determination unit 120 determines whether the deceleration is equal to or greater than the deceleration threshold, that is, whether the first condition is satisfied. If Yes, the process proceeds to step S44, and if No, the process proceeds to step S43.

[0054] In step S43, the determination unit 120 determines whether the deceleration gradient is equal to or greater than the deceleration gradient threshold, that is, whether the second condition is satisfied. If Yes, the process proceeds to step S44, and if No, the process returns to step S42.

[0055] In step S44, the control unit 130 determines whether the detected fluid pressure is lower than the target wheel pressure, and if Yes, the process proceeds to step S45, and if No, the process returns to step S44.

[0056] In step S45, the control unit 130 uses the downstream mechanism 90 to perform braking control in which the downstream mechanism 90 generates a hydraulic pressure that is the difference between the target wheel pressure and the detected hydraulic pressure.

[0057] For example, if the target wheel pressure is 3 MPa, first, in step S41, 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 S44), and in step S45, the downstream mechanism 90 generates a hydraulic pressure that is the difference between the target wheel pressure and the detected hydraulic pressure. Therefore, even if a failure occurs in the upstream mechanism 80, the hydraulic pressure of 3 MPa can be continued in the wheel cylinder 38, and a decrease in braking force can be suppressed.

[0058] (Second processing example) Next, Fig. 5 is a flowchart showing a second processing example of the embodiment. Here, when the control unit 130 performs braking control based on the target wheel pressure 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 performs braking control using the upstream mechanism 80 to generate hydraulic pressure of 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.

[0059] First, in step S51, the control unit 130 uses the upstream mechanism 80 to perform braking control for generating a hydraulic pressure equal to a target wheel pressure by the upstream mechanism 80. Steps S52 and S53 are similar to steps S42 and S43 in FIG.

[0060] Next, in step S54, the control unit 130 sends an instruction to the solenoid valve 33 (differential pressure valve) to maintain the differential pressure at the target wheel pressure.

[0061] 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. Then, in step S54, 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 breaks down and the hydraulic pressure generated by the upstream mechanism 80 becomes smaller, 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.

[0062] 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 third processing example shown in FIG.

[0063] (Third processing example) Fig. 6 is a flowchart showing a third processing example of the embodiment. Here, assuming the case of Fig. 5, when the control unit 130 detects a failure of the upstream mechanism 80 after sending an instruction to the solenoid valve 33 or when the detected hydraulic pressure drops, and sends an instruction to the solenoid valve 33 to increase the differential pressure, the control unit 130 performs braking control to drive the pump motor 40 (Fig. 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 a result of the self-failure detection by the upstream mechanism 80 to the downstream mechanism 90 by communication or the like. Also, when communication from the upstream mechanism 80 is interrupted, it may be determined that the ECU of the upstream mechanism 80 is broken.

[0064] First, steps S61 to S64 are the same as steps S51 to S54 in Fig. 5. After step S64, in step S65, control unit 130 determines whether or not a failure of upstream mechanism 80 has been detected, and if Yes, proceeds to step S67, and if No, proceeds to step S66.

[0065] In step S66, the control unit 130 determines whether or not the detected fluid pressure has decreased, and if Yes, the process proceeds to step S67, and if No, the process returns to step S65.

[0066] In step S67, the control unit 130 sends an instruction to the solenoid valve 33 to increase the pressure difference.

[0067] In this case, in step S68, the control unit 130 performs braking control to increase the hydraulic pressure generated by the downstream mechanism 90 by driving the pump motor 40 (FIG. 1) in the downstream mechanism 90.

[0068] 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 breaks down 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.

[0069] Further thereafter, for example, when the target wheel pressure is to be increased from 3 MPa to 4 MPa, a command is sent to the solenoid valve 33 in step S67 to increase the differential pressure (increase from 3 MPa to 4 MPa), and in step S68 the pump motor 40 (FIG. 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.

[0070] (Fourth Processing Example) Next, a fourth processing example will be described. In the fourth processing example, when the control unit 130 detects a failure in at least one of the upstream mechanism 80 and the downstream mechanism 90 while performing braking control using both the upstream mechanism 80 and the downstream mechanism 90 in the first to third processing examples, the control unit 130 performs braking control using the electric parking brake 2.

[0071] As a result, in the first to third process examples, when braking control is performed using both the upstream mechanism 80 and the downstream mechanism 90, even if a failure is detected in at least one of the upstream mechanism 80 and the downstream mechanism 90, the reduction in braking force can be further suppressed by using the electric parking brake 2. On the other hand, in normal braking control (braking control when neither the first condition nor the second condition is satisfied), braking control is performed using only the upstream mechanism 80 out of the multiple braking mechanisms, thereby suppressing power consumption and deterioration of the braking mechanisms.

[0072] (Fifth Processing Example) Next, a fifth processing example will be described. In the fifth processing example, when the control unit 130 performs braking control using both the upstream mechanism 80 and the downstream mechanism 90 in the first to third processing examples, the control unit 130 also performs braking control using the electric parking brake 2.

[0073] As a result, in the first to third processing examples, when braking control is performed using both the upstream mechanism 80 and the downstream mechanism 90, the electric parking brake 2 is also used for braking control, that is, the redundancy of the braking control is increased from duplex to triplex, thereby further suppressing the decrease in braking force.

[0074] In that case, for example, if the system is capable of independently pressurizing the front and rear wheels by the upstream mechanism 80, the hydraulic braking force for the rear wheels can be reduced by the amount of electric braking force applied by the electric parking brake 2.

[0075] Also, for example, in a system in which the upstream mechanism 80 cannot independently pressurize the front and rear wheels (i.e., four wheels are pressurized equally), the total of the hydraulic braking force and the electric braking force may be controlled to be an appropriate value. In that case, the rear wheels, which generate both the hydraulic braking force and the electric braking force, may be over-pressurized and cause wheel slip. Therefore, as a countermeasure, for example, the upstream mechanism 80 or the electric parking brake 2 may reduce the pressure of the rear wheels in response to wheel slip (ABS (Antilock Brake System) control).

[0076] In this way, according to the brake control device 100 of this embodiment, when brake control is being performed using only the upstream mechanism 80, if at least one of the first condition and the second condition is satisfied, brake control is also performed using the downstream mechanism 90. This makes it possible to reduce the free running distance when a brake mechanism fails for a vehicle equipped with two or more brake mechanisms.

[0077] More specifically, the actions and effects described in the first to fifth processing examples can be achieved.

[0078] Although the embodiment of the present invention has been described above, the above-mentioned embodiment is merely an example and is not intended to limit the scope of the invention. The above-mentioned novel embodiment can be implemented in various forms, and various omissions, substitutions, or modifications can be made without departing from the gist of the invention. In addition, the above-mentioned embodiment and its modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0079] For example, the overall configuration in FIG. 1 is an example, and other overall configurations may be used as long as the present invention can be realized.

[0080] Furthermore, the vehicle to which the present invention is applied may be either an autonomous vehicle or a manually driven vehicle. [Explanation of symbols]

[0081] 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

1. a determination unit that determines whether or not at least one of a first condition that the deceleration is equal to or greater than a deceleration threshold and a second condition that the deceleration gradient is equal to or greater than a deceleration gradient threshold is satisfied, based on data acquired while the host vehicle is traveling; 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.

2. 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.

3. 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 2, wherein the brake control is performed by using the second brake mechanism to generate a hydraulic pressure that is a difference between the target wheel pressure and the detected hydraulic pressure by the second brake mechanism.

4. 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 2, wherein the second brake mechanism is used to send an instruction to the differential pressure valve 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.

5. 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, 5. The brake control device according to claim 4, 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 a hydraulic pressure generated by the second brake mechanism.

6. a third braking mechanism provided in the vehicle includes an electric braking mechanism that generates an electric braking force by driving a motor to press a braking member toward a member to be braked that rotates integrally with the wheel; The control unit is 6. The braking control device according to claim 3, wherein when braking control is being performed using both the first braking mechanism and the second braking mechanism, if a failure is detected in at least one of the first braking mechanism and the second braking mechanism, braking control is performed using the third braking mechanism.

7. a third braking mechanism provided in the vehicle includes an electric braking mechanism that generates an electric braking force by driving a motor to press a braking member toward a member to be braked that rotates integrally with the wheel; The control unit is 6. The brake control device according to claim 3, wherein when performing brake control using both the first brake mechanism and the second brake mechanism, the brake control is also performed using the third brake mechanism.

Images