JP7459773B2 - Vehicle Braking System - Google Patents

Description

The present invention relates to a vehicle braking system that controls hydraulic pressure in a wheel cylinder.

Patent Document 1 describes an example of a braking device that controls hydraulic pressure within a wheel cylinder. This braking device includes a solenoid valve installed in a fluid path connecting a master cylinder and a wheel cylinder, and an electric pump that supplies brake fluid to a portion of the fluid path between the solenoid valve and the wheel cylinder. We are prepared. Then, by driving the electromagnetic valve while discharging brake fluid from the pump, a pressure difference can be generated between a portion of the fluid path on the master cylinder side and a portion on the wheel cylinder side. Such differential pressure can be adjusted by a valve instruction value that is an instruction value for the electromagnetic valve. By adjusting the differential pressure, the hydraulic pressure within the wheel cylinder can be controlled.

In the braking device described in Patent Document 1, a correction process of a valve characteristic, which is a characteristic indicating a relationship between a differential pressure and a valve instruction value, is executed. In the correction process, driving of the electric motor that is the power source of the pump is stopped while the valve instruction value is maintained at a predetermined value. That is, driving of the electric motor is stopped while a load corresponding to a predetermined value is applied to the pump. At this time, the motor rotational speed, which is the rotational speed of the electric motor, decreases due to inertia. In other words, the greater the load applied to the pump, the greater the rate at which the motor rotational speed decreases. Therefore, the above-mentioned valve characteristics are corrected based on the rate at which the motor rotational speed decreases when driving the electric motor is stopped.

JP 2017-165112 A

The rate at which the motor rotation speed decreases when the drive of the electric motor is stopped may vary depending on parameters other than the magnitude of the load applied to the pump. Other parameters that affect the speed at which the motor rotational speed decreases include the degree of aging in the characteristics of the pump and electric motor. Therefore, there is a need for a technique for deriving the valve characteristics of a solenoid valve while also taking into account the current characteristics of the pump and electric motor.

A vehicle braking device for solving the above problem is a device that controls hydraulic pressure in a wheel cylinder provided in a wheel of a vehicle. This braking device includes a hydraulic pressure generating device having a hydraulic pressure chamber connected to the inside of the wheel cylinder via a fluid path, and a hydraulic pressure generator disposed in the fluid path, and a valve instruction value that is an instruction value is used to control the hydraulic pressure in the fluid path. a solenoid valve that is driven to generate a differential pressure between a portion on the hydraulic pressure chamber side and a portion on the wheel cylinder side; and an electric motor as a power source, and the solenoid valve and the wheel cylinder in the fluid path. a control device that controls the fluid pressure in the wheel cylinder by driving the pump that supplies brake fluid to the supply fluid path that is the part between the two, and the solenoid valve and the electric motor to adjust the differential pressure; It is equipped with. The control device maintains the valve instruction value for the solenoid valve at a predetermined value and maintains the motor rotation speed that is the rotation speed of the electric motor with the solenoid valve open. a first acquisition process for acquiring a first characteristic indicating a relationship between the hydraulic pressure in the supply liquid path and a motor current value that is a value of the current flowing through the electric motor; a second acquisition process of acquiring a second characteristic indicating a relationship between the valve instruction value for the electromagnetic valve and the motor current value when the motor rotation speed is held in a state where the motor rotation speed is held at a pressure; A derivation process of deriving a valve characteristic of the electromagnetic valve indicating a relationship between the valve instruction value and the differential pressure based on the first characteristic and the second characteristic is executed.

When the motor speed is maintained with the valve command value held at a specified value and the solenoid valve open, if the hydraulic pressure in the supply fluid line changes, the load on the pump changes, and the motor current value changes. At this time, the motor current value changes in a manner that corresponds to the current characteristics of the pump and electric motor.

If the motor rotation speed is maintained while the hydraulic pressure in the hydraulic pressure chamber is maintained at a predetermined hydraulic pressure, if the valve command value changes and the hydraulic pressure in the supply liquid path changes, the load applied to the pump will change. Motor current value changes. At this time, the motor current value changes in a manner according to the current characteristics of the pump and electric motor.

In the above configuration, the first characteristic indicating the relationship between the hydraulic pressure in the supply liquid path and the motor current value is acquired by the first acquisition process. Through the second acquisition process, a second characteristic indicating the relationship between the valve instruction value and the motor current value is acquired. In the derivation process, a valve characteristic of the electromagnetic valve indicating the relationship between the valve instruction value and the differential pressure is derived based on the first characteristic and the second characteristic. The first characteristic acquired in the first acquisition process and the second characteristic acquired in the second acquisition process reflect the current characteristics of the pump and the electric motor. Therefore, the valve characteristics derived based on the first characteristics and the second characteristics reflect the degree of change over time in the characteristics of the pump and the electric motor.

Therefore, it becomes possible to derive the valve characteristics of the solenoid valve taking into account the current characteristics of the pump and electric motor.

FIG. 1 is a configuration diagram schematically showing a braking device for a vehicle in a first embodiment. 6 is a flowchart illustrating a processing routine for acquiring a first characteristic. 7 is a flowchart illustrating a processing routine for acquiring a second characteristic. 5 is a flowchart illustrating a processing routine for acquiring valve characteristics of a solenoid valve. 4A to 4C are timing charts for acquiring a first characteristic. 13 is a graph showing an example of a first characteristic. (a) to (c) are timing charts when acquiring the second characteristic. The graph which shows an example of a 2nd characteristic. A diagram showing how the valve characteristics of a solenoid valve change. FIG. 11 is a schematic diagram showing a configuration of a vehicle braking device according to a second embodiment. 6 is a flowchart illustrating a processing routine for acquiring a first characteristic.

First Embodiment
A first embodiment of a vehicle braking device will now be described with reference to FIGS.
FIG. 1 illustrates a braking device 40 according to this embodiment, and a plurality of braking mechanisms 20 provided individually for a plurality of wheels 10 .

<Regarding the Brake Mechanism 20>
Each braking mechanism 20 includes a wheel cylinder 21, a rotating body 22 that rotates integrally with the wheel 10, and a friction material 23 that is pressed against the rotating body 22 with a strength corresponding to the WC pressure, which is the hydraulic pressure in the wheel cylinder 21. When the WC pressure is increased, the force pressing the friction material 23 against the rotating body 22 increases, and therefore the braking force applied to the wheel 10 increases.

<Regarding the Braking Device 40>
The braking system 40 includes a hydraulic pressure generating device 50 , a braking actuator 60 capable of individually adjusting the WC pressure in each wheel cylinder 21 , and a control device 100 for controlling the braking actuator 60 .

<Regarding the hydraulic pressure generating device 50>
The hydraulic pressure generating device 50 includes a master cylinder 51. The master cylinder 51 has a hydraulic pressure chamber 52 in which hydraulic pressure is generated according to the amount of operation of a brake operating member 53 by the driver of the vehicle. Examples of the brake operating member 53 include a brake pedal and a brake lever. In the following description, the operation of the brake operating member 53 by the driver may also be referred to as a "braking operation."

When the driver applies the brakes, hydraulic pressure is generated in the hydraulic pressure chamber 52. On the other hand, when the driver is not applying the brakes, the hydraulic pressure chamber 52 is open to the atmosphere, and no hydraulic pressure is generated in the hydraulic pressure chamber 52. In other words, a state in which hydraulic pressure is generated in the hydraulic pressure chamber 52 is a state in which the hydraulic pressure in the hydraulic pressure chamber 52 is higher than atmospheric pressure.

<Regarding the Brake Actuator 60>
The brake actuator 60 includes two hydraulic circuits 611 and 612. Two of the plurality of wheel cylinders 21 are connected to the first hydraulic circuit 611. The remaining two wheel cylinders 21 are connected to the second hydraulic circuit 612.

The first hydraulic circuit 611 includes a fluid path 62 that connects the master cylinder 51 and the wheel cylinder 21, and a differential pressure regulating valve 63 disposed in the fluid path 62. The differential pressure regulating valve 63 is a normally open type linear solenoid valve, and the differential pressure regulating valve 63 has a portion closer to the master cylinder 51 than the differential pressure regulating valve 63 and a portion closer to the wheel cylinder 21 than the differential pressure regulating valve 63. It is driven to adjust the differential pressure between the two parts. That is, by driving the differential pressure regulating valve 63, the differential pressure between the hydraulic chamber 52 and the inside of the wheel cylinder 21 can be adjusted.

The first hydraulic circuit 611 is provided with a holding valve 64 that is closed when restricting an increase in the WC pressure, and a pressure reducing valve 65 that is opened when reducing the WC pressure. The first hydraulic circuit 611 is provided with the same number of holding valves 64 and pressure reducing valves 65 as the number of wheel cylinders 21 connected to the first hydraulic circuit 611. A reservoir 66 is also connected to the first hydraulic circuit 611. The reservoir 66 temporarily stores brake fluid that flows out of the wheel cylinders 21 when the pressure reducing valve 65 is opened.

A pump 67 that supplies brake fluid to a supply fluid path 62a, which is a portion of the fluid path 62 between the differential pressure regulating valve 63 and each wheel cylinder 21, is connected to the first hydraulic pressure circuit 611. Specifically, the pump 67 supplies brake fluid to the fluid path between the differential pressure regulating valve 63 and the holding valve 64. The pump 67 is a pump that uses an electric motor 68 as a power source. The pump 67 can pump up the brake fluid in the reservoir 66 and the brake fluid in the master cylinder 51 and supply them to the supply fluid path 62a.

In addition, since the structure of the second hydraulic pressure circuit 612 is substantially the same as the structure of the first hydraulic pressure circuit 611, a description of the structure of the second hydraulic pressure circuit 612 will be omitted in this specification.
<Regarding the control device 100>
Detection signals from various sensors are input to the control device 100. Examples of the sensors include a current sensor 121, a rotation angle sensor 122, a hydraulic pressure sensor 123, and a brake switch 124. The current sensor 121 outputs a detection signal corresponding to a motor current value Imt, which is the value of a current flowing through the electric motor 68. The rotation angle sensor 122 outputs a detection signal corresponding to a motor rotation speed Nmt, which is the rotation speed of the electric motor 68. The hydraulic pressure sensor 123 detects an MC pressure Pmc, which is the hydraulic pressure in the hydraulic pressure chamber 52, and outputs a detection signal corresponding to the detection result. The hydraulic pressure sensor 123 is connected, for example, to a portion of the hydraulic passage 62 between the differential pressure regulating valve 63 and the hydraulic pressure chamber 52. The brake switch 124 detects whether or not a braking operation is being performed, and outputs a detection signal corresponding to the detection result.

The control device 100 may have any of the following configurations (a) to (c).
(a) The control device 100 includes one or more processors that execute various processes according to computer programs. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions configured to cause the CPU to perform processes. Memory, or computer-readable media, includes any available media that can be accessed by a general purpose or special purpose computer.
(b) The control device 100 includes one or more dedicated hardware circuits that execute various processes. Dedicated hardware circuits may include, for example, application specific integrated circuits, ie ASICs or FPGAs. Note that ASIC is an abbreviation for "Application Specific Integrated Circuit," and FPGA is an abbreviation for "Field Programmable Gate Array."
(c) The control device 100 includes a processor that executes some of the various processes according to a computer program, and a dedicated hardware circuit that executes the remaining processes of the various processes.

The control device 100 has a hydraulic pressure control section 101 as a functional section for controlling the WC pressure. The hydraulic pressure control unit 101 controls the WC pressure by driving the differential pressure regulating valve 63 and the electric motor 68 to adjust the differential pressure DP. The differential pressure referred to here is the differential pressure between the hydraulic pressure chamber 52 and the inside of the wheel cylinder 21. The hydraulic pressure control unit 101 causes the pump 67 to discharge brake fluid by driving the electric motor 68 . In this state, the hydraulic pressure control unit 101 adjusts the valve instruction value Ism, which is the instruction value (instruction current value, differential pressure instruction value) for the differential pressure regulating valve 63. The valve instruction value Ism is an instruction value for the opening degree of the differential pressure regulating valve 63. For example, the valve instruction value Ism correlates with a value indicating the current input to the differential pressure regulating valve 63. Therefore, by increasing the valve instruction value Ism, the differential pressure DP can be increased, and the WC pressure can be increased.

The hydraulic control unit 101 controls the differential pressure adjustment valve 63 using the valve characteristics of the differential pressure adjustment valve 63, which indicate the relationship between the differential pressure DP and the valve instruction value Ism. That is, the hydraulic control unit 101 derives the valve instruction value Ism corresponding to the target value of the differential pressure DP based on the valve characteristics. Then, the hydraulic control unit 101 drives the differential pressure adjustment valve 63 by inputting a current of a magnitude corresponding to the derived valve instruction value Ism to the differential pressure adjustment valve 63.

The control device 100 includes a first characteristic acquisition section 102, a second characteristic acquisition section 103, and a valve characteristic derivation section 104 as functional sections for acquiring the valve characteristics of the differential pressure regulating valve 63.
The first characteristic acquisition unit 102 determines the flow rate of the supply liquid path 62a when the valve instruction value Ism is held at a predetermined value, the differential pressure regulating valve 63 is opened, and the motor rotation speed Nmt is maintained. A first acquisition process is executed to acquire a first characteristic indicating the relationship between the hydraulic pressure and the motor current value Imt. For example, it is preferable to set "0" as the predetermined value. The case where “0” is set as the valve instruction value Ism means that no current is input to the differential pressure regulating valve 63. The specific content of the first acquisition process will be described later.

The second characteristic acquisition unit 103 indicates the relationship between the valve instruction value Ism and the motor current value Imt when the hydraulic pressure chamber 52 is maintained at a predetermined hydraulic pressure and the motor rotation speed Nmt is maintained. A second acquisition process is executed to acquire the second characteristic. For example, atmospheric pressure is set as the predetermined hydraulic pressure. When no braking operation is performed, the hydraulic pressure in the hydraulic pressure chamber 52 can be considered equal to atmospheric pressure. The specific contents of the second acquisition process will be described later.

The valve characteristic derivation unit 104 executes a derivation process for deriving the valve characteristic of the differential pressure regulating valve 63 based on the first characteristic and the second characteristic. The specific content of the derivation process will be described later.
<Flow of processing executed by control device 100 to derive valve characteristics>
The flow of processing executed by the control device 100 to derive the valve characteristics of the differential pressure regulating valve 63 will be described with reference to FIGS. 2 to 9. In this embodiment, when the execution conditions for deriving the valve characteristics are satisfied, the first characteristic acquisition unit 102 of the control device 100 executes the first acquisition process. When the first characteristic is acquired by the first acquisition process, the second characteristic acquisition unit 103 of the control device 100 executes the second acquisition process. When the second characteristic is acquired by the second acquisition process, the valve characteristic derivation unit 104 of the control device 100 executes the derivation process.

First, a processing routine for executing the first acquisition process will be described with reference to FIGS. 2, 5, and 6. The control device 100 repeatedly executes the processing routine shown in FIG.
As shown in FIG. 2, in the first step S11 of this processing routine, the control device 100 determines whether execution conditions for deriving the valve characteristics of the differential pressure regulating valve 63 are satisfied. For example, if a plurality of conditions (A1), (A2), and (A3) shown below are satisfied, it can be considered that the execution condition is satisfied. On the other hand, if at least one of the plurality of conditions (A1) to (A3) is not satisfied, it can be considered that the execution condition is not satisfied.
(A1) The vehicle must be stopped.
(A2) Braking force is applied to the vehicle by the operation of the parking brake device.
(A3) A predetermined period of time or more has elapsed since the previous derivation of the valve characteristics of the differential pressure regulating valve 63.

If it is not determined that the execution condition is met (S11: NO), the control device 100 temporarily ends this processing routine. That is, the first characteristic acquisition unit 102 of the control device 100 does not execute the first acquisition process. On the other hand, if it is determined that the execution condition is met (S11: YES), the control device 100 transitions the process to step S13. In step S13, the control device 100 executes a notification process to notify the driver of the vehicle that a process for deriving the valve characteristics will be executed. After executing the notification process, the control device 100 transitions the process to step S15. That is, the first characteristic acquisition unit 102 starts the first acquisition process.

In step S15, the first characteristic acquisition unit 102 starts driving the electric motor 68. That is, the first characteristic acquisition unit 102 drives the electric motor 68 so that the motor rotation speed Nmt becomes the specified rotation speed NmtTr. For example, the first characteristic acquisition unit 102 may control the electric motor 68 by feedback control using the deviation between the motor rotation speed Nmt and the specified rotation speed NmtTr as an input.

Subsequently, in step S17, the first characteristic acquisition unit 102 requests the driver to perform a braking operation in order to generate hydraulic pressure in the hydraulic pressure chamber 52. Then, in step S19, the first characteristic acquisition unit 102 determines whether a braking operation has been started. For example, the first characteristic acquisition unit 102 determines whether a braking operation has been started based on the detection signal output from the brake switch 124. For example, the first characteristic acquisition unit 102 may determine that the braking operation has been started when the MC pressure Pmc is increasing.

If it is not determined that the braking operation has been started (S19: NO), the first characteristic acquisition unit 102 repeats the determination in step S19 until it is determined that the braking operation has been started. On the other hand, if it is determined that the braking operation has been started (S19: YES), the first characteristic acquisition unit 102 moves the process to step S21.

In step S21, the first characteristic acquisition unit 102 acquires the MC pressure Pmc and the motor current value Imt. Subsequently, in step S23, the first characteristic acquisition unit 102 determines whether the MC pressure Pmc is higher than the MC pressure determination value PmcTh. The MC pressure determination value PmcTh is set as a criterion for determining whether or not the necessary number of samples have been acquired to acquire the first characteristic. The sample here is the MC pressure Pmc and motor current value Imt acquired in step S21.

In step S23, if the MC pressure Pmc is less than or equal to the MC pressure determination value PmcTh (NO), the first characteristic acquisition unit 102 moves the process to step S21. On the other hand, if the MC pressure Pmc is higher than the MC pressure determination value PmcTh (S23: YES), the first characteristic acquisition unit 102 moves the process to step S25. In step S25, the first characteristic acquisition unit 102 acquires the first characteristic.

That is, as shown in Figures 5(a), (b), and (c), the driving of the electric motor 68 starts at timing t11 (S15). The motor current value Imt is adjusted so that the motor rotation speed Nmt becomes the specified rotation speed NmtTr. Then, when a braking operation starts at timing t12 (S19: YES), the MC pressure Pmc starts to increase. Then, at timing t13, the MC pressure Pmc becomes higher than the MC pressure judgment value PmcTh (S23: YES).

As shown in FIG. 5, as the MC pressure Pmc increases, the motor current value Imt increases. When the first acquisition process is executed, no current is input to the differential pressure regulating valve 63, and the differential pressure regulating valve 63 is open. Therefore, the liquid pressure in the supply liquid path 62a is substantially equal to the MC pressure Pmc. An increase in the hydraulic pressure in the supply liquid path 62a means that the hydraulic pressure near the discharge port of the pump 67 is high. In other words, the load applied to the pump 67 increases, making it difficult for the pump 67 to discharge brake fluid. In such a case, in order to maintain the motor rotation speed Nmt, it is necessary to increase the motor current value Imt to increase the motor torque. Therefore, as the MC pressure Pmc increases, the motor current value Imt gradually increases.

The first characteristic acquisition unit 102 monitors changes in the MC pressure Pmc and changes in the motor current value Imt within a period from timing t12 to timing t13. Then, the first characteristic acquisition unit 102 acquires the first characteristic shown in FIG. 6 based on the change in the MC pressure Pmc and the change in the motor current value Imt within the period. That is, in the first characteristic, the larger the motor current value Imt, the higher the MC pressure Pmc. In the first characteristic, when the increase amount of MC pressure Pmc with respect to the increase in motor current value Imt is defined as the increase gradient of MC pressure Pmc, the increase gradient of MC pressure Pmc takes into account the current characteristics of pump 67 and electric motor 68. It becomes the size.

Returning to FIG. 2, after acquiring the first characteristic in step S25, the first characteristic acquisition unit 102 moves the process to step S27. In step S27, the first characteristic acquisition unit 102 stops driving the electric motor 68. The first characteristic acquisition unit 102 then ends this processing routine.

In this embodiment, when the first characteristic is acquired, the driving of the electric motor 68 is stopped. However, in this embodiment, when the first characteristic is acquired, the second acquisition process is started immediately to acquire the second characteristic. Therefore, when the first acquisition process and the second acquisition process are executed consecutively, step S27 of stopping the driving of the electric motor 68 may be omitted in the processing routine shown in FIG. 2.

Next, the processing routine for executing the second characteristic processing will be described with reference to Figures 3, 7, and 8. When the first characteristic is acquired by executing the processing routine shown in Figure 2, the control device 100 executes the processing routine shown in Figure 3.

As shown in FIG. 3, in this processing routine, in the first step S41, the control device 100 executes a notification process to notify the driver that the braking operation will be released. Next, in step S43, the control device 100 determines whether or not a braking operation is being performed. If it is determined that a braking operation is being performed (S43: YES), the control device 100 repeats the determination in step S43 until it no longer determines that a braking operation is being performed. On the other hand, if it is not determined that a braking operation is being performed (S43: NO), the control device 100 can determine that the hydraulic pressure in the hydraulic chamber 52 is maintained at a predetermined hydraulic pressure, and therefore the control device 100 transitions to the process in step S45. That is, the second characteristic acquisition unit 103 of the control device 100 starts the second acquisition process.

In step S45, the second characteristic acquisition unit 103 starts driving the electric motor 68. That is, the second characteristic acquisition unit 103 drives the electric motor 68 so that the motor rotation speed Nmt becomes the specified rotation speed NmtTr. For example, the second characteristic acquisition unit 103 may control the electric motor 68 by feedback control using the deviation between the motor rotation speed Nmt and the specified rotation speed NmtTr as an input. Note that if the processing of step S27 is omitted in the processing routine shown in FIG. 2, the processing of step S45 may be omitted in this processing routine.

Subsequently, in step S47, the second characteristic acquisition unit 103 starts driving the differential pressure regulating valve 63. That is, the second characteristic acquisition unit 103 drives the differential pressure regulating valve 63 based on the valve characteristic of the differential pressure regulating valve 63. At this time, the second characteristic acquisition unit 103 varies the valve instruction value Ism for the differential pressure regulating valve 63 so that the differential pressure DP gradually increases. In this embodiment, the second characteristic acquisition unit 103 gradually increases the valve instruction value Ism.

In the next step S49, the second characteristic acquisition unit 103 acquires the valve instruction value Ism and the motor current value Imt. Then, in step S51, the second characteristic acquisition unit 103 determines whether the valve instruction value Ism is greater than the valve instruction judgment value IsmTh. If the valve instruction value Ism is increased under the condition that brake fluid is discharged from the pump 67, the differential pressure DP increases. The valve instruction judgment value IsmTh is set as a criterion for determining whether the differential pressure DP at this time, i.e., the hydraulic pressure of the supply hydraulic line 62a, has reached the MC pressure judgment value PmcTh. Therefore, if the valve instruction value Ism is greater than the valve instruction judgment value IsmTh, it is deemed that the hydraulic pressure of the supply hydraulic line 62a has reached the MC pressure judgment value PmcTh. On the other hand, if the valve instruction value Ism is equal to or less than the valve instruction judgment value IsmTh, it is deemed that the hydraulic pressure of the supply hydraulic line 62a has not reached the MC pressure judgment value PmcTh.

If the valve instruction value Ism is equal to or less than the valve instruction judgment value IsmTh (S51: NO), the second characteristic acquisition unit 103 proceeds to step S49. On the other hand, if the valve instruction value Ism is greater than the valve instruction judgment value IsmTh (S51: YES), the second characteristic acquisition unit 103 proceeds to step S53. In step S53, the second characteristic acquisition unit 103 acquires the second characteristic.

That is, as shown in Figures 7(a), (b), and (c), the electric motor 68 starts to be driven at timing t21 (S45). The motor current value Imt is adjusted so that the motor rotation speed Nmt becomes the specified rotation speed NmtTr. Then, the differential pressure adjustment valve 63 starts to be driven at timing t22 (S47). Then, the valve instruction value Ism gradually increases, and the differential pressure DP gradually increases. In other words, the fluid pressure in the supply fluid path 62a gradually increases. Then, at timing t23, the valve instruction value Ism reaches the valve instruction judgment value IsmTh.

As shown in FIG. 7, when the valve instruction value Ism increases, the hydraulic pressure in the supply liquid path 62a increases, and thus the motor current value Imt increases. An increase in the hydraulic pressure in the supply liquid path 62a means that the hydraulic pressure near the discharge port of the pump 67 is high. In other words, the load applied to the pump 67 increases, making it difficult for the pump 67 to discharge brake fluid. In such a case, in order to maintain the motor rotation speed Nmt, it is necessary to increase the motor current value Imt to increase the motor torque. Therefore, as the valve instruction value Ism increases, the motor current value Imt gradually increases.

The second characteristic acquisition unit 103 monitors the transition of the valve instruction value Ism and the transition of the motor current value Imt during the period from timing t22 to timing t23. The second characteristic acquisition unit 103 then acquires the second characteristic shown in FIG. 8 based on the transition of the valve instruction value Ism and the transition of the motor current value Imt during that period. That is, in the second characteristic, the valve instruction value Ism increases as the motor current value Imt increases. In the second characteristic, if the increase in the valve instruction value Ism relative to the increase in the motor current value Imt is set to the increase gradient of the valve instruction value Ism, the increase gradient of the valve instruction value Ism is a magnitude that takes into account both the current characteristics of the pump 67 and the electric motor 68 and the current characteristics of the differential pressure adjustment valve 63.

Returning to FIG. 3, after acquiring the second characteristic in step S53, the second characteristic acquisition unit 103 moves the process to step S55. In step S55, the second characteristic acquisition unit 103 stops driving the electric motor 68 and the differential pressure regulating valve 63. The second characteristic acquisition unit 103 then ends this processing routine.

Next, a processing routine for executing the derivation processing will be described with reference to FIGS. 4 and 9.
As shown in FIG. 4, in the first step S71 of this processing routine, the control device 100 determines whether acquisition of the first characteristic and the second characteristic has been completed. If acquisition of at least one of the first characteristic and the second characteristic is not completed (S71: NO), the control device 100 continues the determination in step S71 until both the first characteristic and the second characteristic are acquired. repeat. On the other hand, if acquisition of both the first characteristic and the second characteristic has been completed (S71: YES), the control device 100 moves the process to step S73. In step S73, the valve characteristic derivation unit 104 of the control device 100 executes a derivation process to derive the valve characteristics.

That is, the first characteristic indicates the relationship between the MC pressure Pmc and the motor current value Imt. The second characteristic indicates the relationship between the valve instruction value Ism and the motor current value Imt. Therefore, in the derivation process, the valve characteristic derivation unit 104 derives the third characteristic, which is the relationship between the MC pressure Pmc and the valve instruction value Ism, based on the first characteristic and the second characteristic. When the differential pressure adjustment valve 63 is in an open state, the hydraulic pressure in the supply fluid passage 62a is substantially equal to the MC pressure Pmc. Also, when no hydraulic pressure is generated in the hydraulic pressure chamber 52, the hydraulic pressure in the supply fluid passage 62a is substantially equal to the differential pressure DP. Therefore, in the derivation process, the valve characteristic derivation unit 104 replaces the MC pressure Pmc in the third characteristic with the differential pressure DP to derive the valve characteristic indicating the relationship between the differential pressure DP and the valve instruction value Ism as shown in FIG. 9.

In FIG. 9, the previous valve characteristics, which are the valve characteristics derived by the previous execution of the derivation process, are shown by dashed lines. Also, the current valve characteristics, which are the valve characteristics derived by the current execution of the derivation process, are shown by solid lines.

Returning to FIG. 4, after deriving the valve characteristics in step S73, the valve characteristics deriving unit 104 ends this processing routine.
After the valve characteristics are newly derived in this way, the hydraulic pressure control unit 101 controls the differential pressure regulating valve 63 using the latest valve characteristics.

Note that valve characteristics are prepared for each differential pressure adjustment valve. Therefore, if the brake actuator 60 has multiple hydraulic circuits, the control device 100 derives valve characteristics for each differential pressure adjustment valve.

<Effect>
The operation and effects of this embodiment will be explained.
In this embodiment, the first characteristic is acquired by the first acquisition process. The second characteristic is acquired by the second acquisition process. In the derivation process, the valve characteristic of the differential pressure regulating valve 63 is derived based on the first characteristic and the second characteristic. The first characteristic and the second characteristic reflect the current characteristics of the pump 67 and the electric motor 68. Therefore, the valve characteristics derived based on the first characteristics and the second characteristics reflect the degree of change over time in the characteristics of the pump 67 and the electric motor 68. Therefore, the valve characteristics of the differential pressure regulating valve 63 can be derived in consideration of the current characteristics of the pump 67 and the electric motor 68.

Then, by driving the differential pressure control valve 63 using the newly derived valve characteristic, the WC pressure in the wheel cylinder 21 can be controlled with high precision. In other words, the controllability of the braking force applied to the wheel 10 can be improved.

The magnitude of the load input to the pump can also vary depending on the viscosity of the brake fluid circulating in the hydraulic circuits 611 and 612. The lower the temperature of the brake fluid, the higher the viscosity of the brake fluid.

In this embodiment, the second characteristic is acquired immediately after the first characteristic is acquired. That is, there is almost no difference between the temperature of the brake fluid when the first acquisition process is executed and the temperature of the brake fluid when the second acquisition process is executed. That is, the first characteristic and the second characteristic are acquired in a state where the viscosity of the brake fluid is substantially the same. Therefore, by deriving the valve characteristics based on the first characteristic and the second characteristic, the precision in deriving the valve characteristics can be further improved.

Second Embodiment
A second embodiment of a vehicle braking device will be described with reference to Figures 10 and 11. In the following description, differences from the first embodiment will be mainly described, and the same reference numerals will be used to designate the same or corresponding members as those in the first embodiment, and duplicated description will be omitted.

As shown in FIG. 10, the braking device 40A of this embodiment includes a hydraulic pressure generator 70 in addition to the master cylinder 51A and the brake actuator 60. That is, the hydraulic pressure generator 70 is provided separately from the master cylinder 51A, and is connected to the brake actuator 60. Note that hydraulic pressure is generated in the master cylinder 51A according to the amount of operation of the brake operating member 53.

<About the hydraulic pressure generator 70>
The hydraulic pressure generator 70 includes an electric cylinder 71 and a drive device 75. The drive device 75 has an electric cylinder motor 76. The drive device 75 transmits the power output from the electric cylinder motor 76 to the electric cylinder 71. In the hydraulic pressure chamber 72 within the electric cylinder 71, electric cylinder pressure Psl, which is a hydraulic pressure corresponding to the power input from the drive device 75, is generated. The electric cylinder pressure Psl can be adjusted by the amount of rotation of the electric cylinder motor 76. When the electric cylinder pressure Psl in the hydraulic pressure chamber 72 increases, an amount of brake fluid corresponding to the electric cylinder pressure Psl is supplied from the electric cylinder 71 to the first hydraulic pressure circuit 611 and the second hydraulic pressure circuit 612 of the brake actuator 60. Ru.

That is, in this embodiment, the drive device 75 corresponds to a "pressurizing unit" that drives to automatically adjust the electric cylinder pressure Psl of the hydraulic chamber 72. Also, the hydraulic chamber 72 in the electric cylinder 71 is connected to the inside of the wheel cylinder 21 via a hydraulic line. Therefore, when the differential pressure adjustment valve 63 of the brake actuator 60 is in an open state, the hydraulic pressure in the supply hydraulic line 62a is substantially equal to the electric cylinder pressure Psl.

<Control configuration>
The braking device 40A includes a braking sensor 126 that detects a braking operation amount BPinp, which is the amount of operation of the brake operating member 53 by the driver. The braking sensor 126 outputs a detection signal corresponding to the detected braking operation amount BPinp to the control device 100. A hydraulic pressure sensor 123 provided in the brake actuator 60 detects an electric cylinder pressure Psl, and outputs a detection signal corresponding to the detected electric cylinder pressure Psl to the control device 100.

When the driver is performing a braking operation, the hydraulic pressure control unit 101 of the control device 100 sets a value corresponding to the braking operation amount BPinp as the instruction value for the rotation amount of the electric cylinder motor 76. As a result, the hydraulic pressure control unit 101 can increase the electric cylinder pressure Psl as the braking operation amount BPinp increases. In other words, the WC pressure in each wheel cylinder 21 can be varied according to the braking operation amount BPinp.

Further, by controlling the drive device 75, the hydraulic pressure control unit 101 can adjust the WC pressure in each wheel cylinder 21 even when a braking operation is not performed. For example, the hydraulic pressure control unit 101 sets the instruction value of the rotation amount of the electric cylinder motor 76 to a value corresponding to the target value of the braking force of the vehicle. Thereby, the hydraulic pressure control unit 101 can increase the electric cylinder pressure Psl as the target value of the braking force of the vehicle increases. That is, the WC pressure in each wheel cylinder 21 can be set to a level corresponding to the target value of the braking force of the vehicle.

A vehicle equipped with the braking device 40A of this embodiment has an automatic driving function. That is, the vehicle is equipped with an automatic driving control device 200 that derives various command values such as driving force and braking force when the vehicle is driven automatically. Information related to the command value of the vehicle's braking force, etc. is input to the control device 100 from the automatic driving control device 200.

In this embodiment, the control device 100 executes the first acquisition process, the second acquisition process, and the derivation process prior to the vehicle starting to travel automatically in accordance with the automatic driving function. That is, the control device 100 derives the valve characteristics of the differential pressure adjustment valve 63 of the brake actuator 60 as part of the preparations before the vehicle starts to travel automatically.

<Processing flow for deriving the valve characteristics of the differential pressure regulating valve 63>
A processing routine for executing the first acquisition process is shown in Fig. 11. The control device 100 repeatedly executes this processing routine.

In this processing routine, in the first step S81, the control device 100 determines whether or not the automatic driving mode has been set. When the control device 100 receives an input from the automatic driving control device 200 to start automatic driving of the vehicle, the control device 100 determines that the automatic driving mode has been set. When the automatic driving mode has been set (S81: YES), the control device 100 transitions to step S83. On the other hand, when the automatic driving mode has not been set (S81: NO), the control device 100 temporarily ends this processing routine.

In step S83, the control device 100 executes a notification process to notify the driver that the braking operation by the driver will be invalidated. In other words, until the derivation of the valve characteristics of the differential pressure control valve 63 is completed, the control device 100 will not drive the drive device 75 in response to the braking operation even if the driver performs the braking operation.

Then, the first characteristic acquisition unit 102 of the control device 100 starts the first acquisition process. That is, in step S85, the first characteristic acquisition unit 102 starts driving the electric motor 68 similarly to step S15 above. Subsequently, in step S87, the first characteristic acquisition unit 102 starts driving the drive device 75. The first characteristic acquisition unit 102 drives the drive device 75 so that the electric cylinder pressure Psl gradually increases. That is, the first characteristic acquisition unit 102 generates hydraulic pressure in the hydraulic pressure chamber 72 of the electric cylinder 71 by driving the drive device 75 while the vehicle is stopped.

Then, in step S89, the first characteristic acquisition unit 102 acquires the electric cylinder pressure Psl and the motor current value Imt. In the next step S91, the first characteristic acquisition unit 102 determines whether the electric cylinder pressure Psl is higher than the electric cylinder pressure determination value PslTh. The electric cylinder pressure determination value PslTh is set with the same intention as the MC pressure determination value PmcTh in the first embodiment. That is, the electric cylinder pressure determination value PslTh is set as a criterion for determining whether or not the necessary number of samples have been acquired to acquire the first characteristic. The sample here is the electric cylinder pressure Psl and motor current value Imt acquired in step S89.

In step S91, if the electric cylinder pressure Psl is equal to or less than the electric cylinder pressure determination value PslTh (NO), the first characteristic acquisition unit 102 moves the process to step S89. On the other hand, if the electric cylinder pressure Psl is higher than the electric cylinder pressure determination value PslTh (S91: YES), the first characteristic acquisition unit 102 moves the process to step S93. In step S93, the first characteristic acquisition unit 102 acquires the first characteristic.

In this embodiment, the first characteristic acquisition unit 102 generates hydraulic pressure in the hydraulic chamber 72 of the electric cylinder 71 by driving the drive device 75 while the vehicle is stopped, and acquires the first characteristic based on the hydraulic pressure in the supply hydraulic line 62a and the motor current value Imt when hydraulic pressure is generated in the hydraulic chamber 72. That is, the first characteristic acquisition unit 102 monitors the transition of the electric cylinder pressure Psl and the transition of the motor current value Imt during the period from the start of driving the drive device 75 to the time when the electric cylinder pressure Psl reaches the electric cylinder pressure determination value PslTh. Then, the first characteristic acquisition unit 102 acquires the first characteristic based on the transition of the electric cylinder pressure Psl and the transition of the motor current value Imt during that period. That is, in the first characteristic, the electric cylinder pressure Psl becomes higher as the motor current value Imt becomes larger. In the first characteristic, if the increase in the electric cylinder pressure Psl in response to an increase in the motor current value Imt is defined as the increase gradient of the electric cylinder pressure Psl, the increase gradient of the electric cylinder pressure Psl is determined by taking into account the characteristics of the pump 67 and the electric motor 68 at that time.

Note that when the valve instruction value Ism is set to "0" and the differential pressure regulating valve 63 is in the open state, the hydraulic pressure in the supply liquid path 62a is substantially the same as the electric cylinder pressure Psl. Therefore, it can be said that the first characteristic acquired in step S93 indicates the relationship between the hydraulic pressure in the supply liquid path 62a and the motor current value Imt.

After acquiring the first characteristic in step S93, the first characteristic acquisition unit 102 moves the process to step S95. In step S95, the first characteristic acquisition unit 102 stops driving the electric motor 68 and the drive device 75. The first characteristic acquisition unit 102 then ends this processing routine.

Note that in this embodiment, when the first characteristic is acquired, the driving of the electric motor 68 is stopped. However, in this embodiment, when the first characteristic is acquired, the second acquisition process is started immediately to acquire the second characteristic. Therefore, it is not necessary to stop driving the electric motor 68 in step S95.

When the first characteristic is acquired as described above, the second characteristic acquisition unit 103 of the control device 100 executes the second acquisition process to acquire the second characteristic. Then, the valve characteristic derivation unit 104 of the control device 100 derives the valve characteristic of the differential pressure regulating valve 63 based on the newly acquired first and second characteristics. Note that the process flow for acquiring the second characteristic and the process flow for deriving the valve characteristic are the same as in the first embodiment. Therefore, the description of the process flow for acquiring the second characteristic and the process flow for deriving the valve characteristic will be omitted here.

When the derivation of the valve characteristics of each differential pressure adjustment valve 63 of the brake actuator 60 is completed, the control device 100 outputs to the automatic driving control device 200 a notice that automatic driving of the vehicle is permitted by the automatic driving function. Then, when driving the differential pressure adjustment valve 63 during automatic driving of the vehicle, the hydraulic control unit 101 of the control device 100 controls the differential pressure adjustment valve 63 based on the valve characteristics derived prior to automatic driving.

＜Effects＞
In this embodiment, in addition to the effects of the first embodiment, the following effects can be obtained.

The valve characteristics of the differential pressure control valve 63 are derived before the vehicle starts to travel automatically using the automatic driving function. Therefore, when adjusting the WC pressure in each wheel cylinder 21 by operating the brake actuator 60 during automatic travel, the adjustment accuracy can be increased.

Furthermore, the first characteristic can be acquired without requiring the driver to perform a braking operation.
(Example of change)
Each of the above embodiments can be modified and implemented as follows. The above embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

- In each of the above embodiments, if there is a large deviation between the newly derived valve characteristics and the previously derived valve characteristics, there is a possibility that a malfunction has occurred in the brake actuator 60. Therefore, in such a case, the driver may be notified that there is a possibility that a malfunction has occurred in the brake actuator 60.

- As explained in the second embodiment, when the hydraulic pressure generating device is equipped with a pressurizing section, in order to derive the valve characteristics of the differential pressure regulating valve 63 at a timing different from before the start of automatic driving of the vehicle. Alternatively, a series of processes may be executed. For example, when the driver is not in the vehicle, the valve characteristics may be derived by performing the first acquisition process, the second acquisition process, and the derivation process.

- In each of the above embodiments, a detection value detected by the current sensor 121 is used as the motor current value Imt, but the present invention is not limited to this. For example, the motor current value Imt may be a calculated value of the motor current derived based on the resistance value of the electric motor 68 and the voltage applied to the electric motor 68. In this case, the current sensor 121 may be omitted.

The hydraulic pressure in the hydraulic pressure chamber of the hydraulic pressure generating device does not have to be a detection value detected by a sensor. For example, in the first embodiment, an estimated value of the MC pressure derived based on the amount of braking operation by the driver may be used as the MC pressure Pmc. In the second embodiment, an estimated value of the electric cylinder pressure derived based on the amount of rotation of the electric cylinder motor 76 may be used as the electric cylinder pressure Psl.

- The specified rotation speed NmtTr when the second acquisition process is executed may be substantially the same as the specified rotation speed NmtTr when the first acquisition process is executed. In other words, some deviation between the specified rotation speed NmtTr when the first acquisition process is executed and the specified rotation speed NmtTr when the second acquisition process is executed may be tolerated.

- In each of the above embodiments, the predetermined value when the first acquisition process is executed is set to "0", but this is not limited to this. In other words, when the first acquisition process is executed, it is sufficient that the valve instruction value Ism is held at a constant value, and a value other than "0" may be set as the predetermined value.

- In each of the above embodiments, atmospheric pressure is set as the predetermined hydraulic pressure when the second acquisition process is executed, but this is not limited to this. In other words, when the second acquisition process is executed, it is sufficient that the hydraulic pressure in the hydraulic chamber is maintained at a constant hydraulic pressure, and a hydraulic pressure higher than atmospheric pressure may be set as the predetermined hydraulic pressure.

In each of the above embodiments, after the second characteristic is acquired by the second acquisition process, the first characteristic may be acquired by the first acquisition process.
In the second acquisition process, the valve instruction value Ism may be gradually decreased toward 0 from a state in which the valve instruction value Ism is greater than the valve instruction determination value IsmTh. Then, the second characteristic may be acquired based on the transitions of the valve instruction value Ism and the motor current value Imt at this time.

- In the first embodiment described above, the first acquisition process may have the driver perform a braking operation so that the MC pressure Pmc decreases from a state in which the MC pressure Pmc is higher than the MC pressure judgment value PmcTh. Then, the first characteristic may be acquired based on the trends in the MC pressure Pmc and the motor current value Imt at this time.

- In the second embodiment, in the first acquisition process, the electric cylinder motor 76 may be driven so that the electric cylinder pressure Psl decreases from a state where the electric cylinder pressure Psl is higher than the electric cylinder pressure determination value PslTh. . Then, the first characteristic may be acquired based on the changes in the electric cylinder pressure Psl and the motor current value Imt at this time.

- In each of the above embodiments, the first acquisition process and the second acquisition process are executed consecutively, but this is not limited to the above. For example, the second acquisition process may be executed at a different time from the first acquisition process. In this case, it is preferable to execute the second acquisition process when the brake fluid temperature is approximately the same as when the first acquisition process is executed.

In the second embodiment, the hydraulic pressure generating device may have a different configuration from hydraulic pressure generating device 70, so long as it is equipped with a pressurizing unit. An example of such a hydraulic pressure generating device is the device disclosed in JP 2018-90110 A.

REFERENCE SIGNS LIST 10: Wheel 21: Wheel cylinder 40, 40A: Brake device 50, 70: Fluid pressure generating device 52, 72: Fluid pressure chamber 62: Fluid passage 62a: Fluid supply passage 63: Differential pressure regulating valve which is an example of an electromagnetic valve 67: Pump 68: Electric motor 75: Drive device which is an example of a pressurizing unit 100: Control device

Claims (3)

A vehicle braking device that controls a hydraulic pressure in a wheel cylinder provided in a wheel of the vehicle,
a hydraulic pressure generating device having a hydraulic pressure chamber connected to the inside of the wheel cylinder via a hydraulic passage;
a solenoid valve that is disposed in the fluid passage and that is actuated to generate a pressure difference between a portion of the fluid passage on the fluid pressure chamber side and a portion of the fluid passage on the wheel cylinder side in response to a valve command value that is a command value;
a pump that uses an electric motor as a power source and supplies brake fluid to a supply fluid passage that is a portion of the fluid passage between the solenoid valve and the wheel cylinder;
a control device that controls the hydraulic pressure in the wheel cylinder by driving the solenoid valve and the electric motor to adjust the pressure difference,
The control device includes:
a first acquisition process for acquiring a first characteristic indicating a relationship between a hydraulic pressure in the supply hydraulic line and a motor current value, which is a value of a current flowing through the electric motor, when the valve instruction value for the solenoid valve is held at a predetermined value and the solenoid valve is open and a motor rotation speed, which is a rotation speed of the electric motor, is held;
a second acquisition process for acquiring a second characteristic indicating a relationship between the valve instruction value for the solenoid valve and the motor current value when the hydraulic pressure in the hydraulic pressure chamber is maintained at a predetermined hydraulic pressure and the motor rotation speed is maintained;
a derivation process for deriving a valve characteristic of the solenoid valve, which indicates a relationship between the valve instruction value and the differential pressure, based on the first characteristic and the second characteristic. The hydraulic pressure generating device has a pressurizing part that is driven to automatically adjust the hydraulic pressure in the hydraulic pressure chamber,
In the first acquisition process, the control device generates hydraulic pressure in the hydraulic pressure chamber by driving the pressurizing unit while the vehicle is stopped, and when the hydraulic pressure is generated in the hydraulic pressure chamber. The braking device for a vehicle according to claim 1, wherein the first characteristic is acquired based on the hydraulic pressure in the supply liquid path and the motor current value. The vehicle has an automatic driving function,
The control device includes:
Prior to automatic driving of the vehicle according to the automatic driving function, executing the first acquisition process, the second acquisition process, and the derivation process,
The braking device for a vehicle according to claim 1 or 2, wherein when driving the solenoid valve during automatic driving of the vehicle, the solenoid valve is controlled based on the valve characteristics.