Brake system and motor control method

Abstract

To inhibit vibration of a vehicle body caused by operation of a pump.SOLUTION: A brake system 20 includes a brake pipe 50 which is connected to a brake actuator 40 and a friction brake 30 and in which a brake fluid discharged from a pump 42 of the brake actuator 40 flows. The brake pipe 50 has: a metal pipe 51 connected to the brake actuator 40; and a flexible hose 55 for guiding the brake fluid flowing in the metal pipe 51 to a wheel cylinder 31 of the friction brake 30. A processing circuit 71 of a brake control device 70 increases the rotation number of an electric motor 41 serving as a power source of the pump 42 as a time period that a temperature of the flexible hose 55 is high becomes longer based on heat history of the flexible hose 55.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a braking system and a motor control method mounted on a vehicle. [Background technology]

[0002] Patent Document 1 discloses a braking system that generates a braking force on a wheel by supplying brake fluid discharged from a pump powered by an electric motor to a wheel cylinder through piping. When the braking system is mounted on a vehicle, the piping is fixed to the vehicle body through fasteners. The part of the piping that is fixed to the vehicle body through the fasteners is called the "fixed part."

[0003] The braking system includes a motor control unit that controls the motor rotation speed, which is the number of rotations of the electric motor. The motor control unit adjusts the motor rotation speed so that the antinode of a standing wave, which is a wave that is a combination of an incident wave that travels in the piping in a direction away from the pump and a reflected wave that travels in the piping in the opposite direction to the traveling direction of the incident wave, moves away from the fixed part of the piping. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-84445 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, the above-mentioned piping is composed of a metal pipe, which is a pipe made of metal, and a flexible hose made of rubber. The first sound speed, which is the speed of sound waves generated by the pulsation of the brake fluid flowing in the flexible hose, is different from the second sound speed, which is the speed of sound waves generated by the pulsation of the brake fluid flowing in the metal pipe. However, in the above-mentioned braking system, the motor speed is adjusted on the assumption that the piping is made of a single material. Therefore, the above-mentioned braking system has room for improvement in terms of suppressing the transmission of vibrations caused by the operation of the pump to the vehicle body. [Means for solving the problem]

[0006] A braking system for solving the above problem is a system mounted on a vehicle. The braking system includes an actuator having a pump that discharges brake fluid in response to the drive of an electric motor, a friction brake having a wheel cylinder and generating a braking force on a wheel of the vehicle in response to the hydraulic pressure of the wheel cylinder, and a brake pipe that supplies the brake fluid discharged by the pump to the wheel cylinder and is connected to the actuator and the friction brake. The brake pipe is connected to the actuator and includes a metal pipe made of a metal material, and a flexible hose made of rubber that guides the brake fluid that has flowed through the metal pipe to the wheel cylinder. The braking system includes a motor control unit that increases the motor rotation speed, which is the rotation speed of the electric motor, the longer the period during which the temperature of the flexible hose is high, based on a thermal history, which is a history of changes in temperature of the flexible hose.

[0007] A motor control method for solving the above problem is a method for controlling an electric motor that is a power source of a pump that discharges brake fluid. When brake fluid discharged from the pump is supplied to a wheel cylinder of a friction brake through a brake pipe, a standing wave is generated in the brake pipe, which is a wave obtained by combining an incident wave that travels in the brake pipe in a direction away from the pump and a reflected wave that travels in the brake pipe in a direction opposite to the direction of travel of the incident wave. The brake pipe includes a metal pipe connected to an actuator having the pump, and a flexible hose made of rubber that guides the brake fluid that has flowed through the metal pipe to the wheel cylinder. The motor control method causes a processing circuit that controls the electric motor to execute a process of estimating a thermal history of the flexible hose, a process of estimating a waveform of the standing wave such that the wavelength of the standing wave in the flexible hose becomes longer as the hardness of the flexible hose that can be estimated from the thermal history of the flexible hose increases, and a process of setting a command value for the rotation speed of the electric motor based on the estimated waveform of the standing wave. Effect of the Invention

[0008] The braking system and the motor control method described above have the advantage of being able to suppress the occurrence of vehicle body vibrations caused by the operation of the pump. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a vehicle on which a braking system according to an embodiment is mounted. [Diagram 2] FIG. 2 is a diagram showing the waveform of a standing wave generated in the brake pipe provided in the braking system of FIG. [Diagram 3] FIG. 3 is a graph showing the relationship between the thermal degradation time and the hardness of the flexible member, and the relationship between the thermal degradation time and the speed of sound. [Figure 4] FIG. 4 is a flowchart showing a series of processes executed to update the thermal degradation time in the brake control device provided in the brake system of FIG. [Diagram 5] FIG. 5 is a flowchart showing a series of processes executed to drive the electric motor in the brake control device provided in the brake system of FIG. [Figure 6] FIG. 6 is a flowchart showing a series of processes executed to reset the thermal degradation time in the brake control device provided in the brake system of FIG. [Figure 7] FIG. 7 is a flowchart showing a series of processes executed in the brake control device provided in the brake system of FIG. 1 to store the thermal degradation time in the shared memory. [Figure 8] FIG. 8 is a flowchart showing a series of processes executed in the brake control device provided in the brake system of FIG. 1 for storing the thermal degradation time saved in the shared memory in the second memory. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of a braking system and a motor control method will be described with reference to FIGS. <Vehicle Overview> 1 illustrates a vehicle 10 equipped with a braking system 20. The vehicle 10 further includes a number of wheels 11, a shared memory 100, and a power source 110.

[0011] When the driving switch of the vehicle 10 is on, the power source 110 supplies power to a plurality of actuators and a plurality of electronic control devices mounted on the vehicle. That is, when the driving switch of the vehicle 10 is on, power is supplied from the power source 110 to the braking system 20. On the other hand, when the driving switch is off, the power supply from the power source 110 to the braking system 20 is stopped. An example of a driving switch is an ignition switch.

[0012] The shared memory 100 is a non-volatile memory. The shared memory 100 can be accessed by any of a plurality of electronic control devices. That is, a plurality of electronic control devices are connected to the shared memory 100 via an in-vehicle network 120. An example of the in-vehicle network 120 is a CAN bus. CAN is an abbreviation of "Controller Area Network."

[0013] <Braking system> The braking system 20 includes a brake operating member 21, a friction brake 30, a brake actuator 40, a brake pipe 50, a plurality of sensors, and a brake control device 70. The brake operating member 21 is operated by the driver of the vehicle 10 when decelerating the vehicle 10. An example of the brake operating member 21 is a brake pedal.

[0014] <Friction brake> Each of the multiple friction brakes 30 generates a braking force on the corresponding wheel 11. For example, the friction brake 30 has a wheel cylinder 31, a rotating body 32, and a friction portion 33. The rotating body 32 rotates integrally with the wheel 11. Therefore, a braking force is generated on the wheel 11 by pressing the friction portion 33 against the rotating body 32. The fluid pressure in the wheel cylinder 31 is called the "WC pressure." At this time, the higher the WC pressure, the greater the force pressing the friction portion 33 against the rotating body 32. Therefore, in the friction brake 30, the higher the WC pressure, the greater the braking force generated on the wheel 11.

[0015] <Braking actuator> The brake actuator 40 has an electric motor 41, a pump 42, and a hydraulic circuit. An example of the pump 42 is a gear pump. The electric motor 41 is a power source for the pump 42. The pump 42 discharges brake fluid in response to the driving of the electric motor 41. The hydraulic circuit connects the pump 42 to a brake pipe 50. When brake fluid is discharged from the pump 42, it is supplied to the brake pipe 50 via the hydraulic circuit. When the brake fluid discharged from the pump 42 is supplied to the wheel cylinder 31 via the brake pipe 50, a WC pressure is generated in the wheel cylinder 31. The brake actuator 40 is configured to be able to individually adjust the WC pressure of the multiple wheel cylinders 31.

[0016] <Brake piping> The brake piping 50 supplies brake fluid discharged from the pump 42 to the wheel cylinder 31. A first end of the brake piping 50 is connected to the brake actuator 40, while a second end of the brake piping 50 is connected to the friction brake 30. The braking system 20 includes a plurality of brake piping 50 corresponding to each of the plurality of friction brakes 30.

[0017] The brake piping 50 has a metal piping 51 made of a metal material and a flexible hose 55 made of rubber. The metal piping 51 is connected to the brake actuator 40. The flexible hose 55 is connected to the friction brake 30 and guides the brake fluid that has flowed through the metal piping 51 to the wheel cylinder 31. For example, a first end of the flexible hose 55 is connected to the metal piping 51, while a second end of the flexible hose 55 is connected to the friction brake 30.

[0018] When braking system 20 is mounted on vehicle 10, metal pipe 51 is fixed to the body of vehicle 10 via fasteners 15. Metal pipe 51 is fixed to the body at a plurality of different positions via fasteners 15. When the portion of metal pipe 51 to which fastener 15 is fixed is defined as "fixed portion 52," metal pipe 51 is provided with a plurality of fixed portions 52.

[0019] <Multiple sensors> The multiple sensors output detection signals according to the detection results to the braking control device 70. The multiple sensors include, for example, a hydraulic pressure sensor 61, an outside air temperature sensor 62, and multiple wheel speed sensors 63. For example, the hydraulic pressure sensor 61 detects the hydraulic pressure generated in the hydraulic circuit by the operation of the pump 42. The outside air temperature sensor 62 detects the outside air temperature, which is the temperature around the vehicle 10. The wheel speed sensors 63 output signals according to the rotation speeds of the corresponding wheels 11.

[0020] The hydraulic pressure based on the detection signal of the hydraulic pressure sensor 61 is referred to as the "detected hydraulic pressure Pf." The temperature based on the detection signal of the outside air temperature sensor 62 is referred to as the "outside air temperature TMPout." The rotational speed of the wheels 11 based on the detection signal of the wheel speed sensor 63 is referred to as the "wheel speed VW."

[0021] <Brake control device> The braking control device 70 includes a processing circuit 71. One example of the processing circuit 71 is an electronic control device. In this case, the processing circuit 71 includes a CPU 72, a first memory 73, and a second memory 74. The first memory 73 stores a control program executed by the CPU 72. The CPU 72 executes the control program, whereby the processing circuit 71 operates the braking actuator 40. In other words, the processing circuit 71 controls the braking force generated on the multiple wheels 11.

[0022] The second memory 74 stores the calculation results of the CPU 72. For example, the second memory 74 stores the thermal history of the flexible hose 55 as an example of the calculation results of the CPU 72. In the present embodiment, the second memory 74 is an example of a "storage unit" that stores the thermal history of the flexible hose 55. The thermal history of the flexible hose 55 will be described later.

[0023] The braking control device 70 communicates with other electronic control devices and accesses the shared memory 100 via the in-vehicle network 120. For example, when a predetermined backup condition is met, the processing circuit 71 stores various pieces of information stored in the second memory 74 in the shared memory 100. Also, for example, when a predetermined access condition is met, the processing circuit 71 acquires the various pieces of information stored in the shared memory 100 and stores them in the second memory 74. The braking control device 70 is configured so that the processing circuit 71 and the second memory 74 can execute predetermined processing even after the driving switch is turned off, for example, by a backup power source using a battery or a capacitor (not shown).

[0024] <Functional configuration of the processing circuit> The processing circuit 71 functions as a plurality of functional units as a result of the CPU 72 executing the control program in the first memory 73. For example, the plurality of functional units include a motor control unit M11, a temperature estimation unit M12, a thermal history estimation unit M13, a hardness estimation unit M14, a reset processing unit M15, and a backup processing unit M16.

[0025] <Motor control unit> The motor control unit M11 adjusts the discharge pressure of the brake fluid from the pump 42 by controlling the driving of the electric motor 41. As will be described in detail later, the motor control unit M11 adjusts a motor rotation speed command value NmtTr, which is a command value for the motor rotation speed, in accordance with the thermal history of the flexible hose 55. The motor rotation speed is the rotation speed of the rotor of the electric motor 41. When discharging brake fluid from the pump 42, the motor control unit M11 drives the electric motor 41 based on the motor rotation speed command value NmtTr.

[0026] <Temperature estimation part> The temperature estimation unit M12 estimates a hose temperature TMPhE, which is the temperature of the flexible hose 55. The temperature estimation unit M12 estimates the hose temperature TMPhE based on the outside air temperature TMPout and the amount of heat generated in the friction brake 30 due to the generation of a braking force on the wheel 11. For example, the temperature estimation unit M12 estimates the hose temperature TMPhE so that the higher the outside air temperature TMPout, the higher the hose temperature TMPhE.

[0027] When a braking force is generated on the wheel 11, frictional heat is generated between the friction portion 33 and the rotating body 32. The greater the force pressing the friction portion 33 against the rotating body 32, the greater the amount of frictional heat generated between the friction portion 33 and the rotating body 32. The force pressing the friction portion 33 against the rotating body 32 corresponds to the WC pressure of the wheel cylinder 31. Therefore, the higher the WC pressure, the greater the amount of heat generated in the friction brake 30. Therefore, the temperature estimation unit M12 estimates the WC pressure based on the detected hydraulic pressure Pf. The temperature estimation unit M12 derives an estimated value of the amount of heat generated such that the higher the estimated value of the WC pressure, the greater the estimated value of the amount of heat generated in the friction brake 30. In addition, the temperature estimation unit M12 derives an estimated value of the amount of heat generated such that the longer the duration of the state in which the WC pressure is generated in the wheel cylinder 31, the greater the estimated value of the amount of heat generated in the friction brake 30. Then, the temperature estimation unit M12 estimates the hose temperature TMPhE such that the higher the estimated value of the amount of heat generated, the higher the temperature.

[0028] <Thermal History Estimation Section> As the deterioration of the flexible hose 55 progresses, the hardness of the flexible hose 55 increases. The higher the hardness of the flexible hose 55, the less likely the flexible hose 55 will expand when the brake fluid is supplied to the wheel cylinder 31 by the operation of the pump 42. As a result, as the hardness of the flexible hose 55 increases, the sound velocity, which is the speed of the sound waves generated by the pulsation of the brake fluid flowing through the flexible hose 55, increases. When the sound velocity changes in this way, the waveform of the standing wave generated in the brake pipe 50 changes. The "standing wave" here is a wave that is generated when the brake fluid discharged from the pump 42 flows through the brake pipe 50. In more detail, the standing wave is a wave that is a composite of an incident wave that travels in the brake pipe 50 in a direction away from the pump 42 and a reflected wave that travels in the brake pipe 50 in a direction opposite to the direction in which the incident wave travels.

[0029] 2A and 2B show an example of a standing wave generated in the brake piping 50. The vertical axis in Fig. 2B represents the pulse pressure normalized by dividing the pulse pressure of the brake fluid flowing in the brake piping 50 by the maximum fluid pressure.

[0030] The metal pipe 51 and the flexible hose 55 have different hardnesses. Specifically, the hardness of the metal pipe 51 is higher than that of the flexible hose 55. Therefore, the speed of sound generated in the metal pipe 51 is higher than that in the flexible hose 55. As a result, the wavelength of the standing wave is longer in the metal pipe 51 than in the flexible hose 55. As a result, the waveform of the standing wave generated in the brake pipe 50 becomes as shown in FIG. 2(B).

[0031] The wheel cylinder 31 of the friction brake 30 has a large volume. Therefore, a node X1 of the standing wave appears at the connection portion of the flexible hose 55 with the friction brake 30. Note that the above-mentioned standing wave has multiple nodes X1 and antinodes X2 between the nodes X1.

[0032] Returning to FIG. 1, the thermal history estimation unit M13 estimates the thermal history of the flexible hose 55. The flexible hose 55 has a characteristic that deterioration progresses faster when the temperature is high compared to when the temperature is low. Therefore, the thermal history of the flexible hose 55 is an index indicating the degree of deterioration of the flexible hose 55 caused by the heat received by the flexible hose 55. In this embodiment, the thermal history estimation unit M13 derives the thermal deterioration time TMat as the thermal history of the flexible hose 55. For example, the thermal history estimation unit M13 can derive the thermal deterioration time TMat by using the following relational expression (D1). In the following relational expression (D1), "TMPh" is the temperature of the flexible hose 55. "TMd" is time. In this case, the integrated value of the product of the hose temperature TMPh and the time TMd is derived as the thermal deterioration time TMat.

[0033]

number

[0034] Deterioration of the flexible hose 55 due to heat reception progresses not only while the power supply 110 is on, but also while the power supply 110 is off. Therefore, when the power supply 110 is on, the thermal history estimation unit M13 updates the thermal deterioration time TMat by integrating the product of the hose temperature TMPhE derived by the temperature estimation unit M12 and time.

[0035] Meanwhile, the thermal history estimation unit M13 updates the thermal degradation time TMat based on the vehicle position information and seasonal information when the power supply 110 is off, and the power off time TMoff. The vehicle position information is information related to the position of the vehicle 10. An example of the vehicle position information is information related to the latitude of the current position of the vehicle 10. The seasonal information is information that identifies the season. The power off time TMoff is the duration during which the power supply 110 is off.

[0036] While the power supply 110 is off, the friction brake 30 does not operate, and therefore the temperature of the flexible hose 55 can be considered to be equivalent to the outside air temperature. Therefore, while the power supply 110 is off, the thermal history estimation unit M13 can update the thermal degradation time TMat by integrating the product of the outside air temperature and time.

[0037] The thermal history estimation unit M13 can predict the transition of the outside air temperature during the period when the power supply 110 was off by referring to the vehicle position information and the seasonal information. For example, the thermal history estimation unit M13 derives the average value of the outside air temperature during the period when the power supply 110 was off based on the transition of the outside air temperature during the period when the power supply 110 was off. The thermal history estimation unit M13 can also derive the power off time TMoff by acquiring the time when the power supply 110 was turned off and the time when the power supply 110 was turned on thereafter. The thermal history estimation unit M13 can then substitute the average value of the outside air temperature into "TMPh" in the above relational expression (D1) and substitute the power off time TMoff into "TMd" in the relational expression (D1) to reflect the deterioration caused by the heat reception of the flexible hose 55 during the period when the power supply 110 was off in the thermal deterioration time TMat.

[0038] Fig. 3(A) shows the relationship between the hardness of the flexible hose 55 and the thermal degradation time TMat. Fig. 3(B) shows the relationship between the sound speed, which is the speed of sound waves generated by the pulsation of the brake fluid flowing inside the flexible hose 55, and the thermal degradation time TMat. As shown in Fig. 3(A) and (B), as the thermal degradation time TMat increases, both the hardness and the sound speed of the flexible hose 55 increase. In other words, it can be said that there is a correspondence relationship between the hardness of the flexible hose 55 and the sound speed.

[0039] <Hardness estimation section> The hardness estimation unit M14 estimates the hose hardness Hh based on the thermal history of the flexible hose 55 estimated by the thermal history estimation unit M13. The hose hardness Hh is the hardness of the flexible hose 55. In this embodiment, since the thermal degradation time TMat is derived as the thermal history of the flexible hose 55, the hardness estimation unit M14 estimates the hose hardness Hh based on the thermal degradation time TMat. For example, the hardness estimation unit M14 estimates the hose hardness Hh such that the longer the thermal degradation time TMat, the greater the hardness. In this case, the hardness estimation unit M14 may derive the hose hardness Hh in accordance with the 10°C 2 times rule.

[0040] The thermal degradation time TMat increases as the period during which the temperature of the flexible hose 55 is high increases. Therefore, the longer the period during which the temperature of the flexible hose 55 is high, the higher the hose hardness Hh increases.

[0041] <Reset processing section> When detecting that the flexible hose 55 has been replaced, the reset processing unit M15 resets the thermal history of the flexible hose 55 stored in the second memory 74. Specifically, the reset processing unit M15 resets the thermal degradation time TMat to 0 (zero).

[0042] For example, when an operator performs maintenance on the vehicle 10, such as replacing the flexible hose 55, the operator connects a maintenance tool to the in-vehicle network 120. Then, when the operator replaces the flexible hose 55, the operator causes the maintenance tool to transmit a hose replacement signal indicating that the flexible hose 55 has been replaced to the braking control device 70 via the in-vehicle network 120. In this case, when the reset processing unit M15 receives the hose replacement signal, it detects that the flexible hose 55 has been replaced.

[0043] <Backup processing section> The processing circuit 71 of the braking control device 70 may be replaced with a new electronic control device. Even in this case, the worker connects the maintenance tool to the in-vehicle network 120. Then, the worker transmits a device replacement signal indicating the start of replacement of the braking control device 70 from the maintenance tool to the braking control device 70 via the in-vehicle network 120. In this case, the backup processing unit M16 determines that the above-mentioned predetermined backup condition is satisfied. Then, the backup processing unit M16 stores various information stored in the second memory 74 in the shared memory 100. That is, the thermal history of the flexible hose stored in the second memory 74 is saved in the shared memory 100. Thereafter, when the replacement of the braking control device 70 is completed, the processing circuit 71 of the new braking control device 70, that is, the backup processing unit M16, determines whether or not the above-mentioned access condition is satisfied. For example, when the thermal history of the flexible hose 55 stored in the second memory 74 is initialized, the backup processing unit M16 determines that the above-mentioned access condition is satisfied. Then, the backup processing unit M16 acquires the above-mentioned various information from the shared memory 100. Then, the backup processor M16 stores the acquired various information in the second memory 74.

[0044] <Hose hardness calculation process> A series of processes executed by the processing circuit 71 when deriving the hose hardness Hh will be described with reference to Fig. 4. When the power supply 110 is on, the processing circuit 71 repeatedly executes the series of processes for each predetermined control cycle.

[0045] In step S101, the processing circuit 71 acquires vehicle position information and a current time TM1. The current time TM1 acquired here is the time when the power supply 110 is turned on. Therefore, the time TM1 acquired in step S101 is referred to as the "on time TM1." In the following step S103, the processing circuit 71 acquires season information.

[0046] In the next step S105, the processing circuit 71 derives the power-off time TMoff. In this series of processes, when the power supply 110 is turned off, in step S117 described later, the processing circuit 71 acquires the time TM2 at which the power supply 110 is turned off. The time TM2 acquired in step S117 is referred to as the "off-time TM2." The processing circuit 71 derives the power-off time TMoff as the difference between the off-time TM2 acquired in the previous execution of this series of processes and the on-time TM1 acquired in the current execution of this series of processes.

[0047] Then, in step S107, the processing circuit 71 updates the thermal degradation time TMat based on the degradation of the flexible hose 55 caused by heat reception while the power supply 110 was off. That is, the processing circuit 71 estimates and calculates the average value of the outside air temperature during the period when the power supply 110 was off as the temperature of the flexible hose 55 based on the vehicle position information and seasonal information. Then, the processing circuit 71 updates the thermal degradation time TMat by substituting the estimated temperature of the flexible hose 55 during the period when the power supply 110 was off and the power off time TMoff into the above relational expression (D1). Then, the processing circuit 71 transitions the process to step S109.

[0048] In step S109, the processing circuit 71 estimates the hose temperature TMPhE based on the outside air temperature TMPout and the amount of heat generated in the friction brake 30 due to the generation of a braking force on the wheels 11.

[0049] In the next step S111, the processing circuit 71 updates the thermal degradation time TMat based on the degradation of the flexible hose 55 caused by the heat reception while the power supply 110 is on. For example, the processing circuit 71 updates the thermal degradation time TMat by substituting the time length of the derivation cycle of the hose temperature TMPhE in step S109 and the hose temperature TMPhE derived in step S109 into the above relational expression (D1).

[0050] Then, in step S113, the processing circuit 71 derives the hose hardness Hh based on the thermal degradation time TMat. For example, the processing circuit 71 derives the hardness according to the thermal degradation time TMat as the hose hardness Hh based on the relationship shown in Fig. 3(A). In this way, the processing circuit 71 can derive the hose hardness Hh such that the hose hardness Hh becomes higher as the thermal degradation time TMat is longer.

[0051] In the following step S115, the processing circuit 71 determines whether the power supply 110 will be turned off. For example, the processing circuit 71 determines that the power supply 110 will be turned off when the operation switch is turned off. When the processing circuit 71 determines that the power supply 110 will not be turned off (S115: NO), the processing circuit 71 shifts the processing to step S109. That is, the processing circuit 71 repeats updating the thermal degradation time TMat and deriving the hose hardness Hh by executing the processing of steps S109, S111, and S113. On the other hand, when the processing circuit 71 determines that the power supply 110 will be turned off (S115: YES), the processing circuit 71 shifts the processing to step S117.

[0052] In step S117, the processing circuit 71 acquires the vehicle position information and the off-time TM2, which is the current time, and then ends the series of processes. 4, the processes of steps S107 and S111 are executed by the processing circuit 71 functioning as the thermal history estimation unit M13. The process of step S109 is executed by the processing circuit 71 functioning as the temperature estimation unit M12. The process of step S113 is executed by the processing circuit 71 functioning as the hardness estimation unit M14.

[0053] <Electric motor drive processing> 5, a series of processes executed by the processing circuit 71 when operating the electric motor 41 will be described. When the power supply 110 is on, the processing circuit 71 executes the series of processes at each predetermined control cycle.

[0054] In step S201, the processing circuit 71 derives the sound speed Ch, which is the speed of sound waves generated in the flexible hose 55, based on the hose hardness Hh. As described above, there is a correlation between the hose hardness Hh and the sound speed Ch. Therefore, the processing circuit 71 derives the sound speed Ch so that it increases as the hose hardness Hh increases.

[0055] In the next step S203, the processing circuit 71 estimates the waveform of a standing wave generated in the brake pipe 50 based on the change in the sound speed Ch. Assuming that the motor rotation speed is fixed, as the sound speed Ch increases, the wavelength of the standing wave in the flexible hose 55 becomes longer. This changes the waveform of the standing wave in the brake pipe 50. In other words, the positions of the node X1 and antinode X2 of the standing wave change in the brake pipe 50.

[0056] Although details will be described later, in this embodiment, the motor rotation speed command value NmtTr is set so that node X1 of the standing wave appears near fixed portion 52 of metal pipe 51. Therefore, under the condition that the motor rotation speed is constant, when the sound speed Ch changes and the wavelength of the standing wave in flexible hose 55 becomes longer, node X1 of the standing wave moves away from fixed portion 52 and antinode X2 of the standing wave approaches fixed portion 52.

[0057] Returning to Fig. 5, when the processing circuit 71 estimates the waveform of the standing wave, the processing proceeds to step S205. In step S205, the processing circuit 71 derives a motor rotation speed command value NmtTr such that the value increases as the sound speed Ch derived in step S201 increases. At this time, the processing circuit 71 derives, as the motor rotation speed command value NmtTr, a motor rotation speed at which the node X1 of the standing wave does not move away from the fixed portion 52 of the metal pipe 51. In other words, in step S205, the processing circuit 71 derives the motor rotation speed command value NmtTr in consideration of the waveform of the standing wave estimated in step S203.

[0058] In the next step S207, the processing circuit 71 determines whether or not there is a braking request. If the brake operating member 21 is being operated or if a request to decelerate the vehicle 10 is made from another control device, it is determined that there is a braking request. On the other hand, if neither the brake operating member 21 is being operated nor a request to decelerate the vehicle 10 is made from another control device, it is determined that there is no braking request. If the processing circuit 71 determines that there is a braking request (S207: YES), it shifts the processing to step S209. On the other hand, if the processing circuit 71 determines that there is no braking request (S207: NO), it temporarily ends the series of processing steps shown in FIG. 5.

[0059] In step S209, the processing circuit 71 drives the electric motor 41 to discharge brake fluid from the pump 42. At this time, the processing circuit 71 drives the electric motor 41 based on the motor rotation speed command value NmtTr derived in step S205. As a result, the motor rotation speed becomes substantially equal to the motor rotation speed command value NmtTr.

[0060] As described above, the motor rotation speed command value NmtTr is derived based on the sound speed Ch. The sound speed Ch corresponds to the hose hardness Hh. The hose hardness Hh is derived based on the thermal degradation time TMat, which is an example of the thermal history of the flexible hose 55. Therefore, it can be said that the motor rotation speed command value NmtTr is a motor rotation speed based on the thermal degradation time TMat. Furthermore, the thermal degradation time TMat becomes larger as the period during which the temperature of the flexible hose 55 is high becomes longer. Therefore, it can be said that by driving the electric motor 41 based on the motor rotation speed command value NmtTr, the motor rotation speed becomes larger as the period during which the temperature of the flexible hose 55 is high becomes longer.

[0061] After driving the electric motor 41 in this manner, the processing circuit 71 temporarily ends the series of processes shown in FIG. Of the series of processes shown in FIG. 5, the processes of steps S205, S207, and S209 are executed by the processing circuit 71 functioning as the motor control unit M11.

[0062] <How to replace the flexible hose> 6, a series of processes executed by the processing circuit 71 to reset the thermal degradation time TMat when the flexible hose 55 is replaced will be described. The flexible hose 55 is replaced while the power supply 110 is off. Therefore, the processing circuit 71 executes the series of processes when the power supply 110 is turned on.

[0063] In step S301, the processing circuit 71 determines whether or not it has detected that the flexible hose 55 has been replaced. For example, when the braking control device 70 receives the hose replacement signal from a maintenance tool connected to the in-vehicle network 120, the processing circuit 71 detects that the flexible hose 55 has been replaced. When the processing circuit 71 detects that the flexible hose 55 has been replaced (S301: YES), the processing circuit 71 shifts the processing to step S303. On the other hand, when the processing circuit 71 does not detect that the flexible hose 55 has been replaced (S301: NO), the processing circuit 71 ends the series of processing.

[0064] In step S303, the processing circuit 71 resets the thermal degradation time TMat to 0 (zero). That is, the processing circuit 71 resets the thermal history of the flexible hose 55 stored in the second memory 74. After that, the processing circuit 71 ends the series of processes.

[0065] The series of processes shown in FIG. 6 is executed by the processing circuit 71 functioning as the reset processing unit M15. <Process of storing the thermal history of the flexible hose in the shared memory> With reference to FIG. 7, a series of operations performed by the processing circuit 71 to store the thermal history of the flexible hose 55 in the shared memory 100 when the braking control device 70 is replaced with a new control device will now be described.

[0066] In step S401, the processing circuit 71 determines whether or not replacement of the braking control device 70 is to be started. For example, when the braking control device 70 receives the device replacement signal from a maintenance tool connected to the in-vehicle network 120, the processing circuit 71 can determine that replacement of the braking control device 70 is to be started. When the processing circuit 71 determines that replacement of the braking control device 70 is to be started (S401: YES), the processing circuit 71 can determine that the backup condition is satisfied, and therefore shifts the processing to step S403. On the other hand, when the processing circuit 71 determines that replacement of the braking control device 70 is not to be started (S401: NO), the processing circuit 71 can determine that the backup condition is not satisfied, and therefore ends the series of processing.

[0067] In step S403, the processing circuit 71 stores the thermal degradation time TMat stored in the second memory 74 in the shared memory 100. When the thermal degradation time TMat is stored in the shared memory 100 in this manner, the processing circuit 71 ends the series of processes.

[0068] The series of processes shown in FIG. 7 is executed by the processing circuit 71 functioning as the backup processing unit M16. <Processing for transferring the thermal history of a flexible hose to a new braking control device> With reference to FIG. 8, a series of processes executed by the processing circuit 71 when transferring the thermal history of the flexible hose 55 to the second memory 74 of the new brake control device 70 after replacement will be described.

[0069] In step S501, the processing circuit 71 judges whether or not the thermal degradation time TMat stored in the second memory 74 is an initial value. If the thermal degradation time TMat is the initial value (S501: YES), the processing circuit 71 judges that the above access condition is satisfied because the brake control device 70 has been replaced, and shifts the processing to step S503. On the other hand, if the thermal degradation time TMat is not the initial value (S501: NO), the processing circuit 71 can judge that the above access condition is not satisfied, and therefore ends the series of processing.

[0070] In step S503, the processing circuit 71 acquires the thermal degradation time TMat stored in the shared memory 100 via the in-vehicle network 120. In the following step S505, the processing circuit 71 stores the acquired thermal degradation time TMat in the second memory 74. After that, the processing circuit 71 ends the series of processes.

[0071] The series of processes shown in FIG. 8 is executed by the processing circuit 71 functioning as the backup processing unit M16. <Actions and Effects of the Present Embodiment> (1) The brake piping 50 includes a metal piping 51 and a flexible hose 55. The hardness of the flexible hose 55 is different from the hardness of the metal piping 51. Therefore, when the brake fluid discharged from the pump 42 flows through the brake piping 50, the wavelength of the standing wave in the flexible hose 55 is different from the wavelength of the standing wave in the metal piping 51. Furthermore, the hardness of the flexible hose 55 gradually increases due to the heat received by the flexible hose 55. In other words, the wavelength of the standing wave in the flexible hose 55 becomes longer as time passes.

[0072] Therefore, when the motor rotation speed command value NmtTr is fixed at a predetermined value even if the hardness of the flexible hose 55 changes, the positions of the node X1 and antinode X2 of the standing wave in the metal pipe 51 change due to the change in hardness of the flexible hose 55. In other words, the antinode X2 of the standing wave approaches the fixed portion 52 of the metal pipe 51 due to the change in hardness of the flexible hose 55. As a result, vibration caused by the operation of the pump 42 is easily transmitted to the vehicle body via the brake pipe 50 and the fastener 15.

[0073] Therefore, in the braking system 20, the processing circuit 71 varies the motor rotation speed command value NmtTr based on the thermal history of the flexible hose 55. Specifically, the processing circuit 71 changes the motor rotation speed command value NmtTr based on the thermal history so that the longer the period during which the temperature of the flexible hose 55 was high, the larger the value becomes.

[0074] The processing circuit 71 drives the electric motor 41 according to the motor rotation speed command value NmtTr when generating a braking force on the wheels 11. This prevents the antinode X2 of the standing wave from approaching the fixed portion 52 in the metal pipe 51 even if the hardness of the flexible hose 55 increases due to heat reception.

[0075] Therefore, the braking system 20 can suppress the occurrence of vehicle body vibrations caused by the operation of the pump 42. (2) The processing circuit 71 derives the thermal degradation time TMat as the thermal history of the flexible hose 55. That is, the processing circuit 71 updates the thermal degradation time TMat by integrating the product of the hose temperature TMPhE and time when the power supply 110 is on.

[0076] Here, deterioration of the flexible hose 55 due to heat reception progresses even when the power source 110 is off. When the power source 110 is off, the temperature of the flexible hose 55 becomes substantially the same as the outside air temperature.

[0077] Therefore, the processing circuit 71 estimates the transition of the outside air temperature during the period when the power supply 110 is off based on the vehicle position information and seasonal information. Based on the estimation result, the processing circuit 71 derives the average value of the outside air temperature during the period when the power supply 110 is off. The processing circuit 71 updates the thermal degradation time TMat based on the average value of the outside air temperature and the power off time TMoff. Then, the processing circuit 71 sets the motor rotation speed command value NmtTr based on this thermal degradation time TMat.

[0078] As a result, when a standing wave occurs in the brake piping 50 due to the operation of the pump 42, the braking system 20 can effectively prevent the anti-node X2 of the standing wave from approaching the fixed portion 52.

[0079] (3) When the power supply 110 is on, the processing circuit 71 estimates the hose temperature TMPhE based on the outside air temperature TMPout and the amount of heat generated in the friction brake 30. In other words, the processing circuit 71 can obtain the hose temperature TMPhE without providing a temperature sensor that detects the temperature of the flexible hose 55.

[0080] (4) As the hardness of the flexible hose 55 increases, the speed of sound Ch in the flexible hose 55 increases. As a result, the wavelength of the standing wave in the flexible hose 55 becomes longer. Therefore, the processing circuit 71 derives the hose hardness Hh based on the thermal degradation time TMat. Furthermore, the processing circuit 71 estimates the wavelength of the standing wave in the flexible hose 55 based on the hose hardness Hh, and estimates the waveform of the standing wave generated in the brake piping 50. That is, in the braking system 20, the waveform of the standing wave generated in the brake piping 50 can be estimated with high accuracy.

[0081] Furthermore, the processing circuit 71 sets a motor rotation speed command value NmtTr based on the estimated waveform of the standing wave generated in the brake pipe 50. Then, the processing circuit 71 drives the electric motor 41 based on the motor rotation speed command value NmtTr. As a result, the braking system 20 can drive the electric motor 41 so as to suppress the antinode X2 of the standing wave from approaching the fixed portion 52.

[0082] (5) The flexible hose 55 may be replaced with a new hose. The replaced flexible hose 55 does not receive heat. Therefore, the hardness of the replaced flexible hose 55 is lower than the hardness of the flexible hose 55 before the replacement.

[0083] Therefore, when the flexible hose 55 is replaced, the processing circuit 71 resets the thermal degradation time TMat stored in the second memory 74. As a result, the processing circuit 71 does not adjust the motor rotation speed based on the thermal history of the flexible hose 55 before replacement. In other words, the processing circuit 71 adjusts the motor rotation speed based on the thermal history of the replaced flexible hose 55. Therefore, the braking system 20 can suppress the increase in vehicle body vibration accompanying the operation of the pump 42 caused by the replacement of the flexible hose 55.

[0084] (6) The braking control device 70 may be replaced with a new control device. In the braking system 20, even if the braking control device 70 is replaced with a new control device, the thermal history of the flexible hose 55 is transferred to the second memory 74 of the new braking control device 70. Therefore, the processing circuit 71 of the new braking control device 70 can adjust the motor speed based on the thermal history of the flexible hose 55. Therefore, the braking system 20 can suppress the increase in vehicle body vibration associated with the operation of the pump 42 due to the replacement of the braking control device 70.

[0085] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0086] In the above embodiment, when the braking control device 70 is replaced with a new control device, the heat history of the flexible hose 55 stored in the second memory 74 is stored in the shared memory 100, but this is not limited to the above. For example, when the braking control device 70 is replaced with a new control device, the various information stored in the second memory 74 of the braking control device 70 before replacement is stored in the maintenance tool via the in-vehicle network 120. Then, after the braking control device 70 is replaced, the various information stored in the maintenance tool is stored in the second memory 74 of the new braking control device 70.

[0087] The longer the thermal degradation time TMat, the higher the hose hardness Hh. Therefore, the processing circuit 71 may set the motor rotation speed command value NmtTr based on the thermal degradation time TMat. And the processing circuit 71 does not have to estimate the hose hardness Hh. Even in this case, the processing circuit 71 can change the motor rotation speed command value NmtTr as the hardness of the flexible hose 55 changes.

[0088] A temperature sensor such as a thermistor may be provided in the flexible hose 55. In this case, the processing circuit 71 can detect a hose temperature, which is the temperature of the flexible hose 55, based on a detection signal from the temperature sensor.

[0089] In the above embodiment, the temperature of the flexible hose 55 is estimated based on the exposure of the flexible hose 55 to heat from the outside, such as heat generated by the friction brake 30 or the outside air temperature, but this is not limited to the above. For example, the processing circuit 71 may estimate the temperature of the flexible hose 55 based on the temperature of the brake fluid, taking into account the exposure of heat to the flexible hose 55 from the inside.

[0090] In the above embodiment, the processing circuit 71 estimates the hose temperature TMPhE based on the outside air temperature TMPout and the amount of heat generated in the friction brake 30 as a result of the generation of braking force on the wheels 11, and calculates the thermal degradation time TMat, which is the thermal history, based on the estimated hose temperature TMPhE, but this is not limited to the above. For example, the processing circuit 71 may calculate the thermal history from the amount of heat that the flexible hose 55 is exposed to from the outside air and heat generated by the friction brake 30, without estimating the hose temperature TMPhE.

[0091] It can be assumed that the amount of heat received by the flexible hose 55 during the period when the power supply 110 is off is smaller than that during the period when the power supply 110 is on. Therefore, the processing circuit 71 may update the thermal degradation time TMat without taking into account the period when the power supply 110 is off.

[0092] A plurality of fixed parts 52 are provided on the metal pipe 51 of the brake pipe 50. For example, one of the plurality of fixed parts 52 is set as a "reference fixed part." Of the plurality of fixed parts 52, the fixed part 52 located closest to the friction brake 30 may be set as the reference fixed part, or the fixed part 52 located closest to the brake actuator 40 may be set as the reference fixed part. Also, of the plurality of fixed parts 52, the fixed part 52 located closest to the driver may be set as the reference fixed part, or the fixed part 52 provided at a part of the fixed parts 52 where the vehicle body side is most likely to vibrate may be set as the reference fixed part. Then, the processing circuit 71 may adjust the motor rotation speed command value NmtTr so that the node X1 of the standing wave is located at the reference fixed part.

[0093] In the above embodiment, the motor rotation speed command value NmtTr is adjusted so that the node X1 of the standing wave does not move away from the fixed portion 52, but this is not limiting. For example, the processing circuit 71 may adjust the motor rotation speed command value NmtTr so that the node X1 of the standing wave does not move away from the bent portion of the brake pipe 50. When the antinode X2 of the standing wave is located at the bent portion of the brake pipe 50, the vibration of the pipe increases, and the increased vibration is transmitted to the vehicle body via the fixed portion 52 that fixes the brake pipe 50, so that the vehicle body vibration increases. Therefore, by adjusting the motor rotation speed command value NmtTr so that the node X1 of the standing wave does not move away from the bent portion of the brake pipe 50, the vehicle body vibration caused by the operation of the pump 42 can be suppressed from increasing. Here, when multiple bends are provided in the brake pipe, one of the multiple bends may be set as the "reference bend." For example, among the multiple bends, the bend that is closest to the reference fixed part may be set as the reference bend, or the bend that is farthest from the adjacent fixed part 52 may be set as the reference bend. Then, the processing circuit 71 may adjust the motor rotation speed command value NmtTr so that the node X1 of the standing wave is positioned at the reference bend.

[0094] The wavelength of the standing wave in the metal pipe 51 is "λ1", and the length of one eighth of the wavelength λ1 of the standing wave is the predetermined length. The region in the metal pipe 51 that includes the fixed part 52 is defined as the predetermined region. When a point on the metal pipe 51 that is a predetermined length from the fixed part 52 to the brake actuator 40 side is defined as a first boundary point, and a point on the metal pipe 51 that is a predetermined length from the fixed part 52 to the friction brake 30 side is defined as a second boundary point, the portion of the metal pipe 51 from the first boundary point to the second boundary point is the predetermined region. At this time, the processing circuit 71 may adjust the motor rotation speed command value NmtTr so that the node X1 of the standing wave is located within the above-mentioned predetermined region. For example, when the hardness of the flexible hose 55 increases due to heat reception, changing the waveform of the standing wave generated in the brake pipe 50 and thus shifting the node X1 outside the predetermined region, the processing circuit 71 maintains the state in which the node X1 is located within the predetermined region by increasing the motor rotation speed.

[0095] Although only one brake pipe 50 is shown in FIG. 1, in reality, the braking system 20 includes multiple brake pipes 50. The multiple brake pipes 50 have different lengths. Therefore, the processing circuit 71 may control the electric motor 41 to suppress transmission of brake fluid pulsation to the vehicle body from a reference brake pipe, which is one of the multiple brake pipes 50. In this case, the reference brake pipe is preferably the brake pipe 50 that transmits vibrations caused by brake fluid pulsation to the vehicle body the most. In addition, the reference brake pipe may be the longest brake pipe 50 or the shortest brake pipe 50 among the multiple brake pipes 50.

[0096] The processing circuit 71 is not limited to a circuit having a CPU and a ROM and executing software processing. That is, the processing circuit 71 may have any one of the following configurations (a), (b), and (c).

[0097] (a) The processing circuit 71 includes one or more processors that execute various processes according to a computer program. 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 execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer.

[0098] (b) The processing circuit 71 includes one or more dedicated hardware circuits for executing various processes. Examples of the dedicated hardware circuits include application specific integrated circuits, i.e., ASIC and FPGA. ASIC is an abbreviation for "Application Specific Integrated Circuit" and FPGA is an abbreviation for "Field Programmable Gate Array."

[0099] (c) The processing circuitry 71 includes a processor that executes some of the various processes in accordance with a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes. [Explanation of symbols]

[0100] 10. Vehicle 11...Wheel 20…Braking system 30…Friction brake 31...Wheel cylinder 32...Rotating body 33...Friction part 40...Braking actuator (an example of an actuator) 41...Electric motor 42…Pump 50…Brake piping 51...Metal piping 55...Flexible hose 70...Brake control device 71... Processing circuit (an example of an electronic control device) 73...Second memory (an example of a storage unit) 110...Power supply M11: Motor control unit M12…Temperature estimation section M13…Heat history estimation section M14...Hardness estimation part M15: Reset processing section

Claims

1. A braking system installed in a vehicle, comprising: an actuator having a pump that discharges brake fluid in response to driving of an electric motor; a friction brake having a wheel cylinder and generating a braking force corresponding to a hydraulic pressure of the wheel cylinder on a wheel of the vehicle; a brake pipe for supplying the brake fluid discharged by the pump to the wheel cylinder, the brake pipe being connected to the actuator and the friction brake; the brake piping is connected to the actuator and includes a metal piping made of a metal material, and a flexible hose made of rubber that guides the brake fluid that has flowed through the metal piping to the wheel cylinder, and a motor control unit that increases the motor rotation speed, which is the rotation speed of the electric motor, based on a thermal history, which is a history of changes in the temperature of the flexible hose, as the period during which the temperature of the flexible hose is high becomes longer. Braking system.

2. a thermal history estimation unit that estimates the thermal history of the flexible hose; The thermal history estimation unit is estimating a thermal history of the flexible hose based on an integrated value of the temperature of the flexible hose and time when the power supply of the vehicle is on; A thermal history of the flexible hose is estimated based on information about the location of the vehicle and information about the season when the power is off, and a duration of the state in which the power is off.

2. The braking system of claim 1.

3. The friction brake generates a braking force on the wheel by pressing a friction portion against a rotating body that rotates integrally with the wheel, and a temperature estimation unit that estimates a temperature of the flexible hose based on an outside air temperature, which is the temperature around the vehicle, and an amount of heat generated in the friction brake when a braking force is generated on the wheel, when the power supply is on.

3. The braking system of claim 2.

4. a hardness estimation unit that estimates a hardness of the flexible hose based on the thermal history of the flexible hose estimated by the thermal history estimation unit, The motor control unit increases the motor rotation speed as the hardness increases. A braking system according to claim 2 or 3.

5. A reset processing unit is provided which resets the thermal history of the flexible hose when it is detected that the flexible hose has been replaced.

3. The braking system of claim 2.

6. The braking system includes an electronic control device that functions as the motor control unit and the thermal history estimation unit, the electronic control device having a storage unit that stores the thermal history of the flexible hose, In the braking system, when the electronic control device is replaced with a new one, the thermal history of the flexible hose before the replacement of the electronic control device is stored in the memory unit of the new replaced electronic control device.

3. The braking system of claim 2.

7. A motor control method for controlling an electric motor that is a power source of a pump that discharges brake fluid, comprising: When the brake fluid discharged from the pump is supplied to a wheel cylinder of a friction brake through a brake piping, a standing wave is generated in the brake piping, which is a wave obtained by combining an incident wave traveling in a direction away from the pump in the brake piping and a reflected wave traveling in a direction opposite to the direction in which the incident wave travels in the brake piping, the brake piping includes a metal pipe connected to an actuator having the pump, and a flexible hose made of rubber for guiding the brake fluid flowing through the metal pipe to the wheel cylinder, A processing circuit for controlling the electric motor includes: A process for estimating a thermal history of the flexible hose; A process of estimating a waveform of the standing wave such that the wavelength of the standing wave in the flexible hose becomes longer as the hardness of the flexible hose, which can be estimated from the thermal history of the flexible hose, increases; and setting a command value for the number of revolutions of the electric motor based on the estimated waveform of the standing wave. Motor control methods.

Images