Brake system and design method of brake pipe

Abstract

To inhibit vibration caused by pulsation of a blake fluid flowing in a brake pipe from being transmitted to a vehicle body of a vehicle even if a motor rotation number of an electric motor is not changed.SOLUTION: A brake system includes a brake pipe 50 which connects a brake actuator 40 with a friction brake 30. The brake pipe 50 has a metal pipe 51, a flexible hose 55, and a fluid volume consuming section 57. When a portion, to which a fastener 15 is attached, of the metal pipe 51 is referred to as a fixed part 52, a plurality of fixed parts 52 are provided at the metal pipe 51. When one of the plurality of fixed parts 52 is referred to as a reference fixed part 52A, the fluid volume consuming section 57 is arranged at a portion, which is located closer to the friction brake 30 side relative to the reference fixed part 52A, of the brake pipe 50.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a braking system mounted on a vehicle and a method for designing brake piping provided in the braking system. [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] The range in which the motor rotation speed can be changed is limited by the brake fluid discharge pressure required for the pump and the torque applied to the electric motor. Therefore, in the above system, the motor rotation speed can only be varied within this limited range. As a result, in the above system, the antinode of the standing wave may not be sufficiently separated from the fixed part. In other words, in the above system, there is a risk that the transmission of vibrations caused by the pulsation of the brake fluid in the piping to the vehicle body may not be sufficiently suppressed. [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 corresponding to the hydraulic pressure of the wheel cylinder on the wheels of the vehicle, 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 includes a metal pipe made of metal and connected to the actuator, a flexible hose made of rubber that is connected to the friction brake and leads the brake fluid flowing through the metal pipe to the wheel cylinder, and a fluid consumption unit configured to have a capacity per unit length larger than the capacity per unit length of the brake pipe. The metal pipe is fastened to the body of the vehicle via a fastener. When a portion of the metal pipe to which the fastener is attached is defined as a fixed portion, the metal pipe is provided with a plurality of the fixed portions. When one of the plurality of fixed portions is defined as a reference fixed portion, the fluid consumption unit is disposed in a portion of the brake pipe closer to the friction brake than the reference fixed portion.

[0007] A design method for brake piping for solving the above problem is a design method for brake piping connected to an actuator having a pump for discharging brake fluid and a friction brake having a wheel cylinder. The brake piping includes a metal pipe made of metal connected to the actuator, and a flexible hose made of rubber connected to the friction brake and guiding the brake fluid flowing through the metal pipe to the wheel cylinder. When the metal pipe is fixed to a vehicle body via fasteners, the metal pipe is provided with a plurality of fixing parts to which the fasteners are attached, and when one of the plurality of fixing parts is set as a reference fixing part, a fluid consumption part having a capacity per unit length larger than the capacity per unit length of the brake pipe is arranged in a part of the brake pipe closer to the friction brake than the reference fixing part. When the brake fluid discharged from the pump flows through the brake pipe, a standing wave is generated, which is a wave obtained by combining an incident wave traveling in a direction away from the pump in the brake pipe and a reflected wave traveling in the brake pipe in a direction opposite to the direction of the incident wave. In the brake piping design method, at least one of the size and position of the fluid consumption portion is set so that, when a specified braking control is executed in which the pump's discharge volume falls within a specified discharge volume range, a node of the standing wave is located within a specified region of the metal piping that includes the reference fixed portion. Effect of the Invention

[0008] To suppress the transmission of vibration caused by pulsation of brake fluid flowing in a brake pipe to a vehicle body without changing the motor rotation speed of an electric motor. [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 diagram showing the waveform of a standing wave generated in a brake pipe of the modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of a method for designing a braking system and brake piping will be described with reference to FIGS. FIG. 1 illustrates a vehicle 10 equipped with a number of wheels 11 and a braking system 20 for generating braking forces on the wheels 11 .

[0011] <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.

[0012] <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.

[0013] <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.

[0014] The specifications of the pump 42 and the electric motor 41 are determined based on the performance required for the brake actuator 40. For example, the pump 42 and the electric motor 41 are designed so that the maximum value Qfmax of the discharge flow rate of the brake fluid of the pump 42 is "20 cc / s."

[0015] <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.

[0016] The brake piping 50 has a metal piping 51 made of a metal material and a rubber flexible hose 55. 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.

[0017] When the braking system 20 is mounted on the vehicle 10, the metal pipe 51 is fixed to the body of the vehicle 10 via the fasteners 15. The metal pipe 51 is fixed to the body at a plurality of different positions via the fasteners 15. The portion of the metal pipe 51 to which the fasteners 15 are fixed is referred to as a "fixed portion 52." At this time, the metal pipe 51 is provided with a plurality of fixed portions 52.

[0018] As shown in Fig. 1 and Fig. 2(A), the brake piping 50 further includes a fluid consuming section 57. The fluid consuming section 57 is configured so that the capacity per unit length is larger than the capacity per unit length of the metal piping 51. For example, the inner diameter of the fluid consuming section 57 is larger than the inner diameter of the metal piping 51. In this embodiment, the fluid consuming section 57 is disposed on the friction brake 30 side of the fixed section 52 that is located closest to the friction brake 30 among the multiple fixed sections 52. Details of the fluid consuming section 57 will be described later.

[0019] <Multiple sensors> As shown in Fig. 1, 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] <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 and a memory 73. The 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.

[0021] <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 memory 73. For example, the plurality of functional units includes a motor control unit M11.

[0022] 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. When there is a braking request, the motor control unit M11 drives the electric motor 41 based on a motor rotation speed command value NmtTr, which is a command value for the motor rotation speed. Note that the motor rotation speed is the rotation speed of the rotor of the electric motor 41.

[0023] The motor rotation speed command value NmtTr is changed depending on the type of braking control. Braking control with a relatively low urgency is defined as "prescribed braking control", and braking control with a relatively high urgency is defined as "emergency braking control". Prescribed braking control includes, for example, normal service brakes and braking control during ACC. ACC is "adaptive cruise control". Emergency braking control includes, for example, antilock brake control and collision mitigation brake.

[0024] When a predetermined braking control is executed, the motor control unit M11 sets the motor rotation speed command value NmtTr to such a value that the discharge flow rate Qf of the brake fluid from the pump 42 falls within a predetermined discharge rate range. The upper limit of the predetermined discharge rate range is sufficiently smaller than the maximum value Qfmax. For example, the upper limit of the predetermined discharge rate range is smaller than half of the maximum value Qfmax. Preferably, the upper limit of the predetermined discharge rate range is about one-quarter of the maximum value Qfmax.

[0025] On the other hand, when emergency braking control is executed, the motor control unit M11 sets the motor rotation speed command value NmtTr to such a motor rotation speed that the discharge flow rate Qf of the brake fluid from the pump 42 becomes greater than the upper limit of a predetermined discharge amount range.

[0026] <Brake piping design method> First, standing waves occurring in the brake piping 50 will be described with reference to Figures 2(A) and (B). Standing waves are waves that occur when brake fluid discharged from the pump 42 flows through the brake piping 50. In more detail, standing waves are waves that are a combination of an incident wave that travels in a direction away from the pump 42 within the brake piping 50 and a reflected wave that travels in a direction opposite to the direction in which the incident wave travels within the brake piping 50. Figure 2(B) shows an example of a standing wave occurring when brake fluid is discharged from the pump 42 by executing the above-mentioned predetermined braking control.

[0027] When the brake fluid discharged from the pump 42 flows through the brake piping 50, sound waves are generated in the brake piping 50 due to the pulsation of the brake fluid. When the speed of sound waves is the speed of sound, the higher the hardness of the piping, the higher the speed of sound. The hardness of the metal piping 51 is higher than that of the flexible hose 55. Therefore, the speed of sound in the metal piping 51 is higher than that in the flexible hose 55. As a result, as shown in FIG. 2B, the wavelength of the standing wave is longer in the metal piping 51 than in the flexible hose 55.

[0028] 2A, metal pipe 51 is provided with a plurality of fixed parts 52. When node X1 of the standing wave appears near fixed part 52, vibrations caused by pulsation of brake fluid flowing inside brake pipe 50 are less likely to be transmitted to the vehicle body compared to when node X1 appears at a position away from fixed part 52. Conversely, the closer antinode X2 of the standing wave is to fixed part 52, the more easily vibrations caused by pulsation of brake fluid flowing inside brake pipe 50 are transmitted to the vehicle body.

[0029] In the braking system 20, the brake piping 50 is provided with a fluid consuming section 57. By providing the fluid consuming section 57 in the brake piping 50, it is possible to change the waveform of the standing wave. In other words, by adjusting the size and installation position of the fluid consuming section 57, it is possible to move the position where node X1 of the standing wave appears closer to the fixed section 52.

[0030] Therefore, in the present brake piping design method, the brake piping 50 is designed as follows. One of the multiple fixed parts 52 provided on the metal pipe 51 is defined as the "reference fixed part 52A". For example, the magnitude of the vehicle body vibration when the antinode X2 of the standing wave appears at the position of the fixed part 52 is measured for each fixed part 52. At this time, it is preferable to set the fixed part 52 with the largest vehicle body vibration as the reference fixed part 52A. When determining the reference fixed part 52A in this manner, depending on the vehicle model, the fixed part 52 located closest to the friction brake 30 among the multiple fixed parts 52 may become the reference fixed part 52A, or the fixed part 52 located closest to the brake actuator 40 may become the reference fixed part 52A. In the example shown in FIG. 2, the fixed part 52 located closest to the brake actuator 40 is set as the reference fixed part 52A.

[0031] The size and installation position of the liquid consuming section 57 are set so as to satisfy the following condition (A1). (A1) When the electric motor 41 is driven so that the brake fluid discharge flow rate Qf of the pump 42 falls within a predetermined discharge range, a node X1 of a standing wave appears in the metal pipe 51 within a predetermined region 51A including the reference fixed portion 52A.

[0032] For example, the range of the predetermined region 51A is set as follows. The wavelength of the standing wave in the metal pipe 51 is the first wavelength λ1, and the length of one eighth of the first wavelength λ1 is the designated length Z1. A point on the brake actuator 40 side from the reference fixed part 52A by the designated length Z1 is called the first boundary point Y1, and a point on the friction brake 30 side from the reference fixed part 52A by the designated length Z1 is called the second boundary point Y2. At this time, the part of the metal pipe 51 between the first boundary point Y1 and the second boundary point Y2 is the predetermined region 51A. In this case, the designated length Z1 represents the length to the center point between the node and the adjacent antinode. Therefore, when the node X1 of the standing wave appears in the predetermined region 51A, the distance from the reference fixed part 52A to the node X1 of the standing wave is equal to or less than the distance from the reference fixed part 52A to the antinode X2 of the standing wave. In other words, when node X1 of the standing wave appears in predetermined region 51A, the distance from reference fixed part 52A to antinode X2 of the standing wave will never be closer than the distance from reference fixed part 52A to node X1 of the standing wave.

[0033] It is preferable that the size and installation position of the liquid consuming section 57 are set so as to satisfy the following condition (A2). (A2) The predetermined length L satisfies the following relational expression (D1).

[0034] L=((1 / 2)×n±(1 / 8))·λ1 ···(D1) The predetermined length L is the length of the brake pipe 50 from a node X1 of the standing wave that is located closest to the fluid consumption section 57 on the brake actuator 40 side of the metal pipe 51 relative to the fluid consumption section 57 to the reference fixed section 52A. In the above relational expression (D1), the first wavelength λ1 is the wavelength of the standing wave in the metal pipe 51, and "n" is an integer equal to or greater than 0 (zero).

[0035] The frequency of the pulsation of the brake fluid flowing inside the brake piping 50 is defined as a reference frequency F0. In this case, when the resonant frequency of the brake piping 50 coincides with the reference frequency F0, the amplitude of the pulsation of the brake fluid becomes large. In other words, the greater the deviation between the resonant frequency of the brake piping 50 and the reference frequency F0, the smaller the amplitude of the pulsation of the brake fluid inside the brake piping 50 becomes.

[0036] Here, the brake pipe that is not provided with a fluid consumption section is referred to as a comparative brake pipe. The volume of the brake pipe 50 is larger than that of the comparative brake pipe by the amount of the fluid consumption section 57 provided. The larger the volume of the brake pipe, the smaller the resonant frequency of the brake pipe. Therefore, the resonant frequency of the brake pipe 50 provided with the fluid consumption section 57 is smaller than the resonant frequency of the comparative brake pipe.

[0037] Therefore, it is preferable to set the size of the fluid consumption portion 57 so as to satisfy both of the following conditions (B1) and (B2). The resonant frequency of the brake pipe 50 is defined as a first resonant frequency F1. The resonant frequency of the comparative brake pipe is defined as a second resonant frequency F2.

[0038] (B1) The first deviation is greater than the second deviation. The first deviation is the deviation between the first resonant frequency F1 and the reference frequency F0. The second deviation is the deviation between the second resonant frequency F2 and the reference frequency F0.

[0039] (B2) The difference between the first deviation and the second deviation is equal to or greater than a predetermined value. The predetermined value is a criterion for determining whether the difference between the first deviation and the second deviation is sufficiently large. If the difference between the first deviation and the second deviation is less than the predetermined value, it can be considered that the difference between the first resonance frequency F1 and the second resonance frequency F2 is not so large. Therefore, even if the fluid consumption unit 57 is provided in the brake piping 50, the amplitude of the pulsation of the brake fluid flowing through the brake piping 50 does not become so small.

[0040] <Actions and Effects of the Present Embodiment> (1) The fluid consumption unit 57 is disposed in a portion of the brake piping 50 that is closer to the friction brake 30 than the reference fixed portion 52A. The fluid consumption unit 57 is configured to satisfy the above condition (A1). As a result, the node X1 of the standing wave is located near the reference fixed portion 52A, so that the antinode X2 of the standing wave can be separated from the reference fixed portion 52A. Therefore, when the discharge flow rate of the brake fluid from the pump 42 is within a predetermined discharge flow rate range, the braking system 20 can suppress the transmission of vibrations caused by the pulsation of the brake fluid flowing through the brake piping 50 to the vehicle body.

[0041] (2) Fluid consumption unit 57 is configured to satisfy condition (A2) above. As a result, when the discharge flow rate of brake fluid from pump 42 is within a predetermined range, braking system 20 can effectively suppress the transmission of vibrations caused by pulsation of brake fluid to the vehicle body via reference fixed unit 52A.

[0042] (3) Furthermore, by providing the fluid consumption unit 57 in the brake piping 50, the capacity of the brake piping 50 increases, and accordingly the resonant frequency of the brake piping 50 decreases. More specifically, by providing the fluid consumption unit 57 in the brake piping 50, the braking system 20 can satisfy both of the above conditions (B1) and (B2). This reduces the amplitude of the pulsation of the brake fluid flowing through the brake piping 50. Therefore, even if the vibration caused by the pulsation of the brake fluid is transmitted to the vehicle body via the fixed part 52, the braking system 20 can reduce the amplitude of the vehicle body vibration at that time.

[0043] <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.

[0044] The fluid consumption section 57 provided in the brake pipe 50 does not need to satisfy the above condition (B2) so long as it can satisfy the above condition (B1). If the above condition (A1) can be satisfied by providing the fluid consumption section 57 in the brake pipe 50, it is not essential to satisfy the above condition (A2).

[0045] The brake piping 50 may be provided with a fluid volume consuming section 157 as shown in Fig. 3A. The volume of the fluid volume consuming section 157 is smaller than the volume of the fluid volume consuming section 57 shown in Fig. 2. By providing the fluid volume consuming section 157 in the brake piping 50, it becomes possible to generate a standing wave as shown in Fig. 3B in the brake piping 50. In other words, the amplitude of the standing wave in the metal piping 51 can be made extremely small.

[0046] 2 and 3, the fluid consumption unit 57, 157 is disposed between the fixed portion 52 of the metal pipe 51 that is located closest to the friction brake 30 and the connection point with the flexible hose 55. However, the location of the fluid consumption unit 57, 157 is not limited thereto. For example, the fluid consumption unit 57, 157 may be disposed between the metal pipe 51 and the flexible hose 55.

[0047] 1 illustrates only one brake pipe 50, but in reality, the braking system 20 includes multiple brake pipes 50. Since the distance from the brake actuator 40 to the wheels 11 differs for each wheel 11, the lengths of the metal pipes 51 of the multiple brake pipes 50 differ from one another. Therefore, when a fluid consumption unit is provided in each of the multiple brake pipes 50, the size and installation position of the fluid consumption unit may differ for each brake pipe 50.

[0048] In the above embodiment, the magnitude of the vehicle body vibration when the antinode X2 of the standing wave appears at the position of the fixed part 52 is measured for each fixed part 52, and the fixed part 52 with the largest vehicle body vibration at this time is set as the reference fixed part 52A, but this is not limited. For example, the magnitude of the vehicle body vibration when the node X1 of the standing wave appears at the position of the fixed part 52 may be measured for each fixed part 52, and the fixed part 52 with the smallest vehicle body vibration at this time may be set as the reference fixed part 52A. Also, for example, the fixed part 52 located closest to the driver may be set as the reference fixed part 52A.

[0049] In the above embodiment, the size and installation position of the fluid consumption unit 57 are adjusted so that the position where the node X1 of the standing wave appears is closer to the fixed portion 52, but this is not limiting. For example, the size and installation position of the fluid consumption unit 57 may be adjusted so that the position where the node X1 of the standing wave appears is closer to the bent portion of the brake pipe 50. When the bent portion of the brake pipe 50 is located at the antinode X2 of the standing wave, the vibration of the brake pipe 50 becomes large, and the increased vibration of the brake pipe 50 is transmitted to the vehicle body via the fixed portion 52 that fixes the brake pipe 50, and the vehicle body vibration becomes large. Therefore, by adjusting the size and installation position of the fluid consumption unit 57 so that the position where the node X1 of the standing wave appears is closer to 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 50, 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. The size and installation position of the liquid volume consuming part 57 may be adjusted so that the position where the node X1 of the standing wave appears is brought closer to the reference bend.

[0050] The processing circuit 71 is not limited to a circuit having a CPU and a ROM and executing software processing. In other words, the processing circuit 71 may have any one of the following configurations (a), (b), and (c).

[0051] (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.

[0052] (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."

[0053] (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]

[0054] 10. Vehicle 11...Wheel 15…Fastener 20…Braking system 30…Friction brake 31...Wheel cylinder 40...Braking actuator (an example of an actuator) 41...Electric motor 42…Pump 50…Brake piping 51...Metal piping 51A...Predetermined area 52…Fixed part 52A…Reference fixing part 55...Flexible hose 57,157…Liquid consumption section 70...Brake control device 71... Processing circuit

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 includes a metal pipe made of metal and connected to the actuator, a flexible hose made of rubber and connected to the friction brake and for directing the brake fluid that has flowed through the metal pipe to the wheel cylinder, and a fluid consumption section configured so that a capacity per unit length is larger than a capacity per unit length of the brake piping, the metal pipe is fastened to a body of the vehicle via a fastener, When a portion of the metal pipe to which the fastener is attached is defined as a fixed portion, the metal pipe is provided with a plurality of the fixed portions, When one of the plurality of fixed portions is set as a reference fixed portion, the fluid consumption portion is disposed in a portion of the brake pipe closer to the friction brake than the reference fixed portion. Braking system.

2. When the brake fluid discharged from the pump flows through the brake piping, a standing wave is generated which is a composite wave of an incident wave traveling in a direction away from the pump within the brake piping and a reflected wave traveling in a direction opposite to the direction of the incident wave within the brake piping, When the braking control in which the discharge amount of the pump falls within a predetermined discharge amount range is defined as a predetermined braking control, The fluid consumption unit is configured such that, when the predetermined braking control is being executed, a node of the standing wave is located within a predetermined region of the metal pipe that includes the reference fixed portion.

2. The braking system of claim 1.

3. Let L be a predetermined length of the brake piping from a node of the standing wave located closest to the fluid consumption unit on the actuator side of the metal piping relative to the fluid consumption unit to the reference fixed portion, let λ1 be a wavelength of the standing wave in the metal piping, and let n be an integer equal to or greater than 0 (zero), The predetermined length satisfies the following relational expression: L=((1 / 2)×n±(1 / 8))・λ1 3. The braking system of claim 2.

4. A method for designing brake piping connected to an actuator having a pump that discharges brake fluid and a friction brake having a wheel cylinder, comprising the steps of: the brake piping includes a metal pipe made of metal and connected to the actuator, and a flexible hose made of rubber that is connected to the friction brake and guides the brake fluid that has flowed through the metal pipe to the wheel cylinder, When the metal pipe is fixed to a vehicle body via a fastener, The metal pipe is provided with a plurality of fixing portions to which the fasteners are attached, when one of the plurality of fixed portions is defined as a reference fixed portion, a fluid consuming portion having a capacity per unit length larger than a capacity per unit length of the brake pipe is disposed in a portion of the brake pipe closer to the friction brake than the reference fixed portion, When the brake fluid discharged from the pump flows through the brake piping, a standing wave is generated which is a composite wave of an incident wave traveling in a direction away from the pump within the brake piping and a reflected wave traveling in a direction opposite to the direction of the incident wave within the brake piping, At least one of the size and the position of the liquid consumption portion is set so that a node of the standing wave is located within a range of a predetermined region including the reference fixed portion of the metal pipe when a predetermined braking control is executed in which the discharge amount of the pump falls within a predetermined discharge amount range. How to design brake piping.

5. a pulsation frequency of the brake fluid flowing through the brake piping when the brake fluid is discharged from the pump by executing the predetermined braking control is set as a reference frequency; a resonant frequency of the brake pipe is a first resonant frequency; When the resonance frequency of the brake piping not provided with the fluid consumption portion is defined as a second resonance frequency, A first deviation, which is a deviation between the first resonant frequency and the reference frequency, is greater than a second deviation, which is a deviation between the second resonant frequency and the reference frequency; and The difference between the first deviation and the second deviation is equal to or greater than a predetermined value. The size of the liquid consumption portion is set so as to satisfy any one of the above. The method for designing brake piping according to claim 4.

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