Braking system and method for designing brake pipe

Abstract

A braking system (20) comprises a brake pipe (50) that connects an actuator (40) and a friction brake (30). The brake pipe (50) includes a metal pipe (51), a flexible hose (55), and a fluid amount consumption unit (57). The metal pipe (51) includes fixed portions (52) to which each of a plurality of fasteners (15) is attached. One of the plurality of fixed portions (52) is a reference fixed portion (52A). The fluid amount consumption unit (57) is disposed in a part of the brake pipe (50) between the reference fixed portion (52A) and the friction brake (30).

Description

Braking system and brake piping design method

[0001] The present disclosure relates to a braking system mounted on a vehicle and a method for designing brake piping provided in the braking system.

[0002] Patent Document 1 discloses a braking system that generates braking force on wheels by supplying brake fluid discharged from a pump driven by an electric motor to wheel cylinders through piping. When the braking system is installed on a vehicle, the piping is fixed to the vehicle body via fasteners. The part of the piping that is fixed to the vehicle body via 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 rotation speed of the electric motor, so that the antinode of a standing wave, which is a wave that is a combination of an incident wave traveling in the pipe in a direction away from the pump and a reflected wave traveling in the pipe in the opposite direction to the traveling direction of the incident wave, moves away from the fixed part of the pipe.

[0004] Japanese Patent Application Laid-Open No. 2021-84445

[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, the above system can only vary the motor rotation speed within this limited range. As a result, the above system may not be able to sufficiently separate the antinode of the standing wave from the fixed part. In other words, the above system may not be able to sufficiently suppress the transmission of vibrations caused by brake fluid pulsation in the piping to the vehicle body.

[0006] A braking system according to one aspect of the present disclosure is mounted on a vehicle. The braking system includes: an actuator having a pump configured to discharge brake fluid in response to drive of an electric motor; a friction brake having a wheel cylinder and configured to generate a braking force on a wheel of the vehicle corresponding to the hydraulic pressure in the wheel cylinder; and a brake pipe configured to supply the brake fluid discharged by the pump to the wheel cylinder and connected to the actuator and the friction brake. The brake pipe includes a metal pipe connected to the actuator; a flexible rubber hose connected to the friction brake and guiding brake fluid flowing through the metal pipe to the wheel cylinder; and a fluid consumption unit configured so that its capacity per unit length is greater than the capacity per unit length of the brake pipe. The metal pipe has multiple fixing parts. The metal pipe is fastened to the body of the vehicle via fasteners attached to each of the fixing parts. The portions of the metal pipe to which the fasteners are attached are the fixing parts. The metal pipe is provided with multiple fixing parts. One of the multiple fixing parts is a reference fixing part. The fluid consumption portion is disposed in a portion of the brake pipe between the reference fixed portion and the friction brake.

[0007] A brake pipe design method according to another aspect of the present disclosure is a brake pipe design method connected to an actuator having a pump that discharges brake fluid and a friction brake having a wheel cylinder. The brake pipe includes a metal pipe connected to the actuator and a flexible rubber hose connected to the friction brake and guiding brake fluid flowing through the metal pipe to the wheel cylinder. The metal pipe has multiple fixing portions to which multiple fasteners that fix the metal pipe to a vehicle body are respectively attached. One of the multiple fixing portions is a reference fixing portion. A fluid consumption portion having a capacity per unit length greater than the capacity per unit length of the brake pipe is disposed in a portion of the brake pipe between the reference fixing portion and the friction brake. When brake fluid discharged from the pump flows through the brake pipe, a standing wave is generated, which is a wave that is a combination of an incident wave traveling in the brake pipe in a direction away from the pump and a reflected wave traveling in the brake pipe in a direction opposite to the traveling direction of the incident wave. The brake piping design method includes setting at least one of the size and position of the fluid consumption portion 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 area of ​​the metal piping that includes the reference fixed portion.

[0008] Fig. 1 is a schematic diagram of a vehicle equipped with a braking system according to an embodiment. Fig. 2 is a diagram showing the waveform of a standing wave generated in a brake pipe provided in the braking system of Fig. 1. Fig. 3 is a diagram showing the waveform of a standing wave generated in a brake pipe of a modified example.

[0009] An embodiment of a braking system and a brake piping design method will be described below with reference to Figures 1 and 2. Figure 1 illustrates a vehicle 10 equipped with a plurality of wheels 11 and a braking system 20 that generates braking forces on the plurality of wheels 11.

[0010] <Brake System> The brake system 20 includes a brake operating member 21, a plurality of friction brakes 30, a brake actuator 40, a plurality of brake pipes 50, a plurality of sensors, and a brake control device 70. Fig. 1 shows one friction brake 30 corresponding to one wheel 11 and one brake pipe 50 corresponding to that friction brake 30. 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.

[0011] <Friction Brake> The multiple friction brakes 30 each generate 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, braking force is generated on the wheel 11 by pressing the friction portion 33 against the rotating body 32. The hydraulic pressure in the wheel cylinder 31 is called the "WC pressure." 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.

[0012] <Brake 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 brake pipes 50. When brake fluid is discharged from the pump 42, the brake fluid is supplied to each brake pipe 50 via the hydraulic circuit. When the brake fluid discharged from the pump 42 is supplied to the wheel cylinders 31 via each brake pipe 50, WC pressure is generated in each wheel cylinder 31. The brake actuator 40 is configured to be able to individually adjust the WC pressure of each wheel cylinder 31.

[0013] The specifications of the pump 42 and the electric motor 41 are determined based on the performance required of 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 from the pump 42 is 20 cc / s.

[0014] <Brake piping> Each brake piping 50 supplies brake fluid discharged from the pump 42 to the wheel cylinder 31 of the corresponding friction brake 30. A first end of each brake piping 50 is connected to the brake actuator 40, while a second end of each brake piping 50 is connected to the corresponding friction brake 30.

[0015] Brake piping 50 includes metal piping 51 made of a metal material and a flexible hose 55 made of rubber. Metal piping 51 is connected to brake actuator 40. Flexible hose 55 is connected to friction brake 30 and guides brake fluid flowing through metal piping 51 to wheel cylinder 31.

[0016] When the braking system 20 is mounted on the vehicle 10, the metal pipe 51 is fixed to the vehicle body 10A of the vehicle 10 via a plurality of fasteners 15. The metal pipe 51 is fixed to the vehicle body 10A via the fasteners 15 at a plurality of different positions in the longitudinal direction of the metal pipe 51. The metal pipe 51 has a plurality of fixing portions 52 to which the fasteners 15 are respectively fixed.

[0017] As shown in Figures 1 and 2A, the brake pipe 50 further includes a fluid consumption section 57. The fluid consumption section 57 is configured so that its capacity per unit length is greater than the capacity per unit length of the metal pipe 51. For example, the inner diameter of the fluid consumption section 57 is greater than the inner diameter of the metal pipe 51. The fluid consumption section 57 is also referred to as a large-capacity section. In this embodiment, the fluid consumption section 57 is located between the friction brake 30 and the fixed section 52 that is located closest to the friction brake 30 among the multiple fixed sections 52. Details of the fluid consumption section 57 will be described later.

[0018] 1 , the multiple sensors output detection signals corresponding to the detection results to the brake 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 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 corresponding to the rotational speeds of the corresponding wheels 11.

[0019] <Brake Control Device> The brake control device 70 includes a processing circuit 71. An 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. When the CPU 72 executes the control program, the processing circuit 71 activates the brake actuator 40. In other words, the processing circuit 71 controls the braking force generated on the multiple wheels 11.

[0020] <Functional Configuration of 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.

[0021] 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 a braking request is made, 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. The motor rotation speed is the rotation speed of the rotor of the electric motor 41.

[0022] 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 "predetermined braking control," and braking control with a relatively high urgency is defined as "emergency braking control." Predetermined braking control includes, for example, normal service brake control and braking control during ACC. ACC stands for "adaptive cruise control." Emergency braking control includes, for example, antilock brake control and collision mitigation brake control.

[0023] When the predetermined braking control is executed, the motor control unit M11 sets the motor rotation speed command value NmtTr to a motor rotation speed that causes the brake fluid discharge flow rate Qf of the pump 42 to fall 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 the maximum value Qfmax. Preferably, the upper limit of the predetermined discharge rate range is approximately one-fourth the maximum value Qfmax.

[0024] On the other hand, when emergency braking control is executed, the motor control unit M11 sets the motor rotation speed command value NmtTr to a motor rotation speed that causes the brake fluid discharge flow rate Qf of the pump 42 to be greater than the upper limit of a predetermined discharge amount range.

[0025] <Brake Pipe Design Method> First, with reference to Figures 2A and 2B, a description will be given of standing waves that occur in the brake pipe 50. Standing waves are waves that occur when brake fluid discharged from the pump 42 flows through the brake pipe 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 pipe 50 and a reflected wave that travels in the brake pipe 50 in a direction opposite to the direction in which the incident wave travels. Figure 2B shows an example of a standing wave that occurs when brake fluid is discharged from the pump 42 due to the execution of the above-mentioned predetermined braking control.

[0026] When brake fluid discharged from pump 42 flows through brake pipe 50, sound waves are generated within brake pipe 50 due to the pulsation of the brake fluid. The speed of sound, which is the speed of sound waves, increases as the hardness of the pipe increases. The hardness of metal pipe 51 is greater than that of flexible hose 55. Therefore, the speed of sound within metal pipe 51 is greater than the speed of sound within flexible hose 55. As a result, as shown in FIG. 2B , the wavelength of the standing wave is longer within metal pipe 51 than within flexible hose 55.

[0027] 2A, metal pipe 51 is provided with a plurality of fixed portions 52. When node X1 of the standing wave appears near fixed portion 52, vibrations caused by pulsation of brake fluid flowing inside brake pipe 50 are less likely to be transmitted to vehicle body 10A compared to when node X1 appears at a position farther away from fixed portion 52. Conversely, the closer antinode X2 of the standing wave is to fixed portion 52, the more easily vibrations caused by pulsation of brake fluid flowing inside brake pipe 50 are transmitted to vehicle body 10A.

[0028] In the braking system 20, a fluid consumption section 57 is provided in the brake pipe 50. By providing the fluid consumption section 57 in the brake pipe 50, the waveform of the standing wave can be changed. In other words, by adjusting the size and installation position of the fluid consumption section 57, the position where node X1 of the standing wave appears can be moved closer to the fixed section 52.

[0029] Therefore, in this brake pipe design method, the brake pipe 50 is designed as follows. One of the multiple fixed portions 52 provided on the metal pipe 51 is defined as the "reference fixed portion 52A." For example, the magnitude of vehicle body vibration when antinode X2 of the standing wave appears at the position of each fixed portion 52 is measured for each fixed portion 52. Preferably, the fixed portion 52 that produces the largest vehicle body vibration is set as the reference fixed portion 52A. When determining the reference fixed portion 52A in this manner, depending on the vehicle model, the fixed portion 52 that is closest to the friction brake 30 may become the reference fixed portion 52A, or the fixed portion 52 that is closest to the brake actuator 40 may become the reference fixed portion 52A. In the example shown in FIG. 2 , the fixed portion 52 that is closest to the brake actuator 40 is set as the reference fixed portion 52A.

[0030] The size and installation position of the fluid consumption portion 57 are set 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 that includes the reference fixed portion 52A.

[0031] 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 defined as the first wavelength λ1, and the length of one-eighth of the first wavelength λ1 is defined as the specified length Z1. A point that is the specified length Z1 away from the reference fixed portion 52A toward the brake actuator 40 is called the first boundary point Y1, and a point that is the specified length Z1 away from the reference fixed portion 52A toward the friction brake 30 is called the second boundary point Y2. The portion of the metal pipe 51 between the first boundary point Y1 and the second boundary point Y2 is the predetermined region 51A. The specified length Z1 is half the distance from a node to an antinode adjacent to the node. Therefore, when a node X1 of the standing wave appears within the predetermined region 51A, the distance from the reference fixed portion 52A to the node X1 of the standing wave is equal to or less than the distance from the reference fixed portion 52A to the antinode X2 of the standing wave. In other words, when node X1 of the standing wave appears within specified region 51A, the distance from reference fixed portion 52A to antinode X2 of the standing wave will never be closer than the distance from reference fixed portion 52A to node X1 of the standing wave.

[0032] The size and installation position of the liquid consuming section 57 are preferably set so as to satisfy the following condition (A2): (A2) The predetermined length L satisfies the following relational expression (D1).

[0033] L = ((1 / 2) x n ± (1 / 8)) λ1 (D1) The predetermined length L is the length of the brake pipe 50 from the node X1 of the standing wave located closest to the fluid consumption unit 57 to the reference fixed portion 52A in the portion of the metal pipe 51 between the fluid consumption unit 57 and the brake actuator 40. 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 greater than or equal to 0 (zero).

[0034] The frequency of the pulsation of the brake fluid flowing through the brake pipe 50 is defined as a reference frequency F0. When the resonant frequency of the brake pipe 50 matches the reference frequency F0, the amplitude of the brake fluid pulsation increases. In other words, the greater the deviation between the resonant frequency of the brake pipe 50 and the reference frequency F0, the smaller the amplitude of the brake fluid pulsation within the brake pipe 50.

[0035] Here, the brake pipe not provided with a fluid consumption unit is referred to as the comparative brake pipe. The volume of the brake pipe 50 is larger than that of the comparative brake pipe due to the provision of the fluid consumption unit 57. 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 unit 57 is lower than the resonant frequency of the comparative brake pipe.

[0036] 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, and the resonant frequency of the comparative brake pipe is defined as a second resonant frequency F2.

[0037] (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.

[0038] (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 deviation 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 assumed that the deviation between the first resonance frequency F1 and the second resonance frequency F2 is not very large. Therefore, even if the fluid consumption unit 57 is provided in the brake pipe 50, the amplitude of the pulsation of the brake fluid flowing through the brake pipe 50 does not decrease significantly.

[0039] <Actions and Effects of the Present Embodiment> (1) The fluid consumption unit 57 is disposed in a portion of the brake pipe 50 between the reference fixed portion 52A and the friction brake 30. The fluid consumption unit 57 is configured to satisfy the above-described condition (A1). As a result, the node X1 of the standing wave is located near the reference fixed portion 52A, and the antinode X2 of the standing wave can be separated from the reference fixed portion 52A. Therefore, when the brake fluid discharge flow rate of the pump 42 is within a predetermined discharge rate range, the braking system 20 can suppress transmission of vibrations caused by pulsation of the brake fluid flowing through the brake pipe 50 to the vehicle body 10A.

[0040] (2) The fluid consumption unit 57 is configured to satisfy the above condition (A2). As a result, when the brake fluid discharge flow rate of the pump 42 is within a predetermined discharge rate range, the braking system 20 can effectively suppress the transmission of vibrations caused by brake fluid pulsation to the vehicle body 10A via the reference fixed unit 52A.

[0041] (3) By providing the fluid consumption unit 57 in the brake pipe 50, the capacity of the brake pipe 50 increases, thereby reducing the resonant frequency of the brake pipe 50. Specifically, by providing the fluid consumption unit 57 in the brake pipe 50, the braking system 20 can satisfy both of the above conditions (B1) and (B2). This reduces the amplitude of pulsation of the brake fluid flowing through the brake pipe 50. Therefore, even if vibrations caused by pulsation of the brake fluid are transmitted to the vehicle body 10A via the fixed part 52, the braking system 20 can reduce the amplitude of the vehicle body vibrations.

[0042] <Modifications> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0043] The fluid consumption unit 57 provided in the brake pipe 50 does not need to satisfy the above condition (B2) as long as it can satisfy the above condition (B1). If the provision of the fluid consumption unit 57 in the brake pipe 50 can satisfy the above condition (A1), it is not essential to satisfy the above condition (A2).

[0044] The brake pipe 50 may be provided with a fluid consumption section 157 as shown in Fig. 3A. The volume of the fluid consumption section 157 is smaller than the volume of the fluid consumption section 57 shown in Fig. 2. By providing the fluid consumption section 157 in the brake pipe 50, it becomes possible to generate a standing wave as shown in Fig. 3B in the brake pipe 50. In other words, the amplitude of the standing wave can be made extremely small in the metal pipe 51.

[0045] 2 and 3, the fluid consumption unit 57, 157 is disposed in a portion of the metal pipe 51 between the fixed portion 52, which is closest to the friction brake 30, and the connection point of the metal pipe 51 to the flexible hose 55. However, the location of the fluid consumption unit 57, 157 is not limited to this. For example, the fluid consumption unit 57, 157 may be disposed between the metal pipe 51 and the flexible hose 55.

[0046] Since the distance from the brake actuator 40 to the wheel 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 fluid consumption units are provided on multiple brake pipes 50, the size and installation position of the fluid consumption units may differ for each brake pipe 50.

[0047] 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 portion 52 is measured for each fixed portion 52, and the fixed portion 52 with the largest vehicle body vibration at this time is set as the reference fixed portion 52A. However, this is not limited to this. For example, the magnitude of the vehicle body vibration when the node X1 of the standing wave appears at the position of the fixed portion 52 may be measured for each fixed portion 52, and the fixed portion 52 with the smallest vehicle body vibration at this time may be set as the reference fixed portion 52A. Also, for example, the fixed portion 52 located closest to the driver may be set as the reference fixed portion 52A.

[0048] 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. However, this is not limited to this. 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 increases, and the increased vibration of the brake pipe 50 is transmitted to the vehicle body 10A via the fixed portion 52 that fixes the brake pipe 50. This increases vehicle body vibration. 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 increase in vehicle body vibration caused by the operation of the pump 42 can be suppressed. Here, if the brake pipe 50 has multiple bends, one of the multiple bends may be set as the "reference bend." For example, the reference bend may be set to the bend that is closest to the reference fixed part among the multiple bends, or the bend that is farthest from the adjacent fixed part 52. The size and installation position of the liquid volume consuming part 57 may then be adjusted so that the position where node X1 of the standing wave appears is closer to the reference bend.

[0049] The processing circuitry 71 is not limited to a circuit having a CPU and ROM and executing software processing. In other words, the processing circuitry 71 may have any one of the following configurations (a), (b), and (c):

[0050] (a) The processing circuitry 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 code or instructions configured to cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0051] (b) The processing circuit 71 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application specific integrated circuits (ASICs) or FPGAs. ASIC stands for "Application Specific Integrated Circuit," and FPGA stands for "Field Programmable Gate Array."

[0052] (c) The processing circuitry 71 includes a processor that executes some of the various processes in accordance with a computer program, and dedicated hardware circuits that execute the remaining processes of the various processes.

Claims

1. A braking system to be mounted on a vehicle, comprising: an actuator having a pump configured to discharge brake fluid in response to drive of an electric motor; a friction brake having a wheel cylinder and configured to generate a braking force on a wheel of the vehicle corresponding to the hydraulic pressure in the wheel cylinder; and a brake piping configured to supply the brake fluid discharged by the pump to the wheel cylinder, the brake piping being connected to the actuator and the friction brake, wherein the brake piping comprises: a metal piping connected to the actuator; a flexible rubber hose connected to the friction brake and directing the brake fluid flowing within the metal piping to the wheel cylinder; and a fluid consuming unit configured to have a capacity per unit length greater than the capacity per unit length of the brake piping, the metal piping having a plurality of fixing parts, the metal piping being fastened to a body of the vehicle via fasteners respectively attached to the fixing parts, one of the plurality of fixing parts being a reference fixing part, and the fluid consuming unit being disposed in a portion of the brake piping between the reference fixing part and the friction brake.

2. A braking system as described in claim 1, wherein 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 the opposite direction to the direction of the incident wave within the brake piping, a braking control in which the discharge amount of the brake fluid from the pump falls within a predetermined discharge amount range is a predetermined braking control, and the fluid volume 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 area of ​​the metal piping which includes the reference fixed portion.

3. A braking system as described in claim 2, wherein a predetermined length of the brake piping in a portion of the metal piping between the fluid consumption unit and the actuator is L, the length of the brake piping from the node of the standing wave located closest to the fluid consumption unit to the reference fixed portion, the wavelength of the standing wave in the metal piping is λ1, and n is an integer greater than or equal to 0 (zero), and the predetermined length satisfies the following relationship: L = ((1 / 2) x n ± (1 / 8)) · λ1.

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, wherein the brake piping comprises a metal piping connected to the actuator, and a flexible rubber hose connected to the friction brake and guiding the brake fluid flowing through the metal piping to the wheel cylinder, the metal piping has a plurality of fixing parts to which a plurality of fasteners for fixing the metal piping to a vehicle body are respectively attached, one of the plurality of fixing parts is a reference fixing part, and a fluid consuming part having a capacity per unit length greater than the capacity per unit length of the brake piping is disposed in a portion of the brake piping between the reference fixing part and the friction brake, and when brake fluid discharged from the pump flows through the brake piping, a standing wave is generated which is a wave that is a composite of an incident wave that travels in a direction away from the pump within the brake piping and a reflected wave that travels in the brake piping in a direction opposite to the direction of travel of the incident wave, a brake piping design method including: setting at least one of a size and a position of the fluid consumption portion such that a node of the standing wave is located within a predetermined region of the metal piping that includes the reference fixed portion when a predetermined braking control is executed in which the discharge volume of the pump falls within a predetermined discharge volume range.

5. A method for designing brake piping as claimed in claim 4, comprising setting a size of the fluid consumption unit so as to satisfy all of the following: a pulsation frequency of brake fluid flowing inside the brake piping when brake fluid is discharged from the pump by execution of the specified braking control is a reference frequency, a resonant frequency of the brake piping is a first resonant frequency, a resonant frequency of the brake piping not provided with the fluid consumption unit is a second resonant frequency, a first deviation which is the deviation between the first resonant frequency and the reference frequency is greater than a second deviation which is the deviation between the second resonant frequency and the reference frequency, and a difference between the first deviation and the second deviation is equal to or greater than a specified value.

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