JP7017904B2 - Brake control device, brake control method and brake system - Google Patents

Description

The present invention relates to a brake control device, a brake control method, and a brake system.

A hydraulic brake system is known as a brake system mounted on a vehicle such as an automobile. In the hydraulic brake system, the drive of the pump and the solenoid valve provided in the hydraulic unit is controlled by the brake control device to perform various brake controls.

For example, there is a brake system equipped with a booster that amplifies the force applied to the brake pedal by the driver and transmits it to the master cylinder. In such a braking system, the amplified braking force is determined based on the relationship (F-Pw characteristic) between the preset pedaling force of the brake pedal (pedal pedaling force) and the pressure in the wheel cylinder (wheel cylinder pressure). ..

Japanese Unexamined Patent Publication No. 2016-117358

However, when the braking force is controlled based on the F-Pw characteristic, it is required to increase the rotational speed of the pump motor and increase the amount of hydraulic oil discharged by the pump. Hereinafter, a detailed description will be given with reference to FIGS. 14 and 15.

FIG. 14 is a diagram showing F-Pw characteristics in a brake system equipped with a conventional booster, and FIG. 15 is a diagram showing wheel cylinder pressure and hydraulic oil supplied to the wheel cylinder side in a brake system equipped with a conventional booster. It is a figure which shows the relationship with the quantity (Pw-Vw characteristic).

As shown in FIG. 14, the pressure boosting level by the booster is set so that the F-Pw characteristic (w / o_bost) when the booster is not used becomes the target F-Pw characteristic (tgt_FP). Will be done. In order to realize this target F-Pw characteristic (tgt_FP), it is necessary to drive the pump based on the Pw-Vw characteristic as shown in FIG.

According to this Pw-Vw characteristic, when the brake pedal is suddenly depressed, it is necessary to increase the amount of hydraulic oil discharged by the pump, especially in the region where the wheel cylinder pressure is low (the region surrounded by the broken line). In order to increase the discharge amount of the pump, it is required to increase the rotation speed of the pump motor.

When the rotation speed of the pump motor is increased, an unexpected amount of hydraulic oil is sucked from the master cylinder to the hydraulic pressure circuit side, so that the feeling given to the driver may differ depending on the speed at which the brake pedal is depressed. Further, increasing the rotational speed of the pump motor may reduce NVH (Noise / Vibration / Harshness) characteristics.

The present invention has been made in view of the above problems, and provides a brake control device, a brake control method, and a brake system capable of improving the feeling of a brake pedal given to a driver while suppressing deterioration of NVH characteristics.

According to a certain aspect of the present invention, in the brake control device for controlling the operation of the hydraulic pressure unit, the brake control device includes a discharge amount setting unit and a pump control unit, and the discharge amount setting unit is a piston rod of the master cylinder. Depending on the stroke amount, the amount of hydraulic oil stored in the master cylinder is determined so that the pedaling force of the brake pedal transmitted to the driver increases as the stroke amount increases, and the volume of the pressure chamber of the master cylinder according to the stroke amount. The discharge amount of the pump in the hydraulic pressure unit is set by subtracting the amount of hydraulic oil stored in the master cylinder from the reduced amount of hydraulic oil, and the pump control unit is based on the discharge amount. , A brake control device comprising controlling the drive of a pump is provided.

Further, according to another aspect of the present invention, in the brake control method for controlling the operation of the hydraulic pressure unit, the brake control device transmits to the driver as the stroke amount increases according to the stroke amount of the piston rod of the master cylinder. From the first step of determining the amount of hydraulic oil stored in the master cylinder so that the pedaling force of the brake pedal to be increased and the amount of decrease in the volume of the pressure chamber of the master cylinder according to the stroke amount, the operation by the amount of decrease The second step of setting the discharge amount of the pump of the hydraulic pressure unit by subtracting the amount of hydraulic oil stored in the master cylinder of the oil, and the third step of controlling the drive of the pump based on the discharge amount. A brake control method comprising the above is provided.

Further, according to another aspect of the present invention, in the brake system of the vehicle, the reservoir tank for holding the hydraulic oil, the master cylinder to which the hydraulic oil in the reservoir tank is supplied, and the amount of depression of the brake pedal by the driver are supported. It has a piston rod that moves forward and backward in the master cylinder, a stroke sensor that detects the stroke amount of the piston rod, and at least one pump, and hydraulic oil is supplied from the master cylinder to supply hydraulic pressure to the wheel cylinder. Depending on the unit and the stroke amount, the amount of hydraulic oil stored in the master cylinder is determined so that the pedaling force of the brake pedal transmitted to the driver increases as the stroke amount increases , and the pressure of the master cylinder according to the stroke amount. Based on the discharge amount setting unit that sets the discharge amount of the pump by subtracting the amount of hydraulic oil stored in the master cylinder from the reduced amount of hydraulic oil in the volume of the chamber, and the set discharge amount. A braking system is provided that comprises a pump control unit that controls the drive of the pump.

As described above, according to the present invention, it is possible to improve the feeling of the brake pedal given to the driver while suppressing the deterioration of the NVH characteristics.

It is a schematic diagram which shows the structural example of the brake system of the vehicle which concerns on embodiment of this invention. It is a block diagram which shows the structural example of the brake control device which concerns on the same embodiment. It is a flowchart which shows the drive control processing example of the pump by the brake control device which concerns on the same embodiment. It is explanatory drawing which shows the setting example of the discharge amount of a pump according to the stroke amount of a piston rod. It is a schematic diagram for demonstrating the discharge amount of a pump set by a discharge amount setting part. It is a figure which shows the relationship (FS characteristic) with the stroke amount of a piston rod, and a pedal pedaling force. It is a figure which shows the relationship (Pm-S characteristic) with the stroke amount of a piston rod, and the master cylinder pressure. It is a figure which shows the relationship (Vm-S characteristic) with the stroke amount of a piston rod, and the amount of hydraulic oil stored in a pressure chamber. It is explanatory drawing which shows the application example 1 of the process which sets the discharge amount of a pump based on the stroke amount of a piston rod. It is explanatory drawing which shows the application example 2 of the process which sets the discharge amount of a pump based on the stroke amount of a piston rod. It is a figure which shows the relationship (F-Pw characteristic) with a pedal pedaling force and a wheel cylinder pressure. It is a figure which shows the relationship (Pm-Pw characteristic) with a master cylinder pressure and a wheel cylinder pressure. It is a figure which shows the relationship (Pm-Vw characteristic) with the master cylinder pressure and the amount of hydraulic oil supplied to a wheel cylinder side. It is a figure which shows the F-Pw characteristic in the brake system equipped with the conventional booster. It is a figure which shows the Pw-Vw characteristic in the brake system equipped with the conventional booster.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

<1. Brake system configuration example>
A configuration example of the vehicle brake system 1 according to the present embodiment will be described with reference to FIG.

The brake system 1 of the present embodiment is constructed as a system that amplifies the pedaling force of the brake pedal 10 by the driver and transmits it to the wheel cylinder without using a booster. The brake system 1 shown in FIG. 1 includes a brake pedal 10, a reservoir tank 16, a master cylinder 14, and a hydraulic pressure unit 20.

The brake pedal 10 is stepped on by the driver when braking the vehicle. If it is an element that can input the driver's brake request, it may be replaced with an operating element of the brake pedal 10.

The brake pedal 10 is connected to the piston rod 11. The piston rod 11 is provided with a stroke sensor 8 for detecting a stroke amount which is an axial displacement amount of the piston rod 11.

The reservoir tank 16 holds hydraulic oil as a fluid that generates hydraulic pressure. The reservoir tank 16 is connected to the master cylinder 14 and supplies hydraulic oil into the master cylinder 14.

The master cylinder 14 holds the primary piston 12a and the secondary piston 12b so that they can move forward and backward. The master cylinder 14 shown in FIG. 1 is a tandem type master cylinder 14 and has two pressure chambers 13a and 13b defined by a primary piston 12a and a secondary piston 12b.

The primary piston 12a is provided at the tip of the piston rod 11. The secondary piston 12b is connected to the primary piston 12a via a coil spring 15a arranged in the pressure chamber 13a. A coil spring 15b connected to the secondary piston 12b is arranged in the pressure chamber 13b. In this embodiment, the spring forces of the two coil springs 15a and 15b are the same.

The respective capacities of the two pressure chambers 13a and 13b change according to the stroke amount of the piston rod 11. The two pressure chambers 13a and 13a are connected to the hydraulic circuits 28 and 30, respectively. By operating the brake pedal 10, the primary piston 12a and the secondary piston 12b are pressed via the piston rod 11, and the hydraulic oil moves to the hydraulic circuits 28 and 30.

The hydraulic pressure unit 20 includes two hydraulic pressure circuits 28 and 30 having the same configuration. Hydraulic oil is supplied to one hydraulic circuit 28 from one pressure chamber 13a of the master cylinder 14. Hydraulic oil is supplied to the other hydraulic circuit 30 from the other pressure chamber 13b of the master cylinder 14.

The brake system 1 according to the present embodiment is configured as a so-called X-type piping system in which one front wheel and one rear wheel at diagonal positions of the vehicle are used as a set to control hydraulic pressure by the respective hydraulic pressure circuits 28 and 30. ing.

In the example shown in FIG. 1, the hydraulic fluid is supplied to the wheel cylinder 38a of the hydraulic brake 22a of the right front wheel (FR) and the wheel cylinder 38b of the hydraulic brake 22b of the left rear wheel (RL) via the hydraulic circuit 28. Will be supplied.

Further, the hydraulic fluid is supplied to the wheel cylinder 38c of the hydraulic brake 22c of the left front wheel (FL) and the wheel cylinder 38d of the hydraulic brake 22d of the right rear wheel (RR) via the hydraulic circuit 30.

The brake system 1 is not limited to the X-type piping system. Further, the brake system 1 is not limited to the brake system of a four-wheeled vehicle, but can also be applied as a brake system of a two-wheeled vehicle or other vehicles.

In the brake system 1 according to the present embodiment, the hydraulic pressure circuit 30 has the same configuration as the hydraulic pressure circuit 28. Hereinafter, the hydraulic pressure circuit 28 will be described and the description of the hydraulic pressure circuit 30 will be omitted.

The hydraulic circuit 28 to which hydraulic oil is supplied from the pressure chamber 13a of the master cylinder 14 includes a plurality of solenoid valves. The solenoid valves include a circuit control valve 36 that is normally closed and can be linearly controlled, a suction valve 34 that is normally closed and controlled on and off, and pressure boosters 58a and 58b that are normally open and linearly controllable. It includes pressure reducing valves 54a and 54b that are controlled on and off.

Further, the hydraulic circuit 28 includes three pumps 44a, 44b, 44c driven by the pump motor 96. Hereinafter, when it is not necessary to distinguish them, they are collectively referred to as a pump 44. Further, the hydraulic circuit 28 includes an accumulator 71, a first damper 73 and a second damper 75.

The circuit control valve 36 communicates or shuts off between the master cylinder 14 and the booster valves 58a and 58b. The suction valve 34 communicates or shuts off between the master cylinder 14 and the suction side of the pump 44. The drive of the circuit control valve 36 and the suction valve 34 is controlled by a brake control device (not shown).

The circuit control valve 36 has a bypass flow path 41 with a check valve 40. The check valve 40 enables the hydraulic oil to move from the master cylinder 14 side to the hydraulic brake 22a of the right front wheel and the hydraulic brake 22b of the left rear wheel via the bypass flow path 41. On the other hand, the check valve 40 makes it impossible for the hydraulic oil to move from the hydraulic brake 22a of the right front wheel and the hydraulic brake 22b of the left rear wheel to the master cylinder 14 side via the bypass flow path 41.

The check valve 40 has a hydraulic brake 22a for the right front wheel and a hydraulic brake 22b for the left rear wheel from the master cylinder 14 side when the circuit control valve 36 is closed due to a failure of the circuit control valve 36, for example. Guarantee the movement of hydraulic oil to the side.

The pressure boosting valve 58a and the pressure reducing valve 54a are provided in a pipeline communicating with the wheel cylinder 38a of the hydraulic brake 22a of the right front wheel. The pressure boosting valve 58a and the pressure reducing valve 54a are used to control the hydraulic brake 22a of the right front wheel.

The pressure boosting valve 58b and the pressure reducing valve 54b are provided in an oil passage communicating with the wheel cylinder 38b of the hydraulic brake 22b of the left rear wheel. The pressure boosting valve 58b and the pressure reducing valve 54b are used to control the hydraulic brake 22b of the left rear wheel. The drive of the booster valves 58a and 58b and the pressure reducing valves 54a and 54b is controlled by a brake control device (not shown).

The pressure boosting valve 58a is provided between the circuit control valve 36 and the hydraulic brake 22a on the right front wheel. The booster valve 58a can be linearly controlled, and continuously adjusts the flow rate of hydraulic oil from the master cylinder 14 and the circuit control valve 36 side to the wheel cylinder 38a side of the hydraulic brake 22a of the right front wheel.

The booster valve 58a has a bypass flow path 61a with a check valve 60a. The check valve 60a enables the hydraulic oil to move from the hydraulic brake 22a side of the right front wheel to the master cylinder 14 and the circuit control valve 36 side via the bypass flow path 61a. On the other hand, the check valve 60a makes it impossible for the hydraulic oil to move from the master cylinder 14 and the circuit control valve 36 side to the hydraulic brake 22a side of the right front wheel via the bypass flow path 61a.

The check valve 60a is a bypass flow path from the hydraulic brake 22a side of the right front wheel to the master cylinder 14 and the circuit control valve 36 side when the pressure booster valve 58a is closed due to a failure of the pressure booster valve 58a, for example. Guarantee the movement of hydraulic fluid through 61a.

The pressure reducing valve 54a is a solenoid valve that can be switched between fully open and fully closed. The pressure reducing valve 54a is provided between the wheel cylinder 38a of the hydraulic brake 22a on the right front wheel and the accumulator 71. The pressure reducing valve 54a reduces the pressure by supplying the hydraulic oil supplied to the wheel cylinder 38a of the hydraulic brake 22a of the right front wheel to the accumulator 71 in the valve open state.

The accumulator 71 accumulates or discharges the hydraulic oil while changing the volume according to the pressure of the hydraulic oil supplied via the pressure reducing valves 54a and 54b.

The pressure reducing valve 54a can adjust the flow rate of hydraulic oil flowing from the wheel cylinder 38a of the hydraulic brake 22a on the right front wheel to the accumulator 71 by repeating opening and closing intermittently.

The pressure boosting valve 58b is provided between the pipeline connecting the circuit control valve 36 and the pressure boosting valve 58a and the wheel cylinder 38b of the hydraulic brake 22b on the left rear wheel. The pressure booster valve 58b can be linearly controlled, and the master cylinder 14, the circuit control valve 36, the pressure booster valve 58a, and the wheel cylinder 38b of the hydraulic brake 22b of the left rear wheel from the wheel cylinder 38a side of the hydraulic brake 22a of the right front wheel. Continuously adjust the flow of hydraulic oil to the side.

The booster valve 58b has a bypass flow path 61b with a check valve 60b. The check valve 60b enables the hydraulic oil to move from the hydraulic brake 22b side of the left rear wheel to the master cylinder 14 and the circuit control valve 36 side via the bypass flow path 61b. On the other hand, the check valve 60b makes it impossible for the hydraulic oil to move from the master cylinder 14 and the circuit control valve 36 side to the hydraulic brake 22b side of the left rear wheel via the bypass flow path 61b.

The check valve 60b is a bypass flow from the hydraulic brake 22b side of the left rear wheel to the master cylinder 14 and the circuit control valve 36 side when the booster valve 58b is closed due to a failure of the booster valve 58b, for example. Guarantee the movement of hydraulic fluid through the road 61b.

The pressure reducing valve 54b is a solenoid valve that can be switched between fully open and fully closed. The pressure reducing valve 54b is provided between the wheel cylinder 38b of the hydraulic brake 22b of the left rear wheel and the accumulator 71. The pressure reducing valve 54b reduces the pressure by supplying the hydraulic oil supplied to the wheel cylinder 38b of the hydraulic brake 22b of the left rear wheel to the accumulator 71 in the valve open state.

The pressure reducing valve 54b can adjust the flow rate of hydraulic oil flowing from the wheel cylinder 38b of the hydraulic brake 22b on the left rear wheel to the accumulator 71 by repeatedly opening and closing the pressure reducing valve 54b.

The pump 44 is driven by the pump motor 96 to discharge hydraulic oil. The drive of the pump motor 96 is controlled by a brake control device (not shown). The pump 44 may be, for example, a piston pump or a gear pump. Further, the pumps 44a, 44b, 44c may be independent pumps, or may be a single pump having a plurality of pistons or gears. The number of pumps is not limited to three.

The discharge side of the pump 44 is connected to a pipeline connecting the circuit control valve 36 and the booster valves 58a and 58b. A first damper 73 is provided on the discharge side of the pump 44. The first damper 73 has a function of reducing vibration or vibration noise caused by a change in the flow rate of hydraulic oil in the hydraulic circuit 28.

A variable throttle 31 and a check valve 32 are provided between the pipeline connecting the circuit control valve 36 and the booster valves 58a and 58b and the first damper 73. The variable throttle 31 adjusts the flow rate of the hydraulic oil supplied through the first damper 73.

The check valve 32 allows the hydraulic oil to move from the first damper 73 side to the pipeline side connecting the circuit control valve 36 and the booster valves 58a and 58b, while moving the hydraulic oil in the opposite direction. Make it impossible.

A check valve 69 is provided in the pipeline connecting the pressure reducing valves 54a and 54b and the suction side of the pump 44. The check valve 69 allows the hydraulic oil to move from the pressure reducing valves 54a and 54b to the suction side of the pump 44, but makes it impossible to move the hydraulic oil in the opposite direction.

A first pressure sensor 24 is provided in a pipeline communicating with the pressure chamber 13a of the master cylinder 14. The first pressure sensor 24 detects the pressure (master cylinder pressure) in the pressure chamber 13a.

A second pressure sensor 26 is provided in a pipe line communicating with the wheel cylinder 38a of the hydraulic brake 22a on the right front wheel. The second pressure sensor 26 detects the wheel cylinder pressure. The second pressure sensor 26 may be provided in a pipeline communicating with the wheel cylinder 38b of the hydraulic brake 22b of the left rear wheel. Further, the second pressure sensor 26 may be omitted in the present invention.

A second damper 75 is provided in the pipeline connecting the master cylinder 14 and the circuit control valve 36 or the suction valve 34. The second damper 75 has a function of suppressing a rapid increase in the amount of hydraulic oil sucked from the master cylinder 14 into the hydraulic circuit 28 as the pump 44 is driven. The second damper 75 has a capacity smaller than that of the first damper 73.

The other hydraulic circuit 30 to which hydraulic oil is supplied from the pressure chamber 13b of the master cylinder 14 controls the hydraulic brake 22c of the left front wheel and the hydraulic brake 22d of the right rear wheel. The hydraulic circuit 30 replaces the wheel cylinder 38a of the hydraulic brake 22a on the right front wheel with the wheel cylinder 38c of the hydraulic brake 22c on the left front wheel in the above description of the hydraulic circuit 28, and the hydraulic brake 22b on the left rear wheel. It has the same configuration as the hydraulic circuit 28 except that the wheel cylinder 38b is replaced with the wheel cylinder 38d of the hydraulic brake 22d of the right rear wheel.

<2. Brake control device configuration example>
A configuration example of the brake control device 100 according to the present embodiment will be described with reference to FIG.

In the following description, in order to facilitate understanding, a case of controlling one of the hydraulic circuits 28 that applies a braking force to the hydraulic brake 22a of the right front wheel and the hydraulic brake 22b of the left rear wheel will be described.

The brake control device 100 is similarly configured when controlling the other hydraulic circuit 30 that applies a braking force to the hydraulic brake 22c of the left front wheel and the hydraulic brake 22d of the right rear wheel. Omit.

FIG. 2 is a block diagram showing a configuration example of the brake control device 100. The brake control device 100 is configured to include a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), for example.

A part or all of the brake control device 100 may be composed of an updatable firmware or the like in addition to being composed of a CPU, an MPU, or the like. Further, the brake control device 100 may be a program module or the like executed by a command from a CPU or the like.

Further, although the brake control device 100 shown in FIG. 2 is configured as one control device, the brake control device 100 may be configured by a plurality of control devices capable of communicating with each other.

The brake control device 100 is connected to a stroke sensor 8 that detects the stroke amount of the piston rod 11 and a pressure sensor 24 that detects the pressure in the pressure chamber 13 of the master cylinder 14. The detection signal of each sensor is input to the brake control device 100.

In addition, the brake control device 100 includes a storage unit (not shown) including a storage element such as a ROM (Read Only Memory) or a RAM (Random Access Memory).

The ROM stores information such as various programs executed by a CPU or the like and parameters used for arithmetic processing. The RAM stores information such as detection values detected by each sensor and parameters used for arithmetic processing. The storage unit may include other storage devices such as a CD-ROM and a storage device.

The brake control device 100 includes a stroke amount detection unit 101, a master cylinder pressure detection unit 103, a discharge amount setting unit 105, and a pump control unit 107. A part or all of each of these parts may be a function realized by executing a program by a CPU or the like.

The stroke amount detection unit 101 detects the stroke amount S of the piston rod 11 based on the sensor signal of the stroke sensor 8.

The master cylinder pressure detection unit 103 detects the pressure (master cylinder pressure) Pmc in the pressure chamber 13a of the master cylinder 14 based on the sensor signal of the first pressure sensor 24.

The discharge amount setting unit 105 sets the discharge amount Vact of the pump 44 based on the hydraulic oil amount Vmc stored in the master cylinder 14. The hydraulic oil amount Vmc is determined according to the stroke amount S of the piston rod 11.

When the brake system can detect the master cylinder pressure Pmc as in the brake system 1 according to the present embodiment, the discharge amount setting unit 105 discharges the pump 44 based on the hydraulic oil amount Vmc stored in the master cylinder 14. In addition to setting, the discharge amount Vact (Vact_ref) of the pump 44 may be set based on the master cylinder pressure Pmc.

The pump control unit 107 controls the drive of the pump 44 based on the discharge amount Vact of the pump 44 set by the discharge amount setting unit 105. Specifically, the pump control unit 107 sets the output of the pump motor 96 according to the discharge amount Vact, and drives the pump motor 96 to rotate.

The brake control device 100 of the present embodiment may set the output of the pump motor 96 based on the wheel cylinder pressure Pwc based on the relationship (F-Pw characteristic) between the pedal pedal force F and the wheel cylinder pressure Pwc as in the conventional case. Instead, the output of the pump motor 96 is set based on the amount of hydraulic oil Vmc to be stored in the master cylinder 14.

As a result, the master cylinder pressure Pmc is appropriately controlled according to the amount of depression of the brake pedal 10, and the feeling of the brake pedal given to the driver can be improved.

<3. Brake control device operation example>
Hereinafter, an operation example of the brake control device 100 according to the present embodiment will be specifically described.

(3-1. Flowchart)
FIG. 3 is a flowchart of the drive control process of the pump 44 by the brake control device 100 according to the present embodiment.

The stroke amount detection unit 101 of the brake control device 100 detects the stroke amount S of the piston rod 11 based on the sensor signal of the stroke sensor 8 (step S11).

Next, the master cylinder pressure detection unit 103 of the brake control device 100 detects the master cylinder pressure Pmc based on the sensor signal of the first pressure sensor 24 (step S13).

Next, the discharge amount setting unit 105 of the brake control device 100 determines the hydraulic oil amount Vmc to be stored in the master cylinder 14 (step S15). The hydraulic oil amount Vmc stored in the master cylinder 14 is determined according to the stroke amount S of the piston rod 11.

Next, the discharge amount setting unit 105 of the brake control device 100 sets the discharge amount Vact of the pump 44 based on the hydraulic oil amount Vmc (step S17). At this time, when the brake system 1 can detect the master cylinder pressure Pmc, the discharge amount setting unit 105 sets the discharge amount Vact of the pump 44 based on the hydraulic oil amount Vmc stored in the master cylinder 14. The discharge amount Vact (Vact_ref) of the pump 44 may be set based on the master cylinder pressure Pmc.

Next, the pump control unit 107 of the brake control device 100 controls the output of the pump motor 96 based on the set discharge amount Vact of the pump 44 (step S19). For example, the pump control unit 107 sets a drive instruction value of the pump motor 96 based on the relationship between the discharge amount Vact of the pump 44 stored in advance in the storage unit and the output of the pump motor 96, and sets the drive instruction value of the pump motor 96 in the drive circuit of the pump motor 96. Output a drive command.

The brake control device 100 repeats the above steps S11 to S19, and drives the pump 44 based on the hydraulic oil amount Vmc stored in the master cylinder 14 determined according to the amount of depression of the brake pedal 10 by the driver. To control.

(3-2. Basic example of pump discharge amount setting process)
A basic example of the setting process of the discharge amount Vact of the pump 44 by the discharge amount setting unit 105 will be described in detail with reference to FIGS. 4 to 8.

FIG. 4 is an explanatory diagram showing a basic example of a process of setting the discharge amount Vact of the pump 44 based on the stroke amount S of the piston rod 11.

The discharge amount setting unit 105 moves from the volume reduction Vtotal of the pressure chamber 13a of the master cylinder 14 determined according to the stroke amount S of the piston rod 11 into the pressure chamber 13a of the hydraulic oil for the reduction Vtotal. The value obtained by subtracting the amount of hydraulic oil Vmc to be stored is set as the discharge amount Vact of the pump 44.

The amount of decrease in the volume of the pressure chamber 13a Vtotal corresponds to the amount of decrease from the volume of the pressure chamber 13a when the brake pedal 10 is not depressed.

The hydraulic oil amount Vmc stored in the pressure chamber 13a is specifically set based on the pedal pedaling force F transmitted to the driver via the brake pedal 10 according to the stroke amount S. That is, the hydraulic oil amount Vmc stored in the pressure chamber 13a is the hydraulic oil amount stored in the pressure chamber 13a in order to generate the pedal pedaling force F corresponding to the stroke amount S.

FIG. 5 is a schematic diagram for explaining the discharge amount Vact of the pump 44 set by the discharge amount setting unit 105.

As shown in the following formula (1), the discharge amount Vact corresponding to the stroke amount S of the piston rod 11 is the hydraulic oil corresponding to the decrease amount Vtotal from the decrease amount Vtotal of the volume of the pressure chamber 13a of the master cylinder 14. Of these, it is obtained by subtracting the hydraulic oil amount Vmc stored in the pressure chamber 13a in order to generate the pedal depression force F.

Vact = Vtotal-Vmc ・ ・ ・ (1)
Vact: Amount of hydraulic oil supplied to the wheel cylinder side Vtotal: Amount of decrease in the volume of the pressure chamber Vmc: Volume of hydraulic oil left in the pressure chamber

For example, when the stroke amount S = Sa, the value obtained by subtracting the hydraulic oil amount Vmc_a stored in the pressure chamber 13a from the volume reduction amount Vtotal_a of the pressure chamber 13a is set as the discharge amount Vact_a of the pump 44.

The discharge amount Vact of the pump 44 shown in FIG. 5 does not change suddenly (step by step) with the change of the stroke amount S. Therefore, even when the brake pedal is suddenly depressed, it is possible to reduce the situation in which the rotational speed of the pump motor 96 must be increased to increase the discharge amount of hydraulic oil.

The master cylinder 14 of the brake system 1 according to the present embodiment is a tandem type master cylinder, and both the primary piston 12a and the secondary piston 12b move with the stroke of the piston rod 11.

Therefore, the amount of decrease in the width of the pressure chamber 13a in the stroke direction is half (S × 0.5) of the stroke amount S of the piston rod 11. Therefore, assuming that the diameter of the cross-sectional area of the primary piston 12a is D, the amount of decrease in the volume of the pressure chamber 13 Vtotal can be expressed by the following equation (2).

Vtotal = S × 0.5 × π × (D / 2) ² ... (2)
Vtotal: Decrease in volume of pressure chamber 13a S: Stroke amount of piston rod D: Diameter of cross-sectional area of piston

The hydraulic oil amount Vmc stored in the pressure chamber 13a is set based on the pedal depression force F transmitted to the driver via the brake pedal 10 according to the stroke amount S. 6 to 8 are explanatory views showing that the hydraulic oil amount Vmc stored in the pressure chamber 13a is obtained based on the pedal depression force F at a certain stroke amount S.

FIG. 6 is a diagram showing the relationship (FS characteristic) between the stroke amount S of the piston rod 11 and the pedal pedaling force F. FIG. 7 is a diagram showing the relationship (Pm-S characteristic) between the stroke amount S of the piston rod 11 and the master cylinder pressure Pmc. FIG. 8 is a diagram showing the relationship (Vm-S characteristic) between the stroke amount S of the piston rod 11 and the hydraulic oil amount Vmc stored in the pressure chamber 13a.

The FS characteristic shown in FIG. 6 may be set to the same characteristic as that of the conventional brake system 1. In the FS characteristic, the pedal depression force F with respect to the stroke amount S of the piston rod 11 is set so that the pedal depression force F increases as the depression amount of the brake pedal 10 increases.

The pedal depression force F mainly consists of two elements. One is the urging force Fs of the coil spring 15a, and the other is the return force Fpmc due to the master cylinder pressure Pmc. However, in reality, the return force Fpmc due to the pressure Pmc in the pressure chamber 13a of the two elements becomes dominant.

Therefore, in the present embodiment, the urging force Fs of the coil spring 15a is used to set the initial value when the stroke amount S is zero. In this case, the pedal depression force F can be expressed by the following equation (3).

F = Fpmc + offset
= Pmc × π × (D / 2) ² × (1 / α) + offset ・ ・ ・ (3)
F: Pedal pedaling force Fpmc: Restoring force by master cylinder pressure offset: Initial value according to the urging force of the coil spring Pmc: Master cylinder pressure D: Diameter of the cross-sectional area of the piston α: Pedal ratio

When the pedal pedal force F having the FS characteristic shown in FIG. 6 is replaced with the master cylinder pressure Pmc based on the relationship between the pedal pedal force F represented by the equation (3) and the master cylinder pressure Pmc, the Pm-S shown in FIG. The characteristics are obtained.

Further, based on the relationship between the master cylinder pressure Pmc and the hydraulic oil amount Vmc stored in the pressure chamber 13a, the master cylinder pressure Pmc having the Pm-S characteristics shown in FIG. 7 is replaced with the hydraulic oil amount Vmc, as shown in FIG. Vm-S characteristics can be obtained.

The relationship between the master cylinder pressure Pmc and the hydraulic oil amount Vmc stored in the pressure chamber 13a can be obtained in advance according to the configuration of the master cylinder 14 or the brake system 1.

In this way, the hydraulic oil amount Vmc stored in the pressure chamber 13a can be set for a certain stroke amount S of the piston rod 11 in order to realize the target FS characteristic.

Therefore, the stroke amount as shown in FIG. 5 is based on the information of the setting condition (FS characteristic) of the pedal pedaling force F in the brake system 1, the urging force Fs of the coil spring 15a, the diameter D of the primary piston 12a, and the pedal ratio α. The condition of the discharge amount Vact of the pump 44 with respect to S can be set.

The discharge amount setting unit 105 sets the discharge amount Vact of the pump 44 according to the detected stroke amount S in consideration of the hydraulic oil amount Vmc stored in the pressure chamber 13a according to the preset conditions.

According to the basic example of the setting process of the discharge amount Vact of the pump 44, an appropriate amount of hydraulic oil amount Vmc is stored in the pressure chamber 13a of the master cylinder 14 determined according to the stroke amount S of the piston rod 11. The discharge amount Vact of the pump 44 is set. Therefore, an appropriate master cylinder pressure Pmc is generated according to the amount of depression of the brake pedal.

The discharge amount Vact of the pump 44 to be set does not change suddenly (step by step) with the change of the stroke amount S. That is, it is possible to reduce the situation where the rotation speed of the pump motor 96 must be increased in order to increase the discharge amount of the hydraulic oil by the pump 44.

Therefore, an unexpected amount of hydraulic oil is not sucked from the pressure chamber 13a of the master cylinder 14 to the hydraulic pressure circuit 28 side, and the discomfort of the pedal feeling due to the difference in the depression speed of the brake pedal of the driver is reduced. Can be done. Further, since the situation where the rotation speed of the pump motor 96 must be increased is reduced, the deterioration of NVH characteristics can be suppressed.

(3-3. Application example of pump discharge amount setting process)
(Application example 1)
FIG. 9 is an explanatory diagram showing an application example 1 of a process of setting the discharge amount Vact of the pump 44 based on the stroke amount S of the piston rod 11. In Application Example 1, the discharge amount setting unit 105 sets the discharge amount Vact_ref by adding the capacity adjustment amount Vadj to the discharge amount (basic discharge amount) Vact calculated according to the above basic example.

In the above-mentioned basic example of setting the basic discharge amount Vact, the output of the pump motor 96 is deterministically determined. However, there is a possibility that some error may be included in the input sensor signal or the Pm-Vm characteristic of the master cylinder 14. In order to reduce the influence of such an error, the discharge amount setting unit 105 obtains an additional capacity adjustment amount Vadj and adds it to the basic discharge amount Vact calculated according to the basic example.

The capacity adjustment amount Vadj may be set in advance to a value corresponding to the master cylinder pressure Pmc and stored in the storage unit. In the application example shown in FIG. 9, the capacitance adjustment amount Vadj corresponding to the stroke amount S of the piston rod 11 is set in advance using the Pm-S characteristic shown in FIG. For example, the discharge amount setting unit 105 refers to the data set in advance and stored in the storage unit, and obtains the capacity adjustment amount Vadj based on the stroke amount S.

When the first pressure sensor 24 capable of detecting the master cylinder pressure Pmc is provided as in the brake system 1 shown in FIG. 1, the capacity adjustment amount is adjusted according to the detection value of the first pressure sensor 24. Vadj may be preset. In this case, the discharge amount setting unit 105 obtains the capacity adjustment amount Vadj based on the master cylinder pressure Pmc.

According to Application Example 1 of the setting process of the discharge amount Vact of the pump 44, even if an error is included in the sensor signal or the Pm-Vm characteristic of the master cylinder 14, it is appropriate in the pressure chamber 13a of the master cylinder 14. A large amount of hydraulic oil amount Vmc can be stored. Therefore, the master cylinder pressure Pmc is generated more appropriately according to the amount of depression of the brake pedal.

Further, also in Application Example 1, the discharge amount Vact of the pump 44 set does not change suddenly (step by step) with the change of the stroke amount S. That is, it is possible to reduce the situation where the rotation speed of the pump motor 96 must be increased in order to increase the discharge amount of the hydraulic oil by the pump 44.

Therefore, an unexpected amount of hydraulic oil is not sucked from the pressure chamber 13a of the master cylinder 14 to the hydraulic pressure circuit 28 side, and the discomfort of the pedal feeling due to the difference in the depression speed of the brake pedal of the driver is reduced. Can be done. Further, since the situation where the rotation speed of the pump motor 96 must be increased is reduced, the deterioration of NVH characteristics can be suppressed.

(Application example 2)
In the brake control device 100 according to the present embodiment, the master cylinder pressure Pmc is appropriately generated by controlling the hydraulic oil amount Vmc stored in the pressure chamber 13a of the master cylinder 14. Here, for example, in a region where the wheel cylinder pressure Pwc is relatively high, the wheel cylinder pressure Pwc reacts sensitively to a change in the hydraulic oil amount, so that the wheel cylinder pressure Pwc is controlled based on the stroke amount S of the piston rod 11. It may not be easy.

In Application Example 2, the discharge amount Vact of the pump 44 is based on the sensor signal of the first pressure sensor 24 in a specific region so that the wheel cylinder pressure Pwc is appropriately controlled even in a region where the wheel cylinder pressure Pwc is relatively high. (Vact_ref) is set.

FIG. 10 is an explanatory diagram showing an application example 2 of a process of setting the discharge amount Vact of the pump 44 based on the stroke amount S of the piston rod 11.

In Application Example 2, the discharge amount setting unit 105 is combined with the discharge amount Vact set based on the stroke amount S of the piston rod 11 according to the above basic example, and the master cylinder pressure detected by the first pressure sensor 24. The amount of hydraulic oil Vwc supplied to the wheel cylinders 38a and 38b is calculated so that Pmc becomes a predetermined target pressure Pmc_tgt.

The discharge amount setting unit 105 sets the larger value of the calculated discharge amount Vact and the hydraulic oil amount Vwc to the discharge amount Vact (Vact_ref).

Note that Application Example 2 is an example that can be applied to the brake system 1 provided with the first pressure sensor 24 that detects the master cylinder pressure Pmc as in the brake system 1 shown in FIG.

11 to 13 are explanatory views showing that the hydraulic oil amount Vwc to be supplied to the wheel cylinders 38a and 38b can be obtained based on the master cylinder pressure Pmc. FIG. 11 is a diagram showing the relationship (F-Pw characteristic) between the pedal depression force F and the wheel cylinder pressure Pwc. FIG. 12 is a diagram showing the relationship (Pm-Pw characteristic) between the master cylinder pressure Pmc and the wheel cylinder pressure Pwc. FIG. 13 is a diagram showing the relationship (Pm-Vw characteristic) between the master cylinder pressure Pmc and the hydraulic oil amount Vwc supplied to the wheel cylinders 38a and 38b.

The F-Pw characteristic shown in FIG. 11 may be set in advance so as to show a desired characteristic. In the F-Pw characteristic shown in FIG. 11, the wheel cylinder pressure Pwc is set to increase sharply when the pedal depression force F reaches a predetermined amount, and thereafter to increase as the pedal depression force F increases.

When the pedal pedaling force F of the F-Pw characteristic shown in FIG. 11 is replaced with the master cylinder pressure Pmc based on the relationship between the pedal pedaling force F represented by the above equation (3) and the master cylinder pressure Pmc, Pm-shown in FIG. Pw characteristics are obtained.

Further, the operation of supplying the wheel cylinder pressure Pwc having the Pm-Pw characteristic shown in FIG. 12 to the wheel cylinders 38a and 38b based on the relationship between the wheel cylinder pressure Pwc and the hydraulic oil amount Vwc supplied to the wheel cylinders 38a and 38b. When replaced with the oil amount Vwc, the Pm-Vw characteristic shown in FIG. 13 can be obtained.

The relationship between the wheel cylinder pressure Pwc and the hydraulic oil amount Vwc supplied to the wheel cylinders 38a and 38b can be obtained in advance according to the configuration of the hydraulic brakes 22a and 22b or the brake system 1.

That is, the F-Pw characteristic shown in FIG. 11 can be replaced with the Pm-Vw characteristic shown in FIG. In this way, in order to realize the target F-Pw characteristic, on the wheel cylinder 38a, 38b side based on the target pressure Pmc_tgt required to generate the pedal pedaling force F according to the stroke amount S of the piston rod 11. The amount of hydraulic oil to be supplied Vwc can be set. The hydraulic oil amount Vwc supplied to the wheel cylinders 38a and 38b is equal to the discharge amount of the pump 44.

In this way, the discharge amount setting unit 105 supplies hydraulic oil to the wheel cylinders 38a and 38b so that the target pressure Pmc_tgt of the master cylinder 14 corresponding to the detected stroke amount S is realized according to the preset conditions. Calculate the quantity Vwc.

As shown in FIG. 10, when the value obtained by subtracting the discharge amount Vact calculated according to the basic example from the calculated hydraulic oil amount Vwc exceeds zero, the discharge amount setting unit 105 adds the difference to the discharge amount Vact. Then, the discharge amount Vact_ref of the pump 44 is set.

At this time, a filter function may be provided for setting an upper limit of the value of the difference to be added in order to suppress the sudden increase in the wheel cylinder pressure Pwc due to the sudden increase in the stroke amount S. Further, in the application example 2, the discharge amount setting unit 105 may set the discharge amount Vact_ref by further adding the capacity adjustment amount Vadj described in the application example 1.

A state in which the value obtained by subtracting the discharge amount Vact from the hydraulic oil amount Vwc exceeds zero is likely to occur in a region where the wheel cylinder pressure Pwc is relatively high. That is, in the application example 2, the discharge amount Vact (Vact_ref) of the pump 44 is set according to the basic example or the application example 1 until the wheel cylinder pressure Pwc reaches a relatively high region.

Further, in Application Example 2, after the wheel cylinder pressure Pwc reaches a relatively high region, the target pressure Pmc_tgt of the master cylinder 14 according to the stroke amount S is realized based on the sensor signal of the first pressure sensor 24. The discharge amount Vact_ref of the pump 44 is set.

According to Application Example 2 of the setting process of the discharge amount Vact_ref of the pump 44, an appropriate amount of hydraulic oil amount Vmc is stored in the pressure chamber 13a of the master cylinder 14 according to the stroke amount S of the piston rod 11. The discharge amount Vact_ref of the pump 44 is set. Therefore, the master cylinder pressure Pmc is generated more appropriately according to the amount of depression of the brake pedal.

Further, also in Application Example 2, the discharge amount Vact of the pump 44 set does not change suddenly (step by step) with the change of the stroke amount S. That is, it is possible to reduce the situation where the rotation speed of the pump motor 96 must be increased in order to increase the discharge amount of the hydraulic oil by the pump 44.

Therefore, an unexpected amount of hydraulic oil is not sucked from the pressure chamber 13a of the master cylinder 14 to the hydraulic pressure circuit 28 side, and the discomfort of the pedal feeling due to the difference in the depression speed of the brake pedal of the driver is reduced. Can be done. Further, since the situation where the rotation speed of the pump motor 96 must be increased is reduced, the deterioration of NVH characteristics can be suppressed.

Further, according to Application Example 2, based on the sensor signal of the first pressure sensor 24, the target pressure Pmc_tgt of the master cylinder 14 corresponding to the stroke amount S is realized when the wheel cylinder pressure Pwc becomes a relatively high region. The discharge amount Vact_ref of the pump 44 is set. Therefore, even in a region where the wheel cylinder pressure Pwc is relatively high, the master cylinder pressure Pmc is appropriately controlled, and the pedal feeling can be improved.

As described above, the brake control device 100 according to the present embodiment discharges the pump 44 of the hydraulic pressure unit 20 based on the hydraulic oil amount Vmc stored in the master cylinder 14 determined according to the stroke amount S of the piston rod 11. Set the quantity Vact. Therefore, the master cylinder pressure Pmc is appropriately controlled according to the stroke amount S.

Further, the discharge amount Vact of the pump 44 set by the brake control device 100 according to the present embodiment does not change suddenly (step by step) with the change of the stroke amount S. That is, it is possible to reduce the situation where the rotation speed of the pump motor 96 must be increased in order to increase the discharge amount of the hydraulic oil by the pump 44.

Therefore, an unexpected amount of hydraulic oil is not sucked from the pressure chamber 13a of the master cylinder 14 to the hydraulic pressure circuit 28 side, and the discomfort of the pedal feeling due to the difference in the depression speed of the brake pedal of the driver is reduced. Can be done. Further, since the situation where the rotation speed of the pump motor 96 must be increased is reduced, the deterioration of NVH characteristics can be suppressed.

Further, the brake control device 100 according to the present embodiment has a pressure for generating a pedal pedaling force F out of the hydraulic oil for the reduced amount Vtotal from the reduced amount Vtotal of the volume of the pressure chamber 13 of the master cylinder 14 according to the stroke amount S. The discharge amount Vact of the pump 44 is set based on the value obtained by subtracting the hydraulic oil amount Vmc stored in the chamber 13. Therefore, the master cylinder pressure Pmc is appropriately controlled so that the desired pedal depression force F is generated, and the pedal feeling of the driver can be improved.

Further, the brake control device 100 according to the application example 2 of the present embodiment supplies the hydraulic oil amount to the wheel cylinder 38 side so that the pressure Pmc in the pressure chamber 13 of the master cylinder 14 becomes the target pressure Pmc_tgt corresponding to the stroke amount S. Vwc is obtained, and the discharge amount Vact_ref of the pump 44 is set based on the larger value of the hydraulic oil amount Vwc and the discharge amount Vact. Therefore, even in a region where the wheel cylinder pressure Pwc is relatively high, the master cylinder pressure Pmc is appropriately controlled, and the driver's pedal feeling can be maintained satisfactorily.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

For example, the brake system 1 according to the above embodiment does not include a booster that boosts the force of the driver to depress the brake pedal at a predetermined servo ratio, but the present invention is not limited to this example. The present invention may be applied to a brake system equipped with a booster. In this case, the stroke amount of the output rod of the booster corresponds to the stroke amount of the piston rod.

1 ... Brake system, 8 ... Stroke sensor, 10 ... Brake pedal, 11 ... Piston rod, 13a, 13b ... Pressure chamber, 14 ... Master cylinder, 16 ... Reservoir tank , 22a, 22b, 22c, 22d ... Hydraulic brake, 28, 30 ... Hydraulic circuit, 38a, 38b, 38c, 38d ... Wheel cylinder, 44, 44a, 44b, 44c ... Pump, 96 ... Pump motor, 105 ... Discharge amount setting unit, 107 ... Pump control unit

Claims (5)

In the brake control device (100) that controls the operation of the hydraulic pressure unit (20),
The brake control device (100) is
A discharge amount setting unit (105) and a pump control unit (107) are provided.
The discharge amount setting unit (105) is
The pedaling force (F) of the brake pedal (10) transmitted to the driver increases as the stroke amount (S) increases according to the stroke amount (S) of the piston rod (11) of the master cylinder (14). The amount of hydraulic oil (Vmc) to be stored in the master cylinder (14) is determined.
From the decrease in volume (Vtotal) of the pressure chamber (13) of the master cylinder (14) according to the stroke amount (S), the hydraulic oil for the decrease (Vtotal) in the master cylinder (14). By subtracting the amount of hydraulic oil (Vmc) to be stored in the hydraulic unit (20), the discharge amount (Vact) of the pump (44) in the hydraulic pressure unit (20) is set.
The pump control unit (107)
A brake control device (100) characterized in that the drive of the pump (44) is controlled based on the discharge amount (Vact). The discharge amount setting unit (105) is
The amount of hydraulic oil supplied to the wheel cylinder (38) side so that the pressure (Pmc) in the pressure chamber (13) of the master cylinder (14) becomes the target pressure (Pmc_tgt) corresponding to the stroke amount (S). Vwc) is obtained, and the discharge amount (Vact_ref) of the pump (44) is set based on the larger value of the hydraulic oil amount (Vwc) and the discharge amount (Vact). The brake control device (100) according to claim 1 . In the brake control method for controlling the operation of the hydraulic pressure unit (20),
The brake control device (100)
The pedaling force (F) of the brake pedal (10) transmitted to the driver increases as the stroke amount (S) increases according to the stroke amount (S) of the piston rod (11) of the master cylinder (14). The first step (S15) of determining the amount of hydraulic oil (Vmc) to be stored in the master cylinder (14), and
From the decrease in volume (Vtotal) of the pressure chamber (13) of the master cylinder (14) according to the stroke amount (S), the hydraulic oil for the decrease (Vtotal) in the master cylinder (14). The second step (S17) of setting the discharge amount (Vact) of the pump (44) of the hydraulic pressure unit (20) by subtracting the hydraulic oil amount (Vmc) to be stored in the water pressure unit (20).
A brake control method comprising a third step (S19) for controlling the drive of the pump (44) based on the discharge amount (Vact). In the vehicle braking system (1)
Reservoir tank (16) for holding hydraulic oil,
The master cylinder (14) to which the hydraulic oil in the reservoir tank (16) is supplied, and
A piston rod (11) that moves forward and backward in the master cylinder (14) according to the amount of depression of the brake pedal (10) by the driver.
A stroke sensor (8) that detects the stroke amount (S) of the piston rod (11) and
A hydraulic unit (20) having at least one pump (44) and supplied with hydraulic oil from the master cylinder (14) to supply hydraulic pressure to the wheel cylinder (38).
An operation of storing in the master cylinder (14) so that the pedaling force (F) of the brake pedal (10) transmitted to the driver increases as the stroke amount (S) increases according to the stroke amount (S). The amount of oil (Vmc) is determined, and the amount of decrease (Vtotal) in the volume of the pressure chamber (13) of the master cylinder (14) according to the amount of stroke (S) is increased by the amount of decrease (Vtotal) of hydraulic oil. Of these, a discharge amount setting unit (105) that sets the discharge amount (Vact) of the pump (44) by subtracting the hydraulic oil amount (Vmc) stored in the master cylinder (14) .
A brake system (1) comprising a pump control unit (107) that controls the drive of the pump (44) based on the set discharge amount (Vact). The brake system (1) is
A pressure sensor (24) for detecting the pressure in the pressure chamber (13) of the master cylinder (14) is further provided.
The discharge amount setting unit (105) is the pump so that the pressure (Pmc) in the pressure chamber (13) becomes the target pressure (Pmc_tgt) corresponding to the target pressure (Pwc_tgt) in the wheel cylinder (38). The brake system (1) according to claim 4 , wherein the discharge amount (Vact) of (44) is corrected.

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