JPH1159380A - Brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the quality of control by enhancing responsiveness regarding the detection of pedaling power, in a brake device the control accuracy and control responsiveness of which are enhanced using structurally simple and inexpensive means. SOLUTION: A brake device has a master cylinder 1 and a wheel cylinder 2 connected to each other by a brake circuit 3, and a gear pump 6 which is put into feeding action for at least the wheel cylinder 2 is provided in a part of the brake circuit 3; a bypass circuit 7 is connected to the brake circuit 3 in parallel with the gear pump 6, and a variable orifice 8 is provided in the bypass circuit 7, and a pedaling power sensor 20 is provided as means for detecting the driver's braking operation. A current sensor 10 for detecting the current value of a motor 5 is provided, and a control unit 9 controls the opening of the variable orifice 8 by feeding back the value detected by the current sensor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake device that supplies a dynamic pressure, which is a discharge pressure of a pump, to a wheel cylinder that generates a braking force on wheels, in addition to a master cylinder pressure.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. HEI 4 (1999) -1995 discloses a brake device using a pump to increase and decrease the brake pressure.
JP-A-230462 (hereinafter referred to as the first
Conventional technology) or JP-A-5-147524
(Hereinafter referred to as a second prior art). In the first prior art, a device including a motor, a piston, a speed reducer, a linear ball actuator (a device for converting rotation into reciprocating motion), and the like are provided in a brake circuit connecting the master cylinder and the wheel cylinder.
The hydraulic pressure of the wheel cylinder on the caliper side of the wheel is increased, maintained, and reduced by the fine reciprocating motion of the piston caused by the rotation of the motor. That is, in the first prior art, the ABS (anti-lock brake system) control is performed by a delicate reciprocating motion of a piston due to the rotation of a motor. The hydraulic pressure is generated to increase the hydraulic pressure of the wheel cylinder. In the second prior art, a gear pump operated by rotation of a motor is provided in the middle of a brake circuit that connects a master cylinder and a brake cylinder (wheel cylinder). Is returned to the master cylinder side, and thereafter, when the slip ratio is recovered, the motor is rotated forward to supply the brake fluid of the master cylinder to the brake cylinder to increase the brake cylinder pressure. During normal braking, the gear of the gear pump idles and the flow of brake fluid is allowed.

[0003]

According to the first prior art described above, during ABS control, the hydraulic pressure in the pipeline is reduced, held, and increased by delicate reciprocation of the piston to brake the wheel cylinder. Since the pressure is reduced, held, and increased, the rotation of the motor must be transmitted to the piston as a very delicate movement. As a mechanism for this, a speed reducer, a linear ball actuator (reciprocating the rotation) ), And a control logic with high accuracy is required, resulting in an increase in cost. Even in the second prior art, there is a problem that the control is difficult and the degree of freedom of control is low because the fluid pressure is changed only by the operation of the pump as in the first prior art. Furthermore, both prior arts have a structure in which the brake fluid is supplied or returned between the master cylinder and the wheel cylinder only through a brake circuit provided with a pump in the middle. The operation starts only when the wheel cylinder is supplied to the wheel cylinder.
When the pump supplies the brake fluid to the wheel cylinder in response to the brake depression operation, the rise of the pump is delayed, lacking responsiveness.To assist the pedal effort during normal braking, a pedal booster such as a negative pressure booster is used. It is necessary separately, and there is a problem that the device becomes large and expensive. Therefore, the applicant of the present application has proposed a means for solving the above-mentioned problem.
A brake device described in Japanese Patent Application No. 9-7743 (hereinafter referred to as prior art) has been proposed. This prior art is characterized in that a bypass circuit is provided in parallel with a pump provided in a brake circuit, and a variable orifice capable of changing a cross-sectional area of a flow path is provided in the middle of the bypass circuit. In this prior art,
If the opening of the variable orifice is maximized while the pump is running, the pump will not pressurize, and the master cylinder pressure and the wheel cylinder pressure are equal. From this state, the opening of the variable orifice is reduced. The pump can supply the hydraulic pressure to the wheel cylinder side instantaneously, or the hydraulic pressure on the wheel cylinder side can be returned to the master cylinder side. Therefore, it has a feature that the wheel cylinder pressure can be controlled with high responsiveness while having a simple configuration. By the way, this prior art discloses that the opening degree of the variable orifice is changed according to a detection value of a pedaling force sensor provided on a brake pedal. That is, when the brake pedal is depressed, the master cylinder pressure rises, and the brake operation state by the driver can be detected by detecting the distortion of the brake pedal due to the reaction force as the depressing force by the depressing force sensor. However, this treading force sensor can detect the treading force (distortion) only when the master cylinder pressure rises and a reaction force corresponding to the depressing operation of the brake pedal occurs. The brake pressure needs to rise in the cylinder. However, in the prior art including the prior art, the driver performs the stepping-on operation because the pump is provided in the middle of the brake circuit and the resistance of the circuit is large, and the pipeline of the brake circuit is long. After that, a slight delay occurs until it is detected as the pedaling force. Therefore, when the brake pedal is depressed at a high frequency, a phase delay may occur. In such a case, a phase delay may occur in the control, and appropriate control may not be performed. There was a problem. The present invention has been made by paying attention to the above-mentioned conventional problems. In the prior art, the control performance and the control response can be improved by a simple and inexpensive means compared to the above-mentioned conventional technology. The purpose is to improve control quality by enabling more precise control.

[0004]

Means for Solving the Problems To achieve the above object, an invention according to claim 1 is a master cylinder that generates a hydraulic pressure by a driver's depressing operation of a brake pedal, and a braking operation of the master cylinder and wheels. A brake circuit that connects the wheel cylinder and a pump that is provided in the middle of the brake circuit and that supplies the brake fluid at least from the master cylinder side to the wheel cylinder side; and a pump that is provided in parallel with the pump. Is connected to the master cylinder side of the brake circuit pump, while the other end is connected to the wheel cylinder side of the brake circuit pump, and provided in the middle of the bypass circuit. Variable orifice that can change the flow path cross-sectional area of the Control means for controlling the degree of opening of the variable orifice, wherein the vehicle state detection means includes a tread force sensor for detecting a tread force of the brake pedal, and a load for detecting a load pressure of the pump. Pressure control means, and wherein the control means is configured to perform a control by feeding back a detected value of the load pressure detection means in controlling the opening degree of the variable orifice. . According to a second aspect of the present invention, in the brake device according to the first aspect, the load pressure detecting unit is a current sensor that detects a current value supplied to a motor that is a driving source of the pump. Means. According to a third aspect of the present invention, in the brake device according to the first or second aspect, the control means executes the pedaling force assisting control that narrows the opening of the variable orifice as the rate of change of the detection value of the pedaling force sensor increases. It is a characteristic means. According to a fourth aspect of the present invention, in the brake device according to the first to third aspects, the control means includes:
When the detected value of the load pressure detecting means is fed back, the opening of the variable orifice is determined based on an arithmetic expression including a function of the detected value of the load pressure detecting means. According to a fifth aspect of the present invention, in the brake device of the fourth aspect, the arithmetic expression is the following expression (a): S _OR = K1 / [F] ^1/2 (a) where F = {S _{m / c} × Ip} / K _{b / p} , S _OR is the variable orifice opening area, K1 is a constant, S _{m / c} is the piston area of the master cylinder, Ip is the pump load, and K _{b / p} is the brake The means is characterized by the arm ratio of the pedal.

[0005]

According to the first aspect of the invention, when the driver steps on the brake pedal, the brake fluid corresponding to the amount discharged from the master cylinder is supplied to the wheel cylinder, and the brake pressure is generated in the wheel cylinder. The pressure also increases in the master cylinder. When the brake pressure is generated in the wheel cylinder as described above,
A load corresponding to the brake pressure is applied to the pump.
Then, the load pressure detecting means detects the load pressure of the pump. In addition, a reaction force against the driver's depression operation is generated on the brake pedal due to the generation of the master cylinder pressure, and the pedal depression force is detected by the depression force sensor. The control means controls the opening of the variable orifice based on an input signal obtained from the vehicle state detecting means including the load pressure detecting means and the pedaling force sensor. At this time, the load pressure detecting means corresponds to the brake pressure of the wheel cylinder. The opening degree control is executed by feeding back the pump load pressure detected in step (1). Therefore, even if a phase delay occurs due to a pipeline characteristic of the brake circuit between the stepping operation of the brake pedal by the driver and the generation of the brake pressure in the wheel cylinder, the phase delay is corrected by the feedback, and the high-frequency It can respond to a stepping operation.

Hereinafter, braking force control by controlling the opening of the variable orifice will be described. When the opening of the variable orifice is maximized, the master cylinder side of the pump (hereinafter referred to as the upstream side) and the wheel cylinder side (hereinafter referred to as the upstream side)
This is referred to as the downstream side), and there is no hydraulic pressure difference between the upstream side and the downstream side of the pump. Therefore, even if the pump is operated for supply or recirculation, there is no hydraulic pressure difference between the upstream and downstream of the pump, and the hydraulic pressure of the master cylinder and the hydraulic pressure of the wheel cylinder are the same, and the operation of the brake pedal The braking force is not generated in the wheel cylinder unless the operation is performed. When the variable orifice is throttled while the pump is operating, the flow rate circulating in the bypass circuit decreases, and a hydraulic pressure difference occurs between the upstream side and the downstream side of the pump. Therefore, in the state where the pump is being supplied, when the variable orifice is throttled from the state where the opening degree of the variable orifice is maximized and the hydraulic pressure of the wheel cylinder is equal to the master cylinder pressure, the brake pressure of the wheel cylinder is instantaneously changed to the master pressure. It rises above the hydraulic pressure of the cylinder. Further, if the opening of the variable orifice is maintained at that opening, the brake pressure can be maintained at that pressure. On the other hand, when the variable orifice is opened from this state, the brake pressure decreases until it becomes equal to the master cylinder pressure. In other words, only by adjusting the throttle opening of the variable orifice while the pump is being supplied, delicate control of increasing, holding, and reducing the brake pressure is possible. By controlling the opening degree of the variable orifice, the ABS control can be performed by assisting the brake operation like a booster, or by decreasing, holding, and increasing the brake pressure. Motion stabilization control that generates braking force even when the driver is not performing a brake operation to prevent torque slip of the wheels, or controls the yaw moment of the vehicle in a stable direction by the braking force. You can also do it.

According to the second aspect of the present invention, when a pressure load is applied to the pump, a change corresponding to the load occurs in the current value of the current flowing to the motor which is the drive source of the pump. Therefore, in the present invention, the load pressure of the motor is detected by detecting the current value of the motor by the current sensor.

According to the third aspect of the present invention, the control means executes the pedaling force assisting control that narrows the opening of the variable orifice as the rate of change of the pedaling force increases based on the pedaling force detected by the pedaling force sensor. It is considered that the quicker the driver's stepping-in operation, the higher the need for braking force (urgency), the smaller the opening of the variable orifice, so that the brake pressure in the wheel cylinder is controlled to be higher than the master cylinder pressure. It provides assistance.

According to the fourth and fifth aspects of the present invention, when the detected value of the load pressure detecting means is fed back, the opening of the variable orifice is determined based on an arithmetic expression including a function of the detected value of the load pressure detecting means. Therefore, feedback control can be easily performed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall view showing an embodiment. In the figure, reference numeral 1 denotes a master cylinder, which generates a hydraulic pressure by depressing a brake pedal BP. The master cylinder 1 is connected to a wheel cylinder 2 of each wheel by a brake circuit 3 so that brake fluid flows between the two via the brake circuit 3.

In the middle of the brake circuit 3, a motor 5
A gear pump 6 for discharging a fluid at a predetermined flow rate in accordance with the number of rotations is provided. The gear pump 6 is a circumscribed gear pump or an inscribed gear pump capable of performing a supply operation of supplying brake fluid from upstream to downstream by a forward / reverse rotation of the motor 5 and a reverse operation of returning the brake fluid from upstream to downstream. It is a gear pump. The pump used for this part is not limited to the gear pump, but may be a vane pump or a piston pump.

In parallel with the gear pump 6, a bypass circuit 7 has one end connected to the upstream of the gear pump 6 of the brake circuit 3 (toward the master cylinder 1), and the other end downstream of the gear pump 6 of the brake circuit 3 (to the other end). Wheel cylinder 2
Side). In the middle of the bypass circuit 7, there is provided a variable orifice 8 capable of changing the flow path area of the bypass circuit 7. The variable orifice 8 has a solenoid (not shown), and the opening is changed by a drive current supplied to the solenoid.

Although only one wheel cylinder 2 is shown in the drawing, it is provided for each wheel (four wheels), and the brake circuit 3 is finally branched into four. The gear pump 6, the bypass circuit 7, and the variable orifice 8 may be provided downstream of the position where the brake circuit is branched into four, that is, for each wheel cylinder 2, or two sets of the wheel cylinders 2 may be provided. , 2 downstream, ie, 2
One wheel cylinder 2, 2 may be provided with one set of the configuration consisting of 6, 7, and 8 described above.

In the present embodiment, the drive of the motor 5 and the opening of the variable orifice 8 are controlled by a control unit 9. The control unit 9 includes, as input sensors, a wheel speed sensor, a longitudinal acceleration sensor, a lateral acceleration sensor, a yaw rate sensor, and the like (not shown), a current sensor 10, and a pedaling force sensor 20.

The current sensor 10 is provided as means for detecting the load pressure of the gear pump 6, and detects the value of the current output from the control unit 9 to the motor 5. That is, the output of the gear pump 6 is proportional to the pressure P (Kgf / cm ² ) and the flow rate Q (L / min), and the output of the gear pump 6 is proportional to the output of the motor 5. Therefore, the load on the gear pump 6 acts on the motor 5, which appears as a change in the current value. By the way, if the output of the gear pump 6 is W1,
This output can be represented by _{W1 = P × Q / 612η 1} (η 1 is pump efficiency). And the output W2 of the motor 5
Is W2 = I * V = [eta] ₂ * [eta] ₃ * W1 ([eta] ₂ is the motor efficiency, [eta] ₃ is the motor-pump connection efficiency). Therefore, the load of the gear pump 6 can be detected based on the current value I.

The pedal force sensor 20 includes a brake pedal B
A well-known distortion sensor is provided on the rod portion of P to detect the pedaling force of the driver during braking. Incidentally, when the treading force sensor 20 is used as a means for detecting the braking operation state, the treading force assist is performed while grasping the relationship between the treading force and the treading force assisting force by the treading force assisting control described later (treading force + treading force assisting force = braking force). This makes it possible to obtain a natural braking feeling in the pedal effort assist control described later.

Here, a system for assisting pedaling force control by the control unit 9 will be described. FIG. 2 is a block diagram of a control system according to the present embodiment. In FIG. 2, f is a flow rate characteristic of the master cylinder 1 including a pedal characteristic,
g is the flow rate characteristic of the pipe, h is the flow rate / pressure characteristic of the wheel cylinder 2, x is the pressure / flow rate characteristic of the variable orifice 8, y is the pressure / flow rate characteristic of the pump 6, z is the pressure between the wheel cylinder 2 and the master cylinder 1. The pedal stroke characteristic C is a control characteristic described later.

In this embodiment, the brake pedal BP
The relationship between the pedaling force and the pressure of the master cylinder 1 is expressed mechanically as F = { _{Sm / c} × _{Pm / c} } / _{Kb / p} (1). F is the pedaling force, S _{m / c} is the piston area of the master cylinder, P _{m / c} is the pressure in the master cylinder, K _{b / p}
Is the lever ratio of the brake pedal,
/ A. Therefore, pedaling force and wheel cylinder 2
Is related to the brake pressure P _{w / c} from the above equation (1).
Since ≠ f (P _{w / c} ), an equation using a pump load Ip, which is an alternative value of P _{w / c} , is considered so that it can be a function of the wheel cylinder pressure of F = f (P _{w / c} ). Here, the orifice opening area S _OR can be expressed by S _OR = K1 / (F) ^1/2 (2). Note that F = {S _{m / c} × Ip} / K
_{b / p} . Note that K1 is a constant. in this way,
The control unit 9 calculates the optimum orifice opening area S _OR by using the above equation (2),
This equation is a function of the current to the motor 5 and feeds back a current value that is correlated with the generated brake pressure of the wheel cylinder 2.

Next, the operation of the embodiment will be described. In this embodiment, when an ignition switch (not shown) is turned ON, the control unit 9 is configured to always rotate the motor 5 forward at a constant rotation. From the master cylinder 1 side to the wheel cylinder 2 side.

A) When the brake pedal is not operated In this embodiment, as described above, the motor 5
Performs a constant forward drive, whereby the gear pump 6 performs the supply operation. At this time, the control unit 9 controls the opening of the variable orifice 8 to the maximum. Therefore, the gear pump 6 merely circulates the brake fluid by the bypass circuit 7, and the brake fluid pressure in the wheel cylinder 2 is the same atmospheric pressure as the master cylinder 1.

B) When the brake pedal is operated When the driver steps on the brake pedal BP, the brake fluid corresponding to the amount discharged from the master cylinder 1 is supplied to the wheel cylinder 2 and the brake pressure is generated in the wheel cylinder 2 , A pressure is generated in the master cylinder 1. The master cylinder pressure generates a reaction force to the depression operation of the brake pedal BP. Accordingly, the pedal force sensor 20 detects distortion and outputs a pedal force signal corresponding to the driver's pedal force. On the other hand, in the gear pump 6, a load is applied by the brake pressure generated in the master cylinder 1 and the wheel cylinder 2, and the current sensor 1
The detection value of 0 changes.

The control unit 9 controls the opening of the variable orifice 8 based on a signal from the treading force sensor 20 while feeding back the value detected by the current sensor 10. is a function of the detected values Ip of the sensor 10 (2) based on the equation, it calculates the optimal opening degree S _OR of the variable orifice 8, to control the variable orifice 8 in accordance with the calculation result. Incidentally, the control unit 9 basically determines the variable orifice as the change rate of the treading force or the absolute value of the treading force is larger based on a map in which the rate of change of the treading force or the absolute value component of the treading force is considered. The control for reducing the opening degree of No. 8 is executed.

When the opening of the variable orifice 8 is reduced in this way, a hydraulic pressure difference is instantaneously generated between the upstream side and the downstream side of the gear pump 6, and the brake pressure in the wheel cylinder 2 becomes higher than the master cylinder pressure. In other words, the pedaling force is assisted.

At this time, as shown in FIG.
Braking pressure generated in the wheel cylinder 2 P _1, there is to be determined by the inner diameter φd and the master cylinder pressure P ₀ of the flow rate Q and the variable orifice 8 of the gear pump 6, the brake pressure P ₁ as the value of the inner diameter φd decreases the rate of increase increases, it is possible to obtain a large braking pressure P ₁ with a small depression force. FIG. 2B is a model diagram of the present embodiment. In the present embodiment, when it is detected that the braking operation has been performed, an initial short time (for example, 0.1 s) is detected.
The variable orifice 8 is fully closed by about (ec) to perform control to increase the boosting property.

Thereafter, when the driver releases the brake pedal BP, the control unit 9 widens the opening of the variable orifice 8 in response to the decrease in the value detected by the pedaling force sensor 20. Therefore, the brake pressure of the wheel cylinder 2 decreases, and at this time, the variable orifice 8
Is maximized, the brake pressure of the wheel cylinder 2 decreases until it becomes equal to the master cylinder pressure. Incidentally, at this time, the gear pump 6 can be recirculated to lower the wheel cylinder pressure faster than the master cylinder pressure. However, in the present embodiment, the motor 5 is rotated forward at a constant speed.

Here, FIG. 4 shows an example of the case where the driver depresses the brake pedal BP at a high frequency in the present embodiment. 4A shows the pedal stroke speed, FIG. 4B shows the wheel cylinder pressure, FIG. 4C shows the orifice opening area, and FIG. 4D shows the pedal reaction force (master cylinder pressure). In the present embodiment, since the feedback control based on the detection value of the current sensor 10 is performed as described above, even if the brake pedal BP is operated at a high frequency as shown in FIG. It can be seen that the opening area of the variable orifice 8 is controlled exactly in accordance with the operation, and the brake pressure is generated in the wheel cylinder 2 without causing a phase delay.

As described above, in the embodiment, the motor 5 is rotated at a constant speed and the variable orifice 8 is rotated.
By controlling the inner diameter φd of the motor, the brake pressure can be instantaneously increased, and the delicate brake pressure can be controlled without using a reduction gear.
As compared with the control of the number of rotations of the above, an effect that high control response is obtained and controllability is excellent is obtained. Moreover, in the embodiment, a current sensor 10 for detecting a current value of a current flowing to the motor 5 for operating the gear pump 6 is provided.
0 is fed back to the wheel cylinder 2
In order to execute the control to compensate for the delay in the rise of the pressure in the above, the control quality is improved. In particular, the effect that the controllability when the brake pedal BP is operated at a high frequency is improved.

Further, even in the event that a failure of the motor 5 or the gear pump 6 is encountered, the effect that normal brake performance can be ensured and fail-safe can be improved can be obtained.

Although the embodiment has been described with reference to the drawings, the present invention is not limited to this embodiment. For example, in the embodiment, only the pedal effort assist control has been described. However, as described above, the brake pressure of the wheel cylinder 2 can be reduced, held, and increased by controlling the variable orifice 8, so ABS control for preventing wheel lock of the vehicle can be executed. Even when the driver does not operate the brake pedal BP,
As required, it is possible to generate a braking force on a desired wheel and execute the motion stabilization control for controlling the vehicle attitude in a stable direction.

[0030]

As described above, according to the present invention, a pump is provided in the middle of a brake circuit connecting a master cylinder and a wheel cylinder, and a variable orifice is provided in a bypass circuit provided in parallel with the pump. A load pressure detecting means for detecting the load pressure of the pump is provided, and the control means feeds back a detection value of the load pressure detecting means in controlling the opening of the variable orifice. It is possible to control the brake pressure of the wheel cylinder with, in particular, by performing feedback control, it is possible to eliminate the phase lag in the wheel cylinder even if the driver steps on the brake pedal at high frequency, An effect is obtained that precise control is possible and control quality can be improved. According to the second aspect of the present invention, since a current sensor for detecting a current value supplied to a motor which is a driving source of the pump is used as the load pressure detecting means, the load pressure of the pump can be detected by simple means. In addition to the cost, the effect of being easy to attach and having high versatility is obtained. According to the third aspect of the present invention, it is possible to obtain a brake pressure with a large assist of the pedaling force without using the booster, and it is possible to obtain the effect that the pedaling assist with high control quality can be performed. According to the fourth and fifth aspects of the present invention, when the detected value of the load pressure detecting means is fed back, an arithmetic expression including a function of the detected value of the load pressure detecting means is used, so that a simple configuration is provided. Thus, the effect that the feedback control can be executed is obtained.

[Brief description of the drawings]

FIG. 1 is an overall view showing an embodiment.

FIG. 2 is an explanatory diagram of a mechanism according to the embodiment.

FIG. 3 is a hydraulic characteristic diagram of the embodiment.

FIG. 4 is a diagram showing an operation example of the embodiment.

[Explanation of symbols]

 BP brake pedal 1 master cylinder 2 wheel cylinder 3 brake circuit 5 motor 6 gear pump 7 bypass circuit 8 variable orifice 9 control unit (control means) 10 current sensor 20 pedal force sensor

Claims (5)

[Claims] 1. A brake circuit for connecting a master cylinder for generating a hydraulic pressure by a driver's depressing operation of a brake pedal, a wheel cylinder for performing a braking operation of a wheel and a master cylinder, and provided in the middle of the brake circuit. A pump for supplying brake fluid at least from the master cylinder side to the wheel cylinder side, and a pump provided in parallel with the pump, one end of which is connected to the master cylinder side of the brake circuit pump, A bypass circuit having an end connected to the wheel cylinder side of the brake circuit with respect to the pump, a variable orifice provided in the middle of the bypass circuit and capable of changing a flow path cross-sectional area of the bypass circuit, and a vehicle state detecting means. Control means for controlling the opening of the variable orifice based on the input signal received. And a load pressure detection means for detecting a load pressure of the pump as the vehicle state detection means, wherein the control means includes a variable orifice. A brake device, wherein the control is performed by feeding back a detection value of the load pressure detecting means in controlling the opening. 2. The brake device according to claim 1, wherein said load pressure detecting means is a current sensor for detecting a current value supplied to a motor which is a driving source of said pump. 3. The brake device according to claim 1, wherein the control unit executes a pedaling force assisting control that narrows the opening of the variable orifice as the rate of change of the detection value of the pedaling force sensor increases. 4. The control means is configured to determine the opening of the variable orifice based on an arithmetic expression including a function of the detected value of the load pressure detecting means when feeding back the detected value of the load pressure detecting means. The brake device according to claim 1, wherein the brake device is provided. 5. The arithmetic expression is the following expression (a): S _OR = K1 / [F] ^1/2 (a) where F = {S _{m / c} × Ip} / K _{b / p} , S _OR is a variable orifice opening area, K1 is a constant, S _{m / c} is a piston area of a master cylinder, Ip is a pump load, and K _{b / p} is an arm ratio of a brake pedal. Item 6. The brake device according to item 4.