JPH08332944A - Brake system - Google Patents

Abstract

PURPOSE: To generate large braking force with small brake operation force by determining where the relation of real input-to-output relation of a negative pressure boosting device exists in actuation ranges and non-actuation ranges of a first and a second switching valve, and actuating the switching valves based on the result of determination for a relatively long period. CONSTITUTION: When a vehicle runs, detection signals of a stepping force gauge 22 and a stroke sensor 23 of a brake pedal 2 and a liquid pressure pickup 13 for brake liquid pressure are inputted to a controller 24, and a first and a second switching valves 17, 19 to control a negative pressure boosting device 3 are controlled based on the input signals. In this case, gradient of an actuation boundary line of the first switching valve 17 as a vacuum valve is set to be larger than a gradient α of input/output static characteristics of the negative pressure boosting device 3, and the gradient of an actuation boundary line of the second switching valve 19 as an open air valve is set to be similar to the gradient α. It is determined where pedal stepping force-master cylinder liquid pressure relation exists in actuation ranges and non-actuation ranges of the switching valve 17, 19, and the switching valve 17, 19 are controlled based on the result of determination.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has an input / output characteristic of a negative pressure booster capable of obtaining a large braking force with a comparatively light pedaling force at the time of sudden braking and good controllability at the time of gentle braking. The present invention relates to a brake system that can be changed to have such characteristics.

[0002]

2. Description of the Related Art In recent years, in automobiles such as passenger cars, a brake system using a negative pressure booster has been used in order to obtain a large braking force with a small pedal effort or to reduce the pedal effort. As an example of such a conventional brake system, there is a boom system as shown in FIG.

The brake system shown in FIG. 12 is equipped with a tandem type vacuum booster. In this illustrated state, the vacuum booster 150 has a chamber valve in which the atmospheric valve 151a of the control valve 151 is closed and the vacuum valve 151b is opened. A vacuum is introduced into A, B, C, and D, and the brake is inoperative.

When the brake pedal is depressed and the input shaft 54 moves forward during normal braking from this brake non-operating state, the atmosphere valve 151a of the control valve 151 opens and the vacuum valve 151b closes, so that the atmosphere is transformed into the variable pressure passages 155,1.
They are introduced into the transformer rooms B and D through 56, respectively. As a result, a differential pressure is generated between the chambers A, B and C, D before and after the diaphragms 157, 158, and the diaphragms 157, 15
8 and the power pistons 159 and 160 move forward, and an output is generated from the output shaft 161. Then, the master cylinder 162 is operated by this output, and the normal brake is operated.

The advance of the diaphragms 157, 158 and the power pistons 159, 160 is continued until the atmosphere valve 151a is closed and the atmosphere is not introduced into the variable pressure chambers B, D. As a result, the output depends on the input, that is, the brake pedal depression amount. A large output boosted by a predetermined servo ratio is obtained.

[0006]

By the way, in the negative pressure booster used in the conventional brake system, the driver suddenly depresses the brake pedal with a large pedal force to actuate the sudden braking. In this case, due to the passage diameter of the inflowing air and the opening amount of the atmospheric valve 151a,
The flow rate of the atmosphere flowing into the negative pressure booster becomes restricted. Therefore, the pressure increase in the variable pressure chambers B and D of the negative pressure booster 150 is slow for the large pedal effort, and the variable pressure chambers B and D are low.
It takes time for the pressure of 1 to reach the pressure corresponding to the pedal effort, which causes a delay.

The control valve 151 of the negative pressure booster 150 is also provided.
Has a characteristic that the valve opening amount decreases as the pressure in the variable pressure chambers B and D approaches the control target value. Therefore, the degree of increase in the braking force obtained as indicated by the dotted line in FIG. 9 decreases as it approaches the control target value, and it takes some time for the braking force to reach the control target value. Therefore, also from this fact, the negative pressure booster 15
There will be a delay at 0.

The present invention has been made in view of such a problem, and an object thereof is to make the delay of the negative pressure booster as small as possible even at the time of sudden braking, and at the same time to make it large at the time of sudden braking. It is an object of the present invention to provide a brake system that can reduce the pedal effort when generating a braking force, and can improve the controllability when operating a slow brake.

[0009]

In order to solve the above-mentioned problems, the invention of claim 1 provides a brake operating member, a constant pressure chamber in which a negative pressure is constantly introduced from a negative pressure source, and a negative pressure when the brake is not operated. A variable pressure chamber into which pressure is introduced and the atmosphere is introduced during brake operation, a diaphragm that partitions the constant pressure chamber and the variable pressure chamber and operates by introducing atmospheric pressure into the variable pressure chamber, and a negative pressure is normally introduced. At the same time, the internal chamber into which the atmosphere is selectively introduced when necessary, and the brake operating member is switched and controlled to communicate the variable pressure chamber with the internal chamber when the brake is not operated and to shut off the atmosphere and to communicate with the atmosphere when the brake is operated. And a negative pressure booster equipped with a control valve for shutting off the internal chamber and an output shaft for outputting by operating the diaphragm, and the output shaft of the negative pressure booster. A master cylinder that is operated to generate a brake fluid pressure, a brake cylinder that is introduced with the brake fluid pressure of the master cylinder to generate a braking force, a first passage connected to the internal chamber, and a first passage A normally open first opening / closing valve that communicates with the negative pressure source when necessary and shuts off from the negative pressure source, and a first passage on the inner chamber side of the first opening / closing valve that normally shuts off the atmosphere. A normally-closed second on-off valve that communicates with the atmosphere when necessary, a second passage that introduces the atmosphere flowing through the first passage into the variable pressure chamber, and a second passage that is provided in the second passage, and from the first passage A check valve that allows the flow of air toward the variable pressure chamber but blocks the flow of air from the variable pressure chamber toward the first passage, an operation force detection unit that detects the operation force of the brake operation member, and the master cylinder. Output detection means for detecting any one of the brake fluid pressure, the pressure in the variable pressure chamber of the negative pressure booster, and the fluid pressure in the brake cylinder, and detection signals from the operation force detection means and the output detection means. And an electronic control device that controls the first and second opening / closing valves based on these detection signals, and further, in the electronic control device, in the input / output characteristics of the negative pressure booster. The first and second on-off valve operating boundaries that divide the first and second on-off valves into an operating region and a non-operating region, respectively, when the atmosphere is introduced into the variable pressure chamber only through the control valve, It is set in relation to the input / output static characteristics of the negative pressure booster, and the electronic control unit sets the first and the first on the basis of each detection signal from the operating force detection means and the output detection means. It is characterized in that it is determined whether each of the two opening / closing valves is operated or not operated, and the first and second opening / closing valves are operated and controlled based on the result of the determination.

According to a second aspect of the present invention, the gradient of the first opening / closing valve operation boundary line is larger than the gradient of the static characteristic of the negative pressure booster, and the starting point of the pedal depression force is higher than the rising point of the static characteristic. It is set to the large side, the gradient of the second opening / closing valve operating boundary line is substantially the same as the gradient of the static characteristic of the negative pressure booster, and the starting point thereof is the starting point of the first opening / closing valve operating boundary line. The feature is that it is set to a place where the pedal effort is slightly larger.

Further, in the invention of claim 3, the gradient of the first opening / closing valve operation boundary line is larger than the gradient of the static characteristic of the negative pressure booster, and the starting point of the pedal depression force is higher than the rising point of the static characteristic. It is set to a large side, the gradient of the second opening / closing valve operation boundary line is the same as the gradient of the first opening / closing valve operation boundary line, and the starting point is a pedaling force from the starting point of the first opening / closing valve operation boundary line. It is characterized by being set on the large side of.

Further, in the invention of claim 4, the gradient of the first opening / closing valve operation boundary line is larger than the gradient of the static characteristic of the negative pressure booster, and the starting point of the pedal depression force is higher than the rising point of the static characteristic. It is set to the large side, and the gradient of the second opening / closing valve actuation boundary line is substantially the same as the gradient of the static characteristic of the negative pressure booster in the range of the predetermined value of the pedal depression force or less and its starting point. Is set at a place where the pedal depression force is slightly larger than the starting point of the first opening / closing valve operation boundary line, and is set to be substantially the same as the gradient of the first opening / closing valve operation boundary line in the range in which the pedal depression force exceeds the predetermined value. It is characterized by being.

Further, a fifth aspect of the present invention is a brake operating member, a constant pressure chamber in which a negative pressure is constantly introduced from a negative pressure source, a negative pressure is introduced when the brake is not operated, and an atmosphere is introduced when the brake is operated. Chamber, a diaphragm that divides the constant pressure chamber and the variable pressure chamber and operates by introducing air into the variable pressure chamber, an internal chamber in which negative pressure is normally introduced and atmospheric air is selectively introduced when necessary, Operation of the control valve and the diaphragm, which are switched and controlled by the brake operating member to communicate the variable pressure chamber with the internal chamber when the brake is not operated and shut off from the atmosphere, and communicate with the atmospheric air when the brake is activated and shut off from the internal chamber. And a negative pressure booster having an output shaft for outputting the brake fluid pressure by the output shaft of the negative pressure booster. And Sunda, a brake cylinder for generating a braking force the brake fluid pressure of the master cylinder is introduced, a first passage that communicates with said internal chamber, the first
A proportional control valve that communicates the passage with the negative pressure source in normal times and communicates with the atmosphere in proportion to a control signal input when necessary, and a second that introduces the atmosphere flowing through the first passage into the variable pressure chamber. A passage, and the first passage provided in the second passage
A check valve that allows the flow of air from the passage toward the variable pressure chamber, but blocks the flow of air from the variable pressure chamber toward the first passage; and an operating force detection unit that detects the operating force of the brake operating member. When the atmosphere is introduced into the variable pressure chamber only through the control valve when the gradient of the input / output characteristic of the negative pressure booster is within a predetermined value of the pedal effort based on only the detection signal from the operating force detection means. The gradient of the input / output static characteristics of the negative pressure booster is substantially the same as the gradient of the input / output static characteristics of the negative pressure booster in a range exceeding the predetermined value of the pedal effort. And an electronic controller for controlling the proportional control valve by outputting the control signal.

According to a sixth aspect of the present invention, the electronic control unit is provided with the second opening / closing valve according to any one of the first to fourth aspects, until the output of the negative pressure booster becomes substantially the target braking force. It is characterized in that it is a control device which holds and controls the communication position and maximizes the valve opening of the proportional control valve.

[0015]

In each of the first to fourth aspects of the invention thus constructed, during normal braking, the control valve is switched by the operation of the brake operating member, the atmosphere is introduced into the variable pressure chamber through the control valve, and the negative pressure is doubled. The force device outputs and operates the piston of the master cylinder. In that case, the atmosphere introduced into the variable pressure chamber tries to leak through the second passage, but the check valve prevents the atmospheric leak, and the negative pressure booster outputs the pressure without loss. The master cylinder generates brake fluid pressure, and this brake fluid pressure is supplied to the brake cylinder to normally operate the brake.

At this time, the electronic control unit has the first relation between the actual input and output of the negative pressure booster based on the detection signals from the operating force detecting unit and the output detecting unit.
Then, it is determined whether the second on-off valve is in an operating region or a non-operating region. When a large braking force is required, such as during sudden braking, the relationship between the actual input and output of the negative pressure booster is considerably larger than the second opening / closing valve operation boundary line and is closer to the second opening / closing valve operation area side. As a result, the electronic control unit operates the first and second opening / closing valves for a relatively long period of time based on the result of the determination so that the first opening / closing valve is in the shutoff position and the second opening / closing valve is in the communication position. To As a result, not only the atmosphere is introduced into the variable pressure chamber of the negative pressure booster through the control valve, but also the first and second
It is also introduced relatively often through the passage. As a result, the pressure in the variable pressure chamber becomes large even if the operating force of the brake operating member, which is an input, is small. When a small braking force such as a gentle brake is required, the electronic control device is
And the second on-off valve are not operated or operated for a relatively short time respectively, and the atmosphere is introduced into the variable pressure chamber of the negative pressure booster only through the control valve or in a relatively small amount through the first and second passages. It As a result, the pressure in the variable pressure chamber becomes a pressure corresponding to the operating force of the brake operating member which is an input. Therefore, a large braking force can be obtained even with a comparatively small operating force of the brake operating member, and the controllability is improved when a small braking force such as a slow brake is required. In addition, when a large braking force is required such as during sudden braking, it tends to be accompanied by a large actuation delay, but the atmosphere is also introduced into the variable pressure chamber of the negative pressure booster through the first and second passages. From being
The pressure in the variable pressure chamber rises with almost no delay with respect to the operating force of the brake operating member, which is the input, and the negative pressure booster outputs with almost no delay. Therefore, the response of the negative pressure booster is improved.

Particularly, in the inventions of claims 2 to 4, since the starting point of the second opening / closing valve operating boundary line is set to a place where the pedaling force is slightly larger than the starting point of the first opening / closing valve operating boundary line, The second opening / closing valve does not repeat ON / OFF, and the hunting operation of the second opening / closing valve is prevented. However, since the starting point of the second opening / closing valve operation boundary line is not far apart from the starting point of the first opening / closing valve operation boundary line, the operation start of the second opening / closing valve will not be delayed, and the negative pressure booster Responsiveness is maintained well.

Further, in the fifth aspect of the invention, similarly, the normal brake is operated by operating the brake operating member. At this time, the electronic control device controls the valve opening degree of the proportional control valve based on only the detection signal from the operating force detection means.

Further, in the invention of claim 6, the electronic control device holds the second on-off valve in the communicating position or controls the proportional control valve until the output of the negative pressure booster becomes substantially the target braking force. Since the valve opening degree of is controlled to the maximum, the negative pressure booster outputs with almost no delay. Therefore, the response of the negative pressure booster is further improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a brake system according to the present invention.

As shown in FIG. 1, the brake system 1 of the first embodiment is a tandem brake pedal 2 which is a brake operating member of the present invention, and a tandem which is operated by the depression of the brake pedal 2 during normal braking. Type negative pressure booster 3, a tandem master cylinder 4 that generates brake fluid pressure in each of the two fluid chambers by the output of the negative pressure booster 3, and a tandem master cylinder 4 The brake fluid pressure generated in the other wheel chambers of the tandem master cylinder 4 and the wheel cylinders 6 and 7 of the left and right rear wheels, which are supplied through the fluid pressure passage 5, passes through the fluid pressure passage 8. Wheel cylinders 9 and 10 for the left and right front wheels, which are supplied as a whole, and an anti-skid control device (hereinafter also referred to as ABS) 1 disposed in both hydraulic passages 5 and 8.
1, PV12 disposed in the hydraulic passages 5 and 8 between the tandem master cylinder 4 and the ABS 11, and the brake of the master cylinder 4 disposed in the hydraulic passage 8 between the tandem master cylinder 4 and the PV12. A hydraulic pressure pickup (hereinafter also referred to as hydraulic pressure PU; corresponding to the output detecting means of the present invention) 13 for detecting hydraulic pressure, and a negative pressure source for supplying negative pressure to the negative pressure booster 3 via a negative pressure passage 14. 15 and a first variable pressure passage 16 for branching from the negative pressure passage 14 to selectively feed either the negative pressure of the negative pressure source 15 or the atmosphere to the negative pressure booster 3 (first embodiment of the present invention). (Corresponding to a passage), a normally open first opening / closing valve 17 composed of a solenoid valve disposed in the first variable pressure passage 16 and provided with a communication position and a shut-off position, and a negative pressure double that of the first opening / closing valve 17. A second variable pressure passage 18 communicating the first variable pressure passage 16 on the side of the power device 3 with the atmosphere; A normally closed second on-off valve 19 composed of a solenoid valve disposed in the second variable pressure passage 18 and provided with a shut-off position and a communication position, and a negative pressure booster 3 branched from the first variable pressure passage 16. The third variable pressure passage 20 to be connected (the second aspect of the present invention)
(Corresponding to the passage) and the first
The check valve 21 which allows only the flow of air from the variable pressure passage 16 toward the negative pressure booster 3, and the brake pedal 2
A pedal force meter 22 (corresponding to the operating force detecting means of the present invention) provided on the pedal, a stroke sensor 23 for detecting the stroke of the brake pedal 2, and a brake hydraulic pressure detection of the master cylinder from the hydraulic pressure pickup 13. And a controller 24 that outputs a control signal to the first and second opening / closing valves 17 and 19 while receiving a signal, a pedal depression force detection signal from the pedaling force meter 22 and a pedal stroke detection signal from the stroke sensor 23. . The hydraulic pressure passage 8 below ABS11 is branched into two independent hydraulic pressure passages 8a and 8b for each of the left and right front wheels.

FIG. 2 is an enlarged sectional view showing the negative pressure booster 3. As shown in FIG. 2, the negative pressure booster 3 is the same as a conventional tandem type negative pressure booster, and includes an input shaft 25 connected to the brake pedal 2 and a front shell 26.
A center plate 28 for partitioning an internal space formed by the rear shell 27 into a front chamber and a rear chamber
And the front power piston 2 arranged in the front chamber
9 and the front chamber, which is arranged so as to be located on the rear surface of the front power piston 29, is a constant pressure chamber 30 on the front side.
And a front diaphragm 32 that divides into a front-side variable pressure chamber 31, a rear power piston 33 disposed in the rear chamber, and a rear chamber that is disposed so as to be located on the rear surface of the rear power piston 33. A rear diaphragm 36 that is partitioned into a chamber 34 and a rear-side transformer chamber 35;
By the bellows 38 which is disposed in the constant pressure chamber 30 on the front side and defines and forms the internal chamber 37, the atmospheric valve 39a which is closed when the brake is not operated and opened by the advance of the input shaft 25, and the open when the brake is not operated and the advance of the input shaft 25 is performed. A control valve 39, which comprises a closing vacuum valve 39b and is switched and controlled by the forward movement of the input shaft 25, and a constant pressure chamber 30 on the front side and a constant pressure chamber 34 on the rear side, which are formed outside the bead portion of the front diaphragm 32, are always in communication with each other. Constant pressure passage 40 and atmosphere valve 3
The annular space between 9a and the vacuum valve 39b and the fourth variable pressure passage 41 which always communicates with the rear variable pressure chamber 35, and the fifth variable pressure passage which constantly connects the front variable pressure chamber 31 and the rear variable pressure chamber 35. The variable pressure passage 42, the sixth variable pressure passage 43 that constantly communicates the inner chamber 37 with the annular space outside the vacuum valve 39b, the output shaft 44 that operates the piston of the master cylinder 4, and the output reverse of the output shaft 44. At least a reaction disk 45 for transmitting a force to the input shaft 25 is provided.

A negative pressure passage 14 is provided in the constant pressure chamber 30 on the front side.
Is connected so that the negative pressure is constantly introduced from the negative pressure source 15. The negative pressure introduced into the constant pressure chamber 30 is further always introduced into the constant pressure chamber 34 on the rear side through the constant pressure passage 40. Also, the bellows 38
The first variable pressure passage 16 is connected to the inner chamber 37 of
When the first opening / closing valve 17 is open and the second opening / closing valve 19 is closed, negative pressure is introduced from the negative pressure source 15 into the internal chamber 37, and the first opening / closing valve 17 is closed and the second opening / closing valve 19 is opened. Atmosphere is introduced into the internal chamber 37 during operation.
Furthermore, the third variable pressure passage 20 is connected to the variable pressure chamber 35 on the rear side so that the first open / close valve 17 is opened and the second open / close valve 19 is opened.
Negative pressure is introduced from the negative pressure source 15 into the variable pressure chamber 35 when is closed, and the atmosphere is introduced into the variable pressure chamber 35 when the first opening / closing valve 17 is closed and the second opening / closing valve 19 is open. It has become.

By the way, in the first embodiment, the operating regions of the first and second on-off valves 17, 19 are set based on the relationship between the pedal effort and the master cylinder hydraulic pressure. FIG.
Such first and second on-off valves 1 in the first embodiment
It is a figure which shows the operation area | region of 7,19.

In FIG. 3, the static characteristics of the input and output of the negative pressure booster 3 when the atmosphere is introduced into the variable pressure chambers 31 and 35 only through the atmospheric valve 39a are shown by dotted lines. Further, as shown in FIG. 3, the operation boundary line of the first opening / closing valve 17 is set as shown by a chain line. The operating boundary line of the first on-off valve 17 is set to be considerably larger than the gradient of the static characteristic of the negative pressure booster 3, and the starting point thereof is slightly larger than the pedaling force of the rising point of the negative pressure booster 3. It is set to the pedaling force position. An area on the left side of the operation boundary line is an area (communication position) where the first opening / closing valve 17 is not operated, and an area on the right side is an area (blocking position) where the first opening / closing valve 17 is operated.

The operation boundary line of the second on-off valve 19 is set as shown by a solid straight line. This second on-off valve 1
The operation boundary line 9 is set to be equal to the gradient of the static characteristic of the negative pressure booster 3 shown by the dotted line, and the starting point thereof is set to a place slightly larger than that of the first opening / closing valve 17. An area on the left side of the operation boundary line is an area (shutoff position) where the second opening / closing valve 19 is not operated, and an area on the right side is an area (communication position) where the second opening / closing valve 19 is operated.

Therefore, the region sandwiched between the two operation boundaries is the region where the first on-off valve 17 is operated and the second on-off valve 19 is not operated, and in this region, the first and second on-off valves 17 are provided. , 19 are both set to the shut-off position, and the first variable pressure passage 16 on the negative pressure booster 3 side of the first and second opening / closing valves 17, 19 is held.

The region on the left side of the operation boundary line of the first on-off valve 17 indicated by the alternate long and short dash line is the first and second on-off valves 1.
Areas 7 and 19 are not activated. In this region, the first on-off valve 17 is set to the communication position and the second
The on-off valve 19 is set to the shutoff position, and the first variable pressure passage 1 on the negative pressure booster 3 side with respect to the first and second on-off valves 17 and 19 is opened.
6 is a negative pressure introduction state.

Further, the region on the right side of the operating boundary line of the second on-off valve 19 shown by the solid line is the first and second on-off valves 17 and 19.
Is the area where both are activated. In this region, the first on-off valve 17 is set to the shutoff position and the second on-off valve 19 is set.
Are set to the communication position, the first and second opening / closing valves 17,
The first variable pressure passage 16 closer to the negative pressure booster 3 than 19 is in the atmosphere-introduced state.

Therefore, by setting the first and second on-off valve operating boundaries as shown in FIG. 3, respectively,
The dynamic characteristics of the negative pressure booster 3 are made as close as possible to the static characteristics of the negative pressure booster 3.

In the brake system 1 of the first embodiment constructed as described above, when the brake is not operated as shown in FIGS. 1 and 2, the atmosphere valve 39a is closed and the vacuum valve 39b is opened, and the first opening / closing operation is performed. The valve 17 is open and the second opening / closing valve 19 is closed. Therefore, both constant pressure chambers 30, 3
4. Both the variable pressure chambers 31 and 35 and the internal chamber 37 are in a state where negative pressure is introduced.

During normal braking, the input shaft 25 is advanced by depressing the brake pedal 2, the vacuum valve 39b is closed and the atmospheric valve 39a is opened. As a result, the atmosphere passes through the open atmosphere valve 39a, the annular space between the atmosphere valve 39a and the vacuum valve 39b, and the fourth variable pressure passage 41, and the rear pressure chamber 35.
In addition to being introduced into the transformer chamber 31 on the front side through the fifth transformer passage 42. As a result, a pressure difference occurs between the front diaphragm 32 and the rear diaphragm 36, and the front diaphragm 32,
The front power piston 29, the rear diaphragm 36, and the rear power piston 33 move forward. For this reason, the output shaft 44 also advances and outputs, and operates the piston of the master cylinder 4. In that case, the atmosphere introduced into the rear pressure changing chamber 35 tries to leak through the third pressure changing passage 20, but the check valve 21 blocks the flow of air toward the negative pressure source 15, so Leakage of the atmosphere in the variable pressure chamber 35 on the side is reliably prevented. Therefore, the negative pressure booster 3 outputs the pressure without loss.

The master cylinder 4 generates a brake fluid pressure in the two fluid chambers by the operation of the piston. The brake fluid pressure in one fluid chamber of the master cylinder 4 is supplied to the rear wheel cylinders 6 and 7 of the rear wheels through the fluid pressure passage 5, and the normal brake of the rear wheels is activated. Similarly, the brake fluid pressure of the other fluid chamber is supplied to the front wheel cylinders 9 and 10 of the front wheels through the fluid pressure passage 8 and the left and right branch passages 8a and 8b, and the normal brakes of the left and right front wheels are activated.

At this time, both the pedal depression force detection signal from the pedal force meter 22 and the brake hydraulic pressure detection signal of the master cylinder 4 from the hydraulic pressure pickup 13 are input to the controller 24. Based on these detection signals, the controller 24 determines in which region the relationship between the pedal effort and the master cylinder hydraulic pressure is. At the time of normal braking, the negative pressure booster 3 outputs with a slight delay with respect to the input. Therefore, on the left and right sides of the second opening / closing valve operation boundary line, in the vicinity of this second opening / closing valve operation boundary line. Come to be located.

The controller 24 determines the second relationship between the pedal depression force and the master cylinder hydraulic pressure based on the pedal depression force detection signal and the brake hydraulic pressure detection signal of the master cylinder 4.
If it is detected that the valve is located slightly to the left of the opening / closing valve operation boundary line, it is judged that there is almost no delay and that the response is not affected, and whether the first and second opening / closing valves 17 and 19 are both operated. Alternatively, only the first opening / closing valve 17 is operated. Atmosphere is not introduced into the first variable pressure passage 16 because the second opening / closing valve 19 is not in the communication position. Therefore,
Atmosphere is controlled by the control valve 3 in the variable pressure chambers 31 and 35 of the negative pressure booster 3.
Only introduced through 9. Transformer room 31,3 at this time
The pressure of 5 rises with almost no delay with respect to the pedal effort which is the input, and the negative pressure booster 3 also outputs with little delay with respect to the pedal effort.

Similarly, the controller 24 determines that the relationship between the pedal effort and the master cylinder hydraulic pressure is located on the second opening / closing valve operation boundary line or slightly to the right of the second opening / closing valve operation boundary line based on both detection signals. When it is detected that there is a slight delay and the response is slightly affected, both the first and second on-off valves 17 and 19 are operated. As a result, the first on-off valve 17 is switched to the shut-off position and the second on-off valve 19 is switched to the communication position, so that the atmosphere passes through the second variable pressure passage 18 and the first variable pressure passage 16
The atmosphere in the first variable pressure passage 16 is further introduced into the variable pressure chamber 35 on the rear side through the third variable pressure passage 20.
Therefore, in the variable pressure chambers 31 and 35 of the negative pressure booster 3,
The atmosphere is introduced not only through the control valve 39 but also through the third variable pressure passage 20. As a result, the pressure in the variable pressure chambers 31 and 35 rises with almost no delay with respect to the pedaling force that is the input, and the negative pressure booster 3 outputs the pressure with almost no delay with respect to the pedaling force. Become. When the generated brake fluid pressure of the master cylinder 4 becomes larger than the brake fluid pressure of the master cylinder 4 with respect to the pedal depression force with respect to the second opening / closing valve operation boundary line, the relationship between the pedal depression force and the master cylinder fluid pressure is changed to the second opening / closing. Since it comes to be located on the left side of the valve operation boundary line, the controller 24 deactivates the second opening / closing valve 19 to bring it to the shut-off position. As a result, the atmosphere becomes the third variable passage 2
It is not introduced from 0, the pressure in the variable pressure chambers 31 and 35 rises more than necessary with respect to the pedal effort, that is, the output of the negative pressure booster 3 rises more than necessary with respect to the pedal effort. Suppressed.

When the front diaphragm 32, the front power piston 29, the rear diaphragm 36, and the rear power piston 33 are advanced, the atmosphere valve 39a is gradually closed. When both the atmosphere valve 39a and the vacuum valve 39b are closed, the front diaphragm 32 is closed. The forward movement of the front power piston 29, the rear diaphragm 36 and the rear power piston 33 is stopped. As a result, the output of the negative pressure booster 3 is hardly delayed and the input shaft 2
The output of 5 is boosted by a predetermined servo ratio.

When the brake pedal 2 is released, the pedal depression force becomes almost zero, whereas the brake fluid pressure of the master cylinder 4 is large. Therefore, the controller 24 shows the relationship between the pedal depression force and the master cylinder fluid pressure in FIG. First
It is judged to be on the left side of the opening / closing valve operation boundary line. Therefore, the controller 24 deactivates the first opening / closing valve 17 and switches it to the communication position. Further, the release of the brake pedal 2 causes the input shaft 25 to retract and the vacuum valve 39b to open. As a result, both the front and rear transformer rooms 31, 35
The atmosphere inside is the fifth variable pressure passage 42, the fourth variable pressure passage 41, the annular space between the atmospheric valve 39a and the vacuum valve 39b, the open vacuum valve 39b, the sixth variable pressure passage 43, the internal chamber 37, the first chamber.
The negative pressure source 15 passes through the variable pressure passage 16 and the first on-off valve 17.
Spill toward. Therefore, the front diaphragm 3
2, front power piston 29, rear diaphragm 3
6 and the rear power piston 33 are retracted, and the output shaft 4
4 and the pistons of the master cylinder 4 are also retracted to release the brake, and the brake system is brought into the non-actuated state shown in FIGS. 1 and 2.

A case where the vehicle is highly likely to collide and the driver depresses the brake pedal 2 rapidly and with a large pedal force to apply a sudden brake will be described. Also in this case, the vacuum valve 39b is closed and the atmosphere valve 39a is opened by depressing the brake pedal 2 as in the case of the normal brake described above.
Atmosphere is introduced into. As a result, the negative pressure booster 3 outputs, so that the master cylinder 4 generates brake fluid pressure and the brake is applied. However, in the case of such a sudden braking, even if the brake pedal 2 is rapidly depressed with a large pedaling force, the opening amount of the atmospheric valve 39a and the diameter of the passage through which the atmosphere flows are not so large originally, and the introduced atmosphere is limited. Therefore, each transformer room 31,
The pressure increase at 35 is delayed considerably with respect to the pedal effort. Therefore, the relationship between the pedal effort and the master cylinder hydraulic pressure during the sudden braking is located on the right side of the second opening / closing valve operation boundary line in FIG. When the controller 24 detects this based on both detection signals as described above, it determines that a considerable delay has occurred and the responsiveness is significantly affected, and the first and second on-off valves 17, 19 are Operate together. As a result, the first on-off valve 17 is switched to the shut-off position and the second on-off valve 19 is switched to the communication position, so that the atmosphere is introduced into the first variable pressure passage 16 through the second variable pressure passage 18 and the first variable pressure passage 16 The atmosphere is further introduced into the rear pressure changing chamber 35 through the third pressure changing passage 20. Therefore, in the variable pressure chambers 31 and 35 of the negative pressure booster 3, the atmosphere is filled with the control valve 39.
Not only through the third variable pressure passage 20, but also through the third variable pressure passage 20. As a result, the pressures in the variable pressure chambers 31 and 35 rise with almost no delay with respect to the pedaling force that is the input, and the negative pressure booster 3 outputs with almost no delay with respect to the pedaling force. Become. Then, the brake fluid pressure of the master cylinder 4 generated as described above is
When the brake fluid pressure of the master cylinder 4 with respect to the pedal opening force with respect to the second opening / closing valve operation boundary line becomes larger, the relationship between the pedal depression force and the master cylinder hydraulic pressure comes to be located on the left side of the second opening / closing valve operation boundary line. , The controller 24 deactivates the second on-off valve 19 to the shutoff position,
The output of the negative pressure booster 3 is prevented from increasing more than necessary with respect to the pedal effort.

Thus, in the brake system of the first embodiment, the dynamic characteristics of the input and output of the negative pressure booster 4 are such that the input and output of the negative pressure booster 4 are static during both sudden braking and gentle braking. Since the characteristics can be changed as close as possible, the pedaling force that is the input can be reduced when generating a large braking force during sudden braking, and the controllability of the brake is improved during gentle braking. be able to.

FIG. 4 shows a second embodiment of the present invention, and FIG.
FIG. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In the above-described first embodiment, the gradient of the operation boundary line of the second opening / closing valve 19 is set to be the same as the gradient of the static characteristic of the negative pressure booster 3, but as shown in FIG. In the example, the gradient of the second opening / closing valve operation boundary line is set to be substantially the same as the gradient of the first opening / closing valve operation boundary line. The gradient of this first opening / closing valve operation boundary line is the same as that of the first embodiment. Therefore, the gradient of the second opening / closing valve operation boundary line is made considerably larger than the gradient of the static characteristic of the negative pressure booster 3. Further, the starting point of the second opening / closing valve operation boundary line is located on the side where the pedal effort is larger than the starting point of the first opening / closing valve operation boundary line.

In the second embodiment, the output gradient of the negative pressure booster 3 with respect to the pedal effort is larger than that in the first embodiment, that is, the static characteristic of the negative pressure booster 3. Therefore, a larger braking force can be obtained with a smaller pedal effort. The other structure and effects of the second embodiment are the same as those of the first embodiment.

FIG. 5 shows a third embodiment of the present invention.
FIG. 5 is a view similar to FIG. The same components as those in the first and second embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 5, this third embodiment is a combination of the first and second embodiments described above. That is, in the third embodiment, the gradient of the second opening / closing valve actuation boundary line is in the range where the pedaling force is relatively small, like the second opening / closing valve actuation boundary line in the first embodiment. In the range where the pedal effort is relatively large, the gradient is set to be the same as the gradient of the first opening / closing valve operation boundary line in the same manner as the second opening / closing valve operation boundary line in the second embodiment. Further, the first opening / closing valve operation boundary line of the third embodiment is the first
And the same as that of the second embodiment.

In the third embodiment, the output gradient of the negative pressure booster 3 with respect to the pedal effort is larger than the static characteristic of the negative pressure booster 3 when a large braking force is required during sudden braking. Further, when a small braking force at the time of gentle braking is sufficient, the static characteristics of the negative pressure booster 3 are almost the same. Therefore, a larger braking force can be obtained with a comparatively small pedaling force at the time of sudden braking, and the static characteristics of the negative pressure booster 3 are almost the same at the time of gentle braking, so that the controllability is improved. Other configurations and operational effects of the third embodiment are the same as those of the first and second embodiments.

FIG. 6 shows a fourth embodiment of the present invention and is similar to FIGS. 3, 4 and 5. The same components as those in the first to third embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

In the third embodiment described above, the gradient of the second opening / closing valve actuation boundary line is made the same as the static characteristic of the negative pressure booster 3 within a range where the pedal effort is relatively small, and the pedal effort is relatively low. In the large range, the gradient of the first opening / closing valve operating boundary line is made the same, and when the range of the small pedaling force is changed to the large range, the gradient of the second opening / closing valve operating boundary line is changed in a polygonal line shape. However, as shown in FIG.
In the fourth embodiment, the gradient of the second opening / closing valve operation boundary line in the third embodiment is continuously changed in a curved shape.

FIG. 7 shows a fifth embodiment of the present invention, and FIG.
It is a figure which shows the part corresponding to the arrangement position of the 1st and 2nd on-off valves 17 and 19 of FIG. The same components as those in the first to fourth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

In the first to fourth embodiments described above, the first opening / closing valve 17 which is a vacuum valve and the second opening / closing valve 19 which is an atmospheric valve are individually arranged, but in the fifth embodiment. The first and second opening / closing valves 17 and 19 are constituted by a proportional control valve 47 which is a single solenoid valve. As the proportional control valve 47, a well-known one can be used, and the description of its structure will be omitted. The proportional control valve 47 sets the input / output characteristics of the negative pressure booster 3 as shown in FIG. That is, the input / output characteristics of the negative pressure booster 3 are set to be almost the same as the static characteristics of the negative pressure booster 3 in the range where the pedal effort is relatively small, and the negative pressure is set in the range where the pedal effort is relatively high. It is set so as to be considerably larger than the gradient of the static characteristic of the booster 3.

In the fifth embodiment, since only one valve is used, the number of parts is reduced and the controllability of the valve is improved. Other configurations and operational effects of the fifth embodiment are the same as those of the fourth embodiment.

FIG. 9 is a diagram for explaining the sixth embodiment of the present invention. The same components as those in the first to fifth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. As described above, the control valve of the negative pressure booster 3 generally has a characteristic that the valve opening amount decreases as the pressure in the variable pressure chambers 31 and 35 approaches the control target value. As shown by, there is a delay until the braking force reaches the control target value. In addition, the proportional control valve 47 as shown in FIG.
Even when controlling with, the valve opening becomes maximum at the beginning and the responsiveness is good, but since the valve opening decreases as the output approaches the target value, similarly there is a delay until the target braking force is reached. Will end up.

Therefore, in the sixth embodiment, the second opening / closing valve 19 is held in the communication position to the vicinity of the target braking force, and the valve opening of the proportional control valve 47 is maximized to the vicinity of the target braking force. I am trying to do it.

FIG. 10 shows the first and second on-off valves 17,1.
11 is a circuit diagram for controlling 9 in this way, and FIG.
(A) is a circuit diagram for controlling the proportional control valve 47 in this way.

As shown in FIG. 10 (a), first, the pedal force detected by the pedal force meter 22 as an input sensor is the first
The first constant k ₁ is multiplied by the multiplier 48, and the obtained values are sent to the first and second operational amplifiers 51 and 52, respectively. The first operational amplifier 51 performs an operation based on the value from the first multiplier 48 and the preset first offset value, and outputs the operation result to the first comparator 53. Similarly, the second operational amplifier 52 performs an operation based on the value from the first multiplier 48 and a preset second offset value smaller than the first offset value, and the operation result is output by the second comparator 5
4 is output.

On the other hand, the brake fluid pressure of the master cylinder 4 from the fluid pressure pickup 13 which is an output sensor is multiplied by the second constant k ₂ smaller than the first constant k ₁ by the second multiplier 49, and the obtained value is obtained. It is sent to the first comparator 53. Further, the brake fluid pressure of the fluid pressure pickup 13 is multiplied by a third constant k ₃ smaller than the second constant k ₂ by the third multiplier 50, and the obtained value is sent to the second comparator 54.

The first comparator 53 compares the value related to the pedaling force from the first operational amplifier 51 with the value related to the brake fluid pressure from the second multiplier 49, and the former value is smaller than the latter value. When it is large, it is output, this output signal is amplified by the first amplifier 55 and sent to the second opening / closing valve 19, and the second opening / closing valve 19 is switched and held at the communication position. Further, the second comparator 54 compares the value related to the pedal effort from the second operational amplifier 52 with the value related to the brake fluid pressure from the third multiplier 50, and the former value is larger than the latter value. The output signal is output when the second amplifier 5
Amplified by 6 and fed to the first on-off valve 17, the first on-off valve 17 is switched and held at the shutoff position. Therefore, the second opening / closing valve 19 is held in the communication position until the brake fluid pressure extremely approaches the target value.
The braking force reaches the target braking force relatively quickly as shown by the solid line in FIG. 9, and the delay hardly occurs.

In the control circuit shown in FIG. 11, the pedal depression force f
The proportional control valve 47 is controlled only by itself. That is, as shown in FIG. 4A, the pedal effort from the pedal effort meter 22 which is an input sensor is multiplied by the multiplier 48 by the multiplier k (f).
And the obtained value is a differentiator
And a second function unit 63 which is a proportional amplifier.
As shown in FIG. 6B, the first function unit 62 has an input / output characteristic which shows a so-called differential characteristic in which the output is curvilinearly reduced with time with respect to the input, and the second function unit 63 is Output is constant with respect to input regardless of time,
It has an input / output characteristic showing a so-called proportional characteristic. First
And the sum of the values from the second function units 62 and 63 and the reference value 59.
And are compared by the comparator 60 to create a PWM output. The output of the comparator 60 is amplified by the amplifier 61, and the proportional control valve 47 is driven by this amplified output. As a result, PD control is performed, and the response is improved by compensating for the delay of the control system. Furthermore, if an output sensor is added, PID control can also be configured.

The third variable pressure passage 20 may be provided in the valve body 46 so that the sixth variable pressure passage 43 communicates with the variable pressure chamber 31 on the front side. Further, the check valve 21 may be a check valve of a ball valve type instead of an elastic member such as a rubber plate.

Although the present invention is applied to a two-brake system, the present invention can be applied to a mere one-brake system in addition to the two-brake system, and the negative pressure booster 3 is a single type negative brake system. A pressure booster may be used. Further, the first on-off valve 17 and the second on-off valve 19 in the above-described embodiment may be formed by one two-position three-way valve solenoid valve.

Further, in the above-mentioned embodiment, the hydraulic pressure pickup 13 is adapted to detect the brake hydraulic pressure of the master cylinder 4, but as an output, the pressure in the variable pressure chambers 31, 35 of the negative pressure booster 3 or Wheel cylinder 6,7,9,1
It is also possible to detect a brake fluid pressure of 0 and control the first and second opening / closing valves 17 and 19 using these detected values.

Further, although the pedal force sensor provided on the brake pedal surface is used as the pedal force pickup in the above-described embodiment, the pedal force is detected from the movement of the brake lever or the input member of the negative pressure booster. Good.

Further, in the above-described embodiment, an analog arithmetic unit such as an operational amplifier is used for the control circuit such as a solenoid valve, but it is of course possible to use a digital arithmetic system such as a microcomputer.

[0063]

As is apparent from the above description, according to the brake system of the present invention, when a large braking force is required at the time of sudden braking, a relatively small operating force of the brake operating member produces a large force. A braking force can be obtained, and good controllability can be obtained when a small braking force such as a gentle brake is required. Also, it is possible to almost eliminate the operation delay of the negative pressure booster,
The response of the negative pressure booster can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a brake device used in first to fourth embodiments of a brake system according to the present invention.

FIG. 2 is a sectional view showing an example of a negative pressure booster used in the brake systems of the first to fifth embodiments.

FIG. 3 is a first and a second embodiment of the present invention.
It is a figure explaining control of an on-off valve.

FIG. 4 is a first and a second embodiment of the second embodiment of the present invention.
It is a figure explaining control of an on-off valve.

FIG. 5 is a first and a second embodiment of the third embodiment of the present invention.
It is a figure explaining control of an on-off valve.

FIG. 6 is a first and second example of the fourth embodiment of the present invention.
It is a figure explaining control of an on-off valve.

FIG. 7 is a view partially corresponding to FIG. 1 and partially showing a fifth embodiment of the present invention.

FIG. 8 is a diagram illustrating input / output characteristics of a negative pressure booster according to a fifth embodiment of the present invention.

FIG. 9 is a diagram illustrating a fifth embodiment of the present invention.

FIG. 10 is a first and a second embodiment of the first embodiment of the present invention.
It is a figure which shows the control circuit of an on-off valve.

FIG. 11 is a diagram showing an example of a control circuit for a proportional control valve according to a sixth embodiment of the present invention.

FIG. 12 is a schematic and partial view of a conventional braking system.

[Explanation of symbols]

1 ... Brake system, 2 ... Brake pedal, 3 ... Negative pressure booster, 4 ... Tandem master cylinder, 5,8,8a,
8b ... hydraulic passage, 6, 7 ... rear wheel cylinder, 9,
10 ... Wheel cylinder of front wheel, 11 ... Anti-skid control device (ABS), 13 ... Hydraulic pickup, 14 ...
Negative pressure passage, 15 ... Negative pressure source, 16 ... First variable pressure passage, 17 ...
First on-off valve, 18 ... Second variable pressure passage, 19 ... Second on-off valve,
20 ... Third variable passage, 21 ... Check valve, 22 ... Pedometer, 23 ... Stroke sensor, 24 ... Controller (electronic control device), 25 ... Input shaft, 26 ... Front shell, 27 ... Rear shell, 30 ... Front side Constant pressure chamber, 3
1 ... front-side transformer chamber, 34 ... rear-side constant pressure chamber, 35
… Rear side transformer room, 37… Interior room, 39… Control valve, 39
a ... atmosphere valve, 39b ... vacuum valve, 40 ... constant pressure passage, 41 ...
Fourth variable pressure passage, 42 ... Fifth variable pressure passage, 43 ... Sixth variable pressure passage, 44 ... Output shaft, 47 ... Proportional control valve, 48 ... First multiplier, 49 ... Second multiplier, 50 ... Third multiplier , 51 ... 1st
Operational amplifier, 52 ... second operational amplifier

Claims (6)

[Claims] 1. A brake operating member, a constant pressure chamber to which a negative pressure is constantly introduced from a negative pressure source, a variable pressure chamber to which a negative pressure is introduced when the brake is not operated and an atmosphere is introduced when the brake is operated, and the constant pressure chamber. And a diaphragm that divides the variable pressure chamber and operates by introducing air into the variable pressure chamber, an internal chamber that normally introduces negative pressure and selectively introduces atmospheric pressure when necessary, and the brake operating member An output shaft which is controlled by switching and communicates with the internal chamber when the brake is not operated and shuts off from the atmosphere and at the same time communicates with the atmosphere when the brake is actuated and shuts off from the internal chamber, and an output shaft which is output by the operation of the diaphragm. A negative pressure booster, a master cylinder operated by the output shaft of the negative pressure booster to generate a brake fluid pressure, and a master cylinder Brake cylinder for introducing a brake fluid pressure to generate a braking force, a first passage connected to the internal chamber, the first passage normally communicating with the negative pressure source, and the negative pressure source when necessary. A normally open first on-off valve that shuts off the first passage, and a normally-closed second on-off valve that shuts off the first passage on the inner chamber side of the first on-off valve from the atmosphere during normal operation and communicates with the atmosphere when necessary. A second passage that introduces the atmosphere flowing through the first passage into the variable pressure chamber; and a second passage that is provided in the second passage and allows air to flow from the first passage toward the variable pressure chamber. A check valve that blocks the flow of air toward the first passage, an operation force detection unit that detects an operation force of the brake operation member, the brake fluid pressure of the master cylinder, and the transformer of the negative pressure booster. Chamber pressure And output detection means for detecting any one of the hydraulic pressures of the brake cylinders, detection signals from the operation force detection means and the output detection means, and the first and the second detection signals based on these detection signals. An electronic control device for controlling the second on-off valve, wherein the electronic control device has an operating region and a non-operating region of the first and second on-off valves in the input / output characteristics of the negative pressure booster. The first and second on-off valve operating boundaries that are divided into two are set in relation to the static characteristics of the input and output of the negative pressure booster when the atmosphere is introduced into the variable pressure chamber only through the control valve. In the electronic control unit, the electronic control unit is provided in either an area in which the first and second opening / closing valves are operated or an area in which the first and second opening / closing valves are not operated based on each detection signal from the operation force detection unit and the output detection unit. Brake system characterized by whether the respectively determined, respectively controls the operation of the first and second on-off valve on the basis of the determination result. 2. A gradient of the first opening / closing valve actuation boundary line is larger than a gradient of the static characteristic of the negative pressure booster, and a starting point thereof is set to a larger pedaling force side than a rising point of the static characteristic. In addition, the gradient of the second opening / closing valve operating boundary line is substantially the same as the gradient of the static characteristic of the negative pressure booster, and the starting point thereof is slightly smaller than the starting point of the first opening / closing valve operating boundary line. The brake system according to claim 1, wherein the brake system is set in a large area. 3. The gradient of the first opening / closing valve actuation boundary line is larger than the gradient of the static characteristic of the negative pressure booster, and its starting point is set to a larger side of the pedal effort than the rising point of the static characteristic. In addition, the gradient of the second opening / closing valve operation boundary line is the same as the gradient of the first opening / closing valve operation boundary line, and the starting point thereof is set to a larger pedaling force side than the starting point of the first opening / closing valve operation boundary line. The brake system according to claim 1, wherein: 4. The gradient of the first opening / closing valve actuation boundary line is larger than the gradient of the static characteristic of the negative pressure booster, and the starting point thereof is set on the larger side of pedaling force than the rising point of the static characteristic. In addition, the gradient of the second opening / closing valve operation boundary line is substantially the same as the gradient of the static characteristic of the negative pressure booster in the range of the predetermined value of the pedal effort or less, and the starting point thereof is the first opening / closing valve. The slope of the first opening / closing valve operating boundary line is set to be substantially the same as the position where the pedal pressing force is slightly larger than the starting point of the operating boundary line and in the range where the pedal pressing force exceeds the predetermined value. Claim 1
Brake system as described. 5. A brake operating member, a constant pressure chamber to which a negative pressure is constantly introduced from a negative pressure source, a variable pressure chamber to which a negative pressure is introduced when the brake is not operated and an atmosphere is introduced when the brake is operated, and the constant pressure chamber. A diaphragm that divides the variable pressure chamber and operates by introducing air into the variable pressure chamber, an internal chamber that normally introduces negative pressure and selectively introduces atmospheric pressure when necessary, and switches by the brake operating member. A control valve that communicates with the internal chamber when the brake is not operated and shuts off from the atmosphere while controlling the variable pressure chamber, and that communicates with the atmosphere when the brake is actuated and shuts off from the internal chamber; and an output shaft that outputs by operating the diaphragm. A negative pressure booster provided, a master cylinder that is actuated by the output shaft of the negative pressure booster to generate brake fluid pressure, and a master cylinder A brake cylinder that receives a brake fluid pressure from the cylinder to generate a braking force, a first passage connected to the internal chamber, and a control that is normally connected to the negative pressure source and is input when necessary. A proportional control valve that communicates with the atmosphere in proportion to a signal; a second passage that introduces the atmosphere flowing in the first passage into the variable pressure chamber; A check valve that allows the flow of air toward the chamber but blocks the flow of air from the variable pressure chamber toward the first passage; operating force detection means that detects the operating force of the brake operating member; and the operating force detection. Based on only the detection signal from the means, in the range where the gradient of the input / output characteristics of the negative pressure booster is equal to or less than the predetermined value of the pedal effort, the negative pressure when the atmosphere is introduced into the variable pressure chamber only through the control valve. The control signal is approximately the same as the input / output static characteristic gradient of the booster, and is larger than the input / output static characteristic gradient of the negative pressure booster in a range in which the pedal depression force exceeds the predetermined value. Is output to control the proportional control valve, and a brake system. 6. The electronic control device holds and controls the second opening / closing valve according to claim 1 at a communication position until the output of the negative pressure booster becomes substantially the target braking force. A brake system, which is a control device for controlling the valve opening of the proportional control valve according to claim 5 to a maximum.