JP2001171509A - Brake system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake system ensuring rigid feeling of a brake operation member even in an extreme low G zone. SOLUTION: A pedal stroke pedal stepping force property of a brake system 1 is set such that a pedal stroke is initiated before assistance initiation with a stepping force smaller than conventional assistance initiating stepping force at a jumping moment and that the pedal stepping force and the pedal stroke increase linearly. Further, a pedal stepping force-vehicle deceleration property is set such that vehicle deceleration is generated with stepping force smaller than that with which deceleration is generated in a brake system having conventional jumping property, and that the vehicle deceleration to the pedal stepping force varies linearly or along a recessed curve line. Thus, rigid feeling of a brake pedal can be certainly obtained even in an extremely low G zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a brake system provided with a brake booster such as a negative pressure booster or a hydraulic booster, and more particularly, to a brake pedal having a rigid feeling. The present invention belongs to the technical field of a brake system having improved braking characteristics.

[0002]

2. Description of the Related Art Conventionally, in a brake system of an automobile such as a passenger car, a booster such as a negative pressure booster or a hydraulic booster is used to boost a relatively small pedaling force of a brake pedal. A large braking force is generated, and the brake is operated with the large braking force. In a brake system equipped with such a booster, when the brake pedal is depressed and the pedal depression force is the boost start input of the booster, the booster starts the boost operation and boosts the pedal depression force. Output. When the master cylinder piston of the master cylinder is operated with a large output of the booster, the master cylinder generates a master cylinder pressure, which is a brake pressure, so that a large braking force can be obtained.

By the way, if the booster is not boosted until the pedal depression force reaches the pedal depression force at the boosting start point and no braking force is generated, even if the boosting operation is started, the boosting amount is not increased. Since the required amount is not enough, the brake pedal is felt heavy from the step on the brake pedal to the vicinity of the boosting start point, and the driver feels that the brake is not effective. Therefore, in general, the braking characteristics of a conventional brake system are so-called jumping characteristics in which only the output increases by a certain amount without increasing the pedal effort at the boosting start point. With this jumping characteristic, the braking force rises sharply by the amount of jumping even though the pedal depression force does not increase at the boosting start point, so that the driver feels that the brake pedal is light and the brake works well Become.

[0004]

However, when the jumping characteristic is provided as described above, the reaction force from the booster is not transmitted to the brake pedal during the operation of the jumping characteristic. Although the pedal effort does not increase simultaneously with the start of the force operation, the brake pedal will stroke. For this reason, the driver did not feel the rigidity of the brake pedal, and in this respect, the pedal feeling was not very good.
Particularly, extremely low G region (region where vehicle deceleration is about 1 m / sec ² or less)
In, the feeling of rigidity of the pedal was not remarkable, and the brake feeling was not sufficient.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a brake system capable of reliably obtaining a sense of rigidity of a brake operation member even in an extremely low G range. is there.

[0006]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a brake operation member which strokes when a brake operation force is applied, and a brake operation force of the brake operation member which is doubled. A brake booster that outputs by force, and a master cylinder that generates a brake pressure by operating with the output of the brake booster, so that the brake operates according to predetermined brake characteristics at the brake pressure. In the brake system, the brake characteristic is such that the brake operation member starts a stroke with a brake operation force smaller than the brake operation force at which the brake booster starts boosting, and at least the brake booster doubles. Until the force starts, the brake operation force is linear with respect to the stroke of the brake operation member. With changes, it is characterized in that the brake pressure to the brake operation force is a braking characteristic curve varying linear or convex downward.

Further, the invention of claim 2 is characterized in that the brake characteristics are obtained by adjusting the spring force of each spring provided on the input side of the brake booster. Further, the invention of claim 3 is characterized in that the brake characteristic is obtained by adjusting the spring force of each spring provided on the input side of the master cylinder.

[0008]

According to the present invention thus constructed, since the braking characteristics do not have the jumping characteristics of the conventional braking system, a braking force is generated from a braking operation force smaller than that of the conventional braking system. Characteristics. In addition, the brake characteristics of the present invention are such that the brake operation force and the stroke of the brake operation member change linearly, and the brake pressure with respect to the brake operation force changes linearly or in a downwardly convex curve. It gives a sense of rigidity. In particular, extremely low G
The sense of rigidity of the brake operating member in the region is effectively obtained. Further, the brake pressure at the boost start point input in the brake system of the present invention is generated with substantially the same brake operating force as the brake pressure at the boost start point input in the conventional brake system. Therefore, the feeling of braking effectiveness does not change, and a good braking feeling is obtained. Furthermore, the above-described brake characteristics can be obtained by simply changing the conventionally used members without adding new members, and the brake system of the present invention can be configured relatively easily and inexpensively. .

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically illustrating an example of an embodiment of a brake system according to the present invention, and FIG. 2 is a cross-sectional view illustrating a negative pressure booster used in the brake system. In the following description of the negative pressure booster, “front” and “rear” indicate “left” and “right” in FIG. 2, respectively. As shown in FIG.
The brake system 1 of this example includes a brake pedal (corresponding to a brake operating member of the present invention) 2 which is depressed by a driver during braking, and a pedal return spring 3 which constantly urges the brake pedal 2 to return to a non-operating position.
A negative pressure booster (corresponding to a brake booster of the present invention) 4 which is operated by the brake pedal 2 and boosts and outputs a pedal depression force (corresponding to a brake operating force of the present invention) by a negative pressure; A master cylinder 5 for generating a master cylinder pressure (corresponding to the brake pressure of the present invention) in the brake fluid by the output of the negative pressure booster 4, and a reservoir 6 for storing the brake fluid
The left and right wheel cylinders 7, 8 on the front wheel side where the master cylinder pressure of the master cylinder 5 is supplied as a brake pressure to generate a braking force, and the master cylinder pressure is applied as a brake pressure via a proportioning valve (P valve) 9. The left and right wheel cylinders 10 and 11 on the rear wheel side that generate the braking force by being supplied.

As shown in FIG. 2, the vacuum booster 4 includes a front shell 12 and a rear shell 13 which are connected to each other. A valve body 14 is provided to penetrate the rear shell 13 in an airtight and slidable manner, and a power piston 15 is attached to a distal end of the valve body 14. The power piston 15 is composed of a power piston member 16 attached to the tip of the valve body 14 and a diaphragm 17 provided between the shells 12 and 13 and the valve body 14 on the back of the power piston member 16. ing. The space inside the shells 12 and 13 is partitioned by the power piston 15 into a constant-pressure chamber 18 and a variable-pressure chamber 19. The constant pressure chamber 18 is always connected to a negative pressure source 21 (shown in FIG. 1) via a negative pressure introducing pipe 20 to introduce a negative pressure.

A valve plunger 22 is slidably fitted to the valve body 14, and an input shaft 23 is connected to a rear end of the valve plunger 22. This input shaft 23 is connected to the brake pedal 2. Also,
A valve body 24 is attached to the valve body 14 and an annular first valve seat 25 on which the valve body 24 can be seated.
Is provided. An annular second valve seat 26 on which the valve element 24 can be seated is also provided concentrically inside the first valve seat 25 at the rear end of the valve plunger 22. The valve body 24 and the first valve seat 25 constitute a negative pressure valve 27, and the valve body 24 and the second valve seat 26 constitute an atmospheric pressure valve 28. In this case, the valve element 24 is connected to the negative pressure valve 2
7 and an atmospheric pressure valve 28. Also,
The portion of the valve body 24 that is seated on the first and second valve seats 25 and 26 is movable in the front-rear direction. Due to the valve seat spring 29 contracted between this part of the valve body 24 and the input shaft 23, this part of the valve body 24 is brought into contact with the first valve seat 25.
And the valve return spring 30 contracted between the valve body 14 and the input shaft 23 from the first valve seat 25 via the input shaft 23 and the valve plunger 22. It is always urged in the direction to separate.

Further, a key member 31 is provided so as to penetrate through a radial hole 32 of the valve body 14 and engage with an annular groove 33 of the valve plunger 22. The valve body 14, the valve plunger 22, and the key member 31 are each relatively movable by a predetermined distance from each other. The space 3 outside the first valve seat 25 is provided in the valve body 14.
A negative pressure passage 35 that constantly communicates the pressure chamber 4 with the constant pressure chamber 18 is provided. Further, a variable pressure passage 37 is provided to constantly communicate the space 36 between the inside of the first valve seat 25 and the outside of the second valve seat 26 and the variable pressure chamber 19. Further, the space 38 inside the valve body 24 is always in communication with the atmosphere.

A reaction disk 40 made of an elastic material such as rubber is provided in the concave fitting portion 39 at the tip of the valve body 14.
And the rear end of the output shaft 41 is fitted. The front end of the output shaft 41 penetrates the front shell 12 in an airtight and slidable manner to operate a master cylinder piston (not shown) of the master cylinder 5. Both the valve body 14 and the power piston 15 are constantly urged rearward by a power piston return spring 42 contracted between the front shell 12 and the valve body 14.

In the negative pressure booster 4 shown in FIG. 2, the valve plunger 22 and the reaction disk 39
Is provided between the valve plunger 22 and the reaction disc 39 via the spacing member 49 when the brake is operated (that is, the gap between the valve plunger 22 and the spacing member 43 and the spacing member). 4
Both the gap between 3 and the reaction disc 39 is 0
State). Needless to say, the spacing member 49 can be omitted, and the valve plunger 22 can directly contact the reaction disc 39.

The master cylinder 5 is configured as a tandem-type master cylinder corresponding to a two-brake system in which the front and rear wheels are separate systems, and includes a primary piston 43 operated by an output shaft 41 of the negative pressure booster 4 and A secondary piston 44 is provided. A first return spring 45 is contracted between the pistons 43 and 44, and a second return spring 46 is contracted between the secondary piston 44 and the housing of the master cylinder 5. Further, the master cylinder 5 is provided with a first hydraulic chamber 47 in which the master cylinder pressure is generated by the advance of the primary piston 43 and a second hydraulic chamber 48 in which the master cylinder pressure is generated by the advance of the secondary piston 44. . The first hydraulic chamber 47 is always connected to the left and right wheel cylinders 7, 8 of the front wheel, and the second hydraulic chamber 48 is connected to the left and right wheel cylinders 7, 8 of the rear wheel via the P valve 9. Always connected. The first and second hydraulic chambers 47, 48 are respectively provided with the primary piston 4
3 and the secondary piston 44 are in communication with the reservoir 6 when in the inoperative position shown in the drawing, and are shut off from the reservoir 6 when the primary piston 43 and the secondary piston 44 advance.

In the negative pressure booster 4 configured as described above, when the brake pedal 2 is not depressed and the brake pedal 2 is not operated, the valve body 14, the power piston 15,
The valve plunger 22, the input shaft 23, and the output shaft 41 are all located at the positions shown in FIG. In this position, the negative pressure valve 27 is open and the atmospheric pressure valve 28 is closed. That is, the variable pressure chamber 19 is communicated with the constant pressure chamber 18,
Shielded from the atmosphere. Therefore, a negative pressure is introduced into the variable pressure chamber 19, and no differential pressure is generated between the variable pressure chamber 19 and the constant pressure chamber 18.

When the brake pedal 2 is depressed for performing a normal service brake, the input shaft 23 moves forward and the valve plunger 22 moves forward. Then, the valve body 24 is seated on the first valve seat 25, the negative pressure valve 27 is closed, the second valve seat 26 is separated from the valve body 24, and the atmospheric pressure valve 28 is opened. That is, the variable pressure chamber 19 is cut off from the constant pressure chamber 18 and communicated with the atmosphere. Therefore, the atmospheric pressure valve 28, the space 36, and the variable pressure passage 37, in which the atmosphere of the space 38 is open, are open.
And through the hole 32 into the transformer chamber 19. As a result, a pressure difference is generated between the variable pressure chamber 19 and the constant pressure chamber 18, the power piston 15 advances, and the output shaft 41 advances via the valve body 14. As a result, the negative pressure booster 4 boosts and outputs the pedal depression force.

Since the output shaft 41 presses the primary piston 43 of the master cylinder 5 by the output of the negative pressure booster 4, the primary piston 43 moves forward. Then
The first hydraulic chamber 47 is shut off from the reservoir 6, and a master cylinder pressure is generated in the first hydraulic chamber 47. Further, the secondary piston 44 advances by the master cylinder pressure, and
The hydraulic chamber 48 is shut off from the reservoir 6, and a master cylinder pressure is generated in the second hydraulic chamber 48. These master cylinder pressures correspond to the respective wheel cylinders 7, 8;
The wheel cylinders 7, 8; 10, 11 generate a braking force, and the brake forces act on the brakes on the front and rear wheels to perform service braking. At this time, the reaction force at the time of braking is transmitted from the output shaft 41 to the driver via the reaction disk 40, the spacing member 49, the valve plunger 22, the input shaft 23, and the brake pedal 2 with a magnitude corresponding to the braking force.

In order to release the braking, the brake pedal 2
Is released, the input shaft 23 and the valve plunger 2
Both retreat. As a result, the second valve seat 26 is seated on the valve body 24 to close the atmospheric pressure valve 28 and the valve body 2
4 is separated from the first valve seat 25 and the negative pressure valve 27 is opened. That is, the transformation chamber 19 is shut off from the atmosphere and communicates with the vacuum chamber 18. Therefore, the atmosphere in the variable pressure chamber 19 is supplied to the variable pressure passage 37, the open negative pressure valve 27, and the negative pressure passage 35.
Then, the gas is discharged to the constant pressure chamber 18 and further discharged from the constant pressure chamber 18 to the negative pressure source 21 through the negative pressure introducing pipe 20. Then, due to the spring force of the power piston return spring 42, the power piston 15, the valve body 14, and the output shaft 40 move backward and move to the inoperative position shown in FIG.

When the output shaft 41 is retracted, the primary piston 4 is moved by the spring force of the first return spring 45.
3 also retreats to the inoperative position, so that the first hydraulic chamber 47 communicates with the reservoir 6 and the master cylinder pressure in the first hydraulic chamber 47 gradually decreases and disappears. On the other hand, as the master cylinder pressure in the first hydraulic chamber 47 decreases, the secondary piston 44 also retreats to the non-operation position by the spring force of the second return spring 46, so that the second hydraulic chamber 48 communicates with the reservoir 6. As a result, the master cylinder pressure in the second hydraulic chamber 48 gradually decreases and disappears. Thereby, each wheel cylinder 7, 8, 1
Since the brake pressure of 0,11 gradually decreases and disappears,
The service brake is released.

Incidentally, in the brake system 1 of this example, the brake characteristics are set as follows. That is, (1) Among the brake characteristics, the pedal stroke-pedal force characteristic is a pedal force (i.e., about 15 N) smaller than the boost start pedal force (for example, about 15 N) of the conventional brake system having a jumping characteristic as shown in FIG. , Pedaling force before the start of boosting: about 10 N in the illustrated example), the pedal stroke starts before the boosting starts, and the pedaling force and the pedal stroke linearly increase. This linear increase in pedal effort and pedal stroke is at least in the vicinity of the end of the jumping characteristic in the conventional brake system, that is, the boosting start point (in the illustrated example,
(The pedal stroke is about 6 mm).

(2) Among the brake characteristics, the pedal depression force-vehicle deceleration characteristic is, as shown in FIG. 4, the vehicle deceleration in the conventional brake system (in the present invention, the brake pressure generated by the master cylinder 5 is used. When the brake pressure and the vehicle deceleration substantially correspond to one to one, a pedal depression force (shown by a dotted line: about 15 in the illustrated example) is generated.
N) A deceleration is generated with a smaller pedaling force, and the characteristic is such that the vehicle deceleration with respect to the pedaling force changes linearly (shown by a solid line) or changes according to a downwardly convex curve (shown by a dashed line). The increase of the pedal effort and the vehicle deceleration due to the linear or downwardly convex curve is at least near the end of the jumping characteristic in the conventional brake system, that is, the pedal effort at the boosting start point (about 15 N in the illustrated example). To the point corresponding to. As shown in FIG. 5, the pedal depressing force-vehicle deceleration characteristic indicates that the vehicle deceleration occurs at the start of the pedal stroke, and the vehicle deceleration with respect to the pedal stroke changes linearly (shown by a solid line) or decreases. The characteristic becomes a convex curve (shown by a chain line).

Now, in the brake system 1 provided with the above-described negative pressure booster 4, the factors related to these brake characteristics will be considered. First, considering the time from when the pedal is depressed until the braking force is generated and the vehicle deceleration is generated, the negative pressure valve 27 of the negative pressure booster 4 is closed and the atmospheric pressure valve 28 is closed.
Is open and the atmospheric pressure is introduced into the variable pressure chamber 19: ・ Spring force of the pedal return spring 3: SP ₁・ Spring force of the valve return spring 30 of the negative pressure booster 4: SP ₂・ Negative pressure multiplication Spring force of valve seat spring 29 of force device 4: SP _3. Force due to negative pressure acting on valve element 24 of negative pressure booster 4: P ₀ × A ₁ P ₀ (<0): Introduced negative pressure, A ₁ : Negative pressure P ₀ introduced into the valve element 24
The pressure input area F ₁ F ₁ = SP ₁ + SP ₂ + SP ₃ + P ₀ × A ₁ The pressure P (P ₀ <P <0) of the transformation chamber 19 and the balance equation between the input F and the input F F = SP ₁ + SP ₂ + SP ₃ + P × A ₂ A ₂ : Pressure receiving area of the pressure P of the variable pressure chamber 19 in the valve body 24

Power piston 15 of vacuum booster 4
Is operated to generate an output. ・ Spring force of the power piston return spring 42 of the vacuum booster ₄ : SP ₄・ Power by negative pressure acting on the power piston 15 of the vacuum booster 4: P ₀ × A ₃ A ₃ : Assuming the pressure receiving area of the introduced negative pressure P ₀ of the power piston 15, the output WW of the power piston 15 = (P−P ₀ ) × A ₄ −P ₀ × A ₃ −SP ₄ A ₄ : A pressure receiving area of the pressure P of the transformation chamber 19 of the power piston 15 A balance equation between the output W and the input F W = F × (A ₄ / A ₂ ) −BB = (SP ₁ + SP ₂ + SP ₃ ) × (A ₄ / A ₂₎ -P ₀ ×
_{(A 3 + A 4) -SP} 4

[0025] In a state where the primary piston 43 has generated the master cylinder pressure advances, the spring force of the-first return spring 45: SP ₅ output W and balance equation between the master cylinder pressure _{P 1 W = P 1 × A} 5 + SP ₅ master cylinder pressure P ₁ balance between the input F-type _{P 1 = F × (a 4} / a 2) / a 5 -C C = (B-SP 5) / a 5: constants, and from the master cylinder As factors affecting the input at which the pressure is generated (that is, the input of the boosting start point), each spring force: SP ₁ , SP ₂ , SP ₃ , SP ₄ , SP ₅ The pressure receiving area of each part: A ₁ , A ₂ , A ₃ , A ₄ and A ₅ are raised. In that case, the pressure receiving areas A ₂ , A ₄ and A ₅
Is determined by the vehicle brake, and A ₁ , A ₂ ,
Since A _3, etc. affects the responsiveness of the vacuum booster 4 (i.e. the response of the introduction atmospheric pressure), it can not be freely changed.

From the above, the following three settings and adjustments are made in order to obtain the brake characteristics (1) and (2) set above. (i) The jumping characteristic is not set in the vacuum booster 4.
That is, the gap between the valve plunger 22 and the reaction disk 39 when the atmospheric pressure valve 28 is open and the negative pressure valve 27 is closed is set to be zero (the negative pressure booster 4 in the example shown in FIG. 2). When the spacing member 43 is disposed between the valve plunger 22 and the reaction disk 39 as described above, the gap between the valve plunger 22 and the spacing member 43 and the spacing member 43 and the reaction disk 39
Are set so that the gaps between them are both 0). Note that FIG. 2 shows a slight gap between the spacing member 43 and the reaction disk 39 when not operating, but almost simultaneously when the negative pressure valve 27 is closed and the atmospheric pressure valve 28 is opened from this inoperative state. This gap disappears, and the reaction force is transmitted from the reaction disk 39 to the valve plunger 22 via the spacing member 43. (ii) The spring force that affects the pedal stroke before the operation of the negative pressure booster 4 starts, that is, the negative pressure valve 27 and the valve body 24 of the atmospheric pressure valve 28 are urged from the spring that urges the brake pedal 2. By adjusting the spring force of each spring up to the spring to be adjusted, the pedal depression force at the start of the pedal stroke is adjusted. In other words, adjusting the pedal spring force SP ₁ of the return spring 3, the spring force SP ₃ of the spring force SP ₂ and the valve seat spring 29 of the valve return scan pulling 30 of the vacuum booster 4. (iii) Adjust the spring force of the spring that affects the pedal depression force at which the vehicle deceleration occurs, that is, the spring force of the spring from the spring for biasing the power piston 15 of the vacuum booster 4 to the return spring of the master cylinder 5 By doing so, the pedal depression force at the start of vehicle deceleration generation is adjusted.
That is, the spring force SP ₄ of the power piston return spring 42 and the spring force SP 5 of the first return spring 45 of the master cylinder ₅ are adjusted. In the case of the tandem master cylinder as master cylinder 5 illustrated example, the spring force of the second return spring 46 is set in relation to the spring force SP ₅ of the first return spring 45, the second Ritansupu ring 46 Will also adjust the spring force.

Thus, the brake system 1 of this example
According to the present invention, the braking force is generated from the pedaling force smaller than that of the conventional braking system having the jumping characteristic, and the pedaling force and the pedal stroke are linearly increased, so that the pedal stiffness of the brake pedal 2 can be obtained. it can. In particular, the pedal stiffness in the extremely low G range can be effectively obtained.

Further, the output at the boosting start point input in the brake system 1 of this example (that is, the vehicle deceleration) can be obtained with substantially the same pedal depression force as the output at the boosting start point input in the conventional brake system. A good braking sensation can be obtained without changing the braking effect.
Furthermore, the above-mentioned brake characteristics (1) can be obtained by simply changing the members used conventionally without adding new members.
And (2) can be obtained, and the brake system 1 of this example can be configured relatively easily and inexpensively.

Although the negative pressure booster 4 is used as a booster in the above-described example, the present invention is not limited to this. For example, a hydraulic booster, a booster using compressed air, etc. Any booster can be used as long as it has a pedal stroke-pedal depression force characteristic, a pedal depression force-vehicle deceleration characteristic, and a pedal stroke-vehicle deceleration characteristic.

[0030]

As is apparent from the above description, according to the brake system of the present invention, the braking characteristic does not have the jumping characteristic of the conventional brake system and is smaller than that of the conventional brake system. A characteristic that generates braking force from the brake operation force, and
The brake operation force and the stroke of the brake operation member are changed linearly, and the brake pressure for the brake operation force is changed linearly or in a downwardly convex curve, so that a sense of rigidity of the brake operation member is obtained. be able to. In particular, the rigidity of the brake operation member in the extremely low G region can be effectively obtained.

Also, the brake pressure at the boost start point input in the brake system of the present invention is generated with substantially the same brake operating force as the brake pressure at the boost start point input in the conventional brake system. A good braking feeling can be obtained without changing the feeling of braking effect. Furthermore, since the above-described brake characteristics are obtained by simply changing the conventionally used members without adding new members, the brake system can be configured relatively easily and at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of an embodiment of a brake system according to the present invention.

FIG. 2 is a sectional view showing a negative pressure booster used in the brake system of the example shown in FIG.

FIG. 3 is a graph showing a pedal stroke-pedal force characteristic which is one of the brake characteristics of the brake system of the example shown in FIG.

FIG. 4 is a diagram showing a pedal depression force-vehicle deceleration characteristic which is another one of the brake characteristics of the brake system of the example shown in FIG.

5 is a diagram showing a pedal stroke-vehicle deceleration characteristic which is another one of the brake characteristics of the brake system of the example shown in FIG. 1. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Brake system, 2 ... Brake pedal, 3 ... Pedal return spring, 4 ... Negative pressure booster, 5 ... Master cylinder, 7, 8; 10, 11 ... Wheel cylinder, 14
... valve body, 15 ... power piston, 18 ... constant pressure chamber, 19 ... variable pressure chamber, 21 ... negative pressure source, 22 ... valve plunger, 23 ... input shaft, 24 ... valve body, 27 ... negative pressure valve, 28
... atmospheric pressure valve, 29 ... valve seat spring, 30 ... valve return spring, 41 ... output shaft, 42 ... power piston return spring, 43 ... primary piston, 44 ... secondary piston, 45 ... first return spring, 46 ... second return spring

Claims (3)

[Claims] 1. A brake operating member that strokes when a brake operating force is applied, a brake booster that boosts and outputs a brake operating force of the brake operating member, and operates with an output of the brake booster. And a master cylinder that generates a brake pressure by using the brake pressure, wherein the brake is operated in accordance with predetermined brake characteristics. The brake operation member starts a stroke with a brake operation force smaller than the brake operation force, and at least until the brake booster starts boosting, the brake operation force is reduced with respect to the stroke of the brake operation member. And the brake pressure with respect to the brake operation force Brake system characterized in that a brake characteristic curve varying linear or convex downward. 2. The brake system according to claim 1, wherein the brake characteristic is obtained by adjusting a spring force of each spring provided on an input side of the brake booster. 3. The brake system according to claim 1, wherein the brake characteristic is obtained by adjusting a spring force of each spring provided on an input side of the master cylinder.