JPH0117893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-stage actuation type master cylinder used in a brake device for a vehicle or the like.

Conventionally, a piston is slidably inserted into a cylinder hole of a cylinder body to partition a main pressure chamber and an auxiliary pressure chamber, and a main pressure chamber is connected to a first passage connecting the main pressure chamber and the auxiliary pressure chamber. A first valve that allows liquid movement to the pressure chamber and prohibits movement in the opposite direction is provided, and a second passage that communicates between a reservoir for storing liquid and the auxiliary pressure chamber is provided until the pressure in the auxiliary pressure chamber reaches a predetermined value. A system is known in which a second valve is provided to prohibit liquid movement from the auxiliary pressure chamber to the reservoir, and a throttle is provided in the second passage to limit the maximum flow rate. A relatively large amount of hydraulic fluid is delivered into the piping system compared to the pedal stroke, and then in the second step, a larger ratio (change in pressure divided by change in external force pushing the piston) The pressure inside the pressure chamber is increased.

However, with the above-mentioned restrictor, when sudden braking is applied, the rate of pressure increase in the auxiliary pressure chamber (rate of pressure change per unit time) is large, and the pressure rises quickly before a sufficient amount of hydraulic fluid moves from the auxiliary pressure chamber to the main pressure chamber. Even if the second valve opens, liquid movement in the second passage is limited by the throttling effect produced by the throttle, so that a sufficient amount of working fluid moves from the auxiliary pressure chamber to the main pressure chamber. However, in the conventional type, the throttle is formed from a small hole with a fixed passage area, so the higher the pressure increase rate of the auxiliary pressure chamber, the greater the throttle effect. , the amount of liquid flowing into the reservoir will be insufficient. If the amount of fluid flowing out from the auxiliary pressure chamber to the reservoir is insufficient, the pressure in the auxiliary pressure chamber will exceed the opening pressure of the second valve and become quite high, resulting in the phenomenon of so-called heavy braking when the brake is applied. Not only does this result in a considerable amount of pedal force being required to obtain the necessary high pressure, but also
There is a problem in that relatively high pressure remains in the auxiliary pressure chamber indefinitely, resulting in poor efficiency.

The present invention was made in view of the above-mentioned problems, and aims to provide a two-stage actuation type master cylinder that can prevent the phenomenon of heavy brakes even during sudden braking and improve efficiency. This is because the throttle is a variable throttle whose throttle effect changes depending on the rate of pressure increase in the auxiliary pressure chamber.

A detailed explanation will be given below based on the illustrated embodiment.

FIG. 1 is a side sectional view of a two-stage actuation type master cylinder according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the main part of FIG. 1.

In the figure, the two-stage actuating tandem master cylinder is indicated by 1 as a whole, and this master cylinder 1
is a cylinder hole 4 consisting of a small diameter hole 2 and a large diameter hole 3.
The cylinder body 6 has boss portions 5 and 5a each provided with a boss portion 5, 5a connected to a reservoir for storing hydraulic fluid on the upper side thereof.

A piston 7 is slidably inserted into the cylinder hole 4 following the small diameter hole 2, and a main piston 8 is slidably inserted into the small diameter hole 2 and the large diameter portion 10 into the large diameter hole 3, respectively. It has been inserted as follows. The small diameter portion 9 of the main piston 8 is formed with an extremely small gap formed between it and the inner wall of the small diameter hole 2. Central part 1 between the small diameter part 9 and the large diameter part 10 of the main piston 8
An auxiliary chamber 12 is formed on the side circumference of the piston 1, a first pressure chamber 13 is formed between the pistons 7 and 8, and a second pressure chamber 14 is formed between the slave piston 7 and the closed end of the cylinder hole 4. A supply chamber 15 is formed around the side of the slave piston 7.

A return spring 16 is attached to the left end side of the slave piston 7, and urges the slave piston 7 to the right. Further, a substantially cup-shaped presser foot 17 is arranged adjacent to the return spring 16, and a lip seal 19 is arranged between the presser foot 17 and the flange 18 of the slave piston 7 with its recess facing leftward. A small diameter hole 20 opening toward the right end of this lip seal 19 is
A loosening hole is provided in the flange 18, and is located slightly to the left of the lip seal 19 in the return state (or non-operating state), which will be described later, and communicates the second pressure chamber 14 with the inside of the boss portion 5a. 21, and a replenishment hole 22 that constantly communicates the replenishment chamber 15 with the inside of the boss portion 5a.
is bored in the cylinder body 6. 23 is a lip seal attached to the slave piston 7 to seal the first pressure chamber 13.

A caged spring device 24 is provided on the left end side of the main piston 8, and this device 24 includes a collared retainer 26 that engages with a bolt 25 screwed onto the main piston 8, and a caged spring device 24 that is installed adjacent to the left end of the main piston 8. A return spring 28 is tensioned with a predetermined tension between the spring receiver 27 and the spring receiver 27. The tension of this return spring 28 is greater than the tension of return spring 16. The spring receiver 27 is fitted into a recess of a lip seal 29 fitted to the left end of the small diameter portion 9 of the main piston 8 to prevent the outer lip 31 of the inner lip 30 and outer lip 31 of the lip seal 29 from collapsing. A plurality of presser pieces 32 are formed.

A through hole 33 that opens toward the right end of the inner lip 30 of the lip seal 29 is formed in the small diameter portion 9 of the main piston 8. 34 indicates a recess provided at the left end of the main piston 8 for fitting and abutting a push rod (not shown), and 35 indicates a recess in the large diameter portion 10 of the main piston 8 for sealing against the auxiliary chamber 12 and against the atmosphere. The attached triple lip type lip seal 36 is a stopper provided at the open end of the cylinder hole 4.

Similar to the loosening hole 21, the cylinder body 6 has a first opening located slightly to the left of the lip seal 29.
A loosening hole 3 that communicates between the pressure chamber 13 and the inside of the boss portion 5
7 is bored, and on the other hand, the auxiliary chamber 12 and the boss part 5
A large hole 38 communicating with the inside is bored.

A valve device 39 is screwed into the large hole 38 in a fluid-tight manner.

This valve device 39 has a main body portion 40 as shown in FIG.

In FIG. 2, the main body part 40 has a large diameter part 42 in which a threaded part 41 is formed, and a cylindrical part 43 formed to extend upward from this large diameter part 42, and both parts 42, 4
A valve hole 44 penetrating through the large diameter portion 3 and a large number of small holes 45 penetrating the large diameter portion 42 are respectively formed. Also,
At the lower end of the large diameter portion 42, a cylindrical protrusion 46 that protrudes downward is formed in the central portion.
The lower half of the valve hole 44 is formed to have a diameter that gradually becomes smaller through stepped portions 47 and 48, and the inner end portion of the stepped portion 47 in the radial direction serves as a seat 49, and a seat 49 is provided inside the valve hole 44. Ball 51 so that it is seated at 49,
It is biased by a valve spring 53 whose one end is supported by a holed cover 52 screwed onto the upper end of the valve hole 44 .

A rubber member 54 is attached to the lower part of the main body part 40, and this member 54 has a disc-shaped plate part 55 that can be brought into close contact with the lower surface of the large diameter part 42, and It has a substantially cylindrical tube portion 57 that is integrally provided with a first support portion 56 interposed therebetween.

A stepped portion 58 is formed at the communication portion between the first support portion 56 and the plate portion 55, and this stepped portion 58 is engaged with the protrusion 46. In addition, the cylindrical portion 5
7 has a center hole 59, and a throttle passage 60 formed by reducing the passage area is formed in the middle part of the center hole 59. On the other hand, on the outer peripheral side of the cylindrical part 57, an upper end part is formed. A second collar-like part protrudes radially outward.
A support portion 61 is formed, and this second support portion 61
engages with the stepped portion 48 to move the entire member 54 to the main body portion 4.
The chamber 64 formed between the ball 51 and the second support part 61 and the cylindrical part 57 are connected through the notches 62 and 63 provided in the second support part 61. An annular gap 65 provided between the cylindrical portion 57 and the valve hole 44 corresponding to the radially outer side of the throttle passage 60 is communicated with each other.

66 is a protector that prevents a portion of the plate portion 55 of the member 54 from sinking into the small hole 45 when the plate portion 55 receives the pressure in the auxiliary chamber 12.

In this above-described embodiment, the lip seal 29 together with the end face of the main piston 8 extends from the auxiliary chamber 12 into the first
Forms a first valve A that allows liquid movement to the pressure chamber and prohibits liquid movement in the opposite direction;
and the valve spring 53 form a second valve B that prohibits liquid movement from the auxiliary chamber 12 to the reservoir until the pressure within the auxiliary chamber 12 reaches a predetermined value.

Further, each of the pressure chambers 13 and 14 is connected to an independent piping system via a discharge portion (not shown).

The operation of the master cylinder 1 described above will be described below.

Assuming that it is now in the non-operating state, each member is in the position shown. That is, the main piston 8 is engaged with the stopper 36, the return spring 28 has reached the maximum length limited by the bolt 25 and the retainer 26, and the right end of the slave piston 7 is in contact with the retainer 26. . In this state, each pressure chamber 13,
14 communicates with the reservoir through loosening holes 37 and 21, respectively, and is pressure-free.In addition, the inside of the auxiliary chamber 12 is formed by the lower end surface of the main body 40 and the member, which is generated by the light elastic restoring force of the protector 66. 54 and the plate portion 55 and the small hole 45 in order to communicate with the reservoir, thereby making it pressureless.

In this state, when the brake pedal (not shown) is depressed and the main piston 8 is moved to the left, the lip seal 29 closes the loosening hole 37 and the first pressure chamber 1
At the same time, the slave piston 7 also moves to the left so that the lip seal 19 closes the loosening hole 21 and the second piston 7 is sealed.
The pressure chamber 14 is sealed. Further, as the main piston 8 moves leftward, the volume of the auxiliary chamber 12 begins to decrease, and the protector 66 is elastically deformed and the plate portion 55 of the member 54 comes into contact with the lower end of the main body 40, causing the auxiliary chamber 12 to decrease.
to be sealed.

After this, when the main piston 8 is further moved to the left, the pressure in each pressure chamber 13, 14 and the auxiliary chamber 12 increases, and the pressure liquid in the auxiliary chamber 12 passes through the through hole 33 and passes through the first valve A. The valve opens and the flow flows into the first pressure chamber 13, and from the first pressure chamber 13 the auxiliary chamber 1 flows, albeit at a low pressure.
A large amount of hydraulic fluid equal to the sum of the reduced volumes of the pressure chambers 2 and 13 is discharged. On the other hand, the second pressure chamber 1
The pressure inside the piston 4 increases as the forces acting on the left and right sides of the slave piston 7 are balanced.

Thereafter, when the pressure in the auxiliary chamber 12 reaches a predetermined pressure for opening the second valve B, the pressure liquid in the auxiliary chamber 12 flows into the reservoir through the gap between the ball 51 and the seat 49, and The pressure rise inside stops. When the lip seal 29 completely passes over the loosening hole 37, the lip seal 29 is connected to the loosening hole 37 and the auxiliary chamber 1 through a small passage between the small diameter portion 9 of the main piston 8 and the inner surface of the small diameter hole 2.
2 are in communication with each other, the pressure in the auxiliary chamber 12 can be gradually released to the reservoir, and after the second valve B is opened, the pressure in the auxiliary chamber 12 gradually decreases to no pressure. Therefore, after the second valve B opens, the first valve B opens.
The pressure in the pressure chamber 13 remains the same as before the second valve B opens, because almost all of the acting force from the brake pedal that moves the main piston 8 to the left is used to increase the pressure in the first pressure chamber 13. The pressure is boosted at a relatively large rate.

The above description shows a case where the moving speed of the main piston 8 is small, in other words, a case where the pressure increasing speed in the auxiliary chamber 12 is small; in this case,
The throttling effect caused by the throttling passage 60 of the member 54 does not occur much because the flow rate and flow velocity of the hydraulic fluid are small. The pressure held within the gap 65 and the pressure within the auxiliary chamber 12 are approximately equal, the forces acting on the inside and outside of the cylindrical portion 57 of the member 54 are balanced, and the shape of the cylindrical portion 57 is maintained approximately constant.

Next, a case where the moving speed of the main piston 8 is high, in other words, a case where the pressure increasing speed in the auxiliary chamber 12 is high will be described.

When the main piston 8 suddenly moves to the left, each chamber 12, 13 is sealed, and the pressure in the auxiliary chamber 12 begins to rise rapidly, causing the hydraulic fluid in the auxiliary chamber 12 to close the first valve A. The valve opens to flow into the first pressure chamber 13, and the pressure in the auxiliary chamber 12 is transmitted to the chamber 64, and the pressure in the chamber 64 also reaches the second valve B at a relatively early stage.
When the pressure reaches the level that opens the second valve B, the hydraulic fluid in the auxiliary chamber 12 begins to flow into the reservoir.

At this time, the working fluid in the auxiliary chamber 64 flows through the throttle passage 6.
0, chamber 64, gap between ball 51 and seat 49,
Since the flow rate and flow velocity of the hydraulic fluid are relatively large when it sequentially passes through the valve holes 44 and moves to the reservoir, there is a pressure difference between the chamber 64 and the auxiliary chamber 12 due to the presence of the throttle passage 60. At the same time, the above-mentioned gap exerts a throttling effect, so that a pressure difference is also generated in the chamber 64 and the upper half of the valve hole 44, and as a result, the throttling passage 60 is connected from the auxiliary chamber 12 to the chamber 64. A pressure is maintained that is proportional to the flow rate and flow rate of the working fluid that passes through the gap and moves to the reservoir, in other words, the pressure is proportional to the rate of pressure increase in the auxiliary chamber 12.

Further, since the pressure inside the chamber 64 is transmitted to the gap 65 through the notches 62 and 63, the pressure inside the chamber 64 acts on the outer peripheral surface of the cylindrical portion 57, while the lower half of the cylindrical portion 57 Since the pressure within the auxiliary chamber 12 is acting on the inner circumferential surface of the cylindrical portion 57, the cylindrical portion 57 tends to deform outward due to the differential pressure between the inner and outer circumferential surfaces of the cylindrical portion 57. The amount of deformation becomes large in the region near the lower end opening of the passage 60, and the passage area of the lower end side portion of the throttle passage 60 increases. Following this increase in the lower end portion, the passage area of the throttle passage 60 gradually increases from the lower end side to the upper end side, and the acting force that attempts to deform the cylindrical portion 57 due to the above-mentioned differential pressure becomes When the elastic restoring force of the cylindrical portion 57 is balanced, the passage area of the throttle passage 60 stops increasing.

By increasing the passage area of the throttle passage 60 in this manner, the throttling effect of the throttle passage 60 is reduced, the amount of liquid flowing from the auxiliary chamber 12 into the reservoir can be increased, and the amount of liquid in the auxiliary chamber 12 is increased. To prevent the pressure generated in the auxiliary chamber 12 from becoming higher than necessary even if the pressure is rapidly increased.

As described above, the second valve B is opened and the throttle passage 6
Even after the passage area of 0 increases, if the main piston 8 continues to move rapidly, the auxiliary chamber 12
The hydraulic fluid within flows into the reservoir through a throttle passage 60 having an increased passage area, and
The amount of fluid obtained by subtracting the amount of fluid flowing into the reservoir from the reduced volume of the auxiliary chamber 12 flows into the first pressure chamber 13, and a large amount of working fluid is discharged from the first pressure chamber 13 to the piping system connected thereto. Ru.

Thereafter, when the main piston 8 moves forward sufficiently, the hydraulic fluid in the auxiliary chamber 12 also begins to flow into the reservoir through the loosening hole 37.

Assuming that sufficient hydraulic fluid has been discharged into the piping system at this point, the movement of the main piston 8 will be slow and the pressure in the auxiliary chamber 12 will be released to the reservoir, which will cause an effect on the main piston 8. Almost all of the pressing force is used to increase the pressure within the first pressure chamber 13, and the pressure within the first pressure chamber 13 increases at a large rate in the same way as in the case described above.

In each of the above cases, the operation and the like when the brake operation is completed and the hydraulic pressure is released will be described below.

Now, when the pressing force that is trying to move the main piston 8 to the left is released, each piston 7, 8 will move as follows.
It moves to the right by the elastic restoring force of the return springs 16, 28, and negative pressure is generated inside each chamber 12, 13, 14.

Due to this negative pressure, the member 54 is in the auxiliary chamber 12.
The plate portion 55 is deformed to separate from the lower end of the main body portion 40, and hydraulic fluid flows from the reservoir through the small hole 45.
Working fluid flows into the second pressure chamber 14 from the reservoir or from the auxiliary chamber 12 through the through hole 33, and further, working fluid flows into the second pressure chamber 14 from the supply chamber 15 through the small hole 20. Next, the working fluid that was being sent to the piping system flows back into each pressure chamber 13, 14, returns from each pressure chamber 13, 14 to the reservoir through the loosening hole 21, 37, and flows inside each pressure chamber 13, 14. decreases to no pressure. Further, the auxiliary chamber 12 is formed between the plate portion 55 and the main body portion 4 by the elastic force of the protector 66.
Since it communicates with the inside of the reservoir through the gap created between the lower end of the reservoir and the lower end of the reservoir, there is no pressure.

According to the above embodiment, the following effects are achieved.

That is, the throttle effect of the throttle passage 60 changes as the passage area increases in accordance with the rate of pressure increase in the auxiliary chamber 12. In other words, the higher the rate of pressure increase, the greater the passage area. This increases the amount of fluid flowing into the reservoir from the auxiliary chamber 12, thereby reducing the throttling effect. By increasing the amount of fluid flowing into the reservoir from the auxiliary chamber 12, the fluid pressure generated within the auxiliary chamber 12 can be lowered, allowing low-pressure hydraulic fluid to be transferred to the piping system. When pumping a large amount of low-pressure hydraulic fluid, there is no need for a stronger pedal force than necessary, eliminating the so-called heavy brake phenomenon. Since the change to the process can be performed smoothly and the pressure in the auxiliary chamber 12 can be released in a short period of time, the efficiency at the time of change can be improved, and high pressure can be generated at an earlier stage.

In addition, as a means for increasing the passage area of the throttle passage 60 in proportion to the pressure increase rate in the auxiliary chamber 12, the pressure of the working fluid before passing through the throttle passage 60 is transferred to the inner peripheral side of the cylindrical portion 57. The ball passes through 5
The pressure of the hydraulic fluid before it passes through the gap between 1 and the seat 49 is applied to the outer peripheral surface of the cylindrical portion 57, and the pressure difference between the pressure acting on the inner and outer peripheral surfaces of the cylindrical portion 57 is applied.
When changing the passage area of the throttle passage 60 in proportion to the rate of pressure increase in the auxiliary chamber 12, it is not only possible to change the passage area of the throttle passage 60 relatively accurately, but also has a simple structure. It is a thing,
There is no need to increase the size or complexity of the device. Further, when a pressure difference occurs between the chamber 64 and the auxiliary chamber 12, the pressure acting on the upper end surface side and the lower end surface side of the cylindrical portion 57 pushes the cylindrical portion 57 into the inside of the valve hole 44. However, by integrally providing the first support part 56 on the cylinder part 57 and engaging the first support part 56 with the protrusion 46 of the main body part 40, the cylinder part 57 is prevented from being pushed into the valve hole 44, the cylindrical portion 57 is deformed so as to reduce the passage area of the throttle passage 60 when the cylindrical portion 57 is pushed into the valve hole 44. It is possible to prevent this, to protect the function of changing the passage area of the throttle passage 60 in accordance with the rate of pressure increase in the auxiliary chamber 12, and to achieve the original function of the master cylinder 1 as a whole.

Furthermore, in the above-mentioned embodiment, since the cylindrical portion 57 and the plate portion 55 are integrally formed from synthetic rubber as the member 54, the main body portion 40 is
It is only necessary to change the shape of the lower part of the cylinder and the rubber member, and there is no need to change the cylinder body 6 of the master cylinder 1, and only the valve device 39 can be replaced, resulting in excellent compatibility. Furthermore, since the throttle passage 60 is changed depending on the vehicle model to which the master cylinder 1 is applied, it is necessary to have various dimensions.
Since the other members of the valve device 39 can be used by simply replacing the member 54, compatibility is even greater.

Furthermore, since the throttle passage 60 is located below the ball 51, the hydraulic fluid that has passed through the throttle passage 60 is blown up toward the ball 51, thereby reducing the gap between the ball 51 and the seat 49. The higher the rate of pressure increase in the auxiliary chamber 12, the more intense the blow-up becomes, the gap increases, and the pressure in the chamber 64 becomes lower.
The pressure difference between the chamber 64 and the auxiliary chamber 12 becomes larger, increasing the passage area of the throttle passage 60, and eventually
Depending on the rate of pressure increase in the auxiliary chamber 12, the throttle passage 60
It has the function of changing the passage area.

FIG. 3 is an enlarged side sectional view of a main part showing another embodiment of the present invention.

In the example shown in FIG. 3, points that are particularly different from those shown in FIGS. 1 and 2 will be explained. In addition, the first and second
Items with functions similar to those shown in the drawings are indicated by adding a dot to the previously mentioned symbols, and explanations thereof will be omitted.

In FIG. 3, at the center of the lower end of the main body 40', there is a
A protrusion 70 is provided on the outer circumferential side of the protrusion 70, and a conical bottom surface 7 whose diameter gradually decreases upward.
1, and another annular groove 73 is formed slightly below this annular groove 72.

A valve member 74 made of rubber and having a disc shape with a cylindrical inner circumferential surface is fitted into the annular groove 72 with its inner circumferential surface elastically contacting the bottom surface 71. 74 compresses the inner periphery to the maximum at the lower end along the conical bottom surface 71, thereby deforming the valve member 74 as a whole into a bowl-shape whose arms bend upward, especially the outer periphery. The main body part 40' is positively elastically contacted with the lower end surface of the main body part 40' to improve sealing performance.

Further, a flange 77 of a support portion 76 of a throttle member 75 that is separate from the valve member 74 is fitted into the groove 73, and between the support portion 76 and the protrusion 70, the member 7
A holding plate 79 is provided to prevent the cylindrical portion 78 of No. 5 from being unnecessarily pushed into the valve hole 44'. Further, the gap 65' between the cylindrical portion 78 and the main body portion 40' communicates with the center hole 59' and the chamber 64' through a through hole 80 provided in the upper part of the cylindrical portion 78.

The operation of the example shown in FIG. 3 is almost the same as that of FIGS. 1 and 2, so a description thereof will be omitted.

Although various useful effects have been achieved in the above two embodiments, the present invention is not limited to the above-mentioned embodiments, and can be implemented in various forms.

That is, for example, when the member having the throttle passage and the valve member are formed separately as shown in FIG. 3, instead of actively bringing the valve member into elastic contact with the main body, In the example shown in Figs. 1 and 2, the valve member is brought into elastic contact with the main body when pressure is generated in the auxiliary chamber, and in the example shown in Figs. In an example where the replacement is performed using a passage formed in the main body part 40, as a means for changing the throttling effect of the throttling passage, instead of changing the passage area of the throttling passage, the length of the throttling passage is changed, or the passage area is changed. In this example, one end receives the acting force due to the pressure of the auxiliary chamber, and the other end receives the acting force due to the pressure of the hydraulic fluid located on the reservoir side of the throttle passage, and the elastic body, etc. Examples include providing a piston that receives a mechanical force from the piston, and a passage whose opening area changes in proportion to the amount of movement of the piston, or a passage whose length changes.

As is clear from the above description, according to the present invention, the throttle is a variable throttle whose throttle effect changes depending on the rate of pressure increase in the auxiliary pressure chamber, thereby preventing the phenomenon of heavy braking during sudden braking. In addition, a two-stage operating type master cylinder with improved efficiency is obtained.

[Brief explanation of drawings]

Figures 1 and 2 are views showing one embodiment of the present invention. Figure 1 is a side sectional view, Figure 2 is an enlarged view of the main part, and Figure 3 is the main part of another embodiment of the invention. It is an enlarged view. 1... Two-stage actuation type master cylinder, 12... Auxiliary chamber, 60, 60'... Throttle passage.

Claims (1)

[Claims] 1 A piston is slidably inserted into the cylinder hole of the cylinder body to partition a main pressure chamber and an auxiliary pressure chamber, and a first passage connecting the main pressure chamber and the auxiliary pressure chamber is connected from the auxiliary pressure chamber to the main pressure chamber. Providing a first valve that allows liquid movement to and prohibits liquid movement in the opposite direction,
A second valve that prohibits liquid movement from the auxiliary pressure chamber to the reservoir until the pressure in the auxiliary pressure chamber reaches a predetermined value is provided in a second passage that communicates between a reservoir for storing liquid and the auxiliary pressure chamber, and a second valve is provided in the second passage. A two-stage operation type master cylinder provided with a throttle that limits the maximum flow rate, characterized in that the throttle is a variable throttle whose throttle effect changes depending on the rate of pressure increase in the auxiliary pressure chamber. type master cylinder.