JPH0316298B2 - - Google Patents

Description

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

Conventionally, this type of cylinder body includes a cylinder body having a cylinder hole having a large hole and a small hole, a piston slidably inserted into the large hole and the small hole, and the piston and the cylinder body. a main pressure chamber defined between the bottom of the cylinder hole, an auxiliary pressure chamber defined between the side circumference of the piston and the inner circumference of the large hole, and the main pressure chamber and the auxiliary pressure A first valve is provided in a passage communicating with the auxiliary pressure chamber and allows liquid to move from the auxiliary pressure chamber to the main pressure chamber, but prohibits the reverse, and the auxiliary pressure chamber communicates with a storage tank for storing working fluid. Some devices are known that include a second valve that is provided in the passage and opens to communicate between the two when the pressure exceeds a predetermined pressure.

These systems discharge a large amount of pressurized fluid in a relatively short stroke in the low pressure range in order to apply the brakes more quickly or to reduce the amount of pressure required to press the brake pedal, and in the high pressure range they increase the rate of pressure increase relative to the pedal effort. It is well known that higher pressures can be easily generated.

It is also known that devices such as pneumatic boosters and hydraulic boosters are used to assist in the pedal effort required to operate the master cylinder.

Recently, when such a master cylinder and a booster are installed in combination, the overall length of the combined state of the two has been shortened to reduce the space required and the weight.

However, when a booster and such a master cylinder are combined, a conventional master cylinder forms an auxiliary pressure chamber in a portion adjacent to the booster, but the effective stroke of the piston, etc. in the booster is In order to ensure this, the part forming the auxiliary pressure chamber cannot be deeply inserted into the booster and combined, resulting in a problem that the overall length cannot be shortened. In addition, the piston of the master cylinder has
Since an auxiliary pressure chamber is formed on the side periphery of the piston, the effective stroke of the piston in the auxiliary pressure chamber must be equal to the entire effective stroke of the piston. It is also impossible to make it protrude from the cylinder hole of the cylinder and enter into the booster, and as a result, there is a problem that the overall length cannot be shortened.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a two-stage operating master cylinder that can be shortened overall when combined with a booster. According to the present invention, this object includes: a cylinder body having a cylinder hole having a large hole and a small hole; a piston slidably inserted into the large hole and the small hole; a main pressure chamber defined between the bottom of the cylinder hole, an auxiliary pressure chamber defined between the side circumference of the piston and the inner circumference of the large hole, and the main pressure chamber and the auxiliary pressure A first valve is provided in a passage communicating with the auxiliary pressure chamber and allows liquid to move from the auxiliary pressure chamber to the main pressure chamber, but prohibits the reverse, and the auxiliary pressure chamber communicates with a storage tank for storing working fluid. and a second valve that is provided in the passage and opens to communicate between the two at a predetermined pressure or higher.
In the step-actuation type master cylinder, the second valve is provided in the cylinder body, and the piston is inserted into the outside of the cylinder hole by penetrating through the head slidably fitted into the small hole and the large hole. an annular piston that is slidably fitted into the extension part and the large hole part and defines the auxiliary pressure chamber between the piston and the head part; A protrusion with which the annular piston engages is formed on the outer periphery of the extension on the auxiliary pressure chamber side, and a spring that presses the annular piston toward the protrusion is provided on the opposite side of the annular piston from the auxiliary pressure chamber side. This is achieved by a two-stage actuation type master cylinder, which is disposed in the large hole, and is provided with a stopper at the open end of the large hole, with which the axial piston engages via the protrusion and the annular piston. .

EMBODIMENT OF THE INVENTION Hereinafter, a tandem master cylinder with a negative pressure booster according to an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the tandem master cylinder with a negative pressure booster is indicated as 1 as a whole, and includes a tandem master cylinder part 2 and a negative pressure booster part 3.
It has The tandem master cylinder section 2 is of a two-stage operating type, and its cylinder body 4 is provided with a cylinder hole consisting of a large diameter hole 5 and a small diameter hole 6. A shaft-like piston 7 and a secondary piston 8 are slidably inserted into this cylinder hole, and the rear end side of the shaft-like piston 7 is connected to the outside through the cylinder hole, that is, to a negative pressure booster section which will be described in detail later. It stands out within 3. (In addition, in this specification,
Front and rear refer to left and right in Figure 1. ) A bolt 9 is screwed onto the front end of the shaft-shaped piston 7, a substantially spring-shaped spring receiver 10 is engaged with the head of the bolt 9, and a ring-shaped spring receiver 13 is attached to the shaft.
The spring 11 is stretched between the spring receivers 10 and 13 in a compressed state, and the spring receiver 10 is attached to the rear end of the secondary piston 8.
is brought into pressure contact with the front end of the shaft-shaped piston 7. Further, a large diameter portion 69 as a head formed at the front end of the shaft-shaped piston 7 is in contact with the large diameter portion 69, and the cup seal 1
2 is attached, and a cup seal 17 is also attached to the rear end of the secondary piston 8, thereby forming a first hydraulic pressure generating chamber 18 between the axial piston 7 and the secondary piston 8. Note that the cup seal 12 constitutes a first valve as referred to in this specification. A cup seal 16 is also attached to the front end of the secondary piston 8, and a second hydraulic pressure generating chamber 19 is formed between the piston 8 and the bottom wall of the cylinder body 4. The secondary piston 8 is biased to the right by a return spring 14 stretched between a spring receiver 15 fitted to the front end of the secondary piston 8 and the bottom wall of the cylinder body 4. Although not shown, the cylinder body 4 has a first hydraulic pressure generating chamber 18 and a second hydraulic pressure generating chamber 18.
An output port is formed in communication with each of the hydraulic pressure generating chambers 19, and each of these output ports is connected to a wheel cylinder.

The cylinder body 4 is further formed with boss portions 20 and 21, to which a hydraulic fluid storage reservoir is connected, although not shown. Liquid connection holes 70 and 71 are formed in the boss portions 20 and 21, and a return hole 7 is formed in the cylinder body 4 in communication with these liquid connection holes 70 and 71.
3, 75 and supply holes 74, 76 are formed. A valve device 72 including a second valve, which will be described in detail later, is disposed within the liquid connection hole 71 of one boss portion 21.

An annular piston 77 is slidably fitted into the small diameter portion of the axial piston 7 and the large diameter hole 5 of the cylinder hole, and a spring 84 is disposed within the negative pressure booster section 3.
, and its left position is restricted by an annular protrusion 83 formed in the small diameter portion of the axial piston 7 . Further, the annular piston 77 is prevented from coming off by a stop ring 81, and a seal member 78 is attached to the outer circumference, and a pair of seal members 79 and 80 are attached to the inner circumference. The annular piston 77 and the axial piston 7 constitute a piston corresponding to a conventional primary piston, and an auxiliary piston is provided around the axial piston 7 between the annular piston 77 and the large diameter portion 69 of the axial piston 7. A pressure chamber 82 is formed. This auxiliary pressure chamber 8
2 communicates with the above-mentioned supply hole 76.

The spring 84 that urges the annular piston 77 forward is received by a spring receiver 67 that is fixed to the rear end of the axial piston 7 that protrudes into the negative pressure booster section 3. and annular piston 7
It is arranged concentrically with 7.

Next, the valve device 7 disposed within one boss portion 21
2 will be explained in detail with reference to FIG.

The valve device 72 consists of a first valve part 86 and a second valve part 87, and these valve parts 85 and 87 share a valve body 183. A spring receiver 18 is attached to the valve body 183.
8 is fitted onto the outer edge of the valve body 183, and the stop ring 180 engages with the spring receiver 188, and the seal ring 88 press-contacts with the lower outer edge of the valve body 183. Liquid connection hole 7
Fixed to 1. A first valve chamber 91 is formed between the spring receiver 188 and the valve body 183, and within this valve chamber 91, the ball valve 182 is seated on a valve seat 90 formed in the valve body 183. The ball valve 182 is biased toward the valve seat 90 by a valve spring 181 stretched between it and a spring receiver 188 . Also, the valve body 18
A first through hole 184 is formed in the center of the valve body 183, and this through hole 184 communicates with a second valve chamber 89 formed below the valve body 183. Therefore, communication with the first valve chamber 91 is cut off.

A plurality of second passage holes 186 are further formed around the first passage hole 184 in the valve body 183, and these communicate with the first valve chamber 91, and normally the valve body 1
Communication with the second valve chamber 89 is cut off by a rubber valve member 85 fixed to the lower end of the valve chamber 83 . As described above, the first valve part 86 is composed of the ball valve 182, the valve body 183, the valve seat 90, and the valve spring 181, while the second valve part 87 is composed of the valve body 183 and the rubber valve member 85. configured.

The first valve chamber 91 is the center opening 18 of the spring receiver 188.
9, and the second valve chamber 89 communicates with the inside of the cylinder hole of the cylinder body 4 described above through a return hole 75 and a supply hole 76. Further, a throttle groove 187 is formed in the lower end peripheral portion of the valve body 183, and the first valve chamber 91 and the second valve chamber 8
9 through the throttle groove 187 and the second through hole 186.

The second valve chamber 89 communicates with the first hydraulic pressure generating chamber 18 via the return hole 75 only when the device is not in operation, but constantly communicates with the auxiliary pressure chamber 82 via the supply hole 76. When the pressure in the second valve chamber 89 becomes higher than the pressure in the first valve chamber 91 by a predetermined value or more, the first valve part 86 opens, and the second valve chamber 89 and the first valve chamber 91 are in a state of free communication. . This valve opening pressure is determined by the strength of the valve spring 181, the seating area of the ball valve 182 with respect to the valve seat 90, etc.
It is selected to have a predetermined relationship with the spring 84 that biases it. Further, the valve opening pressure of the second valve portion 87 is sufficiently small, and the first valve chamber 91 communicating with the reservoir
The valve is configured to open when the pressure in the second valve chamber 89 becomes lower than the pressure by a predetermined value or more, that is, when the second valve chamber 89 becomes a negative pressure.

Next, details of the negative pressure booster section 3 will be explained with reference to FIG. 1.

The negative pressure booster section 3 includes a front shell 23 fixed to the flange section of the cylinder body 4 via a seal member 22 with a bolt (not shown), and an outer peripheral bead section 26 of a diaphragm 24 between the front shell 23 and the front shell 23 . It has a casing consisting of a rear shell 25 that is clamped and fixed to a front shell 23, and a movable wall 28 fitted with an inner peripheral bead portion 27 of a diaphragm 24 is movably fitted in the interior space of the casing. A negative pressure chamber 30, which is constantly connected to a negative pressure source via a connection cap (not shown) fixed to the front shell 23, is defined in front of the movable wall 28, and a variable pressure chamber 31 is defined in the rear.

The movable wall 28 is provided with a hub portion 40 that extends rearward from the central portion and slidably fits into the opening 32 of the rear shell 25.
2 and the hub portion 40, there is a dustproof boot 42 integrally formed with a lip portion 41 for sealing between the two, and a dustproof boot 42 that holds the lip portion 41 and connects the hub portion 40.
A support member 43 is disposed to guide the sliding of the support member 43.
is held by. 45 is a retainer for the lip portion 41 to come off.

The movable wall 28 has a center hole 46 that also passes through the hub portion 40, and an output shaft 47 that can come into contact with the shaft-shaped piston 7 at one end is fitted in the front portion. An elastic member 49 is disposed between the center hole 46 and the stepped portion 48 . An input shaft 51 having a plunger valve 50 attached to its front end is disposed behind the elastic member 49, and the plunger valve 50 can come into contact with the elastic member 49, and a U-shaped stopper 52 allows the input shaft 51 to be attached to a movable wall. The amount of movement relative to 28 is limited to a certain value. The center hole 46 further includes a valve seat 53 at the rear end of the plunger valve 50.
A flexible valve member 55 that can be seated on a valve seat 54 formed on the inner wall of the center hole 46 is disposed, and a conical portion and a conical portion are disposed between the flexible valve member 55 and the input shaft 51. Spring 56 integrally formed with the cylindrical portion
are arranged to bias the flexible valve member 55 into a predetermined position in the center hole 46 and toward the valve seats 53 and 54. 57, 58, 59 are spring receivers, and 60 is an air filter.

The movable wall 28 has a center hole 4 in front of the valve seat 54.
A passage 61 communicating between the valve seat 5 and the variable pressure chamber 31 is connected to the valve seat 5.
A passage 62 that opens on the rear side of the housing 4 and connects the center hole 46 and the negative pressure chamber 30 is bored, respectively.

A preload spring 63 is tensioned between the movable wall 28 and the front shell 23 to bias the movable wall 28 to the return position. The return position of the axial piston 7 is regulated by contacting the bottom of a recess 68 formed at the end. The movable wall 28 further includes a reinforcing rim 65.
is formed, thereby receiving the preload spring 63. The other side is supported by a reinforcing/spring receiving plate 29 fixed to the front wall of the front shell 23. Further, a cover member 64 for preventing the output shaft 47 from coming off is fixed to a central protrusion of the movable wall 28 into which the rear end of the output shaft 47 fits. The negative pressure booster section 3 is constructed as described above, and the entire device section is fixed to a toe board (not shown) by a plurality of bolts 66 fixed to the rear shell 25.

The tandem master cylinder with a negative pressure booster according to the embodiment of the present invention is configured as described above.
This effect will be explained below.

When not in operation, the parts are in the state shown.
That is, since the flexible valve member 55 is seated on the valve seat 53 and separated from the valve seat 54, the variable pressure chamber 31 communicates with the negative pressure chamber 30 via the passage 61, the center hole 46, and the passage 62 in this order. Since the negative pressure chamber 36 is always in communication with a negative pressure source, negative pressure is introduced into the variable pressure chamber 31. Since the pressure in the variable pressure chamber 31 and the negative pressure chamber 36 are the same, the movable wall 28 is returned to the return position in contact with the rear shell 25 by the preload spring 63. Further, the axial piston 7 is returned to the illustrated return position by a return spring 14.

Now, when the driver depresses the brake pedal (not shown), the input shaft 51 and the plunger 50 move forward together, so the flexible valve member 55 seats on the valve seat 54 and creates a negative pressure in the variable pressure chamber 31. After the communication with the chamber 30 is cut off, the flexible valve member 55 and the valve seat 53 are separated by the advancement of the plunger valve 50, and the variable pressure chamber 31 is communicated with the atmosphere through the center hole 46 and the air filter 60. Atmospheric pressure is introduced into the variable pressure chamber 31. Transformer room 3
1, a pressure difference is created across the movable wall 28, and the movable wall 28 is moved by the preload spring 6.
3 and move forward, and the shaft-shaped piston 7 is advanced by the output shaft 47.

Cup seal 12 attached to shaft-shaped piston 7
When the liquid passes through the return hole 75, the first hydraulic pressure generating chamber 18
is in a sealed state with respect to the reservoir side, but the pressure in the first hydraulic pressure generating chamber 18 hardly increases at the beginning of forward movement in order to compensate for the liquid loss on the wheel cylinder side. On the other hand, the annular piston 77 also moves forward together with the axial piston 7, so that the volume of the auxiliary pressure chamber 82 decreases. Therefore, the pressure in the auxiliary pressure chamber 82 increases as the annular piston 77 advances, and the pressure difference between the auxiliary pressure chamber 82 and the first hydraulic pressure generating chamber 18 causes the hydraulic fluid to flow between the large diameter portion 69 of the axial piston 7 and the cylinder hole. The outer edge of the cup seal 12 is deformed and the first hydraulic pressure generating chamber 18 is opened.
flow inside. As a result, the fluid loss on the wheel cylinder side connected to the output port of the first fluid pressure generating chamber 18 is quickly compensated for.

When the pressure in the auxiliary pressure chamber 82 reaches the opening pressure of the first valve part 86, the hydraulic fluid in the auxiliary pressure chamber 82 flows through the supply hole 76, the second valve chamber 89, the through hole 184, and the ball valve 18.
2 and the valve seat 90, and is guided to the reservoir side through the first valve chamber 91. This prevents excessive force from being applied to the axial piston 7, that is, the input shaft 51 side. Note that the pressure within the auxiliary pressure chamber 82 increases as the annular piston 77 advances, but immediately before the annular piston 77 abuts the step d between the large diameter hole 5 and the small diameter hole 6 of the cylinder hole, or The spring force of the spring 84 that biases the annular piston 77 is determined so that the valve opening pressure of the second valve portion 87 is reached when the annular piston 77 comes into contact with the annular piston 77 .

The annular piston 77 moves forward together with the axial piston 7, but after the annular piston 77 contacts the stepped portion d, only the axial piston 7 moves forward, and the fluid loss on the wheel cylinder side has already been compensated for. The pressure in the first hydraulic pressure generating chamber 18, that is, in the wheel cylinder connected thereto, increases rapidly. The secondary piston 8 also moves forward together with the axial piston 7, but after the axial piston 7 moves forward slightly, the pressure within the first hydraulic pressure generating chamber 18 begins to rise rapidly, so the pressure difference before and after the secondary piston 8 is also added. Then, the pressure in the second hydraulic pressure generating chamber 19 rapidly moves forward together with the axial piston 7, and the pressure in the second hydraulic pressure generating chamber 19 begins to rise rapidly almost simultaneously with the pressure in the first hydraulic pressure generating chamber 18. In this way, the desired brake can be applied to the vehicle.

Next, when the driver releases the brake pedal, the movable wall 28 moves backward under the spring force of the preload spring 63, and the output shaft 47 moves backward as well. The axial piston 7 and the secondary piston 8 also move backward under the urging force of the return spring 14. At this time, the annular piston 77 also engages with the annular protrusion 83 of the axial piston 7 and retreats together with the axial piston 7. As the annular piston 77 retreats, the pressure in the auxiliary pressure chamber 82 becomes negative, and the rubber valve member 85 of the second valve portion 87 opens. As a result, the hydraulic fluid flows from the reservoir side into the auxiliary pressure chamber 82 through the first valve chamber 91, the second through hole 186, the second valve chamber 89, and the supply hole 76. On the other hand, since the first hydraulic pressure generating chamber 18 is also under negative pressure, the hydraulic fluid that has flowed into the auxiliary pressure chamber 82 is partially further trapped between the large diameter portion 69 of the axial piston 7 and the inner wall of the cylinder hole. The liquid passes through the gap, bends the outer edge of the cup seal 12, and flows into the first hydraulic pressure generating chamber 18. The second hydraulic pressure generation chamber 19 also has a negative pressure, but inside this chamber 19 there is a supply hole 74, a secondary piston 8
Pass through the gap between the large diameter part and the inner wall of the cylinder hole,
The outer edge of the cup seal 16 is bent to allow hydraulic fluid to flow in from the reservoir side. After the second valve part 87 closes, the auxiliary pressure chamber 82 gradually passes through the throttle groove 187.
The hydraulic fluid flows into the auxiliary pressure chamber 82, the first hydraulic pressure generating chamber 18, and the second hydraulic pressure generating chamber 19, so that the pressure in the auxiliary pressure chamber 82, the first hydraulic pressure generating chamber 18, and the second hydraulic pressure generating chamber 19 becomes zero, and each part reaches the state shown in the drawing. Note that the throttle groove 187 also functions to compensate for changes in the volume of the working fluid in the auxiliary pressure chamber 82 due to temperature changes when the first valve part 86 and the second valve part 87 are closed. .

The embodiments of the present invention perform the above-mentioned functions, but also have the following effects.

That is, the loss stroke at the beginning of depressing the brake pedal is compensated by the forward movement of the annular piston 77, and immediately after or at the completion of this compensation, the annular piston 77 is brought into contact with the stepped portion d of the cylinder body 4 and stopped. Exclusively axial piston 7
Since the brake fluid pressure is rapidly increased by the advance of the cylinder, the axial direction of the large diameter hole 5 of the cylinder body 4 is lower than that of the conventional primary piston in which the part corresponding to the annular piston 77 is fixed to the shaft piston 7. The length can be shortened. That is,
In a conventional primary piston, in order to compensate for the stroke in the large diameter hole 5, the length of the large diameter hole 5 is a length that secures the entire effective stroke of the piston, and the length is increased accordingly. In the example, large diameter hole 5
Since it is not necessary to ensure the length of the entire effective stroke of the piston, the length of the large diameter hole 5 can be shortened. Therefore, the length of the cylinder body 4 can be shortened, and as a result, the axial length of the entire tandem master cylinder 1 with a negative pressure booster can be shortened compared to the conventional one. Furthermore, this allows the overall weight to be reduced.

Furthermore, since the axial piston 7 and the annular piston 77 do not constitute a valve, the axial piston 7
There is no need to form a passage in the annular piston 77 to communicate with a reservoir for storing hydraulic fluid, and therefore the structure of these pistons is simple.

Further, when assembling the annular piston 77 to the axial piston 7, since the protrusion 83 is located on the outside of the annular piston 77, the work of assembling the annular piston 77 to the axial piston 7 is easy. Further, instead of closing the opening of the cylinder hole with the end of the extension of the axial piston 7, the extension of the axial piston 7 is made to protrude outside the cylinder hole, and the annular piston 7
7, the length of the cylinder body 4 can be shortened.

Furthermore, since the second valve portion 87 is disposed on the cylinder body 4 side of the supply hole 76, that is, within the liquid connection hole 76, the cylinder body 4 becomes elongated in order to install the second valve portion 87. Never.

Although the embodiments of the present invention have been described above, the present invention is of course not limited thereto, and various modifications can be made based on the technical idea of the present invention.

For example, an annular piston 77 and an axial piston 7
The diameter ratio is not limited to what is shown in the figure, but if the diameter of the small diameter part, that is, the extension part of the axial piston 7 is made even smaller, the ratio of the diameters of An even larger amount of hydraulic fluid can be discharged to the first hydraulic pressure generating chamber 18. Therefore, greater shortening is obtained. Furthermore, if the outer diameters of the extension of the axial piston 7 and the annular piston 77 are made smaller in order to obtain the same amount of hydraulic fluid discharged, the weight of the entire device can be further reduced.

Further, in the above embodiment, one end of the spring 84 that biases the annular piston 77 is received by the spring receiver 67 fixed to the rear end of the axial piston 7, but instead of this, the front end of the movable wall 28, For example, the shape of the cover member 64 may be changed as appropriate so that the cover member 64 is received by the cover member 64.

Further, although a tandem master cylinder has been described in the above embodiments, the present invention is of course also applicable to a single master cylinder.

Furthermore, in the above embodiments, a negative pressure booster and a two-stage tandem master cylinder are combined, but the device to be coupled is not limited to this, and is generally a pneumatic booster or a hydraulic type. It may also be a booster.

Furthermore, although the above embodiments have been described for use in a brake device, the present invention can of course also be applied to a clutch device.

As described above, according to the two-stage actuating master cylinder configured according to the present invention, there is no need to ensure the length of the large hole for the entire effective stroke of the piston in order to compensate for the stroke at the large hole. The length of the cylinder body can be shortened, thus
It is possible to improve the shortening and weight reduction of the entire structure including the device connected thereto.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a tandem master cylinder with a negative pressure booster according to an embodiment of the present invention, and a second
The figure is an enlarged sectional view of the valve device in FIG. 1. In the figure, 1... Tandem master cylinder with negative pressure booster, 2... Tandem master cylinder section, 4... Cylinder body, 5... Large diameter hole, 6
... Small diameter hole, 7 ... Axial piston, 12 ... Cup seal, 18 ... First hydraulic pressure generating chamber, 69 ... Large diameter section, 72 ... Valve device, 76 ... Supply hole, 77 ...
...Annular piston, 82...Auxiliary pressure chamber, 83...
Annular protrusion, 84... Spring, 86... First valve portion, 1
81... Valve spring, 182... Ball valve, 184... First through hole.

Claims (1)

[Claims] 1. A cylinder body having a cylinder hole having a large hole and a small hole, a piston slidably inserted into the large hole and the small hole, and a space between the piston and the bottom of the cylinder hole. A divided main pressure chamber, an auxiliary pressure chamber divided between a side periphery of the piston and an inner circumferential surface of the large hole, and a passage connecting the main pressure chamber and the auxiliary pressure chamber. a first valve that allows fluid to move from the auxiliary pressure chamber to the main pressure chamber and prohibits the reverse; and a passage that communicates between the auxiliary pressure chamber and a storage tank that stores hydraulic fluid, and is provided at a passage that maintains a predetermined pressure. As described above, in the two-stage operating type master cylinder equipped with a second valve that opens to communicate between the two, the second valve is provided in the cylinder body, and the piston is slidably inserted into the small hole. an axial piston having a fitting head and an extension extending through the large hole and projecting to the outside of the cylinder hole; an annular piston that partitions the auxiliary pressure chamber between them, a protrusion with which the annular piston engages is formed on the outer periphery of the extension on the auxiliary pressure chamber side, and the annular piston is directed toward the protrusion. A spring that presses the annular piston is disposed on a side opposite to the auxiliary pressure chamber side, and the axial piston is engaged with the open end of the large hole via the protrusion and the annular piston. A two-stage operating master cylinder equipped with a stopper.