JP3259405B2 - Master cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master cylinder used in a hydraulic brake system for a vehicle, and more particularly to a master cylinder for connecting and disconnecting a communication between a pressure chamber and a reservoir tank. This is suitable for a center valve type master cylinder provided near the passage.

[0002]

2. Description of the Related Art Anti-skid devices are often incorporated in brake systems in accordance with the recent sophistication of vehicles. Further, among such anti-skid devices, there is a type in which hydraulic fluid in a wheel cylinder is returned to a pressure chamber of a master cylinder via a pump when a wheel is locked. In a brake system having an anti-skid device of this type, when the hydraulic fluid is recirculated to the pressure chamber by the pump while the piston is returning to the non-operating position when the brake pedal is depressed, the fluid is returned to the pressure chamber. The pressure in the pressure chamber increases temporarily.

For this reason, in a so-called conventional type master cylinder, a compensating port provided for communicating the pressure chamber with the reservoir tank is intermittently connected by a primary cup fitted to a piston. Due to the increase in the hydraulic pressure, the cup is deformed so as to be pushed into the port, and damage to the cup is accelerated by the movement of the cup and the piston. Therefore, in recent years, a communication passage that constantly connects the supply chamber and the pressure chamber that communicates with the reservoir tank is formed through the center of the piston, and a valve mechanism that closes and opens the communication passage is provided near the communication passage. The provided center valve type (also called portless type) master cylinder is practically used. Further, according to the center valve type master cylinder, there is an effect that the rising and falling characteristics of the fluid pressure are accelerated with respect to the orifice interposed in the anti-skid device due to the high response of the valve mechanism.

FIG. 6 shows an example of a master cylinder using this center valve mechanism. This master cylinder corresponds to a so-called tandem master cylinder composed of the above-mentioned conventional primary piston 1 and a center valve secondary piston 2. Of these, the portion using the center valve mechanism will be described in detail. One of the pressure chambers 3 divided by the secondary piston 2 in the inner hole 11 of the cylinder body 10 as described above is a brake (not shown) for each wheel of the vehicle. The supply chamber 4 is always in communication with the hydraulic line, and the other supply chamber 4 is always in communication with the reservoir tank RT. This piston 2 sites to dispose the supply chamber 4 on the outer circumference and the elongated hole 12 is formed to penetrate the piston 2 in the radial direction as shown in FIG. 6 b, directed from the elongated hole 12 to the pressure chamber 3 side A communication passage 5 is formed through the center of the piston 2. Therefore, the pressure chamber 3 and the supply chamber 4, that is, the reservoir tank RT can communicate with each other through the communication passage 5 and the long hole 12. The cell configuration Dali piston 2, the cell con Dali return spring 31 from the need to return to the inoperative position when the depression release of the brake pedal is biased in the arrow a direction of the return direction, i.e. FIG 6 a.

On the other hand, from when the processing proceeds piston 2 is actuated state depresses the brake pedal, i.e. in the direction of the arrow b in FIG. 6 a need to increase the internal pressure in the pressure chamber 3 to close the communication passage 5, the communication passage 5 Is provided with a valve mechanism 6 for closing and opening it. This valve mechanism 6
Will be described. First, a rod member called a valve stem 13 is loosely fitted and inserted into the communication passage 5 so as to form a predetermined gap therebetween. Further, a stem seat surface 14 having an area larger than the inner diameter of the communication passage 5 is provided at the protruding portion of the valve stem 13 on the pressure chamber 3 side so as to face the communication passage 5. The valve stem 13 and the stem seat surface 14 are mainly made of a hard material such as metal. In the valve stem 13, a valve seal 7 made of a soft material such as rubber is attached to the pressure chamber 3 side from the stem seat surface 14. At this time, the valve seal 7 is attached so that the outer peripheral edge portion 7a of the valve seal 7 exists outside the outer shape of the stem seat surface 14.
On the other hand, the valve seal 7 is in close contact with the end of the communication passage 5 on the pressure chamber 3 side, specifically, the end surface of the piston 2 on the pressure chamber 3 side. A piston seal surface 15 for blocking communication with the piston 4 is formed.

[0006] By the way, as described above, the valve seal 7 made of a soft material is re- moved against the increasing hydraulic pressure in the pressure chamber 3.
In order to press and adhere to the piston seal surface 15, the stem seat surface 14 is
The valve seal 7 must be backed up by the valve stem 13 which comes into contact with the valve chamber 5 and protrudes toward the pressure chamber 3 side, thereby supporting deformation of the valve seal 7 due to hydraulic pressure. In this state, in order to make the valve seal 7 made of a soft material tightly adhere to the piston seal surface 15, the outer peripheral edge 7 a of the valve seal 7 is further moved toward the communication passage 5 from the stem seat surface 14, that is, the piston seal surface. It protrudes to the 15 side.

At the end of the piston 2 on the pressure chamber 3 side, a compression spring 1 for urging the valve seal 7 together with the valve stem 13 against the piston seal surface 15 is provided.
6, whereby the valve seal 7 and the valve stem 13 are constantly pressed toward the return side of the piston 2. However, if the valve seal 7 was always in close contact with the piston seal surface 15 due to the pressing force of the compression spring 16,
The communication between the pressure chamber 3 and the supply chamber 4 by the communication passage 5 cannot be opened. Then, when the piston 2 returns to the predetermined position, the end of the valve stem 13 on the supply chamber 4 side abuts, and the movement of the valve stem 13 and the valve seal 7 is regulated.
To be passed to the pressure chamber 3 supply chamber 4 communicated apart from 5 to fix the stopper pin 17 penetrating a predetermined position of the elongated hole 12 as shown in FIG. 6 b in the cylinder body 10.

[0008] To describe the operation of the center valve type master cylinder, when the piston 2 is returned to a predetermined return position at the time of non-depression of the brake pedal as the first to FIG. 7 a, supply chamber 4 side of the valve stem 13 The end abuts against the stopper pin 17, the valve seal 7 is separated from the piston seal surface 15, and the pressure chamber 3 and the replenishing chamber 4 are opened to communicate with each other via the communication passage 5.

When the brake pedal is depressed to some extent from this state, among the valve seals 7 pressed by the compression spring 16 as the piston 2 advances, first, the end of the outer peripheral edge 7a of the valve seal 7 on the piston seal surface 15 side. the valve stem in a state but abuts on the piston seal surface 15, which further gradually firmly adhered by its own elastic deformation, abuts against the stem seat surface 14 the piston seal surface 15 of the valve stem 13 as shown in FIG. 7 b The valve seal 7 comes into close contact with the piston seal surface 15 by the backup of the valve 13. During this time, the piston 2 advances, so that the hydraulic pressure in the pressure chamber 3 is increased to a considerably high pressure.

When the brake pedal is released or released, the piston 2 starts to return, and the valve seal 7 and the valve stem 13 are also moved in the same direction by the compression spring 16. At this time, when the piston 2 returns to a predetermined position, the supply chamber 4 of the valve stem 13
The side end abuts against the stopper pin 17, and the stem seat surface 14 is moved with the return of the piston 2 to the piston seal surface 1.
When the valve seal 7 is separated from the piston seal 5, the valve seal 7 is separated from the piston seal surface 15 while being elastically restored.

Since the friction between the port and the cup does not occur in the series of pressure increasing / decreasing steps, there is an advantage that the damage due to the friction is smaller than that of the conventional conventional master cylinder.

[0012]

In the center valve type master cylinder, for example, the valve seal 7 is completely removed from the piston seal surface 15 by intermittently stepping twice twice without completely returning the brake pedal. If the valve seal 7 is bent before the space is separated, and the excess hydraulic fluid flows into the pressure chamber 3 from the supply chamber 4,
When the working fluid recirculates into the pressure chamber 3 with the return of the piston 2, the hydraulic pressure in the pressure chamber 3 temporarily increases, and this occurs as a so-called residual pressure. Further, the liquid pressure in the pressure chamber 3 may be temporarily increased due to the reflux into the pressure chamber 3 via a pump as in the anti-skid device.

[0013] Of the series of pressure increasing / decreasing steps described above,
As shown in FIG. 7C, when the stem seat surface 14 and the piston seal surface 15 are slightly separated from each other and the valve seal 7 and the piston seal surface 15 are not yet separated, the residual pressure and the temporary If the boosting occurs, valve seal 7 made of a soft material, as shown in FIG. 8, thereby pushed between the stem seat surface 14 and the piston seal surface 15 by the hydraulic pressure of the pressure chamber 3. When the piston 2 advances again from this state, the valve seal 7 is engaged between the stem seat surface 14 and the piston seal surface 15, and in a severe case, the engagement portion of the valve seal 7 may be damaged.

Various problems with this type of deformation of the valve seal have been discussed in the past.
Some contents are described in JP-A-20961. However, none of these methods solves the problem that the valve seal is pushed or bitten between the stem seat surface and the piston seal surface due to the residual pressure or temporary pressure increase.

The present invention has been developed in view of these problems, and reduces the fluctuations in the hydraulic pressure inside and outside the valve seal until the valve seal separates from the piston seal surface, thereby reducing the valve pressure. It is an object of the present invention to provide a master cylinder capable of suppressing pushing and biting of a seal and preventing damage to the valve seal.

[0016]

According to a first aspect of the present invention, there is provided a master cylinder having a piston which is slidably and liquid-tightly inserted into an inner hole formed in a cylinder body, and includes a piston. In order to allow the separated pressure chamber and the supply chamber to communicate with each other, a communication passage formed through the center of the piston and a protrusion on the pressure chamber side of the valve stem inserted into the communication passage are formed. A stem seat surface larger than the inner diameter of the communication passage, a valve seal attached at least outside the outer shape of the stem seat surface, and the valve seal being in close contact with each other to cut off communication between the pressure chamber and the supply chamber. ,
A piston seal surface provided on the pressure chamber side of the communication passage, a spring member for constantly urging the valve seal together with the valve stem in the direction of the piston seal surface, and the piston advances toward the pressure chamber along the inner hole. An outer peripheral edge of the valve seal protruding from the stem seat surface toward the piston seal surface so that the valve seal is in close contact with the piston seal surface to interrupt communication between the pressure chamber and the supply chamber;
When the piston returns in the direction opposite to the pressure chamber side along the inner hole, the piston abuts on the valve stem urged in the same direction by the spring member to regulate the movement of the valve stem, so that the valve seal is moved by the piston seal. A center valve type master cylinder having a stopper pin fixed to a cylinder body for allowing the pressure chamber and the replenishing chamber to communicate with each other through the communication passage away from the surface of the cylinder. An auxiliary seal, which closes the communication passage before the seal comes into close contact with the piston seal surface and opens the communication passage when the piston returns, after the valve seal separates from the piston seal surface, is provided between the valve stem and the communication passage. Between the pressure chamber side and the auxiliary seal
Means that at least the piston seal surface and the valve seal
At the time of wearing, the pressing force of the piston and spring member
Relatively hard elastic material close enough to the stem sheet surface
When no load is applied, it is shaped like a dish that spreads on the piston seal surface side.
And the bottom of this auxiliary dish seal is
Connected to the stem seat and secured to the valve stem.
The inner diameter of the open end of the dish-shaped auxiliary seal is
Is set to be larger than the inside diameter of
The communication passage is closer than the end of the valve seal on the piston seal surface side.
It is characterized by being projected to the side .

In the master cylinder according to a second aspect of the present invention , the dish-shaped auxiliary seal is provided on the piston seal surface.
Larger than the outer diameter of the open end of the
An auxiliary flow path is formed in a range smaller than the diameter .

[0018]

[0019]

In the master cylinder according to the first aspect of the present invention, when the piston advances, an auxiliary seal interposed between the valve stem and the communication passage is provided on the pressure chamber side.
By closing the communication passage before the valve seal comes into close contact with the piston seal surface and opening the communication passage after the valve seal separates from the piston seal surface when the piston returns, the stem seat surface is After being separated from the sealing surface, fluctuations in hydraulic pressure inside and outside the valve seal still in close contact with the piston sealing surface are suppressed, and deformation of the valve seal made of a soft material due to the fluctuation in hydraulic pressure is minimized. It is possible to suppress pushing and biting of the valve seal between the surface and the piston seal surface.

When no load is applied , the bottom of the dish-shaped auxiliary seal extending toward the piston seal surface is connected to the stem sheet of the valve stem and fixed to the valve stem. The inner diameter of the end is set to be larger than the inner diameter of the communication passage, and the opening end protrudes toward the communication passage from the end of the valve seal closer to the piston seal surface. The opening end of the auxiliary seal abuts, for example, a piston seal surface formed at the end of the communication passage on the pressure chamber side. From this point on, the communication between the pressure chamber and the replenishment chamber is gradually interrupted. The communication passage is closed or almost closed while being deformed so as to be opened outward by being pressed by the spring member and the piston. Then, the valve seal comes into contact with the piston seal surface, and the self-deformation is prevented. The most closely contact when the valve seat surface is in contact with the piston sealing surface I, the pressure chamber at this point is completely raised to high pressure corresponding to a liquid-tight state. On the other hand, when the valve seat surface is slightly separated from the piston seal surface with the return of the piston, the dish-shaped auxiliary seal still substantially closes the communication passage.
Fluctuations in hydraulic pressure inside and outside the valve seal still in close contact with the piston seal surface are small or almost non-existent. For this reason, even if a residual pressure or a temporary pressure rise occurs at this time as described above, the protruding outer peripheral portion of the valve seal hardly deforms, so that the valve seal moves between the stem seal surface and the piston seal surface. There is no push or bite. When the piston returns further, the valve seal separates from the piston seal surface, and during this time, the dish-shaped auxiliary seal gradually deforms into a dish shape due to its own restoring force. At this point, the communication between the pressure chamber and the supply chamber is completely opened only at a point apart from, for example, the piston seal surface formed at the pressure chamber side end of the communication passage. In such a series of pressure-increasing and depressurizing steps, the dish-shaped auxiliary seal is relatively small enough to be in close contact with the stem sheet surface by the pressing force of the piston and the spring member at least when the piston seal surface and the valve seal are in close contact. Since it is a hard elastic material and is formed in a dish shape that spreads to the piston seal surface side, for example, the valve seal is separated from the piston seal surface, and the open end of the dish-shaped auxiliary seal contacts the piston seal surface. In such a case, even if the residual pressure or the temporary pressure rise occurs, the dish-shaped auxiliary seal is hardly deformed such that it is entangled inward. There is no risk of being caught in the passage.

In the master cylinder according to the second aspect of the present invention, the outer diameter of the opening end of the dish-shaped auxiliary seal is larger than the outer diameter.
And a piston in a range smaller than the outer diameter of the stem seat surface.
The auxiliary flow path is formed on the sealing surface, so
The open end of the seal contacts the piston seal surface and
The auxiliary seal is deformed to open outward, and this deformed dish shape
Open end of auxiliary seal is on piston seal surface side of auxiliary flow path
Work inside and outside of the auxiliary seal until the end is closed.
Fluid flows into the replenishing chamber through the auxiliary flow path.
Fluid pressure fluctuations are reduced. Also, the valve seal is
Separated from the ton-seal surface, the dish-shaped
As the auxiliary seal is restored to the dish shape, it is gradually assisted.
A flow path is opened, and a communication path is formed from the opened auxiliary flow path.
The pressurized hydraulic fluid in the pressure chamber gradually returns to the supply chamber
This minimizes fluctuations in hydraulic pressure inside and outside the dish-shaped auxiliary seal.
It will be cheap. Therefore, by reducing the fluctuation of the hydraulic pressure,
It is possible to suppress pushing and biting of the valve seal
I do.

[0022]

1 to 5 show an embodiment of a master cylinder according to the present invention, and particularly correspond to claims 1 and 2. FIG. The master cylinder in these figures is a tandem master cylinder used in a vehicle hydraulic brake system, like the tandem master cylinder described above. The tandem master cylinder includes a conventional primary piston 1 and a center valve secondary piston 2.

Inner hole 1 formed in cylinder body 10
1, a primary cup 32 and a secondary cup 3 are arranged in the order of a primary piston 1 and a secondary piston 2 from the input side of a piston rod (not shown).
3, the respective pistons 1 and 2 are fitted in a liquid-tight and slidable manner. A secondary return spring 31 is interposed on the output side of the secondary piston 2, and a primary return spring 30 is interposed between the secondary piston 2 and the primary piston 1,
Each piston 2 is biased toward the input side of the piston rod.

The primary return spring 30
Are fixed to the output side of the primary piston 1 and the input side of the secondary piston 2 via retainers 34 and 35, respectively.
Are biased away from each other. Thus, the primary piston 1 is positioned in contact with the plate 36 attached to the input side open end of the cylinder body 10.
The retainer 34 provided on the output side of the primary piston 1 has a connecting rod 37 projecting from the primary piston 1 side to the secondary piston 2 side.
It is locked and positioned.

The secondary return spring 31 has a smaller elastic force than the primary return spring 30, and urges the secondary piston 2 positioned by the elastic force of the primary return spring 30 toward the primary piston 1. are doing. The primary piston 1 is provided with an inner hole 1 of the cylinder body 10.
In FIG. 1, a primary supply chamber 39 communicating with the reservoir tank RT through a supply port 38 formed in the cylinder body 10 and a primary pressure chamber 41 communicating with the reservoir tank RT through a compensating port 40 are defined. . Further, the secondary piston 2 is also provided in an inner hole 11 of the cylinder body 10.
A secondary supply chamber 4 that communicates with the reservoir tank RT through a supply port 42 formed in the cylinder body 10;
The secondary supply chamber 4 and a secondary pressure chamber 3 that communicates with the reservoir tank RT via a valve mechanism 6 and a communication passage 5 described below are defined. In addition, each supply room 39,4
As shown in FIG. 1B, is composed of an annular gap provided between the outer peripheral surface of each piston 2 and the inner peripheral surface of the inner hole 11 of the cylinder body 10. Each of the pressure chambers 41 and 3 is connected to a brake pressure line for each wheel of the vehicle through an outlet port (not shown). Further, the secondary piston 2 is restricted from interlocking with the primary piston 1 and being independently moved by the connecting rod 37 and the retainer 35.

At the end of the secondary piston 2 on the side of the secondary pressure chamber 3, a large-diameter concave portion 43 opened to the secondary pressure chamber 3, and a hole is formed from the center of the bottom along the axis of the secondary piston 2. As shown in FIG. 1 b, the communication passage 5 is formed through the annular secondary supply chamber 4 in the radial direction, and the secondary piston 2
A long hole 12 extending in the axial direction of the communication passage 5 is provided.
Is opened up to the long hole 12.

As shown in FIGS. 1 and 2, the valve mechanism 6 forms a predetermined gap between the valve mechanism 6 and the inner peripheral surface of the communication passage 5 of the secondary piston 2, and The valve stem 13 slidably inserted into the valve stem 13, the valve seal 7 attached to the large-diameter concave portion 43 side projection of the valve stem 13, that is, the valve seal 7 attached to the secondary pressure chamber 3 side projection, A compression spring 16 that is in close contact with the bottom surface of the large-diameter concave portion 43 of the secondary piston 2, that is, a piston seal surface 15 formed at the end of the communication passage 5 on the pressure chamber 3 side; That is, a stopper pin 17 which abuts on the end of the replenishing chamber 4 on the side of the communicating chamber and regulates the movement thereof is provided. Is provided.

A protruding portion of the valve stem 13 on the side of the large-diameter concave portion 43 is provided with a seal mounting portion 44 having a narrowed central portion in the axial direction.
Are formed integrally, and a rubber valve seal 7 is attached to the outside of the seal attachment portion 44. As described above, since the valve seal 7 is in close contact with the piston seal surface 15 to block the communication between the pressure chamber 3 and the supply chamber 4 by the communication path 5, the valve seal 7 is made of rubber or the like which is easily elastically deformed.
It is formed of a relatively soft material. The relatively soft rubber valve seal 7 is provided on the piston seal surface 1.
5, it is necessary to protrude from the stem seat surface 14 formed on the piston seal surface 15 side end surface of the seal mounting portion 44 provided also in the sense of restricting the movement of the valve stem 13, An outer peripheral edge 7 a of the valve seal 7 on the piston seal surface 15 side protrudes from the stem seat surface 14. In addition, piston 2
High pressure generated in the pressure chamber 3 during operation causes the valve seal 7
The stem seat surface 1 so that unnecessary deformation does not occur.
4 comes into contact with the piston seal surface 15, more precisely, in this embodiment, through the auxiliary seal, the piston seal surface 1.
5, the valve seal 7 needs to be backed up. The unnecessary deformation of the valve seal 7 expected here is a deformation that is pushed between the stem seat surface 14 and the piston seal surface 15 by the high hydraulic pressure in the pressure chamber 3. Further, the outer shape of the valve seal 7 is formed in a tapered frustoconical shape on the side of the secondary pressure chamber 3, and a recess 45 for engaging the compression spring 16 is formed in the longitudinal center of the generatrix.

The compression spring 16 urges the valve seal 7 and the valve stem 13 toward the piston seal surface 15 in order to bring the valve seal 7 into close contact with the piston seal surface 15. One end is locked by the depression 45 of the valve seal 7, and the other end is locked by a retainer 47 fixed to the opening end of the large-diameter recess 43 via a clip 46. The clip 46 and the retainer 47 are formed with through-holes, so that the large-diameter recess 43 and the pressure chamber 3 are always in communication.

The stopper pin 17 regulates the movement of the valve stem 13 and the valve seal 7 urged by the compression spring 16, and is at least positioned by the secondary return spring 31 and the primary return spring 30. When the piston 2 is not operated with no load, the valve seal 7 and the piston seal surface 15 are separated from each other so that the pressure chamber 3 and the supply chamber 4 communicate with each other through the communication passage 5. This is clearly shown in FIG. Specifically, it is fixed to the cylinder body 10 through the elongated hole 12.

The auxiliary seal 8 is made of a relatively hard material, such as metal or resin, to such an extent that the stem sheet surface 14 comes into contact with the piston seal surface 15 via the dish-shaped auxiliary seal 8. As shown in FIG. 3, the bottom portion is formed in a dish shape penetrating therethrough. Then, the bottom of the dish-shaped auxiliary seal 8 is caulked and fixed to the outer periphery of the valve stem 13 so as to contact the stem seat surface 14. In addition,
The inner diameter of the opening end of the dish-shaped auxiliary seal 8 needs to be at least larger than the inner diameter of the communication passage 5, and the end is desirably rounded in an R shape.

Further, in this embodiment, an auxiliary flow passage 18 is formed at the end of the communication passage 5 on the piston seal surface 15 side.
The auxiliary flow path 18 is for releasing the fluid pressure fluctuation occurring inside and outside the auxiliary seal 8 when the inner surface of the dish-shaped auxiliary seal 8 comes into contact with the piston seal surface 15 with its own elastic deformation. This hard dish-type auxiliary seal 8
The elastic deformation of the piston is facilitated to make it easy to contact the piston seal surface 15 or to separate from the piston seal surface 15. For this reason, this auxiliary flow path 18
As shown in the figure, the piston seal surface 15 is cut in a triangular pyramid shape toward the inner peripheral surface of the communication passage 5, and is formed in a V-shape that gradually becomes deeper toward the communication passage 5.
Are formed at equal angular intervals with respect to the inner peripheral surface. The circumference of the V-shaped auxiliary flow path 18 that continues from the end on the piston seal surface 15 side must be at least larger than the outer diameter of the opening end of the dish-shaped auxiliary seal 8 and the stem sheet. It must be smaller than the diameter of the surface 14. This allows the hydraulic fluid inside and outside the auxiliary seal 8 to flow after the dish-shaped auxiliary seal 8 starts abutting on the piston seal surface 15 as described above, thereby enabling the hydraulic pressure to fluctuate. This is to ensure that the valve seal 7 adheres tightly to the piston seal surface 15 so that unnecessary deformation of the valve seal 7 does not occur. The unnecessary deformation of the valve seal 7 expected here is such that the valve seal 7 is pushed into the auxiliary flow path 18 by the high hydraulic pressure in the compression chamber.

According to the master cylinder valve mechanism 6 of the present embodiment having the above-described structure, when the brake pedal is released and the secondary piston 2 returns to the non-operation state, as shown in FIG. Compression spring 16
The valve stem 13 urged by the valve abuts against the stopper pin 17. In this state, the valve seal 7 and the dish-shaped auxiliary seal 8 are separated from the piston seal surface 15 by the action of the stopper pin 17. As a result, the pressure chamber 3 and the supply chamber 4 communicate with each other, and the fluid pressure in the pressure chamber 3 is reduced to atmospheric pressure or almost atmospheric pressure.

When the second piston 2 advances by depressing the brake pedal from this state, first, as shown in FIG.
And is pressed by the compression spring 16 and the piston 2 to open outward. During this time, specifically, until the open end of the deformed dish-shaped auxiliary seal 8 closes the end of the auxiliary flow path 18 on the piston seal surface 15 side, the hydraulic fluid inside and outside the auxiliary seal 8 Since the fluid flows into the replenishing chamber 4 through the auxiliary flow path 18, the fluctuations in the hydraulic pressure are absorbed, thereby easily deforming the dish-shaped auxiliary seal 8. At this point, since the valve seal 7 has not yet contacted the piston seal surface 15, unnecessary deformation of the valve seal 7 cannot occur.

When the secondary piston 2 further advances, the communication path 5 and the auxiliary flow path 1
8 is closed or almost closed, and then the valve seal 7 comes into close contact with the piston seal surface 15 with its own deformation as shown in FIG. To a high pressure. While the valve seal 7 is in close contact with the piston seal surface 15 in this manner,
The fluid pressure in the valve seal 7 is also considerably increased. At this time, the stem seat surface 14 contacts the piston seal surface 15 via the deformed dish-shaped auxiliary seal 8 to support the valve seal 7 from the inside. Therefore, even if a residual pressure or a temporary pressure rise occurs in the pressure chamber 3 due to the recirculation of the anti-skid, unnecessary deformation such as pushing or biting of the valve seal 7 does not occur.

In this state, when the depression operation of the brake pedal is loosened or released and the secondary piston 2 returns, when the stem seat surface 14 is slightly separated from the piston seal surface 15 as shown in FIG. The dish-shaped auxiliary seal 8 still closes the communication passage 5 substantially, and a considerably high hydraulic pressure is maintained in the valve seal 7 still in close contact with the piston seal surface 15. For this reason, even if the residual pressure or the temporary pressure increase occurs at this point, unnecessary deformation such as pushing or biting of the valve seal 7 is unlikely to occur.

When the secondary piston 2 is further returned, the valve seal 7 is separated from the piston seal surface 15 before long.
During this time, the dish-shaped auxiliary seal 8 is gradually restored to a dish shape by its own restoring force as shown in FIG. 5e. With the restoration deformation of the dish-shaped auxiliary seal 8, the auxiliary flow path 1 gradually increases.
8 is opened, and the pressurized hydraulic fluid in the pressure chamber 3 gradually returns to the replenishing chamber 4 from the opened auxiliary flow path 18 through the communication path 5, whereby the hydraulic pressure inside and outside the dish-shaped auxiliary seal 8 is increased. Fluctuations become smaller.

When the secondary piston 2 returns further, the open end of the dish-shaped auxiliary seal 8 separates from the piston seal surface 15 and, at this time, the pressure chamber 3 and the replenishing chamber 4 via the communication passage 5 are first started. The communication is completely opened and the pressure is reduced to atmospheric pressure or almost atmospheric pressure. Until the moment when the open end of the dish-shaped auxiliary seal 8 separates from the piston seal surface 15,
Since the fluid pressure fluctuations inside and outside the auxiliary seal 8 described above are gradually reduced, the open end of the auxiliary seal 8 is easily separated from the piston seal surface 15, and at this moment, the relatively hard dish-shaped auxiliary seal 8 is moved. There is no deformation.

In the present embodiment, the auxiliary seal 8 is formed in a dish shape, and the opening end of the auxiliary seal 8 is formed in an R-shape. It is possible to prevent a problem that the opening end of the seal 8 is caught or caught in the opening .

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

According to the master cylinder of the present invention as described in the foregoing, dished auxiliary seal is between before the valve seal comes into close contact with the piston sealing surface to valve seal is separated from the piston sealing surface, Fluid pressure fluctuations inside and outside the valve seal are small because the communication passage is closed, and the fluid pressure inside the valve seal is maintained at a considerably high level. Is hardly deformed, so that deformation such as biting or pushing of the valve seal can be suppressed to prevent breakage. The open end of the dish-shaped auxiliary seal is a piston seal.
Deforms so that the auxiliary seal opens outward against the surface
The open end of the deformed dish-shaped auxiliary seal is
Until the piston seal surface side end is closed
Hydraulic fluid inside and outside the auxiliary seal passes through the auxiliary flow path to the supply chamber side
And their hydraulic fluctuations are reduced. Ma
In addition, the valve seal separates from the piston seal
Of the dish-shaped auxiliary seal is restored to the dish shape by the restoring force of
As a result, the auxiliary flow path is gradually opened,
Operation in the pressure chamber through the communication passage from the auxiliary channel
The liquid gradually flows back to the replenishing chamber, which causes
Fluctuations in hydraulic pressure inside and outside the pump are reduced. Therefore, hydraulic pressure fluctuation
By reducing the size, further pushing or biting of the valve seal
And prevent damage to the valve seal
You.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a master cylinder according to the present invention, in which (a) is a longitudinal sectional view and (b) is a sectional view taken along line II of FIG. 1 (a).

FIG. 2 is a longitudinal sectional view of a valve mechanism used in the master cylinder of FIG.

FIG. 3 is a perspective view of a dish-shaped auxiliary seal attached to the valve mechanism of FIG. 2;

FIGS. 4A and 4B show an auxiliary flow path formed in a secondary piston of the master cylinder of FIG. 1, wherein FIG. 4A is a longitudinal sectional view near the auxiliary flow path, and FIG. Figure, (c)
FIG. 4 is a sectional view taken along line BB of FIG.

FIG. 5 is an operation explanatory view of a valve mechanism used in the master cylinder of FIG. 1;

FIG. 6 shows an example of a conventional master cylinder .
(A) is a longitudinal sectional view, and (b) is a II sectional view of FIG.
It is.

7 is a valve mechanism used in the master cylinder of FIG . 6;
It is operation | movement explanatory drawing of FIG.

FIG. 8 shows a valve seat generated by the operation of the valve mechanism shown in FIG . 7;
FIG. 4 is an explanatory view showing a deformed state of the console.

[Explanation of symbols]

1 primary piston 2 Se con Dali piston 3 is communicating path 6 secondaries pressure chamber 4 secondaries supply chamber 5 is the valve mechanism 7 valve seal 8 is dished auxiliary seal 1 0 is the cylinder body 11 is an inner bore 12 length hole 13 is a valve stem 14 a stem seating surface 15 is the piston sealing surface 16 compression spring 17 stopper pin 18 of the auxiliary flow path R T is the reservoir tank

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60T 11/16

Claims (2)

(57) [Claims] 1. A piston, which is slidably and liquid-tightly inserted into an inner hole formed in a cylinder body, and allows a pressure chamber and a supply chamber separated by the piston to communicate with each other. A communication passage penetrating the center of the piston, a stem seat surface larger than the inner diameter of the communication passage formed at a pressure chamber-side protruding portion of the valve stem inserted into the communication passage, and at least the stem seat surface A valve seal mounted on the pressure chamber side of the communication passage for preventing the communication between the pressure chamber and the replenishing chamber with the valve seal attached to the outside of the outer shape of the valve; A spring member that constantly biases the valve seal together with the valve stem in the direction of the piston seal surface; and when the piston advances toward the pressure chamber along the inner hole, the valve seal comes into close contact with the piston seal surface and the pressure increases. Since the communication between the power chamber and the supply chamber is interrupted, the outer peripheral edge of the valve seal protruding from the stem seat surface toward the piston seal surface, and the piston is opposed to the pressure chamber side along the inner hole. When returning to the direction, the spring member contacts the valve stem urged in the same direction to restrict the movement of the valve stem, so that the valve seal is separated from the piston seal surface and the pressure chamber and the supply chamber are separated. In a center valve type master cylinder provided with a stopper pin fixed to a cylinder body so as to be communicated through the communication passage, when the piston advances, the communication passage is provided before the valve seal comes into close contact with the piston seal surface. An auxiliary seal for closing the valve and opening the communication passage after the valve seal separates from the piston seal surface when the piston returns. Interposed pressure chamber side between Temu and the communication path, said auxiliary seal, small
At least the piston seal surface and the valve seal are in close contact
At this point, the stem is pressed by the pressing force between the piston and the spring member.
Relatively hard elastic material that is in close contact with the sheet surface.
It is formed in a dish shape that spreads to the piston seal surface side under load.
The bottom of the dish-shaped auxiliary seal is the bottom of the valve stem.
This is connected to the system seat and fixed to the valve stem.
The inner diameter of the open end of the dish-shaped auxiliary seal is the inner diameter of the communication passage.
And the opening end is
Protrude more toward the communication passage than the end of the bus seal on the piston seal surface side.
A master cylinder characterized by being issued . 2. The dish-shaped auxiliary member is provided on the piston seal surface.
The outer diameter of the opening end of the auxiliary seal is larger than the outer diameter of the stem seal ;
The master cylinder according to claim 1, wherein the auxiliary flow path is formed in a range smaller than the outer diameter of the gutter surface .