Patent ID: 12194967

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are presented to sufficiently transfer the spirit of the present disclosure to those skilled in the art to which the present disclosure pertains. The present disclosure is not limited to the embodiments presented herein and may be embodied in other forms. In the drawings, illustration of components irrelevant to the description will be omitted to clarify the present disclosure, and the sizes of the components may be slightly exaggerated to help understanding.

FIG.1is a perspective view illustrating a master cylinder1according to the present embodiment, andFIG.2is a cross-sectional view illustrating the master cylinder1according to the present embodiment.FIG.3is a cutaway perspective view illustrating the master cylinder1according to the present embodiment.

Referring toFIGS.1to3, the master cylinder1according to the present embodiment includes a hydraulic block110having main bores111and112therein in an axial direction, a first piston121disposed such that one side is inserted into the main bores111and112and the other side is exposed to the outside of the hydraulic block110, a second piston inserted into the main bores111and112more inside than the first piston121, an elastic member123disposed between the first piston121and the second piston124, a mounting block140through which the first piston121is inserted and penetrated and which is coupled to the hydraulic block110, a first sealing member116and a second sealing member177interposed between the hydraulic block110and the mounting block140to seal a flow path and prevent a leakage of the pressing medium, a cap127provided in the first piston121, and a gap flow path100formed by a gap between the first piston121and the cap127.

The hydraulic block110is provided with the main bores111and112extending in the axial direction and having the other side open (a left side inFIG.2). The main bores111and112include a first bore111into which one side (a right side inFIG.2) of the first piston121, which will be described below, is inserted and which is thus provided displaceably and a second bore112which is formed on an inner side (a right side inFIG.2) of the first bore111, into which at least a portion of the second piston124is inserted, and which is thus provided displaceably. That is, the first bore111and the second bore112are arranged in series with respect to the axial direction, the first bore111is disposed more outside than the second bore112on the hydraulic block110, and the second bore112is disposed more inside than the first bore111on the hydraulic block110. A diameter of the second bore112may be smaller than a diameter of the first bore111. Accordingly, as will be described below, the second bore112is provided with a second stepped portion112aformed to be stepped at the other end (a left end inFIG.2) facing the first bore111.

The hydraulic block110includes various flow paths through which the pressing medium is transported in addition to the main bores111and112of the master cylinder1according to the present embodiment. As an example, a hydraulic flow path119may be formed through the other side of the hydraulic block110, and the hydraulic flow path119may be connected to an inspection flow path for inspecting whether the brake device is normally operated, for example, whether there is a leakage of the pressing medium. That is, the hydraulic block110may be understood as a valve block constituting a brake system of a vehicle. The hydraulic block110may be fixedly supported on a vehicle body by a support bracket130. Further, as will be described below, the hydraulic block110may be provided with a shaft bore118through which a shaft20of a displacement detection device (not illustrated) that detects displacement of the pedal moves in the axial direction and a communication bore118aallowing the main bores111and112to communicate with the shaft bore118. A detailed description thereof will be made below with reference toFIGS.20to24.

One side (a right side inFIG.2) of the first piston121may be inserted into the first bore111, and thus the first bore111may be provided to be displaceable in the axial direction. The other side of the first piston121may be exposed to the outside of the hydraulic block110and may be connected to a brake pedal (not illustrated) by means of an input rod11through the mounting block140, which will be described below. The first piston121includes a body portion121aextending in the axial direction and provided in a cylindrical shape and a catching portion121bextending radially from one end (a right side inFIG.2) of the body portion121a. The catching portion121bmay be provided in a state of being accommodated in the first bore111, and an outer diameter of the catching portion121bmay be provided greater than an inner diameter of a sub bore142of the mounting block140. Therefore, when the first piston121returns (moves in a leftward direction inFIG.2), the catching portion121bmay be caught by a mounting protrusion141aof the mounting block140and thus disposed at a certain position in a state in which a stepping force is released from the brake pedal. Further, the first piston121includes a mounting portion121drecessed in the axial direction so that the cap127and the elastic member123, which will be described below, are stably coupled to one surface thereof (a right surface inFIG.2), a hollow portion121eextending from the mounting portion121d, a communication hole121fpenetrated in the radial direction to allow the hollow portion121eto communicate with a connection port149a, and a stepped surface121gformed between the mounting portion121dand the hollow portion121eas an inner diameter of the mounting portion121dis greater than an inner diameter of the hollow portion121e. The gap flow path100is formed by a gap between the first piston121and the cap127, and a detailed description thereof will be made below.

At least a portion of the second piston124may be inserted into the second bore112and may be displaceable in the axial direction. The second piston124may be displaced by the first piston121and the elastic member123, which will be described below. A space partitioned by the first piston121and the second piston124, which will be described below, on the first bore111may constitute a first liquid pressure chamber122, and a space partitioned by an inner wall and the second piston124on the second bore112may constitute a second liquid pressure chamber125. The second liquid pressure chamber125may be provided with a return spring126that elastically supports the second piston124. Further, the compressible and expandable elastic member123may be provided between the first piston121and the second piston124, and an elastic restoring force by compression of the elastic member123may be provided to a driver as a pedal feel. A fastening protrusion123aprotruding from the other side (the left side inFIG.2) of the elastic member123and coupled to the cap127, which will be described below, is provided.

The support bracket130may be fixedly installed in the vehicle body to support the hydraulic block110and the mounting block140, which will be described below. The support bracket130may be provided with a fastening portion131coupled to the mounting block140, which will be described below, and a support portion132fixed to the vehicle body by means of a fixed plate133, the fastening portion131and the mounting block140may be coupled to each other by a plurality of bolts136, and the support portion132and the vehicle body may be fixedly coupled to each other. The support bracket130may be made of a metal material such as steel to ensure sufficient rigidity.

The first piston121exposed to the outside from the hydraulic block110may be inserted into the mounting block140, and the mounting block140may be provided between the hydraulic block110and the support bracket130to fix and support the hydraulic block110. The hydraulic block110may be provided with an installation portion141having one side (a right side inFIG.2) coupled to the other side (the left side inFIG.2) of the hydraulic block110and an extension portion143extending to the other side (the left side inFIG.2) and penetrating the support bracket130.

Further, the mounting block140is provided with a sub bore142formed through and extending in the axial direction. The sub bore142may be provided such that the first piston is inserted thereinto and passes therethrough and thus may be displaced. A first stepped portion142athat is stepped may be provided at one end (a right end inFIG.2) of the sub bore142, and a mounting protrusion141aprotruding axially may be provided at a circumference of one end of the sub bore142on the one side (the right surface inFIG.2) of the installation portion141. The mounting protrusion141ais inserted into the first bore111of the hydraulic block110, an outer circumferential surface of the mounting protrusion141afaces or is in contact with an inner circumferential surface of the first bore111, and thus, easy mounting and coupling between the hydraulic block110and the mounting block140can be promoted.

A boot146that prevents foreign substances such as dust from being introduced into the sub bore142and the hydraulic block110may be provided at the other end of the extension portion143. The boot146may have one end supported by the extension portion143of the mounting block140and the other end supported by the support plate147fixedly installed in the input rod11, and thus may be stretched and expanded according to displacement of the input rod11. Further, a piston spring148that elastically support the input rod11and causes return of the first piston121may be supported by the other end of the extension portion143. The piston spring148may be disposed inside the boot146, and a noise suppression protrusion144that reduces noise and vibration by operation of the piston spring148may be provided between the boot146and the piston spring148. A detailed description thereof will be made below with reference toFIG.25.

The connection port149ahydraulically communicating with a reservoir in which the pressing medium is accommodated may be provided in the sub bore142. At least one seal149bthat prevents leakage of the pressing medium passing through the connection port149amay be provided on one side and the other side of the connection port149a. The seal149bmay be seated and accommodated in a seal groove recessed in an inner circumferential surface of the sub bore142. The connection port129amay communicate with the first liquid pressure chamber122by the gap flow path100, which will be described below, and a detailed description thereof will be described below with reference toFIGS.4to7.

The mounting block140may include a connection flow path145allowing the sub bore142to communicate with the hydraulic flow path119of the hydraulic block110. The hydraulic flow path119of the hydraulic block110may be spaced a predetermined distance from the main bores111and112. Accordingly, the connection flow path145may have one end exposed to one surface of the installation portion141of the mounting block140and the other end connected to the sub bore142by means of the connection port149aor the like, and may be formed to be inclined at a certain angle in the axial direction. In the master cylinder1according to the present embodiment, the hydraulic block110and the mounting block140are individually manufactured for easy installation and assembly, and then the other side of the hydraulic block110and one side of the mounting block140are provided by mutual surface coupling. Accordingly, since it is necessary that the flow path of the hydraulic block110and the bore of the mounting block140communicate with each other, the connection flow path145is inclined by a certain angle in the axial direction and formed through the mounting block140, and thus flow of the pressing medium can be maintained smoothly

A cap127that forms the gap flow path100to remove residual pressure of the pressing medium present in the first liquid pressure chamber122is provided between the first piston121and the elastic member123.

FIG.4is a cutaway perspective view illustrating a state in which the cap127is provided in the first piston121. Further,FIG.5is a perspective view illustrating the cap127, andFIG.6is a cutaway perspective view illustrating the first piston121.FIG.7is an enlarged view illustrating part A ofFIG.2.

Referring toFIGS.4to7, the cap127may be interposed between one side (a right side inFIGS.2and7) of the first piston121and the other side (a left side inFIGS.2and7) of the elastic member123. The cap127includes a body127ainserted into the mounting portion121d, a flange portion127bextending radially from one end (a right end inFIG.7) of the body127a, and a fastening hole127cinto which the fastening protrusion123aof the elastic member123is inserted and mounted.

For stable coupling between the cap127and the first piston121, an outer circumferential surface of the body127aand an inner circumferential surface of the mounting portion121dmay face or be in contact with each other, and an inside of the body127amay have a hollow shape so that the elastic member123may be easily input therein. The body127amay be press-fitted to the mounting portion121d, but the present disclosure is not limited thereto, and the coupling may be performed in various methods.

The gap flow path100includes a first slit101recessed in the outer circumferential surface of the body127ain the axial direction, a second slit102recessed in the other side of the flange portion127bfacing one end (a right end inFIGS.2and7) of the first piston121in the radial direction, and connected to the first slit101, a third slit103recessed in the stepped surface121gof the first piston121and connected to the second slit102, and a fourth slit104recessed in the stepped surface of the first piston121in the circumferential direction and connecting the adjacent third slits103to each other.

As the second slit102is formed on the flange portion127b, the second slit102may hydraulically communicate with the first liquid pressure chamber122. Further, since the second slit102is connected to the first slit101, the third slit103, and the fourth slit104, the first liquid pressure chamber122may hydraulically communicate with the connection port149aby means of a hollow portion121dand the communication hole121f. As the connection port149ais connected to the reservoir (not illustrated), the first liquid pressure chamber122and the reservoir may hydraulically communicate with each other through the gap flow path100.

In description of removing a residual pressure of the pressing medium through the cap127and the gap flow path100, when the vehicle suddenly switches from a normal operation mode of the brake system to a fallback mode due to failure, a liquid pressure of the pressing medium provided by a motor or a pump (not illustrated) of the brake system may be transferred to the first liquid pressure chamber122in a moment. Accordingly, the liquid pressure inside the first liquid pressure chamber122may not be released, and the residual pressure may remain. In this case, it is difficult for the driver to finely control braking of the vehicle, a stepping force of the brake pedal is affected, and thus the driver may feel sense of difference.

Accordingly, when the residual pressure of the pressing medium remains in the first liquid pressure chamber122, the gap flow path100formed by an interval between the first piston121and the cap127may discharge the residual pressure of the pressing medium to the reservoir. In detail, the residual pressure of the first liquid pressure chamber122may be transferred to the hollow portion121dinside the first piston121while sequentially passing through the second slit102, the first slit101, and the third slit103of the cap127, and the pressing medium introduced into the hollow portion121dmay be discharged to the reservoir through the communication hole121fand the connection port149a. Therefore, a drag phenomenon and the like can be prevented, and a stroke of the first piston121can be also maintained at a certain level.

The first and second sealing members116and117may be interposed between the hydraulic block110and the mounting block140to prevent leakage of the pressing medium.

FIG.8is an enlarged view illustrating part B ofFIG.2, andFIG.9is an enlarged view illustrating part E ofFIG.8. Referring toFIGS.2to10, the first sealing member116may be interposed between the one side (a right surface inFIG.2) of the mounting block140and the other side (a left surface inFIG.2) of the hydraulic block110and is provided to seal the hydraulic flow path119of the hydraulic block110and the connection flow path145of the mounting block140. The first sealing member116may be provided in a ring shape extending along an opening of the connection flow path145on one side of the mounting block140or an opening of the hydraulic flow path119on the other side of the hydraulic block110. Further, since the first sealing member116may be inserted into and seated on a first accommodation groove113recessed along the opening of the hydraulic flow path119on the other side of the hydraulic block110, separation of the first sealing member116can be prevented even when the high-pressure pressing medium is transferred from the hydraulic flow path119or the connection flow path145.

The first sealing member116may be provided with a central first body portion116aand a first wing portion116band a second wing portion116con both sides of the first body portion116aso that the leakage can be effectively prevented even when the high-pressure pressing medium is transferred from the hydraulic flow path119or the connection flow path145.

FIG.10is a view illustrating a state in which the first sealing member116is deformed by the liquid pressure of the pressing medium. Referring toFIGS.9and10, the first sealing member116may include the first body portion116aprovided in a center thereof and constituting a main body, the first wing portion116bprotruding to the inner side (an upper side inFIGS.9and10) adjacent to the hydraulic flow path119on the first body portion116a, and the second wing portion116cprotruding to the outer side (a lower side inFIGS.9and10) spaced from the hydraulic flow path119on the first body portion116a. An inner circumferential surface of the first wing portion116band an outer circumferential surface of the second wing portion116c, in other words, a portion facing an inner surface of the first accommodation groove113may be in surface contact with an inner surface of the first accommodation groove113so that the leakage of the pressing medium can be stably prevented even when the high-pressure pressing medium is transferred. To this end, the inner circumferential surface of the first wing portion116band the outer circumferential surface of the second wing portion116cmay be provided to correspond to the shape of the inner surface of the first accommodation groove113. Therefore, as illustrated inFIG.10, even when the pressing medium is transferred from the hydraulic flow path119or the connection flow path145, a contact area between the outer circumferential surface of the second wing portion116cand the inner surface of the first accommodation groove113increases, and thus the leakage of the pressing medium can be suppressed and prevented more effectively.

Further, for easy deformation of the first wing portion116band the second wing portion116cwhen the pressing medium is transferred, a thickness (a width in a left-right direction inFIG.9) of the first wind portion116bor the second wing portion116cmay be provided to be smaller than a thickness of the first body portion116a. In detail, the first body portion116amay be provided in a circular shape in which a cross section becomes greater toward a central portion so that a state in which both sides of the first body portion116aare in contact with the hydraulic block110and the mounting block140is maintained in the first accommodation groove113. The thickness of the first wing portion116bor the thickness of the second wing portion116cmay be provided to be smaller than a diameter of the first body portion116a. Therefore, even when the pressing medium is transferred from the hydraulic flow path119or the connection flow path145, the first body portion116aprimarily seals a gap between the hydraulic block110and the mounting block140, the first wing portion116bor the second wing portion116cis secondarily and easily deformed, the contact area with the first accommodation groove113is quickly expanded, and thus the leakage of the pressing medium can be prevented stably.

FIG.11is an exploded perspective view illustrating the second sealing member117according to the present embodiment, andFIG.12is an enlarged view illustrating part F ofFIG.8. Referring toFIGS.2,11, and12, the second sealing member117may be interposed between the one side (a right surface inFIG.2) of the mounting block140and the other side (a left surface inFIG.2) of the hydraulic block110and is provided to seal the main bores111and112and the shaft bore118of the hydraulic block110.

The shaft bore118may be spaced a predetermined distance from the main bores111and112on the hydraulic block110, may extend in the axial direction, and may be disposed so that the shaft20(not illustrated) of the displacement detection device of the brake pedal may be displaced. The communication bore118ain which a connection member connecting the first piston121and the shaft20is accommodated may be formed between the main bores111and112and the shaft bore118to extend in the axial direction (SeeFIGS.20and19).

The second sealing member117may extend along openings of the main bores111and112and an opening of the shaft bore118on the other side of the hydraulic block110. Further, the second sealing member117may be inserted into and seated on a second accommodation groove114recessed along the openings of the main bores111and112and the opening of the shaft bore118on the other side of the hydraulic block110. Therefore, even when the high-pressure pressing medium is transferred from the main bores111and112or the shaft bore118, separation of the second sealing member117can be prevented.

The second sealing member117may be provided with a central second body portion117aand a third wing portion117band a fourth wing portion117con both sides of the second body portion117aso that the leakage can be effectively prevented even when the high-pressure pressing medium is transferred from the hydraulic flow path119or the connection flow path145.

The second sealing member117may include the second body portion117aprovided in a center thereof and constituting a main body, the third wing portion117bprotruding to an inner side (an upper side inFIG.12) from the main bores111and112or the shaft bore118on the second body portion117a, and the fourth wing portion117cprotruding to the outer side (a lower side inFIG.12) spaced apart from the main bores111and112or the shaft bore118on the second body portion117a. An inner circumferential surface of the third wing portion117band an outer circumferential surface of the fourth wing portion117c, in other words, a portion facing an inner surface of the second accommodation groove114may be in surface contact with the second accommodation groove114so that the leakage of the pressing medium can be stably prevented even when the high-pressure pressing medium is transferred. To this end, the inner circumferential surface of the third wing portion117band the outer circumferential surface of the fourth wing portion117cmay be provided to correspond to the shape of the inner surface of the second accommodation groove114. Therefore, similar to the first sealing member116illustrated inFIG.10, even when the pressing medium is transferred from the main bores111and112or the shaft bore118, a contact area between the outer circumferential surface of the fourth wing portion117cand the inner surface of the second accommodation groove114increases, and thus the leakage of the pressing medium can be suppressed and prevented more effectively.

Further, for easy deformation of the third wing portion117band the fourth wing portion117cwhen the pressing medium is transferred, a thickness (a width in a left-right direction inFIG.12) of the third wind portion117bor the fourth wing portion117cmay be provided to be smaller than a thickness of the second body portion117a. In detail, the second body portion117amay be provided in a circular shape in which a cross section becomes greater toward a central portion so that a state in which both sides of the second body portion117aare in contact with the hydraulic block110and the mounting block140is maintained in the second accommodation groove114. The thickness of the third wing portion117bor the thickness of the fourth wing portion117cmay be provided to be smaller than a diameter of the second body portion117a. Therefore, even when the pressing medium is transferred from the main bores111and112or the shaft bore118, the second body portion117aprimarily seals a gap between the hydraulic block110and the mounting block140, the third wing portion117bor the fourth wing portion117cis secondarily and easily deformed, the contact area with the second accommodation groove114is quickly expanded, and thus the leakage of the pressing medium can be prevented stably.

A bush member is provided to guide a smooth reciprocating movement of the first piston121and the second piston124, and at the same time, to prevent excessive friction and scratches between a piston and a bore.

FIGS.13and14are enlarged views of part A ofFIG.2,FIG.15is a perspective view illustrating a first bush member151, andFIG.16is a perspective view illustrating a damper member152.

Referring toFIGS.2,3, and13to16, the first bush member151is provided to be adjacent to the one side (a right side inFIGS.2,13, and14) of the first piston121, guides a forward movement and a return movement to promote stable sliding of the first piston121, and at the same time, prevents wear and damage due to contact with the mounting block140. The first stepped portion142athat is stepped and has a greater inner diameter than an inner diameter of the sub bore142may be provided at one end (a right end inFIGS.13and14) of the sub bore142, and thus the first bush member151may be provided in a ring shape, and an outer circumferential surface of the first bush member151may be provided in contact with an inner circumferential surface of the first stepped portion142a. An outer circumferential surface of the first bush member151may be press-fitted to the inner circumferential surface of the first stepped portion142ato stably support the first bush member151and prevent separation of the first bush member151on the first stepped portion142a. The first bush member151may be made of a plastic material, and a diameter of an inner circumferential surface of the first bush member151may be provided to correspond to a diameter of an outer circumferential surface of the body portion121aof the first piston121.

When the first piston121returns (moves in a left direction inFIGS.2,13, and14), the damper member152prevents noise and vibration caused by impact between the first piston121and the mounting block140. The damper member152may be disposed adjacent to one end (a right end inFIGS.13and14) on the outer circumferential surface of the first piston121and may be made of an elastically deformable material to alleviate the impact caused by contact between the first piston121and the mounting block140. The damper member152may be retracted into and in close contact with a damper groove recessed in the outer circumferential surface of the first piston121in the circumferential direction so that the damper member152is stably supported on the first piston121and separation therebetween is prevented. Further, the damper member152may have one side (a right side inFIGS.13and14) supported by a catching portion121bof the first piston121and the other side (a left side inFIGS.13and14) provided to face and be in contact with the first bush member151. The damper member152may enter the inside of the first stepped portion142aaccording to the reciprocating movement of the first piston121. The damper member152may be provided with an outer groove152arecessed in at least one of one side and the other side so that compression and restoration can be easily and quickly performed.

The second bush member160is provided to guide a reciprocating movement of the second piston124, and at the same time, to prevent wear and damage caused by contact with the hydraulic block110.

FIG.17is an enlarged view illustrating part C ofFIG.2, andFIG.18is a perspective view illustrating the second bush member160.

Referring toFIGS.2,3,17, and18, the second bush member160may be provided between the second piston124and the second bore112. The second stepped portion112athat is stepped and has a greater inner diameter than an inner diameter of the second bore112may be provided at the other end (a left end inFIG.17) of the second bore112, and thus the second bush member160may be provided in a ring shape and may be provided such that an outer circumferential surface thereof is in contact with an inner circumferential surface of the second stepped portion112a. The outer circumferential surface of the second bush member160may be press-fitted to the inner circumferential surface of the second stepped portion112aso that the second bush member160may be stably supported on the second stepped portion112aand separation therebetween may be prevented. The second bush member160may be made of a plastic material, and a diameter of an inner circumferential surface of the second bush member160may be provided to correspond to a diameter of an outer circumferential surface of the second piston124. Further, the second bush member160may include an inner groove160arecessed in the circumferential direction in the inner circumferential surface thereof to promote smooth sliding of the second piston124. Direct friction between the second piston124and the hydraulic block110can be reduced by the second bush member160, scratches and damages can be prevented, and durability of a product can be improved.

A third bush member170is provided adjacent to the other side (a left side inFIG.2) of the first piston121and is provided to guide the reciprocating movement of the first piston121, and at the same time, to prevent wear and damage caused by contact with the mounting block140.

FIG.19is a perspective view illustrating the third bush member170, and referring toFIGS.2and19, a third stepped portion142bthat is stepped and has a greater inner diameter than an inner diameter of the sub bore142is provided at the other end (a left end inFIG.2) of the sub bore142, and the third bush member170may be inserted into and installed in the third stepped portion142b. Like the first bush member151, the third bush member170may be provided in a ring shape and provided in contact with an inner circumferential surface of the third stepped portion142b. An outer circumferential surface of the third bush member170may be press-fitted to the inner circumferential surface of the third stepped portion142bto stably support the third bush member170and prevent separation of the third bush member170on the third stepped portion142b. The third bush member170may be made of a plastic material, a diameter of an inner circumferential surface of the third bush member170may be provided to correspond to the diameter of the outer circumferential surface of the body portion121aof the first piston121.

FIG.20is a cutaway perspective view of the hydraulic block110.FIG.21is a lateral cross-sectional view of the master cylinder1and shows a state in which a catching step181is caught and supported by a first stopper182, andFIG.22is an enlarged view of part G ofFIG.21. Further,FIG.23is a cross-sectional view in another direction illustrating the main bores111and112, the shaft bore118, and a communication bore118a, andFIG.24is a cross-sectional view in another direction illustrating the state in which the catching step181is caught and supported by the first stopper182.

Referring toFIGS.20to24, the hydraulic block110includes the shaft bore118in which the shaft20of the displacement detection device (not illustrated) that detects displacement of the pedal moves in the axial direction and the communication bore118aallowing the main bores111and112to communicate with the shaft bore118. As a magnet is supported by the shaft20or the shaft20is provided as the magnet, a sensor provided in the displacement detection device detects a change in a magnetic force or a magnetic flux density of the magnet, and thus the displacement of the first piston121can be detected, and the displacement of the brake pedal can be detected on the basis of the displacement of the first piston121. Further, the shaft20and the first piston121may be connected and coupled by a binding member30, and the binding member30may move along the communication bore118a. In this way, as the main bores111and112through which the first and second pistons121and124move and the shaft bore118through which the shaft20moves communicate with each other inside the hydraulic block110, a separate sealing member for sealing each bore is not required, and thus the number of components can be reduced, and a structure can be simplified. Further, since the main bores111and112and the shaft bore118may be arranged adjacent to each other, the hydraulic block110may be miniaturized and reduced in size.

The catching step181extending or protruding in the radial direction may be provided in the outer circumferential surface of the second piston124, and the first stopper182by which the catching step181is caught and supported may be provided in the inner circumferential surfaces of the main bore111and112. As an outer diameter of the catching step181is provided to be greater than an inner diameter of the first stopper182, the catching step181may be caught by the first stopper182. In detail, as the other end (a left end inFIGS.21and18) of the catching step181is in contact with one end (a right end inFIGS.21and18) of the first stopper182, a working stroke can be uniformly maintained by limiting a movement distance of the second piston124in a return direction. Therefore, in a state in which the stepping force is released from the brake pedal, the second piston124may be disposed at a certain position.

The first stopper182may be mounted in the inner circumferential surfaces of the main bore111and112and extend or protrude to the inside of the main bores111and112such that the catching step181is caught and supported thereby. The first stopper182may be in a ring shape and provided with an opening182aand having one open side, and the communication bore118amay be positioned inside the opening182a. Therefore, even though the piston and the binding member30move, interference with the first stopper182can be prevented. The first stopper182may be made of a plastic material and can suppress noise and vibration occurring when contact and collision with the catching step181. Further, a diameter of an inner circumferential surface of the first stopper182is provided to correspond to a diameter of an outer circumferential surface of a portion of the second piston124facing the same, and thus a sagging phenomenon due to a load of the second piston124can be prevented.

A first stopper groove recessed in the circumferential direction may be provided in an inner circumferential surface of the main bores111and112, particularly, the first bore111, so that the first stopper182may be stably supported and mounted on the main bores111and112. The first stopper182is inserted into and seated on the first stopper groove and can thus be stably supported at a predetermined position and prevented from being separated. The first stopper groove may include a separation prevention part184protruding to the inside of the opening182aand facing both ends of the opening182aof the first stopper182, rotation of the first stopper182is prevented by the separation prevention part184, and thus the first stopper182can be prevented from entering the communication bore118a. Further, an inner circumferential surface of the separation prevention part184may be formed to be continuous with the inner circumferential surface of the main bores111and112or the first bore111so that the piston does not interfere with the separation prevention part184. InFIGS.22and23, it is illustrated that both ends of the separation prevention part184are formed to be curved by a grinding to order process to easily manufacture the separation prevention part184on the hydraulic block110. However, this is an example for helping understanding of the present disclosure, the present disclosure is not limited to the corresponding shape, and the shape of both ends of the separation prevention part184may be variously formed depending on a manufacturing method.

FIG.25is an enlarged view illustrating part D ofFIG.2.

Referring toFIG.25, the support plate147may be fixedly installed in the input rod11. the boot146that is contracted and extended according to the displacement of the input rod11may be supported by the support plate147, and the other end of the piston spring148elastically supporting the input rod11and the first piston121.

The support plate147may be provided in a plate shape, fixed to the outer circumferential surface of the input rod11, and firmly support the boot146and the piston spring148, and the boot146may be made of an elastically deformable material such as rubber.

Meanwhile, the input rod11and the first piston121reciprocate by the operation of the brake pedal, the boot146is contracted and extended by the reciprocating movement of the input rod11, and it is required that the inside and the outside of the boot146communicate with each other for smooth deformation of the boot146. In this case, when foreign substances such as dust or moisture are introduced into the boot146, performance of components such as the input rod11and the piston spring148may be adversely affected, furthermore, the possibility that the foreign substances are introduced into the mounting block140or the hydraulic block110increases, and thus performance and durability of a product may be degraded.

Accordingly, the support plate147may include at least one vent hole147apenetrated such that the inside and the outside of the boot146communicate with each other, and the vent hole147amay be inclined at a certain angle in the axial direction. As the inside and the outside of the boot146communicate with each other by the vent hole147a, smooth deformation of the boot146is promoted, and at the same time, as the vent hole147ais inclined at a certain angle, foreign substances such as dust are prevented from directly penetrating into the boot146, and thus inflow of foreign substances can be suppressed.

Meanwhile, after the input rod11and the first piston121move forward by the operation of the brake pedal, when the stepping force of the brake pedal is released or braking is released, the input rod11and the first piston121return to original positions by the piston spring148. In this case, while the piston spring148is compressed and then expanded again, shaking occurs due to an elastic restoring force of the piston spring148itself, and thus noise and vibration occur.

Accordingly, the master cylinder1according to the present embodiment is provided with a noise suppression protrusion144to reduce noise and vibration occurring in the operation of the piston spring148.

FIG.26is a side view in another direction illustrating a second stopper190, andFIG.27is a cross-sectional view along line A-A′ ofFIG.25and is a side view in another direction illustrating a state in which the second stopper190is mounted on the first piston121.

Referring toFIGS.25to27, the noise suppression protrusion144may be provided on the inner circumferential surface of the boot146. The noise suppression protrusion144protrudes inward from the inner circumferential surface of the boot146and is provided to maintain contact with at least a portion of an outer circumferential surface of the piston spring148. The noise suppression protrusion144may be provided integrally with the boot146, and accordingly, like the boot146, the noise suppression protrusion144may be made of an elastically deformable material such as rubber. The noise suppression protrusion144protrudes or extends inward from the inner circumferential surface of the boot146and is in contact with at least a portion of the outer circumferential surface of the piston spring148, and thus the noise suppression protrusion144can absorb resonance generated by the piston spring148, thereby alleviating noise and vibration. At least one point of the outer circumferential surface of the piston spring148and the noise suppression protrusion144may be provided to always maintain a contact state regardless of whether the piston spring148is compressed or expanded.

The second stopper190may be provided on an outer circumferential surface of the other side (a left side inFIG.25) of the first piston121exposed to the outside of the mounting block140. The second stopper190may be mounted to extend or protrude radially from the outer circumferential surface of the first piston121. The second stopper190may be provided in a ring shape and provided with therein an accommodation portion through which the first piston121passes and a mounting opening195having one open side. Therefore, when the first piston121moves forward according to the operation of the brake pedal, the second stopper190is caught by the other end (a left end inFIG.25) of the mounting block140, and thus the working stroke can be uniformly maintained by limiting a forward movement distance of the first piston121. The second stopper190may be inserted into and seated on a second stopper groove121crecessed in the outer circumferential surface of the first piston121in the circumferential direction so that the second stopper190can be stably supported on the outer circumferential surface of the first piston121.

Meanwhile, when the second stopper190is in contact with the other end of the mounting block140, noise and vibration may occur. To reduce the noise and vibration occurring in this case, the accommodation portion of the second stopper190may be divided into two sections having different diameters. In detail, the accommodation portion may be divided into a first accommodation portion191having a first radius d1with respect to a first circle center point191aand a second accommodation portion192having a second radius d2with respect to a second circle center point192a. The second circle center point192amay be eccentric closer to the mounting opening195than the first circle center point191a, and the second radius d2may be provided to be smaller than the first diameter d1. Therefore, when the second stopper190is mounted on the outer circumferential surface of the first piston121, the inner circumferential surface of the second stopper190and the outer circumferential surface of the first piston121are coupled to each other by three contact points193. As the second stopper190and the first piston121are coupled to each other by means of the three contact points193, a fastening force between the two components is promoted, and a contact area is minimized. Further, even when the second stopper190is in contact with the mounting block140on the outer circumferential surface of the first piston121and thus shaking occurs, generation of noise and vibration can be suppressed.

In a master cylinder according to the present embodiment, operation reliability and performance can be improved.

In the master cylinder according to the present embodiment, noise and vibration generated when a piston is displaced can be reduced.

In the master cylinder according to the present embodiment, a working stroke of the piston can be maintained as constant.

In the master cylinder according to the present embodiment, leakage of a pressing medium and inflow of foreign substances can be prevented.

In the master cylinder according to the present embodiment, durability of a product can be improved by alleviating an impact applied to components.

In the master cylinder according to the present embodiment, assembly and miniaturization of the product can be promoted.