Master cylinder of vehicle brake

A master cylinder of a vehicle brake includes a housing, a motor, a screw, a moving piston, a guide, and a pressurizing part. The housing includes a port configured to move hydraulic fluid. The motor is connected to the housing and configured to supply rotation power. The screw is rotatably installed in the motor and configured to rotate in response to the rotation power. The moving piston is engaged with an outside of the screw, and is configured to move in a longitudinal direction of the housing in response to rotation of the screw. The guide is blocked by the housing and constrained from rotating, and is configured to constrain rotation of the moving piston and guide linear movement of the moving piston in the longitudinal direction. The pressurizing part is installed between the housing and the guide, and is configured to pressurize the guide via an elastic force.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean Patent Application No. 10-2019-0069350, filed Jun. 12, 2019, which is hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

Field

Exemplary embodiments generally relate to a master cylinder of a vehicle brake, and, more particularly, to a master cylinder of a vehicle brake that can easily manage a pre-load and tolerance between assembled parts through an elastic body, and, thereby, improve operation reliability.

Discussion

In general, a master cylinder of a vehicle brake generates a braking force for restraining movement of wheels of a vehicle using hydraulic pressure, which is generated in response to a piston in the master cylinder being moved. When a driver steps on a pedal, braking pressure is decided. Therefore, the master cylinder is operated to implement the braking pressure, and the hydraulic pressure generated by the master cylinder is transferred to each of the wheels. Since the master cylinder is typically operated by hydraulic pressure, difficulty arises in precisely moving the piston to implement the braking pressure. In order to address (or solve) such an issue, a method for moving a piston using rotation power of a motor has been suggested, such as in Korean Patent Application No. 10-2016-0095486, laid-open on Aug. 11, 2016, and entitled “Master Cylinder for Brake of Vehicle.” However, since tolerance between assembled parts is not normally managed, friction and interference between the parts may occur. Therefore, there is a need for a structure capable of solving such issues.

The above information disclosed in this section is only for understanding the background of the inventive concepts, and, therefore, may contain information that does not form prior art.

SUMMARY

Some exemplary embodiments are directed to a master cylinder of a vehicle brake capable of easily managing a pre-load and tolerance between assembled parts through an elastic body, and, thereby, improve operation reliability.

According to some exemplary embodiments, a master cylinder of a vehicle brake is includes a housing, a motor, a screw, a moving piston, a guide, and a pressurizing part. The housing includes a port configured to move hydraulic fluid. The motor is connected to the housing and configured to supply rotation power. The screw is rotatably installed in the motor and configured to rotate in response to the rotation power of the motor. The moving piston is engaged with an outside of the screw, and is configured to move in a longitudinal direction of the housing in response to rotation of the screw. The guide is blocked by the housing and constrained from rotating, and is configured to constrain rotation of the moving piston and guide linear movement of the moving piston in the longitudinal direction. The pressurizing part is installed between the housing and the guide, and is configured to pressurize the guide via an elastic force.

In some exemplary embodiments, the motor may include a fixed part, a motor rotating part, and a motor bearing part. The fixed part may be fixed to the housing and may be configured to change magnetism in response to a supplied power. The motor rotating part may be connected to the screw. The motor rotating part may be configured to rotate with the screw and rotate according to the change in the magnetism of the fixed part. The motor bearing part may be installed between the fixed part and the motor rotating part. The motor bearing part may be configured to reduce friction associated with rotation of the motor rotating part.

In some exemplary embodiments, the motor rotating part may include a rotating frame and a rotor. The rotating frame may be rotatably installed in the fixed part. A shape of the rotating frame may cover an end of the moving piston. The rotor may be installed outside the rotating frame and facing the fixed part. The rotor may include magnetism.

In some exemplary embodiments, the screw may include a screw body and a screw rotating shaft. The screw body may be rotatably installed in the rotating frame. The screw may include a spiral gear formed on the outside of the screw. The screw rotating shaft may be extended from the screw body and may be spline-coupled to the rotating frame.

In some exemplary embodiments, a compensation clearance may be provided between the rotating frame and the screw rotating shaft.

In some exemplary embodiments, the pressurizing part may be a plate spring comprising a curved cross-section, and may be configured to pressurize the guide in a direction away from the moving piston.

According to some exemplary embodiments, a master cylinder of a vehicle brake includes a housing, a motor, a screw, a ball member, and a support part. The housing includes a port configured to transmit hydraulic fluid. The motor is connected to the housing and is configured to supply rotation power. The screw is rotatably installed in the motor, and is configured to rotate in response to the rotation power of the motor. The ball member is connected to a screw rotating shaft of the screw, and includes a curved surface. The support part is positioned on opposing sides of the ball member, and rotatably supports the ball member.

In some exemplary embodiments, the support part may include a first support member and a second support member. The first support member may be positioned in the motor and the screw rotating shaft may include a portion extending through the first support member. The second support member may be installed at a position facing the first support member.

In some exemplary embodiments, the first and second support members may be configured to rotate together with the screw rotating shaft.

In some exemplary embodiments, the master cylinder of a vehicle may further include a thrust bearing part installed at a position facing the second support member. The thrust bearing part may be being configured to reduce friction associated with rotation of the second support member.

According to various exemplary embodiments, a pressurizing part implemented as an elastic body may elastically pressurize a guide body in a direction that a support part is installed in a master cylinder, and, as such, may apply a pre-load between assembled parts of the master cylinder. In this manner, tolerance management can be easily performed, and friction and interference between the parts can be reduced.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Unless otherwise specified, the illustrated exemplary embodiments are to be understood as providing exemplary features of varying detail of some exemplary embodiments. Therefore, unless otherwise specified, the features, components, modules, layers, films, panels, regions, aspects, etc. (hereinafter individually or collectively referred to as an “element” or “elements”), of the various illustrations may be otherwise combined, separated, interchanged, and/or rearranged without departing from the inventive concepts.

When an element, such as a layer, is referred to as being “on,” “connected to,” or “coupled to” another element, it may be directly on, connected to, or coupled to the other element or intervening elements may be present. When, however, an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element, there are no intervening elements present. Other terms and/or phrases used to describe a relationship between elements should be interpreted in a like fashion, e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” “on” versus “directly on,” etc. Further, the term “connected” may refer to physical, electrical, and/or fluid connection. In addition, the X-axis, the Y-axis, and the Z-axis are not limited to three axes of a rectangular coordinate system, and may be interpreted in a broader sense. For the purposes of this disclosure, “at least one of X, Y, and Z” and “at least one selected from the group consisting of X, Y, and Z” may be construed as X only, Y only, Z only, or any combination of two or more of X, Y, and Z, such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Various exemplary embodiments are described herein with reference to sectional views, isometric views, perspective views, plan views, and/or exploded illustrations that are schematic illustrations of idealized exemplary embodiments and/or intermediate structures. As such, variations from the shapes of the illustrations as a result of, for example, manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments disclosed herein should not be construed as limited to the particular illustrated shapes of regions, but are to include deviations in shapes that result from, for instance, manufacturing. To this end, regions illustrated in the drawings may be schematic in nature and shapes of these regions may not reflect the actual shapes of regions of a device, and, as such, are not intended to be limiting.

Hereinafter, various exemplary embodiments of a master cylinder of a vehicle brake will be described with reference to the accompanying drawings.

FIG. 1is a cross-sectional view schematically illustrating a structure of a master cylinder of a vehicle brake according to some exemplary embodiments.FIG. 2is a cross-sectional view illustrating a screw in the structure ofFIG. 1configured to compensate for a deflection angle while rotated about a ball member according to some exemplary embodiments.FIG. 3is a cross-sectional view illustrating a screw in the structure ofFIG. 1configured to compensate for eccentricity while moved in a top-to-bottom direction according to some exemplary embodiments.FIG. 4is a diagram illustrating that a compensation clearance is formed between a side protrusion and a rotating frame according to some exemplary embodiments.FIG. 5is a cross-sectional view illustrating that hydraulic pressure is generated on one side of a piston member according to some exemplary embodiments.FIG. 6is a cross-sectional view illustrating that hydraulic pressure is generated on both sides of a piston member according to some exemplary embodiments.FIG. 7is a cross-sectional view illustrating that hydraulic pressure is generated on the other side of a piston member according to some exemplary embodiments.

Referring toFIG. 1, a master cylinder1of a vehicle brake according to some exemplary embodiments includes a housing10, a motor20, a screw30, a moving piston50, a guide90, and a pressurizing part80. The housing10has a port12through which a fluid (e.g., gas, oil, or the like) is moved. For descriptive convenience, the fluid will, hereinafter, be described as oil. The motor20is connected to the housing10and supplies rotation power. The screw30is rotatably installed in the motor20and is rotated by the rotation power received from the motor20. The moving piston50is engaged with the outside of the screw30and moved in the longitudinal direction D of the housing10by the rotation of the screw30. The guide90is blocked by the housing10and constrained from rotating, and guides the moving piston50to linearly move in the longitudinal direction D while constraining the rotation of the moving piston50. The pressurizing part80is installed between the housing10and the guide90and pressurizes the guide90using an elastic force.

A driver's operation to step on a pedal decides (e.g., determines, regulates, etc.) braking pressure. Therefore, the master cylinder1of a vehicle brake is operated to implement the braking pressure, and the generated hydraulic pressure is transferred to each wheel of a vehicle.

The master cylinder1of a vehicle brake according to some exemplary embodiments provides a pre-pressure management assembly structure among assembled parts of the motor20, the screw30, the moving piston50, and the guide90. Thus, the master cylinder1can reduce tolerance between the assembling parts while improving the degree of freedom in design, and, thereby, reduce manufacturing cost. Furthermore, when the master cylinder1of a vehicle brake is driven, active shaft alignment compensation and abrasion gap compensation can be achieved to improve the durability and the system efficiency, and to reduce noise and vibration.

The port12of the housing10, through which oil is moved, is formed on either side of the housing10in the longitudinal direction D, and the housing10has an internal operation space in which a piston member54of the moving piston50is moved. Oil moved by the movement of the piston member54implements the braking pressure associated with the operation of the pedal while being moved through the port12.

As long as the motor20is connected to the housing10and supplies rotation power, various types of driving devices may be used as the motor20. The motor20according to some exemplary embodiments includes a motor bearing part21, a fixed part22, and a motor rotating part26.

The fixed part22may be formed in various shapes, as long as the fixed part22is fixed to the housing10and magnetism is changed by power supply. The fixed part22according to some exemplary embodiments includes a fixed frame23fixed to one side of the housing10and a stator24installed in the fixed frame23facing the motor rotating part26and configured to generate magnetism.

The fixed frame23is connected to one side of the housing10, and the motor rotating part26is rotatably installed in the fixed frame23. Furthermore, the stator24is configured as an electromagnet and is installed in the fixed frame23in a circumferential direction. The stator24rotates the motor rotating part26while magnetic fluxes are changed by a control signal of a control unit (not shown).

The motor rotating part26can be modified in various shapes, as long as the motor rotating part26is connected to the screw30, rotates with the screw30, and rotates according to a change in magnetism of the fixed part22. The motor rotating part26according to some exemplary embodiments includes a rotating frame27and a rotor28. The rotating frame27is rotatably installed in the fixed frame23and installed in a shape to cover an end of the moving piston50. The rotor28is installed outside the rotating frame27facing the fixed part22and has magnetism.

The motor rotating part26according to some exemplary embodiments has a U-shaped cross-section, and is formed in a hollow shape. In some exemplary embodiments, the motor rotating part26is formed in a solid core type, and geared with the outside of a separate shaft whose rotation is constrained by the motor rotating part26. Therefore, when the solid core-type motor rotating part26is rotated, the shaft may move the piston member54while linearly moved, thereby generating hydraulic pressure.

The motor bearing part21is installed between the fixed part22and the motor rotating part26, and reduces friction that occurs when the motor rotating part26is rotated. The rotor28including a plurality of magnets installed in the circumferential direction of the rotating frame27is rotated with the rotating frame27by the change in magnetism of the stator24.

A cover member29is fixed to the fixed frame23and installed in a shape to cover the outside of an end of the rotating frame27. As such, the cover member29blocks introduction of foreign matter.

The screw30may be formed in various shapes, as long as the screw30is rotatably installed in the motor20and rotated by the rotation power received from the motor20. The screw30according to some exemplary embodiments includes a screw body32and a screw rotating shaft34. The screw body32is rotatably installed in the rotating frame27and has a spiral gear formed on the outside thereof. The screw rotating shaft34is extended from the screw body32and spline-coupled to the rotating frame27.

The screw rotating shaft34extended outward from the rotation center of the screw body32has a smaller diameter than the screw body32. As illustrated inFIG. 4, a plurality of side protrusions35protrude from the outside of the screw rotating shaft34facing the rotating frame27. Thus, the rotating frame27and the screw30are spline-coupled to transfer power.

Furthermore, a compensation clearance40is provided between the rotating frame27and the screw rotating shaft34. The side protrusions35formed on the screw30and the rotating frame27are spaced apart from each other by a preset distance, thereby forming the compensation clearance40. Therefore, a degree of freedom is secured for the screw30and a compensator70to move in a top-to-bottom direction, such as shown inFIG. 3. Therefore, it is possible to compensate for coaxiality among the housing10, the screw30, and the motor20when the master cylinder1of a vehicle brake is assembled.

With continued reference toFIG. 1, the moving piston50may be formed in various shapes, as long as the moving piston50is engaged with the outside of the screw30, and moved in the longitudinal direction D of the housing10by the rotation of the screw30. The moving piston50according to some exemplary embodiments includes a moving body52, the piston member54, and a sealing member56.

The moving body52is installed in a shape to cover the outside of the screw body32, and linearly moved by the rotation of the screw body32. The moving body52has one side positioned in the motor rotating part26and the other side positioned in the housing10.

The piston member54is connected to the moving body52extended into the housing10, and moves oil between the housing10and a fixed piston60toward the port12. The piston member54is formed in a ring shape, and fixed to the outside of the other end of the moving body52. The piston member54and the moving body52may be formed as one body, or separately manufactured and then assembled to each other.

When the piston member54and the moving body52are formed as one body, a process of assembling the piston member54and the moving body52is removed, and the axial length of the master cylinder1of a vehicle brake can be reduced. Therefore, a reduction in the number of parts, a reduction in the number of assembling processes, and a reduction in an axial length of the master cylinder1of a vehicle brake can improve system packaging efficiency. The sealing member56is installed on a side surface of the moving body52and a side surface of the piston member54, and moved with the moving body52.

The fixed piston60may be formed in various shapes, as long as the fixed piston60is fixed to the inside of the housing10and the moving piston50is positioned outside the fixed piston60. The fixed piston60according to some exemplary embodiments is positioned on the same axial line as the screw30, and the fixed piston60has one side positioned in the moving piston50and the other side fixed to the housing10. The fixed piston60according to some exemplary embodiments is formed in a cylindrical shape, and the rotation centers of the fixed piston60, the screw30, and the motor rotating part26are positioned on the same axial line.

The compensator70may be formed in various shapes, as long as the compensator70is installed in the rotating frame27and compensates for the coaxiality of the rotating frame27and the screw30. The compensator70in accordance some exemplary embodiments includes a ball member72and a support part74.

The ball member72is connected to the screw rotating shaft34of the screw30positioned in the rotating frame27and has a spherical surface. The support part74is positioned on either side of the ball member72, and rotatably supports the ball member72. The support part74in accordance some exemplary embodiments includes a first support member76and a second support member78. The first support member76is positioned in the rotating frame27such that the screw rotating shaft34is disposed therethrough, and the second support member78is installed at a position facing the first support member76.

The ball member72may be formed in any one shape of a hemisphere and a sphere. In addition, various members with a spherical shape may be used as the ball member72. Two or more positions of the ball member72are supported by the support part74. Both sides of the ball member72in accordance some exemplary embodiments are supported by the first support member76and the second support member78.

The first support member76is positioned between the ball member72and the side protrusions35, and is installed in contact with the inner surface of the rotating frame27facing the ball member72. Since the first support member76facing the ball member72has a concave groove, the first support member76may rotatably support the ball member72with the second support member78.

The second support member78is installed at a position facing the first support member76with the ball member72interposed therebetween, and is rotatably installed through a thrust bearing part110. Since the second support member78facing the ball member72also has a concave groove, the second support member78may rotatably support the ball member72with the first support member76. The first support member76and the second support member78according to some exemplary embodiments may be rotated with the screw rotating shaft34.

The pressurizing part80is installed between the housing10and the guide90, and pressurizes the guide90using an elastic force to apply a pre-load. The pressurizing part80according to some exemplary present embodiments is a plate spring having a curved cross-section, and pressurizes the guide90in the direction that the first support member76is installed. Since the pressurizing part80pressurizes the guide90in a direction away from the moving piston50, a pre-load may be applied when parts are assembled.

Two or more positions of the ball member72are supported by the support part74, and the ball member72contacted with the support part74forms a curved surface at one or more positions. Since the ball member72has an alignment structure positioned between the first support member76and the second support member78, a load transferred from the pressurizing part80to the ball member72may be reduced to facilitate an operation of aligning and assembling parts.

The pressurizing part80is installed on a sidewall of the housing10facing the guide90, and elastically pressurizes the guide90toward the other side (right inFIG. 1) of the housing10.

The pressurizing part80implemented with a plate spring may include a wave washer. The pressurizing part80may be modified in various shapes. For example, the pressurizing part80may be implemented as an elastic member having a curved cross-section. The wave washer is a washer in which the functions of a flat washer and a spring washer are combined, and serves to prevent relaxation while distributing surface pressure. Furthermore, a rubber O-ring may be used as the pressurizing part80, and the pressurizing part80can be modified in various manners. For example, a member including at least one of silicone, synthetic resin, and rubber can be used as the pressurizing part80.

The guide90may be formed in various shapes, as long as the guide90is blocked by the housing10and constrained from rotating, and constrains the rotation of the moving piston50and guides the moving piston50to linearly move in the longitudinal direction D. In some exemplary embodiments, the guide90includes a guide body92, a wing member94, and a fixed protrusion96.

The guide body92has a groove in which the wing member94is inserted so as to move in the longitudinal direction D. The guide body92is positioned outside the moving piston50, and the fixed protrusion96extended from the guide body92is fixedly installed on the housing10. Since the fixed protrusion96is installed at a position facing the pressurizing part80, the fixed protrusion96is pushed by the pressurizing part80and pressurized toward the other side of the housing10.

The wing member94is fixed to the outside of the moving body52, formed in a shape to protrude to the outside of the moving body52, and moved with the moving body52. One side of the wing member94is fixed to the moving body52, and the other side is inserted into the guide body92.

The rotation of the wing member94fixed to the moving body52of the moving piston50is constrained by the guide body92when the screw30is rotated. Thus, the moving body52may serve to decide the position of the piston member54while linearly moved. That is, to implement braking pressure of a driver, the motor20rotates the screw30, and, thus, the moving body52is linearly moved to decide the position of the piston member54. Therefore, the magnitude of the braking pressure of the master cylinder1of a vehicle brake is controlled, and the sealing member56, the fixed piston60, and the housing10that are assembled to the respective components seal the space in which the braking pressure is formed.

The thrust bearing part110is installed between the second support member78and the guide90, and serves to reduce friction, which occurs when the second support member78is rotated.

Hereafter, an exemplary operation of the master cylinder1of a vehicle brake according to some exemplary embodiments will be described in more detail with reference to the accompanying drawings.

When the magnetism of the stator24is changed to implement a braking pressure of the driver, the motor rotating part26is rotated with the rotor28. The motor rotating part26rotates the spline-coupled screw30, and the rotation of the screw30linearly moves the moving piston50in the longitudinal direction D of the housing10.

In addition to the coupling structure in which the screw rotating shaft34is spline-coupled to the rotating frame27, the screw rotating shaft34may be connected to the rotating frame27by connection of a power transmission member. As the power transmission member, various types of connection members may be used, including a gear, key, and coupler for connecting the screw rotating shaft34to the rotating frame27.

The moving piston50facing the screw30is allowed only to linearly move because the wing member94protruding to the outside of the moving piston50is inserted into the guide body92and constrained from rotating.

The braking pressure is formed by the movement of the moving piston50having the piston member54, and oil for forming the braking pressure is moved through the port12.

The master cylinder1of a vehicle brake according to various exemplary embodiments is configured to compensate for axial alignment among the center axis of the motor20, the center axis of the screw30, and the center axis of the moving piston50. When the compensation for the axial alignment among the center axes of the respective parts is desired, the parts may be rotated about the ball member72as illustrated inFIG. 2, which makes it possible to compensate for a deflection angle between the assembled parts. Furthermore, as illustrated inFIG. 3, the screw30may be moved in the top-to-bottom direction to compensate for eccentricity.

Furthermore, a pre-load of a part assembled between the pressurizing part80and the first support member76may be managed through the pressurizing part80and the guide body92implemented as a slidable structure. Since the pre-load value can be managed through the pressurizing part80implemented as an elastic body, tolerance between assembled parts can be reduced, and a degree of freedom in design can be obtained. Furthermore, design values for the compensation for the deflection angle and the eccentricity can be examined and effectively managed.

As illustrated inFIG. 5, a first valve102connected to the port12formed on one side of the housing10may be opened, and a second valve104connected to the port12formed on the other side of the housing10may be closed. In this state, hydraulic pressure is formed only on one side (e.g., left side inFIG. 5) of the piston member54, and transferred to a wheel brake100.

Accordingly, pressure formed by the hydraulic pressure forms a first force F1while the force is transferred in order of the piston member54, the moving body52, the screw body32, the ball member72, and the first support member76. Furthermore, the elastic force of the pressurizing part80forms a second force F2while the force is transferred in order of the fixed protrusion96, the guide body92, the thrust bearing part110, the ball member72and the first support member76. Therefore, since the respective parts are pressed against each other by the first and second forces F1and F2, it is possible to prevent generation of noise or vibration by tolerance between the parts.

As illustrated inFIG. 6, the first valve102connected to the port12formed on the one side of the housing10may be opened, and the second valve104connected to the port12formed on the other side of the housing10may also be opened. In this state, hydraulic pressure is formed on both sides of the piston member54, and transferred to the wheel brake100.

At this time, pressure formed by the hydraulic pressure forms a first force F1while the force is transferred in order of the piston member54, the moving body52, the screw body32, the ball member72and the first support member76. Furthermore, the elastic force of the pressurizing part80forms a second force F2while the force is transferred in order of the fixed protrusion96, the guide body92, the thrust bearing part110, the ball member72, and the first support member76. Furthermore, hydraulic pressure generated by the chamber positioned on the other side (e.g., the right side inFIG. 6) of the piston member54forms a third force F3to pressurize the guide body92toward the other side of the piston member54.

Therefore, since the respective parts are pressed against each other by the first to third forces F1to F3, it is possible to prevent (or at least reduce) generation of noise or vibration by tolerance between the parts.

As illustrated inFIG. 7, the first valve102connected to the port12formed on the one side of the housing10may be closed, and the second valve104connected to the port12formed on the other side of the housing10may be opened. In this state, hydraulic pressure is formed only on the other side (e.g., right side inFIG. 7) of the piston member54, and is transferred to the wheel brake100.

Accordingly, pressure formed by the hydraulic pressure forms a first force F1to move the piston member54toward one side (e.g., the left side inFIG. 7) of the housing10, and the elastic force of the pressurizing part80forms a second force F2to pressurize the guide90to the other side of the housing10, while the force is transferred in order of the fixed protrusion96, the guide body92, the thrust bearing part110, the ball member72, and the first support member76.

The hydraulic pressure of the chamber positioned on the other side of the piston member54forms a third force F3to press the guide90toward the other side of the housing10. Thus, a total force Ftot supplied to the parts positioned between the pressurizing part80and the first support member76is a positive value obtained by subtracting the first force F1from the sum of the second and third forces F2and F3. Therefore, a constant force is transferred from the pressurizing part80toward the first support member76. Therefore, since the parts are pressed against each other by the pre-pressure, it is possible to prevent (or at least reduce) generation of noise or vibration by tolerance between the parts.

That is, the master cylinder1of a vehicle brake according to various exemplary embodiments is configured to apply a single-direction load to the assembled parts, even though hydraulic pressure distribution within both chambers based on the sealing member56of the piston member54is changed in various manners.

The pressurizing part80can continuously compensate for a clearance formed by abrasion of the parts when the master cylinder1of a vehicle brake is used. Furthermore, the structure in which an axial load caused by the hydraulic pressure within the chamber of the housing10is not applied to the pressurizing part80can secure a degree of freedom in design and the durability of the pressurizing part80to apply a pre-load.

Furthermore, the position of the screw30can be corrected so that the screw rotating shaft34of the screw30becomes coaxial with the rotation center of the motor rotating part26and the fixed piston60. Since the rotatable ball member72and the compensation clearance40provide a structure capable of performing active axial compensation between the respective parts when the master cylinder1of the brake for the vehicle is operated, system efficiency can be improved.

Since the sealing area by the guide90is larger than the sealing area by the piston member54as illustrated inFIG. 1, a load may be generated toward the right side of the piston member54even though hydraulic pressure is formed on the right side of the piston member54.

That is, a first sealing length A corresponding to a distance between the outside of the moving body52and the inner wall surface of the housing10is proportional to the area sealed by the piston member54, and a second sealing length B corresponding to a distance between the outside of the moving body52and the outer surface of the guide90is proportional to the area sealed by the guide90. The second sealing length B is larger than the first sealing length A. Therefore, although hydraulic pressure is formed on the right side of the piston member54, more hydraulic pressure may be applied in a direction facing the guide90having a sealing area proportional to the second sealing length B than in a direction facing the piston member54having a sealing area proportional to the first sealing length A. Further, since the guide90is forced into another structure, and, thus, not fixed, but floats, the guide90serves to generate the same load in one direction.

According to various exemplary embodiments, the pressurizing part80implemented as an elastic body elastically pressurizes the guide body92in the direction that the support part74is installed, and, thus, applies a pre-load between the assembled parts. In this manner, tolerance management can be easily performed, and friction and interference between the parts can be reduced. Furthermore, when the master cylinder1of a vehicle brake is operated, system efficiency can be improved through pre-load management between the respective parts. Also, the active shaft compensation efficiency between the power transmission shafts can be improved. Furthermore, tolerance of a single part can be reduced to raise a degree of freedom in design. Moreover, durability can be improved and operating noise can be reduced through the pre-load operating condition. Furthermore, the ball member72and the compensation clearance40can compensate for the coaxiality and right angle degree between the moving piston50and the screw30that are positioned on the same axis as the rotation center axis of the motor rotating part26, and, thereby, improve the operation reliability.

Although certain exemplary embodiments and implementations have been described herein, other embodiments and modifications will be apparent from this description. Accordingly, the inventive concepts are not limited to such embodiments, but rather to the broader scope of the accompanying claims and various obvious modifications and equivalent arrangements as would be apparent to one of ordinary skill in the art.