Master cylinder and brake-by-wire system

A master cylinder includes: a cylinder body; an isolation wall provided inside the cylinder body, arranged between a first chamber and a second chamber to isolate the first chamber and the second chamber, wherein, the isolation wall is integrally formed with the cylinder body; a first piston; a second piston; a first rod provided in connection with the first piston; a second rod provided inside the cylinder body, being in connection with the first piston, wherein, the second rod is supported in the isolation wall; and a cap provided at a first opening of the cylinder body, the first opening is at an end of the second chamber along the axial direction. A brake-by-wire system including the master cylinder is also disclosed herein.

TECHNICAL FIELD

The present disclosure relates to hydraulic brake system components. More particularly, the present disclosure relates to a master cylinder and a brake-by-wire system.

The present invention relates generally to tires and more specifically to a program or application to determine the present value of used tires. The program can be used with any tire, such as, for example, agricultural tires, commercial vehicles tires, both on and offroad, passenger vehicle tires, including trucks, passenger cars, and motorcycles, and aviation tires.

BACKGROUND

Master cylinders are often designed for use with hydraulic braking systems for vehicles. Master cylinders are commonly incorporated into braking assemblies in a variety of vehicles such as, for example, towing trailers, motorcycles, and the like.

In a master cylinder, a piston is slidably fitted in a cylinder body to which operating fluid is introduced from a reservoir, and the cylinder body defines therein a pressure chamber in which the operating fluid is pressurized according to an operation of the piston. The pressure chamber is connected via a pipe to a hydraulic device of a brake system or the like, such that the hydraulic device is operated according to an operation of the piston. The cylinder body is provided with a supply passage for supplying the operating fluid from the reservoir to the pressure chamber, to prevent a pressure in the pressure chamber from becoming negative during an operation of returning the piston or the like.

There are now numerous master cylinders on the market. It was found by the inventors that most of the master cylinders include a number of components. For example, the master cylinder incorporates numbers of components to divide a chamber of the master cylinder into two isolated parts. Therefore, the cost and complexity of the master cylinders are relatively high. It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a master cylinder and a brake-by-wire system. The master cylinder utilizes a wall that is integrally formed with a cylinder body to isolate a first chamber and a second chamber, and a rod is used to apply pressure on a second piston in case of fluid loss in the first chamber. Therefore, the cost and complexity of the master cylinder is lower, and improved security of the master cylinder is achieved.

It is one aspect of the present disclosure to provide a master cylinder. The master cylinder includes:

a cylinder body provided with a first chamber and a second chamber arranged along an axial direction;

an isolation wall provided inside the cylinder body, being arranged between the first chamber and the second chamber to isolate the first chamber and the second chamber, wherein, the isolation wall is integrally formed with the cylinder body;

a first piston provided at least partly in the first chamber, the first piston being movable along the axial direction;

a second piston provided in the second chamber, the second piston being movable in the axial direction;

a first rod provided in connection with the first piston;

a second rod provided inside the cylinder body, being in connection with the first piston, wherein, the second rod is supported in the isolation wall; and

a cap provided at a first opening of the cylinder body, wherein, the first opening is at an end of the second chamber along the axial direction.

According to an embodiment of the present disclosure, a snap ring is provided in the second chamber, the snap ring is attached to a bore of the second chamber and arranged behind the cap.

According to an embodiment of the present disclosure, a first spring is provided to connect the snap ring and the second piston.

According to an embodiment of the present disclosure, a first guide bushing is provided around the second rod, the first guide bushing is press-fit assembled in the isolation wall.

According to an embodiment of the present disclosure, a sealing ring is provided in the isolation wall.

According to an embodiment of the present disclosure, a stepped bore is provided in a front end of the first piston, a rear end of the second rod is incorporated in the stepped bore.

According to an embodiment of the present disclosure, a retaining washer is installed in the stepped bore in front of the rear end of the second rod.

According to an embodiment of the present disclosure, a mounting bracket is provided around the first piston, the mounting bracket extends along the axial direction and is attached to a back end of the cylinder body.

According to an embodiment of the present disclosure, a step portion is provided in a bore of the mounting bracket, a diameter of the step portion is smaller than a diameter of a first part of the first piston, the first part of the first piston is arranged in front of the step portion in the axial direction.

According to an embodiment of the present disclosure, a clearance between an outer wall of the first piston and the bore of the mounting bracket in front of the step portion is smaller than a clearance between the outer wall of the first piston and the bore of the mounting bracket behind the step portion.

According to an embodiment of the present disclosure, an insertion portion is provided between the outer wall of the first piston and the bore of the mounting bracket behind the step portion.

According to an embodiment of the present disclosure, a hollow portion is provided in a rear part of the first piston, the first rod is incorporated in the hollow portion via a retainer, the retainer comprises a wear plate and a housing, the wear plate contacts with a front end of the first rod, the housing surrounds the front end of the first rod.

According to an embodiment of the present disclosure, at least one flange is attached to a bore of the hollow portion, a return spring is arranged between the flange and the mounting bracket.

According to an embodiment of the present disclosure, at least one sensor is arranged on the flange.

According to another aspect of embodiments of the present disclosure, a brake-by-wire system is provided, the brake-by-wire system includes the master cylinder according to any one of above mentioned embodiments.

An advantage of the embodiments of the present disclosure exists in that the cost and complexity of the master cylinder is lower, and improved security of the master cylinder is achieved.

With reference to the following description and drawings, the particular embodiments of the present disclosure are disclosed in detail, and the principle of the present disclosure and the manners of use are indicated. It should be understood that the scope of the embodiments of the present disclosure are not limited thereto. The embodiments of the present disclosure contain many alternations, modifications and equivalents within the scope of the terms of the appended claims.

DETAILED DESCRIPTION

As used herein, the terms “first” and “second” refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “has,” “having,” “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on.” The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment.” The term “another embodiment” is to be read as “at least one other embodiment.” Other definitions, explicit and implicit, may be included below.

Furthermore, in the following description of this disclosure, for the sake of convenience of explanation, a direction of radius taking a central axis C of a bore of a cylinder body as a center is referred to as “a radial direction”, a direction of a circumference taking the central axis as a center is referred to as “a circumferential direction”, a direction along a direction of the central axis is referred to as “an axial direction”, a direction of the “axial direction” pointing from a first chamber to a second chamber is referred to as “a forward direction”, and a direction opposite to the “forward direction” is referred to as “a backward direction”.

A First Aspect of Embodiments

Embodiments of this disclosure provide a master cylinder. The master cylinder1constructed in accordance with one embodiment of the present disclosure is generally shown inFIG. 1. The master cylinder1includes a cylinder body11, an isolation wall12, a first piston13, a second piston14, a first rod15, a second rod16and a cap17.

As shown inFIG. 1, in some embodiments, the cylinder body11has a first chamber111and a second chamber112. The first chamber111and the second chamber112is arranged along an axial direction D. In other words, the first chamber111and the second chamber112are in a tandem relationship with one another. For example, the first chamber111can be located in the back of the second chamber112.

In some embodiments, the isolation wall12is arranged inside the cylinder body11. The isolation wall12is arranged between the first chamber111and the second chamber112to isolate the first chamber111and the second chamber112. The isolation wall12is integrally formed with the cylinder body11.

In some embodiments, the first piston13is at least partially provided in the first chamber111. For example, a front part of the first piston13is located inside the first chamber111and the rear part of the piston13is located outside of the first chamber111. The first piston13is movable along the axial direction D.

In some embodiments, the second piston14is provided in the second chamber112. The second piston14is movable in the axial direction D. The second piston14divides the second chamber112into two isolated parts1121,1122, which includes a first part1121and a second part1122. The first part1121is incorporated in a primary circuit for supplying a fluid. The second part1122is incorporated in a secondary circuit for supplying the fluid.

In some embodiments, the first rod15is connected with the first piston13. For example, the first rod15can be arranged behind the first piston13along the axial direction D, and a front part of the first rod15is incorporated in the first piston13.

In some embodiments, the second rod16is provided inside the cylinder body11and in connection with the first piston13. For example, the second rod16can be arranged in front of the first piston13along the axial direction D, and a rear part of the second rod16is incorporated in the first piston13.

As shown inFIG. 1, the second rod16is supported in the isolation wall12, so that the second rod16penetrates the isolation wall and enters into the second chamber112to push the second piston14when the first piston13pushes the second rod16along the axial direction.

As shown inFIG. 1, the cap17is provided at a first opening113of the cylinder body11. The first opening113is at an end112aof the second chamber112along the axial direction D, for example, the end112ais a front end of the second chamber112. The cap17is used to seal the first opening113, to prevent fluid losing from the first opening113.

As shown inFIG. 1, from a front part of the master cylinder1to a rear part of the master cylinder1, components are arranged in a following order: the cap17, the second piston14, the isolation wall12, the second rod16, the first piston13and the first rod15.

According to the first aspect of embodiments, the master cylinder1utilizes the isolation wall12that is integrally formed with the cylinder body11to isolate the first chamber111and the second chamber112, and the second rod16is used to apply pressure on the second piston14in case of fluid loss in the first chamber111. Therefore, the cost and complexity of the master cylinder is lower, and improved security of the master cylinder1is achieved.

FIG. 2is an enlarged cross-sectional view of a dotted rectangular part A1inFIG. 1. As shown inFIG. 1andFIG. 2, in some embodiments, a snap ring18is provided in the second chamber112. The snap ring18is attached to a bore112bof the second chamber112and arranged behind the cap17. For example, an outer rim of the snap ring18is embedded in the bore112bof the second chamber112. In case of the cap17escapes from the first opening113, the snap ring18still stays in the bore112bof the second chamber112, to prevent the second piston14from escaping out of the second chamber112.

As shown inFIG. 2, a first spring19is provided to connect the snap ring18and the second piston14. When the second rod16pushes the second piston14, the second piston14moves axially in the second chamber112toward the snap ring18which increases the fluid pressure thereby generating a brake force in a brake-by-wire system. As the second rod16pushes the second piston14, the first spring19compresses. When the second rod16is released, the first spring19generates a restoring force in the second part1122of the second chamber112thereby returning the second piston14to its original position.

As shown inFIG. 2, in some embodiments, a first guide bushing20is provided around the second rod16. The first guide bushing20is press-fitted in the isolation wall12. The first guide bushing20guides the second rod16to move along the axial direction.

In some embodiment, a press force travel and displacement is employed during the manufacturing process of the second rod16with force magnitudes above what is seen from the hydraulic loads, thereby ensuring a proper fit of the first guide bushing20.

As shown inFIG. 2, in some embodiments, a sealing ring21is provided in the isolation wall12. The sealing ring21has a generally O-shape or H-shape. The sealing ring21is in a sealing engagement with the second rod16to isolate the first chamber111from the second chamber112.

As shown inFIG. 2, in some embodiments, a stepped bore131is provided in a front end13aof the first piston13. A rear end16aof the second rod16is incorporated in the stepped bore131. The rear end16aof the second rod16is a head of the second rod16.

A clearance between the rear end16aof the second rod16and the stepped bore131is larger than a predetermined value, so that the second rod16is able to float with adequate clearance inside the stepped bore131. Therefore, the second rod16does not bind when moving along the axial direction D.

As shown inFIG. 2, in some embodiments, a retaining washer22is installed in the stepped bore131in front of the rear end16aof the second rod16. For example, the retaining washer22is staked in the stepped bore131. Thus the first piston13is able to apply a pulling force on the second rod16via the retaining washer22.

In some embodiment, the second rod16is a low-cost cold headed design as used in the manufacturing of screws and nails, so as to optimize construction.

FIG. 3is an enlarged view near the first piston and the first rod. As shown inFIG. 3andFIG. 1, in some embodiments, a mounting bracket23is provided around the first piston13. The mounting bracket23extends along the axial direction D and is attached to a back end114of the cylinder body11. For example, the mounting bracket23is attached to the cylinder body11with screws (not shown).

As shown inFIG. 3, in some embodiments, a step portion24is provided in a bore23aof the mounting bracket23. A diameter r1of the step portion24is smaller than a diameter r2of a first part13aof the first piston13. For example, the first part13aof the first piston13is arranged in front of the step portion24in the axial direction D. The step portion24provides a low cost structure of retaining the first piston13against pull-out loads up to 2,000 N.

As shown inFIG. 3, in some embodiments, a front part in front of the step portion24serves as an integral guide bushing which allows for a precise location and guidance of the first piston13.

As shown inFIG. 3, in some embodiments, a clearance C1between an outer wall132of the first piston13and the bore23aof the mounting bracket23in front of the step portion24is smaller than a clearance C2between the outer wall132of the first piston13and the bore23aof the mounting bracket23behind the step portion24. Tight clearances C1around the integral guide bushing and loose clearances C2in the remainder of the bore23aallow for optimum piston fit and the ability to absorb first rod side loads while preventing binding of the first piston13.

As shown inFIG. 3, in some embodiments, an insertion portion25is provided between the outer wall132of the first piston13and the bore23aof the mounting bracket23behind the step portion24for absorbing the side loads of the first rod15.

As shown inFIG. 3, in some embodiments, a hollow portion133is provided in a rear part13bof the first piston13. The first rod15is incorporated in the hollow portion133via a retainer26. The retainer26is a 2-piece assembly including a wear plate261and a housing262. The wear plate261contacts with a front end151of the first rod15and the housing262surrounds the front end151of the first rod15. It should be appreciated that the housing262is made of plastic, and the wear plate261is integrally formed with the first piston13. The first piston13is able to be assembled with the cylinder body11prior to the installation of the first rod15.

As shown inFIG. 3, in some embodiments, at least one flange27is attached to a bore133aof the hollow portion133. According to one embodiment of the present disclosure, the flange27can be a deep-drawn, press-fit flange.

As shown inFIG. 3, in some embodiments, a return spring28is arranged between the flange27and the mounting bracket23.

In some embodiments, at least one sensor is arranged on the flange. The sensor can be a displacement sensor.

As shown inFIG. 3, a bore of the cylinder body11is open at both ends with the second chamber112being sealed with a low cost, stamped steel end cap17and the snap ring18. The cap17is retained by the simple manufacturing process of staking. This allows for drilling from both ends of the cylinder body11as shown by arrows AR1and AR2(shown inFIG. 1) which eases and improves the quality of the bore undercuts for main seals as the reach into the bore by the grooving tool is cut in half. Further, the isolation wall12between the first chamber111and the second chamber112is integral with the cylinder body11as opposed to being a separate piece with seals and retaining ring as is typical of this design, thus the cost and complexity of the master cylinder1is lower. Further, the second rod16is incorporated in the master cylinder1to improve the security of the master cylinder1.

A Second Aspect of Embodiments

It is another aspect of the present disclosure to provide a brake-by-wire system. The brake by wire system, constructed in accordance with one embodiment of the present disclosure, is generally shown inFIG. 4. The brake-by-wire system4includes a pedal feel emulator assembly41, a master cylinder1, electronic booster control valves42, an electronic stability control unit43and a pressure supply unit44. In some embodiments, the master cylinder1has been described in the first aspect of embodiments.

As shown inFIG. 4, in some embodiments, the first part1121of the chamber112is incorporated in a primary circuit411, the second part1122of the chamber112is incorporated in a secondary circuit412. The first piston13serves as an actuator for the pedal feel emulator41when the pedal feel emulator valve (not shown) is opened.

In some embodiments, if the pressure supply unit44is in normal operation, a valve45in the master cylinder1is closed. When the first rod15pushes the first piston13, the first piston13moves forward. In response, fluid in the first chamber111flows into the pedal feel emulator assembly41and the pedal feel emulator assembly41generates a resistance pressure to provide a pedal feel. At the same time, the fluid in the first chamber111also flows into the pressure supply unit44. The pressure supply unit44generates a control signal according to a pressure of the fluid flowing out of the first chamber111. The electronic booster control valves42regulates the fluid flow into the primary circuit411to push the second piston14according to the control signal. Then, the fluid in the second secondary circuit412flows into the electronic stability control unit43to provide a brake force to the wheel brakes46.

In the event of a failure of the pressure supply unit44, the valve45in the master cylinder1opens thereby allowing the fluid in the first chamber111to flow. As the first rod15pushes the first piston13, the first piston13moves forward. Accordingly, the second rod16also moves forward contacting and pushing the second piston14forward thereby allowing the fluid in the second secondary circuit412to flow into the electronic stability control unit43to provide a brake force to the wheel brakes46.

Therefore, reliability of the brake-by-wire system4in the embodiments are strengthened because of the second rod16in case of fluid loss.