Brake hydraulic pressure control apparatus and manufacturing method of same

To prevent occurrence of contamination at the time of press-inserting and fixing a guide ring that guides sliding of a piston.In a brake hydraulic pressure control apparatus (1) including: a base body (2) having a cylinder hole (3); a piston (5) fitted to the cylinder hole (3) in a freely slidable manner; and a guide ring (8) attached to an opening (9) of the cylinder hole (3) and guiding sliding of the piston (5), the guide ring (8) has: a flange portion (8e) in a lower surface (8b) opposing the cylinder hole (3), the flange portion (8e) expanding in a radial direction of the guide ring (8); and bulged portions (8c) arranged at equally-spaced intervals to an outer circumferential surface (8d) of the guide ring (8) and each bulged outward in the radial direction of the guide ring (8) when compared to the flange portion (8e). When seen from a cross section in an axial direction (Ax) of the guide ring (8), each of the bulged portions (8c) has a tapered portion (8f) expanding in the radial direction of the guide ring (8) from the lower surface (8b) toward an upper surface (8a) of the guide ring (8).

BACKGROUND

The present invention relates to a brake hydraulic pressure control apparatus and, in particular, to a hydraulic pressure control apparatus including a cylinder hole that slidably accommodates a piston.

Conventionally, as a brake hydraulic pressure control apparatus, a brake hydraulic pressure control apparatus that has a master cylinder function integrated into a vehicle stabilization controller, to which an electromagnetic valve controlling a flow of a brake fluid and the like are attached, has been known. A base body of such a brake hydraulic pressure control apparatus is provided with a cylinder hole for accommodating a piston that slides according to input of a brake pedal by a driver.

SUMMARY

An opening of the cylinder hole is provided with a guide member for guiding sliding of the piston. There is a case where the guide member is integrally formed with the base body, and there is a case where the guide member is separately formed from the base body and the guide member is thereafter attached to the opening of the cylinder hole.

However, in the case where the guide member is integrally formed with the base body, the guide member is formed such that a part thereof is projected from the rectangular-parallelepiped base body. Thus, a facility for processing the guide member is separately required, which increases processing cost. For this reason, a method for creating the guide member in a separate step and thereafter attaching the guide member to the opening is frequently adopted.

Such a method is available that, in order to attach the guide member to the base body, the guide member is first press-fitted to the opening of the cylinder hole and is thus temporarily fixed thereto and the guide member is then caulked to the base body by plastically deforming the base body.

In order to accurately guide the piston by an inner diameter portion of the guide member and the cylinder hole, accurate coaxiality is requested. However, in the case where a fastening allowance between an outer diameter portion of the guide member and an inner diameter portion of the cylinder hole becomes larger than a predetermined value, sliding resistance against the cylinder hole is increased during press-fitting. As a result, such a problem occurs that surface treatment of the guide member is peeled or that the inner diameter portion of the guide member is deformed.

In order to prevent the above, a strict dimensional tolerance is requested for each of the outer diameter portion of the guide member and the inner diameter portion of the cylinder hole. However, as the dimensional tolerance becomes stricter, processing cost for the guide member is increased.

The present invention has been made in view of the above-described problem as the background and therefore has a purpose of improving a problem that occurs when the guide member is press-fitted to a cylinder hole.

A brake hydraulic pressure control apparatus according to the present invention includes: a base body that has a cylinder hole; a piston that is fitted to the cylinder hole in a freely slidable manner; and a guide ring that is attached to an opening of the cylinder hole and guides sliding of the piston. In the brake hydraulic pressure control apparatus, the guide ring has: a flange portion in a lower surface that opposes the cylinder hole, the flange portion expanding in a radial direction of the guide ring; and bulged portions that are arranged at equally-spaced intervals to an outer circumferential surface of the guide ring and each of which is bulged outward in the radial direction of the guide ring when compared to the flange portion. When seen from a cross section in an axial direction of the guide ring, each of the bulged portions has a tapered portion that expands in the radial direction of the guide ring from the lower surface toward an upper surface of the guide ring.

According to the present invention, it is possible to easily adjust coaxiality between an inner diameter portion of the guide ring and the cylinder hole, and to alleviate a problem of peeling of surface treatment of the guide ring, which is caused when the guide ring is temporarily fixed to the base body.

DETAILED DESCRIPTION

A description will hereinafter be made a brake hydraulic pressure control apparatus according to the present invention with reference to the drawings.

A description will be made on a case where the brake hydraulic pressure control apparatus according to the present invention is mounted to a four-wheeled vehicle. However, the brake hydraulic pressure control apparatus according to the present invention may be mounted to a vehicle (a two-wheeled vehicle, a truck, a bus, or the like) other than the four-wheeled vehicle. A configuration, operation, and the like, which will be described below, merely constitute one example, and the brake hydraulic pressure control apparatus according to the present invention is not limited to a case with such a configuration, such operation, and the like. In the drawings, the same or similar members or portions will be denoted by the same reference sign or will not be denoted by a reference sign. A detailed structure will appropriately be illustrated in a simplified manner or will not be illustrated.

A description will be made on a configuration and operation of a brake hydraulic pressure control apparatus1according to this embodiment.

FIG.1is a view illustrating an exemplary configuration of the brake hydraulic pressure control apparatus1according to the embodiment of the present invention.

As illustrated inFIG.1, the brake hydraulic pressure control apparatus1includes a rectangular-parallelepiped base body2having: a wheel cylinder hole23that communicates with a wheel cylinder; a valve hole24in which a valve for controlling a brake hydraulic pressure is inserted; a motor hole21in which a motor for driving a plunger (not illustrated) is inserted; and a cylinder hole3in which a piston5of the master cylinder is inserted.

InFIG.1, the wheel cylinder hole23and the motor hole21are arranged to a front surface22of the base body2, and the valve hole24is arranged to a back surface of the base body2.

The cylinder hole3that accommodates the piston5is arranged above side surfaces4of the base body2and extends from one of the side surfaces4to the other side surface4in a perpendicular to the side surfaces. InFIG.1, the cylinder hole3is arranged below the wheel cylinder hole23. However, a vertical position of the cylinder hole3can appropriately be changed, and depending on the arrangement of the valve hole24, the motor hole21, and the wheel cylinder hole23, the cylinder hole3may be positioned above the wheel cylinder hole23or below the motor hole21.

A guide ring8is attached to an opening9on the one side surface4side of the cylinder hole3and guides sliding of the piston5.

Next, a description will be made on operation of the piston5.

When a driver operates a brake pedal7, an operation force is transmitted to the piston5via a piston rod6. When the larger operation force than an urging force of the spring10(seeFIG.2), which is arranged in the cylinder hole3and urges the piston5rightward, is transmitted to the piston5, the piston5moves leftward while being guided by the guide ring8and an inner wall of the cylinder hole3. When the operation force becomes smaller than the urging force of the spring10, the piston5moves rightward by the urging force of the spring10. In this way, the piston5can move in the cylinder hole3in a freely slidable manner.

FIG.2(a)is a cross-sectional view of the piston5and the base body2around the piston5.

The piston5has a substantially cylindrical shape, and a bottom portion of a bottomed hole5athat is opened to a right side is connected to a top portion of the piston rod6. The top portion of the piston rod6is formed in a ball shape, and the piston rod6can move vertically with the top portion being a fulcrum.

The piston5has a bottom hole5bthat has an opening on a left side, and a bottom portion of the bottomed hole5bis connected to an end of the spring10.

An annular groove11is formed in the inner wall of the cylinder hole3, and a seal member12is inserted in the annular groove11. The seal member12prevents a brake fluid filled in the cylinder hole3from leaking out of the base body2. In the example inFIG.2(a), the three annular grooves11are provided at equally-spaced intervals in an axial direction of the cylinder hole3, and the seal member12is inserted in each of the annular grooves11.

The opening9of the cylinder hole3is formed as a step portion that has a larger diameter than an inner diameter of the cylinder hole3. The opening9is provided with the guide ring8that is coaxially attached with an axis of the cylinder hole3and guides the piston5.

FIG.2(b)is a perspective view of the guide ring8.

The guide ring8has a ring shape, and has: a lower surface8bthat opposes the cylinder hole3at the time of being assembled to the base body2; an upper surface8athat faces an outer side of the base body2at the time of being assembled to the base body2; and a side wall that connects the upper surface8aand the lower surface8b.

The guide ring8also has a bulged portion8cin an outer circumferential surface8dof the side wall. The bulged portion8cbulges in a radial direction of the guide ring8. The plural bulged portions8care arranged at equally-spaced intervals in a circumferential direction of the guide ring8, and are integrally formed with the side wall. InFIG.2(b), each of the bulged portions8cis formed as a substantially rectangular-parallelepiped raised portion, and a tapered portion8f(seeFIG.4) is formed on the lower surface8bside of the guide ring8. The tapered portion8fexpands in the radial direction of the guide ring8from the lower surface8btoward the upper surface8a.

The guide ring8further has a flange portion8eon the lower surface8b, and the flange portion8eextends in the radial direction of the guide ring8. Together with the lower surface8b, the flange portion8eforms a flat surface of the guide ring8, and comes into contact with the step portion of the opening9at the time of being attached to the base body2, so as to position the guide ring8with the axial direction of the cylinder hole3.

A terminal end8f1on an upper surface side of the tapered portion8fin the bulged portion8chas a larger diameter than the flange portion8e(seeFIG.4). This is a necessary configuration for temporarily fixing the guide ring8to the opening9of the cylinder hole3by the bulged portion8c, and a detailed description thereon will be made below.

FIG.3is a view in which a state where the guide ring8is attached to the base body2is seen from the axial direction of the cylinder hole3.

InFIG.3, the bulged portions8care arranged to be point-symmetric about a center14of the guide ring8. Similarly, fixed portions8h, each of which is arranged between the two adjacent bulged portions8c, are also arranged to be point-symmetric about the center14of the guide ring8. InFIG.3, four each of the bulged portions8cand the fixed portions8hare provided.

Next, a description will be made on a process of fixing the guide ring8to the base body2.

First, the guide ring8is press-inserted in the opening9of the cylinder hole3and is thereby temporarily fixed to the base body2. The guide ring8including the bulged portion8cis formed to have slightly larger diameter RdA-A(seeFIG.4) than the diameter of the opening9. Thus, when the guide ring8is inserted in the opening9, the bulged portion8cis partially subjected to plastic deformation, and the guide ring8is temporarily fixed to the opening9. At the same time, the cylinder hole3and the guide ring8are adjusted such that the axes thereof become coaxial. Meanwhile, the guide ring8including the flange portion8eis formed to have a slightly smaller diameter RdB-B(seeFIG.4) than the diameter of the opening9. Thus, when the guide ring8is inserted in the opening9, the flange portion8edoes not interfere with an inner wall of the opening9, and the guide ring8can temporarily be fixed to the base body2.

After the guide ring8is temporarily fixed to the base body2, a part of the base body2therearound is subjected to the plastic deformation, and the fixed portion8hof the guide ring8between the two adjacent bulged portions8cis covered with the part of the base body2. In this way, the guide ring8is caulked to the base body2.

FIG.4(a)illustrates a cross section that is taken along A-A inFIG.3, andFIG.4(b)illustrates a cross section that is taken along B-B inFIG.3.

As illustrated inFIG.4(a), the bulged portion8cis formed with the tapered portion8fthat expands in the radial direction of the guide ring8from the lower surface8btoward the upper surface8aof the guide ring8when seen from a cross section in an axial direction Ax of the guide ring8.

In the press-insertion process of the guide ring8, in which the guide ring8is temporarily fixed to the base body2, the plastic deformation of the bulged portion8cis initiated from the upper surface-side terminal end portion8f1of the tapered portion8f. Accordingly, compared to a case where the bulged portion8cis not provided with the tapered portion8f, it is possible to suppress a press-insertion stroke dpf. Thus, it is possible to suppress occurrence of contamination that is caused by peeling of surface treatment of the guide ring8resulting from the plastic deformation of the bulged portion8c.

An angle of the tapered portion8fand an axial position of the upper surface-side terminal end portion8f1are appropriately adjusted in consideration of required temporary fixing strength of the guide ring8, ease of adjustment of the coaxiality between the cylinder hole3and the guide ring8, and the like.

FIG.4(b)illustrates a cross-section of the guide ring8including the flange portion8e.

Similar to the bulged portion8c, the flange portion8eis formed with a tapered portion8gthat expands in the radial direction of the guide ring8from the lower surface8btoward the upper surface8aof the guide ring8when seen from the cross section in the axial direction Ax of the guide ring8. In this way, it is possible to avoid the interference with the opening9at the time of inserting the guide ring8in the opening9and to easily assemble the guide ring8.

As illustrated inFIG.4(b), a slight clearance dcris formed between a part of the flange portion8ewith the largest diameter and the opening9. Accordingly, the problems such as peeling of the surface treatment in the flange portion8eat the time of inserting the guide ring8in the opening9do not occur.

In addition, after the guide ring8is temporarily fixed to the opening9, the fixed portions8hof the guide ring8is fixed by plastically deforming a portion2aof the base body2around the opening9. In this way, the guide ring8is firmly fixed to the base body2.

As it has been described so far, according to the brake hydraulic pressure control apparatus in the invention of the present application, the following effects can be exerted.

Since the bulged portion8cis formed with the tapered portion8f, it is possible to suppress the press-insertion stroke dpfto be small, which in turn can suppress peeling of the surface treatment of the guide ring8, which is caused by sliding resistance against the opening9at the time of inserting the guide ring8therein, and the like.

Since the diameter of the flange portion8eis smaller than the diameter of the opening9of the cylinder hole3, it is possible to prevent the occurrence of the contamination from the flange portion8eat the time of inserting the guide ring8.

Since the flange portion8eis formed with the tapered portion8g, it is possible to reduce the possibility of the interference with the inner wall of the cylinder hole3at the time of inserting the guide ring8in the opening9and to facilitate the assembly of the guide ring8.

Since the bulged portion8cis arranged to be point-symmetric about the center14of the guide ring8, it is possible to stabilize temporary fixing of the guide ring8and enhance the coaxiality between the axial direction of the cylinder hole3and the axial direction Ax of the guide ring8.

REFERENCE SIGNS LIST