GB2225396A

GB2225396A - Disc brake mounting structure

Info

Publication number: GB2225396A
Application number: GB8923405A
Authority: GB
Inventors: Hiromichi Matsui
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1988-10-21
Filing date: 1989-10-17
Publication date: 1990-05-30
Also published as: JPH0258126U; GB8923405D0

Abstract

A disc brake mounting structure S fixedly connects one caliper 1B of a disc brake to a steering knuckle or an axle housing. The caliper 1B is formed with an installation section 10 which is connected to a mounting member 13a forming part of the steering knuckle 13. The installation section 10 is made of aluminum alloy and formed with a through-hole 12. A steel insert bushing 11 is press-fitted in the hole 12 and has an internal thread 21. A mounting bolt 20 is screwed into the bushing 11 to be engaged with the internal thread 21 and into a hole 14 of the mounting member 13a, thereby accomplishing a tight connection between the caliper installation section 10 and the mounting member 13a. The bushing 11 is provided with an annular serration 16 and areas on either side of the serration into which aluminum alloy under plastic deformation is relieved. <IMAGE>

Description

DISC BRAKE MOUNTING STRUCTURE The present invention relates to improvements in a disc brake mounting structure through which a disc brake is mounted on a member in connection with road wheels of a vehicle, and more particularly to the disc brake mounting structure in which at least one of a member forming part of a disc brake and a member in connection with the road wheels is made of a light alloy.

It is well known that a disc brake includes a brake caliper in which a brake piston is disposed to be slidably movable under hydraulic pressure. The brake piston is provided with a friction pad which is to be pressed against the surface of a rotor rotating with a road wheel. The brake caliper is integrally formed with an installation section which has a bolt hole formed with an internal thread. A mounting bolt is screwed into this bolt hole and into a steering knuckle which is a member in connection with road wheels, thereby fixedly mounting the brake caliper onto the steering knuckle. Such a disc brake mounting structure is disclosed, for example, in "Porsche 930-turbo Repairing Manual (Reparaturleitfaden), 1978".

In recent years, there has been a tendency that aluminum alloy is used as the material of a steering knuckle and/or an axle housing in connection with road wheels, and a brake caliper in connection with a disc brake. However, aluminum alloy is low in shear strength as compared with cast iron or the like, and therefore the axial length (the engagement length of a mounting bolt) of a mounting structure of the caliper made of aluminum alloy is required to be larger than in case the caliper is made of cast iron.

In other words, a predetermined connection strength is difficult to be obtained if the axial length of the mounting structure is not enlarged. This causes the width of the mounting structure to be increased, which results in degraded mounting characteristics of the disc-brake on a vehicle.

Additionally, when the external thread of the mounting bolt is brought into engagement with the internal thread of the mounting section of the brake caliper, a slight engagement clearance is formed therebetween. When water penetrates into the slight engagement clearance, electrochemical reaction is carried out there since aluminum and iron are different in ionization tendency. As a result, aluminum unavoidably dissolves out. This will cause loosening of the brake caliper.

What is desired is a- disc brake mounting structure which is highly convenient to be mounted on a vehicle and prevents electrocorrosion thereof.

It would also be desirable for the mounting structure to be smaller in dimension and prevent formation of a clearance through which water penetrates.

A disc brake mounting structure of the present invention is comprised of an installation section of a caliper of a disc brake. The caliper is fixedly supported by a mounting member in connection with a road wheel. At least one of the caliper installation section and the mounting member is made of light alloy. The above-mentioned at least one made of light alloy is formed with a hole. A cylindrical bushing made of steel is press-fitted in the hole and formed with an internal thread. A mounting bolt is engaged with the insert bushing internal thread to tightly connect the cylindrical insert with the mounting member.

By virtue of the press-fitted steel insert bushing, no clearance is formed between it and the light alloy of the caliper installation section and/or mounting member in connection with the road wheel. This prevents water from penetrating into the clearance thereby avoiding electrocorrosion in the disc brake mounting structure. Additionally, since the steel insert bushing is high in shear strength, a bolt engagement length to obtain a predetermined connection strength is shortened, thereby facilitating mounting of the disc brake on a vehicle body.

Fig. 1 is a vertical sectional view of an essential part of a disc brake assembly incorporating an embodiment of a disc brake mounting structure according to the present invention; Fig. 2 is a cross-sectional view of an insert bushing forming part of the disc brake mounting structure of Fig. 1; Fig. 3 is a fragmentary sectional view taken in the direction of arrows substantially along the line III-III of Fig. 2; and Fig. 4 is a vertical sectional view of an essential part of the disc brake mounting structure of Fig. 1.

Referring now to Figs. 1 to 4 of the drawings, there is shown an embodiment of a disc brake mounting structure S in accordance with the present invention.

The disc brake mounting structure S is used in combination with a disc brake assembly whose essential part is represented by the reference character D. The disc brake essential part D includes a caliper body 1 made of aluminum alloy.

The caliper body 1 includes outer and inner calipers 1A, 1B. Each caliper 1A, 1B is formed with a cylindrical chamber 2 in which a piston 3 is disposed axially slidably movable. A piston seal 4 is provided to accomplish seal between the piston 3 and the caliper 1A, 1B. A pair of pistons 3, 3 are located coaxially and opposite to each other. A friction pad 5 is fixedly attached to an axial end of each piston 3, so that a rotor R is rotatably disposed between a pair of opposite friction pads 5, 5. The inner caliper 1B is formed at its side-wall with a pipe connector port 8 to which a pipe (not shown) is connected to supply hydraulic fluid into the cylindrical chambers 2, 2. The reference numeral 6 designates a retaining ring, and 7 a piston boot.

The inner caliper 1B is formed integrally with an installation section 10 through which the caliper 1B is fixedly connected to a vehicle body (not shown). The installation section 10 projects from the inner caliper 1B and is formed with a generally cylindrical through-hole 12 whose axis is parallel with the axis of the pistons 3, 3. The through-hole 12 is formed generally corresponding to a caliper mounting hole 14 which is formed in the mounting section 13a of an axle housing or a steering knuckle 13.

A generally cylindrical insert bushing 11 made of steel is formed integrally with an annular flange 15 which is located at an axial end section of the insert bushing 11. The annular flange 15 is coaxial with the axis of the insert bushing 11 and extends radially outwardly. As shown in Figs. 2 and 3, the insert bushing 11 is formed at its outer peripheral surface with annular serration 16 which are coaxial with the axis of the insert bushing 11. The annular serration 16 is located generally at the axially intermediate section of the insert bushing 11. Each straight serration tooth 16a extends parallel with the axis of the insert bushing 11. Annular ranges 17, 18 located on the opposite sides of the serration 16 are formed slightly depressed relative to the annular serration 16 as clearly seen from Fig. 2.

The annular ranges 17, 18 form part of the outer peripheral surface of the insert bushing 11 and coaxial with the axis of the insert bushing 11.

These annular ranges 17, 18 serve as relief recesses into which aluminum alloy under plastic deformation is relieved as shown in Fig. 4. The insert bushing 11 is formed with a threaded bore 19 which axially passes therethrough, so that the inner surface of the inserting bushing 11 is formed with at its inner surface with an internal thread 21 with which a mounting bolt 20 is to be engaged.

The function of the above-arranged disc brake mounting structure S will be discussed hereinafter.

When the insert bushing 11 made of steel is press-fitted into the through-hole 12 of the installation section 10 of the inner caliper 1B made of aluminum alloy, the aluminum alloy makes its plastic deformation. An excessive part corresponding to a deformed amount of the aluminum alloy is relieved or protruded onto the annular ranges (relief recesses) 17, 18 which are formed on the opposite sides of the annular serration 16 of the insert bushing 11, while the press-fitted annular serration 16 is brought into tight contact with the aluminum alloy of the inner caliper installation section 10.

As a result, no clearance is formed between the inner surface of the installation section through-hole 12 and the outer surface of the insert bushing 11.

Assuming that there is a clearance between the surface of the installation section 10 and the surface of the insert bushing 11, water penetrates into the clearance and serves as a medium for electrocorrosion. In other words, when aluminum alloy having a higher ionization tendency is brought into contact with iron having a lower ionization tendency through water, electrochemical reaction occurs so that free electrons move between aluminum alloy and iron with water serving as a medium, resulting in dissolving aluminum alloy out.

In contrast, according to the present invention, there is no clearance between the installation section 10 and the insert bushing 11, and therefore electrocorrosion cannot occur in the caliper mounting section 10 made of aluminum alloy.

During joining the inner caliper installation section 10 with the mounting section 13a of the axle housing 13 or the like, the threaded bore 19 of the insert bushing 11 is brought into coincidence with the caliper mounting hole 14 of the mounting section 13a. In this state, the mounting bolt 20 is screwed into the caliper mounting hole 14 and the threaded bore 19, thereby tightly connecting the axle housing mounting section 3a and the caliper installation section 10 through the insert bushing 11. In this connection, since the insert bushing made of steel is higher in shear strength, a predetermined strength of connection between the installation and mounting sections 10, 13a can be obtained with a relatively small bolt engagement length although the caliper mounting section 10 is made of aluminum alloy. In other words, the bolt engagement length can be minimized according to the present invention. Such a minimized bolt engagement length allows the width of the caliper installation section 10 made of aluminum alloy to be made smaller, thereby facilitating mounting of the disc brake assembly on the vehicle body.

While the principle of the present invention has been shown and described to be applied to a structure in which only the caliper side is made of aluminum alloy, it will be understood that the principle of the present invention may be applied to a case in which only the side in connection of road wheels is made of aluminum or to a case in which both the caliper side and the side in connection with road wheels are made of aluminum alloy.

Claims

- CLIKS:

1. A disc brake mounting structure comprising: an installation section of a caliper of a disc brake; a mounting member in connection with a road wheel, said mounting member fixedly supporting said caliper; means defining a hole in at least one of said caliper installation section and said mounting section, said at least one section being made of light alloy; a cylindrical insert bushing made of steel and press-fitted in said hole, said insert bushing being formed at its inner peripheral surface with an internal thread; and a mounting bolt engaged with said insert bushing internal thread to tightly connect said insert bushing with said mounting member.

2. A disc brake mounting structure as claimed in Claim 1, wherein said insert bushing includes means defining an annular serration at outer peripheral surface of said insert bushing, said annular serration being coaxial with axis of said insert bushing, and means defining an annular recess at the outer peripheral surface of said insert bushing, said annular recess being formed adjacent said serration and radially inward relative to said serration, aluminum being relieved to said annular recess during press-fitting of said insert bushing into said hole of said at least one of said caliper installation section and said mounting section.

3. A disc brake mounting structure as claimed in Claim 2, wherein said annular recess defining means includes means defining first and second annular recesses which are formed at the outer peripheral surface of said insert bushing and located adjacent the annular serration, said first and second annular recesses being located on opposite sides of said annular serration.

4. A disc brake mounting structure as claimed in Claim 1, wherein said light alloy is aluminum alloy.

5. A disc brake mounting structue as claimed in Claim 2, wherein said insert bushing includes means defining an annular flange formed at one end of said insert bushing, said annular flange being coaxial with the axis of said insert bushing and radially outwardly extends, said annular flange being brought into contact with said at least one of said caliper installation section and said mounting member.

6. A disc brake mounting structure as claimed in Claim 5, wherein said annular flange is located such that one of said caliper installation section and said mounting member is put between said annular flange and the other of them.

7. A disc brake mounting structure comprising: an installation section of a caliper of a disc brake, said installation section being made of aluminum alloy; a mounting member in connection with a road wheel, said mounting member fixedly supporting said caliper; means defining a hole in said caliper installation section; a cylindrical insert bushing made of steel and press-fitted in said hole, said insert bushing being formed with an internal thread; and a mounting bolt connecting said installation section and said mounting member, said mounting bolt being engaged with the internal thread of said insert bushing.

8. A disc brake mounting structure substantially as described with reference to, and as shown in, the accompanying drawings,