DISK BRAKE CALIPER HAVING RE-ENFORCING BRIDGE

By Warren L. Gilliland Attorney Docket No. R07-03-4293 CLAIM OF PRIORITY

This application claims priority to U.S. Applications Serial Nos. 11/562,333, filed November 21, 2006 and 11/399,573, filed April 6, 2006.

BACKGROUND OF THE INVENTION

This invention relates generally to a vehicular disk brake apparatus and more particularly to the brake caliper thereof, which has a reinforced bridge for reducing load.

In general, a vehicular or automotive brake operates on a hydraulic system, in which the depression of a brake pedal causes a plunger in the master cylinder to push hydraulic fluid to a braking unit at the wheels. A disk brake is one kind of braking unit. In a conventional opposed caliper disk brake, a fixed caliper straddles a rotor, which is attached to the wheel. In a floating caliper disk brake, the caliper urges piston or pistons on one side of the rotor to apply a pad, while at the same time pushing the caliper housing away from the rotor, drawing the outboard pad up to the rotor. In either case, when fluid from the master cylinder is introduced into the caliper, it urges one or more pistons in the caliper to apply brake pad(s) against the rotor, thereby effectuating a braking force on the rotor and causing the wheel to slow down or stop.

A typical caliper is formed in the shape of a clam for straddling the rotor. Current designs either utilize a one piece housing, or two pieces, slit over the top of the rotor and held together by bolts. In straddling the rotor, one member is disposed on the inboard side of the rotor

and the other member is disposed on the outboard side of the rotor. The members have piston(s) disposed therein.

A basic problem in calipers of this type is that they are subject to high shearing and bending forces, with the load bearing on the bridge section. When such forces are transmitted through the caliper, they act to spread the caliper apart like a clam, a phenomenon often referred to as the "clam shell" effect. The result is decreased braking efficiency, as some of the force generated by the master cylinder is lost in the spreading of the caliper, and there is also the consequent effect of increasing pedal travel, tapered pad wear, spongy pedal and loss of modulation.

To minimize this deflection, caliper designs have typically utilized either a monoblock or a bolting design. For example, in a monoblock caliper, the caliper is formed from a solid body with a bridge section integrally joining the inboard and outboard members of the caliper housing. This type of caliper requires a rather massive bridge section to effectively reduce the clam shell effect that causes the caliper to open at the bottom. A massive bridge is undesirable, however, as it gets in the way of maximizing the rotor diameter.

In a caliper where the members are connected by bolts, as shown in FIG. 1, there is still a clam shell effect, resulting in the pad cocking with respect to the rotor face, which causes an increase in pad drag and wear, and a decrease in braking efficiency. The key stress area of a caliper is typically within the pad boundaries, within the pistons. Although the use of a bolting connection may limit the growth of the outer portion of the caliper, it does nothing to stop the deflection below. In other words, the bottom of the caliper is free to open, and when subjected to high pressures, will still clamp back down on the rotor causing the pad to attempt to wedge into the rotor, causing taper.

For the foregoing reasons, there is a need for a disk brake assembly having a brake caliper that is sufficiently stiff to reduce the clam shell effect. SUMMARY OF THE INVENTION

The present invention is directed to an improved brake caliper that satisfies the need for reducing the clam shell effect. A disk brake apparatus having the features of the present invention comprises a rotor and a brake caliper for applying braking force to the rotor. The brake caliper is basically comprised of a first housing member and second housing member straddling the rotor, with the first and second members connected by a bridge. The caliper housing members have actuating pistons disposed therein, with brake pads associated therewith for engaging the rotor.

The bridge is generally comprised of one or more cross members and associated anchors. For example, in an embodiment shown in FIG. 3, the bridge is formed in the shape of the letter "C" with a cross member and two anchor members. As shown in the embodiment, the anchor members are downward turning arms. This type of bridge is generally referred to as a C-section bridge because of its shape. In this type of bridge, the arms can be integrally formed with respect to the cross member, or they can be separate members fixedly connected to the cross member.

Further, it is to be understood that while the C-section shape is one of the preferred embodiments, the bridge can take a variety of forms and shapes that incorporate the basic combination of cross member and associated anchors. As an example, the bridge can be comprised of a cross member and anchor plates. As another example, the bridge can take the shape of the letter "Y" with two anchor arms spread at an angle and joined by a vertical member. Moreover, the cross member can take various shapes, such as tubular or, as shown in figure FIG.

3, rectangular. In short, various modifications of the bridge may be contemplated without departing from the spirit and scope of the invention as defined by the claims below.

The bridge, as such, provides structural support for the caliper housing members. The caliper housing is commonly made of low tensile strength materials in order to reduce weight, as the weight of the caliper, which tends to be relatively heavy, can affect the operation and suspension of the chassis. However, a low strength caliper will have low load capacity and low structural stiffness. The C-bridge provides structural rigidity by using high tensile strength materials, creating a "bending moment" situation, which improves support to the low strength caliper housing members. By using high strength materials only where needed, the strength of the caliper can be maximized while still minimizing weight.

One key advantage of the present invention to be noted is the use of high tensile strength anchors (i.e. the downward turning arms) in between the pistons of the caliper, especially as assembled to the center portion of the caliper. The use of high strength downward turning arms allows for a stronger bridge design to reduce deflection.

Structurally, the first and second members each have at least one channel provided therein respectively for receiving the anchor members of the bridge, and at least one hole formed therein respectively in substantial alignment with the channels. The bridge has at least two holes formed in the anchor members. The bridge anchor members are capable of fitting flush in the channels of the first and second members, such that the holes in the bridge anchor members coaxially align with the holes in the first and second members. A securing means, such as a bolt, capable of passing through the holes in the first and second caliper housing members and engaging the holes in the bridge, acts to secure the first member and second member to the bridge.

In another embodiment of the brake caliper, the first and second members are secured by a plurality of bridges. Accordingly, the first and second members include a plurality of channels therein for receiving the anchor members of the bridges and a plurality of holes and securing means for connected the bridges to the first and second members.

In yet another embodiment of the invention, first and second members of the brake caliper do not have channels formed therein. Instead, the outside face of the bridge abuts the inside face of the first and second members, such that the holes in the bridge coaxially align with the holes the in first and second members. In this embodiment, the bridge extends into the pad area between the housing members. As such, the bridge could provide additional pad support and retention. This would increase the center rigidity by increasing the cross-section thickness.

An advantage of using a bridge such as the C-section is that it provides superior rigidity, which correspondingly would require less master cylinder volume to fill the pistons since deflection in the caliper is reduced.

In another embodiment of the invention as shown in FIG. 6, an E-section bridge connects the first and second housing members. In contrast to a C-section bridge, this type of bridge can be referred to as an E-section cage because of its profile. The E-section cage as shown has a top rectangular frame that includes two side members joined at the midpoint by a one cross member, with the respective ends of the side members connected by endplates. The profile of the rectangular frame with the two endplates and the midpoint anchor can be described as forming an E-section. At the midpoint of each respective side member where the cross member is connected, each side member is connected to a downward anchor. The two respective downward anchors are not unlike the anchors on the C-section bridge in that each anchor has at least one hole formed therein to be in substantial alignment with corresponding holes on the first and

second housing members. Similarly, integral to the outside face of each respective endplate is a recessed shoulder block having at least one hole formed therein to be in substantial alignment with corresponding holes on the first and second housing members. The center portion of each endplate is cut-out to reduce weight, with the endplate tabbed on the bottom edge as shown.

In the embodiment shown in FIG. 6, the inboard surface of each respective housing member is recessed in relation to the raised shoulders of the housing member. The recessed inboard surfaces of the first and second housing members are such that the endplates and anchors on the rectangular frame of the E-section cage fit between the recessed surfaces when first and second housing members are assembled. When the E-section cage is fitted between the first and second housing members, the recessed shoulder blocks on the endplates fit with the raised shoulders on the first and second housing members. Securing means, such as bolts, capable of passing through the holes in the first and second housing members and engaging the corresponding holes in the anchors and shoulder blocks of the E-section cage, act to secure the first and second housing members to the E-section cage as shown in FIG. 6.

In other contemplated embodiments of the invention, the rectangular frame may include more than two side members or multiple cross members. For example, the rectangular frame may include two side members joined by two cross members with or without endplates. In yet another alternative embodiment, the rectangular frame may include two side members connected by endplates but without a cross member.

An advantage of the E-section cage is that it provides even greater structural rigidity than the C-section bridge because of the rectangular frame. The shoulder blocks on the rectangular frame allow the first and second housing members to be connected at the shoulders in addition to being connected at the anchors at the midpoint of the rectangular frame, resulting in greater

overall rigidity. Hence, the E-section cage allows the mechanical stress to be spread over the body of the cage, with much of the load taken by the shoulder blocks on the rectangular frame, thereby further reducing deflection in the caliper. The greater rigidity of the cage is achieved without sacrificing efficient heat ventilation because of the frame structure and the cut-out in the endplates.

DRAWINGS

FIG. 1 is a perspective view of a prior art brake caliper.

FIG. 2 is a perspective view of a brake caliper according to an embodiment of the present invention.

FIG. 3 is a partially exploded perspective view of the brake caliper according to an embodiment of the present invention.

FIG. 4 is a cross-section view of an embodiment of the present invention.

FIG. 5 is a perspective view of an embodiment of the present invention.

FIG. 6 is a partially exploded perspective view of the brake caliper according to another embodiment of the present invention.

DETAILED DESCRIPTION

A preferred embodiment of a brake caliper is shown in FIGS. 2 and 3. Referring to FIG. 2, the brake caliper 10 has first member 12 and second member 14 straddling the rotor (not shown), with first and second members 12, 14 connected by a bridge 16. FIG. 2 shows brake caliper 10 with bridge 16 connected to first and second members 12, 14. FIG. 3 shows a partially exploded view of brake caliper 10 with bridge 16 unconnected to first and second members 12, 14. It is to be noted that although FIGS. 2 and 3 show a C-section bridge 16, the

bridge can take a variety of form and shape that incorporate the basic combination of cross member and associated anchors.

Referring to FIG. 3, C-section bridge 16 is generally comprised of a cross member 16a and associated anchor arms 16b and 16c. The C-section bridge 16 has at least one hole 16d in arm 16b and at least one hole 16e in arm 16c. The first member 12 has at least one channel 18 provided therein for receiving arm 16b of C-section bridge 16, and at least one hole 20 formed therein in substantial alignment with channel 18. Likewise, second member 14 also has at least one channel 22 provided therein for receiving arm 16c and also at least one hole 24 (as shown in FIG. 4) formed in substantial alignment with channel 22. Referring to FIGS. 3 and 4, the anchor arms 16b, 16c of C-section bridge 16 are capable of fitting flush in channels 18, 22 of first and second members 12, 14, such that holes 16d, 16e in C-section bridge 16 coaxially align with holes 20, 24 in first and second members 12, 14. A securing means 26 passing through holes 20, 24 and engaging holes 16d, 16e secures first member 12 and second member 14 to C-section bridge 16.

First and second members 12, 14 can also be secured by a plurality of C-section bridges 16 as shown in FIG. 5. Accordingly, first and second members 12, 14 would include a plurality of channels 18, 22 therein for receiving anchor arms 16b, 16c, and a plurality of holes 20, 24 for securing means 26 to connect C-section bridges 16 to first and second members 12, 14.

In another embodiment of the invention, first and second members 12, 14 of brake caliper 10 do not have channels 18, 22 formed therein. Instead, the outside face of C-section bridge 16 abuts the inside face of first and second members 12, 14, such that holes 16d, 16e in C-section bridge 16 coaxially align with holes 20, 24 in first and second members 12, 14.

Another embodiment of the invention is shown in FIG. 6. Referring to FIG. 6, an E- section cage 30 connects the first and second housing members 12, 14. In contrast to the C- section bridge 16 shown in FIG. 3, this type of cage can be described as an E-section because of its profile. The E-section cage 30 has a top rectangular frame 32 which includes two side members 34, 36 joined approximately at the midpoint by a cross member 38. At the midpoint of each respective side member 34, 36 where the cross member 38 is connected, each side member 34, 36 is connected to a downward anchor 40. The two respective downward anchors 40 are not unlike the anchors on the C-section bridge 16 in that each anchor 40 has at least one hole 40a formed therein to be in substantial alignment with holes 20 on the first and second housing members 12, 14. The respective ends of the side members 34, 36 are connected by endplates 42. It should be noted that the center portion of each endplate 42 can be cut-out to reduce weight as shown in FIG. 6, with the endplate 42 tabbed on the bottom edge as shown. Integral to the outside face of each respective endplate 42 is a shoulder block 44 that is recessed with respect to the side edges of endplate 42. Each shoulder block 44 has at least one hole 44a formed therein to be in substantial alignment with holes 44b on the first and second housing members 12, 14.

In the preferred embodiment as shown in FIG. 6, the inboard surface of each respective housing member 12, 14 is recessed in relation to the raised shoulders of housing member 12, 14. The recessed inboard surfaces of first and second housing members 12, 14 are such that the endplates 42 and anchors 40 on rectangular frame 32 of E-section cage 30 fit between the recessed surfaces when first and second housing members 12, 14 are assembled. When rectangular frame 32 of E-section cage 30 is fitted between the recessed surfaces of first and second housing members 12, 14, the recessed shoulder blocks 44 on endplates 42 fit with the raised surfaces of the shoulders on first and second housing members 12, 14. A securing means,

such as a bolt, capable of passing through holes 20 in first and second housing members 12, 14 and engaging holes 40a in anchors 40, acts to secure first and second members 12, 14 to E- section cage 30. In addition, other securing means, capable of passing through holes 44b in first and second housing members 12, 14 and engaging holes 44a in shoulder blocks 44 of E-section cage 30, act to further secure first and second members 12, 14 to E-section cage 30.

The embodiments described herein demonstrate an improved brake caliper having reinforced bridge. This brake caliper design will reduce the clam shell effect. Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein.