Multipot type disk brake

If cylinder bores formed in a caliper parallel to each other are communicated together through a pipe casted in the caliper, the pipe tends to come out of the caliper into a cylinder bore. A separate short pipe is provided to communicate the cylinder bores. The pipe has an engaging portion so as to extend in a diametric direction of the short pipe to prevent longitudinal shift of the short pipe. The engaging portions can be provided easily by forming a recess or a protrusion on the outer periphery of the pipe and casting the pipe in the caliper.

BACKGROUND OF THE INVENTION 
This invention relates to a multipot type disk brake having a plurality of 
pistons to press at least one of a pair of opposed friction pads. 
Multipot type disk brakes are disclosed e.g. in unexamined Japanese patent 
publications 5-293626 and 9-177843. Such brakes have a brake fluid supply 
passage defined by a pipe casted in the caliper. 
Such disk brakes have merits that no machining is needed to form the fluid 
passage, that greater freedom of layout of the fluid passage is obtained 
(which makes it possible to reduce the resistance to the flow through the 
passage and thus provide smooth flow of brake fluid), and that it is 
possible to reduce the wall thickness, weight and size of the caliper by 
reinforcing the caliper with the pipe. 
Multipot type disk brakes include a caliper having a plurality of cylinder 
bores, and pistons each inserted in the respective cylinder bores for 
pressing at least one of a pair of opposed friction pads. The other 
friction pad is pressed i) by an outer claw of the caliper (with floating 
type disk brake), ii) by a single piston, or iii) by a plurality of 
pistons (with opposed-piston type disk brakes). 
In an arrangement in which the fluid passage in the caliper is defined by a 
pipe casted in the caliper through which the cylinder bores communicate 
with each other, if the pipe is provided behind the cylinder bores and 
brake fluid is supplied to the cylinder bores through holes extending from 
the pipe to the respective cylinder bores, as disclosed in unexamined 
Japanese patent publication 5-293626, the thickness from the bottoms of 
the cylinder bores to the outer surface of the caliper tends to be large, 
thus unduly increasing the thickness of the caliper. Thus, as an 
alternative measure, arranging a pipe 3 across the cylinder bores 2 has 
been proposed. 
But in this arrangement, in which the pipe 3 has a short pipe 3a separated 
from the remaining pipe portion by the cylinder bores 2, the following 
problems are expected. 
If the short pipe 3a is not bonded strongly to the caliper 1 when the 
former is casted in the latter, or if interfacial peeling occurs between 
the pipe and the caliper due to a difference in thermal expansion 
coefficient between the materials of the pipe and the caliper or 
vibrations during finishing, the pipe 3a may shift longitudinally in the 
hole 4. In the worst case, the pipe may come out of the hole 4, dropping 
into the cylinder bore 2 at one or the other side therof. 
Even if this happens, brake fluid can be supplied smoothly. But the pipe in 
the cylinder bore 2 can damage the outer periphery of a piston (5 in FIG. 
1), or make it impossible to push back the piston to the original position 
to replace a friction pad which has worn. 
An object of this invention is to prevent shift and dropout of a pipe 
casted in the caliper in a simple manner. 
SUMMARY OF THE INVENTION 
According to this invention, there is provided a multipot type disk brake 
which has an opposed pair of friction pads and a plurality of pistons and 
at least one of the friction pads is pressed into frictional contact with 
a disk rotor by the pistons, a caliper formed with cylinder bores parallel 
to each other, the pistons being mounted in the respective cylinder bores, 
the cylinder bores communicating with each other through a fluid passage 
formed in the caliper, and wherein the fluid passage is defined by a pipe 
casted in the caliper so as to extend between the cylinder bores and 
communicate the cylinder bores with each other, 
characterised in that the pipe has a projection or recess in a diametric 
direction so as to closely engage with the caliper. 
In another embodiment of the present invention, the pipe has cutouts so as 
to be disposed at bottoms of the cylinder bores. 
The cutouts of the pipe should be retracted from the inner wall of the 
cylinder bore. 
The engaging portions provided on the pipe can be formed by casting in the 
caliper a pipe having a projection or a recess on or in the outer 
periphery of the pipe. 
The engaging portions provided on the pipe engage the pipe with the caliper 
each other, preventing longitudinal shift of the pipe. Thus, even if the 
pipe shifts slightly due e.g. to weak bonding between the caliper and the 
pipe, the pipe will not come out or drop out of the hole formed by the 
pipe. 
In the arrangement in which the pipe is provided to extend across the 
bottoms of the cylinder bores, the bent portions at both sides of the pipe 
engage the caliper, keeping the pipe in position. Even if the pipe shifts 
slightly, the pipe will never drop out because the pipe is a one-piece 
member. 
Since the pipe ends are retracted from the inner walls of the cylinder 
bores, the pipes will not hinder the sliding movement of the pistons.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a disk brake embodying this invention, which is an 
opposed-piston type disk brake. 
This disk brake includes a caliper 1, which comprises inner and outer 
calipers 1a and 1b separately formed of aluminum alloy or cast iron and 
coupled together by bolts (not shown). 
The inner and outer calipers 1a and 1b are formed with a plurality of (two 
in the embodiment) cylinder bores 2 arranged parallel to each other. A 
piston 5 is inserted in each cylinder bore 2 to press a pair of opposed 
friction pads 6 into frictional contact with both sides of a disk rotor D. 
Also shown in the figure are piston seals 7 having the function of 
retracting the pistons 5, pad pins 8 axially (with respect to the disk) 
slidably supporting the friction pads 6, fluid seals 9 provided at the 
connecting portions between a pipe 3 in the inner caliper 1a and a pipe 3 
in the outer caliper 1b. The pad pins 8 are supported by the calipers with 
its both ends inserted through pin holes (not shown) formed in the inner 
and outer calipers 1a, 1b. 
The pipes 3 as a fluid passage are casted in the inner and outer calipers 
1a and 1b. In other words, the calipers are casted with the pipes 3 put in 
position. Through the pipes 3, the cylinder bores 2 communicate with a 
brake fluid supply port 10. 
Each pipe 3 includes an intermediate short pipe 3a separated from the 
remaining pipe portion. The parallelly arranged cylinder bores 2 
communicate with each other through the pipe 3a provided therebetween. 
The pipe 3a has a projection or bend 11 at its intermediate portion as 
shown on an enlarged scale in FIG. 2. By casting the pipe 3a with the 
projection 11 in the caliper material, an engaging portion extending in a 
diametric direction of the pipe is formed between the pipe 3a and the 
inner caliper 1a (and outer caliper 1b). This portion prevents 
longitudinal shift of the pipe 3a. 
FIG. 3 shows another embodiment in which the pipe 3a has a recess 12. In 
this case, too, an engaging portion extending in a diametric direction of 
the pipe 3 is formed on the pipe 3a. These portions prevent longitudinal 
shift of the pipe 3a. The recess 12 shown in FIG. 3 is formed by drawing 
the pipe 3a at its mid-portion. But such a recess or a projection may be 
formed in any other manner. 
In the arrangement of FIG. 2 or FIG. 3, it is preferable to cut the ends of 
the pipe 3a and the pipe 3 and form a recess 13 in the cylinder bores 2 
around the pipe ends when finishing the cylinder bores 2 so that the pipe 
ends are slightly retracted from the inner walls of the cylinder bores 2. 
With this arrangement, even if the pipe 3 and the pipe 3a should shift 
slightly, the pipe ends will not protrude into the cylinder bores 2. This 
prevents interference of the pipe 3 or the pipe 3a with the pistons 5 
shown in FIG. 1. 
FIG. 4 shows another embodiment of a disk brake in which a pipe 3 extends 
across the bottoms of the cylinder bores 2. 
The pipe 3 has bent portions 15 at both ends, and a middle straight portion 
formed with cutouts 14 which are in the cylinder bore 2 at their bottom. 
The passage in the pipe 3 thus communicates with the cylinder bores 2 
through the holes defined by the cutouts 14. In this embodiment, the bent 
portions 15 (refer also to FIG. 1) engage the inner caliper 1a (and outer 
caliper 1b), thus keeping the pipe 3 in position. Since the pipe 3 
partially penetrates into the cylinder bores 2 so as to extend across the 
cylinder bores 2, it is possible to reduce the thickness t of the caliper 
bottom by the length a by which the pipe 3 penetrates into the cylinder 
bores 2, compared with conventional brakes of this type. 
Further, the cutouts 14 of the pipe 3 are retracted from the inner walls of 
the cylinder bores 2 by forming recesses 13 to prevent the edges of the 
cutouts 14 from protruding into the cylinder bores 2 and interfering with 
the sliding pistons. 
It will be enough if the edges of the cutouts 14 are retracted only 
slightly. The edges of the cutouts may be retracted not by recessing but 
by any other method such as partial machining. 
In any of the embodiments, two cylinder bores 2 are formed in each of the 
inner and outer calipers 1a, 1b. But this invention is also equally 
applicable to opposed-piston type disk brakes having more than two 
cylinder bores in each of the inner and outer calipers, opposed-piston 
type disk brakes having one cylinder bore in one of the inner and outer 
calipers, and floating type disk brakes in which a plurality of cylinder 
bores are formed in only the inner caliper. 
The pipe arrangement of the present invention is also applicable to a fluid 
passage in a fluid pressure system of an antilock brake system. In fact, 
the present invention is applicable to any cast hydraulic unit having 
fluid passages in the form of straight or arcuate pipes that tend to shift 
axially due to poor bonding or due to the pipes not being bonded on 
purpose. That is, by providing engaging portions extending in a diametric 
direction of the pipes, it is possible to easily and reliably prevent 
axial shift or dropout of the pipes.