Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1998-06-03
2001-01-16
Grant, William (Department: 2786)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S227000, C700S301000, C700S304000, C451S051000, C409S131000, C188S01800A, C188S380000, C082S152000
Reexamination Certificate
active
06175778
ABSTRACT:
1. FIELD OF THE INVENTION
This invention relates machining rotors. More specifically, this invention relates to an apparatus and method for machining rotatable disc brake rotors in a new, improved and facilitated manner.
2. Background of the Invention
Motor vehicles use various mechanisms to facilitate braking. Well known among these braking mechanisms is a combination of a disc rotor connected to a wheel of the vehicle. In order to stop or slow the vehicle, pressure is applied by a brake caliper pressing brake pads against one or more outer surfaces of the disc rotor (e.g., using so-called disc brakes), thereby slowing or stopping the rotation of the shaft to which the rotor is connected, and thereby, simultaneously slowing or stopping the rotation of the wheels.
Some rotors have a veined construction. A typical veined rotor
100
is depicted in
FIGS. 1 and 2
, wherein
FIG. 1
shows a front view and
FIG. 2
shows a side view of the rotor
100
. A portion of the rotor
100
(between the lines I and II) is cut away to show the inside veined structure of the rotor. The veined rotor essentially is made up of two disc plates separated and connected by a number of veins. The veins can be straight or curved and the number of veins varies from one rotor to another. For example,
FIGS. 3 and 4
show an example of an unmachined veined rotor with curved veins. The rotor
100
has two outside braking surfaces
102
,
104
, these surfaces being provided by the outer surfaces of the two discs comprising the rotor. The rotor
100
also has two interior non-braking surfaces
101
and
105
which form the interior veined structure of the rotor along with the veins. It is against the two braking surfaces
102
,
104
that pressure is applied (e.g., by brake pads (not shown)) in order to slow or stop the rotation of the wheel drive connected to the rotor
100
. Ideally, the rotor
100
is perfectly circular and these outside braking surfaces
102
,
104
are parallel to each other and flat, as are the interior non-braking surfaces
101
,
105
.
A typical rotor
100
is manufactured by machining a pre-cast rotor. A cast, pre-machined rotor
106
is shown in
FIGS. 5 and 6
which depict front and side views of the pre-cast, un-machined rotor
100
, respectively. The rotor
100
shown in
FIGS. 1 and 2
is produced by appropriately machining the cast rotor
106
.
A number of problems or defects can exist with existing rotors, and some of these problems or defects can be traced back to the manner in which the rotors were machined. For example, as noted above, in order to prevent or avoid uneven heat, uneven mass and uneven temperature and thermal distortion of the rotors surfaces, the surfaces
101
,
102
,
104
and
105
are ideally parallel, symmetrical and flat. In prior machining systems, neither the parallelism, the flatness, the center or the symmetry of these surfaces was determined prior to machining, nor were any of these features assured after machining.
SUMMARY OF THE INVENTION
This invention solves the above and other problems by providing a computer-vision based machining system which is able to determine the center plane of a pre-machined rotor and thereby to position the rotor accurately for machining. In particular, this invention solves these problems by determining the center plane between the two surfaces of the rotor, preferably two non-machinable interior non-braking surfaces of the rotor.
Accordingly, in one aspect, this invention provides a method of machining a rotor by determining a center plane of the two surfaces of the rotor; positioning the rotor based on the determined center plane; and then machining the positioned rotor. The center plane of the rotor is determined using at least one image of the rotor. In some preferred embodiments, the center plane is determined using a series of successive images of the rotor.
Preferably the center plane is determined based on a measure of two interior non-braking surfaces of the rotor.
After the rotor is machined, it can also be inspected by determining the parallelism between the center plane of the outer (braking) surfaces of the machined rotor and the previously determined center plane based on the interior surfaces. Before the rotor is machined it can be inspected for flatness and/or parallelism of the interior, non-braking surfaces. If, based on measures of their parallelism and/or flatness, these surfaces do not comply to specifications, the rotor can be rejected prior to machining.
In another aspect, this invention is a method of machining a brake rotor by positioning an unmachined rotor on a chuck of computer controlled turning center; determining a center plane of the rotor; adjusting the position of the rotor within the turning center based on the determined center plane of the brake rotor; and machining the brake rotor.
In yet another aspect, this invention is a system for machining a rotor. The system includes a turning center having a chuck for mounting the rotor thereon and positioning the rotor on one of the interior non-braking surfaces; an image frame grabber for obtaining images of the rotor; a computer system connected to the turning center and programmed to provide control information to the turning center based on information obtained from the images, wherein the computer system is programmed to determine a center plane of the rotor based on images of the rotor obtained by the image frame grabber. The frame grabber can obtain the images of the rotor while it is mounted on the chuck or when it is at some other location, e.g., on a conveyer system.
In some embodiments the computer system is further programmed to determine the center plane of the rotor based on a series of images of the rotor. The computer system can also be programmed to determine the center plane based on a measure of two non-braking interior surfaces of the rotor.
As noted, this invention overcomes a number of problems and defects with existing rotors. For example, the use of this invention prevents or minimizes uneven heat, uneven mass and uneven temperature and thermal distortion of rotors' surfaces, providing rotors with surfaces which are substantially parallel, symmetrical and flat and which have relatively uniform mass distribution.
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Burgoon Donald Lee
Xu Hong
Grant William
McDieunel Marc
Performance Friction Corporation
Pillsbury Madison & Sutro LLP
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