Contactless eddy current brake for cars

Details Contactless eddy current brake for cars Contactless eddy current brake for cars

1999-02-03

2001-09-11

Oberleitner, Robert J. (Department: 3613)

Brakes

Operators

Electric

C303S152000

Reexamination Certificate

active

06286637

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a contactless eddy current brake for cars.
2. Description of the Prior Art
As well known to those skilled in the art, known contact brakes for cars are designed to be operated by hydraulic or pneumatic pressure, thus pressing against the brake disc of a wheel using frictional brake pads and making a car go slow or stop. However, such known contact brakes are problematic in that the brake pads are frictionally abraded due to frictional contact of the brake pads with the brake disc and there exists a time delay while increasing the frictional pressure against the brake disc. Another problem experienced in the known brakes resides in that the brakes have a large volume and fail to effectively brake the wheels while driving a car at a high speed.
In a detailed description, known contact brakes for cars are devices that frictionally press against the brake disc of a wheel, thus making a car go slow or stop. Such contact brakes are designed to convert kinetic energy of rotating wheels into thermal energy using a mechanical friction means prior to dissipating the thermal energy into the atmosphere, thereby performing a desired braking operation. The contact brakes, operated by hydraulic pressure, are typically classified into two types: drum brakes and disc brakes. The known disc brakes individually comprise a plurality of brake pads, which are positioned around both sides of a brake disc integrated with a wheel, and frictionally press against the brake disc when it is necessary to make a car go slow or stop.
FIG. 8
is a sectional view, showing the construction of a typical disc brake. As shown in the drawing, the disc brake comprises two movable pads or inside and outside pads
20
and
30
which are set in a housing
10
while being parallel to each other with a gap being formed between them. A disc
40
, which is integrated with and rotatable along with a wheel, is positioned in the gap between the two pads
20
and
30
in a way such that the disc
40
is normally spaced apart from both pads
20
and
30
. A cylinder actuator, comprising a piston
50
and a cylinder
60
, is positioned at one side of the inside pad
20
, with the piston
50
being capable of pressing he two pads
20
and
30
against both sides of the disc
40
using pressurized oil from a master cylinder (not shown). The cylinder
60
of the actuator is provided with an oil port
61
at its end wall for selectively introducing the pressurized oil from the master cylinder into said cylinder
60
. A spring
51
is set in an annular groove
52
, formed on the interior wall of the cylinder
60
, so that the spring
51
normally biases the piston
50
relative to the cylinder
60
in a direction where the piston
50
returns to its original position. That is, when a brake pedal (not shown) is released, the spring
51
elastically forces the piston
50
to return from an operational position to a released position.
When operating a brake pedal while driving a car, a back pressure is formed in the master cylinder, so that the master cylinder out puts pressurized oil. The pressurized oil from the master cylinder is, thereafter, introduced into the cylinder
60
of the actuator through the oil port
61
, thus acting on the piston
50
. The piston
50
thereby causes the inside pad
20
to instantaneously press against the disc
40
. In such a case, the housing
10
also moves to the right in the drawing under the guide of a slide unit (not shown) due to the hydraulic pressure acting in the cylinder
60
. Such a movement of the housing
10
causes the outside pad
30
to press against the disc
40
, so that the two brake pads
20
and
30
perform a braking operation. When the brake pedal is released, the piston
50
elastically returns to the original position by the restoring force of the spring
51
, thus allowing the disc
40
to be released from the two pads
20
and
30
.
However, since the above disc brake is necessarily provided with a complex hydraulic system, so that the construction of the brake is undesirably complicated, this results in an increase in the production cost while manufacturing the brakes. Another problem experienced in such brakes resides in that the brakes fail to immediately stop a car, but allow the car to travel a free running distance for a time until the pressurized oil from the master cylinder effectively acts on the piston in the cylinder actuator. This may undesirably cause traffic hazards.
FIG. 9
is a sectional view, showing the construction of a typical eddy current brake used as a retarder. As shown in the drawing, the eddy current brake comprises a stator and a rotor. The stator comprises a coiled solenoid
71
which is supported by an annular frame
70
. The above solenoid
71
surrounds a ring
72
which is coupled to a radial arm
73
. On the other hand, the rotor comprises a magnetic disc
77
, which is made of a magnetic material and is connected to a bent arm
76
. The above rotor is firmly locked to an axle using a bolt
78
, so that the rotor is rotatable in cooperation with the axle. In order to allow the rotor to be rotatable independently of the stator, both a spline
74
and a bearing
75
are interposed between the rotor and stator.
When activating the above brake while driving a car, the coiled solenoid
71
, positioned around the magnetic disc
77
, is turned on, thus forming a magnetic flux. The magnetic flux is perpendicularly introduced Into the magnetic disc
77
prior to flowing to another solenoid (not shown) from said disc
77
. An eddy current is thus induced in the magnetic disc
77
due to the Faraday's law. A Lorentz force is generated by the relative action between the eddy current and the magnetic flux, thus forming a braking torque. However, such an eddy current brake is problematic in that it is not suitable for being used as a main brake system for cars since the braking torque is too low when a car runs at a low speed.
In recent years, a brake, which uses a liquid having a pressure capable of being variable in accordance with the power of the magnetic field or the electric field and overcomes the problems experienced in brakes using the solenoids, has been actively studied. However, the brakes, using such a liquid, are problematic in that they necessarily use expensive devices and have a complex construction. In addition, it is necessary to propose more effective and reliable brake systems in accordance with an increase in the maximum speed of a car.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a contactless eddy current brake for cars, which introduces a magnetic field to a copper brake disc, thus inducing an eddy current in the disc, and applies a contactless braking torque to the disc due to a relative action between the eddy current and the magnetic field formed by an electric magnet, thus providing a desired slip ratio.
Another object of the present invention is to provide a contactless eddy current brake for cars, which is designed to selectively apply a DC current to coils of a core when a car runs at a high speed, or to apply an AC current with different phases to the coils when the car runs at a low speed or is stopped on a slope, thus providing a variable braking torque for the wheels in accordance with conditions of the car, with the DC current being variable in accordance with a pedaling force acting on a brake pedal and the AC current being variable in the frequency in accordance with the pedaling force.
A further object of the present invention is to provide a contactless eddy current brake for cars, which has a controller used for controlling the DC or AC current when a car starts to slip, thus providing an appropriate torque to the wheels.
In order to accomplish the above objects, the present invention provides a contactless eddy current brake for cars, compromising: a brake disc concentrically integ

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