Title: Regenerative brake
Abstract: A lightweight regenerative brake having a large braking force is provided. A regenerative brake 1 comprises a brake disc (10) and a pair of stators (20) to perform regenerative braking. This regenerative brake (1) reduces the heat generated in the brake disc (10), because a part of the kinetic energy of a railway car is regenerated by generation of electricity in a tertiary circuit of the power source side when the brake is applied, and consequently the amount of energy converted into heat energy is decreased. Compared to a conventional regenerative brake, this regenerative brake (1) enables the disc (10) to be made thinner and dispenses with a cooling device such as a fan. Accordingly, a small-sizes and lightweight brake having a large braking force can be constituted using this regenerative brake (1).
Patent Number: 6,897,576 Issued on 05/24/2005 to Ishikawa, et al.
| Inventors:
|
Ishikawa; Sakae (Nagoya, JP);
Saito; Tsutomu (Nagoya, JP);
Sato; Kenji (Nagoya, JP);
Kato; Shigeyuki (Nagoya, JP)
|
| Assignee:
|
Central Japan Railway Company (Nagoya, JP)
|
| Appl. No.:
|
311045 |
| Filed:
|
June 11, 2001 |
| PCT Filed:
|
June 11, 2001
|
| PCT NO:
|
PCTJP01/04928
|
| 371 Date:
|
December 11, 2002
|
| 102(e) Date:
|
December 11, 2002
|
| PCT PUB.NO.:
|
WO0196138 |
| PCT PUB. Date:
|
December 20, 2001 |
Foreign Application Priority Data
| Jun 13, 2000[JP] | 2000-176803 |
| Current U.S. Class: |
290/45; 290/3; 322/1 |
| Intern'l Class: |
H02P 009/00 |
| Field of Search: |
290/1 A,1 R,3,45
322/1,100
316/1
318/1,362,375
|
References Cited [Referenced By]
U.S. Patent Documents
| 3799284 | Mar., 1974 | Hender.
| |
| 4377975 | Mar., 1983 | Scott et al.
| |
| 4994003 | Feb., 1991 | Oldfield.
| |
| 5053632 | Oct., 1991 | Suzuki et al.
| |
| 5283470 | Feb., 1994 | Hadley et al.
| |
| 5340202 | Aug., 1994 | Day.
| |
| 5442276 | Aug., 1995 | Schwartz et al.
| |
| 5915306 | Jun., 1999 | Langhorst et al.
| |
| Foreign Patent Documents |
| 61-266064 | Nov., 1986 | JP.
| |
| 63-314101 | Dec., 1988 | JP.
| |
| 64-030401 | Feb., 1989 | JP.
| |
| 04-207911 | Jul., 1992 | JP.
| |
| 04-322106 | Nov., 1992 | JP.
| |
| 2000/-037002 | Feb., 2000 | JP.
| |
Primary Examiner: Ponmarenko; Nicholas
Attorney, Agent or Firm: Davis & Bujold, P.L.L.C.
Claims
1. A regenerative brake comprising:
a brake disc attached to an axle of a railway car, comprising
a first disc surface;
a second disc surface;
a first stator comprising three or more first stator coils directly opposing
the first disc surface;
a second stator comprising three or more second stator coils directly opposing
the second disc surface;
a rotation speed sensor for measuring a rotational speed of the brake disc;
an inverter; and
a control circuit;
wherein the regenerative brake opposes rotation of the brake disc by exciting
the three or more first stator coils and the three or more second stator coils
across the brake disc, thereby generating a moving magnetic field,
the rotation speed sensor measures the rotational speed of the brake disc;
the control circuit causes the generated moving magnetic field to move at a slower
speed than the rotational speed of the brake disc;
a portion of kinetic energy, resulting from motion of the railway car, is converted
to electricity by the first stator and the second stator;
the electricity generated by the first and second stators is supplied to the
inverter;
the inverter converts the electricity into direct-current electricity; and
the direct-current electricity is supplied to an electrical system for the railway
car.
2. The regenerative brake according to claim 1, wherein the first stator is formed
so as to directly oppose one half of the first disc surface of the brake disc, and
the second stator is formed so as to directly oppose one half of the second disc
surface of the brake disc.
3. The regenerative brake according to claim 2, wherein the first stator is formed
into a first sector extending along a circumference of the brake disc and comprises:
a first stator core in which the three or more first coils are provided along
an arc of the first sector, and
the second stator is formed into a second sector extending along a circumference
of the brake disc and comprises;
a second stator core in which the three or more second coils are provided along
an arc of the second sector.
4. The regenerative brake according to claim 2, wherein the first and second
stators comprise respective elongate first and second stator cores which are arranged
so that a longitudinal length of the respective first and second stator cores extend
parallel to a tangent to a direction of movement of the railway car.
5. The regenerative brake according to claim 1, wherein the regenerative brake
is supplied for a non-powered railway car to facilitate braking of the non-powered
railway car.
6. The regenerative brake according to claim 1, wherein the brake disc further comprises:
a three-layer structure in which a magnetic core is sandwiched between two aluminum
discs; and
the control circuit controlling movement of the magnetic field along a circumference
of the brake disc at a speed slower than the rotational speed of the brake disc
and a speed of movement of the magnetic field being dependent upon the rotational
speed of the brake disc.
7. The regenerator brake according to claim 6, wherein the magnetic core is iron.
8. The regenerative brake according to claim 6, wherein the magnetic core is steel.
9. The regenerative brake according to claim 1, wherein when a slip value of
the regenerative brake reaches 1, the regenerative brake fails to apply a braking force.
10. The regenerative brake according to claim 1, wherein when a slip value of
the regenerative brake ranges from 0 to -1, the regenerative brake applies a braking force.
11. A regenerative brake comprising:
a brake disc attached to an axle of a railway car, the brake disc having a first
and second opposed surfaces;
a first stator having at least three first stator coils located adjacent the
first disc surface;
a second stator having at least three second stator coils located adjacent the
second disc surface;
a rotational speed sensor for measuring the rotational speed of the brake disc;
a control circuit electrically coupled with the rotational speed sensor;
an inverter electrically coupled with the first and second stators and the control
circuit, the regenerative brake retards rotation of the brake disc, during operation
of the regenerative brake, by exciting the at least three first stator coils and
the at least three second stator coils across the brake disc, thereby generating
a magnetic field, the control circuit generating the magnetic field and controlling
movement of the magnetic field along a circumference of the brake disc at a speed
slower than the rotational speed of the brake disc to generate a braking effect
on the rotating brake disc with a speed of movement of the magnetic field being
dependent upon the rotational speed of the brake disc; and
the first stator and the second stator converting kinetic energy of the railway
car to electricity which is supplied to the inverter, the inverter converts the
electricity to a direct current electricity which is supplied to an electrical
system of the railway car.
12. The regenerative brake according to claim 11, wherein the first stator is
arcuate in shape and concentric with the first surface of the brake disc and the
first stator has a radius similar to a radius of the first disc surface, and the
second stator is arcuate in shape and concentric with the second surface of the
brake disc and the second stator has a radius similar to a radius of the second
disc surface.
13. The regenerative brake according to claim 12, wherein the first stator extends
circumferentially about the brake disc and has a first stator core in which the
at least three first stator coils are provided along an arc thereof; and
the second stator extends circumferentially about the brake disc and has a second
stator core in which the at least three second stator coils are provided along
an arc thereof.
14. The regenerative brake according to claim 12, wherein the first and second
stators comprise respectively elongate first and second stator cores which are
arranged so that a longitudinal length of the respective first and second stator
cores extend parallel to a tangent to a direction of movement of the railway car.
15. The regenerative brake according to claim 11, wherein the regenerative brake
is provided on a non-powered railway car to facilitate braking of the non-powered
railway car.
16. The regenerative brake according to claim 11, wherein the brake disc further
comprises a three-layer structure in which a central magnetic core layer is sandwiched
between two aluminum disc layers.
17. The regenerator brake according to claim 16, wherein the central magnetic
core layer comprises iron.
18. The regenerative brake according to claim 16, wherein the central magnetic
core layer comprises steel.
19. The regenerative brake according to claim 11, wherein the regenerative brake
does not apply a braking force when a slip value of the regenerative brake is 1
or greater.
20. The regenerative brake according to claim 11, wherein regenerative brake
applies a braking force when a slip value of the regenerative brake is ranges from
0 to -1.
Description
TECHNICAL FIELD OF THE INVENTION
This invention relates to a regenerative brake for a railway car.
BACKGROUND OF THE INVENTION
Conventionally, there has been an eddy current brake which performs
braking by electromagnetic induction using a three-phase alternating current, as
described in the Unexamined Japanese Patent Publication No. 61-266064. As shown
in FIG. 6, such an eddy current brake 100 comprises a brake disc 102
attached to an axle 106 so that a disc surface 104 is perpendicular
to the axle 106, and a stator 108 which is provided in a position
facing the disc surface 104 and which, when excited, generates a moving
magnetic field which moves to a direction opposite to a rotation direction of the
brake disc 102. The eddy current brake 100 moves the moving magnetic
field so that the slip reaches one (1) or more, as shown in FIG. 7. When
this moving field excited by the stator 108 generates an eddy current on
the disc surface 104, a force operating to a direction opposite to the rotation
direction of the brake disc 102 is applied to the brake disc 102
according to the Fleming's left-hand rule, and thus, braking is performed using
the force.
In the eddy current brake 100, almost all the kinetic energy of a wheel
110 is converted into heat energy by the eddy current passing on the brake
disc 102, and consequently the brake disc 102 becomes hot. However,
it is clearly not structurally preferable that a temperature of the brake disc
102 becomes high exceeding a certain temperature. Therefore, in the conventional
eddy current brake 100, the brake disc 102 is made thick to increase
heat capacity and to facilitate heat radiation. Also, a cooling device such as
a fan is provided to cool the brake disc 102 forcibly so as to prevent the
brake disc 102 from getting too hot exceeding the certain temperature.
On the other hand, to speed up a railway car of a bullet train, etc., it is necessary
to reduce the weight of the car and to enhance the braking force
However, the conventional eddy current brake 100 requires thicker
brake disc 102 to increase heat capacity, etc. and a fan to be provided
to enhance the braking force, thereby resulting in increase in weight.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a regenerative brake for performing
braking by electromagnetic induction, which is small-sized and lightweight in spite
of the larger braking force compared to a conventional eddy current brake.
In order to attain the above object, the present invention provides a regenerative
brake comprising a brake disc attached coaxially to an axle of a wheel of a railway
car and a stator for braking provided in a position facing a disc surface of the
brake disc, wherein the regenerative brake brakes the brake disc by exciting coils
provided on the stator and generating a moving magnetic field which moves to the
same direction with a rotation direction of the brake disc at a lower speed than
a rotation speed of the brake disc, and, along with the braking, regenerates a
part of the kinetic energy of a railway car in the power source side via the stator.
In other words, the regenerative brake of the present invention, if explained
with a graph showing a characteristic curve of a conductive device shown in FIG.
7, does not brake when the slip reaches one (1) or more like the conventional eddy
current brake but does brake when the slip is less than zero.
When braking is performed when the slip is less than zero as such, a part of
the kinetic energy of the railway car is regenerated in the power source side upon
braking and the amount of energy converted into heat energy is decreased compared
with a case of the eddy current brake described in the prior art, resulting in
that less heat is generated in the brake disc. Therefore, with the regenerative
brake of the present invention, there is no need to increase heat capacity of the
brake disc as in the eddy current brake, and consequently it is possible to form
the brake disc thin and to dispense with a cooling device such as a fan.
Accordingly, the regenerative brake of the present invention can be
small-sized and lightweight even though the braking force is larger than that of
the eddy current brake described in the prior art.
Additionally, it is preferable that the stator is formed as large as
it covers a part of the disc surface as in the regenerative brake of the present
invention. Formed as such, a heat radiation effect of the brake disc becomes significant
and the brake disc can be constituted thinner. Also, no cooling device is required.
As a result, the eddy current brake of the present invention can be made small-sized
and lightweight.
Particularly, it is preferable that the stator is formed into a sector
extending along the circumference of the brake disc and comprises a stator core
which is formed to have a plurality of coils provided along the arc of the sector.
Such a stator allows the moving field to move along the rotation direction of the
brake disc and the braking force to operate along the rotation direction of the
brake disc. Therefore, it is possible to apply the braking force to the brake disc efficiently.
As another example, it is preferable that the stator comprises an elongate stator
core which is arranged so that the longitudinal length of the stator core is parallel
to a traveling direction of the railway car. Such arrangement allows the longitudinal
length of the stator core and the traveling direction of the train to be parallel
to each other, and consequently, the air passes on the brake disc efficiently.
Accordingly, since the heat radiation effect is significant and the brake disc
can be made further thinner, the regenerative brake can be made small-sized and lightweight
A power car to which a motor is attached, so-called M car, comprises an inductive
motor and the inductive motor performs regenerative braking. Therefore, there is
no need to attach the eddy current brake of the present invention. However, non-powered
car, so-called T car, does not comprise an inductive motor. Therefore, it is significantly
important to perform regenerative braking with the eddy current brake of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective illustration of one end of a wheel to which a regenerative
brake of the present embodiment is attached;
FIG. 2 is a cross sectional view of a brake disc;
FIG. 3 is a cross sectional view taken along the line A-A′ of FIG. 1;
FIG. 4 is a block diagram of an operation circuit;
FIG. 5 is a front elevation view of the brake disc for explaining the other
example of a stator core;
FIG. 6 is a perspective view of a conventional eddy current brake; and
FIG. 7 is a graph showing a characteristic curve of an induction device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention will now be described, by way of example, with reference to the
accompanying drawings.
FIG. 1 is a perspective view of one end of a wheel to which a regenerative brake
of the present embodiment is attached, FIG. 2 is a cross sectional view of a brake
disc, FIG. 3 is a cross sectional view of a stator (cross sectional view taken
along the line A-A′ of FIG.
1), FIG. 4 is a block diagram of an operation
circuit, and FIG. 5 is a front elevation view of the brake disc.
As shown in FIG. 1, a regenerative brake
1 of the present embodiment comprises
a brake disc
10 and a pair of stators
20 and
21.
The brake disc
10 is attached concentrically to an axle
9 provided
on a truck of a railway car. The brake disc
10, as shown if FIG. 2 in particular,
is composed of a cylindrical portion
14 and a disc portion
16. The
disc portion
16 has a first surface
12 and a second surface
13.
The cylindrical portion
14 is formed into a circular cylinder, and fixes
the brake disc
10 on the axle
9 with the cylindrical portion
14
being fitted on the axle
9. On the other hand, the disc portion
16
is formed in a three-layer structure in which an iron disc
16a is
sandwiched between two aluminum discs
16b, and is integrally attached
to an outer circumferential surface of the cylindrical portion
14 to be
concentric with the cylindrical portion
14. The disc
16a may
be composed of any magnetic body having strength such as steel besides iron. The
disc
16b may be composed of any non-magnetic body having high conductivity.
The stators
20,
21 are arranged to face a disc surface
12
of the brake disc
10 and to interpose the brake disc
10 above the
axle
9. As stators
20,
21 are similar to each other, only
the first stator is shown in detail. The stator
20 is composed of a stator
core
22 and a stator winding
24, as shown in FIG. 3 in particular.
The stator core
22 is formed to extend parallel to a traveling direction
of the railway car and to the disc surface
12. On one side of the stator
core
22 facing to the disc surface
12, a plurality of slits
22a
formed perpendicular to the longitudinal length of the stator core
22
are provided at even intervals along the longitudinal length.
In order to generate a moving field, the stator winding
24 is composed
of coils
24a-
24c of three phases: U phase, V phase
and W phase. The coils
24a-
24c are aligned facing to
the disk surface
12 of the brake disc
10 along the traveling direction
of the railway car so that a winding surface around which a conductive wire composing
each of the coils
24a-
24c is wound is parallel to the
disc surface
12 of the brake disc
10. Each of the coils
24a-
24c
is formed into a concentrated as well as short-pitch winding and is fit into
the slits
22a on the stator core
22 to which the stator winding
24 of each of the phases is to be allocated. Each of the coils
24a-
24c
is attached to one of the stator cores
22 so that the coils
24a-
24c
of an equal phase face to each other and so as not to cancel each other's magnetic
flux. The present embodiment shows the coils
24a-
24c of
a short-pitch winding arranged at each coil pitch of three slots to a pole pitch
of four slots, as an example. However, other constitutions are also acceptable.
An operation circuit for operating the regenerative brake of the present embodiment
is now explained.
FIG. 4 is a block diagram of the operation circuit.
An operation circuit
30 of the present embodiment comprises a converter
32, an inverter
34, a rotation speed sensor
36 and a control
circuit
38, as shown in FIG.
4. The converter
32 converts
electricity of a single phase 440V of a tertiary winding into a direct current,
for use in an auxiliary circuit among the main transformer windings which step
down an extra high tension supplied from an overhead wire to be outputted to the
inverter
34. The auxiliary circuit is a circuit which supplies electricity
to in-vehicle equipment such as an air conditioning apparatus and ventilator.
The inverter
34 converts the direct-current electricity supplied from
the converter
32 into a three-phase alternating current by PWM control and
outputs the same to the stator winding
24. The converter
32 and the
inverter
34 are constituted using an IGBT (insulated gate bipolar transistor) element.
The rotation speed sensor
36 is attached to the brake disc
10 to
measure a rotation speed of the brake disc
10, and outputs a speed signal
indicating the rotation speed of the brake disc
10 to the control circuit
38. The rotation speed of the brake disc
10 is calculated in the
control circuit
38 based on the speed signal inputted from the rotation
speed sensor
36, and according to the calculated result, PWM (pulse width
modulation) control is performed to operate the inverter
32. In the PWM
control, the stator winding
24 is excited and a moving magnetic field is
generated which moves at a speed lower than the rotation speed of the brake disc
10 calculated by the control circuit
38 to the same direction as
the rotation.
In the operation circuit
30, the tertiary circuit which consumes power
supplied from the stator winding
24 upon regenerative braking and converted
into a direct current in the inverter
34 may be inserted between the converter
32 and the inverter
34. Also in the operation circuit
30,
if the power of the auxiliary circuit has already been a direct current, the electricity
may be supplied directly to the inverter
32, and not via converter
32.
If the regenerative brake
1 constituted as the above is controlled using
the operation circuit
30, it operates as follows.
When the regenerative brake
1 of the present embodiment started to brake,
an electric current is passed to the coils
24a-
24c provided
on the stators
20 by PWM control. Then, a moving field is generated which
moves at a speed lower than the rotation speed of the brake disc
10 to the
same direction as the rotation direction of the brake disc
10 through the
disc
16b of the brake disc
10, and an eddy current is generated
on the brake disc
10. As a result, a force is applied to a direction opposite
to the rotation direction according to the Fleming's left-hand rule, and this force
becomes a braking force to brake the brake disc
10.
This braking is a regenerative braking and kinetic energy of the railway car
is partly converted into electricity. The electricity is converted into a direct
current in the inverter
34 which serves as a converter, and is outputted
to the power source side. The kinetic energy is partly converted into heat energy
to heat the brake disc
10.
The following effects are expected when the regenerative brake
1 as explained
above is used.
As above described, if braking is performed when the slip is less than zero, a
part of the kinetic energy of the railway car is regenerated in the power source
side upon braking and the amount of energy converted into heat energy is decreased
compared to that in case of the eddy current brake described in the prior art,
resulting in that less heat is generated in the brake disc. Therefore, there is
no need to increase heat capacity of the brake disc
10 with the regenerative
brake of the present invention as in the eddy current brake, and consequently it
is possible to form the brake disc thin and to dispense with a cooling device such
as a fan. Accordingly, the regenerative brake
1 of the present embodiment
can be constituted small-sized and lightweight compared to the eddy current brake
described in the prior art even if the braking force is increased.
The regenerative brake
1 of the present embodiment is formed as large
as it covers a part of the disc surface of the brake disc
10. Therefore,
a dramatic heat radiation effect can be achieved which allows production of the
thinner brake disc
10 and lack of a cooling device. As a result, the eddy
current brake of the present embodiment can be constituted small-sized and lightweight
compared to the conventional eddy current brake.
In the present embodiment, the longitudinal length of the stator core
22
and the traveling direction of the train is parallel to each other and thereby
the air passes on the brake disc
10 efficiently. Accordingly, since a dramatic
heat radiation effect can be achieved compared to the conventional eddy current
brake and therefore the brake disc
10 can be made further thinner, the regenerative
brake
10 of the present embodiment can be constituted smaller-sized and
lighter-weight than the conventional eddy current brake.
The stator core
22 may be formed into a sector extending along the circumference
of the brake disc
10 and the coils
24a-
24c may
be arranged along the circumference of the sector as shown in FIG.
5. In
this manner, the moving magnetic field moves along the rotation direction of the
brake disc
10 and the braking force operates along the rotation direction
of the brake disc
10. Then, the braking force can be applied to the brake
disc
10 efficiently.
It is not necessary to provide a power car to which a motor is attached, so-called
M car, with the regenerative brake of the present embodiment, since the M car comprises
an induction motor which performs regenerative braking. However, there is a significant
importance in providing a non-powered car, so-called T car, with the regenerative
brake of the present embodiment and performing regenerative braking, since the
T car does not comprise an induction motor.
It is known that a braking force of the conventional eddy current brake gets
small
if a rotation speed of a rotor, namely, the brake disc
10, is slow, and
consequently, a control brake does not work when a speed of a railway car is equal
to or under 70 km per hour.
It is then preferable as in the present embodiment that the moving speed of the
moving magnetic field generated in the stator
20 may be controlled so that,
as shown in FIG. 7, the slip S to the rotation speed of the brake disc
10
corresponding to a rotor is, among a range α of FIG. 7, within a range of
values between the value at which the same torque value (γ, point in FIG.
7) with the maximum torque value (β point in FIG. 7) when the induction device
is treated as a brake is obtained and the value at which the maximum torque can
be obtained, for example.
In this manner, it is possible to obtain an extremely high torque, that is, braking
force, in spite of the low rotation speed of the rotor. Further in this manner,
despite the high braking force, braking requires less primary current. Accordingly,
generation of heat in the brake disc
10 is reduced and the brake disc
10
can be thinner. As a result, the regenerative brake
1 of the present embodiment
can be made lightweight.
The present invention should not be limited to the described embodiment, and
other modifications and variations might be possible without departing from the
scope of the invention.
For instance, the rotation speed sensor
26 measures the rotation speed
of the brake disc
10 in the present embodiment. However, if in advance a
table which shows relevancy between the train speed and the rotation speed of the
brake disc
10 is provided and calculation of the moving speed of the moving
magnetic field is possible as a result of measuring the train speed, thus PWM control
may be directly performed based on the train speed by removing the rotation speed
sensor
26
In addition, the converter
32 and the inverter
34 are composed
of
an IGBT element in the present embodiment. However, they may be composed of an
electric semiconductor such as a GTO thyristor (gate turn-off thyristor), etc.
Moreover, although a short-pitch winding is described in the present embodiment,
other windings such as a distributed winding, etc may be utilized.
INDUSTRIAL AVAILABILITY
As described in details in the above, the regenerative brake of the present invention
can be constituted small-sized and lightweight in spite of a large braking force
compared with the conventional eddy current brake.
*
