U.S. patent number 3,662,689 [Application Number 05/053,773] was granted by the patent office on 1972-05-16 for high speed train utilizing hard superconductor.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Toshio Doi, Ushio Kawabe, Hiroshi Kimura.
United States Patent |
3,662,689 |
Kawabe , et al. |
May 16, 1972 |
HIGH SPEED TRAIN UTILIZING HARD SUPERCONDUCTOR
Abstract
Superconducting high speed train system comprising a rail
including at least one elongated hard superconducting member
disposed horizontally along the running direction of the train and
having a hollow or gap portion extending in the elongated
direction, and a train body including a superconducting magnet for
generating a magnetic field perpendicular to the hard
superconducting member, thereby floating the body from the rail by
the magnetic force acting between the superconducting magnet and
the hard superconducting member.
Inventors: |
Kawabe; Ushio (Tokyo,
JA), Kimura; Hiroshi (Tokyo, JA), Doi;
Toshio (Tokyo, JA) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JA)
|
Family
ID: |
13063254 |
Appl.
No.: |
05/053,773 |
Filed: |
July 10, 1970 |
Foreign Application Priority Data
|
|
|
|
|
Jul 23, 1969 [JA] |
|
|
44/57702 |
|
Current U.S.
Class: |
104/285;
104/286 |
Current CPC
Class: |
B60L
13/04 (20130101); B60L 13/10 (20130101); B60V
3/04 (20130101); B60L 2200/26 (20130101) |
Current International
Class: |
B60L
13/04 (20060101); B60L 13/10 (20060101); B60L
13/00 (20060101); B60V 3/00 (20060101); B60V
3/04 (20060101); B61b 013/08 (); H01f 009/00 () |
Field of
Search: |
;104/148MS,148SS |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3470828 |
October 1969 |
Powell, Jr. et al. |
|
Primary Examiner: La Point; Arthur L.
Assistant Examiner: Libman; George H.
Claims
We claim:
1. A superconducting high speed train system comprising:
train rail means including at least a pair of inhomogeneous hard
superconducting plates disposed along the running direction of a
train, vertically facing to one another, and means for cooling said
superconducting plates to keep them in the superconducting
state;
a body of a train accommodating thereon a superconducting field
coil, means for operating said coil to generate a magnetic field
perpendicular to the surface of said hard superconductor plates and
means for cooling said coil to keep the same in the superconducting
state, whereby floating the train body by the interaction of the
magnetic field established by said superconducting coil means and
the weak magnetic field formed in the gap of said pair of hard
superconductor plates; and means for driving said train body in the
floated state.
2. A superconducting high speed train system comprising:
train rail means including at least a pair of inhomogeneous hard
superconductor plates disposed in vertically facing relation to
each other along the running direction of a train, means for
cooling said superconductor plates to keep them in the
superconducting state, and ladder-shaped circuit means for allowing
a current to flow perpendicularly to the running direction of the
train;
a body of a train including superconducting coil means for
generating a magnetic field perpendicular to the surfaces of said
hard superconductor plates and said ladder-shaped circuit, and
means for cooling said coil means to keep the same in the
superconducting state, whereby floating the train by the
interaction of the magnetic field generated by said superconducting
coil means and the weak magnetic field formed in the gap of said
pair of hard superconductor plates; and means for controlling the
current flowing through the ladder-shaped circuit means whereby
propelling the train by the force caused by the magnetic field
generated by said superconducting coil means and the current
flowing through said ladder-shaped circuit means.
3. A superconducting high speed train system according to claim 2,
in which said ladder-shaped circuit means includes a number of
ladder-shaped unit circuits, each having an appropriate length and
said control means includes switch means provided to the respective
unit circuits for controlling the magnitude and the direction of
the flow of current, thereby controlling the starting, braking or
speed of the train.
4. A superconducting high speed train system comprising:
train rail means including two pairs of inhomogeneous hard
superconductor plates disposed in horizontally and vertically
facing relation to one another along the running direction of a
train, means for cooling said superconductor plates to keep them in
the superconducting state, and ladder-shaped circuit means for
allowing current to flow perpendicularly to the running direction
of the train;
a body of a train including first superconducting coil means for
generating a magnetic field perpendicularly to the surfaces of a
pair of said hard superconductor plates facing vertically and said
ladder-shaped circuit means, second superconducting coil means for
generating a magnetic field perpendicularly to the surface of
another pair of said hard superconductor plates facing
horizontally, whereby the train is floated by the interaction of
the magnetic field generated by said first superconducting coil and
the weak magnetic field in the gap of said pair of hard
superconductor plates facing vertically, and controlled the
position thereof by the interaction of the magnetic field generated
by said second superconducting coil and the weak magnetic field
formed in the gap of said another pair of hard superconductor
plates facing horizontally; and means for controlling the current
flowing through said ladder-shaped circuit means whereby the train
is propelled by the force caused by the magnetic field generated by
said first superconducting coil means and the current flowing
through said ladder-shaped circuit means.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a high speed train utilizing the
properties of a superconductor and more particularly to a
hovercraft high speed train utilizing the magnetic shielding effect
of an inhomogeneous hard superconductor.
2. Description of the Prior Art
In recent years, keeping pace with the development in various forms
of transportation, researches are being proceeded in the field of
trains to provide larger capacities and higher speeds. Although a
high speed train of about 200 Km/hr is realized, higher speed
trains of above 300 Km/hr cannot be realized practically according
to conventional structures.
Namely, according to the conventional method, the wheels of a train
are driven by a motor and the train moves due to the friction
between the wheels and the rails. But above a certain speed,
vibrations of the body become so large as to cause the possibility
of running off the rails and also problems of skid occurs. Thus it
becomes necessary to float a train from the rail and to drive it in
such a floated state to provide a speed above 300 Km/hr. But since
the weight of a train is so large, there have been no appropriate
means to float a train from the rail and thus it has been
impossible to realize a train which can run at a speed above 300
Km/hr.
Considering these points, an object of the invention is to provide
a novel hovercraft high speed train.
SUMMARY OF THE INVENTION
More specifically, an object of the invention is to provide a high
speed train utilizing the magnetic floating effect to float the
train above the ground and drive it in a floated state to provide a
speed higher than 300 Km/hr.
For this purpose, an inhomogeneous hard superconductor is used
according to this invention to provide a sufficiently large
floating force by the magnetic shielding effect.
Other object, advantages and features of this invention will be
apparent from the following detailed description when read in
conjunction with accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are magnetization curves of a soft and a hard
superconducting material, respectively.
FIG. 3 illustrates the principle of magnetic floating according to
the invention.
FIG. 4 illustrates the magnetic shielding effect.
FIG. 5 is a schematic diagram for illustrating the driving
principle according to the invention.
FIG. 6 is a schematic diagram of a driving system according to the
invention.
FIG. 7 is a schematic partial cross section of a rail according to
the invention.
FIGS. 8 and 9 are schematic cross-sectional views of embodiments of
the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Firstly, the known principle of magnetic floating utilizing a soft
superconductor will be described.
FIG. 1 shows a magnetization curve with the abscissa representing
external magnetic field H.sub.e and the ordinate representing
magnetization (-M). As is apparent from the figure, upon the
application of an external magnetic field a soft superconductor is
magnetized in the opposite direction (showing a diamagnetic
characteristic) with a magnitude in proportion to that of H.sub.e.
However, at a certain magnetic field H.sub.cl, the magnetization
suddenly reduces to zero and the superconducting state is broken.
This value H.sub.cl is called the lower critical magnetic field and
the region of H.sub.e < H.sub.cl is called the perfect
diamagnetic region or the Meissner region. In this region, current
flows in a surface layer of the soft superconductor in a thickness
of about several angstroms and thus the external field cannot
penetrate into the interior of the said soft superconductor any
further, keeping the internal magnetic field zero. When a body the
internal magnetic field of which is zero is placed in a magnetic
field having a certain gradient, certain force acts on the body and
it has become possible to float the body in the direction along
which said magnetic field decreases. Thus, the body of a train can
be floated from the ground by the use of this principle.
In the case of utilizing the Meissner effect of a soft
superconductor as is described above, however, the maximum floating
force is expressed by H.sub.cl.sup.2 /8.pi. and this is limited by
the magnitude of the critical magnetic field H.sub.cl. Although it
is possible to obtain a superconductor having a rather large
critical magnetic field H.sub.cl, there still exists a restriction
and practically it is quite difficult to float a very heavy body
such as a train.
Whereas, the present invention is based on the use of the magnetic
shielding effect of an inhomogeneous hard superconductor which can
provide a floating force several thousand times greater than that
in the case of utilizing the Meissner effect.
Among inhomogeneous hard superconductors, there are Nb-Zr-Ti,
Nb.sub.3 Sn, V.sub.3 Ga, Nb.sub.3 (Al.sub.0.8 Ge.sub.0.2), etc.
each of which shows a magnetization characteristic as shown in FIG.
2. Namely, with the increase of an applied magnetic field, the
intensity of the magnetization (-M) of a hard superconductor placed
in the magnetic field increases in linear proportion therewith up
to the lower critical magnetic field H.sub.cl, but above H.sub.cl
the rate of increase of the magnetization (-M) gradually decreases
with a certain point forming a peak and then the magnetization
begins to decrease. Finally, at the upper critical magnetic field
H.sub.c2, the superconducting state is broken for the first time.
While the region of H.sub.e < H.sub.cl is called the Meissner
region similar to the preceding case, the region of H.sub.cl <
H.sub.e < H.sub.c2 is called the magnetic shielding region. In
this magnetic shielding region, a spatial region of less magnetic
field, i.e. magnetic field diluted space, is formed in a hard
superconductor placed in the field due to a completely different
principle from said Meissner effect. Namely, a magnetic field
penetrates into a hard superconductor to such an extent where the
pinning force due to dislocations and/or precipitation defects in
the hard superconductor is balanced by the Lorentz's force that the
magnetic flux due to an external field tends to penetrate into the
hard superconductor. Consequently, an induction current flows in a
surface region, to the inner boundary of which said magnetic flux
could penetrate. By this induction current, the magnetic flux due
to the external field is prevented from penetrating into the hard
superconductor further to form a region of extremely less magnetic
flux in the hard superconductor. In this case, the depth of
penetration of the magnetic flux into the hard superconductor
depends on the intensity of the external field and is about 10
times larger than that of the surface layer in which current flows
by the meissner effect. Thus, the magnetic shielding effect
produces a region of less magnetic field in a hard superconductor,
while the Meissner effect produces a region of no magnetic field in
a superconductor. Thus, the magnetic characteristics of the two are
quite different, but in both cases a superconductor placed in a
magnetic field having a uniform gradient receives a force in the
direction along which the magnetic field decreases.
The magnetic shielding effect of an inhomogeneous hard
superconductor will become more apparent from the following
experiment.
Now, discs 1 and 2 formed of inhomogeneous hard superconductor are
disposed parallel to each other by supporting members 3 and 4, as
is shown in FIG. 3. And a superconducting solenoid 5 is disposed in
such a position to produce a magnetic field H substantially
perpendicular to the disc surfaces. With such a structure, the
relation of the change of the external magnetic field H and the
magnetic field H' at the center of the gap of the parallel discs is
studied and the result is shown in FIG. 4. As is shown in FIG. 4,
when the intensity of an applied magnetic field H is increased from
zero, the internal magnetic field H' is almost unchanged in the
first stage and keeps small values near zero. That is, the
penetration of the magnetic flux is prevented by the shielding
characteristic of the superconductor discs 1 and 2. When the
intensity of the external magnetic field H reaches the critical
point H.sub.c2 of the hard superconductor, the superconducting
state is broken and the internal magnetic field H' takes a value
almost equal to the external magnetic field H. Then, the intensity
of the external field H is gradually decreased. Even when the
external field H is decreased to zero, the internal field H' does
not reduce to zero and a certain magnetic field H.sub.c2 ' remains
between the parallel discs. Namely, a hard superconductor has a
magnetic capturing characteristic.
The former property of a hard superconductor, i.e., the magnetic
shielding property, is utilized in this invention. For example,
when the external magnetic field is 20 kilogauss, the magnetic
field in the gap of the discs is about 2 kilogauss showing that the
magnetic field is very weak between the discs. Thus, if there
exists a gradient .phi. in the magnetic field H as is shown in FIG.
3, the structure 1 to 4 is floated upward to the direction along
which the magnetic flux decreases. In this case, the structure is
stable in the radial direction. And in the gravitational direction
it is stable at a position where the floating force is balanced
with the gravitational force. This is completely contrary to the
case of a ferro-magnetic body. When the structure 1 to 4 is fixed,
a force acts on the superconducting solenoid 5 to move it
downward.
The high speed train according to the present invention is floated
by the above-described principle with the maximum floating force
expressed by (1-.gamma.)H/8 .pi. (dyne/cm.sup.2) (H.sub.cl < H
< H.sub.c2). Here, .gamma. is the magnetic shielding factor and
in FIG. 4 .gamma. = H'/H. H.sub.c2 is the upper critical magnetic
field as shown in FIG. 2 and has a value about 100 times larger
than the usual lower critical magnetic field of a soft
superconductor. The factor .gamma. can be brought to a value very
near to zero by the geometrical configuration and the material.
Thus, an apparatus utilizing the magnetic shielding characteristic
can afford a floating force about several thousand times larger
than that of the conventional apparatus utilizing the Meissner
effect.
Next, the principle of driving a train according to the invention
will be described. Since the driving force of the conventional
train is due to the friction between the wheels and rails, a new
type of drive becomes necessary for a friction-less train such as
this invention. FIG. 5 illustrates the principle of the driving
system, in which reference numeral 5' indicates a saddle-shaped
solenoid, 6 a ladder-shaped conductor, and 7 a DC source. The
saddle-shaped solenoid 5' works with the superconducting coil 5 of
FIG. 3 for generating a magnetic field H in the direction indicated
by an arrow H in the figure. In the ladder-shaped conductor 6, a
current I is allowed to flow by the DC source 7 in the direction
indicated by an arrow I. Thus, a force acts on the saddle-shaped
solenoid in the direction indicated by an arrow F.
Letting the magnetic field generated by the saddle-shaped solenoid
be H (gauss), the distance between the conducting rails l (cm), the
current flowing from the dc source 7 to the ladder-shaped conductor
I (ampere), the number of crosstie-shaped conductors providing
reaction to said generated magnetic field p, and the total weight
of a train M (gram weight), the driving acceleration dv/dt of the
saddle-shaped solenoid 5' is expressed by:
dv/dt = PIlH/10M (cm/sec.sup.2)
Thus, for example, if P=10, I = 10 (A), l = 1.5 (m), H = 50 (KG)
and M = 50 (ton), the hovercraft superconducting train is
theoretically driven with an acceleration of 15.sup. . g
(cm/sec.sup.2), an acceleration fifteen times larger than
gravitational acceleration. Further, if the effective cross section
of the magnetic field of the saddle-shaped solenoid is arranged to
be 1(m) .times. 5(m) and the magnetic shielding factor .gamma. =
0.2, the maximum floatable weight is 5,000 (ton). These values are
sufficiently large for practical purposes. In the practical form, a
multiplicity of ladder-shaped conductors I, II, III, . . . are
formed in the rail for a train and supplied with a current from
power lines 8 through respective control switches 93, 92, 91, . . .
as is shown in FIG. 6. In the figure, a train is supposed to be
running on the region II in the direction indicated by an arrow. In
this state, the control switch 91 is turned off and the switch 92
is on. When the control switch 93 is connected in such a way that
current is allowed to flow in the opposite direction as is shown in
FIG. 6, a train passing above this region receives a braking force.
By the control of the intensity and the direction of the current
flow in the respective ladder-shaped conductors, a train can easily
be started, stopped or reversed in its running direction.
Next, an embodiment of a high-speed hovercraft superconducting
train according to this invention utilizing the above-described
magnetic floating and driving method will be described.
In FIG. 8, curved plates 10, 11, 12 and 13 formed of a hard
superconducting material such as an Nb.sub.3 Sn sintered body are
placed to form opposing pairs by 10 and 12, and 11 and 13, and are
supported by supporting structure 14 to 17 at the four corners. The
use of curved plates facilitates the effective use of the applied
magnetic field in such a manner that the external field is wholly
applied perpendicular to these curved plates. The portion 18
surrounded by these curved hard superconductor plates forms a
refrigerant passage. For example, liquid helium or helium gas at a
very low temperature is allowed to flow through this passage to
keep the plates 10 to 13 in the superconducting state. These
structures are contained in a rail 19 formed of concrete. In the
upper surface of said rail 19, ladder-shaped conducting circuits 6
are formed along the running direction of the train.
FIG. 7 is a partially cross-sectional schematic perspective view of
a rail for a high speed train in which similar parts as those of
FIG. 8 are indicated by similar reference numerals.
The body of a high speed train is, for example, divided into the
upper and the lower part. In the upper part, seats 20 are disposed
in double-layered chambers and double-glassed windows 21A to 21D
are formed in the wall of both chamber. On the other hand, the
lower part has a reversed U shaped corss section and rides on the
rail 19. A saddle shaped coil 5 such as shown in FIG. 5 is disposed
in the lower part in a position facing the ladder-shaped conducting
circuit of the rail. Further in positions facing against the hard
superconducting plates 11 and 13, control solenoids for guiding the
rail 22 and 23 are respectively provided. On the bottom portion of
the body, safety tires are provided.
When a current is allowed to flow through the saddle-shaped
solenoid 5 to produce magnetic flux .phi..sub.1 in such a
structure, there is formed beneath the solenoid a magnetic field
having a certain gradient. Whereas, in the portion 18 surrounded by
the hard superconducting plates 10 to 13, an extremely weak
magnetic field can only exist due to the magnetic shielding effect
of the superconducting plates. Thus, the structure comprising the
plates 10 to 13 receives a force in the direction of the magnetic
field. But since the structure is fixed to the ground, the body
receives a lifting force and floats to a height where the weight of
the body and the floating force balance. Further, when a current I
is allowed to flow through the ladder-shaped circuit 6, the body of
the train receives a force and begins to move in the direction of
the front side of the figure. The greater the intensity of the
magnetic field by the solenoid 5 is, the higher will be the speed
at which the train runs and the greater the floating force so
obtained. When the intensity of the magnetic field is decreased,
the speed of the train decreases and the floating force decreases.
If the magnetic field is further decreased to zero, the train runs
on safety tires 24 and 25 for some distance and halts.
Further, a current allowed to flow through the solenoids 22 and 23
produces magnetic fluxes .phi..sub.2 and .phi..sub.3. The solenoids
22 and 23 receive a force by the interaction with the lesser
magnetic field region 18 to a direction along which the magnetic
flux decreases. This interaction prevents rolling of the body.
Thus, by the above construction, an extremely large floating force
can be provided by the use of the magnetic shielding characteristic
of a hard superconductor and a train can be driven at a very high
speed.
FIG. 9 shows another embodiment of the invention in which the body
of a train is hung down from concrete rails.
In the concrete rails 41 and 42, discs 30 to 32 and 33 to 35 formed
of curved hard superconductors are supported by supporting members
36 and 37 to be mutually parallel, respectively. These discs 30 to
35 are immersed in liquid helium and held in the superconducting
state. On the upper surface of said rails 41 and 42, ladder-shaped
circuits 61 and 62 are formed.
The body of the train is separated into a double structured
passenger car portion in which seats 20A to 20F are disposed and a
portion containing field coils 51 and 52. These two portions are
connected by a connecting shaft 38. Liquid helium is also contained
in the upper portion to keep the field coils 51 and 52 in the
superconducting state. There are also provided safety tires 39 and
40.
In the above system, a train is floated by the interaction of the
magnetic field established by superconducting field coils 51 and 52
and the weak magnetic field in the gap of the curved discs 30, 31,
32 and 33, 34, 35 and is further driven by the interaction of the
field by the field coils 51 and 52 and the currents flowing through
the ladder-shaped circuits 61 and 62 to run above the rails at a
very high speed.
This embodiment provides an advantage in that the stability of the
rail guiding of a train is very large.
In the above embodiments the Lorentz's force acting on the magnetic
field and the current in the ladder-shaped conductor is utilized to
drive a train, but other means such as a linear motor or jet
propelling can also be employed in place of the Lorentz's
force.
As is apparent from the foregoing description, a large floating
force needed for floating a train can be easily provided with less
power consumption by the utilization of the magnetic shielding
effect of a hard superconductor according to the invention.
Further, the magnetic field established by the field coil for
floating the train can also be utilized for propelling a train to
reduce the manufacturing cost. Further, the control of starting,
halting, or varying the speed of a train can be extremely easily
done by controlling the magnitude and the direction of the current
flowing through the ladder-shaped circuit.
* * * * *