FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“ELECTRONIC DEVICE”
MITSUBISHI ELECTRIC CORPORATION of 7-3,
Marunouchi 2-chome, Chiyoda-ku, Tokyo 100-8310, Japan
The following specification particularly describes the invention and the manner in which it is
to be performed.
2
DESCRIPTION
Title of Invention
ELECTRONIC DEVICE
Technical Field5
[0001] The present disclosure relates to an electronic device.
Background Art
[0002] An electronic device, such as a propulsion control device or a power supply
device installed on a railway vehicle, includes a housing accommodating electronic
components. To safely perform maintenance work on the electronic components, some10
electronic devices have structures that suppress power supply to the electronic devices
when covers of the housings are opened. Examples of the electronic devices of this type
are disclosed in Patent Literature 1.
Citation List
Patent Literature15
[0003] Patent Literature 1: Unexamined Japanese Utility Model Application
Publication No. H4-76530
Summary of Invention
Technical Problem
[0004] The electronic device disclosed in Patent Literature 1 includes a microswitch20
that switches on and off in response to opening and closing of the cover of the housing,
and a relay that is disposed in an electrical circuit for pantograph rise and switches
between energized and disconnected states in response to the microswitch state. When
the cover is opened, the relay switches to the disconnected state, electrically
disconnecting the main circuit from the power supply. Thus, even if a switch for25
pantograph rise is accidentally operated during maintenance work, no power is supplied
to the electronic device.
3
[0005] To further ensure the safety of main circuit maintenance work in the
electronic device disclosed in Patent Literature 1, high-voltage electronic components in
the main circuit, such as a capacitor, need to be discharged before maintenance work,
with the main circuit electrically disconnected from a power supply when the cover is
opened, as described above. To further enhance the safety of the electronic device, a5
switch may be provided to electrically connect the capacitor to a discharge resistor when
the electronic device is turned off, ensuring the capacitor is discharged. The switch is
formed, for example, as an electronically controllable switch. However, occurrence of a
malfunction in the electronically controllable switch may cause incapability to connect
the capacitor to the discharge resistor and discharge the capacitor before maintenance10
work.
[0006] Under such circumstances, an objective of the present disclosure is to
provide an electronic device with high safety.
Solution to Problem
[0007] To achieve the above objective, an electronic device according to the present15
disclosure includes a housing, a discharge switch, a first cover, and a displacement
limiting member. The housing has a first opening. The housing accommodates an
electronic component and a discharge resistor for discharging the electronic component.
The discharge switch is accommodated in the housing and includes a pair of terminals
and a movable member. One of the pair of terminals is electrically connected to the20
electronic component, and the other of the pair of terminals is electrically connected to
the discharge resistor. The movable member is made of a conductor and is positioned in
a conductive position where the movable member is in contact with both of the pair of
terminals or in a non-conductive position where the movable member is spaced apart
from at least one of the pair of terminals. The first cover is openable and closable and25
covers the first opening. The displacement limiting member allows the movable
member to be positioned in the conductive position when the first cover is opened and
4
maintains the movable member in the non-conductive position when the first cover is
closed. When the movable member of the discharge switch is positioned in the
conductive position, the electronic component is electrically connected to the discharge
resistor, and when the movable member of the discharge switch is positioned in the non-
conductive position, the electronic component is electrically disconnected from the5
discharge resistor.
Advantageous Effects of Invention
[0008] The displacement limiting member included in the electronic device of the
present disclosure allows the movable member to be positioned in the conductive position
when the first cover is opened. This leads to electrical connection of the electronic10
component with the discharge resistor when the first cover is opened. The electronic
device can thus have high safety.
Brief Description of Drawings
[0009] FIG. 1 is a circuit diagram of an electronic device according to Embodiment
1;15
FIG. 2 is a perspective view of the electronic device according to Embodiment 1;
FIG. 3 is a diagram illustrating a displacement limiting member and a discharge
switch according to Embodiment 1, the discharge switch being in an on state;
FIG. 4 is a diagram illustrating the displacement limiting member and the
discharge switch according to Embodiment 1, the discharge switch being in an off state;20
FIG. 5 is a perspective view of the discharge switch according to Embodiment 1;
FIG. 6 is a perspective view of a discharge switch according to Embodiment 2, the
discharge switch being in an off state;
FIG. 7 is a perspective view of the discharge switch according to Embodiment 2,
the discharge switch being in an on state;25
FIG. 8 is a perspective view of a housing according to Embodiment 3;
FIG. 9 is a perspective view of an electronic device according to Embodiment 3;
5
FIG. 10 is a diagram illustrating a displacement limiting member, a discharge
switch, and a key holder according to Embodiment 3, the discharge switch being in an on
state;
FIG. 11 is a diagram illustrating a displacement limiting member, a discharge
switch, and a key holder according to Embodiment 3, the discharge switch being in an off5
state;
FIG. 12 is a diagram illustrating a modified example of a displacement limiting
member, a discharge switch, and a key holder included in a first modified example of an
electronic device according to an embodiment, the discharge switch being in an on state;
FIG. 13 is a diagram illustrating a modified example of the displacement limiting10
member, the discharge switch, and the key holder included in the first modified example
of the electronic device according to the embodiment, the discharge switch being in an
off state; and
FIG. 14 is a diagram illustrating a modified example of a displacement limiting
member, a discharge switch, and a key holder included in a second modified example of15
the electronic device according to the embodiment;
Description of Embodiments
[0010] An electronic device according to one or more embodiments of the present
disclosure is described below in detail with reference to the drawings. In the drawings,
the same or equivalent components are provided with the same reference signs.20
[0011] Embodiment 1
As an example of an electronic device, a direct current (DC)-three-phase converter
is installed on a railway vehicle to convert DC power supplied from a DC power supply
to three-phase alternating current (AC) power and to supply the AC power to a motor.
An electronic device 1 according to Embodiment 1 is described using the DC to three-25
phase AC power converter as an example. The electronic device 1 illustrated in FIG. 1
is installed in a railway vehicle of a DC feeding system. The electronic device 1
6
converts supplied DC power into AC power to be supplied to a load device 91 and
supplies the converted AC power to the load device 91. The load device 91 is, for
example, a three-phase induction motor that generates propulsion of the railway vehicle.
[0012] The electronic device 1 illustrated in FIG. 1 includes an input terminal 1a to
be connected to a power supply, and an input terminal 1b to be grounded. The5
electronic device 1 further includes a power conversion circuit 11 that converts DC power
supplied from a power supply into AC power, a capacitor C1 connected between the
input terminals 1a and 1b, and a discharge circuit 12 connected in parallel with the
capacitor C1. The discharge circuit 12 includes a switching element SW1 and a
discharge resistor R1 that are connected in series, and a discharge switch 21 and a10
discharge resistor R2 that are connected in series.
[0013] The input terminal 1a is connected to a power supply, specifically, a current
collector through, for example, a contactor or a reactor, which is not illustrated. The
current collector receives power from an electrical substation through a power supply
line. For example, the current collector is a pantograph or a current collector shoe, and15
the power supply line is an overhead power line or a third rail. The input terminal 1b is
short-circuited to rails through, for example, a ground brush, a ground ring, or a wheel,
which are not illustrated, and is grounded.
[0014] The capacitor C1 is located between primary terminals of the power
conversion circuit 11 and is charged with the DC power supplied from the power supply.20
The capacitor C1 and the unillustrated reactor together serve as an LC filter to reduce
harmonic components generated by switching operation of the power conversion circuit
11.
[0015] The power conversion circuit 11 converts the DC power supplied through
the capacitor C1 into three-phase AC power and outputs the three-phase AC power to the25
load device 91. The voltage and frequency of the three-phase AC power output by the
power conversion circuit 11 is adjustable. The power conversion circuit 11 includes a
7
plurality of switching elements, such as insulated-gate bipolar transistors (IGBTs), gate
turn-off thyristors (GTOs), metal-oxide-semiconductor field effect transistors
(MOSFETs).
[0016] The plurality of switching elements included in the power conversion circuit
11 is controlled by control signals supplied from an unillustrated power conversion5
control device, and switches on and off. The plurality of switching elements performs
switching operation to cause the power conversion circuit 11 to perform power
conversion.
[0017] The switching element SW1 and the discharge resistor R1 are connected in
parallel with the capacitor C1. The switching element SW1 is electrically controlled by10
an unillustrated switching controller. For example, the switching element SW1 has a
configuration similar to that of the switching element included in the power conversion
circuit 11. The switching element SW1 is controlled by a control signal output by the
switching controller and switches on and off.
[0018] Upon turn-on of the switching element SW1, the discharge resistor R1 is15
electrically connected to the capacitor C1 and the capacitor C1 is discharged. With the
switching element SW1 being off, the discharge resistor R1 is electrically disconnected
from the capacitor C1. For example, when a voltage between terminals of the capacitor
C1 becomes overvoltage, the switching controller turns on the switching element SW1 to
discharge the capacitor C1. Then, when the voltage between the terminals of the20
capacitor C1 is within a target voltage range, the switch controller turns off the switching
element SW1. This causes the capacitor C1 to be electrically disconnected from the
discharge resistor R1.
[0019] The discharge switch 21 and the discharge resistor R2 are connected in
parallel with the capacitor C1. The discharge switch 21 is switched on and off by25
mechanical operation. Upon turn-on of the discharge switch 21, the discharge resistor
R2 is electrically connected to the capacitor C1 and the capacitor C1 is discharged.
8
With the discharge switch 21 being off, the discharge resistor R2 is electrically
disconnected from the capacitor C1.
[0020] The structure of the electronic device 1 is described in detail below. As
illustrated in FIG. 2, the electronic device 1 includes a housing 31 that accommodates an
electronic component that is a component of the electronic device 1 illustrated in FIG. 15
and discharge resistors R1 and R2 for discharging a capacitor C1, which is an example of
the electronic component. The housing 31 has a first opening 31a to enable
maintenance work of the component of the electronic device 1.
[0021] The electronic device 1 further includes a first cover 32 that is openable and
closable and covers the first opening 31a, and a cooling device 81 thermally connected to10
electronic components that are accommodated inside the housing 31 and generate heat
when energized. The cooling device 81 cools the electronic components by dissipating
the heat transferred from the electronic components to the surrounding air.
[0022] In FIG. 2, the Z-axis direction indicates the vertical direction. The
direction in which the first opening 31a extends through is defined as a Y-axis direction.15
The axis orthogonal to the Z-axis and the Y-axis is defined as the X-axis. The same
applies to the subsequent figures. For example, the electronic device 1 is mounted
under a floor of the railway vehicle by an unillustrated suspension device, with the Y-axis
aligned with the width direction of the railway vehicle and the X-axis aligned with the
travel direction of the railway vehicle.20
[0023] The housing 31 has the first opening 31a on the side surface, specifically, on
a surface facing in a negative Y-axis direction.
[0024] The first cover 32 rotates around a rotation axis AX1 parallel to the Z-axis,
thereby opening and closing the first opening 31a. The first cover 32 is made of a plate-
like material that can cover the entire first opening 31a and the surrounding area of the25
first opening 31a.
[0025] The cooling device 81 includes, for example, a heat-receiving block
9
thermally connected to the electronic components inside the housing 31, fins attached to
the heat-receiving block and exposed outside the housing 31, and a cover that covers the
heat-receiving block and the fins and has ventilation holes. Heat generated by the
electronic components is transferred through the heat-receiving block and the fins to the
air that flows through the ventilation holes of the cover into the interior of the cover,5
thereby cooling the electronic components.
[0026] The structure to enhance safety of the electronic device 1 is described in
detail below. FIGS. 3 and 4 are diagrams illustrating the electronic device 1 as viewed
from the interior of the housing 31 to the first cover 32. To simplify the drawings,
FIGS. 3 and 4 simply illustrate the discharge switch 21 among the components of the10
electronic device 1 accommodated in the interior of the housing 31. With the first cover
32 opened as illustrated in FIG. 3, the discharge switch 21 is turned on. As illustrated in
FIG. 4, with the first cover 32 closed, the discharge switch 21 is turned off.
[0027] The discharge switch 21 includes a pair of terminals 22a and 22b and a
movable member 23 positioned in a conductive position or a non-conductive position.15
Preferably, the discharge switch 21 further includes an urging member 24 that urges the
movable member 23 to the conductive position. The discharge switch 21 further
includes a terminal holding member 25 that holds the pair of terminals 22a and 22b.
[0028] The electronic device 1 further includes a fixed frame 33 fixed to an inner
surface of the housing 31, and a support member 34 that is attached to the fixed frame 3320
and supports the discharge switch 21. The electronic device 1 further includes a
displacement limiting member 35 that allows the movable member 23 to be positioned in
the conductive position when the first cover 32 is opened and maintains the movable
member 23 in the non-conductive position when the first cover 32 is closed.
[0029] As illustrated in FIG. 5, which is a perspective view of the discharge switch25
21, in Embodiment 1, the terminals 22a and 22b each have a shape sandwiching the
movable member 23 in the Z-axis direction. One of the terminals 22a and 22b is
10
electrically connected to the electronic component to be discharged, that is, the capacitor
C1. The other of the terminals 22a and 22b is electrically connected to the discharge
resistor R2. In Embodiment 1, the one of the terminals 22a and 22b is electrically
connected to a point of connection between the input terminal 1a and the power
conversion circuit 11 illustrated in FIG. 1, and the other of the terminals 22a and 22b is5
electrically connected to the discharge resistor R2.
[0030] The movable member 23 is made of a conductor. In Embodiment 1, the
movable member 23 is made of a plate-like metal member. The movable member 23 is
positioned in the conductive position where the movable member 23 is in contact with
both the terminals 22a and 22b as illustrated in FIGS. 3 and 5, or in the non-conductive10
position where the movable member 23 is spaced apart from at least one of the terminals
22a and 22b as illustrated in FIG. 4. In Embodiment 1, as illustrated in FIG. 5, one end
of the movable member 23 is fixed to the terminal 22b by a fastening member. The
movable member 23 revolves around a rotation axis AX2 extending in parallel to the Z-
axis, with one end fixed to the terminal 22b.15
[0031] The discharge switch 21 includes a pair of urging members 24 positioned
such that the movable member 23 is between the pair of urging members 24 in the Z-axis
direction. The urging members 24 urge the movable member 23 to the conductive
position. In Embodiment 1, the urging members 24 are made of an elastic body that
deforms under external force and returns to an original shape when the external force is20
removed. The movable member 23 is positioned in the conductive position when the
elastic body has the original shape. Specifically, the urging members 24 is made of a
coil spring having one end attached to the terminal holding member 25 and the other end
attached through an insulating member 26 to the movable member 23. When the coil
spring is at its natural length, the movable member 23 is in the conductive position.25
When the movable member 23 rotates clockwise from the position in FIG. 5, as viewed
in the positive Z-axis direction, to the non-conductive position, the urging member 24
11
made of the coil spring generates a force in the direction of returning to its natural length.
In other words, the urging members 24 pull the movable member 23 from the non-
conducting position toward the conducting position. This urges the movable member
23 from the non-conducting position toward the conducting position.
[0032] The terminal holding member 25 holds the terminals 22a and 22b insulated5
from each other. The terminal holding member 25 is made of an insulating material, for
example, resin.
[0033] As illustrated in FIGS. 3 and 4, the fixed frame 33 is fixed to the inner
surface of the housing 31 in contact with the inner surface of the housing 31. The fixed
frame 33 has such high rigidity and strength as to resist deformation under the expectable10
maximum vibration from the railway vehicle. For example, the fixed frame 33 is made
of a metal member, such as iron or aluminum. The fixed frame 33 may be fixed to the
housing 31 firmly enough to maintain a constant positional relationship relative to the
housing 31 under vibrations from the railway vehicle that is traveling. The fixed frame
33 is fixed to the housing 31 with a fixing method such as fastening by a fastening15
member, adhesive bonding, welding, or brazing.
[0034] The support member 34 has such high rigidity and strength as to resist
deformation under the expectable maximum vibration from the railway vehicle. For
example, the support member 34 is made of a metal member, such as iron or aluminum.
The support member 34 may be fixed to the fixed frame 33 firmly enough to maintain a20
constant positional relationship relative to the fixed frame 33 under vibrations from the
railway vehicle that is traveling. The support member 34 is fixed to the fixed frame 33
with a fixing method such as fastening by a fastening member, adhesive bonding,
welding, or brazing.
[0035] The terminal holding member 25 included in the discharge switch 21 is25
attached to the support member 34. The terminal holding member 25 may be fixed to
the support member 34 firmly enough to maintain a constant positional relationship
12
relative to the support member 34 under vibrations from the railway vehicle that is
traveling. For example, the terminal holding member 25 is fixed to the support member
34 by fastening by a fastening member.
[0036] The displacement limiting member 35 includes a contact portion 35a having
a plate-like shape, attached to a side of the first cover 32 facing an interior of the housing5
31, and extending in a direction away from the first cover 32. The displacement
limiting member 35 has such high rigidity and strength as to resist deformation under the
expectable maximum vibration from the railway vehicle. For example, the
displacement limiting member 35 is made of a metal member, such as iron or aluminum.
The displacement limiting member 35 may be fixed to the first cover 32 firmly enough to10
maintain a constant positional relationship relative to the first cover 32 under vibrations
from the railway vehicle that is traveling. The displacement limiting member 35 is
fixed to the first cover 32 with a fixing method such as fastening by a fastening member,
adhesive bonding, welding, or brazing. The displacement limiting member 35 is
preferably insulated.15
[0037] As illustrated in FIG. 4, with the first cover 32 closed, the contact portion
35a of the displacement limiting member 35 comes in contact with the movable member
23 and pushes the movable member 23 toward the positive Y-axis direction. The
movable member 23 thereby revolves around the rotation axis AX2 with one end fixed to
the terminal 22b to move away from the terminal 22a. As a result, the movable member20
23 is positioned in the non-conductive position. With the first cover 32 closed, the
displacement limiting member 35 maintains the movable member 23 in the non-
conductive position.
[0038] During operation of the railway vehicle, , the power conversion circuit 11
performs power conversion by means of switching operation of a plurality of switching25
elements in the power conversion circuit 11. When the railway vehicle stops operating,
that is, when the electronic device 1 stops operating, the power conversion control device
13
turns off the plurality of switching elements of the power conversion circuit 11. Then,
the switching controller turns on the switching element SW1, and the capacitor C1 is
electrically connected to the discharge resistor R1 and is discharged.
[0039] Maintenance work on the electronic device 1 is performed with the
operation of the electronic device 1 stopped. In the maintenance work, when the first5
cover 32 is opened as illustrated in FIG. 3, the contact portion 35a of the displacement
limiting member 35 moves away from the movable member 23 as the first cover 32
rotates. Thus, the urging member 24 urges the movable member 23 from the non-
conductive position to the conductive position. As a result, the movable member 23
comes in contact with the terminals 22a and 22b and the discharge switch 21 is turned on.10
Upon turn-on of the discharge switch 21, the capacitor C1 is electrically connected to the
discharge resistor R2 and is discharged. This enables the capacitor C1 to be discharged
with the discharge resistor R2 even when the capacitor C1 cannot be discharged with the
discharge resistor R1 due to a failure of the switching element SW1.
[0040] As described above, the displacement limiting member 35 included in the15
electronic device 1 according to Embodiment 1 allows the movable member 23 to be
positioned in the conductive position when the first cover 32 is opened. The discharge
switch 21 is then turned on, and the capacitor C1 is electrically connected to the discharge
resistor R2 and is discharged. In other words, when the first cover 32 is opened, the
mechanical operation causes the discharge switch 21 to be turned on, thereby enabling20
the capacitor C1 to which a high voltage is applied to be discharged. Even when the
capacitor C1 cannot be discharged by the discharge resistor R1 due to a failure of the
switching element SW1, the discharge switch 21 being turned on by the mechanical
operation, which is the opening of the first cover 32, enables the capacitor C1 to be
discharged with the discharge resistor R2, thereby ensuring safety of the maintenance25
work.
[0041] Embodiment 2
14
The structure of the discharge switch is not limited to the above example, but can
be any structure that is in the off state when the first cover 32 is closed and in the on state
when the first cover 32 is opened. The electronic device 1 including a discharge switch
having a structure different from that of Embodiment 1 is described in Embodiment 2.
[0042] The electronic device 1 according to Embodiment 2 includes a discharge5
switch 51 illustrated in FIGS. 6 and 7. The structure of the electronic device 1 other
than the discharge switch 51 is similar to that of Embodiment 1. The discharge switch
51 is connected in series with the discharge resistor R2. The discharge switch 51 and
the discharge resistor R2 connected in series are connected in parallel with the capacitor
C1.10
[0043] The discharge switch 51 is switched on and off by mechanical operation.
Upon turn-on of the discharge switch 51, the discharge resistor R2 is electrically
connected to the capacitor C1 and the capacitor C1 is discharged. With the discharge
switch 51 being off, the discharge resistor R2 is electrically disconnected from the
capacitor C1.15
[0044] The discharge switch 51 includes a pair of terminals 52a and 52b, a movable
member 53 positioned in the conductive position or the non-conductive position, and an
urging member 54 that urges the movable member 53 to the conductive position. The
discharge switch 51 further includes a terminal holding member 55 that holds the pair of
terminals 52a and 52b and a movable member holder 56 that holds the movable member20
53.
[0045] In Embodiment 2, the terminals 52a and 52b each have a columnar shape
extending in the Y-axis direction. One of the terminals 52a and 52b is electrically
connected to the electronic component to be discharged, that is, the capacitor C1. The
other of the terminals 52a and 52b is electrically connected to the discharge resistor R2.25
In Embodiment 2, the one of the terminals 52a and 52b is electrically connected to a point
of connection between the input terminal 1a and the power conversion circuit 11
15
illustrated in FIG. 1, and the other of the terminals 52a and 52b is electrically connected
to the discharge resistor R2.
[0046] The movable member 53 is made of a conductor. In Embodiment 2, the
movable member 53 is made of a metal member having a columnar shape and extending
in the Y-axis direction, as illustrated in FIG. 6. The movable member 53 has holes into5
which the terminal 52a and 52b are fitted. The movable member 53 is positioned in the
conductive position where the movable member 53 is in contact with both the terminals
52a and 52b as illustrated in FIG. 7, or in the non-conductive position where the movable
member 53 is spaced apart from both the terminals 52a and 52b as illustrated in FIG. 6.
[0047] The discharge switch 51 includes the urging member 54 extending in the Y-10
axis direction. The urging member 54 urges the movable member 53 to the conductive
position. The urging member 54 is made of an elastic body that deforms under external
force and returns to an original shape when the external force is removed. The movable
member 53 is positioned in the conductive position when the elastic body has the original
shape. Specifically, the urging member 54 is made of a coil spring having one end15
attached to the terminal holding member 55 and the other end attached to the movable
member holder 56. When the coil spring is at its natural length, the movable member
53 is in the conductive position as illustrated in FIG. 7.
[0048] When the movable member holder 56 holding the movable member 53
moves from the position of FIG. 7 to the positive Y-axis direction and the movable20
member 53 is positioned in the non-conductive position, the urging member 54 made of
the coil spring generates a force in the direction of returning to its natural length. This
urges the movable member holder 56 to the negative Y-axis direction. In other words,
the movable member 53 is urged from the non-conducting position toward the
conducting position.25
[0049] The terminal holding member 55 holds the terminals 52a and 52b insulated
from each other. The terminal holding member 55 is made of an insulating material, for
16
example, resin. In Embodiment 2, as illustrated in FIG. 6, the terminal holding member
55 has a box shape opening in the positive Y-axis direction and accommodates the
terminals 52a and 52b inside, spaced apart from each other. An attachment portion 55a
having a flat-plate shape and having a main surface orthogonal to the Y-axis is provided
on the side of the terminal holding member 55 facing in the positive X-axis direction.5
An attachment portion 55b having a flat-plate shape and having a main surface
orthogonal to the Y-axis is provided on the side of the terminal holding member 55
facing in the negative X-axis direction.
[0050] The movable member holder 56 is made of an insulating material, for
example, resin. In Embodiment 2, the movable member holder 56 has a box shape10
opening in the negative Y-axis direction and accommodates the movable member 53,
with a portion of the movable member 53 exposed. An attachment portion 56a having a
flat-plate shape and having a main surface orthogonal to the Y-axis is provided on the
side of the movable member holder 56 facing in the positive X-axis direction. An
attachment portion 56b having a flat-plate shape and having a main surface orthogonal to15
the Y-axis is provided on the side of the movable member holder 56 facing in the
negative X-axis direction.
[0051] The urging member 54 has one end attached to the attachment portion 55a
of the terminal holding member 55 and the other end attached to the attachment portion
56a of the movable member holder 56. The movable member holder 56 is attached to20
the terminal holding member 55 via an extending-contracting mechanism 57 that is
extendable and contractible in the Y-axis direction. Specifically, the extending-
contracting mechanism 57 has one end attached to the attachment portion 55b of the
terminal holding member 55 and the other end attached to the attachment portion 56b of
the movable member holder 56.25
[0052] With the first cover 32 closed, the contact portion 35a of the displacement
limiting member 35 comes in contact with the attachment portion 56a of the movable
17
member holder 56 and pushes the movable member holder 56 in the positive Y-axis
direction. As a result, the movable member 53 moves in the positive Y-axis direction
integrally with the movable member holder 56 and spaced apart from both the terminals
52a and 52b. In other words, the movable member 53 is positioned in the non-
conductive position. With the first cover 32 closed, the displacement limiting member5
35 maintains the movable member 53 in the non-conductive position.
[0053] During operation of the railway vehicle, the power conversion circuit 11
performs power conversion by means of switching operation of a plurality of switching
elements in the power conversion circuit 11. When the railway vehicle stops operating,
that is, when the electronic device 1 stops operating, the power conversion control device10
turns off the plurality of switching elements of the power conversion circuit 11. Then,
the switching controller turns on the switching element SW1, and the capacitor C1 is
electrically connected to the discharge resistor R1 and is discharged.
[0054] Maintenance work on the electronic device 1 is performed with the
operation of the electronic device 1 stopped. In the maintenance work, when the first15
cover 32 is opened, the contact portion 35a of the displacement limiting member 35
moves away from the movable member holder 56 as the first cover 32 rotates. Thus, the
urging member 54 urges the movable member holder 56 to the negative Y-axis direction.
As a result, as illustrated in FIG. 7, the movable member 53 is urged from the non-
conductive position to the conductive position, and the movable member 53 comes in20
contact with both the terminals 52a and 52b and the discharge switch 51 is turned on.
Upon turn-on of the discharge switch 51, the capacitor C1 is electrically connected to the
discharge resistor R2 and is discharged. This enables the capacitor C1 to be discharged
with the discharge resistor R2 even when the capacitor C1 cannot be discharged with the
discharge resistor R1 due to a failure of the switching element SW1.25
[0055] As described above, the displacement limiting member 35 included in the
electronic device 2 according to Embodiment 2 allows the movable member 53 to be
18
positioned in the conductive position when the first cover 32 is opened. The discharge
switch 51 is then turned on, and the capacitor C1 is electrically connected to the discharge
resistor R2 and is discharged. In other words, when the first cover 32 is opened, the
mechanical operation causes the discharge switch 51 to be turned on, thereby enabling
the capacitor C1 to which a high voltage is applied to be discharged. Even when the5
capacitor C1 cannot be discharged by the discharge resistor R1 due to a failure of the
switching element SW1, the discharge switch 51 being turned on by the mechanical
operation, which is the opening of the first cover 32, enables the capacitor C1 to be
discharged with the discharge resistor R2, thereby ensuring safety of the maintenance
work.10
[0056] Embodiment 3
The electronic device may include an interlock mechanism that suppresses closing
of the first cover 32 when another cover that is different from the first cover 32 is
unlocked. An electronic device 2 according to Embodiment 3 is described, focusing on
differences from that of Embodiment 1.15
[0057] As illustrated in FIG. 8, the housing 31 included in the electronic device 2
has second openings 31b and 31c on a side opposite to the side in which the first opening
31a is made. As illustrated in FIG. 9, the electronic device 2 includes a second cover 36
that is openable and closable and covers the second opening 31b and a second cover 37
that is openable and closable and covers the second opening 31c. The electronic device20
2 further includes a locking mechanism 38 that locks the second cover 36 and a locking
mechanism 39 that locks the second cover 37.
[0058] The second cover 36 rotates around a rotation axis AX3 parallel to the Z-
axis, thereby opening and closing the second opening 31b. The second cover 36 is
made of a plate-like material that can cover the entire second opening 31b and the25
surrounding area of the second opening 31b.
[0059] The second cover 37 rotates around a rotation axis AX4 parallel to the Z-
19
axis, thereby opening and closing the second opening 31c. The second cover 37 is
made of a plate-like material that can cover the entire second opening 31c and the
surrounding area of the second opening 31c.
[0060] A key 40 of the locking mechanism 38 is removable only when the second
cover 36 is locked. A key 41 of the locking mechanism 39 is removable only when the5
second cover 37 is locked.
[0061] As illustrated in FIGS. 10 and 11, the electronic device 2 includes a key
holder 61 that holds the key 40. The electronic device 2 further includes a key holder 62
that holds the key 41 illustrated in FIG. 9. To simplify the drawings, the key 41 is not
illustrated in FIGS. 10 and 11. The structure of the electronic device 2 other than the10
key holders 61 and 62 is similar to that of Embodiment 1. To simplify the drawings,
FIGS. 10 and 11 simply illustrate the discharge switch 21 among the components of the
electronic device 2 accommodated in the interior of the housing 31, and the rotation axis
AX2 is not illustrated therein.
[0062] The key holder 61 includes a holding mechanism 61a that is positioned15
either in the unlocked position where the key 40 can be inserted and removed as
illustrated in FIG. 10 or in the locked position where removal of the inserted key 40 is
suppressed as illustrated in FIG. 11. The key holder 61 further includes an opening-
closing limiting mechanism 61b that suppresses closing of the first cover 32 when the
holding mechanism 61a is positioned in the unlocked position as illustrated in FIG. 1020
and allows the first cover 32 to be closed when the holding mechanism 61a is positioned
in the locked position as illustrated in FIG. 11.
[0063] An insertion direction of the key 40 to the holding mechanism 61a matches
the direction in which the first opening 31a extends through, specifically, the Y-axis
direction. The holding mechanism 61a has a shape rotatable around a rotation axis AX525
extending in the insertion direction of the key 40. In other words, the holding
mechanism 61a is rotatable around the rotation axis AX5 in parallel to the Y-axis. The
20
opening-closing limiting mechanism 61b is made of a projection attached to the holding
mechanism 61a and extending in a radial direction orthogonal to the rotation axis AX5 of
the holding mechanism 61a. The projection rotates around the rotation axis AX5 as the
holding mechanism 61a rotates.
[0064] The structure of the key holder 62 is similar to that of the key holder 61.5
The key holder 62 includes a holding mechanism 62a that is positioned either in the
unlocked position where the key 41 can be inserted and removed or in the locked position
where removal of the inserted key 41 is suppressed. The key holder 62 further includes
an opening-closing limiting mechanism 62b that suppresses closing of the first cover 32
when the holding mechanism 62a is positioned in the unlocked position as illustrated in10
FIG. 10 and allows the first cover 32 to be closed when the holding mechanism 62a is
positioned in the locked position as illustrated in FIG. 11.
[0065] An insertion direction of the key 41 to the holding mechanism 62a matches
the direction in which the first opening 31a extends through, specifically, the Y-axis
direction. The holding mechanism 62a has a shape rotatable around a rotation axis AX615
extending in the insertion direction of the key 41. In other words, the holding
mechanism 62a is rotatable around the rotation axis AX6 parallel to the Y-axis. The
opening-closing limiting mechanism 62b is made of a projection attached to the holding
mechanism 62a and extending in a radial direction orthogonal to the rotation axis AX6 of
the holding mechanism 62a. The projection rotates around the rotation axis AX6 as the20
holding mechanism 62a rotates.
[0066] As illustrated in FIG. 10, when an attempt is made to close the first cover 32
when the holding mechanisms 61a and 62a are positioned in the unlocked position, the
contact portion 35a of the displacement limiting member 35 attached to the first cover 32
comes in contact with the opening-closing limiting mechanisms 61b and 62b made of25
projections. This suppresses closing of the first cover 32. When the holding
mechanisms 61a and 62a are positioned in the unlocked position, the keys 40 and 41 may
21
be removed from the holding mechanisms 61a and 62a. This enables the second covers
36 and 37 to be locked. In other words, with the second covers 36 and 37 unlockable,
closing of the first cover 32 is suppressed.
[0067] As illustrated in FIG. 11, when the holding mechanisms 61a and 62a are
positioned in the locked position, the contact portion 35a of the displacement limiting5
member 35 attached to the first cover 32 does not come in contact with the opening-
closing limiting mechanisms 61b and 62b made of projections. This enables the first
cover 32 to be closed. The key 40 removable from the locking mechanism 38 only
when the second cover 36 is locked as described above is inserted into the holding
mechanism 61a. When the holding mechanism 61a into which the key 40 is inserted10
rotates from the unlocked position to the locked position, removal of the key 40 is
suppressed, thereby preventing unlocking of the second cover 36. Similarly, the key 41
removable from the locking mechanism 39 only when the second cover 37 is locked is
inserted into the holding mechanism 62a. When the holding mechanism 62a into which
the key 41 is inserted rotates from the unlocked position to the locked position, removal15
of the key 41 is suppressed, thereby preventing unlocking of the second cover 37. Thus,
when the second covers 36 and 37 are locked, the keys 40 and 41 are inserted in the
corresponding holding mechanisms 61a and 62a, and the holding mechanisms 61a and
62a are in the locked position, the first cover 32 can be closed.
[0068] As described above, the electronic device 1 according to Embodiment 320
includes an interlock mechanism that suppresses closing of the first cover 32, with the
second covers 36 and 37 unlockable. This can promote secure lock of the second covers
36 and 37, and the electronic device 2 can thus have high safety.
[0069] The present disclosure is not limited to the above embodiments. The
electronic devices 1 and 2 are not limited to DC to three-phase converters, but can be any25
devices that include the discharge resistor R2 and the discharge switch 21 or the
discharge switch 51. As an example, the electronic devices 1 and 2 may be a power
22
conversion device that is installed on a railway vehicle of an AC feeding system and
converts the AC power supplied from the power supply to the three-phase AC power.
In this case, in addition to the components illustrated in FIG. 1, the electronic devices 1
and 2 may include a converter that converts AC power to DC power, and the capacitor
C1 may be discharged with the DC power output by the converter.5
[0070] As another example, the electronic devices 1 and 2 may be a DC-DC
converter that is installable on the railway vehicle of the DC feeding system and converts
the DC power supplied from a power supply to the DC power to be supplied to the load
device 91, and outputs the converted AC power.
[0071] As another example, the electronic devices 1 and 2 may include a plurality10
of power conversion circuits 11 and capacitors C1 provided for the respective power
conversion circuits 11. Here, the electronic devices 1 and 2 may include a common
discharge circuit 12 shared by the plurality of power conversion circuits 11 or may
include discharge circuits 12 for the respective power conversion circuits 11. In a case
where the discharge circuit 12 is provided for each of the plurality of power conversion15
circuits 11, each discharge switch 21 or each discharge switch 51 may be provided in a
position adjacent to the first opening 31a. Thus, when the first cover 32 is closed, the
movable member 23 of each discharge switch 21 or the movable member 53 of each
discharge switch 51 may be positioned in the conductive position, and when the first
cover 32 is opened, the movable member 23 of each discharge switch 21 or the movable20
member 53 of each discharge switch 51 may be maintained in the non-conductive
position.
[0072] The discharge circuit 12 may only include the discharge switch 21 and the
discharge resistor R2 without having the switching element SW1 and the discharge
resistor R1. Similarly, the discharge circuit 12 may only include the discharge switch25
51 and the discharge resistor R2.
[0073] The structures of the electronic devices 1 and 2 are not limited to the above
23
examples. Any configuration can be adopted that allows the movable member 23 of
each discharge switch 21 or the movable member 53 of each discharge switch 51 to be
positioned in the non-conductive position when the first cover 32 is closed, and allows
the movable member 23 of each discharge switch 21 or the movable member 53 of each
discharge switch 51 to be maintained in the conductive position when the first cover 32 is5
opened.
[0074] As an example, the first cover 32 may rotate around a rotation axis parallel
to the X-axis to open and close the first opening 31a. Here, the first cover 32 may be
positioned vertically above the first cover 32 and rotate around the rotation axis extending
in parallel to the X-axis, or may be positioned vertically below the first cover 32 and10
rotate around the rotation axis extending in parallel to the X-axis.
[0075] The structure, attachment position, electrical connection position, the
attachment direction, and the like of the discharge switch 21 or the discharge switch 51
are not limited to the above examples, but may be any configuration that allows the
discharge switch to be turned off when the first cover 32 is closed and to be turned on15
when the first cover 32 is opened.
[0076] As an example, the discharge switches 21 and 51 do not necessarily have the
urging members 24 and 54. A modified example of the electronic device 1 including
the discharge switch 21 without having the urging member 24 is illustrated in FIGS. 12
and 13. When the first cover 32 is closed from a state where the first cover 32 is opened20
as illustrated in FIG. 12, the contact portion 35a of the displacement limiting member 35
comes in contact with the movable member 23 before the first cover 32 is completely
closed. When the first cover 32 further moves to the housing 31, the contact portion 35a
of the displacement limiting member 35 lifts up an end of the movable member 23
vertically upward while coming in contact with the movable member 23. This causes25
the movable member 23 to revolve around the rotation axis AX2. Specifically, the
movable member 23 rotates clockwise as viewed in the negative Y-axis direction.
24
When the first cover 32 is completely closed as illustrated in FIG. 13, the one end of the
movable member 23 is spaced apart from the terminal 22a. As a result, the discharge
switch 21 is turned off.
[0077] When the first cover 32 is opened from the state of FIG. 13 and the contact
portion 35a of the displacement limiting member 35 moves away from the movable5
member 23, one end of the movable member 23 moves vertically lower by its own
weight. This causes the movable member 23 to revolve around the rotation axis AX2.
Specifically, the movable member 23 rotates counterclockwise as viewed in the negative
Y-axis direction. Then, as illustrated in FIG. 12, the movable member 23 comes in
contact with both the terminals 22a and 22b. As a result, the discharge switch 21 is10
turned on.
[0078] As another example, one of the terminals 22a and 22b of the discharge
switch 21 may be electrically connected to a point of connection between the input
terminal 1b and the power conversion circuit 11, and the other of the terminals 22a and
22b may be electrically connected to the discharge resistor R2.15
[0079] As another example, the discharge switches 21 and 51 are preferably
switches that switch on and off by mechanical operation as described above, but may be
made of electronic switches, specifically, optical switches, microswitches, or the like, that
are turned on when the first cover 32 is opened and are turned off when the first cover 32
is closed.20
[0080] The urging members 24 and 54 are not limited to coil springs, but can be
made of any elastic body, such as leaf springs, disc springs, or rubber. The urging
members 24 and 54 may cause urging to the conductive position as indicated by the
aforementioned embodiments or may cause urging to the non-conductive position.
When the urging members 24 and 54 cause urging to the non-conductive position, for25
example, the displacement limiting member 35 attached to the first cover 32 may engage
with the movable members 23 and 53 when the first cover 32 is opened, and urge the
25
movable members 23 and 53 to the conductive position.
[0081] The structure of the displacement limiting member 35 is not limited to the
above examples, and may have any structure that allows the displacement limiting
member 35 to come in contact with the movable member 23 or the movable member 53
when the first cover 32 is closed, and thereby allows the movable member 23 or the5
movable member 53 to be maintained in the non-conductive position. As an example,
the displacement limiting member 35 may have one end connected to the first cover 32
and have a columnar shape extending in the Y-axis direction.
[0082] The embodiments described above may be combined as appropriate. As
an example, the electronic device 2 may include a discharge switch 51 illustrated in10
Embodiment 2. As another example, the electronic device 2 may include the discharge
switch 21 and the displacement limiting member 35 illustrated in FIGS. 12 and 13.
[0083] The structure of the interlock mechanism included in the electronic device 2
is not limited to the above examples. As an example, the electronic device 2 may
suppress closing of the first cover 32 when the holding mechanisms 61a and 62a are15
positioned in the unlocked position by a member separate from the displacement limiting
member 35. A modified example of the electronic device 2 including a protrusion
member 42 separate from the displacement limiting member 35 is illustrated in FIG. 14.
[0084] The protrusion member 42 is attached to a side of the first cover 32 facing
the interior of the housing 31 and has a shape extending in a direction away from the first20
cover 32. When an attempt is made to close the first cover 32 when the holding
mechanisms 61a and 62a are positioned in the unlocked position, the protrusion member
42 attached to the first cover 32 comes in contact with the opening-closing limiting
mechanisms 61b and 62b made of projections. This suppresses closing of the first cover
32. When the holding mechanisms 61a and 62a are positioned in the locked position,25
the protrusion member 42 attached to the first cover 32 does not come in contact with the
opening-closing limiting mechanism 62b and 62b made of projections. This enables the
26
first cover 32 to be closed. Here, it is sufficient that the displacement limiting member
35 has a shape that comes in contact with the movable member 23 and does not come in
contact with the opening-closing limiting mechanisms 61b and 62b.
[0085] The orientation in which the electronic devices 1 and 2 are mounted on the
railway vehicle may be any condition other than the above-mentioned examples. The5
electronic devices 1 and 2 may be installed in any movable body such as an automobile,
an aircraft, or a vessel, rather than a railway vehicle, or installed at any stationary
location.
[0086] The load device 91 is not limited to a three-phase induction motor, but rather
may be a synchronous electric motor, or a DC electric motor. The load device 91 is not10
limited to a motor, but may be any device installed in the railway vehicle.
[0087] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
persons skilled in the art will recognize that changes may be made in form and detail
without departing from the broader spirit and scope of the invention. Accordingly, the15
specification and drawings are to be regarded in an illustrative rather than a restrictive
sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of
equivalents to which such claims are entitled.
Reference Signs List20
[0088] 1, 2 Electronic device
1a, 1b Input terminal
11 Power conversion circuit
12 Discharge circuit
21, 51 Discharge switch25
22a, 22b, 52a, 52b Terminal
23, 53 Movable member
27
24, 54 Urging member
25, 55 Terminal holding member
26 Insulating member
31 Housing
31a First opening5
31b, 31c Second opening
32 First cover
33 Fixed frame
34 Support member
35 Displacement limiting member10
35a Contact portion
36, 37 Second cover
38, 39 Locking mechanism
40, 41 Key
42 Protrusion member15
55a, 55b, 56a, 56b Attachment portion
56 Movable member holder
57 Extending-contracting mechanism
61, 62 Key holder
61a, 62a Holding mechanism20
61b, 62b Opening-closing limiting mechanism
81 Cooling device
91 Load device
AX1, AX2, AX3, AX4, AX5, AX6 Rotation axis
C1 Capacitor25
R1, R2 Discharge resistor
SW1 Switching element
28
WE CLAIMS
[Claim 1] An electronic device, comprising:
a housing having a first opening and configured to accommodate an electronic
component and a discharge resistor for discharging the electronic component;
a discharge switch accommodated in the housing, the discharge switch including5
a pair of terminals, one of the pair of terminals being electrically connected
to the electronic component, the other of the pair of terminals being electrically connected
to the discharge resistor, and
a movable member made of a conductor and positioned in a conductive
position where the movable member is in contact with both of the pair of terminals or in a10
non-conductive position where the movable member is spaced apart from at least one of
the pair of terminals;
a first cover being openable and closable and configured to cover the first opening;
and
a displacement limiting member that allows the movable member to be positioned15
in the conductive position when the first cover is opened and maintains the movable
member in the non-conductive position when the first cover is closed, wherein
when the movable member of the discharge switch is positioned in the conductive
position, the electronic component is electrically connected to the discharge resistor, and
when the movable member of the discharge switch is positioned in the non-conductive20
position, the electronic component is electrically disconnected from the discharge
resistor.
[Claim 2] The electronic device according to claim 1, wherein
the displacement limiting member is attached to a side of the first cover facing an25
interior of the housing and has a contact portion having a plate-like shape and extending
in a direction away from the first cover, and contact of the displacement limiting member
29
with the movable member, with the first cover closed, maintains the movable member in
the non-conductive position.
[Claim 3] The electronic device according to claim 1 or 2, wherein
the movable member has an end fixed to one of the pair of terminals and has a5
shape revolvable around the fixed end.
[Claim 4] The electronic device according to claim 1 or 2, wherein
the movable member has a shape to be fitted to both of the pair of terminals in the
conductive position, and the movable member is spaced apart from both of the pair of10
terminals in the non-conductive position.
[Claim 5] The electronic device according to any one of claims 1 to 4, wherein
the discharge switch further includes an urging member that urges the movable
member to the conductive position.15
[Claim 6] The electronic device according to claim 5, wherein
the urging member has an elastic body that deforms under external force and return
to an original shape when the external force is removed, and
the movable member is positioned in the conductive position when the elastic body20
has the original shape.
[Claim 7] The electronic device according to any one of claims 1 to 6, wherein
the housing further includes one or more second openings, and
the electronic device further comprising:25
one or more second covers being openable and closable and configured to
cover the one or more second openings,
30
one or more locking mechanisms to lock the one or more second covers and
allow a key to be removable only when the one or more second covers are locked, and
a key holder disposed inside the housing and configured to hold the key.
[Claim 8] The electronic device according to claim 7, wherein5
the key holder includes
a holding mechanism positioned at either an unlocked position that allows
insertion and removal of the key or a locked position that suppresses removal of the key
inserted therein, and
an opening-closing limiting mechanism that suppresses closing of the first cover10
when the holding mechanism is position in the unlocked position and allows the first
cover to be closed when the holding mechanism is positioned in the locked position.
[Claim 9] The electronic device according to claim 8, wherein
an insertion direction of the key to the holding mechanism matches a direction in15
which the first opening extends through,
the holding mechanism has a shape rotatable around a rotation axis extending in
the insertion direction of the key, and
the opening-closing limiting mechanism is made of a projection attached to the
holding mechanism and extending in a radial direction orthogonal to the rotation axis of20
the holding mechanism, the projection rotating as the holding mechanism rotates.
[Claim 10] The electronic device according to claim 9, wherein
upon the holding mechanism being positioned in the unlocked position, the
displacement limiting member attached to the first cover comes in contact with the25
projection, thereby suppressing closing of the first cover.
31
[Claim 11] The electronic device according to claim 9, further comprising:
a protrusion member attached to a side of the first cover facing an interior of the
housing and extending in a direction away from the first cover, wherein
upon the holding mechanism being positioned in the unlocked position, the
closing of5 projection comes in contact with the protrusion member, thereby suppressing
the first cover.