Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-04-16
2001-09-18
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C165S104330, C174S015200, C361S700000, C361S715000
Reexamination Certificate
active
06292363
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a servo amplifier for use in a controller for various industrial machinery such as a machine tool, a robot, an injection molding machine, a wire electric discharge machine and an electrical press machine.
2. Description of the Related Art
FIG. 7
illustrates a circuitry structure of a servo amplifier generally known in the art. An alternating current from a three-phase alternating-current power supply
1
is converted to a direct current by a semiconductor module
2
constituted by a rectifier circuit such as a diode bridge circuit, and then smoothed by an electrolytic capacitor
3
. Subsequently, the direct current is converted into a desired alternating current under PWM control by a semiconductor module
4
and a control circuit
5
which constitute an inverter circuit, so as to drive control a servomotor
6
. In
FIG. 7
, a circuit A
7
includes a charging circuit for gradually charging the electrolytic capacitor
3
when the power supply is turned on, a circuit B
8
includes a direct-current voltage detection circuit and a dynamic braking circuit for absorbing a regenerative current, a circuit C
9
includes a current detection circuit, and a circuit D
10
includes circuits for dynamic braking and for detecting electric current.
A general servo amplifier is constituted by parts or components shown in
FIG. 7
except the three-phase power supply
1
and the servomotor
6
, that is, the semiconductor modules
2
and
4
, the control circuit
5
, the electrolytic capacitor
3
and the circuits
7
to
10
. In some servo amplifiers, the semiconductor module
2
constituting a rectifier circuit is not accommodated in the same unit case which contains the other parts or components. In the servo amplifier described above, the semiconductor modules
2
and
4
are components which mainly generate heat, although the circuits
7
-
10
include heat generating parts.
FIG. 4
is a diagram of the amplifier having the above-described servo amplifier circuitry as viewed from the bottom of the amplifier for showing the internal arrangement thereof.
The aforementioned parts or components constituting the servo amplifier are separately mounted on two printed circuit boards
11
and
12
which are arranged opposite to each other. One or both of the semiconductor modules
4
and
2
are mounted on the printed circuit board
11
or
12
so that heat radiating surfaces
4
a
and
2
a
thereof are parallel to the printed circuit board
11
,
12
. In the example shown in
FIG. 4
, one or both of the semiconductor modules are mounted on the printed circuit board
11
. The heat radiating surface
4
a,
2
a
of the semiconductor module
4
,
2
has a large area for enhancing heat radiation, but since the heat radiating surface
4
a,
2
a
extends parallel to the printed circuit board
11
,
12
, the size of the heat radiating surface
4
a,
2
a
does not affect width of the servo amplifier, thus permitting reduction in the width of the amplifier. A flat heat pipe
23
is attached to the heat radiating surface
4
a,
2
a
of the semiconductor module
4
,
2
, and a heat sink
24
is attached to a portion of the flat heat pipe
23
which is exposed outside from the rear of a unit case
20
. This arrangement permits heat generated by the semiconductor module
4
,
2
to be conducted to the heat sink
24
and radiated therefrom away from a region in the unit case
20
where the other components are disposed.
The heat sink
24
is produced by die casting or the like as a one-piece structure including a flange
21
for mounting the servo amplifier on a locker or a casing of a controller. The length of the heat sink
24
in the width direction of the unit case
20
is smaller than the width of the unit case
20
. Namely, the heat sink
24
is formed such that the width thereof is smaller than the width of the unit case
20
. The unit case
20
is provided for preventing electric shock, supporting the printed circuit boards
11
and
12
, and improving external appearance, and is securely fixed to the flange
21
. In
FIG. 4
, reference numeral
22
denotes a terminal of the semiconductor module
4
,
2
.
In conventional servo amplifiers, the width of the amplifier is restricted by height of tall components among components
13
other than the semiconductor module
2
,
4
, which is for example a relay or an electrolytic capacitor
3
, and other components of small height are mounted in spaces not interfering with such tall components. As a result, the width of the servo amplifier is determined by the height of the tallest component among the components mounted on the printed circuit boards
11
and
12
.
Further, heat generated by the semiconductor module
4
,
2
is radiated from the heat pipe
23
and the heat sink
24
, to cool the module
4
,
2
, but there are some other components of the servo amplifier in the unit case
20
which generate considerable heat and need to be cooled. To cool such components, a fan motor is provided in the amplifier to carry out forced air cooling.
On the other hand, there is requirement of downsizing of apparatus into which the servo amplifier is incorporated, and thus the servo amplifier is desired to be downsized. To downsize the servo amplifier, it is the best way to make the amplifier thinner by reducing its width, in view of mounting compatibility with existing types and also matching in shape with other types. However, if the servo amplifier and thus the unit case thereof are reduced in size, the components of the servo amplifier are densely arranged within the unit case, and heat generating components contained in the unit case need to be cooled with higher efficiency since heat generated by the components adversely affects the other surrounding components.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a servo amplifier of small thickness. A further object of the invention is to provide a downsized and thin servo amplifier capable of efficiently cooling heat generating components therein.
According to the present invention, a semiconductor module constituting an inverter essential to a servo amplifier, and first and second printed circuit boards are arranged so that a heat radiating surface of the semiconductor module and surfaces of the printed circuit boards are parallel to inner wall surfaces of a unit case. Components mounted on the first and second printed circuit boards have heights substantially equal to or smaller than the thickness of the semiconductor module and also the sum of height of parts positioned in confronting relation with each other on the first and second printed circuit boards is made substantially equal to or smaller than the thickness of the semiconductor module, so that a distance between the inner walls of the unit case can be made substantially equal to a total thickness of the semiconductor module and the printed circuit board.
In the case where a heat sink is attached to the heat radiating surface of the semiconductor module, height of components mounted on the printed circuit boards is made substantially equal to or smaller than the sum of the thicknesses of the semiconductor module and the heat sink, and also the distance between the inner walls of the unit case is made substantially equal to the sum of the thicknesses of the semiconductor module, the heat sink and the printed circuit boards. Further, in the case where a flat heat pipe with a heat sink is attached to the heat radiating surface of the semiconductor module and the heat sink is positioned outside the unit case along the same, height of components on the printed circuit boards is made substantially equal to or smaller than the sum of the thicknesses of the semiconductor module and the heat pipe, and the distance between the inner walls of the unit case is made substantially equal to the sum of the thicknesses of the semiconductor module, the heat pipe and the printed circuit boards.
Also, guide plates are provided in the unit case to define air passages
Inaba Kiichi
Nakamura Hideyuki
Shinohara Tatsuo
Suzuki Naoyuki
Takeshita Makoto
Fanuc Ltd.
Staas & Halsey , LLP
Thompson Gregory
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