Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2002-01-18
2004-05-04
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C219S069110
Reexamination Certificate
active
06731026
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an improvement in an electric discharge machining apparatus using linear motor drive which supplies a machining power to in a space between an electrode and a workpiece to cause an electric discharge, w and allows the electrode and the workpiece to relatively move by means of a linear motor, thereby machining the workpiece into a desired shape.
BACKGROUND ART
FIG. 4
is a configuration view of a conventional electric discharge machining apparatus using linear motor drive-which is disclosed in Japanese Patent Application Laid-open Publication No. 8-309620. In this drawing, the reference numeral
1
denotes an electrode, the reference numeral
2
denotes a workpiece, the reference numeral
3
denotes a spindle head, the reference numeral
4
denotes a chuck, the reference numeral
5
denotes a head, the reference numeral
6
denotes a machining tank, the reference numeral
7
denotes a machining liquid, the reference numeral
8
denotes an X-axis driving linear motor, the reference numeral
9
denotes a Y-axis driving linear motor, and the reference numeral
10
denotes a Z-axis driving linear motor. The electrode
1
is held by the chuck
4
which is connected with the spindle head
3
. Further, the workpiece
2
is fixed in the machining tank
6
and dipped in the machining liquid
7
. The X-axis driving linear motor
8
, the Y-axis driving linear motor
9
and the Z-axis driving linear motor
10
constitutes a driving device which drives the respective axes to cause the electrode
1
and the workpiece
2
move in relation to each other. Additionally, a moving part and a fixed part of each axis driven by the X-axis driving linear motor
8
, the Y-axis driving linear motor
9
and the Z-axis driving linear motor
10
are linearly supported by a linear guiding mechanism (not shown) so as to allow relative movement.
The electric discharge machining apparatus using linear motor drive is such that in an electric discharge machining apparatus which supplies an inter-electrode space between the electrode
1
and the workpiece
2
with a machining power by means of a machining power supply unit (not shown), and carries out electric discharge machining on the workpiece
2
to make it into a desired shape, while allowing relative movement of the electrode
1
and the workpiece
2
by means of a driving device, as shown in
FIG. 4
, a direct driving system by the X-axis driving linear motor
8
, the Y-axis driving linear motor
9
and the Z-axis driving linear motor
10
as shown in
FIG. 4
is employed.
Such an electric discharge machining apparatus using linear motor drive provides higher positioning accuracy in comparison with those of the type that employs a driving device which involves rotation/longitudinal motion conversion for converting a rotation output of a servo motor to a longitudinal motion by means of a ball screw, because an error such as lead error of ball screw can be eliminated. Furthermore, since there is no power transmission element for carrying out conversion of rotation/longitudinal motion, backlash is eliminated as well as the rigidity is improved, which improves the positioning accuracy and the quick responsibility. Therefore, the electric discharge machining apparatus using linear motor drive can realize high speed and high accuracy electric discharge machining.
FIG. 5
is an explanatory view showing a configuration of a linear motor used in a conventional electric discharge machining apparatus using linear motor drive. In the drawing, the reference numeral
11
denotes a moving part, the reference numeral
12
denotes a fixed part, the reference numeral
13
denotes an iron core, the reference numeral
14
denotes a coil, the reference numeral
15
denotes cooling piping, the reference numeral
16
denotes a magnet, the reference numeral
17
denotes a magnet supporting plate and the reference numeral
18
denotes abase plate, and the moving part
1
which is on the primary side of the linear motor and the fixed part
2
which is on the secondary side of the linear motor are supported by a linear guiding mechanism (not shown) so that they can linearly move in relation to each other. Since the heat generated by the coil
14
can efficiently be cooled by forming the cooling piping in the iron core
13
, it is possible to improve the rated characteristics. The configuration described above is disclosed in U.S. Pat. No. 4,839,545, for example.
Because of heat conduction and heat transfer due to heat generation of the driving device of the electric discharge machining apparatus, thermal expansion and thermal distortion will occur in the mechanical structure of the electric discharge machining apparatus. Since machining accuracy on the order of &mgr;m is requested for an electric discharge machining apparatus, it is necessary to control these thermal expansion and thermal distortion.
In the conventional electric discharge machining apparatus using linear motor drive having the configurations illustrated in
FIGS. 4 and 5
, the moving part
11
which is on the primary side of the linear motor is cooled for the purpose of improving rated characteristics of the linear motor, while on the contrary, the fixed part
12
which is on the secondary side of the linear motor is not cooled. In such a conventional electric discharge machining apparatus using linear motor drive, thermal expansion and thermal distortion will occur in the fixed part
12
because of heat transfer from the moving part
11
to the fixed part
12
and dielectric loss of the magnet
16
. Therefore, in the electric discharge machining apparatus using linear motor drive in which machining operation proceeds as the electrode
1
and the workpiece
2
move in relation to each other by means of the X-axis driving linear motor
8
, the Y-axis driving linear motor
9
and the Z-axis driving linear motor
10
and in which high machining accuracy on the order of &mgr;m is requested, the relative positional accuracy of the electrode
1
and the workpiece
2
is deteriorated, which leads the first problem that the machining accuracy of the workpiece
2
decreases.
An electric discharge machining apparatus is often installed in the vicinity of a graphite working machine for machining a graphite electrode, a machining center for performing pre-working on a workpiece and the like, so that usually a lot of dust exists in the vicinity of the electric discharge machining apparatus. Furthermore, volatilization of machining liquid of the electric discharge machining apparatus also occurs.
Moreover, it is difficult to seal the driving parts of the linear motor because they move in the longitudinal direction, and also it is difficult to seal the linear guiding mechanism which supports between the moving part
11
and the fixed part
12
of the linear motor.
Therefore, in the conventional electric discharge machining apparatus using linear motor drive, there arises a second problem that the fixed part
12
, the magnet
16
and the moving part
11
of the linear motor get damaged because of the above mentioned dust and volatilization of machining liquid.
DISCLOSURE OF THE INVENTION
The present invention was devised for solving the above mentioned problems. It is an object of the present invention to provide an electric discharge machining apparatus using linear motor drive capable of efficiently conducting cooling operation for preventing thermal expansion and thermal distortion of a mechanical structure due to a rise in temperature of driving parts of linear motor.
It is an another object of this invention to provide an electric discharge machining apparatus using linear motor drive capable of efficiently protecting the driving parts and the like of linear motor from dust.
An electric discharge machining apparatus using linear motor drive according to the present invention is an electric discharge machining apparatus using linear motor drive in which a machining power supply unit supplies a machining power in a space between an electrode and a workpiece and the workpiece is m
Enya Toshihiro
Kanaya Takashi
Kawaguchi Tsuneo
Jones Judson H.
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
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