Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-04-07
2001-08-14
Enad, Elvin (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06274953
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for preventing malfunction of a switching circuit for a linear motor, and more particularly to a system for preventing malfunction of a switching circuit for a linear motor capable of preventing malfunction of the switching circuit due to magnet flux generated from permanent magnets mounted on a movable element.
2. Description of the Conventional Art
Linear motors are, generally, used in accurate transfer control of objects, such as machining tools, industrial robots, etc.
A conventional linear motor, shown in
FIGS. 1 and 2
, is comprised of a stator element
1
and a movable element
2
. The stator element
1
has plural armature coils
3
arranged in a longitudinal direction of the stator element
1
, and the movable element
2
has a plurality of permanent magnets
4
provided opposing to the plural armature coils
3
. A plurality of permanent magnets
4
disposed to face the plural armature coils
3
are arranged to have their polarities of N pole and S poles separated to each other.
When electric current flows to the plural armature coils
3
, the linear motor generates a thrust allowing the movable element
2
to be moved, by Fleming□s left-hand rule. To create such a thrust able to move the movable element
2
, the current flows into the armature coil
3
should be controlled. At this time, the current flowing into the armature coil
3
may be controlled using plural Hall sensors
6
mounted on the stator element
1
.
On the other hand, the plural Hall sensors
6
output a constant level of voltage when the sensors
6
sense magnetic flux created from the sensing magnet
5
mounted on the movable element
2
. The output voltage is used for controlling switches (not shown) employed to control the current flows into the armature coils
3
. With the controlled current flows into the armature coils
3
by the turning ON/OFF of the switches, the thrust for moving the movable element
2
can be generated.
While the use of the sensing magnets coupled to the movable element
2
are needed to control the ON/OFF of the switches, malfunction of a switching circuit may occur due to relatively stronger intensity of magnet flux generated from the permanent magnets of the movable element
2
.
To prevent such an occurrence, a dummy magnet (not shown), independently of the generation of the thrust, mounted on both sides of the movable element
2
, is employed to prevent malfunction of the switching circuit
20
which may be caused by the magnet flux from the permanent magnet
4
. In case such a dummy magnet is used so as to prevent abnormal operation of the Hall sensor
6
, the weight of the movable element
2
increases, which requires to design the linear motor capable of producing higher thrust.
SUMMARY OF THE INVENTION
Such problems are solved by this invention having an object of providing a system for preventing malfunction of a switching circuit for a linear motor having a stator element and a movable element, the motor comprising sensing magnets provided at a longitudinal one side of a movable element having a plurality of permanent magnets mounted thereon, a plurality of Hall sensors mounted on the stator element and used for controlling current flow into a plurality of armature coils by turning on/off a switching circuit, based upon the sensing of magnet flux generated from the sensing magnets, and dummy sensing magnet provided at one side end of the sensing magnet in such a manner that its polarity is opposite to that of the sensing magnet, and for preventing magnets flux generated from the plural permanent magnets from introducing into the plural Hall sensors.
REFERENCES:
patent: 5864192 (1999-01-01), Nagate et al.
Chun Jang Sung
Hwang Hyun Joo
Hwang Ji Hyun
Kim Do Hyun
Enad Elvin
Jones Judson H.
Mirae Corporation
Rosenberg , Klein & Lee
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