Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Reexamination Certificate
2000-03-21
2002-08-06
Tso, Edward H. (Department: 2838)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
Reexamination Certificate
active
06430021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a controller and a method for controlling a current supplied to a contact in a circuit, in order to make the contact have a better electrical contact by means of removing a contact obstacle, such as an insulation coating on the contact.
2. Description of the Related Art
In a detection circuit which informs the output side of a state transition based on a current change through a switch opening/closing, an obstacle such as an insulation coating on a contact lowers the conductivity of the contact. Conventionally, in order to solve this problem, a large current is supplied to the contact so as to remove the obstacle, by using a discharging arc. However, if the large current necessary for the arc is always supplied, a load will be heated, which makes it impossible to reduce the device size.
FIG. 10
shows a conventional current controller for switch contact, used for a safety switch of an elevator and the like, disclosed in Japanese Unexamined Patent Publication HEI 1-221817. According to this, an opening or a closing of the contact is detected. A simulated load is connected to the device. The simulated load causes an arc current to flow for a specific period of time after the detection of the contact closing in order to clean the contact.
In
FIG. 10
, when a contact
1
of the switch is open, a photo-coupler
113
is in an “off” state because no charge is supplied from a resistance
114
. A transistor
110
, acts as a switching unit, and is in the “on” state because resistors
111
,
112
and
117
are connected to the power supply. However, when contact
1
is open, no charge is supplied to a resistor
109
that functions as a simulated load. Additionally, photo-coupler
103
of the load circuit is “off”, and the brake is in the braked state since no charge is supplied to a break-coil
106
.
Then, when contact
1
of the switch is closed, contact
1
starts chattering. A current needed for discharging arc is steadily supplied to contact
1
through the resistance
109
and the on-state transistor
110
. Therefore, contact
1
is cleaned in order to maintain the contact reliability.
Upon contact
1
being closed, a trigger current is supplied to the photo-coupler
113
through the resistance
114
, so that the photo-coupler
113
is turned on. Then, the trigger current for the transistor
110
is bypassed through a resistance
116
. Capacitor
115
discharges after a delay time that is controlled by the relation between the capacitor
115
and the resistance
116
. During the discharge time, the transistor
110
does not instantly turn off, and becomes “off” after a specific period of time. At this time, the current supplied to contact
1
is small. The circuit is not is under the influence of the contact closing because the chattering has already finished and contact
1
has already closed.
In the conventional current controller for a switching device, an arc current charged only at the moment of the contact closing cleans the contact. Namely, the arc is not discharged at the time of the contact opening. Therefore, the cleaning time of the contact in the prior art is almost half of the cleaning time when the arc current being always supplied. In addition, if the contact is open for a long time, no charge is conducted at the time of the contact closing because an oxide coating and the like forms on the contact. Consequently, no arc is discharged, which decreases the reliability of the contact.
SUMMARY OF THE INVENTION
One of objects of the present invention is to solve the above-noted problems. Specifically, it is one of the objects to realize a compact-sized and less-power-consuming current controller and a current controlling method cleaning, in which the arc current is supplied at both the contact opening and closing. This method further ensures the same contact reliability as when the arc current is always supplied.
According to one aspect of the present invention, a current controller, for controlling a current supplied to a contact having an external power supply, comprises:
a contact monitoring unit that monitors an opening and a closing of the contact;
a logical computing unit that analyzes a transition of the contact, from open to close or close to open, based on a monitoring result from the contact monitoring unit; and
a short-circuit unit for short-circuiting an input route based on a command from the logical computing unit;
wherein the logical computing unit turns on the short-circuit unit when the logical computing unit detects a chattering at the opening of the contact, and turns off the short-circuit unit after the chattering ends at the closing of the contact.
According to another aspect of the current controller of the present invention, the contact monitoring unit, the logical computing unit, and the short-circuit unit are semiconductors.
According to another aspect of the current controller of the present invention, the short-circuit unit is connected in series to an electric charge storing unit.
According to one aspect of the present invention, a current controller, for controlling a current supplied to a contact having an external power supply, comprises:
a switching unit, connected to an input route in series, for generating oscillations by repeating connecting and disconnecting the input route in a high frequency;
a contact monitoring unit for monitoring the oscillations of the switching unit;
a logical computing unit for analyzing a transition of the contact based on a monitoring result from the contact monitoring unit; and
a switch control unit, based on a direction from the logical computing unit, for stopping the oscillations of the switching unit when a chattering is detected at an opening of the contact, and for starting the oscillations of the switching unit after the chattering ends at a closing of the contact.
According to another aspect of the current controller of the present invention, the contact monitoring unit comprises a monitoring resistor of a low resistance value, so that a large arc current is supplied to the contact.
According to another aspect of the present invention, the current controller further comprises a measuring unit for measuring a state of the contact in analog, and an analog/digital converting unit for converting an output from the measuring unit into digital and informing the logical computing unit of a converted output.
According to another aspect of the present invention, the current controller further comprises a deterioration detecting unit for detecting a contact deterioration degree and changing a notice based on a contact information from the contact monitoring unit.
According to another aspect of the present invention, the current controller further comprises an alarm unit for warning contact deterioration.
According to another aspect of the present invention, the current controller is for detecting an excitation noise of a contact coil and predicting the opening of the contact.
According to another aspect of the present invention, the current controller is for canceling a process for the opening of the contact, after a specific period of time following the predicting the opening of the contact.
According to one aspect of the present invention, a current controlling method, for controlling a current supplied to a contact having an external power supply, comprises:
monitoring an opening and a closing of the contact;
analyzing a transition of the contact based on a monitoring result after the monitoring; and
short-circuiting an input route based on a direction by the analyzing;
wherein the short-circuiting is started when a chattering at the opening of the contact is detected in the analyzing, and the short-circuiting is stopped after the chattering ends at the closing of the contact.
According to one aspect of the present invention, a current controlling method, for controlling a current supplied to a contact having an external power supply, comprises:
generating oscillations by repeatedly connecting and disconnecting an input r
Tibbits Pia
Tso Edward H.
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