Electrostatic coating apparatus
A current detection resistor is connected between an output terminal of a high voltage generator and an air motor. A coater current detector detects a coater current supplied to a coater based on a potential difference taking place on both terminals of the current detection resistor. The high-voltage control device serves to discriminate based on the coater current detected by the coater current detector whether the coater is caused to be close to a coating object. When it is discriminated that the coater is caused to be close to the coating object, the high-voltage control device outputs a shut-off signal for shutting off supply of the power supply voltage to the power supply voltage control device.
1. An electrostatic coating apparatus, comprising:
a coater to spray paint onto a coating object;
a high voltage generator which boosts a power supply voltage to generate a high voltage and outputs the high voltage to said coater;
a power supply voltage control device which supplies said power supply voltage to said high voltage generator; and
a high-voltage control device which outputs a setting signal for setting said power supply voltage to said power supply voltage control device and controls said high voltage outputted from said high voltage generator, wherein:
a current detection resistor is connected between said high voltage generator and said coater,
a coater current detector which detects an amount of current IB supplied to said coater is provided,
said coater current detector comprises:
an input side voltage-dividing circuit which divides a voltage applied to an input terminal of said current detection resistor;
an output side voltage-dividing circuit which divides a voltage applied to an output terminal of said current detection resistor; and
a coater current computing processor configured to subtract a current Iro flowing in said output side voltage-dividing circuit from a current Irf flowing in said current detection resistor to compute said amount of current IB supplied to said coater, said current Irf flowing in said current detection resistor being determined based on an input side voltage detection value detected by said input side voltage-dividing circuit and an output side voltage detection value detected by said output side voltage-dividing circuit and said current Iro flowing in said output side voltage-dividing circuit being determined based on said output side voltage detection value detected by said output side voltage-dividing circuit, and
said high-voltage control device is configured to output a shut-off signal for shutting off supply of said power supply voltage to said power supply voltage control device when said amount of current IB supplied to said coater detected by said coater current detector determines that said coater is within a predetermined distance of said coating object.
2. The electrostatic coating apparatus according to claim 1 , further comprising a full return current detector which detects a full return current flowing in a high-voltage application path including said high voltage generator,
wherein said high-voltage control device is configured to comprise a full return current extraordinary state processor which outputs a shut-off signal for shutting off supply of said power supply voltage to said power supply voltage control device when an absolute value of a full return current detected by said full return current detector exceeds a predetermined shut-off threshold current value, or when a variation amount of said full return current exceeds a predetermined shut-off threshold variation amount.
3. The electrostatic coating apparatus according to claim 1 , wherein said high-voltage control device is configured to comprise a coater current extraordinary state processor which outputs a shut-off signal for shutting off supply of said power supply voltage to said power supply voltage control device when an absolute value of said amount of current IB supplied to said coater detected by said coater current detector exceeds a predetermined shut-off threshold current value, or when a variation amount of said current IB supplied to said coater exceeds a predetermined shut-off threshold variation amount.
4. The electrostatic coating apparatus according to claim 1 , further comprising a leakage current detector which detects a leakage current flowing without passing through said coating object,
wherein said high-voltage control device comprises:
a coating object current computing processor which subtracts a leakage current detected by said leakage current detector from said amount of current IB supplied to said coater detected by said coater current detector to compute a coating object current flowing between said coater and said coating object, and
a coating object current extraordinary state processor which outputs a shut-off signal for shutting off supply of said power supply voltage to said power supply voltage control device when an absolute value of said coating object current by said coating object current computing processor exceeds a predetermined shut-off threshold current value.
5. The electrostatic coating apparatus according to claim 4 , wherein said high-voltage control device is configured to further comprise an insulation deterioration alarm processor which serves to notify that insulation deterioration takes place in said coater when said leakage current detected by said leakage current detector indicates that insulation deterioration at an initial stage takes place.
6. The electrostatic coating apparatus according to claim 1 , wherein
said output side voltage-dividing circuit includes two voltage-dividing resistors connected in series, and
said coater current computing processor computes the current Iro flowing in said output side voltage-dividing circuit based on said output side voltage detection value and resistance values of said two voltage-dividing resistors of said output side voltage-dividing circuit.
7. An electrostatic coating apparatus, comprising:
a coater to spray paint onto a coating object;
a high voltage generator configured to boost a power supply voltage to generate a high voltage and output the high voltage to said coater; and
power supply voltage control circuitry configured to supply said power supply voltage to said high voltage generator;
processing circuitry configured to output a setting signal that sets said power supply voltage to said power supply voltage control circuitry and control said high voltage outputted from said high voltage generator;
a current detection resistor connected between said high voltage generator and said coater; and
a coater current detector configured to detect an amount of current IB supplied to said coater, said coater current detector including
an input side voltage-dividing circuit which divides a voltage applied to an input terminal of said current detection resistor; and
an output side voltage-dividing circuit which divides a voltage applied to an output terminal of said current detection resistor, wherein
the processing circuitry is configured to
subtract a current Iro flowing in said output side voltage-dividing circuit from a current Irf flowing in said current detection resistor to compute said amount of current IB supplied to said coater, said current Irf flowing in said current detection resistor being determined based on an input side voltage detection value detected by said input side voltage-dividing circuit and an output side voltage detection value detected by said output side voltage-dividing circuit and said current Iro flowing in said output side voltage-dividing circuit being determined based on said output side voltage detection value detected by said output side voltage-dividing circuit, and
output a shut-off signal to shut off supply of said power supply voltage to said power supply voltage control circuitry when said amount of current IB supplied to said coater detected by said coater current detector determines that said coater is within a predetermined distance of said coating object.