JPS638816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spark prevention method and device for a high voltage generator used in electrostatic painting, and more specifically, a spark prevention method and device that operate simultaneously with power-on of the high voltage generator. It is related to.

Electrostatic painting is an effective technique for saving paint and painting time, but since this technique uses high voltage, there is always a risk of spark accidents. Furthermore, since the paint used in electrostatic painting is flammable in most cases, the occurrence of sparks can lead to the worst case scenario of causing a fire accident. For this reason, high voltage generators for electrostatic coating are generally provided with a spark prevention circuit. Conventionally, this type of spark prevention circuit has a configuration in which the output load current of the high voltage generator, that is, the load current flowing between the coating machine and the object to be coated, is normally connected to the ground output terminal side of the high voltage generator. Continuously or intermittently detects an abnormal increase in load current that may be a precursor to a spark, and then shuts off the input power, grounds the high voltage output terminal, or both, thereby preventing the occurrence of a spark. This is to prevent this in advance. However, this type of spark prevention circuit causes the following problem when detecting an abnormal increase in load current. That is, since the load current is detected at the ground output terminal side of the high voltage generator, a commercial frequency alternating current is superimposed on the signal current waveform. This is a grounding connection from the commercial power supply connected to the primary winding side to one end of the secondary winding through a stray capacitance between the primary and secondary windings of the power transformer of the high voltage generator. This is because alternating current flows into the output terminal.

The amplitude of this alternating current signal is typically several times larger than the load current signal. Therefore, to detect abnormal increases in load current, conventional devices use various types of high-cut filters to remove the superimposed alternating current signal. However, by using such a high frequency cutoff filter,
Since signals with frequencies near the commercial frequency (50Hz or 60Hz) are blocked, if the frequency included in the signal representing an abnormal increase in load current caused by the approach of a grounded object that generates a spark is near the commercial frequency, This cannot be detected. That is,
Conventional prevention devices have the disadvantage that the frequency band of the signal that can be detected must be sufficiently lower than the commercial frequency, and because of this, they cannot prevent sparks from being generated by grounded objects that approach at relatively high speeds. .

In order to detect spark occurrence at an earlier point in time, the present inventors have devised a spark prevention device that includes a circuit that detects a spark precursor current from a signal ground terminal and differentiates the detected signal. However, in a device including such a differentiating circuit, it is necessary to strictly remove the ripple component of the signal, so the above-mentioned drawbacks have been a particularly big constraint.

The present inventors have repeatedly conducted systematic experiments and analyzes in order to develop a method and apparatus that solve the problems of the conventional apparatus described above, and as a result they have arrived at the present invention.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional device described above, and to enable the device to operate effectively even when the frequency of the spark precursor signal increases to the commercial frequency band.

An object of the present invention is to detect the occurrence of a spark at an early point in time and to cut off the high voltage with sufficient margin even when a grounded object approaches the gun at a high speed.

The present invention (invention described in claim 1)
extracts the high voltage output of the high voltage generator as a detection signal for detecting signs of spark generation, creates a differential value signal in which differential values of the detection signal appear continuously, and generates the differential value signal. and a reference level, and when the level of the differential value signal exceeds the reference level, this is detected as a sign of generation of the spark, and the supply of the high voltage output to the electrostatic coating machine is blocked. A method for preventing sparks in electrostatic painting, which is characterized by activating a prevention means to prevent sparks in electrostatic coating.

The spark prevention method for electrostatic painting of the present invention having the above-described configuration extracts a detection signal for detecting a sign of spark generation from the high voltage output of the high voltage generator, so that commercial frequency alternating current is not superimposed. Since there is no spark, there is an advantage that even if the frequency of the spark precursor signal increases to the commercial frequency band, the spark prevention operation can be performed effectively.

Furthermore, the spark prevention method of the present invention creates a differential value signal in which the differential values of the detection signal are continuous, and determines signs of spark generation based on this differential value signal, so spark generation can be detected at an early point in time. It also has the advantage of being able to cut off the high voltage with a margin even if a grounded object approaches at a high speed.

Conventionally, as shown in Japanese Patent Application Laid-Open No. 53-21240, the load current is extracted as a detection signal for detecting a sign of spark generation at a terminal in the ground return path of a high voltage generator. A signal with a constant value added is sampled and held at each predetermined sampling period,
Means for comparing the load current value and the hold value within each sampling period, and detecting this as a sign of spark generation when the load current value exceeds the hold value, and lowering the voltage of the high voltage output. There is one that is designed to operate.

However, this method has a problem in that it may malfunction if the value sampled and held at a certain point in time corresponding to the sampling period is an abnormally large or small value.

In other words, the larger the hold value is, even if the load current shows an increasing tendency that can be detected as a sign of spark generation, it will not be detected as a sign of spark generation unless the load current value exceeds the held large value. . In addition, the smaller the hold value is, the more sparks will occur if the load current exceeds the held small value, even if the load current fluctuates in a normal state that does not need to be caught as a sign of spark generation. It is detected as a sign of.

In this regard, the spark prevention method of the present invention includes:
Since the increasing tendency of the load current is monitored by the continuous differential value signal, the previous value is irrelevant, so the above-mentioned malfunction does not occur. It is effective.

Furthermore, in the case of the sample-and-hold method, even if the load current changes suddenly during the sampling period due to, for example, a piece of metal falling between the painting head and the object to be coated, the hold value will still be exceeded. Until now, it has not been possible to detect it, and the detection operation of the sign of spark generation is delayed, and there are also problems in that spark generation cannot be prevented.

Regarding this point as well, the spark prevention method of the present invention constantly monitors the increasing tendency of the load current using the differential value at each time, so there is no need to wait for the load current to reach a certain value. Since this detects the occurrence of sparks, it is possible to reliably prevent the occurrence of sparks.

Next, the present invention (the invention set forth in claim 8) extracts the high voltage output of the high voltage generator as a detection signal for detecting a sign of spark generation, and A differential value signal in which differential values appear continuously and an absolute value signal in which absolute values continuously appear are generated, and the level of the differential value signal is set as a differential value reference. At the same time as comparing the level, the level of the absolute value signal is compared with an absolute value reference level, and when at least one of the differential value signal and the absolute value signal exceeds the reference level for each, this is determined as the spark generation signal. A method for preventing sparks in electrostatic painting, characterized by detecting a precursor and activating a blocking means for blocking the supply of the high voltage output to an electrostatic coating machine.

According to the spark prevention method of the present invention having such a configuration, in addition to having the same merits as the method according to the invention described in claim 1 above,
It has the following advantages:

In other words, in parallel with the detection using the differential value signal,
Detection is also performed using an absolute value signal that is not differentiated from the detection signal, and if a sign of spark generation is detected on at least one side, the supply of high voltage output to the electrostatic sprayer is blocked. It is now possible to detect precursors of spark occurrence, such as when the load current slowly increases, which cannot be detected by differential processing, and expands the lower limit of the frequency band of the detection signal that can detect precursors of spark occurrence. Can be done. In other words, the precursor to spark generation may rise slowly, and this needs to be dealt with, but if only the differential value signal is used to detect low frequency bands, it will not be detected as a precursor to spark generation. If only the differential value signal is used for detection, the lower limit of the frequency band will be restricted.According to the present invention, such restrictions can be overcome. This means that it can be eliminated.

The present invention (the invention set forth in claim 20) provides a system for applying a high voltage output of a high voltage generator and extracting the high voltage output as a detection signal for detecting a sign of spark generation. a voltage divider means; an operation instruction circuit to which the detection signal is input; and an operation instruction circuit that detects a sign of spark occurrence based on the detection signal and generates an operation instruction signal; and a blocking means that operates upon receipt of the high voltage output to block the supply of the high voltage output to the electrostatic coating machine, and the operation instruction circuit includes a differentiating circuit that differentially processes the detection signal. a signal generating circuit that generates a differential value signal in which the differential value of the detection signal is continuously expressed by the differentiating circuit; and a signal generation circuit that compares the level of the differential value signal with a reference level, When the level exceeds the reference level, this is detected as a sign of spark generation,
An electrostatic coating comprising: a comparison circuit that generates the detection signal; and an output circuit that receives the detection signal and outputs the operation instruction signal upon receiving the detection signal. This is a spark prevention device.

In the electrostatic coating spark prevention device configured in this way, the high voltage output of the high voltage generator is taken out as a detection signal for detecting signs of spark generation via a voltage divider, and the signal generation circuit In this step, a differential value signal whose differential values are continuous is created from this detection signal. Then, the comparison circuit compares the level of this differential value signal with the reference level,
When the level of the differential value signal exceeds the reference level, this is detected as a sign of spark generation, and a detection signal thereof is generated. This detection signal causes the output circuit to output an operation instruction signal to activate the blocking means and cut off the supply of high voltage output to the electrostatic sprayer.

The effects of the spark prevention device for an electrostatic coating machine according to the present invention having the above-described configuration and operation will be described below.

First, by detecting the detection signal at the high-voltage output terminal rather than at the ground terminal as in the conventional case, the AC component of the commercial frequency superimposed on the signal is reduced.
That is, the primary of the power transformer of the high voltage generator,
The commercial frequency alternating current that flows through the secondary winding due to capacitive coupling between the secondary windings affects the signal taken out at the ground terminal as is, but at the high voltage output terminal, the voltage Since it is several hundred to one thousand times more powerful than the power supply, the effect is also a few hundred to one thousandth, so small that it can be ignored. In the present invention, the AC component included in the signal is caused by the pulsation of the discharge current of the gun, the pulsation of the inverter output current generally included in the high voltage generation circuit, or the fluctuation of the power supply voltage, but all of them are at the commercial frequency. Since the high-frequency vibrations are more than an order of magnitude higher than the above, even if a high-frequency cutoff filter, that is, a low-pass filter, is installed to cut off these vibrations, this will cause
The component representing the spark precursor to be detected is not attenuated.

Second, since the detection signal is used to determine whether or not a spark is generated, spark generation can be detected at an earlier point in time. High voltage can be cut off with sufficient margin.

Furthermore, like the invention described in claim 1 above, the detection operation is more reliable than that using a sampling and holding circuit.

Furthermore, since the detection signal is extracted by a voltage divider, the apparatus is simplified and the voltage level of the detection signal can be freely selected by changing the voltage division ratio.

Next, typical embodiments for carrying out the present invention will be described.

A first aspect of the present invention is to detect output fluctuations of a high voltage generator of an electrostatic coating high voltage generator as voltage fluctuations.

The first aspect has the following effects. The electrical output to be detected is the voltage applied to the paint gun. As the abnormal ground object approaches, the load current flowing through the gun increases. At this time, the gun voltage drops abnormally due to the resistor inserted on the output side of the high voltage generator. The first aspect detects this abnormal voltage drop as a spark precursor signal.
This has the advantage that the detectable range can be extended to the commercial frequency band, as well as the advantage that there is no malfunction when starting the power supply. In other words, conventional spark prevention circuits cannot distinguish between the large charging current that flows transiently to charge stray capacitance between the coating material and the object to be coated when the power is turned on, and the load current that abnormally increases as a precursor to sparking. , which caused malfunctions. On the other hand, if an abnormal drop in the voltage at the high voltage output terminal is detected as in the first aspect of the present invention, since the voltage is in the process of increasing in the transient state when the power is turned on, it may be mistakenly detected as a sign of spark generation. It is clear that it is impossible to detect it.

A second aspect of the present invention is to detect output fluctuations of a high voltage generating section of an electrostatic coating high voltage generator as current fluctuations.

The second aspect has the following effects.
A second aspect of the invention is to sense the load current flowing through the gun as the electrical output of the high voltage terminal. In addition to directly detecting fluctuations in the output current, for example, by extracting changes in the current flowing through a protective resistor inserted into the output side of a high voltage generator as a signal from the potential difference between the two ends, it is possible to detect an abnormal increase in gun current. It can be detected as a sign of occurrence. In addition to the basic feature of expanding the detectable range to the commercial frequency band, these methods have the feature of increasing detection sensitivity.

In other words, for a signal corresponding to the normal current,
Since the proportion of the signal corresponding to the spark precursor current is large, there is no need to increase the protective resistance (smaller is better from the viewpoint of painting efficiency), and the gain of the differentiator circuit of the operation instruction circuit is also larger than in the case of voltage detection. There's no need to.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on an embodiment of the apparatus using drawings. The first embodiment device belongs to the first aspect of the present invention.

Figure 1 shows the electrical system of the electrostatic coating system and a block diagram of the first embodiment of the system, in which 1 is a high voltage generator, 2 is an electrostatic coating machine, and 3 is a grounded object to be coated. be. To explain the configuration of the high voltage generator 1, an AC power source is connected to a high voltage generator 5 via a primary power cutoff switch 4. The high voltage generating section 5 has a general configuration combining a step-up transformer and a voltage doubler rectifier circuit, and generates a high voltage between the ground terminal 5a of the step-up transformer and the high voltage terminal 5b. The high voltage terminal 5b is connected to the high voltage output terminal 1a of the high voltage generator 1 via a protective resistor 6, and a high voltage is connected between the electrostatic coating machine 2 and the object to be coated 3 via this terminal. By applying
This creates a so-called electrostatic field. The protective resistor 6 is generally always provided for the purpose of circuit protection in the event of a load short circuit in the high voltage generator 1, and usually has a resistance value of about 5M to 100M. Also connected to the high voltage output terminal 1a are a voltage divider 8 consisting of resistors 81 and 82 as a voltage detection means and an output grounding switch 7 as a blocking means, each of which is grounded. In this voltage divider, the resistor 81 on the high voltage side is usually
For a high resistance value of 1GΩ or more, the resistance 82 on the ground side is
Select between 10KΩ and 100KΩ. In this way, the voltage divider 8
divides the high voltage at the high voltage output terminal 1a to 1/10 ⁵ to 1/10 ⁴ , converts it into a voltage signal with an easily controllable voltage level, and uses this as a detection signal to detect signs of spark generation. The signal is supplied to the operation instruction circuit 10.
This operation instruction circuit 10 detects a sign of spark occurrence from the voltage signal mentioned above and acts as a prevention means.
This circuit provides an operation instruction signal to the next power cutoff switch 4 and the output grounding switch 7 to activate them, thereby preventing the occurrence of sparks.

An example of the configuration of the operation instruction circuit 10 is shown in FIG. The input inverting circuit 11 inverts the polarity of the voltage signal input from the voltage divider 8 and outputs the signal to the low-pass filter 12 . The low-pass filter 12 removes high frequency components from this signal and outputs a signal. The differentiating circuit 13 outputs a signal obtained by differentiating the signal inputted from the low-pass filter 12.

The comparison circuit 14 compares the signal input from the differentiating circuit 13 with the level of a preset reference signal, detects this as a sign of spark generation when it exceeds the reference signal level, and outputs the detection signal. Output. The output circuit 15 is activated when the detection signal is input from the comparison circuit 14 and outputs an operation instruction signal to the output terminal 10a of the operation instruction circuit 10. Note that the input inversion circuit 11, low-pass filter 12, and differentiation circuit 13 constitute a signal generation circuit.

The primary power cutoff switch 4 as a blocking means is
This is a general electromagnetic relay that shuts off the primary power supply based on an operation instruction signal. An example of the configuration of the output grounding switch 7 constituting the blocking means is shown in FIG. An electrode 71 connected to the high voltage side and a ground electrode 72 are opposed to each other with a distance that does not normally cause sparks. A starting electrode 73 is provided near the ground electrode 72,
This is connected to the output terminal 7 of the pulsed high voltage generation circuit 74.
Connect 4a. This high voltage generation circuit generates a high voltage pulse when an operation instruction signal pulse is input to the input terminal 74b.

The device of the first embodiment configured as described above operates as follows.

First, let's talk about the case where the device is in operation and an abnormal increase in load current occurs as a sign of spark generation. As a result, the high voltage output terminal 1a
, that is, the voltage applied to the paint sprayer 2 is abnormally lowered. This abnormal voltage drop is converted to an easily controllable voltage level by a voltage divider 8 consisting of resistors 81 and 82,
Thereafter, it is input to the operation instruction circuit 10. In the operation instruction circuit 10, the input inversion circuit 11 first inverts the polarity of the input signal, the low-pass filter 12 removes high frequency components, and the differentiation circuit 13 calculates the rate of increase in load current (per unit time), which is a sign of sparking. is converted into a differential value signal corresponding to the current increase (current increase). This uninterrupted continuous differential value signal is input to a comparison circuit 14, and it is determined whether or not it exceeds a certain set reference value. This set reference value is a preset value that corresponds to the rate of change when an abnormal drop in voltage occurs as a precursor to sparking, and if this value is exceeded, the signal that is determined to be a precursor to sparking is It is output to the output circuit 15. This signal is input as an operation instruction signal to the primary cutoff switch 4 and the output grounding switch 7 as blocking means, so that the input current is cut off and there is a gap between the starting electrode 73 and the grounding electrode 72 of the output grounding switch 7. A discharge occurs, which triggers a spark between the high voltage electrode 71 and the ground electrode 72, and the high voltage output terminal is grounded in an extremely short time, thereby preventing the occurrence of sparks in the paint sprayer 2. can do.

Now, the feature of the device of the first embodiment based on the above-mentioned operation is that the sign of spark occurrence is detected at the high voltage output terminal instead of the ground terminal of the high voltage generator as in the conventional case. The two exchanges should not overlap. Therefore, the filter circuit can be simplified, and the upper limit of the frequency band of the component representing a detectable sign of spark generation can be expanded to the vicinity of the commercial frequency, that is, several tens of hertz.

In addition, the differential value signal is one in which the differential value continues without interruption, and the increasing tendency of the load current is constantly monitored using the differential value at each time. The operation is not affected by the previous load current value, and the sign of spark generation is detected without waiting for the load current value to reach a certain value, so spark generation can be detected extremely reliably. It is something that can be prevented.

Furthermore, since the method detects the voltage drop of the gun, there is no possibility of malfunction due to charging current when the power is turned on. Furthermore, since this embodiment uses a resistive voltage divider as the voltage detector, the device is simplified, and by changing the voltage division ratio, the voltage level of the input signal to the operation instruction circuit can be freely selected. .

Furthermore, since a spark switch is used as the output grounding switch as the blocking means, it can withstand use of high voltage and can short-circuit the high voltage in an extremely short period of time.

Next, the present invention will be explained based on a second embodiment of the apparatus.

The device of the second embodiment belongs to the first aspect of the present invention, and determines the operation of the blocking means from both the absolute value and the differential value of the precursor signal.
The differences will be mainly explained with reference to FIG. The electrostatic coating machine 2 and the object to be coated 3 are the same as those shown in FIG.
The high voltage generator 1' includes the same primary power cutoff switch 4, high voltage generator 5, protective resistor 6, output grounding switch 7, resistive voltage divider 8 as in FIG. 1, and operation instruction circuit 10' different from that in FIG. It is made up of.

The operation instruction circuit 10' is constructed as shown in FIG. The input level conversion circuit 11' adjusts the voltage signal inputted from the voltage divider 8 so that it reaches zero level when no spark is generated, in order to remove the DC component that is unnecessary for the following signal processing. A signal is output to the low pass filter 12. The low-pass filter 12 removes high frequency components from this signal and outputs the signal to the differentiating circuit 13 on one side and to the second comparison circuit 14a on the other side. Differential circuit 1
3 outputs a signal obtained by differentiating the signal input from the low-pass filter 12 to the first comparison circuit 14b.

First and second comparison circuits 14a and 14b
compares the signals input from the low-pass filter 12 and the differentiating circuit 13 with the level of a separately set reference signal, detects this as a sign of spark generation when it exceeds the reference signal level, and detects this. Output a signal.

OR circuit (OR circuit) 1 as an output circuit
5' is activated when a signal is input from at least one of the two comparison circuits 14a and 14b, and outputs an operation instruction signal to the output terminal 10'a of the operation instruction circuit 10'.

The apparatus of the second embodiment constructed as described above operates as follows.

An abnormal increase in load current as a precursor to a spark is detected as a voltage drop signal by the protective resistor 6 and the voltage divider 8, as in the first embodiment, and is input to the operation instruction circuit 10'.

In this circuit, first, the input level conversion circuit 11'
The DC level of the input signal is set to zero, the high frequency component is removed by the low-pass filter 12, and then the signal is converted by the differentiating circuit 13 into a signal corresponding to the rate of increase in the load current, which is a sign of sparking. This signal is sent to the first comparator circuit 14b as in the first embodiment.
If it exceeds a set reference value, it is determined that it is a sign of sparking, and a signal is output to the OR circuit 15'. On the other hand, the output signal of the low-pass filter 12 is input to the second comparison circuit 14a without passing through the differentiation circuit 13, and is compared with a reference value set in advance as a value corresponding to an abnormal drop in voltage that is a precursor to sparking. When this value is exceeded, a signal that is determined to be a sign of a spark is output to the OR circuit 15'. If the abnormal voltage drop is fast, the signal from the comparator circuit 14b is taken out, and if it is slow, the signal from the comparator circuit 14a is taken out as the output of the OR circuit 15', and used as an operation instruction signal to the primary blocking means. Activate cutoff switch 4 and output ground switch.

This cuts off the input power and grounds the high voltage output terminal in an extremely short time.
The generation of sparks in the coating machine 2 can be prevented.

Now, the unique advantage of this embodiment due to the above-mentioned operation is that, first, as an input circuit of the operation instruction circuit 10',
Since the input level conversion circuit 11' is provided, the DC component of the input signal can be reduced to zero.
As a result, only the desired signal can be amplified in the subsequent circuit.

In addition, a circuit that compares the spark precursor signal without differentiating it is provided in parallel with a circuit that compares the differential value signal, so it is effective even against slowly increasing load currents that cannot be detected by differentiation processing. It is to operate. That is, the lower limit of the frequency band of the detectable spark precursor signal can be expanded.

Next, the present invention will be explained based on a third embodiment of the apparatus. The device of the third embodiment belongs to the second aspect of the present invention, and detects a sign of spark generation as a current change, and also detects the activation of the blocking means based on both the absolute value and the differential value of the detection signal. The difference from the above-mentioned embodiment will be mainly explained using FIGS. 6 and 7.

The electrostatic coating material 2 and the object 3 to be coated are the same as in FIG. The high voltage generator 1'' includes a primary power cutoff switch 4, a high voltage generator 5, a protective resistor 6, the same as in FIG.
Supplying high voltage to the coating material 2 via the terminal 1″a,
An electrostatic field is formed between it and the object 3 to be coated. The same output grounding switch 7 as in the first embodiment and a first voltage divider 8 consisting of resistors 81 and 82 are connected between the high voltage output terminal 1''a and the ground.High voltage terminal 5
A second voltage divider 9 consisting of resistors 91 and 92 is connected between b and ground. Resistor 91 and resistor 81, and resistor 92 and resistor 82 each have the same resistance value, the former being 1GΩ or more, and the latter being 10KΩ or more.
Select 100KΩ. In this way, the voltage divider 8 divides the high voltage at the high voltage terminal 1''a, and the voltage divider 9 divides the high voltage at the high voltage terminal 5b into 1/10 ⁵ to 1/10 ⁴ respectively, and then the differential amplifier 16.Differential amplifier 1
6 amplifies and outputs a signal proportional to the difference between the two signals input from voltage dividers 8 and 9. As in the second embodiment, the output signal of the differential amplifier 16 is transmitted to the low-pass filter 12, the differentiating circuit 13, and the first and second differential circuits of the operation instruction circuit 10'' as shown in FIG.
The signal is output from the output terminal 10'a as an operation instruction signal via the comparison circuits 14a and 14b and the OR circuit 15' as an output circuit.

The structure and function of the primary power cutoff switch 4 and output grounding switch 7 as blocking means are exactly the same as in the first embodiment.

The apparatus of the third embodiment constructed as described above operates as follows.

First, a case will be described in which the device is in an operating state and an abnormal increase in load current occurs as a sign of spark generation.This abnormal increase in load current increases the voltage drop across the protective resistor 6. The voltage across the protective resistor 6 is divided by the voltage dividers 8 and 9 and input to the differential amplifier 16, so the output of the differential amplifier 16 contains the potential difference across the protective resistor 6, that is, the load current. A signal proportional to the increase in is output.
This signal is first passed through the low-pass filter 1 in the operation instruction circuit 10'' in exactly the same way as in the second embodiment.
2 removes the high frequency component, the differentiating circuit 13 converts the signal into a signal proportional to the rate of increase in load current, the first comparison circuit 14b compares it with a set reference value, and when the signal exceeds the set reference value, the signal is sent to the OR circuit 15'. Generate a signal. on the other hand,
In the second comparator circuit 14a, the low-pass filter 1
The output of 2 is compared with a set reference value, and when it exceeds this value, a signal is generated to the OR circuit 15'. OR circuit 1
5' is the first and second comparison circuit 14a or 14
When a signal is input from either of b, an operation instruction signal is generated, and this signal activates the primary power cutoff switch 4 and the output grounding switch 7, thereby preventing the generation of sparks in the paint sprayer 2. .

Now, the unique advantage of this embodiment due to the above-described operation is that the load current flowing through the gun is detected as the electrical output of the high voltage terminal. Since the ratio between the spark precursor signal and the normal signal is larger for the current signal than for the voltage signal, there are advantages in that the protective resistance can be small and the gain of the differentiator circuit can also be relatively small. Since two resistive voltage dividers are used as the current detector, the device is simplified and the level of the detection signal can be easily adjusted by changing the voltage dividing ratio of the resistors.

In the above embodiments, the output grounding switch 7 and the primary power cutoff switch 4 have been described as blocking means, but the present invention is not limited to these, and is intended to cut off the application of high voltage to the electrostatic atomizer. It can be applied to anything. The output grounding switch explained in the embodiment prevents the application of high voltage and at the same time also grounds the charge remaining in the electrostatic atomizer and immediately makes it zero, so it has the advantage of preventing sparks caused by the charge remaining in the electrostatic atomizer. has.
Furthermore, when the application of high voltage is blocked, in the embodiment, the primary power source is cut off, so wasteful consumption of power can be eliminated, and there is also an energy saving effect.

In addition, the output grounding switch 7 has been explained using a three-electrode spark discharge switch as an example, but is of course not limited to this, and may include a thyratron, thyristor switch, high-speed electromagnetic relay, etc.
In short, any device can be used as long as it can ground high voltage in a short time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the device of the present invention;
2 is a circuit configuration diagram of the operation instruction circuit 10 in FIG. 1, and FIG. 3 is a circuit diagram of the output grounding switch 7 in FIG.
4 is a diagram showing the second embodiment of the present invention, FIG. 5 is a circuit diagram of the operation instruction circuit 10'' in FIG. 4, and FIG. 6 is a diagram showing the second embodiment of the present invention. FIG. 7, which is a diagram showing the apparatus of the third embodiment, is a circuit configuration diagram of the operation instruction circuit 10' in FIG. 6. 1... High voltage generator, 2... Electrostatic coating machine, 4
...Primary power cutoff switch, 5...High voltage generation section, 6...Protection resistor, 7...Output grounding switch,
8, 9... Voltage divider, 10, 10', 10''... Operation instruction circuit, 11... Input inversion circuit, 11'... Level conversion circuit, 12... Low pass filter, 13
... Differentiation circuit, 14, 14a, 14b ... Comparison circuit, 15, 15' ... Output circuit, 16 ... Differential amplifier.

Claims (1)

[Claims] 1. A high voltage output from a high voltage generator is extracted as a detection signal for detecting a sign of spark generation, and a differential value signal is created in which differential values of the detection signal appear continuously. , Compare the level of the differential value signal with a reference level, and when the level of the differential value signal exceeds the reference level, detect this as a sign of generation of the spark, and apply the high voltage to the electrostatic atomizer. A method for preventing sparks in electrostatic painting, characterized by activating a blocking means for blocking the supply of output. 2. The method for preventing sparks in electrostatic coating according to claim 1, wherein the detection signal is extracted so as to detect a sign of spark generation as a voltage fluctuation of the high voltage output. 3. The method for preventing sparks in electrostatic coating according to claim 1, wherein the detection signal is an output of a voltage divider means to which the high voltage output is applied. 4. The voltage divider means comprises a voltage divider to which the high voltage output is applied on the high voltage output terminal side of the protective resistor in the high voltage generator. How to prevent sparks in electrostatic painting. 5. The step of creating the differential signal includes detecting, from the detection signal, pulsations in the discharge current of the gun in the electrostatic atomizer or fluctuations in the power supply voltage to the high voltage generator, before differential processing of the detection signal. 2. The method for preventing sparks in electrostatic coating according to claim 1, further comprising the step of removing a high frequency component which is caused by a component and has a frequency one order or more higher than the commercial frequency. 6. Claim 1, wherein the blocking means includes a primary power cutoff switch consisting of an electromagnetic relay inserted between the primary side of the transformer in the high voltage generator and the power source. Method for preventing sparks in electrostatic painting as described in . 7. The device according to claim 1, wherein the blocking means includes an output grounding switch consisting of a spark switch inserted between the high voltage output terminal of the high voltage generator and the ground. How to prevent sparks in electrostatic painting. 8 The high voltage output of the high voltage generator is extracted as a detection signal for detecting a sign of spark generation, and the differential value signal in which the differential value of the detection signal appears continuously and the absolute value of the detection signal and an absolute value signal that continuously appears, compare the level of the differential value signal with a differential value reference level, and at the same time compare the level of the absolute value signal with the absolute value reference level, and compare these differential value signals and the absolute value. When at least one of the signals exceeds the respective reference level, detecting this as a sign of spark generation and activating a blocking means for blocking the supply of the high voltage output to the electrostatic sprayer. Features a spark prevention method for electrostatic painting. 9. The method for preventing sparks in electrostatic coating according to claim 8, wherein the detection signal is extracted so as to detect a sign of spark generation as a voltage fluctuation of the high voltage output. 10. The method for preventing sparks in electrostatic coating according to claim 8, characterized in that the detection signal is extracted so as to detect a sign of spark generation as a current fluctuation of the high voltage output. 11. Claim 8, wherein the detection signal is an output of voltage divider means to which the high voltage output is applied.
Method for preventing sparks in electrostatic painting as described in section. 12. The electrostatic capacitor according to claim 11, wherein the voltage divider means comprises a voltage divider to which the high voltage output is applied on the high voltage output terminal side of the protective resistor in the high voltage generator. How to prevent paint sparks. 13 The step of creating the differential value signal includes the step of removing a DC component from the detection signal to create a level conversion signal, and detecting the pulsation of the discharge current of the gun in the electrostatic atomizer or the high voltage signal from the level conversion signal. a step of removing a high frequency component that is caused by fluctuations in the power supply voltage to the voltage generator and has a frequency one order or more higher than the commercial frequency; and differential processing of the signal from which the high frequency component has been removed to obtain the differential value. 13. The method for preventing sparks in electrostatic coating according to claim 12, comprising: a step of generating a signal; and a step of generating a signal. 14 The step of creating the absolute value signal includes the step of removing a DC component from the detection signal to create a level conversion signal, and determining from the level conversion signal the pulsation of the discharge current of the gun in the electrostatic atomizer or the high A step of removing a high frequency component that is caused by fluctuations in the power supply voltage to the voltage generator and has a frequency one or more orders of magnitude higher than the commercial frequency to obtain the absolute value signal. A method for preventing sparks in electrostatic coating according to claim 12. 15. Claim 1, characterized in that the voltage divider means comprises first and second voltage dividers to which the high voltage output is separately applied to each end of the protective resistor in the high voltage generator. The method for preventing sparks in electrostatic coating according to item 11. 16 The step of creating the differential value signal includes the step of differentially amplifying the outputs of the first and second voltage dividers, and the step of differentially amplifying the outputs of the first and second voltage dividers, and detecting the pulsation of the discharge current of the gun in the electrostatic atomizer or the high a step of removing a high frequency component that is caused by fluctuations in the power supply voltage to the voltage generator and has a frequency that is one order of magnitude higher than the commercial frequency; and performing differential processing on the signal from which the high frequency component has been removed to obtain the differential value signal. The method for preventing sparks in electrostatic coating according to claim 15, comprising the steps of: 17 The step of creating the absolute value signal includes the step of differentially amplifying the outputs of the first and second voltage dividers, and from the differential amplification signal, the pulsation of the discharge current of the gun in the electrostatic atomizer or the high A step of removing a high frequency component that is caused by fluctuations in the power supply voltage to the voltage generator and has a frequency one order or more higher than the commercial frequency to obtain the absolute value signal. A method for preventing sparks in electrostatic coating according to claim 15. 18. Claim 8, wherein the blocking means includes a primary power cutoff switch consisting of an electromagnetic relay inserted between the primary side of the transformer in the high voltage generator and the power source. Method for preventing sparks in electrostatic painting as described in . 19. The device according to claim 8, wherein the blocking means includes an output grounding switch consisting of a spark switch inserted between the high voltage output terminal of the high voltage generator and the ground. How to prevent sparks in electrostatic painting. 20 The high voltage output of the high voltage generator is applied,
Voltage divider means for extracting the high voltage output as a detection signal for detecting a sign of spark generation; and the detection signal is input, and the voltage divider means operates by detecting the sign of spark generation based on the detection signal. an operation instruction circuit that generates an instruction signal; a blocking means that is configured to receive the operation instruction signal and is actuated upon receiving the operation instruction signal to block the supply of the high voltage output to the electrostatic coating machine; The operation instruction circuit includes a differentiation circuit that performs differential processing on the detection signal, and a signal generation circuit that uses the differentiation circuit to generate a differential value signal in which differential values of the detection signal appear continuously. , comparing the level of the differential value signal with a reference level, and when the level of the differential value signal exceeds the reference level, detecting this as a sign of spark generation;
An electrostatic coating system comprising: a comparison circuit that generates the detection signal; and an output circuit that receives the detection signal and outputs the operation instruction signal upon receiving the detection signal. Spark prevention device. 21. The electrostatic capacitor according to claim 20, wherein the voltage divider means comprises a voltage divider to which the high voltage output is applied on the high voltage output terminal side of the protective resistor in the high voltage generator. Paint spark prevention device. 22 The signal generation circuit includes: a level conversion circuit to which the output signal of the voltage divider is applied, removes the DC component thereof and outputs a level conversion signal; A component caused by pulsations in the discharge current of a gun in an electrostatic sprayer or fluctuations in the power supply voltage to the high-voltage generator, and is 1.5 m below the commercial frequency.
Removes high frequency components with frequencies that are orders of magnitude higher,
22. The electrostatic coating spark prevention device according to claim 21, further comprising: a high-frequency cutoff filter that outputs a signal from which high frequency components have been removed to the differentiating circuit. 23. The voltage divider means comprises first and second voltage dividers to which the high voltage output is separately applied to each end of the protective resistor in the high voltage generator. The spark prevention device for electrostatic coating according to item 20. 24 The signal generating circuit includes: a differential amplifier to which the output signals of the first and second voltage dividers are allocated and applied to each input terminal; the output of the differential amplifier is input; and the output signal of the differential amplifier is inputted; , a component caused by pulsations in the discharge current of the gun in the electrostatic sprayer or fluctuations in the power supply voltage to the high-voltage generator, which is 1 kHz higher than the commercial frequency.
Removes high frequency components with frequencies that are orders of magnitude higher,
24. The electrostatic coating spark prevention device according to claim 23, further comprising: a high-frequency cutoff filter that outputs a signal from which high frequency components have been removed to the differentiating circuit. 25. Claim 20, characterized in that the blocking means includes a primary power cutoff switch consisting of an electromagnetic relay inserted between the primary side of the transformer in the high voltage generator and the power source. A spark prevention device for electrostatic painting as described in . 26. The static electricity generator according to claim 20, wherein the blocking means includes an output grounding switch consisting of a spark switch inserted between the high voltage output terminal of the high voltage generator and ground. Electric coating spark prevention device.