JPH0124547B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high voltage device for electrostatic coating that applies high voltage to a coating machine via a high voltage cable. Conventionally, an electrostatic coating apparatus shown in FIG. 1 has been known. In the drawing, 1 indicates the commercial power source E, for example -90
A high voltage generator that boosts the voltage to [kV], the high voltage generator 1 is composed of a step-up transformer 2, a voltage doubler rectifier 3, etc., and a high voltage cable 4 is connected to the high voltage generator 1.
A coating machine 5 is connected via. The rectifier 3 of the high voltage generator is activated when a higher current (hereinafter referred to as overcurrent) flows in the high voltage cable 4 than during normal painting due to various causes described later, and the overcurrent is eliminated in one system. A safety circuit 6 is connected which shuts off the primary side of the step-up transformer 2 upon detection. Further, a resistor 7 of, for example, 100 [MΩ] is provided on the output side of the high voltage generator 1, and a resistor 7 of, for example, 100 [MΩ] is provided, and the
160 to prevent spark discharge from the paint sprayer 5.
A resistor 8 of [MΩ] is provided. 9 is a paint source such as a paint tank that supplies paint to the coating machine 5; 10
indicates an object to be coated, and the object to be coated 10 is connected to the ground 11 together with the seal braid 4A of the high voltage cable 4. In the electrostatic coating apparatus configured in this way, a negative high voltage generated by the high voltage generator 1 is applied to the coating machine 5 via the high voltage cable 4, and the paint source 9
The paint supplied to the coating machine 5 is charged to a negative potential, and the charged paint is electrostatically atomized and applied to the object 10 at ground potential. By the way, during this electrostatic coating, an overcurrent may flow in the high voltage cable 4 due to the following reasons. First, there is a predetermined resistance between the coating machine 5 and the object to be coated 10, but for example, if the electrode of the coating machine 5 comes into contact with the object to be coated 10 during painting, the resistance between the coating machine 5 and the object to be coated will be The resistance between the two becomes zero. Therefore, the total high voltage supply line resistance is the sum of the resistance 7 on the output side of the high voltage generator 1 and the resistance 8 inside the paint sprayer 5, that is, (100
+160) [MΩ], and overcurrent flows. Second, when the paint is a metallic paint containing fine metal particles, for example, fine aluminum particles, a so-called "bridging phenomenon" occurs, and the electrode of the coating machine 5 mentioned above is connected to the object 1 to be coated.
There is a risk that an overcurrent will flow in the same way as when contacting zero. Thirdly, the high voltage cable 4 connected to the atomizer 5 is complicatedly bent and damaged due to frequent movement of the atomizer 5 along the shape of the object 10 to be coated. The core wire of the cable 4 comes into contact with the shield braid 4A and shorts to the ground 11, causing an overcurrent to flow, and the total high voltage supply line resistance is only the resistance value of the output side resistor 7 of the high voltage generator 1, 100 [MΩ]. Become. Here, for example, the applied high voltage is -90 [kV], -60 [kV]
[kV], -30 [kV], the above-mentioned calculated values of overcurrent are summarized as shown in Table 1.

[Table] The following Table 2 shows an example of the overcurrent calculation value in Table 1 and a corresponding measurement example of the overcurrent of the high voltage cable 4.

[Table] The safety circuit 6 detects an overcurrent set in advance with reference to Table 1 or Table 2 and shuts off the power supply E side of the high voltage generator 1. Since current detection is carried out in one system, it is necessary for the operator to change the set value of the overcurrent to be detected depending on the type of coating machine 5, the type of paint, etc.
However, since the overcurrent is weak, it is not only difficult to set it appropriately, but also has the disadvantage that if the setting conditions are mistaken, an accident may occur. The present invention improves the drawbacks of the prior art, and features a multistage voltage setting device that sets the output voltage of a high voltage generator in multiple stages, and a predetermined setting value for the high voltage cable. a multi-stage overcurrent detector that outputs a detection signal by detecting that a current of the above amount has flowed; and a multi-stage abnormality determination of the detection signal from the multi-stage overcurrent detector corresponding to the set voltage of the multi-stage voltage setting device. It consists of a multi-stage abnormality discriminator that outputs an abnormal signal, and the multi-stage voltage setting device is set to an appropriate voltage according to the type of coating machine and the type of paint, and the set voltage and the multi-stage overcurrent detector are The detection signal is input to an abnormality discriminator, and the abnormality discriminator discriminates abnormalities in multiple stages according to the set voltage, so that the power to the high voltage generator can be cut off, or the operation of the entire coating equipment can be cut off. The present invention provides an electrostatic coating device configured as follows. The present invention will be explained below using FIG. 2. In the drawings, the same components as in FIG. It never changes. However, the present invention uses the commercial power source E and the high voltage generator 1.
A multi-stage voltage setting device 21 is provided between the high-voltage cable 4 to set the output voltage of the high-voltage generator 1 in multiple stages, and a multi-stage voltage setting device 21 is connected to the positive side of the high-voltage generator 1 and is connected to the A multistage overcurrent detector 22 outputs a detection signal by detecting that a current flows, and logically determines the detection signal of the multistage overcurrent detector 22 in accordance with the set voltage of the multistage voltage setting device 21. It is generally composed of a multi-stage abnormality discriminator 23 that discriminates abnormalities in multiple stages. 24 is a setting switch section, and the setting switch section 24 is, for example, -90
It consists of three setting switches 24A, 24B, and 24C that set voltages to [kV], -60 [kV], and -30 [kV], and each setting switch 24A, 24B, and 24C is connected to a multi-stage voltage setting device 21 as described later. , are connected to the multi-stage abnormality discriminator 23. Next, the multi-stage voltage setter 21 connects the voltage setting switches 24A, 24B, 24C and the signal line 25.
For example, 100
A step-up transformer 26 whose primary side is a commercial power supply E of [V] and which steps up the voltage to about 200 [V], and each of the above-mentioned relays inserted in parallel to the secondary side of the step-up transformer 26.
RA, RB, RC contacts RA-1, RB-1, RC-
1, and the voltage setting switches 24A, 24B, 2
Delay element 27A, 2 inserted between 4C and relays RA, RB, RC to prevent overvoltage during voltage switching
It is composed of 7B and 27C. The multi-stage voltage setting device 21 includes voltage setting switches 24A, 2
If you select either 4B or 24C and close it,
The contacts RA-1,
When RB-1 and RC-1 are closed, the negative side of high voltage generator 1 receives, for example, -90 [kV], -60 [kV], -30
[kV] DC high voltage is output. In addition, the multi-stage overcurrent detector 22 includes four detectors 22A, 22B, 22 that independently detect overcurrent.
C, 22D, and a resistor 28 provided between the positive side of the high voltage generator 1 and the ground 11 at the front stage of the detector 22A, and each of the detectors 22A, 22B, 22C, and 22D will be described later. Sensitivity setter 29A, 29B, 29C,
29D, the positive input terminal is connected to the positive side of the high voltage generator 1, and the negative input terminal is connected to the sensitivity setting device 29A,
Comparators 30A, 30B, 30C, 30D connected to 29B, 29C, 29D, respectively,
Each of the comparators 30A, 30B, 30C, 30
Amplifiers 31A, 31B, connected to the output side of D
It is composed of 31C and 31D. Here, the sensitivity setting devices 29A, 29B, 29C, and 29D described above are connected to sensitivity setting resistors 32A, 32 having the same resistance value.
Comparator 30 for B, 32C, 32D
Connection position 33 with A, 30B, 30C, 30D
By making A, 33B, 33C, and 33D different, the overcurrent value to be detected can be set to 350, for example.
The current is set to [μA], 180 [μA], 120 [μA], and 60 [μA]. By the way, the voltage setting switches 24A, 24B,
24C are sequentially closed, if current i flows from the positive side of rectifier 3 toward resistor 28, resistor 2
Voltages V _A , V _B , V _C are generated on the positive side of 8, while sensitivity setters 29A, 29B, 29C, 29D
are the sensitivity setting resistors 32A, 32B, 32C,
32D connection position 33A, 33B, 33C, 33
v _A , v _B , v _C , and v _D are generated between D and earth 11. Therefore, each detector 22A, 22B, 22C,
22D comparators 30A, 30B, 30C,
30D can compare the voltages V _A , V _B , V _C and v _A , v _B , v _D , so each comparator 30 A, 30
B, 30C, 30D compare both voltages, and connect the high voltage cable 4 with sensitivity setters 29A, 29B, 29C,
A detection signal is output when a current exceeding the set current by 29D flows. Furthermore, the multi-stage abnormality discriminator 23 has an AND circuit 34
A, 34B, 34C, 35A, 35B, an abnormal output relay RD, RE having OR circuits 36, 37 and normally closed contacts RD-1, RE-1, respectively, an alarm 38 such as a lamp or a buzzer, and the relay. Drivers 39A and 39B for driving RD, RE and alarm 38
and a delay element 40 for overvoltage prevention during voltage switching.
It is roughly composed of A, 40B, and 40C. The signal lines 25A, 25B, 25C connected to the voltage setting switches 24A, 24B, 24C are connected to the AND circuit 34 via delay elements 40A, 40B, 40C.
It is connected to the input sides of A, 34B, 34C, 35A, and 35B, respectively, as shown. On the other hand, the signal line 41A connected to the output side of the comparator 30A via the amplifier 31A is connected to the input side of OR circuits 36 and 37, and the signal line 41A is connected to the output side of the comparator 30A via the amplifier 31A.
Signal lines 41B, 41C, 41 connected to the output sides of comparators 30B, 30C, 30D via
D is AND circuit 34A, 34B, 34C, 35
A and 35B are connected as shown. Further, the output sides of the AND circuits 34A, 34B, and 34C are connected to the input side of the OR circuit 37, and the AND circuit 35
The output sides of A and 35B are connected to the input sides of OR circuits 36 and 37, respectively. An abnormal output relay is connected to the output side of the OR circuit 36 via the driver 39A.
RE is connected, and an abnormal output relay RD and an alarm 38 are connected to the output side of the OR circuit 37 via a driver 39B. In addition, the abnormal output relay
The normally closed contact RD-1 of the RD is inserted between the power supply E and the step-up transformer 26, and the normally closed contact RE-1 of the abnormal output relay RE is provided as a switch for cutting off the external device 42. Here, the external device 4
2 is, for example, a paint pump or color change valve that supplies paint from the paint source 9 to the coating machine 5, and the contact RE-1
stops the paint pump by opening the
Alternatively, the color change valve or the paint on/off valve is closed in an emergency to stop the supply of paint, thereby stopping the operation of the coating machine 5. From the above points, to describe the function of the multi-stage abnormality discriminator 23, when the voltage setting switch 24A is closed and -90 [kV] is set, the current flowing through the high voltage cable 4 is detected by the detector 22B. Setting current
Detector 22A setting current 350 at 180 [μA] or more
[μA] or less, an abnormality determination signal is output from the AND circuit 34A based on the detection signal from the detector 22B, and the signal is output from the driver 39 via the OR circuit 37.
B excites relay RD, and its contact RD-1
is opened, the power supply E of the high voltage generator 1 is cut off, and the alarm 38 is activated. In addition, when the set current of the detector 22A is 350 [μA] or more, the detector 2
The detection signal from 2A excites the relay RE by the driver 39A via the OR circuit 36, opens the contact RE-1 to stop the external device 42, and excites the relay RD via the OR circuit 37 to turn on the power. E is shut off, and the operation of the entire coating machine 5 is stopped. Similarly, close the voltage setting switch 24B and -
When 60 [kV] is set, the current flowing through the high voltage cable 4 is the set current 120 of the detector 22C.
[μA] or more, the set current of the detector 22B is 180 [μA]
In the following cases, an abnormality determination signal is output from the AND circuit 34B based on the detection signal from the detector 22C, and the power supply E is cut off by the relay RD. Further, when the set current of the detector 22B is 180 [μA] or more, an abnormality determination signal is output from the AND circuit 35B based on the detection signal from the detector 22B.
The external device 42 is stopped by the relay RE via the OR circuit 36, and the power supply E is cut off by the relay RD via the OR circuit 37. Furthermore, close the voltage setting switch 24C and -
30 [kV], the current flowing through the high voltage cable 4 is set to 60 [kV] of the detector 22D.
[μA] or more, the set current of the detector 22C is 120 [μA]
In the following cases, an abnormality determination signal is output from the AND circuit 34C based on the detection signal from the detector 22D, and the power supply E is cut off. In addition, when the set current of the detector 22C is 120 [μA] or more, the detector 22C
Based on the detection signal from 2C, an abnormality determination signal is output from the AND circuit 35A, and the external device 42 is stopped and the power supply E is cut off. The present invention is configured as described above, and includes voltage setting switches 24A, 24B, 24C and a detector 22.
B, 22C, and 22D correspond to each other, and the detector 22A sets the upper limit of the current flowing through the high voltage cable 4. If a current exceeding this set value flows, an abnormality is detected regardless of the voltage setting value. Then, completely stop the coating equipment. Now, when the voltage setting switch 24A is closed,
Relay via signal line 25A and delay element 27A
RA is excited and closes the contact RA-1, and a high voltage of -90 [kV] is generated on the negative side of the high voltage generator 1, which is applied to the paint sprayer 5 via the high voltage cable 4. , comparators 30A, 30B, 3
Voltage V _A is input to each positive input terminal of 0C, 30D, and sensitivity setter 29A, 29B,
Voltages v _A , v _B , v _C , and _D given according to the set currents of 29C and 29D are respectively input. As is clear from Tables 1 and 2, at a high voltage of -90 [kV], approximately 60 [μA] normally flows through the high voltage cable 4. For example, if a bridge phenomenon occurs and a current of 300 [μA] flows through the high voltage cable 4,
A corresponding current also flows through the resistor 28, activating the comparators 30B, 30C, and 30D, and activating the amplifiers 31B, 31C, and 31D.
Detection signals are output from B, 31C, and 31D. As a result, the AND circuit 34 of the abnormality discriminator 23
The closing signal of the detection signal switch 24A is input to A, and an abnormality determination signal is output from the AND circuit 34A. This output signal excites the abnormal output relay RD by the driver 39B via the OR circuit 37, opens its normally closed contact RD-1, cuts off the power supply E, and activates the alarm 38 to prevent the occurrence of a bridge phenomenon. Announce what you have done. That is, since the AND circuits 34B and 34C cannot perform a logical product, no abnormality determination signal is output, and only the AND circuit 34A determines the bridge phenomenon and only cuts off the high voltage. After the bridging phenomenon disappears by cutting off the high voltage, if the high voltage is turned on again, electrostatic painting can be continued without stopping the painting line. On the other hand, if a core wire short-circuit accident occurs due to dielectric breakdown of the high voltage cable 4 and a current of 380 [μA] flows, the comparators 30A, 30B, 30C, 3
All detection signals are output from 0D. As a result, both relays RD and RE are excited via the OR circuits 37 and 36 by the detection signal from the comparator 30A, and the power supply E is cut off and the external device 4
2 and completely stop the coating equipment. In this case, it is assumed that the high voltage cable 4, coating machine 5, etc. has been damaged and the coating line is stopped, the cable 4 is replaced and other repairs and inspections are carried out, and after confirming safety, electrostatic coating is resumed. do. Also, when the voltage setting switch 24B is closed, -60 [kV] is applied to the high voltage cable 4, and the detector 2
Abnormalities such as bridging are detected when the current exceeds the set current of 2C, and abnormalities such as dielectric breakdown are detected when the current exceeds the set current of the detector 22B, and the high voltage is cut off and the entire coating equipment is stopped in the same way as described above. be able to. As described above, according to the present invention, it is possible to distinguish between equipment damage accidents due to insulation breakdown and abnormal levels due to bridging phenomena or electrode short circuits, and to perform operations corresponding to the extent of the abnormal levels.
Not only can it prevent accidents, but it also has an automatic safety monitoring function for electrostatic coating equipment. In the above-described embodiment, relays RA, RB, and RC were used to switch the multi-stage voltage setting device 21, but an electronic switch such as a thyristor may be used, or a directly operated manual switch may be used in place of the relay. In addition, the set voltage value of the multi-stage voltage setter 21 is -
90 [kV], -60 [kV], -30 [kV], and set current values of sensitivity setting devices 29A, 29B, 29C, 29D.
Although 350 [μA], 180 [μA], 120 [μA], and 60 [μA] have been described, these set values may be other values depending on the type of coating machine 5 and the type of paint. Also, the abnormality discriminator 23 includes OR circuits 36, 37 and an AND circuit 34.
A, 34B, 34C, 35A, and 35B are used in the above description, but a variable logic discrimination method using a combination of a diode matrix and a logic element may also be used.On the other hand, abnormality discrimination can be performed by program control using a microcomputer. You may also configure a container. Further, in the embodiment of the present invention, the high voltage is set by switching the secondary side of the step-up transformer 26, but the high voltage may be set by other methods, such as by switching the secondary side of the step-up transformer 2. Of course. As described in detail above, the present invention sets the overcurrent to be detected in multiple stages corresponding to the set voltage depending on the type of coating machine and the type of paint, and detects the overcurrent flowing through the high voltage cable in multiple stages. Since it is possible to detect the abnormality and activate the abnormality discriminator, it is possible to reliably maintain the safety of the paint sprayer. In addition, when an abnormal level such as an electrode short circuit or bridging phenomenon is determined, only the power supply is cut off, and when an abnormal level such as an insulation breakdown accident is determined, the power supply is cut off.
Since the operation of the entire coating machine can be stopped, countermeasures can be taken depending on the type of accident, and even minor abnormalities such as bridging can be handled without stopping the painting line each time. Electric painting can be resumed. Furthermore, it has numerous effects, including an automatic safety monitoring function that automatically monitors the extent of accidents.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an electrostatic coating apparatus according to the prior art, and FIG. 2 is an electric circuit diagram of an electrostatic coating apparatus according to the present invention. 1...High voltage generator, 4...High voltage cable, 5...
Painting machine, 21... Multi-stage voltage setting device, 22... Multi-stage overcurrent detector, 23... Abnormality discriminator.

Claims (1)

[Scope of Claims] 1. A high voltage generator that generates a high voltage to be supplied to a coating machine via a high voltage cable, a multistage voltage setting device that sets the output voltage of the high voltage generator in multiple stages; a multistage overcurrent detector that outputs a detection signal by detecting that a current exceeding a predetermined set value flows through a high voltage cable; and a multistage overcurrent detector that outputs a detection signal in response to a set voltage of the multistage voltage setting device. An electrostatic coating device comprising a multi-stage abnormality discriminator that performs multi-stage abnormality determination on the detection signal obtained by the method and outputs an abnormality determination signal. 2. Claim 1, wherein when the multi-stage abnormality discriminator determines an abnormality level such as an electrode short-circuit bridge phenomenon, the power source of the high voltage generator is cut off.
The electrostatic coating device described in Section 1. 3. The apparatus according to claim 1, wherein when the multi-stage abnormality discriminator determines an abnormality level such as dielectric breakdown of the high voltage cable, the power to the high voltage generator is cut off and the operation of the entire coating apparatus is stopped. Electrostatic painting equipment.