Net cutting pilot arc control circuit of air plasma cutting machine

Abstract

The invention discloses a cutting net pilot arc control circuit of an air plasma cutting machine, and belongs to the technical field of air plasma cutting machines. In order to solve the problem of how to overcome the problem of frequent time delay and failure when a cutting machine adopts high-frequency arc striking to switch from a main arc to a pilot arc. According to the technical scheme, the positive electrode of a rectifier is connected with the positive electrode end of a cutting gun through a Hall sensing chip U1; the Hall sensing chip U1 is connected with a logic control circuit, the logic control circuit is connected with a transistor G1, the Hall sensing chip U1 collects current signals output by a main arc of the cutting gun and transmits the current signals to the logic control circuit, and when the logic control circuit judges that the collected current signals are larger than a given current value, the logic control circuit controls the transistor G1 to be switched off. When the logic control circuit judges that the acquired current signal is smaller than or equal to a times of a given current value, the logic control circuit controls the transistor G1 to be switched on, the coefficient a is smaller than 1, and the efficiency of the circuit is far away from the effect of secondary high-frequency arc striking before high voltage.

Description

Technical Field

[0001] The invention relates to the technical field of air plasma cutting machines, in particular to a mesh cutting arc maintenance control circuit of an air plasma cutting machine. Background Art

[0002] The existing air plasma cutting machine has the problem of unsmooth conversion between pilot arc and main arc in the net cutting function. Under the net cutting function, when the gun leaves the workpiece, there is no need to hit the high-frequency pilot arc again when the main arc switches to the pilot arc.

[0003] When cutting a mesh, the cutting gun will cut on the mesh workpiece, and the cutting nozzle will continuously contact the metal workpiece close to and far away from the metal workpiece. When approaching the metal workpiece, the cutting gun will switch from the pilot arc to the main arc, and when leaving the workpiece, the main arc will extinguish in a very short time. At this time, the cutting gun needs to be switched to the pilot arc state, because as the cutting gun moves, the cutting gun will soon contact the metal workpiece again, and the cutting nozzle needs to be in the pilot arc state to switch to the main arc again for cutting. Existing cutting machines use high-frequency arc ignition again when switching from the main arc to the pilot arc, and high-frequency arc ignition will often be delayed and fail. Summary of the invention

[0004] In order to solve the above-mentioned technical problems and shortcomings: how to overcome the problem of frequent delays and failures when the cutting machine switches from the main arc to the pilot arc using high-frequency arc ignition, the present invention creates a method of combining a current sampling circuit, a pilot arc driving circuit and a given circuit to allow the main arc to quickly switch to the pilot arc, thereby greatly improving the user's mesh cutting efficiency and usage experience.

[0005] In order to achieve the above-mentioned purpose and other related purposes, the present invention adopts the following technical solutions:

[0006] An air plasma cutting machine cutting arc control circuit includes a transformer, a rectifier, a transistor G1, and a cutting gun, wherein the cutting gun has a positive terminal, a negative terminal, and a 0V terminal, one side of the transformer is used to connect a power supply, and the other side of the transformer is connected to the rectifier, the positive electrode of the rectifier is connected to the 0V terminal of the cutting gun through the transistor G1, the negative electrode of the rectifier is connected to the negative terminal of the cutting gun through an inductor, and the positive electrode of the rectifier is connected to the positive terminal of the cutting gun through a Hall sensor chip U1;

[0007] The Hall sensor chip U1 is connected to a logic control circuit, which is connected to the transistor G1. The Hall sensor chip U1 collects the current signal output by the main arc of the cutting torch and transmits it to the logic control circuit. When the logic control circuit determines that the collected current signal is greater than a given current value, the logic control circuit controls the transistor G1 to turn off. When the logic control circuit determines that the collected current signal is less than or equal to a times the given current value, the logic control circuit controls the transistor G1 to turn on, and the coefficient a is less than 1.

[0008] Preferably, the logic control circuit includes a resistor R3, a resistor R4, an optocoupler U3, a comparator module U2B, a comparator module U2C, a comparator module U2A, a transistor switch circuit, a logic “OR” gate circuit, and an optocoupler chip U6.

[0009] The output end of the Hall sensor chip U1 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the resistor R4, the collector of the optocoupler U3, and the inverting end of the comparator module U2B, the other end of the resistor R4 is grounded, the in-phase end of the comparator module U2B is connected to the first reference circuit, the output end of the comparator module U2B is connected to the inverting end of the comparator module U2C, the control end of the transistor switch circuit, and the cathode of the optocoupler U3, the anode of the optocoupler U3 is connected to the first voltage source, the emitter of the optocoupler U3 is connected to the inverting end of the comparator module U2A, the in-phase end of the comparator module U2A is connected to the second reference circuit, the output end of the comparator module U2A is connected to the collector of the transistor switch circuit and an input end of the logic "OR" gate circuit, the output end of the comparator module U2C is connected to the other input end of the logic "OR" gate circuit, the output end of the logic "OR" gate circuit is connected to the input end of the optocoupler chip U6, and the output end of the optocoupler chip U6 controls the on and off of the transistor G1.

[0010] Preferably, the first reference circuit includes a first reference voltage source, a resistor R8 and a resistor R7, the first reference voltage source is connected to one end of the resistor R8, the other end of the resistor R8 is connected to one end of the resistor R7 and the in-phase end of the comparator module U2B, and the other end of the resistor R7 is grounded.

[0011] Preferably, the second reference circuit includes a first reference voltage source, a potentiometer VR1, a comparator U4A, a comparator U4B, a resistor R9, a resistor R11 and a resistor R10; the first reference voltage source is connected to one end of the resistor of the potentiometer VR1, the other end of the resistor of the potentiometer VR1 is connected to the inverting end of the comparator U4A and grounded, the adjustment end of the potentiometer VR1 is connected to the non-inverting end of the comparator U4A and one end of the resistor R9; the other end of the resistor R9 is connected to the output end of the comparator U4A and the non-inverting end of the comparator U4B, the inverting end of the comparator U4B is grounded, the output end of the comparator U4B is connected to one end of the resistor R11, the other end of the resistor R11 is connected to one end of the resistor R10 and the non-inverting end of the comparator module U2A, and the other end of the resistor R10 is grounded.

[0012] Preferably, the transistor switching circuit includes a resistor R13, a resistor R14 and a transistor Q1, one end of the resistor R13 is connected to the output end of the comparator module U2B, the other end of the resistor R13 is connected to one end of the resistor R14 and the base of the transistor Q1, the emitter of the transistor Q1 and the other end of the resistor R14 are grounded together, and the collector of the transistor Q1 is connected to the output end of the comparator module U2A.

[0013] In summary, the invention has at least one of the following beneficial technical effects:

[0014] 1. When cutting the net, the cutting gun will cut on the mesh workpiece, and the cutting nozzle will continuously contact the metal workpiece close to and far away from the metal workpiece. When it is close to the metal workpiece, the cutting gun will switch from the pilot arc to the main arc. When it leaves the workpiece, the main arc will be extinguished in a very short time. At this time, the cutting gun needs to be switched to the pilot arc state, because as the cutting gun moves, the cutting gun will soon contact the metal workpiece again, and the cutting nozzle needs to be in the pilot arc state to switch to the main arc for cutting again. The existing cutting machine switches from the main arc to the pilot arc by re-using high-frequency arc ignition, and high-frequency arc ignition will often have delays and failures. This circuit cancels the step of secondary high-frequency arc ignition; a logic control circuit is connected to the Hall sensor chip U1, and the logic control circuit is connected to the transistor G1. The Hall sensor chip U1 collects the current signal output by the main arc of the cutting gun and transmits it to the logic control circuit. When the collected current is greater than 8A, G1 is closed and the pilot arc is disconnected; when the cutting gun is far away from the metal workpiece, the main arc decreases. When the main arc current drops to less than two-thirds of the given current, G1 is opened and the pilot arc is opened. The efficiency of this circuit is much higher than the secondary high-frequency arc ignition before high voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a first partial circuit diagram of an embodiment of the present invention;

[0016] Figure 2 It is a partial circuit diagram of a logic control circuit of an embodiment of the present invention;

[0017] Figure 3 It is a second reference circuit diagram of an embodiment of the present invention.

[0018] Description of the reference numerals of the main components:

[0019] 100, rectifier; 200, cutting gun; 300, logic control circuit; 400, transistor switch circuit; 500, first reference circuit; 600, second reference circuit. DETAILED DESCRIPTION

[0020] The following is an explanation of the embodiments of the present invention by specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0021] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention. The illustrations only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0022] The specific implementation manner of the present invention will be further described below in conjunction with the accompanying drawings.

[0023] Example:

[0024] An air plasma cutting machine cutting arc control circuit, reference Figure 1 As shown, it includes a transformer, a rectifier 100, a transistor G1, and a cutting gun 200. The transistor G1 can be a PMOS tube. The cutting gun 200 has a positive terminal, a negative terminal, and a 0V terminal. One side of the transformer is used to connect to the power supply, and the other side of the transformer is connected to the rectifier 100. The rectifier 100 is composed of diodes D1-D4. The rectifier 100 is used to convert AC into DC. The positive electrode of the rectifier 100 is connected to the 0V terminal of the cutting gun 200 through the transistor G1, the negative electrode of the rectifier 100 is connected to the negative terminal of the cutting gun 200 through the inductor, and the positive electrode of the rectifier 100 is connected to the positive terminal of the cutting gun 200 through the Hall sensor chip U1.

[0025] The Hall sensor chip U1 is connected to a logic control circuit 300, refer to Figure 2 and Figure 3 As shown, the logic control circuit 300 is connected to the transistor G1, and the Hall sensor chip U1 collects the current signal output by the main arc of the cutting torch 200 and transmits it to the logic control circuit 300. When the logic control circuit 300 determines that the collected current signal is greater than a given current value (the given current in this example is 8A), the logic control circuit 300 controls the transistor G1 to turn off. When the logic control circuit 300 determines that the collected current signal is less than or equal to a times the given current value, the logic control circuit 300 controls the transistor G1 to turn on, and the coefficient a is less than 1. In this example, a is 2 / 3 (two-thirds).

[0026] Specific combination Figure 2 and Figure 3 The logic control circuit 300 includes a resistor R3, a resistor R4, an optocoupler U3, a comparator module U2B, a comparator module U2C, a comparator module U2A, a transistor switch circuit 400, a logic “OR” gate circuit, and an optocoupler chip U6.

[0027] The output end of the Hall sensor chip U1 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the resistor R4, the collector of the optocoupler U3, and the inverting end of the comparator module U2B, the other end of the resistor R4 is grounded, the in-phase end of the comparator module U2B is connected to the first reference circuit 500, the output end of the comparator module U2B is connected to the inverting end of the comparator module U2C, the control end of the transistor switch circuit 400, and the cathode of the optocoupler U3, the anode of the optocoupler U3 is connected to the first voltage source, the emitter of the optocoupler U3 is connected to the inverting end of the comparator module U2A, the in-phase end of the comparator module U2A is connected to the second reference circuit 600, the output end of the comparator module U2A is connected to the collector of the transistor switch circuit 400, and an input end of the logic "OR" gate circuit, the output end of the comparator module U2C is connected to the other input end of the logic "OR" gate circuit, the output end of the logic "OR" gate circuit is connected to the input end of the optocoupler chip U6, and the output end of the optocoupler chip U6 controls the on and off of the transistor G1.

[0028] The first reference circuit 500 includes a first reference voltage source (this voltage is 5V), a resistor R8 and a resistor R7, the first reference voltage source is connected to one end of the resistor R8, the other end of the resistor R8 is connected to one end of the resistor R7 and the in-phase end of the comparator module U2B, and the other end of the resistor R7 is grounded. The judgment reference of the comparator signal comparison is obtained by the resistor R7 and the resistor R8 resistor voltage division method.

[0029] refer to Figure 3 As shown, the second reference circuit 600 includes a first reference voltage source, a potentiometer VR1, a comparator U4A, a comparator U4B, a resistor R9, a resistor R11 and a resistor R10; the first reference voltage source is connected to one end of the resistor of the potentiometer VR1, the other end of the resistor of the potentiometer VR1 is connected to the inverting end of the comparator U4A and grounded, the adjustment end of the potentiometer VR1 is connected to the in-phase end of the comparator U4A and one end of the resistor R9; the other end of the resistor R9 is connected to the output end of the comparator U4A and the in-phase end of the comparator U4B, the inverting end of the comparator U4B is grounded, the output end of the comparator U4B is connected to one end of the resistor R11, the other end of the resistor R11 is connected to one end of the resistor R10 and the in-phase end of the comparator module U2A, and the other end of the resistor R10 is grounded. It can be seen that the output value V1 of the second comparison reference circuit can be controlled by adjusting the potentiometer VR1.

[0030] The transistor switch circuit 400 includes a resistor R13, a resistor R14 and a transistor Q1, one end of the resistor R13 is connected to the output end of the comparator module U2B, the other end of the resistor R13 is connected to one end of the resistor R14 and the base of the transistor Q1, the emitter of the transistor Q1 and the other end of the resistor R14 are grounded together, and the collector of the transistor Q1 is connected to the output end of the comparator module U2A.

[0031] In this embodiment, the comparator modules U2A, U2B, and U2C can be integrated into a chip U2, and the chip model is TL084. Similarly, the comparators U4A and U4B can be integrated into a chip U4, and the chip model is TL084. The model of the chip U5 is SN74LVC1G32. The model of the chip U6 is HCPL-3120-500E.

[0032] Working principle:

[0033] The principle of this circuit is to sample the current signal on the main arc through the Hall sensor chip U1, convert it into a voltage analog voltage signal and connect it to the sixth pin of the comparator module U2B through the resistor R3. When the current collected by the Hall sensor chip U1 is greater than 8A, the voltage of the sixth pin of the comparator module U2B will be higher than the fifth pin, and the output end of the comparator module U2B will output a low level 0V. The 0V signal passes through the comparator module U2C (follower) to the output end, and the output end is connected to the first pin of the logic "OR" gate circuit. The seventh pin of the comparator module U2B has a 0V signal. The other path is connected to the optocoupler U3 through the resistor R6. The optocoupler U3 is turned on, and the resistor R3 and the second pin of the comparator module U2A are turned on. The first pin of the comparator module U2A outputs a low level of 0V and is connected to the second pin of the logic "OR" gate circuit (U5). At this time, the first pin and the second pin of the logic "OR" gate circuit are both 0V. At this time, the fourth pin of the logic "OR" gate circuit outputs a high level and is connected to the third pin of the logic optocoupler U6. The logic optocoupler U6 is turned on, and the logic optocoupler U6 outputs a high level signal, which passes through the resistor R1 to turn off the transistor G1, and the arc is disconnected.

[0034] When the cutting gun 200 is away from the metal workpiece, the main arc decreases, and the sampling signal of the Hall sensor chip U1 decreases. When the main arc current drops to less than two-thirds of the given current (8A), the given voltage passes through the first pin of the comparator U4A to the seventh pin of the comparator U4B, and is divided by resistors R11 and R10 to the third pin of the comparator module U2A. The third pin is two-thirds of the given voltage. The sampling voltage of the Hall sensor chip U1 is conducted to the second pin of the comparator module U2A through resistor R3 and the optical coupler U3. At this time, the inverting end is lower than the in-phase end. The first pin of U2A outputs a high level to the "OR" gate circuit U5, and the "OR" gate circuit U5 outputs a high level to the logic optical coupler U6 to turn on the transistor G1, and the arc is opened. The efficiency of this circuit is much higher than the secondary high-frequency arc before the high voltage.

[0035] Therefore, when cutting a mesh, the cutting gun 200 will cut on the mesh workpiece, and the cutting nozzle will continuously contact the metal workpiece and the metal workpiece. When it is close to the metal workpiece, the cutting gun 200 will switch from the pilot arc to the main arc. When it leaves the workpiece, the main arc will be extinguished in a very short time. At this time, the cutting gun 200 needs to be switched to the pilot arc state, because as the cutting gun 200 moves, the cutting gun 200 will soon contact the metal workpiece again, and the cutting nozzle needs to be in the pilot arc state to switch to the main arc again for cutting. The existing cutting machine switches from the main arc to the pilot arc by re-using high-frequency arc ignition, and high-frequency arc ignition often has Delay and failure, this circuit cancels the step of secondary high frequency; the logic control circuit 300 is connected to the transistor G1 through the Hall sensor chip U1, the Hall sensor chip U1 collects the current signal of the main arc output of the cutting gun 200, and transmits it to the logic control circuit 300. When the collected current is greater than 8A, G1 is turned off and the pilot arc is disconnected; when the cutting gun 200 is away from the metal workpiece, the main arc decreases. When the main arc current drops to less than two-thirds of the given current, G1 is turned on and the pilot arc is opened. The efficiency of this circuit is much higher than the secondary high frequency arc initiation before high voltage.

[0036] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, any equivalent changes made to the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An air plasma cutting machine arc cutting control circuit, comprising a transformer, a rectifier, a transistor G1, and a cutting gun, wherein the cutting gun has a positive terminal, a negative terminal, and a 0V terminal, one side of the transformer is used to connect to a power source, and the other side of the transformer is connected to the rectifier, the positive electrode of the rectifier is connected to the 0V terminal of the cutting gun through the transistor G1, and the negative electrode of the rectifier is connected to the negative terminal of the cutting gun through an inductor, characterized in that: The positive electrode of the rectifier is connected to the positive terminal of the cutting gun through the Hall sensor chip U1; The Hall sensor chip U1 is connected to a logic control circuit, which is connected to the transistor G1. The Hall sensor chip U1 collects the current signal output by the main arc of the cutting torch and transmits it to the logic control circuit. When the logic control circuit determines that the collected current signal is greater than a given current value, the logic control circuit controls the transistor G1 to turn off. When the logic control circuit determines that the collected current signal is less than or equal to a times the given current value, the logic control circuit controls the transistor G1 to turn on, and the coefficient a is less than 1.

2. The arc-maintaining control circuit for cutting mesh of an air plasma cutting machine according to claim 1, characterized in that: The logic control circuit includes a resistor R3, a resistor R4, an optical coupler U3, a comparator module U2B, a comparator module U2C, a comparator module U2A, a transistor switch circuit, a logic "OR" gate circuit, and an optical coupler chip U6. The output end of the Hall sensor chip U1 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the resistor R4, the collector of the optocoupler U3, and the inverting end of the comparator module U2B, the other end of the resistor R4 is grounded, the in-phase end of the comparator module U2B is connected to the first reference circuit, the output end of the comparator module U2B is connected to the inverting end of the comparator module U2C, the control end of the transistor switch circuit, and the cathode of the optocoupler U3, the anode of the optocoupler U3 is connected to the first voltage source, the emitter of the optocoupler U3 is connected to the inverting end of the comparator module U2A, the in-phase end of the comparator module U2A is connected to the second reference circuit, the output end of the comparator module U2A is connected to the collector of the transistor switch circuit and an input end of the logic "OR" gate circuit, the output end of the comparator module U2C is connected to the other input end of the logic "OR" gate circuit, the output end of the logic "OR" gate circuit is connected to the input end of the optocoupler chip U6, and the output end of the optocoupler chip U6 controls the on and off of the transistor G1.

3. The arc-maintaining control circuit for cutting mesh of an air plasma cutting machine according to claim 2, characterized in that: The first reference circuit includes a first reference voltage source, a resistor R8 and a resistor R7. The first reference voltage source is connected to one end of the resistor R8. The other end of the resistor R8 is connected to one end of the resistor R7 and the in-phase end of the comparator module U2B. The other end of the resistor R7 is grounded.

4. The arc-maintaining control circuit for cutting mesh of an air plasma cutting machine according to claim 2, characterized in that: The second reference circuit includes a first reference voltage source, a potentiometer VR1, a comparator U4A, a comparator U4B, a resistor R9, a resistor R11 and a resistor R10; The first reference voltage source is connected to one end of the resistor of the potentiometer VR1, the other end of the resistor of the potentiometer VR1 is connected to the inverting end of the comparator U4A and grounded, the adjustment end of the potentiometer VR1 is connected to the non-inverting end of the comparator U4A and one end of the resistor R9; the other end of the resistor R9 is connected to the output end of the comparator U4A and the non-inverting end of the comparator U4B, the inverting end of the comparator U4B is grounded, the output end of the comparator U4B is connected to one end of the resistor R11, the other end of the resistor R11 is connected to one end of the resistor R10 and the non-inverting end of the comparator module U2A, and the other end of the resistor R10 is grounded.

5. The arc-maintaining control circuit for cutting mesh of an air plasma cutting machine according to claim 2, characterized in that: The transistor switch circuit includes a resistor R13, a resistor R14 and a transistor Q1, one end of the resistor R13 is connected to the output end of the comparator module U2B, the other end of the resistor R13 is connected to one end of the resistor R14 and the base of the transistor Q1, the emitter of the transistor Q1 and the other end of the resistor R14 are grounded together, and the collector of the transistor Q1 is connected to the output end of the comparator module U2A.

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