SI25006A - Pulse generator with adjustable and controled upward impulse current - Google Patents

Abstract

The object of the invention is a pulsed generator for submerged electroerosive treatment having a ignition part and a power section in which the rate of increasing the current is set with the voltage supply of the power section of the generator uj. This voltage is the sum of the average voltage of the uep discharges and the chosen voltage difference between the voltage of the power supply of the generator and the discharge voltage due. In the circuit (d) these values are summed up and the signal for voltage control uj is sent. In the circuit (e), the flow rate of the diej / dt is controlled with the impulse current measurement from the sensor (h) and the time required to increase the current to the selected values. In case the torque rise time is less than the selected value of the spindle with the signal from the circuit (e), the pulse is interrupted. The energy efficiency of the generator is increased by turning off the resistance in the strong part of the generator Rj until the current reaches the selected maximum value of the shells. The influence of the resistor Rj and the additional inductance L on the rate of increase of the diej / dt current is excluded because the resistance or additional inductance L is switched on only when the current reaches the selected value of the elements. The efficiency of the generator is also increased in such a way that the side discharges with less energy input are interrupted and the following pulse is switched on after the selected pause t0.

Description

PULSE GENERATOR WITH ADJUSTABLE AND CONTROLLED PULSE FLOW

The subject of the invention is a pulse generator intended for submersible electric treatment, which allows the setting and control of the increase of the impulse current IU (t) at the time of discharge between the electrode and the workpiece in a dielectric fluid. The invention belongs to class B 23H 7/26 of the international patent classification.

The technical problems that the circuit (d) (Painted) solves is the setting of the rate of increase of the average impulse current IU (t) selected for individual combinations of electrode material and workpiece material and machining modes. For the generator part, the difference between the source voltage for the unit uj generator voltage and the discharge voltage ue is important for increasing the current: duej = uj - ue.

The constant value of the selected dueji voltage is important for the stability of the selected mode technology. Changing the voltage of the uj generator power is possible without interruption of the process and can be continuous.

For the ignition part of the generator, the difference between the source voltage for the ignition part of the uv generator and the discharge voltage ue is important for increasing the current: duev = uv - ue.

• ·

For each treatment mode, the supply voltage of the power section of the ujt generator is pre-selected, which in some cases of processing is not altered and the discharge voltage ue is adjusted. Such is the case of processing when we do not want a higher supply voltage of the power portion of the uj generator due to the higher discharge voltage ue n. BC at the first rough processing stages.

Another problem solved by the circuit (s) is the interruption of bad impulses, which are recognized by too fast a rise in current. If the current rise time for the selected current difference iejn thorn is less than the selected one, the pulse is interrupted.

In the event of intermittent pulses occurring, a Sod signal is obtained from the circuit (e), which, through the CNC, causes breaks in the machine and ensures the supply of fresh dielectric to the working slot.

The problem with generators with resistor Rj is that the value of the resistor varies depending on the current selected by iejml technology. This affects the rate of increase of the current and also results in heat losses. The resistor Rj begins to perform its function only when the selected value of the current ijmi is reached. The problem is solved with the transistor TRRj, which is connected in parallel to the resistor Rj. When the TRRj transistor is switched on, the resistance in the generator power circuit is reduced, practically to the resistance of the TRRj transistor. When the current of the IJ generator strength rises to the IJm value of the circuit (s), it sends a signal that turns off the TRRj transistor and flows through the resistor

Rj. In many cases, the IJ discharge current does not reach the IJmi current value. In these cases, the TRRj transistor is switched on at all times.

In the case of generators without resistor Rj, the regulation of the iJ current is such that the transistor TRj is switched off when the iJ current reaches the selected iJmi value. When the current drops by the selected die value, the transistor TRj is switched on again until the iJmi current value is reached again (Figure 4). This is repeated until the end of the impulse. In order to have an adequate frequency of pulses on and off, the generator circuit must have adequate inductance. If the sum of the inductance of the cable Lk and the generator Lj is not sufficient, the inductance must be increased by the series-coupled additional inductance L. This inductance begins to perform its function only when the current of the IJ generator strength reaches the selected Ijmi value. If the inductance L is switched on throughout the pulse, it can reduce the rate of increase of current. This problem is solved by switching the TRL transistor in parallel with the inductance L. When this is turned on, the effect of the inductance L is virtually nullified. Therefore, the circuit (s) is sent to the circuit (j) when the pulse current reaches the I / E value, ie the I / O signal which switches off the TRL transistor and therefore flows through the inductance L.

Electro-erosion treatment gives rise to side charges with higher discharge voltage ue. This phenomenon is described in EP 2 848 349 A1. In the event that the discharge voltage is greater than the supply voltage of the uj strength part, the current of the ij strength part does not drain and the discharge takes place only with the ignition current iev. When the discharge voltage ue drops below the value uj, the current from the output part of the iej generator also flows (Figure 5). These impulses produce less energy with less material withdrawal. In addition, these discharges take place on the side surface of the electrode and increase the side gap. This is especially not desirable at rough processing rates and it is better to interrupt such impulses and, after a pause, select those selected in technology to start a new impulse.

Most modern electric power plants make it possible to change the voltage of the generator part in several stages. However, they do not allow changing these voltages continuously and depending on the course of the erosion process. The generator made according to the patent Sl 20254 A allows for a stepwise change in the voltage of the power section, but does not allow for the adjustment of these voltages to the course of the electro-erosion process during processing. Generator according to the patent Sl 22476 A, although it is possible to change the voltage of the power part during processing, but in order to change the rate of increase and the magnitude of the discharge current due to the stabilization of the erosion process and not the stability of the technology of the selected mode.

The impulse generator of the invention will be explained on the basis of an embodiment and the accompanying drawings, of which:

Figure 1: Schematic of a generator for erosion treatment.

Figure 2: Discharge parameters for erosion treatment.

Figure 3: Impact of the working gap impedance on the discharge voltage ue and the increase in the discharge current ij.

Figure 4: Current increments at generator without resistance Rj and added • inductance L.

Figure 5: Pulse interruption due to too much delay in turning on the dtrO generator power section.

The impulse generator of the invention consists (Figure 1) of the generator power section with power source (b), transistor TRj, resistor Rj, diodes D, connections in the generator with inductance Lj and added inductance L. The generator power part has its capacitance Cj. In the voltage sensor (c), the discharge voltage ue is measured and in the current sensor (h) the discharge current ij.

The discharge voltage signal ue is supplied to the circuit (d) in the last third of the normal discharge when the discharge voltage is lowest. To control the voltage of the uj generator power, it is necessary to calculate the average uep charge voltage, which is calculated by measuring the voltage supplied in the last third of the discharge ue into the circuit (d) by the sensor u (c) and calculating the average uep voltage in the circuit (d). for the selected number of pulses n from unit (f). This value is added to the selected value of the difference in voltage between the voltage of the originating source and the voltage dueji due to the sum uj = uep + dueji from the circuit (d) controlling the supply voltage of the generator part (b).

The charge voltage ue is influenced by the size of the gap and its conductivity (Figure 3). The size of the slot is influenced by the setting of the servosystem. In demanding conditions, machining is carried out for better rinsing with a larger slot. This results in a higher discharge voltage ue and, consequently, a smaller voltage difference duej. The average discharge current of the IJ is smaller. Duej is achieved by increasing the supply voltage of the uj generator. Of course, a change in the voltage uj is possible at a rate that is enabled by the power supply to the generator part. These times are from a few ms to a few 10 to 100 ms.

The ignition part of the generator consists of the power source (a), the transistor TRv, the resistor Rv, the cables with Lv inductance and its capacitance Cv. In unit (g), select the ignition voltage of the uv source, which is not changed during treatment with the selected mode.

Both parts of the generator are connected to the electrode and the workpiece by cables with inductance Lk and capacitance Ck. Most generators have in parallel slots connected by additional capacitors of different capacitance C, which are switched on or off by switch Sc. Capacitance in the ignition and power generator circuits has the greatest influence in fine machining. For electrodes with a large work surface, the capacitance of the gap between the electrode and the Ceo workpiece is also greatly influenced. This may be so large that it limits the attainment of low roughness because capacitive discharges with energy occur depending on the size of the capacitance! All over.

A discharge current signal from the sensor (h) IU is fed into the circuit (s). From unit (f) the selected values of the current of discharge of the current are required to measure the time of rising of the current of the thorn, the individual stages of the current dieji, the selected technological value of the supply voltage of the power part of the generator ujt, the selected value of the minimum time of rising to the selected value of the impulse current of the spikes, and selected value of minimum rise time for selected value of impulse flow rate dtrni. From the circuit (d) the average discharge value uep and from the voltage sensor (c) the signal of the start of the discharge of the strength of the trO generator is deduced. The circuit (s) specifies when the discharge is interrupted due to a too rapid rise in current. The signal is fed into the oscillator (s) that controls the transistors TRj and TRv.

The discharge voltage at the point tj ue (tj) (Figure 2) depends on the combination of the electrode material and the workpiece and the resistance of the working slot Re (ie). The resistance of the working slot is influenced by the local contamination of the working slot and the size of the working slot. The local contamination of the working gap is influenced by the shape of the electrode and the separation of erosion products from the working slot. The size of the working slot is influenced by the direction of the electrode's movement with respect to the machining surface and the setting of the servosystem. Slot in the direction of movement of the servosystem - the frontal slot is always smaller than the side slot. With the servosystem we influence the size of the frontal slot.

The discharge current at the point ie ie (ie) is the sum of the current of the ignition part of the generator iev (ie) and the strength of the generator iej (ie) (Figure 2):

ie (tj) = iev (tj) + iej (tj).

The resistance of the working gap between the impulse Re (ie) cannot be measured, but from the voltage and impulse current at the selected point, ie, the resistance of the circuit can be calculated.

• · ·

The impedance of the circuit connected to this part of the generator Ztj (ie) and the supply voltage of the power section of the generator uj are important for the rate of increase of the current of the generator part.

Ztj (tj) = uj / iej (tj).

For known constant resistances in the generator circuit, the resistance Rgj is the sum of the constant resistance Rj, the resistance of the power supply cables of the generator part Rkj, the diode resistance RD and the transistor resistor at the point ie Rtrj (ie) in the generator section:

Rgj (tj) = Rj + Rkj + Rtrj (tj) + RD.

A transistor TRRj is connected in parallel to the resistor Rj. When the TRRj transistor is on, the resistance in the generator circuit is reduced, practically to the resistance of the TRRj transistor Rtrrj, which is much smaller than the resistance Rj (Rj »Rtrrj). As the current of the IJ generator power rises to the IJM value, a signal is output from the circuit (s) that turns off the transistor TRRj and flows through the resistor Rj. In many cases, the IJ discharge current does not reach the IJmi current value. In these cases, the TRRj transistor is switched on at all times. When the TRRj transistor is on, the resistance in the generator part is:

Rgj (tj) ~ ^Rtrr j ^{+ Rk} j ⁺ Rtrj (tj) + RD.

The resistance of the gap connected to the power section of the generator Rej (tj) is the difference between Ztj (tj) and Rgj (tj).

Ray (tj) = Ztj (tj) - Rgj (tj).

• ·

The current flowing through the circuit of the generator part at the point tj iej (ie) depends on the voltage uj and the impedance of the circuit for the generator section Ztj (tj).

iej (tj) = uj / Ztj (tj).

With the discharge time fe, the resistance is cut and the impedance value of the circuit Ztj (t) decreases and the discharge current iej (t) increases accordingly. The magnitude of the current iej (t) at the same impedance value Ztj (t) depends on the magnitude of the voltage of the power section of the generator uj.

For the rate of increase of the current of the ignition part of the generator, an important part of the impedance of the circuit that is connected to this part of the generator Ztv (ie) and the supply voltage of the ignition part of the generator uv.

Ztv (tj) = uv / iev (tj).

The resistance of the gap is connected to the ignition part of the generator Rev (tj) and is the difference between the impedance Ztv (tj) and the resistance of the ignition part of the generator Rgv (tj).

Rev (tj) = Ztv (tj) - Rgv (tj).

For known constant resistances in the generator ignition circuit, the resistance of the ignition part of the generator Rgv is the sum of the constant resistance Rv, the resistance of the power supply cables Rkv and the resistor of the transistor at the point ie Rtvj (ie) in the ignition part of the generator:

Rgv (tj) = Rv + Rkv + Rtvj (tj).

The current flowing through the ignition part of the generator at the point tj iev (ie) depends on the voltage of the origin uv and the impedance of the ignition circuit of the generator Ztvtj).

• · iev (tj) = uv / Ztv (tj).

With the discharge time, the resistance is cut, and thus the impedance value of the circuit Ztv (t) decreases and the discharge current iev (t) increases accordingly. Since the supply voltage of the ignition part uv is large compared to the supply voltage of the uj power part, the rate of increase of current from the ignition generator is also high (Figure 2).

The impedance and thus the rate of increase of current from the power part of the generator diej / dt is also influenced by the inductance of the circuit of the power part of the generator Lj with the inductance of the common cable Lk and the added inductance L and the difference between the voltage of the power part of the generator uj and the discharge voltage ue duej:

diej / dt = duej / (Lj + Lk + L).

The impedance and thus the rate of increase of the current from the ignition part of the generator diev / dt is influenced by the inductance of the ignition circuit of the generator Lv with the inductance of the common cable Lk and the difference between the voltage of the ignition part of the generator uv and the discharge voltage ue duev:

diev / dt = duev / (Lv + Lk).

In normal discharges, the increase in current from both the output and the ignition part of the generator is less than is allowed by the inductance of the generator power circuit (Lj + LK) and the inductance (Lv + LK) of the generator ignition circuit. If the inductance L is switched on all the time, the impulse may reduce the rate of increase of current. Some manufacturers of erosion devices get trapezoidal current in this way.

To eliminate the effect of inductance L, the TRL transistor is switched on in parallel with the inductance L. When this is turned on, the effect of the inductance L is virtually nullified. Therefore, the circuit (s) is sent to the circuit (j) when the pulse current reaches the IJ value, a IJ signal that switches off the TRL transistor and therefore the whole current flows through the inductance L. In many cases, the IJ does not reach IJ. In these cases, the TRL transistor remains switched on and the inductance effect of L is eliminated (Figure 4).

The occurrence of lateral discharges is detected by the increased discharge voltage ue. The onset of tdO discharge is detected by the circuit (d) with a voltage drop in the gap below the selected utd value from unit (f). The circuit (e) measures the delay of the power on the dtrO generator. The IJ current flows when the discharge voltage drops below the supply voltage of the uj generator power section and is detected in the sensor (h). In circuit (e), compare dtrO with the selected value from unit (f). If dtrO is greater than the selected dtrOi value (Figure 5), the pulse is interrupted and the next pulse resumes after the selected pause tO.

Successful use of erosion treatment requires a generator that ensures the consistency of optimally selected technology and prevents the appearance of harmful impulses in the erosion process. It must be energy efficient without unnecessary energy losses. In addition, • ·

the influence of parameters with constant values (eg Rj and L) on the increase of current should be minimized. Only in this case will the process of increasing the flow in the erosion process have the greatest influence on the course of the process, especially by changing the impedance of the working gap.

An important parameter that guarantees us the constancy of the technology chosen is the rate of increase of current mainly through the strength of the die / dt generator. This depends on the difference between the selected voltage of the generator part uj and the discharge voltage ue: duej = uj ue. Since the discharge voltage ue depends on the course of the erosion process (Figure 3), it is necessary to adjust the supply voltage of the power section uj so that the difference duej is constant.

The impulse generator according to the invention allows to calculate the average uep voltages for the selected number of normal discharge n from the measured discharge voltage in the last third of the normal discharge ue from the sensor (c) in the circuit (d). Therefore, signal from oscillator (i) is also required. Uep value is added to the selected dueji (d) value, so that the voltage to control the strength uj · is calculated.

uj = uep + duej.

The rate of increase of the current of the power part of the diej / dt generator depends on the resistance of the working gap. This changes from impulse to impulse (Figure 3). As the resistance decreases, the discharge current of the IJ increases. With too fast a decrease in resistance, the current increases more rapidly, but the density of the supplied energy decreases. The lower energy density results in a worse overheating of the material in the future crater at the discharge site and thus a lower material withdrawal. With insufficient energy density, material is no longer taken away, and the energy input is large enough to cause additional contamination of the working gap due to the dielectric decay. Such impulses must be interrupted with the supply of energy, as this damages the normal course of erosion treatment. Therefore, such pulses with the signal from the circuit (e) are interrupted (Figure 1). It is first necessary to detect the start of the discharge of trO with the current from the generator part. This is determined so that the voltage sensor (c) detects a voltage drop on the power section of the power source. The current sensor (h) measures the impulse current iej. In circuit (e), the rise time tr is measured between the start of the discharge trO and the selected pulse current value iejn. In the event that the rise time of the thorn current is less than the selected rise time of the thorn current <thorn, the pulse is interrupted by the signal from the circuit (e).

Alternatively, the current pulse is divided into several stages with the same difference in die flow. Flow rise time measurements are started at trO and the rise time to iej1 is equal to diej.

iej1 - diej.

The next flow of iej2 is the sum of the flow of iej1 and die. iej2 - iej1 + diej.

The summation of the current continues until the maximum impulse current is reached (Fig. 2):

iejm = iej (n-1) + diej.

For each die rise rate, the dtr rise time was measured. If the beaker of rising current dtr is less than the selected value dtr <dtri, the pulse is interrupted.

For resistor generators, the energy efficiency of the generator part is influenced by the constant resistance of the generator Rj. The value of this varies depending on the current iJmi flow. This resistance also affects the rate of increase of current. Both influences are extinguished at the rising stage of the discharge current iej when the resistance Rj is switched off. Therefore, the circuit (j) reacts Rj only when the discharge current reaches the value of ijmi. In the case that by the end of the pulse the discharge current of the power part of the IJ generator does not reach the IJM value, then no additional resistor Rj is activated (Figure 3).

For generators without resistance in the generator circuit, a certain inductance is required which allows the regulation of the current during the pulse. In the generator circuit, the inductance of the cable Lk, the inductance of the generator part Lj and additional inductance L. are present. This is included in the generator circuit when the sum of the inductance of the Lk cable and the generator part Lj is too small. If the additional inductance L is continuously switched on, it can limit the rate of increase of the die / dt current to a lower value than is allowed by the course of the erosion process due to the impedance change of the working rye. If the circuit (j) turns on the inductance L only when it reaches the iUmi value, the effect of the additional inductance L is eliminated. In the event that by the end of the pulse, the discharge current of the IJ generator power does not reach the IJmi value, then no additional inductance L is activated (Figure 4).

The efficiency of the generator is also increased by interrupting lateral discharges that have less energy. The interruption after the selected pause between pulses tO is followed by the following pulse (Figure 5). The occurrence of lateral discharges is detected by the increased discharge voltage ue. Until the voltage drops from the source of the uj power section, the current from the ij generator power section does not drain. If the time from the start of the discharge until the moment when the discharge voltage ue drops below the source voltage uj dtrO is greater than the selected value dtrOi, then the pulse is interrupted and after the selected pause tO until the next pulse.

Claims (9)

PATENT APPLICATIONS 1. Impulse generator for submersible electro-erosion treatment, characterized in that it consists of the ignition part of the generator with a voltage source (a), the select unit ignites a voltage (g), the transistor of the ignition part TRv, the resistance of the ignition part Rv and the strength part of the generator with a source of voltage (b) transistors of TRj strength, resistor Rj, diode D, additional inductance L, circuit (d), which selects the voltage of the generator unit uj and circuit (e), which interrupts the impulse in the oscillator (bad) i), circuits G) for switching on and off the resistor Rj or additional inductance L. Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that the measured voltage in the last third of the discharge ue is introduced into the circuit (d) by the sensor (c) and the average uep voltage for the selected number of impulses n is calculated in the circuit (d) , which is added to the selected value of the difference in voltage between the voltage of the originating source and the voltage dueji due to the sum of uj = uep + dueji from the circuit (d) to control the supply voltage of the generator part (b). Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that the impulse current Ie is fed to the circuit (e) by a current sensor (h) and the current treatment mode is selected from unit (f) and when i reaches the value ijmi comes from the circuit (e) signal to the circuit (j) the signal that transistor TRRj switches off and flows through the resistor Rj. Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that the impulse current Ie is fed to the circuit (e) by a current sensor (h) and the current treatment mode is selected from unit (f) and when i reaches the value ijmi comes from the circuit e signal to the circuit (j) a signal that switches the TRL transistor off and flows the entire current through the inductance L. 5. Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that the impulse current ijn is measured in the circuit (e) by the current sensor (h), and the current value from the unit (f) is selected from the start of supplying the current from the amperage of circuit trO, in circuit (e) the measured time required for the increase of the current of the thorn is comparable with the selected value of the allowed time of increase of the current of the thorn, which depends on the selected value of the difference in voltage between the voltage of the source and the discharge voltage due and , that thorn <thorn, impulse interrupted. 6. Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that in the case where the source voltage of the generator part remains constant and is equal to the selected value ujt, the difference in voltage between the voltage of the source and the voltage is calculated in the circuit (e) duej discharge, to the circuit (e) is supplied by a current sensor (h) the measured impulse current ij and from the unit (f) the selected value of the current ijni from the start of supplying current from the power section trO, in the circuit (e) the measured time is required for increasing current of the spike, which is compared with the selected value of the allowed rise time of the spike current, which depends on the calculated value of the difference in voltage between the voltage of the origin and the discharge voltage duej, and if the spike <spikes, the pulse is interrupted. 7. Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that the impulse current Ie is fed to the circuit (e) by the current sensor (h) and the value of the intensification of the current is selected from unit (f) from the start of supplying current from of the trO strength to the maximum impulse current iejn, in the circuit (e) the time required to increase the dtr current for the individual stages of the dieji current is measured, which is comparable to the selected value of the allowed rise time dtri, which depends on the selected value of the difference in voltage between the voltage of the origin and the discharge voltage duej and the pulse is interrupted if dtr <dtri. 8. Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that when the source voltage of the generator part remains constant and is equal to the selected value ujt, the impulse current measured (h) is fed to the circuit (e) by the current sensor (h). ie, and from unit (f) the value of the intensification of the dieji current from the start of supplying the current from the trO output to the maximum impulse current iejn, in the circuit (e) the measured time required to increase the dtr current for the individual stages of the dieji current and after the value of the allowed rise time of the current dtri, which depends on the measured value of the difference in voltage between the voltage of the power source and the discharge voltage duej in the event that dtr <dtri, the pulse is interrupted. 9. Impulse generator for submersible electro-erosion treatment according to claim 1, characterized in that a signal for the start of discharge is introduced into the circuit (e) when the voltage on the gap drops under voltage utd and the ignition current of the generator iev flows and the delay time dtrO is measured, when the current of the IJ generator part is detected, which is detected by the sensor (h) and if the delay time dtrO is greater than the selected value dtrOi (dtrO 2 dtrOi) from the control unit (e) a signal Si terminates and is discharged. the next impulse begins after the time of pause tO.