JPH0157483B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high-voltage coil used in copying machines and the like as a high-voltage power source using a self-excited oscillation inverter. In a copying machine, in order to electrostatically remove the charged copy paper from the photoreceptor drum after the transfer process is completed, and at the same time perform a static neutralizing action that eliminates the static electricity on the copy paper, a high-voltage alternating current is usually applied. is being applied. In order to obtain this high voltage, conventionally, the voltage is increased by using an iron resonant transformer powered by a commercial power source, and the high voltage of the commercial frequency is used in the process. However, fero-resonant transformers have drawbacks such as the large size and weight of the entire device, the difficulty of automatic control that automatically changes the output voltage according to the copy process, and poor output voltage fluctuation characteristics. In recent years, there has been a shift to compact, high-performance semiconductor-type high-voltage power supplies that use semiconductor inverters. This semiconductor high-voltage power supply had the problem of being more expensive than the iron-resonant type, but this problem is gradually being overcome. Further, in semiconductor type high voltage power supplies, the frequency is usually set to about 400 to 500 Hz. This is because if the frequency is increased, the power supply can be made smaller and cheaper, but if the frequency is increased too much, the voltage is high (about 4 to 5 kV), so wiring and chassis are required to route the wiring between the power supply and the photoreceptor drum. Leakage current increases due to stray capacitance between the photoreceptor and the frame, and the final load current flowing into the photoreceptor drum changes and fluctuates significantly. This becomes more noticeable as the frequency becomes higher. Furthermore, the higher the frequency, the better the copy process. Therefore, there is naturally a limit to the increase in frequency. On the other hand, if the frequency is low, the power supply device will naturally become larger, and there is no point in using semiconductors. Taking these points into consideration, the frequency of the high-voltage alternating current of the semiconductor power supply used for static elimination and paper peeling in the above-mentioned copying process is determined to be approximately 400 to 500 Hz. This type of semiconductor power supply, that is, an inverter, can be classified into separately excited type and self-excited type. In the case of separately excited method, a frequency generator is required,
Furthermore, since the control circuit is complicated, the device becomes expensive, and the device has the drawbacks of being large in size due to the large number of parts. In the case of a separately excited system, the frequency is usually fixed, so if the natural frequency f ₀ of the circuit and the set frequency f ₁ do not match, the reactive current will increase by f ₀ − f ₁ . This may cause problems such as distortion of the output waveform. However, in practice, it is impossible to match f ₀ and f ₁ , and depending on the required value of frequency accuracy from a performance standpoint, the self-excitation method is often advantageous.
Typically, this type of output frequency range is required to be controlled within ±5%. When high precision in output frequency is not required, it is desirable to adopt a self-excitation system with a simple circuit configuration. However, this type of high-voltage power supply has a load current of
Since the voltage is around 1mA and the voltage is high, the secondary side (output side) winding must be a thin wire of about 0.06 to 0.08φ.
The coil will be wound around 30,000 times. Therefore, there is stray capacitance between the windings and between the winding and the ground, and in the inverter's oscillation circuit, this stray capacitance component and the inductance component on the primary winding side constitute a tank time constant circuit. Therefore, if this natural frequency matches the self-excited oscillation frequency, loss due to reactive current in the tank circuit can be suppressed to a minimum, and input/output conversion efficiency is improved. Therefore, the first problem with the conventional self-excitation method is
The figure and FIG. 2 will be explained. First, the stray capacitance Co generated in the secondary high-voltage winding coil Ns is determined by variations in the coating thickness of the winding, variations in the insulating paper between the coil layers, the length of the insulating paper, the tensile strength during winding, and the rotation during winding. There are many variable factors such as speed, number of turns per layer, insulation treatment (varnish insulation treatment) status of coil 1, etc., and it is impossible to control them. The required frequency _f11 can be adjusted by inserting another tank capacitor _C1 on the side or by providing an air gap G where the cores 2 and 3 meet to adjust the inductance. However, in order to match this frequency f ₁₁ , the tank capacitor
Adjusting the value of _C1 and changing the air gap G are extremely complicated tasks in practice, and conventionally require a large number of man-hours. For this reason,
In order to bring the timing of the voltage applied to the base of the oscillation transistor Q closer to the frequency _f11 , correction was made by designing the base circuit constants, but this is insufficient. The present invention has been made in view of these points, and it is an object of the present invention to obtain a high-voltage coil for a self-oscillation type inverter with less variation in the required frequency by processing the coil itself. In the present invention, the coil section is made to have a high potential at the beginning of winding and a low potential at the end of winding, and interlayer paper is inserted in each layer for several layers from the beginning of winding, and then every few turns thereafter, so that the coil section itself The structure is such that the stray capacitance can be easily adjusted, and thereby the self-excited oscillation frequency can be easily adjusted and a frequency with little variation can be obtained. An embodiment of the present invention will be explained based on FIGS. 3 and 4. Here, what is shown in FIG. 3 is not a preferred example, but is an explanatory diagram for better understanding of the embodiment shown in FIG. 4. First, as a result of studying the stray capacitance Co of the secondary winding Ns, the following facts were obtained. That is,
According to experiments focusing on factual phenomena, the secondary winding Ns
The frequency f ₁₁ changes the most depending on the impregnation treatment of the impregnated insulator such as insulating varnish. Further, there is a large variation depending on the impregnation state. This variation in the impregnation state means that variation on the high potential side of the secondary winding Ns causes a larger variation in the frequency _f11 . Therefore, what is shown in Figure 3 is
The winding wire 6 is wound with the low potential side being the winding start L and the high potential side being the winding end H, an insulating interlayer paper 5 is inserted between each layer 4, thereby forming a coil portion 7. In this case, the stray capacitance Co is H at the end of the winding and the core 8
Co ₁ formed between each layer 4
There are Co ₂ , Co ₃ , and Co ₄ formed between each winding 6,
The combination of these becomes Co. The current flowing through these stray capacitances is determined by the voltage applied between each stray capacitance Co, and the sum of all these becomes a phase-advanced reactive current. Therefore, Ic = ωCoVx will flow. Here, Vx is a general term for voltages applied to each stray capacitance Co. Therefore, the main factors that determine the stray capacitance Co are the dielectric constant εs of the winding 6 and interlayer paper 5, and the thickness t of their insulators. However, experiments have shown that these variations do not significantly affect the stray capacitance Co when an impregnated insulator with a specified variation is used. That is, the oscillation frequency f ₁₁ is shown in the table below when comparing a case where only the secondary winding Ns is varnished and a case where the secondary winding Ns is not varnished under the conditions of the same oscillation circuit, the same core, and the same gap. However, in the circuit shown in FIG. 1, the tank capacitor C ₁ connected in parallel with the primary winding N ₁ is not used.

[Table] Looking at the results, it can be seen that the frequency variation becomes larger after the varnish treatment, and the frequency itself decreases after the varnish treatment. This is winding 6
This is because the varnish was impregnated into the interlayer paper 5 during this period, and the conductivity ε increased. This difference in the degree of impregnation of the varnish results in a difference in electrical permeability ε and also in frequency. Therefore,
The problem is how to reduce the variation in frequency f ₁₁ after varnish treatment. For this reason, in the present invention, a structure as shown in FIG. 4 was adopted. That is, the winding end L of the secondary winding Ns is grounded as the low potential side, and the interlayer paper 5 is inserted in each layer for several layers from H at the beginning of winding, depending on the frequency dispersion, and after that, it is inserted in every multiple layers. ing. By doing so, the desired effect can be obtained at minimum cost, and the reason is as follows. First, when a core assembly transformer equipped with the coil section 7 is treated with varnish, the varnish leaks out from the coil section 7 when a drying process is performed after the varnish impregnation process. This is more noticeable in the outer layers of the coil.
On the other hand, in the inner layer, the varnish that has adhered to the core 8 flows in, so there is relatively little varnish flowing out, and even after the varnish treatment, there is a lot of varnish sticking, so there is little air space due to varnish flowing out. For this reason, the end of volume L
By grounding as the low potential side, stray capacitance
Co ₁ , Co ₃ , and Co ₄ are relatively constant values with little variation. Therefore, the variation is large in the stray capacitance Co ₂ on the low potential side, and the variation in the stray capacitance Co as a whole is small. The fact that this stray capacitance Co is small means that the oscillation frequency is stable and its fluctuations are reduced. Furthermore, the insulating interlayer paper 5 is interposed between each layer 4 for several layers from the beginning H of the winding, and the interlayer paper 5 is interposed between every plural layers 4 toward the end L of the winding. Reduce the variation in stray capacitance Co,
Moreover, the oscillation frequency can be changed easily and simply. In this type of coil section 7, at a frequency of about 400 to 500Hz, the diameter of the winding 6 is about 0.06φ, the voltage generated between the layers is low at about 0.15v/TURN, and the winding 6 is coated. Considering the dielectric strength obtained, it is possible to sufficiently withstand voltage and life even without inserting an interlayer paper 5 into each layer 4. Therefore, in order to increase the space factor of the coil portion 7 and to reduce its size, interlayer paper 5 is inserted every several layers. This will reduce the variation in stray capacitance Co ₂ and reduce the overall stray capacitance Co
The variation will also be reduced. For this reason, the secondary winding
It may be thought that if all the Ns are covered with interlayer paper 5 every few layers, the variation in the stray capacitance Co will be reduced, but this will cause the following drawbacks. In other words, the more the interlayer paper 5 is reduced, the more the winding 6 is reduced.
It can be tightened and rolled tightly. This is because the interlayer paper 5 as a buffering material is eliminated. As the space factor improves, the mechanical stress applied between the windings 6 becomes stronger, and becomes more significant as it approaches the lower layer of the coil section 7 and the winding start H. This stress becomes stronger as the insulation treatment with varnish or resin compound hardens. Therefore, the stress on the winding 6 becomes large, causing damage to the insulation coating of the winding 6, an increase in stray capacitance due to the absence of the interlayer paper 5, an increase in reactive current, an interlayer short circuit, and a shortened life. As for the stray capacitance Co, as mentioned above, the higher potential side has a greater influence on the characteristics. This is also clear from the fact that the potential gradient with respect to the potential of the core 8 and the like is larger than the potential gradient with respect to the low potential side of the coil portion 7. Therefore, the winding start H is on the high potential side to prevent variations in the stray capacitance Co, and interlayer paper 5 is inserted in each layer 4 to increase the space factor.
This minimizes the variation in winding stress on the high potential side of the winding start H, thereby preventing the winding stress. That is, in the H number of layers at the beginning of winding, interlayer paper 5 is inserted between each layer 4. By inserting interlayer paper 5 every few layers on the L side at the end of the winding, the value of the self-oscillation frequency can be changed. Furthermore, even if the high potential side of the winding start H is covered with several layers and interlayer paper 5 is inserted between each layer 4, the varnish will not leak out; on the contrary, the varnish will be stopped by the interlayer paper 5 and the amount of varnish deposited will be large, and air will not leak out. Layers tend to be smaller. Therefore, the dielectric constant ε between the windings 6 is increased, and the stray capacitance Co ₁ can be changed to the extent that the self-oscillation frequency f ₀ can be changed depending on the number of layers of the interlayer paper 5 inserted in each layer. The results of this experiment are shown in the table below.

[Table] Of course, these experimental values were obtained under the conditions of the same oscillation circuit, the same core, and the same gap. Note that the interlayer paper 5 used had a thickness of 25 μm. In the present invention, as described above, the starting side of the winding is set at a high potential, and the interlayer paper inserted in each layer from the beginning of the winding is inserted once in each layer toward the end of the winding, so that the self-excited oscillation frequency can be increased. Therefore, the degree of freedom in design and production increases, making it possible to provide a high-voltage power supply with little variation, and having effects such as high reliability and long life. .

[Brief explanation of drawings]

Figure 1 is a partial circuit diagram of a self-oscillating inverter.
FIG. 2 is a sectional view of the transformer, FIG. 3 is a partially enlarged sectional view, and FIG. 4 is a sectional view showing one embodiment of the present invention. 4...layer, 5...interlayer paper, 6...winding, 7...coil part, H...start of winding, L...end of winding.

Claims (1)

[Claims] 1 In a coil that is wound with an interlayer paper interposed between the windings and insulated with an impregnating agent and solidified, the beginning of winding is on the high potential side, the end of winding is on the low potential side, and A high-voltage coil characterized in that a coil portion is formed by inserting an interlayer paper in each of the first few layers, and inserting the interlayer paper once every several layers after that.