JPS6384949A - Constant current drive of electrothermal transfer recorder - Google Patents

Abstract

PURPOSE:To make printing density uniform by providing a constitution in which variation occur between a first level range enabling recording at a first voltage in accordance with a third voltage level supplied to each constant current drive and a second level range allowing no recording. CONSTITUTION:A drive 5 is composed mainly of an operating amplifier (OP amp) 7, and receives an output from a character generator applied as a third voltage V1 via a gate circuit 8 with regard to a positive phase input. A first voltage V1 which is an output from OP amp 7 is connected to a recording electrode 1, and further is connected to a return electrode 2 through a recording resistor R2. This return electrode 2 is connected to an inverse phase input of the OP amp 7 and at the same time is connected to a fixed second voltage V2 via a constant voltage diode D. Printing is performed or not performed depending on variation in the first voltage V1. However, the voltage V1 increases or decreases depending on the magnitude of recording resistance R2 generated in a transfer medium 4. In this way, the voltage is adjusted so that an electric current may be supplied at constant level. This suppress variations in dot density and provides uniform density printing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a constant current drive device in an electrical transfer recording device used in printers, typewriters, word processors, other hard copy producing devices, etc.

Conventional technology On the transfer material C: At least one or more recording electrode and return electrode are brought into contact with each other on the transfer medium placed, and the selected recording electrode is provided integrally with the selected recording electrode or at a separate position C: Applying two voltages C between the return electrode provided separately (;
Therefore, apparatuses for electrical transfer recording are already known.

And in both of them, constant voltage drives were used.

However, such a device has drawbacks such as (1) uneven density between characters, and (2) uneven density of dots within one character.

The cause of such concentration non-uniformity is (
1) Current unevenness occurs due to the pace of the transfer medium, that is, uneven resistance of the ink layer, uneven coating of ink, uneven electrical contact, etc.; (2) multiple recording electrodes C;
When applied simultaneously to the knees, the current from the middle electrode is shielded by the current from the surrounding electrodes, effectively creating a high resistance and reducing the current. It is presumed that this is because the current changes due to a change in the resistance between the two.

Problems to be Solved by the Invention Several proposals have been made to eliminate these drawbacks by using a constant current drive device. One is the number of styluses applied at the same time (N is the number of styli applied), and the current value is constant C2 so that the total current value does not change even if N changes, and the other is the number of styli applied at the moment of recording , one voltage C representing the various resistance values under each recording electrode at that time: Compensation for the C voltage common to all applied recording electrodes is attempted.

However, such a constant current drive device has the disadvantage that it is not possible to independently provide constant current characteristics for each recording electrode, and furthermore, the circuit thereof cannot be easily constructed.

Therefore, an object of the present invention is to eliminate the drawbacks of the conventional current transfer recording device as described above, and to provide each recording electrode (2) with independent constant current property (;therefore, the density of printed characters can be made uniform). and furthermore, to provide a constant current drive device whose circuit can be made simple.

Means for Solving the Problems The present invention achieves the above objects by connecting each recording electrode to the output first voltage of each correspondingly provided constant current drive device. 62. Connect the return electrode to a fixed second voltage via a constant voltage diode, and connect the recording resistor between the recording electrode and the return electrode (: the first voltage changes accordingly, and the recording resistor C maintains a constant current). The third voltage input to each constant current drive device is set at C2 so that the voltage flows between the second level range where the first voltage can be recorded and the second level range where it is unrecordable according to the level of the third voltage input to each constant current drive device. It is characterized by the fact that it changes.

Effect C: As described above, when the recording resistance changes, the first voltage applied to the corresponding recording electrode changes.
Regardless of the resulting change in recording resistance, a constant current is always applied to the recording electrodes to suppress the occurrence of shading in printing.

Embodiment In FIG. 1C, 1-1 to 1-N are recording electrodes, 2 is a return electrode, 3 is a transfer material, and 4 is a transfer medium consisting of Jl/N, which is different from conventionally known ones. The same is true.

5-1 to 5-N are each recording electrode 1-1 to 5-N according to the present invention.
1-Nl and 2 respectively indicate constant current drive devices provided, and vt-t""Vl-N respectively indicate the recording electrodes l.
-1-1-N (2 outputs of the connected drive devices 5-1 to 5-N (1st voltage) Fixed second voltages v3-1 to V3-N are respectively output from character generators (not shown) or the like directly or via gate circuits to drive devices 5-1 to 5-NC; third voltages applied Note that in C; above, the gate circuit may be omitted.

Figure 2 (; indicates one recording electrode in the above 1:
One embodiment of a related circuit is shown, and this embodiment I:
In this case, the driving device 5 mainly consists of an operational amplifier (hereinafter referred to as an OP amplifier) 7c. The positive phase input C: is outputted from a character generator, etc. (:) and is applied as the third voltage v3 via the gate circuit 8.

The first voltage ■l which is the output of the OP amplifier 7 is the recording electrode IK=
R2 is a recording resistor in the resistor, and the first voltage vl is connected to the return electrode 2 (:) through this recording resistor R2. It is connected to a fixed second voltage v2 via a constant voltage diode D, and the return electrode 2 is common to all drive devices 5-1 to 5-NC.

In the above-mentioned device, the level C of the rs3 voltage v3 which is the output of the character generator, etc. In other words, the drive device 5 is turned on and off.

Then, the change in the first voltage vl≦: Therefore, the recording electrode IC
The voltage V
l increases or decreases depending on the magnitude of the recording resistor R2 generated in the transfer medium 4, and is adjusted so that a constant current flows through the recording resistor R3. In this case, the magnitude of the recording resistor R2 is , resistance unevenness of the transfer medium 4, and contact unevenness C2. Furthermore, even if the resistance of the transfer medium 4 itself is made uniform, there is a difference between one recording electrode and other recording electrodes around it. In other words, the positional relationship between the two recording electrodes may vary depending on whether the recording electrode is located at the edge I or the center C of the recording head, in other words, depending on the character number turn C2. has the uneven resistance as described above, and since a constant current flows directly from each drive device 5C directly to the recording electrode no matter what kind of letter or turn there is, uniform letters and dots can be exchanged.In the above case, the OP amplifier 7C may be replaced with another circuit having an equivalent function.

In this way, the circuit shown in Figure 2 shows the number of recording electrodes C.
: Fig. 3 shows the state in which the wires are connected accordingly.

In the case of Fig. 2, there is a single circuit, but in Fig. 3, it consists of multiple circuits, so the current passing through the constant voltage diode D changes depending on the number N (2) of recording electrodes L. Therefore, if this is not a diode, If a resistor, which works effectively in a single circuit, is used here, the voltage applied between its terminals will change, and this change will affect the voltages v and C, disrupting the constant current property.

However, in this invention, as described above, by using the constant voltage diode D and making this diode D have a Zener voltage equal to the voltage set in a single circuit, the eight recording electrodes l (: Even if they are applied simultaneously and the resulting current is N times the current value of the single circuit C0, that is, NIo, the voltage across its terminals is equal to that in the single circuit C: (: maintained, thereby causing the voltage There is no effect on v1.

Due to the constant current driving device, there is no density unevenness between characters, and there is almost no density unevenness between characters; overall C;
Uniform print quality was obtained.

However, as a result of careful study of the results, the inventor found that the letter I
It was discovered that the density around the end of the vertical line in the area was low, and the following analysis was performed on this phenomenon.

First, if the recording resistor is R2 and the current flowing through it is the amount of heat generated directly under the stylus, the amount of heat generated is (V is the recording resistor I: applied voltage). In a constant voltage drive device, when multiple styluses are applied simultaneously (when forming a vertical line), C: As mentioned above, the effective R2 for the stylus at the center becomes large, and (2) becomes constant and decreases, resulting in a lighter density.

Inverted C: R2 is low and the amount of heat generated is large near the end. Next, in the constant current driving device, the amount of heat generated by the central stylus increases according to I2R2 due to the lower part of the knee, and around the edges, the amount of heat generated decreases and the density becomes lighter due to the smaller R2.

The above are the analysis results of the concentration drop around the edges in the constant current drive device.

The situation during this time will be supplemented using the graphs in Figures 4 and 5.

Fig. 4 is a characteristic diagram of a constant voltage drive device, and Fig. 5 is a characteristic diagram of a constant current drive device.Load resistance C: current, voltage,
Power (current x voltage) is shown in arbitrary units. Load resistance range A is the range of recording resistance that varies in an actual recording system, and ranges B and O are the resistance ranges of the edge peripheral stylus and center stylus during vertical line recording, respectively.

In the constant voltage drive shown in FIG. 4, while the voltage V is constant, the electric current decreases greatly in a hyperbolic manner C as shown in the figure. Naturally, the electric power W of one stylus also decreases according to the electric current (2), and as a result, the electric power of the central stylus decreases, and thus the concentration decreases.

In the constant current drive shown in Figure 5, it is difficult to create an ideal constant current device, so in reality 1: is as shown in the figure. It is.

The voltage rises and begins to saturate at a certain point.The power increases as shown by the dotted line 5: On the other hand, it starts to saturate at a certain point.
ri(: decreases after changing.Actually 4: is as shown in the figure(:
The peak is located beyond the actual usage range, and the power often increases. The density of the stylus around the end is therefore reduced. As can be seen from FIGS. 4 and 5, when looking at the power, the two show opposite characteristics in terms of increase and decrease, but they are considered to be equivalent in terms of change. However, it is still unclear whether constant current drive devices can provide more uniform printing quality.
Maybe it's just the difference in slope.

Now, what should be noted in Fig. 5 is that there is a plain part where the electric power remains constant. What will happen if we further smooth this as shown in Fig. 6, C: Practical usage range C? In the practical usage range, we can expect that the electric current will be constant and that complete uniformity of the dot density will be obtained.

This is essentially a constant power drive. This characteristic is achieved by adjusting the characteristic of the OP amplifier and R1. That is, by changing the characteristics of the constant current drive device to bring it a little closer to the characteristics of the constant voltage drive deviceC2,
A substantially constant power drive is obtained.

When the conditions were adjusted to have characteristics close to those shown in FIG. 6 and recording was performed, uniform characters were obtained compared to the constant current drive device, and uniform dot density was obtained both in the center and around the edges of the vertical line.

Effects of the Invention The present invention is as described above, and a constant current drive device is provided for each recording electrode to drive each recording electrode.

The output of the corresponding constant current drive device is connected to the first voltage 5: and the return electrode is connected to a common fixed second voltage 5: through the constant voltage diode, and the recording resistance between the recording electrode and the return electrode is connected. (= Changing the 11th! pressure accordingly (= Therefore, a constant current flows directly through the recording resistor, and the level C of the third voltage input to each constant current drive device. Since the current is ≦≦2 so as to vary between recordable and unrecordable levels, the current supplied to each recording electrode and the recording medium (-) is controlled by the resistance unevenness of the medium and the variation in effective resistance due to the printed pattern. Constant C: is maintained by compensating for
As a result, the occurrence of density unevenness between printed characters and dot density unevenness of printed characters is suppressed, and there is an effect that good quality printing can be achieved with uniform density as a whole. Furthermore, the characteristics of the driving device are as shown in FIG. 6. C: Constant power type (; C: Therefore, there is no decrease in density around the edges, and the printing quality is more uniform than the whole (2).

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the basic configuration of the present invention, FIG. 2 is a circuit diagram of the constant current drive unit same as above, FIG. 3 is a circuit diagram of an embodiment of the present invention, and FIG. The characteristic diagram of the voltage drive device, Fig. 5 is the characteristic diagram of the constant current drive device, and Fig. 5 is the characteristic diagram of the constant current drive device.
Figure (Actual usage range I: Inserted and smooth (This is a characteristic diagram with a curved line. l...Recording electrode 2...Return electrode 3...Transfer material 4...Transfer medium 5...Constant current Drive device D... Constant voltage diode Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. Contact at least one recording electrode and return electrode on the transfer medium placed on the transfer material, and provide the selected recording electrode integrally with the recording electrode or as a separate body at a different location. In an apparatus that performs current transfer recording by applying a voltage between a provided return path electrode, a constant current drive device is provided corresponding to each recording electrode, and each recording electrode is connected to the output of each constant current drive device. by connecting the return electrode to a fixed second voltage via a constant voltage diode, and varying the first voltage depending on the recording resistance between the recording electrode and the return electrode; a first level range in which a constant current is allowed to flow through the recording resistor, and the first voltage can be recorded in accordance with the level of a third voltage input to each constant current drive device;
A constant current drive device characterized in that the constant current drive device changes between a second level range in which recording is not possible.