JPS59140080A - Driving method of thermal head - Google Patents

Abstract

PURPOSE:To enable to reduce the size of a capacitor for maintaining a uniform density, by driving each heating element in a thermal head in shifted phases. CONSTITUTION:Timing-controlling signals 22, 23 are maintained at an H (high) level for a period of time T1, and recording is conducted by a corresponding thermal head. The signals 22, 23 are set at an L (low) level for the subsequent period of time T2, and cooling of the thermal head and feeding of a recording paper is conducted in this period. The signals 22, 23 are phase-shifted from each other by 180 deg.. Accordingly, the capacitance of two condensers C1, C2 can be reduced to about 2/3 of that in the conventional system.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 1 The present invention relates to a normal head driving method used in a self-recording device that performs thermal recording.

[Technical Background of the Invention J For example, in a thermal transfer recording device, a thermal head is used to apply a thermal pulse to an ink donor sheet (thermal recording medium). Then, this is selectively heated, and the ink in the heated portion is transferred to the recording paper that has been rolled together, thereby recording information such as characters and graphics.

FIG. 1 shows the main part of a recording section of such an apparatus which performs side-line sequential recording/j-type C' recording.

The thermal head 1 is configured such that energization of its individual heat generating elements (or heat generating elements) is controlled by a single normal head drive 1ifM2. That is, the thermal head drive device 2 connected to a power source 3 is equipped with a large number of switching elements, and selectively applies a voltage to the lead wire 1 according to the recording data 4. Each line 1 to line 5 is 1
It is connected correspondingly to the heat-generating elements in the units 1 to 1, and the heat-generating elements to which the electric power is applied are energized and heated. When the recording for one line is thus truncated, the recording sheets 1 to 1 themselves or the recording paper (not shown) are sub-scanned, and the next one line is recorded. In this way, line-by-line (17?'') recording is performed sequentially.

FIG. 2 shows temporal changes in the current flowing through the printhead in a conventional recording apparatus. Here, three arbitrary lines, +2 (N) to J2. The case of (N+2) is shown. When the number of heat-generating elements that are energized at the same time changes for each line, the peak of the pulse current flowing from the thermal head driving device to one normal head changes accordingly, as shown in this figure. The range of variation in this current value is approximately several tens of amperes at most. thermal l
Since there is a resistance valve in the lead wire connecting the bed drive device and the thermal head and in the lead wire inside the thermal head, if the current value fluctuates significantly, the voltage drop applied to each individual heating element will also be significant. It will fluctuate. Particularly when the thermal head drive device and the thermal head are housed in different coupes and placed at different locations, the couple connecting them becomes long, so the amount of energy applied to each injector varies greatly. Figure 3 shows a conventional two-color recording device 6 that has been improved in this way.
There is a sign that shows the main part of. A pair of cables 8.9 is connected between the power source 6 and the head drive device 7 of this device. Resistors R1 and R2 are connected to these cables 8
．． 9 represents the resistance valve. The thermal head drive device 7 is equipped with two sets of drivers '11, 12, the output sides of which are individually connected to two thermal heads 13, 14 for recording in different colors. . Further, controllers 15 and 16 are individually connected to the control input sides of these drivers 11 and 12. -10,000 components [J-Ra 15] perform ON/A control of a large number of switching elements (1 to transistors) in the driver 11, and drive the multi-head 11. The other controller 1 to L1-16 is connected to the thermal head 1 in the same way.
2 drive (-j).Two thermal heads 11.12
When recording paper (not shown) successively comes into contact with adjacent a3 and these through an ink donor seam, two-color recording is performed.

By the way, Den-g! Inside 6, a densifier C1 is connected to its output side. This capacitor C1 is designed to withstand the pulse current.

Further, inside the thermal head driving device 7, a capacitor 02 is connected to the input terminal of each driver 11, 12. Since the capacitor C2 is called a ``decoupling'' capacitor, it is charged during the period when the driving of each driver 11.12 is stopped, thereby reducing the voltage difference caused by the circuit 8.9.

``Disadvantages of conventional technology'' In such two-color recording devices, it is difficult to prevent uneven print density.
In order to do this, it was necessary to prepare two capacitors with extremely large capacities, such as C1 and C2.
1, C2 is 30.0001- or 15.0 respectively
Capacity at the level of OOF was indispensable. It goes without saying that a recording device that performs time-parallel °C recording using three or more recording colors requires a large storage capacity. The use of such a large capacity capacitor poses an obstacle to device miniaturization and shutdown.

OBJECT OF THE INVENTION In view of the above circumstances, Akira Kibuto states that his object is to provide a four-normal head driving method that can miniaturize these capacitors for preventing density unevenness.

[Method for Achieving the Object] In the present invention, the above-mentioned object is achieved by driving a plurality of thermal heads in a phase-shifted C manner.

The present invention will be described in detail with reference to Examples below.

Embodiment J FIG. 4 shows a two-color recording apparatus employing the thermal head driving method of this embodiment.

The same parts as in Figure 3 are labeled with the same congratulatory symbols, and their explanations are omitted as appropriate. The capacity of the two 11 dens 01 and C2 is reduced to about 2/'3 C compared to the conventional one. 1, the condensate shown in Figure 3-'JC
The capacities of 1 and C2 are 30.0OOF and 15.00F, respectively.
Assuming that there are 0OOF, the capacitances of these capacitors C1 and C2 used in this embodiment are 20 and 0, respectively.
At OOF and 10.0OOF, a timing control signal 22.23 is sent from the timing setting circuit 21 to control the drive timing and timing of the thermal head 13.14. is being supplied.

Figure 5) shows waveforms of two timing control signals. These timing controls (No. 8 22.2
3 is at the 1-((high) level for a period of time [1, and recording is performed by the corresponding thermal head at this time. Also, it becomes the 0-) level for the next time 1゛2, and at this time the thermal head's recording is performed. Cooling and recording paper〈Figure 1!
The movement f) is performed.

These timing control signals 22,23 are
B O antiphase is shifted.

Figure 6 shows the method for driving a two-color recording device (a).
Accordingly, the current waveform represents the current consumed by the entire thermal head 13, and FIG. 11 represents the current consumed by the entire other thermal head 14. The temporal change in the total current consumption as seen from the power supply 6 side is shown in Figure C.
2F
4 current consumption is added. However, the time during which this tightened current flows is much shorter than the time quotient T1.

Therefore, even if the capacitance 141 of the two containers C1 and C2 is quite small, a drop in the electric current applied to each heating element can be sufficiently prevented. , FIG. 6 (1 shows, for reference, the change in total current consumption as seen from the power supply side according to the conventional method.

Embodiment C described above describes the υ-nle head driving lj method applied to a recording apparatus using two 1J-maru heads. A similar effect can be obtained by shifting the drive timings of the two.

[Effects of the Invention] As described above, according to the present invention, it is possible to reduce the burden on the power source and improve the quality of recorded images by simply shifting the drive timing of the thermal head.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the general configuration of a part of a recording device using one normal head, and Fig. 2 is a diagram showing the general configuration of a part of a recording device using one normal head. A waveform diagram showing temporal changes in current, Fig. 3 is a circuit diagram showing the main parts of a two-color recording device that employs a conventional thermal head drive system, and Fig. 4 shows an example of an implementation of the present invention. FIG. 5 is a circuit diagram showing the main parts of a two-color recording device that adopts the linear head drive method in this example. FIG. FIG. 6 is a diagram of various waveforms for explaining the method of driving the thermal head in this apparatus. 6... Power supply, 7... Thermal head drive device, 13.14.
...Nurn head, 15.16...Controller, 21...Timing setting circuit. Applicant: Fuji Xerox Co., Ltd. Representative
Person Patent Attorney Yamanouchi 1u Yu 1st Division Youka 4th Figure 5 Time

Claims (1)

[Claims] In a recording device using multiple thermal heads that perform recording operations by repeatedly energizing intermittently using the same power source,
C1: A method for driving a thermal head characterized in that the timing of energization is different in at least a part of each of the four non-narrow heads in which current is applied to the same h zone.