JP2580613B2 - Recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus that performs multi-gradation recording by applying a voltage to a heating element, and in particular, always has an optimal amount of energy even when the temperature of a head changes. Can be supplied to the heating element.

2. Description of the Related Art In general, a thermal printer generates heat by selectively applying energy to a large number of heating elements provided on a thermal head, thereby performing recording on recording paper. A pulse output from the apparatus main body at a width corresponding to the multi-gradation recording data is applied to the heating element of the thermal head, and recording is performed by raising the heating element to a predetermined temperature. However, if the applied voltage changes due to fluctuations in the power supply voltage or the like, the recorded image will have uneven shading.

In response to such fluctuations in voltage, the conventional technique of making the amount of power supplied to the heating element substantially constant and preventing the above-described unevenness in shading is described in Japanese Patent Publication No. Sho 62-15357. It has been disclosed. In this recording apparatus, the power consumption of the heating element is output as a signal, the signal is squared and integrated, and the level of the signal is determined based on the integrated value. When the signal level reaches a certain value, the power supply to the heating element is cut off.

However, in the above-described printing apparatus, since the head temperature is not considered, for example, when printing is continuously performed, the same level of power is supplied even though the head is storing heat, There is a problem that the recording density becomes higher than a specified value.

Further, in a thermal printer, it is not known whether the thermal head is gradually storing heat or, conversely, whether the thermal head is descending. There is also a problem that a multi-gradation recorded image cannot be obtained.

In view of the above problems, the present invention provides a recording apparatus that can obtain a high-quality recorded image with no density difference by grasping the progress of the temperature of the head and supplying optimal energy. The purpose is to do.

Means for Solving the Problems In order to achieve the above object, a temperature measuring means for calculating a temperature of a thermal head near a temperature detecting element based on a detection result of a temperature detecting element provided in the thermal head is to be recorded. Storage means for storing the thermal head temperature for a plurality of lines before the line, using the previous plurality of lines and the current thermal head temperature near the temperature sensor,
If the thermal head temperature is rising, predict the thermal head temperature near the heating element higher than the current thermal head temperature, if the thermal head temperature is falling,
Predicting means for predicting the thermal head temperature near the heating element substantially the same as the current thermal head temperature, and determining the recording energy according to the thermal head temperature near the heating element predicted by the predicting means, Calculating means for calculating a comparison reference value based on the recording energy; head voltage measuring means for measuring a voltage applied to the heating element at fixed time intervals; and squaring the value measured by the head voltage measuring means. And comparing the value added by the integration circuit with the comparison reference value, and when the value added by the integration circuit exceeds the comparison reference value, terminates the voltage application to the heating element. And a comparison control means.

Operation According to the above configuration, the thermal head temperatures near the temperature detecting element for a plurality of lines before the line to be recorded are stored, and the current temperature near the heating element of the thermal head is predicted based on this temperature. The recording energy to be supplied is calculated from the temperature, and during recording, the applied voltage is measured at regular time intervals. Then, the measured voltages are squared and added, and when the added value exceeds a comparison reference value calculated based on the recording energy value, the voltage application to the heating element is terminated.

Embodiment Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a configuration diagram of a main part of a thermal transfer recording apparatus according to the present invention. In the figure, 1
Is a thermal head having a large number of heating elements 2 for transferring the ink of the ink film to the recording paper, and 3 is connected to a thermistor 4 as a temperature detecting element provided on the thermal head 1 and based on a detection result of the thermistor 4. A temperature measuring unit 5 for calculating the temperature of the head by using the RAM 6 for storing a plurality of temperature measurement data calculated by the temperature measuring unit 3 and other information, and an operation of the entire apparatus such as recording and paper feeding. (Central processing unit) 7 and a device drive control unit including a ROM 8 storing an operation program and the like, and a recording data output from the device drive control unit 5 is thermally transferred at a predetermined timing. A recording control unit 10 that sends a strobe signal and a latch signal to the head 1 and generates a strobe signal and a latch signal. With measured at regular intervals that adds by squaring the voltage, an energy monitor to terminate the voltage application to the heating element 2 when the added value exceeds the comparison reference value to be described later.

The thermal head 1 is configured such that 1280 heating elements 2 are arranged in a line at 6 dots / mm, recording is performed for each row, and the thermal head 1 is divided into four parts and driven by a driver IC 11. The thermistor 4 is provided on the base of the thermal head.

As shown in FIG.
Heating element 2 by the measurement pulse output every 10 μs from
Voltage measuring unit 12 for measuring the voltage V applied to the head
And V ² that squares the voltage measured by the head voltage measurement unit 12
A conversion table 13, an adder 15 for adding the value of the register 14 to the value of from V ² conversion table 13, a comparator 16 that the value stored in the register 14 determines whether greater than the comparison reference value to be described later And more.

The head voltage measuring unit 12 measures the difference between the heating element applied voltage and a certain reference voltage, and outputs the result of A / D conversion. V ² conversion table 13 is converted into a value that can be calculated as a real energy applied to the measurement results. Energy E per dot is Since R is constant, the measured voltage V = V _X −V _R (V _X is an actual voltage, V _R is a reference voltage) is converted into V _X ² as follows.

^{_{V- → V X 2 = (V}} + V R) 2 For example, when the reference voltage 10V, which 256 equally dividing the variation range as 12.56～10V, the digital output voltage and V ² converted thereto from the head voltage measuring section 12 The output of Table 13 is as follows.

Such V ² conversion table 12 may be constituted by a memory of 14 bits × 256 words.

As shown in FIG. 3A, a portion of the RAM 6 for storing the temperature measurement data is constituted by a memory register 6a, and stores the head temperature data calculated by the temperature measurement unit 3. . The memory register 6a stores addresses T ₀ to
T ₄ to a temperature data of the head when previous 4 lines including temperature data and the previous current head is recorded is stored, the record of the current line is completed, in FIG. 3 (b) as shown, stored until it moves to the temperature data T ₀ through T ₃ are sequentially repeated lowered T ₁ through T ₄ having been stored, the temperature data at that time is stored in the T _0. That is,
T ₀ is the data of the current head temperature, T ₁ is one line temperature before the head, the temperature of T ₂ is two lines before the head · · · T ₄ is four lines before the head temperature.

In this embodiment, the recording energy is determined using the current temperature T ₀ , the temperature T _{2 two} lines before, and the temperature T ₄ four lines before. This is because the temperature in the vicinity of the heating element 2 rises as the heating element 2 is driven.
The main reason is that when the head temperature is rising, the temperature is sensed to be lower, and when the head temperature is falling, the temperature is considered to be almost the same near the thermistor 4. It is. However, this is the thermal head 1
This is an example in which no forced cooling means is provided. Further, when the thermistor 4 is at a constant temperature, it is considered that recording of a certain density is continued, and the temperature of the head is considered to be slightly higher than the thermistor 4. Therefore, the temperature T of the head to be recorded can be predicted as follows. That is, when T ₄ <T ₂ <T ₀ , When T ₄ <T ₂ = T ₀ , T = T ₀ + (T ₂ −T ₄ ) When T ₄ = T ₂ = T ₀ , T = T ₀ + aa: constant value T ₄ = T ₂ > T _{When 0} , T = T ₀ T ₄ > T ₂ > T ₀ , the relationship between the predicted temperature of T = T ₀ or more and the measured temperature of the thermistor 4 is as shown in FIG. When the temperature is rising, the predicted temperature is determined to be higher than the measured temperature, and when the temperature is falling, the measured temperature and the predicted temperature are determined to be the same.

When the predicted temperature is determined, a comparison reference value is determined based on the result as shown in FIG. For example, when the resistance value of the heating element 2 is 300Ω and printing is performed at 0.3 mJ / dot, Thus, V ² N = 0.3 × 300 × 100 = 9000. Here, Δt = 10 (μs), N is the number of measurement pulses, and the output from the V ² conversion table 13 is 100 times (V ² × 1
00), so it is actually 900000.

Therefore, the printing time based on the comparison reference
The output of V ² conversion table 13 when the 12V is because 14400 The output of V ² conversion table 13 when the voltage is 10V, the so 10000 And the pulse time is 10 μs, so each is 0.63 ms,
0.9 ms.

Next, the operation of the thermal transfer recording apparatus of this embodiment will be described with reference to the flowchart of FIG. When the printing operation is started, the thermistor 4 is first energized, and the temperature measuring section 3 calculates the temperature of the head based on the temperature data of the thermistor 4 (step S1). This measurement result is stored in the memory register 6a and initialized (step S
2). Then, the device drive control unit 5 determines the recording energy to be applied to the heating element 2 based on the temperature measurement result of the head (step S3). One line is recorded with the determined recording energy (step S4), and the process advances to step S5 to feed one line of paper. Then, it is determined whether or not all the data has been recorded (step S6),
If there is more data to be recorded,
At S7, the temperature of the head is measured, and the content of the memory register 6a is updated as described above (Step S8). Thereafter, returning to step S3, the recording energy is determined again from the temperature measurement result.

Next, the operation of the energy monitoring unit 10, which monitors the recording energy supplied to the heating element 2, will be described with reference to the flowchart of FIG. When the application of the voltage to the heating element 2 is started (step S11), the register 14 is cleared (step S12), and the voltage V
Measurement is started (step S13). This measurement is V ²
The output unit 15, which is digitally output to the conversion table 13 and squared here (step S14) and output to the adder 15, adds the numerical value stored in the register 14 to the value (step S15). 14 and is incremented by the new numerical value in the register 14. Further, the numerical value is output to the comparator 16 and compared with a comparative reference value set based on the previously determined recording energy, and it is determined whether or not the numerical value is exceeded (step S1).
6). Here, when the numerical value has not yet reached the comparison reference value, since recording of one block has not been completed, the recording is continued, so that the process returns to step S13 to continue the processing. Conversely, recording of one block is completed in step S16,
That is, when the value obtained by squaring and adding based on the applied voltage exceeds the comparison reference value, the recording of that block has been properly performed, and the recording of the next block is performed. And
When the recording of all the divided blocks is completed (step S17), a signal for cutting off the voltage applied to the heating element 2 is output, and the recording of the line is completed (step S17).
S18).

Since the above-mentioned comparison reference value is a value calculated from the temperature predicted based on the temperature measurement data of the four lines before the line to be recorded, it can be rewritten as needed to obtain the optimum reference value. Can be applied. In this case, the comparator 16 may have a structure in which a comparison data register and a comparator are combined. Therefore, the energy to be printed can be changed according to the temperature change of the head, and recording can always be performed at a constant density even when there is a temperature change or a voltage change.

In particular, in the case of multi-tone printing, n-tone printing is generally performed with n times the unit energy. If this unit energy is used as the above-mentioned comparison reference value, this comparison reference value is offset by the offset up to the rise in density. A desired gradation record can be obtained by multiplying the number of times by adding the number of gradations. Therefore, as the number of gradations to be recorded increases, recording at a predetermined density at the time of intermediate gradation becomes possible.

Effect of the Invention As described above, the recording apparatus according to the present invention uses the previous plurality of lines and the current thermal head temperature near the temperature measuring element, and uses the current thermal head near the heating element that is spatially separated. Predict the temperature, determine the recording energy according to the temperature, calculate a comparison reference value based on the recording energy, measure the voltage to the heating element during recording, and square the measured value. By comparing this value with the comparison reference value, the voltage applied to the heating element is terminated, so that even if the head accumulates heat due to continuous recording, the temperature is maintained at that temperature. An optimal amount of energy can be applied, and recording can always be performed at a specified density. In particular, the temperature near the heating element of the thermal head is higher than the temperature currently detected by the thermometer when the temperature detected by the thermometer is rising.
When the temperature detected by the temperature sensing element is falling, the temperature is substantially the same as the temperature currently detected by the temperature sensing element. However, the present invention takes into account the state and considers the temperature of the thermal head near the temperature sensing element. Is predicted and the amount of energy to be applied to the heating element according to the temperature is determined, so that fine energy control can be performed, and an accurate multi-gradation recorded image can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a thermal transfer recording apparatus as one embodiment of the present invention, FIG. 2 is a configuration diagram of an energy monitor unit, and FIGS. 3A and 3B show contents of a memory register. FIG. 4 is a graph showing the relationship between the measured temperature of the thermistor and the predicted temperature, FIG. 5 is a graph showing the relationship between the measured temperature and the comparison reference value, and FIG. 6 explains the operation of the temperature measuring unit. FIG. 7 is a flowchart for explaining the operation of the energy monitoring unit. DESCRIPTION OF SYMBOLS 1 ... Thermal head, 2 ... Heating element, 3 ... Temperature measuring unit, 4 ... Thermistor, 5 ... Device drive control unit, 6 ... RAM, 6a ... Memory register, 9 ... Recording control unit, 10 ...... energy monitor, 12 ...... head voltage measuring unit, 13 ...... V ² conversion table, 14 ...... register, 15 ...... adder, 16 ...... comparator.

Claims (1)

(57) [Claims] 1. A recording apparatus for forming an image on recording paper by selectively generating heat from a plurality of heating elements provided in a thermal head, wherein the temperature detecting element is provided based on a detection result of the temperature detecting element provided on the thermal head. Temperature measuring means for calculating the temperature of a nearby thermal head; storage means for storing the thermal head temperatures for a plurality of lines before a line to be recorded; and thermal head temperatures near the previous plurality of lines and the current temperature detecting element. When the thermal head temperature is increasing, the thermal head temperature near the heating element is predicted to be higher than the current thermal head temperature, and when the thermal head temperature is decreasing, the current thermal head temperature and Estimating means for estimating a thermal head temperature in the vicinity of the heating element which is substantially the same as the heating element; Calculating means for determining a recording energy according to a nearby thermal head temperature and calculating a comparison reference value based on the recording energy; and head voltage measuring means for measuring a voltage applied to the heating element at regular time intervals. An integration circuit for squaring and adding the value measured by the head voltage measurement means; comparing the value added by the integration circuit with the comparison reference value; And a comparison control means for terminating the voltage application to the heating element when the value is exceeded.