JPH05112029A - Device for controlling energy to be applied to thermal head - Google Patents

Abstract

PURPOSE:To control an energy to be applied to a thermal head at a high speed without using a high-speed CPU. CONSTITUTION:An energy operator 35 holds a data table containing arithmetic heating energy values per voltage value at predetermined sampling intervals on sampling voltage values sequentially detected by a sequential voltage detection part 34 as address values. A heating energy value is found by referring to data corresponding to a detected voltage value in the data table. With the use of a data table using a resistance value of a thermal head as an upper address value and a voltage value as a lower address value, a required heating energy value is found by referring to data based on the respective address values. In an integrator 36, an initial value is so set that an overflow occurs when an energy is accumulated to a reference energy value corresponding to a stable density or higher, and the presence or absence of a carrier is discriminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head applied energy control device, and more particularly to a thermal head applied energy control device in a thermal recording device such as a facsimile machine using a battery as a power source.

[0002]

2. Description of the Related Art In recent years, there has been a demand for miniaturization of a recording apparatus, and a thermal recording apparatus has been developed which uses a battery as a power source and drives a thermal element. In this type of thermal recording device, the voltage fluctuates due to exhaustion of the battery power supply and load fluctuation, so generally, the terminal voltage is not directly applied to the load, and a regulator or a DC / DC converter is not used. It is used to stabilize the voltage.

However, recently, as described in Japanese Patent Application Laid-Open No. 2-2033, without using a stabilized power source,
The voltage of the battery power source applied to the thermal head is detected by an A / D converter, the heat energy is calculated by the CPU, and the pulse width is controlled. FIG. 7 is a block diagram of the conventional example. Various signals for driving and controlling the thermal head are output from the thermal interface 1, and the thermal interface 1 receives a drive voltage V
_H is input as digital data by the A / D converter 2. Then, the pulse width control of the drive pulse for driving the thermal head is performed by the CPU 3 and the ROM so that the thermal element is heated to obtain a stable print density.
4 and RAM5 are performing the calculation.

As one means for controlling the pulse width, as described in Japanese Patent Application Laid-Open No. 61-188163, the driving voltage is sampled several times and the heat generation energy value Pt between each sampling is calculated. A cumulative energy value ΣPt from the start is obtained by the accumulator, and pulse width control is performed to stop energization of the thermal head when a predetermined reference energy value W at which the density stabilizes is reached.

FIG. 8 is a block diagram showing the conventional example, and FIG. 9 is a signal waveform diagram of each part of FIG. As shown in FIGS. 8 and 9 (c) and (f), the sampling voltage value ADV is output from the A / D converter 8 of the cumulative energy output means 7 by the first sampling clock (SCLK1) generated from the timer 6. To do. Voltage / power converter 9
As shown in FIGS. 9D and 9G, the second sampling clock (S
CLK2) sampling interval T at heat generation energy value P
Calculate and output t.

FIG. 10 is a calculation flowchart of a heat generation energy value in a conventional sampling interval. As shown in FIG. 10, in step 500, the sampling voltage value ADV is read by the A / D converter 8. Then step 50
At 1, the square operation (A
DV) ² is performed, the thermal head resistance value R is divided in step 502, and the sampling interval T is multiplied in step 503. As a result, the heat generation energy value Pt = {(AD
V) ² / R} · T is required. Then, in the accumulator 10, the calculated heat generation energy values Pt are sequentially accumulated according to the following equation, and the accumulated energy value ΣP is obtained as shown in FIG.
Output t.

ΣPt = Pt ₁ + Pt ₂ + ... Ptn =
(V ₁ ² / R) T + (V ₂ ² /R)T+...+(V _n ² /
R) T Further, in the pulse width control means 11, this cumulative energy value ΣPt is compared with the reference energy value W from the terminal 12 and the comparator 13
, And when they match, the recording end signal E of FIG.
The pulse width is controlled by outputting ND and stopping the energization of the heating element 14 of the thermal head.

[0008]

As described above, in the conventional thermal head applied energy control device,
As shown in (e) of FIG. 11 which shows a timing chart of the pulse width control operation, from the start of sampling of the A / D converter until the result is obtained, that is, FIG. 9 (c).
(D) SCLK1 and SCLK2 sampling T /
Within 2 hours, the sampling process of the A / D converter as shown in FIG. 11 (f) and the output of the result are performed.
Then, as shown in FIG. 11 (g), at the same time as the result output, the heat generation energy value Pt at the sampling time T
Is calculated, that is, Pt = (ADV ² / R) T is calculated, the cumulative energy value ΣPt is calculated by the accumulator 10 and the reference energy value W necessary to obtain a stable concentration is compared. There is.

However, the above arithmetic processing is
For example, if 16-bit addition processing is performed using 8-bit CUP, the processing time requires several tens of μs, and the square operation requires 1
Since it takes more than ms, conventionally, in order to control the pulse width by performing a large number of samplings within the driving pulse width of the thermal head, a high-speed A / D converter or CPU
Had to use.

As a result, there is a problem that the device becomes expensive and noises and the like are easily generated because the clock signal has to have a high frequency. Further, if the processing is performed without increasing the speed as described above, there is a problem that the sampling interval becomes long, the fine pulse width cannot be controlled, and uneven density occurs. The present invention has been made in view of the above-mentioned conventional problems, and provides a thermal head applied energy control device capable of performing high-speed applied energy control of a thermal head without using a CPU or the like capable of high-speed processing. The purpose is to do.

[0011]

According to a first aspect of the present invention, there is provided a thermal head driving means for driving a thermal head, a sequential voltage detecting means for sequentially detecting a recording voltage during printing of the thermal head, and the detected voltage value. Heat generation energy conversion means for converting heat energy for a predetermined interval based on
A cumulative energy output means for cumulatively computing the generated heat energy and outputting a cumulative energy computed value is compared with the cumulative energy computed value and a reference energy value for obtaining a proper print density in each preset environment. A pulse width control means for controlling the drive pulse width of the thermal head drive means on the basis of the comparison result, in the thermal head applied energy control device, the heat generation energy conversion means uses the voltage value sequentially detected as an address value. It is characterized in that it has a data table in which the calculation results of the heat energy for a predetermined interval for each voltage value are stored in advance, and the heat energy is obtained based on the address value.

According to a second aspect of the present invention, in the thermal head applied energy control device according to the first aspect, the heat generation energy converting means sets the resistance value of the thermal head as an upper address value and sequentially detects the voltage value as a lower address value. As a characteristic feature, the present invention is characterized in that it has a data table in which heat energy calculation results for a predetermined interval for each voltage value in each resistance value are stored in advance, and heat energy is obtained based on the upper address value and the lower address value.

According to a third aspect of the present invention, in the thermal head applied energy control device according to the first or second aspect, the accumulated energy calculated value is set so that an overflow flag is set when the accumulated energy calculated value exceeds a reference energy value. An initial value is set, and the drive pulse width of the thermal head drive means is controlled based on the presence or absence of the overflow flag.

[0014]

According to the first aspect of the present invention, the data table in which the calculation result of the heating energy is stored in advance for each voltage value is used, and the data table is referred to by using the voltage value as the address value to generate heat according to the voltage value. Seeking energy. According to the second aspect of the invention, the data table in which the calculation result of the heat energy for each voltage value at each resistance value of the thermal head is stored in advance is used, and the resistance value and the detected voltage value of the thermal head are respectively set to the upper address values. , The lower-order address value is referred to, and the heat generation energy corresponding to the resistance value and the voltage value is obtained.

According to the third aspect of the present invention, the initial value of the cumulative calculation value is set so that the overflow flag is set when the cumulative calculation value of the heat energy exceeds the reference energy value, and the presence or absence of the overflow flag is detected. As a result, the drive pulse width of the thermal head is controlled.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a facsimile apparatus incorporating a thermal head applied energy control apparatus according to an embodiment of the present invention. The facsimile device 21 shown in FIG. 1 is supplied with all electric power from a battery power source 22. The scanner 23 reads the original image and extracts the image information, the encoding / combining unit 24 encodes the image information to be transmitted and combines the received image information, and the stepping motor unit 25 transmits the transmitting original and recording paper. Is a drive system for moving. The plotter 26 records the image information on the thermosensitive recording paper and has a thermal head, and a large number of heat generating elements are arranged on the thermal head. The network control device 27 performs a predetermined outgoing / incoming operation by connecting the line L, transmitting a selection signal which is a destination telephone number, detecting an incoming call, and the like. The modem 28 modulates and demodulates image information and transmits it, and also transmits various procedure signals in the transmission control procedure. The communication controller 29 controls the network controller 27 and the modem 28 to execute facsimile communication. The operation display unit 30 displays the operation of the device, and the operator uses it to perform various operations. System control unit
Reference numeral 31 includes a microcomputer and various electronic circuits, and controls each unit in the facsimile device 21. In this embodiment, the system control unit 31 controls the thermal head of the plotter 26 to heat the heating element to a predetermined temperature and perform the printing operation. The power supply unit 32 has a battery power supply 22 for supplying electric power to the entire apparatus described above, supplies a battery output directly to the plotter 26, and regulates the parts other than the plotter 26 by the stabilized power supply 33. Supply voltageized power.

A sequential voltage detecting section (sequential voltage detecting means) 34 converts a recording voltage by the battery power source 22 during printing of the thermal head into digital voltage data by an A / D converter (not shown) and performs sampling in synchronization with a sampling clock signal. By doing so, the voltage value can be sequentially detected. Energy calculator (heating energy conversion means) 35
Calculates the heat generation energy value Pt for a predetermined interval based on the recording voltage value sequentially detected by the voltage detector 34. The energy calculator 35 of the present embodiment is provided with a data table that stores, as data, the calculation result of the heat energy for a predetermined interval for each voltage value.

FIG. 2 is a diagram showing an example of a data table of the thermal head applied energy control device according to the first aspect of the invention. In the data table shown in FIG. 2, the sampled voltage value ADV is used as an address value, and the calculation result of (ADV) ² × T is stored on the data side. For example, in the case of FIG. 2, when the sampling time T = 10 μs, the data of the voltage value ADV = 24V has the address value of 18H.
It becomes (24V), and the corresponding data stores 240 H (5.76 × 10 ^-3 ) which is the calculated value for obtaining the heat generation energy. As described above, by using the above table, the calculation of the heat energy value can be speeded up only by referring to the data table instead of the conventional calculation processing shown in FIG.

The integrator (cumulative energy output means) 36 is
The detected heat generation energy value Pt is subjected to integral calculation processing to calculate a cumulative energy value ΣPt. The pulse width control unit (pulse width control means) 37 controls the applied pulse width so that the calculation result of the integrator 36 heats the heating element to a stable coloring temperature of the thermosensitive recording paper under each environment and raises the temperature. To do.

Next, the operation will be described. FIG. 3 is a calculation flowchart using the data table of FIG. In step 100, the digital voltage value ADV = 24V (18H) from the A / D converter of the sequential voltage detector 34 of FIG. 1 is detected. In step 101, the voltage value is used as an address and the data table of FIG. 2 is referred to to obtain a previously stored calculation result (ADV) ² × T = 5.76 × 10 ⁻³ (J), that is, 576 = 240 H. .. Then, by dividing the value obtained in step 102 by the resistance value of the thermal head,
Exothermic energy can be obtained easily and quickly.

FIG. 4 is a diagram showing an example of a data table in the thermal head applied energy control device according to the invention of claim 2, and FIG. 5 is a calculation flowchart using the data table of FIG. In the embodiment of claim 1 above, division is performed by the resistance value of the thermal head in step 102 of FIG. However, the embodiment of claim 2 is characterized in that, as shown in FIG. 4, the upper address of the data table is the resistance value of the thermal head, and a data table is provided for each resistance value.

According to the operation of claim 2, as shown in FIG. 5, in step 200, the resistance value of the thermal head is input by bit setting or software setting, and in step 201, the upper address value of the data table is set. Step 202
Then, in step 203, the lower address value is set by the digital voltage value ADV from the A / D converter of the voltage detecting section 34. Then, in step 204, Pt = {(ADV) ²
The heat generation energy value Pt can be obtained only by referring to the data table that stores the calculation result of / R} × T.

As an example thereof, as shown in FIG. 4, when the sampling time T = 10 μs, the thermal head resistance value R = 3000Ω (hexadecimal number: BB8H) and the sampling voltage value ADV = 24V (hexadecimal number: 18H). Data is stored in COH (1.92 × 10) at address BB8 / 18H in the data table.
^-6 J) is stored. By using this data table, first, the resistance value of the thermal head is set by a bit switch or the like, and the resistance value is selected as an upper address value from each data table group. Next, the sampling voltage value from the A / D converter of the sequential voltage detection unit 34 is input to the energy calculator 35, the input voltage value is set as a lower address value, and the heating energy value Pt of the data table to be obtained is referred to. To do.

As described above, in the above embodiment, since the heat generation energy value is obtained by using the data table in which the resistance value of the thermal head is added in addition to the sampling voltage value, the processing time can be further shortened and the speed can be increased. it can. FIG. 6 is a flow chart for explaining the operation described in claim 3, where (a) is a comparative example and (b) is this embodiment. Figure 6
As shown in (a), conventionally, in step 300, the integrator is set to an initial value A = 0. That is, the integrated calculation value Σ
Clear Pt to 0. Next, in step 301, the heat generation energy value Pt calculated each time sampling is performed is added, and the result value ΣPt is compared with the reference energy value W in step 302. If ΣPt <W, step 303
Then, the value of ΣPt is substituted into A of step 301, the heat generation energy value Pt by the next sampling is added, and the result value is similarly compared with W. If ΣPt ≧ W, the accumulated heat energy value is equal to or greater than the reference energy value, so the application of energy to the thermal head is stopped and the pulse width is controlled (step 304).

However, in the comparison operation in step 302 of FIG. 6A, since ΣPt over several tens of bits is compared with W, the comparison is started from the upper 8 bits and divided into several times to C.
Since the comparison is performed with 8 bits of PU, the processing becomes complicated and the processing time is long. In this embodiment, the integrator is set to the initial value B in step 400 as shown in FIG. 6 (b). This initial value B is the heat generation energy value P
This is a value for which the overflow flag is set when the integral calculation value ΣPt of t becomes equal to or larger than the reference energy value W. For example, in the case of 16 bits, B = 10000 (H) -W
Becomes Then, in step 401, the heat generation energy value Pt referred to in the data table every time sampling is performed.
Is added, and it is determined in step 402 whether or not the resulting value ΣPt overflows, depending on whether the carrier is “1” or “0”. If the carrier does not overflow at "0", it has not reached the reference energy value W, so in step 403 the value of ΣPt is substituted into B in step 401, and Pt is added in the same manner as above. If ΣPt overflows and the carrier becomes “1”, step 40
At 4, the application of energy to the thermal head is stopped and the pulse width is controlled.

As described above, in the thermal head applied energy control apparatus of this embodiment, since the initial value of the integrator is set as described above, it is not necessary to perform successive comparison processing with the reference energy value, and the carrier is "1". It suffices to see whether it is "0" or "0", and the processing can be further speeded up.

[0027]

As described above, according to the first aspect of the present invention, the heat generation energy value is referred to by referring to the data table in which the calculation result of the heat generation energy for each voltage value is stored in advance using the voltage value as the address value. Therefore, complicated arithmetic processing can be omitted and the speed can be increased.

According to the second aspect of the invention, since the heat energy value is obtained by using the data table in which the resistance value of the thermal head is the upper address value and the voltage value is the lower address value, the calculation process is further omitted. As a result, it is possible to increase the speed and reduce the unevenness of printing density due to the variation in the resistance value. According to the invention of claim 3,
Since the initial value of the integral calculation value ΣPt of the integrator is set so that the overflow flag is set when the accumulated energy becomes equal to or more than the reference energy value W, it is not necessary to divide and compare by the processing bit of the CPU, and whether the overflow flag exists Only by doing so, easy and high-speed processing can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a facsimile apparatus including a thermal head applied energy control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a data table of a thermal head applied energy control device according to the first aspect of the invention.

FIG. 3 is a calculation flowchart using the data table of FIG.

FIG. 4 is a diagram showing an example of a data table of a thermal head applied energy control device according to a second aspect of the invention.

FIG. 5 is a flowchart explaining the operation according to claim 2;

FIG. 6 is a flow chart for explaining the operation according to claim 3, wherein (a) is a comparative example and (b) is this embodiment.

FIG. 7 is a block diagram of a conventional example.

FIG. 8 is a block diagram of another conventional example.

9 is a signal waveform diagram of each part in FIG.

FIG. 10 is a calculation flowchart of a heat generation energy value at a sampling interval in a conventional example.

FIG. 11 is a timing chart of a pulse width control operation.

[Explanation of symbols]

 26 Plotter (Thermal head drive means) 31 System control section 32 Power supply section 34 Sequential voltage detection section (Sequential voltage detection means) 35 Energy calculator (Exothermic energy conversion means) 36 Integrator (Cumulative energy output means) 37 Pulse width control section (Pulse width control means)

Claims (3)

[Claims] 1. A thermal head driving means for driving a thermal head, a sequential voltage detecting means for sequentially detecting a recording voltage during printing of the thermal head, and conversion into heat energy for a predetermined interval based on the detected voltage value. Heating energy conversion means, cumulative energy output means for cumulatively calculating the heating energy and outputting a cumulative energy calculation value, and for obtaining the cumulative energy calculation value and a proper print density in each preset environment. A pulse width control means for comparing the drive pulse width of the thermal head drive means on the basis of the comparison result with a reference energy value, and a thermal head applied energy control device comprising: The detected voltage value is used as an address value, and the heat energy calculation result for a predetermined interval for each voltage value is calculated. A thermal head applied energy control device having a data table in which fruits are stored in advance, and heat energy is obtained based on an address value. 2. The thermal head applied energy control device according to claim 1, wherein the heat generation energy conversion means uses the resistance value of the thermal head as an upper address value and the sequentially detected voltage value as a lower address value. A thermal head applied energy control device having a data table storing in advance the heat energy calculation results for a predetermined interval for each voltage value, and determining the heat energy based on the upper address value and the lower address value. 3. The thermal head applied energy control device according to claim 1, wherein an initial value of the cumulative energy calculated value is set so that an overflow flag is set when the cumulative energy calculated value becomes equal to or more than a reference energy value. A thermal head applied energy control device for controlling the drive pulse width of the thermal head drive means based on the presence or absence of the overflow flag.