JPH06143641A - Thermal line printer - Google Patents

Abstract

PURPOSE:To simplify an initial adjusting work for equalizing print density regardless of fluctuation of average resistance of heating element between different heads by providing a control means for selecting an applying voltage or conduction time depending on the average resistance of heating element in each thermal line head. CONSTITUTION:Applying voltage to a print head 6 is regulated by selecting the pulse width of strobe signal. An appropriate pulse width is selected based on the room temperature and the average resistance of heating element in thermal head with reference to a table stored in a ROM 2. When a printer is started, a CPU 1 reads out ON/OFF state of a dip switch at an average resistance input section 8 and selects one table depending on the state thus read out. The CPU 1 then designates one strobe width in a based on the output from a temperature sensor in the thermal head. Strobe signals, each having pulse width selected depending on the average resistance of heating element, are applied subsequently to the thermal line head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal line printer.

[0002]

2. Description of the Related Art In a thermal line head used in a thermal line printer, the resistance values of the heating elements in one head are relatively uniform, but the average value of those heating elements varies considerably from head to head. There is. Particularly in the production of thermal line heads having the same specifications, among the thermal line heads of one lot, the variation in the average resistance value for each head produced initially is large, and the variation becomes smaller as the production process stabilizes. . Therefore, if a large number of heads with the same specifications are used, using only the product after the process is stable does not significantly reduce the overall yield, but in the case of a relatively small amount of production, the head in the early stage of manufacturing must also be used. Goodbye. In this case, if the printer incorporating the thermal element does not compensate for the variation in the average resistance value of the heating elements of the thermal line head, the printers of different quality have different print densities.

Therefore, conventionally, the power supply voltage in the printer is made adjustable, the applied voltage value for a constant input power is calculated from the data of the average resistance value of the heating element of the built-in thermal line head, and the output voltage of the power supply is set to the voltage. The method of adjusting the variable resistor for voltage adjustment of the power supply circuit while measuring with a meter was adopted. Alternatively, the control device in the printer may be provided with a function for selecting the power applied to the thermal line head, for example, by determining a number of strobe pulse widths and providing a means for selecting one of them. When a thermal line head is incorporated in the device, a method is used in which which power, for example, strobe pulse width, is selected by calculation based on its average resistance, and the power used, for example, an appropriate strobe pulse width is instructed using a DIP switch or the like. It was being done.

[0004]

SUMMARY OF THE INVENTION In a thermal line printer, the present invention simplifies the work of initial adjustment for making the print density of the printer uniform for variations in the average resistance value of the heating elements of the thermal line head. The purpose is to do.

[0005]

Means for Solving the Problems In a controller of a printer, a correspondence table of average resistance of a thermal line head and applied voltage or quantity of electricity, and means for storing an average resistance value of the thermal line head inputted from the outside Means for inputting the resistance value data to the storing means, and a thermal line head applied voltage or an electric quantity (current X time) is determined from the table based on the stored data and applied to the thermal line head. A means for controlling the electric power to be provided is provided.

[0006]

Since the average resistance of the heating element of the thermal line head is known, it can be input to the above-mentioned storage means. The printer controller determines the voltage or the amount of electricity applied to the thermal line head based on the stored data. Therefore, when the thermal line head is attached to the printer, the adjustment operation performed by a human only needs to input the value of the average resistance of the thermal line head by the means for inputting data to the storage means, measuring the output voltage of the power supply device, It is not necessary to calculate the required voltage for each thermal line head.

[0007]

FIG. 1 shows a controller of a thermal line printer according to an embodiment of the present invention. In the figure, 1 is a CPU, 2 is a ROM that stores a printer control program, 3 is a RAM that stores print data and other various data, 4 is an interface that receives print data and the like from an external device, and 5 is a print control unit. The print head 6 and the paper feed motor 7 are driven by the operation from the command. Needless to say, the print head 6 is a thermal line head.
Reference numeral 8 is an input section for inputting the average resistance value of the heating elements of the print head 6 used in the section according to the present invention, and 9 is a data bus for transferring data between the above sections and the CPU 1.

The average resistance value input section 8 is a DIP switch in this embodiment, and the resistance value is manually input. Since the DIP switch is kept in the ON / OFF state, it also serves as a storage means for the input data. Since the average resistance value of the heating elements of the thermal line head is provided to the user as one of the characteristic data for each thermal line head by the manufacturer of the thermal line head, the user side sets the resistance value with the DIP switch. . When the printer is started, the CPU 1 reads the on / off state of the dip switch 8, sets the voltage value and the like to be applied to the thermal line head according to the correspondence table built in the ROM, and controls printing.

The printing operation of the thermal line printer is performed as follows. The print data for one dot row is set in the latch circuit in the print head 6, and then the CPU
When a strobe signal is applied from 1 to the gate in the print head 6, the gate corresponding to the set bit is turned on for the duration of the pulse width of the strobe signal according to the set or reset state of each bit of the latch circuit. Then, the heating element connected to the gate is energized. In the present invention, the power applied to the print head is adjusted by selecting the pulse width of this strobe signal. The table shown in Table 1 is stored in the ROM for the selection of the pulse width, and an appropriate pulse width is selected according to the room temperature and the average resistance value of the heating elements of the thermal head. This table divides the average value of the heat generation resistance into 11 ranks, and gives the correspondence between the head temperature and the strobe pulse width for each rank. One of the 11 tables is specified by the average resistance. The pulse width corresponding to the temperature is selected according to the head temperature at that time, that is, the room temperature. The CPU reads the on / off state of the dip switch of the average resistance value input section 8 at the time of starting the printer, selects one of the above tables according to the result, and further outputs the output of the temperature sensor provided in the thermal head. Specifies the strobe width of one of the tables selected by. Thereafter, a strobe signal having a strobe pulse width selected according to the average resistance of the heating elements of the thermal line head thus mounted is applied to the thermal line head.

FIG. 2 is a flowchart of the strobe pulse width selecting operation of the above-mentioned control device. It is checked whether the average resistance value is set (a). If it is not set, an error or warning display (b) is displayed to prompt the setting, and when it is set (YES), the next step ( Read the value set in c) and check if it is within the specified range. If NO, display an error or warning (d). If it is within the specified range, use the above table. The pulse width of the strobe signal is selected by (e), and the print controller 5 is controlled (f) so that the strobe pulse having the selected width is output.

Although a dip switch is used for the average resistance input section 8 in the above-mentioned embodiment, since the data setting is a binary number in the dip switch, it is necessary to change the average resistance value to a binary number, and a person who performs assembly and adjustment is required. Or it is troublesome for the person who maintains the printer. If a decimal digital number switch such as a thumb rotary switch is used instead of the DIP switch, the resistance value can be input as it is, and the input result is held in the same manner as the DIP switch, so that no separate storage means is required. The average resistance input unit 8 is a means for writing data in the backup area of the RAM 3 so that the average resistance value is held in the backup area of the RAM.
U1 may set the applied power to the head based on the data there. When the printer is operated by the command from the host computer and the transfer print data, the control unit of the printer in the present invention is the host computer, and the means for storing the average resistance data of the thermal line head is also the memory in the host computer. The means for inputting the average resistance data is the input keyboard of the host computer. In this case, when the host computer causes the printer to print, the data of the average resistance value of the thermal line head of the printer is stored in the RAM of the printer, and the controller of the printer selects the strobe pulse width. In the above description, the power applied to the thermal line head is adjusted by selecting the pulse width of the strobe signal, but it goes without saying that the output voltage of the power supply may be variably selected. Further, the control device may be provided with a calculation program instead of having a relational table of the average resistance value of the thermal line head and the voltage and the like, and the voltage and the like may be determined by calculation in the control device.

[0012]

According to the present invention, the adjustment work for the difference in the average resistance of the thermal line head at the time of assembling and adjusting the thermal line printer or at the time of replacement of the thermal line printer for maintenance simply inputs the value of the average resistance to the printer. All that is required is to eliminate the hassle of setting while measuring the power supply voltage or calculating the applied power.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a flowchart of the operation of the above embodiment.

[Explanation of symbols]

 1 CPU 2 ROM 3 RAM 4 Interface 5 Print Control Unit 6 Print Head 7 Paper Feed Motor 8 Average Resistance Input Unit 9 Data Bus

[Table 1]

Claims (4)

[Claims] 1. A thermal line printer comprising control means for selecting a voltage to be applied to the thermal line head or an energization time in accordance with an average resistance value of a heating element of the thermal line head. 2. A means for externally inputting an average resistance value of a heating element of a thermal line head to a printer control device,
Means for storing the input data of the average resistance value, means for selecting the voltage or quantity of electricity applied to the thermal line head based on the stored data in the means for storing, and the selected voltage or electricity. A thermal line printer comprising means for controlling a voltage applied to the thermal line head or an amount of electricity according to the amount. 3. A relational table between the average value of the heating elements of the thermal line head incorporated in the control device by the means for selecting the electric power or the electric amount applied to the thermal line head and the voltage or the electric amount suitable for it. The thermal line printer according to claim 1 or 2, wherein 4. The means for controlling the voltage or quantity of electricity applied to the thermal line head is means for changing the pulse width of the strobe signal applied to the thermal line head. Thermal line printer.