JP3852808B2 - Line thermal printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a line thermal printer that performs thermal history control.
[0002]
[Prior art]
Conventionally, line-type thermal printers are widely used in label printers that print barcodes or the like on labels, and receipt printers that print merchandise transaction information on receipts. In such a line thermal printer, a thermal head in which a large number of heating elements are arranged in a row is used, the arrangement direction of the heating elements is a main scanning direction, and the relative movement direction of the thermal head and the recording medium is a sub scanning direction. Print on the recording medium.
[0003]
On the other hand, in a thermal printer, printing is performed by directly coloring a thermal paper by selective heat generation of a heating element, or by melting ink ribbon by selective heating of a heating element and transferring ink to a recording medium. . Due to such a structure, the heat-generating action of the heat generating element during printing is inevitable, which causes the deterioration of the printing density uniformity. Therefore, conventionally, drive control of the heating element called thermal history control is performed to ensure the uniformity of the print density.
[0004]
Here, a conventional example of heat history control will be described based on the timing chart of FIG. FIG. 4 is an example in which thermal history control is realized by software control. First, as an outline of the printing operation, the thermal head includes a shift register and a latch circuit, and the control unit of the thermal printer periodically generates a printing interrupt pulse for each line of the printing operation. In response, the print data for one line (displayed as “raw” in FIG. 4) is transferred to the shift register and stored (all not shown). Then, the control unit of the thermal printer inputs the latch signal a to the latch circuit in response to the print interrupt pulse, and activates the strobe signal. Thus, prior to the operation of transferring the print data to the shift register, the history data already stored in the shift register (indicated as “history” in FIG. 4) is transferred to the latch circuit by the latch signal and transferred to the latch circuit. The recorded history data is output as a head drive signal to the driver of the thermal head when the strobe signal is activated. Subsequently, when a predetermined time elapses after the generation of the print interrupt pulse, the timer 0 interrupt b is executed, and the latch signal c is output to the latch circuit accordingly. As a result, the print data transferred to the shift register is transferred to the latch circuit. At this time, the print data is output as a head drive signal to the driver of the thermal head when the strobe signal is active. In parallel with such processing, the output of the latch signal c generates history data of the next line with reference to the print data, and is transferred and stored in the shift register. Subsequently, when a predetermined time elapses after the generation of the print interrupt pulse, the timer 1 interrupt d is executed, and the strobe signal that has been activated in response thereto is deactivated.
[0005]
By executing such processing, while the strobe signal is active, the selective heating operation of the heating elements for one line in the main scanning direction is performed. Then, by combining the selective heat generation of one line of the heating element in the main scanning direction with the relative movement of the thermal head and the recording medium in the sub-scanning direction, printing according to the print data on the recording medium is performed. Is done.
[0006]
Subsequently, the thermal history control will be described in more detail. The latch signal a is input to the latch circuit in accordance with the print interrupt pulse and the strobe signal is activated, so that it is output as a head drive signal to the head driver of the thermal head immediately before the occurrence of the print interrupt pulse. Is the history data ("History" in FIG. 4) stored in. This history data is data for driving a heating element that is not driven to generate heat in the previous line among the heating elements that are driven to generate heat this time according to print data (“raw” in FIG. 4). The print data transferred to the shift register during driving of the heating element based on such history data is output from the shift register by outputting a latch signal c to the latch circuit in response to the timer 0 interrupt b. The data is transferred to the latch circuit, and is output as a head drive signal to the head driver of the thermal head only while the strobe signal is active. Therefore, in the thermal history control illustrated in FIG. 4, the heating elements are driven to generate heat in accordance with the history data and the subsequent print data. In this case, the heating elements that were not driven to generate heat in the previous line are stored in the history data. The heating element driven by heat according to both the print data and the print data is driven by heat according to only the print data. Therefore, the heat generation drive time of the heat generating element driven to generate heat in the previous line is shorter than that of the heat generating element not driven to generate heat. As a result, variation in the heat generation temperature of each heat generating element that may occur according to the heat generation history is corrected, and uneven printing density is prevented.
[0007]
[Problems to be solved by the invention]
However, in the thermal history control as illustrated in FIG. 4, data transfer of print data to the shift register and output of a head drive signal based on the history data are performed between the latch signal a and the latch signal c. There is a problem that the output time of the head drive signal based on the history data becomes too long. This is because, under heat history control by software control, a certain amount of time is required to complete the print data transfer, so the time between the latch signal a and the latch signal c is transferred to the print data transfer. This is because it cannot be shortened beyond the time required for the operation. As a result, the drive time of each heating element becomes too long, making it difficult to express a low density, or when using high-sensitivity paper or a high-sensitivity transfer ribbon or under high-temperature environments, print quality deteriorates. There is an inconvenience.
[0008]
An object of the present invention is to enable control so that the output time of a head drive signal does not become too long even when thermal history control is performed by software control.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, in a line thermal printer that performs line-type image recording on a recording medium using a thermal head, the shift register that registers the transferred print data and history data, and the input of a latch signal A latch circuit that latches print data and history data transferred from the shift register and outputs a head drive signal corresponding to the latched print data and history data when the strobe signal becomes active, and printing for each line of printing operation Print interrupt pulse generation means for periodically generating interrupt pulses, reference pulse generation means for generating a reference pulse at a predetermined time after generation of a print interrupt pulse and before generation of the next print interrupt pulse, and printing in response to an interrupt pulse, before the reference pulse generator, the print data of the current line to the shift register The data was the data transfer, and means for latching the historical data of the current line being resist to the shift register by inputting a latch signal to the latch circuit prior to the data transfer to the latch circuit, according to the reference pulse Before the next print interrupt pulse is generated , a latch signal is input to the latch circuit to cause the latch circuit to latch the print data of the current line transferred and registered to the shift register. hand stage you data transfer and generates the history data of the next line to the shift register by referring to the print data of the line, the time amount corresponding reference pulse is determined with reference to the reference pulse after printing interrupt pulse generator by activating the strobe signal back from, it is the data transferred to the shift register cashier Maintaining a first head drive signal output means for outputting a head drive signal based on historical data of the current line being collected by the strobe signal is already based on the occurrence of a reference pulse when the active its state strobe When the signal is not active, the strobe signal is activated to output a head drive signal based on the print data of the current line that is transferred to the shift register and registered, and then deactivate the strobe signal. Second head drive signal output means.
[0010]
Therefore, the data transfer time of the print data to the shift register is ensured only after the print interrupt pulse is generated and before the reference pulse is generated. The head drive signal based on the history data transferred to the shift register is generated from the reference pulse by the time determined with reference to the reference pulse within the time after the generation of the print interrupt pulse and before the generation of the reference pulse. Output in a row. For this reason, the output time of the head drive signal based on the history data is set to an arbitrary time within the time after the generation of the print interrupt pulse and before the generation of the reference pulse, regardless of the data transfer time of the print data to the shift register. It becomes possible to set to. Therefore, even when thermal history control is performed by software control, it is possible to perform control so that the output time of the head drive signal does not become too long.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. This embodiment is an example applied to a label printer.
[0012]
FIG. 1 is a longitudinal side view of the entire label printer. A label printer 1 according to the present embodiment includes a printer main body 3 that includes a printing mechanism unit 2 and executes a printing operation, and a paper holder that holds a label paper 4 as a recording medium fed to the printing mechanism unit 2 of the printer main body 3. 5 are connected to each other. The printer main body 3 includes a guide path 6 that guides the label sheet 4 fed from the sheet holder 5 to a predetermined path, and includes the printer rear portion 2 in the guide path 6. The printing mechanism unit 2 includes a printing unit 9 including a platen 7 and a thermal head 8 that are arranged to face each other via a guide path 6, and a ribbon mechanism unit that guides and conveys an ink ribbon 10 between the platen 7 and the thermal head 8. 11. The thermal head 8 has a line-type structure in which a large number of heating elements (not shown) are arranged in a row in a direction perpendicular to the guide path 6 of the label paper 4. The paper holder 5 rotatably supports the label paper 4 wound and held in a roll shape.
[0013]
FIG. 2 is a block diagram of electrical connection of each part. A CPU 12 that executes various arithmetic processes and centrally controls each unit is provided, and a ROM 13 that stores fixed data such as an operation program and a RAM 14 that stores variable data are connected to the CPU 12 via a bus line 15. ing. The CPU 12 is connected to a motor driver 18 that drives a stepping motor 16 that is a driving source of the platen 7 in the printing unit 9 and a DC motor 17 that is a driving source of the ribbon mechanism unit 11 via the bus line 15. A head driver 19 for driving the thermal head 8 is connected via the bus line 15. Although not shown in FIG. 1, the label printer 1 includes a display device 21 and a key 22 on the front panel 20, and a display controller 23 that drives the display device 21 and an input controller 24 that receives a signal from the key 22. It is connected to the CPU 12 via the bus line 15. Further, the CPU 12 is connected to the CPU 12 via the bus line 15, for example, an I / O port 26 for taking in signals from various sensors 25 that detect the presence or absence of the label paper 4 in the guide path 6, and print data. And a communication interface 27 used for receiving data.
[0014]
In such a label printer 1, according to the operation program stored in the ROM 13, the CPU 12 outputs a drive control signal for each part while using the RAM 14 as a work area, thereby executing a printing operation. That is, the thermal head includes a shift register and a latch circuit (both not shown), and print data temporarily stored in the RAM 14 and its history data are transferred to the shift register for each line. Such print data and history data are transferred from the shift register to the latch circuit by inputting a latch signal to the latch circuit, and a head drive signal corresponding to the print data and history data output from the latch circuit is sent to the head driver. 19, the heating element of the thermal head 8 is selectively driven, whereby the ink on the ink ribbon 10 is transferred to the label paper 4. The label paper 4 is conveyed to the platen 7 by driving the stepping motor 16 in synchronization with the driving of the heat generating elements, and the label paper 4 moves in the sub-scanning direction with respect to the thermal head 8. Thereby, printing on the label paper 4 is performed. That is, printing according to the print data is performed on the label paper 4 by printing on the label paper 4 in the sub-scanning direction and the main scanning direction.
[0015]
FIG. 3 is a timing chart of various signals during the printing operation. Here, in the label printer 1 of the present embodiment, thermal history control is performed during the printing operation. This thermal history control will be described. The CPU 12 periodically generates a printing interrupt pulse for each line of the printing operation (printing interrupt pulse generating means), and print data (FIG. 3) used for printing the line in response to the generation of the printing interrupt pulse. Data is transferred to a shift register provided in the thermal head 8 and stored (print data transfer means). The data transfer time at this time is Th. Then, prior to such data transfer of print data, the CPU 12 inputs a pulsed latch signal a to the latch circuit in accordance with the print interrupt pulse. As a result, the history data (indicated as “history” in FIG. 3) already stored in the shift register immediately before the occurrence of the print interrupt pulse is transferred from the shift register to the latch circuit. The history data transfer from the shift register to the latch circuit at this time is performed at a very high speed without depending on the clock frequency of the CPU 12, for example, since the history data for one line is performed at a time.
[0016]
Next, when n hours have elapsed after the occurrence of the print interrupt pulse after the data transfer time Th has elapsed (approximately the middle between the current print interrupt pulse and the next print interrupt pulse), the latch signal b is again transmitted. Input to the latch circuit. The latch signal b is a signal generated in response to a timer 0 interrupt c as a reference pulse generated under the timer management of the CPU 12. Under such control of the CPU 12, the function of the reference pulse generating means is executed. When such a latch signal b is generated, the history data of the next line is generated with reference to the print data transferred to the shift register, and this is transferred and stored in the shift register (history data transfer means). In this case, in the heat history control of the present embodiment, control is performed to shorten the heat generation time in the current line of the heat generating element that has generated heat in the previous line, and here, heat is generated in the next line. The drive data of the heating elements that did not generate heat in the current line in the heating elements becomes the history data.
[0017]
Next, the heating operation of each heating element in the thermal head 8 will be described. First, in the heat history control of the present embodiment, the heat generation time of the heat generating element that performs the heat history control is T2, and the heat generation time of the heat generation element that does not perform the heat history control is T1 longer than T2. More specifically, when the heating element that has generated heat in the previous line also generates heat in the current line, the heat generation time should be shortened in consideration of the animal heat action of the heat generation element. The heating element that performs the thermal history control is a heating element that has a heat generation time of T2. On the other hand, when a heating element that did not generate heat in the previous line is caused to generate heat in the current line, the heating element is a heating element that does not need to consider animal heat action, that is, a heating element that does not perform thermal history control. Therefore, the heat generation time is T1 longer than T2. In the present embodiment, the timer 0 interrupt c is used as a reference pulse, the strobe signal is activated from the time when (T1-T2) time has passed from this reference pulse, and is activated when T2 time has elapsed from the reference pulse. By setting the strobe signal to a low level, a head drive signal corresponding to the history signal and the subsequent print signal is output to the head driver 19 of the thermal head 8 only while the strobe signal is active. At this time, the head drive signal corresponding to the history data transferred to the shift register in the previous line is sent from the time point (T1-T2) after the reference pulse to the time point when the reference pulse is generated. 19 (first head drive signal output means), and until T2 time elapses after the generation of the reference pulse, data is transferred to the shift register over Th time and instantly sent to the latch circuit by the latch signal b A head drive signal corresponding to the transferred print data is output to the head driver 19 (second head drive signal output means).
[0018]
Here, the timing at which the print data and history data are output from the shift register via the latch circuit and the head drive signal is output to the head driver 19 is determined by the timer 1 interrupts d and e. That is, the strobe pulse is activated by the timer 1 interrupt d, and data is output from the shift register. Then, the strobe pulse becomes low level by the timer 1 interrupt e, and the data output from the shift register is stopped. At this time, the generation timing of the timer 1 interrupts d and e is determined by the timer management of the CPU 12. In other words, since the heat generation time of the heat generating element that does not perform the thermal history control requires T1 time, the timer 1 interrupt d is set when the time (T1-T2) time has passed from the timer 0 interrupt c that is the reference pulse. Need to be generated. On the other hand, since the heat generation time of the heat generating element that performs the thermal history control is sufficient for the T2 time shorter than the T1 time, the timer 10% is obtained when T2 time elapses after the timer 0 interrupt c as the reference pulse. It is sufficient to generate a process e. As a result, when the timer 1 interrupt d occurs and the strobe signal becomes active, the head drive based on the history data of the current line transferred to the shift register in the previous line and transferred to the latch circuit by the latch signal a A signal is output to the head driver 19. When the timer 1 interrupt d is generated and the latch signal b is input to the latch circuit, the print data that has been transferred to the shift register during the transfer time Th in the current line is transferred to the latch circuit at a high speed. A head drive signal based on the print data transferred at high speed to the latch circuit is output to the head driver 19, and the output operation is continued while the timer 1 interrupt e is generated and the strobe signal is active. As a result, heat history control is performed in which the heat generating elements that perform heat history control are driven to generate heat for T2 hours, and the heat generating elements that do not perform heat history control are driven to generate heat for T1 hours longer than T2 hours. As a result, the variation in the heat generation temperature of each heat generating element that may occur according to the heat generation history is corrected, and uneven print density is prevented.
[0019]
On the other hand, in this embodiment, the data transfer time of the print data requires Th time, and this Th time is ensured between the latch signal a and the latch signal b. On the other hand, the output of the head drive signal corresponding to the print data and history data stored in the shift register and transferred to the latch circuit continues until the strobe pulse becomes active and becomes inactive. In this case, active / inactive of the strobe pulse depends on the timer 1 interrupt d and the timer 1 interrupt e which are not constrained by the latch signal a and the latch signal b. Therefore, the output time (T1-T2) of the head drive signal based on the history data can be set to an arbitrary time regardless of the data transfer time of the print data to the shift register. Therefore, even when thermal history control is performed by software control, it is easy to perform control so that the output time of the head drive signal does not become too long. As a result, it is possible to freely express light and shade, and high-quality printing can be performed even when high-sensitivity paper or a high-sensitivity transfer ribbon is used or in a high-temperature environment.
[0020]
【The invention's effect】
According to the first aspect of the present invention, the data transfer time of the print data to the shift register is ensured only after the print interrupt pulse is generated and before the reference pulse is generated, and the data is transferred to the shift register within that time. Since the head drive signal based on the history data is output from the reference pulse for a time determined based on the reference pulse, within the time after the generation of the print interrupt pulse and before the generation of the reference pulse, Regardless of the data transfer time of the print data to the shift register, the output time of the head drive signal based on the history data can be set to an arbitrary time. Therefore, even when thermal history control by software control is performed Thus, it is possible to perform control so that the output time of the head drive signal does not become too long. As a result, it is possible to freely express light and shade, and high-quality printing can be performed even when high-sensitivity paper or a high-sensitivity transfer ribbon is used or in a high-temperature environment.
[Brief description of the drawings]
FIG. 1 is an overall longitudinal side view showing an embodiment of the present invention.
FIG. 2 is a block diagram showing electrical connection of each part.
FIG. 3 is a timing chart of various signals during a printing operation.
FIG. 4 is a timing chart of various signals during a printing operation according to a conventional example.
[Explanation of symbols]
6 Guide route 4 Recording medium (label paper)
8 Thermal head

Claims (1)

In a line thermal printer that performs line-type image recording on a recording medium using a thermal head,
A shift register for registering the transferred print data and history data;
A latch circuit that latches print data and history data transferred from the shift register by inputting a latch signal, and outputs a head drive signal corresponding to the print data and history data latched when the strobe signal becomes active;
A printing interrupt pulse generating means for periodically generating a printing interrupt pulse for each line of the printing operation;
Reference pulse generating means for generating a reference pulse at a predetermined time after generation of a print interrupt pulse and before generation of the next print interrupt pulse;
In response to the print interrupt pulse , before the reference pulse is generated, the print data of the current line is transferred to the shift register, and the latch signal is input to the latch circuit prior to the data transfer to register the shift register. Means for causing the latch circuit to latch the history data of the current line being
In response to the reference pulse , before the next print interrupt pulse is generated, the latch data is input to the latch circuit to latch the print data of the current line that is transferred to the shift register and registered in the latch circuit. is allowed, and hand stage by referring to the print data of the current line to generate historical data of the next line you data transferred to the shift register,
By activating the strobe signal from the reference pulse for the time determined based on the reference pulse after the generation of the print interrupt pulse, the history data of the current line registered and transferred to the shift register is registered. First head drive signal output means for outputting a head drive signal based thereon;
Based on the generation of the reference pulse, when the strobe signal is already active, the state is maintained, and when the strobe signal is not active, the strobe signal is activated, whereby the data is transferred to the shift register and registered . A second head drive signal output means for outputting a head drive signal based on the print data of the current line and then deactivating the strobe signal ;
A line thermal printer.

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