JPH0418370A - thermal printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to thermal compensation for thermal printers.

[Prior Art] In a conventional thermal printer, the energy applied to each heating resistor of a thermal head is set based on the lowest environmental temperature and the lowest temperature of the thermal head.

To explain in more detail, in the case of a thermal printer that can record at temperatures above 0°C, the energy that can be recorded on the recording paper when both the environmental temperature and the temperature of the thermal head are 0°C is
It is set to be applied to each heating resistor of the thermal head. Further, the applied energy in this state is the maximum, and therefore, when the applied voltage to the thermal head is constant, the time for energizing each heating resistor of the thermal head is the longest.

[Problems to be Solved by the Invention] However, the above-mentioned conventional technology requires a power supply for a thermal head that can print at the lowest temperature, resulting in a large capacity (wattage) power supply, making it expensive and large. It has an intercondylar point.

In addition, when controlling the density of each recording dot by controlling the energy applied to each heating resistor of the thermal head (multilevel recording), the heating resistor of the thermal head is energized at low and high temperatures. The time ratio for this is about 4:1. Therefore, when performing multilevel recording at high temperatures, the minimum value of the current pulse width is several μs. In this case, since there is a difference of 100 nSlj in the switching characteristics of the individual switching elements (transistors, FITs, etc.) for causing current to flow through the heating resistor, a difference occurs in the energy applied to the heating resistor, and the recording of the same concentration Even when an attempt is made to record dots, there is a problem in that the density differs for each dot corresponding to the heating resistance value, which deteriorates the image quality.

Therefore, the present invention is intended to solve these problems.
The purpose is to provide a device that reduces the capacity of the power applied to the thermal head, is inexpensive and compact, and reduces the influence of differences in switching characteristics of individual switching elements on image quality.

[Means for Solving the Problems] The thermal printer of the present invention includes a thermal head having a plurality of heating resistors, and by changing the energy applied to each heating resistor of the thermal head,
In a thermal printer that records on paper via thermal paper or an ink ribbon, there is a detection means for detecting the temperature of the thermal head, and a standby system that energizes each heating resistor of the thermal head when not printing based on the output value from the detection means. It is characterized by having a heating means.

[Example] FIG. 1 is a block diagram of an embodiment of the invention.

The detection means 1.1 detects the temperature of the thermal head 103 from the resistance value of a heat sensitive element 106α such as a thermistor arranged on the thermal head 105.

One embodiment of the detection circuit 101 is shown in FIG. 1°1α is a comparator, and 101b and 101c are reference resistors. The resistance values of the reference resistors 1o1b are equal, and the reference resistor 1
Assuming that the resistance value of 01C is α[KΩ], the detection signal 101d is inverted when the resistance value of the heat-sensitive element 103α is equal to or less than α[KΩ]. Below, the detection signal is 10 below the detection temperature.
1d is L [Low], detection signal 101d is higher than the detection temperature
will be explained as H[atghl.

The detection signal 101d is manually input to the control means 105. When the detection signal 101d is L, the control means 105 drives the preheating means 102 and selects the preheating means 102 with the selector 107.

When the preheating means 102 is driven, the thermal head 1
05 to the signals shown in FIG. 3 [Data, CLK, LATC
H] is output. During printing, the Data signal is a signal that selectively turns on or off the switch element 105d in the thermal head 105;
The Data signal from 02 is a signal that turns on all the switch elements 103d. The CLK signal is the shift register IQ! This is a clock for DBta to shift within b. When one line of data is input into the shift register 105b, the data in the shift register 105b is input to the latch circuit 105C by the DATOH signal.

Next, when the Sel signal is set to H and the gate circuit 103f is opened, all the switch elements 105d are turned on, and the heating resistor 10
! , etg knee current flows and generates heat. The Sel signal remains high for a certain period of time and repeats the subsequent operation.

By performing the above operation, the temperature of the thermal head 103 gradually rises, and when it reaches the detection temperature, the detection means 10? Therefore, the detection signal 7D1d is output as H.

An embodiment of the preheating means 102 is shown in FIG. The oscillator 401 is an oscillator that oscillates at twice the frequency of the CLK signal, and the output from the oscillator 401 is passed through the 1/2 frequency divider 40.
2, the frequency is divided into a 1/2 frequency clock.

When the control signal 105α of the preheating means 102 outputted from the control means 105 becomes H[atghl, the edge cutter 403 outputs a clock synchronized with 1/2 frequency. Due to this clock, the Data signal becomes H[Ht
gh]. The OLK signal is the AND of the Data signal and the output of the 1/2 period 402.

Divide period 404 divides the output of 7/2 frequency divider 402. When the Data signal is L [Low], the frequency divider 404 does not perform frequency division operation. When the heat generating resistor 103e on the thermal head 106 is formed of R heat generating resistors, the carry forming unit 405 calculates (yc+1 ) Outputs the clock on the clock. By this clock, Da
The ta signal is set to L [Low]. Let the inverter signal of this clock be the LATCH signal.

The Sel signal is obtained from the logical product of the frequency-divided signal of the 1/2 frequency divider 402 and the control signal 105α.

When the detection signal 101d is H, the control means 105
The driving of the preheating means 1[]2 is stopped.

Therefore, the heat generation of the heating resistor 103g stops at this point, and the temperature rise of the thermal head stops.

In this state, the thermal printer receives print data 1 from the outside.
06α can be received. The control means 105 replaces the preheating means 102, drives the print control means 106, and selects the print control means 106 with the selector 107.

The state in which the preheating means 102 is driven is that after the power of the thermal printer is turned on, until the detected temperature is reached, and the interval between printing is long, and the thermal head 105 is operated until the detected temperature is reached or below.
This is the case when the temperature of

Preferably, the detection temperature is set to one value between 20°C and 50°C.

When the preheating means 102 is driven to generate heat in the heating resistor 103e, it is necessary to arrange the thermal head 105 and the thermal paper or ink ribbon so that they do not come into contact with each other.

As an example of the detection means 101, FIG. 2 shows an example using a comparator 101α, but an A/D converter may also be used.

When a CPU is used as the control means 105, the detection signal 10
Even after 1d changes to H, the pre-biased heating means 102 is driven for a short time to cause the heating resistor 103e to generate heat. On the other hand, even after the detection signal 101d shifts to L, the pre-biased heating means 102 is not driven for a while, so that hysteresis is provided by software.

[Effects of the Invention] As described above, according to the invention, when the detected temperature of the thermal head 106 is set to a certain temperature, the heating resistor 103e
Since the thermal head 106 is also at a certain temperature, it is possible to record on the paper by applying approximately 1/2 the energy compared to when the thermal head 106 records on the paper at a low temperature.

Therefore, the capacity of the applied power source 104 can be reduced, and an inexpensive, small, and lightweight thermal printer can be realized.

Further, the ratio of the time during which electricity is applied to the heating resistor I03g of the thermal head 103 at low temperatures and at high temperatures is about 2:1. Therefore, the influence on the density of printed dots due to differences in the switching characteristics of the switching elements 105d can be reduced to 1/2.
It will be effective if it can be reduced to about 2.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a circuit diagram showing one embodiment of the detection means of the present invention. FIG. 3 is a timing chart diagram for explaining the present invention in detail. FIG. 4 is a block diagram showing an embodiment of the preheating means of the present invention. 101...Detection means 102...Preheating means 103...Thermal head 104...
...Applying power supply 105 ... Control means 106 ... Print control means Above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki (1 other person) )Data Figure 3

Claims (1)

[Claims] A thermal head having a plurality of heating resistors is provided, and by changing the energy applied to each heating resistor of the thermal head, recording is performed on paper via thermal paper or an ink ribbon. A thermal printer comprising: a detection means for detecting the temperature of the thermal head; and a preheating means for energizing each heating resistor of the thermal head when not printing based on the output value from the detection means. .