JPS63276572A - Printer - Google Patents

Abstract

PURPOSE:To make the hardness of a platen constant and to enhance printing quality, by providing a heater for heating the platen and detecting the temp. of the platen to control intermittent heating and holding the platen to constant temp. CONSTITUTION:When the temp. of a platen 10 is detected by a temp. sensor 12 to be converted to voltage, said voltage is compared with reference voltage by the comparator 20 in a control circuit 18 and the transistor 21 of a switch part 19 is turned ON/OFF according to the magnitude thereof to make a heater 11 intermittent. When the optimum temp. of the platen 10 is within a range of Tb-Ta, the objective temp. thereof is set to the temp. Tc between the temps Tb, Ta. This temp. Tc corresponds to the voltage obtained by dividing the constant voltage Vz in the control circuit 18 by resistors R3, R4 and this voltage is inputted to the comparator 20 as the reference voltage to be compared with the voltage from the temp. sensor 12. The transistor 21 is turned ON/OFF according to the output of the comparator 20 and control is performed so that the temp. of the platen 10 becomes the objective temp. Tc.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to printers that use platens, such as impact printers, thermal printers, and inkjet printers.

BACKGROUND OF THE INVENTION For example, in a printer that prints on paper on a rubber platen using the printing pressure of a type wheel, changes in the hardness of the platen greatly affect print quality. That is,
If the platen is hard, the curvature of the platen and the curvature of the type wheel do not match well, which tends to cause uneven printing density and increases noise. On the other hand, if it is soft,
The printing ribbon is forced onto the platen by the type wheel, causing ink smearing on the printing surface and reducing print density.

The temperature of the platen is a major factor that changes the hardness of the platen, but in the past, the temperature has not been controlled at all.

Purpose The present invention aims to stabilize the hardness of the platen itself by keeping its temperature constant, thereby improving printing quality.

Configuration Therefore, the printer according to the present invention includes a heat-retaining means for keeping the platen at a constant temperature.

Next, embodiments of the invention will be described with reference to the drawings.

In Fig. 1, the platen (10) has a built-in heater (11) using a heating wire, and a temperature sensor (12) is installed outside the platen (10) as shown in Fig. 2. The temperature sensor (12) is arranged at a predetermined interval on the opposite side of the print wheel (13), and the temperature of the outer surface of the platen (10) is detected. As this temperature sensor (12), for example, a thermistor resistor is used, and as shown in FIG. 3, it is attached to a bracket (15) fixed to the frame (14) of the printer.

In that case, the gap between the temperature sensor (12) and the platen (10) is approximately 5 m, taking into account both paper passing and heat detection.
A value of about m is appropriate. In addition, (16) in FIG. 2 is an ink ribbon.

FIG. 4 shows an electric circuit that intermittently controls the heater (11) based on temperature detection by the temperature sensor (12), and shows a temperature detection section (17) including the temperature sensor (12) and a control circuit (18).
) and a switch section (19). Platen (1
0) is detected by the temperature sensor (12) and converted into a voltage, that voltage is compared with a reference voltage by a comparator (20) in the control circuit (18), and the switch part (19) is ) transistor (
21) is turned on and off, and the heater (11) is turned on and off.

Now, the optimum temperature of the platen (10) is Tb-T in Figure 5.
When the temperature is within the range a, the target temperature is set to Tc, which is between Tb and Ta. This Tc is the control circuit (18) in FIG.
This voltage corresponds to the voltage obtained by dividing the constant voltage Vz by the resistors R3 and R4, and this voltage is input as a reference voltage to the comparator (20) and compared with the voltage from the temperature sensor (12). Then, the transistor (21) is turned on and off according to the output of the comparator (20), and the platen (10)
control so that the temperature becomes the target temperature Tc.

In FIG. 5, the control temperature fluctuates above and below Tc, and the range of the fluctuation is determined by the resistors R2 and R9 in FIG. Therefore, the resistors R2 and R9 must be selected to such values that the temperature fluctuation does not exceed the range Tb - Ta.

In the above embodiment, the heater (11) is connected to the platen (10).
Although it is built in, it may also be installed externally. Figure 6 shows an example of this, in which the heater (11) is connected to the paper guide plate (22).
Place one or two on the outside of the In this case, the paper guide plate (22) may be made of metal and used as a heat conductor to conduct the heat of the heater (11), or may be provided with an opening for heat radiation. In addition, the code|symbol (23) in the figure is a bushy roller.

In addition, as shown in Fig. 7, the heater (11) is connected to a large number of electric heating parts (
By dividing the heating element into two parts and arranging them in the axial direction of the platen (10), any part of the platen (10) can be selectively heated. Since the printing area of the platen (10) is normally biased to one side, the temperature will drop in that printing area (for example, if you print about 20 sheets of A4 size paper vertically in a row, the temperature on the left side will drop). In such a case, the area where the temperature decreases = 4- can be particularly heated.

effect According to the present invention, there are the following effects.

■ Since the platen can be kept at a constant temperature, it is possible to prevent print quality from deteriorating due to changes in platen hardness.

■ In the case of a printer that uses a type wheel, the sound of the type wheel hitting the platen becomes louder when the temperature of the platen decreases, but the noise can be reduced by warming the platen.

■ In the case of inkjet printers, printing speed can be increased because the ink can dry faster.

■ In the case of thermal printers, the amount of current applied to the print head can be reduced by controlling the temperature of the platen.

■ In the case of a thermal transfer printer, the amount of transfer ink can be adjusted.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of one embodiment of the present invention, Fig. 2 is a simplified side view thereof, Fig. 3 is a perspective view of an example of mounting a temperature sensor, Fig. 4 is an electric circuit diagram, and Fig. 5 is a diagram of the platen. It is a temperature control curve diagram. FIGS. 6 and 7 are a simplified side view and a simplified front view of other examples, respectively.

Claims (1)

[Claims] 1. A printer characterized in that it is equipped with a heat-retaining means for keeping the platen at a constant temperature. 2. The printer according to claim 1, wherein the heat retaining means includes a heater that heats the platen and a temperature control means that detects the temperature and controls on/off. 3. The printer according to claim 2, wherein the heater is built into the platen. 4. The printer according to claim 2, wherein the heater is divided into a plurality of parts and arranged in the axial direction outside the platen.