JPS5952076B2 - Thermal printing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal printing method employing a preheating method.

2. Description of the Related Art In a thermal printing method using a heating head equipped with a large number of dot-shaped heating elements, a preheating method is already known in which the heating head is preheated during printing standby to increase printing speed.

However, in the conventional preheating method, the head substrate is preheated while the heating head is always kept in contact with the thermal paper during standby and printing. Therefore, the preheating temperature is naturally limited to a temperature at which the thermal paper does not develop color even if the thermal paper and the heating head are in contact for a long time during standby. In other words, if the temperature at which the moving thermal paper is heated by a heating element during printing and develops color is called the coloring temperature, then in the conventional method, the preheating temperature (the temperature of the head substrate heated for preheating) and the coloring temperature Since there is a large difference in temperature, it takes time for the heating element to reach the coloring temperature after electricity is applied to the heating element during printing. In order to shorten this time, it is necessary to increase the amount of heat generated by each heating element during printing, that is, the applied current value, or to decrease the transport speed of the thermal paper. In the former case, the power consumption of the entire heating head becomes large. In addition, there are two known methods for preheating conventional heating heads: using a heater separate from the heating element for printing, and using the heating element itself for printing, but in both cases, the printing cycle during printing is Since the preheating cycle and preheating cycle are performed overlappingly, a large amount of power is consumed at once.

By the way, for example, ticket vending machines installed at Obekai stations are flooded with a large number of passengers, especially during rush hours, so there is a constant demand for increased ticket printing speed, and the conventional thermal preheating method At present, some printing methods are still unsatisfactory.

Thus, an object of the present invention is to provide a thermal printing method with significantly improved printing efficiency, that is, a thermal printing method in which printing speed is further increased and power consumption is reduced.

The first feature of this invention is that the heating head is kept away from the thermal paper during standby.

This makes it possible to increase the preheating temperature of the heating head to a temperature at which color will develop if the heating head is brought into contact with the thermal paper for a longer time than the contact time with the moving thermal paper during printing. This preheating temperature is naturally much higher than the preheating temperature in the conventional method in which the heating head and the thermal paper are in constant contact. The shorter the contact time for one printing, for example in the case of ticket printing, the greater the difference between the upper limit of the preheating temperature in this invention and the upper limit of the preheating temperature in the conventional method. . Therefore, the time from the preheating temperature to the color development temperature during printing is shortened, so the printing speed is increased. The second feature of this invention is that if the preheating temperature is set so that the heating head and the moving thermal paper are brought into contact for a longer time than the contact time between the heating head and the moving thermal paper during printing, color will develop. This is due to the fact that the temperature was set to such a level.

When the preheating temperature is set above the above-mentioned temperature, while the heating head is in contact with the moving thermal paper during printing, color will also develop in heating elements and their surroundings other than the heating element that is energized for printing. This causes the printed content to become unclear. The above temperature then makes it possible to obtain the maximum printing speed within the printing properties of the thermal paper used and to obtain a reasonable print quality. The third feature of this invention is that preheating is stopped at the same time as the heating head is brought into contact with the thermal paper during printing. The purpose is to perform conventional printing using thermal elements.

Since preheating is stopped at the same time as the heating head contacts the thermal paper during printing, the temperature of the head substrate does not reach the coloring temperature due to the amount of heat generated from the heating element energized for printing. Therefore, the power is turned on. This skillfully prevents printing quality from deteriorating due to color development on the thermal paper in areas other than the heated heating elements. Furthermore, since preheating is stopped during printing, current is applied only to the heating elements necessary for printing, so a large amount of power is not consumed at once. Furthermore, even if preheating is stopped, the head substrate is maintained at a temperature close to the preheating temperature due to the heat generated by the heating elements used for printing. This last effect is stable when printing something that takes a short printing time and has a moderate character density, such as a ticket. In the printing method according to the present invention, the preheating temperature is limited to a strict range in relation to the outside temperature, the printing characteristics of the thermal paper, the moving speed of the thermal paper, the contact time of the heating head and the thermal paper, etc. .

Therefore, it is desired that the preheating temperature (that is, the temperature of the head substrate) or the amount of heat generated by the heating element can be arbitrarily adjusted in relation to the above conditions. Methods for adjusting the preheating temperature include a method of adjusting the current value applied to the heating circuit and a method of adjusting the application time. Next, we will explain a specific example of the method of the present invention using a printing control device that employs each of the above two preheating temperature adjustment methods in a method of preheating using the dot-shaped heating elements themselves, based on the drawings. This will be explained in detail.

1 and 2 show an example in which the first method of preheating temperature adjustment is adopted, and FIGS. 3 and 4 show an example in which the second method is similarly adopted. In FIG. 1, H is a heating circuit formed by connecting a large number of series circuits of dot-shaped heating elements H, , H2 to Hn and switching elements Swl, sw2 to Swn in parallel to one common conducting wire COM;
A is a switch circuit formed by connecting in parallel a printing power switch PSW and a bias power switch BSW having a bias adjustment circuit BC, and the two parallel circuits H and SW
a are connected in series.

The printing power switch PSW and bias power switch B
The SW preferably consists of two electronic switching elements, such that when one is turned ON, the other is turned OFF.
An interlock switch can be used. Further, a fixed resistor, a variable resistor, a transistor, etc. can be used for the bias adjustment circuit BC. In order to keep the preheating temperature constant throughout the seasons, it is preferable to use a transistor. In addition, in FIG. 1, ES represents the parallel circuit H,
This is a power supply connected in series to SWa. HC is a heat generation control circuit connected to each switching element of the heat generation circuit H, and when it receives a preheating command signal from the main control circuit MC, it gives a long conductive signal to all the switching elements, and prints from the main control circuit. When a signal is received, a short conductive signal is given only to the heating element selected according to the printed content. In this way, when the printing press is powered on, the main control circuit MC gives a preheating signal to the heat generation control circuit HC, so this circuit HC gives a conduction signal to all the switching elements Swl, sw2 to Swn. .

At this point, the switch circuit SWa is normally in the bias power supply switch BS as shown in the figure.
Since W is set to 0N, a bias current having a value lower than the current value applied during printing is uniformly applied to all heating elements by the bias adjustment circuit BC. Therefore, the head substrate is heated at a uniform temperature. Since such a thermal bias is applied during standby, the temperature of the head substrate tends to rise even if the applied current value during standby is lower than that during printing. Therefore, by providing the bias adjustment circuit BC, the temperature of the head board during standby, that is, the preheating temperature, can be adjusted to
The temperature is set such that the thermal paper does not develop color even if the heating head and the thermal paper are in contact for a time equal to the contact time during printing, but develops color if they are in contact for a longer time than the contact time. In this way, when the printing machine in the standby state satisfies the printing start conditions, the main control circuit MC
outputs a print start signal, which is applied first to a heating head lifting means (not shown) and secondly to the switch circuit SWa.

The means for raising and lowering the heating head is a commonly used means such as a solenoid, and the heating head is held apart from the thermal paper during printing standby, and based on the printing start signal,
Bring the heating head into contact with the thermal paper. Further, the switch circuit SWa is operated based on the print start signal, and turns off the bias power switch BSW and turns on the print power switch PSW. Further, the main control circuit MC outputs the print start signal and at the same time the heat generation control circuit HC
Stop outputting the preheating signal that was being given to the Main control circuit MC
In order to apply a matrix signal of characters, etc. read from a storage unit storing characters, etc. to be printed to the heat generation control circuit HC as a print signal, following the output of the print start signal,
This circuit HC provides a conductive signal only to the switching element corresponding to the content of the print signal. The printing power switch P
Since the SW is currently set to 0N, the current necessary for printing flows through the heating element connected to the switching element to which the conduction signal is applied. Since the heating head substrate has been preheated to a temperature close to the color development temperature, the energized heating element reaches a high temperature in a shorter time than before. Therefore, even if the moving speed of the thermal paper is increased, sufficient color development and clear printing results can be obtained. That is, printing speed is significantly increased. While the main control circuit MC is outputting a print signal,
Preheating by heating circuit H has been stopped, but since many heating elements generate heat at the coloring temperature for printing during printing, the temperature of the head board is almost the same as during preheating due to the excess heat. is maintained.

When printing is completed in this way, the main control circuit MC activates the switch circuit by canceling the print start signal that was given to the switch circuit SWa during the print cycle, or by giving a new print end signal to the switch circuit SWa. The operating state of the circuit SWa is changed, the bias power switch BSW is turned ON, and the printing power switch PSW is turned OFF.

Furthermore, upon completion of printing, the main control circuit MC again provides a preheating signal to the heating control circuit HC, and as a result, the heating circuit H returns to the initial preheating cycle during standby. The heating circuit H'' of the control device shown in FIG. 2 consists of one switching element S.
Multiple heating elements Hal, Hb in wl, sw2 to Swn
Parallel circuits of 1, Ha2, Hb2 to Han, Hbn are connected in series, a large number of the series circuits are connected in parallel, and the heating elements of each series circuit are connected to a plurality of common conductors COM1, C.
It is configured by being connected in parallel to OM2. In the switch circuit SWb in this case, the printing power switch PSW and the bias power switch BSW can be switched in three stages in conjunction with each other, and the printing power switch PSW is connected to the first common conductor C.
When 0N is applied to OMl or the second common conductor COM2 side, bias power switch BSW is turned OFF, and switch PS
When W is turned 0FF, switch BSW is turned 0N and the first
, a bias current is allowed to flow through both of the second common conductive lines COM1 and COM2. And main control circuit MC
has the function of controlling the printing power switch PSW depending on which heating element group of the first common conducting wire or the second common conducting wire is used for printing. With this configuration, during standby, the bias power switch BSW is turned ON, and heat is generated at a uniform temperature from all heating elements. Therefore, it is possible to make the preheating temperature higher when the heating head is separated from the thermal paper. Subsequently, the control device shown in FIGS. 3 and 4 applies a current equal to the current value applied during printing to all heating elements sequentially and for a short time during preheating.
The periodic application preheats the substrate during standby. The heating circuit H in FIG. 3 has the same configuration as the embodiment in FIG. 1, and includes a switch circuit SWc and one common conductor COM.
In this case, the switch circuit SWc is composed of one power switch PSW. It is not necessary to provide the switch circuit SWc. A ring counter or other pulse generating circuit PG, which is operated by a preheating signal from the main control circuit MC and periodically generates pulses, is connected to the heat generation control circuit HC'. This pulse generating circuit can arbitrarily adjust the frequency of the pulses it generates. With this configuration, during printing standby, the heating head (not shown) is separated from the thermal paper by known means based on a signal from the main control circuit MC, and the power switch PSW is turned ON.

In addition, the pulse generating circuit PG periodically generates pulses in response to a preheating signal from the main control circuit MC, which is used for heat generation control.
From all terminals of circuit HC' to all switching elements SW, SW of heating circuit H. ~SWn sequentially and periodically as a conduction signal. Therefore, all the heating elements generate heat uniformly, preheating the head board. This preheating temperature is used to adjust the frequency of the pulse generation circuit PG. The temperature is set such that the thermal paper does not develop color even if the heating head is brought into contact with the thermal paper for a time equal to the contact time during printing, and the paper develops color when the heated head is brought into contact for a time longer than the contact time. The upper limit value is due to changes in outside temperature, errors in thermal paper conveyance speed, and heating temperature. It is determined by taking into consideration errors in contact time, etc. The heating circuit H' in FIG. 4 has the same structure as the embodiment shown in FIG. 2, and the switch circuit SWd has the same structure as the switch circuit SWb in FIG. 2 except that the bias power switch BC is removed.

The action of the main control circuit MC on the switch circuit SWb is the same as that shown in FIG. However, main control circuit MC, pulse generation circuit PG, heat generation control circuit HC'
The operation between the heating circuit H' and the heating circuit H' is the same as in the embodiment shown in FIG. According to the above two embodiments, all of the heating elements for printing are instantaneously, sequentially and periodically energized to preheat, so that less power is consumed at once.

Furthermore, since preheating is performed by applying a current equal to the current value applied during printing, the electric circuit for heating is simplified. The present invention is not limited to preheating using heating elements for printing, but also includes cases where preheating is performed at a predetermined temperature using a heater other than these.

In this case, in order to keep the preheating temperature constant regardless of changes in the outside temperature, if a heater with an automatic temperature compensation circuit such as a thyristor is used, a high printing speed and excellent printing quality can be maintained at all times. As described above, according to the present invention, printing efficiency can be significantly improved compared to conventional methods.

[Brief explanation of the drawing]

The drawing shows a circuit diagram of a printing control device used to implement the method of the invention.

Claims (1)

[Scope of Claims] 1. In a thermal printing method using a heating head equipped with dot-shaped heating elements, (a) the heating head is held away from the thermal paper during printing standby, and the heating head is kept in contact with the thermal paper for a long time during printing. The head substrate is preheated to a temperature that will produce color if it is kept in contact with the thermal paper for a longer period of time, and (b) when printing, the preheating is stopped and the heating head is brought into contact with the thermal paper at the same time. , a thermal printing method characterized in that printing is performed using the heating element. 2. Preheat the head substrate by instantaneously and periodically applying a current equal to the current value applied to the dot-shaped heating elements for printing to all of the heating elements for printing during standby. Claim 1 characterized in that
The thermal printing method described in section. 3. The thermal printing method according to claim 1, wherein the preheating temperature can be arbitrarily adjusted by adjusting the frequency of the conductive signal for applying current to the heating element.