JPH034394B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a printing device.

Serial printers are classified into impact type and non-impact type depending on the printing method. Typical examples of the former are wire dot printers that use wires (needles) as printing elements;
There are type matrix printers that create an impact on the type matrix itself. Known examples of the latter include inkjet printers that utilize ink droplets, discharge printers that utilize electrical discharge phenomena, and thermal printers that utilize color development due to heat, and the present invention can be applied to any type of dot printer. A wire dot printer using a wire as a printing element will be described below.

In a wire dot printer, a plurality of wires are arranged in a straight line at predetermined intervals, and the wires are selectively driven to form dots, and characters, etc. are expressed by a collection of the dots. The structure of a wire dot printer is shown in FIG. Reference numeral 1 denotes a platen, and a sheet 2 is set on the platen 1, and is intermittently subjected to a line feed operation (line feed) by a line feed means (not shown). 3 is a carrier, and this carrier is moved in the axial direction of the platen 1 by a driving electric motor, for example, a pulse motor 4. This is because when the pulse motor 4 rotates the lead screw 5, the carrier 3, which is screwed into the lead screw 5, moves linearly in the direction of arrow A. 6 indicates a guide shaft that guides the movement of the carrier 3. A printing head 7 is mounted on the carrier 3 and has a plurality of wires as printing elements. This wire is built into the print head 7 and is selectively driven by an element drive unit (not shown) such as a magnet, and presses the print paper 2 against the platen 1 via the ink ribbon 8 to form dots on the print paper. Form. The main component of the print head is a magnet.

For this reason, many insulators are used in the magnet windings and their surroundings, and since these are generally organic materials, they are weak against heat and are prone to thermal breakdown. Also,
A dot-forming wire is driven by a magnet, but the direct current resistance of the winding forming the magnet changes due to self-heating and an increase in ambient temperature, which changes the excitation current and affects the dot-forming operation by the wire.

The present invention thus provides a new printing device that eliminates various troubles caused by the heat of the printing head, and the details thereof will be explained below with reference to the drawings.

FIG. 2 shows a side view of the print head 7. A temperature sensing element 9 is fixed to the outer case of the print head 7. The temperature sensing element 9 may be built into the print head 7.

FIG. 3 is a graph showing the relationship between print head temperature and time. Assuming that the printing operation starts at time t ₀ , the print head temperature h gradually rises, and at a certain temperature h ₁ approximately becomes constant. The temperature h ₁ is a dangerous temperature and the print head 7 suffers from the various disturbances mentioned above.

Therefore, a temperature _h2 lower than the temperature _h1 is set, and if the temperature of the print head 7 exceeds _h2 , the printing operation is stopped. As a result, the temperature of the print head 7 decreases as shown by the solid line.

FIG. 4 shows its control block diagram. IFC is an interface circuit that receives print information from the outside.
Receive control information etc. PRC is a printer control circuit, which controls a carrier control section (not shown) and the like based on control information. LBF is a line buffer circuit that stores print information input via the interface circuit IFC in the form of character patterns. WDC is a wire drive circuit that drives an electromagnetic element according to the print information (character pattern) stored in the line buffer circuit LBF. Reading of print information from the line buffer circuit LBF is performed by a read signal from the printer control circuit PRC, which is sent via the gate G to the wire drive circuit WDC.

Reference numeral 9 denotes a temperature sensing element, which is made of, for example, a bimetal element BIM. As is well known, the bimetal element BIM has contacts that close when the temperature exceeds a predetermined set temperature, and open when the temperature is lower than that. The output signal of the bimetal element BIM is input to the printer control circuit PRC.

The line buffer monitoring circuit LPE monitors the memory contents of the line buffer circuit LBF, that is, it constantly monitors whether all printing information for one line has been printed, and the monitoring signal is sent to the printer control circuit.
Entering into PRC. The printer control circuit PRC has a gate G and a line buffer circuit.
Controls the transmission of LBF print information to the wire drive circuit WDC. Line buffer circuit LBF
If the print information is not transmitted from the wire drive circuit WDC to the wire drive circuit WDC, printing on the print medium is naturally stopped.

Now, one line of print information, control information (control information indicating the end of one line of print information, e.g. LF code)
When input to the interface circuit IFC, the print information is stored in the line buffer circuit LBF.
And the control information is the printer control circuit
Input to PRC, printer control circuit
Since there is no output from the bimetal element BIM, the PRC moves the carrier via the carrier drive control section and provides a read signal to the line buffer circuit LBF. Thereby, the printing information is supplied to the wire drive circuit WDC via the gate G, and printing is started. As printing continues, the temperature of the print head 7 increases accordingly, reaching the set temperature.
When h2 is reached, the contact of the bimetal element BIM closes and outputs a signal. At that time, the printer control circuit PRC calculates the logical product of the output signal of the bimetal element BIM and the monitoring signal of the line buffer monitoring circuit LPE without closing the gate G immediately after the contact of the bimetal element BIM closes.
Close.

In other words, the gate G is blocked by a bimetal element.
This is done when the BIM contacts are closed and all the printing information for one line stored in the line buffer circuit LBF has been printed, and the printing operation is stopped when the gate G is closed.

By stopping printing, the temperature of the print head 7 decreases. In addition, in bimetal element BIM, the temperature at which the contacts normally close and the temperature at which they open are approximately the same, so
Bimetal element BIM repeatedly opens and closes in a short period of time, and depending on the length of the printed information for one line, the printer may also print and stop repeatedly in a short period of time, resulting in disadvantages such as significant damage to bimetal element BIM. arise.

Therefore, in this example, the bimetal element BIM
The temperature h2 at which the contact closes and the temperature h3 at which the contact opens are made different, h2 >> h3, and the so-called hysteresis function as shown by the solid line in Fig. 3 is achieved using a bimetal element.
This is stored in the BIM so that the printing operation does not start during the time period from when the contact closes and printing is stopped until the temperature drops to a predetermined value.

As explained above, according to the present invention, the temperature of the print head can be kept below a predetermined temperature, and various problems caused by temperature rise can be eliminated. Also, instead of stopping printing based on the output signal alone when an output signal is received from the temperature sensing element, printing is stopped in response to an output that monitors the printing execution status of the printing information stored in the line buffer. Because of this, it is also possible to prevent the print information transferred from the host device and stored in the line buffer from disappearing before being printed.

[Brief explanation of the drawing]

Figure 1 is an overall schematic diagram of a wire dot impact printer, Figure 2 is a side view of the print head, and Figure 3 is a graph showing the relationship between print head temperature and time.
FIG. 4 shows a block diagram of the printer. 7...Print head, 9...Temperature detection element,
BIM: bimetal element, LBF: line buffer circuit, PRC: printer control circuit.

Claims (1)

[Scope of Claims] 1. A line buffer that stores print information, and a print control unit that reads the print information stored in the line buffer, wherein control information indicating the end of one line of print information stored in the line buffer is input. In a printing device that moves the print head space along the surface of the platen when the print head is moved, and prints the print information stored in the line buffer on the print medium in synchronization with the movement, the temperature of the print head is detected. a detection element, and a print information monitoring circuit that monitors whether or not all of the print information stored in the line buffer has been printed, and when an output signal from the temperature detection element is received, an output signal is output from the print information monitoring circuit, Printing on the print medium is stopped in response to a signal indicating that printing of all the print information stored in the line buffer has been completed, and printing on the print medium can be resumed in a state where the temperature of the print head has decreased. printing device.