JPH03114847A - Printer - Google Patents

Abstract

PURPOSE:To enable an automatic adjustment of printing densities by changing over an ordinary printing mode to a resistance reading mode and by setting a pulse width of printing pulse signals depending on read-out resistance values of a printing element. CONSTITUTION:Changeover is performed from an ordinary printing mode to a resistance reading mode by means of a changeover means 8, so that a connection between a printing element 2 and a power source for printing Vhd is changed over to a connection between the printing element 2 and a read means 6, whereby the means 6 reads resistance values of the element 2 to send said values to a pulse width set means 10. In the means 10 relationships between resistance values and pulse width of printing pulse signals are set in advance, whereby a pulse width control means 4 is set for a specific width based on the inputted resistance values. Thereafter, the connection with the printing element 2 is changed over to the side of the power source Vhd and adjustment of printing density is completed. As a result, dispersions of resistance values of the printing element between heads which are generated in the manufacture of heads can be automatically adjusted with ease.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to printers for analytical instruments, etc., and printers generally used for office automation equipment, such as facsimiles, and the head portion thereof is a thermal print head, an inkjet head, a wire head, etc.

The present invention relates to a printer having a printing element including a resistor.

(Prior Art) In printers equipped with thermal print heads, etc., if there are variations in the resistance values of printing elements between the head parts, if printing is performed by applying a printing pulse signal of the same pulse width to those printers, Print density varies between printers.

Conventionally, an adjustment circuit such as a volume control circuit is provided in the drive circuit of the head section, and when printing is actually performed, an operator observes the print density and uses the adjustment circuit to adjust variations in print density.

Sometimes the head is replaced, but each time the head is replaced, the print density is checked and the operator makes adjustments using the adjustment circuit.

(Problem to be solved by the invention) It requires skill for a worker to adjust the print density when shipping a printer equipped with a thermal print head, or to adjust the print density when the head is replaced. However, it is also a nuisance.

Accordingly, one aspect of the present invention provides a printer that can automatically adjust the print density to be constant in each printer even if there is variation in resistance value between head parts, thereby eliminating the troublesome adjustment. The purpose is to

(Means for solving problems) The present invention will be explained with reference to FIG.

2 is a printing element; 4 is a pulse width variable means for varying the pulse width of a printing pulse signal applied to the printing element 2 during printing;
6 is a reading means for reading the resistance value of the printing element 2, and 8 is a switching means for switching between the normal printing format and the resistance reading format. The switching means 8 is the printing element 2 in the normal printing mode.
is connected to the printing power supply Vhd, and when the resistance reading mode is used, the printing element 2 is connected to the reading means 6. Reference numeral 10 denotes a pulse width setting means for setting the pulse width of the printing pulse signal through the pulse width variable means 4 based on the resistance value of the printing element 2 read by the reading means 6.

(Function) The operation of automatically adjusting print density according to the present invention will be explained with reference to FIG.

When adjusting the print density, the switching means 8 switches from the normal printing mode to the resistance reading mode, and the connection between the printing element 2 and the printing power supply Vhd is switched to the connection between the printing element 2 and the reading means 6. It will be done. Reading means 6
reads the resistance value of the printing element 2, and the read resistance value is sent to the pulse width setting means 10. The relationship between the resistance value and the pulse width of the print pulse signal is preset in the pulse width setting means 10, and the pulse width of the pulse width variable means 4 is set based on the input resistance value.

Thereafter, the switching means 8 switches the format and switches the connection with the printing element 2 to the printing power supply Vhd side. This means that the adjustment of print density has been completed.

(Example) FIG. 3 represents one embodiment.

This embodiment represents an embodiment in which the present invention is applied to a printer equipped with a thermal print head.

Reference numeral 1 denotes a printer head, which includes a plurality of printing elements 2-1 to 2-1.
2-n are arranged. The printing elements 2-1 to 2-n are heating resistor elements. Each heating resistor element 2-1 to 2-n
heating resistor elements 2-1 to 2-n depending on the printed data.
One NAND gate 12-1~
12-n is connected. NAND gate 12-1
A flip-flop 14 is connected to one input terminal of ~12-n.
Print data is input through the input terminal, and a print pulse signal is input to the other input terminal for a period of time set by the timer 16.

A switch 18 is commonly connected to all the heating resistor elements 2-1 to 2-n, one contact 18a of the switch 18 is connected to the printing power supply Vhd for normal printing, and the other contact 18b is connected to the resistance value. As well as being connected to the constant current generator 22 when reading.

It is connected to an A/D converter 24 to read the resistance value. The switch 18 is a switch operated by a relay 19, and the relay 19 is driven via a flip-flop 20. The switch 18 is connected to the contact 18a on the printing power supply side when the relay 19 is not activated, and is switched to the resistance value reading side contact 18b when the relay 19 is activated.

Reference numeral 26 denotes a CPU that controls the printing operation of this printer, measures the resistance value when adjusting print density, and sets the pulse width of the print pulse signal.

A flip-flop 1 is connected to the bus 28 connected to the CPU 26.
4. In addition to the timer 16, flip-flop 20, and A/D converter 24, a ROM 30 that stores programs for printing operations and print density adjustment operations, and a RAM 32 that stores externally input printing data are connected. There is.

Comparing with FIG. 1, the pulse width variable means 4 has a timer 16
The switching means 8 is realized by a switch 18. The reading means 6 is realized by a relay 19 and a flip-flop 20, an A/D converter 24, a CPU 26, and a ROM 30.
The pulse width setting means 10 is implemented by the CPU 26.
Realized by ROM3 (1) and RAM32.

Next, the operation of the embodiment shown in FIG. 3 will be explained.

Adjust the print density before printing. Therefore, C.P.
The relay 19 is activated via the flip-flop 20 by the instruction from U26, and the switch 18 is switched to the contact 18b side.

Now, to explain the case where the resistance value R1 of the heat generating resistor element 2-1 is measured as the resistance value of the printer head 1, the NAND gate 12 which selects the heat generating resistor element 2-1.
The surface input is set to high level so that the output of -1 becomes GND level.

The output potentials of the other NAND gates 12-2 to 12-n are set to high level.

As a result, the constant current generator 2 is connected to the 1 heating resistor element 2-1.
A constant current flows from the heating resistor element 2-1, and a voltage is generated according to the resistance value of the heating resistor element 2-1. The CPU 26 is an A/D converter 24
The voltage is read through the heating resistor element 2-1 to determine the resistance value of the heating resistor element 2-1. The relationship between the printing density and the resistance value of the heating resistor element is set in advance in the ROM 30 as a calculation formula or table. The CPU 26 determines the pulse width of the print pulse signal from the obtained resistance value according to a predetermined relationship, and sets the pulse width in the timer 16.

Thereafter, the operation of the relay 19 is stopped via the flip-flop 20, and the switch 18 is switched to the printing power supply Vhd side. As a result, the print density FA! ! is completed.

When printing, print data for n heating resistor elements of the printer head 1 is stored in the flip-flop 14 and supplied to one input terminal of each NAND gate 12-1 to 12-n. A print pulse signal with a pulse width set to
The heating resistor element selected by the print data input to the other input terminal of the print pulse signal is energized for a time corresponding to the pulse width of the print pulse signal, thereby printing with a constant density.

With this printer, if you switch to a mode that adjusts the printing density when the power is turned on and measure the resistance value of the heating resistor element to keep the printing density constant, you can temporarily adjust the resistance of the heating resistor element. Print density can be kept constant even if the value changes due to use.

The print density can be adjusted not only when the head unit is installed in the printer and shipped, but also when the head unit is replaced after long-term use.

In addition, 1. For example, when a thermal print head is removed and an inkjet head is installed in its place, the resistance value of the printing element of the inkjet head is measured and the print density is adjusted to the optimum value based on the resistance value. can also be used.

In the embodiment, one of the plurality of printing elements of the printer head
Although the resistance value of each printing element is measured, the resistance values of a plurality of printing elements may be measured and the average value thereof may be determined.

The example uses a thermal print head, but
When using an inkjet head.

The same can be applied to the case where a wire tod head is used.

The present invention not only adjusts the print density, but also has a function that can determine that the printing element is defective if its resistance value falls outside a certain range, thereby preventing head defects or damage. It can also be detected.

The embodiment implementing each means in FIG. 1 is not limited to that shown in FIG. 3.

(Effects of the Invention) In the present invention, in addition to the normal printing mode, a mode for reading the resistance value of the printing element is provided, and both modes are switched between. Since the pulse width of the printing pulse signal is automatically adjusted so that the printing density is constant according to the resistance value, it is easy to reduce the variation in the resistance value of the printing element between heads that occurs during head manufacturing. This eliminates the need for one operator to adjust the print density during assembly.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the present invention, FIG. 2 is a flowchart showing the operation of the invention, and FIG. 3 is a circuit diagram partially showing an embodiment as a block diagram. 2...Printing element, 4...Pulse width variable means, 6...Reading means, 8...Switching means, 10...Pulse Width setting means.

Claims (1)

[Claims] (1) In a printer having a printing element including a resistor in the head section, a pulse width variable means for varying the pulse width of a printing pulse signal applied to the printing element during printing, and a reading means for reading the resistance value of the printing element. , comprising a switching means for switching between a normal printing format and a resistance reading format, and a pulse width setting means for setting the pulse width of the printing pulse signal through the pulse width variable means based on the resistance value of the printing element read by the reading means. A printer characterized by: