JPH0686124B2 - Printer head drive voltage adjustment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drive voltage adjusting method for a printer head, such as an inkjet printer, in which the drive voltage of a printer head needs to be adjusted.

(B) Conventional Technology Conventionally, an ink jet printer, which is an example of a rotary drum scanning type printer, employs a head driving method as disclosed in JP-A-58-45984.

That is, the head driving method will be described with reference to FIG. 3 and the following drawings. FIG. 3 shows a schematic configuration of an ink jet type color printer.
The four ink heads (4), (5), (6), and (7) are shared by the support member (head) so as to face the outer periphery of the rotating drum (3) rotated by the belt (2). It is supported by a carriage (8). The ink heads (4), (5), (6), and (7) respectively eject yellow, magenta, cyan, and black ink droplets toward the recording paper on the rotating drum (3) to record each color. Ink heads (4), (5),
The attachment positions (or ink droplet ejection positions) of (6) and (7) to the support member (8) are different in the circumferential direction of the rotating drum (3), but are the same in the axial direction. .

In addition, the support member (8) includes two pulleys (9),
It is connected to the wire (11) wound between (10),
Pulse motor (12) connected to one pulley (9)
The support member (8) intermittently moves from left to right.

Further, in the rotary encoder (13) connected to the rotary drum (3), as shown in FIG. 4, the rotary drum (3) has a predetermined angle (recording density on the circumference of the rotary drum (3), that is, 1). Pulse signals A and B, which generate one pulse each time it rotates (corresponding to a dot), and a rotating drum (3)
A pulse signal Z in which one pulse appears each time the gyro rotates once
The pulse signals A and B are different in phase from each other by 90 °, and identify the rotation direction of the rotary drum (3).

Then, the rotary drum (3) is rotated by the servo motor (1) to perform main scanning, and the pulse motor (12) supports the ink heads (4), (5), (6) and (7). Move (8) left and right to perform sub-scanning,
In the meantime, each ink head (4), (5), (6),
A signal is given to (7) to eject ink droplets, and predetermined recording is performed.

This recording is performed by applying an AC voltage to the ink heads (4) when ejecting ink droplets and not applying an AC current when ink droplets are not ejected. In this way, the drive of the ink heads (4) ... Is controlled with or without applying an alternating current.

By the way, in the ink head, the ink ejection state changes depending on the peak and the peak value of the applied AC voltage, and the shape of dots formed on the paper surface changes. The manner of this change is unique to each head. In order to keep the recording quality above a certain level, the dot shape on the recording paper must be optimum. Therefore, it is necessary to add an AC current having an optimum peak and peak value to each ink head (4).

FIG. 4 shows a conventional ink head drive circuit. FIG. 4 is for driving one ink head, and in order to drive four ink heads, four same circuits are required.

The inputs of (A) and (B) input to the operational amplifier (01) are pulses having a certain fixed width. Then, the operational amplifier (01) and the resistors (R1), (R2), (R3) constitute addition and subtraction. Also, an operational amplifier (02) and a resistor (R4),
(R5), capacitors (C1), and (C2) are low-pass filters, and the same circuit is provided in the subsequent stage. The pulses of (A) and (B) input to the operational amplifier (01) become a pseudo sine wave at point D, which is the output of the operational amplifier (03), due to the adder / subtractor circuit and the two-stage low-pass filter.
This is shown in FIG. 4 (b). The operational amplifier (04) functions as a buffer and sends the output at point D to the amplifier circuit at the next stage through the resistor (R10). The output waveform at point D is uniformly amplified by the amplifier circuit and drives the ink head. The semi-fixed resistor (VR1) adjusts the positive and negative amplitudes of the pseudo sine wave with respect to the GND level so that they are equal. The peak and peak value E of the output waveform at point D is the operational amplifier (01) (02)
The voltage that can be obtained by the circuit using (03) is divided by (R8), (VR2), and (R9) and input to the operational amplifier (04). This voltage divider circuit limits the peak and peak values and is adjusted by a semi-fixed resistor (VR2).
That is, the pseudo sinusoidal AC voltage applied to the ink head is adjusted by the semi-fixed resistor (VR2). This adjustment must be performed after mounting the ink head on the printer, performing test recording, and observing the condition of the recording quality. And the AC voltage of the output terminal (Z) can be monitored by the test pin (TP).

(C) Problems to be Solved by the Invention Conventionally, in this type of printer, the drive voltage of the head is adjusted as follows. The range of possible peaks and peak values at the output terminal (Z) voltage is empirically from 2.0V to 0.
It is 8V. First, monitor the test pin (TP) with a synchroscope. After that, semi-fixed resistance (VR2) so that the voltage at the output terminal (Z) changes in steps of 0.1V from 2.0V to 0.8V.
Adjust. Then, the recording quality is checked every 0.1 V, and the voltage with the best quality is set as the optimum voltage for that head,
After that, drive at that voltage.

However, this adjustment is frequently performed every time the head is replaced, not only at the time of manufacturing and assembling the printer, but also at the time of service maintenance, so that workability is extremely poor. In addition, it is necessary to have an instrument that can monitor the voltage of the synchroscope, etc., and because the semi-fixed resistance is turned while adjusting the voltage to be measured, there is a problem that there is variation between adjustments and accurate adjustment cannot be performed. It was

(D) Means for Solving the Problems The present invention is a printer head drive voltage adjustment method for controlling the drive of a printer head according to the voltage applied to the printer head, wherein an adjustment value of the drive voltage composed of digital data is digitally adjusted. It is characterized in that it is input to an analog converter, a reference current value is subjected to predetermined integration processing corresponding to the input value, and the drive voltage of the printer head is set based on the integration value.

(E) Operation According to the present invention, the drive voltage can be adjusted in accordance with the input value only by inputting the adjustment value composed of digital data.

(F) Example Hereinafter, one example of the present invention will be described with reference to FIG.
FIG. 1 shows an ink head drive circuit to which the present invention is applied. In this figure, the circuit composed of operational amplifiers (01) (02) (03) is the same circuit as that shown in FIG. The operational amplifier (04) and the resistors (R8) (R9) form a non-inverting amplifier circuit. The operational amplifier (04) amplifies the AC voltage at the output point D of the operational amplifier (03) up to a peak-to-peak voltage of 3.2V. The output from the operational amplifier (04) is a resistor (R10) (R1
1) via a digital-to-analog converter (hereinafter D / A
It is called a converter. ) (10) Input terminal (IN). The present invention uses this D / A converter (10) to adjust the drive voltage. That is, the D / A converter (10) operates as follows. Assuming that the current input to the input terminal (IN) is Io, the drive voltage adjustment value is 8 from B _{0 to} B ₇ .
It is controlled by bit digital input data and output from the output terminal (OUT). The value indicated by 8 bits is 10
Assuming that X is a decimal number, this value can be in the range of 0≤X≤255. Then, the output current becomes X / 256I ₀ . Vref applied to one end of the resistor (R11) is a reference voltage, and the resistor (R11) creates a reference current. The resistor (R10) converts the AC voltage at the output F point of the operational amplifier (04) into an AC current and inputs it to the D / A converter (20). Since this D / A converter (20) is a current control type, the output at point G is in the form of a change in current value, and the operational amplifier (05), resistor (R12), semi-fixed resistor (VR
The circuit in 3) performs current-voltage conversion. Operational amplifier (0
Since the voltage waveform of the output (H) of 5) has a form in which a DC bias component is added, the DC is cut by the capacitor (5) and input to the buffer of the operational amplifier (06). The peak and peak values of the AC voltage at point F, which is the output of the operational amplifier (04), are 3.2V, and this D / A converter (20) uses an 8-bit digital input to operate in 3.2V / 256 = 12.5mV units. AC voltage value can be controlled. With the Z output, the voltage may be controlled in steps of 0.1V, and in this case, 256-step voltage control is sufficient with 32-step control. With this, 3.2V / 32 ＝
With 0.1V, it will be possible to control the peak and peak value of the AC voltage in units of 0.1V. This can be achieved by ignoring the lower 3 bits of the 8-bit digital input. In that sense, the 3-bit inputs of B _{0 to} B ₂ are connected to the ground. Experiential driving voltage of ink head is 0.8V
Because it is ~2.0V B ₃ ~B ₇ input data D1~D5 to the terminal is set in the DIP switch or the like so that the voltage value of the range. For example, at 0.8V Therefore, when X = 8, D5-D1 are set to "01000", and when 2.0V, Therefore, when X = 20, D5 to D1 are set to "10100". D1 ~ D5
Is actually output from the combination circuit of the rotary DIP switch and the arithmetic circuit.
It can be easily done by turning the DIP switch. The semi-fixed resistor (VR3) is used to adjust the conversion ratio of the current-voltage conversion circuit, and is adjusted so that the peak and peak of the AC voltage at the Z output are exactly 0.1V steps. This D / A converter (20) has an orthodox type,
For example, DAC-08 can be used. Connect the synchroscope to the test pin (TP) when assembling and manufacturing the printer, and adjust the semi-fixed resistors (VR1) and (VR3) accurately. Once this adjustment has been made, the drive voltage value that is adjusted each time the ink head is mounted during subsequent manufacturing / assembly or service maintenance does not require a synchroscope as in the past, but a 0.8V rotary DIP switch is used. Can be easily set to any voltage in the range of to 2.0V. As a result, the workability is significantly improved.
Also, there is no variation between adjustments, and it is possible to make accurate 0.1V increments at any time. In addition, the digital data is suitable for being handled by a micro computer, and the ink head drive voltage can be made variable for each dot.

In the above-described embodiment, the ink jet printer has been described as an example, but the present invention is not limited to this, and the invention can be applied to a printer that requires adjustment of the drive voltage of the printer head.

(G) Effect of the Invention As described above, according to the present invention, the drive voltage of the printer head can be easily adjusted by only inputting the digital data, and the workability is greatly improved.

[Brief description of drawings]

FIG. 1 is a printer head drive circuit diagram to which the invention is applied, FIG. 2 is a schematic configuration diagram of an inkjet printer, FIG. 3 is a waveform diagram of a pulse signal output from a rotary encoder, and FIG. 4 is a conventional printer. It is a head drive circuit diagram. 01,02,03,04,05,06 …… operational amplifier, 20 …… D / A converter.

Claims (1)

[Claims] 1. A printer head drive voltage adjustment method for controlling drive of a printer head according to a voltage applied to the printer head, wherein an adjustment value of a drive voltage composed of digital data is input to a digital-analog converter, and the input value is input. Corresponding to, the reference current value is subjected to predetermined integration processing, and the drive voltage of the printer head is set based on the integration value.