JPS62130856A - Controller for exciting voltage in ink jet recorder - Google Patents

Abstract

PURPOSE:To enhance the accuracy in detecting the speed of an ink droplet, by providing a means for detecting the temperature of an ink, a means for detecting the viscosity of the ink, and a means for controlling an exciting voltage through feedback of a detection signal to a head-exciting circuit. CONSTITUTION:A signal of ink temperature detected by an appropriate ink temperature detector and a signal of ink viscosity detected by an appropriate viscosity detector are inputted to a CPU 22, and the evaporating rate of the ink is calculated. Next, the ink cutting distance Lb at that time is calculated from the temperature and the evaporating rate. Based on the difference between the ink cutting distance Lb and a reference Lbo, an exciting voltage (DELTAVp) by which a voltage Vp is to be corrected is determined, and a signal indicating this quantity is fed back to a sine wave generating and amplifying circuit 16 to correct the voltage Vp, whereby it is possible to obtain the condition of Lb=Lbo.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excitation voltage adjusting device for an inkjet recording apparatus.

Figure 7 is a block diagram for explaining an example of an inkjet recording device (Japanese Unexamined Patent Publication No. 59-41273) previously proposed by the present applicant.As is well known, the ink cartridge 1
The ink in the ink tank 13 to which the ink tank 4 is attached is sucked by the pump 1 and is force-fed to the accumulator 2. The pressure vibration of the pressurized ink sent to the accumulator 2 is suppressed by the accumulator 2 and the filter 3, and the ink ejecting head 4
leading to. In the ink ejecting head 4, as is well known, the electrostrictive vibrator is excited at a constant frequency and a constant amplitude to apply pressure vibrations at a constant frequency and a constant amplitude to the ink within the head. As a result, ink is ejected from the nozzle of the head 4, and due to this pressure vibration, the ejected ink separates into particles at a position that has advanced a predetermined distance from the nozzle. This particle formation corresponds to pressure vibrations applied to the pressurized ink in the head 4, and the ejected ink is formed into particles at a rate of one ink droplet per cycle of pressure vibration. By applying a voltage to the charging electrode 5 in synchronization with the timing at which the ejected ink is turned into particles, the turned ink particles have an electric charge.

Charged ink particles and uncharged ink particles are formed depending on whether or not a charging voltage is applied to the electrode 5 as the ink becomes particles.

The charged ink particles are deflected by the electric field of the deflection electrode 6 and collide with the recording paper 7, but the uncharged ink particles go straight and hit the gutter 8.
The ink collides with the ink, is sucked by the pump 11 through the filter 1o, is discharged into the air vent tank 12, and returns to the ink tank 13.

FIG. 8 is a diagram showing the configuration of an electrical system that energizes each mechanical element shown in FIG. 7 and performs charge recording control. applies excitation electricity Vp.

A charging signal amplifier circuit 17 applies a pulsed charging voltage Vc to the charging electrode 5, and a deflection voltage generating circuit 1 applies a pulsed charging voltage Vc to the deflection electrode 6.
8 applies a constant level of high voltage -Vd. One end of a core of a shielded wire 9 is connected to the conductive gutter 8, and a charge detection circuit 19 is connected to the other end of the core. Pumps 1 and 11 are pump drivers 15 and 2, respectively.
It is electrically energized at 0. In this case, in order to charge the ink at a predetermined timing in detecting the flying speed of ink particles (ink pressure search), and in order to apply a search pulse voltage to the electrode 5 in a phase search in which the center of the charging voltage pulse is aligned with the separation phase of the ink particles. , and a timing pulse generator 26 for ink pressure retrieval in order to apply recording charge voltages with stepwise different levels to the electrodes 5 during printing recording.
Search charge signal generator 25 and record charge signal generator 24
are provided, and signals from these generators are selectively applied to the charge signal amplification circuit 17 by the gate circuit 23. The operation timing of each part of the electric circuit is controlled by a pulse generator 21.
is determined based on a plurality of types of timing pulses generated, and the microcomputer 22 performs energization and control of each part.

In the ink droplet speed control in the charge control type inkjet recording apparatus as described above, the time from when the ink droplet is charged until the droplet enters the gutter is used as a substitute value for the speed. Also.

It is known that the distance from when a droplet is charged to the gutter, that is, from when the ink exits the nozzle until it is cut into droplets, greatly contributes to this control accuracy. That is,
Even if the droplet speed is the same, if the ink cutting distance (hereinafter abbreviated as Lb) changes due to changes in ink temperature and evaporation rate,
The timing of charging changes, and as a result, the time from charging to the gutter changes.

However, in the above-mentioned inkjet recording device, the ink droplet velocity is determined by the time it takes for the ink droplet to arrive at the charged gutter and the distance between the charging electrode and the gutter, and the ink droplet velocity is determined by changes in temperature and evaporation rate. Since changes in cutting length are not taken into consideration, the accuracy of speed detection is poor.

Purpose The present invention was made in view of the above-mentioned circumstances.
Particularly, the purpose of this invention is to improve the detection accuracy of ink droplet speed in controlling the ink droplet speed in a charge-controlled inkjet recording apparatus.

In order to achieve the above object, the present invention provides a charge control type inkjet recording device that continuously ejects ink droplets from a nozzle and performs recording by selectively charging and deflecting the ink droplets. The apparatus is characterized by comprising means for detecting temperature, means for detecting ink viscosity, and means for feeding back these detection signals to the head excitation circuit to adjust the excitation voltage. Hereinafter, the present invention will be explained based on examples.

The present invention aims to improve the accuracy of ink drop flight speed control by always keeping the ink drop cutting distance constant regardless of the ink conditions (temperature, evaporation rate).

Figure 4 shows the relationship between ink temperature and ink viscosity when the ink evaporation rate is used as a parameter, and Figure 5 shows the relationship between the ink pressure and head excitation voltage when the ink evaporation rate is used as a parameter. A diagram showing the relationship between the ink temperature and the ink cutting distance (Lb) in the no-satellite state (however,
Evaporation rate A>B), Figure 6 is a diagram showing the relationship between the head excitation voltage (Vp) and the ink cutting distance (Lb).The curve in Figure 6 varies vertically or horizontally depending on the temperature and evaporation rate. However, it is known that the slope of the linear portion between ■ and ■ is almost constant.

FIG. 1 is a block diagram showing the configuration of an electrical system for explaining one embodiment of an inkjet recording apparatus according to the present invention, and FIG. 2 is a flow chart for explaining control operations. Parts that function similarly to the illustrated circuit are given the same reference numerals as in FIG. 8.

Accordingly, in the present invention, the CPU 22 in FIG. 1 is provided with the relationship shown in FIGS.
b (Lbo) and the slope ■ of the straight line portion are input as memory. The ink temperature signal detected by an appropriate ink temperature detection device and the ink viscosity signal detected by an appropriate viscosity detection device are imported into the CPU 22.1. The evaporation rate of the ink is calculated from the relationship shown in FIG. 4. Lb at that time is calculated from the relationship shown in FIG. 5 from the zero-order temperature and evaporation rate.

Then, the excitation voltage (Δ
vP) is determined, and the signal is sent to the sine wave generation and amplification circuit 16.
By feeding back the VP, it is possible to correct the VP, and as a result, Lb=Lbo.

Effect Figure 3 shows the relationship between Lb fluctuation and charging efficiency (the amount of charge induced in a droplet per charging voltage of 1 V).As Lb becomes shorter, the charging efficiency decreases due to the edge effect of the charging electrode, and as a result, the character size decreases. becomes smaller. Conversely, when Lb increases, the charging efficiency increases due to the influence of the deflection electrode, and as a result, the character size increases.However, by keeping the Lb constant according to the present invention, the accuracy of such character size can be improved. I can do it.

[Brief explanation of drawings]

FIG. 1 is an electrical block diagram for explaining an embodiment of an inkjet recording apparatus according to the present invention, and FIG.
A flowchart for explaining the control operation according to the present invention, FIG. 3 is a diagram showing the relationship between Lb fluctuation and charging efficiency, FIG. 4 is a diagram showing the relationship between ink temperature and ink viscosity, and FIG. 5 is a diagram showing the relationship between ink temperature and ink viscosity. , FIG. 6 is a diagram showing the relationship between head excitation voltage and ink cutting distance, and FIGS. 7 and 8 are diagrams that show the relationship between ink temperature and ink cutting pressure. 6 is a block diagram of a mechanical system and a block diagram of an electrical system for explaining an example of an inkjet recording apparatus according to the present invention. 3.10...Filter; 4...Ink jet head;
5... Charged electrode, 6... Deflection electrode, 7... Recording paper, 8... Conductive gutter, 9... Shield wire, 12...
... Air vent tank, 13... Ink tank, 14... Ink cartridge, 26°°° timing pulse generator, 2
7... Ink pressure adjustment circuit, 30... Ink viscosity detection device. Patent applicant: Ricoh Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure M & 7

Claims (1)

[Claims] In a charge-controlled inkjet recording device that continuously ejects ink droplets from a nozzle and performs recording by selectively charging and deflecting the ink droplets, means for detecting the temperature of the ink and means for detecting the viscosity of the ink. 1. An excitation voltage adjustment device for an inkjet recording apparatus, comprising: and means for feeding back these detection signals to a head excitation circuit to adjust the head excitation voltage.