JPS6256152A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To enhance the detection accuracy of an ink droplet speed in the control of the ink droplet speed in a charge control type ink jet recording apparatus, by calculating an ink cutting distance from the viscosity of ink detected by a viscosity detector and correcting the ink droplet speed detected from the calculated value. CONSTITUTION:Almost linear relation is present between the viscosity mu of ink and an ink cutting distance Lb when a head was fixed at a constant droplet speed under constant exciting voltage. A proper ink viscosity detector 30 is provided between a gutter 8 and a pump 11 and the inclination (a) of the viscos ity muo of the ink and the cutting distance Lb of the ink at a reference time, the distance Xo between charge and the gutter 8 at the reference time and the time to taken from the charge to the gutter 8 at the reference time are preliminarily inputted to CPU22. When the time (t) between when an ink droplet is charged and reach the gutter is input CPU22 in order to control the ink droplet speed, the viscosity mu' of the ink simultaneously detected at that time by the viscosity detector 30 is input and processed by CPU22. Thereafter, t' and to are compared to control the pressure of the pump.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording apparatus, and more particularly to control of ink droplet velocity in a charge-controlled inkjet recording apparatus.

Fig. 4 is a block diagram for explaining an example of an inkjet recording device (Japanese Unexamined Patent Publication No. 59-41273) proposed earlier by the present applicant, and as is well known, the ink cartridge 14 The ink in the ink tank 13 in which the ink tank 13 is attached is sucked by the pump 1 and sent under pressure 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 reaches the ink ejecting head 4. As is well known, in the ink ejection head 4, the electrostrictive vibrator is excited at a constant frequency and a constant amplitude, and applies pressure vibrations at a constant frequency and a constant amplitude to the ink within the head. 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 the pressure vibrations applied to the pressurized ink in the head 4, and the ejected ink is formed at one rate per cycle of pressure vibration.
The ink particles are divided into particles.

The charging electrode 5 is connected to the timing when the ejected ink becomes particles
The ink particles formed into five particles by applying a voltage to the 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, while the uncharged ink particles go straight and collide with the gutter 8, pass through the filter 10, are sucked by the pump 11, and are discharged into the air vent tank 12. and ink tank 1
Return to 3.

FIG. 5 is a diagram showing the configuration of an electrical system that energizes each mechanical element shown in FIG. 4 and performs charge recording control. applies excitation voltage Vp.

A charging signal amplifier circuit 17 applies a pulsed charging voltage Ve to the charging electrode 5, and a deflection voltage generating circuit 18 applies a pulsed charging voltage Ve to the deflection electrode 6.
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 electrically powered by pump drivers 15 and 20, respectively. In this case, in order to charge the ink at a predetermined timing during ink droplet flying speed detection (ink pressure test), a test pulse voltage is applied to the electrode 5 during a phase test in which the center of the charging voltage pulse is aligned with the separation phase of the ink droplets. The electrode 5 is used for applying a recording charge voltage of different levels stepwise during printing and recording.
A timing pulse generator 26. for ink pressure measurement is applied to the timing pulse generator 26. A test charge signal generator 25 and a recording charge signal generator 24 are provided, and signals from these generators are selectively applied to the charge signal amplification circuit 17 by a gate circuit 23. The operation timing of each part of the electric circuit element is determined based on a plurality of types of timing pulses generated by a pulse generator 21, 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. Furthermore, it is known that variations in the ink cutting distance greatly contribute to this control accuracy. Even if the velocity of 9 droplets is the same, the ink cutting distance (hereinafter abbreviated as Lb) may vary depending on the ink temperature and evaporation rate. ) changes, the timing of charging changes, and as a result, the time from charging to the gutter changes.

However, the above inkjet recording apparatus.

The ink drop velocity is defined as the time it takes for the ink drop to arrive at the charged gutter and the charge 1! This is determined based on the distance between the electrode and the gutter, and does not take into account changes in the cut length of the ink due to changes in temperature evaporation rate, so the accuracy of speed detection is not good.

Mame-15 This 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.

Structure In order to achieve the above object, the present invention includes an ink droplet generator having one or more nozzles, a charging electrode that selectively charges each ink droplet, and a deflection electrode that deflects the charged ink droplet. In an inkjet recording device that performs printing by colliding the electrically deflected ink droplets with a recording paper, the inkjet recording device includes an ink viscosity detection device, an ink droplet speed detection device, and an ink viscosity detection device and an ink droplet velocity detection device. and a storage device having a relational expression as a memory, the ink cutting distance is calculated from the ink viscosity detected by the viscosity detection device, and the detected ink droplet velocity is corrected from the calculated value. be. An explanation will be given below based on one embodiment of the present invention.

The present invention deals with L when the temperature and evaporation rate change as described above.
The variation in b is calculated and the time from charging to the gutter is corrected and used as a substitute value for the droplet velocity, thereby improving the accuracy of ink droplet flying velocity control.

Figure 3 shows the relationship between ink viscosity μ and cutting distance Lb when the head is fixed at a constant droplet velocity and constant excitation voltage.
The relationship between the ink viscosity μ and the cutting distance Lb is almost linear,
Multiply by Lb illusion aμ+b (a and b are constants). Also, a
, b are values specific to the head under conditions of constant drop velocity and constant excitation voltage.

FIG. 1 is a block diagram showing the configuration of a mechanical system for explaining an embodiment of an inkjet recording apparatus according to the present invention, and FIG. 2 is a block diagram showing the configuration of an electrical system. 4 and 5 have the same reference numerals as in FIGS. 4 and 5.

In the present invention, as shown in FIG. 1, a suitable ink viscosity detection device 30 is provided between the gutter 8 and the pump 11.
In addition, the CPU 22 in FIG. 2 has previously calculated the ink viscosity μ0 at the reference time, the slope a of the straight line in FIG. 3, the distance between the charge and the gutter at the reference time In order to control the droplet speed, when the time t from when an ink droplet is charged to when it reaches the gutter is input into the CPU 22, the ink viscosity detected by the viscosity detection device 30 at that time is also input. Take μ′ and divide by two. Then, the CPU 22 performs the processing, and then compares t' with t and O.

Control pump pressure.

As is clear from the above explanation, according to the present invention, it is possible to improve the control accuracy of the flying velocity V of ink droplets, thereby improving the printing quality, and also improving the reliability of the head. There are advantages such as improved performance.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a mechanical system for explaining an embodiment of an inkjet recording apparatus according to the present invention, and FIG.
Figure 3 is a block diagram of the electrical system. Figures 4 and 5 are diagrams showing the relationship between ink viscosity and ink cutting distance, and are mechanical block diagrams and electrical block diagrams for explaining an example of an inkjet recording device previously proposed by the applicant. It is a diagram. 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, 27... Ink pressure adjustment circuit, 30... Ink viscosity detection device. Patent applicant Ricoh Co., Ltd. 1m1 diagram

Claims (1)

[Claims] An ink droplet generating device having one or more nozzles, a charging electrode that selectively charges each ink droplet, and a deflection electrode that deflects the charged ink droplet, and records the electrically deflected ink droplet. An inkjet recording device that performs printing by colliding with paper, has an ink viscosity detection device, an ink droplet velocity detection device, and a storage device that stores a relational expression between ink viscosity and ink column cutting distance, An inkjet recording apparatus characterized in that an ink column cutting distance is calculated from the ink viscosity detected by the ink viscosity detection device, and the detected ink droplet velocity is corrected based on the calculated value.