JPS6153232B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording apparatus, and more particularly to an inkjet recording apparatus in which sub-scanning feed is step feed.

In facsimile, scanning is based on the same principle for both transmission and reception, and is divided into main scanning and sub-scanning (feeding). The main scanning of the receiving device is
A received image is formed directly from electrical signals representing pixels, and sub-scanning is an operation in which the sub-scanning is slightly shifted in a direction perpendicular to the main-scanning.

For example, in the case of cylindrical scanning, a small synchronous motor is used as the drive source, and the rotation of the motor is reduced by a worm gear and a helical gear before being transmitted to the rotation transmission shaft.

Generally, feeding in the sub-scanning direction is carried out by moving the feeding guide part by little by rotating the feed screw shaft.
Move the cylinder in the feed direction. However, especially in facsimile, a step motor is used because there is no cumulative error due to mechanical causes in the reproduced image for feeding in the sub-scanning direction.

In addition, multiple heads are often used to improve recording speed or to record color images, but problems such as overlapping images and color misalignment require more step feed than analog sub-scanning. This can improve accuracy.

On the other hand, when an inkjet recording device is used for facsimile reception, the recording paper can be plain paper, is inexpensive, can print extremely quietly, and can print up to 500
It is attracting attention because it is capable of high-speed printing at characters per second and can perform multicolor recording using multiple nozzles.

The inkjet recording method includes a method in which an electric signal is applied to a piezoelectric element attached to the head and ink particles are ejected using only the pressure waves generated by the electric signal (for example, the ink-on-demand method), or a method in which ink particles are ejected from the ink supply system. A method in which ink is continuously ejected from the nozzle by applying pressure, and ink particles are sent in any direction by applying voltage to the deflection electrode provided at the tip of the nozzle (pressure excitation method)
etc. These methods differ in whether or not they require pressure pumps, deflection electrodes, and high voltage.
In either case, a tank is filled with ink, and the ink is supplied from an ink passage through a filter to a nozzle in the head.

By the way, when such an inkjet recording device is used in facsimile, it is particularly important to use a head that ejects ink using pressure waves accompanying changes in the volume of a pressurized chamber within the head (for example, an ink-on printer).
When step feed is used for sub-scanning (on a demand-type head), the sudden movement causes an impact force on the head, which can cause ink to drip from the ink jet orifices or cause instability in jetting due to air being mixed in. become.

When recording by placing a head, tank, etc. on a scanning table, the influence of vibration due to acceleration and deceleration during step feeding is large, and air enters from both sides of the nozzle, reducing jet performance. Furthermore, even when only the head is mounted on the scanning table, the influence of vibration is quite large.

The purpose of the present invention is to eliminate such drawbacks and to prevent ink dripping from the jet orifices and air intrusion from the jet orifices that occur during step feed in an inkjet recording device that uses step feed for sub-scanning. The purpose is to prevent it.

Hereinafter, details of the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram of an inkjet recording apparatus showing an embodiment of the present invention.

The drum 1 is rotated in the main scanning direction 40 by the main scanning motor 3, and the timing belt 5 is moved by the step motor 4, which is a sub-scanning motor.
is fed in steps in the sub-scanning direction 41. ink·
When ink is supplied from the tank 9 through the tube 8, the piezoelectric element (piezo crystal) vibrates due to the electric signal applied through the lead wire 11, and a pressure wave proportional to the electric signal is generated, causing the head 20 to vibrate. Ink particles are ejected from the nozzles and are printed on recording paper held by a paper presser 2 on a drum 1.

In FIG. 1, only the head 20 is mounted on the support stand 6, but the ink tank 9, tube 8, etc. may all be mounted thereon.

For ink-on-demand methods, head 20
An electric signal is applied to a piezoelectric element attached to a piezoelectric element, and ink particles are ejected only by the pressure waves generated by the electric signal, and the ink is supplied only by capillary action without applying pressure. Therefore, if vibrations are applied to the head during acceleration and deceleration of step feed, ink may move through the tube 8 and drip from the nozzle, or air may enter the nozzle, resulting in poor jetting performance. will decrease.

In the present invention, a solenoid valve 10 is connected in the middle of the tube 8 between the ink tank 9 and the head support 6, the solenoid valve 10 is closed immediately before the step feed operation, and the solenoid valve 10 is closed immediately after the step feed operation. By opening the tube 8, the ink in the tube 8 is prevented from moving even if vibrations are applied by the feeding operation. FIG. 2 is a detailed cross-sectional view of the ink supply system of FIG. 1.

In the injection head 20, the piezo crystal 27 is distorted in response to the electrical signal from the electrode 22.
Causes resonance.

Vibration plate 2 due to vibration of piezo crystal 27
8 vibrates, as a result of which the ink in the inner chamber 24 is pressurized and ink droplets are ejected from the ejection port 25. In such an inkjet recording apparatus, for example, when one line of printing on the main scanning drum 1 is completed and the printing line simultaneously passes the paper presser bar 2 and moves to the next line within a predetermined time,
Vibration occurs due to acceleration and deceleration of step feed.

In FIG. 2, the vibration direction is perpendicular to the plane of the paper.

In order to reduce the influence of vibration caused by step feeding, the solenoid valve 10 closes the valve immediately before the scanning table 6 moves to block the movement of ink between the ink tank 9 and the ink head 20, and prevents the scanning table 6 from moving. Immediately after moving, open the valve and remove ink tank 9 and ink head 2.
0 and introduces the ink into the chamber 23 outside the head 20.

FIG. 3 is a block diagram showing a control system of the solenoid valve shown in FIG. 2.

When the electromagnetic valve control circuit 30 receives the control signal 33, the electromagnetic valve control circuit 30 uses its output to drive the valve drive control section 31 to close the electromagnetic valve 10. At this time, control signal 3
3 is also sent to a delay circuit 34, which drives the pulse motor 4 with an output slightly delayed from when the solenoid valve is closed. After a certain period of time after the solenoid valve is closed, the step motor 4 finishes its operation and before the electric signal is sent to the electrode 22 of the head 20, the valve drive control section 3
1 to open the solenoid valve 10.

For example, the solenoid valve 10 may be a device that opens and closes by the electrical action of a well-known coil, or a valve drive control unit 3.
1 includes a well-known voltage application circuit that controls the coil to apply a constant voltage, and a solenoid valve control section 3.
0, a well-known microcomputer etc.
Each can be used.

Even if vibration is applied to the head 20 due to step feeding, the ink in the tube 8 is shut off by the solenoid valve 10, so air is not mixed in from the head injection port 25, and the amount of ink is reduced.

As explained above, according to the present invention, since the ink supply between the head and the ink tank is opened and closed immediately before and after step feed, smooth printing is possible during the recording time, and the step feed time is It is possible to reduce the influence of vibration and prevent ink from dripping from the ejection port and air from entering the ejection port.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the mechanism of an inkjet recording device showing an embodiment of the present invention, Fig. 2 is a detailed cross-sectional view of the ink supply system shown in Fig. 1, and Fig. 3 shows the control system of the solenoid valve shown in Fig. 2. FIG. 1...Drum, 2...Paper presser, 3...Main scanning motor, 4...Sub-scanning motor, 5...Timing
Belt, 6...Head support stand, 7...Support rod, 8
...Tube, 9...Ink Tank, 10...
Solenoid valve, 11...Lead wire, 20...Head, 2
2... Electrode, 23... Outer chamber, 24... Inner chamber, 25... Injection port, 26... Connection passage, 27...
...Piezo crystal, 28...Diaphragm, 29...
...Ink, 30...Solenoid valve control section, 31...Valve drive control section, 32...Step start signal.

Claims (1)

[Claims] 1. In an ink-on-demand type inkjet recording device in which an electric signal is applied to a piezoelectric element attached to a head to generate a pressure wave and ink particles are ejected, and the sub-scanning feed is a step feed, the ink storage A means for opening and closing the ink supply path flowing into the tube is provided in the middle of the ink tube that connects the ink tube to the head, and the opening and closing means closes the ink supply path immediately before the sub-scanning step feeding operation, and the ink supply path is closed immediately before the sub-scanning step feeding operation. An inkjet recording device characterized in that the inkjet recording device is controlled so that the ink supply path is opened immediately after the inkjet recording device.