JPS58108165A - Ink jet printer - Google Patents

Abstract

PURPOSE:To obtain an ink jet printer capable of outputting high-quality pictures without imposing burden to charge power source and pump by adjusting the drive frequency of the pump when a charge voltage necessary for obtaining a desired deflection reaches a set upper or lower limit voltage. CONSTITUTION:In an ink supplier 5, ink is supplied to an ink jet head 1 by a reciprocally driven quantitative flow pump, and ink collected by a garter 4 is recovered. Ink droplets injected at a charge electrode 2 are selectively charged according to a picture information and deflected by a polarizing electrode 3, and the deflection is detected and controlled by charge voltages by means of a charge voltage controller 7. Also, when a charge voltage necessary for obtaining a desired deflection reaches a preset upper limit voltage, the drive frequency of the pump is lowered within the range of 0.5%, and also when it reaches a present lower limit voltage, that of the pump is rasied within the range of 0.5% by means of a controller 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved inkjet printing apparatus.

A charge deflection type that uses a reciprocating constant flow pump to supply ink under pressure to the inkjet head, ejects this ink as ink droplets from the nozzle of the inkjet head, and selectively charges and deflects the ejected ink droplets for printing. In an inkjet printing device, there are generally the following three methods for adjusting the amount of deflection of charged ink droplets.

The first is the pump pressure control method, which changes the speed of the ink droplet ejected from the nozzle and therefore changes the residence time when passing through the deflection electrode, thereby changing the amount of deflection. However, this method requires the pump to have a wide flow rate adjustment range, and has the drawback that the response speed is slow because the ink supply path is an elastic body and has fluid resistance.

Next, regarding the charging voltage control method, this method is usually adopted and has a fast response speed. However, the charging voltage adjustment range is large, and if the charging voltage is too high or too low, deflection distortion occurs and image quality deteriorates.

The other method is a deflection voltage control method, but it is difficult to control with high precision, and there is a risk of electric discharge if the deflection voltage is increased.

Note that a method of detecting the amount of deflection by arranging a detection electrode on or close to the trajectory of the deflected ink droplets is known.

The present invention eliminates the drawbacks of the prior art described above, and the amount of deflection is adjusted mainly by controlling the charging voltage. To provide an inkjet printing device which adjusts the driving frequency of a pump when the voltage reaches a certain voltage, and obtains high image quality without imposing any burden on a pop or a charging power source. Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, in which 1 is an inkjet head, and 2 is a device that selectively charges ink droplets ejected from the inkjet head 1 according to image information. A charging electrode 3 is a deflection electrode that deflects charged ink droplets, 4 is a gutter that collects ink droplets that are not charged and travels straight, and 5 is an ink supply system that supplies ink to the head 1, and the gutter 4 captures the ink droplets. An ink tank that collects collected ink and refills with new ink, a reciprocating constant flow pump that sends out ink, a 7-cumulator that smooths out pulsating flow, a filter that controls ink, and an on/off control for ink supply. Contains electromagnetic pulp, etc.・
6 is a deflection amount detection electrode that detects the amount of deflection of an ink droplet; 7 is a charging voltage control device that receives the detection result of the deflection amount and controls the charging voltage to obtain the required amount of deflection; 8 is a charging voltage and a reference voltage. This is a comparator that compares the voltage, and has a predetermined upper limit voltage and lower limit voltage as reference voltages. 9 is a pump drive frequency control device.

Next, the operation of this embodiment will be explained. Figure 2 shows the relationship between the charging voltage and the amount of deflection. Curve A is for the case where the inkjet printing device is in the standard state. At this time, if the ink droplet is charged at the standard charging voltage VcaK, the standard The amount of deflection can be obtained. However, this is an ideal situation, and in reality, ink droplets may be caused by changes in the pump flow rate due to environmental temperature changes, changes over time, changes in the physical properties of the ink, dirt on the electrodes, misalignment of the head, electrodes, recording medium, etc. The kinetic energy, charging efficiency, deflection electric field, etc. change, and therefore it is necessary to adjust the charging voltage to obtain the required amount of deflection. Therefore, when the flow rate of the pump decreases, the deflection electric field increases, or the charging efficiency increases, the curve shifts to curve B@ in FIG. 2, and at this time, the charging voltage is lowered in order to obtain the standard deflection amount.

However, when the charging voltage becomes lower than VC2, deflection distortion appears, so Vc2 is set as the lower limit voltage, and when the charging voltage reaches the lower limit voltage VC2, the pump drive frequency control device is activated by the output from the comparator 8. , increase the pump drive frequency within a range of 0.5%.

Further, when the state of the printing device shifts to C@ due to a cause opposite to that on the curve B side, the charging voltage is increased to obtain the standard deflection amount. However, when the charging voltage exceeds Vct, deflection distortion appears, so this Vcl is set as the upper limit voltage, and when the charging voltage reaches Vcl K, the pump drive frequency is lowered within 0.5 inch.Vcl
, ve2 is 1ηl2ηyu=Tachihicho 0.1Vell
Set vca.

In the case of a reciprocating constant flow pump, the response speed is generally slow, although it depends on the volume of the accumulator. However, if the amount of change in the drive frequency is increased, the volume of the print will change due to changes in the ink flow rate (for example, in the case of a serial printer, the maximum deflection height is 5 to 6 mm, and the flow chamber conversion rate is When the deflection height is 1%, the deflection height changes by a certain amount), and the flow rate change rate is 0.
If it is 5 inches or less, the height fluctuation of the print will be almost indistinguishable in a reciprocating constant flow pump with a slow response speed. - As explained above, according to the present invention, when the charging voltage required to obtain the required deflection amount reaches the predetermined upper limit voltage or lower limit voltage, the driving frequency of the reciprocating constant current pump By adjusting the charging voltage, the charging voltage can be kept within the range from the upper limit voltage to the lower limit voltage.
Therefore, it is possible to print high-quality images without causing deflection distortion or placing a burden on the charging power source or pump.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention;
FIG. 2 is an explanatory diagram of the operation. 1 ・・・・・・・・・ Inkjet head, 2
・・・・・・・・・Charged electrode, 3・・・・・・・・・
Deflection electrode, 4...Gutter, 5...
...Ink supply system, 6...Deflection amount detection electrode, 7...Charging voltage control device, 8...Comparison Vessel, 9...
...Pump drive frequency control device.

Claims (1)

[Claims] An ink supply device that supplies ink under pressure to an inkjet head using a reciprocating constant flow pump, a charging electrode that ejects ink droplets from a nozzle of the inkjet head and selectively charges the ink droplets, and a charging electrode that deflects the charged ink droplets. In a charged deflection type inkjet printing device, which is equipped with a deflection electrode that deflects the deflected ink droplet, and a device that detects the deflection amount of the deflected ink droplet and controls the deflection amount using a charging voltage, the deflected ink droplet obtains the required deflection amount. . When the required charging voltage reaches a predetermined upper limit voltage, the driving frequency of the reciprocating constant flow pump is lowered within a range of 0.5%, and when the charging voltage reaches the predetermined lower limit voltage. An inkjet printing apparatus characterized by comprising means for increasing the driving frequency of the reciprocating constant flow pump within a range of 0.5 seconds.