JPS58153659A - Constant flow rate control device for liquid supplying apparatus - Google Patents

Abstract

PURPOSE:To obtain the titled device which can cope with the fluctuation in minute flow rate accompanied by the change in an environment and can obtain excellent picture quality by using an ink jet printer, and wherein the state of the particle formation is observed and the pump driving is controlled. CONSTITUTION:An observing device 8 for the ink particles jetted from a nozzle 3 is constituted by a light emitting element 40 and a light receiving element 41. The phases of the passing signal (SENS signal) of the particles and the signal (US signal) of an ultrasonic vibrator 32 are compared in a circuit 50. An output Vin from the circuit is supplied to a voltage controlled oscillator 51. The oscillator 51 outputs a reference frequency f0 (=US signal) when the input voltage Vin is OV, and oscillates a frequency which is higher or lower than the frequency f0 (by DELTAf) based on whether the Vin is higher or lower than OV. The frequency (f) is inputted to a driving part 52 constituted by a solenoid, and the solenoid is driven at the equal frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant flow rate control device for a liquid supply device used in an inkjet printer or the like.

In general, an inkjet printer uses a constant flow pump because a constant flow rate supply device is required as the liquid supply device in order to uniformly form particles. However, this pump could not cope with minute fluctuations in flow rate due to changes in load, especially changes in ink viscosity due to changes in temperature.

In particular, the size of printed characters is 2 to 3 times more sensitive to the discharge flow rate of the ink supply unit (pump) (if the ink flow rate changes by 1%, the character size changes by 2 to 3%).
In order to obtain stable print dimensions, constant flow characteristics of the ink supply section are essential.Also, it is necessary to prevent printing distortion caused by many small droplets flying through the air before reaching the recording paper. , the distance between ink particles λ(
(proportional to the ink flow rate), and stabilizing this is important in accurately performing distortion correction and obtaining good print quality.

The present invention provides a constant flow rate control device that can sufficiently cope with the minute fluctuations in flow rate as described above, and in particular, it is possible to supply a constant flow rate by controlling the drive of a pump while observing the state of particle formation. This is an inkjet printer that can provide stable image quality.

The present invention will be described in detail below with reference to an embodiment of the drawings.

FIG. 1 is a diagram showing the configuration of an inkjet printer equipped with a device according to the present invention.

Reference numeral 1 denotes a drive unit for a constant flow pump 2, which is a DC solenoid in the embodiment. In addition to the DC solenoid, a drive source such as a motor may also be used.

3 is a nozzle, 4 is a charging electrode, 5 is a deflection electrode, 6 is a gutter for collecting unnecessary ink, 7 is a recording medium, 9 is an ink tank, and 10 is a control circuit for the drive unit 1, which includes a preload DC solenoid.

Further, 8 is an ink particle observation device for controlling the control circuit 10, which is composed of a light emitting element and a light receiving element, and its output changes every time a particle passes.

The constant flow pump 2 connects the cavity of the cylinder 20 to the piston 2.
1 and a diaphragm 23 to form pressure chambers 24 and 25. The plunger 22 is reciprocated by the driving unit 1, which is a DCC solenoid, so that the pressure in the pressure chambers 24 and 25 is increased or decreased.

Therefore, ink from the ink tank 9 is supplied to the pressure chamber 24 via the valve 25, and further via the valve 26 to the pressure accumulation chamber 27.
supplied to The ink supplied to the pressure accumulating chamber 27 is supplied to the nozzle 3 via the filter 30 and the electric valve 31 to be ejected, and this ink is turned into particles by the ultrasonic vibrator 32.

On the other hand, the ink collected in the gutter 6 is sucked into the pressure chamber 25 via the valve 28, and further returned to the ink tank 9 via the valve 29 through 1°.

FIG. 2 specifically shows the configuration of the ink particle observation device 8 described above.

In FIG. 2, 40 is a light emitting diode, and light emitted from the light emitting diode 40 is focused by a lens 43 and guided to a light receiving element 41 through a slit 42. In FIG.

Therefore, the output from the light receiving element 41 changes every time an ink particle passes, and this frequency becomes the same value as the atomization frequency (signal (US signal) of the ultrasonic vibrator 32), but as the flow rate changes, The phase of the detection signal changes. Therefore, by comparing the phases of a certain reference signal, that is, the US signal, and the detection signal (SEMS signal) from the light receiving element 41, the ink flow rate state can be determined.

Considering the flow rate and phase difference, the distance λ between ink particles, the particle velocity V, the US signal frequency fi, and the flow rate Q
The relationship is given by the following equation, where O8N is the nozzle cross-sectional area.

In addition, the phase difference φ (phase difference=φ, US−φBENllll+
) is given by the following equation. t is the distance between the nozzle and the sensor.

The degree of change in φ with respect to Q is μ, that is, when the flow rate Q changes by +1%, φ changes by -1%.

The phase detection between the above US signal and 5ENS signal is ±2π(r
ad)], and when expressed as -2π<x<2π, the output appears depending on the change in X. For example, sensor position z = = 30 (ms +), interparticle distance λ = 0.2 (m), the phase difference φ from the particulate signal is φ=2π7=300π (rad). Now, if this control system is working and the control error is in the range of ±π (rad), this is ±0.33% for the entire φ, and the error range for the flow rate is also 0.33%. Therefore, highly accurate control is possible.

From the above, by observing the particle passage signal (SENS signal) and comparing the phase with the US signal, it becomes possible to control the flow rate to be constant.

Specifically, a control system shown in FIG. 3 is configured.

FIG. 3 shows the control circuit 10 of FIG. 1, and 50 is a circuit for detecting the phase difference between the US signal and the SEMS signal, and an output corresponding to the phase difference is obtained.

That is, in (4) of Fig. 5), (0 is the US signal and SEM
The output state of the circuit 50 for comparing the S signal is shown in FIG.
) are in the same phase state, and at this time the circuit 50 output Vi
n is OV. ° Figure 5 (B) also shows the SEMS signal (
f) is shifted in the positive direction (f>fO), and at this time, the output vinu of the circuit 50 becomes high, and furthermore, as shown in FIG.
Q is a state in which the 5ENS signal (f) is shifted in the negative direction (
f(f.), and at this time the output Vin of the circuit 50 becomes low.

The relationship between these phase states and the output vin is also shown in FIG. 4←).

The output vin of the circuit 5o is supplied to a voltage controlled oscillator 51, and as shown in FIG. 4(a), this oscillator 51 has a reference frequency f when the input voltage Vin is Ov.

(fo=US signal), and if Vin is higher than Ov, the reference frequency f. becomes higher (Δf), and if Vin becomes lower than OV, then f. oscillates at a lower frequency.

The frequency f obtained in this manner is input to a driving section 52 (corresponding to 1 in FIG. 1) consisting of a DC solenoid, and the solenoid is driven at the same frequency.

In this case, the ink flow rate is proportional to the frequency f. Therefore, by feeding back the SEMS signal to the pump drive, it is possible to control the ink flow rate to supply a constant flow rate.

Next, FIG. 6 shows another embodiment of the particle state observation device 8 shown in FIG. 2, in which a piezoelectric element 8A is provided in the gutter 6 to extract particle collision vibration as an electric signal. Therefore, this is used as the 5ENS signal mentioned above.

In addition, the above-mentioned particle signal (US signal) is used as a reference signal.
It is also possible to use a plurality of sensors as shown in FIG. 2 and detect the phase difference between them without using the sensor.

As described above, the present invention includes a means for observing the formation period of ink particles from ink particles ejected from a nozzle, and a means for observing the formation period of ink particles observed by the means and for converting the liquid into particles at the nozzle portion. means for detecting a phase difference with a particulate signal of the pump; and means for determining a driving frequency of the pumping means based on the detection by the means, the pumping means being operated at a driving frequency determined based on the phase difference. By controlling the inkjet printer, it is possible to sufficiently cope with minute fluctuations in flow rate due to environmental changes, and to obtain an inkjet printer that can obtain good image quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an inkjet printer equipped with a device according to the present invention, FIG. 2 is a diagram showing the configuration of an ink particle observation device, and FIG. 3 is a diagram showing the specific configuration of the control circuit in FIG. 1. Figures 4 (A) and (B) are characteristic diagrams of the configuration in Figure 3, Figures 5 (G) and @), (C'l are signals indicating the operation of the phase detection circuit in Figure 3). The waveform diagram, FIG. 6, is a diagram showing seven embodiments of the observation device shown in FIG. 2. 1: Drive unit, 2: Constant flow pump, 3: Nozzle, 8: Ink particle observation device, 9 : ink tank, 10: control circuit,
32: Ultrasonic transducer, 40: Light emitting diode, 41: Light receiving element, 50: Phase detection circuit, 51: Oscillator.

Claims (1)

[Scope of Claims] 1. In an apparatus for supplying liquid from a liquid tank to a nozzle by a pump means, and ejecting the liquid into particles from the nozzle, the formation cycle of the ink particles from the ink particles ejected from the nozzle. means for detecting a phase difference between the formation cycle of ink particles observed by the means and a particle formation signal for forming liquid into particles at the nozzle portion; and pump means based on the detection by the means. A constant flow rate of a liquid supply device characterized in that the constant flow rate is supplied by means for determining a drive frequency of the pump means, and a drive frequency determined based on the phase difference. Control device.