JPS61268452A - Nozzle clogging detection for ink jet recorder - Google Patents

Abstract

PURPOSE:To utilize 'wait' time to detect nozzle clogging with the help of an ink droplet out phase detection means by charging ink droplets on a charging signal having a longer time width than the (t) cycle of vibration applied to ink and detecting their existence with a detection electrode. CONSTITUTION:A pressurized ink is injected through a nozzle 3 and at the same time, a vibration of fixd cycle is applied to the ink. Then it is charged by a charging electrode 7 the moment when it is atomized into droplets. At that time, the time width of the charging signal is made longer than a single cycle of vibration applied to ink by an electric distortion vibrator 4. That is, the m-1 pieces of ink droplets are charged by making the time width of the charging signal on the charging electrode 7m times as much as a single cycle of an exciting signal (a) by the electric distortion vibrator 4. The ink droplets collide with a detection electrode 11 after being deflected, releasing the electric charge to be transmitted by a detection circuit 12. If no detection is made by the detection electrode 11, it is judged as clogging. Thus it is possible to utilize the conventional ink droplet cut phase detection means as such and detect any clogging by utilizing 'wait' time until a stable state after the making of a power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to multi-nozzle charge deflection type inkjet recording and a method for detecting nozzle clogging in the apparatus.

(Prior Art) Generally, in a charge deflection type inkjet recording device, pressurized ink introduced into a liquid chamber is ejected as an inkjet stream from a nozzle communicating with this liquid chamber, and at the same time, a constant periodic vibration is applied to the ink. In synchronization with this, the leading edge of the inkjet flow is sequentially formed into droplets, forming a continuous flow of ink droplets. At the moment the ink droplets are formed into droplets, they are selectively charged by a charging electrode, and the charged ink droplets are deflected by a deflection electrode and fly, colliding with the recording medium to adhere and print, while uncharged ink droplets travel straight. and captured in the gutter for reuse.

Among such charge deflection type inkjet recording devices,
A multi-nozzle type with multiple nozzles has 1
If the nozzle becomes clogged at any time, normal printing will not be possible. In models with a small number of nozzles, if even one nozzle becomes clogged, the ink pressure changes, making it possible to detect clogging, but in models with a large number of nozzles, the ink pressure changes. Therefore, it is difficult to detect clogging.

2. Description of the Related Art Conventionally, there is a recording apparatus equipped with so-called ink droplet cutting phase detection means for detecting whether or not the timing of forming an inkjet stream into droplets and charging by a charging electrode is appropriate.

This is a method in which a specific ink droplet is charged, a detection electrode is placed on the trajectory -L of the deflected ink droplet, and it collides with the ink droplet to detect whether or not it is charged normally. If the ink drop is present, it will not reach the sensing electrode because it will not be charged and therefore not deflected. Therefore, the timing is adjusted so that normal charging is performed.

If this ink drop cutting phase detection is performed for all nozzles, it is possible to detect nozzle clogging at the same time.

(Problems to be Solved by the Invention) However, detection of the cutting phase of ink droplets must be performed after the recording device, which has been powered on, is stable in a steady state and ready for printing operation. Normally, this is done for only one or a small number of nozzles, but if this is done for all nozzles, there is a problem in that it requires a considerable amount of time and results in a large hourly loss.

41 The present invention utilizes the cutting phase detection means of ink droplets as is, and makes effective use of the waiting time until the recording device is turned on and stabilized in a steady state to detect the presence or absence of clogging in all nozzles. That is.

(Means for solving the problem) Any one or more consecutive ink droplets of the formed ink droplets are charged by a charging signal having a time width longer than at least one period of vibration applied to the ink. Then, this charged ink droplet is detected by a detection electrode. This operation is performed sequentially for all nozzles.

(Function) Even if the recording device is still in an unstable state after the power is turned on, and the timing of ink droplet digestion and charging by the charging electrode is different, the time width will be longer than one cycle of the vibration applied to the ink. If the ink droplet is charged by the charge signal, at least one ink droplet will definitely be charged, and this should be detected by the detection electrode. If this is not detected, it means that the nozzle that ejected the ink droplet is clogged. become.

(Example) Embodiments will be described in detail below based on the drawings.

FIG. 1 shows an embodiment of the present invention. Reference numeral 1 denotes an inkjet head, which has a liquid chamber 2 into which pressurized ink is introduced from an ink supply system (not shown). Reference numeral 3 denotes nozzles communicating with the liquid chamber 2, and a plurality (n) of nozzles are arranged in a horizontal line at equal intervals. Reference numeral 4 denotes an electrostrictive vibrator, which is fixed to a diaphragm 5 constituting one side of the liquid chamber 2, and to which an excitation signal of a constant period is applied by an AC power source 6. Reference numeral 7 denotes a charging electrode provided independently corresponding to each nozzle 3, and each charging electrode 7 is connected to a charging signal generating circuit 8, respectively. 9a and 9b are a pair of deflection electrodes, one of which is the deflection electrode 9;
A high voltage is applied to a to deflect the charged ink droplets. Reference numeral 10 denotes a gutter that collects non-charged ink droplets, and the collected ink droplets are returned to the ink supply system as recovered ink for reuse. Reference numeral 11 designates a detection electrode that is arranged on the flight trajectory of the charged ink droplets as necessary to detect the charged ink droplets, and 12 is a detection circuit thereof. 13 is a C P TJ that controls the charge signal generation circuit 8 .

Next, the operation of this embodiment will be explained. First, to explain the normal recording operation, pressurized ink introduced into the liquid chamber 2 of the inkjet head 1 is ejected as an inkjet stream from n nozzles 3, and at the same time is transmitted through the diaphragm 5 by the electrostrictive vibrator 4. A constant period of vibration is applied to the ink. The tip of the inkjet flow is sequentially converted into droplets in synchronization with the applied vibration, resulting in a flow of ink droplets that fly at regular intervals. The ink droplet is selectively charged by the charging electrode 7 at the moment it is formed into a droplet, and the charged ink droplet is charged by the deflection electrode 9a.
, 9b, the ink drops collide with and adhere to a recording medium (not shown), forming a single character, while uncharged ink droplets travel straight and are collected by the gutter 10 and collected.

It is necessary to charge the ink droplets at the moment when the tip of the inkjet stream is formed into droplets, and even if a charging voltage is applied after the tips of the inkjet streams are formed into droplets, they are not charged. However, since it is necessary to selectively charge only the targeted ink droplets, the charging signal must be a pulse with a time width narrow enough not to affect adjacent ink droplets. Therefore, the timing of forming the ink droplets and applying the charging voltage is extremely important. In order to detect whether or not this timing is appropriate, the ink droplets that are charged and deflected as necessary are received by the detection electrode 11, and the electric charge held by the ink droplets is extracted and measured by the detection circuit 12, which is the so-called ink droplet cutting phase. Detection methods are conventionally known. This detection result is CPU13
If the timing needs to be adjusted, the charge signal generation circuit 8 is controlled to adjust the timing. However, it is meaningless to perform this detection when the recording apparatus is in an unstable state after power is turned on, and it is necessary to perform this detection after the apparatus has stabilized in a steady state and is ready for printing operation.

Next, a method for detecting nozzle clogging will be explained.

In this case, the time width of the charging signal is set to be longer than at least one cycle of the vibration that the electrostrictive vibrator 4 applies to the ink. Now, as shown in FIG. 2, the time width of the charging signal b1 applied to the first charging electrode 7 corresponding to the first nozzle 3 is equal to the duration of the excitation signal a applied to the electrostrictive vibrator 4. Taking m times one period ensures that at least m-1 ink droplets are charged regardless of the cutting phase of the ink droplets.

The charged ink droplets are deflected by the deflection electrodes 9a and 9b and collide with the detection electrode 11, emitting charges and transmitting the signal to the detection circuit 12. If the detection electrode 11
If there is no detection of a charged ink drop at , the first nozzle is clogged. After clogging detection for the first nozzle is completed, the same detection operation is performed for the second nozzle. Third. ...
, for the n-th nozzle. That is, the second. Third
．． ..., a charging signal b21b31...l having a time width m times the period of the excitation signal a is sequentially applied to the n-th charging electrode.
bn is applied to charge the ink droplet, and it is determined whether the charged ink droplet can be detected by the detection electrode 11. If even one of the nozzles 3 is detected to be clogged, printing will not begin.

FIG. 3 shows an example of the configuration of the detection circuit 12.
To explain the operation using FIG. 4, an ink droplet charged by the charging signal collides with the detection electrode 11, and the charge released there is integrated by the capacitance C of the shielded cable 14 and the input resistance R. This becomes input signal C. This input signal C is amplified by an amplifier 15, and its output signal d
is input to the comparator 16 and compared with the reference voltage -Vref, and in the region below this reference voltage, the comparator 16
The output is obtained. This output signal e is converted into a TTL level signal f by the switching circuit 17 and transmitted to the CPU. Note that the polarity of the signal is not limited to this.

(Effects of the Invention) As explained above, according to the present invention, at least one ink droplet is charged by a charging signal having a time width longer than one cycle of vibration applied to the ink, and this ink droplet is transferred to the detection electrode. If the nozzle that ejected the ink droplet is detected by The presence or absence of clogging can be detected. Moreover, this detection can be performed by using the conventional means for detecting the cutting phase of ink droplets as is, and by effectively utilizing the waiting time for the device to stabilize in a steady state after power is turned on. There is no time loss, incomplete printing can be prevented, and waste of recording paper can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a multi-nozzle charging deflection type inkjet recording apparatus to which an embodiment of the present invention is applied, FIG. 2 is a diagram showing the relationship between the excitation signal waveform and the charging signal waveform, and FIG. 3 is a diagram showing the relationship between the excitation signal waveform and the charging signal waveform. FIG. 4, a configuration diagram of the detection circuit, is a signal waveform diagram of each part in the detection circuit. 1... Inkjet head, 2... Liquid chamber,
3... Nozzle, 4... Electrostrictive vibrator, 7...
-Charging electrode, 8...Charging signal generation circuit, 9a, 9b
... Deflection electrode, 11... Detection electrode, 12... Detection circuit. Figure 1 1 Isokune/Tohe 7 Do 2 ・；Liquid surprise 3 ノ Also ゛1 Eclipse, 9b Embezzlement 4 was cunning 11” experiment was 4L murder 12 Renbai old man

Claims (3)

[Claims] (1) It has a plurality of nozzles that communicate with the liquid chamber, and a vibrator applies vibrations at a constant frequency to the pressurized ink introduced into the liquid chamber, and the inkjet flow ejected from each nozzle is synchronized with the vibrations. an inkjet head that converts the ink droplets into droplets to form a continuous flow of ink droplets; a charging device that selectively charges each of the ink droplets; a deflection device that deflects the charged ink droplets; and a deflection device that deflects the charged and deflected ink droplets. In a multi-nozzle inkjet recording apparatus equipped with a detection means for detecting, one or more continuous ink droplets that have been formed into droplets are charged with a charging signal having a time width longer than at least one cycle of the vibration; The method is characterized in that the operation of detecting charged ink droplets by the detection means is performed for each nozzle in sequence, and the nozzles in which charged ink droplets are detected are determined not to be clogged, and the nozzles in which the charged ink droplets are not detected are determined to be clogged. A method for detecting nozzle clogging in an inkjet recording device. (2) The nozzle of the inkjet recording apparatus according to claim 1, wherein the detection means also serves as means for detecting whether the timing of forming and charging the ink droplets is appropriate. clogging detection method. (3) The inkjet recording apparatus according to claim (1), wherein the operation of detecting clogging of the nozzles is performed using a waiting time until the recording apparatus stabilizes after power is turned on. How to detect clogged nozzles.