JPS63260451A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To prevent a liquid passage from clogging by selectively supplying recording ink and cleanser, and removing an impurity film in the passage with the cleanser. CONSTITUTION:Ink in a tank is supplied through a supply tube 5, a switching valve 4, a supply tube 2b, a pressure pump 3 and a supply tube 2a to an ink jet head 1 at the time of normal use, foamed according to the driving state of an electrothermal converter, and ink droplets are splashed from the end of a liquid passage. When impurities in a nozzle are removed, the head 1 is moved to a nonprinting area, and discharged materials from the nozzle are collected by a gutter. Then, the valve 4 is switched from the tube 5 to a supply tube 7, and the pump 3 is driven, cleanser is filled into the head, driven to be discharged at 2.5 KHz by a driver 9 to discharge the cleanser from the nozzle. The cleanser may have lower viscosity than that of the ink.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording device, and more particularly to an inkjet recording device that can prevent clogging of an orifice and/or a liquid path.

[Conventional technology]

An inkjet recording apparatus uses an inkjet recording method in which ink droplets are intermittently ejected from an orifice onto a recording paper or the like in accordance with a recording signal. A recording head commonly used in such an inkjet recording device generally includes a fine liquid ejection opening (orifice), a liquid path communicating with the orifice, an energy acting part provided in a part of this liquid path, and an energy acting part in the acting part. It comprises energy generating means for generating droplet forming energy to act on the liquid.

Energy generating means for generating such energy include recording methods using electromechanical transducers such as piezo elements, irradiating electromagnetic waves such as lasers, absorbing them into the liquid and generating heat, and the action of the heat generated. There are a recording method in which droplets are ejected and made to fly, a recording method in which an electrothermal transducer is used, and the like. Among these, inkjet recording heads that use electrothermal converters as energy generating means can have liquid ejection ports (orifices) arranged in high density to eject recording droplets and form flying droplets. Therefore, it is possible to record with high resolution. In addition, by applying recent IC technology and micro-processing technology, it has become possible to provide inkjet recording heads that are easy to implement with multiple nozzles and high-density packaging, and that are also highly productive and inexpensive to manufacture in large quantities. ing.

FIG. 3 is a perspective view showing an example of an inkjet recording head.

The recording head 101 forms an electric/thermal converter 103 and an electrode 104 on a substrate 102 using a semiconductor manufacturing process such as etching, vapor deposition, or sputtering, and a wall 105 formed between the electrodes, and a wall 105 formed between the electrodes. It is constructed by shielding the upper surface with a top plate 106. Also, the top plate 10
6 is attached with a connector 109 to which a liquid supply pipe 107 is connected, and a common liquid chamber 10B is formed at the lower part of the connector 109.

Adjacent wall 105, top plate 106, and electricity/thermal converter 1
03 forms a liquid path 110, and the opening end of this liquid path 110 is narrower than the other portion to form an orifice 111.

In the above configuration, the recording liquid (ink) 112 is supplied into the common liquid chamber 108 of the recording head 101 through the liquid supply pipe 107 from a liquid storage chamber (not shown). The liquid 112 supplied into the common liquid chamber 108 is supplied into the liquid path 110 by capillary action, and is stably held by forming a meniscus on the orifice surface at the tip of the liquid path.

Here, by energizing the electricity/thermal converter 103,
The liquid on the surface of the electric/thermal converter is heated, a bubbling phenomenon occurs, and droplets are ejected from the orifice surface 111 due to the energy of the bubbling. With the above configuration, it is possible to manufacture a multi-orifice inkjet recording head with 128 or 256 orifices with a high-density orifice arrangement such as an orifice density of 16/mm.

By the way, when recording is performed using the above-described recording head, it is important to prevent the occurrence of non-ejection in order to maintain the reliability of print quality. The following three factors can be cited as causes of this non-ejection.

(1) Clogged liquid path due to dirt, etc.

(2) Due to drying of the ink at the tip of the liquid path due to long-term non-use, the viscosity increases or the ink sticks.

(3) Foreign matter such as impurities mixed into the ink or cutting oil during equipment processing.

Among the above causes of non-discharge, a solution to factor (1) is to install a pump in the path that supplies ink to the head, and apply pressure to force the ink to be discharged from the orifice leading to the liquid path. Therefore, it is effective to remove dust. Regarding the factor (2), a) the head is sealed with a camp to prevent it from drying out, and b) the dried ink is discharged by pressurizing the pump as in the case of dust clogging. C) A method of ejecting dry ink by applying a print signal to a non-print area is effective.

Note that among the factors (3), the mixing of cutting oil and the like does not immediately cause clogging of the fluid path, but non-discharge occurs through the following process.

That is, in an inkjet head using an electric/thermal converter, as shown in FIG.
Of the heat Q given by 03, part of it goes out from the orifice together with the ejected ink droplets (Q2), and the other part is released out of the liquid path through the substrate or top plate (Q3). ), and the remaining amount of heat Ql-(Q2+Q3)
is stored in the liquid path and increases the temperature within the liquid path. As the temperature in the liquid path increases, the amount of heat dissipated also increases, so the temperature in the liquid path remains constant at a certain temperature. When the discharge is continuous and stable, this equilibrium temperature is low enough for the bubbles to disappear. However, when impurities such as cutting oil are mixed in, they are heated on the electricity/thermal converter 103 and deposited as a film. Since this becomes a heat insulating film, the amount of heat dissipated through it decreases, the temperature in the liquid path rises, and eventually the bubbles do not disappear, resulting in non-discharge.

FIGS. 5 and 6 are pulse waveform diagrams and surface temperature characteristic diagrams of the relationship between drive pulses and surface temperature when normal and when impurities are generated. As shown in FIG. 5, when the drive pulse rises, the surface temperature of the electrothermal transducer begins to rise and reaches its maximum when the drive pulse turns off. After the drive pulse turns off, the surface temperature drops and the next drive pulse turns on.
Before this occurs, the surface temperature returns to the initial temperature and prepares for the next foaming. Therefore, the surface temperature of the electric/thermal converter repeats the same temperature characteristic every time a driving pulse is applied.

However, when a film of impurities is formed on the surface of the electric/thermal converter 103 as shown in FIG. 7, the flow of heat passing through the liquid path decreases. For this reason, as shown in FIG. 6, since the surface temperature is heated by the next drive pulse before it becomes sufficiently low, the temperature rises, the bubbles do not disappear, and non-ejection occurs.

Such non-discharge does not occur when discharging is performed in the M tone even if a small amount of impurity is mixed in. The reason for this is that the impurities on the surface of the electric/thermal converter are removed by the energy of bubble generation and disappearance. It is removed and discharged to the outside of the liquid path during discharge. Therefore, no film remains on the surface of the electrical/thermal converter.

As described above, since ejection failure is likely to occur in the liquid path, sufficient countermeasures are desired in the inkjet recording head.

[Problem that the invention seeks to solve]

However, in conventional inkjet recording devices, if impurities are mixed in during unstable ejection due to dust clogging or ink sticking, the ink flow deteriorates in the electric/thermal converter, resulting in a long period of time. When the liquid is heated and a film is formed due to oxidation and fixation of impurities, the temperature inside the liquid path increases, causing non-discharge.

Once a non-ejection occurs, the heat from the ejected ink droplets does not flow out, and the cooling from new ink supply is no longer achieved, so the temperature further increases, promoting the accumulation of a film of impurities, and making the non-ejection even more severe. .

For this type of non-discharge, the film of impurities cannot be removed even if the ink is forcibly discharged by applying pressure with a pump.Also, there is a method of supplying cleaning liquid and discharging it under pressure to clean the inside of the liquid path. Various methods have also been proposed, but even with such methods, it is difficult to sufficiently remove the impurity film clinging to the surface of the electrothermal converter.

〔the purpose〕

The purpose of the present invention is to solve the above-mentioned problems of the prior art,
To provide an inkjet recording device in which a liquid path can be cleaned at any time and clogging of the liquid path can be prevented.

[Means for solving problems]

The present invention makes it possible to prevent clogging of the liquid path by selectively supplying recording ink and cleaning liquid to an inkjet recording head and removing impurity films in the liquid path with the cleaning liquid, thereby achieving the above object. It is something to do.

[Effect]

According to the above means, the cleaning liquid supplied into the head instead of the recording ink can be sent into the liquid path to remove the impurity film adhering to the inside of the liquid path, and can be discharged from the orifice communicating with the liquid path. It is possible to configure an inkjet recording apparatus that does not cause a non-ejection state.

〔Example〕

The present invention will be specifically described below with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram showing one embodiment of the present invention.

A pressure pump 3 is connected to the inkjet head I equipped with an electric/thermal converter as shown in FIG. 3 via a supply pipe 2a, and a switching valve 4 is connected to the pressure pump 3 via a supply pipe 2b. are connected. The switching valve 4 has an ink supply pipe 5.
An ink tank 6 is connected to the ink tank 6 through a cleaning liquid supply pipe 7, and a cleaning liquid tank 8 is connected to the cleaning liquid tank 8 through a cleaning liquid supply pipe 7. Further, a drive circuit 9 for applying a predetermined drive current to the electric/thermal converter is connected to the inkjet head l. The ink tank 6 contains recording ink, and the cleaning liquid tank 8 contains cleaning liquid having a lower viscosity than the recording ink.

In the above configuration, during normal use, the switching valve 4 is switched to the ink tank 6 side, and the ink in the tank flows through each of the supply pipe 5, the switching valve 4, the supply pipe 2b, the pressure pump 3, and the supply pipe 2a. The ink is supplied to the inkjet head 1 via the inkjet head 1, foams depending on the driving state of the electric/thermal converter, and ink droplets fly from the tip of the ink path. The electric/thermal converter is driven to eject at 2.5KH2 by a drive circuit 9', for example.

Ink is supplied to the nozzles by driving the pressure pump 3 at the start and end of printing, and dry ink, dust, etc. accumulated in the nozzles are forcibly discharged. Further, when printing is started or when the head is in a non-printing area even during printing, ink is ejected blankly for a predetermined number of pulses to discharge dry ink.

Next, a case will be described in which impurities inside the nozzle are removed.

First, the inkjet head is moved to a non-printing area. In this non-printing area, the ejected material from the nozzle is captured by the gutter and therefore does not reach the printing surface. Then, the switching valve 4 is switched from the supply pipe 5 to 7, and the supply pipe 2b is made to communicate with the cleaning liquid supply pipe 7. Next, after driving the pressure pump 3 and filling the head 1 with cleaning liquid,
The drive circuit 9 performs a 2.5 KHz discharge drive to discharge the cleaning liquid from the nozzle. Since the cleaning liquid has a lower viscosity than ink and is easier to eject, it is ejected even if an impurity film is formed on the electrothermal transducer that would prevent recording ink from being ejected. Then, the impurity film is removed by the energy of cavitation generated when bubbles are repeatedly generated and extinguished at high speed on the electrothermal converter, and is discharged from the head through the orifice together with the cleaning liquid.

Note that ethyl ercole can be used as the cleaning liquid. In addition, distilled water 46.9wt%, diethylene glycol 20.1wt%, ethyl alcohol 33%
A mixed solution of wt% can also be used as a cleaning solution. In short, the cleaning rate of the cleaning liquid is lower than the viscosity of the ink (
All you need is that.

Further, in the above embodiment, the recording ink or cleaning liquid is supplied to the head by the pressure pump 3, but the pressure pump may not be provided and the recording ink or cleaning liquid may be supplied by suction from the liquid path side of the inkjet head 1. .

FIG. 2 is a block diagram showing another embodiment of the invention.

In this embodiment, the same parts as in FIG. A suction pump 12 is connected to the suction cap 10 via a suction pipe 11, and a drain tank 13 is connected to the pump 12.

Next, the operation of the configuration shown in FIG. 2 will be explained.

During normal printing operation, the suction cap lO is removed from the head l, the suction pump 12 is not operated, and the supply pipe 2 to the head is connected to the ink supply pipe 5, , the ink in the tank 6 is supplied, and the drive circuit 9 performs ejection drive at 2.5 KHz.

As a result, ink droplets are ejected from the orifice communicating with the liquid path, and the ejected ink droplets fly toward the recording surface.

On the other hand, when it is desired to remove impurities, the ink jet head is first evacuated to a non-printing area, and then the switching valve 4 is switched from the supply pipe 5 to the supply pipe 7. Next, the suction cap 10 is brought into contact with the end face of the flow path of the inkjet head l, and the suction pump 12 sucks the cleaning liquid from the tank 8, filling the head with the cleaning liquid.

Subsequently, the drive circuit 9 is operated at 2.5 KH2 for a predetermined period of time to empty the cleaning liquid. After empty discharge is completed,
The switching valve 4 is switched to connect the supply pipe 2 and the supply pipe 5.

Next, the suction pump 12 is activated to fill the head 1 with recording ink again, and the printer waits in preparation for normal printing operation. The cleaning liquid and ink sucked by the suction pump 12 are discharged to a drain tank 13.

Note that the impurity removal operation in each of the above embodiments can be performed at any time, not only when a discharge failure occurs. For example, the occurrence of ejection failure can be prevented by performing the process at power-on, at the start of printing, at the end of copying, at every predetermined time, every predetermined number of prints, etc.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, recording ink and cleaning liquid are selectively supplied into the head, and the inside of the nozzle is cleaned with the cleaning liquid, so that impurities inside the nozzle can be reliably removed. , it is possible to prevent ejection failure, improve printing quality, and improve reliability of the head.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a block diagram showing another embodiment of the invention, Fig. 3 is a perspective view showing an example of an inkjet recording head, and Fig. 4 is a head Figures 5 and 6 are waveform diagrams showing the relationship between drive pulses and surface temperature during normal ejection and when an impurity film is generated. Figure 7 is a diagram showing the head with an impurity film generated. FIG. 1------- Inkjet head, 2.2a
s2b・・・-・・−・−Supply pipe, 3−・−・−−−
−・−Pressure pump, 4−・−−−−1−−−・Switching valve, 6−・−−−−−−−−−− Ink tank, 8−
・・・・−・−−1 Cleaning liquid tank, 9−・・～・−11−−−Drive circuit, 10−・・・・−−−・Absorption camp, 12−−−−−− ...-Suction pump. Agent Patent Attorney Yasushi Ooto Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

Scope of Claims: (1) In an inkjet recording apparatus equipped with an inkjet head that heats ink in a liquid path by an electric/thermal converter and ejects ink droplets from an orifice communicating with the liquid path, A means for selectively supplying recording ink and cleaning liquid is provided, and the cleaning liquid is supplied into the liquid path when impurities in the liquid path are removed, and the impurities are removed by driving the discharge of the electric/thermal converter. An inkjet recording device featuring: (2) The inkjet recording apparatus according to claim 1, wherein the viscosity of the cleaning liquid is lower than the viscosity of the ink. (3) The cleaning liquid is supplied to the head when the apparatus is powered on.Claim 1: The cleaning liquid is supplied to the head immediately before the printing operation of the inkjet recording apparatus according to claim 1. The inkjet recording device according to item 1. (5) The inkjet recording apparatus according to claim 1, wherein the cleaning liquid is supplied to the head after printing is completed. (6) The inkjet recording apparatus according to claim 1, wherein the cleaning liquid is supplied to the head at predetermined time intervals. (7) The inkjet recording apparatus according to claim 1, wherein the cleaning liquid is supplied to the head every predetermined number of prints.