1. Field of the Invention
The present invention relates to an ink jet recording apparatus and a discharge recovery method thereof. More particularly, the present invention relates to an ink jet recording apparatus, a discharge recovery method, and its cleaning medium, this apparatus having means for recovering its defective discharge or non-discharge, which means includes a sheet-like cleaning medium.
2. Related Background Art
An ink jet recording apparatus exhibits a multiplicity of advantages such that noise to be generated during its recording performance can be limited to a satisfactory low level and it can use plain paper at the time of recording. Therefore, it attracts a great attention.
In particular, a so-called ON-DEMAND type of ink jet recording apparatus uses a piezoelectric element or a magnetostrictive element each of which is an electromechanical transducing element or an exothermic resistance element which is an electrothermal transducing element. It performs recording by discharging ink from its discharge ports by rapidly applying a pressure to the ink positioned in an energy acting chamber thereof or in the vicinity thereof at the time of performing the recording. It exhibits a great advantage such that it does not need to be provided with any means for recovering unnecessary ink or a high potential power source for polarization. The reason for this lies in that it consumes ink by discharging an ink droplet as needed for performing recording.
As described above, the ink jet recording apparatus exhibits various advantages. However, it can generate cloggings due to adhesions of dust or paper dust generated from the recording paper, invasion of air bubbles into the inside of the discharge port, or increase in the viscosity of the ink due to the evaporation of the ink positioned in the vicinity of the discharge port. As the case may be, ink can be dried and solidified.
Therefore, it is critical for the ink jet recording apparatus to perform proper treatments (abbreviated to ink jet recovery treatment) for the purpose of overcoming these various factors which can deteriorate the recording quality.
A method is well known, as the method of recovering the ink jet, that an ink absorber made of a polymeric porous material or the like is pressed to the discharge port (for example, see U.S. Pat. No. 4,223,322). According to this method, utilizing a fact that ink which has been brought into contact with the ink absorber is taken out through the jetting port due to a capillary phenomenon, the above-described ink whose viscosity has been increased or the air bubbles can be, together with the thus-taken out ink, discharged outside the discharge port. Furthermore, since this method is a method in which the ink absorber is directly brought to abut against or contact the discharge port, it can effectively act to remove an ink droplet or dust stacked to the end surface of the discharge port in addition to its original action to take out the ink in the discharge port, these ink droplet or dust stacked to the end surface of the discharge port causing non-discharge failures or directional errors through which the ink droplet flies, which error being a so-called slippage.
As the other discharge recovering method, there is a method in which a pump or the like is used so as to forcedly discharge ink disposed in the vicinity of the discharge port (for example, see U.S. Pat. No 4276554, U.S. Pat. No. 4599625, U.S. Pat. No. 4419677, U.S. Pat. No. 4543591, U.S. Pat. No. 4410900, U.S. Pat. No. 4383263).
This method can be divided into two types, one of which is a method in which the pressure of the ink in the discharge port is increased so as to inject the ink in the vicinity of the discharge port, and the other is a method in which the pressure in the outer portion of the discharge port is decreased so as to absorb the ink in the vicinity of the discharge port. In either of these methods, since ink flows from the discharge port, it is preferable to provide a member for absorbing and accumulating the discharged ink (abbreviated to "waste ink" hereinafter).
Specifically, as a member for instantaneously absorbing the waste ink discharged from the discharge port, a polymeric porous material or the like is used. As the accumulating member, an accumulating reservoir, a so-called waste liquid tank, which accumulates the waste ink which has been temporarily captured by the absorbing member is generally used. For example, see U.S. patent application Ser. No. 786,179 filed on Oct. 10, 1985 and U.S. Pat. No. 4,682,184.
The characteristics required for this absorbing member and the above-described ink absorber for use in the discharge recovering method are completely the same as each other. Therefore, it is possible to make this absorbing member have three functions (A) to absorb out the ink in the discharge port, (B) to remove an ink droplet or dust stacked to the end surface of the portion in the vicinity of the discharge port, (C) to instantaneously absorb the waste ink which has been forcedly discharged through the discharge port. In general, since such absorbing member has the three functions (A) to (C), it is disposed at the position opposing the discharge port, and is communicated with a waste liquid tank positioned at the predetermined position with a flexible tube or the like.
As a recovery method which is effective to the above-described cloggings, invasion of air bubbles, increase in the viscosity of ink and solidifications of ink, there is a method of forcibly discharging the ink in the vicinity of the discharge port.
However, in the ink jet recording method, and more particularly in an ink jet recording head comprising a so-called full-multi type (full-line type) of recording head in which the discharge port are arranged in the range which corresponds to the width of the recording medium, the platen for restricting the recording surface is disposed closely to and opposing the overall range of the provided discharge port. Therefore the platen and the absorbing member need to be replace each other at the time of performing the above-described discharge recovery. Furthermore, it is required to bring the absorbing member into abutment against the discharge port.
To this end, an apparatus was disclosed in which the platen thereof is brought to a position far away from the recording head thereof, and the absorbing member can be, in this state, opposed to the recording head (the apparatus disclosed by the assignee of the present invention in U.S. Pat. No. 4,692,778). However, it is preferable to make the movable range of the platen and/or absorbing member as small as possible so as to replace the size of the recording apparatus. It is rather preferable to omit this.
Furthermore, since its waste liquid tank, of course, has its capacity, it needs to be provided with a sensor for detecting the fact that the tank has been filled and a proper means for notifying the operator, in accordance with this detection, the fact that the waste liquid tank has been filled in order to prevent the overflow of the tank. In addition, the operator needs to replace the waste liquid tank which has been filled with the waste ink with a new one. Such changing operation causes a problem that hands are contaminated during this changing work.