1.  Field of the Invention
The present invention relates to an inkjet apparatus capable of ejecting an ink and a treatment liquid for insolubilizing or coagulating a color material in the ink; and a method for judging replacement timings for components constituting the apparatus. 
2.  Description of the Related Art
When ejecting a liquid from a print head, droplets (hereinafter, also called a mist) each smaller than a main droplet are also generated in an inkjet apparatus.  In this case, for example, a so-called serial printing apparatus suffers from a phenomenon that the mist adheres, for example, to a face (hereinafter, also called an ejection face) of an inkjet head provided with ejection openings due to influences of an air current generated by the movement of the inkjet head, an air current generated by the ejection of the main droplet, or other causes.  Even if two or more kinds of ink mists that do not react with each other adhere to the ejection face, fixed adhesion of the ink mists due to a reaction does not occur; or otherwise, the degree of adhesion is negligible, if any.  However, in the case of an ink mist and a mist of a treatment liquid, the ink mist and the mist of the treatment liquid react with each other on the ejection face, and thus the mists fixedly adhere thereto.  Particularly, the fixed adhesion of the mists to a portion near the ejection openings may cause a phenomenon such as ejection failure or deflection of the ejection direction from an appropriate direction.  Consequently, undesirable lines, unevenness, or the like may be generated in outputted images to deteriorate the image quality. 
Against such problems, Japanese Patent Laid-Open No.  H11-240165 (1999) has made a proposal as follows.  Specifically, the number of ejected dots is counted (i.e., ‘dot count’ is performed) for each of inkjet heads for the respective color inks.  In addition, for each ink color, a smaller value is determined as a threshold value as the possibility of adhesion of the ink and the treatment liquid to the corresponding inkjet head is higher.  Then, when the count value exceeds the threshold value, a recovery operation such as wiping is performed at least on the inkjet head of the ink color in question.  Thereby, an appropriate recovery operation such as wiping can be performed in accordance with the amount of mist adhering to the inkjet head.  This makes it possible to prevent fixed adhesion near nozzles of the inkjet head. 
However, a mist does not adhere only to an ejection face.  While floating in an air current within a printing apparatus, a mist may adhere also to components constituting the apparatus such as a mechanism for moving a print medium and an inkjet head relative to each other, a mechanism for performing the above recovery operation, and a sensor for performing a desired detection for a printing operation.  In other words, the problem of fixed adhesion by a reaction between the ink and the treatment liquid may occur not only on the inkjet head but also on components constituting a printing apparatus.  As the fixed adhesion develops, the performance of each component is reduced, and the performance of the printing apparatus main body cannot be maintained in the end.  For this reason, it is necessary to know how much the fixed adhesion on each of these components in the apparatus main body is developed and to make a maintenance such as replacement of the component when it is estimated that the component performance is reduced to such an extent that the performance of the printing apparatus main body cannot be maintained. 
The technique disclosed in Japanese Patent Laid-Open No.  H 11-240165 (1999), however, is made only for a recovery operation to prevent fixed adhesion on ejection faces of the inkjet heads of the respective colors, but is not made in consideration of fixed adhesion on other components within the main body.  Meanwhile, in fact, a condition of fixed adhesion to the inkjet head and the other components within the main body as well as a timing for a maintenance such as replacement of a component are different between a case where the treatment liquid and ink are used together and a case where the ink is used alone.  Nevertheless, Japanese Patent Laid-Open No.  H 11-240165 (1999) only focuses on the recovery operation for preventing fixed adhesion on the ejection faces of inkjet heads of the respective colors, but does not take the above point into consideration as well.