Ink-jet printing apparatus and facsimile apparatus

In an ink-jet printing apparatus employing an ejection failure detecting construction for optically detecting the number of ink droplets interrupting a light path, when a power source for an apparatus is turned on, a home position is detected. A carriage is shifted from this point at a constant speed, and ink ejection is performed sequentially within zones P1 to P2 where a photosensor is present. Then, among variations of output of the photosensor by sequential ink ejection, the number of steps S of a motor up to a timing where the maximum output Vmax is output. In a subsequent process for detecting ejection failure, ejection is performed at this position.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates generally to an ink-jet printing apparatus to
 be employed in a facsimile apparatus, a printer, a copy machine and so
 forth. More specifically, the invention relates to a technology for
 detecting ejection failure caused by plugging of ejection openings in an
 ink-jet head or running out of an ink.
 2. Description of Related Art
 Various systems for performing printing on printing media, such as paper,
 OHP sheet and so forth have been known. Amongst, an ink-jet printing
 system is to directly eject an ink toward the printing medium. Such
 ink-jet system is advantageous in relatively low running cost and low in
 the level of noise to be generated associated with an operation thereof.
 On the other hand, in the ink-jet system, it becomes necessary to quickly
 detect running out of the ink by consuming all of the ink in an ink tank
 or ejection failure caused by plugging of ejection openings or so forth,
 to prevent printing failure from occurring, previously.
 As an example of a construction for detecting such ejection failure, there
 has been known a method to perform printing operation of a mark for
 judgement of presence or absence of the ink on a printing medium, and to
 make judgement whether the mark is printed or not by means of a reflection
 type photosensor, in viewpoint of detection of remaining amount of the
 ink. However, this method requires printing of the mark which is actually
 unnecessary, only for detecting presence and absence of the ink.
 Therefore, the printing apparatus employing such method is not user
 friendly.
 In the ink-jet printing apparatus, as a method for detecting faulty
 condition of ejection, such as running out of the ink, ejection failure
 due to plugging and so forth, there has been known a technology for
 passing the ejected ink droplet between a light emitting element and a
 photo-sensing element of a transmission type photosensor and detecting
 ejection failure based on whether the light between the elements is
 interrupted or not.
 In one example of construction of the above-mentioned transmission type
 photosensor, a lens is integrally formed on a light emitting surface of
 the light emitting element. By this, substantially parallel light is
 projected toward the photo-sensing element. On the other hand, in a
 photo-sensing surface of the photo-sensing element, an aperture in the
 order of 0.7 mm.times.0.7 mm is formed on a light axis by a molding
 member. By this, in the overall range between photo-sensing and light
 emitting, detecting range is limited at approximately 0.7 mm in height and
 approximately 0.7 mm in width. Further, the light emitting element and the
 photo-sensing element are arranged so that a light axis extending
 therebetween is in parallel to ejection opening array of the ink-jet head
 and intersects with a flying path of the ejected ink droplet. Also, a
 distance between the light emitting element and the photo-sensing element
 is set to be wider than a range of the ejection opening array. By this,
 all of the ink droplets ejected from respective ejection openings of the
 ink-jet head may pass through the detection range between the light
 emitting element and the photo-sensing element. Thus, when the ink
 ejection is performed normally and the ink droplet passes the detection
 range, the ink droplet interrupts the light beam from the light emitting
 side to reduce the amount of light reaching at the photo-sensing side to
 cause variation of output of the photo-sensing element. The ejected ink
 droplet is a fine liquid droplet having a diameter less than or equal to
 50 .mu.m. Therefore, normally, a single ink droplet ejected from single
 ejection opening may not interrupt the light emitted from the light
 emitting side completely. Instead, light interruption ratio is gradually
 increased depending upon number of ejection openings ejecting ink.
 Accordingly, when the output of the transmission type photosensor varies
 in a magnitude greater than or equal to a given amount, ink ejection is
 judged as normal. Conversely, when the variation magnitude of the
 transmission type photosensor is less than or equal to the given amount,
 failure of ink ejection can be detected.
 The above-described technology for detecting ejection failure may perform
 detection without adding any special parts for the ink-jet head.
 Therefore, it can be employed as effective means for detection of ejection
 failure.
 When the ejection failure is to be detected in a manner set forth above, it
 becomes necessary to accurately position a light axis of the photosensor
 and the ejection opening array of the ink-jet head so that ink ejected
 from respective ejection openings may cross a light path of the photo
 sensor. In such case, basically, a shifting magnitude of the ink-jet head
 from a reference position to the position of the light axis is
 preliminarily set and positioning is performed by shifting the ink-jet
 head for the preliminarily set shifting magnitude.
 However, due to variations of performance of respective components of a
 mechanism, which variations are caused when manufacturing the mechanism,
 for shifting of the head or due to fluctuation in ejection angle of the
 ink caused by a variation of performing of the ink-jet head, an ink
 droplet ejected from each ejection opening may be deviated from the light
 axis of the photosensor in a magnitude of 1 mm at the maximum, even when
 the positioning operation set forth above is performed. In view of a fact
 set forth above, the prior art is designed to perform ejection in a range
 of approximately 2 mm at both sides of the light axis, which range is
 greater than the range of deviation of the ejected ink droplet, upon
 detection of the ejection failure. Then, detection of ejection failure is
 performed by judging whether an output of the photosensor exceeds a
 predetermined amount when the ejection is performed, or not.
 In the prior art as set forth above, since the ink is ejected in the range
 of approximately 2 mm at both sides of the light axis upon detection of
 ejection failure, the number of ink droplets to be ejected through each
 ejection opening becomes about 50 to 100. Therefore, when number of the
 ejection openings provided in the ink-jet head is, for example, 64, the
 overall number of the ink droplets to be ejected through respective of the
 ejection openings becomes about 3200 to 6400 to cause relatively large
 amount of ink consumption. As a result, the running cost of the ink-jet
 printing apparatus is raised.
 Further, in the case that relatively large tolerance is given for
 respective components of an ink jet apparatus for lowering of production
 cost of the ink-jet printing apparatus, the fluctuation in positioning
 between the light axis and the head becomes further greater so that it
 becomes necessary to widen the range in which the ejection for detection
 of the ejection failure needs to be performed. Therefore, ink consuming
 condition becomes worse.
 SUMMARY OF THE INVENTION
 It is an object of the present invention to provide an ink-jet printing
 apparatus which can remarkably reduce ink amount to be used for detection
 of ejection failure even when precision of respective components relating
 to positioning between a photosensor and an ink-jet head is not so high.
 Another object of the present invention is to provide an ink-jet printing
 apparatus which can detect relationship between a detecting means and the
 ink-jet head in position by performing ink ejection within a predetermined
 range and on the basis of a distribution of an output of the detecting
 means, and whereby a range of performing ejection of the ink upon
 detection of the ejection failure can be minimized.
 A further object of the present invention is to provide an ink-jet printing
 apparatus which can satisfactorily detect ejection failure even when
 offset of the ejecting position relative to the photosensor is present
 upon detection of ejection failure due to tolerance of the components, use
 environment and period, individual difference of the ink-jet head or so
 forth.
 In a first aspect of the present invention, there is provided an ink-jet
 printing apparatus employing an ink-jet head having a plurality of
 ejection openings to perform printing by ejecting an ink toward a printing
 medium, comprising:
 detecting means having a light emitting element and a photosensing element;
 moving means for moving the ink-jet head and the detecting means relatively
 to each other;
 ejection control means for making the moving means to relatively move the
 detecting means and the ink-jet head and for, during relative movement of
 the detecting means and the ink-jet head, performing ejection from the
 ink-jet head within a predetermined first moving range including a light
 path formed between the light emitting element and the photosensing
 element;
 range determining means for determining a second moving range included in
 the first moving range on a basis of output of the detecting means varying
 depending upon ink ejection from the ink-jet head within the first
 shifting means; and
 ejection failure detecting means for making the moving means to relatively
 move the ink-jet head and the detecting means, for performing ejection
 from the ink-jet head within the second moving range during relative
 movement of the ink-jet head and the detecting means, and for detecting
 ejection failure of the ejection opening on a basis of output of the
 detecting means upon ejection performed within the second moving range.
 In a second aspect of the present invention, there is provided an ink-jet
 printing apparatus for performing printing by ejecting an ink from an
 ink-jet head toward a printing medium, comprising:
 an ink tank storing the ink, the ink tank being exchangeably provided in
 the ink-jet printing apparatus;
 scanning means for reciprocally scanning the ink-jet head;
 detecting means for making the ink-jet head to perform ejection of ink and
 performing detection of an ink amount in the ink tank;
 control means for moving the ink-jet head in the vicinity of a nominal
 detecting position of the detecting means and controlling operation of the
 detecting means at respective of a plurality of positions in the vicinity
 of the nominal detecting position; and
 correcting means for correcting a position at which the detecting means
 performs the detection on a basis of a result of detection obtained from
 the detecting means at respective of the plurality of positions.
 In a third aspect of the present invention, there is provided a facsimile
 apparatus for performing printing output on a basis of received data by
 employing an ink-jet head having a plurality of ink-jet openings,
 comprising:
 detecting means having a light emitting element and a photosensing element;
 moving means for moving the ink-jet head and the detecting means relatively
 to each other;
 ejection control means for making the moving means to relatively move the
 detecting means and the ink-jet head and for, during relative movement of
 the detecting means and the ink-jet head, performing ejection from the
 ink-jet head within a predetermined first moving range including a light
 path formed between the light emitting element and the photosensing
 element;
 range determining means for determining a second moving range included in
 the first moving range on a basis of output of the detecting means varying
 depending upon ink ejection from the ink-jet head within the first
 shifting means; and
 ejection failure detecting means for making the moving means to relatively
 move the ink-jet head and the detecting means for performing ejection from
 the ink-jet head within the second moving range during relative movement
 of the ink-jet head and the detecting means, and for detecting ejection
 failure of the ejection opening on a basis of output of the detecting
 means upon ejection performed within the record moving range.
 In a fourth aspect of the present invention, there is provided a facsimile
 apparatus for performing printing output on the basis of received data
 employing an ink-jet head having a plurality of ink ejection openings,
 comprising:
 an ink tank storing the ink, the ink tank being exchangeably provided in
 the ink-jet printing apparatus;
 scanning means for reciprocally scanning the ink-jet head;
 detecting means for making the ink-jet head to perform ejection of ink and
 performing detection of an ink amount in the ink tank;
 control means for moving the ink-jet head in the vicinity of a nominal
 detecting position of the detecting means and controlling operation of the
 detecting means at respective of a plurality of positions in the vicinity
 of the nominal detecting position; and
 correcting means for correcting a position at which the detecting means
 performs the detection on a basis of a result of detection obtained from
 the detecting means at respective of the plurality of positions.
 In a fifth aspect of the present invention, there is provided a detection
 position correcting method for a ink-jet printing apparatus employing an
 ink-jet head having a plurality of ejection openings to perform printing
 by ejecting an ink toward a printing medium, the method comprising the
 steps of:
 moving the ink-jet head and detecting means having a light emitting element
 and a photosensing element relatively to each other;
 during relative movement of the detecting means and the ink-jet head,
 performing ejection from the ink-jet head within a predetermined first
 moving range including a light path formed between a light emitting
 element and a photosensing element;
 determining a second moving range included in the first moving range on a
 basis of output of the detecting means varying depending upon ink ejection
 from the ink-jet head within the first shifting means; and
 moving the ink-jet head and the detecting means, performing ejection from
 the ink-jet head within the second moving range during relative movement
 of the ink-jet head and the detecting means, and detecting ejection
 failure of the ejection opening on a basis of output of the detecting
 means upon ejection performed within the record moving range.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 The preferred embodiment of the present invention will be discussed
 hereinafter in detail with reference to the accompanying drawings.
 Although the invention has been illustrated and described with respect to
 exemplary embodiment thereof, it should be understood by those skilled in
 the art that the foregoing and various other changes, omissions and
 additions may be made therein and thereto, without departing from the
 spirit and scope of the present invention. Therefore, the present
 invention should not be understood as limited to the specific embodiment
 set out above but to include all possible embodiments which can be
 embodied within a scope encompassed and equivalents thereof with respect
 to the feature set out in the appended claims.
 (First Embodiment)
 FIG. 1 is a section showing one embodiment of a facsimile apparatus, in
 which the present invention is applied.
 At first, discussion will be given for general construction of the
 facsimile apparatus with reference to FIG. 1. In FIG. 1, a reference sign
 A denotes a reading portion for optically reading an original, a reference
 sign B denotes a printing portion employing an ink-jet printing apparatus,
 a reference sign C denotes a feeder portion separating a sheet, such as
 printing paper or so forth stacked in a sheet cassette and supplying the
 sheet to the printing portion B. It should be noted that a mechanical
 construction of respective parts are similar to those known in the art.
 A transporting path of a printing paper P is as shown by arrow G. More
 specifically, the printing paper P stacked in a feeder cassette 1 of the
 feeder portion C is picked up by a feeder roller 2 and a separation claw 3
 and fed into the printing portion B by a transporting roller 24 as
 transporting means. In the printing portion B, ink is ejected from an
 ink-jet head 5 for performing printing. Subsequently, after transporting a
 certain distance within the apparatus, the printed paper is discharged and
 stacked in a discharge paper stacker 7 by a discharge roller 6.
 Next, discussion will be given for detailed construction of the printing
 portion B with reference to FIG. 2.
 In FIG. 2, the shown embodiment of the ink-jet head 5 (not shown in FIG. 2)
 is the type formed integrally with an ink tank for replacement together
 with the ink tank when ink in the tank has run out. Namely, the ink-jet
 head and the ink tank construct an ink-jet cartridge 50 of the type of
 cartridge. The ink-jet head 5 arranges 64 ejection openings in one row at
 a density of 360 DPI. Electro-thermal transducing elements are arranged in
 respective of ink passages corresponding to respective ejection openings.
 Heat generation of the electro-thermal transducing element causes film
 boiling to generate a bubble so that ink is ejected through the ejection
 opening by pressure of the bubble.
 A carriage 15 detachably mounting the ink-jet cartridge 50 is slidably held
 by a guide bar 16 and abutting portion 15a for reciprocal movement in a
 direction perpendicular to the transporting direction (the transporting
 direction is called auxiliary scanning direction, and shown by an arrow G
 in FIG. 2), namely in a primary scanning direction (shown by an arrow H in
 FIG. 2). Reciprocal motion of the carriage 15 is performed by means of a
 pulley 17 driven by a carriage motor 30 (see FIG. 3) and a timing belt 18
 wound therearound. At this time, an ejection signal and an electric power
 to be supplied to the ink-jet head 5 are supplied from an electrical
 circuit or so forth in a main body of the facsimile apparatus through a
 flexible cable 19.
 Further, a cap 20 is arranged at a position corresponding to a position of
 the carriage 15 in stand-by state (a home position) and moves up and down
 as required to cover a surface of the ink-jet head 5 where the ejection
 openings are provided at the upwardly moved position for avoiding of
 evaporation of ink and deposition of dust. Here, control of relative
 position between the ink-jet head 5 and the cap 20 in the primary
 direction is performed with employing a carriage home sensor 21 and a
 light shielding plate 15b provided on the carriage 15. As the carriage
 home sensor 21 and a transmission type photo-interrupter is employed. When
 the carriage 15 is moved to the stand-by position (home position), a part
 of a light irradiated from the carriage home sensor 21 is interrupted by
 the light shielding plate 15b. Utilizing this, the predetermined position
 where the ink-jet head 5 and the cap 20 are mutually opposing is detected.
 The printing paper P is fed upwardly from the lower side of the printing
 portion in the drawing. Then, the printing paper P is deflected into the
 horizontal direction by the transporting roller 4 and a paper guide 22 to
 be transported in the direction of arrow G. The transporting roller 4 and
 the discharge roller 6 are respectively driven by a feeder motor 31 (see
 FIG. 3) for feeding the printing paper in the direction of arrow G at high
 precision in synchronism with reciprocating motion of the carriage 15.
 Spurs 23 are arranged at a plurality of positions opposing to the
 discharge roller 6 by an unknown bearing member with a given interval in a
 direction parallel to the primary scanning direction so that they may
 guide and transport the printing paper immediately after printing without
 affecting the printed image even when they contact with non-fixed image.
 Therefore, the spurs 23 are formed of a material having high water
 repelling characteristics and designed to contact with the printing paper
 P only at a teeth like peripheral portion.
 A photosensor 8 is arranged at a position between the cap 20 and one end of
 the printing paper P to be transported and corresponding to the range
 where the ejection opening array of the ink-jet head 5 passes. The
 photosensor 8 is a transmission type photo-interrupter capable of
 optically detecting the ink droplet ejected from each ejection opening of
 the ink-jet head 5. Ink ejection failure of the ink-jet head can be judged
 on the basis of the output of the photosensor 8.
 The photosensor 8 to be employed in the shown embodiment uses an infrared
 ray LED as the light emitting element. On the light emitting surface of
 the LED, a lens is formed integrally. By this, a substantially parallel
 light beam can be projected. As the photo-sensing element of the
 photosensor 8, a photo-transistor is employed. On a photo-sensing surface
 of the photo-sensing element is formed an aperture of 0.7 mm.times.0.7 mm
 on the light axis, by a molding method. Thus, in overall range between
 photo-receiving and light emitting, a detection range is restricted at 0.7
 mm in height and 0.7 mm in width. Further, the light emitting element and
 the photo-sensing element are arranged so that a light axis extending
 therebetween is parallel to the ejection opening array of the ink-jet head
 and so that the distance between the light emitting element and the
 photo-sensing element becomes greater than the range of the ejection
 opening array of the ink-jet head 5. By this, when the ejection opening
 array of the ink-jet head 5 is positioned corresponding to the light axis,
 all of ink droplets ejected from respective ejection openings may pass the
 detection range between the light emitting element and the photo-sensing
 element. Thus, the photosensor 8 may output a value corresponding to
 number of ink droplets, namely number of ejection openings normally
 ejecting.
 As set forth above, the photosensor 8 to be employed in the shown
 embodiment is the one similar to that discussed with respect to the prior
 art. Accordingly, due to fluctuation of characteristics of the
 photo-sensing element and the light emitting element of the sensor, play
 in assembling of these elements, and so forth, the sensor may have an
 error in output in the order to 20% at the maximum.
 It should be noted that control of relative position between the ejection
 opening array of the ink-jet head and the light axis of the photosensor 8
 is performed by employing a carriage home sensor 21 provided in the main
 body of the apparatus similar to positioning with the cap 20, set forth
 above. More specifically, a predetermined distance for shifting from the
 home position detected by the sensor 21 to the light axis of the
 photosensor is converted into number of steps of the motor for driving the
 carriage and preliminarily set the number of steps as a constant value in
 a sequence.
 Next, discussion will be given for the major part of an electric circuit of
 the preferred embodiment of a facsimile apparatus with reference to a
 block diagram of FIG. 3.
 In FIG. 3, a reference numeral 24 denotes a control portion controlling
 overall the facsimile apparatus. The control portion 24 includes CPU 25,
 such as a microprocessor and so forth, ROM 26 for storing control programs
 to be executed by the CPU 25 and various data, RAM 27 to be used as work
 area of the CPU 25 and temporarily storing various data, and so forth. The
 control portion is formed as a circuit on a substrate in the apparatus. An
 output of the photosensor 8 is converted into a digital value by an A/D
 converter and can be subjected to processing of the CPU 25. The carriage
 motor 30 and the feeder motor 31 are motors which can be controlled to a
 rotation angle by number of pulse steps issued by motor driver circuits 33
 and 32, respectively, so that the CPU 25 can control rotation of motors 30
 and 31. The output of the carriage home sensor 21 is input to the control
 portion 24 and used for controlling shifting of the ink-jet head.
 FIG. 4 is a flowchart showing a sequence relating to detection of ejection
 failure on a basis of the above-mentioned construction of the shown
 embodiment, FIG. 5 is a diagrammatic illustration showing a construction
 in the shown embodiment of the apparatus relating to detection of ejection
 failure, and FIG. 6 is a timing chart of the foregoing sequence. The shown
 embodiment of process for detection of ejection failure will be discussed
 hereinafter with reference to these figures.
 Upon turning ON of power supply for the facsimile apparatus (step S1), the
 carriage 15 is moved to detect the home position of the carriage 15 by a
 carriage home sensor 21 (step S2). Next, by moving carriage at a constant
 speed (approximately 300 mm/sec) from the home position, ink is ejected
 sequentially at a frequency of 6 kHz through all of the ejection openings
 while moving the head 5 within a range of approximately 4 mm from a
 predetermined position P1 approximately 2 mm ahead of reaching the
 position of the ejection opening array 5c of the ink-jet head 5 at the
 detecting position of the photosensor 8, to a predetermined position P2
 approximately 2 mm beyond the detecting position, and thereafter the
 carriage is stopped, as shown in FIG. 5 (step S3). Here, the number of
 ejections of the ink is determined depending upon the moving speed of the
 carriage and ejecting range. 80 droplets are ejected from respective
 ejection openings.
 During sequential ejection, outputs of the photosensor 8 are sampled at
 fine time interval (100 .mu.sec) via the A/D converting circuit 28 (step
 S4). Furthermore, a maximum value Vmax which is a maximum value of output
 distribution of the photosensor on a basis of the sampled data and a
 period t1 for moving the carriage from the home position to the position
 outputting the Vmax are derived. Then, on a basis of the carriage speed
 and the period t1, number of steps S of the carriage motor 30 needed for
 moving the head from the home position to the position outputting the Vmax
 is derived (step S5, see FIG. 6). The number of steps S thus derived is
 stored in RAM 27 (step S6). Then, the apparatus is placed in stand-by
 state until a printing command is input (step S7).
 In response to the printing command, the printing paper P is picked up and
 fed to the printing portion B. Then, printing for one page of image data
 is performed (step S8). Whenever printing for one page is completed, an
 operation for detecting ejection failure due to running out of the ink,
 plugging of the ejection openings or so forth is performed. More
 specifically, at first, with reference to the data of number of steps S
 stored in RAM 27, the carriage 15 is moved to the position corresponding
 to the number of steps S of the carriage motor 30 from the home position
 and stopped thereat (step S9). By this movement of the carriage, the
 position of the ejection opening array 5c of the ink-jet head 5
 corresponds to the light axis of the photosensor 8 so that the ejected ink
 droplet may fly across the light path of the sensor 8.
 It should be noted that, in the shown embodiment, this relationship in
 position is basically maintained unless the ink-jet head or the component
 of the apparatus is exchanged. However, it may be possible to perform
 process for deriving the number of steps S upon ON-set of power supply for
 the apparatus for more precise re-set. Also, by this, even when a
 relationship between the number of steps S and the actually detected
 position changes at respective portion of the apparatus with time, such
 offset can be adjusted. It should be noted that, upon obtaining
 distribution of the outputs of the photosensor 8, it is possible that a
 part of a plurality of the ejection openings causes ejection failure.
 However, since appropriate positional relationship between the head and
 the photosensor is established at the position where the output
 distribution becomes maximum, no significant problem will arise. Further,
 it is also possible to make the number of steps S to correspond to a
 narrower range between P1 to P2 rather than to correspond to one point,
 for performing the following process.
 Next, ejection is performed through all of the ejection openings of the
 head for ejecting respective 10 ink droplets (step S10). During this
 ejection, the outputs of the photosensor 8 are sampled in the similar
 process to that of step S4 (step S11). Then, on a basis of the sampled
 data, an error operation is performed (step S14) under judgement that
 ejection failure is caused when the output of the photosensor 8 does not
 reach the given value (step S12). For example, a received data is stored
 in a memory, an error display is output and printing operation is
 terminated. On the other hand, when judgement is made that the output of
 the sensor 8 is greater than or equal to the given value and the next page
 to be printed is present (steps S12 and S13), picking up of next printing
 paper is initiated to repeat the similar operation. If data for the next
 page is not present, the apparatus returns to the stand-by state at step
 S9 (step S13).
 It should be noted that, as set forth above, even in the process to obtain
 the appropriate positional relationship between the head and the
 photosensor, ink ejection is performed in wider range in certain extent to
 consume the ink. However, since this process is performed only at ON-set
 of power supply, and in case of the shown embodiment, subsequently
 performed ejection for detecting ejection failure is performed only at the
 position determined in the process set forth above for each page.
 Therefore, the ink consuming amount can be much smaller than that in the
 prior art.
 It should be noted that while the foregoing construction has been discussed
 with respect to an example for performing high speed sampling by employing
 the A/D converting circuit, it is also possible to employ a comparator
 circuit constituted of a relatively inexpensive operational amplifier
 instead of employing the A/D convertor, to set a given threshold value for
 the output value of the sensor, to measure a period by causing
 interruption in the control portion at a timing where the sensor output
 exceeds the threshold valve and at a timing where the sensor output drops
 below the threshold value, and to approximate the intermediate point
 between the foregoing two timings as the time t1, at which the maximum
 value is obtained.
 Next, a principle of ejection of the ink-jet head to be employed in the
 printing portion in the shown embodiment of the ink-jet printing apparatus
 will be discussed.
 The ink-jet head generally has a fine liquid ejection opening (orifice), a
 liquid passage (ink passage), an energy acting portion providing in a part
 of the liquid passage and an energy generating element for generating
 thermal energy to act on the liquid in the energy acting portion. The
 ink-jet head is replaceably provided for the carriage.
 As other energy generating elements for generating energy, one employing an
 electromechanical transducer, such as piezoelectric element, one
 irradiating an electromagnetic wave, such as laser or so forth to be
 absorbed by the liquid presenting therein to cause generation of heat and
 thus eject liquid droplet by action associated with heat generation to fly
 the liquid droplet, and so forth are known. Amongst, a system for ejecting
 the liquid by a thermal energy generated by an electrothermal transducing
 element as employed in the shown embodiment, is suitable for high
 resolution printing since the liquid ejection openings (orifices) can be
 arranged at high density.
 Further, the ink-jet head employing the electrothermal transducing element
 is easy to reduce a whole size, can take advantage of IC technology and/or
 micro-processing technology which are remarkable in advance of technology
 and in improvement of reliability in a recent semiconductor field, is
 satisfactorily effective, and is easily to make into elongated or flat
 (two-dimensional) configuration to permit increasing number of ejection
 openings to easily achieve high package density. Furthermore, such ink-jet
 head has high mass-productivity and thus can be supplied at low production
 cost.
 Such ink-jet head employing the electrothermal transducing element as the
 energy generating means and produced through semiconductor fabrication
 process generally has a construction, in which liquid passages are
 provided corresponding to respective ink ejection openings, the
 electrothermal transducing element as means for forming liquid droplet to
 fly by ejecting the liquid through the corresponding ink ejection opening
 by applying the thermal energy for the liquid filling respective liquid
 passages independently of each other. To respective liquid passages, the
 liquid is supplied from a common liquid chamber communicated with
 respective liquid passages.
 Concerning production method of the ink-jet head, the assignee of the
 present application has proposed a method, in which at least a solid layer
 for forming the liquid passage, an active energy beam setting material
 layer to be at least used in formation of a peripheral wall of the liquid
 passage and a second substrate are stacked on a first substrate in order,
 thereafter, a mask is formed on the second layer to irradiate an active
 energy beam from the upper side of the mask for consolidating at least the
 portion forming the peripheral wall of the active energy beam setting
 material, further, the non-solidified portion of the active energy beam
 setting material layer is removed from the region between two substrates
 to form at least the liquid passages (see U.S. Pat. No. 5,030,317).
 FIG. 7 is a partially sectioned perspective view showing the internal
 structure of the ink-jet head 5 to be employed in the shown embodiment.
 The ink-jet head 5 is formed with electrothermal transducers by depositing
 heating resistors 103 and electrodes 104 on a substrate 102 through
 semiconductor fabrication process, such as etching, deposition, sputtering
 and so forth. On the substrate 102, the active energy beam setting resin
 layer 210 having the liquid passage 110 and an upper plate 106 are
 laminated. The common liquid chamber 108 formed by lamination of the
 foregoing elements is adapted to temporarily store the ink to be supplied
 to respective liquid passages. In turn, the ink is supplied to the common
 liquid chamber 108 from an ink tank (not shown) through a liquid supply
 tube 107. On the other hand, 109 denotes a connector for connection with
 the liquid supply tube.
 The ink supplied to the common liquid chamber 108 is supplied to each
 individual liquid passage 110 by capillary effect and is held stably by
 formation of meniscus at the ink ejection opening 111 at the tip end of
 the liquid passage. When power is supplied to the heating resistor 103 in
 such condition, the ink on the heating resistor 103 is heated to cause
 bubbling by film boiling. Then, by growth of the bubble, a liquid droplet
 is ejected through the ink ejection opening 111.
 It should be noted that while the ink is ejected from all of the ejection
 openings (64 ejection openings) at step S4 in the first embodiment of the
 sequence for detecting ejection failure, it is possible to obtain the
 optimal positional relationship of the ink jet head and the photosensor by
 causing ejection through a part of ejection openings. Here, a part of
 ejection openings, for example, means first to sixteenth ejection openings
 out of 64 ejection openings. By limiting only these ejection openings, the
 ink consuming amount can be further reduced as intended by the present
 invention to lower running cost.
 It should be noted that when the output of the photosensor does not reach
 the predetermined amount in the case that a part of the ejection openings
 are used, namely when it is possible that ejection failure is potentially
 caused in a part of the ejection openings, it is possible to derive the
 foregoing positional relationship with employing another part of the
 ejection openings.
 Further, even when the optimal positional relationship between the head and
 the photosensor is derived with utilizing a part of the ejection openings
 at every time of process for detecting the ejection failure, the ink
 consuming amount can be still restricted to less than that in the prior
 art.
 As set forth above, according to the first embodiment as set forth above,
 the positional relationship between the photosensor and the ink-jet head
 can be obtained on a basis of the distribution of the output of the
 photosensor by performing ejection of ink within a predetermined first
 range. Therefore, the range of ink ejection in the process of detection of
 ejection failure can be performed within a second range which is the
 minimum range. As a result, even when precision in positioning of the
 detecting means, such as the photosensor or so forth and the head is not
 so high, ink ejection failure can be certainly detected with reduced
 amount of ink consumption.
 (Second Embodiment)
 In the first embodiment set forth above, the distribution of the output of
 the photosensor is derived by sequentially performing ejection with moving
 the head within the predetermined range in the process for determining the
 position to perform ejection for detecting the ejection failure, whereas
 in the second embodiment, the distribution of the output of the
 photosensor are determined at a plurality of ranges which are smaller than
 the predetermined range in the former embodiment, and, depending upon the
 derived distribution of the output of the photosensor, the position to
 perform ejection is determined.
 The shown embodiment is an application of the present invention for the
 apparatus similar to the facsimile apparatus shown in FIG. 1. FIG. 8 is a
 perspective view showing the detail of a printing portion B. Like elements
 to those in FIG. 2 will be identified by the same reference numerals, and
 the discussion thereof is neglected for keeping disclosure simple enough.
 In the shown embodiment, a detecting sensor 44 has a light emitting element
 44a and a photo-sensing element 44b, as a transmission type
 photo-interruptive sensor to detect presence and absence of ink by
 detecting an ink droplet ejected across a light axis therebetween. The
 detecting sensor 44 is arranged at the opposite side to a portion where a
 cap 20 is provided, relative to the scanning range of a carriage 15. By
 arranging the detecting sensor 44 at such position, it becomes possible to
 avoid staining of the detecting sensor due to discharge of the ink
 splashed associating with the ejection recovering process.
 FIG. 9 is a block diagram showing a construction of a control system of the
 shown embodiment of the facsimile apparatus.
 In FIG. 9, a reference numeral 24 denotes a control portion for controlling
 the overall operation of the whole apparatus. The control system 24 has
 CPU, ROM 26 storing control program and various data and RAM 27 or so
 forth to be used by CPU 25 as work region in execution of various
 processes and temporarily storing various data. On the other hand, a part
 of ROM 26 is formed with EPROM for storing information concerning the
 ink-jet ejecting position, in operation for detecting the ejection failure
 which will be discussed later.
 The ink-jet head 5 is electrically connected to the control portion 24 via
 the flexible cable 19. In the flexible cable 19, a control signal line and
 an image signal line for feeding a control signal and image signal from
 the control portion 24 to the ink-jet head 5 are included. On the other
 hand, an output of the detecting sensor 44 is converted into a digital
 signal by an A/D converter circuit and thus can be processed by CPU 25. A
 carriage motor 30 is a motor which can be driven for revolution depending
 upon number of pulse steps supplied from a motor driver circuit 33. Also,
 the control portion 24 controls the carriage motor 30 via a motor driver
 circuit 33, a transporting motor 31 via a motor driver circuit 32, and a
 reading motor 52 via a motor driver circuit 53. The detection output of
 the carriage home sensor 21 is input to the control portion 24.
 The control portion 24 is also connected to an input device of the image
 data, such as a reading sensor 48, a printer interface 54 for receiving
 printing instruction and/or printing data from an external computer 56, a
 line control circuit 55 for receiving reception data from a telephone
 network 57 and so forth, for operation of facsimile transmission and
 reception, copying and as a printer of the external computer. Further, the
 control portion 24 is also connected to an operation panel 58, through
 which a user of the apparatus performs various operations and enters
 various commands. In the operation panel 58, an LCD 59 for performing
 message display is provided.
 FIG. 10 is a block diagram showing an electrical construction of the
 detecting sensor 44.
 In FIG. 10, a reference numeral 44a denotes an infrared ray LED as the
 light emitting element, a reference numeral 44b denotes a phototransistor
 as the photosensing element for receiving the infrared light, a reference
 numeral 83 denotes a comparator for comparing the output of the
 phototransistor with a predetermined reference voltage (Vref), and a
 reference numeral 84 denotes a pulse width measuring portion for measuring
 continuing period (pulse width) of the pulse output from the comparator.
 The pulse width measuring portion 84 takes the pulse width of a clock
 (reference clock) input thereto as a reference pulse width and counts a
 cycle of the reference clock during continuing period of the pulse output
 from the comparator 83 for outputting the counted value to an internal
 register of the pulse width measuring portion 84.
 In the construction set forth above, when the ink is not ejected from the
 ink-jet head 5, there is nothing interrupting the infrared light emitted
 from the infrared ray LED 44a. Thus, a high (H) level signal is input to
 the comparator 83 from the phototransistor 44b as the photo-sensing
 element. In contrast to this, when ink ejection is performed, the ejected
 ink interrupts infrared light from the infrared ray LED 44a, and the
 output from the phototransistor 44b is lowered in a corresponding
 magnitude to interruption amount of the infrared light. When the output
 level drops lower than the reference voltage Vref input to the comparator
 83, the output signal to the pulse width measuring portion 84 from the
 comparator 83 is reversed. Subsequently, when ink ejection through the
 ink-jet head 5 is completed, the output of the phototransistor 44b is
 resumed to be high (H) level to be elevated across the reference voltage
 Vref set in the comparator 83, so that the output from the comparator 83
 to the pulse width measuring portion 84 is reversed again.
 Thus, to the pulse width measuring portion 84, a pulse having a pulse width
 corresponding to the period where the output of the detecting sensor 44 is
 held below the reference voltage, is input. As set forth above, a width of
 this pulse is measured or counted utilizing the reference clock and stored
 in the internal register of the pulse width measuring portion 84. The
 counted value is read out by CPU 25 of the control portion 84 and is used
 for detection of ejection failure. In the alternative, it is possible to
 transfer to and store the counted value indicative of the pulse width in
 RAM 27 of the control portion 24 and to read out by the CPU 25 after
 completion of ink ejection.
 It should be noted that the clock frequency of the reference clock to be
 employed in the shown embodiment is approximately 56.5 [1/msec], and a
 threshold value of judgement whether ink is ejected or not is set at 80
 pulses.
 FIG. 11 is a perspective view showing a construction of the detecting
 sensor 44. As shown in FIG. 11, in the shown embodiment, for increasing
 light interruption rate of the light axis by the ejected ink, slits are
 provided at a side of the light emitting element 44a and at a side of the
 photosensing element 44b to enhance precision in detection.
 FIG. 12 is an illustration showing a set position of the detecting sensor
 44.
 In FIG. 12, an arrow designated by a reference numeral 91 shows the range
 where the ink-jet head may move. In the shown embodiment of the facsimile
 apparatus, the width of B4 size printing paper is set as a maximum
 printing width. In addition to the maximum printing width, accelerating
 and decelerating ranges are provided. Therefore, a maximum width for
 moving the ink-jet head 5 is 371.9 mm. Further, a reference numeral 92
 denotes a position of the ink-jet head, at which detection of ejection
 failure is performed, and an arrow designated by a reference numeral 93
 represents ejecting direction of the ink. In the shown construction, the
 printing paper P is transferred from the distal side to proximal side in
 the perpendicular direction to the surface of the paper of the drawing.
 FIG. 13 is an illustration showing a positional relationship between the
 ink ejecting position for detecting the ejection failure, as shown in FIG.
 12, and the light axis of the detecting sensor which is set as data. In
 the drawings, with respect to the designed position of the light axis of
 the detecting sensor 44, three ejection initiating points, points L, C and
 R, are indicated.
 Due to tolerance of the components of the apparatus, dimensional tolerance
 in assembling of the apparatus, and variation of dimensions due to use
 environmental condition of the apparatus, the light axis position of the
 detecting sensor 44 set as data may be relatively deviated with respect to
 the actual light axis position toward the carriage home sensor 21 or
 opposite side thereto. Namely, by such variation in dimension,
 experimentarily, the relative light axis position is frequently deviated
 in a magnitude of 1.31 mm toward the carriage home sensor or 1.41 mm
 toward the opposite direction.
 Accordingly, in detection of the ejection failure in the prior art, it is
 required to perform ejection of the ink with moving the ink-jet head in a
 magnitude of 2.72 mm across the designed light axis position in
 consideration of this width (2.72 mm) as set forth above.
 In such case, assuming that the printing density in the shifting direction
 of the head 5 is 360 DPI, it becomes necessary to perform about 62 times
 of ink ejection for respective ejection openings within the range of 2.72
 mm. On the other hand, in the prior art, detection of ejection failure is
 performed every time of completion of printing operation for one sheet of
 printing paper. Therefore, in order to make it possible to print on 1400
 sheets of printing papers on average per one ink cartridge with employing
 the ink-jet head having 128 ejection openings for monochrome printing,
 extra amount of ink in the extent of CI=62.times.128.times.1400=11110400
 becomes necessary.
 In contrast to this, in the shown embodiment, upon exchanging of the ink
 cartridge, detection of ink ejection is performed at three regions having
 printing initiation points L, C and R at both sides of a designed
 (nominal) light axis position. The foregoing three points are set at the
 positions respectively corresponding to 672, 669 and 666 steps in the
 number of driving pulses of the carriage motor 30. Then, the ink ejection
 is performed so that respective of the three points L, C and R become the
 ejection initiation points.
 Here, assuming that the ink ejection width in respective of three regions
 of ink ejection is about 1.76 mm and the printing density in the shifting
 direction of the ink-jet head 5 is 360 DPI, approximately 40 times of ink
 ejection becomes necessary. It should be noted that the shifting speed of
 the carriage 15 is 277 mm/sec.
 Then, in the ejection detecting operation performed for three times upon
 exchanging of the ink cartridge, the position where the level drop of the
 output from the photosensor 44b becomes maximum (position where the output
 D of the detecting sensor 44 becomes maximum), that is, the position where
 the ink interrupts the light most efficiently, is taken as the position
 for ejection in detection of the ejection failure during subsequent actual
 printing operation. At this time, number of ink ejection is set at the
 same number for the foregoing detection of ejection to be performed upon
 exchanging of the ink cartridge.
 By this, the ink consuming amount (CI) necessary for detecting ejection
 failure with respect to one ink cartridge, when the ink-jet head having
 128 of ejection openings for monochrome printing is employed, becomes
 CI=40.times.128.times.3+40.times.128.times.1400=7183360.
 Comparing this with the ink consuming amount in the prior art, the ink
 consuming amount required for detection of ejection failure is reduced to
 be approximately 65% of that required in the prior art. Also, upon
 detection of ejection at exchanging of the ink cartridge, ink ejection is
 performed over wider range than that in the prior art, and it becomes
 possible to adapt for unexpectedly large offset of the light axis.
 Next, discussion will be given for ink ejecting position setting process
 for ejection failure detecting operation in the construction set forth
 above, with reference to a flowchart of FIG. 14. The shown process is
 executed upon exchanging of the ink cartridge.
 At first, at step S101, the ink ejecting position (P) for detecting
 ejection failure is provisionally set at the point C which has been
 previously set (P=C). Next, at step 102, the detecting sensor 44 is turned
 ON to cause emission of light from the light emitting element 44a. Also,
 at step S103, with taking the foregoing provisionally set position or
 other position set in relation to the provisional position, as the
 ejection initiation position, the ink-jet head 5 is moved within the
 above-mentioned range and ink ejection is performed for the
 above-mentioned times (e.g. 25 times). Then, at step S104, the output of
 the detecting sensor 44 is transferred to RAM 27 of the control portion 24
 and stored therein. Thereafter, at step S105, the detecting sensor 44 is
 turned OFF and light emission of the light emitting element 44a is
 terminated.
 At step S106, check is performed if detection process with taking three
 points L, C, R as the provisionally set position and other positions set
 in relation to the provisionally set position is completed or not. If
 judgement is made that process is completed, the process is advanced to
 step S108, and otherwise, the process is advanced to step S107 for moving
 the ink-jet head 5 to set the ink ejecting position (P) to the point C or
 the point L or point R, and then to return the process to step S102. Thus,
 detection of ink ejection within a range associated with the three points
 is performed.
 Upon completion of detection of ink ejection at three positions, output
 D(L) obtained by performing detection of ejection with respect to the
 point L, output D(C) obtained by performing detection of ejection with
 respect to the point C and output D(R) obtained by performing detection of
 ejection with respect to the point R are stored in RAM 27.
 Subsequently, processes of step S108 and subsequent steps are performed
 with employing this data.
 At step S108, comparison of the outputs D(L) and D(C) is performed. If
 D(L)&gt;D(C), the process is advanced to step S109 for comparing the outputs
 D(L) and D(R). Then, if D(L)&gt;D(R), the process is advanced to step S110.
 As a result, amongst ejecting positions associated with the foregoing
 three points, the ejecting position L' corresponding to the maximum output
 relating to the point L is set as the ink ejecting position (P) for
 detection of ejection failure. Thereafter, the process goes END.
 On the other hand, at step S108, if D(L).ltoreq.D(C), the process is
 advanced to step Slll for performing comparison of D(R) and D(C). Here, if
 D(R)&gt;D(C), the process is advanced to step S112 for setting the ejecting
 position R' corresponding to the maximum output relating to the point R as
 the ink ejecting position (P) for detection of ejection failure.
 Thereafter, the process goes END. On the other hand, if D(R).ltoreq.D(C)
 as checked at step S111, the process is advanced to step S113 for setting
 the ejecting position C' corresponding to the maximum output relating to
 the point C which is provisionally set, as the ink ejecting position (P)
 for detection of ejection failure. Thereafter, the process goes END.
 The ink ejecting position for detecting ejection failure determined in the
 manner set forth above, is effective until next occurrence of exchanging
 of the ink cartridge. Then, the information of the ink ejecting position
 thus determined is stored in EPROM.
 Accordingly, with the second embodiment discussed above, with respect to
 offset of the ink ejecting position for detecting ink ejection to be
 caused due to tolerance of components of the apparatus, dimensional
 tolerance in assembling of the apparatus, and variation of dimensions due
 to use environmental condition of the apparatus, correction is performed
 upon exchanging of the ink jet cartridge, in which the head and the tank
 are integrated to determine the position for detecting ejection failure at
 the position where the light from the detecting sensor can be interrupted
 most effectively. Therefore, more precise detection of ejection failure
 can be performed.
 Further, once the position is determined, the ink ejection amount in
 detection of ejection failure after completion of actual printing
 operation can be reduced. Thus, ink consuming amount associated with
 detection of ejection failure can be reduced so that greater amount of ink
 can be used for actual printing operation.
 While the number of ink ejections upon ejection detection operation is
 discussed as 25 times, it is possible to use other values as long as not
 affecting precision in detection. Also, it is possible to vary number of
 ejections of the ink at every ink ejecting position. Furthermore, the
 predetermined value is employed in the shown embodiment as threshold value
 for detection; the present invention should not be specified to the shown
 arrangement. For example, it is possible to set at a given ratio of the
 output of the detecting sensor upon detection of ejection which is
 performed upon exchanging of the ink.
 Further, in the shown embodiment, the positions to be candidate points for
 determining the positions for ejection to be performed upon exchanging of
 the ink cartridge are three. However, the present invention should not be
 limited to this. For example, it can be other values, and is not necessary
 to be always set as the constant value but can be variable. Also, when
 ink-jet head for monochrome printing and ink-jet head for color printing,
 when the detection means is provided, ink ejection amount, the ejection
 frequency, ejecting speed may vary the ink supply amount per respective
 inks in detection of the ink ejection amount, the number of ink ejections
 ink ejecting position and offset amount from the design value of the light
 axis of the sensor may be set separately for respective color inks in
 detection of ejection.
 Further, respective embodiments set forth above have been exemplarily
 discussed in terms of application for the facsimile apparatus, but the
 present invention is applicable not only for the facsimile but also in
 various printing apparatuses employing the ink-jet printing system. It is
 possible to apply the present invention for an ink-jet printer to be
 connected to a host apparatus, such as a computer or so forth for
 outputting image, character and so forth. In such case, it is desirable to
 perform detection of ejecting condition of the ink by the photosensor in
 advance of initiation of printing or in advance of initiation of printing
 per one page. In the facsimile apparatus, since printing is performed with
 receiving the data transmitted through the telephone network and storing
 the received data in the memory, whether printing for one page is
 performed appropriately or not is checked after printing for one page.
 When inappropriate printing due to occurrence of ejection failure is
 detected, it is possible to interrupt printing and store data of the
 relevant page and subsequent pages in the memory for preventing loss of
 received data. In the printer performing printing with connecting to the
 host or so forth, it is easy to enter a command for re-output since the
 user is present in the vicinity of the apparatus. Also, by checking
 occurrence of ejection failure before printing one page, it is possible to
 detect ejection failure at earlier timing than checking after printing. By
 this, it becomes possible to eliminate a period of printing under the
 condition where the ejection failure occurs. In addition, the printing
 medium, such as the paper or so forth, can be saved. Therefore, detection
 of the ejecting condition in advance of printing is desired.
 On the other hand, in the facsimile apparatus, there is apparatus having a
 printing portion which can be used as general printing portion. In such
 facsimile apparatus, in addition to a terminal for connection with
 telephone line, a terminal for connection with the computer or so forth is
 provided so as to achieve both functions as the facsimile apparatus and
 the printer by manual switching by the user or automatic switching by
 preferentially outputting the side from which data is transmitted.
 Further, while the foregoing embodiments have been discussed for examples
 to perform monochrome printing with mounting one ink cartridge, in which a
 tank storing the ink and the printing head are integrated, the present
 invention is applicable for the printing apparatus mounting a plurality of
 cartridges corresponding to a plurality of colors of inks to form a color
 image.
 On the other hand, in the facsimile apparatus which can be used as printer
 as set forth above, it becomes possible to form a black monochrome image
 when used as the facsimile and to form a color image when used as the
 printer by a construction exchangeably mounting the cartridge ejecting a
 single color ink and the cartridge storing a plurality of color inks for
 color printing. In such construction, it is possible that when the
 apparatus is used as the facsimile, detection of ejecting condition by the
 photosensor is performed every time of printing for one page, as set forth
 above, and when the apparatus is used as the printer, detection of the
 ejecting condition is not performed. Particularly, when the apparatus is
 used as the printer, commanding of outputting again is relatively earlier
 than that in the case of the facsimile apparatus. Therefore, by setting
 not to perform detection of ejecting condition, ink consumption can be
 restricted to lower running cost.
 Furthermore, in the embodiments as set forth above, the invention is
 discussed in relation to the facsimile apparatus employing a printing
 apparatus in which the ink jet cartridge integrally having the head and
 the ink tank is detachably provided. The present invention is not only
 applied to this type of the printing apparatus but to printing apparatuses
 in which the head and the ink tank comprising the ink jet cartridge are
 provided in a detachable manner from each other, and in which the head and
 the ink tank are provided seperately. In these constructions of the
 printing apparatus, in the case that a life of the head is long so that a
 frequency of exchanging of the head is less than that of the ink tank, the
 above-described correction operation of the detection position for
 detecting the ejection failure may be performed for each exchange of the
 head. On the other hand, in the case that the head of a permanent type is
 employed, since it is necessary to consider change of ejection position of
 the head with time, the correction operation may be performed at a
 predetermined interval or at time when printing of a predetermined amount
 have been completed.
 The present invention achieves distinct effect when applied to a recording
 head or a recording apparatus which has means for generating thermal
 energy such as electrothermal transducers or laser light, and which causes
 changes in ink by the thermal energy so as to eject ink. This is because
 such a system can achieve a high density and high resolution recording.
 A typical structure and operational principle thereof are disclosed in U.S.
 Pat. Nos. 4,723,129 and 4,740,796, and it is preferable to use this basic
 principle to implement such a system. Although this system can be applied
 either to on-demand type or continuous type ink jet recording systems, it
 is particularly suitable for the on-demand type apparatus. This is because
 the on-demand type apparatus has electrothermal transducers, each disposed
 on a sheet or liquid passage that retains liquid (ink), and operates as
 follows: first, one or more drive signals are applied to the
 electrothermal transducers to cause thermal energy corresponding to
 recording information; second, the thermal energy induces sudden
 temperature rise that exceeds the nucleate boiling so as to cause the film
 boiling on heating portions of the recording head; and third, bubbles are
 grown in the liquid (ink) corresponding to the drive signals. By using the
 growth and collapse of the bubbles, the ink is expelled from at least one
 of the ink ejection orifices of the head to form one or more ink drops.
 The drive signal in the form of a pulse is preferable because the growth
 and collapse of the bubbles can be achieved instantaneously and suitably
 by this form of drive signal. As a drive signal in the form of a pulse,
 those described in U.S. Pat. Nos. 4,463,359 and 4,345,262 are preferable.
 In addition, it is preferable that the rate of temperature rise of the
 heating portions described in U.S. Pat. No. 4,313,124 be adopted to
 achieve better recording.
 U.S. Pat. Nos. 4,558,333 and 4,459,600 disclose the following structure of
 a recording head, which is incorporated to the present invention: this
 structure includes heating portions disposed on bent portions in addition
 to a combination of the ejection orifices, liquid passages and the
 electrothermal transducers disclosed in the above patents. Moreover, the
 present invention can be applied to structures disclosed in Japanese
 Patent Application Laying-open Nos. 123670/1984 and 138461/1984 in order
 to achieve similar effects. The former discloses a structure in which a
 slit common to all the electrothermal transducers is used as ejection
 orifices of the electrothermal transducers, and the latter discloses a
 structure in which openings for absorbing pressure waves caused by thermal
 energy are formed corresponding to the ejection orifices. Thus,
 irrespective of the type of the recording head, the present invention can
 achieve recording positively and effectively.
 The present invention can be also applied to a so-called full-line type
 recording head whose length equals the maximum length across a recording
 medium. Such a recording head may consist of a plurality of recording
 heads combined together, or one integrally arranged recording head.
 In addition, the present invention can be applied to various serial type
 recording heads: a recording head fixed to the main assembly of a
 recording apparatus; a conveniently replaceable chip type recording head
 which, when loaded on the main assembly of a recording apparatus, is
 electrically connected to the main assembly, and is supplied with ink
 therefrom; and a cartridge type recording head integrally including an ink
 reservoir.
 It is further preferable to add a recovery system, or a preliminary
 auxiliary system for a recording head as a constituent of the recording
 apparatus because they serve to make the effect of the present invention
 more reliable. Examples of the recovery system are a capping means and a
 cleaning means for the recording head, and a pressure or suction means for
 the recording head. Examples of the preliminary auxiliary system are a
 preliminary heating means utilizing electrothermal transducers or a
 combination of other heater elements and the electrothermal transducers,
 and a means for carrying out preliminary ejection of ink independently of
 the ejection for recording. These systems are effective for reliable
 recording.
 The number and type of recording heads to be mounted on a recording
 apparatus can be also changed. For example, only one recording head
 corresponding to a single color ink, or a plurality of recording heads
 corresponding to a plurality of inks different in color or concentration
 can be used. In other words, the present invention can be effectively
 applied to an apparatus having at least one of the monochromatic,
 multi-color and full-color modes. Here, the monochromatic mode performs
 recording by using only one major color such as black. The multi-color
 mode carries out recording by using different color inks, and the
 full-color mode performs recording by color mixing.
 Furthermore, although the above-described embodiments use liquid ink, inks
 that are liquid when the recording signal is applied can be used: for
 example, inks can be employed that solidify at a temperature lower than
 the room temperature and are softened or liquefied in the room
 temperature. This is because in the ink jet system, the ink is generally
 temperature adjusted in a range of 30.degree. C.-70.degree. C. so that the
 viscosity of the ink is maintained at such a value that the ink can be
 ejected reliably.
 In addition, the present invention can be applied to such apparatus where
 the ink is liquefied just before the ejection by the thermal energy as
 follows so that the ink is expelled from the orifices in the liquid state,
 and then begins to solidify on hitting the recording medium, thereby
 preventing the ink evaporation: the ink is transformed from solid to
 liquid state by positively utilizing the thermal energy which would
 otherwise cause the temperature rise; or the ink, which is dry when left
 in air, is liquefied in response to the thermal energy of the recording
 signal. In such cases, the ink may be retained in recesses or through
 holes formed in a porous sheet as liquid or solid substances so that the
 ink faces the electrothermal transducers as described in Japanese Patent
 Application Laying-open Nos. 56847/1979 or 71260/1985. The present
 invention is most effective when it uses the film boiling phenomenon to
 expel the ink.
 Furthermore, the ink jet recording apparatus of the present invention can
 be employed not only as an image output terminal of an information
 processing device such as a computer, but also as an output device of a
 copying machine including a reader, and as an output device of a facsimile
 apparatus having a transmission and receiving function.
 The present invention has been described in detail with respect to various
 embodiments, and it will now be apparent from the foregoing to those
 skilled in the art that changes and modifications may be made without
 departing from the invention in its broader aspects, and it is the
 intention, therefore, in the appended claims to cover all such changes and
 modifications as fall within the true spirit of the invention.