Ink jet apparatus and method for detecting ink nondischarge based on ink temperature

If one page of recording is terminated, a carriage moves to a position at which a recording head is located opposite a cap. Then, the ink is discharged through nozzles of the recording head onto temperature detecting element within the cap. Temperature change of the temperature detecting element upon contact with the ink is output from a detecting circuit, and the normal discharge of ink is detected by discharge detecting means. In this way, a decrease in the ink remaining or the detection of ink nondischarge can be securely made.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an ink discharge detecting method for an 
ink jet recording apparatus, and the ink jet recording apparatus. 
2. Related Background Art 
Conventionally, a variety of recording apparatuses for recording onto a 
recording medium such as a paper or OHP sheet have been proposed, and 
especially, an ink jet recording apparatus which directly jets the ink 
from a recording head onto a recording sheet, has gained wide acceptance 
as a recording apparatus having the advantages of low running costs and 
silent recording operation. 
On the other hand, the method for detecting that the amount of ink has 
decreased in such an ink jet recording apparatus involves optically 
detecting a float moving up or down within an ink tank, or detecting the 
variation in resistance between electrodes provided within an ink tank. 
However, the above conventional methods had a drawback that since a 
detecting member such as a float or electrodes was necessary within the 
ink tank, the detecting member had to be also exchanged integrally with 
the cartridge to be exchanged when the amount of ink within the ink tank 
decreased, for example, in the case of a disposable recording head of the 
cartridge type in which the recording head was formed integrally with the 
ink tank, so that costs and wastes increased. 
Further, the above conventional methods involved detecting analogue 
variation of ink quantity which resulted from decreasing amount of ink 
within the ink tank, whereby if the detected result was below a preset 
threshold, the ink absence was detected, at which time the ink within the 
recording head was not completely absent in practice, with the result that 
the decrease in the amount of ink was detected while a slight amount of 
the ink was left within the ink tank. Accordingly, there was a problem 
that because the waste ink unusable for the recording was produced, the 
running costs increased. Also, there was a problem that the ink level 
within the ink tank shifted up or down, along with the movement of the ink 
tank, bringing about malfunctions. 
SUMMARY OF THE INVENTION 
The present invention is devised to resolve the above-mentioned problems of 
the conventional art, and its object is to provide an ink jet recording 
apparatus and an ink discharge detecting method in which the decrease in 
ink remain or undischarge of ink can be securely detected with the amount 
of waste ink unusable for the recording reduced. 
Also, it is another object of the invention to provide an ink jet recording 
apparatus for recording using a recording head which discharges heated ink 
onto a recording medium through discharge ports, characterized by 
comprising temperature detecting means, which is contactable with the ink 
discharged through said discharge ports, for detecting temperature change 
arising upon contact with said ink, positioning means for positioning said 
recording head and said temperature detecting means at relatively opposed 
locations so that the ink discharged through said discharge ports make 
contact with said temperature detecting means, and discharge detecting 
means for detecting discharge or undischarge of ink based on a detecting 
result of said temperature detecting means. 
Also, it is another object of the invention to provide an ink jet recording 
apparatus for recording using a recording head having a plurality of 
nozzles which discharges the ink, characterized by comprising discharge 
detecting means for detecting the presence or absence of ink discharge 
from said recording head, varying means for varying the number of 
discharged ink droplets per unit time, and a control circuit for 
controlling the number of discharged droplets per unit time in making 
discharge detection by said discharge detecting means to be different from 
that during the recording, using said varying means. 
Also, it is another object of the invention to provide an ink jet recording 
apparatus for recording using a recording head having a plurality of 
nozzles which discharges the ink, characterized by comprising discharge 
detecting means for detecting the presence or absence of ink discharge 
from said recording head, varying means for varying the volume of 
discharged ink droplets per unit time, and a control circuit for 
controlling the volume of discharged droplets per unit time in making 
discharge detection by said discharge detecting means to be different from 
that during the recording, using said varying means. 
Also, it is another object of the invention to provide an ink jet recording 
apparatus for recording using a recording head having a plurality of 
nozzles which discharges the ink, characterized by comprising discharge 
detecting means for detecting the presence or absence of ink discharge 
from said recording head, and selecting means for selecting the discharge 
state from each discharge port of said recording head when discharge 
detection is made by said discharge detecting means, said recording head 
provided with a discharge port array having a plurality of discharge ports 
arranged. 
Also, it is another object of the invention to provide an ink jet recording 
apparatus for recording using a recording head having a plurality of 
nozzles which discharges the ink, characterized by comprising discharge 
detecting means for detecting the presence or absence of ink discharge 
from said recording head, input means for indicating the start of 
discharge detection, and a control device for controlling discharge 
detection with said discharge detecting means to be performed periodically 
or when input is made into said input means. 
Also, it is another object of the invention to provide an ink discharge 
detecting method of an ink jet recording apparatus for recording using a 
recording head which discharges the ink onto a recording medium through 
discharge ports, characterized by including a process of discharging the 
ink from said discharge ports to make contact with an objective, a process 
of detecting the physical change produced in said objective by the 
discharged ink, and a process of detecting the discharge or undischarge of 
ink based on a detected result of said physical change. 
Also, it is another object of the invention to provide an ink discharge 
detecting method of an ink jet recording apparatus for recording using a 
recording head in which the discharge direction of the ink discharged 
through a plurality of discharge ports onto a recording medium may lie in 
a horizontal direction or oblique to the horizontal direction, 
characterized by including a process of discharging the ink from said 
discharge ports to make contact with an objective, a process of detecting 
the physical change produced in said objective by the discharged ink, and 
a process of detecting the discharge or undischarge of ink based on a 
detected result of said physical change, wherein when discharge detection 
is made, the ink is discharged selectively from the discharge ports 
located upward in a vertical direction, among discharge ports of said 
recording head. 
Also, it is another object of the invention to provide an ink remain 
detecting method of an ink jet recording apparatus for recording using a 
recording head which discharges the ink through discharge ports onto a 
recording medium, characterized by including a process of discharging the 
ink from said discharge ports to make contact with an objective, a process 
of detecting the physical change produced in said objective by the 
discharged ink, and a process of detecting the ink remain based on a 
detected result of said physical change. 
Also, it is another object of the invention to provide an ink discharge 
detecting method performed with an ink jet recording apparatus having a 
recording head having a plurality of nozzles which discharges the ink, and 
discharge detecting means for detecting the presence or absence of ink 
discharge from said recording head, characterized in that the number of 
discharged ink droplets per unit time is made variable, so that the number 
of discharged droplets per unit time in making discharge detection may be 
different from that during the recording. 
Also, it is another object of the invention to provide an ink discharge 
detecting method performed with an ink jet recording apparatus having a 
recording head having a plurality of nozzles which discharges the ink, and 
discharge detecting means for detecting the presence or absence of ink 
discharge from said recording head, characterized in that the volume of 
discharged ink droplets per unit time is made variable, so that the volume 
of discharged droplets per unit time in making discharge detection may be 
different from that during the recording. 
With the above constitution, if one page of recording is terminated, the 
carriage is moved to a position at which the recording head is located 
opposite a cap. Then, the ink is discharged through the nozzles of the 
recording head onto a temperature detecting element within the cap. 
Temperature change of the temperature detecting element upon contact with 
the ink is output from a detecting circuit, and the normal discharge of 
ink is detected by discharge detecting means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of the present invention will be described below 
with reference to the drawings. 
Embodiment 1-1 
FIG. 1 is a view showing an ink jet recording apparatus to which the 
present invention is applied. In FIG. 1, 1 is a recording head, or in this 
embodiment, an ink jet recording head of the cartridge type in which an 
ink tank is contained therein and the whole recording head is exchanged 
for a new one when the ink becomes absent. 2 is a carriage for 
reciprocating the recording head 1 in a direction orthogonal to a 
conveying direction (sub-scan direction) of recording sheet 12 as 
indicated by the arrow, i.e., in a main scan direction, while carrying the 
recording head 1 at good precision, in which the carriage is slidably held 
by a guide rod 11 and an abutting portion 2a. Reciprocating of the 
carriage 2 is performed by a pulley 4 driven by a motor not shown, and a 
timing belt 3, in which a print signal and the power to be given to the 
recording head 1 is supplied via a connector contained in the carriage 2 
through a flexible cable 7 from an electric circuit in a main device. 
15 is a cap serving as ink receiving means, which is placed corresponding 
to a stand-by position (home position) of the carriage 2, and moved up or 
down as required to make close contact with the recording head 1 to cover 
a nozzle unit, thereby preventing the evaporation of ink or contamination 
of dirts. 
In this embodiment, to position the recording head 1 and the cap 15 at 
relatively opposed locations, a carriage home sensor 10 provided on the 
main device of recording apparatus and a light shielding plate 2a provided 
on the carriage 2 are used. The carriage home sensor 10 is composed of a 
photo-interrupter of the transmission or reflection type, which detects 
that when the carriage 2 is moved to the stand-by position, light 
transmitted from a portion of the carriage home sensor 10 is interrupted 
from passing therethrough by the light shielding plate 2a, or the 
recording head 1 and the cap 15 are positioned at relatively opposed 
locations, using reflected light. 
Recording sheet 12 is supplied from the lower side upwardly in the figure, 
and bent to a horizontal direction by a sheet supply roller 5 and a paper 
guide 6 to be conveyed in a direction (sub-scan direction) as indicated by 
the arrow. The sheet supply roller 5 and a sheet exhaust roller 9 are 
driven by respective drive systems, not shown, to convey the recording 
sheet 12 in the sub-scan direction at high precisions, in cooperation with 
the carriage 2 which is reciprocated, as required. 8 is a so-called spur 
shaft made of a water repellent material, and having spurs 8a spaced away 
at a predetermined interval so that they make contact with the recording 
surface of recording sheet 12 only at their circumferential blade-like 
portions, whereby even if they make contact with unfixed ink on the 
recording sheet immediately after the printing, the recording sheet 12 can 
be guided and conveyed without exerting adverse effects on the image. 
The recording head 1 for use in this embodiment is a recording head of the 
ink jet system with a resolution of 360DPI, and having 64 nozzles, in 
which the ink can be discharged through discharge ports at the top end of 
nozzles by the use of the pressure of film boiling arising in the ink due 
to heating by electricity-heat converters provided within the nozzles. 
Next, a discharge principle of recording head for use with the ink jet 
recording apparatus in this embodiment as recording means of the present 
invention will be described below. A recording head unit to be applied to 
the ink jet recording apparatus typically comprises minute liquid 
discharge ports (orifices), liquid channels, energy exerting portions each 
provided on a part of each liquid channel, and energy generating means for 
generating liquid droplet forming energy to be applied to the liquid 
residing in said energy exerting portions, and is exchangeable. 
Examples of energy generating means for generating such energy may include 
using electromechanical transducer such as piezo element, directing an 
electromagnetic wave such as a laser to the liquid to be heated by 
absorption to discharge fine liquid droplets under the action of the 
heating, or heating the liquid by the use of electricity-heat converters 
to discharge the liquid. Among them, a recording head unit for use with 
the ink jet recording system of discharging the liquid by heat energy 
allows the recording to be made at high resolutions because liquid 
discharge ports (orifices) for discharging liquid droplets to form flying 
liquid droplets for recording can be arranged at high densities. 
Also, the recording head unit using electricity-heat converters as energy 
generating means makes it possible to provide an ink jet recording head 
which is easy to fabricate in multi-nozzle form and allows for high 
density packaging, with excellent mass productivity and low manufacturing 
costs, because the whole recording head can be easily made in compact 
size, and by fully utilizing many merits of the IC technology or micro 
process technology which has achieved remarkable technical advancements 
with improved reliability in the recent semiconductor fields, the longer 
and planar (two dimensional) construction can be easily accomplished. 
An ink jet recording head unit fabricated through a semiconductor 
fabrication process by using electricity-heat converters as energy 
generating means is typically provided with liquid channels corresponding 
to ink discharge ports, and electricity-heat converters as means for 
applying heat energy to the liquid filling the liquid channels to 
discharge the ink through corresponding ink discharge ports to form flying 
liquid droplets, wherein the liquid is supplied from a common liquid 
chamber to each liquid channel. As to the fabrication method for the ink 
discharge unit, there is an application for a method in which on a first 
substrate are laminated sequentially a solid layer for forming at least 
liquid channels, an active energy line curable material layer for use to 
form at least walls of liquid channels, and a second substrate, then a 
mask is laminated on the second substrate, active energy line is directed 
from upward of said mask toward at least the walls of liquid channels on 
the active energy line curable material layer to cure them as the 
constitutional portion, and then uncured portions of the solid layer and 
the active energy line curable material layer are removed from between two 
substrates to form at least liquid channels (see Japanese Laid-open Patent 
Application No. 62-253457). 
FIG. 2 shows a schematic constitution of the ink jet recording head unit. 
The recording head unit 101 is constituted of an active energy line 
curable material layer 210 which has been cured, having electricity-heat 
converters 103, electrodes 104 and liquid channels 110 formed as the film 
on a substrate 102 which is a first substrate, through a semiconductor 
fabrication process such as etching vapor deposition and sputtering, and a 
ceiling plate 106. In such recording head unit 101, recording liquid 112 
is supplied from a liquid reservoir through a liquid supply tube 107 to a 
common liquid chamber 108. 
109 is a connector for liquid supply tube. Recording liquid 112 in the 
common liquid chamber 108 is supplied into liquid channels 110 owing to 
capillary phenomenon, and retained stably with meniscuses formed on the 
ink discharge ports 111 at the top end of liquid channels. Thus, if 
electricity-heat converters 103 are energized, the liquid on the plane of 
electricity-heat converters is heated, giving rise to foaming phenomenon 
due to film boiling to discharge liquid droplets through ink discharge 
ports 111 by growth of bubbles. With the above constitution, a 
multi-nozzle ink jet recording head unit can be fabricated having a high 
density arrangement of liquid channels with a discharge port density of 
400 dots/inch. 
Accordingly, the temperature of discharged ink droplets becomes greatly 
higher than room temperature owing to heating by electricity-heat 
converters, the temperature change upon contact with ink droplets is 
detected by temperature detecting means, and the detected temperature is 
compared with room temperature, whereby the normal or abnormal discharge, 
or the presence or absence of ink within the ink tank can be examined. In 
this embodiment a temperature detecting element 16 is provided within the 
cap 15, and with the recording head 1 and the temperature detecting 
element 16 positioned at relatively opposed locations, the ink is 
discharged toward the temperature detecting element 16, and the presence 
or absence of ink discharge can be judged by monitoring the output of the 
temperature detecting element 16. 
Herein, the temperature detecting element 16 may include, but not limited 
to, those of detecting the temperature change as a physical quantity, and 
detecting the temperature change as a chemical change of substance; for 
example, the temperature change caused by the contact with the ink is 
detected as a change in the current or voltage on the basis of the change 
in the resistance value of a resistor. 
FIG. 3 is a cross-sectional view showing the details of the cap 15. In FIG. 
15, 15a is a cap main body formed of an elastic material such as a rubber, 
which is held by a cap support 15b and pressed against the surface of 
recording head 1 which is placed opposed to the cap, thereby sealingly 
enclosing the nozzles 1a of the recording head 1 to prevent the nozzles 1a 
from clogging due to evaporation of ink. On the other hand, when the 
clogging occurs in the nozzles 1a, the pressure within the cap 15 is 
caused to decrease by activating a suction pump not shown connected to one 
end of a suction tube 17, so that the ink is discharged through the 
nozzles 1a of the recording head 1, thereby removing the clogging to 
recover the recording head 1. 
18 is an ink absorbing member, which is configured to absorb the ink 
discharged from the discharge ports 1a, and have the feature of retaining 
the interior of cap 15 in a highly humid state by absorbing the ink, 
thereby preventing the nozzles 1a from drying and clogging. 
16 is a temperature detecting element for detecting the absence of ink, 
which is a small thermistor in this embodiment. The temperature detecting 
element 16 is placed at a position substantially opposite the nozzles 1a, 
when the recording head 1 is at a stand-by position, so that if the ink is 
discharged from the discharge ports 1a of the recording head 1, ink 
droplets will impinge correctly on the outer face of the temperature 
detecting element 16, whereby it is possible to detect the presence or 
absence of ink discharge by detecting the presence or absence of 
temperature change. 
FIG. 4 is a block diagram showing a schematic configuration of a main part 
of the recording apparatus in this embodiment. In FIG. 4, 21 is a control 
unit for controlling the whole of the recording apparatus, comprising a 
CPU 23 such as a microprocessor, a ROM 25 storing a control program for 
the CPU 23 as shown in flowchart of FIG. 5, and various data, and a RAM 27 
useful as the work area for the CPU 23 and for temporarily storing various 
data. 
16 is the temperature detecting element as previously described, 29 is a 
detection circuit connected to the temperature detecting element 16, 31 is 
an A/D converting circuit for converting an analog signal output from the 
detection circuit 29 into digital signal to be sent to a control unit 21, 
33 is a head driving circuit for driving the recording head 1 in 
accordance with an instruction of the control unit 21, 35 is an image data 
input circuit for inputting image data sent from the host into the control 
unit 21, 37 is an alarm circuit for making an alarm for the occurrence of 
ink undischarge or ink absence, based on a signal sent out from the 
control unit 21, which detects the ink nondischarge or ink absence based 
on the output from the temperature detecting element 16, and 39 is an 
image memory for once storing print data of one page. Carriage driving 
means 32 for driving the carriage 2 is connected to the control unit 21. 
FIG. 5 is a flowchart showing a control processing with the control unit 
21. A detection sequence for ink discharge will be described with 
reference to the flowchart of FIG. 5. If a print start signal is received, 
the print data of one page sent is once stored in the image memory 39 
(step S1). Then, data is printed by the recording head 1 based on data of 
the image memory 39 (step S2). If recording of one page is terminated, the 
carriage 2 is moved by the carriage driving means 32 under the control of 
the control unit 21 to a stand-by position at which the recording head 1 
is placed opposite the cap 15 (step S3), wherein whether or not the 
carriage 2 has moved to the stand-by position can be detected by the 
carriage home sensor 10. 
In a state where the cap 15 is separated about 1 mm from the nozzle face, 
each nozzle of the recording head discharges 200 ink droplets toward the 
temperature detecting element 16 (step S4). The temperature of discharged 
droplets is from about 50.degree. to 60.degree. C., which is above room 
temperature, whereby a signal from the temperature detecting element 16 is 
input into the detection circuit 29 consisting of a bridge circuit and an 
amplifier circuit as shown in FIG. 6. 
The detection circuit 29 as shown in FIG. 6 is constituted of the bridge 
circuit for converting the change in resistance of the temperature 
detecting element 16 with respect to temperature change into the voltage 
change, and the amplifier circuit for amplifying the voltage change thus 
obtained. By monitoring the voltage value output from the amplifier 
circuit, the temperature change of the temperature detecting element 16 
can be detected. The voltage value output from the detection circuit 29 is 
converted from analog to digital form by the A/D converting circuit 31, 
and then input into the control unit 21. 
The control unit 21 compares the input voltage value with a predetermined 
threshold (a voltage value corresponding to a temperature above the 
highest ambient temperature allowable with the recording apparatus and 
below the temperature of ink droplets, for example, 40.degree. C.), 
whereby if its value is greater than the threshold, the control unit 21 
judges that the output of temperature detecting element 16 has changed 
(Yes at step S5), and that the ink has been discharged, that is, there is 
some ink remaining, so that its page has been completely printed, and 
erases data of the image memory 39 (step S6). And to prevent discharged 
ink from depositing within the cap, the ink collected within the cap 15 is 
sucked as waste ink via a suction tube 17 by a suction pump, not shown, so 
as to completely remove waste ink from within the cap 15 (step S7). 
On the other hand, if the voltage value output from the detection circuit 
29 and input into the control unit 21 is equal to or less than the 
threshold, the control unit 21 judges that no output of the temperature 
detecting element 16 has changed (No at step S5), and that no ink is 
discharged, that is, there is no ink remaining. And it issues an alarm 
signal indicating the ink absence to the alarm circuit 37, and displays an 
ink absence alarm (step S8), prompting the user to exchange the recording 
cartridge, wherein since its page has not been completely printed as the 
ink is used up in the course of the recording, print data is left stored 
in the image memory 39. 
Then, when the recording cartridge is exchanged by the user who has 
recognized the alarm signal (Yes at step S9), the return operation 
including an initial filling operation of filling new liquid channels for 
ink supply with the ink is performed (step S10). And data of one page is 
again printed from the top portion of the page, based on data stored in 
the image memory 39 (step S11), and then the procedure returns to step S3 
to execute the operation following the step S3. In this way, the ink 
absence detection sequence is executed. While in the first embodiment the 
temperature detecting element 16 is provided within the cap 15, it will be 
understood that the temperature detecting element 16 is not necessarily 
provided within the cap 15, and an ink absence detection unit may be 
separately disposed at a predetermined site on a main scan passage of the 
carriage and provided with the temperature detecting element 16 and a 
waste ink withdrawing means to enable ink discharge from the recording 
head. For example, in a color printer with a plurality of recording heads, 
it is common to have a cap as ink receiving means individually for each 
ink color to avoid the mixing of ink colors, and if the temperature 
detecting element is provided within each cap, temperature detecting 
elements corresponding to the number of recording heads are required, but 
it will be understood that if as previously described, the ink absence 
detection unit is provided separately, and each color ink is discharged in 
sequence from each recording head by moving the carriage to respective 
position, it is only necessary to provide a single temperature detecting 
element. 
Since the embodiment 1-1 uses a small spherical thermistor as the 
temperature detecting element, which forms a spot-like temperature 
measuring portion, for a recording head of large print width and having a 
discharge port array of more nozzles, the nozzles may be only partially 
monitored, resulting in a risk of false detection. Accordingly, to cope 
with such recording head of large print width and having a discharge port 
array of more nozzles, the temperature measuring portion of the 
temperature detecting means is of a shape in which it is placed opposite 
the discharge ports of the discharge port array, when the recording head 
and the temperature detecting means are positioned at relatively opposed 
locations, and specifically, if the temperature detecting means is linear 
or planar, more reliable temperature detection will be made. 
Further, the present invention is not limited to recording apparatuses of 
the ink jet recording system in which the ink is discharged by the use of 
heat energy generated by electricity-heat converters provided within 
nozzles, as shown in the embodiment 1-1. FIG. 7 is a cross-sectional view 
of an ink jet recording head using a piezo-electric (piezo) element 41 
which is electricity-heat converter, instead of electromechanical 
transducers for use with the ink discharge in the embodiment 1-1. This is 
an ink jet recording system in which piezo-electric element 41 is placed 
on the outer surface of a nozzle tube 40, and is caused to deform by an 
electrical signal issued to this piezo-electric element 41, so that an ink 
droplet is discharged due to the change in the volume of ink chamber 
within the nozzle tube, but it should be noted that in this ink jet 
recording system, it is also possible to detect ink discharge as in the 
embodiment 1-1 by providing heating means 43 for heating the ink up to an 
appropriate temperature in the neighborhood of a nozzle to raise the 
temperature of flying ink droplets above room temperature. It goes without 
saying, in this case, that the temperature of ink droplets is controlled 
to be above a predetermined threshold temperature. 
The heating method with heating means 43 may include those of heating the 
ink through the wall of nozzle tube by winding a narrow nichrome wire 
around the nozzle tube 40, and directly heating the ink by boring the wall 
face of nozzle tube and embedding a small heat generating element 
electrically insulated. 
As above described, the recording apparatus according to the present 
invention allows the presence or absence of ink discharge to be detected, 
and therefore allows the ink nondischarge caused by some reason to be 
detected. If there occurs an unexpected failure, such as nondischarge 
owing to fixing of ink within nozzles or malfunction of electric circuit 
of the recording head not to permit application of discharge signal, the 
occurrence of such failure can be detected. 
However, the recording apparatus according to the present invention makes 
it possible to detect ink nondischarge, the ink nondischarge can be 
considered as the decrease in the ink remain quantity within the ink tank. 
Embodiment 1-2 
FIG. 8 is a block diagram showing the schematic configuration of a 
recording apparatus in embodiment 1-2. In FIG. 8, 51 is an ambient 
temperature detecting element for detecting the ambient temperature of the 
recording apparatus to be used, wherein this detecting element is composed 
of the same element as the temperature detecting element 16, and provided 
outside of a cap 15, as well as being connected to a detection circuit 29. 
FIG. 9 is a circuit diagram showing the detection circuit 29, consisting of 
a bridge circuit using a temperature detecting element 16 and an ambient 
temperature detecting element 51 for outputting the voltage proportional 
to the difference between resistance values of both elements, that is, the 
difference between both temperatures, and an amplifier circuit for 
amplifying the voltage thus obtained. By monitoring the voltage value 
output from this amplifier circuit, the temperature change of the 
temperature detecting element 16 relative to the ambient temperature can 
be detected. 
53 is a comparator which outputs a signal "1" when the output from the 
detection circuit 29 is above a predetermined threshold, and a signal "0" 
when at or below the predetermined threshold, which signal is then sent to 
a control unit 21. FIG. 10 shows the relation between the output waveform 
from the detection circuit 29 and the discharge signal to the nozzles of 
recording head, with the time indicated in the axis of abscissas and the 
output voltage value from the detection circuit 29 indicated in the axis 
of ordinates of output waveform. In the figure, the straight line as 
indicated by Vth shows the threshold level. 
Since other configuration of FIG. 9 is the same as in the embodiment 1-1, 
the explanation thereof is omitted. The detection sequence of ink 
discharge is the same as the control procedure as shown in the flowchart 
of FIG. 5 in the embodiment 1-1. Note that the judgment at step S5 is made 
by checking to determine whether or not the output voltage value 
corresponding to the difference between temperatures of the temperature 
detecting element 16 and the ambient temperature detecting element 51 
exceeds a predetermined threshold. 
According to the embodiment 1-2, when the ambient temperature decreases, 
its difference from the temperature of temperature detecting element 16 
increases, whereby there is the effect of being less affected by 
instantaneous temperature changes caused by electrical noise of recording 
apparatus air currents. 
Note that in the embodiment 1-2, when discharging the ink through all the 
discharge ports at step S4, it is preferable to discharge the ink toward 
the temperature detecting element 16 while the carriage member 2 is moved 
1 mm, that is, the recording head 1 is moved 1 mm in a main scan 
direction. Herein, the reason of discharging the ink while the carriage 2 
is moved 1 mm is to prevent the ink from not hitting the temperature 
detecting element 16 due to displaced impinging position of ink droplets, 
wherein the recording head 1 is moved along with the movement of the 
carriage member 2, and flying ink droplets may also be moved about 1 mm 
within an opening portion of the cap 15, resulting in a higher probability 
of impingement upon the temperature detecting element 16, and thereby 
provide more reliable temperature detection. 
In this way, even with a small detection area of the temperature detecting 
element, it is possible to make temperature detection without malfunction 
by discharging the ink while the recording head is moved, thereby 
dispersing ink droplets over a large range to extend the detectable area. 
Note that this embodiment, like the embodiment 1-1, can also utilize an ink 
jet recording head using piezo-electric (piezo) elements which are 
electromechanical transducers, instead of electricity-heat converters for 
ink discharge. In such recording head using piezo-electric elements, if 
there is a difference between the temperature of ink droplets and the 
ambient temperature, the ink discharge can be detected, whereby it is 
possible to realize the power-saving by varying the heating temperature 
with heating means depending on the ambient temperature. 
Embodiment 1-3 
While in the second embodiment as above described, the ambient temperature 
detecting element is provided apart from the temperature detecting 
element, and the presence or absence of ink discharge is judged based on 
the difference between the temperature detected by the temperature 
detecting element and the ambient temperature (room temperature), it 
should be noted that the substantially same effects can be obtained by 
altering the detection sequence using only the temperature detecting 
element, like the embodiment 1-1, without using the ambient temperature 
detecting element. FIG. 11 is a flowchart showing such a sequence. The 
different point from that shown in FIG. 5 is that after the carriage 
member 2 is moved to a stand-by position (cap position) at step S23, the 
ambient temperature is measured using a temperature detecting element 16 
and its output value is temporarily stored in a RAM 27 of the control unit 
21 (step S24), and after each nozzle is caused to discharge 200 ink 
droplets, the output change of the temperature detecting element 16 is 
checked by detecting the difference between the output value of 
temperature detecting element 16 and that before ink discharge temporarily 
stored as previously described, whereby the presence or absence of ink 
discharge is judged. 
The block diagram showing the schematic configuration of a main portion of 
the recording apparatus in embodiment 1-3 is the same as that shown in 
FIG. 4, and the detection circuit 29 is the same as that shown in FIG. 6. 
In the embodiment 1-3, if the interval between the measurement of the 
ambient temperature at step S24 and the temperature measurement with the 
temperature detecting element 16 after ink discharge at step S26 is made 
very short, e.g., about several hundreds msec, the change in the ambient 
temperature within this interval can be substantially ignored. 
Embodiment 1-4 
In this embodiment 1-4, an ink absorbing member is provided around the 
periphery of the temperature detecting element 16, and if an ink droplet 
adhering to the surface of temperature detecting element 16 grows to some 
extent of volume the ink droplet is contacted with and absorbed into the 
ink absorbing member to prevent the ink droplet from growing beyond a 
certain size. 
As previously described, the ink within the cap 15 is removed by a suction 
pump, not shown, but in order not to degrade the sensitivity or thermal 
response ability, it is desirable to remove as many ink droplets adhering 
to the temperature detecting element 16 as possible. In this embodiment 
1-4, the shape of ink absorbing member 18 is devised as shown in FIG. 12, 
and the distance A between the temperature detecting element and the ink 
absorbing member is set so that if an ink droplet reaches a size A as 
shown in FIG. 12, the ink droplet is absorbed into the ink absorbing 
member, and prevented from further growing. It is preferable that this 
distance A is 2 mm or less. 
In this way, by setting the distance between the temperature detecting 
element 16 and the ink absorbing member 18 at a predetermined value, it is 
possible to prevent the sensitivity or thermal response ability caused by 
adhering ink from degrading, and improve the detection precision of the 
temperature detecting element 16. 
Embodiment 1-5 
The embodiment 1-5 is that the surface of temperature detecting element 16 
is made water repellent so that the ink may be unlikely to adhere to the 
surface of temperature detecting element 16. In particular, it is 
preferable that the surface of temperature detecting element 16 is thinly 
coated with water repellent material not to make the thermal response 
ability worse. 
The method of making water-repellent the surface of temperature detecting 
element 16 may include forming at least the surface of temperature 
detecting element 16 with a water repellent material. For example, there 
are methods that the temperature detecting element 16 is dipped in a 
dispersant having the powder of water repellent material dispersed, or 
coated with said dispersant, and then burned by heating, or that the 
temperature detecting element 16 is dipped in a dispersant having the 
powder of water repellent material dispersed, or coated with said 
dispersant, and then cured by irradiation of ultraviolet ray, or that the 
surface of temperature detecting element 16 is pasted (lined) with a film 
made of water repellent material, or that when the water repellent 
material is polyolefine type, the temperature detecting element 16 is 
coated with the powder of this water repellent material, and then 
deposited by heating. 
The material having high water repellency is preferably a fluororesin or a 
polyolefine type resin from the aspect of ink resistance. Specifically, 
examples of fluororesin material may include tetrafluoroethylene resin, 
perfluoroalkoxy resin, tetrafluoroethylene-hexafluoropolypropylene 
copolymer resin, and fluorovinylidene resin, and examples of polyolefine 
type resin may include polyethylene and polypropylene. 
This embodiment 1-4 is intended to prevent the false detection that the 
absence of ink is judged despite of some quantity of ink remain because 
discharged ink droplets may adhere to the temperature detecting element 16 
to inhibit the sensitivity or thermal response ability of the temperature 
detecting element 16, and to prevent ink droplets left intact and 
stiffened on the temperature detecting element 16 from degrading the 
sensitivity or thermal response ability. 
Further, with a combination of the embodiment 1-5 and the embodiment 1-4, 
it is possible to facilitate the removal of ink adhering to the surface of 
temperature detecting element 16, further enhancing the effects of the 
embodiment 1-4. 
If the operation of detecting the presence or absence of ink discharge, 
that is, undischarge due to ink shortage, based on the presence or absence 
of rise in temperature by causing ink droplets heated by the recording 
head to impinge directly against the temperature detecting means provided 
within the cap as above described, is performed for each recording of one 
sheet, for example, there is the advantage that there is no need for 
providing any special detecting member on the recording head or ink tank. 
In particular, this is an effective method as ink absence detecting means 
applicable to the so-called disposable type head in which the recording 
head and the ink tank are integrally formed, and exchanged for new one if 
the ink is used up. 
Next, an embodiment with a second constitution of the present invention 
will be described. 
Where the ink absence is detected with the above method, there is a case 
that complete nondischarge does not take place at once when the ink is 
used up, but a transient state may take place, for example, incomplete 
unstable discharge or intermittent discharge may take place, owing to 
various unstable factors inside of the recording head, whereby there is a 
risk that the false detection may occur. That is, this occurs with such a 
case that though the ink is almost used up and printing is obscure, the 
discharge is normally performed only at the detection time so that the 
apparatus can not recognize the ink absence. Such a false detection 
becomes a particularly serious problem associated with the unmanned 
recording machine such as a facsimile apparatus. 
This embodiment is such that the amount of discharged droplets per unit 
time is made greater than normally in such a way as to perform the 
discharge to the temperature detecting means at a higher frequency than 
when the normal print is performed, or discharge larger droplets, so that 
more negative pressure is generated within the liquid channel by the 
discharge to cause undischarge due to absence of ink at earlier time, 
thereby preventing the occurrence of transient state. 
A series of sequence control as shown in FIG. 5 has a feature that, when 
200 droplets are discharged at step S4, the ink is discharged at a higher 
frequency than the maximum frequency for the normal print. This feature is 
able to prevent malfunctions, such as obscure printing or intermittent 
occurrence of nondischarge, owing to the transient phenomenon arising 
immediately before nondischarge caused by the absence of ink. 
To explain this operation, the internal pressure change and ink discharge 
condition of the ink jet recording head will be described. FIG. 13 is a 
schematic view showing the inside of recording head, and FIG. 14 shows how 
the pressure at a point R within the head liquid chamber of FIG. 13 
changes with increasing number of recording sheets (consumption of ink) 
when the head is caused to discharge the ink at the maximum frequency of 
the normal print. 
A sponge member 1310 accommodated as negative pressure generating means 
within a common liquid chamber 1312 retains the ink supplied through an 
inlet port 1311 due to capillary action. The pressure at the point R is a 
negative pressure with reference to the atmospheric pressure, because the 
ink retained in the sponge member 1310 is discharged from each ink 
discharge port 1313 a fixed amount of discharged droplets. This negative 
pressure gradually increases (pressure drop) as shown by a curve S in FIG. 
14, because the capillary action generated by the sponge member 1310 
increases when the ink remain decreases. If the negative pressure reaches 
a certain level, the force tending to discharge the ink can not overcome 
the negative pressure, resulting in nondischarge, and then shortage of 
ink, but this boundary may fluctuate due to numerous unstable factors of 
the situation in which the recording head is placed, whereby it is 
considered that an unstable region having a certain width as shown in FIG. 
14 exists. In this unstable region, the actual obscure printing or the 
intermittent occurrence of nondischarge may take place, and there is such 
a rare case that even though the ink is almost used up and the printing is 
obscure, the discharge may be normally performed only at the time of 
detection, so that the apparatus can not recognize the absence of ink 
normally. 
In this embodiment, to cope with such failures, the discharge at the time 
of detection is made at a higher frequency than the normal maximum 
frequency. If the frequency is higher, the outflow amount of ink 
increases, so that the negative pressure increases, as represented by a 
curve W in FIG. 14. Accordingly, for example, even if nondischarge is 
detected in accordance with the number of recording sheets as indicated at 
a point Y, taking into consideration the unstable region, that number is 
still located at a point T in the normal print frequency region, so that 
the nondischarge is detected before the unstable region is entered. 
Namely, if the nondischarge is caused to occur at earlier time, and the 
absence of ink is notified, the previously-mentioned malfunctions can be 
avoided. 
Embodiment 2-1 
FIG. 15 is a block diagram showing the configuration of a first embodiment 
for changing the amount of discharged liquid droplets. 
This embodiment has a clock circuit 1501 provided between a control unit 21 
and a head driving circuit 33 in the block diagram as shown in FIG. 4. 
Other configuration is the same as that shown in FIG. 4, and the 
explanation thereof is omitted with the same numerals attached. 
The method of changing the amount of discharged liquid droplets in this 
embodiment is as follows. 
The head driving circuit 33 as shown in FIG. 15 is connected to the clock 
circuit 1501 to determine its discharge amount. The clock control circuit 
1501 is configured to generate two kinds of frequency of 3 KHz and 4 KHz 
upon a command from the control unit 21. The ink jet recording head for 
use with this embodiment can exhibit the best performance at a frequency 
of 3 KHz, whereby data is sent out at a clock frequency of 3 KHz in the 
normal print and then printed. On the contrary, when 200 droplets are 
discharged at step S4 in FIG. 5, CPU 23 within the control unit 21 selects 
the clock of 4 KHz, enabling the discharge at a higher frequency than 
normally. To make such a control, ROM 25 stores two kinds of clock 
switching operation as the recording procedure, so that a series of 
recording operations are automatically performed. 
The present invention is also applicable to the other method in which the 
absence of ink is notified by discharging the ink periodically, and 
confirming that the discharge is completely made, for example, a method in 
which a trial discharge pattern is recorded on a portion of recording 
sheet, and read to determine whether the pattern is present or absent by 
an optical sensor. 
Likewise, the present invention is applicable to a method in which with 
temperature detecting means provided within the recording head, the 
difference is checked between elevated temperatures when discharge is 
completely made and when discharge is not made due to absence of ink. 
Embodiment 2-2 
FIG. 16 is a block diagram showing the configuration of a second embodiment 
for changing the amount of discharged liquid droplets. 
This embodiment has a pulse width setting circuit 1601 provided between the 
control unit 21 and the head driving circuit 33 in the block diagram as 
shown in FIG. 4. Other configuration is the same as that shown in FIG. 4, 
and the explanation thereof is omitted with the same numerals attached. 
The method of changing the amount of discharged liquid droplets in this 
embodiment is as follows. 
The head driving circuit 33 as shown in FIG. 15 is connected to the pulse 
width setting circuit 1601 for determining the width of discharge pulse. 
The pulse width setting circuit 1601 is configured to have two settable 
pulse widths of 7 .mu.s and 10 .mu.s upon a command from the control unit 
21. The ink jet recording head for use in this embodiment is designed to 
exhibit the best print performance at a pulse width of 7 .mu.s, wherein 
the amount of liquid droplets at this pulse width is 80 ng. In the normal 
print, the printing is performed at a pulse width of 7 .mu.s, but when 200 
droplets are discharged at step S4 in FIG. 5, the CPU 23 within the 
control unit 21 selects the pulse width of 10 .mu.s. If the pulse width is 
10 .mu.s, the applied energy increases about 40%, resulting in increased 
discharge power. At the same time, the ink viscosity may reduce due to 
temperature elevation of the head, so that the amount of liquid droplets 
increases to 90 ng. 
As above described, the amount of liquid droplets can be changed by 
switching the pulse width. To make such a control, the ROM 25 stores an 
operation program of switching two pulse widths as the recording 
procedure, whereby a series of recording operations are automatically 
performed. 
In the above-described embodiment, the timing of notifying the absence of 
ink occurs more early by using a higher discharge frequency at the time of 
detection than normally, but it will be appreciated that as it is only 
necessary to increase the amount of discharged liquid droplets per unit 
time, the same effects can be also achieved by increasing the amount of 
pulse energy applied to the recording head and providing a larger liquid 
droplet discharged. 
The present invention is also applicable to the other method in which the 
absence of ink is notified by discharging the ink periodically, and 
confirming that the discharge is completely made, for example, a method in 
which a trial discharge pattern is recorded on a portion of recording 
sheet, and read to determine whether the pattern is present or absent, by 
an optical sensor. 
Likewise, the present invention is applicable to a method in which with 
temperature detecting means provided within the recording head, the 
difference is checked between elevated temperatures when discharge is 
completely made and when discharge is not made due to absence of ink. 
Next, an embodiment of a third configuration of the present invention will 
be described. 
As with each method as above described, when the absence of ink is 
detected, it is apprehended that a considerable amount of ink may be 
consumed to make detection, so that the waste ink and the running costs 
increase. 
This embodiment is to resolve the above problem by restricting the 
discharge nozzles to be used for detection to some part of them, so that 
the amount of used ink is reduced, and the waste ink and the running costs 
are reduced. 
In this embodiment, in a series of sequence control, as shown in FIG. 5, 
200 droplets at step S4 are discharged only by nozzles provided opposite a 
detecting portion of the temperature detecting element 16 of the recording 
head 1. 
Embodiment 3-1 
FIG. 17 shows a detected discharge condition when this embodiment is 
applied. FIG. 17 is a cross-sectional view of the cap 15 as shown in FIG. 
3 taken along the central line of the suction tube 17. 
The recording head 1 for use in this embodiment has 64 nozzles 1a, with a 
resolution of 360 dots/inch, and thus has a discharge width of about 4.5 
mm, but a corresponding detecting portion of the temperature detecting 
element 16 has only a width of about 1 mm, whereby even if the discharge 
operation with all the nozzles is performed, the ink not making contact 
with this portion will be wastefully consumed without participating in the 
detection. Accordingly, by using only this portion of 1 mm as a discharge 
region 1701, the ink which is wastefully used in the other portion can be 
saved. The setting of discharge region in this embodiment is as follows. 
The ROM 25 in the block diagram as shown in FIG. 4 is provided with a 
storage area for storing a discharge pattern corresponding to a 
discharging portion and a non-discharging portion when detection is made. 
The CPU 23 refers to data of this area when detection is made and sends 
out a discharge pattern stored therein as discharge data to the head 
driving circuit 33. In this embodiment, because the detecting portion of 
the temperature detecting element 16 is about 1 mm width, as previously 
described, a pattern in which twenty nozzles opposite the detecting 
portion of the temperature detecting element 16 among 64 nozzles 1a 
participate in the discharge is written in the ROM 25. 
While this embodiment has been described with a recording apparatus of the 
type in which the recording sheet is conveyed in a horizontal direction, 
and the ink is discharged downward from the recording head, it will be 
appreciated that the present invention is also applicable to a recording 
apparatus of the type in which the ink is discharged transversely (along a 
vertical direction) from the recording head and the recording sheet is 
conveyed from the lower side upwardly. In this case, it is further 
preferable to provide a detection and discharge region on the top portion 
of the recording width, as shown in FIG. 18. This is due to the fact that 
in the type in which the ink is discharged downwardly from the recording 
head, substantially equal negative pressure occurs in each nozzle, with 
the probability of nondischarge being equal irrespective of the position 
of discharge nozzle, but in the type in which the ink is discharged 
transversely from the recording head, greater negative pressure occurs in 
upper nozzles in the recording width due to the action of gravity, which 
result in higher probability of undischarge. Therefore, there is such a 
case that even if the discharge is confirmed on the lower side, the 
nondischarge may occur on the upper side, whereby the detection and 
discharge region provided on the top portion of the recording width allows 
the discharge condition to be confirmed securely without giving rise to 
any of the failures as above mentioned. 
The discharge region is not necessarily provided as a block, but may be of 
a comb or stagger shape of selected discharge ports as long as the 
detected signal level can be sufficiently obtained. 
Also, the same effects can be expected in the other method in which the 
absence of ink is notified by discharging the ink periodically, and 
confirming that the discharge is completely made, for example, a method in 
which a trial discharge pattern is recorded on a portion of recording 
sheet and read to determine whether the pattern is present or absent by 
recording the trial discharge pattern by the use of a part of the nozzles. 
Likewise, the present invention is applicable to a method in which with 
temperature detecting means such as a thermistor provided within the 
recording head, the presence or absence of ink is confirmed by checking 
the difference between elevated temperatures when discharge is completely 
made and when discharge is not made due to the absence of ink. 
Next, an embodiment of a fourth configuration of the present invention will 
be described. 
As with each method as above described, when the ink absence detection is 
made, and the recording head is exchanged because the absence of ink is 
detected, there is a risk that if there is no difference in external 
appearance between a new recording head and the recording head without 
ink, the recording head without ink may be mounted again by mistake. 
This embodiment is to resolve the above problem by providing means which 
allows the user to manually perform the ink absence detection, in addition 
to automatic detection for each page which is normally performed, thereby 
allowing the user to confirm that when the recording head is exchanged, a 
recording head to be mounted contains the quantity of ink to avoid the 
above inconvenience. 
Embodiment 4-1 
FIG. 19 is a block diagram showing the configuration of this embodiment, 
and FIG. 20 is a flowchart showing the essence of control operation in 
this embodiment. 
This embodiment is provided with an ink absence check button 1901 for 
enabling the ink absence check to be performed by the control unit 21 in 
the block diagram as shown in FIG. 4. Other configuration is the same as 
that shown in FIG. 4, and the explanation thereof is omitted with the same 
numerals attached. 
The operation of this embodiment will be described with reference to FIG. 
20. 
In a stand-by state other than for the recording operation, the CPU 23 
monitors that the ink absence check button 1901 is pushed as shown in FIG. 
20 (step S201). If the ink absence check button 1901 is not pushed, the 
CPU 23 monitors that a signal for starting printing is input (step S202), 
and if that signal is input, the procedure jumps to step S1 in the 
flowchart as shown in FIG. 5. 
If the ink absence check button 1901 is pushed at step S201, the carriage 2 
is moved to stand-by position (cap position) (step S203), and 200 droplets 
are discharged from each of all nozzles of the recording head 1 (step 
S204). Thereafter, if the output of temperature detecting element 16 is 
changed (step S205), the ink presence is displayed on a display unit, not 
shown, (step S206), and waste ink within the cap is sucked and removed 
(step S207). Then the procedure returns to step S201. 
If the output of temperature detecting element 16 is not changed at step 
S205, an alarm message indicating the ink absence is displayed on the 
display unit as previously described (step S208). Thereafter, if the 
recording cartridge is exchanged (step S209), a predefined return 
operation is performed (step S210), and the procedure transfers to step 
S207. If the recording cartridge is not exchanged, the procedure transfers 
to step S208, where an alarm message is displayed again to prompt the user 
to exchange the recording cartridge. 
This embodiment permits the user to know the presence or absence of ink at 
any time. That is, this embodiment provides such control means that if the 
ink presence is detected, a message "ink present" is displayed on the 
display unit, not shown, while if it is not detected, an ink absence alarm 
is displayed. 
In this way, when the recording head is exchanged, a confirmation as to 
whether or not there remains the ink can be made, whereby the recording 
head which is empty is prevented from being mounted by mistake. 
While in the above-described embodiment, the discharge operation at step 
S204 for ink detection is performed through all the nozzles, it will be 
naturally understood that it can be performed through a part of the 
nozzles as in the third configuration of the present invention. 
This embodiment is also applicable to the other method in which the absence 
of ink is notified by discharging the ink periodically, and confirming 
that the discharge is completely made, for example, a method in which a 
trial discharge pattern is recorded on a portion of recording sheet, and 
read to determine whether the pattern is present or absent, by an optical 
sensor. 
FIG. 21 is a block diagram showing a schematic configuration in which a 
recording apparatus of the present invention is applied to the information 
processing apparatus having the features of word processor, personal 
computer, facsimile terminal equipment, and copying machine. In the 
figure, 2101 is a control unit for controlling the whole apparatus, 
wherein it comprises a CPU such as a microprocessor or various I/O ports, 
and controls by outputting or inputting a control signal or data signal to 
or from each of sections, respectively. 2102 is a display section, which 
displays various kinds of menus, document information, and image data read 
by an image reader 2107 on the display screen. 2103 is a transparent, 
pressure sensitive touch panel provided on the display section 2102, which 
enables the entry of an item or coordinate value on the display section 
2102 by depressing its surface with a finger or the like. 
2104 is an FM (Frequency Modulation) sound source section, which makes the 
FM modulation for the music information created on the music editor, which 
is stored in and read from a memory 2110 or an external storage device 
2112 as the digital data. An electrical signal from the FM sound source 
section 2104 is converted into audible sound by a speaker section 2105. A 
printer section 2106 is useful as the output terminal for a word 
processor, a personal computer, a facsimile terminal equipment or a 
copying machine, to which a recording apparatus according to the present 
invention is applied. 
2107 is an image reader section which reads original data 
photoelectrically, and is provided midway on the conveying path of 
original to read a facsimile or copying original, and other various types 
of original. 2108 is a FAX receiving/transmitting section for FAX 
transmitting original data read by the image reader section 2107 or for 
FAX receiving facsimile signals that are transmitted, having an interface 
facility with the outside. 2109 is a telephone section, comprising various 
telephone features, such as ordinary telephone or automatic answering 
telephone. 2110 is a memory section comprising a ROM for storing system 
programs, manager programs and other application programs, character 
fonts, and dictionaries, a RAM for storing an application program loaded 
from the external storage device 2112 and character information, and a 
video RAM. 
2111 is a keyboard section for inputting document information or various 
commands. 2112 is the external storage device which is a storage medium 
consisting of floppy disk or hard disk, wherein this external storage 
device 2112 is used to store character information, music or audio data, 
and user's application programs. 
FIG. 22 is an appearance view of the information processing apparatus as 
shown in FIG. 21. In the figure, 2201 is a flat panel display formed of a 
liquid crystal for displaying various kinds of menus, graphic data or 
document information. On this display 2201 is installed the touch panel, 
which enables the entry of coordinate or specified item by depressing the 
surface of the touch panel with a finger or the like. 2202 is a handset to 
be used when the apparatus functions as a telephone. 
A keyboard 2203 is detachably connected via a cord to a main device, and is 
used to input various character information or data. The keyboard 2203 is 
also provided with various function keys 2204. 2205 is an opening for 
insertion of the floppy disk. 
2207 is a paper laying board for laying thereon a paper to be read by the 
image reader section 2107, in which a read paper is exhausted from the 
rear side of device. In the facsimile reception, received data is recorded 
by an ink jet printer 2207. 
It should be noted that the display section 2201 may be a CRT, but is 
preferably a flat panel such as a liquid crystal display using a 
ferroelectric liquid crystal. This is because the display can be made more 
compact, thinner, and lighter. When the above mentioned information 
processing apparatus functions as a personal computer or word processor, 
various information input from the keyboard 2111 in FIG. 16 are processed 
according to a predetermined program by the control unit 2101, and output 
to the printer 2106 as the image. When it functions as a receiver for the 
facsimile terminal equipment, the facsimile information input from the FAX 
receiving/transmitting section 2108 via the transmission line are received 
according to a predetermined program by the control section 2101, and 
output to the printer section 2106 as the received image. 
And when it functions as a copying machine, an original is read by the 
image reader section 2107, and original data that was read is output via 
the control unit 2101 to the printer section 2106 as the copied image. 
Note that it functions as a transmitter for the facsimile terminal 
equipment, original data that was read by the image reader section 2107 is 
processed for transmission according to a predetermined program by the 
control unit 2101, and transmitted by the FAX receiving/transmitting 
section 2108 via the transmission line. It should be noted that the above 
mentioned information processing apparatus can be of the integral type in 
which an ink jet printer is contained within the main device as shown in 
FIG. 23, in which its portability can be enhanced. In the same figure, 
like reference numerals are affixed to parts having the same functions as 
those in FIG. 22. 
Thus, if a recording apparatus according to the present invention is 
applied to the multifunctional information processing apparatus as above 
described, higher quality recording images can be obtained so that the 
features of the information processing apparatus can be further improved. 
The present invention brings about excellent effects particularly in an ink 
jet recording apparatus for recording by forming flying ink droplets by 
the use of heat energy among the various ink jet recording systems. 
As to its representative constitution and principle, for example, one 
practiced by use of the basic principle disclosed in, for example, U.S. 
Pat. Nos. 4,723,129 and 4,740,796 is preferred. This system is applicable 
to either of the so-called on-demand type and the continuous type. 
Particularly, the case of the on-demand type is effective because, by 
applying at least one driving signal which gives rapid temperature 
elevation exceeding nucleate boiling corresponding to the recording 
information on electricity-heat converters arranged corresponding to the 
sheets or liquid channels holding a liquid (ink), heat energy is generated 
at the electricity-heat converters to effect film boiling at the heat 
acting surface of the recording head, and consequently the bubbles within 
the liquid (ink) can be formed corresponding one by one to the driving 
signals. By discharging the liquid (ink) through an opening for 
discharging by growth and shrinkage of the bubble, at least one droplet is 
formed. By making the driving signals into the pulse shapes, growth and 
shrinkage of the bubbles can be effected instantly and adequately to 
accomplish more preferably discharging of the liquid (ink) particularly 
excellent in response characteristic. 
As the driving signals of such pulse shape, those as disclosed in U.S. Pat. 
Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can 
be performed by employment of the conditions described in U.S. Pat. No. 
4,313,124 of the invention concerning the temperature elevation rate of 
the above-mentioned heat acting surface. 
As the constitution of the recording head, in addition to the combination 
of the discharging orifice, liquid channel, and electricity-heat converter 
(linear liquid channel or right-angled liquid channel) as disclosed in the 
above-mentioned respective specifications, the constitution by use of U.S. 
Pat. Nos. 4,558,333 or 4,459,600 disclosing the constitution having the 
heat acting portion arranged in the flexed region is also included in the 
present invention. In addition, the present invention can be also 
effectively made the constitution as disclosed in Japanese Laid-Open 
Patent Application No. 59-123670 which discloses the constitution using a 
slit common to a plurality of electricity-heat converters as the 
discharging portion of the electricity-heat converter or Japanese 
Laid-Open Patent Application No. 59-138461 which discloses the 
constitution having the opening for absorbing pressure wave of heat energy 
correspondent to the discharging portion. 
In addition, the present invention is effective for a recording head of the 
freely exchangeable chip type which enables electrical connection to the 
main device or supply of ink from the main device by being mounted on the 
main device, or a recording head of the cartridge type having an ink tank 
integrally provided on the recording head itself. 
Also, addition of a restoration means for the recording head, a preliminary 
auxiliary means, etc., to the recording head is preferable, because the 
effect of the present invention can be further stabilized. Specific 
examples of these may include, for the recording head, capping means, 
cleaning means, pressurization or suction means, electricity-heat 
converters or another type of heating elements, or preliminary heating 
means according to a combination of these, and it is also effective for 
performing stable recording to perform preliminary mode which performs 
discharging separate from recording. 
Further, as the recording mode of the recording device, the present 
invention is extremely effective for not only the recording mode only of a 
primary color such as black, etc., but also a device equipped with at 
least one of plural different colors or full color by color mixing, 
whether the recording head may be either integrally constituted or 
combined in plural number. 
Though the ink is considered as the liquid in the embodiments as above 
described, another ink may be also usable which is solid below room 
temperature and will soften or liquefy at or above room temperature, or 
liquefy when a recording enable signal is issued. 
In addition, in order to avoid the temperature elevation due to heat energy 
by positively utilizing the heat energy as the energy for the change of 
state from solid to liquid, or to prevent the evaporation of ink by using 
the ink which will stiffen in the shelf state, the use of the ink having a 
property of liquefying only with the application of heat energy, such as 
liquefying with the application of heat energy in accordance with a 
recording signal so that liquid ink is discharged, or may solidify prior 
to reaching a recording medium, is also applicable in the present 
invention. In such a case, the ink may be held as liquid or solid in 
recesses or through holes of a porous sheet, which is placed opposed to 
electricity-heat converters, as described in Japanese Laid-Open Patent 
Application No. 54-56847 or No. 60-71260. The most effective method for 
the ink as above described in the present invention is based on the film 
boiling. 
Further, a recording apparatus according to the present invention may be 
used in the form of being provided integrally or separately as the image 
output terminal in an information processing equipment such as a word 
processor or computer, a copying machine in combination with a reader, or 
a facsimile terminal equipment having the transmission and reception 
feature. 
In particular, when the recording apparatus is used as a recording unit for 
the facsimile terminal equipment, received image is once stored in memory 
and then recorded, the discharge monitor as previously described is 
performed for each one page of recording, and the contents of memory are 
erased after the confirmation that the normal print has been made, whereby 
when the ink is used up, received data which is stored in memory can be 
output again after the exchanging of the head. 
The present invention which is constituted as above described can exhibit 
the following effects. 
An ink jet recording apparatus and an ink discharge detecting method can be 
provided in which decreased ink remaining or ink nondischarge can be 
securely detected. 
Also, it is possible to prevent the occurrence of such a failure that 
recording sheets are wastefully consumed or invaluable data is lost 
because the recording operation is continued despite of almost depletion 
of ink remain, so that the reliability of the recording apparatus can be 
improved. 
Detection of the absence of ink remaining takes place when the ink 
remaining is almost depleted, whereby the ink is not wastefully used, 
resulting in reduced running costs. 
In an ink jet recording apparatus in which the absence of ink is notified 
by monitoring the discharge to be completely performed in such a way as to 
discharge the ink periodically, for example, between pages, it is possible 
to prevent false detection due to unstable discharge condition immediately 
before the absence of ink, and to prevent the occurrence of such a failure 
that recording sheets are wastefully consumed, or invaluable data is lost 
because the recording operation is continued despite of almost depletion 
of ink remaining, so that the reliability of the recording apparatus can 
be improved. 
Also, it is possible to reduce the amount of ink to be used for detecting 
the absence of ink. Therefore, the percent of the amount of ink to be used 
other than for the recording is lessened, resulting in increased 
recordable number of recording sheets and reduced running costs. The ink 
used for detection must be withdrawn as waste ink, but as this amount of 
ink will decrease, the waste ink tank can be made smaller, thereby 
contributing to the compactness of the entire apparatus. 
Since the ink absence detection can be made at any time by the user, it is 
possible to judge the ink remain by executing the ink absence detecting 
operation even by using such a recording head that the ink remain is not 
known from the outside. Therefore, it is possible to prevent the recording 
head which is empty from being mounted by mistake, thereby eliminating 
wasteful consumption of recording sheets.