Ink jet recording apparatus with a heat pipe for temperature stabilization

An ink jet recording apparatus records by discharging ink from plural recording heads toward a recording medium. Each of the recording heads has a heat pipe mounted thereon, and protruding therefrom so as to have a length which is greater than the recording width of the corresponding recording head. The protruding portions of each heat pipe extending from the recording heads have a heat discharging member attached thereto. That member constitutes a single blower fan for applying an air stream to the heat discharging members corresponding to the recording head, and plural air stream control means for applying the air stream produced by the blower fan to the heat discharging members individually or independently.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates an ink jet recording apparatus wherein an 
image is recorded by discharging ink from an ink discharge port toward a 
recording medium. 
The present invention also relates to a device for controlling a 
temperature of ink jet recording means, which utilizes a heat exchanging 
means such as a heat pipe acting as a means for adjusting a temperature of 
an ink jet recording head. 
The present invention is effective for an ink jet recording apparatus, 
preferably full color ink jet recording apparatus which has one or more 
recording means of full-line type that can record along a maximum width of 
a recording medium. 
2. Related Background Art 
In the past, image recording methods utilizing thermal energy, such as heat 
sensitive recording methods, heat transfer recording methods or the like 
have widely been used with facsimiles, copying machines and the like, 
since they are highly reliable and provide good quality of an images. 
Recently, in order to obtain higher recording speed, higher reliability and 
a better image, interest has been directed to a so-called ink jet 
recording apparatus wherein a desired image is formed by discharging ink 
by the use of thermal energy generated in response to a predetermined 
recording signal. 
In such apparatus wherein the desired image is recorded by utilizing 
thermal energy, in order to achieve the high speed recording, a so-called 
recording head of full-line type which is designed to record the image by 
providing a plurality of heating elements along the whole width of a 
recording medium has been proposed. 
If the image is formed (as a solid recording) on a partial area of the 
recording medium as shown in FIG. 1 by using a recording head of the 
full-line type, the temperature of a portion of the full-line type 
recording head which corresponds to the solid recording area will be 
increased to generate uneven distribution of temperature in the recording 
head as shown in FIG. 2A(1). Such uneven temperature distribution in the 
recording head causes overheating of some of the heat generating or 
heating elements and/or changes in the viscosity of ink, and, for example, 
if a half-tone recording area is then formed, the image recorded in the 
half-tone recording area will have the dispersion in density as shown in 
FIG. 2B(4), thus worsening the quality of the image. 
In order to solve the problem regarding the occurrence of such local 
increase in temperature or uneven distribution of temperature, some of the 
inventors have proposed a technique wherein a heat exchanging means such 
as a heat pipe is attached to an ink jet recording head to improve such 
problem, as described in U.S. patent application Ser. No. 07/822,333, 
having an effective filing date of Dec. 28, 1989. 
Although such proposed technique wherein the heat pipe is merely attached 
to the recording head provides a satisfactory temperature adjustment 
during the recording operation at a low speed, it does not attain the 
temperature adjustment satisfactorily during the high speed recording 
operation. 
That is to say, in the proposed technique, by attaching the heat pipe to 
the recording head as mentioned above, the dispersion in temperature as 
shown in FIG. 2B(4) could be avoided during the low speed recording 
operation; however, particularly, if the recording of the image was 
effected on A4 size sheets by utilizing the recording head of full-line 
type at a high speed (for example, 40 sheets per minute), an adequate 
temperature adjustment could not be attained. 
For example, when the image as shown in FIG. 1 was recorded on 60 sheets 
continuously by utilizing the recording head including the heat pipe 
attached thereto, the temperature of a portion of the recording head which 
corresponds to the solid recording area A was increased up to 50.degree. 
C. as shown in FIG. 2A(2) even if the temperature of the recording head 
was adjusted to 40.degree. C. In this case, the recording density in the 
half-tone recording area created the dispersion in density of 0.10 at the 
maximum as seen from FIG. 2B(5), thus worsening the quality of the image. 
In consideration of the above results, the inventors have proposed a 
recording head unit wherein both a heat pipe 2 and means for keeping the 
temperature of the heat pipe 2 even or uniform are associated with a 
recording head 1 of full-line type. In this arrangement, the recording 
head 1 has a plurality of orifices disposed along the width of the head 
and facing toward a recording medium A and further has elements for 
applying thermal energy to ink supplied to each orifice. Further, in order 
to balance or equilibrate the temperature through the whole recording 
head, the heat pipe 2 is provided with heating means 3, heat discharging 
and cooling means 4, temperature detecting means 5 and the like (which act 
as means for adjusting the temperature of the heat pipe 2) so that the 
temperature of the heat pipe is adjusted by selectively activating the 
heating means 3 or the cooling means 4 through control means 6 on the 
basis of a detection result from the detecting means 5. Accordingly, the 
heat exchange between the recording head and the heat pipe (the 
temperature of which is adjusted) is permitted, thereby providing the even 
temperature distribution through the whole recording head. 
However, in a multi-color recording apparatus, a plurality of such 
recording head units must be arranged in parallel along the recording 
medium A. Consequently, the whole apparatus becomes bulky, complicated and 
expensive. In particular, the heat discharging and cooling means 4 becomes 
bulky and expensive since it includes heat discharge fins and a blower, 
with the result that a distance between the adjacent recording head units 
must be increased. Thus, there arise problems that it is difficult to 
obtain the registration (coincidence in positions where the colors are 
superimposed) at high accuracy and the whole apparatus becomes bulky. 
In consideration of the above problems, as shown in FIG. 4, in the 
multi-color recording apparatus, the provision of a common positive heat 
discharging means 4 including a heat discharging means 17 and a cooling 
means 4b (for cooling the discharging means 17) associated with extension 
portions 2a-l-2d-l of heat pipes 2a-2d extending outside of the recording 
area has been proposed. In this arrangement, the heat pipes 2a-2d are 
associated with the recording heads 1a-1d, respectively, and the heat 
pipes 2a-2d include heating means 3a-3d and temperature detecting means 
5a-5d, respectively, in the recording area. With this arrangement, since 
the distance between the recording head units can be reduced, the above 
registration can be effected conveniently. 
However, in this case, if the particular recording head among the recording 
heads 1a-1d is used continuously (i.e., for example, the recording 
operation is performed by using only black ink), since the control signal 
of the cooling means 4b is controlled on the basis of the detected 
temperature of said recording head, the heat pipes corresponding to the 
non-used recording heads will also be cooled. Consequently, since the 
temperature detecting means associated with the non-used recording heads 
detect the reduction in temperatures of the corresponding recording heads 
and send the detected signals to the control means 6, the heating means 
corresponding to the non-used recording heads are also activated, with the 
result that the cooling and the heating are simultaneously effected 
totally, thus generating the considerable loss of the electric power. 
On the other hand, as shown in FIG. 4, in the recording apparatus wherein 
the plurality of recording heads are arranged in parallel to form a color 
image, as mentioned above, a distance d between the recording heads is 
required to be reduced as much as possible within a range that any 
recording head is not influenced by the adjacent recording head. This 
requirement is desired in view of the improvement in the above 
registration (position alignment between the recording head and/or 
position alignment between the recording areas) and the compactness of the 
recording system, and, thus, the shorter distance d between the recording 
heads is preferable. Further, if the color image is recorded by reading 
the color image, the longer the distance d between the recording heads, 
the more the memory amount for storing the image data is increased, which 
leads to increasing cost of the recording system. This is also one of the 
reasons that the distance d between the recording heads must be reduced. 
Further, in the recording apparatus wherein the heat pipe is attached to 
the recording head, the heat conveying capacity of the heat pipe must be 
considered. That is to say, since the heat conveying capacity of the heat 
pipe has a certain limitation, in order to obtain the adequate thermal 
feature, it is necessary to use a heat pipe which can transmit more 
calories than the maximum calories that can be transmitted from the 
recording head to the heat pipe or from the heat pipe to the recording 
head. 
The limitation of the heat conveying capacity varies in accordance with a 
diameter R of the heat pipe, and the larger heat conveying capacity is 
obtained as the diameter of the heat pipe is increased. 
Accordingly, in the recording apparatus wherein the plurality of recording 
heads are arranged as shown in FIG. 4, inconsistent requirements (i.e., 
the distance d between the recording heads must be reduced, and at the 
same time the diameters of the heat pipes must be increased) are present. 
In order to alleviate such inconsistency, it can be considered that each 
heat pipe is designed to have a flat configuration as shown in FIG. 4 so 
that a thickness of the heat pipe is smaller than the distance d between 
the recording heads. In this case, however, an area of each heat pipe 
extending outwardly of a contacting area between the heat pipe and the 
corresponding recording head had the poor heat exchanging ability. That is 
to say, as shown in FIG. 4, since the whole heat pipe was designed to have 
the flat configuration, the maximum heat conveying capacity of each heat 
pipe was reduced by 10% in comparison with that of the cylindrical heat 
pipe. The reason therefor will be derived from the fact that the conveying 
capacity of the vapor of the operating liquid generated in a heat input 
area or contacting area between the heat pipe and the corresponding 
recording head is reduced. Such reduction in the heat conveying capacity 
causes no problem in the heat input area. However, the heat discharging 
area is greatly influenced by such reduction in the heat conveying 
capacity, which results in the reduction in the heat exchanging ability. 
The reason therefor will be derived from the fact that the vapor of the 
operating liquid generated in the input area cannot be effectively 
transmitted to the whole heat discharging area due to the reduction in the 
heat conveying capacity. 
Now, it is considered that heat discharging fins are formed by press 
fitting a plurality of aluminium plates each having a thickness, for 
example, of about 0.3 mm, as shown in FIG. 4. 
This method is preferable to provide the heat discharging means in the 
point that surface areas of the whole fins can be increased and the cost 
is inexpensive. However, when the heat pipes are designed to have the flat 
configuration, the dispersion will occur in surface shapes of the heat 
pipes. If such dispersion in the surface shapes is great, it was difficult 
to fix the fins by the press fit to obtain the stable thermal contacting 
condition between the heat pipes and the fins. 
By the way, from another point of view, an ink jet recording apparatus 
utilizing a heat pipe is disclosed in the Japanese Patent Publication No. 
62-55990. This Publication teaches an arrangement wherein the heat pipe is 
attached to a recording head of full-line type, for applying the heat 
generated in the recording head to a recorded recording medium to dry ink 
on the recording medium. This known technique aims to utilize the waste 
heat of the recording head, which is quite different from the problem to 
be solved by the present invention. The heat pipe of this known technique 
has a uniform cross-section and is designed in an inverted C-shaped 
configuration for closely contacting with the whole recording area of the 
recording head to absorb the waste heat from the recording head. Thus, 
this publication merely teaches the re-use of heat to the recorded image, 
but does not refer to the above-mentioned problems regarding the recording 
head itself in the recording process. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide an ink jet 
recording apparatus which has a simple construction totally and wherein 
the heating and cooling are effected regarding all of heat pipes in 
common, the temperature of recording heads can be performed uniformly and 
effectively, the ink discharging condition is stable, and the stability of 
a recorded image is improved. Another object of the present invention is 
to provide a multi-color ink jet recording apparatus which is devised to 
reduce the distance between the recording heads and to achieve high heat 
exchanging efficiency. 
A further object of the present invention is to provide an ink jet 
recording apparatus wherein the air stream from a common blower fan is 
selectively applied to any one of heat dischargers (radiators) of heat 
pipes corresponding to recording heads to cool only the heat pipe to be 
cooled, whereby the temperature gradient due to the heat resistance 
between the plural recording heads can be corrected to strictly control 
the temperature of the recording heads and to reduce the above-mentioned 
loss of the electric power. 
A still further object of the present invention is to provide a recording 
apparatus which can stabilize the recording effected by a plurality of 
recording heads and obtain a good image. 
Other object of the present invention is to provide an ink jet recording 
apparatus which can uniformly heat recording heads up to desired 
temperatures for a short time and maintain the temperatures of the 
recording heads at the desired values uniformly and correctly. 
A further object of the present invention is to provide an ink jet 
recording apparatus which can control the temperatures of the recording 
heads uniformly and stably. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
plurality of recording heads disposed in parallel toward a predetermined 
area at a predetermined timing and which is characterized in that first 
heat pipes juxtaposed to the corresponding recording heads are extended 
outwardly of recording areas of the recording heads, and second heat pipes 
are connected to the extended portions of the corresponding first heat 
pipes at the outside of the recording areas. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
plurality of recording heads toward a recording medium at a predetermined 
timing and which is characterized in that each of the recording heads has 
a heat pipe juxtaposed thereto and extending, at its one end, outwardly of 
a recording area of the corresponding recording head, and the one ends of 
the heat pipes are attached to a heat-conductive block to be connected to 
each other. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
plurality of recording heads disposed in parallel toward a predetermined 
area at a predetermined timing and which is characterized by branch 
portions juxtaposed to the corresponding recording heads, and a common 
portion for connecting the branch portions to each other. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
plurality of recording heads disposed in parallel toward a predetermined 
area at a predetermined timing and which is characterized in that each of 
the recording heads has a heat pipe juxtaposed thereto and extending, at 
its one end, outwardly of a recording area of the corresponding recording 
head, the one ends of the heat pipes being attached to a connecting member 
for thermally connecting the heat pipes to each other, the connecting 
member including a cooling means and a plurality of heating means for 
heating a plurality of portions of the connecting member, a plurality of 
temperature detecting means being provided in the vicinity of the heating 
means, for detecting the temperature of the connecting member, and an 
activation control means being further provided for controlling the 
activation of the cooling means and the activation of the heating means on 
the basis of the detected temperature values from the temperature 
detecting means. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
plurality of recording heads toward a recording medium and which is 
characterized in that each of the recording heads has a heat pipe mounted 
thereon and protruding to have a length longer than a recording width of 
the corresponding recording head, the protruded portion of each heat pipe 
protruded from the recording head having a heat discharging member 
attached thereto, and there are provided a single blower fan adapted to 
apply an air stream to the heat discharging members corresponding to the 
recording heads, and a plurality of air stream control means adapted to 
apply the air stream created by the blower fan to the heat discharging 
members individually or independently. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
plurality of recording heads disposed in parallel toward a predetermined 
area at a predetermined timing and which is characterized in that each of 
the recording heads has a heat pipe juxtaposed thereto and extending, at 
its one end, outwardly of a recording area of the corresponding recording 
head, the one ends of the heat pipes being attached to a connecting member 
for thermally connecting the heat pipes to each other, the connecting 
member having a cooling means including heat discharging fins, a blower 
fan and an orientation means for deflecting an air stream from the blower 
fan. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
plurality of recording heads toward a recording medium and which is 
characterized by heat transmitting members capable of transferring (i.e., 
giving and receiving) the heat between them and the recording heads, a 
container accommodating extensions of the heat transmitting members 
extending from heat transfer areas between the heat transmitting members 
and the recording heads and including therein heat transferring medium 
(liquid) for permitting the heat transfer between the heat transmitting 
members and the recording heads through the extensions, and a control 
means for controlling the temperature of the heat transferring liquid. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein an image is formed by flying ink toward a recording 
medium and which is characterized in that it comprises a recording head 
having a plurality of electrical/thermal converting elements used for 
discharging ink, and a heat exchanging means including a first heat 
exchanging portion contacting with substantially the whole longitudinal 
area of one side of the recording head for performing the heat exchange 
between it and the recording head and a second heat exchanging portion 
spaced from and disposed outwardly of the recording head, and that the 
first heat exchanging portion has an elongated rectangular cross-section 
and the second heat exchanging portion has a circular cross-section. 
A further object of the present invention is to provide an ink jet 
recording apparatus wherein the recording is effected by discharging ink 
from a plurality of recording heads toward a predetermined area of a 
recording medium at a predetermined timing and which is characterized in 
that each of the recording heads is provided with a heat exchanging means 
including a first heat exchanging portion contacting with substantially 
the whole longitudinal area of one side of the recording head for 
performing the heat exchange between it and the recording head and a 
second heat exchanging portion spaced from and disposed outwardly of the 
recording head, at least the first heat exchanging portion having an 
elongated rectangular cross-section, and that, when a shorter side of the 
elongated rectangular first heat exchanging portion is d.sub.1, a distance 
between the recording heads is d and a distance between a side surface of 
the first heat exchanging portion of each heat exchanging means and an 
adjacent side surface of the corresponding recording head is d.sub.3, the 
following relations are satisfied: 
5.ltoreq.d.ltoreq.20 mm, 5.ltoreq.d.sub.1 .ltoreq.20 mm, 0.ltoreq.d.sub.3 
.ltoreq.15 mm, d&gt;d.sub.1. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein a color image is formed by flying ink toward a recording 
medium from a plurality of ink jet recording heads of full-line type 
disposed through the whole width transverse to a moving direction of the 
recording medium and which is characterized in that it comprises a heat 
exchanging means including a first heat exchanging portion contacting with 
substantially the whole longitudinal area of one side of the recording 
head for performing the heat exchange between it and the recording head 
and a second heat exchanging portion spaced from and disposed outwardly of 
the recording head, and that the first heat exchanging portion has an 
elongated rectangular cross-section and the second heat exchanging portion 
has a circular cross-section. 
Other object of the present invention is to provide a temperature 
controlling device for an ink jet recording means, which controls the 
temperature of the ink jet recording means while contacting the latter, 
and which is characterized by a heat exchanging means including a first 
heat exchanging portion contacting with the recording means for performing 
the heat exchange and heat transfer between it and the recording means 
with respect to an arrangement direction of electrical/thermal converters 
included in the recording means and having an elongated rectangular 
cross-section and a second heat exchanging portion spaced from and 
disposed outwardly of the recording means and having a circular 
cross-section, and a control means for controlling the temperature of the 
heat exchanging means, having a heating means for heating the heat 
exchanging means and a cooling means for colling the heat exchanging 
means, these heating and cooling means being arranged at an area of the 
second heat exchanging portion spaced from a recording area of the 
recording means. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein an image is formed by flying ink toward a recording 
medium and which is characterized by an ink jet recording head unit 
comprising an ink jet recording head having a plurality of 
electrical/thermal converting elements for discharging ink, a heat 
exchanging means including a first heat exchanging portion contacting with 
substantially the whole longitudinal area of one side of the recording 
head for performing the heat exchange between it and the recording head a 
second heat exchanging portion spaced from and disposed outwardly of the 
recording head, a heating means disposed between the first and second heat 
exchanging portions for heating the heat exchanging means, and a 
temperature detecting means of contact type disposed in contacting 
relation to a longitudinal central area of the first heat exchanging 
portion to detect the temperature of the heat exchanging means; a cooling 
means acting on the second heat exchanging portion of the heat exchanging 
means to aid the heat discharge from the second heat exchanging portion; 
and an activation controlling means for controlling the activation of the 
cooling means and/or the heating means on the basis of the detected 
temperature value from the temperature detecting means 
A further object of the present invention is to provide an ink jet 
recording apparatus wherein a color image is formed by flying ink toward a 
recording medium from a plurality of ink jet recording heads of full-line 
type disposed through the whole width transverse to a moving direction of 
the recording medium and which is characterized by heat exchanging means 
each including a first heat exchanging portion contacting with 
substantially the whole longitudinal area of one side of each of the 
recording heads for performing the heat exchange between it and the 
corresponding recording head and a second heat exchanging portion spaced 
from and disposed outwardly of each recording head; heating means each 
disposed between the first and second heat exchanging portions of each 
heat exchanging means for heating the corresponding heat exchanging means; 
temperature detecting means of contact type each disposed in contacting 
relation to a longitudinal central area of the first heat exchanging 
portion of each of the heat exchanging means to detect the temperature of 
the corresponding heat exchanging means; cooling means each acting on the 
second heat exchanging portion of each of the heat exchanging means to aid 
the heat discharge from the second heat exchanging portion; and activation 
controlling means each for controlling the activation of the corresponding 
cooling means and/or heating means on the basis of the detected 
temperature value from the corresponding temperature detecting means. 
A still further object of the present invention is to provide a temperature 
controlling device which controls the temperature of the ink jet recording 
means while contacting the latter and which is characterized by a heat 
exchanging means contacting with the recording means for performing the 
heat exchange and heat transfer between it and the recording means with 
respect to an arrangement direction of electrical/thermal converters 
included in the recording means, and a control means for controlling the 
temperature of the heat exchanging means, having a heating means for 
heating the heat exchanging means and a cooling means for cooling the heat 
exchanging means, these heating and cooling means being arranged at an end 
area spaced from a recording area of the recording means. 
Other object of the present invention is to provide an ink jet recording 
apparatus wherein the recording is effected by discharging ink from a 
recording head toward a recording medium and which is characterized by an 
ink jet recording head unit comprising a heat pipe having a protruded 
portion protruding to have a length longer than a recording width of the 
recording head, a cooling means disposed on the protruded portion for 
cooling the recording head, and a heating means provided for variably 
changing the heat capacity applied to the recording head through the heat 
pipe; a temperature detecting means for detecting the temperature of the 
ink jet recording head unit; and an activation controlling means for 
controlling the activation of the cooling means and/or heating means on 
the basis of a detected temperature value from the temperature detecting 
means. 
According to the present invention, since the heat pipes mounted on the 
plurality of recording heads are integrally connected to each other by 
using the heat-conductive block, other heat pipes, integral heat pipes or 
heat transmitting medium, it is possible to perform the heat transfer 
between the heat pipes, whereby the recording heads and the 
heat-conductive block can be maintained at the same temperature. Further, 
since the temperature of the heat-conductive block is detected by the 
temperature detecting means and the activation controlling means activates 
the heating means or the cooling means on the basis of the detected 
temperature to heat or cool the heat-conductive block, it is possible to 
transmit the heat to all of the recording heads uniformly and to control 
for keeping all of the recording heads at a predetermined uniform 
temperature. 
Furthermore, the loss of the electric power is minimized, the construction 
becomes simple, the distance between the recording heads can be reduced, 
and the registration can easily be attained. 
In addition, since the temperature of the plural recording heads are 
controlled through the heat pipes, the temperatures of the recording heads 
can be controlled totally. Even when the heat amounts of the respective 
recording heads are different, since the operating fluids can properly 
move in the heat pipes to discharge the heat, the uniformalization of heat 
can be achieved. 
The heating means or the cooling means are activated on the basis of the 
connecting member detected by the temperature detecting means, whereby the 
recording heads are heated or cooled through the connecting member. Since 
the cooling means has the orientation means to change the direction of the 
air stream from the blower fan, it is possible to direct the air stream 
toward the higher temperature area defined by the detected temperature 
value from the temperature detecting means. Further, since the connecting 
member thermally connects the heat pipes juxtaposed to the respective 
recording heads to each other, it is possible to transmit the heat to all 
of the recording heads uniformly, thereby uniformalizing the temperature 
of the recording heads. 
In the present invention, since the first heat exchanging portion of the 
heat pipe has the elongated rectangular cross-section, the distance d 
between the recording heads can be reduced, which results in the cost-down 
and compactness of the recording apparatus. Further, the heat pipes can 
easily be attached to the corresponding recording heads. 
In addition, according to the present invention, since the second heat 
exchanging portion of the heat pipe has the circular cross-section, it is 
possible to effectively transmit the vapor of the operating liquid 
(generated by the first heat exchanging portion) in the heat pipes to the 
whole heat discharging area, and, thus, to easily adjust the whole 
recording head unit at substantially a uniform temperature. 
Since the heat pipe to be cooled can be selectively cooled by the action of 
the control means for controlling the air stream from the fan, the heat 
discharging operation by means of the heat discharging means and the 
heating operation by means of the heating means can be prevented from 
being performed on the same heat pipe, thus eliminating the loss of the 
electric power. 
Furthermore, since the temperature detecting means is disposed in 
contacting relation to the longitudinal central area of the first heat 
exchanging portion of the heat exchanging means, wherever the recording 
heads be positioned, the change in the temperature of the recording heads 
can be detected through the heat exchanging means at good response. 
In addition, since the temperature adjusting means for the recording heads 
are provided individually and independently when the color recording is 
effected by using a plurality of recording heads, it is possible to adjust 
the temperature of the recording heads individually and stably. 
Further, since the temperature controlling means for the heat exchanging 
means is arranged in the end area of the heat exchanging means spaced from 
the recording area of the recording means (having the heat exchanging 
means for adjusting the temperature thereof), it is possible to adjust the 
temperature without affecting the thermal influence upon the recording 
means, and, even when a plurality of recording means are arranged side by 
side, since the distance between the recording means can be reduced 
adequately, it is possible to reduce the production cost of the image and 
improve the registration accuracy. 
In the ink jet recording apparatus according to the present invention, 
since the heat medium in the heat pipes can be returned, it is possible to 
control the temperatures of the recording heads uniformly and stably. 
Further, by providing the heat means for variably changing the heat 
capacity applied to the recording heads through the heat pipes, the heat 
can be applied to the recording heads more largely at the start of the 
recording apparatus so that the recording heads can be quickly warmed up. 
When the heat pipes are integrally fixed by the connecting member, the heat 
transfer between the recording heads can be permitted through the 
connecting member to effectively utilize the heat in the recording heads, 
and all of the recording heads can be selectively cooled by a single 
cooling means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be explained in connection with embodiments 
thereof with reference to the accompanying drawings. 
FIG. 5 is a schematic perspective view of an ink jet recording apparatus 
according to a preferred embodiment of the present invention. 
The ink jet recording apparatus 21 shown in FIG. 5 comprises four recording 
heads 22a, 22b, 22c and 22d each being provided at its bottom surface with 
3456 nozzles (not shown) arranged at intervals of 16 dots/mm. Each 
recording head is adapted to record by a length of 216 mm successively per 
one recording line under a control of a head driver 41. The recording 
heads 22a, 22b, 22c and 22d correspond to ink colors of black, cyan, 
magenta and yellow, respectively, and are fixedly held and supported by 
two holders 31 so as to keep a distance between the recording heads in a 
direction X constant. Heat pipes 23a, 23b, 23c and 23d each having a 
length longer than a longitudinal length of the recording heads 22a, 22b, 
22c and 22d, respectively, are fixed to the corresponding recording heads 
in a thermal transferrable relation. The ends of the heat pipes 23a, 23b, 
23c, 23 d directed to a direction Y are aligned with corresponding ends of 
the recording heads 22a, 22b, 22c, 22d, and the other ends of the heat 
pipes extend outwardly of recording areas of the recording heads. The 
extensions (extending outside of the recording areas) of the heat pipes 
23a, 23b, 23c, 23d are connected to each other by a heat discharging block 
24 acting as a connecting member. As shown in FIGS. 5 and 6, above the two 
heat pipes 23a and 23b, a heater 25a acting as a heating means controlled 
by a heater driver 42a is disposed on an upper surface of the heat 
discharging block 24, whereas, above the remaining heat pipes 23c and 23d, 
a heater 25b acting as a heating means controlled by a heater driver 42b 
is disposed on an upper surface of the heat discharging block 24. Fins are 
attached to a bottom surface of the heat discharging block 24. Fins are 
attached to a bottom surface of the heat discharging block 24, and a fan 
26 controlled by a fan driver 43 is arranged below the fins and acts as a 
cooling means for positively cooling the block 24 by directing an air 
stream to the fins of the heat discharging block. Further, a temperature 
sensor 27a acting as a temperature detecting means is arranged in the 
vicinity of the heat pipe 23a positioned near one end surface (right end 
surface in FIG. 6) of the heat discharging block 24, and, similarly, a 
temperature sensor 27b acting as a temperature detecting means is arranged 
in the vicinity of the heat pipe 23d positioned near the other end surface 
(left end surface in FIG. 6) of the heat discharging block 24. A 
temperature controller 44 receives information from the temperature 
sensors 27a, 27b and activates the heaters 25a, 25b or the fan 26 through 
the heater drivers 42a, 42b or the fan driver 43 on the basis of the 
received information. 
Four ink tanks 28a, 28b, 28c and 28d contain therein black ink, cyan ink, 
magenta ink and yellow ink, respectively, in correspondence to the 
recording heads 22a, 22b, 22c and 22d. These inks are supplied to the 
corresponding recording heads 22a, 22b, 22c and 22d by means of 
circulation motors (or pumps) 29a, 29b, 29c and 29d attached to the ink 
tanks 28a, 28b, 28c and 28d. The circulation motors 29a, 29b, 29c, 29d are 
controlled independently by means of a circulation motor driver 45. 
The ink supply from the ink tanks 28a, 28b, 28c, 28d to the recording heads 
22a, 22b, 22c, 22d is effected by the capillary phenomena of nozzles in 
the recording heads 22a, 22b, 22c, 22d, and a head of each ink in each ink 
tank 28a, 28b, 28c, 28d is set to be lower than the orifice surface (not 
shown) in the recording heads 22a, 22b, 22c, 22d by a predetermined level. 
A seamless belt (referred to merely as "belt", hereinafter) 34 driven by a 
motor 35 controlled by a motor driver 47 is adapted to convey a recording 
medium 51 in the direction X and is provided at its outer surface with 
high resistive (about 10.sup.14 .OMEGA.cm) layer having a thickness of 
about 50 .mu.m. An inner surface of the belt 34 is earthed. A charger 32 
controlled by an electrostatic charger driver 46 charges the outer surface 
of the belt 34 to +1500 Volts or about. Similarly, a charger 33 controlled 
by the electrostatic charger driver 46 applies the negative or minus 
charge to the recording medium 51 so that the recording medium is 
electrostatically attracted to the surface of the belt 34. A sheet feeding 
mechanism 37 driven by a motor 36 controlled by a motor driver 48 feeds 
the recording medium 51 accommodated in a cassette 38 up to a position of 
the belt 34. 
A control circuit 49 systematically controls the operation sequence of the 
head driver, 41, heater drivers 42a, 42b, fan driver 43, temperature 
controller 44, circulation motor driver 45, electrostatic charger driver 
46 and motor drivers 47, 48. The heater drivers 42a, 42b, fan driver 43, 
temperature controller 44 and control circuit 49 constitute an activation 
controlling means for selectively activating the heaters 25a, 25b and the 
fan 26 on the basis of information from the temperature sensors 27a and 
27b. 
Next, the temperature control regarding the recording apparatus according 
to the illustrated embodiment will be explained. In this case, it is 
assumed that an upper limit temperature is 41.degree. C. and a lower limit 
temperature is 40.degree. C. 
When a power source is turned ON, after the fundamental operations required 
to the recording have been performed, the recording operation is started. 
The fan 26 is not driven immediately after the power is turned ON and is 
kept in an OFF condition. On the other hand, both of the heaters 25a and 
25b are turned ON as soon as the power is turned ON, thereby heating the 
recording heads 22a, 22b, 22c, 22d through the heat discharging block 24 
and the heat pipes 23a, 23b, 23c, 23d. Subsequently, the temperature 
control will perform in accordance with the following steps. 
FIG. 7 shows a flow chart for the temperature control. 
First of all, it is judged whether the temperature being detected by the 
temperature sensors 27a and 27b are both lower than 41.degree. C. (step 
S61). If these temperature are below 41.degree. C., the fan 26 is turned 
OFF (step S62). If at least one of the above temperatures is higher than 
41.degree. C., the fan 26 is turned ON (step S63). Next, it is judged 
whether the temperature being detected by the temperature sensor 27a is 
lower than 40.degree. C. (step S64). If the temperature is below 
40.degree. C., the heater 25a is turned ON (step S65). If the temperature 
is higher than 40.degree. C., the heater 25a is turned OFF (step S66). 
Further, it is judged whether the temperature being detected by the 
temperature sensor 27b is lower than 40.degree. C. (step S67). If the 
temperature is below 40.degree. C., the heater 25b is turned ON (step 
S68). If the temperature is higher than 40.degree. C., the heater 25b is 
turned OFF (step S69). 
The above-mentioned temperature control sequence is repeated so long as the 
command for stopping the temperature control is generated (step S70). 
In the normal character printing or recording, since the heat amount 
emitted from the recording heads 22a, 22b, 22c and 22d is a little, the 
temperatures of the recording heads can be suppressed below 40.degree. C. 
by the natural cooling of the heat discharging block 24, and, thus, the 
satisfactory temperature adjustment could be attained by controlling the 
ON/OFF condition of only the heaters 25a, 25b. However, when it is desired 
to record an image, since the heat capacity emitted from the recording 
heads 22a, 22b, 22c and 22d is great, it was necessary to adjust the 
temperature positively or forcibly by using the fan 26. 
For example, if the solid recording was effected by using only the 
recording head 22a with discharge frequency of 2 KHz while not performing 
the heating and cooling operations, the difference in temperature between 
the recording heads 22a and 22d became about 5.degree. C. due to the heat 
resistance of wicked portions (not shown) of the heat pipes 23a, 23b, 23c, 
23d, heat resistance of the heat discharging block 24 and the difference 
in the heat resistance between the heat pipes 23a, 23b, 23c, 23d and the 
heat discharging block 24 and the like. Thus, it was necessary to cool the 
recording head 22a and to heat the recording head 22d. Under the 
circumstances, by performing the temperature control in accordance with 
the sequence through the steps S61-S70, the above difference in 
temperature could be corrected and it was possible to obtain the image of 
high quality with stabilization of the discharge of ink and the fixed 
diameter of each dot without increasing the distance between the recording 
heads. 
In the illustrated embodiment, while two temperature sensors and two 
heaters were used, each of these elements may be one or three or more. 
Incidentally, it should be understood that, as the numbers of these 
elements are increased, the dispersion in temperature between the 
recording heads can be corrected more finely. Further, a plurality of fans 
for directing the air stream to the fins may be provided so that only the 
fan corresponding to the heated recording head can be driven, whereby the 
dispersion in temperature between the recording heads can be corrected 
more positively. 
According to the illustrated embodiment, since the temperatures of the 
recording heads can be controlled uniformly and stably along the 
longitudinal direction thereof, the discharge condition of ink is greatly 
stabilized, thereby improving the stability of the image. Further, since 
the cooling means is disposed at the areas of the heat pipes extending 
outwardly of the recording areas, the flying ink discharged from the 
recording head in the recording area is not disturbed. 
In addition, since the temperature of the plurality of recording heads can 
be controlled uniformly and stably by fixing the heat pipes by means of 
the connecting member thermally connecting the pipes to each other, the 
disorder in the recorded characters can be prevented. Further, the 
temperatures of all of the recording heads can be controlled by a single 
cooling means. 
Furthermore, the temperatures of the recording heads can be detected with 
high accuracy, whereby the temperatures of the recording heads can be 
controlled more stably. 
Incidentally, an example of the arrangement that the cooling is effectively 
performed by using a single fan is shown in FIG. 8. In this example, the 
fan 26 controlled by the fan driver 43 and a deflection or orientation 
wing 60 controlled by an orientation wing driver are disposed below the 
heat discharging block 24, so that the heat discharging block 24 can be 
forcibly cooled totally or partially by changing the direction of the air 
stream from the fan 26 to the fins of the heat discharging block 24. The 
temperature controller 44 receives information from the temperature 
sensors 27a, 27b and controls for selectively activating the heater 25 or 
the fan 26 and the orientation wing 60 through the heater driver 42 or the 
fan driver 43 and the orientation wing driver on the basis of the received 
information. 
Next, the temperature control regarding the recording apparatus according 
to this embodiment will be explained. In this case, it is assumed that an 
upper limit temperature is 41.degree. C. and a lower limit temperature is 
40.degree. C. When a power source is turned ON, after the fundamental 
operations required for recording have been performed, the recording 
operation is started. The fan 26 is not driven immediately after the power 
is turned ON and is kept in an OFF condition. On the other hand, the 
heater 25 is turned ON as soon as the power is turned ON, thereby heating 
the recording heads 22a, 22b, 22c, 22d through the heat discharging block 
24 and the heat pipes 23a, 23b, 23c, 23d. Subsequently, the temperature 
control will performed in accordance with the following steps. 
This temperature control will be described with reference to FIG. 9. 
First of all, after the power source has been turned ON, it is judged 
whether the temperatures being detected by the temperature sensors 27a and 
27b are both higher than 40.degree. C. (step S301). If these temperatures 
are above 40.degree. C., the heater 25 is turned OFF (step S302). Next, it 
is judged whether the temperatures being detected by the temperature 
sensor 27a, 27b are lower than 41.degree. C. (step S304). If the 
temperatures are below 41.degree. C., the fan 26 is turned ON (step S305) 
and the orientation wing 60 is set to a position H shown in FIG. 8 (step 
S307). In the step S304, if at least one of the temperature sensors 27a, 
27b detects the temperature higher than 41.degree. C., the fan 26 is 
turned ON (step S306), and, in this condition, it is judged whether the 
temperature sensor 27a detects the temperature higher than 41.degree. C. 
(step S308). If the temperature sensor 27a does not detect the temperature 
higher than 41.degree. C., since the other sensor 27b detects the 
temperature higher than 41.degree. C., it is necessary to cool the element 
detected by the temperature sensor 27b. Accordingly, in this case, the 
orientation wing 60 is set to a position G in FIG. 8 (step S310). 
On the other hand, in the step S308, if the temperature sensor 27a detects 
the temperature higher than 41.degree. C., then it is judged whether the 
other temperature sensor 27b detects the temperature higher than 
41.degree. C. (step S309). As a result, if the temperature sensor 27b does 
not detect the temperature higher than 41.degree. C., since only the 
temperature sensor 27a detects the temperature higher than 41.degree. C., 
it is necessary to cool the element detected by the temperature sensor 
27a. Accordingly, in this case, the orientation wing 60 is set to a 
position I in FIG. 8 (step S311). Whereas, if the temperature sensor 27b 
also detects the temperature higher than 41.degree. C., since both of the 
sensors 27a and 27b detect the temperature higher than 41.degree. C., the 
orientation wing 60 is set to the position H shown in FIG. 8 to cool the 
whole heat discharging block 24 (step S307). 
On the other hand, in the step S301, if at least one of the temperature 
sensors 27a and 27b detects the temperature lower than 40.degree. C., the 
heater 25 is turned ON (step S303), and, in this condition, the 
abovementioned step S304 and subsequent steps are repeated. In this case, 
when both of the temperature sensors 27a, 27b detect the temperature lower 
than 40.degree. C. and when only one of these sensors detects the 
temperature lower than 40.degree. C. and the other sensor detects the 
temperature higher than 40.degree. C. and lower than 41.degree. C., only 
the heating by means of the heater 25 is effected; whereas, when one of 
the temperature sensors 27a, 27b detects the temperature lower than 
40.degree. C. and the other temperature sensor detects the temperature 
higher than 41.degree. C., the heating by means of the heater 25 is 
effected, and at the same time, the orientation wing 60 is set to the 
position G or I in FIG. 8 to cool the element detected by the temperature 
sensor detecting the temperature higher than 41.degree. C. by the fan 26. 
The above-mentioned temperature control sequence is repeated so long as the 
command for stopping the temperature control is generated (step S312). 
Incidentally, as shown in FIG. 10, the fan 26 acting as the cooling means 
may be pivotally mounted for rocking movement around a pivot 70, and the 
activation of the fan 26 including the rocking movement thereof may be 
controlled by a temperature controller through the fan driver 43. Also in 
this case, the same advantage as that mentioned above can be obtained. 
According to the illustrated embodiment, since the connecting member can be 
partially or totally cooled or the whole heating can be selectively 
controlled on the basis of the information given from the plural 
temperature detecting means for detecting the temperature of the 
connecting member, the gradient in temperature due to the difference in 
heat resistances between the recording heads can be corrected, thereby 
strictly controlling the temperatures of the recording heads. Thus, it is 
possible to stabilize the ink discharge feature and the diameters of the 
dots, thereby permitting the recording with high quality. 
Further, since the cooling means is constituted by only the single fan and 
the direction of the air stream from the fan can be changed to effectively 
cool the connecting member, the whole recording apparatus can be compact 
and inexpensive and the power consumption can be reduced. 
Further, the temperature adjustment may be effected by providing a 
plurality of plate-shaped air stream controlling means (corresponding to 
the number of the recording heads) between the heat discharging fins and 
the blower fan. That is to say, as shown in FIG. 11, a common fan 26 is 
arranged below fins 17 attached to the heat pipes 23 in the areas of the 
latter protruding outwardly of the recording areas of the recording heads. 
Further, between the blower fan 26 and the heat discharging fins 17, 
blades 71 acting as the plate-shaped air stream controlling means are 
pivotally mounted on pivot shafts in correspondence to the heat pipes. By 
providing small motors such as stepping motors in association with the 
pivot shafts, these blades can be rotated independently in response to a 
control signal from a apparatus controller (activation controlling means) 
49. 
According to the illustrated embodiment, since the air stream controlling 
means is provided, it is possible to direct the air stream from the single 
common blower to the heat discharging members (fins) of any of heat pipes 
corresponding to a desired recording head, and, thus to cool only the heat 
pipe to be cooled, thereby minimizing the loss of the electric power. 
Further, since the blower fan can be used in common, the registration can 
advantageously be achieved, and the whole apparatus can be small-sized. 
Next, the temperature control when two temperature sensors, a single heater 
and two fans are used will be explained with reference to FIG. 12. 
First of all, after the power source has been turned ON, it is judged 
whether the temperatures being detected by the temperature sensors 27a and 
27b are both higher than 40.degree. C. (step S71). If these temperatures 
are above 40.degree. C., the heater 25 is turned OFF (step S72). Next, it 
is judged whether the temperature being detected by the temperature sensor 
27a is higher than 41.degree. C. (step S74). If the temperature is higher 
than 41.degree. C., one of the fan 26a is turned ON (step S75), and if the 
temperature does not reach 41.degree. C., the fan 26a is turned OFF (step 
S76). Further, it is judged whether the temperature being detected by the 
temperature sensor 27b is higher than 41.degree. C. (step S77). If the 
temperature is higher than 41.degree. C., the other fan 26b is turned ON 
(step S78), and if the temperature does not reach 41.degree. C., the fan 
26b is turned OFF (step S79). On the other hand, in the step S71, if the 
temperature being detected by at least one of the temperature sensors 27a, 
27b is lower than 40.degree. C., the heater 25b is turned ON (step S73), 
ant at that condition, it is judged whether the temperature being detected 
by the temperature sensor 27a is higher than 41.degree. C. (step S74). As 
a result, if the temperature is higher than 41.degree. C., the fan 26a is 
turned ON (step S75), whereas, if it does not reach 41.degree. C., the fan 
26a is turned OFF (step S76). Further, it is judged whether the 
temperature being detected by the other temperature sensor 27b is higher 
than 41.degree. C. (step S77). If the temperature is higher than 
41.degree. C., the other fan 26b is turned ON (step S78), and if the 
temperature does not reach 41.degree. C., the fan 26b is turned OFF (step 
S79). 
The above-mentioned temperature control sequence is repeated so long as the 
command for stopping the temperature control is generated (step S80). 
According to the illustrated embodiment, by selectively controlling the 
cooling or the heating of the connecting member on the basis of the 
information given from the plural temperature detecting means for 
detecting the temperature of the connecting member, the gradient in 
temperature due to the difference in heat resistances between the 
recording heads can be corrected, thereby strictly controlling the 
temperatures of the recording heads. Thus, it is possible to stabilize the 
ink discharge feature and the diameters of the dots, thereby permitting 
the recording with high quality. 
Further, since the plurality of cooling means are provided and the 
connecting member is made of material having good heat-conductivity, even 
if one of the cooling means is damaged, the connecting member can be 
cooled by the other normal cooling means. 
Next, the temperature control when a single temperature sensor, a single 
heater and a single fan are used will be explained with reference to FIG. 
13. 
First of all, when the power source is turned ON (step S81), it is judged 
whether the temperature detected by the temperature sensor 27 is included 
within a set temperature range (step S82). If the detected temperature is 
within the set temperature range; the same judgements are repeated every 
predetermined time periods until the power source is turned OFF. On the 
other hand, if the detected temperature is out of the set temperature 
range, it is judged whether the detected temperature is higher than a 
temperature corresponding to an upper limit of the set range (step S83). 
If higher, the fan 26 is activated to cool the heat discharging block 24 
(step S84); whereas, if lower, since the detected temperature is lower 
than the temperatures in the set range, the heater 25 is activated to heat 
the heat discharging block 24 (step S85). While the heat discharging block 
24 is being cooled or heated by the blower fan 26 or the heater 25, it is 
still being judged whether the detected temperature is included in the set 
temperature range (step S86), and, if the detected temperature is 
increased or decreased out of the set range, the step S83 and the 
subsequent steps are repeated, whereas, if the detected temperature is 
within the set temperature range, the heater 25 or the blower fan 26 is 
stopped. Thereafter, the step S82 and the subsequent steps are repeated 
until the power source is turned OFF (step S88), thereby maintaining the 
temperatures of the recording heads of line type 22a, 22b, 22c, 22d within 
the set temperature range. 
For example, if only the recording head of line type 22a is frequently used 
so that the temperature thereof is increased, the temperature of the 
recording head 22a is dispersedly transmitted to the other recording heads 
of line type 22b, 22c, 22d uniformly through the heat pipes 23a, 23b, 23c, 
23d. Thus, the increase or decrease in temperature of any specific 
recording head can be prevented. Further, as a result that the temperature 
of the heated recording head 22a is dispersedly transmitted to the other 
recording head, if the temperature detected by the temperature sensor 27 
is increased higher than the set temperature range, the controller 44 
activates the blower fan 26 to cool the heat-conductive block 24 so that 
the temperature of the heat-conductive block 24 is lowered within the set 
temperature range, whereby the temperatures of the recording heads 22a, 
22b, 22c and 22d are also returned 
Incidentally, generally, in the recording of the color image, when three 
color ink are to be discharged simultaneously, since they are replaced by 
the black ink by UCR treatment, three recording heads of line type are 
almost not used simultaneously; thus, the heat discharging means 4 may be 
designed to have the cooling ability in consideration of the increase in 
temperature regarding the total ink discharge of three or less recording 
heads of line type. 
As mentioned above, according to the illustrated embodiment, since the heat 
pipes mounted on the corresponding recording heads are connected to the 
heat-conductive block to permit the heat transfer between the recording 
heads, the following advantages can be obtained. 
That is to say, it is possible to perform the temperature control of the 
recording heads only by a single temperature detecting means, a single 
heating means and a single heat discharging means, thus making the 
recording apparatus small-sized and inexpensive. 
Further, the loss of the electric power due to the heat discharge can be 
prevented, and, thus, it is possible to perform the heating and the heat 
discharging efficiently. 
Further, the cooling ability of the heat discharging means can be set to 
have a lower value, thus permitting the compactness of the heat 
discharging means. 
In addition, since the distance between the recording heads can be reduced, 
the registration can be achieved advantageously. 
In the above, the arrangement wherein the plurality of heat pipes are 
connected to each other through the heat-conductive block was explained. 
With this arrangement, it is possible to adjust the temperatures of the 
plurality of recording heads uniformly; however, a unique connection of 
heat pipes capable of providing more uniform temperature adjustment will 
now be explained hereinbelow. 
FIG. 14 shows an example of a full color recording head block (referred to 
merely as "color recording head" hereinafter) comprising a plurality (four 
in this embodiment) of recording head units, according to the present 
invention. The reference numerals 20A, 20B, 20C and 20D denote recording 
head units for cyan ink, magenta ink, yellow ink and black ink, 
respectively; 23a, 23b, 23c, 23d denote heat pipes as heat exchanging 19 
denotes a common heat-conductive member for connecting one ends of these 
heat pipes 23a-23d; and 17 denotes a plurality (five in this embodiment) 
of heat discharging fins attached to the common heat-conductive member 19. 
Incidentally, although not shown in the drawings, the common 
heat-conductive member 19 has an appropriate heating means. Further, the 
heat pipes 23a-23d and the common heat-conductive member 19 may be good 
heat-conductive material such as aluminium; particularly, since the 
aluminium has greatly high heat-conductivity larger than that of copper by 
several tens to several hundreds times, these elements were made of 
aluminium in this embodiment. 
Incidentally, in the illustrated embodiment, each recording head comprised 
a multi-type recording head having 256,400 dpi nozzles to perform the 
recording of full-color image. In this case, the temperatures of the 
recording head units 20A-20D were adjusted to 45.degree. C. under the 
control of a heating means such as posister and a cooling means such as a 
fan. Incidentally, the fan had a maximum wind velocity of 2 m/sec to 
adjust the temperatures of the recording heads to 45.degree. 
C..+-.5.degree. C. through five fins 17 (each having a dimension of 40 
mm.times.40 mm, a distance therebetween being 10 mm), thereby obtaining a 
good recorded image without dispersion in density due to the temperature 
distribution in each recording head and between the recording heads. 
In the recording apparatus so constructed, it was ascertained that the 
cooling ability thereof might be greatly less than when the recording 
heads constituted by the recording units each having fins were used. The 
main reason is that, in the ordinary full-color image recording, four 
recording head units are not driven simultaneously because the 
simultaneous recording can be effected by 2-2.7 colors at the most due to 
UCR (under color removal), and, accordingly, the cooling ability required 
to discharge the heat generated by activating 2-2.7 recording heads 
simultaneously is merely requested. 
Next, a further embodiment of the present invention will be explained with 
reference to FIG. 15. 
In this embodiment, a comb-shaped heat pipe 23 is used, which heat pipe 
comprises plate-like heat pipe portions (referred to as "branched 
portions" hereinafter) 23a-23d branched from a base portion (common 
heat-transmitting portion) 23e and extending along support members 12A-12D 
for the corresponding recording units 20A-20D, the branched portions being 
connected to the corresponding support members. The substantial 
construction of this embodiment is similar to that shown in FIG. 14. 
In the illustrated embodiment, the recording is performed by discharging 
the ink of different color from the ink discharge opening of each 
recording head while shifting the recording medium 51 with respect to the 
recording head units 20A-20D in a direction X. At the same time, on the 
basis of a detected temperature from a temperature sensor 27 mounted 
between one support member 12A and the heat pipe branched portion 23a, the 
controller 44 controls to keep the temperature of the support member 12A 
at a predetermined value by selectively activating or deactivating the fan 
26 and the heater 25. Also in this embodiment, similar to the previous 
embodiments, it is possible to control for maintaining the temperatures of 
the support members 12A-12D for the recording head units 20A-20D at 
substantially the same value. 
FIG. 16 shows a still further embodiment of the present invention. This 
embodiment is applied to two recording head units 20A and 20B arranged in 
parallel. In this embodiment, a heat pipe 23 is formed in a U-shaped 
configuration, where a base of U is used as a common portion 23e and two 
legs of U are used as branched portions 23a and 23b extending along and 
fixed to the support members 12A and 12B for the recording head units 20A 
and 20B. 
Incidentally, since the temperature control of the recording head units of 
this embodiment during the recording operation is similar to that of the 
previous embodiment, the explanation thereof will be omitted. 
FIGS. 17 to 19 show a further embodiment of the present invention. In this 
embodiment, the heat transfer between a single heat pipe and a plurality 
of recording heads is permitted through a block having good 
heat-conductivity to uniformalize the temperatures of the recording heads 
and to maintain the temperatures of the recording heads at a predetermined 
value during the recording operation by heating or cooling the heat pipe. 
FIG. 18 shows a construction of the heat-conductive block for holding the 
recording heads and acting as a heat transmitting medium. The 
heat-conductive block 70 is made of good heat-conductive material such as 
aluminium, copper or heat pipe and is shaped as shown to have upright unit 
support portions 71A-71D and grooves 72A-72D formed in a base along one 
sides of the corresponding support portions. The recording head units 
20A-20D are arranged in contacting relation to one side surfaces of the 
support portions 71A-71D, respectively, to transfer the heat between them 
and the corresponding support portions efficiently, and are received in 
the corresponding grooves 72A-72D. 
The base of the block 70 further includes a heat pipe holding bore 73 
extending perpendicular to the planes of the support portions 71A-71D and 
disposed on a side opposite to the support portions. The heat pipe 23 is 
integrally assembled with the block 70, as shown in FIG. 17, by press 
fitting the heat pipe 23 into the heat pipe holding bore 73. 
FIG. 19 schematically shows the heat pipe 23. The fundamental construction 
of the heat pipe 23 itself is similar to those of the previous 
embodiments; but, the construction thereof will be now described again in 
detail. 
The heat pipe 23 is made of good heat-conductive material such as copper 
and the like to have tubular configuration. In this embodiment, it has a 
circular cross-section. The reference numeral 61 denotes a porous liquid 
holding member called a wick adhered to an inner surface of the heat pipe 
23 and acting to hold, by capillary phenomenon, operating liquid (not 
shown) enclosed in the heat pipe. The heat pipe 23 itself is hollow, and 
when the interior of the pipe is maintained in a vacuum condition, the 
operating liquid exists as saturated vapor in the hollow interior 62 of 
the heat pipe. Thus, if the heat pipe 23 is heated at its portion, for 
example a portion C in FIG. 19, by a heating means (not shown), the 
operating liquid held by the wick 61 is vaporized and the vapor flows or 
shifts toward a lower temperature portion, for example a portion D in FIG. 
19 at a high speed as shown by the arrow E, and then the vapor is cooled 
at the portion D to return to the liquid form, which is held by the wick 
again and then is shifted by the capillary phenomenon toward the portion C 
as shown by the arrow F. 
In this way, in the heat pipe 23, since the heat applied thereto is changed 
to the latent heat in the operating liquid and is transported to the 
remote location at the high speed, by arranging such heat pipe 23 as shown 
in FIG. 17, it is possible to maintain the whole heat-conductive block 70 
at substantially the same temperature, and, thus, to control or adjust all 
of the recording head units 20A-20D at substantially a predetermined 
uniform temperature through the block 70. Incidentally, in FIG. 17, the 
reference numerals 74A-74D denote leaf springs for urging the recording 
head units 20A-20D against the corresponding support portions 71A-71D; and 
16 denotes a sheet feed roller for the recording medium 51. In this 
embodiment, the recording medium 51 is fed to the direction X, and the 
block 70 carrying the recording head units 20A-20D thereon and mounted on 
a carriage (not shown) is scanned in the direction B, by an appropriate 
shifting means (not shown). During the scanning movement of the carriage 
or block, the recording operation can be performed by discharging the ink 
from the recording head units 20A-20D toward the recording medium 51. 
Incidentally, since the temperature control of the recording head units of 
this embodiment during the recording operation is similar to those of the 
previous embodiments, the explanation thereof will be omitted. In this 
embodiment, each recording head unit is constituted by a recording head 
having 256 nozzles with discharge opening pitch of 16/mm and having a 
longitudinal length of 20 mm, and the height of each support portion 
71A-71D is selected to correspond to the dimension of the recording head. 
By selecting the thickness of each support portion properly, the change in 
temperature between the support portions could be minimized. 
FIG. 20 shows an alteration of the embodiment shown in FIG. 17. In this 
alteration, in place of fins 17 mounted on the heat pipe 23, fins 17 are 
formed on the bottom surface of the heat-conductive block 70 to extend 
along the heat pipe 23. In this case, by selecting an adequate number and 
dimensions of the fins 17, it is possible to cool the block 70 with 
natural cooling action while the block is being moved. Alternatively, it 
is possible to forcibly cool the block from a direction G by providing an 
appropriate cooling means (not shown). In this case, the cooling ability 
of the cooling means may be small. 
As mentioned above, according to the embodiments shown in FIGS. 17 and 20, 
since the plurality of recording head units are held by the single block 
having the good heat-conductivity and the high speed heat transmitting 
means such as the heat pipe is provided to the block to permit the heating 
and heat discharging of the block through the heat transmitting means, by 
merely providing a single heat transmitting means, it is possible to 
perform the temperature control of the plural recording head units by 
means of a single cooling means and heating means through the single heat 
transmitting means. 
As mentioned above, according to the illustrated embodiments, since the 
cooling and the heating can be effected efficiently by providing the heat 
pipe comprising the branched portions juxtaposed to the corresponding 
recording head units and the common portion connecting the branched 
portions to each other, it is possible to easily control the temperature 
and to save the energy. 
Incidentally, as shown in FIG. 21, heat pipes 23a-23d juxtaposed to the 
corresponding recording heads may be interposed between separate flat heat 
pipes 18 and 19 to create the thermal communication between the recording 
heads so that the temperatures of the plural recording heads can be 
adjusted to have substantially the same temperature value. In FIG. 21, 
each heat pipe 23 thermally contacting with the corresponding recording 
head has a first flat section connected to the corresponding recording 
head, and a second flat section extending outwardly of the recording area 
of the corresponding recording head and interposed between the separate 
flat heat pipes 18, 19 to be thermally connected to the other heat pipes. 
These first and second sections of each heat pipe are orthogonal to each 
other (i.e., one is offset with respect to the other by 90 degrees). 
The second flat heat pipes 18, 19 extend across all of the heat pipes 
23a-23d associated with the recording head units 20A-20D to pinch the 
second sections of the heat pipes 23a-23d . A plate-shaped heating means 
such as a heater 25 is disposed on the second heat pipe 18, and a 
temperature detecting means 27 is also disposed on a bottom surface of the 
heat pipe 18 between the heat pipes 23b and 23c. Further, below the second 
heat pipe 19, a heat discharging means having comb-shaped fins 17 is 
arranged. And, a cooling means such as a blower for forcibly cooling the 
fins is also provided. 
Incidentally, the heat pipe 18 or 19 has a conventional construction 
wherein wick networks are arranged on upper and lower inner surface 
thereof and a plurality of sintered metal wicks are arranged at a 
predetermined intervals. These heat pipes 18, 19 are connected to the flat 
surface of the heat pipes 23a-23d (i.e., second flat sections), heating 
means 17 and heat discharging means 17. An output signal from the 
temperature detecting means 27 is sent to the controller 44, which 
supplies an activation signal to the heating means 25 or the heat 
discharging means 17 on the basis of such output signal. 
Each recording head unit is provided with a thermal energy generating 
element (electric/thermal converting element) acting as a discharge energy 
generator for generating thermal energy used for discharging ink, whereby 
the ink is discharged by utilizing the abrupt change in pressure due to 
the formation of bubble in the ink by means of the thermal energy. With 
this arrangement, the change in temperature of each recording head units 
20A-20D is transmitted to the heat pipes 18, 19 through the heat pipes 
23a-23d, and then the temperatures of the recording head units are 
uniformalized by the heat transfer. By detecting the temperature of the 
heat pipe 18, the latter is cooled or heated. The change in temperature so 
generated in the heat pipe 18 is transmitted to the heat pipes 23a-23d to 
control the temperatures of the recording heads 22a-22d. Thus, the loss of 
the electric power is minimized, and the construction of the recording 
apparatus becomes simple because the heating means 25, heat discharging 
means 17 and cooling means 26 are used in common, and the registration can 
easily be attained because the distance between the recording head units 
20A-20D can be reduced. 
As mentioned above, in the illustrated embodiment, since the heating means, 
heat discharging means and cooling means are used in common, the recording 
apparatus itself becomes simple, the loss of the electric power is 
minimized, the apparatus becomes inexpensive, and the registration can be 
easily attained since the distance between the recording head units can be 
reduced. 
Next, another example of the thermal connection between the heat pipes is 
shown in FIG. 22. In FIG. 22, one ends of heat pipes 23a-23d juxtaposed to 
corresponding recording heads 22a-22d are inserted into a liquid medium 
container 75 which contains heat transferring liquid for transferring the 
heat between the heat pipes 23a-23d. The container 75 is provided at its 
one surface with a comb-shaped heat discharging means 17, below which a 
blower fan 26 for cooling the heat transferring liquid in the container 75 
through the heat discharging means 17 is arranged. 
The one ends of the heat pipes 23a-23d extend into the container 75 as 
mentioned above and define extensions 22A-22D, respectively. Between the 
extensions and the wall of the container 75 through which the extensions 
extend into the container, there are provided seals 76 for preventing the 
leakage of the liquid from the container. The reference numeral 25 denotes 
a heater for heating the liquid in the container; 77 denotes an agitator 
for agitating the liquid in the container to uniformalize the temperature 
of the liquid and to provide good heat exchange efficiency between the 
heat pipes 23a-23d; 77A denotes an impeller of the agitator; and 77B 
denotes a motor for driving the impeller. 
The temperature of the heat transferring liquid in the liquid medium 
container 75 is detected by a temperature sensor 27. By inputting the 
detected temperature to a controller 44, the latter controls the 
activation and deactivation of the heater 25 and the blower fan 26 to 
maintain the temperature of the liquid constant. 
Thus, according to the illustrated embodiment, since the temperatures of 
the heat pipes 23a-23d can be uniformalized by heating or cooling these 
heat pipes uniformly through a single container 75 containing the heat 
medium liquid to permit the temperature control of the recording heads 
22a-22d and to uniformalize the temperatures of the recording heads, even 
when only one recording head (for example, head 22a) is frequently used 
and the other recording heads are not used during the recording operation, 
the heat generated in the recording head 22a can be transmitted indirectly 
to the other recording heads 22b-22d, and, thus, it is possible to 
maintain the temperature of each recording head at a value required to 
perform the proper recording, with the efficient use of electric power. 
Further, when the color recording is performed, in a normal condition, 
three colors of ink are not discharged simultaneously because these are 
generally replaced by the black ink by UCR (under color removal) 
treatment. Accordingly, in setting the value of the electric power used 
for the heat discharging, the number of the recording heads to be used may 
be limited to three, thus eliminating the provision of the heat 
discharging means having excessive cooling ability. 
Incidentally, since the recording heads 22a-22d and the heat pipes 23a-23d 
are constructed as a unit by integrally connecting these elements to each 
other, the attachment of these elements to the liquid medium container 75 
can be simplified, and, by making the seals 76 of flexible material such 
as rubber sheet, the position adjustment of the recording heads 22a -22d 
can easily be done. 
As mentioned above, according to the illustrated embodiment, since there 
are provided the heat transmitting members capable of transferring the 
heat between the recording heads, the container for receiving and holding 
the extensions of the heat transferring members extending outwardly of the 
heat transferring areas between the recording heads and the members and 
for accommodating heat medium liquid capable of permitting the heat 
exchange between it and the heat transferring members, and the control 
means for controlling the temperature of the heat medium liquid, the 
following advantages are obtained. 
That is to say, it is possible to control the temperatures of a plurality 
of recording heads uniformly by using a single heating means and a single 
cooling means, thus making the recording apparatus compact and 
inexpensive. 
Further, the efficiency of the electric power to be used can be improved, 
and particularly, the electric power used for the cooling can be 
minimized. 
In addition, by assembling the recording heads and the heat transferring 
members integrally, they can be removably mounted on the container, thus 
facilitating the replacement of the assembly. 
Next, an embodiment regarding the positional relationship between adjacent 
recording heads and the configuration of the heat pipe for improving the 
heat exchanging ability will be explained. 
FIG. 23 is a schematic perspective view showing an example of a recording 
head unit 20 comprising a recording head 22 and a heat pipe 23 acting as a 
heat exchanging means, which forms a part of an ink jet recording system 
according to the present invention. 
In FIG. 23, the recording head 22 is constituted by a full-line type 
recording head having discharge openings disposed through the whole width 
of a recording medium. The recording head used in this embodiment has 4736 
discharge openings arranged side by side at an interval of 63.5 .mu.. And, 
a thermal energy generating element (not shown) is provided at each 
discharge opening of the recording head 22. When the thermal energy 
generating element is energized, the temperature of the ink in the 
vicinity of the thermal energy generating element is abruptly increased to 
cause the film boiling and to form a bubble in the ink. The ink is 
discharged from each discharge opening by utilizing the abrupt change in 
pressure in the ink due to the formation of such bubble. 
The heat pipe 23 is made of copper and acts as the heat exchanging means, 
and includes a first heat exchanging section 23E contacting with the whole 
longitudinal area of one side of the recording head to perform the heat 
exchange therebetween, and a second heat exchanging section 23F extending 
outwardly of a recording area of the recording head. The copper is 
preferable since it has high heat-conductivity. By using this heat pipe, 
the uniform temperature control of the recording head can easily be 
effected. 
Now, with respect to the heat pipe to be used, the heat conveying capacity 
of the heat pipe must be considered. That is to say, since the heat 
conveying capacity of the heat pipe has a certain limitation, in order to 
obtain the adequate thermal feature, it is necessary to use a heat pipe 
which can transmit more calories than the maximum calories that can be 
transmitted from the recording head to the heat pipe or from the heat pipe 
to the recording head. 
The limitation of the heat conveying capacity varies in accordance with 
diameter of the heat pipe, and the larger heat conveying capacity is 
obtained as the diameter R of the heat pipe is increased. 
On the other hand, when the color image is recorded by using a plurality of 
recording heads as will be described later, the longer the distance d 
between the recording heads, the more the memory capacity for storing the 
image data is increased, which leads increases in the cost of the 
recording system. 
Also in order to improve the accuracy in the registration (alignment 
between the recording heads) and to achieve the compactness of the 
recording apparatus, the shorter distance d between the recording heads is 
preferable. 
In consideration of the above requirements, according to this embodiment, 
in the heat pipe 23, the first heat exchanging section 23E for effecting 
the heat exchange due to the heat transfer between the heat pipe 23 and 
the recording head 22 is constituted by a flat heat pipe having an 
elongated rectangular cross-section by flattening a circular pipe by the 
press, and the second heat exchanging section 23F for mainly effecting the 
heat discharge has a circular cross-section. 
In this case, "flat" configuration means that, as shown in FIG. 23, it has 
at least one planar portion 23G, and the shortest diameter d.sub.1, the 
longest diameter d.sub.2 of the pipe and the diameter of the original 
circular pipe have the following relation; d.sub.2 &lt;R&lt;d.sub.1. 
Incidentally, there is the following relation: d.sub.1 &lt;d (head-to-head 
distance). 
By using the heat pipe having such configuration, it is possible to reduce 
the distance between the recording heads. Further, it is possible to 
efficiently perform the heat exchange without reducing the heat conveying 
capacity of the heat pipe. 
The recording head 22 is attached to one side surface of the heat pipe 23 
by means of equidistantly spaced retainers (for example, four) 81, 82 with 
the interposition of, for example, silicone grease. A plate-shaped portion 
82 of each retainer is made of SUS or phosphoric bronze and has a 
thickness of 0.3 mm and a dimension of 27.6 mm.times.10 mm. Since the 
plate-shaped portion 82 is very thin, if it contacts the heat pipe 
directly, a thermal problem such as heat loss is negligible. 
In attaching the heat pipe 23 to the recording head 22, the heat pipe may 
be attached to a base side of the recording head on which the 
electric/thermal converters for generating the thermal energy used to 
discharge the ink are formed, or may be attached to the other side, i.e., 
top plate side opposite to the base side. However, in order to prevent the 
heat generated by the electric/thermal converters from being accumulated 
on the base and to improve the quality of the recorded image, the heat 
pipe is preferably attached to the base side. 
Heat discharging fins 17 acting as a cooling means are attached to the 
second heat exchanging section 23E by press fit. Further, in order to 
maximize the heat discharging ability of the fins 17, a fan 26 
constituting a part of the cooling means is arranged near and below the 
heat discharging fins 17 so as to direct an air stream in a direction 
opposite to the ink discharging direction. The position of the fan 26 is 
not limited to the illustrated one, but the fan may be installed at an 
optimum position where there causes no problem regarding the ink mist 
(described later) and where the heat discharge assist effect and/or the 
compactness of the recording apparatus can be achieved. Incidentally, 
while the fan 26 was installed on the body of the apparatus, it may be 
installed on the recording unit. The heat discharging fins 17 are disposed 
in planes perpendicular to a longitudinal direction of the heat pipe. By 
so arranging the fins 17, the air stream supplied from the bottom of the 
fins by the fan 26 is prevented from flowing toward the recording head 
(recording area). Consequently, the ink mist is prevented from flying 
within the recording apparatus and the problems caused by the flying of 
the ink mist can be reduced. 
The heat discharging fins 17 may be made of material having good heat 
discharging feature, as similar to the heat pipe 23. However, since copper 
is heavy, the fins are preferably made of light material having good heat 
discharging feature. 
For example, the fins may be made of aluminum material which has less heat 
discharging ability than copper but is lighter than the latter. 
A temperature sensor 27 acting as a temperature detecting means for 
detecting the temperature of the heat pipe 23 is disposed at a 
predetermined position on a peripheral surface of the heat pipe at an 
intermediate of the length of the recording head 22. Further, a heater 25 
acting as a heating means for heating the heat pipe 23 is disposed at a 
predetermined position outside of the recording area of the recording head 
22 as will be described later. 
The temperature sensor used in this embodiment comprises a bean-like PCB 
type thermistor having a dimension of .phi.1.5 (diameter of contacting 
area with the heat pipe).times.2.5 mm (thickness). The sensor has 
preferably the larger dynamic range within a temperature range to be 
detected (for example, 0.degree. C.-70.degree. C.), and also preferably a 
high sensitivity. 
As mentioned above, the sensor 27 is mounted on the intermediate portion of 
the recording head with respect to the longitudinal direction thereof. In 
the illustrated embodiment, the whole length of the recording head is 330 
mm, and, accordingly, the sensor 27 is arranged so that the center thereof 
is positioned at a location spaced from the head end by 165 mm. 
Further, in view of the positional relationship between the discharge 
openings and the sensor, the latter is positioned between 2348th (from the 
head end) opening and 2356th opening. 
Incidentally, the temperature detecting means (sensor) may be of the 
contacting type directly attached to the heat pipe, or may be of the 
non-contacting type. Particularly, as is the present embodiment, when it 
is desired to detect the temperature of the heat pipe more stably with 
good response feature, it is preferable to use the sensor of the 
contacting type. 
The reasons for arranging the sensor at the longitudinal central position 
of the recording head are as follows. 
That is to say, when the local solid recording is effected, the change in 
the temperature distribution TD along the longitudinal direction HL of the 
heat pipe. More particularly, the solid recordings are effected as shown 
in FIGS. 24A, 24B and 24C, the temperature of an area of the recording 
head corresponding to the solid recording area is increased, and the heat 
is transferred to the heat pipe so that the temperature of an area of the 
heat pipe corresponding to the heated area of the head is slightly 
increased more than the remaining area. For example, if the temperature 
sensor is arranged at one end of the heat pipe, when the solid recording 
is effected on the recording medium at an area corresponding to the other 
end of the heat pipe, the detection of that temperature is delayed, with 
the result that it is difficult to perform the proper temperature control. 
On the other hand, by arranging the temperature sensor at the longitudinal 
central position of the recording head which corresponds to a position 
nearest to any position on the recording head, even if the change in 
temperature occurs at any position on the recording head, such change in 
temperature can be quickly detected, thus permitting the proper 
temperature control with good response feature. 
Further, the temperature sensor may be disposed at a predetermined location 
on the peripheral surface of the heat pipe corresponding to the 
longitudinal central position of the recording head (or the longitudinal 
central portion of the discharge opening forming area). 
For example, as shown in FIG. 23, the sensor is disposed at a central 
portion 27-2 on the peripheral surface of the heat pipe having an oval 
cross section. 
The position of the temperature sensor 27 is not limited to the above 
position 27-2, but the sensor may be disposed at a position 27-3 
corresponding to an end of a larger diameter of the oval in the vicinity 
of the discharge opening forming area of the recording head, or at a 
position 27-1 corresponding to the other end of the larger diameter of the 
oval opposite to the position 27-3. In any cases, the temperature sensor 
provides the proper temperature control with good response feature; 
however, preferably, by disposing the temperature sensor at the position 
27-3 nearest the discharge opening forming area where the heating elements 
are arranged, it is possible to perform the temperature control with more 
excellent response feature. 
On the other hand, the heater 25 for heating the heat pipe 23 is attached 
to the heat pipe 23 by means of an appropriate attachment 83 at an area 
between the heat discharging fins 17 mounted on the heat pipe 23 and the 
recording area of the recording head. 
In the illustrated embodiment, two heaters 25 are used, and these heaters 
are attached to the extension of the heat pipe extending outwardly of the 
recording area of the recording head through the attachment 83 made of 
copper having good heat-conductivity, at a side opposite to a side where 
the ink discharge openings are provided, because it is preferable to 
arrange the heaters with small installation space and without increasing 
the distance between the recording heads for example when a plurality of 
recording heads are arranged side by side. 
The attachment 83 for attaching the heaters to the heat pipe is thermally 
contacted to the heat pipe with an appropriate contacting area so that the 
heat flux (generated by the heating of the heaters 25) tending to create a 
"drive-out" phenomenon in the heat pipe is not concentrated in the heat 
pipe. 
Further, in the illustrated embodiment, a power transistor is used as the 
heater (since it is compac but has a large heating value); the material 
and thickness of the attachment are so selected that the power transistor 
is not heated higher than a rated temperature when the heat pipe is 
heated. 
Incidentally, as shown in FIG. 25, the heater 25 may be directly attached 
to the heat pipe. In this case, it is preferable to attach the heater to 
the heat pipe with such a contacting area as to prevent a so-called 
"drive-out" phenomenon in which the operating fluid in the heat pipe is 
vaporized up not to flow the liquid by activating the heater. 
Further, if the heater 25 is arranged too near the recording head 22, the 
recording head 22 is directly influenced upon the heat of the heater 
without through the heat pipe 23; accordingly, it is preferable that the 
heater is spaced from the recording head at a certain distance. 
FIGS. 26 and 27 show a recording apparatus which is constituted by 
arranging the recording heads 22 shown in FIG. 23 side by side to permit 
the color recording with cyan ink, magenta ink, yellow ink and black ink. 
That is to say, since a plurality of recording head units 20 each having 
the construction as shown in FIG. 23 are arranged side by side, the 
temperature sensors 27, heaters 25, heat discharging fins 17 and fans 26 
are provided individually in the corresponding recording heads 22. Of 
course, it is possible to thermally connect a plurality of heat pipes to 
each other as previously mentioned. In this case, the above elements 25, 
17 and 26 may be single, respectively, other than the temperature sensors 
27. 
In this way, by adjusting the temperatures of the recording heads 22 
independently, it is possible perform the temperature control with higher 
accuracy. 
By the way, in the recording performed by using the recording heads 
arranged side by side, there arise problems regarding the registration and 
the memory cost. More specifically, when the distance between the 
recording heads is long, it is very difficult to obtain the accuracy of 
the head-to-head distance and it is necessary to increase the capacity of 
the memory. Accordingly, the shorter distance between the recording heads 
is preferable. To this end, as shown in FIG. 27, each heater 25 is 
disposed on the corresponding heat pipe at a position which does not 
influence upon the distance between the recording heads, i.e., a position 
on a side of heat pipe which is opposed to a side where the discharge 
openings of the recording head are arranged. That is, each heater is 
arranged at an upper side of the heat pipe. 
Incidentally, among four recording head units 20 arranged side by side, in 
the first and fourth recording head units, the heaters 25 are not 
necessarily disposed at the upper sides of the respective heat pipes, but 
may be disposed on outer sides of the heat pipes. 
The recording head units 20 having the above-mentioned construction are so 
designed that the temperatures of the recording heads 22 can be adjusted 
to a desired temperature value by selectively activating the heaters 25 or 
the fans 26 through the controller 44 on the basis of the detected 
temperature from the temperature sensors 27. 
Incidentally, the fan 26 may be of sirocco type which is compact but can 
provide an adequate wind capacity. 
As mentioned above, each heat pipe has the first heat exchanging section 
23E having a flat configuration and the second heat exchanging section 23F 
having a cylindrical configuration. In the case where a plurality of 
recording heads including such heat pipes are arranged side by side to 
permit the color recording, when the shorter diameter of the first heat 
exchanging section 23E is d.sub.1, the longer diameter thereof is d.sub.2, 
the distance between the heat pipe and the adjacent recording head is 
d.sub.3 and the distance between opposed surfaces of the adjacent 
recording heads is d, it is necessary meet the relation d&gt;d.sub.1 between 
at least d.sub.1 and d. 
The reasons for deforming each heat pipe 23 as mentioned above will be 
described. For example, it is assumed that the head-to-head distance d=10 
mm or less is requested upon the requirements regarding the memory cost, 
construction of the apparatus, accuracy of the registration and the like. 
Incidentally, the distance d=10 mm is determined by the requirements of 
the apparatus, itself and thus, in the recording apparatuses of other 
embodiments, other values of distance will be requested. 
On the other hand, when a recording head of A3 full-line type (400 dpi) 
having an maximum average heat discharging capacity (value obtained by 
deducting the heat amount absorbed by ink from the heat amount generated 
by the whole recording head and then by dividing the result by time) is 
used as the recording head in the above-mentioned recording apparatus, it 
is necessary to use a heat pipe of a diameter R (12.7.phi.) having the 
heat conveying capacity of 100-120 W. 
Therefore, the head-to-head distance d and the diameter R of the heat pipe 
which are requested as above gives the relation d&lt;R, which does not meet 
the aforementioned relation d&gt;d.sub.1. 
Accordingly, in order to meet the relation d&gt;d.sub.1, the area 
corresponding to the first heat exchanging section 23E of the heat pipe 
was deformed in the flat configuration having a thickess of 5 mm. 
In the illustrated embodiment, the above-mentioned values d, d.sub.1, 
d.sub.2 and d.sub.3 were the follows: 
d=10 mm, d.sub.1 =5 mm, d.sub.2 =15 mm, d.sub.3 =5 mm. Incidentally, the 
thickness of the recording head was about 13 mm. The present embodiment is 
not limited to such values, but may use various values so long as the 
following relations are met. 
That is to say, the distance between the recording heads is desirable to be 
included within a range 0.ltoreq.d.ltoreq.20 (mm) in consideration of the 
accuracy of the registration. To the contrary, the diameter of the heat 
pipe is requested to be included within a range 10 .ltoreq.R.ltoreq.30 
(mm) in view of the optimum heat exchanging feature. 
Accordingly, although it is necessary to deform the heat pipe in the flat 
configuration as mentioned above by the press, if the shorter diameter 
d.sub.1 is too short, it is feared that the flowing of the operating 
liquid in the heat pipe is badly influenced; thus, as a stable dimension, 
the shorter diameter is preferable to be included within a range 5 
.ltoreq.d.sub.1 .ltoreq.20 (mm). 
Further, the distance d.sub.3 between the side surfaces of the adjacent 
heat pipe 23 and of the recording head 22 is preferable to be included 
within a range 0.ltoreq.d.sub.3 .ltoreq.15 (mm). 
The excessive longer distance d.sub.3 is undesirable in view of the 
accuracy of the registration and/or the memory capacity, and the excessive 
shorter distance d.sub.3 causes the danger that one recording head will 
influence an adjacent recording head. Further, unless the head-to-head 
distance d and the shorter diameter d.sub.1 meets the relation d&gt;d.sub.1, 
the adjacent recording head and heat pipe are contacted with each other, 
thus enabling the stable temperature control of the recording heads. 
In addition, as a range which can minimize the above-mentioned had thermal 
influence between the adjacent heat pipe and recording head, the shorter 
diameter d.sub.1 of the heat pipe and the distance d.sub.3 between the 
heat pipe and the adjacent recording head has preferably a relation 
d.sub.3 .gtoreq.d.sub.1. 
Further, as mentioned above, the second heat exchanging section has the 
cylindrical configuration, on which 38 aluminum plates each having a 
thickness of 0.3 mm (dimension thereof is 20.times.80 mm) are pressfitted 
at a pitch of 2 mm to form the heat discharging fins. In this way, by 
deforming the first heat exchanging section 23E of each heat pipe in the 
flat configuration, it is possible to use the heat pipes providing the 
adequate heat conveying capacity, and the second heat exchanging section 
(heat discharging section) 23F has the adequate heat discharging ability, 
thereby permitting the temperature adjustment of the whole recording heads 
at the desired temperature value. 
Next, an example of the operation of the illustrated embodiment will be 
explained. 
When a record start switch (not shown) is turned ON, first of all, the 
temperature of the heat pipe 23 is detected by the temperature sensor 27. 
When the detected temperature is lower than a predetermined temperature 
(referred to as "set temperature" hereinafter) which must be kept during 
the recording operation (for example, 48.degree. C. (+4.degree. C., 
-3.degree. C.) in the illustrated embodiment), the controller 44 activates 
the heater 25 to heat the recording head 22 through the heat pipe 23. In 
this case, the contacting area 23G between the heat pipe 23 and the 
recording head 22 acts as a condensation area where the operating fluid in 
the heat pipe 23 can be liquidized, and thus, the operating fluid 
vaporized by the heat from the heater 25 can be uniformly dispersed 
through the condensation area and is condensed to uniformly discharge the 
latent heat, with the result that the recording head 22 is subjected to 
the uniform heat flux, whereby the recording head is quickly and uniformly 
heated to reach the set temperature. When the recording head reaches the 
set temperature, the heater 25 is turned OFF. 
When the recording head 22 reaches the set temperature, it is judged that 
the recording is permissible. In this point, if a predetermined image 
signal is inputted, the some of the electric/thermal converting elements 
corresponding to the image signal are energized to apply the thermal 
energy to the associated ink, thereby discharging the ink from the 
associated ink discharge openings. The discharged ink is flying toward the 
recording medium 51 and is absorbed by the latter to form a desired image 
thereon. When the recording operations are continued, the recording head 
is heated by the residual thermal energy remaining in the recording head 
(among the applied thermal energy). In this case, if the detected 
temperature from the temperature sensor 27 deviates from the set 
temperature by a tolerable value or more, the controller 44 activates the 
fan 26 to direct the air stream to the fins 17, thereby starting the heat 
discharge of the recording head 22 through the heat pipe 23. In this case, 
the contacting area 23G between the heat pipe 23 and the recording head 22 
acts as a vaporization area for the operating liquid, with the result that 
the greater capacity of operating liquid can be vaporized in a zone into 
which the greater heat flux is flowing, and the lesser capacity of 
operating liquid can be vaporized in a zone into which the lesser heat 
flux is flowing, and, thus, the operating liquid is vaporized in 
accordance with the heat values. Further, in a zone into which no heat 
flux is flowing, the operating fluid once vaporized is condensed there to 
discharge the latent heat for supplying the heat value. Since the vapor 
has no heat resistance and the transfer of heat can be effected 
instantaneously, the uniformalization of the interfacial temperature 
between the operating liquid in the vaporization area and the vapor can be 
effected instantaneously. Accordingly, even when the heat flux flowing 
into the heat pipe has local dispersion, the interfacial temperature can 
be maintained substantially constant. Accordingly, even if the heat flux 
having the local dispersion is created in response to the image signal, 
the recording head 22 can be maintained to substantially constant value, 
by the action of the uniformalization of temperature in the heat pipe 23. 
And, the heat amount remaining after the uniformalization of the 
interfacial temperature is transported to the second heat exchanging 
section 23F of the fins 17 instantaneously, and is condensed there to 
generate the heat value. The generated heat value is transmitted to the 
air stream fed by the fan 26 through the fins 17 and thus is dispersed in 
the air. 
The image recording operation is stably continued while the temperature of 
the recording head is maintained at substantially the set temperature as 
mentioned above, by properly activating or deactivating the fan 26 through 
the controller 44 on the basis of the detected temperature from the 
temperature sensor 27. 
Incidentally, the temperature of the recording head to be adjusted is not 
limited to the abovementioned 48.degree. C. (+4.degree. C., -3.degree. 
C.), but may be properly determined in accordance with the ink and 
recording head to be used and the service conditions; however, it is 
preferable that the set temperature is adjusted within a range from about 
35.degree. C. to about 60.degree. C. 
Further, the temperature control may be performed by always activating the 
cooling means (i.e., ON/OFF control for the cooling means is not 
performed) and by adjusting the temperature of the recording head by means 
of the heating means at need, or by always activating the heater (heating 
means) (i.e., ON/OFF control for the heating means is not performed) and 
by adjusting the temperature of the recording head by the ON/OFF control 
of the cooling means at need, as well as by properly performing the ON/OFF 
control of the heating means and the cooling means as mentioned above. 
As mentioned above, by mounting the heat pipe on the recording head and by 
heating or cooling the recording head through the heat pipe on the basis 
of the temperature of the recording head, it is possible to heat or cool 
the elongated recording head uniformly, and, thus, to control the 
temperature of the elongated recording head uniformly and stably. 
Consequently, the ink discharge condition is considerably stabilized, thus 
greatly improving the stability of the image. Further, with the 
arrangement as this embodiment, since the fins and fan are disposed out of 
the recording area of the recording head, the strong air stream from the 
fan can be prevented from flowing into the recording area, thus preventing 
the disturbance of the flying ink, thereby improving the stability of the 
image. 
Since the temperature of the recording head is controlled in this way, even 
when the image as shown in FIG. 1 is continuously recorded on sixty A4 
size recording mediums, the dispersion in temperature in the longitudinal 
direction of the recording head can be greatly suppressed, as shown in 
FIG. 2A(3). 
Consequently, the dispersion in density of the half-tone recording area 
after 60 sheets have been recorded can also been greatly suppressed, as 
shown in FIG. 2B(6). 
As a comparison, an example of the temperature control in the recording 
system wherein the temperature sensor is disposed at a position 84 shown 
in FIG. 23 on the recording head 22 will be explained. 
In this example, when the image as shown in FIG. 1 is continuously recorded 
on sixty A4 size recording mediums, as shown in FIG. 2A(2), the great 
dispersion in temperature occured in the longitudinal direction of the 
recording head, and the dispersion in density of the half-tone recording 
area after 60 sheets have been recorded was also great, as shown in FIG. 
2B(5). The reason is that, since the heat generated in the solid recording 
area of the recording head 22 is difficult to be transmitted to the 
temperature sensor 84, the difference between the detected temperature at 
the temperature detecting position 84 and the temperature in the solid 
recording area is great, thus making the proper control of the cooling 
means difficult. 
To the contrary, according to the embodiment shown in FIG. 23, since the 
temperature of the recording head is detected through the heat pipe having 
substantially the same temperature through its length regardless of the 
temperature difference in the recording head, at the longitudinal central 
position of the contacting area between the heat pipe 23 and the recording 
head 22, it is possible to control the cooling means the heating means 
with high accuracy, and, thus, to maintain the temperature of the 
recording head at substantially the constant temperature value at all 
times. 
Further, as a comparison, if a cylindrical heat pipe (having a diameter of 
10.phi.) which can be disposed between the recording heads was used, since 
the maximum heat conveying capacity of this heat pipe was less than that 
of the heat pipe of the illustrated embodiment by about 50%, such heat 
pipe could not utilized. For example, when the electric power of 80 W was 
generated as in the case of the previous embodiment, the difference in 
temperature of about 10.degree. C. was created between both ends of the 
first heat exchanging section, thus worsening the quality of the image. 
In this way, by deforming the cross-section of the first heat exchanging 
section in the elongated rectangular shape and by keeping the second heat 
exchanging section in the circular cross-section, the following advantages 
are obtained: 
That is to say, first of all, since the first heat exchanging section of 
the heat pipe has the elongated rectangular cross-section, it is possible 
to reduce the distance d between the adjacent recording heads, to reduce 
the cost of the recording system, to make the system small-sized and to 
facilitate the attaching of the heat pipe to the recording head. Further, 
since the second heat exchanging section has the circular cross-section, 
the vapor of the operating liquid generated in the first heat exchanging 
section can be transmitted to the whole second heat exchanging section 
efficiently, thus improving the heat discharging ability and easily 
adjusting the temperature of the whole recording head or of the whole 
contacting area between the heat pipe and the recording head to 
substantially uniform temperature value. 
Further, since the temperature detecting means is disposed on the first 
heat exchanging section of the heat pipe (heat exchanging means) at the 
longitudinal central position thereof, the change in temperature of the 
recording head at any position thereof can be detected through the heat 
pipe with good response feature. 
Further, since the temperature adjusting means for the recording heads are 
independently arranged when the color recording is performed by using a 
plurality of recording heads, it is possible to adjust the temperatures of 
the recording heads independently and stably. 
In addition, since the temperature controlling means is provided in the end 
areas of the heat pipe (heat exchanging means) extending outwardly of the 
recording area of the recording means which is associated with the heat 
exchanging means, it is possible to adjust the temperature without 
affecting the thermal influence upon the recording means, and, even when 
the plurality of recording means are arranged side by side, it is possible 
to reduce the distance between the recording heads adequately, thus 
reducing the memory cost and improving the accuracy of the registration. 
By the way, since object of the adjustment of the temperature of the 
recording head through the heat pipe was to control the temperature of the 
recording head at a given temperature range near the set temperature, the 
degree of the heating and cooling could not be greatly increased, and, 
thus, it took a long time to increase the temperature of the recording 
head from its stand-by condition (room temperature) to the set 
temperature. Particularly, this was serious when the elongated recording 
head was used or when the members such as fins were attached to the 
recording apparatus. 
Next, an ink jet recording apparatus which can bring the temperature of the 
recording head up to the set temperature for a short time and then 
maintain the temperature of the recording head at the set temperature with 
accuracy will be explained with reference to FIG. 28. 
As shown in FIG. 28, in this embodiment, in addition to the construction of 
the recording apparatus as mentioned above, a plurality (two in FIG. 28) 
of heaters for heating the heat pipe are provided. That is to say, on one 
side of the heat pipe 23, a heater 25 for heating the heat pipe and a 
heater 85 for the warm-up are arranged. Since the other construction of 
the apparatus may be the same as any of those of the previously described 
embodiments, the explanation thereof will be omitted. 
Next, the operation of the apparatus according to this embodiment will be 
explained. 
When a record start switch (not shown) is turned ON, first of all, the 
temperature of a support portion side of the recording head 22 is detected 
by the temperature sensor 27. When the detected temperature is lower than 
a predetermined temperature (referred to as "set temperature" hereinafter) 
which must be kept during the recording operation (for example, 50.degree. 
C. in the illustrated embodiment), the controller 44 activates the heater 
25 and the warm-up heater 85 to heat the support portion of the recording 
head 22 through the heat pipe 23. In this case, the contacting area 
between the heat pipe 23 and the support portion acts as a condensation 
area where the operating fluid in the heat pipe 23 can be liquidized, and 
thus, the operating fluid vaporized by the heat from the heater 25, 85 can 
be uniformly dispersed through the condensation area and is condensed to 
uniformly discharge the latent heat, with the result that the support 
portion is subjected to the uniform heat flux, whereby the support portion 
is quickly and uniformly heated. 
When the support portion reaches the set temperature, the adjustment of ink 
in the discharge opening is performed by an appropriate restoring means 
(not shown), and then the recording medium 51 is fed in a direction A by 
means of a feeding means (not shown). When the recording medium 51 reaches 
a position opposing the discharge opening, the thermal energy is applied 
to the ink in response to an image signal, thus discharging the ink from 
the discharge opening. The discharged ink is flying toward the recording 
medium 51 and is absorbed by the latter to form a desired image thereon. 
When the recording operations are continued, the recording head is heated 
by the residual thermal energy remaining in the recording head (among the 
applied thermal energy), and thus, the support portion is also heated. In 
this case, if the detected temperature from the temperature sensor 27 
deviates from the set temperature by a tolerable value or more, the 
controller 44 activates the fan 26 to direct the air stream to the fins 
17, thereby starting the heat discharge of the recording head 22 through 
the heat pipe 23. In this case, the contacting area between the heat pipe 
23 and the support portion acts as a vaporization area for the operating 
liquid, with the result that the greater capacity of operating liquid can 
be vaporized in a zone into which the greater heat flux from the support 
portion is flowing, and the lesser capacity of operating liquid can be 
vaporized in a zone into which the lesser heat flux is flowing, and, thus, 
the operating liquid is vaporized in accordance with the heat values. 
Further, in a zone into which no heat flux flowing, the operating fluid 
once vaporized is condensed there to discharge the latent heat for 
supplying the heat value. Since the vapor has no heat resistance and the 
transfer of heat can be effected instantaneously, the uniformalization of 
the interfacial temperature between the operating liquid in the 
vaporization area and the vapor can be effected instantaneously. 
Accordingly, even when the heat flux having the local dispersion is 
flowing into the support portion in response to the image signal, the 
temperature of the support portion can be maintained at substantially 
constant temperature value due to the temperature uniformalization action 
in the heat pipe 23. And, the heat capacity remaining after the 
uniformalization is transferred to the fins 17 instantaneously, and is 
condensed there to generate the heat value. The generated heat value is 
transmitted to the air stream fed by the fan 26 through the fins 17 and 
thus is dispersed in the air. 
The image recording operation is stably continued while the temperature of 
the support portion is maintained at substantially the set temperature as 
mentioned above, by properly activating or deactivating the fan 26 through 
the controller 44 on the basis of the detected temperature from the 
temperature sensor 27. 
As mentioned above, by mounting the heat pipe on the recording head and by 
heating or cooling the recording head through the heat pipe on the basis 
of the temperature of the recording head, it is possible to heat or cool 
the elongated recording head uniformly, and, thus, to control the 
temperature of the elongated recording head uniformly and stably. 
Consequently, the ink discharge condition is considerably stabilized, thus 
greatly improving the stability of the image. Further, with the 
arrangement as this embodiment, since the fins and fan are disposed out of 
the recording area of the recording head, the strong air stream from the 
fan can be prevented from flowing into the recording area, thus preventing 
the disturbance of the flying ink, thereby improving the stability of the 
image. 
Now, the measured data of the change in temperature along the longitudinal 
length of the support portion constituting the recording head 22, measured 
at a plurality of different points is shown in FIG. 29. 
In FIG. 29, the abscissa indicates a time elapsed after the heater 25 or 85 
is turned ON, and the ordinate in FIG. 29A indicates a temperature value 
of the contacting area between the heat pipe 23 and the support portion. 
The temperatures are detected at three points, a first of which is a 
position (p.sub.1) directly below the heater 25, a second of which is a 
position (P.sub.2) spaced apart from the position (P.sub.1) by 10 cm in 
the longitudinal direction, and a third of which is a position (P3) spaced 
apart from the position (P.sub.1) by 20 cm in the longitudinal direction. 
The set temperature is selected to 50.degree. C., and the detected 
temperature at the first position is given to the controller 44 as a 
controlling temperature. Before the warm-up, the temperature of the 
support portion corresponds to the room temperature of 28.degree. C. 
When both of the heaters 25 and 85 are used, at the beginning of the 
warm-up, since the detected temperature from the temperature sensor 27 is 
28.degree. C. and is lower than the set temperature (50.degree. C.) as 
shown in FIG. 29A, as shown in FIGS. 29B and 29C, the controller 44 
activates the heaters 25 and 85 until the set temperature (50.degree. C.) 
is reached (thereafter, these heaters are turned OFF), and then controls 
the heater 25 solely to bring the detected temperature to 50.degree. C. 
Even when the heater 25 is used solely, as shown in FIG. 29D, the control 
regarding the heater 25 is the same as the previous case, except that the 
control regarding the heater 85 is omitted (i.e., the heater 85 is always 
turned OFF or there is no heater 85). 
As apparent from FIG. 29, the warm-up time (time required to reach the set 
temperature of 50.degree. C.) by using both of the heaters 25 and 85 is 
shorter than that by using the heater 25 solely by a half or less. 
However, in both cases, there is substantially no difference in 
temperature in the longitudinal direction of the support portion, and the 
temperature after the warm-up is maintained in a range of .+-.1.degree. C. 
or less around the set temperature. 
According to the illustrated embodiment, by heating and/or cooling the 
recording head through the heat pipe, it is possible to control the 
temperature of the elongated recording head uniformly, and, thus, to 
stabilize the ink discharge condition and improve the stability of the 
image. Since the heat pipe is used, it is no need to match the dimension 
of the heating means to the dimension of the recording head and/or to 
control the heating means by means of a plurality of heating means 
uniformly, thus reducing the cost and facilitating the assembling of the 
apparatus. 
In addition, by providing the heating means capable of variably changing 
the heat capacity applied to the recording head through the heat pipe, it 
is possible to shorten the time from the record demand to the recording 
permissible condition (i.e., warm-up time), thus omitting the high speed 
recording. Further, after the warm-up time has been elapsed, the heat 
value of the heating means can be reduced, thus saving the electric power 
for the heating and heat discharging. 
In addition, when the heat pipes are integrally fixed through the 
connecting member, by permitting the heat transfer between the recording 
heads and by changing-over the heat capacity at the warm-up operation and 
at the recording operation by means of the heating means, it is possible 
to shorten the warm-up time (required to bring the recording head from the 
room temperature to the set temperature) of each recording head and to 
control the temperatures of the recording heads at a constant temperature 
value uniformly during the recording operation. As a result, the following 
advantages are obtained. 
That is to say, it is possible to cool the plural recording heads by a 
single cooling means, thus making the recording system small-sized and 
reducing the cost of the apparatus. 
Further, the electric power for the heating and heat discharging can be 
minimized. 
In addition, the maximum electric power required for the heat discharging 
can be reduced, thus making the cooling means small-sized. 
Further, it is possible to reduce the distance between the recording heads 
due to the use of a single small-sized cooling means, thus improving the 
registration operation. 
Furthermore, it is possible to shorten the time required from the image 
demand to the image output, and to record the stable image. 
The present invention provides excellent advantages by adopting an ink jet 
recording apparatuses, particularly, bubble jet recording heads and 
recording apparatuses proposed by Canon co., Ltd (Japan). 
The typical construction and principle thereof are preferably realized by 
referring the fundamental principle disclosed in U.S. Pat. Nos. 4,723,129 
and 4,740,796. Although such apparatus can be applied to both of so-called 
"on-demand" type and "continuous" type, particularly, it is advantageously 
applicable to the on-demand type, since, by applying at least one drive 
signal corresponding to the image information and capable of providing 
abrupt temperature increase exceeding the nucleate boiling point to the 
electric/thermal converters arranged in correspondence to the sheet and 
the liquid paths containing ink, the electric/thermal converters can 
generate the thermal energy to create the film boiling on the heat active 
surfaces of the recording heads, thus generating the bubble in the liquid 
(ink) corresponding, by one-to-one, to the drive signal. Due to the growth 
and vanishment of the bubble, the ink is discharged from the discharge 
opening to form at least one ink droplet. The drive signal is preferably 
formed as a pulse type, since, in this case, the growth and disappearance 
of the bubble are effected instantaneously and properly, whereby the ink 
is discharged with good response feature. The drive signal of pulse type 
may be ones described in U.S. Pat. Nos. 4,463,359 and 4,345,262. 
Incidentally, by adopting the conditions described in U.S. Pat. No. 
4,313,124 disclosing the invention regarding the temperature increase 
ratio of the above-mentioned heat active surface, it is possible to 
perform the further excellent recording. 
As the construction of the recording head, the present invention includes 
the construction wherein the heat acting portion is disposed in an arcuate 
area as disclosed in U.S. Pat. Nos. 4,558,333 and 4,459,600, as well as 
the constructions wherein the discharge openings, liquid paths and 
electric/thermal converters are combined (straight liquid paths or 
orthogonal liquid paths). In addition, the present invention can 
applicable to the construction wherein each discharge opening is 
constituted by a slit with which a plurality of electric/thermal 
converters associated in common as disclosed in the Japanese Patent 
Laid-Open No. 59-123670 and the construction wherein openings for 
absorbing the pressure wave of the thermal energy are arranged in 
correspondence to the discharge openings as disclosed in the Japanese 
patent Laid-Open No. 59-138461. 
Further, as a recording head of full-line type having a length 
corresponding to a maximum width of a recording medium to be recorded, the 
construction wherein such length is attained by combining a plurality of 
recording heads as disclosed in the above patent specifications or a 
single recording head integrally formed may be adopted; the present 
invention can be applied to either of them with more excellent advantages. 
In addition, the present invention is applicable to a removable recording 
head of tip type wherein, when mounted on the recording apparatus, 
electrical connection between it and the recording apparatus and the 
supply of ink from the recording apparatus can be permitted, or to a 
recording head of cartridge type wherein a cartridge is integrally formed 
with the head. 
Further, it is preferable to add the head restoring means and/or 
preliminary assisting means to the recording head constituting the ink jet 
recording apparatus according to the present invention, since the 
advantages of the present invention become invincible. These means 
includes, for example, a capping means, cleaning means, pressurizing or 
absorbing means, and preliminary heating means constituted by the 
electrical/thermal converter, or other heating elements, or the 
combination thereof. Further, it is advantageous that a preliminary 
discharging mode for discharging ink independently of the ink discharge 
for the recording is performed, in order to achieve the stable recording 
operation. 
Finally, regarding the recording modes of the recording apparatus, not only 
the recording mode using mainly the black ink, but also the multi-color 
recording mode or full-color recording mode using the combination of the 
plural recording heads can be used; also in this case, the present 
invention is advantageously applicable.