JPH01108052A - Recording apparatus - Google Patents

Abstract

PURPOSE:To prevent the change of an image resulting from the temperature difference, by mounting a plurality of recording heads each provided with a temperature detecting means and a heating means, and a cooling means which cools the recording heads at one time. CONSTITUTION:Each of recording heads 3 is provided with a temperature detecting means 4 and a heater 5. For example, a recording unit 1 is comprised of four recording heads 3a, 3b, 3c and 3d which are arranged, for example, to respectively correspond to yellow, magenta, cyan and black. The temperature detecting means 4 may be a temperature IC, a thermistor, a thermocouple, a varistor, etc. A power transistor or a heat generating element, etc. may be used for the heater 5. Moreover, it is possible to cool the recording head unit 1 by driving an air blower of, e.g., fan-type provided opposite to the recording heads 3a-3d.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording apparatus, and more particularly to a recording apparatus having a plurality of recording heads that perform recording using thermal energy.

[Prior Art] Various recording devices have been known for a long time, and among them, recording devices that use heat as recording energy, such as bubble jet recording, thermal recording, and thermal transfer recording, have a simple configuration and are capable of color printing. Compared to other recording devices, it is seen as more promising in the future because it is easier to record. Among such recording apparatuses that use heat as recording energy, a plurality of recording heads may be provided especially for the purpose of color recording, speeding up recording, and the like.

[Problems to be solved by the invention] A recording head that uses this kind of thermal energy as recording energy;
For example, in a recording device equipped with multiple bubble jet recording heads, each recording head performs recording in response to an image recording signal sent from a control device to an electrothermal transducer, which is a thermal energy generation source for each recording head. In this case, there may be a difference in the amount of heat generated by the electrothermal transducer for each recording head. This difference in the amount of heat generated by the electrothermal converter of each recording head is expressed as a temperature difference between each recording head, and in the case of inkjet recording, the difference in head temperature becomes a difference in the temperature of the recording ink, which means a difference in the temperature of the recording ink between each head. This results in a difference in ink viscosity, which causes variations in the amount of ink ejected between the heads, resulting in unevenness in images due to density differences.

Particularly when performing full-color recording using recording heads installed for different color inks, if the temperature of each color head fluctuates and the temperature difference between the heads becomes large, not only the temperature difference but also the color balance will fluctuate, resulting in a stable The problem was that it was difficult to obtain a color image.

[Means for Solving the Problems] To this end, the present invention includes a plurality of recording heads each having a temperature detection means and a heating means, and a cooling means for cooling the plurality of recording heads simultaneously. The present invention is characterized by comprising a control means for detecting the temperature of the recording head by the means and controlling the heating operation by the heating means and the cooling operation by the cooling means in order to eliminate the temperature difference between the plurality of recording heads.

[Function] According to the present invention, by appropriately controlling the cooling operation of the recording head by the cooling means and the heating operation by the heating means, it is possible to control the temperature difference between a plurality of recording heads. image fluctuations can be prevented.

[Example] The present invention will be described below with reference to the drawings.

In the following, a case where the present invention is applied to an inkjet recording apparatus using a bubble jet method will be exemplified.

FIG. 1 shows an example of the configuration of an inkjet recording apparatus according to the present invention. Here, 1 is a recording unit mounted on a carriage 2, in which a pulse voltage according to an image recording signal is applied to an electrothermal transducer, and the thermal energy generated from the electrothermal transducer causes foaming to eject ink. It has a plurality of recording heads 3 for recording.

FIG. 2 shows an enlarged view of the recording unit 1, in which each recording head 3 is provided with a temperature detection means 4 and a heater 5. In this example, the recording unit 1 includes four recording heads 3a, 3b, 3c, and 3d, each of which can correspond to, for example, yellow, magenta, cyan, and black.

As the temperature detection means 4, a temperature IC, a thermistor, a thermocouple, a varistor, etc. can be used. Further, as the heater 5, for example, a power transistor or a heating element can be used.

Referring again to FIG. 1, reference numeral 7 denotes an air blowing means, for example, in the form of a fan, provided for the recording heads 38 to 3d, and by driving this, the head unit 1 can be cooled. 13 is a paper feed motor;
A recording medium P such as paper is conveyed in the direction f in the figure by a roller 12 coupled to the shaft of a motor 13 in response to the drive of the recording medium P.

The roller 14 is a roller that cooperates with the roller 12 to regulate the recording medium P to be flat and to form a recording surface for the recording unit 1.

Reference numeral 15 indicates a belt for driving the carriage to which the carriage 2 is fixed; reference numeral 1B indicates a motor for driving the belt 14 in the S direction in the figure; and reference numeral 18 indicates a guide rail for the carriage 2. That is, the carriage 2 can move in the S direction in the figure along the guide rail 18 in accordance with the drive of the motor 16, and can perform recording on the recording surface.

Further, the detection signal of the temperature detection means 4 is manually inputted to the control device shown in the third figure, and the control device 9 controls the driving of the heater 5 and the air blowing means 7 based on this temperature signal, thereby controlling the temperature of each recording head appropriately. Make sure to keep the temperature within the set temperature range.

FIG. 3 shows an example of the configuration of a control system that can be used in the apparatus shown in FIG. The output signal of the temperature detection means 4 of each recording head 3 is taken into the control device 9 via the conversion amplifier 8^ and the A/D converter 8 as digital data of the current temperature of each recording head. On the other hand, the control device 9 issues a drive signal to the heater 5 via the heater drive circuit 10 when the recording head is at a low temperature and requires heating, and to the blower means 7 when the recording head is at a high temperature and requires cooling.

The control device 9 includes, for example, a CPU that performs control operations according to the processing procedures described later with reference to FIG. 5, FIG. 7, FIG. 8, or FIG. 9, a ROM that stores programs and other fixed data corresponding to the processing procedures, and It can be in the form of a microcomputer having a working RAM and the like.

Next, aspects of control by the above configuration will be explained based on each embodiment thereof.

(Example 1) FIG. 4 shows an algorithm of control operation according to this example, and T
I%T2 and T3 are the upper limit of the set temperature range, respectively.
These are the center value and the lower limit value. As is clear from FIG. 4, the on/off set temperatures of the heater 5 and the air blower 7 are changed to provide hysteresis when the head temperature changes from low to high temperature and from high to low temperature. . This is because it is difficult to control the center temperature of the recording head 3 so that it is always T2, so an upper limit T0 and a lower limit T3 are set according to the set temperature range, and the head temperature is set within that set temperature range. This is to control.

FIG. 5 shows a first embodiment of the control procedure for the heater 5 and the blower means 7. In FIG.

When the power is turned on and during recording, the temperature of each head 38 to 3d is detected in step S1, and if there is a head whose temperature is higher than the upper limit T of the set temperature range, the blower means 7 is turned on in step S2 to blow all the heads. cooled down. In step S3, temperature is detected and it is determined whether the temperature of all heads is below the center T2 of the set temperature range.If the determination is positive, the blower means 7 is turned off in step S4, and if the determination is negative, the step continues. Repeat S3.

If it is determined in step S1 that the temperature of all heads is already lower than the upper limit T of the set temperature range, or in step S1,
After the process of 4, the process proceeds to step Sll, where the temperature of each head is detected again, and if there is a head whose temperature is lower than the lower limit T3 of the set temperature range, the heater of each head is turned on and heated in steps 512 to 518. In step 519, the temperature is detected and it is determined whether all the heated heads are at a temperature equal to or higher than the center 12 of the set temperature range.If the determination is positive, the heater is turned off in step 520, and if the determination is negative, the step continues. Repeat 519.

If all four heads have already reached the lower limit T of the set temperature range in step Sll, then the process ends. On the other hand, after the processing in step 520, the process proceeds to step St, and the subsequent processing is repeated so that all four heads are maintained within a predetermined set temperature range.

By performing such a control operation, it becomes possible to cope with recording in a low-temperature environment or when the head temperature rises gradually or suddenly during continuous recording. In this way, when the head temperature is always maintained within the appropriate set temperature range and the temperature difference between the heads is suppressed, image fluctuations caused by the temperature difference between the heads are suppressed and a stable image is obtained. It will be done.

Furthermore, FIG. 6 shows the correspondence between temperature changes and density (0, D value) in the recording apparatus shown in FIG. In inkjet recording, recording density 400dp
i (dot/inch) recording head and dye density 2wt
% recording ink, a density change of 0.04 was achieved at a temperature change of 5° C., as shown in this figure.

(Embodiment 2) Next, another embodiment of the control according to the present invention will be described.

In (Embodiment 1), when the power is turned on and during recording, if even one of the four recording heads 3 is higher than the upper limit T1 of the set temperature range, cooling is started by the air blower 7, and the four recording heads are The blowing means 7 was controlled so as to be turned off when all the head temperatures became equal to or lower than the center T of the set temperature range.

On the other hand, it is possible to cope with the case where the head temperature is extremely high or the cooling capacity of the air blowing means 7 is low, thereby shortening the processing time in step S3, and the CPU The embodiment shown in FIG. 7 is configured to simplify the control by adding steps 515 and the like for setting a timer to the procedure shown in FIG.

That is, in FIG. 7, in step S2, the blowing means 7
At the same time as turning on, a timer for measuring an appropriate time is set in step 515, and then the process moves to step S3. Then, temperature is detected here, and it is determined whether the temperature is below the center value T2 of the set temperature range,
If the determination is affirmative, the process immediately proceeds to step S4 to end the cooling, and if the determination is negative, the process proceeds to step S6. In step S6, it is determined whether the set time has elapsed or not, and if the determination is affirmative, the process proceeds to step 55 and subsequent steps while keeping the air blowing means in the on state. If the set time has not yet elapsed, steps S3 and subsequent steps are repeated.

By providing step 515 etc. for setting the timer in this way, the process is stagnant for a long time in step S3,
It is no longer possible to move on to the next operation or it does not take a long time to move on, making it possible to have a wide range of applications.

(Embodiment 3) FIG. 8 shows a third embodiment of the control according to the present invention. Similar to (Embodiment 2), this embodiment shortens processing time and simplifies control by CPU. It is suitable for In this example, for example, a counter is provided in a predetermined area of RAM or the like to count the number of times the scan is performed in the S direction, and a process for setting a limit on the number of times step S3 is executed is performed according to the count value. This is what I decided to do.

That is, after the processing in step S2, a counter is reset in step S7, and if a negative determination is made in step S3, it is determined in step S8 whether or not an appropriate number of scans has been reached. If an affirmative determination is made, the process moves to step S5, and if a negative determination is made, the process returns to step S3.

By providing step S7 for resetting the counter in this way, the process is not stalled for a long time in step S3 and cannot move on to the next operation, or it does not take a long time to move, and it can be applied in a wide range of applications. becomes.

(Example 4) Next, still another embodiment of the present invention will be described.

In the above-mentioned (Example 1) to (Example 3), when the power is turned on, during recording, or at an appropriate timing, the temperature of all four recording heads is set within the set temperature range.
The cooling operation by the blowing means 7 and the heating operation by the heater 5 were controlled. Even if there is almost no temperature difference between the four print heads, if the temperatures of those four print heads are outside the set temperature range, control is performed.
The temperature of the four recording heads was maintained within a set temperature range. In contrast, this example is configured to more easily suppress image fluctuations caused by head temperature differences, and employs the procedure shown in FIG. 9. In this embodiment, the cooling operation by the air blower 7 and the heating operation by the heater 5 are controlled so that the temperature difference ΔT between all recording heads is approximately zero.

In FIG. 9, step 51 is performed when the device power is on.
In step 01, the temperature of each head is detected, and in step 5102, (Tmax+Tm1n)/2 is calculated from the highest print head temperature Tmax and the lowest print head temperature Tmax, and is set as the reference temperature Ts. In step 5103, the air blowing means 7 is operated to cool down the temperature of all print heads, including the print head whose temperature is Tm1n, to below the reference temperature (step 5104). Step 5105.51
In step 06, the individually attached heaters 5 are operated and controlled to a reference temperature so that the temperature difference ΔT between the heads becomes approximately 0''.

Such a control operation makes it possible to cope with the case where the head temperature gradually or suddenly increases during continuous recording. When the temperature difference between the heads is suppressed in this way, image fluctuations caused by the temperature difference between the heads are suppressed, and a stable image can be obtained.

It is most desirable to perform control during recording at all times in real time, but if the purpose is sufficiently achieved, CP
In order to simplify the control by u, it is also possible to provide an appropriate timer and perform control every predetermined time, or every predetermined number of scans.

Further, the present invention is applicable to an inkjet recording apparatus having a plurality of recording heads, even if the plurality of recording heads are provided corresponding to predetermined ink colors to perform multicolor recording, or gradation It goes without saying that it is also applicable to a system in which a plurality of recording heads are provided corresponding to predetermined densities for expression.

In addition, the format of the recording unit is not limited to the serial printer type as shown in the above example, but also a line having multiple recording heads with ink ejection orifices aligned across the entire width of the recording medium, corresponding to the ink color and density. Of course, it may be in the form of a printer.

Further, in the above example, the ink temperature is controlled by the control device 9 having a CPU, but it goes without saying that it can be controlled by hardware by combining a comparator or other appropriate logic circuit.

In addition, the present invention is of course applicable to any recording method such as bubble jet recording, thermal recording, thermal transfer recording, etc.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a recording device with a simple configuration that can suppress image fluctuations caused by temperature differences between heads and easily obtain a stable image. did it.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of the configuration of an inkjet printing apparatus as an example of a printing apparatus to which the present invention can be applied; FIG. 2 is a perspective view showing an example of the structure of a recording unit thereof; FIG. A block diagram showing an example of the configuration of the #J control system applicable to the illustrated printing apparatus; FIG. 4 is an explanatory diagram for explaining an algorithm for temperature control of the print head by the control system shown in FIG. is a flowchart showing a first embodiment of the recording head temperature control means by the control system shown in FIG. 3; FIG. 6 is an explanatory diagram for explaining the effect of temperature control; FIGS. 7 to 9 are , respectively, are flowcharts showing second to fourth embodiments of the temperature control procedure by the control system shown in the third figure. DESCRIPTION OF SYMBOLS 1... Recording unit, 2... Carriage, 3.3a, 3b, 3c, 3d --- Recording head, 4...
- Temperature detection means, 5... Heater, 7... Air blowing means, 9... Control device. Figure 2. Figure 3 (Tota) 0 Shiba Jitenki role Figure 4 Figure 6 Figure 9

Claims (1)

[Scope of Claims] 1) A plurality of recording heads each having a temperature detection means and a heating means, and a cooling means for cooling the plurality of recording heads simultaneously, wherein the temperature of the recording head is determined by the temperature detection means. 1. A recording apparatus comprising: a control means for detecting a temperature difference between the plurality of recording heads and controlling a heating operation by a heating means and a cooling operation by a cooling means to eliminate a temperature difference between the plurality of recording heads. 2) In the recording device according to claim 1,
A printing apparatus, wherein the control means performs the control to maintain the temperature of the print head within a predetermined temperature range. 3) In the recording device according to claim 1,
A recording device characterized in that the cooling means has the form of a blowing means.