JPH03227643A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To make the diameter o recording dots uniform regardless of temperature of a recording head and thereby obtain a high-quality image in terms of density by detecting the temperature of the recording head and controlling the waveform of an electric signal connected to each electrothermal conversion device in accordance with the detection results. CONSTITUTION:In a control part which controls a head drive circuit 14A of a recording head 14, a waveform data ROM unit 33 stores pulse width corresponding to each temperature of the recording head 14 previously as waveform data. A sequence control ler 32 consisting of CPU and other components controls the transfer of a recorded image signal from a recorded image signal buffer 31 to a head drive circuit 14A as well as waveform data from the waveform data ROM unit 33 to the head drive circuit 14A. At the same time, the controller 32 transfers a latch signal, a clock signal and a preset signal to the head drive circuit 14A at a proper timing. In addition, the control ler 32 controls a heater 114 via a temperature adjustment circuit 22 according to outputs from thermisters 15, 16, 17, as a temperature detection device arranged on the recording head 14. Thus the controller 32 maintains the temperature of the record ing head 14 at a best-suited level and at the same time, selects between pieces of waveform data stored in the waveform ROM unit 33 properly and sends the selected waveform data to the recording head 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording device.

Among current printing apparatuses, so-called inkjet printing apparatuses are widely used as highly reliable apparatuses that can obtain high image quality at high speed. However, with this recording device,
Since the viscosity of the recording liquid changes depending on the temperature of the recording head and the diameter of the recording dots changes, there is a problem in that density fluctuations occur in the recorded image and the recording quality may deteriorate.

Therefore, in this inkjet recording apparatus, it is common to perform recording by controlling the temperature of the recording head to a certain constant temperature.

Furthermore, there are various types of inkjet recording methods, and one of them is an inkjet recording method that uses thermal energy. The device heats the recording liquid rapidly, and this heating causes a bubbling phenomenon in the recording liquid.The bubbling energy causes the recording liquid to be ejected from the liquid ejection port (orifice).One of its features is that it can be integrated. This means that it is easy. Incidentally, it is easy to integrate, for example, 128 to 256 discharge ports with an interval of 63.5 μm. Therefore, it has excellent advantages not found in other inkjet recording methods, such as being able to record high-quality images at high speed.

FIG. 1O is a diagram showing the configuration of such an inkjet recording apparatus. In FIG. 10, 201A and 201B are a pair of rollers provided to nip and convey the recording medium R in the sub-scanning direction (2).

In 2028, 202Y, 202M and 202C are
Each of these is a full multi-type recording head for recording black, yellow, magenta, and cyan in which ejection ports are arranged over the entire width of the recording medium R, and are arranged in that order from the upstream side in the recording medium conveyance direction. Also, 200
is a recovery system, and during ejection recovery processing, the recording medium R
202C instead of the recording head 2028.

Here, in the recording head 2028, 202Y, 202
Each of M and 202C is provided with a plurality of external heaters and temperature detection means for temperature control for the reason mentioned above, and the plurality of external heaters are activated depending on the temperature of the recording head. By heating them independently or simultaneously, the head temperature is made uniform, thereby making the recording dot diameter uniform and preventing image quality deterioration.

[Problems to be Solved by the Invention] However, even in the above example, it was difficult to obtain sufficient uniformity of the temperature of the recording head, that is, uniformity of the recording dot diameter.

The main reason for this is that the heat-generating parts and ink inside the print head are indirectly heated by an external heater, so after detecting the temperature of the print head, the external heater heats the print head and the temperature of the print head increases. It takes time to do it, and it's accurate in the head!・Nono / 7″ 1 Shoji 6 I Wound 1 Shozusa t Door 11!
There was a problem in that the arrangement of the external heater and the control device were also very complicated.

In particular, in the case of a so-called full multi-type recording head in which ejection ports are provided throughout the recording area of the recording material, the temperature cannot be controlled uniformly over the entire area of the recording head due to its long length. There was a problem with how it was more difficult to do.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet recording apparatus that can make the diameter of recording dots uniform with a simple configuration and obtain high-quality images even if the temperature of the recording head is uneven.

[Means for Solving the Problems] In order to achieve the above object, the present invention is arranged to correspond to each of a plurality of ejection ports, and generates thermal energy used for ejecting ink. It has a plurality of electrothermal conversion means to perform the electrothermal conversion $Ele! call ministry 1 at
14 += Suya I# No. Δ W Irako Ki φ t= J-x ノ ＾ In the jet recording device, a temperature detection means for detecting the temperature of the recording head, and according to the output of the temperature detection means, The apparatus is characterized by comprising waveform control means for individually controlling the waveform of the electric signal supplied to each of the plurality of electrothermal conversion means.

[Function] According to the present invention, the temperature detection means detects the temperature of the recording head, and depending on the result, the diameter of the dots formed on the recording medium by the operation of each electrothermal conversion means is made uniform. The waveform control means controls the waveform of the electric signal, which is the recording energy, supplied to each electrothermal conversion means so that the recording energy is supplied to each electrothermal conversion means.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit block diagram showing a drive circuit for a so-called full line type inkjet recording head according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a heating element consisting of an electrothermal conversion element provided corresponding to each of about 3000 ejection ports provided corresponding to the width of the recording paper being conveyed, and the heating element 1 generates heat. The heat generated generates bubbles in the ink, and ink droplets are ejected from the ejection port by fluctuations in the ink as the bubbles expand and contract. The potential difference between both ends of each heating element 1 is maintained at a driving voltage value of 8 via each switching transistor 3. The bases of the transistors 3 are connected to the outputs of the respective AND gates 5.

In FIG. 1, numeral 13 is a shift register that stores a 1-bit waveform data signal that is serially transferred from the control section of the inkjet recording apparatus.

The drive pulse in this example modulates the pulse width,
It is expressed in 16 steps of pulse width. Therefore, four consecutive bits of the waveform data signal constitute waveform data of one drive pulse. As a result, the shift register 13 has approximately 30
It is composed of approximately 3000×4 bits corresponding to 00 heating elements 1. Reference numeral 11 denotes a counter provided for each heating element, in which waveform data to be transferred in 4-bit parallel from the shift register 13 is set in accordance with a preset signal from the recording apparatus control section. The counters 11 are each based on the set waveform data, that is,
In this example, the clock pulses transferred from the control section are counted by a value corresponding to the pulse width of the waveform, and the output is set to "H" while this counting is performed.

In FIG. 1, numeral 9 denotes a shift register for storing a 1-bit serially transferred recording image signal, and is composed of approximately 3000 bits corresponding to each heating element 1. Reference numeral 7 denotes a data buffer that latches the recording image signal output from the shift register 9 in accordance with a latch signal and outputs this signal. Each of the AND gates 5 described above has two inputs, the corresponding output of the data buffer 7 and the corresponding output of the counter 11.

FIG. 2 shows that by continuously sending various signals listed above to the head drive circuit 14A shown in FIG. 1 of the recording head 14,
FIG. 2 is a block diagram showing in detail a control section that controls this head drive circuit.

In FIG. 2, 31 is a recorded image signal buffer for temporarily storing recorded image signals continuously sent from a host device such as a microcomputer. It is possible to adjust the discrepancy between the drive timing on the recording head 14 side and the drive timing using this signal. Note that the device that transfers the recorded image signal is not limited to a host device such as a computer, but may also be a document reading section of a copying machine, a facsimile machine, a word processor, or simply a keyboard in a printer device that uses the inkjet recording device of this example as a printer. It may also be equipped with an input device such as.

Again in FIG. 2, numeral 33 is a waveform data ROM in which waveform data of the drive pulses described above is stored. In this embodiment, control is performed using a look-up table method, and pulse widths corresponding to each temperature are stored in advance as waveform data in the waveform data ROM 33.

Furthermore, in FIG. 2, 32 is a sequence controller consisting of a CPU, etc., and a recording image signal buffer 31
The recording image signal is transferred from the head drive circuit 14A to the head drive circuit 14A, and the waveform data is transferred from the waveform data ROM 33 to the head drive circuit 14A.
It controls the transfer of waveform data to A, and also transfers the latch signal, clock signal, and preset signal to the head drive circuit 14A at appropriate timing.

The sequence controller 32 also controls the recording head 14.
Thermistors 15 and 16 which are temperature detection means arranged in
．． 17, the heater 1 is controlled via the temperature control circuit 22.
14 to maintain the temperature of the recording head 14 appropriately, and also appropriately selects waveform data stored in the waveform data ROM 33 and sends it to the recording head 14 at an appropriate timing.

Here, the arrangement of the thermistors 15, 16, and 17 will be explained using FIG. 3, which is a front view of the recording head 14.

In FIG. 3, 111 is a first substrate made of A[, 1
12 is a second substrate made of metal such as silicon; 113;
is a top plate, and this substrate 113 is formed with a plurality of liquid passages, each of which includes a liquid discharge port 113A for ejecting flying liquid droplets, and is an electrothermal conversion means. Heat generating elements are arranged on the second substrate 112 corresponding to each of the liquid paths. 114 is a heater for temperature control.

And the thermistor 15.16°1 which is the temperature detection means
7, in order to appropriately measure the temperature of the second substrate 112,
They are arranged at the center and both ends of the substrate 112.

Generally, the temperature gradient in the arrangement direction of the ejection ports 113A causes the above-mentioned image deterioration, so it is preferable to arrange thermistors at the center of the recording head 14 and at both ends thereof.

Next, the operation of this embodiment shown in FIGS. 1 and 2 will be explained as follows.
This will be explained using FIG. 4, which is a timing chart showing the transfer timing of each signal.

First, the sequence controller 32 activates the thermistor 1 at predetermined intervals, for example, every 5 lines of recording.
5. Input the output signal of 16.17. Then, according to the output signal, the external heater 114 is
At the same time, appropriate waveform data is selected from the waveform data ROM 33 for each of the approximately 3000 flow path heating elements and transferred to the shift register 13 (fourth
Figure, time point ■).

Next, when the recording operation is started, the recording image signal is transferred from the recording image signal buffer 31 to the shift register 9 in synchronization with the timing of recording paper conveyance, etc. (time point ■)
. When this transfer is completed, the recording image signal is latched in the data buffer 7 by the latch signal °'L'' (time point ■), and the output of these data to the AND gate 5 is set.

Further, prior to the °°L"° pulse of the latch signal, the waveform data stored in the shift register 13 is set in each counter 11 by "Lo" (time point ■) of the preset signal.

When the output from the data buffer 7 is set by the latch signal being 'L' (time point ■), the clock signal begins to be transferred (time point ■), and the counter 11 converts this clock signal pulse into the waveform data set to this counter. During this counting period, the output of this counter to the AND gate 5 is set to "H".

As a result of the operation of each signal shown above, logic "H" is output from the counter 11 corresponding to the heating element 1 corresponding to the recording image signal °゛H°° outputted from the data buffer 7. A drive pulse with a period width of
This causes ink droplets to be ejected.

As described above, 1912 minutes of printing corresponding to the length of the ejection port array of the print head is performed. While the recording head is being driven for one line, that is, between the latch signal °゛L'° and the next latch signal °゛L°゛, the recording image signal of the next line is transferred to the shift register 9. The information is input and recorded in the same manner as described above.

Next, the results of a recording experiment using this example will be explained.

As a method, as shown in Fig. 5, the recording paper P is
While moving the recording head in the direction indicated by the arrow, that is, to the left with respect to the recording head 14,
) was recorded in an inverted letterform, and the density distribution of each portion of the recording paper P was measured.

In addition, a multi-nozzle with 400 dpi and 256 discharge ports was used in the experiment, and the temperature control circuit was equipped with so-called on/off control that energized the heater 114 when the temperature T2 of the thermistor 6 became 45 degrees Celsius or lower. I let it happen.

Furthermore, the temperature of each part of the recording head 14 to which the thermistor is attached before recording was as shown in FIG. 6, and there was a temperature difference of about 5° C. between the center and both ends.

Under the above conditions, the discharge port having a heating element controlled based on the temperature signal T1 from the thermistor 15 is
O, 1 to 50, and the temperature signal T2 from the thermistor 16
The discharge ports controlled by the temperature signal T3 from the thermistor 17 were selected as Nos. 51 to 205, and the discharge ports controlled by the temperature signal T3 from the thermistor 17 were selected as Nos. 206 to 256. The pulse width was changed as follows according to each temperature signal Ti (i·1 to 3).

The results of recording on the recording paper P in this manner and measuring the density distribution of each part are shown in FIGS. 7(2) and 8(2). For comparison with the present invention, Figures 7 (1) and 8 (1) show the results of measuring the density distribution in each part in the conventional example, that is, when recording was performed with a constant pulse width (7 μs). It is.

First, as shown in FIG. 7 (1), in the conventional example, 1 degree increases as recording progresses from point 0 to point b, leading to non-uniform density between c and b. In the conventional example, the concentration distribution in the direction connecting points a and b is as shown in Figure 8 (1).The reason for this non-uniformity in concentration is that the temperature at point a has not increased much, but at point b. This is due to the fact that the temperature there increased as a result of continuous recording from point 0. On the other hand, according to the embodiment of the present invention, between cb and cb
The results showed that the concentration distribution between the two was uniform as shown in FIG. 7 (2) and FIG. 8 (2), respectively.

As is clear from FIGS. 7 and 8, according to this embodiment, the image density can be made uniform, that is, the dot diameter can be made uniform, and a high-quality image can be obtained.

In this example, the driving voltage is kept constant (24,0
Although the pulse width is changed by changing the pulse width to V), it is also possible to obtain the same results as in this embodiment by setting the pulse width to a constant value, for example, 7 μs, and changing the drive voltage according to the detected temperature.

Furthermore, in the case of an inkjet recording apparatus that forms flying droplets by a two-part pulse as shown in FIG. 9, each condition (zl) of the two-part pulse is determined.

Z2+ Z3. By appropriately changing the dot diameter (Vop) according to the head temperature, it is possible to change the dot diameter with high precision, so it is possible to obtain a higher quality image than with a single pulse device.

For example, if the drive voltage Vop is kept constant at 24.0 (V), the interval 2. ．． 22,2. depending on the temperature.

In the present invention, the driving conditions, that is, the kind of electrical signal to be supplied to each electrothermal conversion means, may be appropriately selected depending on the thermal characteristics of the recording head. It is best to check the temperature distribution before making your selection.

Furthermore, the temperature detection means is not limited to a temperature sensor such as a thermistor (for example, it may be one that can indirectly detect the temperature state of the recording head from image information).

In addition, in the embodiments described above, either the width (time) or the height (voltage) of the drive pulse was controlled depending on the temperature of the recording head, but the present invention also includes a case where both of these are controlled. The invention includes.

The present invention brings about excellent effects particularly in bubble jet recording heads and recording apparatuses among ink jet recording systems. This is because such a system can achieve higher recording density and higher definition.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. The electrothermal converter that is
By applying at least one drive signal corresponding to recording information and providing a rapid temperature rise above nucleate boiling, the electrothermal transducer generates thermal energy to cause film boiling on the thermally active surface of the recording sheet. This is effective because it results in the formation of bubbles in the liquid (ink) that correspond one-to-one to this drive signal. The growth and contraction of the bubble causes liquid (ink) to be ejected through the ejection opening to form at least one droplet. When this drive signal is in the form of a pulse, the growth and contraction of the bubbles is carried out immediately and appropriately, and liquid ejection with particularly excellent responsiveness can be achieved, which is more preferable. This pulse-shaped drive signal is described in U.S. Pat. No. 4,463,359 and U.S. Pat.
262 is suitable. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed.

The configuration of the recording head includes, in addition to the combination configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting section. The present invention also includes configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose configurations in which the wafer is placed in a bending region. In addition, Japanese Patent Application Laid-Open No. 1989-5 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters.
No. 9-123670 and Japanese Patent Application Laid-Open No. 59/1989 which discloses a configuration in which a discharge portion is made to correspond to an opening that absorbs pressure waves of thermal energy.
The effects of the present invention are also effective even if the structure is based on the publication No.-138461. In other words, regardless of the form of the printhead, printing can be performed reliably and efficiently.

Furthermore, as a full-line type recording head whose length corresponds to the maximum width of a recording medium that can be recorded by a recording device, there are configurations that satisfy the length by a combination of multiple recording heads, and a configuration in which a single recording head formed in one piece is used. The present invention can be effectively applied to any of the configurations of the recording head. In addition, even the serial type shown above can be installed on the main body of the device, allowing for electrical connection to the main body of the device and supply of ink from the main body of the device.Replaceable chip type recording heads. Alternatively, the present invention is also effective when using a cartridge type recording head that is integrally provided with the recording head itself.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention, because the effects of the present invention can be further stabilized. Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

In addition, regarding the type and number of recording heads installed, for example, in addition to one type that corresponds to single-color ink, there is also a plurality of recording heads that correspond to multiple inks with different recording colors and densities. It may be something that can be done.

In addition, the inkjet recording apparatus of the present invention may take the form of an image output terminal for information processing equipment such as a computer, a copying apparatus combined with a reader, etc., or a facsimile apparatus having a transmitting/receiving function. It may be something.

[Effects of the Invention] As described above, according to the present invention, even if the temperature of the recording head is uneven, the diameter of the recording dots can be made uniform, and a high-quality image can be obtained at that density.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a drive circuit for a recording head according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a control section that controls the drive circuit shown in FIG. 1, and FIG. , a front view of a recording head according to an embodiment of the present invention, FIG. 4 is a timing chart showing signal waveforms of each part of the control section shown in FIG. 5, and FIG. 5 is a front view of a recording head according to an embodiment of the present invention. An explanatory diagram for explaining the experiment. Figure 6 is an explanatory diagram showing the temperature of each part of the recording head before the recording experiment. Figures 7 and 8 show the density of each part of the image after the recording experiment. FIG. 9 is a waveform diagram showing the configuration of a two-part pulse, and FIG. 10 is a configuration diagram showing the configuration of a full-line type inkjet recording apparatus. DESCRIPTION OF SYMBOLS 1... Heating element, 3... Transistor, 5... AND gate 7... Data buffer, 9.13... Shift register, 11... Counter, 14... Recording head, 14A. ...Head drive circuit, 15, 16.17... Thermistor, 22... Temperature control circuit, 32... Sequence controller, 33... Waveform data ROM 113A... Discharge port, 114... Heater , Vop...drive voltage, Z+, Za...pulse width, Z2...pulse interval. 14 Figure 6 (1) (2) Figure 1O

Claims (1)

[Scope of Claims] 1) A plurality of electrothermal conversion means are disposed corresponding to each of a plurality of ejection ports and generate heat energy used for ejecting ink, and the electrothermal conversion means An inkjet recording apparatus that performs recording by supplying an electric signal to a converting means, comprising: a temperature detecting means for detecting the temperature of the recording head; and each of the plurality of electrothermal converting means according to the output of the temperature detecting means. An inkjet recording apparatus comprising: waveform control means for individually controlling waveforms of the electrical signals supplied to the inkjet recording apparatus. 2) The inkjet recording apparatus according to claim 1, wherein the waveform of the electric signal is controlled by changing at least one of the time and voltage value of an electric pulse forming the electric signal.