JPH03234629A - Image recording device - Google Patents

Abstract

PURPOSE:To shorten a waiting time for the title device by providing a recording head that forms flight droplets in accordance with electric signals, and by making the recording performed by changing waveform of the electric signals until the temperature at the recording head rises to a specified level. CONSTITUTION:A recording head 1 is equipped with an electrothermal converter 7 that produces thermal energy for causing ink to have film boiling for forming flight droplets. Recording data SI in the same bit numbers as that of the electrothermal converter 7 are transferred in serial order to a shift register 4 and are read into a latch circuit 5. Then discharge of liquid is made by selectively electrifying the electrothermal converter 7 in which recording data signal can be on only when pulse duration setting signals ENB are being on. Immediately after the device is switched on, a temperature sensor 30 and a thermostatic heater 20 start their operations to set the temperature in the recording head 1 at a specified level. In the meantime, the pulse durations of a driving signal are optionally changed until the temperature is set at the specified level. Thereby image density can be kept roughly at a fixed level, assuring the recording of quality image, without allowing a waiting time to be set after the switching-on of the device.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an image recording device.

[Prior Art] Image recording apparatuses in the form of so-called inkjet recording apparatuses that form flying droplets to form images are widely used because they can achieve high reliability and high image quality. In particular, the "bubble jet method", which has an electrothermal converter (discharge heater) in the recording head and uses thermal energy to form flying droplets, is attracting attention as it can achieve faster speeds, higher reliability, and higher image quality. has been done.

Generally, in an inkjet recording system, the viscosity of the ink changes depending on its temperature, and therefore the ejection characteristics change, resulting in changes in image characteristics (density, dot diameter). Therefore, in order to maintain stable image characteristics at all times, the recording head is controlled to a predetermined temperature to record the image.

[Problems to be Solved by the Invention] However, when the heat capacity of the recording head becomes large, a long waiting time is required until the recording head is heated to a predetermined temperature after the device is powered on.

Therefore, a proposal has been made to constantly detect the head temperature and change the head drive voltage waveform according to the detected temperature, thereby eliminating the need to heat the head to a predetermined temperature, or in other words, eliminating the standby time. There is.

However, in this case, since the recording head is often used at low temperatures, a large amount of driving energy is applied, which shortens the life of the ejection heater. Furthermore, since the responsiveness of head temperature detection is generally poor, it is difficult to quickly prevent density fluctuations due to changes in head temperature.

Therefore, it can be said that it is more advantageous to heat the recording head to a predetermined temperature and adjust the temperature in order to always record stable images.

[Means for Solving the Problems] The present invention aims to solve the above problems, and for this purpose, the present invention provides a recording head that forms flying droplets in response to an electric signal, and a recording head that forms flying droplets in response to an electric signal. and means for changing the waveform of the electrical signal according to the temperature of the recording head until the temperature of the recording head reaches the predetermined temperature after the device is powered on. It is characterized by:

[Function] According to the present invention, since it is possible to perform recording by changing the electric signal waveform until the temperature of the recording head reaches the predetermined temperature after the device is powered on, the waiting time can be shortened. can be measured.

[Example 1 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the configuration of a line printer capable of full-color recording as an image recording apparatus to which the present invention can be applied.

In FIG. 1, 201A and 201B are a pair of rollers provided to nip and convey the recording medium R in the sub-scanning direction v3. 2028, 202Y, 202M, and 202C are full multi-type recording heads that perform black, yellow, magenta, and cyan recording in which nozzles are arranged over the entire width of the recording medium R, and in that order, they are arranged on the upstream side in the recording medium conveyance direction. It is better placed.

A recovery system 200 faces the print head 2028 to 202C instead of the print medium R during ejection recovery processing, and performs processing to improve the ejection state of the print head.

FIG. 2 shows an inkjet recording head that can be applied to the configuration shown in FIG.
This is a so-called full multi-type device in which discharge ports are aligned.

Here, 54 is a heating resistor that forms an electrothermal conversion element that generates heat in response to energization, causes foaming in ink, and causes ink to be ejected. It is formed through a process. 52A
Reference numeral 56 indicates a liquid path forming member for forming a discharge port 52 and a liquid path 53 communicating therewith in correspondence with the heating resistor 54. Reference numeral 56 represents a top plate. Moreover, 55 is a liquid chamber commonly communicated with each liquid path 53, and stores ink supplied from an ink supply source (not shown).

FIG. 3 shows an example in which a temperature adjustment means is attached to the inkjet recording head used in this example. Here, 1 is a recording head main body corresponding to the recording head 2020 to 2028K, 20 is a temperature control heater for heating the recording head 1 to a predetermined temperature or higher, and 30 is a temperature detector for detecting the head temperature. .

Note that the temperature control heater 20 used had a total output of 25 W.

FIG. 4 shows an example of the electrical configuration of the above inkjet recording head and its drive system. The recording data (SI), which has the same number of bits as the electrothermal converter 7, is sequentially transferred to the shift register 4 in the driving ICa in synchronization with the data transfer clock (CLK), and after inputting all data, a latch signal ( LAT) is read into the latch circuit 5. After that, according to the input of the divided drive signal (EI) and the divided drive signal transfer lock (ECK), the drive IC 3 is sequentially activated by the flip-flop (F/F) 6, and the pulse width setting signal (ENB) is activated. The liquid is ejected by selectively energizing the electrothermal transducer 7 in which the recording data signal is ON only while the recording data signal is ON. Note that lO is a control unit that controls the above operations.

In this example, the temperature of the recording head 1 is adjusted to a predetermined value using the temperature detector 3 and the temperature control heater 20 immediately after the power is turned on, and the pulse width of the drive signal is adjusted appropriately until then. Make sure to change it.

FIG. 5 shows that the temperature control heater 2
0 is appropriately controlled so that the recording head 1 reaches the initial temperature (2 in the figure).
A temperature curve from 0°C to a predetermined temperature (45°C in the figure) is shown.

As is clear from the figure, conventionally, a waiting time of approximately 2 minutes is required to reach a predetermined temperature. If an image is recorded before this predetermined temperature is reached (the drive electric signal waveform of the electrothermal transducer is the same as that after the temperature adjustment, for example, 24.
OV and a pulse width of 7 μs), it was not possible to obtain the desired image density (for example, a halftone image with a duty of 50%) as shown by the broken line in FIG.

In contrast, in one embodiment of the present invention, the driving voltage is 24.
For OV, for example, if the head temperature is 30°C or lower, the pulse width is 8.5 μs, if the temperature is between 30°C and 40°C, the pulse width is 8 μs, and if the head temperature is 40°C or higher, the pulse width is 7 us. The drive electric signal waveform was changed accordingly. According to this, as shown by the solid line (■) in FIG. 6, it was possible to keep the image density almost constant, and it was possible to record a good image without waiting time after turning on the power of the apparatus.

Note that the data for specifying the pulse width to be selected as described above can be generated by an appropriate method, but for example, temperature data and pulse width data may be created in a table and R
The pulse width data can be stored in an OM or the like, read out in response to input of temperature data detected by the temperature detector 30, and used to output the pulse width setting signal ENB.

Furthermore, since the temperature increase of the print head 1 involves not only the temperature control heater 20 but also the drive of the ejection heater in the apparatus of this example, it is necessary to quickly adjust the temperature of the print head 1 to a predetermined temperature range without overshooting. , a pause period may be provided as appropriate for driving the temperature control heater 2. Also, by providing such a pause period, the types of pulse width data can be reduced (for example, data used in a predetermined temperature range and the corresponding It is also possible to simplify the pulse width data table (for example, by setting it to two stages with the data used at the initial time outside the range).

(Example 2) Furthermore, instead of changing the pulse width of the drive electric signal,
A similar effect can be obtained by changing the driving voltage. For example, when the pulse width is fixed at 7.0 μs, when the head temperature is 30°C or less, the drive voltage is set to 26V,
Almost the same results as in the above example could be obtained by applying 25V when the temperature was 30 to 40°C and 24V when the temperature was 40°C or higher.

Note that the same configuration or modification as the upper side can be applied to this example as well. Further, this example and the upper side may be combined.

(Example 3) In addition to controlling as shown above, the form of the pulse itself may be changed. For example, by using the two-split pulse shown in Figure 4, it was possible to improve the image density at lower temperatures (below 30°C) and maintain the uniformity of the image (solid line in Figure 7). ■).

(Others) The present invention brings about excellent effects particularly in a bubble jet type recording head and recording apparatus among inkjet recording types.

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 the continuous type, but especially in the case of the on-demand type, the ink is placed in correspondence with the sheet holding the liquid (ink) and the liquid path. The electrothermal converter that
By applying a single drive signal that corresponds to the recorded information and causes a rapid temperature rise exceeding nucleate boiling, the electrothermal transducer generates thermal energy, causing film boiling on the heat-active surface of the recording head. This is effective because it causes bubbles in the liquid (ink) that correspond one-to-one to this drive signal.The growth and contraction of these bubbles causes the liquid (ink) to flow through the ejection opening. The liquid (ink) is ejected to form a small (one droplet at a time).If this drive signal is in the form of a pulse, bubble growth and contraction occur immediately and appropriately, making it possible to eject liquid (ink) with particularly excellent responsiveness. , is more preferable.As this pulse-shaped drive signal,
U.S. Pat. No. 4,463,359, U.S. Pat. No. 4,345,26
Those described in Specification No. 2 are 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 recording head, recording can be performed reliably and efficiently.

Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by a recording apparatus.

Such a recording head may have either a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration in which a single recording head is formed in one direction. 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 a capping means for the recording head, a cleaning means, a pressurizing or suction means, a preheating means using an electrothermal transducer or a heating element separate from this, or a combination thereof, and recording. It is also effective to perform a preliminary ejection mode in which ejection is performed in a manner different from that for 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, in addition to being used as an image output terminal for information processing equipment such as a computer, the inkjet recording apparatus of the present invention may also take the form of a copying machine combined with a league, etc., or a facsimile machine having a transmission/reception function. It may be something.

[Effects of the Invention] As described above, according to the present invention, it was possible to construct an image recording device that can be used for a short period of time immediately after the device is powered on. Also,
At this time, it has become possible to constantly record good images without density changes over a long period of time without shortening the life of recording elements such as ejection heaters.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a schematic configuration of an inkjet recording apparatus to which the present invention can be applied, FIG. 2 is a perspective view showing an example of the configuration of a recording head thereof, and FIG. FIG. 4 is a block diagram showing an example of the electrical configuration of the recording head and its control section; FIG. 5 is a diagram illustrating the state of head temperature rise due to temperature adjustment; FIG. 6 is an additional schematic diagram. 7 is a diagram for explaining the present invention in detail, and FIG. 7 is a waveform diagram for explaining another embodiment of the present invention. 1, 202G, 202M, 202Y, 2028K...
・Recording spatula lO...Control unit, 20...Temperature control heater, 30...Temperature detector, ENB...Signal for pulse width setting. Figure 1 Figure 2 Figure 5

Claims (1)

[Claims] 1) a recording head that forms flying droplets in response to an electrical signal;
temperature control means for keeping the recording head at a predetermined temperature; and changing the waveform of the electrical signal according to the temperature of the recording head until the temperature of the recording head reaches the predetermined temperature after the device is powered on. An image recording device characterized by comprising: means for causing the image to appear. 2) The recording head has an electrothermal transducer for generating thermal energy that causes film boiling in the ink as the energy used to form the flying droplets. The image recording device described.