JPH0439057A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To prevent the occurrence of variation in image density for every recording head by providing a temperature detection means for detecting the temperature of the recording head, a heating means for heating the recording head, and a liquid drop amount control means for controlling a liquid drop amount of delivery ink by controlling the temperature of the recording head. CONSTITUTION:A carriage 3 loaded with a head unit 1 is reciprocated along a guide rail 4 by a carriage motor 6. A material to be recorded 7 is fed in an arrow direction (f) by a pair of feed rollers 9 driven by a feed motor 8 and a pair of holding rollers 10. The carriage motor 6 and the feed motor 8 are controlled by an MPU 30 through an I/O port 37. A temperature detection signal from a temperature detection means 51 provided on each recording head 2 is inputted to the MPU 30. The ON/OFF operation of a heater 52 provided on each recording head 2 is controlled in accordance with the temperature of the recording head 2 to control a liquid drop amount of delivery ink. In this case, since a liquid drop amount of delivery ink is controlled to be equal for every recording head 2, a variation in image density can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus that performs recording by ejecting ink from a recording head onto a recording material.

[Prior Art] Recording devices such as printers, copiers, and facsimiles are configured to record images consisting of dot patterns on sheet-like recording materials such as paper and thin plastic plates based on image information. has been done.

The recording device may be an inkjet type,
It can be classified into wire dot type, thermal type, laser beam type, etc. Among these, inkjet type (ink side recording device) is configured to perform recording by ejecting ink onto a recording material.

Inkjet recording apparatuses have advantages such as low noise because they are non-impact type, and the ability to easily record color images using multicolored inks.

Among these, film boiling type inkjet recording apparatuses that eject ink using thermal energy have the advantage that it is easy to create a multi-head configuration in which ejection ports are arranged in a high density on a print head.

[Technical problem to be solved by the invention] However,
With conventional multi-film boiling type inkjet recording heads, there are variations in the electrothermal converter used for ink ejection, which makes it difficult to record.

There is a considerable difference in the amount of ejected ink droplets even between individual printers.
If the device is driven under the same conditions as it is, there is a technical problem that the color balance will be disrupted and the image quality will deteriorate, especially in the case of full-color recording.

Furthermore, in order to improve the yield of printheads, it has been required to correct variations in the amount of droplets of ejected ink.

The present invention has been made in view of these technical problems, and provides an inkjet that can effectively control the amount of ink droplets ejected from a printhead and suppress variations in image density from printhead to printhead. The purpose is to provide a recording device.

[Means for solving problems]

The present invention provides an inkjet recording apparatus that performs recording by ejecting ink from a recording head onto a recording material, including a temperature detection means for detecting the temperature of the recording head, a heating means for heating the recording head, and a temperature detecting means for detecting the temperature of the recording head. A droplet amount control means that controls the amount of ejected ink droplets by controlling the amount of ink droplets ejected from the print head can be effectively controlled, and the amount of ejected ink droplets of the print head can be controlled effectively. Inkjet that can suppress variations in image density.

This provides a print recording device.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a schematic perspective view illustrating the main structure of an inkjet recording apparatus to which the present invention is applied.

In FIG. 1, numeral 1 is a head unit mounted on a carriage 3, and the head unit 1 includes a plurality of (four in the illustrated example) recording heads 2A, 2B, 2C12D.
have.

A plurality of ejection ports are formed on the ejection port surface of each of the recording heads 2A to 2D.

Further, inks of different colors are ejected from each of the recording heads 2A to 2D. For example, in the case of a color inkjet recording apparatus, each of the recording heads 2A to 2D is ejected from each of the recording heads 2A to 2D.
It can be made to correspond to magenta, noan, and flag ink colors.

Each of the recording heads 2A to 2D is an ink-end recording head that ejects ink using thermal energy, and is equipped with an electrothermal converter for generating thermal energy.

Further, the inkjet recording heads 2A to 2D perform recording by ejecting ink from ejection ports by the growth of bubbles due to film boiling produced by thermal energy applied by the electrothermal converter.

In FIG. 1, a carriage 3 on which the head unit 1 is mounted is movably supported along a guide rail 4, and is reciprocated by a carriage motor 6 via a timing belt 5.

A sheet-shaped recording material 7 made of paper, a thin plastic plate, etc. is moved along a predetermined path by a pair of conveyor rollers 9 driven by a conveyor motor (paper feed motor) 8 and a pair of holding rollers 10 that cooperate with the pair of conveyor rollers. , the paper is transported (paper fed) in the direction of arrow f at a predetermined timing and a predetermined pitch.

While this recording material 7 is held flat at the recording position facing the recording heads 2A to 2D, the recording head 2A
Recording is performed while performing main scanning in ~2D, and when recording for one line is completed, the recording material 7 is pitch-fed in the direction of arrow f, and the next line is recorded.

The carriage 3 includes an ink tank 13A for supplying ink of a color corresponding to each recording head 2A to 2D.
~13D are replaceably installed.

Each recording head 2A to 2D and each ink tank 13A-13
D are connected through an ink supply pipe 11 and an ink return pipe 12, respectively.

A home position H is set at a predetermined position within the movement range of the carriage 3 and outside the recording area, and a recovery device 14 is installed at the home position H to recover from ink failure in the recording heads 2A to 2D. It is arranged.

This recovery device 14 includes a cap 1 that can seal the ejection port surface (the surface on which the ejection port is formed) of each of the recording heads 2A to 2D.
5 is provided.

The recovery device 14 is disposed at a position where the recording heads 2A to 2D face each other when the carriage 3 comes to the home position H, and in addition to capping (sealing the ejection port surface) after recording is completed, the recovery device 14 removes water from the recording head. It is used to receive ink that has been ejected incorrectly, and to perform a recovery operation such as pressurizing and circulating ink to the recording head to eliminate ink ejection failure.

Further, the carriage 3 is equipped with a density reading means 53 for measuring the recording density of the image pattern recorded by the recording heads 2A to 2D.

FIG. 2 is a perspective view schematically showing the structure of the plurality of recording heads 2A to 2D mounted on the carriage 3.

In FIG. 2, reference numeral 11 indicates an ink supply pipe that supplies each ink to each of the recording heads 2A to 2D, and 12 indicates an ink return pipe that returns ink from each of the recording heads 2A to 2D to an ink tank 13.

Further, each of the recording heads 2A to 2D includes temperature detection means 51A, 51B for detecting the temperature of each recording head.
51C151D and heaters 52A, 52B, and 52C152D for heating the individual recording heads are provided.

As the temperature detecting means 51A to 51D, for example, a temperature IC, a thermistor, a thermocouple, a varistor, etc. can be used.

Further, as the heaters 52A to 52D, for example,
A power transistor or a heating element can be used.

The temperature signals detected by each of the temperature detection means 51A to 51D are sent to the control unit of the recording apparatus (MPU 30 in FIG. 4).
).

Each of the heaters 52A to 52D is controlled to be turned on or off by a control unit of the recording apparatus according to the temperature signal.

FIG. 3 shows the recording head 2 (the recording head 2A in FIG. 1).
2D is a partial perspective view schematically showing an ink ejection section (showing the entirety of 2D or any one of them).

In FIG. 3, a predetermined gap (for example, 0
．． A plurality of discharge ports 17 are formed at a predetermined pitch in the vertical direction on the discharge port surface 16 facing each other at a distance of about 5 mm, and each liquid passage 19 communicates between the common liquid chamber 18 and each discharge port 17. An electrothermal converter (such as a heating resistor) 20 for generating energy for ink ejection is arranged along the wall surface.

The corresponding electrothermal transducer 20 is driven based on an image signal or an ejection signal to boil the ink in the liquid path 19, and the pressure generated at that time causes the ink to be ejected. ing.

FIG. 4 is a block diagram showing the configuration of a control system of the inkjet recording apparatus shown in FIG. 1.

In FIG. 4, the electrothermal transducer 20 of the recording head 2
is driven by a driver 21, and the driver 21
For voltage switching circuit 2 from 1liifI22
3 is restored and power is supplied.

A timer 31 is also provided in the MPU 30 of the control system shown in FIG.

In FIG. 4, 32 is an I10 port for receiving signals from the host device, 33 is a ROM storing control programs, etc., 34 is a character generator, and 35 is an image generator. This is a RAM in which signals and the like are stored.

Furthermore, the carriage motor 6 and the transport motor 8 are
It is controlled by the MPU 30 via the I10 boat 37.

Furthermore, the MPU 30 is asked whether or not there is a recording material 7, whether there is a remaining amount of ink, whether the carriage 3 is at the home position H, or whether the ink tank 13 (all of the ink tanks 13A to 13D, or all of them) A detection signal from a sensor group 38 that detects the presence or absence of an arbitrary one of them is input via the I10 boat 37.

Further, temperature detection means 5 provided in each recording head 2
The temperature detection signal from 1 (indicating all of the temperature detection means 51A to 51D or any one of them) is M
The MPU 30 manually turns on and off the heaters 52 (all of the heaters 52A to 52D, or one of them) provided in each of the recording heads 2 by the MPU 30. It is controlled according to the temperature of 2.

Furthermore, the concentration signal from the concentration reading means 53 is also
The signal is input to the MPLJ30.

Therefore, according to the present invention, from the recording head 2 to the recording material 7
In an inkjet recording apparatus that performs recording by ejecting ink, a temperature detection means 51 that detects the temperature of the recording head 2, a heating means 52 that heats the recording head 2,
An inkjet recording apparatus is provided, which includes a droplet amount control means that controls the amount of ejected ink droplets by controlling the temperature of the recording head 2.

In this case, control is performed so that the amount of ink droplets ejected from each recording head 2 is equal, thereby eliminating variations in image density.

Example 1: Figure 5 shows a film boiling type recording head having 128 ejection ports arranged at a density of 400 dpi and a dye density of 2 wt.
5 is a graph showing the distribution of the number of print heads with respect to the edge density (OD value) when 50 print heads are used to perform low density printing at 100% duty using 50% water-soluble ink.

According to FIG. 5, 47 of the 50 recording heads are distributed in the range of 1.1 to 1.4 in terms of OD value, while the remaining three are distributed outside this range.

One of the causes of such variations is due to variations in the resistance value of the electrothermal converter 20 shown in FIG. 3.

Therefore, in this embodiment, the temperature of the print head 2 is used as a method for correcting the density variation of the print head 2.

That is, the fact that the ink viscosity decreases and the amount of ejected droplets increases as the temperature of the recording head 2 increases is utilized.

FIG. 6 is a graph showing the relationship between the variation in OD value (print density) of each print head and the temperature required for each print head at that time.

For example, when recording is performed at a head temperature of 30°C, the OD value for each recording head is as shown in Figure 6. To the record of, respectively, 1.1, ].

2.1.3.1.4, first, head N
o, 3-1 is 60°C based on the characteristics of head temperature and OD value.
Then, 0D=1.4.

Next, head No. 3-2 is 0 at 50'C.
D = 1.4, and head No. 3-3 has 0D = 1.4 at 40°C. By controlling the temperature to such a temperature, the OD value for each recording heel L' is kept at a constant value of 1.4. can be kept.

FIG. 7 is a flowchart showing the sequence of control operations for the amount of ink ejected droplets (recording density) in this embodiment.

In practice, as shown in FIG. 7, the control for keeping the OD value constant for each recording head as described above is performed by turning on the power in step 5101 and then adjusting the temperature in steps 5102 and 5103. Using the detection means 51, heater 52, etc., the temperature of the recording head is set to 30°.
It operates so that C.

Subsequently, in step 5104, the recording head performs edge recording, and in step 5105, the density reading means 53 reads the ○D (i) of each edge recording, and in step 5106, as shown in FIG. The appropriate temperature of the print head is determined based on the characteristics of the throat temperature and the OD value, and temperature control is performed to maintain the temperature of the print head at the appropriate temperature.

It should be noted that the above-mentioned determination of the appropriate temperature does not necessarily have to be done in the recording device, but can be determined for each recording head at an appropriate time such as when the recording head is shipped, depending on the variations in the electrothermal transducers. The appropriate temperature may be determined.

As described above, variations in the amount of ink droplets ejected from print head to print head can be controlled by changing the temperature of each print head so that printing with a constant OD value is obtained.

Example ■: In this example, variations in the amount of ink ejected from each recording head are corrected by controlling the head temperature as described above, and at the same time, slight variations are corrected by changing the drive pulse width of the electrothermal transducer. By making the layers uniform, - control with high layer accuracy can be achieved.

That is, as explained with reference to FIG. 6, even when correction is performed to make the print density of each print head equal to 0D=1.4, OD! -io, there is a possibility that variations of about 1 or less may remain.

Therefore, after controlling the temperature of the print head, the drive pulse width is decreased for print heads with a high OD value, and the drive pulse width is increased for print heads with a low OD value. If this is done, the OD value for each recording head can be corrected with even higher accuracy.

In fact, in an inkjet recording device that uses a film boiling recording head with a density of 400 dpi and 128 ejection ports and a water-soluble ink with a dye concentration of 2 wt%, the normal driving pulse width was set to 15 μsec. In this case, if this driving pulse width is decreased by 14 μs, the concentration will decrease to OD#.
The concentration decreased by about 0.05, and when increasing to 16 μsec, the concentration increased by about OD',004.

Embodiment ■: In this embodiment, variations in the amount of ink ejected from each recording head are corrected to be uniform by controlling the head temperature as described above, and minute variations are corrected by driving the electrothermal transducer. By changing the voltage (pulse voltage) and making it uniform, highly precise control of the layers can be achieved.

That is, as explained with reference to FIG. 6, even when the recording density of the recording head is corrected to be equal to 0D=1.4, OD! =i0.1 or less may remain.

Therefore, after controlling the temperature of the print head, the drive voltage is lowered for the print head with a higher OD value, and the oD value is lowered.
If control is performed to increase the drive voltage for a print head with a lower value, the OD value of each print head can be corrected with even higher precision.

In fact, when the normal driving voltage was set to 40V in an inkjet recording bag (■) using a film boiling type recording head in which 128 ejection ports were formed at a density of 400dpi and a water-soluble ink with a dye concentration of 2wt%. Then, when this driving voltage is lowered to 39V, the concentration becomes OD! = i becomes lower by about 0.06, and when raised to 41V, the concentration becomes OD', 0.
The price has increased by about 04.

After controlling the temperature of the recording head, by changing both the pulse width of the head drive pulse and the drive voltage, control is performed to correct and equalize the above-mentioned variation in the amount of ejected droplets. You can also do that.

As explained above, the temperature detection means 51 of the recording head 2
A heating means (heater) 52 for the recording head 2 is provided, and a droplet amount control means for controlling the amount of ejected ink droplets by changing the temperature of the recording head 2 using these elements is provided. An inkjet recording device was obtained that can effectively suppress variations in recording density and can record stable high-quality images.

In particular, an inkjet recording apparatus has been developed that is capable of properly maintaining color balance in full-color recording and is suitable for obtaining high-quality color images.

Furthermore, by correcting the amount of ejected droplets based on variations in electrothermal transducers and the like for each individual print head, it was also possible to improve the yield of print heads.

In the above embodiments, the present invention was explained by taking as an example a case where the present invention is applied to a serial scan type inkjet recording apparatus in which the recording head 2 is mounted on the carriage 3. It can be similarly applied to inkjet recording devices of other recording methods, such as a line-type inkjet recording device that uses a line-type recording head that covers the recording area in the paper width direction of the material, and can achieve the same effects. It is.

Further, in the above embodiment, four recording heads 2A to 2D are used.
Although the description has mainly been given to the case of a color inkjet recording apparatus using a color inkjet recording apparatus, the present invention is applicable to monochrome recording using one recording head, or gradation recording using multiple recording heads with the same color but different densities. The present invention can be similarly applied to inkjet recording apparatuses, etc., regardless of the number of recording heads, and can achieve similar effects.

The present invention brings about particularly excellent effects in an inkjet recording apparatus using an inkjet recording head of the bubble jet type proposed by Canon Co., Ltd. among inkjet recording types.

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, it is necessary to place the liquid (ink) on the sheet or liquid path where it is held. By applying at least one drive signal that corresponds to recorded information and causes a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer being recorded, the electrothermal transducer is caused to generate thermal energy, and the recording is performed. This method is effective because film boiling is performed on the heat-active surface of the head, resulting in the formation of bubbles in the liquid (ink) in one-to-one correspondence with this drive signal.

Due to the growth and contraction of these bubbles, liquid (
ink) to form at least one droplet.

If this drive signal is in the form of a pulse, bubble growth and contraction will occur immediately and appropriately, so liquids with particularly excellent responsiveness (
Ink) can be ejected, which is more preferable. As this pulse-shaped drive signal, those described in US Pat. No. 4,463,359 and US Pat. No. 4,345,262 are passed.

Furthermore, if the conditions described in US Pat. No. 4,313,11 regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be achieved.

The configuration of the recording head includes, in addition to the combined 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. US Pat. No. 4,558,333 and US Pat. No. 4,459,600 disclose a configuration in which the
The present invention also includes a configuration using the specification of the above specification.

In addition, for multiple electrothermal converters, a common slip y
) as a discharge part of an electrothermal converter, and JP-A No. 1982 discloses a configuration in which an opening for absorbing pressure waves of thermal energy corresponds to a discharge part. The present invention is also effective as a configuration based on Publication No. 138461.

Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be increased by combining multiple recording heads as disclosed in the above-mentioned specification. Either a configuration that satisfies the above requirements or a configuration as a single recording head formed integrally may be used, but the present invention can more effectively exhibit the above-mentioned effects.

In addition, a replaceable 1,000-knob type recording head that is attached to the device body enables electrical connection to the device body and ink supply from the device body, or a print head that is integrated into the recording head itself. The present invention is also effective when a cartridge type recording head is used.

Further, it is preferable to add recovery means, preliminary auxiliary means, etc. for the recording head, which are provided as a configuration of the recording apparatus of the present invention, because the effects of the present invention can be further stabilized.

Specifically, these include capping means, cleaning means, pressure or suction means, preheating means for the recording head 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.

Furthermore, the recording mode of the recording device is not limited to a recording mode in which only the mainstream color such as black is used; the recording head may be configured integrally or in combination with a plurality of recording heads; The present invention is also extremely effective for devices equipped with at least one full color image.

In the embodiments of the present invention described above, the ink is explained as a liquid, but it is an ink that solidifies at room temperature or lower, and is softened or liquid at room temperature, or in the above-mentioned inkjet, the ink itself is heated at 30°C or higher. Since the temperature is generally controlled within a range of 70° C. or less so that the viscosity of the ink is within the stable ejection range, it is sufficient that the ink is in a liquid state when the recording signal is applied.

In addition, it is possible to proactively prevent temperature rise caused by thermal energy by using it as energy to transform the ink from a solid state to a liquid state, or to prevent ink from evaporating by preventing ink from solidifying when left unused. In any case, ink may be liquefied by applying thermal energy in response to a recording signal and ejected as liquid ink, or it may already begin to solidify when it reaches the recording material. It is also applicable to the present invention to use ink that is liquefied only by thermal energy.

In such a case, as in Japanese Patent Application Laid-open No. 54-56847, the ink is held as a liquid or solid in the recesses or through holes of the porous sheet and is placed facing the electrothermal transducer. It may be in any form.

In the present invention, the most effective method for the above-mentioned ink is the one that implements the above-mentioned film boiling method.

(Effects of the Invention) As is clear from the above description, according to the present invention, in an inkjet recording apparatus that performs recording by ejecting ink from a recording head onto a recording material, temperature detection means for detecting the temperature of the recording head is provided. Since the configuration includes a heating means for heating the print head and a droplet amount control means for controlling the amount of ejected ink droplets by controlling the temperature of the print head, the droplet amount of ink ejected from the print head is reduced. Provided is an inkjet recording apparatus that can effectively control the amount of ink and suppress variations in image density of the recording head.

Further, according to the present invention, in the above configuration, the droplet amount control means controls the plurality of recording heads so that the amount of ink droplets ejected from each recording head is equal. Provided is an inkjet recording apparatus that can properly maintain color balance during color recording and can form high-quality color images.

Furthermore, according to the present invention, in the above configuration, in addition to the temperature of the print head, the ejection drive pulse width or the ejection drive voltage is controlled so that the amount of ink droplets ejected from each print head is equal. , - An inkjet recording apparatus capable of correcting variations in the amount of ejected ink droplets with high precision is provided. La, 3(l MPU (control unit), 51.5

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing the main structure of an inkjet recording apparatus to which the present invention is applied, FIG. 2 is a partial perspective view showing the structure of the head unit in FIG. 1, and FIG. 3 is a partial perspective view showing the structure of the head unit in FIG. Fig. 4 is a block diagram showing the control system of the printing apparatus shown in Fig. 1, and Fig. 5 shows an example of the distribution of variations in OD values for 50 printing heads. FIG. 6 is a graph showing variations in the OD value of the print heads and the temperature required for each print head, and FIG. FIG. Below, symbols representing main components in the drawings are listed. 1-1111 Head Unisoto, 2.2A~2D---
---Recording head, 3-1, carriage, 7--Recording material, 13A to 13D--Ink tank, 17--
--Discharge port, 19--One liquid path, 20-----m-Electrothermal converter, 22■A to 51D-Temperature detection means, 52.5
2A-52D - Heater, 53 fA degree reading means. 2nd figure 4th book stream 5th OP

Claims (6)

[Claims] (1) In an inkjet recording device that performs recording by discharging ink from a recording head onto a recording material, there is a temperature detection means for detecting the temperature of the recording head, a heating means for heating the recording head, and a temperature control unit for controlling the temperature of the recording head. An inkjet recording apparatus comprising: a droplet amount control means for controlling the amount of droplets of ejected ink by controlling the amount of droplets of ejected ink. (2) The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus has a plurality of recording heads, and the droplet amount control means controls the amount of ink droplets ejected from each recording head to be equal. . (3) The droplet amount control means controls the ejection drive pulse width or the ejection drive voltage in addition to the temperature of the printhead so that the amount of ink droplets ejected from each printhead is equal. The inkjet recording device according to claim 2. (4) It has a test pattern recording means for causing the recording head to record a test pattern, and a reading means for reading the test pattern of the recording head, and the droplet amount control means records the test pattern according to the reading signal of the reading means. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus controls the temperature of the head. (5) A claim characterized in that the recording head is an inkjet recording head that ejects ink using thermal energy and is equipped with an electrothermal converter for generating thermal energy. Item 1. The inkjet recording device according to item 1. (6) The inkjet recording apparatus according to claim 5, wherein the recording head discharges the ink from the discharge port by the growth of bubbles due to film boiling caused by the thermal energy applied by the electrothermal converter. .