Image recording device and control method

Abstract

To suppress a difference in ink discharge amounts between recording elements, while reducing a temperature difference between recording element rows to perform recording operation.SOLUTION: An image recording device includes a plurality of recording element selection patterns with different heating levels. In at least one recording element selection pattern, the central recording element group has a lower heating level than the end recording element group. In at least one recording element selection pattern, the central recording element group has a higher heating level than the end recording element group. These recording element selection patterns are combined to perform temperature control.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image recording apparatus and a control method. [Background technology]

[0002] Inkjet recording devices are known that apply drive pulses to recording elements to eject ink, thereby ejecting ink onto a recording medium to record an image. In such inkjet recording devices, if the temperature of the ink is low when ejecting the ink, a decrease in the ejection amount or ejection failure may occur. If such a phenomenon occurs, the quality of the recorded image will deteriorate. In response to this, it is known that if the temperature of the printhead before the start of printing is lower than a predetermined threshold temperature, a drive pulse is applied to the printing elements to drive the printing elements at a level at which ink is not ejected, thereby heating the printhead. This type of heating method is called a short pulse heating method.

[0003] On the other hand, when multiple printing elements in a printing element array are driven uniformly, the ends of the printing element array are less likely to become hotter than the center, and as a result, when the ends of the printing element array reach the target temperature, the temperature in the center may significantly exceed the target temperature (hereinafter, also referred to as the overshoot phenomenon).

[0004] Patent Document 1 describes a method of performing heating in two stages to suppress the occurrence of the overshoot phenomenon. Specifically, it describes that in the first heating step, multiple printing elements in the printing element array are uniformly driven, and in the second heating step, printing elements on the end side of the printing element array are driven. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-183821 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when temperature adjustment control by short pulse heating (hereinafter referred to as temperature adjustment control) is performed in the method disclosed in Patent Document 1, a temperature difference in ink occurs between the heated and non-heated printing elements. When ink is ejected in this state, a difference in the amount of ink scorched on the heater occurs due to the relative temperature difference. As a result, a difference in the ejection amount occurs at the ejection ports corresponding to the heated and non-heated printing elements, and there is a concern that image unevenness may occur.

[0007] The present invention has been made in view of the above problems, and has an object to execute a printing operation while reducing the temperature difference between printing element arrays and suppressing the difference in the amount of ink ejected from each printing element. [Means for solving the problem]

[0008] The present invention is characterized in that the recording head has a plurality of recording elements that generate thermal energy to be applied to ink, and a plurality of ejection ports that are arranged corresponding to the recording elements and eject ink, and is provided with an ejection port array in which the plurality of ejection ports are arranged, and a temperature adjustment control means that applies a voltage to the recording elements corresponding to the plurality of ejection ports such that ink is not ejected from the ejection ports, thereby heating the ink, the temperature adjustment control means controls the heating of the recording elements by a plurality of recording element selection patterns that select the recording elements to be heated, the plurality of recording element selection patterns including a first recording element selection pattern in which the heating degree of the recording element group in the center of the ejection port array is lower than that of the recording element group at the ends of the ejection port array, and a second recording element selection pattern in which the heating degree of the recording element group in the center of the ejection port array is higher than that of the recording element group at the ends of the ejection port array, and the temperature adjustment control means controls the temperature by combining the plurality of recording element selection patterns. Effect of the Invention

[0009] According to the present invention, it is possible to execute a printing operation while reducing the temperature difference between the printing element arrays and suppressing the difference in the ink ejection amount between the printing elements. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating a recording apparatus according to an embodiment of the present invention. [Diagram 2] 2A and 2B are a schematic external view of a recording head and a plan view showing a discharge element substrate. [Diagram 3] FIG. 2 is a cross-sectional view of a discharge element substrate. [Figure 4] FIG. 2 is a diagram illustrating the configuration of a control circuit of the recording apparatus. [Diagram 5] FIG. 2 is a diagram showing a schematic diagram of a driving pulse applied when performing short pulse heating. [Figure 6] FIG. 13 is a schematic diagram for explaining divided driving when performing short pulse heating. [Figure 7] 13 is a diagram showing a transition of the minimum temperature of the ejection port array when temperature adjustment control is performed. FIG. [Figure 8] 11 is a table showing an example of a printing element selection pattern during second heating control in the first embodiment. [Figure 9] 11 is a table showing a printing element selection pattern driving order during second heating control in the first embodiment. [Figure 10] 13 is a table showing a printing element selection pattern driving order during second heating control in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <First embodiment> Hereinafter, examples of each embodiment of the present invention will be described with reference to the drawings. However, the following description does not limit the scope of the present invention. The recording device may be, for example, a single-function printer having only a recording function, or may be, for example, a multi-function printer having multiple functions such as a recording function, a FAX function, and a scanner function. In addition, the recording device may be, for example, a manufacturing device for manufacturing color filters, electronic devices, optical devices, microstructures, etc., using a predetermined recording method.

[0012] In the following explanation, "recording" refers not only to the formation of meaningful information such as characters and figures, but also to the formation of images, patterns, structures, etc. on a recording medium, or the processing of the medium, regardless of whether the information is visible to humans or not.

[0013] In addition, the term "recording medium" refers not only to paper used in general recording devices, but also to materials capable of receiving ink, such as cloth, plastic film, metal plate, glass, ceramics, resin, wood, and leather. In particular, the term "non-permeable recording medium / low-permeable recording medium" refers to a non-absorbent recording medium / low-absorbent recording medium. Examples of non-permeable recording media include those that are not made as recording media for aqueous inkjet ink, such as glass, plastic, film, and Yupo. Examples of non-permeable recording media include those that are not surface-treated for inkjet printing (i.e., do not form an ink-absorbing layer), such as those in which plastic is coated on a substrate such as a plastic film or paper. Examples of plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene. Examples of low-permeable recording media include recording media such as printing paper used in offset printing, such as art paper and coated paper.

[0014] This article explains printing paper (low-absorption recording medium) that has very low permeability to water-based ink compared to inkjet paper. Printing paper is the official (real) printing paper used in actual production printing in offset printing to make products (merchandise). Paper is made from pulp, and uncoated paper is used as is, while coated paper is used with a smooth coating of white pigments, etc. In inkjet recording, this coated paper is more susceptible to image problems due to ink overflow and drying problems. The coating layer is a mixture of a sizing agent (synthetic resin, etc.) that limits the liquid absorption of the gaps between the pulp and prevents bleeding of water-based pens, a filler (kaolin, etc.) that improves opacity, whiteness, smoothness, etc., and a paper strength enhancer (starch, etc.), which is applied at a rate of several to 40 g / m2. The average radius of the capillary pores of coated paper is normally distributed around 0.06 μm, and moisture is permeated by a large number of capillaries (capillary phenomenon). However, because its pore volume is much smaller than that of inkjet paper, the permeability of water-based inks is low, and the ink overflows onto the paper surface, causing noticeable image defects and drying problems.

[0015] This article explains PVC sheets, which have no permeability to water-based inks compared to inkjet paper. PVC sheets are soft sheets made from polyvinyl chloride resin as the main ingredient and plasticizers added, and are excellent for printability in gravure printing and screen printing, and for embossing (creating a embossed pattern). This combination allows for a wide variety of expressions, and is used in many products such as tarpaulins, canvas, and wallpaper. Because PVC resin is the main ingredient, it has no permeability to water-based inks, and the ink overflows on the paper surface, causing noticeable image and drying problems.

[0016] Other examples include glass, plastic, film, Yupo, and other materials that are not made as recording media for aqueous inkjet inks. Also included are materials that have not been surface-treated for inkjet printing (i.e., do not have an ink-absorbing layer), such as plastic films, paper, and other substrates coated with plastic. Examples of plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, and the like.

[0017] Furthermore, the term "ink" should be interpreted broadly in the same manner as the definition of "recording" above. Therefore, it refers to a liquid that can be applied onto a recording medium to form an image, design, pattern, etc., or to process the recording medium, or to process the ink (for example, to solidify or insolubilize the coloring material in the ink applied to the recording medium).

[0018] In order to briefly explain the features of the embodiments, first, an outline of the device configuration, head configuration, etc. common to the embodiments will be explained in detail. Next, the process flow that is a feature of the present invention will be explained according to multiple embodiments.

[0019] (Summary of the entire device) Fig. 1(a) is an external view of an inkjet recording apparatus (hereinafter also referred to as an image recording apparatus) according to this embodiment. The inkjet recording apparatus of this embodiment is a so-called serial scan type image recording apparatus, and scans a carriage on which a recording head is mounted in a Y direction intersecting with the X direction in which a recording medium P is transported. During this scan, ink droplets are applied by driving recording elements provided on a recording head 9, thereby recording an image on the recording medium P. In the figure, the X direction is the direction in which the recording medium P is transported, the Y direction is the direction in which the carriage scans, and the Z direction is the direction intersecting with the X direction and the Y direction.

[0020] The configuration of the image recording device and the operation during recording will be described with reference to FIG. 1. First, from a state in which the recording medium P is held on the spool 6, a paper feed motor (not shown) drives a paper feed roller via a gear, and the recording medium P is fed and transported to a position where the recording head 9 can perform recording. Meanwhile, at a predetermined transport position, a carriage motor (not shown) scans the carriage unit 2 carrying the recording head 9 along a guide shaft 29 extending in the Y direction in the figure. The recording head 9 is detachably mounted on the carriage unit 2. Then, while one scan is performed, the recording elements provided on the recording head 9 are driven at a timing based on a position signal obtained by the encoder 7. By driving the recording elements, ink droplets are ejected from the ejection openings and land on the recording medium P. In one scan of the recording head 9, an image can be recorded in an area corresponding to the arrangement range of the recording elements provided on the recording head 9. The recording width corresponding to the arrangement range of the recording elements is called a bandwidth. In this embodiment, the scanning speed of the carriage unit 2 is 40 inches per second, and the recording resolution is 1200 dots per inch, ie, 1200 dpi (dots / inch).

[0021] After one scan, the recording medium P is transported a predetermined amount in the X direction. Then, in the next scan, an image is recorded in an area of ​​the next band width. The image recording device may be configured to transport the band width, i.e., the range of the recording element arrangement, between scans, or may be configured to transport the recording medium P after multiple scans without transporting it for each scan. Also, in n scans, ink is applied based on thinned data, and transport is repeated by 1 / n band width between scans, thereby completing an image by using different recording elements to record in the same area (so-called multi-pass recording).

[0022] 1(b), the print head 9 of this embodiment has a plurality of print elements for ejecting ink arranged in the X direction in the figure. A flexible wiring board 1 for supplying signal pulses for driving the print elements and head temperature control signals is attached to the print head 9, and the other end of the flexible wiring board 1 is connected to a control circuit for controlling the image recording device.

[0023] A carriage belt can be used to transmit the driving force from the carriage motor to the carriage unit 2. Instead of a carriage belt, it is also possible to use other driving methods, such as one that includes a lead screw that is rotationally driven by the carriage motor and extends in the main scanning direction (Y direction), and an engagement portion that is provided on the carriage unit 2 and engages with a groove in the lead screw.

[0024] The fed and transported recording medium P is sandwiched between a feed roller and a pinch roller and guided to the recording position on the platen 4, i.e., the main scanning area of ​​the recording head 9. In the resting state, the face of the recording head 9 is capped, so the cap is opened prior to recording to make the recording head 9 and carriage unit 2 ready for scanning. Then, when one scan's worth of recording data is accumulated in the buffer, the carriage motor 3 is caused to scan the carriage unit 2, and an image is recorded on the recording medium P as described above.

[0025] In this figure, the environmental temperature and humidity sensor 8 is indicated by a dashed line. In general, the environmental temperature and humidity sensor 8 is placed away from components that are sources of vibration or heat, such as motors and heaters, in order to eliminate errors and measurement noise. It is provided in a position that is difficult to see, such as the back side of the device, and is shown in a see-through form in this specification for the sake of explanation.

[0026] FIG. 1(b) is a schematic diagram showing the operation of the recording medium P and the recording head in a serial scan type recording device, and is a top view of the recording head 9 and the recording medium P. The operation of the serial recording method will be described using this diagram. Driven by the carriage motor 3, the recording head 9 mounted on the carriage unit 2 scans back and forth in the width direction (Y direction) perpendicular to the conveying direction (X direction) of the recording medium P. As described above, in the serial recording type image recording device, multi-pass recording can be performed by relative scanning of the recording head 9 and the recording medium P, in which different recording elements eject ink droplets onto the same area. This multi-pass recording can suppress uneven density caused by variations in the recording characteristics of each recording element.

[0027] (Recording head configuration) Fig. 2 is a schematic diagram for explaining the configuration of the recording head 9. Fig. 2(a) is a schematic perspective view shown from the direction in which ink is ejected. Fig. 2(b) is an enlarged view of the recording element substrate on the left side of Fig. 2(a), and Fig. 2(c) is a schematic perspective view showing the connection between the device and the head on the back side of Fig. 2(a).

[0028] In FIG. 2(a), two recording element substrates 10 are arranged side by side in the recording head 9. On one of the recording element substrates, a plurality of recording element arrays 11-14 capable of ejecting black (Bk), gray (Gy), light gray (Lgy), and light cyan (Lc) inks are arranged. On the other recording element substrate, a plurality of recording element arrays 15-18 capable of ejecting cyan (C), light magenta (Lm), magenta (M), and yellow (Y) inks are arranged. Ink is supplied from a supply port 25 to a common ink liquid chamber 26 inside the recording head 9, and is further supplied to each recording element via an ink flow path inside the recording head 9.

[0029] FIG. 2B is a plan view showing a detailed configuration of the recording element substrate 10. Of the two recording element substrates arranged side by side on the recording head 9, this is a recording element substrate on which the recording element arrays 11 to 14 are arranged. In this embodiment, two recording element arrays are provided for each ink color. In each recording element array, 768 recording elements are provided at a pitch of 600 dpi in the X direction, and further, a total of 1536 recording elements for each color are arranged with a half pitch, that is, a shift of 1200 dpi, from the opposing recording element array. Each recording element has an ejection port, and ink droplets are ejected from the ejection port by driving the recording element. In addition, temperature sensors S6, S7, S8, and S9, which are diode sensors, are arranged at the end of the recording element substrate 10 in the X direction, and can detect the temperature of the recording element substrate 10. The temperature sensors S6 to S9 are located at a position about 0.2 mm away from the outermost ejection port position of the recording element array in the sub-scanning direction, and are located at the middle position of the two recording element arrays in the Y direction. Temperature sensors S1, S2, S3, S4, and S5 consisting of diodes for detecting the temperature of the central portion of the printing element array are formed in the central portion of the printing element array in the X direction, and are also disposed in the middle position between the two printing element arrays.

[0030] Sub-heaters 19 and 20 for keeping the print head 9 warm are formed to surround the print element substrate 10, and are located 1.2 mm outside the outermost print element array in the Y direction and 0.2 mm outside the temperature sensors S6, S7, S8, and S9 in the X direction.

[0031] The connection between the recording head 9 and the main body will be described with reference to FIG. 2(c). The recording head and the main body are electrically connected through the contact pads 21 and the flexible substrate wiring 1 in FIG. 1. Electrical signals for controlling the ejection and heat retention of ink droplets, as well as power consumed by the recording head, are supplied to the recording head through the contact pads. When connecting, a pin-like receiving mechanism may be provided on the main body side as a fixing mechanism, and the recording head may be pressed against the main body to fix it, thereby providing a stable connection. The power source for supplying power used in the ejection operation and the power source for supplying power used in heat retention may be provided with individual pin wiring, or may be provided with a common wiring. If the voltage value used for ejection and the voltage value used for heat retention are common, the number of terminals can be reduced by sharing the pin wiring. Even if the voltages are different, they can be shared by providing a constant voltage output electronic circuit on the recording head side. The wiring configuration of the electrical connection is not limited to the above.

[0032] FIG. 3 is a cross-sectional view taken along line AA' in FIG. 2(b). In this figure, 27 is a support substrate, 22 is a recording element, and 23 is an ejection port. Ink flow paths 24 as flow paths are formed between the support substrate 27 and an orifice plate 28, and partitions (not shown) are provided between the multiple flow paths 24. The recording element 22 in this embodiment is an electrothermal conversion element that converts electrical energy into thermal energy to generate heat. The recording element 22 is provided on the support substrate 27 so as to face the ink ejection port 23, and a protective film or the like is formed on the surface of the recording element 22. Ink is supplied to each flow path 24 from below in FIG. 3 through a common liquid chamber 26 that communicates with each flow path 24.

[0033] (Control system configuration example) 4 is a diagram showing an example of a control circuit of an image recording apparatus. A programmable peripheral interface (hereinafter referred to as PPI) 101 receives a command signal or a recording information signal including recording data sent from a host computer 100, and transfers it to an MPU 102. At the same time, it sends status information of the image recording apparatus to the host computer 100 as necessary. It also inputs and outputs data to and from a console 106 having a setting input unit where the user sets various settings for the image recording apparatus and a display unit that displays messages to the user. It also receives input of signals from a sensor group 107 including a home position sensor that detects that the carriage unit 2 or the recording head 9 is at the home position, a capping sensor, etc.

[0034] The MPU (microprocessing unit) 102 controls each part in the image recording device according to a control program stored in a control ROM 105. The RAM 103 stores received signals or is used as a work area for the MPU 102, and also temporarily stores various data. The print buffer 121 is a memory area that stores recording data expanded in the RAM 103, etc., and has a capacity for recording multiple lines. In addition to the above control program, the control ROM 105 can store fixed data corresponding to data used in the control process described later (for example, data for determining the combination of temperature sensors related to the main parts of this embodiment). Each of these parts is controlled by the MPU 102 via an address bus 117 and a data bus 118.

[0035] Motor drivers 114, 115 and 116 are motor drivers for driving the capping motor 113, the carriage motor 3 and the paper feed motor 5 under the control of the MPU 102, respectively.

[0036] The sheet sensor 109 detects the presence or absence of a recording medium, i.e., whether the recording medium has been supplied to a position where recording can be performed by the recording head 9. The driver 111 is a driver for driving the recording elements of the recording head 9 in response to a recording information signal. As described above, the environmental temperature and humidity sensor 8 detects the environmental temperature and humidity in the installation environment of the recording apparatus main body. There are no limitations on where the environmental temperature and humidity sensor 8 is placed, so long as it is configured to detect the ambient temperature of the apparatus.

[0037] The power supply unit 120 supplies power to each of the above-mentioned components, and includes an AC adapter and a battery as a drive power supply device. The power supply unit 120 in this embodiment serves both to supply power for ejecting ink droplets from the recording elements of the recording head 9 and to supply power to a sub-heater for keeping the temperature constant.

[0038] In a recording system consisting of an image recording device and a host computer 100, when the host computer 100 transmits recording data via a parallel port, an infrared port, or a network, a required command is added to the beginning of the data. The command includes, for example, the type of recording medium on which recording is performed, the medium size, the recording quality, and whether or not to automatically identify objects. The types of recording medium include, for example, plain paper, OHP sheet, glossy paper, and special recording medium types such as transfer film, thick paper, and banner paper. The medium sizes include A0 size, A1 size, A2 size, B0 size, B1 size, and B2 size. The recording quality includes draft, high quality, medium quality, emphasis of a specific color, monochrome / color type, and the like. In addition, when a configuration is adopted in which a treatment liquid is applied to improve the fixability of ink on the recording medium, information specifying whether or not to apply the treatment liquid is transmitted as a command.

[0039] In accordance with these commands, the image recording device reads data required for recording from ROM 105 and performs recording based on that data. Data required for recording includes, for example, the number of recording passes (number of scans) when performing the above-mentioned multi-pass recording, data for determining the amount of ink applied per unit area of ​​the recording medium, and the recording direction. Other data include the type of mask for thinning data applied when performing multi-pass recording, and drive conditions based on the temperature sensor detection value in the recording head 9 (for example, the shape and application time of the drive pulse applied to the heat generating portion). In addition, data such as the dot size, recording medium transport conditions, number of colors to be used, and even carriage speed may be included.

[0040] The embodiment will be described using an image recording apparatus having the above configuration as an example, but the configuration described here is merely one example of an apparatus configuration for realizing the present embodiment. It goes without saying that the present embodiment can be applied even if, for example, the number of recording inks or the number of control units are different.

[0041] (Short pulse heating method) In this embodiment, the ink is heated (short pulse heating) by driving the recording elements 22 to such an extent that ink is not ejected between reciprocating scans of the print head or immediately before the first scan to the print medium. Furthermore, in this embodiment, the 768 recording elements 22 in the printing element array are divided into multiple printing element groups along the Y direction, and short pulse heating is performed by divided driving that determines whether or not to apply a drive pulse to each divided printing element group.

[0042] FIG. 5 is a diagram showing a schematic diagram of a driving pulse applied when short pulse heating is performed in this embodiment.

[0043] In this embodiment, the driving voltage is 24 V, and rectangular pulses with a pulse width of 0.1 to 0.2 μsec are applied to the heating elements at a frequency of 10 kHz, where a frequency of 10 kHz means that the time interval between rectangular pulses is approximately 100 μsec.

[0044] 6 is a schematic diagram for explaining the division driving in this embodiment. In this embodiment, the 768 recording elements 22 are divided into a total of 48 recording element groups (B1 to B48), with each group consisting of 16 consecutive recording elements in the X direction. A recording element ON / OFF pattern (hereinafter also referred to as a recording element selection pattern) for performing short pulse heating is set for each of these recording element groups B1 to B48.

[0045] It should be noted that the number of divisions here is not limited to this, and the number of recording elements included in each of the divided recording element groups may differ.

[0046] In this embodiment, as described above, short pulse heating is performed between reciprocating scans or immediately before the start of printing. When performed between reciprocating scans, short pulse heating is started in the deceleration region of the carriage 1 from when printing on the printing medium is completed until the carriage is reversed. Furthermore, if the target temperature (threshold value) is not reached by the time the carriage is reversed, the short pulse heating waits at the carriage reverse section and continues until the target temperature is reached.

[0047] In this embodiment, the short pulse heating control is performed in two stages. Specifically, the first heating control is performed first to uniformly drive multiple printing elements in the printing element array, and then the second heating control is performed to combine and drive multiple printing element selection patterns.

[0048] FIG. 7 shows the transition of the minimum temperature of the ejection port array when the temperature adjustment control is performed in this embodiment.

[0049] First, in the first heating control, the drive pulse shown in FIG. 5 is applied to all of the printing element groups B1 to B48 in the printing element array until the temperature output value of the diodes arranged in the ejection port array reaches the target temperature T1 in the figure. This makes it possible to quickly bring the head temperature close to the target temperature. If the ejection ports to be used in the next recording are limited, the drive pulse may be applied only to the printing element group including the printing elements of the ejection ports to be used. Then, the head temperature is increased to the final target temperature T2 by the second heating control.

[0050] (Drive method for second heating control) FIG. 8 shows an example of the print element selection pattern (driving rate 50%) during the second heating control. Three types of patterns are shown here. In the second heating control, three print element selection patterns, including print element groups that are not driven, are switched in units of the driving frequency of the short pulse heating to heat the ejection port array while uniformizing the temperature. In the first heating control in the previous stage, all ejection ports are driven, but the ejection ports closer to the ends have a relatively lower temperature than the ejection ports closer to the center because heat is diffused to the outside. To compensate for this, in the conventional technology, temperature control has been performed using only a pattern such as pattern 1 in which the driving rate of the other ends is low compared to the ends B1 or B48. However, as mentioned above, with only pattern 1, the temperature of the ejection heater-ink interface of the print element groups other than the ends that remain in a non-heated state is relatively low, and conversely, the temperature of the ejection heater-ink interface of the print element groups at the ends that remain in a heated state is relatively high. As a result, a difference occurs in the amount of ink "burnt" on the heater. "Kogi" refers to a phenomenon in which coloring materials and additives contained in a liquid are decomposed at the molecular level by being heated at high temperatures on the heater, changing into substances that are difficult to dissolve, and are physically adsorbed on the heat acting part. If the amount of kogi differs greatly between heaters, there is a concern that image defects may occur because differences in heat conduction from the heater to the liquid occur and ejection amount differences are likely to occur. Therefore, in this embodiment, contrary to pattern 1, by switching to pattern 2 in which the end recording element group B1 or B48 is not driven and heating, the relative temperature difference between ejection ports is reduced, and the risk of image defects is suppressed. As a result, there are no recording elements that are not heated during heating.

[0051] Pattern 2, which has a low drive rate for the end printing element group, is used less frequently than pattern 1. For example, patterns 1 and 2 are used at a ratio of 8:2. As a result, the average heating time of the end printing elements is longer than that of the central printing elements. By shortening the time when the end is not driven, it is possible to both uniformize the temperature distribution of the entire ejection port array and reduce the relative temperature difference between ejection ports. Although these patterns may be driven in sequence, it is preferable to disperse them as much as possible. Figure 9 shows an example of the pattern drive order. Pattern 2 is used for drive order 5 and drive order 10, and pattern 1 is used for the rest. After driving up to drive order 10, drive is repeated from drive order 1. The longer the time that the heated and unheated states continue for each ejection port, the more likely it is that differences in the amount of ink scorching will occur as described above, so it is better to drive pattern 1 in segments of 4 times rather than driving it 8 times in succession.

[0052] Furthermore, in this embodiment, the drive rates of the printing element groups are the same between the patterns, but different patterns may be selected for each.

[0053] In this embodiment, the end recording element group is B1 or B48 (16 recording elements from the end), but this is not limited to this, and the part that is likely to become low in temperature may be the end recording element group. The end recording elements may be fewer than 16 recording elements, or may be more than 16.

[0054] Also, the overall drive rate in the second heating control is not limited to this, and may be varied depending on the environmental temperature, etc. When the environmental temperature is high, the heating efficiency is high, so a short pulse heating pattern in which the drive rate of the end recording element group is low may be selected.

[0055] According to this embodiment, it is possible to reduce the temperature difference between individual ejection ports while maintaining the temperature uniformity across the entire ejection port array, and to suppress image unevenness caused by variations in the amount of heater burn.

[0056] <Second embodiment> In the second embodiment, similar to the first embodiment, the second heating control is performed by switching between a plurality of patterns including a pattern in which the degree of heating at the end is low. However, in the second embodiment, the patterns are combined so that the overall driving time of the printing element group closer to the end is longer.

[0057] FIG. 10 shows an example of a pattern drive order in the second embodiment. In the first embodiment, for example, the drive time of print element group B4 was 20% of the total, while the drive time of B5 was 80% of the total, meaning that the print element groups closer to the ends had shorter drive times. Considering that heat is more likely to escape and less likely to heat up closer to the ends, it is preferable to relatively lengthen the drive time closer to the ends. In FIG. 10, for any two print element groups, the one closer to the ends has a longer drive time. For example, the drive time of print element group B4 is 69% of the total, and the drive time of print element group B5 is 63% of the total.

[0058] Furthermore, in this embodiment, the drive rates of the printing element groups are the same between the patterns, but different patterns may be selected for each.

[0059] Moreover, the overall drive rate in the second heating control is not limited to this, and may be varied depending on the environmental temperature, etc. When the environmental temperature is high, the heating efficiency is high, so a short pulse heating pattern with a low drive rate may be selected.

[0060] According to this embodiment, it is possible to reduce the temperature difference between individual ejection ports while ensuring a higher temperature uniformity across the entire ejection port array than in the first embodiment. [Explanation of symbols]

[0061] 2 Carriage unit 3 Carriage motor 8. Environmental temperature and humidity sensor 9. Recording Head 10 Recording element board 11~18 Recording element array 19, 20 Sub heater 22 Recording element 23 Spit out

Claims

1. a print head including a plurality of print elements that generate thermal energy to be applied to ink, and a plurality of ejection ports that are provided corresponding to the print elements and eject ink, the print head being provided with an ejection port array in which the plurality of ejection ports are arranged; a temperature adjustment control means for applying a voltage to recording elements corresponding to the plurality of ejection ports so as not to eject ink from the ejection ports, thereby heating the ink; the temperature adjustment control means controls heating of the recording elements according to a plurality of recording element selection patterns for selecting the recording elements to be heated; the plurality of printing element selection patterns include a first printing element selection pattern in which a heating degree of a printing element group in a central portion of the ejection port array is lower than that of a printing element group in an end portion of the ejection port array, and a second printing element selection pattern in which a heating degree of a printing element group in a central portion of the ejection port array is higher than that of a printing element group in an end portion of the ejection port array, The image recording apparatus according to claim 1, wherein the temperature control means controls the temperature by combining the plurality of recording element selection patterns.

2. 2. The image recording apparatus according to claim 1, wherein the temperature control means uses the first recording element selection pattern more frequently than the second recording element selection pattern.

3. 2. An image recording apparatus according to claim 1, wherein said temperature control means alternates heating and non-heating of all recording elements, and no recording element is non-heated throughout the entire period of ink heating.

4. 3. The image recording apparatus according to claim 2, wherein an average heating time of a first recording element is longer than an average heating time of a second recording element that is closer to the center of the ejection port array than the first recording element.

5. 2. The image recording apparatus according to claim 1, wherein said temperature control means heats all of the ejection ports until the temperature of the recording head reaches a predetermined temperature.

6. 2. The image recording apparatus according to claim 1, wherein the plurality of recording element selection patterns are switchable by a frequency at which a voltage is applied.

7. a carriage on which the recording head is mounted, The carriage scans in a scanning direction, 7. The image recording apparatus according to claim 1, wherein the ejection opening array has the plurality of ejection openings arranged in a direction intersecting the scanning direction.

8. A control method for controlling a print head having a plurality of printing elements that generate thermal energy to be applied to ink, a plurality of ejection ports that are provided corresponding to the printing elements and eject ink, and an ejection port array in which the plurality of ejection ports are arranged, comprising the steps of: a temperature control step of controlling application of voltage to recording elements corresponding to the plurality of ejection ports in order to heat the ink; heating of the recording elements is controlled by a plurality of recording element selection patterns for selecting the recording elements to be heated in the temperature adjustment step; the plurality of printing element selection patterns include a first printing element selection pattern in which a heating degree of a printing element group in a central portion of the ejection port array is lower than that of a printing element group in an end portion of the ejection port array, and a second printing element selection pattern in which a heating degree of a printing element group in a central portion of the ejection port array is higher than that of a printing element group in an end portion of the ejection port array, The image recording apparatus according to claim 1, wherein the temperature control step performs temperature control by combining the plurality of recording element selection patterns.

Images