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 Art

[0002] An inkjet recording apparatus that ejects ink onto a recording medium by applying a drive pulse to a recording element to eject the ink and records an image is known. In such an inkjet recording apparatus, when the temperature of the ink at the time of ejection is low, a decrease in ejection amount or non-ejection may occur. When such a phenomenon occurs, the image quality of the recorded image deteriorates. On the other hand, when the temperature of the recording head before the start of recording is lower than a predetermined threshold temperature, it is known to heat the recording head by applying a drive pulse to the recording element to drive the recording element such that the ink is not ejected. Such a heating method is called a short pulse heating method.

[0003] On the other hand, when a plurality of recording elements in a recording element array are uniformly driven, the temperature of the end portion of the recording element array is less likely to increase compared to the central portion. Therefore, when the temperature of the end portion of the recording element array reaches the target temperature, a phenomenon (hereinafter also referred to as an overshoot phenomenon) may occur in which the temperature of the central portion greatly exceeds the target temperature.

[0004] Patent Document 1 describes performing heating in two stages in order to suppress the occurrence of the overshoot phenomenon. Specifically, it is described that in the previous heating, a plurality of recording elements in the recording element array are uniformly driven, and in the subsequent heating, the recording elements on the end portion side of the recording element array are driven.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when temperature control is performed by short-pulse heating using the method disclosed in Patent Document 1 (hereinafter referred to as temperature control), a temperature difference in the ink occurs between the heated and unheated recording elements. If ejection is performed in this state, a difference in the amount of ink burnt on the heater occurs due to the relative temperature difference. As a result, a difference in ejection volume occurs at the ejection ports corresponding to the heated and unheated recording elements, raising concerns about image unevenness.

[0007] This invention has been made in view of the above problems, and aims to perform a recording operation while reducing the temperature difference between the recording element arrays and suppressing the difference in ink ejection amount between each recording element. [Means for solving the problem]

[0008] The present invention includes a recording head having a plurality of recording elements that generate thermal energy to the ink, a plurality of ejection ports provided corresponding to the recording elements for ejecting ink, and an ejection port row in which the plurality of ejection ports are arranged, and a voltage that does not cause ink to be ejected from the ejection ports is applied to the recording elements corresponding to the plurality of ejection ports, thereby heating the ink. Temperature control is performed by The system includes a temperature control means, and the temperature control means selects the recording element to be heated by a plurality of recording element selection patterns. of heating By doing so, temperature control is performed such that the recording element in the center of the discharge port row is heated to a high degree and temperature control is performed such that the recording element in the center of the discharge port row is heated to a low degree. The plurality of recording element selection patterns are the output row most Recording element at the edge Driven by, The recording element in the center of the aforementioned row of discharge ports Do not drive A first recording element selection pattern and the output port row most Recording element at the edge Without driving it, The recording element in the center of the aforementioned row of discharge ports to drive The temperature control means has a second recording element selection pattern, and the temperature control means controls the first recording element selection pattern and the second recording element selection pattern. Switch and execute the temperature control, and the temperature control Executing During the period , the above most Recording element at the edge but Heated state and unheated state This includes the period in which this occurs.It is characterized by the following: [Effects of the Invention]

[0009] According to the present invention, it is possible to perform a recording operation while reducing the temperature difference in the recording element array and suppressing the difference in ink ejection amount for each recording element. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram illustrating the recording device according to this embodiment. [Figure 2] This is a schematic diagram of the recording head's external appearance and a plan view showing the ejection element substrate. [Figure 3] This is a cross-sectional view of the ejection element substrate. [Figure 4] This is a diagram showing the configuration of the control circuit of the recording device. [Figure 5] This diagram schematically shows the drive pulse applied when performing short-pulse heating. [Figure 6] This is a schematic diagram illustrating the segmented drive operation during short-pulse heating. [Figure 7] This figure shows the change in the minimum temperature of the discharge port row when temperature control is performed. [Figure 8] This table shows an example of a recording element selection pattern during the second heating control in the first embodiment. [Figure 9] This table shows the driving sequence of the recording element selection pattern during the second heating control in the first embodiment. [Figure 10] This table shows the driving sequence of the recording element selection pattern during the second heating control in the second embodiment. [Modes for carrying out the invention]

[0011] <First Embodiment> Examples of embodiments of the present invention will be described below 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 multifunction printer having a plurality of functions such as a recording function, a FAX function, and a scanner function. Further, for example, it may be a manufacturing device for manufacturing a color filter, an electronic device, an optical device, a micro-structure, etc. by a predetermined recording method.

[0012] In the following description, "recording" not only refers to the case of forming significant information such as characters and figures, but also regardless of whether it is significant or not. Further, it also represents the case of forming an image, a pattern, a pattern, a structure, etc. on a recording medium widely, or performing processing on the medium, regardless of whether it is made apparent so that a human can perceive it visually.

[0013] Also, the "recording medium" not only represents paper used in a general recording device, but also represents cloth, plastic film, metal plate, glass, ceramics, resin, wood, leather, etc. that can receive ink. In particular, the "non-permeable recording medium / low-permeable recording medium" is a non-absorbent recording medium / low-absorbent recording medium. Examples of the non-permeable recording medium include those not manufactured as a recording medium for aqueous inkjet ink such as glass, plastic, film, and Yupo. Further, for example, those not surface-treated for inkjet printing (that is, those not forming an ink absorption layer), such as those in which plastic is coated on a base material such as a plastic film or paper, are included. Examples of the plastic include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc. Specific examples of the low-permeable recording medium include recording media such as printing paper used in offset printing such as art paper and coated paper.

[0014] This section describes printing paper (a low-absorption recording medium) which has significantly lower water-based ink penetration compared to inkjet-specific paper. Printing paper refers to the official (real) printing paper used in offset printing to create the final product. Paper is made from pulp, and paper used in its raw state is called uncoated paper. Coated paper has its surface smoothly coated with white pigment or other materials. Coated paper exhibits more pronounced image defects due to ink bleeding and drying defects in inkjet recording. The coating layer is made by applying a mixture of coatings ranging from several to 40 g / m2, including a sizing agent (such as synthetic resin) that limits liquid absorption in the gaps between pulp fibers and prevents bleeding of water-based pens, a filler (such as kaolin) that improves opacity, whiteness, and smoothness, and a paper strength enhancer (such as starch). The average radius of capillary pores in coated paper is normally distributed around 0.06 μm, and moisture penetrates through numerous capillaries (capillary action). However, because its pore volume is much smaller than that of inkjet-specific paper, water-based inks do not penetrate well, causing ink to overflow on the paper surface and resulting in significant image and drying problems.

[0015] This section explains PVC sheets, which have absolutely no permeability to water-based inks compared to inkjet-specific paper. PVC sheets are soft sheets manufactured using polyvinyl chloride resin as the main raw material with added plasticizers. They have excellent printability in gravure printing and screen printing, as well as embossing (creating raised and recessed patterns by pressing). Because these combinations allow for a wide range of expressions, they are used in many products such as tarpaulin, canvas, and wallpaper. However, because polyvinyl chloride resin is the main raw material, they have absolutely no permeability to water-based inks, and the ink overflows on the paper surface, resulting in significant image degradation and drying problems.

[0016] Other examples include materials not manufactured as recording media for water-based inkjet inks, such as glass, plastic, film, and Yupo. Also, examples include materials that have not undergone surface treatment for inkjet printing (i.e., do not form an ink-absorbing layer), such as plastic films or paper coated with plastic. Examples of plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene.

[0017] Furthermore, "ink" should be interpreted broadly, similar to the definition of "record" above. Therefore, it refers to a liquid that, when applied to a recording medium, can be used to form images, patterns, designs, etc., or to process the recording medium, or to process the ink (for example, to solidify or insolubilize the colorants in the ink applied to the recording medium).

[0018] To briefly describe the features of the embodiments, we will first provide a detailed overview of the device configuration, head configuration, and other general aspects common to the embodiments. Next, we will describe the processing flow, which is a characteristic of the present invention, according to several embodiments.

[0019] (Summary of the entire device) Figure 1(a) is an external view of the inkjet recording apparatus (hereinafter also referred to as the 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 a carriage equipped with a recording head is scanned in the Y direction, which intersects with the X direction in which the recording medium P is transported. During this scan, ink droplets are applied by driving the recording elements provided on the recording head 9, and an image is recorded 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 that intersects with the X and Y directions, respectively.

[0020] Figure 1 will be used to illustrate the configuration of the image recording device and its operation during recording. First, with the recording medium P held in the spool 6, the paper feed roller is driven via gears by a paper feed motor (not shown), and the recording medium P is fed and transported to a position where the recording head 9 can record. Meanwhile, at a predetermined transport position, the carriage unit 2, on which the recording head 9 is mounted, is scanned along a guide shaft 29 extending in the Y direction in the figure by a carriage motor (not shown). The recording head 9 is detachably mounted on the carriage unit 2. During one scan, the recording elements provided on the recording head 9 are driven at timings based on the position signal obtained by the encoder 7. This driving of the recording elements causes ink droplets to be ejected from the ejection port and land on the recording medium P. In one scan of the recording head 9, an image can be recorded over an area corresponding to the arrangement range of the recording elements provided on the recording head 9. This recording width corresponding to the arrangement range of the recording elements is called the 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, or 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 over an area of ​​the next bandwidth. The image recording device may transport the bandwidth, i.e., the array range of the recording elements, between each scan, or it may transport the recording medium P after multiple scans instead of transporting it after each scan. Alternatively, ink may be applied based on the downsampled data in n scans, and the transport of a width of 1 / n bandwidth may be repeated between each scan, thereby completing the image by using different recording elements for recording over the same area (so-called multi-pass recording).

[0022] As will be explained in more detail later using Figure 1(b), the recording head 9 of this embodiment has multiple recording elements for ejecting ink arranged in the X direction in the figure. A flexible wiring board 1 is attached to the recording head 9 to supply signal pulses for driving each recording element and signals for head temperature control, and the other end of the flexible wiring board 1 is connected to a control circuit that performs control of 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. Alternatively, other drive systems can be used, such as a system comprising a lead screw rotated by the carriage motor and extending in the main scanning direction (Y direction), and an engaging portion provided on the carriage unit 2 that engages with the groove of the lead screw.

[0024] The paper-fed recording medium P is gripped and transported by the paper feed roller and 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 idle state, the face of the recording head 9 is capped, so prior to recording, the cap is opened to make the recording head 9 or carriage unit 2 scannable. Once one scan's worth of recording data is accumulated in the buffer, the carriage motor 3 causes the carriage unit 2 to scan, and an image is recorded on the recording medium P as described above.

[0025] In this figure, the ambient temperature and humidity sensor 8 is shown by a dashed line. Generally, the ambient temperature and humidity sensor 8 is positioned away from motors, heaters, and other vibration or heat-generating components to eliminate errors and measurement noise. It is located in a position that is difficult to see, such as on the back of the device, and in this specification, it is shown in a transparent form for explanatory purposes.

[0026] Figure 1(b) is a schematic diagram showing the operation of the recording medium P and the recording head in a serial scan 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 explained using this figure. 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 transport direction (X direction) of the recording medium P. As mentioned above, in a serial recording image recording device, multi-pass recording can be performed by using relative scanning between the recording head 9 and the recording medium P, which causes different recording elements to eject ink droplets in the same area. This multi-pass recording can suppress density unevenness due to variations in the recording characteristics of each recording element.

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

[0028] In Figure 2(a), two recording element substrates 10 are arranged side by side in the recording head 9. One recording element substrate has multiple recording element rows 11-14 arranged on it, each capable of ejecting black (Bk), gray (Gy), light gray (Lgy), and light cyan (Lc) inks. The other recording element substrate has multiple recording element rows 15-18 arranged on it, each capable of ejecting cyan (C), light magenta (Lm), magenta (M), and yellow (Y) inks. The ink is supplied from the supply port 25 to the common ink chamber 26 inside the recording head 9, and then supplied to each recording element via the ink flow path inside the recording head 9.

[0029] Figure 2(b) is a plan view showing the detailed configuration of the recording element substrate 10. It is a recording element substrate on which recording element rows 11 to 14 are arranged, among the two recording element substrates placed side by side on the recording head 9. In this embodiment, two rows of recording element rows are provided for each ink color. Each recording element row has 768 recording elements at a pitch of 600 dpi in the X direction, and furthermore, a total of 1536 recording elements for each color are arranged with a half-pitch, or 1200 dpi, offset from the opposing recording element row. Each recording element has an ejection port, and ink droplets are ejected from the ejection port when the recording element is driven. Temperature sensors S6, S7, S8, and S9, which are diode sensors, are arranged at the edge of the recording element substrate 10 in the X direction, and the temperature of the recording element substrate 10 can be detected. Temperature sensors S6 to S9 are located approximately 0.2 mm away in the sub-scanning direction from the outermost ejection port position of the recording element row, and are positioned midway between the two recording element rows in the Y direction. In the X direction, temperature sensors S1, S2, S3, S4, and S5, each consisting of a diode for detecting the temperature of the central part of the recording element array, are formed in the center of the recording element array, and these are also positioned in an intermediate position between two recording element arrays.

[0030] The subheaters 19 and 20 for keeping the recording head 9 warm are formed to surround the recording element substrate 10, and are located 1.2 mm outside the outermost row of recording elements 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 unit will be explained using Figure 2(c). The recording head and the main unit are electrically connected via the contact pad 21 and the flexible circuit board wiring 1 shown in Figure 1. Electrical signals that control ink droplet ejection and heat retention, as well as the power consumed by the recording head, are supplied to the recording head via the contact pad. For connection, a receiving mechanism such as a pin may be provided on the main unit side for fixing, and the recording head may be pressed against the main unit to fix it, thereby ensuring a stable connection. In addition, the power supply that provides the power used for ejection and the power supply that provides the power used for heat retention may have separate pin wiring or may have common wiring. If the voltage value used for ejection and the voltage value used for heat retention are the same, the number of terminals can be reduced by using common pin wiring. Even if the voltages are different, they can be made common by providing a constant voltage output electronic circuit on the recording head side. Note that the wiring configuration of the electrical connection is not limited to the above.

[0032] Figure 3 is a cross-sectional view taken along line AA' in Figure 2(b). In this figure, 27 is a support substrate, 22 is a recording element, and 23 is an ejection port. The ink flow path 24 is formed between the support substrate 27 and the orifice plate 28, and partition walls (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 via a common liquid chamber 26 that communicates with each flow path 24 from the bottom in Figure 3.

[0033] (Example of control system configuration) Figure 4 shows an example of the control circuit of an image recording device. The programmable peripheral interface (hereinafter referred to as PPI) 101 receives command signals and recording information signals, including recording data, sent from the host computer 100 and transfers them to the MPU 102. At the same time, it sends status information of the image recording device to the host computer 100 as needed. It also performs data input and output with the console 106, which has a setting input unit for the user to make various settings for the image recording device and a display unit that displays messages to the user. It also receives input signals from a group of sensors 107, including a home position sensor that detects whether the carriage unit 2 or the recording head 9 is in the home position, and a capping sensor.

[0034] The MPU (microprocessing unit) 102 controls each part of the image recording device according to the control program stored in the control ROM 105. The RAM 103 stores received signals, is used as the work area for the MPU 102, and temporarily stores various data. The print buffer 121 stores the recorded data expanded in the RAM 103, etc., and is a memory area with a capacity for recording multiple lines. In addition to the control program described above, 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 part of this embodiment). Each of these parts is controlled by the MPU 102 via the address bus 117 and the data bus 118.

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

[0036] The sheet sensor 109 detects the presence or absence of a recording medium, that is, whether or not the recording medium has been supplied to a position where it can be recorded by the recording head 9. The driver 111 is a driver for driving the recording elements of the recording head 9 in accordance with the recording information signal. As described above, the ambient temperature and humidity sensor 8 detects the ambient temperature and humidity in the environment in which the recording device is installed. The location where the ambient temperature and humidity sensor 8 is placed is not limited as long as it is configured to detect the ambient temperature of the device.

[0037] The power supply unit 120 is a power supply unit that supplies power to each of the above-mentioned parts, and is equipped with an AC adapter and a battery as a drive power supply device. In this embodiment, the power supply unit 120 is responsible for both supplying power to eject ink droplets from the recording element of the recording head 9 and supplying power to the sub-heater for maintaining temperature.

[0038] In a recording system consisting of an image recording device and a host computer 100, when recording data is transmitted from the host computer 100 via a parallel port, infrared port, or network, a required command is added to the beginning of the transmission. This command may include, for example, the type of recording medium, the size of the medium, the recording quality, and whether or not automatic object detection is performed. Recording medium types include, for example, plain paper, OHP sheets, glossy paper, and special recording media such as transfer film, cardboard, and banner paper. Medium sizes include A0, A1, A2, B0, B1, and B2. Recording quality options include draft, high quality, medium quality, emphasis on specific colors, and monochrome / color. Furthermore, if a configuration is adopted to apply a processing solution to improve ink fixation on the recording medium, information determining whether or not this solution is applied is transmitted as a command.

[0039] In accordance with these commands, the image recording device reads the data necessary for recording from ROM 105 and performs recording based on that data. The data necessary for recording includes, for example, the number of recording passes (number of scans) when performing the multi-pass recording described above, the amount of ink to be printed per unit area of ​​the recording medium, and data that determines the recording direction. In addition, there is the type of mask used for data decimation when performing multi-pass recording, and driving conditions based on the temperature sensor detection value in the recording head 9 (for example, the shape and duration of the driving pulse applied to the heat-generating part). Furthermore, there may also be data such as the dot size, recording medium transport conditions, the number of colors used, and the carriage speed.

[0040] An embodiment of the image recording device having the above configuration will be described as an example, but the device configuration described here is merely one example of a device configuration that realizes this embodiment. Needless to say, this 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 element 22 to the extent that ink is not ejected between reciprocal scans of the recording head or immediately before the first scan of the recording medium. Furthermore, in this embodiment, the 768 recording elements 22 in the recording element array are divided into multiple recording element groups along the Y direction, and short-pulse heating is performed by divided driving, which determines whether or not to apply a drive pulse to each divided recording element group.

[0042] Figure 5 schematically shows the drive pulses applied when performing short-pulse heating in this embodiment.

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

[0044] Figure 6 is a schematic diagram illustrating the segmented drive in this embodiment. In this embodiment, the 768 recording elements 22 are divided into 48 groups (B1 to B48), with each group consisting of 16 recording elements in the X direction. For each of these recording element groups B1 to B48, an ON / OFF pattern for recording elements (hereinafter also referred to as a recording element selection pattern) is set for short-pulse heating.

[0045] Note that the number of divisions here is not limited to this, and the number of recording elements in each further divided group of recording elements may be different.

[0046] In this embodiment, as described above, short-pulse heating is performed between round-trip scans or immediately before the start of recording. When performed between round-trip scans, short-pulse heating is started within the deceleration region of carriage 1 from the end of recording on the recording medium until carriage reversal. Furthermore, if the target temperature (threshold) is not reached by the time of carriage reversal, the carriage reversal unit waits and short-pulse heating is continued until the target temperature is reached.

[0047] In this embodiment, short-pulse heating control is performed in two stages. Specifically, the first heating control, which is executed first, uniformly drives multiple recording elements in the recording element array, and then the second heating control is executed, which drives multiple recording element selection patterns in combination.

[0048] Figure 7 shows the transition of the minimum temperature of the discharge port row when temperature control is performed according to this embodiment.

[0049] First, in the first heating control, the drive pulse shown in Figure 5 is applied to all of the recording element groups B1 to B48 in the recording element row until the temperature output value of the diodes arranged in the output port row reaches the target temperature T1 shown in the figure. This makes it possible to quickly raise the head temperature to near the target temperature. If the output port to be used for the next recording is limited, the drive pulse may be applied only to the recording element group that includes the recording element of the output port to be used. Subsequently, the head temperature is raised to the final target temperature T2 by the second heating control.

[0050] (Driving method in the second heating control) Figure 8 shows an example of a recording element selection pattern (50% drive rate) during the second heating control. Three types of patterns are shown here. In the second heating control, the ejection port row is heated while achieving temperature uniformity by switching between three recording element selection patterns, including a group of recording elements that are not driven, in units of the drive frequency of short-pulse heating. In the preceding first heating control, all ejection ports are driven, but heat diffuses to the outside of ejection ports closer to the ends, resulting in a relatively lower temperature compared to ejection ports closer to the center. To compensate for this, conventional technology has performed temperature control using only patterns with a low drive rate other than the ends, such as pattern 1, relative to the ends B1 or B48. However, as mentioned above, with only pattern 1, the temperature of the ejection heater-ink interface of the recording element group other than the ends, which remains unheated, is relatively low, while the temperature of the ejection heater-ink interface of the recording element group at the ends, which remains heated, is relatively high. As a result, there is a difference in the amount of ink "burnt" on the heater. "Burning" refers to the phenomenon where colorants and additives contained in a liquid are decomposed at the molecular level when heated to high temperatures on a heater, transforming into poorly soluble substances that are physically adsorbed onto the heat-acting area. If the amount of burning differs significantly between heaters, differences in heat conduction from the heater to the liquid will occur, making it easier for differences in discharge volume to occur, which raises concerns about image defects. Therefore, in this embodiment, the objective is to reduce the relative temperature difference at each discharge port by switching to pattern 2, in the opposite direction to pattern 1, in which the end recording element group B1 or B48 is not driven, thereby suppressing the risk of image defects. As a result, there are no recording elements that are not heated during the heating process.

[0051] Pattern 2, which has a low drive rate for the edge recording elements, is used less frequently than Pattern 1. For example, Patterns 1 and 2 are used in an 8:2 ratio. This ensures that the average heating time for the edge recording elements is longer than the average heating time for the central recording elements. This achieves both uniform temperature distribution across the entire nozzle row and reduction of relative temperature differences between nozzles by shortening the time the edges are not driven. These patterns can be driven sequentially, but it is desirable to distribute them as much as possible. Figure 9 shows an example of pattern driving sequence. Pattern 2 is used in driving sequence 5 and driving sequence 10, and Pattern 1 is used for all others. After driving up to driving sequence 10, the sequence is repeated starting from driving sequence 1. The longer the time that a nozzle remains in a heated state and the longer the time it remains unheated, the more likely it is that differences in ink burning will occur as described above. Therefore, it is better to drive Pattern 1 in intervals of four rather than driving it eight times consecutively.

[0052] Furthermore, although the driving rate of the recording element group is the same across patterns in this embodiment, different patterns may be selected for each element.

[0053] Furthermore, in this embodiment, the edge recording element group is designated as B1 or B48 (16 recording elements from the edge), but this is not limited to this; the edge recording element group can be any part that tends to have a lower temperature. The number of recording elements may be fewer than 16, or more than 16.

[0054] Furthermore, the overall drive rate in the second heating control is not limited to this and may be varied depending on the ambient temperature, etc. When the ambient temperature is high, the heating efficiency is high, so a short-pulse heating pattern with a low drive rate for the edge recording element group may be selected.

[0055] This embodiment makes it possible to reduce temperature differences between individual discharge ports while maintaining temperature uniformity across the entire discharge port row, thereby suppressing image unevenness caused by variations in heater burnt-out amounts.

[0056] <Second Embodiment> In the second embodiment, similar to the first embodiment, heating control is performed by switching between multiple patterns, including a pattern with a lower degree of heating at the edges, in the second heating control. However, in the second embodiment, the patterns are combined such that the overall driving time is longer for recording element groups closer to the edges.

[0057] Figure 10 shows an example of the pattern driving sequence in the second embodiment. In the first embodiment, for example, the driving time for recording element group B4 was 20% of the total, while the driving time for B5 was 80% of the total, indicating that recording element groups closer to the edges had shorter driving times. Considering that heat dissipates more easily and heats up less near the edges, it is preferable to have relatively longer driving times closer to the edges. In Figure 10, for any two recording element groups, the driving time is longer closer to the edges. For example, the driving time for recording element group B4 is 69% of the total, and the driving time for recording element group B5 is 63% of the total.

[0058] Furthermore, although the driving rate of the recording element group is the same across patterns in this embodiment, different patterns may be selected for each element.

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

[0060] This embodiment makes it possible to reduce temperature differences between individual discharge ports while ensuring temperature uniformity across the entire discharge port row, compared to the first embodiment. [Explanation of symbols]

[0061] 2 carriage units 3. Carriage Motor 8. Ambient temperature and humidity sensor 9 Recording head 10 Recording element substrate 11-18 Recording element array 19, 20 Sub-heater 22 Recording 23. Spit out

Claims

1. A recording head having a plurality of recording elements that generate thermal energy to the ink, and a plurality of ejection ports provided corresponding to the recording elements for ejecting ink, and an ejection port row in which the plurality of ejection ports are arranged, The system includes a temperature control means that applies a voltage to the recording elements corresponding to the plurality of ejection ports that is such that ink is not ejected from the ejection ports, thereby performing temperature control by heating the ink. The temperature control means heats the recording elements by selecting a plurality of recording element selection patterns to select the recording elements to be heated, thereby performing temperature control that results in a high degree of heating of the recording element in the center of the discharge port row and temperature control that results in a low degree of heating of the recording element in the center of the discharge port row. The plurality of recording element selection patterns include a first recording element selection pattern that drives the recording element at the outermost end of the ejection port row but does not drive the recording element in the center of the ejection port row, and a second recording element selection pattern that does not drive the recording element at the outermost end of the ejection port row but drives the recording element in the center of the ejection port row. The image recording apparatus is characterized in that the temperature control means performs the temperature control by switching between the first recording element selection pattern and the second recording element selection pattern, and during the period in which the temperature control is performed, the recording element at the outermost end is in a heated state and a non-heated state.

2. The image recording apparatus according to claim 1, characterized in that the temperature control means makes the frequency of use of the first recording element selection pattern during the period of temperature control higher than the frequency of use of the second recording element selection pattern.

3. The image recording apparatus according to claim 1, characterized in that the temperature control means repeatedly alternates between a heated state and a non-heated state for all recording elements by switching between the first recording element selection pattern and the second recording element selection pattern.

4. The image recording apparatus according to claim 2, characterized in that the average heating time at the outermost recording element of the discharge port row during the period of temperature control is longer than the average heating time at the central recording element of the discharge port row during the period of temperature control.

5. The image recording apparatus according to claim 1, characterized in that the temperature control means heats all discharge ports until the temperature of the recording head reaches a predetermined temperature.

6. The image recording apparatus according to claim 1, characterized in that the plurality of recording element selection patterns can be switched by the frequency at which voltage is applied.

7. The image recording apparatus according to claim 1, characterized in that the recording element at the very end of the discharge port row is the recording element located at the very end of the plurality of recording elements arranged in the discharge port row.

8. Having a carriage on which the aforementioned recording head is mounted, The carriage scans in the scanning direction, The image recording apparatus according to any one of claims 1 to 7, characterized in that the discharge port row has the plurality of discharge ports arranged in a direction intersecting the scanning direction.

9. The image recording device according to claim 1, characterized in that the degree of heating is the average heating time during the period of temperature control.

10. A control method for controlling a recording head having a plurality of recording elements that generate thermal energy to be supplied to the ink, and a plurality of ejection ports provided corresponding to the recording elements for ejecting ink, wherein an ejection port row is provided in which the plurality of ejection ports are arranged, The system includes a temperature control step that controls the application of a voltage to a recording element corresponding to the plurality of ejection ports to prevent ink from being ejected from the ejection ports in order to heat the ink. In the temperature control step, the recording elements are heated by selecting a plurality of recording element selection patterns to select the recording elements to be heated, thereby performing a temperature control step in which the recording element in the center of the discharge port row is heated to a high degree and a temperature control step in which the recording element in the center of the discharge port row is heated to a low degree. The plurality of recording element selection patterns include a first recording element selection pattern that drives the recording element at the outermost end of the ejection port row but does not drive the recording element in the center of the ejection port row, and a second recording element selection pattern that does not drive the recording element at the outermost end of the ejection port row but drives the recording element in the center of the ejection port row. The control method is characterized in that the temperature control step is performed by switching between the first recording element selection pattern and the second recording element selection pattern, and during the period in which the temperature control step is performed, the recording element at the outermost end is in a heated state and a non-heated state.

11. The control method according to claim 10, characterized in that the degree of heating is the average heating time during the period of the temperature control step.

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