Recording device and method for controlling the recording device

Abstract

Providing recording devices and other equipment that can suppress the occurrence of condensation. [Solution] An inkjet recording apparatus comprising: a recording head having a plurality of recording element substrates for ejecting ink; heating means for heating each of the plurality of recording element substrates to a target temperature; acquisition means for acquiring the temperature of a plurality of locations within each of the plurality of recording element substrates a plurality of times; and control means for comparing the highest temperature of each of the plurality of locations within the recording element substrate acquired by the acquisition means with a first temperature, and lowering the target temperature if it is determined that the highest temperature is lower than the first temperature for a first consecutive number of times.

Description

Technical Field

[0001] The present invention relates to a recording apparatus and a control method for the recording apparatus.

Background Art

[0002] In an inkjet recording apparatus, ink is ejected from a recording head having ejection ports to record an image on a recording medium. As a method of generating energy for ejecting ink from the ejection ports of the recording head, there are a method of pressurizing the ink using an electromechanical conversion element such as a piezo element, a method of generating foaming by heating the ink with an electrothermal conversion element having a heating resistor, and the like. Hereinafter, the electrothermal conversion element is also referred to as a heater.

[0003] Generally, in an inkjet recording apparatus, the amount of ink ejected from the ejection ports (hereinafter referred to as the ejection amount) has the characteristic that the ejection amount is large when the ink temperature is high and the ejection amount is small when the ink temperature is low. Therefore, in the case of a recording head having a plurality of ejection ports, the temperature difference of the ink near each ejection port leads to a difference in the ejection amount. Therefore, conventionally, temperature control by heat has been performed to equalize the ejection amounts of each ejection port (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the configuration described in Patent Document 1, a temperature detection means is provided for each recording element substrate having multiple ejection ports, and a temperature lower than the maximum value of the temperature acquired by the temperature detection means (acquired temperature) is set as the target temperature for each temperature detection means. However, if the acquired temperature changes rapidly, the target temperature also changes rapidly, and at the moment when the system switches from an ink ejection state to a non-ejection state, the surface of the ejection port may fall below the dew point temperature of the air near the ejection port. As a result, condensation occurs around the ejection port, leading to a decrease in image quality, such as water droplets falling onto the recording medium and misalignment of the ink ejected from the ejection port.

[0006] Therefore, the object of the present invention is to provide a recording device that can suppress the occurrence of condensation, and a method for controlling the recording device. [Means for solving the problem]

[0007] The above objective is achieved by the present invention as follows. That is, the recording device according to the present invention is characterized by comprising: a recording head having a plurality of recording element substrates for ejecting ink; a heating means for heating each of the plurality of recording element substrates to a target temperature; an acquisition means for acquiring the temperature of a plurality of locations within each of the plurality of recording element substrates a plurality of times; and a control means for lowering the target temperature if, for each of the plurality of recording element substrates, the highest temperature of each of the plurality of locations within the recording element substrate acquired by the acquisition means a plurality of times is compared with a first temperature, and the highest temperature is determined to be lower than the first temperature for a first consecutive number of times. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a recording device that can suppress the occurrence of condensation, and a method for controlling the recording device. [Brief explanation of the drawing]

[0009] [Figure 1]A schematic diagram showing the general configuration of an inkjet recording device. [Figure 2] A block diagram illustrating the control system of an inkjet recording device. [Figure 3] Detailed block diagram of the printer control unit. [Figure 4] A diagram showing the structure of the recording head. [Figure 5] A diagram showing the structure of the recording element substrate. [Figure 6] A diagram showing the flow of liquid within the recording element substrate. [Figure 7] A diagram illustrating temperature control for a recording element substrate. [Figure 8] A flowchart illustrating the entire moisturizing control process. [Figure 9] A flowchart of a conventional variable temperature control system. [Figure 10] A psychrometric chart illustrating the changes in temperature and humidity when implementing conventional variable temperature control. [Figure 11] Flowchart of variable temperature control in the first embodiment. [Figure 12] A psychrometric chart illustrating the changes in temperature and humidity when implementing variable temperature control in the first embodiment. [Figure 13] Flowchart of variable temperature control in the second embodiment. [Modes for carrying out the invention]

[0010] The present invention will be described in more detail below with reference to preferred embodiments.

[0011] <First Embodiment> Figure 1 is a schematic diagram showing the general configuration of an inkjet recording device (recording device) 100. In this embodiment, the recording device 100 is a sheet-fed recording device that records an image on a recording medium 101 using two types of liquids: a reaction solution and ink. Hereinafter, the reaction solution and ink will be collectively referred to as liquids. The X direction corresponds to the width direction (overall length direction) of the recording device 100, the Y direction corresponds to the depth direction of the recording device 100, and the Z direction corresponds to the height direction (gravity direction) of the recording device 100. Furthermore, since the recording medium 101 is transported in the X direction, the X direction also corresponds to the transport direction of the recording medium, and the Y direction also corresponds to the width direction of the recording medium.

[0012] The recording device 100 includes a transport unit 107 for transporting the recording medium 101, a paper feeding unit 106 for feeding the recording medium 101 to the transport unit 107, and a paper discharge unit 108 for collecting the printed recording medium 101 from the transport unit 107. The recording device 100 also includes a first recording head for applying a reaction liquid that reacts with ink onto the recording medium 101, and a second recording head for applying ink to the area of ​​the recording medium 101 to which the reaction liquid has been applied, and for recording an image. The first recording head and the second recording head are collectively referred to simply as the recording head 102. Between the transport unit 107 and the paper discharge unit 108, a unit (not shown) having functions such as drying, fixing, cooling, and paper inversion may be added at any position depending on the system.

[0013] FIG. 2 is a block diagram showing an overview of a control system that controls the recording apparatus 100. This control system includes, as components, a recording data generation unit 201, an operation control unit 202, a printer control unit 203, a recording medium conveyance control unit 204, and an inkjet device 205. The recording data generation unit 201 is a module that generates recording data, and sends the generated recording data to the printer control unit 203. Note that the recording data generation unit 201 may be provided inside the recording apparatus 100, or may be constituted by an external print server or the like. The operation control unit 202 is a module for being operated by a user or a service technician, or for receiving instructions. Specifically, the operation control unit 202 includes an operation panel provided in the recording apparatus 100 and an operation PC connected to the recording apparatus 100. In this embodiment, the operation control unit 202 will be described as an operation panel. The printer control unit 203 is a module that performs a recording process. The recording medium conveyance control unit 204 is a module for conveying a recording medium. The inkjet device 205 is a module used for recording.

[0014] FIG. 3 is a block diagram showing the printer control unit 203 in detail. In FIG. 3, it is shown as a figure including other configurations shown in FIG. 2. The printer control unit 203 includes a CPU 301, a ROM 302, a RAM 303, an ASIC 304, and a head control unit 305. The CPU 301 controls the entire recording apparatus 100. The control program of the CPU 301 and the like are stored in the ROM 302. The RAM 303 temporarily stores data, or is used as a work memory when executing a program. The ASIC 304 is an integrated circuit for specific use incorporating a network controller, a serial IF controller, a head data generation controller, a motor controller, and the like. The head control unit 305 generates ejection data used in the inkjet device 205, and generates a drive voltage for an ejection heater and a sub-heater.

[0015] (Recording head) The recording head will be described below with reference to FIG. 1. The recording head 102 is a full-line head extending in the paper width direction (Y direction). A plurality of ejection ports 402 (details will be described later) are arranged in a range covering the width of the image recording area of the recording medium 101 with the maximum usable size on the recording head 102. On the lower surface in the gravitational direction (on the side of the recording medium 101) of the recording head 102, an ejection port surface where the ejection ports are open is provided. In this embodiment, a thermal inkjet recording head that ejects the liquid in the ejection port by heating the recording element will be described as an example, but the liquid ejection method of this recording head is just an example. For example, it is also applicable to a piezo-type recording head that ejects liquid using mechanical deformation of a piezo element and other types of inkjet recording heads.

[0016] When recording on the recording medium 101, the ejection port surface of the recording head 102 is fixed facing the recording medium 101 (transport unit 107) being transported while maintaining a minute gap of about 1 millimeter from the surface of the recording medium 101 being transported. The position of the recording head at this time is called the "recording position".

[0017] As shown in FIG. 1, a plurality of recording heads are arranged along the transport direction (X direction) as the recording head 102. In this embodiment, the first recording head for applying the reaction liquid is provided upstream in the transport direction from the second recording head for applying ink, and four second recording heads are provided in order downstream in the transport direction from the first recording head. These four second recording heads correspond to line-type recording heads for four colors of Bk (black), Ye (yellow), Ma (magenta), and Cy (cyan). Note that the types of colors, the order of colors, and the number of colors are not limited to this example. The liquid ejected by the recording head 102 is supplied from an ink tank (not shown) to the recording head 102 via an ink tube.

[0018] Figure 4 is a plan view showing the structure of the discharge surface of the recording head 102, and is a view of the recording head 102 from the -Z direction. As shown in Figure 4, in the recording head 102, multiple recording element substrates 401, each having multiple discharge ports 402 for discharging liquid, are arranged in a line in the paper width direction (Y direction). Positioning members 404 for the recording head 102 are provided at both ends of the row of recording element substrates 401. The positioning members 404 are configured to be able to contact a recording head positioning member (not shown) provided on the opposite transport unit side. The contact between this recording head positioning member and the positioning member 404 allows the distance between the discharge surface of the recording head 102 and the transport belt 107a to be defined. The sealant 403 is a member for protecting the electrical terminals of the recording element substrate 401.

[0019] Multiple discharge ports 402 for discharging liquid are provided in a row on the discharge port surface of the recording head 102. The multiple discharge ports 402 are arranged along a direction (Y direction) perpendicular to the transport direction (X direction) of the recording medium 101. Any row formed by multiple discharge ports 402 arranged in the Y direction is called a "discharge port row". On the recording element substrate 401, the multiple discharge port rows are arranged so that their respective positions in the X direction are different. Specifically, there are 16 discharge port rows in the X direction, each having 512 discharge ports arranged at 600 dpi (dots / inch). In addition, two adjacent discharge port rows are positioned with a 1200 dpi offset in the Y direction.

[0020] (Recording element substrate) The configuration of the recording element substrate 401 in this embodiment will be explained using Figure 5, which shows the structure of the recording element substrate. Figure 5(a) is a plan view of the side of the recording element substrate 401 on which the discharge ports 402 are formed, Figure 5(b) is an enlarged view of the part indicated by A in Figure 5(a), and Figure 5(c) is a plan view of the back side of Figure 5(a). Hereafter, the direction in which the row of discharge ports, in which a plurality of discharge ports 402 are arranged, extends will be referred to as the "discharge port row direction." As shown in Figure 5(b), a recording element 15, which is a heating element (pressure generating element) for foaming a liquid using the thermal energy it generates, is arranged at a position corresponding to each discharge port 402. A pressure chamber 23 containing the recording element 15 is partitioned by a partition wall 22. The recording element 15 is electrically connected to a terminal 16 by electrical wiring (not shown) provided on the recording element substrate 401. Then, the recording element 15 generates heat and boils the liquid based on a pulse signal input from the control circuit of the recording device 100 via electrical wiring. The force of this boiling discharges the liquid from the discharge port 402. As shown in Figure 5(b), along each row of discharge ports, a liquid supply path 18 extends on one side and a liquid recovery path 19 extends on the other side. The liquid supply path 18 and the liquid recovery path 19 are flow paths provided on the recording element substrate 401 that extend in the direction of the row of discharge ports, and are in communication with the discharge port 402 via a supply port 17a and a recovery port 17b, respectively.

[0021] As shown in Figure 5(c), a sheet-like cover plate 20 is laminated on the back surface of the recording element substrate 401 where the ejection port 402 is formed. The cover plate 20 is provided with multiple openings 21 that communicate with the liquid supply passage 18 and the liquid recovery passage 19, which will be described later. In this embodiment, four supply openings 21a are provided on the cover plate 20 for each liquid supply passage 18, and three recovery openings 21b are provided for each liquid recovery passage 19, but the number of openings is not limited to these.

[0022] Figure 6 is a perspective view showing a cross-section of the recording element substrate 401 and cover plate 20 in Figure 5(a) II. Here, the flow of liquid within the recording element substrate 401 will be explained. The cover plate 20 functions as a lid, forming part of the walls of the liquid supply passage 18 and liquid recovery passage 19 formed in the substrate 11 of the recording element substrate 401. The recording element substrate 401 is formed by laminating a substrate 11 made of Si or the like and an ejection port forming member 12 made of a photosensitive resin, with the cover plate 20 bonded to the back surface of the substrate 11. The liquid supply passage 18 and liquid recovery passage 19 formed by the substrate 11 and the cover plate 20 are connected to a common supply passage (not shown) and a common recovery passage (not shown), respectively, and a differential pressure is generated between the liquid supply passage 18 and the liquid recovery passage 19. Due to this differential pressure, the liquid in the liquid supply passage 18 provided in the substrate 11 flows to the liquid recovery passage 19 via the supply port 17a, pressure chamber 23, and recovery port 17b (arrow C in Figure 6). This flow allows thickened ink, foam, and foreign matter generated by evaporation from the discharge port 402 to be recovered into the liquid recovery path 19 in the discharge port 402 and pressure chamber 23, where the discharge operation is not in progress. Furthermore, it is possible to suppress the thickening of the ink in the discharge port 402 and pressure chamber 23, and the increase in the concentration of solid components (such as pigments) in the ink.

[0023] The liquid flowing through the liquid recovery channel 19 merges with a common recovery channel (not shown) and is recovered in a buffer tank (not shown). Furthermore, the liquid pumped from the buffer tank (not shown) is supplied again to the liquid supply channel 18 via a common supply channel (not shown), thus forming a liquid circulation system. A heat exchanger (not shown) is installed along the common supply channel, and the liquid entering the liquid supply channel 18 is maintained at 25°C.

[0024] The temperature control of the recording element substrate will be explained using Figure 7. Figures 7(a) and (b) schematically show how each recording element substrate 401 is divided into multiple temperature control areas 300 for temperature adjustment. A temperature sensor 701 and an individually controllable sub-heater 702 are provided for each of the 40 areas separated by dashed lines. The printer control unit 203 (see Figure 2) uses the temperature sensor 701 and the sub-heater 702 to adjust the temperature based on the temperature set for each area. That is, the control unit 203 drives the sub-heater 702 only in areas where the temperature detected by the temperature sensor 701 is below the target temperature.

[0025] The control signal to the sub-heater when adjusting the temperature, and the drive signal to the heater when ejecting ink, are adjusted in real time based on the output value of the temperature sensor 701. The amount of ink ejected is controlled by applying PWM (Pulse Width Modulation) control to the drive pulse for the heater, which switches the on-time (pulse width) of the pulse. When driving the heater for recording elements arranged on the same element substrate, the same drive pulse with PWM control is applied. Furthermore, when driving the heater for multiple recording elements on the same element substrate, the same drive pulse is applied, and the design ensures that the amount of liquid ejected is constant under the same temperature environment and the same drive pulse. However, when the heater is driven with the same drive pulse for multiple recording elements on the same element substrate, the amount of liquid ejected from each recording element will differ depending on the temperature distribution of the element substrate containing those multiple recording elements. In other words, by reducing this variation in temperature, density unevenness in the recorded image can be suppressed. Temperature variations in the recording element substrate are caused by differences in heating and heat dissipation characteristics across different areas of the substrate, and it is known that these variations increase with higher print duty cycles. A high print duty cycle image refers to an image with a high ink ejection density or a large ejection volume. Furthermore, temperature variations in the recording element substrate become even more pronounced when ink is constantly flowing through the substrate due to ink circulation.

[0026] The problems that this embodiment aims to solve will be described in detail below. First, an overview of the temperature control of the recording element substrate will be described. Figure 8 shows a flowchart of the entire temperature control in this embodiment. Here, the series of processes shown in this flowchart are executed, for example, by the CPU 304 loading the program code described in the ROM 302 into the RAM 303 and executing it. Some or all of the functions in Figure 8 may be executed by hardware such as an ASIC, FPGA, or electrical circuit. This flowchart is assumed to start when the recording operation begins.

[0027] In S101, the printer control unit 203 sets the temperature-controlled recording element board. In this embodiment, the recording element board on which temperature control will be performed is selected according to the paper size on which the recording operation will be performed. In other words, temperature control is performed only on the recording element board corresponding to the area on which the recording operation will be performed (hereinafter referred to as the recording area). The recording element board selected here is the recording element board on which temperature control is permitted.

[0028] In S102, the printer control unit 203 performs preheating control. Preheating control operates the subheater until the target temperature is reached by supplying energy such that the power required to drive the subheater is less than a predetermined amount, when power supply related to ejection (such as power supply to the heater) is not being provided, such as when ejection is not taking place.

[0029] In S103, the printer control unit 203 performs variable temperature control. Details of the variable temperature control will be described later. In S104, the printer control unit 203 performs temperature maintenance control. Temperature maintenance control is performed to maintain the target temperature by supplying energy such that the sum of the power supplied for ejection and the power supplied to the subheater falls below a predetermined amount, when power is being supplied for ejection, such as when ejection is in progress.

[0030] In S105, the printer control unit 203 determines whether printing of one page has been completed. If it determines that printing of one page has not been completed, it returns to S103; if it determines that it has been completed, it proceeds to S106.

[0031] In S106, the printer control unit 203 determines whether recording of all pages has been completed. If it determines that recording of all pages has not been completed, it returns to S101; if it determines that it has been completed, this processing flow is terminated.

[0032] The variable temperature control in S103 will be explained using Figure 9. Figure 9 is a flowchart detailing the variable temperature control in S103. Variable temperature control is a process that changes the target temperature of each recording element substrate according to the temperature distribution of the recording head 102, and the process shown in Figure 9 is a conventional process.

[0033] In S201, the printer control unit 203 sets the target temperature T1 and the variable temperature control determination temperature T2 (T2 > T1). T1 is the temperature of the recording element substrate that is maintained for image recording and is used as the default value. The variable temperature control determination temperature T2 is the threshold temperature used to determine whether to switch the target temperature maintained for the recording element substrate. The temperatures set here are to be common values ​​used for multiple element substrates, and these values ​​are stored in advance in the ROM 302 or the like.

[0034] In S202, the printer control unit 203 acquires the highest output value among the multiple temperature sensors 701 located at multiple locations on the recording element board for which temperature control is permitted, and sets it as Tmax. This operation is performed for each recording element board.

[0035] In S203, the printer control unit 203 determines whether Tmax is greater than or equal to T2. If Tmax is greater than or equal to T2, the process proceeds to S204; otherwise, the process proceeds to S205.

[0036] In S204, the printer control unit 203 changes the target temperature to T3. Here, T3 is a temperature greater than T1 and less than T2, and there is a relationship of T1 < T3 < T2. T3 may use a value previously held in the ROM 302 or the like. When the target temperature is changed to T3, among the plurality of sub-heaters provided on the recording element substrate, the printer control unit 203 drives the sub-heater corresponding to the area where the temperature is less than T3 until the temperature in the area reaches T3. Then, the printer control unit 203 drives the sub-heater corresponding to the area where the temperature is T3 or higher so as to maintain the temperature of the corresponding area at T3. Then, it proceeds to S206.

[0037] In S205, the printer control unit 203 sets the target temperature to T1. That is, it is set to maintain the original target temperature. In this case, among the plurality of sub-heaters provided on the recording element substrate, the printer control unit 203 drives the sub-heater corresponding to the area where the temperature is less than T1 until the temperature T1 in the area is reached. Then, the printer control unit 203 drives the sub-heater corresponding to the area where the temperature is T1 or higher so as to maintain the temperature of the corresponding area at T1.

[0038] In S206, the printer control unit 203 determines whether the processing has been completed for all the recording element substrates for which temperature control is permitted. If it is determined that the processing has been completed for all the recording element substrates, this processing flow is terminated. If the printer control unit 203 determines that there is an unprocessed recording element substrate, it returns to S202 and repeats the control with the unprocessed recording element substrate as the processing target.

[0039] By the above processing, the maximum temperature Tmax of each of the plurality of recording element substrates is compared with a predetermined temperature (T2). When Tmax ≧ T2, the target temperature is set to T3, which is a temperature lower than T2. Thereby, for each of the plurality of recording element substrates, the target temperature to be maintained for the recording element substrate is set according to the highest temperature of the recording element substrate at that time. In other words, when the highest temperature in the recording element substrate decreases, the target temperature for the recording element substrate is decreased.

[0040] Here, we consider the changes in temperature and moisture content near the outlet surface when recording high-duty images. Figure 10 shows the changes in temperature and humidity near the outlet surface when recording high-duty images, as shown in the psychrometric chart. The vertical axis represents absolute humidity, which indicates the amount of water vapor contained in the air, and the horizontal axis represents the dry-bulb temperature, which indicates the air temperature measured by the thermometer. In Figure 10, the line representing 100% relative humidity is shown. Here, relative humidity is an indicator that represents what percentage of the maximum amount of water vapor possible at that temperature the amount of water vapor in the air represents, and a relative humidity exceeding 100% means that condensation will occur.

[0041] When recording high-duty images, a large amount of ink droplets are ejected from the nozzle surface, and a large amount of ink is applied to the recording medium surface. As a result, the relative humidity in the space of approximately 1 millimeter between the nozzle and the recording medium becomes very high due to the effect of evaporating moisture. Furthermore, the temperature of the recording element substrate rises due to the high number of times the heater is driven for the recording element. Consequently, the amount of saturated water vapor in the space between the nozzle surface and the recording medium increases, resulting in an even higher moisture content in the space (Figure 10 (a) → (b)).

[0042] Since the recording medium 101 is being transported in the +X direction, a transport airflow in the +X direction is generated in the space between the ejection port surface and the recording medium. It is known that the airflow in the space of approximately 1 millimeter between the ejection port surface and the recording medium follows a Couette flow. The airflow on the surface of the recording medium, about 1 millimeter away from the ejection port surface, has a velocity in the +X direction that is almost the same as the transport velocity, but as it approaches the ejection port surface, the flow velocity gradually decreases, and the airflow near the surface of the ejection port surface is theoretically considered to be 0 m / sec. In other words, during high-duty recording, high-humidity air remains stationary near the surface of the ejection port surface without being moved by the transport airflow. High-temperature water vapor containing a lot of moisture moves relatively slowly downstream in the transport direction along the ejection port surface, following a Couette flow. Next, consider the state when the recording operation stops, that is, when the ink ejection operation stops, from a state where a high-duty image was being recorded (for example, between pages). With the cessation of the recording operation, the temperature of the recording element plate, which had been heated, drops rapidly, and consequently the target temperature of the recording element substrate also drops. Therefore, the high-temperature water vapor containing a large amount of moisture, which was moving relatively slowly downstream in the transport direction from the discharge surface on the Couette flow, comes into contact with a component that is colder than the air temperature (for example, a recording element substrate whose temperature has dropped rapidly). As a result, the amount of saturated water vapor decreases as the air cools. Consequently, the moisture that can no longer be held in the air forms water droplets as "condensation" on the contacted component (Figure 10 (b) → (c)). From the above, it can be said that the condition under which condensation occurs on the discharge surface is when the surface temperature of the discharge surface after discharge has stopped due to recording a high-duty image falls below the dew point temperature of the air near the discharge surface.

[0043] When condensation occurs on the ejection port surface of the recording element substrate, water droplets gradually combine, forming a relatively large wet area. If this wet area expands and approaches the ejection port, it affects the ink trajectory when ink is ejected from that port, causing a shift in the application position on the recording medium. As a result, this can lead to image unevenness and a decrease in line quality and character quality. In addition, water droplets falling onto the recording medium or a decrease in the concentration of solid components (such as pigments) in the ink can lead to image defects. Therefore, when recording high-duty images continuously, the recording operation can be temporarily interrupted and the ejection port surface cleaning process can be performed to suppress the decrease in recording quality due to condensation. However, performing the cleaning process significantly reduces user convenience, such as decreasing the productivity of the recording device and causing downtime.

[0044] Next, the temperature control method of the present invention, which solves the condensation that occurs in conventional temperature control, will be explained using Figure 11. Figure 11 is a flowchart showing the variable temperature control method of this embodiment, and corresponds to S103 in Figure 8. This process is performed for each recording element board. The series of processes shown in this flowchart are performed, for example, by the CPU 304 loading the program code described in the ROM 302 into the RAM 303 and executing it. Alternatively, some or all of the functions in Figure 11 may be executed by hardware such as an ASIC, FPGA, or electrical circuit.

[0045] In S301, the printer control unit 203 sets the initial target temperature T1 and the variable temperature control determination temperature T2. Here, T2 is a value used to determine whether the maximum temperature (Tmax) of the acquired temperature is lower than the target temperature (T1). Note that the parameters set here are common values ​​used for multiple recording element boards, and these values ​​are stored in advance in the ROM 302 or similar.

[0046] Since S302 is the same process as S202, the explanation is omitted. Then, the process proceeds to S303. In S303, the printer control unit 203 determines whether Tmax is less than or equal to T2. If the printer control unit 203 determines that Tmax is less than or equal to T2, the process proceeds to S304. If it determines that Tmax is greater than T2, the process returns to S302 and performs the control to obtain the current Tmax again.

[0047] In S304, the printer control unit 203 determines how many consecutive times the state Tmax ≤ T2 has been determined. If the state Tmax ≤ T2 has been determined a number of times equal to a predetermined value N, the process proceeds to S305; otherwise, it returns to S302 and performs the control to obtain the current Tmax again.

[0048] In S305, the printer control unit 203 sets the target temperature to T3 and terminates this flowchart. Note that T3 is a temperature lower than T1, and a value previously stored in ROM 302 or similar may be used. In this case, the printer control unit 203 drives the subheaters among the multiple subheaters provided on the recording element board that correspond to regions where the temperature is below T3 until the temperature in that region reaches T3. Then, the printer control unit 203 drives the subheaters that correspond to regions where the temperature is T3 or higher to maintain the temperature in the corresponding region at T3.

[0049] Through the above process, the highest temperature Tmax inside the recording element substrate is compared with a predetermined temperature (T2). If Tmax is determined to be less than or equal to T2 for a predetermined number of consecutive times (N times), the target temperature is set to T3, which is lower than T1. In other words, when the highest temperature inside the recording element substrate falls below a certain temperature (first temperature), the target temperature is not immediately switched in response. Instead, the timing of the target temperature switch can be slowed down, so that the switch occurs only when the temperature has been determined to be less than or equal to T2 for N consecutive times based on multiple temperature acquisitions. Therefore, even if the highest temperature inside the recording element substrate drops sharply, the target temperature will not drop sharply. As a result, it is possible to suppress the surface of the ejection port after the ejection operation stops due to high-duty image recording from falling below the dew point temperature of the air near the ejection port (Figure 12(b)→(c)). Consequently, the occurrence of condensation on the ejection port surface can be suppressed.

[0050] For each parameter listed in this embodiment, a suitable value can be determined. For example, if the value of N is set too small, the effect of slowing down the timing of switching the target temperature will be reduced. Conversely, if the value is set too large, the effect of the variable temperature control function, which performs temperature control by applying feedback based on the current temperature of the recording element substrate, will be reduced. Therefore, for example, it is preferable to set the time obtained by the product of the temperature acquisition time interval and N to be longer than the non-ejection period, such as between pages during recording, so that the target temperature can be switched based on the temperature information for one page's ejection period. In other words, it is preferable to make the time for switching the target temperature longer than the non-ejection period expected during the recording operation. With such a configuration, it becomes possible to switch the target temperature at an appropriate timing. Specifically, if the temperature acquisition interval is 25 msec and the non-ejection period is 50 msec, this can be achieved by setting N to a value greater than 2.

[0051] <Second Embodiment> This embodiment describes a configuration that suppresses excessive temperature rise of the recording head, reduces power consumption, and suppresses condensation on the ejection port surface of the recording element substrate. The same configuration as in the first embodiment (such as the overall configuration of the recording device) will not be described.

[0052] The variable temperature control according to this embodiment will be explained with reference to Figure 13. Figure 13 is a flowchart of the variable temperature control corresponding to S103 in Figure 8, and this process is performed for each recording element board. The series of processes shown in this flowchart are performed, for example, by the CPU 304 loading the program code described in the ROM 302 into the RAM 303 and executing it. Alternatively, some or all of the functions in Figure 13 may be executed by hardware such as an ASIC, FPGA, or electrical circuit.

[0053] In S401, the printer control unit 203 sets the target temperature T1 and the variable temperature control determination temperatures T2 and T3 (T2>T1>T3). The parameters set here are common values ​​used for multiple recording element boards, and these values ​​are pre-stored in the ROM 302 or similar. The variable temperature control determination temperatures T2 and T3 are threshold temperatures used to determine whether to switch the target temperature maintained for the recording element board. In this embodiment, T2 is a value used to determine whether the highest acquired temperature (Tmax) is higher than the target temperature (T1). T3 is a value used to determine whether the highest acquired temperature (Tmax) is lower than the target temperature (T1).

[0054] Since S402 is the same process as S202 and S302, its explanation is omitted. The process then proceeds to S403. In S403, the printer control unit 203 determines whether Tmax is greater than or equal to T2. If Tmax is greater than or equal to T2, the process proceeds to S404; otherwise, the process returns to S402 and performs the control to obtain the current Tmax again.

[0055] In S404, the printer control unit 203 determines how many consecutive times the state Tmax ≥ T2 has been determined. If the state Tmax ≥ T2 has been determined a number of times equal to a predetermined value N, the unit proceeds to S405; otherwise, it returns to S402 and performs the control to obtain the current Tmax again.

[0056] In S405, the printer control unit 203 sets the target temperature to T4. Here, T4 is a temperature higher than T1. When the target temperature is changed to T4, the printer control unit 203 drives the subheaters among the multiple subheaters provided on the recording element substrate that correspond to regions where the temperature is below T4 until the temperature in those regions reaches T4. Then, the printer control unit 203 drives the subheaters that correspond to regions where the temperature is T4 or higher to maintain the temperature in those regions at T4.

[0057] In S406, the printer control unit 203 determines whether Tmax is less than or equal to T3. If Tmax is less than or equal to T3, the unit returns to S407; otherwise, it returns to S402 and performs the control to obtain the current Tmax again.

[0058] In S407, the printer control unit 203 sets the target temperature to T5. Here, T5 is a temperature lower than T1. When the target temperature is changed to T5, the printer control unit 203 drives the subheaters among the multiple subheaters provided on the recording element substrate that correspond to regions where the temperature is below T5 until the temperature in that region reaches T5. Then, the printer control unit 203 drives the subheaters that correspond to regions where the temperature is T5 or higher to maintain the temperature in the corresponding region at T5.

[0059] Through the above process, the printer control unit 203 compares the highest temperature Tmax in the recording element substrate with a predetermined temperature (T2), and sets the target temperature to T4, which is higher than T1, if it is determined that Tmax is T2 or higher for a predetermined number of consecutive times (N times). The printer control unit 203 also compares the highest temperature Tmax in the recording element substrate with a predetermined temperature (T3), and sets the target temperature to T5, which is lower than T1, if it is determined that Tmax is T3 or lower for a predetermined number of consecutive times (M times). In other words, when the highest temperature in the recording element substrate rises above a certain temperature (second temperature) or falls below a certain temperature (first temperature), the target temperature is not immediately switched in response, but rather the timing of the target temperature switch can be slowed down, such as when it is determined that the temperature is higher for N (M) consecutive times based on multiple temperature acquisitions. Therefore, even if the highest temperature in the recording element substrate rises rapidly, the target temperature does not rise rapidly, and thus unnecessary power consumption can be suppressed.

[0060] Furthermore, even if the maximum temperature inside the recording element substrate drops sharply, the target temperature will not drop sharply, thereby preventing the surface of the ejection port after ejection stops due to high-duty printing from falling below the dew point temperature of the air near the ejection port (Figure 12(b)→(c)). As a result, the occurrence of condensation on the ejection port surface can be suppressed. In addition, as in the first embodiment, suitable values ​​can be determined for each parameter mentioned in this embodiment.

[0061] In this embodiment, N is set to 3 times and M to 6 times, but N and M can be changed as appropriate, specifically to 2 or more times. Increasing the number of times can slow down the timing of the target temperature change, but increasing it too much will increase the processing time. Therefore, it is preferable to keep it to 10 times or less.

[0062] <Other Embodiments> In the first and second embodiments, the highest output value obtained from multiple temperature sensors 701 located at multiple locations on a recording element substrate that is permitted to control temperature is acquired as Tmax. However, the present invention is not limited to the above configuration and can also be applied to a configuration in which only a single temperature sensor is provided on each recording element substrate. In this case, the output value obtained from the temperature sensor is compared with a predetermined temperature. Of course, it can also be applied to a configuration that has only a single recording element substrate.

[0063] Furthermore, the present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by reading and executing one or more processor programs in the computer of that system or device. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0064] This embodiment includes the following configuration and method.

[0065] (Configuration 1) An inkjet recording apparatus comprising: a recording head having a plurality of recording element substrates for ejecting ink; heating means for heating each of the plurality of recording element substrates to a target temperature; acquisition means for acquiring the temperature of a plurality of locations within each of the plurality of recording element substrates multiple times; and control means for comparing the highest temperature of each of the plurality of locations within the recording element substrate acquired by the acquisition means with a first temperature, and lowering the target temperature if it is determined that the highest temperature is lower than the first temperature for a first consecutive time.

[0066] (Configuration 2) The acquisition means is the inkjet recording apparatus described in Configuration 1, provided on the recording element substrate.

[0067] (Configuration 3) An inkjet recording apparatus according to Configuration 1 or 2, wherein the product of the first number of times and the time interval for acquiring the temperature by the acquisition means is longer than the time during which the recording element substrate stops ejecting the ink when a page is switched during the recording operation.

[0068] (Configuration 4) The inkjet recording apparatus according to any one of Configurations 1 to 3, wherein the control means determines that the highest temperature is higher than the second temperature which is higher than the first temperature for a second consecutive number of times.

[0069] (Configuration 5) The inkjet recording apparatus according to any one of Configurations 1 to 4, wherein a plurality of heating means are provided within the recording element substrate.

[0070] (Configuration 6) An inkjet recording apparatus comprising: a recording head having a plurality of recording element substrates for ejecting ink; heating means for heating each of the plurality of recording element substrates to a target temperature; acquisition means for acquiring the temperature inside each of the plurality of recording element substrates multiple times; and control means for lowering the target temperature if, for each of the plurality of recording element substrates, the acquired temperature is determined to be lower than the first temperature for a first consecutive number of times.

[0071] (Method 1) A control method for an inkjet recording apparatus comprising: a recording head having a plurality of recording element substrates for ejecting ink; heating means for heating each of the plurality of recording element substrates to a target temperature; and acquisition means for acquiring the temperature of a plurality of locations within each of the plurality of recording element substrates a plurality of times, wherein for each of the plurality of recording element substrates, the highest temperature of the plurality of locations within the recording element substrate acquired by the acquisition means is compared with a first temperature, and if it is determined that the highest temperature is lower than the first temperature for a first consecutive number of times, the target temperature is lowered. [Explanation of symbols]

[0072] 100 Recording device 101 Recording media 102 Recording head 203 Printer Control Unit 304 CPU 401 Recording element substrate 402 Discharge port

Claims

1. A recording head having multiple recording element substrates for ejecting ink, Each of the plurality of recording element substrates is provided with a heating means for heating the temperature inside the recording element substrate to a target temperature, For each of the plurality of recording element substrates, an acquisition means is provided for acquiring the temperature of multiple locations within the recording element substrate multiple times. For each of the plurality of recording element substrates, the highest temperature of each of the plurality of locations within the recording element substrate acquired by the acquisition means is compared with the first temperature multiple times. An inkjet recording apparatus comprising: a control means for lowering the target temperature if it is determined that the maximum temperature falls below the first temperature for a first consecutive number of times.

2. The inkjet recording apparatus according to claim 1, wherein the acquisition means is provided on the recording element substrate.

3. The inkjet recording apparatus according to claim 1, wherein the product of the first number of times and the time interval for acquiring the temperature by the acquisition means is longer than the time during which the recording element substrate stops ejecting the ink when a page is switched during the recording operation.

4. The inkjet recording apparatus according to claim 1, wherein the control means raises the target temperature when it is determined for a second consecutive number of times that the maximum temperature is higher than the second temperature which is higher than the first temperature.

5. The inkjet recording apparatus according to claim 1, wherein a plurality of heating means are provided within the recording element substrate.

6. A recording head having multiple recording element substrates for ejecting ink, Each of the plurality of recording element substrates is provided with a heating means for heating the temperature inside the recording element substrate to a target temperature, For each of the plurality of recording element substrates, an acquisition means for acquiring the temperature inside the recording element substrate multiple times, For each of the plurality of recording element substrates, the temperature acquired multiple times within the recording element substrate by the acquisition means is compared with the first temperature. An inkjet recording apparatus comprising: a control means for lowering the target temperature if it is determined that the acquired temperature falls below the first temperature for a first consecutive number of times.

7. A recording head having multiple recording element substrates for ejecting ink, Each of the plurality of recording element substrates is provided with a heating means for heating the temperature inside the recording element substrate to a target temperature, A control method for an inkjet recording apparatus comprising acquisition means for acquiring the temperature of multiple locations within each of the multiple recording element substrates multiple times, For each of the plurality of recording element substrates, the highest temperature of each of the plurality of locations within the recording element substrate acquired by the acquisition means is compared with the first temperature. A control method for an inkjet recording apparatus, characterized in that if the highest temperature is determined to be below the first temperature for a first consecutive number of times, the target temperature is lowered.

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