JP2007152583A - Recorder and method for detecting ink ejection state - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting ink ejection state without wasting a recording medium or ink, and to provide a recorder. <P>SOLUTION: The recorder is constituted to record an image on a recording medium by inputting a drive signal to a recording head equipped with a plurality of recording elements thereby driving the recording head to eject ink liquid drops from the nozzles in the recording head. In such a recorder, an induction current is generated from an electromagnetic field which varies according to the state of ink ejected from the recording head by means of a loop provided on the back of a platen for mounting the recording medium oppositely to the ink ejection plane of the recording head. Subsequently, magnetic field strength is detected from the generated induction current and compared with a predetermined threshold, and then ejection state of ink is judged based on the comparison results. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a recording apparatus and an ink discharge state detection method, and more particularly to a recording apparatus including a recording head that performs recording in accordance with an ink jet method and an ink discharge state detection method applied to the apparatus.

  2. Description of the Related Art Conventionally, various countermeasures have been taken in an ink jet recording apparatus (hereinafter referred to as a recording apparatus) in order to prevent ink ejection failure and twist from an ink jet recording head (hereinafter referred to as a recording head). The ink ejection failure or misalignment may occur suddenly due to internal or external factors such as bubbles or dust during continuous ink ejection, or increase in ink viscosity or ink sticking after long-term unused Some things happen sometimes. As a specific countermeasure for preventing these problems, a recording apparatus is provided with a head refreshing mechanism, and various patterns are recorded before, during, or during the ejection of ink for image formation. However, every time this mechanism is operated, valuable ink for image formation is discharged.

  Further, when an ink ejection failure suddenly occurs in the recording operation for some reason, the recording medium may be wasted.

  On the other hand, the level required for electrical design, mechanism design, process design, head design, etc. in pursuit of ink ejection stability is increasing in order to maintain and improve the ejection performance of the recording head, which is highly accurate every day. . As a result, the amount of ink introduced from the ink supply source to the common liquid chamber and the flow of ink from the common liquid chamber to the discharge section is different for each discharge nozzle and each discharge nozzle as long as normal ink discharge is performed. It is known that it is infinitely stable with blocks.

  On the other hand, the flow of ink inside the nozzle is subtly hindered due to bubbles and dust from inside and outside, and damage to the recording element, and the cause of the subsequent inhibition of ink flow due to the above factors (cause) ) May be produced in the nozzle. It has been clarified in experiments and computer simulations that a turbulent ink flow occurs in the nozzle in such a state as compared with a nozzle in a normal ink ejection state.

Now, in order to prevent the occurrence of ink ejection failure or deviation from affecting the actual recording, a technology for detecting ink ejection failure from the recording head has been developed, and many proposals have been made so far. For example, Patent Document 1 proposes to improve the detection accuracy by controlling the number of ejected dots when detecting an ink ejection failure based on the number of ink ejections. When a photo interrupter sensor is used, light is emitted from the light emitting element to the light receiving element, ink is ejected so as to block the optical axis, ink is present when the optical axis is blocked, and the optical axis is not blocked A method for determining that no ink is available has also been proposed.
JP-A-11-227174

  However, the conventional ink ejection failure detection technology detects the ink that has exited the ejection port and feeds back the result to the subsequent recording control. As described above, it still discharges valuable ink. It is accompanied. At present, there are few means capable of detecting an ink ejection failure without using ink ejection, and no invention has been made to predict ink ejection failure.

  Therefore, a measure to take measures before an ink ejection instability occurs during a recording operation for some reason and subsequent misalignment or ejection failure occurs, thereby returning the ink ejection to a normal state without wasteing the recording medium or ink. Is desired.

  The present invention has been made in view of the above-described conventional example, and an object thereof is to provide an ink discharge state detection method and a recording apparatus capable of detecting an ink discharge state without wasting a recording medium or ink. .

  In order to achieve the above object, the recording apparatus of the present invention has the following configuration.

  That is, recording is performed in which a drive signal is input to a recording head including a plurality of recording elements and ink droplets are ejected from the nozzles of the recording head by driving the plurality of recording elements to record an image on a recording medium. An apparatus is provided on the back surface of the platen that faces the ink ejection surface of the recording head and the platen on which the recording medium is placed, and changes according to the ejection state of the ink ejected from the recording head. A loop for generating an induced current due to a change in electromagnetic field; a detecting means for detecting a magnetic field intensity from the induced current generated by the loop; and a comparing means for comparing the magnetic field intensity detected by the detecting means with a predetermined threshold value And determination means for determining the ink ejection state based on the comparison result by the comparison means.

  Here, when a recording signal is input to the recording head at a frequency of several to several tens of KHz, ultra long wave electromagnetic waves are generated from the plurality of recording elements. The propagation direction of the electromagnetic wave changes with the ink ejection state.

  In this recording apparatus, the magnetic flux of the electromagnetic wave traverses a region formed by the loop. In this case, when the ink ejection state is normal, the traveling direction of the electromagnetic wave is perpendicular to the region, whereas when the ink ejection state is unstable, the traveling direction of the electromagnetic wave is the region. Lean against.

  Furthermore, it is desirable to have a recovery control means for controlling the recovery operation of the recording head according to the determination result by the determination means.

  The plurality of recording elements may be electrothermal transducers or electromechanical transducers.

  According to another invention, a drive signal is input to a recording head having a plurality of recording elements, and ink droplets are ejected from the nozzles of the recording head by driving the plurality of recording elements. An ink discharge state detection method for a recording apparatus for recording an image on an ink discharge step of applying a drive signal to the recording head to discharge ink, and facing the ink discharge surface of the recording head, the recording medium A current generation step for generating an induced current from an electromagnetic field that changes in accordance with the ejection state of the ink ejected from the recording head, and an induction generated in the current generation step A detection step for detecting a magnetic field intensity from an electric current; a comparison step for comparing the magnetic field strength detected in the detection step with a predetermined threshold; and the comparison process. Based on the comparison result by, comprising an ink discharge status detection method characterized by comprising a determination step of determining ejection state of the ink.

  Therefore, according to the present invention, it is possible to detect the ink discharge state from the recording head without wastefully using ink. Thereby, the ink can be effectively used for original image recording.

  Further, it is possible to maintain good recording by detecting that the ink ejection state is poor and performing, for example, a recovery operation of the recording head. As a result, the recording medium is not wasted due to recording failure.

  Furthermore, since the amount of ink to be discarded can be reduced by, for example, about 20 to 30%, the size of the waste ink tank for storing the ink can be reduced, which contributes to the reduction in the size of the recording apparatus main body. .

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  In this specification, “recording” (sometimes referred to as “printing”) does not represent only the case of forming significant information such as characters and graphics. In addition to this, an image, a pattern, a pattern, or the like is widely formed on a recording medium regardless of whether it is significant involuntary, or whether it is manifested so that a human can perceive it visually, or It also represents the case where the medium is processed.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Further, “ink” (sometimes referred to as “liquid”) should be interpreted widely as in the definition of “recording (printing)”. That is, by being applied on the recording medium, it is used for forming an image, pattern, pattern, etc., processing the recording medium, or processing the ink (for example, solidification or insolubilization of the colorant in the ink applied to the recording medium). It shall represent a liquid that can be made.

  Furthermore, unless otherwise specified, the “nozzle” collectively refers to an ejection port or a liquid channel communicating with the ejection port and an element that generates energy used for ink ejection.

<Description of Inkjet Recording Apparatus (FIG. 1)>
FIG. 1 is an external perspective view showing an outline of the configuration of an ink jet recording apparatus 1 which is a typical embodiment of the present invention.

  As shown in FIG. 1, an ink jet recording apparatus (hereinafter referred to as a recording apparatus) has a recording head 3 mounted on a carriage 2 for performing recording by discharging ink according to an ink jet system. A driving force generated by the carriage motor M1 is transmitted to the carriage 2 from the transmission mechanism 4, and the carriage 2 is reciprocated in the arrow A direction. At the time of recording, for example, a recording medium P such as recording paper is fed through the paper feeding mechanism 5 and conveyed to a recording position, and recording is performed by ejecting ink from the recording head 3 to the recording medium P at the recording position. Do.

  Further, in order to maintain the state of the recording head 3 satisfactorily, the carriage 2 is moved to the position of the recovery device 10 and the ejection recovery process of the recording head 3 is intermittently performed.

  In addition to mounting the recording head 3 on the carriage 2 of the recording apparatus 1, an ink cartridge 6 for storing ink to be supplied to the recording head 3 is mounted. The ink cartridge 6 is detachable from the carriage 2.

  The recording apparatus 1 shown in FIG. 1 is capable of color recording. For this reason, the carriage 2 contains four inks containing magenta (M), cyan (C), yellow (Y), and black (K) inks, respectively. An ink cartridge is installed. These four ink cartridges are detachable independently.

  Now, the carriage 2 and the recording head 3 can achieve and maintain a required electrical connection by properly contacting the joint surfaces of both members. The recording head 3 applies energy according to a recording signal to selectively eject ink from a plurality of ejection ports for recording. In particular, the recording head 3 of this embodiment employs an ink jet system that ejects ink using thermal energy. For this reason, the recording head 3 is provided with an electrothermal transducer for generating thermal energy. The electrical energy applied to the electrothermal converter is converted to thermal energy, and the ink is ejected from the discharge port using the pressure change caused by the growth and contraction of bubbles caused by film boiling caused by applying the thermal energy to the ink. To discharge. The electrothermal transducer is provided corresponding to each of the ejection ports, and ink is ejected from the corresponding ejection port by applying a pulse voltage to the corresponding electrothermal transducer in accordance with the recording signal.

  As shown in FIG. 1, the carriage 2 is connected to a part of the driving belt 7 of the transmission mechanism 4 that transmits the driving force of the carriage motor M <b> 1, and slides in the direction of arrow A along the guide shaft 13. It is guided and supported freely. Accordingly, the carriage 2 reciprocates along the guide shaft 13 by forward and reverse rotation of the carriage motor M1. A scale 8 is provided for indicating the absolute position of the carriage 2 along the direction of movement of the carriage 2 (the direction of arrow A). In this embodiment, the scale 8 uses a transparent PET film on which black bars are printed at the necessary pitch, one of which is fixed to the chassis 9 and the other is supported by a leaf spring (not shown). Yes.

  Further, the recording apparatus 1 is provided with a platen (not shown) facing the discharge port surface where the discharge port (not shown) of the recording head 3 is formed. Then, the carriage 2 on which the recording head 3 is mounted is reciprocated by the driving force of the carriage motor M1, and at the same time, a recording signal is given to the recording head 3 to eject ink, thereby conveying the recording medium P conveyed onto the platen. Recording is performed over the full width.

  Further, in FIG. 1, reference numeral 14 denotes a conveyance roller driven by a conveyance motor M2 to convey the recording medium P, and 15 denotes a pinch roller that abuts the recording medium P against the conveyance roller 14 by a spring (not shown). Reference numeral 16 denotes a pinch roller holder that rotatably supports the pinch roller 15, and reference numeral 17 denotes a conveyance roller gear fixed to one end of the conveyance roller 14. Then, the transport roller 14 is driven by the rotation of the transport motor M2 transmitted to the transport roller gear 17 through an intermediate gear (not shown).

  Further, reference numeral 20 denotes a discharge roller for discharging the recording medium P on which an image is formed by the recording head 3 to the outside of the recording apparatus, and is driven by transmitting the rotation of the transport motor M2. . The discharge roller 20 abuts on a spur roller (not shown) that presses the recording medium P by a spring (not shown). Reference numeral 22 denotes a spur holder that rotatably supports the spur roller.

  Furthermore, the recording apparatus 1 includes a recording head at a desired position (for example, a position corresponding to the home position) outside the range of reciprocal motion for recording operation of the carriage 2 on which the recording head 3 is mounted (outside the recording area). A recovery device 10 for recovering the ejection failure 3 is provided.

  The recovery device 10 includes a capping mechanism 11 for capping the ejection port surface of the recording head 3 and a wiping mechanism 12 for cleaning the ejection port surface of the recording head 3. In conjunction with capping of the ejection port surface by the capping mechanism 11, ink is forcibly discharged from the ejection port by a suction means (suction pump or the like) in the recovery device, and the viscosity in the ink flow path of the recording head 3 is increased. The ejection recovery process such as removing the ink and bubbles is performed.

  Further, when the recording head 3 is not in operation or the like, the ejection port surface of the recording head 3 is capped by the capping mechanism 11 to protect the recording head 3 and to prevent ink evaporation and drying. On the other hand, the wiping mechanism 12 is disposed in the vicinity of the capping mechanism 11 and wipes ink droplets adhering to the ejection port surface of the recording head 3.

  The capping mechanism 11 and the wiping mechanism 12 can keep the ink ejection state of the recording head 3 normal.

<Control Configuration of Inkjet Recording Apparatus (FIG. 2)>
FIG. 2 is a block diagram showing a control configuration of the recording apparatus shown in FIG.

  As shown in FIG. 2, the controller 600 includes an MPU 601, a ROM 602, a special purpose integrated circuit (ASIC) 603, a RAM 604, a system bus 605, an A / D converter 606, and the like. Here, the ROM 602 stores a program corresponding to a control sequence to be described later, a required table, and other fixed data. The ASIC 603 generates control signals for controlling the carriage motor M1, the transport motor M2, and the recording head 3. The RAM 604 is used as a development area for image data, a work area for program execution, and the like. A system bus 605 connects the MPU 601, the ASIC 603, and the RAM 604 to each other to exchange data. The A / D converter 606 inputs analog signals from the sensor group described below, performs A / D conversion, and supplies a digital signal to the MPU 601.

  In FIG. 2, reference numeral 610 denotes a computer (or a reader for image reading, a digital camera, etc.) serving as a supply source of image data, and is collectively referred to as a host device. Image data, commands, status signals, and the like are transmitted and received between the host apparatus 610 and the recording apparatus 1 via an interface (I / F) 611.

  Reference numeral 620 denotes a switch group, which includes a power switch 621, a print switch 622, a recovery switch 623, and the like. The print switch 622 is used for instructing the start of printing. The recovery switch 623 is used to instruct the start of processing (recovery processing) for maintaining the ink ejection performance of the recording head 3 in a good state. These switches are used to receive command inputs from the operator.

  Reference numeral 630 denotes a sensor group for detecting the apparatus state, and includes a position sensor 631, a temperature sensor 632, and the like. The position sensor 631 is a sensor for detecting a home position h such as a photocoupler, and the temperature sensor 632 is a sensor provided at an appropriate position of the recording apparatus and used for detecting an environmental temperature.

  Further, 640 is a carriage motor driver that drives a carriage motor M1 for reciprocating scanning of the carriage 2 in the direction of arrow A, and 642 is a conveyance motor driver that drives a conveyance motor M2 for conveying the recording medium P. Further, reference numeral 644 denotes a carriage substrate mounted on the carriage 2, which electrically connects the recording head 3 to supply power from the recording apparatus and transfer an image signal and a control signal.

  Furthermore, reference numeral 650 denotes a power supply unit that supplies necessary power to each unit of the recording apparatus.

  Next, an embodiment in which the ink discharge state detection method according to the present invention is applied to the recording apparatus having the above configuration will be described.

  First, the principle of the ink discharge state detection method according to this embodiment will be described.

  FIG. 3 is a schematic diagram showing how ink is normally ejected from the recording head.

  Usually, the driving frequency of the recording head 3 is in the range of several to several tens KHz, and a pulse current flows through the recording element (heater) provided in the nozzle of the recording head at this frequency, and the recording is performed according to this current. Electromagnetic waves are generated from the element. This electromagnetic wave is a so-called very low frequency (Very Low Frequency), and most of the electromagnetic field emitted from the drive source for ejection is a VLF wave.

  FIG. 4 is a schematic diagram showing a state of an electromagnetic field generated along with ink ejection.

  As shown in FIG. 3, when the ink is normally ejected from the recording head 3, as shown in FIG. 4A, the nozzle acts as a waveguide with respect to the electromagnetic wave. That is, there is an electromagnetic field that propagates in the same direction as the ink ejection direction in a general waveguide mode due to electromagnetic waves that propagate while reflecting off the nozzle wall. This electromagnetic field propagates at a speed almost equal to the speed of light traveling in the vacuum at the moment when the drive voltage is applied to the recording element (heater) of the recording head. The schematic diagram of FIG. 4A represents a state in which an electric field and a magnetic field are orthogonal and travel as a transverse wave.

  In this embodiment, in order to achieve miniaturization, micro magnetic field probes 100 having loops in which conductors are formed by etching on a substrate are arranged in a line in the carriage moving direction on the platen of the recording apparatus. FIG. 4B shows the arrangement cross section together with the cross section of the recording medium P and the platen, and FIG. 4C shows the micro magnetic field probe 100 viewed from a direction perpendicular to the cross section.

  The inner portion of the loop of the micro magnetic field probe 100, that is, the region through which the magnetic flux (flux of magnetic lines) from the recording head 3 penetrates is a region of 2.5 mm × 15 mm in this embodiment. This dimension is determined with a margin so that an electromagnetic field having the same direction as that of a normally flying ink droplet can pass through the number of nozzles in the nozzle row direction. By detecting the induced current I (FIG. 4C) generated by the electromagnetic field passing through the minute magnetic field probe 100, the magnetic field strength of the electromagnetic field (the number of magnetic lines passing through the probe) can be determined.

  When ink is normally ejected, the electromagnetic wave travels in a direction perpendicular to a region inside the loop formed by the loop.

  5 to 6 are block diagrams showing the configuration of the ink discharge state detection circuit according to this embodiment. As shown in FIG. 5, the induced current generated by the minute magnetic field probe 100 is averaged by the averaging circuit 101, and the OR circuit 102 takes the logical sum of the induced currents obtained from the plurality of minute magnetic field probes. The calculation result is sent to the magnetic field strength detection circuit 103, and the detection result is expressed by a value in mG (milli gamma) unit and sent to the unstable ejection determination circuit (comparator) 105. The unstable ejection determination circuit (comparator) 105 determines the difference between the magnetic field strength at the time of normal ink ejection and the obtained magnetic field strength. A detection signal from the magnetic field intensity detection circuit 103 is input to the a terminal (+ side) of the comparator. FIG. 6 shows a detailed circuit configuration of the magnetic field strength detection circuit 103.

  5 to 6, the magnetic field probe 100 directly under the recording medium P detects an electromagnetic field generated when the recording head 3 is driven as the carriage 2 moves. As shown in FIG. 4, the micro magnetic field probe 100 is arranged in a plurality of rows on the platen, and any one of the probes can detect an electromagnetic field emitted from the recording head being driven. .

  FIGS. 7 and 8 are diagrams schematically showing a state in which an electromagnetic field is disturbed in a state immediately before an unstable ink ejection that occurs suddenly when the recording head is driven and an unstable ink ejection state, respectively.

  FIG. 9 is a diagram schematically showing a state in which an electromagnetic field is disturbed at a nozzle that has failed to eject ink due to damage to a recording element or the like.

  As can be seen from a comparison of FIGS. 7 to 9, when the ink discharge becomes unstable, the propagation direction of the electromagnetic field emitted from the recording element changes compared to that in the normal discharge. Compared with the case where ink is normally ejected as shown in FIGS. 4 to 5, the propagation direction of the electromagnetic wave changes, and the propagation direction is inclined with respect to the region formed by the loop of the minute magnetic field probe. As a result, the electromagnetic field intensity received by the minute magnetic field probe 100 changes.

  This phenomenon is due to the difference that the flow of ink as a medium through which the electromagnetic field propagates is laminar in normal ejection, turbulent in unstable, and air in the non-ejection state is air. This is caused by the property that the traveling direction of the light is slightly refracted. A subtle shift in the traveling direction of the electromagnetic wave becomes a difference in the number of magnetic lines of force that pass through the micro magnetic field probe, thereby changing the magnetic field strength.

  FIG. 10 is a diagram showing an actual input value to the unstable discharge determination circuit 105. In FIG.

  In FIG. 10, the bold and thin solid line portions in the graph represent the time change of the magnetic field strength during carriage movement. According to FIG. 10, there is a clear difference between the magnetic field strength during normal ink ejection and that during unstable ink ejection. Therefore, by monitoring the change in the magnetic field strength averaged over an appropriate time, the ink ejection state changes from a normal state to an unstable state, and it is predicted that an ink ejection failure will occur from this tendency. It becomes possible.

  Therefore, when this ink discharge state detection method is used, the following recording control becomes possible.

  FIG. 11 is a flowchart showing recording control with ink discharge state detection.

  That is, in step S10, ink is ejected from the recording head 3 along with the recording operation. Subsequently, in step S20, the induced current (I) is detected by the micro magnetic field probe 100. Further, in step S30, the induced current is averaged over a certain time in the averaging circuit 101, and the magnetic field strength detection circuit 103 detects the magnetic field strength (H) from the induced current detected by any of the plurality of averaging circuits.

  Next, in step S40, a signal representing the magnetic field strength (H) is input to the unstable ejection determination circuit (comparator) 105, and this is compared with a predetermined threshold value (Th). Here, if H ≧ Th, it is determined that ink ejection is normally performed, and the process returns to step S10 to continue the recording operation. On the other hand, if H <Th, it is determined that the ink ejection is unstable, and the process proceeds to step S50 to execute the recovery operation of the recording head. Since this recovery operation is publicly known, a description thereof is omitted here.

  After the recovery operation is completed, the process returns to step S10.

  The micro magnetic field probe 100 uses a probe that is sensitive to an electromagnetic field formed by an electromagnetic wave in the so-called VLF frequency band in the range of the drive frequency of the recording head 3 to 20 KHz, and does not pick up other frequency components that cause noise. Needless to say, a magnetic field measurement when driving at a higher frequency than this must use a loop probe whose sensitivity improves with frequency.

  Therefore, according to the embodiment described above, by monitoring the change in the magnetic field strength, it is predicted that the ink ejection state changes from the normal state to the unstable state, and the ink ejection failure occurs from the tendency. It becomes possible.

  Further, since the ink discharge state detection according to this embodiment is not accompanied by ink discharge for this detection and can be performed by ink discharge accompanying a normal recording operation, valuable ink resources can be effectively used for actual recording. Can do. Furthermore, since it is possible to accurately grasp the ink ejection state, it is possible to reduce the frequency of the recovery operation of the recording head, so that it is possible to reduce ink consumption accompanying the recovery operation.

  In the above embodiment, an example in which a heater is used as the recording element has been described. However, the present invention can be applied even if an electromechanical transducer (piezo) element is used as the recording element. The same verification as described above was attempted using a recording head having a drive frequency of -10 KHz using a piezo element. According to the verification result, an average value of 4 mG at a certain time was found between the magnetic field strength during normal ink ejection and the magnetic field strength during unstable ink ejection.

  Accordingly, the threshold value of the magnetic field strength set on the (−) side of the unstable ejection determination circuit is set to 3.5 mG, and control is performed so that the recording head recovers when the difference in magnetic field strength exceeds this value. Then good results can be obtained. Specifically, it becomes possible to complete the recording without ejection failure or twist until the end of the page without entering the recovery operation in the middle of recording and discharging the recording medium in the ink ejection failure state from the apparatus. When the recording apparatus is configured not to perform the recovery operation at a timing other than the recording operation, the amount of waste ink can be reduced by 30% compared to the conventional case.

  In the above embodiments, the liquid droplets ejected from the recording head are described as ink, and the liquid stored in the ink tank is described as ink. However, the storage is limited to ink. It is not a thing. For example, a treatment liquid discharged to the recording medium may be accommodated in the ink tank in order to improve the fixability and water resistance of the recorded image or to improve the image quality.

  The above embodiments are provided with means (for example, an electrothermal converter, a laser beam, etc.) for generating thermal energy as energy used for performing ink ejection, particularly in the ink jet recording system. The thermal energy causes a change in the state of the ink, thereby achieving high recording density and high definition.

1 is an external perspective view showing an outline of a configuration of an inkjet recording apparatus 1 that is a typical embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the recording apparatus illustrated in FIG. 1. FIG. 4 is a schematic diagram illustrating a state in which ink is normally ejected from a recording head. It is a schematic diagram which shows the mode of the electromagnetic field which generate | occur | produces with ink discharge. , 3 is a block diagram illustrating a configuration of an ink discharge state detection circuit. FIG. FIG. 6 is a diagram schematically illustrating a state in which an electromagnetic field is disturbed in a state immediately before an unstable ink discharge that occurs suddenly when a recording head is driven. It is the figure which showed typically the state where the electromagnetic field is disturb | confused in an ink discharge unstable state. FIG. 6 is a diagram schematically illustrating a state in which an electromagnetic field is disturbed at a nozzle that has failed to eject ink due to damage to a recording element or the like. It is a figure which shows the actual input value to the unstable discharge determination circuit 105. 6 is a flowchart illustrating recording control with ink discharge state detection.

Explanation of symbols

3 Recording head 601 MPU
603 ASIC
604 RAM
610 Host device

Claims (8)

A recording apparatus that records an image on a recording medium by inputting a drive signal to a recording head including a plurality of recording elements and ejecting ink droplets from nozzles of the recording head by driving the plurality of recording elements. There,
A platen on which the recording medium is placed;
A loop that opposes the ink ejection surface of the recording head and is provided on the back surface of the platen, and that generates an induced current due to a change in electromagnetic field that varies with the ejection state of the ink ejected from the recording head;
Detecting means for detecting magnetic field intensity from the induced current generated by the loop;
Comparison means for comparing the magnetic field intensity detected by the detection means with a predetermined threshold;
A recording apparatus comprising: a determination unit that determines a discharge state of the ink based on a comparison result by the comparison unit.   The recording apparatus according to claim 1, wherein a recording signal is input to the recording head at a frequency of several to several tens of KHz, so that an ultra long wave electromagnetic wave is generated from the plurality of recording elements.   The recording apparatus according to claim 2, wherein the propagation direction of the electromagnetic wave changes according to a discharge state of the ink.   The recording apparatus according to claim 3, wherein the magnetic flux of the electromagnetic wave traverses an area formed by the loop. When the ink ejection state is normal, the traveling direction of the electromagnetic wave is perpendicular to the region,
The recording apparatus according to claim 4, wherein the traveling direction of the electromagnetic wave is inclined with respect to the region when the ink ejection state is unstable.   The recording apparatus according to claim 1, further comprising a recovery control unit configured to control the recovery operation of the recording head according to a determination result by the determination unit. The recording apparatus according to claim 1, wherein the plurality of recording elements are electrothermal transducers or electromechanical transducers. A recording apparatus for recording an image on a recording medium by inputting a drive signal to a recording head including a plurality of recording elements and ejecting ink droplets from nozzles of the recording head by driving the plurality of recording elements. An ink discharge state detection method comprising:
An ink ejection step of ejecting ink by applying a drive signal to the recording head;
An induced current is generated from an electromagnetic field that changes in accordance with the ejection state of the ink ejected from the recording head by a loop provided on the back surface of the platen on which the recording medium is placed, facing the ink ejection surface of the recording head. Current generation process to
A detection step of detecting the magnetic field intensity from the induced current generated in the current generation step;
A comparison step of comparing the magnetic field intensity detected in the detection step with a predetermined threshold;
A determination step of determining the ink discharge state based on a comparison result of the comparison step.

Images