JP2006187981A - Discharge sensing means - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a discharge sensing accuracy from decreasing by performing an adjustment of a light-receiving/emitting section prior to an actual discharge sensing. <P>SOLUTION: This discharge sensing means senses an ink droplet discharging state of an inkjet recording device equipped with a recording head. The discharge sensing means comprises a light emitting means which irradiates a beam, a light receiving means which receives the beam, a light emission controlling section which feeds a driving current for driving the light emitting means, and a detecting section which picks up an output level from the light receiving means. Before the discharge of ink droplets is performed, the beam is emitted, and the adjusting motion for the driving current is performed in such a manner that the output level from the detecting section may become a predetermined reference value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording apparatus and an ink discharge state detection method, and more particularly, to a recording apparatus that performs recording on a recording medium from a recording head having a plurality of ink discharge nozzles that discharge ink according to an inkjet method, and the recording apparatus. The present invention relates to an ink discharge state detection method.

  In a printer using a recording head according to an ink jet system, an image is formed by directly discharging ink onto a recording medium from a fine ink discharge nozzle provided in the recording head. Therefore, impurities (dust) are mixed in the ink discharge nozzle, the ink is stuck on the ink discharge surface of the recording head, etc., or the ink discharge nozzle is clogged, or the ink is heated by a heater to cause film boiling. When ink is ejected by pressure, ink ejection failure occurs due to disconnection of the heater, etc., and white streaks due to non-ejection of the ink occur in the recorded image, which may deteriorate the quality of the recorded image.

  In order to solve such problems, various improvements have been attempted. For example, the ink discharge from the recording head is stopped at a predetermined position so as to cross the beam light of the optical sensor, the ink is discharged so as to cross the beam light, and the defective nozzle is detected from the output of the optical sensor. A configured device has also been proposed. In the case of a color printer, a plurality of recording heads are mounted corresponding to the number of ink colors. Therefore, the plurality of recording heads are sequentially stopped at their predetermined positions in order to eject ink. Become.

  For example, Patent Document 1 proposes a method for detecting the presence or absence of ink for each nozzle of a plurality of nozzles arranged in an ink jet recording head. That is, in the case of the method, a light emitting means for irradiating one end of the scanning path with a light beam and a light receiving means for receiving the light beam, and ink droplets ejected from a plurality of recording heads are the light beams. The light reception state changes when the signal is cut off. The presence or absence of ink is detected based on the magnitude of the change.

Japanese Patent Laid-Open No. 11-17984

  As a light emitting source of such an image recording apparatus, in general, from the viewpoint of being inexpensive and small, a light emitting diode (hereinafter referred to as LED), a semiconductor laser (hereinafter referred to as LD), A light emitting element such as an LD excitation solid-state laser is often used. For the same reason, photodiodes are often used as light receiving / receiving light sources.

  However, the light receiving unit and the light emitting unit are not always kept in a constant state due to changes in ambient conditions and changes over time. For example, in the light emitting section, what is used as a light emitting source generally has a temperature dependency, and in particular, the light emission amount (output level) of a laser light source that is amplified by a resonator and laser-oscillated like an LD-pumped solid-state laser. ) Is characterized by large fluctuations even with slight temperature changes.

  In addition, since both LED and LD change with time, the light emission amount gradually changes even if the drive current is constant. Also in the light receiving unit, mist generated by the ink ejection operation adheres to the light emitting surface or the light receiving surface, so that the light receiving amount decreases even with the same light emitting amount. In this way, even if the light emitting source is driven under the same conditions, the output result on the light receiving side varies. This means that even when ink droplet ejection detection is performed, the results vary, which causes a decrease in detection accuracy. In some cases, there is a risk of false detection.

  The present invention has been made paying attention to the above-mentioned problems of the prior art, and an object thereof is to adjust the light emitting / receiving section before actual discharge detection to prevent a decrease in discharge detection accuracy.

  In order to achieve the above object, according to the present invention, there is provided a discharge detecting means for detecting an ink droplet discharge state of an ink jet recording apparatus provided with a recording head, a light emitting means for irradiating beam light, and a light receiving means for receiving the beam light. And a light emission control unit that supplies a drive current for driving the light emitting unit, and a detection unit that picks up an output level from the light receiving unit, and emits the beam light before discharging the ink droplets, The drive current adjustment operation is performed so that the output level of the detection unit becomes a predetermined reference value.

  According to the present invention, by adjusting the light emitting / receiving unit before the actual discharge detection, a change in the light emission amount due to a temperature change of the light receiving unit or a change over time, or a foreign matter due to mist or the like in the light receiving unit or the light emitting unit. It is possible to absorb variations in the detection level caused by a decrease in the light reception level due to adhesion, and to prevent a decrease in detection accuracy.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a three-dimensional perspective view showing a detailed configuration of a printer including a recording head that performs recording in accordance with an ink jet system that is a representative embodiment of the present invention.

  As shown in FIG. 1, the recording head 5 is a cartridge-type recording head that can be replaced with a new recording head when the head life is reached.

  In FIG. 1, a carriage 15 reciprocates in a direction (main scanning direction, arrow H direction) orthogonal to the conveyance direction (sub-scanning direction, arrow G direction) of the recording paper P while holding the recording head 5 with high accuracy. . The carriage 15 is slidably held by the guide rod 16 and the abutting portion 15a. The carriage 15 is reciprocated by a pulley 17 and a timing belt 18 that are driven by a carriage motor (not shown). At this time, a recording signal and electric power supplied to the recording head 5 are supplied to the electric power of the apparatus main body by a flexible cable 19. It is supplied from the circuit. The recording head 5 and the flexible cable 19 are connected by press contact with each other.

  Further, a cap 20 is provided at the home position of the carriage 15 to function as an ink receiver. The cap 20 moves up and down as necessary. When the cap 20 is raised, the cap 20 is in close contact with the recording head 5 and covers the nozzle portion to prevent ink evaporation and dust adhesion.

  By the way, in this apparatus, in order to position the recording head 5 and the cap 20 so as to be relatively opposed to each other, a carriage home sensor 21 provided in the apparatus main body and a light shielding plate 15b provided in the carriage 15 are provided. It is used. The carriage home sensor 21 uses a transmissive photo interrupter. When the carriage 15 moves to the standby position, the light irradiated from a part of the carriage home sensor 21 is blocked by the light shielding plate 15b. Is used to detect that the recording head 5 and the cap 20 are in a relatively opposed position.

  The recording paper P is fed upward from the lower side in the figure, is bent in the horizontal direction by the feeding roller 2 and the paper guide 22, and is conveyed in the arrow G direction (sub-scanning direction). The feeding roller 2 and the paper discharge roller 6 are respectively driven by a recording motor (not shown), and transport the recording paper P in the sub-scanning direction with high accuracy in conjunction with the reciprocating movement of the carriage 15 as necessary.

  Further, a spur 23 that is made of a material having high water repellency in the sub-scanning direction and that contacts the recording paper P only by its blade-shaped circumferential portion is provided. The spurs 23 are disposed at a plurality of locations at a position facing the paper discharge roller 6 and spaced apart by a predetermined length in the main scanning direction by the bearing member 23a, and even if they contact an unfixed image on the recording paper immediately after recording. The recording paper P is guided and conveyed without affecting the image.

  As shown in FIG. 2, the photo sensor 8 is disposed between the cap 20 and the end of the recording paper P at a position facing the nozzle row 5 c of the recording head 5, and is ejected from the nozzles of the recording head 5. It is a transmissive photointerrupter that directly optically detects drops.

  FIG. 2 is an enlarged perspective view showing a detailed configuration near the photo sensor of the printer shown in FIG.

  The photosensor 8 used here uses an infrared LED as the light emitting element 81, a lens is integrally formed on the LED light emitting surface, and the beam light 83 can be projected almost in parallel toward the light receiving element 82. A phototransistor is used for the light receiving element 82.

  In FIG. 2, P1 is an area where recording has already been performed on the recording paper P, P2 is an area where recording will be performed from now on, S1, S2, and Sn are the drop trajectories of ink droplets ejected from the recording head. Reference numeral 71 denotes a scale attached in parallel along the moving direction of the recording head 5, and 72 denotes a linear encoder attached to the recording head 5.

  During the movement of the recording head 5, the linear encoder 72 detects the position of the recording head 5 by reading the scale 71. This position serves as a reference for image recording and also serves as reference information for detecting a defective nozzle described later.

  The member 84 is a member that receives ink droplets ejected for detecting defective nozzles, and is attached to the support base 85. Although not shown, a small amount of cleaning water is intermittently poured into the member 84. The ink is discharged together with the water by a suction pump (not shown).

  FIG. 3 shows the structure of an ink drop detector that uses a digital signal processing element in the printer together with an analog sensing element in the printer shown in FIG.

  The digital signal processing element includes a peak detector 32, a printer processor 36 and a memory 35. The analog sensing element includes a light emitting unit 81, a light receiving unit 82, a band pass filter (BPF) 30, and a sensitivity amplifier 31.

  Next, how the actual ink droplet detection operation is performed in the above detection system will be described below.

  First, discharge for state detection is performed from the recording head 5 by a control signal 60 (FIG. 4A) from the discharge controller 37. The light beam 83 emitted from the light emitting element 81 toward the light receiving element 82 is blocked by ink droplets sequentially ejected from the nozzles provided in the recording head 5. This light shielding is detected by a change in the light receiving output of the light receiving element 82, and the ink droplet ejection state of each nozzle is determined. The BPF 30 is a filter for improving the S / N ratio of the detection signal obtained from the output of the light receiving element 82, and noise is removed and shaped.

  However, since it is a weak signal with a low voltage level in the shaped state, it is not suitable for processing by the printer processor 36 as it is. Therefore, the sensitivity amplifier 31 amplifies the signal. The signal waveform after passing through the BPF 30 and amplified is shown in FIG. The amplified signal (FIG. 4-b) is supplied to the peak detector 32. The peak detector 32 holds and outputs the peak value of the amplified signal (FIG. 4-b). The held peak waveform (FIG. 4-c) is converted into an output value (FIG. 4-e) digitized by the A / D converter 33.

  Then, the discharge controller 37 sends a latch signal (FIG. 4-g) to the F / F (flip-flop) 34 to temporarily hold the digitized output. The print processor 36 reads the latched data (FIG. 4G) and stores it in the memory 35. Thereafter, the discharge controller sends a clear signal (FIG. 4F) to the peak detector 32. When the clear signal (FIG. 4-f) is sent, the peak detector 32 returns the peak value to “0” and prepares for the next discharge peak value. At this time, the output of the peak detector 32 is as shown in FIG. Further, the printer processor 36 writes values into the delay register 1 and the delay register 2 inside the ejection controller 37 in accordance with the correction values for each ink type and ink color read from the memory 38. It is assumed that the correction value has already been clarified through experiments.

  Here, FIG. 5 shows an internal configuration of the discharge control unit.

  A discharge signal is transmitted to the recording head 5 by the discharge controller 38. From the timing of the discharge control signal, the clear signal generating unit 39 generates a clear signal for the P / H unit 32 and the latch signal generating unit 40 generates a latch signal for the latch unit. The output from the clear signal generator 39 is delayed as the value of the delay register 41 increases. Similarly, in the delay register 42, the output from the latch signal generation unit 40 is delayed as the value increases. The values of the delay register 41 and the delay register 42 are set by the printer processor 36.

  In the above configuration, an example of an actual detection operation is shown.

  At the beginning of the detection operation, first, the printer processor 36 reads the correction value from the memory 38 and writes the read correction value into the delay register 41 and the delay register 42. By setting the correction value in advance for each detection condition such as the type of ink to be used and the color of the ink, more accurate ejection detection can be performed.

  Then, the printer processor 36 writes a light emission value (digital value) in the light emission control unit 80. The light emission value from the light emitting element 81 increases as the light emission value increases. Next, the printer processor 36 requests the discharge controller 37 to generate a control signal for discharge detection. Upon receiving the request, the ejection controller 37 transmits a head drive signal to the recording head 5, and the recording head 5 ejects ink droplets for each nozzle at the positions of the light emitting element 81 and the light receiving element 82. FIG. 6 shows the ejection signal at this time and the output waveform of the ink droplet of the ink droplet obtained by optical detection.

  FIG. 6A shows a head drive signal sent from the discharge controller 37 to the recording head 5, and discharges one nozzle at a time from the “H” level to the “L” level. FIG. 6B shows the output of the sensitivity amplifier 31 after the ejection waveform obtained by the light receiving element 82 is shaped and amplified. 6C shows an output waveform of the P / H unit 32, and FIG. 6D shows a peak hold clear signal sent from the discharge controller 37 to the P / H unit 32. FIG. At this time, the timing of clearing (when the clear timing (FIG. 6D) becomes “H” level) is defined by time T1 after the head drive signal in FIG. 6A becomes “L”.

  The time T1 is determined by the value set in the delay register 41 for the ink A by the printer processor 36. FIG. 6E shows the output of the A / D converter 33. The peak value of the waveform in FIG. 6B is digitally output, and “0” is output when the P / H portion is cleared. In the present embodiment, the peak values obtained from time t1 to t5 are t1: 30, t2: 50, t3: 30, and t4: 20. FIG. 6F shows a signal waveform for latching the output of the A / D converter 33, which is latched by the F / F 34 when the level changes from "L" to "H". The latch timing is defined by time T2 after the head drive signal in FIG. 6A changes from “H” to “L”. The time T2 is determined by the value set in the delay register 42 by the printer processor 36. The output of the F / F 34 is as shown in FIG. 6-g, and the detection is normally performed when the print processor 36 reads the output of the F / F 34.

  FIG. 7 shows the internal configuration of the light emission control unit 80. In FIG. 7, the port IC 91 holds the light emission value set from the print processor 36. The held light emission value is digital / analog converted by the D / A converter 92 and amplified by the AMP 93. The gain of the AMP 93 is such that the output of the D / A conversion and the output of the voltage / current converter 94 are linear. The output of the AMP 93 is converted into a current by the current-voltage converter 94 and becomes a drive current for the light emitting element 81.

  In the discharge state detection means for detecting the discharge of ink droplets with the above-described configuration, the light amount adjustment of the light emitting / receiving unit, which is the object of the present invention, is performed.

  Next, the light quantity adjustment procedure of the light emitting / receiving unit in the present invention will be described below.

  FIG. 8 shows a case where the light emitting / receiving process is normally performed. In the waveform 101, the horizontal axis represents time, the vertical axis represents set voltage, and the waveform 102 represents time, and the vertical axis represents received light amount. It is assumed that the amount of received light increases as it goes upward. Here, the set voltage indicates a light emission voltage for light emission set by the printer processor 36 in the discharge port section. The received light amount is a value read by the print processor 36 by causing the F / F 34 to latch the amount of light received by the light receiving element 82 via the P / H unit 32 and the A / D conversion unit 33. The received light amount Lx is a reference received light amount, and the print processor 36 adjusts the set voltage so that the received light amount becomes the reference value Lx. The print processor 36 outputs a latch signal of the F / F 34 to the discharge controller 37 at each time t1 to t5.

  At time t0, since “0” is written in the port IC 91, the light emitting element 81 does not emit light. Next, the print processor 36 gradually increases the set voltage from '0' to Va from time t0 to t1 as an initial light emission sequence. The reason why the light emitting element is gradually increased is to prevent damage to the light emitting element, and Va may be set next to ‘0’ when using a light emitting element that is not damaged even if Va is initially set. After the print processor 36 sets the set voltage Va, a time when the amount of received light is stabilized is assumed to be t2.

  Since the received light amount La (waveform 102) at time t2 is less than the reference value Lx, the print processor 36 increases the set voltage to Vb (waveform 101). After the print processor 36 sets the set voltage Vb, a time when the amount of received light is stabilized is set to t3.

  At time t3, the received light amount Lb does not reach the reference value Lx, so the print processor 36 increases the set voltage to Vc. Here, the adjustment process is simplified if the increase (Vc−Vb) of the set voltage is double the previous increase (Vb−Va). After the print processor 36 sets the set voltage Vc, the time when the amount of received light is stabilized is assumed to be t4.

  At time t4, since the received light amount Lc exceeds the reference value Lx, the print processor 36 increases the set voltage to Vd. Here, the adjustment process is simplified if the decrease (Vc−Vd) of the set voltage is ½ times the previous increase (Vc−Vb). After the print processor 36 sets the set voltage Vd, the time when the amount of received light is stabilized is set to t5.

  Since the received light amount Ld becomes equal to the reference value Lx at time t5, the print processor 36 records the current set voltage value in the memory 38 and performs light emission control with the recorded set voltage value in the next ejection detection operation. . In the next light emission / emission amount adjustment, the recorded setting value is set to the initial setting voltage Va, so that the adjustment time can be shortened.

  The light emission / reception amount adjustment process is terminated. Here, the adjustment process is simplified if the decrease (Vc−Vd) of the set voltage is ½ times the previous increase (Vc−Vb). After the print processor 36 sets the set voltage Vd, the time when the amount of received light is stabilized is assumed to be t4.

  Next, FIG. 9 shows a case where there is an abnormality in the light emitting unit or the light receiving unit, and the light emitting / receiving process is not normally performed.

  In the waveform 103, the horizontal axis represents time, the vertical axis represents the set voltage, and in the waveform 104, the horizontal axis represents time, and the vertical axis represents the amount of received light. The print processor 36 outputs a latch signal of the F / F 34 to the discharge controller 37 at each time t1 to t5.

  At time t0, after the print processor 36 sets the set voltage Ve in the same manner as in FIG. 8, the time when the amount of received light is stabilized is assumed to be t2.

  At time t2, the received light amount Le (waveform 102) is less than the reference value Lx, so the print processor 36 increases the set voltage to Vf (waveform 101). After the print processor 36 sets the set voltage Vf, the time when the amount of received light is stabilized is set to t3.

  At time t3, the received light amount Lf is less than the reference value Lx, so the print processor 36 increases the set voltage to Vg. Here, the adjustment process is simplified if the increase (Vg−Vf) of the set voltage is doubled from the previous increase (Vf−Ve). After the print processor 36 sets the set voltage Vg, the time when the amount of received light is stabilized is set to t4.

  Even at time t4, the received light amount Lg does not reach the reference value Lx, so the print processor 36 raises the set voltage to Vh. Here, it is assumed that the maximum drive current of the light emitting element in the present embodiment is the set voltage Vz. If Vz <Vg + (Vg−Vf) * 2, if the set voltage is simply increased in the same manner as before, the set voltage Vz is exceeded. Therefore, the new set voltage at time t4 is Vz. After the print processor 36 sets the set voltage Vz, a time when the amount of received light is stabilized is set to t5.

  At time t5, the received light amount Le (waveform 102) is less than the reference value Lx, but is already at the maximum set voltage Vz, so the print processor 36 determines that there is an abnormality in the light emitting / receiving unit. Here, an error message can be issued to a display unit (not shown) in the recording apparatus to notify the user of an abnormality in the light emitting / receiving unit.

  In the present embodiment, the detection method performs the ink droplet detection operation for each nozzle. However, as another detection method, a recording medium for detecting the ink discharge status outside the effective recording area by the recording head is used. The same effect can be obtained also in an apparatus that is provided and detects an ink droplet by recording a predetermined pattern on a recording medium in the previous period and reading the pattern with an optical reading device.

  The light amount adjustment procedure may be performed immediately after the device is turned on or immediately before the ejection detection sequence for detecting the ink droplet ejection state.

  In addition, as a form of the recording apparatus according to the present invention, a copying apparatus combined with a reader or the like as well as an image output terminal of an information processing device such as a computer or a separate unit, and further a transmission / reception function are provided. It may take the form of a facsimile machine. Note that the present invention can be applied to an apparatus (for example, a copier, a facsimile machine, etc.) composed of a single device even if it is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a printer, etc.). You may do it.

FIG. 3 is a three-dimensional perspective view illustrating a detailed configuration of a printer including a recording head that performs recording according to an ink jet method that is a representative embodiment of the present invention. FIG. 2 is an enlarged perspective view showing a detailed configuration near a photo sensor of the printer shown in FIG. 1. FIG. 3 is a block diagram illustrating the configuration of an ink detector that uses existing digital signal processing in a printer with an analog sensing element. It is a time chart of each signal when the detection signal obtained from the photo sensor is processed by the ink drop detector. It is an internal block diagram of a discharge controller. It is a time chart of each signal when ink droplet discharge detection is performed. It is an internal block diagram of a discharge control part. It is a time chart when the light quantity adjustment of a light emitting / receiving part is performed. It is a time chart when the light quantity adjustment of a light emitting / receiving part is performed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Recording head 5c Nozzle row 8 Photo sensor 15 Carriage 16 Guide rod 17 Carriage motor 18 Timing belt 19 Flexible cable 20 Cap 21 Carriage home position sensor 22 Paper guide 23 Spur 23-a Bearing member 30 BFP
31 Sensitivity amplifier 32 Peak detector 33 A / D converter 34 F / F
35 Memory 36 Printer processor 37 Discharge controller 38 Discharge controller 39 Clear signal generator 40 Latch signal generator 41, 42 Delay register 71 Scale 72 Linear encoder 80 Light emission controller 81 Light emitter 82 Light receiver 91 Port IC
92 D / A converter 93 AMP
94 Voltage-current converter P Recording paper

Claims (6)

In the discharge detection means for detecting the ink droplet discharge state of the ink jet recording apparatus provided with the recording head,
A light emitting means for irradiating the light beam; a light receiving means for receiving the light beam; a light emission control section for supplying a driving current for driving the light emitting means; and a detection section for picking up an output level from the light receiving means. The discharge detection means characterized in that the light beam is emitted before the ink droplet is discharged, and the drive current is adjusted so that the output level of the detection unit becomes a predetermined reference value. .   If the detected value does not reach the reference value even when the maximum drivable current is supplied in the light emission control unit, it is determined that the light emitting / receiving unit is abnormal, and the detection unit displays on the display means. The discharge detection means according to claim 1, wherein the discharge detection means is controlled to perform.   2. The ejection detecting means according to claim 1, wherein ink droplets ejected from the recording head are provided so as to block the beam light.   A recording medium for detecting the ink discharge status is provided outside the effective recording area by the recording head, a predetermined pattern is recorded on the recording medium, and ink droplets are detected by reading the pattern with an optical reading device. The discharge detection means according to claim 1, wherein the discharge detection means is performed.   The discharge detection unit according to claim 1, wherein the adjustment operation is executed in a sequence immediately after the printing apparatus is turned on.   The discharge detection unit according to claim 1, wherein the adjustment operation is executed immediately before a discharge detection sequence for detecting an ink droplet discharge state.

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