JP4483316B2 - Inkjet recording apparatus and optical path detection method - Google Patents

Description

  The present invention relates to an ink jet recording apparatus and an optical path detection method, and more particularly to a serial head type ink jet recording apparatus having a detecting device for detecting a nozzle shortage having a light emitting element and a light receiving element, and a light emitting element and a light receiving element. The present invention relates to an optical path detection method for detecting an optical path to be performed.

  In recent years, an inkjet head (for example, because high-definition image recording can be performed on various recording media such as paper, fabric, and resin film, the running cost is low, and the image recording operation is quiet. Hereinafter, inkjet recording apparatuses that perform recording by discharging ink onto a recording medium from a plurality of ink discharge ports provided in a head) are widely used.

  In such an ink jet recording apparatus, when the ink discharge port of the head is clogged with ink or the like and the ink discharge function is lowered, so that the recording performance of high-definition images is remarkably impaired when the so-called nozzle shortage occurs. The head surface is frequently cleaned.

  FIG. 9 is a schematic diagram illustrating nozzle missing detection in a serial head type inkjet recording apparatus. The ink jet recording apparatus 100 includes a detection device 101 including a light emitting element 102, a light receiving element 103, an ink tray 104, and the like, and an optical path 105 is formed between the light emitting element 102 and the light receiving element 103. In the nozzle missing detection, the head 107 provided with a plurality of ink discharge ports 106 is moved in the main scanning direction X and positioned above the detection device 101. Then, a discharge start signal is sequentially sent to each ink discharge port 106, and ink I is sequentially discharged from each ink discharge port 106 toward the ink tray 104.

  At this time, if the ink I is normally ejected from the ink ejection port 106 by sending an ejection start signal, the ejected ink droplet 108 blocks the optical path 105 and the output from the light receiving element 103 changes greatly. However, if the ink ejection port 106 has a nozzle shortage, the ink I is ejected only insufficiently, and the change in output from the light receiving element 103 is reduced. Even if the ejection start signal is sent, if the ink I is not ejected at all from the ink ejection port 106, the optical path 105 is not blocked, and the output from the light receiving element 103 does not change at all. Accordingly, by monitoring the signal output from the light receiving element 103, it can be determined whether or not the ink ejection port has a nozzle shortage.

  Even when there are a plurality of heads 107, as shown in FIG. 10, by performing the nozzle missing detection shown in FIG. 9 while sequentially moving the head 107 in the main scanning direction X, the nozzle missing of each ink ejection port is removed. Can be detected.

  In order to establish such nozzle missing detection, the relative positional relationship between the head and the detection device is such that the ink droplets ejected from the ink ejection port of the head accurately block the optical path of the detection device. It is necessary to. However, in constructing the apparatus, it is inevitable that a positional deviation or the like due to a dimensional tolerance of each apparatus constituting the ink jet recording apparatus such as a head or a solid difference of each constituent apparatus occurs. For each device, the optimum relative position between the head and the detection device must be determined.

  As a method for determining the optimum relative position between the head and the detection device, for example, when there are a plurality of heads, the test pattern recorded by one head is used as a reference and the test pattern is recorded for each remaining head. A method is known in which the ejection timing is corrected in comparison with a test pattern (see Patent Document 1), the reference head is aligned with the optical path of the detection device, and nozzle missing detection is performed for all the heads. Yes. Such correction of the ejection timing between the heads is an indispensable adjustment work in the ink jet recording apparatus having a plurality of heads, but the work becomes too complicated if it is performed every time for detecting the missing nozzle.

Therefore, as a simpler method and apparatus, the output distribution from the light receiving element of the detection device is obtained by moving the head within a predetermined movement range including the optical path while discharging ink from the ink discharge port, and the output distribution is maximized. An ink jet recording apparatus that detects nozzle shortage at a position (see Patent Document 2) and a recording apparatus that corrects the detection position by ejecting and detecting ink at a plurality of positions near the detection apparatus (Patent Document 3) are proposed. Has been.
JP-A-63-153151 Japanese Patent No. 3145898 Japanese Patent No. 3162997

  The devices and methods described in Patent Document 2 and Patent Document 3 are based on the idea of discovering (detecting) the optical path of the detection device by ejecting ink while changing the relative position of the head and the detection device. This is what is called an optical path detection method.

  However, as in the device described in Patent Document 2, in order to determine the maximum value from the normal distribution output from the light receiving element of the detection device, a configuration usually called hill-climbing control, While comparing the data with the current data, the maximum value is known when the peak is passed. Therefore, an A / D converter and a memory are required, resulting in a complicated and expensive circuit configuration. Furthermore, when detecting minute droplets as in the ink jet recording apparatus, a weak signal is DC-amplified, and the S / N is not necessarily good.

  In addition, when detecting only the change in the signal and performing AC amplification, the degree of amplification can be increased, and since the maximum amplitude is detected, the S / N is improved. There is a problem that the circuit configuration becomes complicated, and further, a delay time is generated in the acquisition circuit having the maximum amplitude, so that the position indicating the accurate maximum value is shifted.

  Furthermore, such an optical path detection method often requires a large amount of ink to be consumed, resulting in an increase in running cost.

  Further, in the apparatus described in Patent Document 3, only an optimal position is selected from several positions that are considered to be near the optical path, and therefore the selected position is not necessarily a position that can detect a nozzle shortage with high sensitivity. Absent. Furthermore, normally, in such a circuit configuration of the detection device, a filter using a capacitor or the like is used, but a time delay occurs in increasing or decreasing the voltage. In recent years, ink droplets ejected from a head have been miniaturized, and development of an ink jet recording apparatus capable of detecting ink droplets with high sensitivity has been demanded.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus having a simple circuit configuration and capable of detecting the optical path of the detection apparatus while suppressing the ink discharge amount as much as possible to detect missing nozzles with high sensitivity. It is an object of the present invention to provide a simple and reliable optical path detection method for detecting the optical path of the detection device.

In order to solve the above problem, the ink jet recording apparatus according to claim 1,
In an inkjet recording apparatus that uses an inkjet head having a plurality of ink ejection openings to perform recording by ejecting ink onto a recording medium.
A moving device for reciprocatingly scanning the inkjet head along a main scanning direction ;
A light-emitting element and a light receiving element, the presence or absence of ink discharged from the ink discharge ports of the ink jet head, an optical path is formed along a direction perpendicular to the main scanning direction by the light emitting element and the light receiving element A detection device for detecting with,
With
In performing ejection for detecting an optical path formed between the light emitting element and the light receiving element by relatively moving the detection device and the inkjet head,
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head in one of the main scanning directions in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. detecting a position as one end of the optical path,
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head to the other side of the main scanning direction in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. detecting a position as the other end of the optical path,
In the range of both ends of the detected optical path , ejection for detecting the presence or absence of ink is performed.

According to the first aspect of the present invention, ink is ejected intermittently from the ink ejection port while the inkjet head is moved in one of the main scanning directions to detect one end of the optical path. Similarly, by detecting the other end of the optical path while moving the head in the opposite direction, the optical path formed between the light emitting element and the light receiving element of the detection device can be detected.

According to a second aspect of the invention, in the ink jet recording apparatus according to claim 1, the discharge for sensing the presence or absence of the ink, and performs at the center of both ends of the optical path.

According to the invention described in claim 2, the center of both ends of the optical path, i.e., it detects the presence of ink by ejecting ink toward the optical axis of light emitted toward the light receiving element from the light emitting element it can.

The invention according to claim 3 is an optical path detection method,
In an inkjet recording apparatus, a detection device for detecting the presence or absence of ink ejected from an ink ejection port of an inkjet head capable of reciprocating scanning along the main scanning direction is used, and a light-emitting element and a light-receiving element that constitute the detection apparatus An optical path detection method for detecting an optical path formed along a direction orthogonal to the main scanning direction by:
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head in one of the main scanning directions in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. After detecting the position of as one end of the optical path,
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head to the other side of the main scanning direction in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. and detecting the position as the other end of the optical path.

According to the invention described in claim 3, the ink is ejected while reciprocating the head, by monitoring the output voltage from the light receiving element can detect both ends of the optical path, it is possible to detect the light path.

According to the invention described in claim 1, to detect the end of the optical path in the scanning of the one main scanning direction of the inkjet head, therewith to detect the other end of the optical path in the scanning in the opposite direction in the main scanning direction of the other Therefore, it is possible to accurately detect the positions of both ends of the optical path in the main scanning direction . In addition, the detection device can detect both ends of the optical path with a simple circuit configuration using only the peak hold means and the low-pass filter means. By intermittently ejecting ink from the ink ejection port, an optical path formed between the light emitting element and the light receiving element of the detection device can be detected. At that time, it is sufficient if both ends of the optical path are detected. Therefore, ink discharge can be stopped as soon as one end or the other end of the optical path is detected. Thus, it is possible to specify the range of the optical path of the detection device that can be detected. In the present invention, since the optical path can be reliably detected as described above, it is possible to detect the missing nozzle with high sensitivity within the range of both ends of the optical path.

According to the invention described in claim 2, the center of both ends of the optical path, i.e., it detects the presence of ink by ejecting ink toward the optical axis of light emitted toward the light receiving element from the light emitting element Therefore, in addition to the above-described effects, it is possible to detect missing nozzles with higher sensitivity.

According to the invention described in claim 3, the ink is ejected while reciprocating the head, by monitoring the output voltage from the light receiving element, it is possible to detect both ends of the optical path, to easily detect the optical path Can do. Moreover, as in the prior art, to choose the best location from the position of several points which appear to the optical path near the present invention to accurately detect the both ends of the optical path, it is possible to reliably detect the light path .

  Hereinafter, embodiments of the ink jet recording apparatus of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing an ink jet recording apparatus according to the present embodiment. As shown in FIG. 1, the ink jet recording apparatus 1 has a rod-shaped guide rail 2, and a carriage 3 is supported on the guide rail 2, and the carriage 3 includes a main scanning motor (not shown). The carriage drive mechanism can reciprocate in the direction of arrow X along the guide rail 2 (hereinafter referred to as main scanning direction X).

  The carriage 3 is provided with an ink ejection port (not shown) that performs recording by ejecting ink of each color such as yellow (Y), magenta (M), cyan (C), and black (K) to the recording medium P. The inkjet head 4 (hereinafter referred to as the head 4) is mounted. That is, in the present embodiment, the carriage drive mechanism including the main scanning motor or the like corresponds to a moving device that reciprocates the head 4.

  The carriage 3 is equipped with sub ink tanks for storing the inks of the respective colors to be supplied to the head 4, and the inks connected to the ink tanks for storing the inks of the respective colors are mounted on the respective sub ink tanks. Supply pipes are connected to each other. Ink is appropriately supplied from the ink tank to the sub ink tank via the ink supply pipe.

  The head 4 scans in the main scanning direction X in accordance with the reciprocating movement of the carriage 3 along the guide rail 2, and ejects ink of each color onto the recording medium P from the ink ejection port to record on the recording medium P. Is configured to do. In this embodiment, at that time, the head 4 is set so as to eject ink both in the forward direction and in the backward direction to perform ink jet recording.

  The central part of the movable range of the carriage 3 is a recording area for recording on the recording medium P. In this recording area, the recording medium P is transported in the sub-scanning direction Y orthogonal to the main scanning direction X. A device 5 is provided. The transport device 5 is provided with a drive roller 7 for rotating the transport belt 6 and tension rollers 8, 8 that rotate following the operation of the transport belt 6 and apply tension to the transport belt 6 in parallel. The drive roller 7 and the tension rollers 8, 8 support an endless transport belt as a transport member for supporting the recording medium P in a plane and transporting the recording medium P to a position facing the ink discharge port of the head 4. 6 is stretched. At a position facing the ink discharge port of the head 4 via the conveyance belt 6, there is a flat electrostatic adsorption device 9 for charging the conveyance belt 6 and electrostatically adsorbing the recording medium P to the conveyance belt 6. Is provided.

  The conveyance device 5 is configured to intermittently convey the recording medium P by repeating conveyance and stopping of the recording medium P in accordance with the reciprocation of the carriage 3 during recording.

  In the present embodiment, a home position (not shown) of the carriage 3 is provided outside the recording area in the moving direction of the carriage 3. The carriage 3 is moved to the home position when the operation is stopped or the like, and the ink discharge port of the head 4 is covered with a cap (not shown) provided at the home position to prevent the ink discharge port from drying. .

  A nozzle missing detection device is provided outside the recording area opposite to the home position in the movement direction of the carriage 3 (that is, the main scanning direction X). FIG. 2 is a schematic diagram illustrating a detection device of the ink jet recording apparatus according to the present embodiment. In the detection device 10, a light emitting element 11 made of an LED (Light Emitting Diode) is disposed in a state of irradiating light in a sub-scanning direction Y below a guide rail (not shown), and is located at a certain distance from the light emitting element 11. The planar light receiving element 12 made of a photodiode is arranged in a state in which the optical axis 13 of the light emitted from the light emitting element 11 is perpendicularly incident.

  A casing-shaped shield case 14 that blocks outside light is disposed around the light receiving element 12, and light irradiated from the light emitting element 11 is allowed to pass through a surface of the shield case 14 that faces the light emitting element 11. The detection hole 15 is formed in a circular shape centered on the optical axis 13. In FIG. 2, the spread of the light emitted from the light emitting element 11 and the detection hole 15 are emphasized, but actually, the light spreading from the light emitting element 11 is emitted, and the diameter is about 3 mm. The light passing through the detection hole 15 reaches the light receiving element 12 and is detected by the light receiving element 12.

  As described above, the bottomed rectangular ink tray 17 is vertically below the optical path 16 formed by the light emitting element 11 and the light receiving element 12, that is, the long side is oriented parallel to the optical axis, that is, the long side. Are moved in the sub-scanning direction Y, and the head 4 is moved vertically above the optical path formed by the light emitting element 11 and the light receiving element 12 by the movement of the carriage 3 in the main scanning direction X. When it comes, the row of the ink discharge ports 19 on the nozzle surface 18 of the head 4, the optical axis 13 of the light emitted from the light emitting element 11, and the center line 20 of the ink tray 17 are arranged in parallel on the same plane. Has been placed. Therefore, when the ink I is ejected from the ink ejection port 19 of the head 4, the ink I passes through the lower optical path 16 and then drops to the lower ink tray 17.

  FIG. 3 is a block diagram illustrating a circuit configuration of the detection device. The detection device 10 is configured such that the output value of the light receiving element 11 is amplified by the current amplifying means 21 and further AC-amplified by the AC amplifying means 22. The output current amplified by the current amplifying means 21 is sent to the light emitting element 12 via the amplitude feedback means 23. The output voltage a amplified by the AC amplification means 22 is input to the peak hold means 24, the output voltage b is compared with the reference voltage Vref by the first comparison means 25, and the output voltage b is higher than the reference voltage Vref. If the output voltage b is lower than the reference voltage Vref, a detection voltage c that outputs 0 V is output to the central processing unit 26 (hereinafter referred to as CPU 26) of the ink jet recording apparatus. The output voltage a amplified by the AC amplification means 22 is input to the low-pass filter means 27, and the output voltage d is compared with the output voltage a by the second comparison means 28 to be turned ON / OFF signal. The detected voltage e converted into an ON / OFF signal is output to the CPU 26.

  A signal for turning on or off the light emitting element 11 is sent from the CPU 26 to the light emitting element 11 via the amplitude feedback means 23. Further, the CPU 26 is configured to receive position signals Ea and Eb (position signals Ea and Eb respectively correspond to the A phase and the B phase of the encoder sensor) from the encoder sensor attached to the carriage 3. ing.

  Next, the operation of the inkjet recording apparatus 1 of the present embodiment and the optical path detection method in the present embodiment will be described.

  During recording, the carriage 3 reciprocates in the main scanning direction X along the guide rail 2 of the inkjet recording apparatus 1 (see FIG. 1). In addition, the head 4 mounted on the carriage 3 scans the upper side of the recording medium P in the main scanning direction X in accordance with the reciprocating movement of the carriage 3, and ejects ink of each color from the ink ejection port to the recording medium P. To record.

  As described above, in the present embodiment, the head 4 is set to perform ink jet recording both in the forward direction and in the backward direction. Specifically, in a state where the transport belt 6 stops moving and the recording medium P is stationary, the head 4 ejects ink to the recording medium P while scanning in the forward direction of the main scanning direction X, The head width is recorded. When the scanning of the head 4 in the forward direction is completed, the conveying belt 6 moves to convey the recording medium P in the sub-scanning direction Y by the head width and stop it. Then, the head 4 records the head width by ejecting ink in the same manner while the head 4 scans in the backward direction. When the scanning of the head 4 in the backward direction is completed, the conveying belt 6 moves again and conveys the recording medium P in the sub-scanning direction Y by the head width and stops. By repeating this, an image is recorded on the recording medium P in a planar shape.

  Since the head 4 mounted on the carriage 4 receives the missing nozzle detection, it moves in the main scanning direction X and is carried above the detection device 10.

  Here, a detection method of the optical path 16 formed by the light emitting element 11 and the light receiving element 12 of the detection apparatus 10 will be described based on the structure (see FIG. 2) and circuit configuration (see FIG. 3) of the detection apparatus 10.

  First, referring to FIG. 4 and FIG. 5 and the like, what waveform output is obtained from the circuit configuration of the detection device 10 when the ink I is discharged from the ink discharge port 19 of the head 4 in the detection device 10. While explaining. For simplicity, the case where there is one head 4 will be described here. The position of the head 4 is specified by linear encoder position signals Ea and Eb (see FIG. 5) input to the CPU 26 of the ink jet recording apparatus 1 from an encoder sensor attached to the carriage 3 on which the head 4 is mounted. The horizontal axis in FIG. 5 is the time axis.

  When the head 4 is moved at a constant speed in the main scanning direction X, and the ink discharge port 19 of the head 4 reaches the position vertically above the position A where the ink tray 17 can store ink, the CPU 26 intermittently connects the head 4 to the head 4. A discharge start signal s (see FIG. 5) is sent. For the ejection start signal s, for example, an ink ejection port 19 is selected from a plurality of ink ejection ports 19 of the head 4 at an arbitrary ratio (for example, 1 in 10), and the selected plurality of ink ejection ports 19 are selected. Ink I is discharged from the ink.

  However, when the ink discharge port 19 is still above the position A, the ink I discharged from the ink discharge port 19 in response to the discharge start signal s is formed by the light emitting element 11 and the light receiving element 12 of the detection device 10. Therefore, there is no change in the waveform of the output voltage a obtained by amplifying the output current from the light receiving element by the current amplifying means 21 and the AC amplifying means 22.

  When the head 4 further advances in the main scanning direction X and the ink I ejected from the ink ejection port 19 of the head 4 reaches the position B where the ink I passes through the optical path 16 and begins to be blocked, a change in the amount of light is detected and the AC amplification means 22 A sinusoidal signal change occurs in the output voltage a. At that time, the output voltage b in which the peak value of the output voltage a is maintained is output from the peak hold means 24 to which the output voltage a is input. The output voltage b and the reference voltage Vref are compared by the first comparison unit 25. When the output voltage b exceeds the reference voltage Vref, the detection voltage c output from the first comparison unit 25 changes from 0 to a high voltage state. .

  To be precise, an AC waveform starts to appear weakly in the waveform of the output voltage a from the AC amplifying means 22 at a position closer to the position A than the position B where the detection signal c changes from 0 to a high voltage state. However, since the presence or absence of the ink I cannot be clearly detected with such a weak waveform, in this embodiment, if the peak of the waveform does not exceed the reference voltage Vref, the ink I is not regarded as having passed through the optical path 16. I am going to do that.

  The output voltage a is input to the low-pass filter unit 27, and the low-pass filter unit 27 outputs an output voltage d as shown in FIG. This output voltage d is compared with the original output voltage a by the second comparison means 28, and the detection voltage e output from the second comparison means 28 is 0 so as to correspond to the peak value portion of the AC waveform of the output voltage a. The state changes from a high voltage state to a comb-like waveform.

  As the head 4 further advances in the main scanning direction X, the peak value of the output voltage a from the AC amplifying means 22 increases, and when it exceeds the position C, the peak value decreases. Meanwhile, the detection voltage c remains in a high voltage state, and the detection voltage e repeats a comb-like waveform.

  When the head 4 further advances in the main scanning direction X and reaches the position D where the ink I ejected from the ink ejection port 19 of the head 4 does not pass through the optical path 16, the comb-like waveform of the detection voltage e is repeated. However, the detection voltage c maintains a high voltage state for a while. This is because the peak hold means 24 has a function of maintaining the peak value of the output voltage a, and the output voltage b is attenuated only very slowly, so that the AC waveform of the output voltage a from the AC amplifying means 22 disappears. This is because if the output voltage b from the peak hold means 24 is higher than the reference voltage Vref, the high voltage state continues.

  Next, a method for detecting the optical path 16 formed by the light emitting element 11 and the light receiving element 12 using the detection device 10 will be described.

  In the present invention, as the optical path detection method, the detection voltage c output from the first comparison means 25 is used, and one edge of the optical path 16 (hereinafter referred to as the first scan) in the head 4 in one direction (hereinafter referred to as the first scan). For example, the position B) in the above description is detected, and the other edge of the optical path 16 (for example, the position D in the above description) is detected by scanning in the opposite direction (hereinafter referred to as second scanning). Adopt a method to detect.

  This optical path detection method of the present invention will be described more specifically with reference to the flowchart of FIG.

  The CPU 26 of the inkjet recording apparatus 1 drives a main scanning motor that moves the head 4 onto the detection apparatus 10 (step S1), and starts the first scanning of the head 4. And a lighting signal is sent to the light emitting element 11 via the amplitude feedback means 23 of the detection apparatus 10, and the light emitting element 11 is lighted (step S2). It is determined whether or not the head 4 is in the vicinity of the optical path 16 while confirming the position signals Ea and Eb of the linear encoder input from the encoder sensor attached to the carriage 3 on which the head 4 is mounted (step S3). For example, if the position A in FIG. 4 is determined in advance and the linear encoder position corresponding to the position A is stored, and the head 4 moves to the linear encoder position, the head 4 is in the vicinity of the optical path 16. to decide.

  If it is determined that the head 4 is in the vicinity of the optical path 16, the ink I is ejected from the plurality of ink ejection ports 19 selected from the plurality of ink ejection ports 19 of the head 4 (step S4). At that time, as shown in FIG. 5, three or four droplets are ejected intermittently at intervals of about 2 milliseconds from the selected plurality of ink ejection ports 19.

  The CPU 26 starts the discharge of the ink I from the ink discharge port 19 and simultaneously detects the detection voltage c output from the first comparison unit 25 of the detection device 10 in synchronization with the rising of the position signals Ea and Eb from the encoder sensor. Is input (step S5). The reason why the detection voltage c is monitored in synchronization with the rising of both the position signals Ea and Eb is to increase the position sensitivity twice. Then, it is determined whether or not the detection voltage c is in a high voltage (active) state (step S6). If the detection voltage c is not in an active state, the detection voltage c is continuously monitored.

  When the CPU 26 determines that the detection voltage c is in an active state, the CPU 26 stores the position of the linear encoder (step S7), and stops the discharge of the ink I from the ink discharge port 19 of the head 4 (step S8). In this way, first, one edge of the optical path 16 (more precisely, a linear encoder position corresponding to one edge of the optical path 16) is detected by the first scanning of the head 4.

  The CPU 26 moves the head 4 that has stopped ejecting the ink I by a predetermined distance in the first scanning direction (step S9), and then reversely drives the main scanning motor (step S10). Start scanning. Thereafter, similarly to the case of the first scanning, it is determined whether or not the head 4 is in the vicinity of the optical path 16, for example, the position D in FIG. 4 (step S 11), and the head 4 is in the vicinity of the optical path 16. If it is determined, the ink I is ejected from the selected plurality of ink ejection ports 19 of the head 4 (step S12). At the same time, the detection voltage c is input in synchronization with the rise of the position signals Ea and Eb from the encoder sensor (step S13), and it is determined whether or not the detection voltage c is in a high voltage (active) state (step S13). S14).

  If the CPU 26 determines that the detection voltage c is in an active state, the CPU 26 stores the position of the linear encoder (step S15) and stops the discharge of the ink I from the ink discharge port 19 of the head 4 (step S16). In this way, the other edge of the optical path 16 (more precisely, the linear encoder position corresponding to the other edge of the optical path 16) is detected by the second scanning of the head 4.

  In the ink jet recording apparatus 1 of the present invention, the head 4 is positioned within the range of both edges of the optical path 16 detected in this way, and ejection for detecting the presence or absence of the ink I is performed from the ink ejection port 19. Detect nozzle missing. At this time, it is preferable to detect the missing nozzle with high sensitivity when the head 4 is positioned at the center of both edges of the optical path 16.

  Therefore, in the present embodiment, after the other edge of the optical path 16 is detected by the second scanning of the head 4 by the optical path detection method and the ejection of the ink I from the ink ejection port 19 of the head 4 is stopped (described above In step S16, the center position is calculated as the center of the optical path 16 from each linear encoder position corresponding to the two edges of the optical path 16, and stored (step S17). Thereafter, a turn-off signal is sent to the light-emitting element 11 via the amplitude feedback means 23 of the detection device 10 to turn off the light-emitting element 11 (step S18), and the detection of the optical path 16 is finished.

  In the optical path detection method of the present invention, the optical path 16 is detected as described above. In addition, when there are a plurality of heads 4, the above-described operation may be performed for each head 4, and the optical path detection is performed for one head 4 according to the flowchart. You may make it move only the physical distance between the heads 4. FIG.

  Next, nozzle missing detection in the inkjet recording apparatus 1 will be specifically described using the flow chart of FIG. 7 and the time lapse of the output voltage from the circuit configuration of the detection apparatus 10 of FIG. The missing nozzle detection is performed mainly by monitoring the comb-like waveform of the detection voltage e output from the second comparison means 28 of the detection device 10.

  First, the CPU 26 of the inkjet recording apparatus 1 drives a main scanning motor to detect a missing nozzle at a predetermined position within the range of both edges of the optical path 16 detected by the optical path detection method or at the center of both edges. 4 is moved to align the row of the ink discharge ports 19 with the optical path 16 (step S19). Then, the light emitting element 11 is turned on (step S20).

  The CPU 26 determines whether or not the detection voltage e is output within a predetermined time after the light emitting element 11 is turned on (step S21). If the output of the detection voltage e is not confirmed, the light emitting element 11 and the light receiving element 12 are detected. Is determined to be defective, and the missing nozzle detection is terminated. When the output of the detection voltage e is confirmed within a certain time, preliminary ejection is performed from all the ink ejection ports 19 of the target head 4 (step S22).

  An optical path for confirming whether or not the ejection of the ink I is accurately detected by ejecting the ink I from the plurality of ink ejection ports 19 selected from the plurality of ink ejection ports 19 of the head 4. Confirmation discharge is performed (step S23). After a certain time, it is determined whether or not the detection voltage e is output (step S24). If the output of the detection voltage e is not confirmed, it is determined that the positions of the head 4 and the optical path 16 are misaligned, and the nozzle shortage is detected. End detection.

  Note that the lighting confirmation of the light emitting element 11 (step S21) and the positional deviation determination of the edge 4 (step S23) are performed by monitoring the detection voltage c output from the first comparison means 25 of the detection device 10. Also good.

  When the output of the detection voltage e is confirmed, the CPU 26 first substitutes 1 for m (step S25), and sends a discharge start signal to the mth ink discharge port 19 (step S26). The detection voltage e corresponding to the ejection of the ink I from the mth ink ejection port 19 output after a certain time is stored (step S27). Then, the ejection of the ink I from the mth ink ejection port 19 (step S26) and the storage of the detection voltage e (step S27) are performed for all the ink ejection ports 19 of the target head 4 (step S28, S29). When nozzle missing detection is completed for all the ink ejection ports 19, the light emitting element 11 is turned off (step S30), and nozzle missing detection is finished.

  In nozzle missing detection, as shown in FIG. 8, for example, when the detection voltage e that should correspond to the ejection of ink I from the third ink ejection port 19 is 0, the third ink ejection port It can be seen that 10 has a nozzle missing. The ink discharge port 19 in which the nozzle is missing is appropriately treated for recovery.

  As described above, according to the inkjet recording apparatus of the present invention, the output from the light receiving element is AC-amplified by intermittently ejecting ink from the ink ejection port while moving the inkjet head in one direction of the main scanning direction. A linear encoder position where the voltage is equal to or higher than a predetermined voltage value is detected as an edge of the optical path. Then, immediately after the edge is detected, the ink ejection is stopped. Similarly, while moving the head in the opposite direction, the opposite edge of the optical path is detected and ink ejection is stopped.

  Therefore, even if the output voltage from the light receiving element is not normally distributed as in the conventional example, the ink can be ejected with a simple circuit configuration as shown in FIG. 3 and with a small ink ejection amount. It is possible to specify the range of the optical path of the detection device that can detect with high sensitivity.

  Further, according to the optical path detection method of the present invention, since the ink is ejected while the head is moved as described above and the output voltage from the light receiving element is monitored, the optical path can be detected easily and reliably. .

  In the present embodiment, the CPU 26 detects the detection voltage c that is a peak hold waveform output from the first comparison means 25 via the peak hold means 24 in synchronization with the rise of the position signals Ea and Eb from the encoder sensor. In the case where it is determined whether or not is active (see step S6 in FIG. 6), the comb-like detection voltage e output from the second comparison means 28 via the low-pass filter means 27 is active. It may be configured to determine whether or not. When the detection voltage e via the low-pass filter means 27 is used, as described above, the output is accompanied by a time delay. In the present invention, the optical path 16 is scanned in the first scan of the head 4 by the same scanning procedure. One edge is detected, and the other edge of the optical path 16 is detected by the second scanning in the opposite direction. Therefore, when the detection voltage e via the low-pass filter means 27 is used, the range is narrower than when the detection voltage c via the peak hold means 24 is used, but the center position is via the peak hold means 24. This is because the position is almost the same as the center position when the detection voltage c is used.

  Further, in the present embodiment, the case where the optical path detection is performed by moving the inkjet head 4 with respect to the detection device 10 fixed to the inkjet recording apparatus 1 has been described. However, for example, the detection device for the stationary inkjet head 4 Even if 10 is moved or both are moved together, the essential features of the present invention are not impaired.

  Furthermore, although the inkjet recording apparatus 1 has the conveyance belt 6, the inkjet recording apparatus 1 can be applied to an inkjet recording apparatus that does not include the conveyance belt 6.

  Also, in the present embodiment, the case where the recording medium P is paper, fabric, film, or the like wound in a roll shape has been shown. However, for example, an apparatus of a type that performs recording by taking out the recording medium P such as paper from a cassette. It can also be applied to.

It is the schematic which shows the inkjet recording device of this embodiment. It is the schematic which shows the detection apparatus of the inkjet recording device of this embodiment. It is a block diagram which shows the circuit structure of a detection apparatus. It is the schematic which shows the positional relationship of an inkjet head and an optical path. It is a figure which shows the waveform of the output voltage output from the circuit structure of a detection apparatus. It is a figure which shows the flowchart of the optical path detection method of this invention. It is a figure which shows the flowchart of a nozzle missing detection. It is a figure which shows the waveform of the output voltage output from the circuit structure of a detection apparatus in the case of nozzle missing detection. It is the schematic which shows the nozzle missing detection in a serial head type inkjet recording device. It is the schematic which shows the nozzle missing detection in the serial head type inkjet recording device when there are a plurality of heads.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 4 Inkjet head 10 Detection device 11 Light emitting element 12 Light receiving element 16 Optical path 19 Ink ejection port I Ink P Recording medium

Claims (3)

In an inkjet recording apparatus that uses an inkjet head having a plurality of ink ejection openings to perform recording by ejecting ink onto a recording medium.
A moving device for reciprocatingly scanning the inkjet head along a main scanning direction ;
A light-emitting element and a light receiving element, the presence or absence of ink discharged from the ink discharge ports of the ink jet head, an optical path is formed along a direction perpendicular to the main scanning direction by the light emitting element and the light receiving element A detection device for detecting with,
With
In performing ejection for detecting an optical path formed between the light emitting element and the light receiving element by relatively moving the detection device and the inkjet head,
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head in one of the main scanning directions in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. detecting a position as one end of the optical path,
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head to the other side of the main scanning direction in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. detecting a position as the other end of the optical path,
An ink jet recording apparatus that performs discharge for detecting the presence or absence of ink within a range of both ends of a detected optical path . Discharge for detecting the presence or absence of the ink jet recording apparatus according to claim 1, characterized in that at the center of both ends of the optical path. In an inkjet recording apparatus, a detection device for detecting the presence or absence of ink ejected from an ink ejection port of an inkjet head capable of reciprocating scanning along the main scanning direction is used, and a light-emitting element and a light-receiving element that constitute the detection apparatus An optical path detection method for detecting an optical path formed along a direction orthogonal to the main scanning direction by:
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head in one of the main scanning directions in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. After detecting the position of as one end of the optical path,
The main scanning direction in which the ink is first detected by the detection device by causing the ink jet head to scan the ink jet head to the other side of the main scanning direction in the vertical direction of the optical path and intermittently discharging ink from the ink discharge port. And detecting the position of the optical path as the other end of the optical path.

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