JP2016190357A - Image forming device, method for determining non-discharge of nozzle of image forming device, program and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a discharge failure of a nozzle without consuming ink and a paper.SOLUTION: The image forming device comprises: light emitting means that irradiates a nozzle surface of a head; image reading means that photographs the nozzle surface of the head; lifting means that lifts up the head; moving means that moves the light emitting means and the image reading means to immediate below the lifted-up head; image comparing means that compares image data of the nozzle surface with a preset reference value; and determining means that determines whether there is a discharge failure of a nozzle or not from results by the image comparing means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus, a nozzle non-ejection determination method of the image forming apparatus, a program, and a recording medium.

  In the ink jet printer, the nozzle of the head corresponds to one pixel of the printed matter, which may directly affect the image quality. On the other hand, when a nozzle has a discharge failure, it is an important technique to grasp the discharge failure of the nozzle because the image quality deteriorates unless the pixel in charge of the nozzle is corrected in any way. .

In addition, in a line type printer that increases the speed by arranging a plurality of heads, the driving frequency of the head is lower than that of a serial machine, so that the printing speed can be increased.
However, since the head is not scanned with respect to the printing paper during printing, the nozzles of the head directly affect the image of the printed matter. In other words, it is necessary to prevent nozzle ejection defects, and maintenance of the nozzles is indispensable.
Therefore, as a nozzle maintenance means, a technique for detecting an ejection failure of a nozzle by reading paper printed in a test mode has been proposed (for example, see Patent Document 1).
Patent Document 1 discloses a method of obtaining a read image signal by reading a line-shaped test pattern recorded on paper by driving a head for the purpose of determining ejection failure of a nozzle.

  However, although the technique described in Patent Document 1 can surely detect the ejection failure of the nozzle, there is a problem in that ink and paper are wasted.

  Therefore, an object of the present invention is to detect nozzle ejection defects without consuming ink or paper.

  In order to solve the above problem, the invention described in claim 1 is directed to a light emitting unit that irradiates a nozzle surface of a head, an image reading unit that images the nozzle surface of the head, an elevating unit that raises the head, and a lift A moving means for moving the light emitting means and the image reading means directly below the head; an image comparing means for comparing the image data of the nozzle surface with a preset reference value; and a result of the image comparing means And determining means for determining the presence or absence of ejection failure of the nozzle.

  According to the present invention, it is possible to detect a nozzle ejection failure without consuming ink or paper.

1 is an explanatory diagram of an overall configuration of an ink jet printer as an image forming apparatus. FIG. It is explanatory drawing about arrangement | positioning of the head of a line printer. It is the schematic of the whole structure of the discharge detection part which performs discharge detection of the ink nozzle in an inkjet printer. FIG. 4 is an example of a hardware block diagram of the engine control board shown in FIG. 3. FIG. 4 is an example of a functional block diagram of an engine control board shown in FIG. 3. (A), (b), (c) is explanatory drawing about the method of discharge detection. (A), (b) is another explanatory drawing about the method of discharge detection. It is an example of the flowchart about the method of discharge detection. It is explanatory drawing about the discharge detection by a bubble etc. FIG. It is explanatory drawing regarding the discharge detection when a foreign material adheres to a nozzle. It is another example of the functional block diagram of the inkjet printer as an image forming apparatus. It is an example of the flowchart which shows operation | movement of the inkjet printer shown in FIG. It is explanatory drawing about the discharge detection with respect to multiple rows of ink heads. It is explanatory drawing about the setting of a designated pixel. It is an example of the flowchart about the setting of a designated pixel.

<Embodiment 1>
[Constitution]
FIG. 1 is an explanatory diagram of the overall configuration of an ink jet printer as an image forming apparatus. FIG. 1 shows a state in which normal printing can be performed.
The ink jet printer 10 of the present invention stocks an apparatus main body, a paper tray 18 for loading paper 19 as a recording medium mounted on the apparatus main body, and a paper 19 on which an image is recorded (formed) mounted on the apparatus main body. And a paper discharge tray 24. The ink jet printer 10 has a cartridge loading portion protruding from the front surface to the front side on one end side of the front surface of the apparatus main body and lower than the upper surface, and operation portions such as operation keys and indicators are provided on the upper surface of the cartridge loading portion. Has been placed. Reference numeral 20 denotes an ink supply pipe for supplying ink to the head 22, and reference numeral 23 denotes a high voltage power source for discharging the charged surface of the transport belt 16.

  On the paper tray 18 as a paper stacking unit (also referred to as a pressure plate), a paper feeding unit for feeding the stacked paper 19 is disposed. The paper feed unit is made of a material having a large friction coefficient (for example, rubber) facing the paper feed roller 15 (also referred to as half moon roller) 15 for separating and feeding the paper 19 one by one from the paper tray 18 and the paper feed roller 15. A paper separation pad 14 is provided. The sheet separation pad 14 is biased by a spring or the like so as to face the sheet feeding roller 15 side.

The ink jet printer 10 includes a transport unit for transporting the paper 19 fed from the paper feed unit below the recording head 22. The conveyance unit includes a conveyance belt 16, a counter roller, a conveyance guide 12, a charging roller 13, and a tip roller 21.
The transport belt 16 is a belt for electrostatically attracting and transporting the paper 19. The counter roller is a roller that conveys the sheet 19 fed from the sheet feeding unit via the conveyance guide 12 with the conveyance belt 16 interposed therebetween. The conveyance guide 12 is a member for causing the sheet 19 sent vertically upward to change its direction by 90 ° and to follow the conveyance belt 16. The pressure roller is urged toward the conveying belt 16 by a pressing member such as a spring. The charging roller 13 is a means for charging the surface of the conveyor belt 16.

  Here, the conveyance belt 16 is an endless belt, and is configured to be wound around the conveyance roller 25 and the tension roller 17 and to circulate in the belt conveyance direction P1. The charging roller 13 is arranged so as to come into contact with the surface layer of the conveyor belt 16 and to rotate following the rotation of the conveyor belt 16, and for example, 2.5N is applied to both ends of the shaft as a pressing force.

  A conveyance guide 12 serving as a guide member is disposed on the back side of the conveyance belt 16 so as to correspond to a printing area by the head 22. The upper surface of the conveyance guide 12 protrudes toward the head 22 from the tangent line of two rollers (the conveyance roller 25 and the tension roller 17) that support the conveyance belt 16. As a result, the conveyance belt 16 is pushed up and guided by the upper surface of the conveyance guide 12 in the printing region, so that highly accurate flatness is maintained.

A plurality of grooves are formed in the main scanning direction, that is, in a direction orthogonal to the conveyance direction, on the surface side of the conveyance guide 12 that contacts the conveyance belt 16 to reduce the contact area with the conveyance belt 16 so that the conveyance belt 16 is smooth. It is possible to move along the surface of the conveyance guide 16.
As a paper discharge unit for discharging the paper 19 recorded by the head 22, a separation claw for separating the paper 19 from the conveyor belt 16, a paper discharge roller and a paper discharge roller are provided below the paper discharge roller. A paper discharge tray 24 is provided. Here, the height from between the paper discharge roller and the paper discharge roller to the paper discharge tray 24 is increased to some extent in order to increase the amount that can be stored in the paper discharge tray 24.

  A double-sided printing paper reversing unit 11 is detachably attached to the back surface of the apparatus main body. The double-sided printing paper reversing unit 11 takes in and reverses the paper 19 returned by the reverse rotation of the transport belt 16 and feeds it again between the counter roller and the transport belt 16. Further, a manual paper feed unit may be provided on the upper surface of the double-sided printing paper reversing unit 11.

The head 22 is fixed directly below the block 70, and a nut (or ball screw) 73 is fixed to the block 70 so that the central axis is vertical. A feed screw 72 passes through the nut 73 so as to be rotatable in the vertical direction. The upper end of the feed screw 72 is connected to the output shaft of the motor M1 (71). The motor M1 (71) is fixed to the frame of the inkjet printer 10.
When the feed screw 72 is rotated by the forward rotation of the motor M1 (71) to detect nozzle discharge failure, a force in the direction of arrow P2 is generated on the nut 73, and the block 70 and the head 22 are raised in the direction of arrow P2. The force to be transmitted is transmitted. The ascending distance of the block 70 is set to such a length that a light source 230, a line sensor 240, and a base 90, which will be described later, can move horizontally between the head 22 and the conveyor belt 16.

  Reference numeral 81 denotes a motor M2, and one end (right side in the figure) of a feed screw 82 is connected horizontally to the output shaft of the motor M2 (81). The other end (in this case, the left side) of the feed screw 82 passes through a nut (or ball screw) 83 in a rotatable manner. The nut 83 is fixed to the base 90. On the base 90, a light source 230 and a line sensor 240 (both shown in FIG. 3) described later are mounted. The feed screw 82 is rotated by the forward rotation of the motor M2 (81). A force in the direction of arrow P1 toward the motor M2 (81) is generated in the nut 83 in which the feed screw 82 is inserted. With this force, a force in the direction of arrow P1 is transmitted to the base 90, and the light source 230 and the line sensor 240 move in the direction of arrow P1. The moving distance of the base 90 is set to about the length of the head 22 in the sub-scanning direction. For example, a pulse motor is used as the motor M1 (71) and the motor M2 (81), but the motor M1 (71) is not limited to this.

FIG. 2 is an explanatory diagram of the arrangement of the heads of the line printer.
In the line printer, as shown in FIG. 2, a plurality of heads 1 to 8 are arranged in the main scanning direction. In a serial printer with one head, the head moves in the main scanning direction for printing, but in a line printer, printing is performed by ejecting ink on the spot without moving a plurality of heads arranged in the main scanning direction. .
In a serial printer, one head prints the entire print portion, but in a line printer, since the print portion per head is smaller than that of a serial printer, the drive frequency of the head is also reduced.

FIG. 3 is a schematic diagram of the overall configuration of an ejection detection unit that detects ejection of ink nozzles in an inkjet printer.
FIG. 3 shows a case where the light source 230 and the line sensor 240 are moved directly below the head 22 together with the base 90 in order to detect nozzle ejection defects.
A rod-like light source 230 and a line sensor 240 are mounted on the base 90 so as to be parallel to the longitudinal direction of the head 22. The line sensor 240 is an element that captures a line-shaped area with a CCD arranged in a line. Since the imaging surface of the line sensor 240 is the nozzle surface of the head 22, it is upward. The light source 230 is, for example, an LED (Light Emitting Diode) array, and is set to irradiate the bottom surface, which is the nozzle surface of the head 22.
The base 90 is made of resin or metal, and a nut 83 is fixed to one end face (left side in the figure), but a cylindrical member 85 is fixed to the other end face (right side in this case) Parallel guide bars 84 may be inserted.
When the motor M1 (71: FIG. 1) and the motor M2 (81) are driven in reverse rotation, the base 90 moves in the direction of arrow P3, and the head 22 descends in the direction of arrow P4 and returns to the position shown in FIG.
The head 22, the line sensor 240, and the light source 230 are connected to the engine control board 26 by wires such as a wire harness or a flexible board as a control board.

FIG. 4 is an example of a hardware block diagram of the engine control board shown in FIG.
The engine control board 26 includes a CPU 31, ROM 32, RAM 33, I / O 34, a head drive circuit 35, a line sensor drive circuit 36, a light source drive circuit 37, a motor M1 drive circuit 38, and a motor M2 drive circuit 39. The engine control board 26 is connected to the head 22, the line sensor 240, the light source 230, the motor M1 (71), and the motor M2 (81).
The CPU 31 is an element that controls the head 22, the light source 230, the line sensor 240, the motor M1 (71), and the motor M2 (81). The ROM 32 is a non-volatile memory that stores a control program, such as a flash memory. The RAM 33 is a memory for temporarily storing the control program, image data, and document data read from the ROM 32. The I / O 34 is an input / output circuit for receiving image data or document data from the outside and sending a response signal. The head drive circuit 35 is a circuit that drives the head 22, the line sensor drive circuit 36 is a circuit that drives the line sensor 240, and the light source drive circuit 37 is a circuit that drives the light source 230. The head drive circuit 35 is a circuit that drives the head 22 by ejecting ink from the nozzles. The motor M1 drive circuit 38 is a circuit for driving the motor M1 (71) in forward rotation, reverse rotation, or stopping, and the motor M2 drive circuit 39 is for driving the motor M2 (81) in forward rotation, reverse rotation, or It is a circuit to stop.

  CPU is an abbreviation for Central Processing Unit, ROM is an abbreviation for Read Only Memory, and RAM is an abbreviation for Random Access Memory. I / O is an abbreviation for Input / Output, and CCD is an abbreviation for Charge-Coupled Device.

FIG. 5 is an example of a functional block diagram of the engine control board shown in FIG.
The engine control board 26 includes control means 41, storage means 42, first image comparison means 43, second image comparison means 44, light emission control means 45, discrimination means 46, image capture means 47, designated pixel setting means 48, reference A value setting unit 49, a head driving unit 50, a line sensor driving unit 51, a light source driving unit 52, a head lifting / lowering unit 64, a head moving unit 65, and a determination unit 66 are provided. The engine control board 26 is connected to the ink ejecting means 61, the image reading means 62, and the light emitting means 63.

  The control means 41 has a function of ejecting ink from the ink ejecting means 61, a function of photographing the ink ejecting means 61 in a slightly driven state, which will be described later when the ink ejection is stopped, and an ink ejecting means 61 from the light emitting means 63 when the ink ejection is stopped. This is a means for controlling the function of irradiating light, the function of raising the ink ejecting means 61 when the ink ejection is stopped, and the function of moving the image reading means 62 and the light emitting means 63 when the ink ejection is stopped.

The storage unit 42 has a function of storing a setting history of a designated pixel as a detection target, and is realized by the ROM 32 and the RAM 33.
The first image comparison unit 43 and the second image comparison unit 44 have a function of comparing images captured by the image capture unit 47 and are realized by the CPU 31.
The light emission control means 45 has a function of controlling the light emission of the light emission means 63, and is realized by the CPU 31.
The discriminating means 46 is a means having a function of discriminating between dirt on the image reading means 62 and foreign matter adhering to the nozzle surface, and is realized by the CPU 31.
The image capturing unit 47 has a function of capturing an image from the image reading unit 62 and is realized by the CPU 31.
The head driving unit 50 has a function of driving the ink ejection unit 61 to perform printing by ejecting ink from the nozzles onto the paper 19 during printing, and finely driving the nozzles when detecting ejection failure of the nozzles. There are two types of fine driving: fine movement with the ink exposed from the nozzle surface and fine movement with the ink drawn from the nozzle surface.

The line sensor driving unit 51 is a unit that drives the image reading unit 62 and is realized by the line sensor driving circuit 36.
The light source driving means 52 is means for driving the light emitting means 63 and is realized by the light source driving circuit 37.
The head raising / lowering means 64 is means for raising the ink ejection means 61 when ink ejection is stopped and returning it to its original state after detection in order to detect ejection failure of the nozzles. The head lifting / lowering means 64 has a function of lowering the ink ejection means 61 and is realized by the motor M1 drive circuit 38, the block 70, the motor M1 (71), the feed screw 72, and the nut 73.
The head moving unit 65 is a unit that moves the image reading unit 62 and the light emitting unit 63 directly below the ink ejecting unit 61 when the ink ejection is stopped, and returns the original state after the detection in order to detect ejection failure of the nozzle. The head moving means 65 has a function of moving the image reading means 62 and the light emitting means 63 in the reverse direction, and is realized by the motor M2 drive circuit 39, the motor M2 (81), the feed screw 82, the nut 83, and the base 90. The
The determination unit 66 has a function of determining the presence or absence of nozzle ejection failure from the results of the first image comparison unit 43 and the second image comparison unit 44, and is realized by the CPU 31.

[Operation]
6A, 6 </ b> B, and 6 </ b> C are explanatory diagrams of a discharge detection method.
The ink forms a droplet film called a meniscus with respect to an ink nozzle (hereinafter referred to as a nozzle) in the head 22. Since the nozzle is composed of an actuator that expands and contracts by applying a potential of a piezoelectric element or the like, the droplet is ejected by applying a potential to eject the ink droplet from the nozzle to the actuator.
Further, it is possible to vibrate the meniscus film by applying an electric potential to the actuator within a range where the droplets are not ejected. This operation is referred to as fine driving, and the case where the meniscus vibrates toward the outside of the nozzle as shown in FIG. 6 (a) is referred to as fine driving 1, and the meniscus is used as the nozzle as shown in FIG. 6 (b). The case where the vibration vibrates inward is referred to as fine drive 2.
The waveforms of fine drive 1 and fine drive 2 are waveforms showing constant values such that fine drive 1> fine drive 2 as shown in FIG.
The above control is controlled by a drive circuit in the engine control board 26. However, when the drive circuit is mounted on the head, the control is performed by the drive circuit, so the control can also be performed by the head, and the control of the drive circuit by the engine control board will be described as an example. .
In addition, the line sensor will be described here using a mono image resolution of 4 pixels per nozzle, but the number of pixels is not specified.

  On the left side of FIG. 6A, light is emitted obliquely from the light source 230 to the nozzle surface of the head 22. The line sensor 240 images the ink exposed from the nozzle surface of the head 22. The positional relationship between the pixels of the line sensor 240 and the nozzle openings is shown on the lower right side of FIG. 6A, and the output (reflected light amount) and line of the line sensor 240 are shown on the upper right side of FIG. The relationship with the pixels of the sensor 240 is shown. The line sensor output for each pixel is approximately “0” → almost “127” → “285” → almost “127” → almost “0” → almost “0” → almost “127” → “285” → almost “127” → It has changed to almost “0”.

On the left side of FIG. 6B, light is emitted obliquely from the light source 230 to the nozzle surface of the head 22. The line sensor 240 images the ink drawn from the nozzle surface of the head 22. The positional relationship between the pixels of the line sensor 240 and the nozzle openings is shown on the lower right side of FIG. 6B, and the output (reflected light amount) and line of the line sensor 240 are shown on the upper right side of FIG. The relationship with the pixels of the sensor 240 is shown. The line sensor output for each pixel is approximately “255” → approximately “127” → approximately “255” → approximately “127” → approximately “255” → approximately “127” → approximately “255” → approximately “127” → approximately “255” "
Comparing the line sensor outputs on the upper right side of FIG. 6A and the upper right side of FIG. 6B, it can be seen that the former amplitude is larger than the latter amplitude.

FIGS. 7A and 7B are other explanatory views of the discharge detection method.
The difference between the method shown in FIGS. 7A and 7B and the method shown in FIGS. 6A and 6B is that a designated pixel of the line sensor is output.
On the left side of FIG. 7A, light is emitted obliquely from the light source 230 to the nozzle surface of the head 22. The line sensor 240 images the ink exposed from the nozzle surface of the head 22. The positional relationship between the pixels of the line sensor 240 and the nozzle openings is shown on the lower right side of FIG. 7A, and the output (reflected light amount) and line of the line sensor 240 are shown on the upper right side of FIG. The relationship with the pixels of the sensor 240 is shown. Of the line sensor 240, a line sensor designated pixel 24a and a reference value 1 are shown. Reference value 1 is a line sensor output of 30 or less. The line sensor designated pixel data has a reference value of 1 or less at a position corresponding to the line sensor designated pixel 24a.

  On the left side of FIG. 7B, light is emitted obliquely from the light source 230 to the nozzle surface of the head 22. The line sensor 240 images the ink drawn from the nozzle surface of the head 22. The positional relationship between the pixels of the line sensor 240 and the nozzle openings is shown on the lower right side of FIG. 7A, and the output (reflected light amount) and line of the line sensor 240 are shown on the upper right side of FIG. The relationship with the pixels of the sensor 240 is shown. Of the line sensor 240, a line sensor designated pixel 24a and a reference value 2 are shown. The line sensor designated pixel data is larger than the line sensor output “210” of the reference value 2 at the position corresponding to the line sensor designated pixel 24a, and the line sensor output is “127” at other positions.

FIG. 8 is an example of a flowchart of the discharge detection method.
When the discharge detection is started, it is determined whether or not a time has elapsed since the previous printing (S1). Wait until the time elapses (S1 / NO), and when the time elapses (S1 / YES), the light source controller supplies power to the light source (S2) and outputs a signal for generating fine drive 1 from the drive circuit (S2). S3). The designated pixel output of the line sensor is read by the image capturing means as the image capturing unit (S4), and the image comparison unit 1 compares with the reference value 1 (S5). Determine whether or not the reference value has been exceeded (S6), and if it has exceeded (S6 / YES), output a signal to generate fine drive 2 from the drive circuit (S7) and specify the line sensor at the image capture unit Read the pixel output (S8). The second image comparison means as the image comparison unit 2 performs comparison with the reference value 2 (S9), determines whether or not the reference value is exceeded (S10), and if it exceeds (S10 / YES), it is normal If so, the discharge detection is terminated (S11).

  If the reference value is not exceeded (S6 / NO, S10 / NO), it is determined that there is an abnormality (S12), the abnormality information is stored in the memory, and the process ends (S13).

  That is, when carrying out discharge detection, a signal for turning on the light source control unit is transmitted to light the light source. A control signal for fine drive 1 is transmitted from the drive circuit to the ink ejection mechanism. The ink ejecting mechanism performs an operation corresponding to the fine driving 1 for the nozzle, and vibrates the ink meniscus of the nozzle opening outward.

  The image capture unit captures data (light quantity) from the pixel of the line sensor designated by the instruction from the CPU, and sends the data to the image comparison unit 1 and the image comparison unit 2.

The image comparison unit 1 and the image comparison unit 2 compare the data sent from the image capturing unit with the reference values 1 and 2 set in advance. If the comparison result exceeds the reference value, the image comparison unit 1 and the image comparison unit 2 are normal. Judge abnormalities. Abnormal information is stored in the memory for the nozzles determined to be abnormal.
Here, the abnormality information stores information such as the nozzle number, the pixel number, and which result of the image comparison units 1 and 2 was NG.
In this embodiment, the output (the amount of reflected light) of the line sensor is read with 8-bit resolution. In addition, it is assumed that the output (the amount of reflected light) of the line sensors other than the designated pixel is fixed to 127 (0X-7F), and normal / abnormal judgment will be described below.

When the fine driving 1 is performed, if the meniscus is normal, the output (the amount of reflected light) of the line sensor becomes a value of 0 to 30 (0X-1E). By comparing the reference value 1 to 30 (0X-1E), it is possible to determine whether the fine drive 1 is normal or abnormal.
Normal = fine drive 1 <reference value 1 (0X-1E)
When fine driving 2 is performed, if the meniscus is normal, the output of the line sensor (the amount of reflected light) is
The value is 210 (0X-D2) to 255 (0X-FF).
By comparing the reference value 2 with 210 (0X-D2), it is possible to determine whether the fine drive 2 is normal or abnormal.
Normal = fine drive 2> reference value 2 (0X-D2)

FIG. 9 is an explanatory diagram of discharge detection using bubbles or the like.
Discharge detection is performed as described in FIGS. At this time, if the output of the line sensor does not exceed the reference value 1, which is a threshold value, it can be determined that the amount of displacement is small due to some cause of the meniscus state.
On the left side of FIG. 9, light is emitted obliquely from the light source 230 to the nozzle surface of the head 22. The line sensor 240 images the ink exposed from the nozzle surface of the head 22. The lower right side of FIG. 9 shows the positional relationship between the pixels of the line sensor 240 and the nozzle openings, and the upper right side of FIG. 9 shows the output (the amount of reflected light) of the line sensor 240 and the pixels of the line sensor 240. The relationship is shown.
The ink exposed from the nozzles of the head 22 is indicated by a broken line when normal, and is indicated by a solid line when abnormal. The line sensor output for the line sensor designated pixel 24a is less than “30” when normal, but is almost “127” when abnormal.

FIG. 10 is an explanatory diagram relating to discharge detection when a foreign object adheres to the nozzle.
On the left side of FIG. 10, light is emitted obliquely from the light source 230 to the nozzle surface of the head 22. The line sensor 240 images the ink exposed from the nozzle surface of the head 22. The lower right side of FIG. 10 shows the positional relationship between the pixels of the line sensor 240 and the nozzle openings, and the upper right side of FIG. 10 shows the output (the amount of reflected light) of the line sensor 240 and the pixels of the line sensor 240. The relationship is shown. When the line sensor output corresponding to the line sensor designated pixel 24a is normal, the reference value 2 exceeds the reference value 2 and is almost “255”, whereas the abnormality due to the foreign matter is less than the reference value 2, and “130” and “210”. The abnormality due to the contamination of the sensor is less than “130”.
Discharge detection is performed as described in FIGS. At that time, if the output of the line sensor does not exceed the reference value 2 which is a threshold value, the attachment of foreign matter or the contamination of the line sensor is considered. In this case, if the output of the line sensor does not exceed 130, it can be determined that the sensor is dirty.

<Embodiment 2>
[Constitution]
The appearance and hardware block diagram of the light source, the line sensor, and the engine control board are the same as those in FIGS.

FIG. 11 is another example of a functional block diagram of an ink jet printer as an image forming apparatus.
The difference between the functional block diagram shown in FIG. 11 and the functional block diagram shown in FIG. 5 is that there is one image comparing means.
In other words, this image forming apparatus switches and uses the reference value of one image comparison means 60.

  By enabling the reference value 1 or the reference value 2 to be switched by a command from the CPU 31, it is possible to reduce the number of image comparison units.

[Operation]
FIG. 12 is an example of a flowchart showing the operation of the ink jet printer as the image forming apparatus shown in FIG.
When the discharge detection is started, it is determined whether or not time has elapsed since the previous printing (S21). If the time has not elapsed (S21 / NO), if the time has elapsed (S21 / YES), the light source controller supplies power to the light source (S22), and the drive circuit outputs the fine drive signal 1 (S23). ), The reference value is set to the reference value 1 (S24). The image capturing unit reads the designated pixel output of the line sensor (S25), and the image comparison unit compares with the reference value 1 (S26), and determines whether the reference value is exceeded (S27). When the reference value 1 is exceeded (S27 / YES), the fine drive signal 2 is output from the drive circuit (S28), the reference value is set to the reference value 2 (S29), and the line sensor is specified by the image capture unit. Read the pixel output (S30). The image comparison unit compares with reference value 2 (S31), determines whether the reference value is exceeded (S32), and if it exceeds the reference value (S32 / YES), determines that it is normal and detects Is finished (S33).
If it is determined that the reference value is not exceeded (S27 / NO, S32 / NO), it is determined that there is an abnormality (S34), the abnormality information is stored in the memory, and the detection is terminated (S35).

  That is, when carrying out discharge detection, a signal for turning on the light source control unit is transmitted to light the light source. A control signal for fine drive 1 is transmitted from the drive circuit to the ink ejection mechanism. The ink ejecting mechanism performs an operation corresponding to the fine driving 1 for the nozzle, and vibrates the ink meniscus of the nozzle opening outward.

  The image capture unit captures data (light quantity) from the pixel of the line sensor designated by the command from the CPU as the control means, and sends the data to the image comparison unit. The image comparison unit is set with a reference value 1 by a command from the CPU, compares the data sent from the image capturing unit with the set reference value 1, and determines that an abnormality is found if it does not exceed the comparison result. . Abnormal information is stored in the memory for the nozzles determined to be abnormal. If the reference value 1 is exceeded, a control signal for fine drive 2 is transmitted, data (light quantity) is fetched from the pixel of the line sensor designated by the instruction from the CPU, and the data is sent to the image comparison unit. The image comparison unit sets the reference value 2 in response to a command from the CPU, compares the data sent from the image capturing unit with the set reference value 2, and determines that there is an abnormality if it does not exceed the comparison result.

FIG. 13 is an explanatory diagram of ejection detection for a plurality of rows of ink heads.
As described with reference to FIGS. 3 to 12, ejection detection is performed on the nozzles of each ink head. Here, the case of a four-color ink head of K / C / M / Y will be described as a plurality of rows of ink heads.

For each ink head, an ejection detection unit equipped with a line sensor and a light source is moved parallel to the nozzle surface using a drive source such as a motor.
When the head 22 is moved like a serial printer, the head may be moved.
Fine driving 1 and 2 are performed on the nozzles of the head 22.
The line sensor 240 outputs the state of the meniscus on the nozzle surface as data (light quantity) while sequentially moving from the right side (nozzle C: cyan: blue side) in FIG. 13 to the left.
With respect to the data output from the line sensor 240, the CPU, the image capture unit, and the image comparison unit determine whether there is an abnormality in the nozzle.

FIG. 14 is an explanatory diagram regarding the setting of the designated pixel.
On the left side of FIG. 14, light is emitted obliquely from the light source 230 to the nozzle surface of the head 22. The line sensor 240 images the ink drawn from the nozzle surface of the head 22. The lower right side of FIG. 14 shows the positional relationship between the pixels of the line sensor 240 and the nozzle openings, and the upper right side of FIG. 14 shows the output (the amount of reflected light) of the line sensor 240 and the pixels of the line sensor 240. The relationship is shown. If the line sensor output is within the range between the reference value 3a and the reference value 3b, one pixel number is written in the memory.

FIG. 15 is an example of a flowchart for setting a designated pixel.
When the designated pixel setting is started, power is supplied from the light source control unit to the light source (S41), the nozzle image data is read out by the image capturing unit (S42), and the nozzle image data is stored in the memory (S42). S43). The image comparison unit reads the reference values 3a and 3b (S44), the image comparison unit reads the nozzle image data (S45), and determines whether or not it is within the range of the reference value 3a to the reference value 3b (S46). When it is within the range from the reference value 3a to the reference value 3b (S46 / YES), one pixel number is written in the memory, and the setting of the designated pixel is completed (S47). If it is not within the range from the reference value 3a to the reference value 3b (S46 / NO), the abnormal process is performed and the setting of the designated pixel is completed (S48).

That is, when the designated nozzle setting condition such as the first power-on is reached, the following is performed as the designated pixel setting.
The light source controller emits light from the light source, and the image capturing unit reads the output of the line sensor as nozzle image data. The read image data is stored in the memory. The image comparison unit compares the reference values 3a and 3b that are determined in advance by evaluation or the like and stored in the memory with the image data stored in the memory, and the data of each pixel is determined from the reference value 3a based on the comparison result. If it is out of the range of value 3b, abnormal processing is performed. If the data of each pixel is within the range from the reference value 3a to the reference value 3b, one pixel number is stored in the memory for one nozzle port, and the process ends. Further, by storing the nozzle row numbers in the memory, it is possible to set designated pixels for a plurality of nozzle rows.

  Further, the setting history of the designated pixel may be stored in the nonvolatile memory, and may not be executed unless there is a user or service instruction, such as when the power is turned on next time.

<Program>
The image forming apparatus according to the present invention described above is realized by a program that causes a computer to execute processing. As an example, the case where the function of the present invention is realized by a program will be described below.

For example,
A computer readable program of an image forming apparatus,
Computer
A procedure for irradiating the nozzle surface of the head to the light emitting means,
Procedure for photographing the nozzle surface of the head on the image reading means,
Procedure to raise the head to the lifting means,
A procedure for causing the moving means to move the light emitting means and the image reading means directly below the raised head;
A procedure for comparing the image data of the nozzle surface with a preset reference value in the image comparison means,
A procedure for determining whether or not there is a discharge failure of the nozzle of the head from the result of the procedure to be compared in the determination means,
A program for executing

  Such a program may be stored in a computer-readable recording medium.

<Recording medium>
Here, examples of the recording medium include computer-readable storage media such as CD-ROM, flexible disk (FD), and CD-R, semiconductor memories such as flash memory, RAM, ROM, and FeRAM, and HDD.

  CD-ROM is an abbreviation for Compact Disc Read Only Memory. Flexible disk means Flexible Disk (FD). CD-R is an abbreviation for CD Recordable. FeRAM is an abbreviation for Ferroelectric RAM and means a ferroelectric memory. HDD is an abbreviation for Hard Disc Drive.

<Effect>
As described above, according to the present embodiment, whether or not ejection is possible is determined based on whether or not the meniscus fluctuation amount exceeds the reference value. That is, the state of the meniscus is changed by finely driving the nozzle with respect to the meniscus generated at the nozzle opening at the time of ejection detection, and the change amount of the meniscus at that time is detected. As a result, in the line printer, it is possible to reduce consumption of ink and paper in detecting whether ejection is possible.

In addition, according to the present embodiment, the state of the nozzle can be determined in a short processing time without consuming ink or paper.
Further, according to the present embodiment, the cause can be specified, so that maintenance time can be shortened and ink consumption due to maintenance can be reduced.
Further, according to the present embodiment, the circuit of the image comparison unit can be reduced, and the cost can be reduced.
Moreover, according to this embodiment, the accuracy of discharge detection can be improved.
Further, according to the present embodiment, it is possible to shorten the first print and shorten the power-on.

  The above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention. is there. For example, in the above-described embodiment, the case where the light source, the line sensor, and the head are moved has been described. However, the present invention is not limited to this, and the ink is physically separated from the ink by a shielding unit such as a shutter. Contact may be blocked.

DESCRIPTION OF SYMBOLS 10 Inkjet printer 11 Paper reversing unit for double-sided printing 12 Transport guide 13 Charging roller 14 Paper separation pad 15 Paper feed roller 16 Transport belt 17 Tension roller 18 Paper tray 19 Paper 20 Ink supply pipe 21 Tip roller 22 Head 23 High voltage power supply 24 Ejection Paper tray 25 Transport roller 230 Light source 240 Line sensor

Japanese Patent No. 5296825

Claims (8)

A light emitting means for irradiating the nozzle surface of the head;
Image reading means for photographing the nozzle surface of the head;
Elevating means for raising the head;
Moving means for moving the light emitting means and the image reading means directly below the head after ascending;
Image comparison means for comparing the image data of the nozzle surface with a preset reference value;
An image forming apparatus comprising: a determination unit that determines whether or not there is a discharge failure of the nozzle from the result of the image comparison unit.   The image forming apparatus according to claim 1, further comprising a determination unit configured to determine dirt on the image reading unit and foreign matter attached to the nozzle surface.   2. The image forming apparatus according to claim 1, further comprising reference value setting means for setting the reference value according to a command from a control means. Designated pixel setting means for setting designated pixels as detection targets;
Capturing means for capturing data of the designated pixel;
The image forming apparatus according to claim 1, further comprising:   2. The image forming apparatus according to claim 1, further comprising storage means for storing a setting history of the designated pixel.   Raising the head, irradiating the nozzle surface of the head after ascending and photographing the nozzle surface, comparing the image data of the nozzle surface with a preset reference value, and from the comparison result, the nozzle of the head A method for determining non-ejection of nozzles in an image forming apparatus, wherein the presence or absence of ejection failure is judged. A computer readable program of an image forming apparatus,
The computer is
A procedure for irradiating the nozzle surface of the head to the light emitting means,
A procedure for photographing the nozzle surface of the head on an image reading unit;
A procedure for raising the head to the lifting means;
A procedure for causing the moving means to move the light emitting means and the image reading means directly below the raised head;
A procedure for comparing image data of the nozzle surface with a preset reference value in an image comparison means;
A procedure for determining the presence or absence of defective ejection of the nozzles of the head from the result of the comparing procedure in the determining means;
A program for running   A recording medium on which the program according to claim 7 is recorded.