JP2005219395A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with a means for surely and accurately detecting inferiority of operation of a print head. <P>SOLUTION: The image forming apparatus is equipped with a detecting means for detecting a position for starting movement of the print head, and a comparing means for comparing the number of pulses of an outward trip moving from the position for starting the movement to a position for completing the movement in the sub-scanning direction with the number of pulses of a return trip moving from the position for completing the movement to the position for starting the movement, and is constituted so that the inferiority of the operation of the print head is judged by the result of the comparison. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly, to a print head in which a large number of pixel forming elements capable of recording pixel information on a recording material are arranged along the main scanning direction. The image forming apparatus includes an image forming unit that forms a two-dimensional image on the recording material and moves the print head by pulse control.

As the image forming apparatus configured as described above, for example, the one disclosed in Patent Document 1 exists. Patent Document 1 shows a perspective view of the entire image forming apparatus configured as described above as FIG. Further, an EUb corresponding to the first two-dimensional image forming means of the present invention is built in the inside. The location where the EUb is built is illustrated in FIG. 2, which is a cross-sectional view of FIG. As shown in FIG. 3, the exposure unit EUb (image forming means for forming a two-dimensional image of the present invention) is close to the emulsion surface of the photographic paper CP (recording material of the present invention) supported on the exposure table 4. A frame member 20 disposed above the exposure table 4 and a digital exposure head 21 (a print head of the present invention) having a large number of light emitting elements disposed along the main scanning direction. It has a structure. The digital exposure head 21 is configured to reciprocate along a sub-scanning direction using a ball screw mechanism 24 that is an example of a driving unit. Further, regarding the moving method, a method using a timing belt or the like is described as another embodiment.
Then, based on the given print data, each element array 21r, 21g, 21b is driven while the digital exposure head 21 is transported along the sub-scanning direction by the ball screw mechanism 24, whereby the exposure table 4 has the above-mentioned. It is described that a predetermined image is line-exposed on a photographic paper CP held in a stationary state on a support surface to form a two-dimensional image (the numbers are cited in the literature).

JP 2002-333682 (paragraph numbers [0019] to [0021], [0025], FIGS. 1 to 3)

  In the image forming apparatus configured as described above, if the print head is not moved in the sub-scanning direction accurately in synchronization with the line exposure of the image data in the main scanning direction, the two-dimensional image is accurate with respect to the recording material. Not formed. For example, when the timing belt mechanism for moving the print head or the ball screw mechanism is mechanically caught or when a stepping out occurs in a motor for supplying power to the mechanism, an accurate image cannot be formed. In other words, when a catch occurs, an image that is smaller than the intended image or an image that includes line skipping is formed, and the print head stops due to motor step-out or malfunction of the mechanism. If this happens, image formation will be interrupted at that position.

  Even when an accurate image is not formed by the movement of the print head as described above, some kind of image is recorded on the recording material, and as a result, the recording material is wasted. Further, the print head having such a configuration generally returns to the initial position once the image formation for one image is completed, and forms the next image, and the previous image formation was defective. The next image formation may be performed without the operator knowing. In addition, such an image forming apparatus is often used in an apparatus for printing a large number of photographs in a photo print shop or the like, and therefore frequently prints continuously. If repeated defects occur during continuous printing, the amount of recording material that is wasted increases accordingly, and it takes time to start over. In addition, the printer may be buried in a large number of prints, and a photo print shop or the like may give a defective print to the end user without noticing the defect.

  Furthermore, due to the rapid spread of digital cameras and personal computers in recent years, the eye-catchingness of photographic images by general users has also improved. There is also the possibility of being pointed out if you take it home and watch it carefully. With such changes in social conditions, there is a need for a method for detecting malfunctions of the print head reliably and accurately.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus having means for detecting malfunction of a print head reliably and accurately.

  In order to achieve the above object, according to the first characteristic configuration of the present invention, as described in claim 1 of the claims, the detection means for detecting the movement start position of the print head, and the movement of the print head Comparing means for comparing the number of forward pulses to be moved from the start position to the movement completion position in the sub-scanning direction and the number of backward pulses to be moved from the movement completion position to the movement start position. The point is to determine the malfunction of the print head.

  According to the above characteristic configuration, the print head is reliably and highly accurate by comparing the number of control pulses in each of the forward path and the return path when the print head reciprocates in the sub-scanning direction from the movement start position. The effect that it is possible to detect this malfunction is obtained. The movement control in the sub-scanning direction needs to be accurately controlled in synchronization with the image data in the main scanning direction. In order to ensure accuracy, the drive motor and the like are often controlled by pulse control. In the present invention, since the determination is performed based on the number of pulses output in synchronization with the image data to be printed, the determination accuracy is also improved. For this reason, it is possible to satisfactorily detect even a defect that is overlooked in a print shop. As a result, it is possible to reduce the waste of the photosensitive material due to defective printing and to increase the satisfaction of the end user.

  According to the second feature configuration of the present invention, as described in claim 2 of the claims, in addition to the first feature configuration described above, the image forming apparatus optically transmits two-dimensional image information to the recording material. And a plurality of image forming means for projecting to the second image forming means for forming an image and controlling the image forming range by the second image forming means by blocking the projected two-dimensional image information And a part of the shielding means is performed using the print head.

  According to the second characteristic configuration described above, in an image forming apparatus having a plurality of image forming means, when an image is formed using one method (the second image forming means), it is not used for image formation. Even when the print head portion of one image forming apparatus is configured to be used as the projection image blocking means, the image can be blocked with high accuracy in the same manner. That is, since the projected image is blocked using the driving means and the control means for moving the print head, the comparison of the number of reciprocating pulses for controlling the print head is also performed as to whether or not the blocking is performed at a set position. It becomes possible to judge by. As a result, even when an image is formed using the second image forming means, it is possible to form an image with high accuracy and to reduce the loss print.

  According to the third feature configuration of the present invention, as described in claim 3 of the claims, in addition to the first and second feature configurations described above, a malfunction of the print head is determined from the comparison result. In this case, the determination result is notified.

  According to the third characteristic configuration described above, the determined malfunction of the print head is configured to notify the user of the image forming apparatus that an abnormality has occurred in the operation of the print head. I came to understand. Therefore, when a failure is indicated, the user can stop or interrupt the subsequent printing, or check or check the print head. As a result, it is possible to reduce the occurrence of continuous misprinting due to an abnormality in the print head.

Hereinafter, an embodiment of the present invention will be described by taking an image forming apparatus in a photographic print system called a minilab as an example.
FIG. 1 is a perspective view showing an appearance of an example of an image forming apparatus according to the present invention. FIG. 2 is a schematic block diagram of the image forming apparatus.
The image forming apparatus 300 includes an exposure processing unit Ex that exposes a given image onto photographic paper (an example of a recording material), and a development processing unit De that develops the exposed photographic paper.
The exposure processing unit Ex is pulled out of a photographic paper magazine 1 capable of storing a long unexposed photographic paper LP in a roll shape, and a drawer roller unit 2 for drawing out the photographic paper LP from the photographic paper magazine 1 by an appropriate length. Cutter 3 for cutting photographic paper LP, rectangular sheet-like photographic paper CP made by cutter 3 is received and given to exposure table 4 that is fixedly supported, and photographic paper CP that is supported on exposure table 4 An exposure unit EU that exposes an image at an exposure position EP, an intermediate transport mechanism that receives the photographic paper CP exposed by the exposure unit EU from the exposure table 4, and delivers the photographic paper CP to the development processing unit De.

The exposure table 4 includes a rubber film-like endless belt 5, support rollers 6 a, 6 b, 6 c that support the endless belt 5 at at least three points, and two support rollers 6 a, 6 c arranged at substantially the same level. In order to convey the portion of the endless belt 5 stretched around the roller 3 toward the roller pair assembly 8 (an example of an intermediate conveying mechanism) from the cutter 3, these support rollers 6a, 6b, 6c are based on instructions from the control unit CU. A driving motor M6 that rotates at least one of the driving motor M6. In FIG. 2, for the sake of convenience, the configuration for driving 6c is illustrated. In addition, a large number of through holes are formed on the entire surface of the endless belt 5, and the back surface side of the endless belt 5 stretched between the two support rollers 6 a and 6 c described above is disposed on the endless belt 5. A suction device 7 is disposed for fixing the photographic paper CP placed on the endless belt 5 through the through hole with a negative pressure.
The leading end of the photographic paper CP provided from the cutter 3 is fixed on the endless belt 5 by the suction device 7, and subsequently, based on the rotational drive of the endless belt 5 and the subsequent stop of the endless belt 5, the exposure unit EU It is arranged at the lower exposure position EP.

For example, when the photographic printer is used for color photographic processing, the development processing unit De includes a number of processing tanks (not shown) that hold processing solutions such as a color developer, a bleach-fix solution, and water for washing. In order to guide the photographic paper CP one after another to the developing processing liquid in each processing tank, a transport rack (not shown) disposed in each processing tank is provided. Downstream of the processing tank, a drying processing unit (not shown) for drying the developed photographic paper CP and a discharge port 12 for discharging the finished photographic print out of the photographic printer are provided. ing.
The exposure unit EU includes a first exposure unit 100 (an example of an image forming unit) having a line exposure head and a second exposure unit 200 (an example of a second image forming unit) having a projection exposure unit.

As shown in FIG. 3, the first exposure unit 100 includes a frame member 20 disposed above the exposure table 4 so as to face the emulsion surface of the photographic paper CP supported on the exposure table 4. And an exposure head 21 (an example of a print head) having a large number of light emitting elements (an example of a pixel forming element) arranged along the main scanning direction.
The exposure head 21 has an exposure head main body 22 in which a large number of light emitting elements are incorporated, and a support member 23 that extends in the main scanning direction to support the exposure head main body 22. The support member 23 has a base end portion 23a at a position displaced toward one end of the exposure head main body 22 in the main scanning direction, and an arm portion 23b extending from the base end portion 23a to one side in the main scanning direction. The exposure head body 22 is supported by the arm portion 23b.

The first exposure unit 100 is provided with a ball screw mechanism 24 (an example of a driving unit) that reciprocates the exposure head 21 along the sub-scanning direction. The ball screw mechanism 24 rotationally drives the ball screw 25 that is rotatably supported by the frame member 20, the ball nut 23 N that is fixed to the base end portion 23 a of the support arm 23 so as to be screwed to the ball screw 25, and the ball screw 25. Drive motor M25. The ball screw 25 extends along the sub-scanning direction. When the ball screw 25 is rotated by the drive motor (shift motor) M25, the operation force in the sub-scanning direction by the ball screw 25 is transmitted to the ball nut 23N as a predetermined operated position of the exposure head 21 in the main scanning direction. .
Further, the first exposure unit 100 is provided with a guide mechanism for guiding the exposure head 21 accurately and linearly in the sub-scanning direction. The linear guide member 27 supported by the frame member 20 so as to extend in parallel with the ball screw 25 is an example of the guide mechanism. The linear guide member 27 has a non-circular cross-sectional shape, and also functions as a guide mechanism that regulates the rotation of the exposure head 21 around the ball screw 25.

  A vacuum fluorescent tube (VF) type exposure head is used as the exposure head 21, and a first element array 21r in which first vacuum fluorescent tube elements emitting a red light beam are arranged in the main scanning direction, and a green color are used. The second vacuum fluorescent tube element that emits the second light fluorescent beam is arranged in the main scanning direction, and the third vacuum fluorescent tube element that emits the blue light beam is arranged in the main scanning direction. A third element array 21b. Each of the element arrays 21r, 21g, and 21b has a vacuum fluorescent tube element having a required density and a length corresponding to the width of the photographic paper CP. Each of the first, second, and third vacuum fluorescent tube elements is an example of a light emitting element that can form a latent image of minute dots (an example of pixel information) on the photographic paper CP by emitted light. . As the exposure head 21, in addition to a vacuum fluorescent tube type exposure head, a liquid crystal shutter type exposure head provided with a light source composed of an LED or the like and a liquid crystal that turns on / off light emission from the light source in units of pixels, or In addition, a number of optical fiber cables extending from a halogen lamp or the like, a PLZT type exposure head, and the like can be used.

Image information when an image is formed using the first exposure unit 100 of the image forming apparatus 300 is given via the control unit CU. The image information input means includes the following forms. Using a film scanner 13 composed of a light source 13a and a sensor 13b typified by a CCD, there is provided means for optically reading an image of the exposed and developed photographic film F and converting it into digital image data. In addition, device driver means DD for taking out image information and additional information associated therewith from an optical recording medium such as a floppy disk, MO, CD-R, flash memory or other image information medium is provided.
The control unit CU creates print data based on the image information and additional information given through these input means. The print data includes the information obtained by developing additional information such as the frame number, frame name, shooting date and time, and shooting conditions of the photograph into image information.

Then, the control unit CU drives each of the element arrays 21r, 21g, and 21b while transporting the exposure head 21 along the sub-scanning direction by the ball screw mechanism 24 based on the print data, thereby exposing the exposure table 4. A predetermined image can be line-exposed on the photographic paper CP held stationary at the exposure position EP on the support surface.
More specifically, the main scanning print data is output from each light emitting element of the exposure head 21, and the exposure head 21 is moved in the sub-scanning direction in synchronization with the output of the main scanning print data of each line. A latent image of a two-dimensional image is formed on the paper CP. The movement of the exposure head 21 is driven by the motor M25 as described above, but is pulse-controlled by the control unit CU because high precision is required.

Specific pulse control will be described below.
When printing at a sub-scanning resolution of approximately 200 dpi, it is necessary to advance the exposure head 21 by 0.125 mm in the sub-scanning direction as indicated by Equation 1 with respect to one main scanning line.
25.4 / 200 = 0.127≈0.125 [mm] (Expression 1)
The distance FL that the exposure head 21 travels by one rotation of the ball screw is
FL = 0.25mm (Formula 2)
Then, in order to advance one main scanning line in the sub-scanning direction, the ball screw 25 needs to be rotated 0.5 times as shown in Expression 3.
0.125 / 0.25 = 0.5 [rotation] (Formula 3)
In order to make the ball screw rotate once, the number of pulses MP that need to be given to the motor M25 is:
MP = 80 (Formula 4)
Then, in order to advance one main scanning line in the sub-scanning direction, as shown in Equation 5,
80 × 0.5 = 40 [pulse] (Formula 5)
Is required. Therefore, when an image of 1000 lines is exposed in the sub-scanning direction, as shown in Equation 6,
40 × 1000 = 40000 [pulse] (Formula 6)
Is required.

Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 4, 5, and 6.
When an image is formed using the exposure unit 100, target image information is prepared in the image processing unit 40 in the control unit CU. The image processing unit 40 includes a memory (not shown) and various image processing function units such as an image conversion unit. The image processing unit 40 generates print data from the film scanner 13, the device driver DD, data created by the control unit 41, and the like. The control unit 41 calculates the number of pulses VP that need to be given to the motor M25 from the information on the number of pixels of the image data to be printed, as shown in Equations 1 to 6, and stores it in the sub-scanning pulse number register 50 (step S1). ). The control unit 41 sets the movement direction of the exposure head 21 (exposure head main body 22, the same applies hereinafter) to the forward direction FW, and controls the rotation direction of the motor M25. Specifically, the forward direction FW is set in the rotation direction register 52, and the motor control unit 55 refers to the rotation direction register 52 to control the rotation direction of the motor M25 (step S2).

  Next, after performing necessary processing such as pre-emission of the exposure head 21, the exposure head 21 is moved from the home position HP which is the standby position to the head portion EP1 of the exposure position EP. The reason for the movement after the pre-emission is to prevent the photographic paper CP from being exposed by irradiating unnecessary light to the photographic paper CP. In the above calculation example, the calculation example of only the number of pulses corresponding to the image information to be exposed has been described, but the number of pulses necessary for movement from the home position HP to the exposure start position EP1 is also calculated by the control unit 41. The number of pulses VP that need to be given to the motor M25 is a value obtained by adding this. The pulse generator 54 starts outputting pulses in response to an instruction from the controller 41 and outputs pulses until the number of pulses VP stored in the sub-scanning pulse register 50 is reached. The number of pulses output by the pulse generator 54 is counted by the pulse counter 51 (step S3). The motor control unit 55 outputs a motor drive signal and controls the motor M25 according to the pulse generated by the pulse generation unit 54 and the determined rotation direction. The control unit 41 and the image processing unit 40 output print data in accordance with this movement, and move the exposure head 21 from the exposure start position EP1 to the exposure end position EP2 that is the end part of the exposure position EP. Expose the dimensional image. The comparison unit 53 outputs a coincidence detection signal to the control unit 41 when the pulse number PC counted by the pulse counter 51 matches the pulse number VC stored in the sub-scanning pulse number register 50. The control unit 41 instructs the pulse generation unit 54 to stop the pulse output, and the exposure head 21 stops. The movement of the exposure head 21 so far is referred to as an outward path.

  When the exposure to the exposure end position EP2 is completed, the control unit 41 sets the traveling direction of the exposure head 21 to the reverse direction BK (step S4). The drive motor M25 is driven in the direction opposite to the forward path until the rotation direction is reversed and the exposure head 21 returns to the home position HP. At this time, the control unit 41 resets the pulse counter 51 before starting the generation of the drive pulse (step S5). Then, drive pulses are generated while counting is continued until the exposure head 21 reaches the home position HP. Whether or not the exposure head 21 has reached the home position HP is detected by the home sensor HS. When it is detected that the home position HP has been reached, the controller 41 instructs the pulse generator 54 to stop generating the drive pulse (step S6). The movement of the exposure head 21 so far after the end of the forward path is called a return path.

When the exposure head 21 completes the above-described reciprocating movement of the forward path and the backward path, the control unit CU includes the number of pulses VP calculated as necessary for the forward path (equivalent to the number of pulses actually output in the forward path) and the backward path. The actually output pulse number PC is stored in the sub-scanning pulse number register 50 and the pulse counter 51, respectively. These two numerical values are the number of pulses related to the movement of the exposure head 21 in the forward path and the return path of the same path, respectively. Therefore, when the reciprocating movement of the exposure head 21 is completed normally, the two pulse numbers substantially coincide. Here, the reason for substantially matching is that minute error elements such as play of the drive mechanism such as the ball screw 25 and backlash of the drive mechanism that occurs at the time of reversal occur.
Therefore, for the match detection:
PC = VP (Formula 7)
May be subject to the exact match of
PC≈VP (Formula 8)
As described above, it is further preferable that the matching condition is determined in consideration of the error factor. In the flowchart shown in FIG. 6, the conditional expression of Expression 7 is described for the sake of convenience (step S7), but it is of course not limited to this. As an example of coincidence detection in consideration of an error factor, the values of the pulse numbers VP and PC stored as digital information in the control unit CU can be bit-shifted to obtain coincidence as shown in Equation 9.
PC / 8 = VP / 8 (Formula 9)
Expression 9 is an example in which the lower 3 bits are shifted and compared only by the upper data. Rather than comparing two numerical values, calculating the difference, and comparing whether the difference is within the allowable error range, the bit shift or simple match comparison is more concise Time can be shortened.

  In the above example, the pulse counter 51 is reset when the motor M25 is reversed. However, there is a method in which the pulse counter 51 is used as a subtraction counter. That is, the pulse counter 51 is composed of a counter that can be switched between the increment and decrement functions, and the increment / decrement of the pulse counter 51 is also switched when the motor M25 is controlled in reverse. When the motor M25 is reversely controlled, the number of pulses actually output in the forward path is set in the pulse counter 51 as an initial value. The pulse counter 51 continues to decrement by the pulse output from the pulse generator 54 until the exposure head is detected by the home sensor HS. When the reciprocating movement of the exposure head 21 is completed normally, the pulse number PC of the pulse counter 51 substantially coincides with zero. Here, an example in which a subtraction counter is used in the return path has been described. However, a subtraction counter can be similarly used in the forward path.

The method for determining the coincidence between the calculated pulse number VP and the counted pulse number PC has been described above. However, when the two coincide substantially, the process is completed without any problem. This is because the number of pulses in the forward path and the backward path of the exposure head 21 are compared, and the number of pulses substantially matches, so that it can be confirmed that the exposure head 21 has correctly reciprocated and that normal exposure has been completed (step S8a).
However, when both do not substantially match, it is determined that there is an abnormality. Of course, when the movement of the exposure head 21 stops in the middle of the outward path, the rotation number of the motor M25 per pulse is out of order, or the ball spring 25 is caught, and the movement of the exposure head 21 in synchronization with the number of pulses. This is the case when there is a high probability that In this case, since the exposure head 21 has not been moved normally, there is a high probability that the image exposed on the photographic paper CP is defective, and the control unit CU detects that it is abnormal. Then, the exposure process is finished (step S8b).
In this way, it is possible to determine whether or not the exposure head 21 has operated normally by comparing the number of pulses in the forward path and the backward path of the exposure head 21.

On the other hand, although the determination process is a little complicated, it is possible to perform more accurate determination by comparing not only simple matching but also size comparison, and adding the magnitude relationship between the number of pulses in the forward path and the backward path as a determination factor. Become. For example,
PC <VP (Formula 10)
If so, the moving distance of the return path is shorter than the calculated value. In this case, the exposure head 21 has not advanced to the original exposure end position EP2. Therefore, the ball spring mechanism 24 is caught on the outward path, and as a result, the exposed image may be shrunk, or depending on the line, there may be a double exposure, or it may stop completely. It is possible that this has happened. Therefore, it is determined that the formed image is defective and abnormal. vice versa,
PC> VP (Formula 11)
If so, the moving distance of the return path is longer than the calculated value. In this case, it is considered that a catch or the like has occurred on the return path. In this case, it is considered that the image is formed correctly because it is a defect on the return path. Therefore, the printing operation may be continued and the next image formation may be performed without determining that there is an abnormality. However, if it is completely stopped on the return path, the exposure head 21 has not returned to the start position of the next image formation, and therefore it is determined as abnormal. In this case, detection by the home sensor HS will not be performed indefinitely, and if it is set to time out in a certain time, it can be detected.
As described above, even when the calculated pulse number VP and the counted pulse number PC are not substantially equal to each other, it is possible to continue the printing operation under a certain condition without determining that all are abnormal. Therefore, it is possible to satisfactorily determine the abnormality without having to stop the image forming apparatus unnecessarily.

  Next, a second embodiment according to the present invention will be described. The image forming apparatus 300 taken up in this example also includes a second exposure unit 200 (an example of a second image forming unit) that forms an image by projecting light transmitted through an exposed and developed photographic film. As shown in FIG. 2, the second exposure unit 200 includes a film carrier 14 that supports the photographic film F that has been exposed and developed, and a lamp house 15 that is disposed above the film carrier 14. White light emitted from a halogen lamp 15a (an example of a light source) provided in the lamp house 15 passes through a correction color filter 17 and a mirror tunnel (not shown), and is then supported by a film carrier 14 on a photographic film F. Irradiate. The transmitted light thus formed passes through the condenser lens 18 and the shutter 19 and exposes the photographic paper CP placed at the exposure position EP on the support surface of the exposure table 4. Thus, the latent image of the image carried on the photographic film F around the optical axis OA is formed on the photographic paper CP. At this time, the exposure head 21 of the first exposure unit 100 is retracted to the home position HP so as not to disturb the optical path OP of the projection light. Although the light may be projected directly from the halogen lamp 15a onto the photographic film F, in this example, the light is projected through the mirror 15b as shown.

  When performing exposure by the second exposure unit 200, in order to form white edges and the like on the four sides of the photographic paper CP by shielding a part of the photographic paper CP held on the exposure table 4 from the transmitted light, Mask means is provided so as to face the exposure table 4. In the present embodiment, the mask means is provided with a frame member 20 constituting the first exposure unit 100 as a common frame. Referring to FIG. 3, the mask means includes a pair of first light shielding plates 30a and 30b extending in the sub-scanning direction of the exposure head 21 and a pair of second light shielding members extending in the main scanning direction. It consists of plates 31a and 31b. The first light shielding plates 30a and 30b and the second light shielding plates 31a and 31b are both supported on the frame member 20 so as to be movable in the gap between the lower surface of the exposure head 21 and the photographic paper CP.

The first light shielding plates 30a and 30b are connected to a part of a timing belt 37 stretched between a pair of pulleys 36, and are driven to rotate the timing belt based on an instruction sent from the control unit CU. It can be moved by a motor (not shown). The second light shielding plates 31a and 31b are also connected to a part of the timing belt 39 stretched between the pair of pulleys 38, and the instructions sent from the control unit CU are the same as the first light shielding plates 30a and 30b. The movement operation is possible based on The first exposure unit 100 and the second exposure unit 200 are not used simultaneously as exposure means. The exposure head 21 in the first exposure unit 100 extends along the main scanning direction, and the operation is controlled by the control unit CU. Therefore, one of the second light shielding plates 31a and 31b can be replaced with a light shielding plate fixed to the exposure head 21 itself. The position control of the light-shielding plates 30a, 30b, 31a, 31b is important for directly affecting the formed image, and the position is detected using individual sensors or the like (not shown). . However, as described above, one of the four light shielding plates 31a or 31b is configured to be interlocked with the exposure head 21, so that one of the sensors of the second light shielding plate can be used as the exposure head. Therefore, it is possible to detect a movement defect with high accuracy equivalent to 21. The details of the detection method are the same as the detection for the exposure head 21 described above.
Note that when the exposure operation by the second exposure unit 200 is performed, the exposure head 21 is retracted to the home position HP, but one of the second light shielding plates 31a and 31b is provided in the exposure head 21. In this case, of course, it is moved to a position necessary for blocking the projection light.

Next, a third embodiment according to the present invention will be described.
An image forming apparatus 300 exemplified in the present invention has a configuration as shown in FIG. 1 and includes a monitor MT that can display images, settings, and the progress of printing. When an operation failure of the exposure head 21 (or the light shielding plate 31a or 31b linked to the exposure head 21) is detected according to the embodiment of the present invention described so far, as shown in the flowchart illustrated in FIG. The result is displayed on the monitor MT (step S9). By displaying on the monitor MT, the user of the image forming apparatus 300 can quickly and clearly know whether or not the printing is proceeding smoothly and that a defect has occurred. In addition, in the case of a defect, not only a determination as to whether or not it is defective, but also a block diagram of the entire image forming apparatus 300 is displayed on the monitor MT, and a part including an expected cause of the defect is blinked. You may do it. Regardless of which method is used, the user using the image forming apparatus 300 can quickly know that a misprint has occurred, and the exposure head 21 (or the light shielding plate 31a linked to the exposure head 21). Alternatively, it is possible to reduce misprints caused by the malfunction of 31b).
It is also possible to notify by sound using a buzzer (not shown) or the like, and it is also possible to send a message that asks for confirmation by voice. Further, not only display on the monitor MT and notification by voice, but also notification while stopping the continuous printing operation until the user notices the display of the defective state of the exposure head 21 and stops the apparatus. It is also possible to reduce misprints occurring during the period.

[Another embodiment 1]
The case where the first exposure unit 100 performs the exposure operation only in the forward path of the exposure head 21 has been described above. However, there is also an image forming apparatus in which the first exposure unit 100 is configured to perform exposure on both the forward path and the return path in order to perform higher-speed printing. The present invention can be configured in the same manner even in an exposure unit that performs exposure in both such forward and backward paths.
An exposure unit that performs reciprocal exposure has home positions HP in both the forward and reverse directions. This is because it is necessary to retract the exposure head 21 in both directions from the optical path of the second exposure unit 200. Here, the home position when operating in the forward direction is referred to as the home position HP, and the home position on the opposite side across the exposure position EP from the forward direction is referred to as the stop position SP. 2 and 4 show the home position HP and the stop position SP based on the names when the exposure head 21 operates in the forward direction described above. In addition, detection sensors for detecting the home position HP and the stop position SP are also shown as a home position sensor HS and a stop position sensor SS in accordance therewith.

  In the following, the operation of the exposure unit that performs exposure in both the forward path and the return path will be described with reference to the flowchart shown in FIG. As already described, the necessary number of pulses from the home position HP to the exposure start position EP1 can be calculated. Further, as described above, the necessary number of pulses from the exposure start position EP1 to the exposure end position EP2 is also determined from the number of sub-scan lines of the print data. Accordingly, the necessary number of pulses VC from the home position HP to the exposure end position EP2 is stored (step S1), and the count value PC by the pulse counter 51 reaches the calculated value VC, as in the case of performing only the forward exposure. A pulse is output (step S3), and the exposure head 21 is moved. Next, in this embodiment, since the exposure operation is performed in a reciprocating manner, the exposure head 21 does not return to the home position HP after completing the exposure up to the exposure end position EP2. The process proceeds to the stop position SP that faces the home position HP and the exposure position EP. Here, the distance between the home position HP and the stop position SP is determined structurally, and the number of pulses necessary for the exposure head 21 to move the distance can also be calculated from the structure. Therefore, the necessary pulse number VP2 from the exposure end position EP2 to the stop position SP can be easily obtained and stored in the sub-scanning pulse number register 50 (step S4a). Then, the exposure head 21 is moved from the exposure end position EP2 to the stop position SP while keeping the forward direction FW without setting the head movement direction to BK as the reverse direction. Specifically, the pulse counter 51 is reset to zero (step S5), and a motor pulse is output until the exposure head 21 is detected by the stop position sensor SS, and the exposure head 21 is moved to the stop position SP for output. Pulses are counted (step S6a). When the exposure head 21 reaches the stop position SP, the pulse output is stopped, and the calculated pulse number VP2 is compared with the count value PC (step S7a). Here, the calculated pulse number VP2 is compared with the value of the count value PC, and if they substantially match, it is determined that the exposure head 21 has operated normally.

  Further, a method like the flowchart shown in FIG. 9 may be used. First, the necessary number of pulses from the home position HP to the stop position SP is stored in the sub-scanning pulse number register 50 as the calculated pulse number VP (step S1a). In this case, the count is continued up to the stop position SP without performing the reset of the pulse counter 51 at the exposure end position EP2 which has been executed in step S5 in the embodiment described so far. Step S6a). When the exposure head 21 reaches the stop position SP, the pulse output is stopped by an instruction from the control unit 41, and the pulse number VP stored in the sub-scanning pulse number register 50 is compared with the count value PC of the pulse counter 51. (Step S7b). Here, if the calculated pulse number VP and the value of the count value PC substantially match, it is determined that the exposure head 21 has operated normally.

1 is a perspective view showing an external appearance of an image forming apparatus according to the present invention. 1 is a schematic block diagram of the image forming apparatus of FIG. Schematic diagram showing the structure of the first exposure unit of FIG. Schematic explaining the movement of the exposure head of FIG. Schematic block diagram of the control device of FIG. A flowchart of a routine for determining the operation of the exposure head of FIG. A flowchart of a routine for determining the operation of the exposure head of FIG. A flowchart of a routine for determining the operation of the exposure head of FIG. A flowchart of a routine for determining the operation of the exposure head of FIG.

Explanation of symbols

100 First exposure unit 200 Second exposure unit 300 Image forming apparatus 21 Exposure head HP Home position SP Stop position HS Home position sensor SS Stop position sensor EP1 Exposure start position EP2 Exposure end position MT monitor

Claims (3)

A print head in which a large number of pixel forming elements capable of recording pixel information on the recording material are arranged along the main scanning direction is moved along the sub-scanning direction intersecting the main scanning direction, and then the recording material is moved to the recording material. An image forming apparatus comprising image forming means for performing dimensional image formation, and control means for moving the print head by pulse control,
Detecting means for detecting a movement start position of the print head;
Comparing means for comparing the number of forward pulses for moving the print head from the movement start position to the movement completion position in the sub-scanning direction and the number of return pulses for moving the movement from the movement completion position to the movement start position. And
An image forming apparatus, wherein a malfunction of the print head is determined from the comparison result. The image forming apparatus includes a plurality of image forming means and a second image forming means for optically projecting two-dimensional image information onto the recording material to form an image,
A shielding means for controlling the image forming range by the second image forming means by blocking the projected two-dimensional image information;
The image forming apparatus according to claim 1, wherein a part of the shielding unit is performed using the print head. 3. The image forming apparatus according to claim 1, wherein the determination result is notified when a malfunction of the print head is determined based on the comparison result. 4.

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