JP2005250105A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and an image forming method which can detect the floating of a recording medium on a drum without requiring a distance measuring sensor separately. <P>SOLUTION: In the image forming method, a sheet-like recording medium is wound around an outside surface of the drum, and light is radiated from a recording head arranged in opposition to the drum while rotating the drum, to expose the recording medium on the drum. In this case, a distance between a recording surface of the recording medium wound around the drum and the recording head is measured before exposure by a distance measuring function of an auto-focus mechanism for properly maintaining a focus position of the recording head during exposure, and it is determined whether the measured distance is within a prescribed range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cylindrical outer surface scanning type image forming apparatus having an autofocus mechanism and an image forming method.

  An image forming apparatus that winds a photosensitive material, which is a sheet-like recording medium, around the outer surface of a cylindrical drum, exposes the photosensitive material to the photosensitive material while the photosensitive material is sucked and fixed, and records the image by exposing the photosensitive material. Is known. In such an image forming apparatus, when the photosensitive material is lifted from the outer surface of the cylindrical drum, there is a possibility that the optical focus is shifted on the photosensitive material surface and the image is blurred or the photosensitive material is peeled off from the cylindrical drum during exposure. There is sex. For this reason, conventionally, there is a function of monitoring the floating of the recording medium by the distance measuring sensor. For example, in Patent Document 1 described below, a monitoring device monitors whether or not a printing plate is reliably wound around a drum by a distance measuring sensor composed of a reflective optical sensor having a light emitting part and a light receiving part, and a controller.

  As a cause of the problem that the recording medium floats or peels off at the time of exposure, for example, the recording medium is floated and wound from the beginning and can be sucked into the drum as it is to cause wrinkles. For this reason, if it can be confirmed whether the recording medium is correctly set on the drum before the exposure, it is possible to detect a problem such that the recording medium is peeled off or a part of the image is out of focus during the exposure.

However, if a distance measuring sensor or the like is newly added as described above to detect the floating of the recording medium, the number of parts increases and the cost increases. In addition, if it is attempted to detect the floating state of the recording medium over the entire drum, there is a problem that it takes time to detect and the productivity of image formation of the apparatus is reduced.
JP 2003-287903 A

  An object of the present invention is to provide an image forming apparatus and an image forming method that can detect the floating of a recording medium on a drum without requiring a separate distance measuring sensor. Also provided are an image forming apparatus and an image forming method that can reduce the time required to detect the floating of the recording medium.

  In order to achieve the above object, an image forming apparatus according to the present invention winds a sheet-like recording medium around an outer surface of a drum, and emits light from a recording head disposed facing the drum while rotating the drum. In an image forming apparatus that exposes a recording medium on the drum, an autofocus mechanism for measuring the distance of the recording head to the drum by a distance measuring function and maintaining a focus position appropriately during exposure, and a coil wound around the drum A distance between the recording surface of the recording medium and the recording head is measured by a distance measuring function of the autofocus mechanism before exposure, and if the measured distance is not within a specified range, means for determining an error; It is characterized by providing.

  According to this image forming apparatus, the distance between the recording surface of the recording medium and the recording head is measured before exposure using the distance measuring function of the autofocus mechanism for keeping the focal position of the recording head properly during exposure. When the measured distance is not within the specified range, it is judged as an error, and it can be judged that the recording medium is floating, so the floating of the recording medium on the drum is detected without the need for a separate distance measuring sensor. it can.

  In the image forming apparatus, the recording head is configured to move in a sub-scanning direction for exposure from a home position at an end portion of the drum positioned before exposure, and to integrally include the focus mechanism. When the distance between the recording surface of the recording surface on the drum in the vicinity of the home position and the recording head is measured by the distance measuring function before, and the measured distance is not within the specified range Can be determined to be an error. Most of the wrinkles and the like that are formed on the recording medium on the drum are formed so as to extend in the rotation axis direction (sub-scanning direction) of the drum, so that the drum near the home position where the recording head is positioned before exposure is used. Floats such as wrinkles can be detected simply by measuring the drum around one end at the end. For this reason, it takes less time to detect the floating of the recording medium.

  In the image forming method according to the present invention, a sheet-like recording medium is wound around the outer surface of a drum, and light is emitted from a recording head disposed facing the drum while rotating the drum, and the recording medium on the drum is exposed. In the image forming method, the recording head and the recording surface of the recording medium wound around the drum before the exposure by the distance measuring function of the autofocus mechanism for keeping the focal position of the recording head properly during the exposure. Measuring the distance, and determining whether or not the measured distance is within a specified range.

  According to this image forming method, the distance between the recording surface of the recording medium and the recording head is measured before exposure using the distance measuring function of the autofocus mechanism for keeping the focal position of the recording head properly during exposure. When the measured distance is not within the specified range, it is judged as an error, and it can be judged that the recording medium is floating, so the floating of the recording medium on the drum is detected without the need for a separate distance measuring sensor. it can.

  In the image forming method, the distance between the recording surface and the recording head for one round is measured on the recording surface on the drum near the home position at the end of the drum where the recording head is positioned before exposure. By measuring by function, the wrinkles or the like that can be formed on the recording medium on the drum are mostly formed by extending in the drum rotation axis direction (sub-scanning direction), so the recording head is positioned before exposure. It is possible to detect wrinkles and the like by measuring only about one revolution of the drum at the end of the drum near the home position. For this reason, it takes less time to detect the floating of the recording medium.

  Further, it is preferable to stop the exposure when the measured distance is not within the specified range. When the floating of the recording medium is detected, the exposure is stopped, so that it is possible to prevent a problem that a part of the image is out of focus.

  According to the image forming apparatus and the image forming method of the present invention, the autofocus mechanism for adjusting the focal position of the recording head can be used for the detection of the floating of the recording medium, and the recording medium on the drum is not required to have a separate distance measuring sensor. Can be detected, so the number of parts does not increase and the cost of the apparatus does not increase. In addition, since it takes less time to detect the floating of the recording medium, the image forming productivity of the apparatus is not adversely affected.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the appearance of the entire image forming apparatus according to the present embodiment. FIG. 2 is a view of the inside of the image forming apparatus of FIG. 1 as viewed from the front side. FIG. 3 is a plan view of the main part of the drum and the optical unit of the image forming apparatus shown in FIG. 2 as viewed from above.

  As shown in FIGS. 1 and 2, the image forming apparatus 1 according to the present embodiment creates a color proof (calibration sample) for confirming a pattern, color tone, sentence, character, etc. to be printed out. An exposure unit 11 that exposes a sheet-like silver salt color photosensitive material (hereinafter also simply referred to as “recording paper”) as a recording medium to form an image, and a developing unit that develops the exposed photosensitive material. 21. In order to create a color proof, halftone dot image data is created from raster data by an RIP (Raster Image Processor) which is an external image processing apparatus, and this halftone dot image data is transferred from the RIP to the exposure unit 11. It has become.

  The exposure unit 11 includes a front panel 5 that can be opened and closed so that maintenance can be performed from the front side, a display unit 2 that includes various information displays and a touch panel and can be input for operation of the entire apparatus, and a roll-shaped recording paper is provided inside. Loading units 12 and 12 ′ capable of loading the accommodated cartridge 13 after the paper feed covers 3 and 4 are opened. FIG. 1 shows a state before and after the cartridge 13 is loaded in the loading units 12 and 12 ′.

  The development unit 21 includes an upper panel 6 that can be opened and closed for maintenance, and a replenishment panel 7 that is provided on the front surface so as to be opened and closed for replenishment of a developing solution or the like.

  As shown in FIG. 2, the exposure unit 11 of the image forming apparatus 1 includes loading units 12 and 12 ′ for loading and storing a dedicated cartridge 13 that stores recording paper wound inside in a roll shape, and a loading unit 12. , 12 ′, a feeding unit 14 composed of a pair of conveying rollers 40, 41, 42 and the like for feeding recording paper from a cartridge 13 and a recording paper S fed from the feeding unit 14 are vacuumed on the outer peripheral surface. A rotating drum 10 that rotates in the rotation direction R for main scanning while sucking and holding; an optical unit 16 that exposes a recording surface of recording paper on the rotating drum 10 with a light beam such as LED light or laser light; A sub-scanning unit 17 that transports the optical unit 16 in the sub-scanning direction (perpendicular to the paper surface in FIG. 1) H (FIG. 3) for sub-scanning, and a peeling member that peels off the recording paper on the rotary drum 10 after image recording. 15. The exposed recording paper is conveyed to the developing unit 21 through the outlet 19 and the connecting portion 19a.

  The image forming apparatus 1 shown in FIG. 2 further includes a driven roller 31 that is arranged downstream of the conveying roller pair 42 and is driven to rotate following the conveyance of the recording paper fed toward the rotating drum 10, and the recording paper between the rotating drum 10. A driven roller 31 for conveying the recording paper, an accumulating guide member 18 for guiding the recording paper when the recording paper peeled from the rotating drum 10 by the peeling member 15 is conveyed by the rotating drum 10 and the driven roller 31, and an accumulating guide. A pair of conveying rollers 32 that further conveys the recording paper sent by the member 18 to the outlet 19 and a part of the accumulating guide member 18 are opened to accumulate the recording paper that has reached the conveying roller pair 32. The accumulator 30 is formed, and a detection sensor 33 that detects the leading edge of the recording paper disposed near the downstream side of the conveying roller pair 32.

  A relatively narrow driven roller 43 disposed in the vicinity of the downstream side of the conveying roller pair 42 is driven to rotate along with the movement of the recording paper, and a rotary encoder (not shown) is connected coaxially with the driven roller 43. . The rotary encoder rotates with the driven roller 43 and measures the amount of rotation, whereby the length of the recording paper that passes through the conveying roller pair 42 and is wound around the rotary drum 10 can be obtained. Further, the downstream conveying roller pair 32 has a one-way clutch structure, and can freely rotate in the feeding direction to the downstream side of the recording paper.

  A cut portion 10a for cutting the recording paper is arranged in the vicinity of the downstream side of the pair of conveyance rollers 40 and 41 in FIG. 2, and each cut portion 10a has a rotary cutter that is rotationally driven by a motor (not shown). Then, the recording sheet is cut into a predetermined length based on the above-described measurement of the recording sheet length.

  The developing unit 21 in FIG. 2 performs wet development on the exposed recording paper sent from the exposure unit 11, and includes a developing unit 23 that performs development processing of the recording paper, a fixing unit 24 that performs fixing processing, and a stable unit. The stabilization unit 25 that performs processing, the drying unit 26 that performs drying processing, and the dried recording paper are discharged from the discharge unit 27 to the external stacking unit 28 by the conveyance roller pair 27a and the like.

  As shown in FIG. 3, in the rotary drum 10 of the image forming apparatus 1, the rotary shaft 14a of the rotary shaft portion 14 ′ and the rotary shaft 15a of the rotary shaft portion 18 can rotate to the support bases 34a and 34b via bearings 33a and 33b. Is pivotally supported. One rotary shaft 15a of the rotary drum 10 is provided with a drive pulley 35a, which is connected to an output pulley 35b of a drum drive pulse motor M6 by a belt 36, and driven by the drum drive pulse motor M6. The rotating drum 10 rotates. A rotary encoder 37 is provided on the rotary shaft 15a of the rotary drum 10, and a pulse signal for rotation is output and used for pixel clock control synchronized with the rotation of the drum.

  The other rotary shaft 14a of the rotary drum 10 is connected to the suction blower P1. A large number of suction holes 31c are formed on the surface of the rotating drum 10 so as to extend linearly in the direction of the rotation axis, and the inside of the rotating drum 10 is depressurized by driving the suction blower P1, and the recording paper is placed on the surface of the rotating drum 10. Adsorbed.

  The optical unit 16 is configured on the stage 17 a of the sub-scanning unit 17, is configured to be movable in parallel with the drum axis by the sub-scanning unit 17, and is exposed to the recording surface of the recording paper sucked by the rotary drum 10 with a light beam. And write the image. As shown in FIG. 3, the optical unit 16 includes an LED unit 320, an LED unit 321, and an LED unit 322 as light sources having different three wavelengths. Each LED unit 320, 321, 322 includes a light emitting diode (LED) disposed on a substrate for 32 channels, and the light beam from each LED unit 320, 321, 322 passes through mirrors 325, 326, 327. Then, the image is exposed from the optical head 331 to the recording surface of the recording paper on the rotary drum 10. The exposure shutter 332 is opened / closed by an exposure solenoid 333 to open / close the optical path at the start / end of exposure.

  The optical head 331 of the optical unit 16 includes a plurality of lenses including a condensing lens 331a (indicated by a broken line in FIG. 4), and the light beam from each of the LED units 320, 321, and 322 is recorded on the recording paper on the rotary drum 10. Focus on the recording surface.

  The plurality of LED units 320, 321, and 322 are configured to emit light of, for example, B (blue) having a wavelength of about 450 nm, G (green) having a wavelength of about 540 nm, and R (red) having a wavelength of about 650 nm. When a silver salt color photosensitive material is exposed by each LED unit, Y (yellow) is developed by B, M (magenta) is produced by R, and C (cyan) is produced by G.

  In the optical unit 16, the stage 17a of the sub-scanning unit 17 is fixed to the moving belt 340, and is guided by a pair of guide rails 341 and 342 to move in the sub-scanning direction H parallel to the drum axis and in the opposite direction H ′. It is provided as possible. The moving belt 340 is stretched over a pair of pulleys 343 and 344. One pulley 344 is connected to the output shaft 345 of the sub-scanning motor M7, and the optical unit 16 is sub-scanned in parallel with the drum axis by driving the sub-scanning motor M7. Move in the direction H and in the opposite direction H ′.

  Further, as shown in FIG. 3, a photometric unit 57 composed of a light receiving element such as a photodiode is arranged at an extended position parallel to the drum axis on the outer peripheral surface of the rotary drum 10, and the optical unit at the home position shown in FIG. 16 moves slightly in the direction H ′, and the light beams from the LED units 320 to 322 enter the photometry unit 57, whereby the light quantity of the light beams of the LEDs of the respective channels can be measured.

  As shown in FIG. 3, the suction blower P1 sucks the inside of the rotating drum 10 through the suction connecting pipe 51 by an air suction pump, and negative pressure is applied to the inside of the rotating drum 10 before exposure by the exposure unit 11 so that the recording paper is placed on the outer peripheral surface. Adsorb.

  Next, an autofocus mechanism that changes the relative distance between the optical head 331 of the optical unit in FIG. 3 and the recording surface of the recording paper on the drum for focus adjustment will be described with reference to FIGS. FIG. 4 is a side view showing an autofocus mechanism which is a focus adjustment mechanism of the optical head on the optical unit of FIG. FIG. 5 is a block diagram showing a control system for detecting the autofocus mechanism and recording sheet floating in FIG.

  As shown in FIGS. 3 and 4, the autofocus mechanism 61 is disposed on the stage 17 a and has a mounting base 62 to which the optical head 331 is attached and a mounting base 62 via a rotating shaft 63 a on which a ball screw is formed. The stepping motor 63 for moving the optical head 331 in the horizontal direction of FIG. 4 with respect to the circumferential surface of the rotary drum 10 and the reflection disposed for the distance measuring function in the vicinity of the optical head 331 on the stage 17a of FIG. Mold optical sensor 65.

  The reflection type optical sensor 65 of FIG. 3 in the autofocus mechanism 61 irradiates the recording surface of the recording paper adsorbed on the outer peripheral surface of the rotating drum 10 by receiving light from the light emitting unit, and receives the reflected light to thereby rotate the rotating drum 10. 4 is measured, and the position of the optical head 331 is finely adjusted in the horizontal direction in FIG. 4 so as to keep the focus position of the optical head 331 properly based on the measured distance. It is like that.

  As shown in FIG. 5, the control unit 60 of the image forming apparatus 1 includes a central processing unit (CPU), controls the autofocus mechanism 61 during exposure, and based on the distance measurement result by the reflective optical sensor 65. A stepping motor 63 is generated by generating the number of drive pulse signals necessary for the stepping motor 63 from the driver 67 so that the distance d between the lens 331a on the front surface of the optical head 331 and the recording surface S1 of the recording sheet of the rotary drum 10 is constant. To drive.

  As described above, the stepping motor 63 is rotated to rotate the rotating shaft 63a on which the ball screw is formed, whereby the optical head 331 is moved with respect to the stage 17a and the mounting base 62 to adjust the focus position of the optical head 331. .

  Further, the controller 60 drives the sub-scanning motor M7 before exposure to slightly move the optical unit 16 at the home position in FIG. 3 in the sub-scanning direction H so that the optical head 331 is recorded on the end of the rotary drum 10 at the recording paper. 4, the drum is rotated once, and the reflection type optical sensor 65 of the autofocus mechanism 61 measures the distance d in FIG. 4 for one round, and whether the measured distance is within a predetermined specified range. The determination unit 68 determines whether or not.

  When a wrinkle SW is generated on the recording paper as indicated by a broken line in FIG. 4, the measured distance is not within the specified range. Therefore, the determination unit 68 determines that an error has occurred, and displays that fact on the display unit 69, for example. A warning is given and the operation of the image forming apparatus 1 is stopped.

  Next, the recording sheet floating detection operation of the image forming apparatus 1 of FIGS. 1 to 5 will be described with reference to FIGS. FIG. 6 is a flowchart for explaining the operation of detecting the floating of the recording sheet of the image forming apparatus 1 of FIGS. FIG. 7 is a perspective view schematically showing a state in which wrinkles are formed on the recording paper on the drum that can be detected in FIG.

  First, the recording paper is transported from the loading section 12 or 12 ′ of FIGS. 1 and 2 toward the rotary drum 10 by a pair of transport rollers 40 to 42, and the recording paper cut into a predetermined length by the cutting section 10 a is rotated. 10 is wound (S01), and the suction blower P1 is operated and held by suction (S02).

  The optical unit 16 is at the home position in FIG. 3 in the sub-scanning direction H. However, as shown in FIG. 7, the optical head 331 and the reflective optical sensor 65 face one end S2 of the recording paper on the rotary drum 10, and the recording is performed. The optical unit 16 is moved slightly in the sub-scanning direction H and stopped so that the distance to the surface can be measured (S03).

  The distance d in FIG. 4 is measured for one turn while rotating the rotating drum 10 in the rotation direction R at the position of FIG. 7 (S04). It is determined whether or not the measured distance is within a predetermined specified range (S05). If the measured distance is within the specified range, an image is formed by exposing the recording surface S1 of the recording paper (S06), and exposure is performed. The completed recording paper is transported to the developing unit 21 to perform phenomenon processing (S07), and the developed recording paper is discharged to the stacking section 28 through the discharge section 27 (S08).

  If the distance measured in step S05 is not within the predetermined range, the recording surface S1 of the recording paper S on the rotary drum 10 has a wrinkle SW or the like as shown in FIG. It is determined that there is (S09), a warning is displayed on the display unit 69 (S10), and the operation of the image forming apparatus 1 is stopped (S11).

  As a result, it is possible to prevent inconvenience that the exposure is stopped and a part of the image formed on the recording surface S1 of the recording paper S becomes out of focus, and the user can record wrinkles from the rotary drum 10. It is possible to return to the normal state by removing the signal and supplying a new record.

  As described above, according to the present embodiment, the autofocus mechanism 61 for adjusting the focal position of the optical head 331 can also be used for detecting the floating of the recording paper, so that no separate distance measuring sensor is required. For this reason, the number of parts does not increase and the cost of the apparatus is not increased.

  When the recording paper is wrinkled, as shown in FIG. 7, the wrinkle SW is almost always formed extending in the longitudinal direction (sub-scanning direction H) of the rotary drum 10, so that the optical unit 16 is moved slightly. Then, the measurement can be completed only by rotating the rotary drum 10 once at the one end S2 of the recording paper S on the rotary drum 10. In this way, it is only necessary to check the vicinity of one end S2 of the recording paper S, and it is not necessary to measure the entire rotating drum 10, so that the time required for detecting the floating of the recording paper can be reduced. The image forming productivity is not adversely affected.

  As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the technical idea of the present invention. For example, it is needless to say that the image forming apparatus according to the present invention can be applied to other than the creation of a color proof. For adjusting the position of the optical head 331 in FIG. 4, for example, a piezo element or the like may be used instead of the stepping motor.

  Further, the longitudinal position of the rotary drum 10 that detects the floating of the recording paper is not limited to the position as shown in FIG. 7, and may be a position slightly moved in the longitudinal direction from the one end S <b> 2 of the recording paper S. Good.

1 is a perspective view illustrating an appearance of an entire image forming apparatus according to an embodiment. FIG. 2 is a diagram of the inside of the image forming apparatus in FIG. 1 viewed from the front side. FIG. 3 is a plan view of a main part when a drum and an optical unit of the image forming apparatus of FIG. 2 are viewed from above. It is a side view which shows the autofocus mechanism of the optical head on the optical unit of FIG. FIG. 5 is a block diagram illustrating a control system for detecting the autofocus mechanism and recording sheet floating in FIG. 4. 6 is a flowchart for explaining an operation of detecting the floating of the recording sheet of the image forming apparatus 1 of FIGS. FIG. 7 is a perspective view schematically showing a state in which wrinkles are formed on the recording paper on the drum that can be detected in FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Rotating drum 11 Exposure unit 16 Optical unit 21 Developing unit 60 Control part 61 Autofocus mechanism 63 Stepping motor 65 Reflection type optical sensor 68 Judgment part 69 Display part 331 Optical head (recording head)
H Sub-scanning direction P1 Suction blower S Recording paper (recording medium)
S1 Recording surface S2 One end SW wrinkle d distance

Claims (5)

In an image forming apparatus in which a sheet-like recording medium is wound around an outer surface of a drum, light is emitted from a recording head arranged to face the drum while rotating the drum, and the recording medium on the drum is exposed.
An autofocus mechanism for measuring the distance of the recording head to the drum by a distance measuring function and keeping the focus position properly during exposure;
The distance between the recording surface of the recording medium wound around the drum and the recording head is measured by the distance measuring function of the autofocus mechanism before exposure, and an error occurs when the measured distance is not within a specified range. An image forming apparatus. The recording head is configured to move in a sub-scanning direction for exposure from a home position at an end of the drum located before exposure, and to integrally include the focus mechanism.
Before the exposure, the distance between the recording surface of the recording surface on the drum near the home position and the recording head is measured by the distance measuring function, and the measured distance is not within the specified range. The image forming apparatus according to claim 1, wherein an error is determined in the case. In an image forming method in which a sheet-like recording medium is wound around an outer surface of a drum, light is emitted from a recording head arranged to face the drum while rotating the drum, and the recording medium on the drum is exposed.
Measuring the distance between the recording surface of the recording medium wound around the drum and the recording head before exposure by a distance measuring function of an autofocus mechanism for maintaining the focal position of the recording head properly during exposure; ,
Determining whether or not the measured distance is within a prescribed range. The distance between the recording surface and the recording head for one round is measured by the distance measuring function on the recording surface on the drum near the home position at the end of the drum where the recording head is positioned before exposure. The image forming method according to claim 3. 5. The image forming method according to claim 3, wherein the exposure is stopped when the measured distance is not within the specified range.

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