JP2008213482A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can elongate a life of a laser by a smaller control load. <P>SOLUTION: The image forming apparatus has a light detecting means, a synchronous detection signal generating means, and an image data control circuit. The light detecting means carries out main scanning control by illuminating an image forming face with two or more precedently/succeedingly scanning laser lights by repetitively deflecting the lights by a constant angle, detects the laser light reaching inside a deflection range and outside an image write region by this control, and generates an analog signal. The synchronous detection signal generating means controls a timing for generating each write position signal on the basis of the analog signal of a plurality of pulses output from the light detecting means. The precedent laser light and the succeeding laser light are controlled to be turned on/off within the image write region by an on/off control means for detecting the synchronous detection signal, and a control circuit independent of the image data control circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a digital color image forming apparatus such as a color laser printer, a color digital copying machine, and a digital composite machine thereof.

  In general digital color image forming apparatuses, a pre-exposure device composed of an LED array, a primary charger having a grid, an image exposure device using a laser as a light emitting element, and a surface potential of the photoconductor drum in addition to the photoconductor drum. A surface potential meter for detection, a developing device, a transfer charger, a separation charger, a cleaning device (not shown) and the like are included. Since the operation of this digital color image forming apparatus is well known, a description thereof will be omitted.

  Incidentally, as shown in FIG. 7, in a conventional light beam writing scanning optical system used for an LBP (laser beam printer) or the like, a polygon mirror 1 that scans light from the laser diode 6 and the laser diode 6 is used. A scanning lens 2, a bending mirror 5 that bends the reflected light from the polygon mirror 1 obtained via the scanning lens 2, a BD mirror 3 provided at a predetermined position in a region immediately before the writing position by the light beam, and a BD mirror A BD sensor 4 that detects the reflected light from 3 is attached in the optical box 7.

  In this case, the laser beam from the laser diode 6 is emitted toward the polygon mirror 1 and scanned by the polygon mirror 1. The scanned laser beam is guided to the bending mirror 5 by the scanning lens 2 and is bent by the bending mirror 5.

  Further, the laser beam is synchronously detected so that writing can be performed from a specified position on the photosensitive member for each line. That is, the reflected laser beam from the BD mirror 3 is detected by the BD sensor 4, and the writing position is temporally defined by the detection signal.

  FIG. 8 shows the relationship between the laser light power and the BD detection signal output with respect to the scanning time. In FIG. 8, the time for turning on the laser diode 6 for detection is t1, and the time for turning on the laser diode 6 in the entire writing effective region is t0. The pulse width of the detection signal obtained as a result of receiving the detection light by the BD sensor 4 is t3. As described above, t1 is a value including a laser beam scanning speed error margin to some extent so that the BD sensor 4 can reliably perform synchronization detection.

  However, in such a conventional example, the time for turning on the laser diode 6 as detection light at the time of synchronous detection is relatively long compared to the time for turning on the laser diode 6 for actually performing optical writing. In view of the ON life of the product, these values are not negligible, and this is a major bottleneck for extending the life in product design.

  Therefore, in order to solve the above-described problems, the conventional image forming apparatus has the laser light power of the synchronization detection period for detecting the write synchronization in the period of scanning the laser light for a predetermined time from the synchronization detection period. By reducing the laser beam power by a predetermined amount from the laser beam power in the effective scanning period after elapses, the lifetime of the laser is made longer (see, for example, Patent Document 1).

In other words, the image forming apparatus is configured such that the laser light power in the synchronization detection period for detecting write synchronization in the period scanned by the scanning unit is greater than the laser light power in the effective scanning period after a predetermined time has elapsed from the synchronization detection period. It is characterized by comprising control means for reducing only a fixed amount.
JP-A-6-51219

  However, this apparatus has a mechanism that requires switching between laser beam power control in the synchronization detection period and other periods, and the control period is performed for each main scanning line. There is a problem that the control load of the image forming apparatus increases because it is necessary.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to extend the life of a laser while eliminating the above-mentioned problems / problems. That is, an object of the present invention is to provide an image forming apparatus capable of extending the life of a laser with a smaller control load.

  In order to achieve the above object, according to the first aspect of the present invention, the image forming apparatus is an image forming apparatus that forms a color image by repeatedly charging, exposing, and developing the photosensitive member. Means for performing main scanning control by irradiating the image forming surface by repeatedly deflecting two or more laser beams scanned in the preceding / following direction by a predetermined angle, and within a deflection range by the main scanning control and in an image writing area Synchronous detection that controls the timing to generate each writing position signal based on the light detection means that detects the laser light that reaches the outside and generates an analog signal, and the multi-pulse analog signal output by the light detection means It has a signal generating means and an image data control circuit.

  According to the second aspect of the present invention, the image forming apparatus further includes a control circuit independent of an image data control circuit for controlling on / off of the preceding laser beam and the succeeding laser beam in the image writing area. The image forming apparatus according to claim 1, comprising:

  According to the third aspect of the present invention, the image forming apparatus includes a control circuit independent of the on / off control means and the image data control circuit for detecting the synchronization detection signal. 3. An image forming apparatus according to claim 2, wherein the on / off of the laser beam and the following laser beam is controlled.

  According to a fourth aspect of the present invention, the image forming apparatus further includes means for supplying data corresponding to a white image to the image data control circuit when each laser beam is turned off in the image writing area. The image forming apparatus described in any one of the above.

  According to the fifth aspect of the present invention, the image forming apparatus controls the writing linear velocity when either the preceding laser beam or the following laser beam is turned off in the image writing area. 5. The image forming apparatus according to claim 1, further comprising means for linking functions.

  According to the present invention, in an image forming apparatus that forms a color image by repeatedly performing charging, exposure, and development on a photoconductor, at least two laser beams having a mechanical configuration that scans in a preceding and following manner. The main scanning control is performed by irradiating the image forming surface repeatedly with a certain angle, and detecting the laser beam that reaches the outside of the image writing area within the deflection range by this laser beam scanning control and generates an analog signal And a synchronization detection signal generating means for controlling the timing for generating each writing position signal based on an analog signal of a plurality of pulses output from the light detecting means, and an image data control circuit. In the image forming apparatus, LD1 and LD2 are turned on / off control for detecting the synchronization detection signal, and image data control is performed. By controlling lighting / extinguishing in the image writing area by a control circuit independent of the road, the succeeding LD is extinguished so that image formation can be performed even when only the preceding LD is lit. Regardless, the power control of each LD can be made constant.

  According to the present invention, in the above image forming apparatus, when each LD is turned off in the image writing area, the data corresponding to the white image is given to the image data control circuit, thereby loading the LD control circuit. It is reduced.

  According to the present invention, in the above-described image forming apparatus, when either the LD 1 or the LD 2 is turned off in the image writing area, the writing linear velocity is reduced by linking the function for controlling the writing linear velocity. By speeding up and doubling the resolution, it is possible to obtain an image equivalent to that when two LDs are lit even when one of the LDs is lit.

  Next, embodiments of an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  The present invention is an image forming apparatus that forms a color image by repeatedly performing charging, exposure, and development on a photoconductor, and includes at least two laser beams having a mechanical configuration that scans in a preceding and following manner. Main scanning control is performed by irradiating the image forming surface by repeatedly deflecting by a certain angle, and an analog signal is generated by detecting laser light reaching the outside of the image writing area within the deflection range by this laser light scanning control 1 The image detector comprises: two photodetecting means; synchronization detection signal generating means for controlling the timing for generating each writing position signal based on the analog signal of a plurality of pulses output by the photodetecting means; and the image data control circuit. The present invention relates to a forming apparatus. Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

  First, the operation of the image forming apparatus according to the embodiment of the present invention will be systematically described with reference to FIG. FIG. 1 shows a schematic block diagram of a control system of a color printer used as an example of an image forming apparatus in the present embodiment. Based on this, description will be made sequentially below.

  This block diagram includes a host machine 101, a controller 102, a key input unit (operation panel) 103, a main control unit 104, a memory unit 105, a printer drive control unit 106, and a printer unit 107. .

  The printer drive control unit 106 controls driving of each unit of the printer unit 107. The controller 102 controls image data from the host machine 101. The memory unit 105 stores the image data transferred to the controller 102. A key input unit (operation panel) 103 includes various settings for clearing the setting mode and starting / stopping the operation, the number of prints, the paper size, enlargement / reduction, and other settings. The main control unit 104 controls each unit in accordance with a signal from the key input unit 103, outputs a command signal to the printer drive control unit 106, and starts a printing operation.

  The present invention relates to a printer drive control unit 106, a printer unit 107, and a main control unit 104 that controls the system.

  First, in the main control unit 104, image data from the controller 102 is transferred to the printer drive control unit 106. The printer drive control unit 106 has a function of driving the printer unit 107 based on the transferred image data and printing the image data. Printing is performed by repeating this operation in the main scanning and sub-scanning directions by the printer drive control unit 106 (writing unit 200 in FIG. 2).

  Next, the internal operation of the printer unit 107 in FIG. 1 will be briefly described with reference to FIG.

  A latent image is formed on the photosensitive belt 201 by laser light exposed from the writing unit 200 (same as the printer drive control unit 106 in FIG. 1), and toner development is performed by the developing unit 202 of each of Magenta, Cyan, Yellow, and Black. I do. The photosensitive member is removed / charged by a charging brush 203, a static elimination (brush) 204, and a photosensitive member cleaning 205.

  Thereafter, intermediate transfer is performed by the intermediate transfer belt 206, the cleaning brush roller 207, and the primary transfer brush 208, and the paper fed from the paper feed tray 209 is conveyed by the secondary transfer roller 210 to form an image.

  The formed image is thermally fixed by the fixing unit 211, passes through the branch unit 212, and is discharged to the main body, or in the case of FIG.

  By the series of operations described above, printing based on print data input from the host machine 101 via the controller 102 is performed.

  Hereinafter, main operations of the image forming apparatus according to the embodiment of the present invention will be described.

  In the image forming apparatus having the configuration described so far, the present embodiment relates to the writing unit 200 in FIG. 2, and the main control unit 104 and the writing control unit (printer drive control unit 106) shown in FIG. It is against. In relation to these, the 2LD method will be further described.

  First, a first example as an embodiment of the image forming apparatus according to the present invention will be described.

  The first embodiment is an image forming apparatus that forms a color image by repeatedly performing charging, exposure, and development on a photoconductor, and includes at least two laser beams having a mechanical configuration that scans in the preceding and following directions. The main scanning control is performed by irradiating the image forming surface repeatedly with a certain angle, and detecting the laser beam that reaches the outside of the image writing area within the deflection range by this laser beam scanning control and generates an analog signal And a synchronization detection signal generating means for controlling the timing for generating each writing position signal based on an analog signal of a plurality of pulses output from the light detecting means, and an image data control circuit. In the image forming apparatus, the preceding laser beam (hereinafter referred to as LD1 or preceding LD) and the following laser beam (hereinafter referred to as LD2 or following L). The subsequent LD is turned off by controlling the turning on / off in the image writing area by a control circuit independent of the image data control circuit and the on / off control for detecting the synchronization detection signal. The aim is to enable image formation even when only the preceding LD is lit, and to make the power control of each LD constant regardless of the image area.

  The first embodiment will be described in more detail with reference to the circuit configuration diagram shown in FIG. 3 and the timing diagrams of FIGS.

  The LD1 and LD2 are turned on / off by setting from the register 301 (FIG. 3) of the LD control circuit in the write control unit attached to the write unit 200 of FIG.

  Here, the lighting control timing of the normal synchronization detection LD1 and LD2 is as shown in FIG.

  First, the preceding LD, that is, LD1 is turned on outside the image writing area from a position that coincides with a preset register setting value and the main scanning counter value, and a synchronization detection pulse signal is obtained from a synchronization detection signal generating means (not shown). . This corresponds to the comparison circuit 304 → OR circuit 305 → AND circuit 308 of FIG.

  Thereafter, the succeeding LD, that is, LD2 is turned on from a position that matches the other register set value and the main scanning counter value, and a second synchronization detection signal pulse is obtained. This corresponds to the comparison circuit 306 → OR circuit 307 → AND circuit 309 in FIG.

  The writing position control of the main scanning is performed by these two synchronization detection signal pulses. In this control, a register flag (LDDT_OFFALL) is prepared to turn off both the LD1 and LD2 data regardless of whether the image writing area is outside or outside the image writing area. The data is turned off in all periods.

  On the other hand, for these register flags (LDDT_OFFALL), register flags (LDDT1OFF, LDDT2OFF) for turning off each LD only in the image writing area are prepared.

  By taking the logic of these register flags, the LDDT_OFFALL flag is turned OFF (“L”), and the LDDT1OFF is turned ON (“H”), thereby turning off LD1 only in the writing image area and turning the LDDT_OFFALL flag OFF ( “L”), and setting LDDT2OFF to ON (“H”) gives control to turn off LD2 only in the writing image area (see NOR circuits 302 and 303 in FIG. 3).

  As a result, the lighting function outside the writing image area necessary for lighting for synchronization detection remains as it is, and only the writing image data is turned off, so that the LD data for synchronization detection is normally lit and the synchronization detection is performed. Abnormal operations such as abnormalities can be avoided. That is, although the 2LD method is used, it is possible to form an image by lighting only one of the LDs (see FIG. 5). In addition, with the logic circuit configuration of FIG. 3, lighting / extinguishing is performed in other combinations.

  Furthermore, since the LD in the writing image area is controlled by either turning on / off, it can be realized with a simple circuit configuration that does not involve the control of the LD power.

  Next, a second example, which is an embodiment of the image forming apparatus according to the present invention, will be described with reference to FIG.

  In the image forming apparatus of the first embodiment, the second embodiment provides the load on the LD control circuit by giving data corresponding to a white image to the image data control circuit when each LD is turned off in the image writing area. The aim is to reduce this.

  In this embodiment, when each LD is turned off in the image writing area, data corresponding to a white image is given to the image data control circuit described above, and each image data from the image data control circuit in the writing image area is given. On the other hand, a mechanism for giving white image data to LD1 data corresponding to LDDT1OFF or LD2 data corresponding to LDDT2OFF is provided.

  As a result, even if the register flags (LDDT1OFF, LDDT2OFF) of the second embodiment are not used, the same control is possible if the LDDT_OFFALL flag is turned OFF. Can be reduced (see FIG. 6).

  Next, a third example as an embodiment of the image forming apparatus according to the present invention will be described.

  In the image forming apparatus of the first embodiment, the third embodiment is linked with a function for controlling the writing linear speed when either one of the LDs 1 and LD2 is extinguished in the image writing area. The aim is to obtain an image equivalent to that when two LDs are lit even if one of the LDs is lit by setting the speed to half speed and doubling the resolution.

  In this embodiment, when either LD1 or LD2 is extinguished in the image writing area, the function for controlling the writing linear velocity is linked. For example, when the LDDT2OFF flag is turned on and LD2 is extinguished. Although only LD1 is printed, the image at this time is an image in which LD1 is printed every two lines.

  Therefore, the resolution in the sub-scanning direction is doubled by setting the writing linear speed to half speed. In other words, an image that originally was 600 dpi at 2 LD would be equivalent to 300 dpi by printing only LD 1, so this is 1200 dpi (equivalent to 600 at 1 LD).

  By adopting such a configuration, if one of the LDs is turned off as long as the magnification is not considered as a problem, an image having the same quality as that of the original 2LD can be secured even with one LD.

  The above embodiment uses the color printer shown in FIGS. 1 and 2, but any image forming apparatus having the same functions as those shown in the first to third embodiments can be used. The kind is not asked.

  That is, the present invention is not limited to a color printer, but can be widely applied to other image forming apparatuses such as a color copying machine, a color facsimile, and a complex machine thereof.

1 is a schematic block diagram of a control system in an embodiment of an image forming apparatus according to the present invention. 1 is a configuration diagram of a color printer as an embodiment of an image forming apparatus according to the present invention. FIG. 1 is a circuit configuration diagram of an LD control circuit in an embodiment of an image forming apparatus according to the present invention. FIG. 5 is a timing chart of turning on / off the LD1 and LD2 of the 2LD system. FIG. 5 is a timing chart for controlling on / off of LD1 and LD2 in an embodiment of the image output apparatus according to the present invention. FIG. 6 is a timing chart for controlling on / off of LD1 and LD2 in another embodiment of the image output apparatus according to the present invention. It is a perspective view of the light beam writing scanning optical system used for the conventional LBP. It is a figure which shows the relationship with respect to the scanning time of the laser beam power and BD detection signal output in the conventional LBP.

Explanation of symbols

6 Laser diode 104 Main control unit 106 Printer drive control unit 107 Printer unit 200 Writing unit 301 Register 302, 303 NOR circuit 304, 306 Comparison circuit 305, 307 OR circuit 308, 309 AND circuit

Claims (5)

An image forming apparatus that forms a color image by repeatedly performing charging, exposure, and development on a photoreceptor,
The image forming apparatus includes:
Means for performing main scanning control by irradiating the image forming surface by repeatedly deflecting two or more laser beams scanned in the preceding / following direction by a predetermined angle;
A light detection means for detecting an optical signal within the deflection range by the main scanning control and outside the image writing area to generate an analog signal;
Synchronization detection signal generating means for controlling the timing for generating each writing position signal based on the analog signal of a plurality of pulses output by the light detecting means;
An image data control circuit;
An image forming apparatus comprising:   2. The control circuit according to claim 1, further comprising a control circuit independent of the image data control circuit for controlling on / off of the preceding laser beam and the succeeding laser beam in the image writing area. Image forming apparatus.   The lighting / light-off control means for detecting the synchronization detection signal and a control circuit independent of the image data control circuit are used to turn on / off the preceding laser beam and the following laser beam in the image writing area. The image forming apparatus according to claim 2, wherein turning off is controlled.   4. The apparatus according to claim 1, further comprising means for supplying data corresponding to a white image to the image data control circuit when the laser beams are turned off in the image writing area. 5. Image forming apparatus.   The apparatus further comprises means for interlocking a function for controlling a writing linear speed when any one of the preceding laser beam and the following laser beam is turned off in the image writing area. The image forming apparatus according to any one of claims 1 to 4.

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