JP5576730B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an electrostatic latent image on a latent image carrier by optically scanning a latent image carrier such as a photosensitive drum or a photosensitive belt with a light emitting element.

  A so-called electrophotographic image forming apparatus controls the lighting of a light emitting element in accordance with image data for image formation, and optically scans the photosensitive drum by the light emitted from the light emitting element, thereby statically moving the photosensitive drum. An electrostatic latent image is formed. The electrostatic latent image is developed with toner, transferred to a recording medium such as paper, and image formation is performed. An example of the light emitting element is an LD (Laser Diode).

As is well known, the light emission amount of the LD decreases as the cumulative lighting time increases. When the light emission amount of the LD decreases, the print density deteriorates, for example, the print density decreases.
Therefore, the drive control unit of the LD executes so-called feedback control that controls the light emission amount of the LD to be constant. The control will be described with reference to FIG.

  FIG. 8A is a graph for explaining the relationship between the cumulative lighting time of LD (cumulative number of printed sheets) and the light emission amount of LD, and FIG. 8B shows the cumulative lighting time of LD and the drive current value of LD. It is a graph explaining a relationship.

  For example, as shown by lines 80a and 80b in FIG. 8A, the light emission amount of the LD decreases as the cumulative lighting time of the LD becomes longer. The line 80a illustrates a state in which the light emission amount of the LD linearly decreases as the cumulative lighting time of the LD becomes longer, and the line 80b shows the light emission amount of the LD nonlinearly as the cumulative lighting time of the LD becomes longer. The state which falls is illustrated.

  Therefore, the drive control unit of the LD detects the light emission amount of the LD with a light receiving element such as a PD (Photo Diode). Then, the drive current value of the LD is increased and adjusted as indicated by symbols Y1 and Y2, and the light emission amount of the LD is controlled to be constant (feedback control) as indicated by symbols Y3 and Y4. As a result, the print density can be maintained appropriately, and the quality of the printed matter can be maintained.

  When the increase adjustment of the LD drive current value is continued, the LD drive current value reaches the drive limit current value as indicated by reference numeral Y5. Then, the drive control unit of the LD forcibly stops the light emission (drive) of the LD. As a result, the image forming operation in the image forming apparatus is completely stopped.

Japanese Patent Application Laid-Open No. 2004-151561 discloses an image forming apparatus that detects an LD degradation state due to an increase in the cumulative lighting time of the LD and makes an operator (user) recognize the LD degradation state.
The image forming apparatus disclosed in Patent Document 1 obtains five detection points related to the light quantity value-driving current value characteristic, calculates differential efficiency η at two adjacent detection points, and calculates the value of the differential efficiency η ( LD degradation state) is displayed on the display.

JP-A-11-204890

  Even if the degradation state of the LD is displayed as in the image forming apparatus disclosed in Patent Document 1, the operation of the image forming apparatus is suddenly stopped if the drive current value of the LD reaches the drive limit current value. If the operation of the image forming apparatus suddenly stops in this way, there is a problem in business and the user is very inconvenient.

  SUMMARY An advantage of some aspects of the invention is that it not only notifies the deterioration state of the LD but also controls the operation of the image forming apparatus in accordance with the deterioration state of the LD.

First technical means is a light emitting element for optical scanning the image bearing member to form an electrostatic latent image corresponding to the image data to the image bearing member, at power-on start, every predetermined number of printed sheets, A light emission amount detection unit that detects the light emission amount of the light emitting element at any timing for each predetermined operating time, and a storage unit that stores a drive current threshold value and a reference light emission amount value lower than the drive limit current value of the light emitting element The timing interval for detecting the light emission amount of the light emitting element is changed and the drive current value of the light emitting element is adjusted according to the difference between the drive current threshold value of the light emitting element and the drive current value of the light emitting element. And a control unit that controls the light emission amount of the light emitting element to the reference light emission amount value. When the control unit detects that the drive current value of the light emitting element exceeds the drive current threshold value, a warning is provided. After performing notification, the drive current is An image forming apparatus characterized by the drive current value for driving the light emitting element.

  According to a second technical means, in the first technical means, after the light emitting element is driven by the driving current of the driving current threshold value, the light emitting amount of the light emitting element becomes less than a predetermined light emitting amount threshold value. When this is detected, a warning is notified and thereafter the image forming operation of the image forming apparatus is stopped.

A third technical means is a light emitting element for optical scanning the image bearing member to form an electrostatic latent image corresponding to the image data to the image bearing member, at power-on start, every predetermined number of printed sheets, A light emission amount detection unit that detects the light emission amount of the light emitting element at any timing for each predetermined operating time, and a storage unit that stores a drive current threshold value and a reference light emission amount value lower than the drive limit current value of the light emitting element The timing interval for detecting the light emission amount of the light emitting element is changed and the drive current value of the light emitting element is adjusted according to the difference between the drive current threshold value of the light emitting element and the drive current value of the light emitting element. And a control unit that controls the light emission amount of the light emitting element to the reference light emission amount value. When the control unit detects that the drive current value of the light emitting element exceeds the drive current threshold value, a warning is provided. After the notification, the reference light emission The value is decreased and changed to a predetermined light emission amount value determined in advance, the drive current value of the light emitting element is adjusted, and the light emission amount of the light emitting element is controlled to the reduced reference light emission amount value. The image forming apparatus.

  According to a fourth technical means, in the third technical means, after the control unit reduces and changes the reference light emission amount value to a predetermined light emission amount value, the drive current value of the light emitting element is changed to the drive When it is detected that the current threshold value has been exceeded, a warning notification is given and thereafter the image forming operation of the image forming apparatus is stopped.

According to a fifth technical means, in the second or fourth technical means, when the control unit stops the image forming operation of the image forming apparatus, the image forming apparatus is executing an image forming process. When the end of the image forming process is detected, the image forming operation of the image forming apparatus is stopped.

  According to the present invention, the user can recognize the deterioration state of the LD and know that the LD needs to be replaced and repaired by the first warning notification. Further, since the image forming operation of the image forming apparatus is stopped after the second warning notification, inconvenience due to the sudden stop of the image forming operation can be avoided.

1 is a functional block diagram of an image forming apparatus according to the present invention described in Embodiment 1. FIG. 6 is a graph illustrating LD drive control and warning notification according to the first embodiment. It is a figure which shows an example of alerting | reporting. It is a flowchart explaining LD drive control and warning alerting | reporting of Example 1. FIG. It is a graph explaining LD drive control of Example 2 and warning information. It is a flowchart explaining LD drive control of Example 2 and warning alerting | reporting. 1 is an overall cross-sectional view for explaining an outline of an image forming apparatus according to the present invention. It is a graph explaining the process which increases the drive current value of LD and controls the light emission amount of LD uniformly.

Example 1
FIG. 1 is a functional block diagram of an image forming apparatus 1 according to the present invention.
The image forming apparatus 1 includes an optical scanning device 10, an image forming unit 20, and a display unit 30.

  The optical scanning device 10 includes LD units 10Y, 10M, 10C, and 10K for YMCK (Yellow, Magenta, Cyan, and Key (Black)). In the following description, functional blocks of the LD unit 10Y for Y will be described, but the LD units 10M, 10C, and 10K also have similar functional blocks.

The image forming unit 20 includes a photosensitive drum, a printing unit, and the like, and executes image forming processing (printing processing).
The display unit 30 is composed of a liquid crystal panel or the like, and displays an operation screen and status information of the image forming apparatus 1.

The LD unit 10Y includes an LD 11, a PD 12, an LD drive control IC 13, a storage unit 14, and a control IC (control unit) 15.
The LD 11 is a light emitting element that optically scans the photosensitive drum in order to form an electrostatic latent image corresponding to image data on a photosensitive drum (see FIG. 7) that is a latent image carrier of the image forming unit 20.
The PD 12 has a function of detecting the light emission amount of the LD 11 and outputs a current corresponding to the detected light emission amount to the LD drive control IC 13.

The LD drive control IC 13 is an IC that performs drive control of the LD 11, and includes a drive current adjustment unit 13a and a light emission amount detection unit 13b.
The drive current adjustment unit 13a includes, for example, a drive current setting register (not shown) and a DAC (Digital to Analog Converter), reads a digital value written in the drive current setting register by the control IC 15 and reads the digital value. It converts into an analog value by DAC and adjusts the drive current value of LD11.
The LD drive control IC 13 drives the LD 11 with the drive current having the adjusted drive current value.

  The light emission amount detection unit 13b includes a light emission amount detection register (not shown) and an ADC (Analog to Digital Converter), converts the current value of the current output from the PD 12 into a digital value by the ADC, and writes the digital value to the light emission amount detection register. Thus, the light emission amount of the LD 11 is detected.

The storage unit 14 includes, for example, a storage element such as a nonvolatile memory or a storage device such as an HDD, and includes a reference light emission amount value 14a, a light emission amount threshold value 14b, an initial drive current value 14c, a drive current threshold value 14d, and a drive limit current. The value 14e is stored. The initial drive current value 14c, the drive current threshold value 14d, and the drive limit current value 14e are values determined for each YMCK LD according to the characteristics for each YMCK LD.
Details of each value (14a-14e) will be described later.

  The control IC 15 includes functions for controlling the LD drive control IC 13, the image forming unit 20, and the display unit 30, and includes a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable). Gate Array).

The control IC 15 functions as a control unit that increases and adjusts the drive current value of the LD 11 to control the light emission amount of the LD 11 to the reference light emission amount value 14a.
Specifically, the control IC 15 detects the light emission amount of the LD 11 by the light emission amount detection unit 13b of the LD drive control IC 13, and increases and adjusts the drive current value so that the light emission amount of the LD 11 becomes the reference light emission amount value 14a. Then, the drive current value after the increase adjustment is output to the drive current adjustment unit 13a of the LD drive control IC 13, and is written in the drive current setting register of the drive current adjustment unit 13a.
The LD drive control IC 13 drives the LD 11 with the drive current having the adjusted drive current value. As a result, the light emission amount of the LD 11 is controlled to the reference light emission amount value 14a.

  Further, when the control IC 15 detects that the drive current value of the LD 11 exceeds the drive current threshold 14d, the control IC 15 displays a warning (warning notification) on the display unit 30, and thereafter the LD 11 is driven by the drive current of the drive current threshold 14d. Drive control. That is, after the warning is displayed, the drive current value of the LD 11 is not adjusted to increase even if the light emission amount of the LD 11 decreases.

  Further, when the control IC 15 detects that the light emission amount of the LD 11 has become less than the light emission amount threshold value 14b, the control IC 15 displays a warning on the display unit 30, and also the operation of the image forming unit 20, that is, the image formation of the image forming apparatus 1. Stop operation.

FIG. 2 is a graph illustrating LD drive control and warning notification executed in the image forming apparatus 1 according to the first embodiment.
The vertical axis of the graph in FIG. 2 indicates the LD drive current value / LD light emission amount, and the horizontal axis indicates the LD cumulative lighting time (cumulative number of printed sheets).

A line 2a indicates the reference light emission amount value 14a and is the light emission amount of the LD 11 for obtaining the optimum print density.
When the light emission amount of the LD 11 decreases from the reference light emission amount value 14a, the print density also decreases and the quality of the printed matter deteriorates. The value of the light emission amount of the LD 11 that can tolerate this deterioration corresponds to the light emission amount threshold value 14b indicated by the line 2b. The light emission threshold 14b is a predetermined value lower than the reference light emission value 14a, and is set to 70% of the reference light emission value 14a in this embodiment. The light emission amount threshold value 14b can be changed within a range in which the quality degradation of the printed matter is acceptable.

  A line 2c indicates the drive current value of the LD 11 and is increased and adjusted from the initial drive current value 14c of the LD 11. The initial drive current value 14c indicates a drive current value for controlling the light emission amount of the LD 11 to the reference light emission amount value 14a at the time of initial lighting when the LD 11 is not deteriorated.

The line 2d indicates the drive current threshold 14d, and the drive current threshold 14d is a value lower than the drive limit current value 14e corresponding to the maximum rated current of the LD 11 indicated by the line 2e. In this embodiment, the drive current threshold 14d is set to 120% of the initial drive current value 14c. Thus, the drive current threshold value 14d can be determined for each LD by setting the drive current threshold value 14d based on the initial drive current value 14c of the LD.
When the drive current value exceeds the drive current threshold 14d, the control IC 15 issues a warning notification.

  A line 2e indicates the drive limit current value 14e of the LD 11. When a drive current having a drive limit current value of 14e or more is output to the LD 11, the LD 11 is destroyed.

  As described above, when the drive current value of the LD 11 is constant, the light emission amount of the LD 11 decreases as the cumulative lighting time of the LD 11 becomes longer. Therefore, the control IC 15 executes an LD emission amount detection process and an LD drive current value detection process to increase and adjust the drive current value of the LD 11 as indicated by reference numeral X1, and as indicated by reference numeral X2, the LD 11 The amount of emitted light is kept constant.

When the increase adjustment of the drive current executed by the control IC 15 is continued, the drive current value of the LD 11 output to the drive current adjustment unit 13a (the drive current value after the increase adjustment) output to the line 2d as indicated by reference numeral X3. The drive current threshold 14d shown is exceeded.
When the control IC 15 detects that the drive current value of the LD 11 output to the drive current adjusting unit 13a exceeds the drive current threshold 14d, the control IC 15 performs a first warning display (warning notification) on the display unit 30. The contents of the warning display include, for example, an error display dialog shown in FIG.

  Then, the control IC 15 sets the drive current value of the LD 11 output to the drive current adjustment unit 13a as the drive current threshold 14d. That is, the control IC 15 stops the increase adjustment of the drive current value of the LD 11 and thereafter makes the drive current value of the LD 11 constant (drive current threshold 14d) as indicated by reference numeral X4 in FIG.

  The LD 11 is driven and controlled by the drive current of the drive current threshold 14d. As described above, as the cumulative lighting time of the LD 11 becomes longer, the light emission amount of the LD 11 gradually decreases as indicated by reference numeral X5.

  When the control IC 15 detects that the light emission amount of the LD 11 is less than the light emission amount threshold value 14b indicated by the line 2b, as shown by the symbol X6, the control IC 15 performs a second warning display (warning notification) on the display unit 30. Thereafter, the operation of the image forming unit 20 is stopped. The contents of the warning display include, for example, an error display dialog shown in FIG.

  In this way, before the image forming operation of the image forming apparatus stops, the user can know the degradation state of the LD by the first warning notification.

  When the light emission amount control of the LD of the present invention is not performed, the drive current of the LD is increased and adjusted as indicated by reference numeral X7 in FIG. 2, and the operation of the image forming apparatus is stopped at the time indicated by reference numeral X8. However, by performing the operation control of the LD of the present invention, the operation time of the image forming apparatus 1 can be extended to the time indicated by the symbol X6. At this time, although the print density is lowered, the user can use the image forming apparatus, so that convenience is improved.

  In addition, since the image forming operation of the image forming apparatus is stopped after the second warning notification, the user can avoid the inconvenience due to the sudden stop of the operation.

When the control IC 15 stops the operation of the image forming unit 20 and the image forming unit 20 is executing an image forming process (printing process), the image forming unit 20 is detected after detecting the end of the image forming process. Stop the operation.
By doing so, it is possible to prevent problems such as the occurrence of a jam due to the printing process being forcibly stopped during the printing process.

  The line 2c corresponding to the drive current value of the LD, the initial drive current value 14c, and the line 2d corresponding to the drive current threshold 14d described in FIG. 2 are examples, and the drive current value of the LD depends on the difference in the characteristics of the LD. In addition, the initial drive current value 14c and the drive current threshold 14d are different.

FIG. 4 is a flowchart illustrating LD drive control and warning notification described in the first embodiment.
When the control IC 15 detects that the light emission amount detection timing of the LD 11 has been reached (step S1 / YES), the light emission amount detection unit 13b of the LD drive control IC 13 detects the light emission amount of the LD 11 (step S2). The detection timing is, for example, every predetermined number of printed sheets (for example, every 5000 sheets), every predetermined operation time (for example, every 300 hours), or the like when the power is turned on.

  Next, when the control IC 15 detects that the light emission amount of the LD 11 has become less than the reference light emission amount value 14a (step S3 / YES), whether or not the first warning notification has been executed, that is, the first time It is determined whether a warning has been notified (step S4). The determination is made by referring to a warning notification flag described later.

  When the first warning notification is not executed (step S4 / NO), here, when the warning notification flag is off, the control IC 15 adjusts the drive current value of the LD 11 to increase the light emission amount of the LD 11. Control is made to the reference light emission amount value 14a (step S5).

  When the control IC 15 detects that the drive current value of the LD 11 exceeds the drive current threshold value 14d (step S6 / YES), the control IC 15 displays a warning on the display unit 30, and thereafter drives the drive current value of the LD 11 after that. As the current threshold 14d (step S7), the process returns to step S1. At this time, the warning notification flag is turned on. The warning notification flag is stored in the storage unit 14, for example.

  Thereafter, when the processing of steps S1 to S3 is executed, the light emission amount of the LD 11 is less than the reference light emission amount value 14a (step S3 / YES), and the first warning notification is executed (step S4 / YES) Here, when the warning notification flag is on, the control IC 15 displays a second warning on the display unit 30 and thereafter stops the operation of the image forming unit 20 (step S8).

(Example 2)
Unlike the operation of the control IC 15 described in the first embodiment, when the control IC 15 described in the second embodiment detects that the drive current value of the LD 11 exceeds the drive current threshold 14d, a warning display (warning) Notification) and thereafter, the reference light emission value 14a is decreased and changed to a predetermined light emission value. Then, the drive current value of the LD 11 is adjusted to control the light emission amount of the LD 11 to the reduced reference light emission amount value.
The predetermined light emission amount value is stored in the storage unit 14.

  When the control IC 15 detects that the drive current value of the LD 11 exceeds the drive current threshold value 14d after changing the reference light emission amount value 14a to a predetermined light emission amount value, the control IC 15 issues a warning notification and thereafter Then, the operation of the image forming unit 20 is stopped.

  FIG. 5 is a graph illustrating LD drive control and warning notification executed in the image forming apparatus 1 according to the second embodiment. The same lines as those described in FIG. 2 are denoted by the same reference numerals as those in FIG.

  As described above, for example, the control IC 15 increases and adjusts the drive current value of the LD 11 as indicated by reference numeral X1 at an arbitrary timing during the operation of the image forming apparatus. The light emission amount is controlled to a reference light emission amount (constant).

  If the increase adjustment of the LD drive current value executed by the control IC 15 is continued, the drive current value of the LD 11 output to the drive current adjustment unit 13a exceeds the drive current threshold 14d indicated by the line 2d as indicated by reference numeral X3. .

When the control IC 15 detects that the drive current value of the LD 11 exceeds the drive current threshold 14d, for example, as shown in FIG. 3A, the control IC 15 displays a warning on the display unit 30.
Then, as indicated by reference numeral X14 in FIG. 5, the control IC 15 changes the reference light emission amount value 14a to a predetermined light emission amount value that is set in advance. In the present embodiment, the predetermined light emission amount value is set to 70% of the reference light emission amount value 14a, and corresponds to the light emission amount threshold value 14b indicated by the line 2b.

  When the control IC 15 decreases and changes the reference light emission value 14a to a predetermined light emission value, adjusts the drive current value of the LD 11, and controls the light emission amount of the LD 11 to the reduced reference light emission value. As indicated by reference numeral X15, the drive current value of the LD 11 decreases.

  Thereafter, the control IC 15 adjusts the drive current value of the LD 11 to increase and controls the light emission amount of the LD 11 to the reduced reference light emission value (predetermined light emission value). If the control is continued, as described above, the drive current value of the LD 11 increases as indicated by the symbol X16 as the LD lighting time becomes longer.

As indicated by reference numeral X17, the drive current value of the LD 11 output to the drive current adjustment unit 13a exceeds the drive current threshold 14d indicated by the line 2d.
When the control IC 15 detects that the drive current value of the LD 11 output to the drive current adjustment unit 13a has exceeded the drive current threshold 14d, for example, as shown in FIG. Warning notification) and thereafter the operation of the image forming unit 20 is stopped.

  In this way, even after the first warning notification, the printing process can be continued while maintaining the light emission amount of the LD 11 at the reduced reference light emission amount value (light emission amount threshold value).

FIG. 6 is a flowchart illustrating LD drive control and warning notification described in the second embodiment.
The processing of steps S11 to S16 is the same as the processing of steps S1 to S6 described with reference to the flowchart of FIG.

  After the process of step S15 is executed, when the control IC 15 detects that the drive current value of the LD 11 exceeds the drive current threshold value 14d (step S16 / YES), a warning is displayed on the display unit 30 and thereafter. Then, the reference light emission amount value 14a is reduced and changed to a predetermined light emission amount value (step S17). Then, the process returns to step S11.

  Thereafter, the processing of steps S11 to S13 is executed, and the light emission amount of the LD becomes less than the reference light emission amount value 14a (step S13 / YES), and the first warning notification is executed (step S14 / YES). The control IC 15 adjusts the drive current value of the LD 11 to increase and controls the light emission amount of the LD 11 to the reduced reference light emission amount value (predetermined light emission amount value) (step S18).

  When the control IC 15 detects that the drive current value of the LD 11 has exceeded the drive current threshold 14d (step S19 / YES), the control IC 15 displays a warning (warning notification) on the display unit 30 and controls the operation of the image forming unit 20. Stop (step S20). When the drive current value of the LD 11 does not exceed the drive current threshold 14d (step S19 / NO), the process returns to step S11.

(Note 1 of Example 1 and Example 2)
In the functional block diagram described with reference to FIG. 1, the storage unit 14 is provided for each LD unit. However, one storage unit 14 is provided, and the initial drive determined for each LD for YMCK is provided in the storage unit 14. The current value 14c, the drive current threshold 14d, and the drive limit current value 14e may be stored.

  The present invention can also be applied to an image display apparatus provided with only one LD control unit (LD control unit for K).

(Configuration common to Example 1 and Example 2)
The control IC 15 changes the timing interval for detecting the light emission amount of the LD 11 according to the difference between the drive current threshold 14d of the LD 11 and the drive current value of the LD 11. For example, in the initial setting, when the detection timing of the LD light emission amount is every 5000 prints, the LD light emission amount is proportional to the difference between the drive current threshold 14d of the LD 11 and the drive current value of the LD 11 being small. The detection timing is decreased from every 5000 printed sheets to shorten the detection timing interval.

  By shortening the detection timing interval in this way, it is possible to accurately adjust the drive current of the LD 11 and control the operation of the image forming apparatus. Further, since warning notification can be performed accurately, the possibility that the operation of the image forming apparatus stops suddenly can be reduced as much as possible.

(Supplementary note 2 of Example 1 and Example 2)
In addition, the light emission threshold value 14b, the drive current threshold 14d, and the predetermined light emission value set in advance described in the second embodiment can be changed.
In order to perform the change, the image forming apparatus 1 includes an input operation unit (operation panel) for inputting the values and a storage processing unit for storing values input via the input operation unit in the storage unit 14. What is necessary is just to provide. In this way, the administrator of the image forming apparatus 1 can change each value via the input operation unit provided in the image forming apparatus 1.

(Outline of image forming apparatus)
FIG. 7 is an overall cross-sectional view for explaining the outline of the image forming apparatus 1 according to the present invention.
The optical scanning device 10 generates a photosensitive drum 21 (Y photosensitive drum 21Y, M photosensitive drum 21M, C photosensitive drum 21C, K photosensitive drum 21K) by light emitted from an LD (see FIG. 1). Is electrostatically scanned to form an electrostatic latent image on the photosensitive drum 21 in accordance with the image data.

The charger 22 is a charging unit for uniformly charging the surface of the photosensitive drum 21 to a predetermined potential.
The developing unit 23 develops the electrostatic latent image formed on each photosensitive drum 21 with yellow (Y), magenta (M), cyan (C), and black (K) toners (not shown). It is to be imaged.

The cleaner unit 24 removes and collects toner remaining on the surface of the photosensitive drum 21 after development and image transfer.
Four photosensitive drums 21, chargers 22, developing units 23, and cleaner units 24 are provided for each color.

  The intermediate transfer belt unit 25 includes an intermediate transfer belt 25a, an intermediate transfer belt drive roller 25b, an intermediate transfer belt driven roller 25c, an intermediate transfer roller 25d, and an intermediate transfer belt cleaning unit 25e.

The intermediate transfer belt 25a is provided in contact with the photosensitive drum 21, and is stretched and rotated by an intermediate transfer belt drive roller 25b, an intermediate transfer belt driven roller 25c, and an intermediate transfer roller 25d.
Also, a color toner image (multicolor toner image) is formed by sequentially superimposing and transferring the toner images of the respective colors formed on the photosensitive drum 21 on the intermediate transfer belt 25a.

The intermediate transfer belt drive roller 25b is a roller for driving the intermediate transfer belt 25a.
The intermediate transfer belt driven roller 25c is a roller for supporting the intermediate transfer belt 25a from the back side in order to bring the intermediate transfer belt 25a into contact with a cleaning blade (not shown) of an intermediate transfer belt cleaning unit 25e described later.

  The intermediate transfer roller 25d is disposed so as to be in contact with the back side of the intermediate transfer belt 25a, and is based on a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm, and the surface thereof is a conductive elastic material (for example, EPDM, urethane foam). Etc.).

A high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 25d, and the toner on the photosensitive drum 21 is applied by the applied transfer bias. The image is transferred to the intermediate transfer belt 25a.
Four intermediate transfer rollers 25d are provided corresponding to each color of YMCK.

As described above, the electrostatic images visualized according to the hues on the photosensitive drums 21 are stacked on the intermediate transfer belt 25a.
The image information thus laminated is transferred onto the recording sheet by the intermediate transfer belt 25a and the transfer roller 26 disposed at the contact position between the recording sheet and the intermediate transfer belt 25a.

  At this time, the intermediate transfer belt 25a and the transfer roller 26 are pressed against each other at a predetermined nip, and a voltage for transferring the toner onto the recording paper is applied to the transfer roller 26 (what is the toner charging polarity (−))? Reverse polarity (+) high voltage).

  The toner that is not transferred onto the recording paper by the transfer roller 26 and remains on the intermediate transfer belt 25a causes toner color mixing in the next process, and is therefore removed and collected by the intermediate transfer belt cleaning unit 25e. Is done.

The paper feed cassette 27a is a tray for storing recording paper. Note that recording paper can also be placed in a manual paper feed cassette 27b provided outside the image forming apparatus 1.
The paper discharge tray 28 is a tray for collecting printed recording sheets face down.

  Further, the recording paper supplied from the paper feed cassette 27 a and the manual paper feed cassette 27 b is discharged to the image forming apparatus 1 via the transfer roller 26 and the fixing unit 43 as indicated by reference numeral S (two-dot chain line). A substantially vertical sheet conveyance path for feeding to the sheet tray 28 is provided.

  In the vicinity of the sheet conveyance path S, a transfer roller 26, pickup rollers 40a and 40b, a plurality of conveyance rollers 41a to 41d, a registration roller 42, a fixing unit 43, and the like are disposed.

The pickup roller 40a is provided near the end of the paper feed cassette 27a, picks up recording paper one by one from the paper feed cassette 27a, and supplies it to the paper transport path S.
Similarly, the pickup roller 40b is provided near the end of the manual paper feed cassette 27b, picks up recording paper one by one from the manual paper feed cassette 27b, and supplies it to the paper transport path S.

  The transport rollers 41 a to 41 d are small rollers for promoting and assisting the transport of the recording paper, and a plurality of the transport rollers 41 a to 41 d are provided along the paper transport path S.

  The registration roller 42 temporarily holds the recording sheet conveyed in the sheet conveying path S, and transfers the recording sheet to the transfer roller 26 at a timing when the leading edge of the toner image stacked on the intermediate transfer belt 25a is aligned with the leading edge of the recording sheet. It has the function to convey.

  The fixing unit 43 includes a heat roller 43a, a pressure roller 43b, and an external heating belt 43c for heating the heat roller 43a from the outside.

  The heat roller 43a has a function of fusing, mixing, and pressing the multi-color toner image transferred to the recording paper and thermally fixing the recording paper with the pressure roller 43b by thermocompression bonding the toner to the recording paper. doing. The heat necessary for thermocompression bonding is supplied through the external heating belt 43c.

The document table 50 is made of a translucent member such as glass and presses the reading surface of the document.
The document cover unit 51 is configured to be rotatable in the direction of the arrow M. By opening the document cover unit 51, the document can be manually placed on the document placement table 50. The document cover unit 51 is provided with an automatic document transport device 52 for automatically transporting a document on the document placement table 50.
Although an example of application to an image forming apparatus using a photosensitive drum as a latent image carrier has been illustrated and described, the present invention is applied to an image forming apparatus using another latent image carrier such as a photosensitive belt. Obviously, this is also applicable.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Optical scanning apparatus, 10Y, 10M, 10C, 10K ... Y LD unit, M LD unit, C LD unit, K LD unit, 11 ... LD, 12 ... PD, 13 ... LD drive control IC, 13a... Drive current adjustment unit, 13b... Emission amount detection unit, 14... Storage unit, 14a... Reference emission amount value, 14b. 14e ... Drive limit current value, 15 ... Control IC, 20 ... Image forming unit, 21 ... Photoconductor drum, 21Y ... Photoconductor drum for Y, 21M ... Photoconductor drum for M, 21C ... Photoconductor drum for C, 21K ... K photosensitive drum, 22 ... charger, 23 ... developer, 24 ... cleaner unit, 25 ... intermediate transfer belt unit, 25a ... intermediate transfer belt, 25b ... intermediate transfer belt drive roller 25c ... Intermediate transfer belt driven roller, 25d ... Intermediate transfer roller, 25e ... Intermediate transfer belt cleaning unit, 26 ... Transfer roller, 27a ... Paper feed cassette, 27b ... Paper feed cassette, 28 ... Paper discharge tray, 30 ... Display section, 40a, 40b ... pickup roller, 41a ... transport roller, 42 ... registration roller, 43 ... fixing unit, 43a ... heat roller, 43b ... pressure roller, 43c ... external heating belt, 50 ... document placement table, 51 ... document cover section 52. Automatic document feeder.

Claims (5)

A light emitting element that optically scans the latent image carrier in order to form an electrostatic latent image according to image data on the latent image carrier;
A light emission amount detection unit for detecting the light emission amount of the light emitting element at a timing of every predetermined number of printed sheets or every predetermined operation time at power-on startup ;
A storage unit for storing a drive current threshold value and a reference light emission amount value lower than the drive limit current value of the light emitting element;
According to the difference between the drive current threshold value of the light emitting element and the drive current value of the light emitting element, the timing interval for detecting the light emission amount of the light emitting element is changed and the drive current value of the light emitting element is adjusted. A control unit for controlling the light emission amount of the light emitting element to the reference light emission amount value,
When the control unit detects that the drive current value of the light emitting element exceeds the drive current threshold value, the control unit performs a warning notification and thereafter drives the light emitting element with the drive current of the drive current threshold value. Image forming apparatus. The image forming apparatus according to claim 1.
When the control unit detects that the light emission amount of the light emitting element is less than a predetermined light emission amount threshold after driving the light emitting element with the drive current of the drive current threshold, the control unit performs warning notification and thereafter the image. An image forming apparatus, wherein an image forming operation of the forming apparatus is stopped. A light emitting element that optically scans the latent image carrier in order to form an electrostatic latent image according to image data on the latent image carrier;
A light emission amount detection unit for detecting the light emission amount of the light emitting element at a timing of every predetermined number of printed sheets or every predetermined operation time at power-on startup ;
A storage unit for storing a drive current threshold value and a reference light emission amount value lower than the drive limit current value of the light emitting element;
According to the difference between the drive current threshold value of the light emitting element and the drive current value of the light emitting element, the timing interval for detecting the light emission amount of the light emitting element is changed and the drive current value of the light emitting element is adjusted. A control unit for controlling the light emission amount of the light emitting element to the reference light emission amount value,
When the control unit detects that the drive current value of the light emitting element has exceeded the drive current threshold value, it performs a warning notification and thereafter reduces the reference light emission value to a predetermined light emission value. And adjusting the drive current value of the light emitting element to control the light emission amount of the light emitting element to the reduced reference light emission amount value. The image forming apparatus according to claim 3.
When the controller detects that the drive current value of the light emitting element has exceeded the drive current threshold after changing the reference light emission amount value to a predetermined predetermined light emission amount value, the control unit issues a warning notification. And thereafter, the image forming operation of the image forming apparatus is stopped. The image forming apparatus according to claim 2 or 4 ,
When the image forming apparatus is executing an image forming process when stopping the image forming operation of the image forming apparatus, the control unit detects an end of the image forming process and detects an image of the image forming apparatus. An image forming apparatus, wherein a forming operation is stopped.

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