JP5938367B2 - Sensor characteristic correction method - Google Patents

Description

The present invention relates to a sensor characteristic correction how.

  In an image forming apparatus using an electrophotographic process, generally, in order to stabilize an image, a toner is transferred to an intermediate transfer belt to form a patch image (reference image), and the toner portion is detected by a sensor. A value corresponding to the toner amount (toner density) is calculated from the output value of the sensor. Based on this result, the process conditions at the time of printing are reset and controlled so as to obtain an appropriate density.

  In order to stably control the density, it is important to accurately detect a value corresponding to the toner amount, and a certain image forming apparatus calculates a coverage corresponding to the toner amount according to the following equation (for example, Patent Document 1).

Coverage = 1-((P-Po)-(S-So) * K) / ((Pg-Po)-(Sg-So) * K)

  Here, P is a P wave output at the time of toner pattern detection, S is an S wave output at the time of toner pattern detection, Po is a P wave dark potential, So is an S wave dark potential, Pg Is the P-wave output when detecting the belt background, Sg is the S-wave output when detecting the belt background, and K is a constant.

JP 2006-201521 A

  In the above-described technique, when calculating the value corresponding to the toner amount, the value of (S−So) is multiplied by a constant K to correct the sensor output value. If there is a difference, no correction is made in accordance with the variation in the output value. Therefore, in the image forming apparatus, an error occurs in the detection of the toner amount due to the variation, and as a result, an error occurs in the toner density.

  The sensor is adjusted in advance so that its output value falls within a certain range (for example, within ± 3% of the target value). By narrowing this range, the above-mentioned variation is reduced, but the time required for sensor adjustment is lengthened. Moreover, if this range is too narrow, individuals that cannot be adjusted within the range may occur.

The present invention has been made in view of the above problems, and a sensor characteristic correction method for correcting a sensor characteristic so that a toner density by an image forming apparatus becomes an appropriate density even if the output characteristics of the sensor vary. The purpose is to obtain the law .

The sensor characteristic correction method according to the present invention is based on an adjustment step of adjusting an output value of a sensor for an image forming apparatus within a predetermined allowable range with respect to a target value, an output value after adjustment of the sensor, and the target value A storage step of storing a correction coefficient in a memory; and a density correction unit in the image forming apparatus reads the correction coefficient from the memory, and the sensor attached to the image forming apparatus based on the read correction coefficient And a correction step of correcting a value indicating the toner amount specified from the output value. The memory is provided in the image forming apparatus, and the sensor is attached to the image forming apparatus before the adjustment step. In the correction step, A is the correction coefficient, P is a P wave output when toner is detected by the sensor, S is an S wave output when toner is detected by the sensor, and Po is the P wave output of the sensor. The dark potential, So is the dark potential of the S wave of the sensor, Pg is the P wave output when the background of the belt on which the toner is formed is detected by the sensor, and Sg is the sensor. The S-wave output when the background of the belt on which the toner is formed is detected in the image forming apparatus, and when K is a constant, the value indicating the toner amount is 1-((P-Po)- (S−So) × A × K) / ((Pg−Po) − (Sg−So) × A × K). The correction coefficient A is expressed by the equation A = {(P-Po) /, where B is the target value of {(P-Po) / (S-So)} when adjusting the output value of the sensor. It is calculated by (S-So)} / B.

  According to the present invention, even if the output characteristics of the sensors used in the image forming apparatus vary, the sensor characteristics are corrected so that the toner density by the image forming apparatus becomes an appropriate density.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus to which a sensor whose characteristics are corrected by a sensor characteristic correction method according to an embodiment of the present invention is attached. FIG. 2 is a block diagram illustrating a part of the electrical configuration of the image forming apparatus according to the first embodiment. FIG. 3 is a diagram illustrating an optical system of the sensor in FIG. FIG. 4 is a flowchart for explaining the sensor characteristic correction method according to the first embodiment. FIG. 5 is a diagram for explaining an error in coverage due to variations in sensor output values. FIG. 6 is a diagram for explaining the coverage obtained by correcting the output value of the sensor with variation. FIG. 7 is a block diagram illustrating a part of the electrical configuration of the image forming apparatus according to the second embodiment. FIG. 8 is a flowchart for explaining the sensor characteristic correction method according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.

  FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus to which a sensor whose characteristics are corrected by a sensor characteristic correction method according to an embodiment of the present invention is attached. The image forming apparatus is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copying machine, or a multifunction machine.

  The image forming apparatus of this embodiment has a tandem color developing device. The color developing device includes photosensitive drums 1a to 1d, exposure devices 2a to 2d, and developing units 3a to 3d. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black. The exposure apparatuses 2a to 2d are apparatuses that form electrostatic latent images by irradiating the photosensitive drums 1a to 1d with laser light. The exposure apparatuses 2a to 2d include a laser diode that is a light source of laser light and optical elements (lenses, mirrors, polygon mirrors, etc.) that guide the laser light to the photosensitive drums 1a to 1d.

  Further, around the photosensitive drums 1a to 1d, a charger such as a scorotron, a cleaning device, a static eliminator and the like are arranged. The cleaning device removes residual toner on the photosensitive drums 1a to 1d after the primary transfer, and the static eliminator neutralizes the photosensitive drums 1a to 1d after the primary transfer.

  In the developing units 3a to 3d, toner containers filled with toners of four colors of cyan, magenta, yellow, and black are respectively mounted. The toner is supplied from the toner containers, and constitutes a developer together with the carrier. An external additive such as titanium oxide is added to the toner. The developing units 3a to 3d form toner images by attaching the toner to the electrostatic latent images on the photosensitive drums 1a to 1d.

  The photosensitive drum 1a, the exposure device 2a, and the developing unit 3a develop magenta, and the photosensitive drum 1b, the exposure device 2b, and the developing unit 3b develop cyan, the photosensitive drum 1c, and exposure. Yellow development is performed by the apparatus 2c and the development unit 3c, and black development is performed by the photosensitive drum 1d, the exposure apparatus 2d, and the development unit 3d.

  The intermediate transfer belt 4 is an annular image carrier that contacts the photosensitive drums 1a to 1d and primarily transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 4 is a kind of intermediate transfer member. The intermediate transfer belt 4 is stretched around the driving roller 5 and circulates in the direction from the contact position with the photosensitive drum 1d to the contact position with the photosensitive drum 1a by the driving force from the driving roller 5.

  The transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4 and secondarily transfers the toner image on the intermediate transfer belt 4 to the paper. The sheet on which the toner image has been transferred is conveyed to the fixing device 9 and the toner image is fixed on the sheet.

  The roller 7 has a cleaning brush, and the cleaning brush is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the transfer of the toner image onto the paper. The roller 7 also removes the external additive together with the toner carried on the region where the external additive has adhered on the intermediate transfer belt 4 during density correction.

  The sensor 8 irradiates the intermediate transfer belt 4 with a light beam and detects the reflected light. When adjusting the toner density, the sensor 8 irradiates a predetermined region of the intermediate transfer belt 4 with a light beam, detects reflected light (measurement light) of the light beam, and outputs an electrical signal corresponding to the light amount.

  This sensor 8 is a sensor whose characteristics are corrected by the sensor characteristic correction method according to the embodiment.

  FIG. 2 is a block diagram illustrating a part of the electrical configuration of the image forming apparatus according to the first embodiment. In FIG. 2, a print engine 11 controls a drive source (not shown) that drives the above-described roller, a bias application circuit that applies a development bias and a primary transfer bias, and exposure devices 2a to 2d to feed paper, A processing circuit for executing printing and paper discharge. The developing bias is applied between the photosensitive drums 1a to 1d and the developing units 3a to 3d, respectively, and the primary transfer bias is applied between the photosensitive drums 1a to 1d and the intermediate transfer belt 4, respectively.

  In this embodiment, the print engine 11 has a density correction unit 21. The density correction unit 21 develops the test pattern on the photosensitive drums 1a to 1d, transfers the test pattern to the intermediate transfer belt 4, and outputs the output value of the sensor 8 by the measurement light from a predetermined measurement area before the test pattern is carried. The coverage corresponding to the toner density of the test pattern is specified based on the output value of the sensor 8 from the measurement light from the predetermined measurement area carrying the test pattern, and the density correction is performed based on the specified coverage. Do.

  FIG. 3 is a diagram illustrating an optical system of the sensor 8 in FIG.

  As shown in FIG. 3, the sensor 8 includes a light source 51 that emits light, a beam splitter 52 on the light source side, a light receiving element 53 on the light source side, a beam splitter 54 on the light receiving side, a first light receiving element 55, A second light receiving element 56.

  The light source 51 is, for example, a light emitting diode. The beam splitter 52 transmits the P-polarized component and reflects the S-polarized component among the light rays from the light source 51. The light receiving element 53 on the light source side is, for example, a photodiode, detects the S-polarized component from the beam splitter 52, and outputs an electrical signal corresponding to the amount of light. This electrical signal is used for stable control of the light source 51.

  The P-polarized component light that has passed through the beam splitter 52 on the light source side is incident on the surface (the toner image 41 or the ground) of the intermediate transfer belt 4 and reflected. The reflected light at this time has a regular reflection component and a diffuse reflection component, and the regular reflection component is P-polarized light.

  The beam splitter 54 transmits the P-polarized component (that is, the regular reflection component) of the reflected light and reflects the S-polarized component. The first light receiving element 55 is, for example, a photodiode, detects the light of the P-polarized component transmitted through the beam splitter 54, and outputs an electrical signal corresponding to the amount of light. The second light receiving element 56 is, for example, a photodiode, detects the S-polarized component light reflected by the beam splitter 54, and outputs an electrical signal corresponding to the light quantity.

  The density correction unit 21 calculates the toner density while specifying the correction amount of the toner density based on the output of the first light receiving element 55 and the output of the second light receiving element 56.

  At that time, the density correction unit 21 calculates the coverage according to the following equation.

  Coverage = 1-((P-Po)-(S-So) * A * K) / ((Pg-Po)-(Sg-So) * A * K)

  Here, A is a correction coefficient for each sensor 8, P is a P wave output when the toner is detected by the sensor 8, S is an S wave output when the sensor 8 detects the toner, and P 0 is a sensor 8. P0 is a dark potential of the S wave of the sensor 8, S0 is a dark potential of the S wave of the sensor 8, Pg is a P wave output when the background of the intermediate transfer belt 4 is detected by the sensor 8, and Sg is intermediate by the sensor 8. This is the S wave output when the background of the transfer belt 4 is detected, and K is a constant.

  The correction coefficient A is specified when adjusting the output value of the sensor 8. The target value of the output value (P-Po) / (S-So) of the sensor 8 is B, and the actual measured value of (P-Po) / (S-So) obtained when the sensor 8 is adjusted is B '. Then, A = B ′ / B.

  Next, the sensor characteristic correction method according to the first embodiment will be described. FIG. 4 is a flowchart for explaining the sensor characteristic correction method according to the first embodiment.

  In the first embodiment, first, before the sensor 8 is attached to the image forming apparatus, the output value is adjusted by the adjustment plate as described above (step S1).

  Specifically, the output value of the sensor 8 is adjusted so that the measured value B ′ falls within an allowable range of ± 3% of the target value B. Adjustment of the output value of the sensor 8 is performed by forming toners of a plurality of densities on an adjustment plate that reproduces the surface of the intermediate transfer belt 4 and specifying the measurement value B ′ at that time. That is, the output value of the sensor 8 is adjusted so that the measured value B ′ falls within the allowable range of the target value B for all of the toners having a plurality of densities formed on the adjustment plate.

  Then, the correction coefficient A based on the measured value B ′ and the target value B is stored in the memory 8a in the sensor 8 (step S2). The memory 8a is a non-volatile memory.

  After the correction coefficient A is stored in the memory 8a in the sensor 8 in this way, the sensor 8 is attached to the image forming apparatus (step S3).

  Thereafter, the density correction unit 21 reads the correction coefficient A from the memory 8a in the sensor 8 (step S4), and calculates the coverage according to the above-described equation using the correction coefficient A when adjusting the density. Based on the above, the toner density during printing is adjusted (step S5).

  As described above, according to the first embodiment, the correction coefficient A based on the output value after adjustment of the sensor 8 and the target value is stored in the memory 8a in the sensor 8, and the density correction in the image forming apparatus is performed. The unit 21 reads the correction coefficient A from the memory 8a, and corrects the coverage corresponding to the toner amount specified from the output value of the sensor 8 attached to the image forming apparatus based on the read correction coefficient A. .

  As a result, even if the output characteristics vary among the individual sensors 8, the sensor characteristics are corrected so that the toner density by the image forming apparatus becomes an appropriate density.

  FIG. 5 is a diagram for explaining an error in coverage due to variations in the output value of the sensor 8. FIG. 6 is a diagram for explaining the coverage obtained by correcting the output value of the sensor 8 having variations. As shown in FIG. 5, when the correction by the correction coefficient A is not performed, an error occurs in the coverage due to the variation in the measured value B ′ within the above-described allowable range. By correcting with the correction coefficient A in FIG. 6, the coverage error due to the variation in the measured value B ′ is eliminated as shown in FIG.

Embodiment 2. FIG.

  In the sensor characteristic correction method according to the second embodiment of the present invention, the adjustment is performed with the sensor 8 attached to the image forming apparatus, and the correction coefficient A is stored in the memory in the image forming apparatus, not in the sensor 8.

  FIG. 7 is a block diagram illustrating a part of the electrical configuration of the image forming apparatus according to the second embodiment. The image forming apparatus in the second embodiment has a memory 12. The memory 12 is a non-volatile memory and stores the correction coefficient A described above.

  The other configurations of the image forming apparatus and the sensor 8 in the second embodiment are the same as those in the first embodiment. However, the sensor 8 in the second embodiment may not have the memory 8a.

  Next, a sensor characteristic correction method according to the second embodiment will be described. FIG. 8 is a flowchart for explaining the sensor characteristic correction method according to the second embodiment.

  In the second embodiment, the sensor 8 is attached to the image forming apparatus before adjusting the output value of the sensor 8 (step S11).

  Next, the output value is adjusted by the adjustment plate (step S12). At this time, for example, with the intermediate transfer belt 4 removed, the adjustment plate is fixed to a position (toner amount measurement position) where the intermediate transfer belt 4 is originally disposed with a jig or the like, and a plurality of the adjustment plates as described above. The measured value B ′ for the concentration is adjusted.

  Then, the correction coefficient A based on the measured value B ′ and the target value B is stored in the memory 12 in the image forming apparatus (step S13). At this time, for example, the measured value B ′ and the target value B or the correction coefficient A are recorded on a data sheet or the like, and the correction coefficient A is input by operating an operation panel (not shown) of the image forming apparatus. When the correction coefficient A is input, the correction coefficient A is stored in the memory 12 as one of set values, for example.

  Thereafter, the density correction unit 21 reads the correction coefficient A from the memory 12 (step S14), and calculates the coverage according to the above formula using the correction coefficient A during density adjustment, and based on the coverage, The toner density during printing is adjusted (step S15).

  As described above, according to the second embodiment, the corrected output value of the sensor 8 and the correction coefficient A based on the target value are stored in the memory 12 in the image forming apparatus, and the density in the image forming apparatus is stored. The correction unit 21 reads the correction coefficient A from the memory 8a, and corrects the coverage corresponding to the toner amount specified from the output value of the sensor 8 attached to the image forming apparatus based on the read correction coefficient A. To do.

  As a result, even if the output characteristics vary among the individual sensors 8, the sensor characteristics are corrected so that the toner density by the image forming apparatus becomes an appropriate density.

  In the second embodiment, since the output value is adjusted in a state where the sensor 8 is attached to the image forming apparatus, the sensor characteristics including the attachment error of the sensor 8 are corrected. Therefore, the sensor characteristics are corrected more accurately.

  Each of the above-described embodiments is a preferred example of the present invention, but the present invention is not limited thereto, and various modifications and changes can be made without departing from the scope of the present invention. It is.

  The present invention is applicable to a sensor of an image forming apparatus, for example.

8 Sensor 8a, 12 Memory 21 Density correction part 51 Light source (an example of light emitting element)
55,56 Light receiving element

Claims (1)

An adjustment step of adjusting the output value of the sensor for the image forming apparatus within a predetermined allowable range with respect to the target value;
A storage step of storing a correction coefficient based on the output value after adjustment of the sensor and the target value in a memory;
The density correction unit in the image forming apparatus reads the correction coefficient from the memory, and indicates the toner amount specified from the output value of the sensor attached to the image forming apparatus based on the read correction coefficient. A correction step for correcting the value;
With
The memory is provided in the image forming apparatus,
Before the adjustment step, the sensor is attached to the image forming apparatus,
In the correction step, A is the correction coefficient, P is a P wave output when toner is detected by the sensor, S is an S wave output when toner is detected by the sensor, and Po is a dark potential of the P wave of the sensor. So is the dark potential of the S wave of the sensor, Pg is the P wave output when the sensor detects the background of the belt on which the toner is formed in the image forming apparatus, and Sg is the sensor. When the background of the belt on which the toner is formed in the image forming apparatus is detected as an S wave output and K is a constant, the value indicating the toner amount is 1-((P-Po)-(S -So) * A * K) / ((Pg-Po)-(Sg-So) * A * K)
The correction coefficient A is expressed by the equation A = {(P−Po) / (S) when the target value of {(P−Po) / (S−So)} is B when adjusting the output value of the sensor. -So)} / B,
Sensor characteristic correction method characterized by

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