JP6073777B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  A color image forming apparatus expresses various color densities and gradations using usually four colors of toner for forming a color image. For this reason, in the color image forming apparatus, it is necessary to periodically adjust the density and gradation of each of the four color toners (see, for example, Patent Document 1).

  In the image forming apparatus, the developing bias and the light amount of the exposure apparatus are adjusted for density adjustment (see, for example, Patent Document 2). Usually, a toner pattern for developing bias adjustment and a toner pattern for light quantity adjustment are formed in order, and the development bias adjustment by the toner pattern for development bias adjustment and the light quantity adjustment by the toner pattern for light quantity adjustment are performed independently.

JP 2010-008960 A JP 2003-270874 A

  However, as described above, when various adjustments are made by sequentially forming a development bias adjustment toner pattern and a light amount adjustment toner pattern, the total length of the adjustment toner pattern becomes long, and the time required for the adjustment is increased. Will become longer.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can be adjusted in a short time.

An image forming apparatus according to the present invention includes a photosensitive drum, an exposure device that irradiates light to the photosensitive drum to form an electrostatic latent image, and a toner layer that is transferred to the electrostatic latent image on the photosensitive drum. And a controller for controlling the developing bias so that the entire amount of the toner layer on the developing roller is transferred to the electrostatic latent image on the photosensitive drum. The controller changes the light amount of the exposure apparatus in the sub-scanning direction in correspondence with a toner pattern for adjusting the light amount of the exposure apparatus during adjustment, and adjusts the developing bias. The light quantity adjusting toner pattern and the developing bias adjusting toner pattern are formed side by side in the main scanning direction while changing the developing bias in the sub scanning direction corresponding to the developing bias adjusting toner pattern. The developing bias adjustment toner pattern is a saturated density toner pattern, the light quantity adjustment toner pattern is a non-saturated density low gradation toner pattern, and the photosensitive drum is made of amorphous silicon. .

  According to the present invention, adjustment can be performed in a short time in the image forming apparatus.

FIG. 1 is a side view showing a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of the developing device 3a in FIG. FIG. 3 is a block diagram illustrating a configuration example of a controller in the image forming apparatus illustrated in FIG. FIG. 4 is a diagram showing an example of a light amount adjusting toner pattern and a developing bias adjusting toner pattern formed in the image forming apparatus shown in FIGS.

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

  FIG. 1 is a side view showing a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. This 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, an exposure device 2, and developing devices 3a to 3d. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black. The exposure device 2 is a device that forms an electrostatic latent image by irradiating the photosensitive drums 1a to 1d with laser light. The exposure apparatus 2 includes a laser diode that is a light source of laser light and an optical element (lens, mirror, polygon mirror, etc.) that guides the laser light to the photosensitive drums 1a to 1d.

  The developing devices 3a to 3d form toner images by attaching the toner in the toner cartridges to the electrostatic latent images on the photosensitive drums 1a to 1d. The photosensitive drum 1a and the developing device 3a develop magenta, the photosensitive drum 1b and the developing device 3b develop cyan, and the photosensitive drum 1c and the developing device 3c develop yellow. Then, black development is performed by the photosensitive drum 1d and the developing device 3d.

  The intermediate transfer belt 5 is an annular intermediate transfer member that contacts the photosensitive drums 1a to 1d and transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 5 is stretched around the driving roller 6 and circulates in the direction from the contact position with the photosensitive drum 1a to the contact position with the photosensitive drum 1d by the driving force from the driving roller 6.

  The transfer roller 7 brings the conveyed paper into contact with the intermediate transfer belt 5 and transfers the toner image on the intermediate transfer belt 5 to the paper. The sheet on which the toner image is transferred is conveyed to a fixing device (not shown), and the toner image is fixed on the sheet.

  The sensor 8 irradiates the intermediate transfer belt 5 with light and detects the reflected light. In particular, the sensor 8 detects the density of the toner pattern (each toner color patch) on the intermediate transfer belt 5 during adjustment. The sensor 8 is a reflective optical sensor that measures the density of toner marks for adjustment.

  FIG. 2 is a cross-sectional view showing an example of the developing device 3a in FIG. In FIG. 2, the developing device 3a is illustrated, but the developing devices 3b to 3d have the same configuration.

  As illustrated in FIG. 2, the developing device 3 a includes a housing 11, a stirring screw 12, a magnetic roller 13, and a developing roller 14.

  A toner container (not shown) is connected to the developing device 3a, and toner is supplied from the toner container into the housing 11 via a supply port (not shown). In the housing 11, the two-component developer containing toner and carrier is stirred by the stirring screw 12. A magnetic material is used for the carrier.

  The magnetic roller 13 holds a two-component developer in a brush shape on its surface. The toner in the two-component developer moves to the developing roller 14 in accordance with a transport bias that is a voltage between the magnetic roller 13 and the developing roller 14.

  The developing roller 14 holds the toner transferred from the magnetic roller 13 as a thin toner layer on the surface thereof. The toner layer formed on the surface of the developing roller 14 is transferred to the photosensitive drum 1a by a developing bias that is a voltage between the developing roller 14 and the photosensitive drum 1a.

  The photosensitive drum 1a is an image carrier on which an electrostatic latent image is formed by the exposure device 2. For the photosensitive drum 1a, a photosensitive drum having a high relative dielectric constant such as an amorphous silicon photosensitive drum is used.

  FIG. 3 is a block diagram illustrating a configuration example of a controller in the image forming apparatus illustrated in FIG.

  The controller 31 electrically controls each part in the image forming apparatus. The controller 31 includes an ASIC (Application Specific Integrated Circuit), a microcomputer, and the like. The development bias setting circuit 32 is a circuit that sets the development bias (voltage between the photosensitive drum 1a and the development roller 14) to a designated voltage. The driver circuit 33 is a circuit that drives a light source (laser diode or the like) of the exposure apparatus 2.

  The controller 31 includes a development bias setting unit 41, a light amount setting unit 42, and a toner density specifying unit 43.

  The development bias setting unit 41 uses the development bias setting circuit 32 to set the development bias. The light quantity setting unit 42 uses the driver circuit 33 to set the light quantity of the exposure apparatus 2. The toner density specifying unit 43 specifies the density of the toner mark on the intermediate transfer belt 5 based on the output of the sensor 8.

  The developing bias setting unit 41 controls the developing bias so that the entire toner layer on the developing roller 14 is transferred to the electrostatic latent image on the photosensitive drum 1a during normal printing. At the time of adjustment, the lower limit value of the developing bias value that can transfer the entire toner layer on the developing roller 14 to the electrostatic latent image on the photosensitive drum 1a is specified and set as the developing bias value at the time of normal printing. .

  FIG. 4 is a diagram showing an example of a light amount adjusting toner pattern and a developing bias adjusting toner pattern formed in the image forming apparatus shown in FIGS.

  As shown in FIG. 4, the controller 31 adjusts the light amount of the exposure device 2 in the sub-scanning direction in association with the light amount adjustment toner pattern 61 for adjusting the light amount of the exposure device 2 by the light amount setting unit 42 during adjustment. In addition, the development bias setting unit 41 changes the development bias in the sub-scanning direction in correspondence with the development bias adjustment toner pattern 62 for adjusting the development bias, and the light amount adjustment toner pattern 61 and the development bias adjustment. The toner pattern 62 is formed side by side in the main scanning direction.

  The light amount adjustment toner pattern 61 includes a cyan patch, a magenta patch, a yellow patch, and a black patch corresponding to a plurality of light amount setting values, and the development bias adjustment toner pattern 62 corresponds to a plurality of development bias setting values. It has a cyan patch, a magenta patch, a yellow patch, and a black patch.

  In this image forming apparatus, the developing bias adjusting toner pattern 62 is a saturated density (maximum density) toner pattern, and the light amount adjusting toner pattern 61 is a non-saturated density (low density) toner pattern. For the developing bias adjustment toner pattern 62 (that is, the saturated density toner pattern), the amount of toner transferred from the developing roller 14 to the photosensitive drum 1a does not change even if the amount of light changes. With respect to the toner pattern 61 (that is, the toner pattern with a non-saturated density), the amount of toner transferred from the developing roller 14 to the photosensitive drum 1a does not change even when the developing bias changes.

  Specifically, the photosensitive drums 1a to 1d having a high dielectric constant such as an amorphous silicon photosensitive member are used, and the entire toner layer on the developing roller 14 is transferred to the electrostatic latent images on the photosensitive drums 1a to 1d. In a development system, an electric field of an electrostatic latent image between pixels is continuously low and saturated in a pattern with a high dot area ratio such as a saturated toner pattern (here, development bias adjusting toner pattern 62). Even if the amount of exposure light is changed, the toner density is not affected. On the other hand, in the case of a non-saturated low gradation toner pattern (here, the light amount adjustment toner pattern 61) such as one isolated dot, the dot area ratio is low, and toner is sufficiently supplied according to the light amount. Even if the bias is changed, the toner density is not affected.

  Therefore, even if the light amount adjusting toner pattern 61 and the developing bias adjusting toner pattern 62 are arranged in the main scanning direction and both the light amount and the developing bias are changed in the sub scanning direction (that is, in the line, the exposure is performed). The light amount of the apparatus 2 (the light amount at the time of light emission) and the development bias are not changed), the density measurement value of the light amount adjustment toner pattern 61 and the density measurement value of the development bias adjustment toner pattern 62 are accurately obtained.

  In this embodiment, at the time of adjustment, the controller 31 increases the light amount and the developing bias of the exposure apparatus 2 along the sub-scanning direction and decreases the other while increasing the light amount of the exposure apparatus 2 and the developing bias. The bias adjustment toner pattern 62 is formed side by side in the main scanning direction.

  Next, the operation of the image forming apparatus will be described.

  The controller 31 adjusts the density and gradation at a predetermined adjustment timing.

  At this time, as described above, the controller 31 causes the light amount setting unit 42 to change the light amount of the exposure apparatus 2 for each patch for each toner color in accordance with the light amount adjustment toner pattern 61 and also to develop the developing bias setting unit. 41, the light amount adjusting toner pattern 61 and the developing bias adjusting toner pattern 62 are arranged in the main scanning direction while changing the developing bias corresponding to the developing bias adjusting toner pattern 62 for each patch for each toner color. Let it form.

  Then, the controller 31 uses the toner density specifying unit 43 to specify a density measurement value for each patch based on the output signal of the sensor 8, and based on the density measurement value, the light amount and development of the exposure apparatus 2 during normal printing. Adjust the bias.

  As described above, according to the above-described embodiment, the controller 31 controls the developing bias so that the entire amount of the toner layer on the developing roller 14 is transferred to the electrostatic latent image on the photosensitive drum 1a. Then, at the time of adjustment, the controller 31 changes the light quantity of the exposure apparatus 2 in correspondence with the light quantity adjustment toner pattern 61 for adjusting the light quantity of the exposure apparatus 2 and also adjusts the development bias for adjusting the development bias. While changing the developing bias corresponding to the toner pattern 62, the light amount adjusting toner pattern 61 and the developing bias adjusting toner pattern 62 are formed side by side in the main scanning direction.

  As a result, the light amount adjustment toner pattern 61 and the development bias adjustment toner pattern 62 are formed in parallel, so that the total length of the adjustment toner pattern is shortened, and the adjustment can be performed in a short time without degrading the adjustment accuracy. It can be carried out.

  The above-described embodiments are preferred examples of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. is there.

  The present invention is applicable to, for example, an image forming apparatus that automatically adjusts density and gradation.

DESCRIPTION OF SYMBOLS 1a-1d Photosensitive drum 2 Exposure apparatus 14 Developing roller 31 Controller 61 Light quantity adjustment toner pattern 62 Development bias adjustment toner pattern

Claims (2)

A photosensitive drum;
An exposure device that irradiates the photosensitive drum with light to form an electrostatic latent image;
A developing roller holding a toner layer to be transferred to the electrostatic latent image on the photosensitive drum;
A controller for controlling the developing bias so as to transfer the entire amount of the toner layer on the developing roller to the electrostatic latent image on the photosensitive drum,
The controller changes a light amount of the exposure apparatus in the sub-scanning direction in correspondence with a light amount adjustment toner pattern for adjusting a light amount of the exposure apparatus during adjustment, and a developing bias for adjusting the developing bias The light quantity adjusting toner pattern and the developing bias adjusting toner pattern are formed side by side in the main scanning direction while changing the developing bias in the sub scanning direction corresponding to the adjusting toner pattern ,
The development bias adjusting toner pattern is a saturated density toner pattern,
The light amount adjustment toner pattern is a low-gradation toner pattern with a non-saturated density,
The photosensitive drum is made of amorphous silicon;
An image forming apparatus.   The controller increases the light amount of the exposure apparatus and the developing bias along the sub-scanning direction, and decreases the other while adjusting the light amount adjusting toner pattern and the developing bias adjusting toner pattern along the sub-scanning direction. The image forming apparatus according to claim 1, wherein the image forming apparatuses are arranged side by side in the main scanning direction.

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