JP2012053213A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of transfer deviation of an image with respect to recording paper.SOLUTION: An image forming apparatus comprises correction means which makes toner image forming means form a toner image with uniform density on an image carrier circumferentially, which transfers the toner image on the image carrier to a transfer conveyance belt by making the transfer conveyance belt run as making the image carrier rotate, and which corrects a rotating speed of the image carrier or a running speed of the transfer conveyance belt so that density unevenness may not be caused when the occurrence of the density unevenness of the toner image on the transfer conveyance belt is detected on the basis of a detection result of density detection means.

Description

  The present invention relates to an image forming apparatus.

  In an electrophotographic image forming apparatus, when a large-diameter photosensitive drum is used, the conveyance and separation of recording paper (performance for separating the recording paper attached to the photosensitive drum during transfer) is improved. Therefore, a transfer conveyance belt is used instead of the transfer roller. The transfer / conveying belt conveys the recording paper while electrostatically adsorbing it onto the surface of the belt member, and transfers the toner image by pressing the recording paper against the peripheral surface of the photosensitive drum. Since the transfer conveyance belt has a larger contact area with respect to the recording paper than the transfer roller, a high suction force can be obtained, and the radius of curvature can be set larger than that of the photosensitive drum, so that the separability can be improved. An image forming apparatus including such a transfer conveyance belt is disclosed in, for example, Patent Document 1 below.

JP 2002-123095 A

  However, in the above-described prior art, the suction force between the photosensitive drum and the transfer conveyance belt is larger than when the transfer roller is used, so if there is a difference in the surface speed between the photosensitive drum and the transfer conveyance belt, When transferring from the photosensitive drum to the recording paper, a stick-slip phenomenon, so-called transfer deviation, is likely to occur.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to suppress a transfer shift with respect to a recording sheet.

  In order to achieve the above object, according to the present invention, as a first solving means relating to an image forming apparatus, an image carrier comprising a cylindrical member and carrying a toner image formed on a circumferential surface while rotating in the circumferential direction; A toner image forming means for forming a toner image on the peripheral surface of the image carrier, and conveying the recording paper while adsorbing the recording paper, and transferring the toner image by pressing the recording paper against the peripheral surface of the image carrier. An image forming apparatus comprising a transfer conveyance belt, a density detection means for detecting the density of a toner image formed on the transfer conveyance belt, and a toner image having a uniform density in the circumferential direction on the image carrier Is formed on the toner image forming means, rotated on the image carrier and run on the transfer conveyance belt, thereby transferring the toner image on the image carrier onto the transfer conveyance belt, When the toner image on the transfer / conveying belt is detected to have density unevenness based on the detection result of the degree detecting means, the rotation speed of the image carrier or the transfer / conveying belt is set so that density unevenness does not occur. And a means for correcting the traveling speed of the vehicle.

  According to the present invention, as the second solving means relating to the image forming apparatus, in the first solving means, the density detecting means outputs a voltage value corresponding to the density of the toner image, and the correcting means When the value is out of the allowable range, a means that density unevenness occurs in the toner image is adopted.

  According to the present invention, the toner image formed on the image carrier with a uniform density in the circumferential direction is transferred onto the transfer conveyance belt, and the toner formed on the transfer conveyance belt based on the detection result of the density detection means When it is detected that density unevenness has occurred in the image, the rotational speed of the image carrier or the running speed of the transfer conveyance belt is corrected so that density unevenness does not occur. The cause of density unevenness and transfer deviation is the difference in surface speed between the image carrier and the transfer conveyance belt. By detecting density unevenness, it is found that the surface speed of the image carrier is different from that of the transfer conveyance belt. The rotational speed of the image carrier or the running speed of the transfer / conveying belt is corrected so as not to occur, that is, the surface speed of the image carrier and the transfer / conveying belt is corrected to be constant. Thereby, generation | occurrence | production of transcription | transfer deviation can be suppressed.

FIG. 3 is a functional configuration diagram illustrating characteristic components of the printer A according to the embodiment of the present invention. 6 is a flowchart illustrating an operation of the printer A according to the embodiment of the present invention. It is a graph which shows the voltage value of the detection signal which the optical sensor 7 of the printer A which concerns on embodiment of this invention outputs.

Embodiments of the present invention will be described below with reference to the drawings.
A printer (image forming apparatus) A according to the present embodiment is connected to a plurality of client computers via a local area network, and forms an image on a recording sheet based on an electrophotographic method when a print instruction is received from the client computer. is there. As shown in FIG. 1, the printer A includes a photosensitive drum (image carrier) 1, a charging unit 2, a laser scanning unit 3, a developing unit 4, a cleaner 5, a transfer conveyance belt 6, an optical sensor (density detection means) 7. A fixing roller 8 and an image forming engine (correction means) 9. As for the printer A, only the characteristic components described above will be described, and description of other components will be omitted. The charging unit 2, the laser scanning unit 3, and the developing unit 4 constitute a toner image forming unit in the present embodiment.

The photosensitive drum 1 is formed of a cylindrical member that supports a toner image formed on the peripheral surface based on the electrostatic latent image. The photosensitive drum 1 extends in the depth direction when viewed from the front of the printer A, and the image forming engine 9 Under the control, a drive source (not shown) capable of speed adjustment such as a motor rotates in the circumferential direction during image formation.
The charging unit 2 is disposed so as to face the photosensitive drum 1 and makes the peripheral surface of the photosensitive drum 1 in a charged state under the control of the image forming engine 9.
The laser scanning unit 3 forms an electrostatic latent image by irradiating the peripheral surface of the charged photosensitive drum 1 with laser light under the control of the image forming engine 9.

The developing unit 4 forms a toner image based on the electrostatic latent image on the peripheral surface of the photosensitive drum 1 by supplying toner to the peripheral surface of the photosensitive drum 1 under the control of the image forming engine 9 ( develop.
The cleaner 5 removes the toner remaining on the photosensitive drum 1 under the control of the image forming engine 9 after the toner image is transferred from the photosensitive drum 1 to the recording paper.

  The transfer conveyance belt 6 is provided so as to be in contact with the photosensitive drum 1, conveys a recording sheet fed from a paper feed cassette (not shown) to the photosensitive drum 1, and records a toner image on the photosensitive drum 1. The sheet is transferred onto a sheet, and includes a belt member 6a, a driving roller 6b, a driven roller 6c, and a transfer roller 6d.

  The belt member 6a is an endless belt stretched between the driving roller 6b and the driven roller 6c, and is provided so as to pass between the photosensitive drum 1 and the transfer roller 6d. Travel in the transport direction. The belt member 6a conveys the recording sheet while adsorbing the recording sheet by the electric charge supplied from the transfer roller 6d, and transfers the toner image onto the recording sheet by pressing the recording sheet against the peripheral surface of the photosensitive drum 1.

The driving roller 6b is disposed opposite to the driven roller 6c with a certain distance, supports the belt member 6a together with the driven roller 6c, and applies a running force in the transport direction to the belt member 6a, not shown. A drive source such as a motor is connected via a clutch. In other words, the drive roller 6b is driven to rotate by the drive source under the control of the image forming engine 9, thereby causing the belt member 6a to travel in the transport direction.
The driven roller 6c is a roller that rotates as the belt member 6a travels.

  The transfer roller 6d is disposed opposite to the photosensitive drum 1 so as to sandwich the belt member 6a. The transfer roller 6d includes a charger that supplies a predetermined charge to the belt member 6a, and a drive source such as a motor (not shown) is interposed via a clutch. It is connected. The transfer roller 6d is pressed against the photosensitive drum 1 while adsorbing the recording paper to the belt member 1a by supplying charge to the belt member 6a by a charger while being rotated by a drive source under the control of the image forming engine 9. The toner image formed on the peripheral surface of the photosensitive drum 1 is transferred to the recording paper.

  The optical sensor 7 is provided on the downstream side in the transport direction with respect to the photosensitive drum 1, and detects the density of the toner image formed on the belt member 6a. The optical sensor 7 irradiates light onto the belt member 6 a of the transfer conveyance belt 6, detects the reflected light amount of the light, and outputs a voltage value corresponding to the reflected light amount to the image forming engine 9 as a detection signal. The optical sensor 7 outputs a higher voltage value as the density of the toner image is higher, and outputs a lower voltage value as the density of the toner image is lower.

  The fixing roller 8 includes a heating roller having a heater therein and a pressure roller pressed against the heating roller, and heats the recording paper by sandwiching and conveying the recording paper on which the toner image is transferred by the two rollers. And pressurizing to fix the toner image on the recording paper. The recording paper on which the toner image is fixed by the fixing roller 8 is conveyed toward a paper discharge roller (not shown).

  The image forming engine 9 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an interface circuit for inputting / outputting signals to / from each of the above-described units. The overall operation of the printer A is controlled on the basis of the control program. The control program stored in the ROM includes a transfer control program. The image forming engine 9 determines the rotational speed of the photosensitive drum 1 and the traveling speed of the transfer conveyance belt 6 based on the transfer control program. Control. The details of the processing executed by the image forming engine 9 will be described as the operation of the printer A below.

Next, the operation of the printer A according to this embodiment having the above-described configuration will be described in detail with reference to FIGS.
In the printer A, the image forming engine 9 forms a toner image having a uniform density in the circumferential direction on the circumferential surface of the photosensitive drum 1 at a predetermined timing, rotates the photosensitive drum 1, and transfers and conveys the belt 6. The toner image is transferred onto the transfer / conveying belt 6 (step S1).

  That is, the image forming engine 9 charges the photosensitive drum 1 to the charging unit 2 at a predetermined timing, causes the laser scanning unit 3 to form an electrostatic latent image on the peripheral surface of the photosensitive drum 1, and the developing unit 4. By supplying toner toward the photosensitive drum 1, a toner image having a uniform density in the circumferential direction is formed on the peripheral surface of the photosensitive drum 1. Then, the image forming engine 9 rotates the photosensitive drum 1 and causes the transfer conveyance belt 6 to travel in the conveyance direction to transfer the toner image from the photosensitive drum 1 onto the belt member 6 a of the transfer conveyance belt 6. When the toner image on the photosensitive drum 1 is correctly transferred to the belt member 6a, a toner image having a uniform density in the running direction is formed on the belt member 6a. The predetermined timing is when the power is turned on or when a predetermined number of images are formed.

  Returning to FIG. 2, after step S <b> 1, the image forming engine 9 causes the optical sensor 7 to detect the density of the toner image on the belt member 6 a, and based on the detection signal input from the optical sensor 7, density unevenness is applied to the toner image. Whether or not has occurred is determined (step S2). That is, when the detection signal is input from the optical sensor 7, the image forming engine 9 determines whether or not the voltage value of the detection signal is outside the allowable range. The image forming engine 9 detects that the density unevenness occurs when the voltage value is outside the allowable range, and detects that the density unevenness does not occur when the voltage value is within the allowable range. To do.

  The voltage value of the detection signal indicates the toner density in the circumferential direction of the photosensitive drum 1 as shown in FIG. The image forming engine 9 determines whether the voltage value falls between the upper limit value and the lower limit value (see FIG. 3) of the reference allowable range, and when the voltage value is out of the allowable range even at one location. Determines that density unevenness has occurred. Naturally, as shown in FIG. 3, the image forming engine 9 determines that density unevenness has occurred when the voltage values at three locations exceed the upper limit value. In FIG. 3, the portion with a high voltage value is a portion with a high toner concentration, and the portion with a low voltage value is a portion with a low toner concentration.

  Returning to FIG. 2, if the image forming engine 9 determines “NO” in step S <b> 2, that is, if density unevenness has not occurred, it returns to step S <b> 1. If the image forming engine 9 determines “YES” in step S2, that is, if density unevenness occurs, the rotational speed of the photosensitive drum 1 or the transfer conveyance belt 6 prevents the density unevenness from occurring. Is corrected (step S3).

  That is, the image forming engine 9 corrects the rotational speed of the photosensitive drum 1 or the traveling speed of the transfer conveyance belt 6 so that the voltage value of the detection signal input from the optical sensor 7 does not fall outside the allowable range in step S3. By preventing the voltage value of the detection signal from being outside the allowable range, the surface speeds of the photosensitive drum 1 and the transfer conveyance belt 6 can be made constant.

  As described above, in this embodiment, the toner image formed on the photosensitive drum 1 with a uniform density in the circumferential direction is transferred onto the transfer conveyance belt 6, and the transfer conveyance belt is based on the detection result of the optical sensor 7. 6, the rotational speed of the photosensitive drum 1 or the running speed of the transfer conveyance belt 6 is corrected so that the density unevenness does not occur when it is detected that the density unevenness is generated in the toner image formed on the toner image 6. The cause of density unevenness and transfer deviation is the difference in surface speed between the photosensitive drum 1 and the transfer conveyance belt 6, and the fact that the surface speed between the photosensitive drum 1 and the transfer conveyance belt 6 differs by detecting the density unevenness. The rotational speed of the photosensitive drum 1 or the traveling speed of the transfer conveyance belt 6 is corrected so that density unevenness is not found, that is, the surface speed of the photosensitive drum 1 and the transfer conveyance belt 6 is corrected to be constant. To do. Thereby, generation | occurrence | production of transcription | transfer deviation can be suppressed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the toner image formed on the photosensitive drum 1 is transferred to the transfer conveyance belt 6, but the present invention is not limited to this.
For example, the toner image formed on the photosensitive drum 1 may be transferred to a recording sheet instead of the transfer conveyance belt 6 and density unevenness may be detected based on the toner image.

DESCRIPTION OF SYMBOLS A ... Printer, 1 ... Photosensitive drum (image carrier), 2 ... Charging part, 3 ... Laser scanning unit, 4 ... Development unit, 5 ... Cleaner, 6 ... Transfer conveyance belt, 7 ... Optical sensor (Density detection means) ), 8... Fixing roller, 9... Image forming engine (correction means)

Claims (2)

An image carrier comprising a cylindrical member and carrying a toner image formed on the circumferential surface while rotating in the circumferential direction, a toner image forming means for forming a toner image on the circumferential surface of the image carrier, and a recording sheet An image forming apparatus comprising: a transfer conveyance belt that conveys the toner image by pressing the recording paper against a circumferential surface of the image carrier;
Density detecting means for detecting the density of the toner image formed on the transfer conveyance belt;
A toner image having a uniform density in the circumferential direction is formed on the image carrier by the toner image forming unit, and the toner image on the image carrier is rotated by the image carrier and run on the transfer conveyance belt. Is transferred onto the transfer / conveying belt, and the toner image on the transfer / conveying belt is detected based on the detection result of the density detecting means so that the unevenness of density does not occur. An image forming apparatus comprising: a correction unit that corrects the rotation speed of the image carrier or the traveling speed of the transfer conveyance belt. The density detection means outputs a voltage value corresponding to the density of the toner image,
The image forming apparatus according to claim 1, wherein the correcting unit detects that density unevenness has occurred in a toner image when the voltage value is outside an allowable range.

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