JPH11316476A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the image quality of an image formed on a recording medium by highly accurately executing the calibration of a device. SOLUTION: A paper P, fed from a paper feeding tray 40 to a feeding path 42, is fed to a density detection position after the image for the calibration of the device is formed by an image forming unit 2. The density of the image for the calibration of the device on the paper P is detected at the density detection position by a detecting unit 3. The image forming unit 2 is controlled by a control part, so that a recording image having desired density is formed on the paper P based on the density of the image for the calibration of the device detected. The fluttering of the paper P is suppressed by a paper guiding part 5 arranged at the density detection position, so that the density of the image for the calibration of the device on the paper P is detected accurately by the detecting unit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a recording medium, such as an electrophotographic or ink-jet type printer or a copying machine, and more particularly to an image forming apparatus having a function of calibrating an image forming process. Related to the device.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus has been calibrated to improve the image quality of an image formed on a sheet. In particular, in an electrophotographic image forming apparatus in which an image is formed through an image forming process including a plurality of steps such as charging, exposure, development, and transfer, an image finally formed on a sheet is formed for each step. Various controls are performed to enhance the image quality.

An example of such an image forming apparatus is disclosed in Japanese Patent Application Laid-Open No. 4-55868. The image forming apparatus includes: an image forming unit that forms a test pattern on a sheet in a test mode and forms a recording image on a sheet in a normal mode; and a test pattern detection unit that detects reflected light from the test pattern on the sheet. A paper transport mechanism for transporting the paper to the image forming unit and the test pattern detecting unit, and a control unit for calibrating the image forming unit so that the difference between the level of the reflected light detected by the test pattern detecting unit and the reference value is reduced. Is provided. According to this device, since the image forming unit is calibrated based on the test pattern, the image quality can be kept constant even if the device changes over time. In addition, although the transport of the paper is not described in the above publication, usually, a plurality of transport rollers are arranged in the paper transport path at intervals shorter than the length in the transport direction of the paper, and the plurality of transport rollers are synchronized. The sheet is driven to convey the sheet to the image forming unit and the test pattern detecting unit.

[0004]

However, according to the conventional image forming apparatus, even if a plurality of transport rollers are driven synchronously, the peripheral speed of the transport rollers is reduced due to a difference in roller diameter or a play in the drive system. When reading the reflected light from the test pattern, the distance between the paper and the test pattern detection unit and the inclination of the paper fluctuate. There is a problem that the amount of light incident on the light receiving unit of the pattern detection unit fluctuates, and a reading error occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of calibrating the apparatus with high accuracy and improving the image quality of an image formed on a recording medium.

[0006]

In order to achieve the above object, the present invention conveys a recording medium along a predetermined conveyance path,
In an image forming apparatus that forms an image on the recording medium, an image forming unit that forms a calibration image or a recording image on the recording medium, and fluttering based on conveyance of the recording medium on which the calibration image is formed. Suppressing means for suppressing, detecting means for detecting the density of the calibration image on the recording medium in a state where fluttering of the recording medium is suppressed by the suppressing means, and detecting the density of the image for calibration detected by the detecting means. A control unit for controlling image forming conditions of the image forming unit based on a density to set a density of the recorded image to a desired density.

[0007]

FIG. 1 shows an electrophotographic image forming apparatus according to a first embodiment of the present invention. In the image forming apparatus 1, an image for device calibration or an image to be output to a user (hereinafter, referred to as a “recorded image”) is charged, exposed, developed, and transferred to a sheet P at an image forming position according to a mode.
An image forming unit 2 formed through a predetermined image forming process of transfer and fixing, a detecting unit 3 provided at a density detecting position and detecting the density of an apparatus calibration image formed on the sheet P by the image forming unit 2; And a paper transport mechanism 4 for transporting the paper P to the image forming unit 2, the detection unit 3, and the like.

The image forming unit 2 includes an image carrier 20 on which an electrostatic latent image is formed, a charging unit 21 for uniformly charging the surface of the image carrier 20, and an image on the charged image carrier 20. Exposure unit 22 that forms an electrostatic latent image on image carrier 20 by performing exposure based on a signal, developing unit 23 that develops the electrostatic latent image with toner, and transfers the developed toner image onto paper P And a fixing unit 2 for fixing the toner image on the paper P
5 is provided.

The paper transport mechanism 4 discharges a paper tray 40 for supplying paper P before image formation, paper P on which an apparatus calibration image is formed, and paper P on which a recording image is formed. And a discharge tray 41. The paper feed tray 40 includes a paper feed roller 40a that feeds the paper P one by one from the paper feed tray 40 by driving a paper feed motor (not shown).
A transport path 42 from the paper feed tray 40 to the paper output tray 41
Are formed, and a plurality of transport rollers 43 for transporting the paper P by driving a paper transport motor (not shown) are provided in each part of the transport path 42.

Further, the apparatus 1 is provided with a paper guide section 5 for suppressing fluttering of the paper P at a density detection position of the transport path 42.

FIGS. 2A to 2C show the detection unit 3 and the paper guide unit 5. FIG.

As shown in FIG. 2B, the detection unit 3 is disposed behind the fixing unit 25 on the transport path 42 in the process direction, and emits light at an angle of 45 degrees with respect to the surface of the sheet P. The light source 30 to be irradiated is arranged at an angle of 90 degrees with respect to the surface of the paper P, and the light diffusely reflected on the surface of the paper P is input through the condenser lens 31 and the input light is photoelectrically converted. A photodiode 32 that outputs the detection signal as an electric signal.

As shown in FIGS. 2 (a) and 2 (b), the paper guides 5 are opposed to each other with a gap G slightly larger than the maximum thickness of the target paper P, and are substantially the same as the width of the paper P. A lower guide member 50 and an upper guide member 51 having widths of? The side of the lower guide member 50 and the upper guide member 51 on which the paper P enters is a slope 5 facing outward.
0a and 51a. The light source 30 of the detection unit 3 is provided on the upper guide member 51 immediately below the detection unit 3.
An opening 51b for passing incident light from the device and reflected light from the device calibration image is provided. Inclined surfaces 50a, 51
By providing a, the paper P can smoothly enter the gap G between the guide members 50 and 51. As shown in FIG. 2C, the lower guide member 50 has
A slit-like concave portion 50b whose bottom surface is used as the calibration surface 50c of the detection unit 3 is formed along the paper transport direction 7. By forming the concave portion 50b, contact between the paper P and the calibration surface 50c can be prevented, and contamination of the calibration surface 50c due to contact with the paper P can be prevented. In addition, since paper dust and dust are discharged from the concave portion 50b due to the movement of air accompanying the paper conveyance, it is possible to prevent a problem that paper dust and dust are accumulated in the concave portion 50b. In addition, a separate blowing mechanism is provided,
The paper dust and dust in b may be blown off. The color of the calibration surface 50c may be determined according to the calibration algorithm of the detection unit 3. For example, black or white is used. Here, white is used. The calibration surface 50
The color of c is Y (yellow), M (magenta), C (cyan), K (black), R in the case of a color image forming apparatus.
(Red), G (blue), or B (green).

FIG. 3 shows an example of a device calibration image. As shown in the figure, the device calibration image has a plurality of density patterns 6a, 6b, and 6c having different densities formed along the paper transport direction 7 so as to pass through a density detection position immediately below the detection unit 3. . Further, the density patterns 6a, 6b, 6c
Are formed to have concentrations of 0.30, 0.80, and 1.55, respectively.

FIG. 4 shows a control system of the apparatus 1. The device 1 has a control unit 10 for controlling the entire device 1. The control unit 10 includes a program memory 11 for storing a program of the control unit 10 and a device calibration device for forming a device calibration image. An image memory 12 that stores an image signal, a recorded image signal for forming a recorded image, and the like; and an image processing unit 1 that performs predetermined processing on the image signal from the image memory 12
3, the image forming unit 2, the detection unit 3, and the paper transport mechanism 4 are connected.

The control unit 10 executes the device calibration mode and the normal mode according to the program stored in the program memory 11. In the device calibration mode, the control unit 10 controls the detection unit 3 based on the detection signal from the detection unit 3. In addition to the calibration, the image forming conditions, that is, the image processing unit 13, the charging unit 2 of the image forming unit 2,
1, exposure unit 22, developing unit 23, transfer unit 24, fixing unit 25
The operation of each part or part of is controlled.

Next, the operation of the apparatus 1 according to the first embodiment having the above configuration will be described. (1) Device calibration mode When the operator turns on the power of the device 1, the control unit 10
Executes the device calibration mode according to the program stored in the program memory 11 as described below. First, the controller 10 drives a paper feed motor and a paper transport motor (not shown) of the paper transport mechanism 4 to feed the paper P from the paper feed tray 40 and supplies the paper P to the transport path 42. Transport path 4
2 is transported to the image forming position by the rotation of the transport roller 43 driven by the paper transport motor. At the same time, the control unit 10 reads out the device calibration image signal from the image memory 12, performs predetermined processing on the device calibration image signal by the image processing unit 13, and based on the processed device calibration image signal. Image forming unit 2
Control. The image forming unit 2 forms an image for device calibration on the paper P. That is, the exposure unit 22 of the image forming unit 2 forms an electrostatic latent image on the image carrier 20 that is uniformly charged by the charging unit 21 based on the device calibration image signal. The developing unit 23 develops the electrostatic latent image with toner, and the transfer unit 24 prints the developed toner image on paper P
The image is transferred to the upper side, and the fixing unit 25 fixes the toner image on the sheet P. In this way, a device calibration image composed of a plurality of density patterns 6a, 6b, 6c as shown in FIG. The paper P on which the device calibration image is formed passes through the density detection position while the flutter is suppressed by the paper guide unit 5. When the sheet P passes through the density detection position, the detection unit 3 detects the density of the calibration surface 50c of the lower guide member 50 as shown in FIG. Output and then Figure 2
As shown in (b), the density of the density patterns 6a, 6b, 6c is detected and output to the control unit 10 as a detection signal. The paper P in which the density of the device calibration image has been detected is discharged to the paper discharge tray 41.

Next, the control unit 10 calibrates the detection unit 3 based on a detection signal output from the detection unit 3 and indicating the density of the calibration surface 50c. Also, the calibration surface 50c
The output voltage of the detection unit 3 when the density is detected is V ₀ , and the output voltages of the detection unit 3 when the density patterns 6a, 6b and 6c are read are V ₁ , V ₂ and V ₃ , respectively.
In this case, the control unit 10 determines that V ₁ / V ₀ , V ₂ /
Each of the image processing unit 13, the charging unit 21, the exposure unit 22, the developing unit 23, the transfer unit 24, and the fixing unit 25 of the image forming unit 2 or the fixing unit 25 is set such that V ₀ and V ₃ / V ₀ have predetermined values. Controls some actions.

(2) Normal Mode When the apparatus calibration mode ends and the operator performs settings necessary for printing, the control unit 10 executes the normal mode according to the program stored in the program memory 11. In the normal mode, the control unit 10 reads a recording image signal from the image memory 12 and controls each unit of the image forming unit 2 based on the recording image signal.
At the same time, the paper P is conveyed from the paper feed tray 40 to the image forming position, where a recording image is formed by the image forming unit 2. The paper P on which the recording image has been formed is discharged to the paper discharge cassette 41.

According to the apparatus 1 according to the first embodiment described above, since the paper guide section 5 for suppressing the fluttering of the paper P is provided at the density detection position, the density of the apparatus calibration image can be accurately determined. Can be detected. As a result, the calibration of the apparatus can be performed with high accuracy, and the image quality can be improved. Further, since the concave portion 50b is formed in a slit shape, it is possible to prevent a trouble that paper dust and dust accumulate.

FIG. 5 shows an image forming apparatus according to a second embodiment of the present invention. This apparatus 1 does not include the paper guide unit 5 as in the first embodiment, and has an interval L shorter than the length of the paper P in the transport direction 7 before and after the density detection position.
And a front conveyance roller 43A and a rear conveyance roller 43B whose peripheral speeds can be independently controlled. By controlling the control unit 10 to make the peripheral speed of the rear transport roller 43B faster than that of the front transport roller 43A and to apply tension to the paper P, fluttering of the paper P is suppressed. To increase the peripheral speed of the rear transport roller 43B,
The rotation speed of the roller may be increased, and the diameter of the roller may be increased.

According to the second embodiment, the paper P is tensioned at the density detection position to suppress the fluttering of the paper P, so that the apparatus is similar to the first embodiment. The density of the calibration image can be detected with high accuracy. As a result, the calibration of the apparatus can be performed with high accuracy, and the image quality can be improved. Further, since the paper guide section 5 becomes unnecessary, the configuration can be simplified.

The present invention is not limited to the above-described embodiment, but can be variously modified. For example, in the first embodiment, the guide members 50 and 51 are provided vertically above and below the conveyance path 42 at the density detection position.
Only 0 may be used. By providing the lower guide member 50, the paper P is pressed against the lower guide member 50 by gravity, so that the fluttering of the paper P is reduced. As a result,
The paper P is larger than when the guide members 50 and 51 are provided on the upper and lower sides.
Although the fluttering slightly increases, a remarkable effect on the fluttering of the paper P is observed as compared with the case where the guide members 50 and 51 are not provided.

[0024]

As described above, according to the image forming apparatus of the present invention, the density of the calibration image is detected while the fluttering of the recording medium is suppressed, and the image forming conditions are controlled based on the detection result. Therefore, the calibration of the apparatus can be performed with high accuracy, and the image quality of the image formed on the recording medium can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2A is a plan view, FIG. 2B is a cross-sectional view, and FIG.
Is a sectional view.

FIG. 3 is a diagram showing an apparatus calibration image according to the first embodiment.

FIG. 4 is a block diagram illustrating a control system of the image forming apparatus according to the first embodiment.

FIG. 5 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming unit 3 Detecting unit 4 Paper transport mechanism 5 Paper guide part 6a, 6b, 6c Density pattern 7 Paper transport direction 10 Control part 11 Program memory 12 Image memory 13 Image processing part 20 Image carrier 21 Charging part Reference Signs List 22 Exposure unit 23 Developing unit 24 Transfer unit 25 Fixing unit 30 Light source 31 Condensing lens 32 Photodiode 40 Paper feed tray 40a Paper feed roller 41 Paper discharge tray 42 Transport path 43 Transport roller 43A Front transport roller 43B Rear transport roller 50 Below Side guide members 50a, 51a Inclined surface 50b Recess 50c Calibration surface 51 Upper guide member 51b Opening G Gap L Interval P Paper

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisao Ito 430 Nakai-cho, Nakai-machi, Ashigarakami-gun, Kanagawa Prefecture Inside Green Tech Nakai Fuji Xerox Co., Ltd.

Claims (8)

[Claims] 1. A recording medium is transported along a predetermined transport path,
In the image forming apparatus for forming an image on the recording medium, image forming means for forming a calibration image or a recording image on the recording medium, and fluttering based on conveyance of the recording medium on which the calibration image is formed. Suppressing means, suppressing means, detecting means for detecting the density of the calibration image on the recording medium in a state where fluttering of the recording medium is suppressed by the suppressing means, of the calibration image detected by the detecting means An image forming apparatus comprising: a controller configured to control image forming conditions of the image forming unit based on a density to set a density of the recorded image to a desired density. 2. The image forming apparatus according to claim 1, wherein said suppressing means is a guide member having a contact surface provided along said transport path so as to contact said recording medium. 3. An image forming apparatus according to claim 2, wherein said guide member has a pair of said contact surfaces at positions facing each other via said conveyance path. 4. The image forming apparatus according to claim 2, wherein said guide member has a calibration surface for calibrating said detection means. 5. The image forming apparatus according to claim 4, wherein said guide member has a concave portion having a bottom surface as said calibration surface. 6. The image forming apparatus according to claim 5, wherein said concave portion has a slit shape along a conveying direction of said recording medium. 7. The image forming apparatus according to claim 6, wherein said suppressing means is provided with an air blowing mechanism for blowing air to said slit-shaped concave portion and removing paper dust, dust and the like accumulated in said concave portion. 8. The image forming apparatus according to claim 1, wherein said suppressing means includes a front conveying roller provided at an interval shorter than a length of the recording medium in a conveying direction at a position before and after a position where the density of the calibration image is detected on the conveying path. 2. The apparatus according to claim 1, further comprising: a side conveyance roller; and a driving unit configured to rotationally drive the peripheral side of the rear side conveyance roller to be faster than the front side conveyance roller to apply a predetermined tension to the recording medium. Image forming device.