JPH07271265A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of surely detecting resist mark particularly even if the color of the resist mark is the same kind of color as that of carrier member and forming the image less in positional deviation and excellent in quality. CONSTITUTION:A mark detection means 5 for the registration correcting device equipped in the image forming device is constituted of a lighting means 50 for projecting light from the direction oblique to the aerial surface of the carrier member on which a resist mark 6 is transferred, a scanning optical detector 51 for discriminating and receiving the light beam reflected from the carrier member or the resist mark by the projecting light in accordance with the arriving position, a measuring means 52 for measuring the time required from the reference signal position to the specified voltage for every scanning output signal, a voltage transforming means 53 for successively outputting the voltage corresponding to the respective time required, and an arithmetic means 54 for calculating the positional information of the resist mark based on the voltage information of the area exceeding the specified voltage in the voltage information.

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 capable of forming a high quality image with very little positional (color) deviation.

[0002]

2. Description of the Related Art In general, a multi-transfer type image forming apparatus has a plurality of image forming units for forming an image corresponding to image information on an image carrier such as a photosensitive drum, and each of the image forming units. The image forming apparatus is provided with a transfer / conveying unit that sequentially transfers and conveys the image formed on the image carrier onto one recording sheet. For example, each image forming unit forms an image for each color and A color image can be formed by sequentially transferring and superimposing images.

In this type of image forming apparatus, factors such as a speed error of each drum, a speed error of a transfer / conveyance unit, and an image writing timing error, as well as a factor such as a change in initial setting condition due to an external force or environmental change. As a result, there is a peculiar problem that the transfer forming positions of the images of the respective colors do not exactly coincide with each other, and a slight color shift occurs in the obtained color image.
Therefore, in order to solve the problem of the color misregistration, a so-called registration device (hereinafter, also abbreviated as a registration control device) that accurately corrects and controls the image forming position to the original position according to the misregistration caused by various factors Is equipped with.

By the way, in the conventional registration control device, a registration mark (positioning mark) is formed by each image forming unit mainly on a belt-shaped transfer conveyance member of the transfer conveyance unit, and the registration mark is optically detected by an image sensor or the like. The position information of the mark is detected by the detector, the position deviation amount is calculated by the signal processing means on the basis of the position information, and the image forming position in each image forming portion is corrected by the correction means according to the position deviation amount. The color misregistration is suppressed by correcting However, in an image forming apparatus equipped with such a registration control device, the color of the transfer / conveying member is generally black or orange due to the material or the like thereof, and therefore black, yellow, magenta, or similar colors are used in particular. When detecting the registration mark (including the same color), there is a problem that it is extremely difficult to detect the light amount difference and the color difference. As a result, the image forming position may not be properly corrected based on the mark detection information, and color misregistration may not be sufficiently suppressed. Such a problem is that the color of the intermediate transfer member is generally black or pink even when the transfer member of the transfer / transport unit is configured as an intermediate transfer member.
Since it was orange, it occurred similarly.

Therefore, in order to solve the above-mentioned problems, that is, in order to easily identify the registration mark from the mark forming region of the transfer / transport member,
An image forming apparatus has been proposed in which a portion corresponding to the mark forming area is achromatic in white or a transparent member is used as the transfer / conveying member (Japanese Patent Laid-Open No. 63-300259). Gazettes such as Sho 63-300262). However, the above-mentioned solution means has a problem that the transport member is restricted because at least a part corresponding to the mark forming area has to be configured differently, and there is room for improvement. Was to leave.

[0006]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to reliably detect a registration mark without being influenced by the conditions of the conveyance member, particularly even when the registration mark has the same color as the conveyance member. It is therefore an object of the present invention to provide an image forming apparatus capable of forming a high-quality image that is capable of forming a high-quality image with very little misalignment.

[0007]

In order to achieve the above object, an image forming apparatus of the present invention has an image carrier on which an image is formed according to image information, and a rotation of the image carrier. A conveying member that transfers and conveys an image on the carrier while moving, a mark detecting unit that detects a registration mark transferred and formed on the conveying member and outputs position information of the mark, and the position of the registration mark. An image forming apparatus including a signal processing unit that outputs positional deviation information based on information and a registration correcting apparatus that includes a correcting unit that corrects an image forming position based on the positional deviation information. The means emits light obliquely to the area surface of the conveying member on which the registration mark is transferred and the illumination light of the illumination means. A scanning photodetector that discriminates and receives reflected light from a conveying member or a registration mark according to its arrival position, and an output signal for each scan obtained by the scanning photodetector from a reference signal position to a predetermined voltage Measuring means for measuring the required time until reaching, voltage conversion means for outputting a voltage according to each required time obtained by the measuring means over time, and predetermined voltage information obtained by the voltage converting means It is characterized in that it is configured by an arithmetic means for calculating the position information of the registration mark based on the voltage information in the range exceeding the voltage.

[0008]

According to the present invention, the detection (identification) of the registration mark transferred and formed on the conveying member is performed by the difference in the arrival position of each reflected light from the conveying member or the registration mark to the photodetector.
That is, since the change in the arrival position of the reflected light according to the difference in the height of the reflecting surface is used, the mark detection is performed even when the reflected light or the transmitted light is transmitted even when the registration mark has the same color as the conveying member. Unlike the conventional technique that is performed based on the difference in the light amount of light, the mark can be reliably detected.
Incidentally, conventionally, if the registration mark has the same color as that of the conveying member, it is difficult to detect the mark because it is difficult to obtain the difference in light amount. Therefore, according to the device of the present invention including the registration control device that performs such mark detection, it is possible to form a high-quality image with very little positional deviation.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an image forming apparatus according to an embodiment of the present invention. 1a, 1 in the figure
Reference numerals b, 1c, and 1d denote photosensitive drums as image bearing members arranged side by side. Similarly, around the photosensitive drums 1a to 1d, a charging device 10, an image exposure device 11, and a toner developing device 1 are similarly provided.
2, a transfer charger 13, and a cleaning device 14 are sequentially arranged. Then, yellow, magenta, cyan, and black single-color toner images are formed on the surfaces of the respective photosensitive drums 1a to 1d by electrophotography.

Reference numeral 2 denotes a sheet conveying belt as a conveying member. The sheet conveying belt 2 is stretched around a driving roll 20 and a driven roll 21 and rotates in synchronization with the rotation of the photosensitive drums 1a to 1d, and at the same time, the recording sheet 3 is attracted to the surface of the belt by a charger. It is configured to be electrostatically attracted by 22 and to be passed through a transfer position where the photoconductor drums 1a to 1d and the transfer charger 13 face each other. In addition, the static eliminator 23 and the cleaning device 2 are provided at predetermined positions on the paper transport belt 2.
4 etc. are arranged.

Reference numeral 4 denotes a registration device. The registration control device 4 is displaced based on the mark detection means 5 arranged in proximity to the sheet conveying belt 2 and the position information of the registration mark obtained by the mark detection means 5. The signal processing unit 40 that outputs information and the correction unit 41 that corrects the image forming position based on the positional deviation information obtained by the signal processing unit 40 constitute the main part.

As for the registration mark 6 used in the registration control device 4, as shown in FIGS. 1 and 2, a mark image signal of a predetermined pattern is sent from the mark formation instructing means 42 to each of the image exposure devices 11a to 11d. , Each photosensitive drum 1a-
The mark toner image formed on d is appropriately transferred to a predetermined area of the sheet conveying belt 2 to be formed.

The mark detecting means 5 is, as shown in FIG. 3, an illuminating means 50, a scanning type photodetector 51 and a measuring means 5.
2. The voltage converting means 53 and the calculating means 54 form the main part. In the figure, reference numeral 55 is a control device for collectively controlling the operation timing and the like in each of the above-mentioned constituent means. In this embodiment, one mark detecting means 5 is provided at one end of the conveyor belt 2, but one mark detecting means 5 may be provided at each end of the belt. It is selected appropriately.

The illuminating means 50 includes a light source such as an LED (light emitting diode) and an LD (laser diode). The light from the light source is shaped and condensed by an optical system such as a lens (not shown), and the light is registered. Irradiation is performed obliquely to the area surface of the transport belt 2 on which the marks are formed. It is preferable that the irradiation light is condensed and irradiated by an optical system so that the irradiation light has a spot shape narrower than the size of the registration mark, and thus, the mark detection with higher accuracy becomes possible. Further, the irradiation angle is appropriately set within the range of the angle at which the reflected light can be extracted efficiently.

The scanning type photodetector 51 is an image pickup device or the like capable of identifying the arrival position of the reflected light from the conveyor belt 2 or the registration mark 6 on the conveyor belt by the irradiation light of the illuminating means 50. In the embodiment, a CCD line sensor 51a having a desired number of pixels is used. This CCD
The line sensor 51a is installed at a position and an orientation that can accurately receive various reflected lights obtained from the conveyor belt 2 or the registration mark 6 by the irradiation light of the illuminating means 50. In this embodiment, the light receiving surface is a conveyor belt. It is installed so that it is parallel to the two surfaces and the pixel line is along the moving direction of the conveyor belt 2 (see FIGS. 1 and 2).

The measuring means 52 measures the time required for the output signal for each scan obtained from the scanning photodetector 51 to reach a predetermined voltage from the reference signal position (see FIG. 6). Here, "each scan" means that the results of light reception (scanning) by one pixel line in the CCD line sensor 51a of the scanning photodetector 51 are sequentially extracted. Further, the reference signal is a pulse signal of a constant frequency for extracting the light reception result for one line of pixels in the CCD line sensor 51a in synchronism with it, and is appropriate according to the required resolution, sensor sensitivity, etc. It is set to a different frequency. Further, the predetermined voltage is a threshold voltage that is appropriately set in order to accurately extract only the light reception result of the reflected light from the conveyor belt or the registration mark while eliminating noise components and the like from the output signal.

The voltage converting means 53 outputs the voltage corresponding to each required time obtained by the measuring means 52 with time (see FIG. 7). Here, to output with time means to convert the required time data sent from the measuring means 52 into a predetermined voltage value at any time and output it. The value of the voltage corresponding to each required time is set arbitrarily.

The calculation means 54 calculates the position information of the registration mark based on the voltage information (portion) exceeding the predetermined voltage in the voltage information (voltage output waveform) obtained by the voltage conversion means 53 (FIG. 7). Here, the predetermined voltage means that a portion having a higher voltage value in the voltage output waveform as the voltage information corresponds to the registration mark, and therefore the high voltage portion is appropriately extracted to eliminate noise components and the like. It is the set threshold voltage.

As a method of calculating the position information of the registration mark based on the voltage information exceeding the predetermined voltage, the following method is adopted in this embodiment, but the method is not particularly limited to this. That is, the first and last times of the part (range) of the voltage output waveform that exceeds the predetermined voltage are measured, and calculations such as simple averaging of both times are performed and the average value is used as the mark detection position (representative value). ) As
The mark detection position data is multiplied by the process speed of the conveyor belt or the like, and the result is used as the position information of the registration mark.

The position information (signal) of the registration mark thus obtained is sent to the signal processing means 40. The signal processing means 40 compares the position information of the registration mark with a predetermined preset value according to a known method,
The difference is sent to the correction means 41 as positional deviation information. The correction unit 41 converts the positional deviation information into a correction amount according to a known method, and corrects the image forming position based on the correction amount. The correction of the image forming position is performed by, for example, moving the image exposure device, changing the image writing timing, changing the driving speed of the photosensitive drum, changing the feeding speed of the conveying belt, or the like.

The registration mark is formed at a time when normal image formation is not performed (for example, before formation of a normal image or in the middle of image formation), and after use, it is erased by a cleaning device or the like. . Further, the registration marks are transferred or formed on the conveyor belt sequentially or simultaneously by the photosensitive drums 1a to 1d. Further, the pattern of the registration mark is set appropriately and is not particularly limited.

Next, the operation of the image recording apparatus of this embodiment having such a configuration will be specifically described.

First, image formation by this image recording apparatus is performed as follows. That is, four color toner images of yellow, magenta, cyan, and black are individually formed on the respective photosensitive drums 1a to 1d, while
The recording sheet 3 is fed and conveyed by the sheet conveying belt 2 in synchronization with this image forming process. Then, on the recording paper 3, the photoconductor drums 1a to 1d and the transfer chargers 13a to 13d.
The single color images are sequentially transferred and superposed on each other at the transfer portion facing d, thereby forming a full color image.

The sheet conveying belt 2 of this embodiment is a black belt made of a polycarbonate base material having a thickness of 150 μm, and is stretched around the driving roll 20 and the driven roll 21 with a tension of about 5 kgf.

On the other hand, the registration by the registration control device 4 is performed as follows. First, the paper transport belt 2
A resist mark 6 is formed on top. That is, when the mark image signal is sent from the mark formation instructing means 42 to the image exposure devices 11a to 11d, the mark toner images based on the signal information are respectively formed on the photoconductor drums 1a to 1d by the image exposure devices 11a to 11d. , The photosensitive drum 1 (a
By activating d) to d) at a predetermined timing,
For example, as shown in FIG. 2, the registration mark 6 is formed of a line pattern having a line width of several 100 μm, which is parallel to the direction of the rotation axis of the photosensitive drum and is continuously arranged at equal intervals in the rotation direction of the photosensitive drum. Is transferred and formed on the end area of the paper transport belt 2.

Next, mark detection is performed by the mark detection means 5. That is, the registration mark 6 is sequentially moved right below the mark detecting means 5 by the rotation of the sheet conveying belt 2, and the irradiation light from the illuminating means 50 (spot diameter: about 5).
0 μm, irradiation angle: 30 ~ from the direction perpendicular to the conveyor belt surface
The reflected light from the conveyor belt 2 or the registration mark 6 at that time is discriminated and received by the scanning photodetector 51 according to its arrival position.

Here, the light emitted by the illumination means 50 is emitted.
Arrival of reflected light that reaches the scanning photodetector 51 (light receiving surface)
The principle of different (incident) positions will be described. That is,
As shown in FIG. 4, the irradiation light s from the illumination means 50 is
If there is no gist mark 6, the surface 2a of the conveyor belt 2
Reflected light at point A₁And the registration mark 6
If there is a mark, it is reflected at point B on the mark surface 6a and is reflected.
Light r ₂Therefore, the reflected light r₁, R₂Is a scanning type
Reach different light receiving surfaces (pixel parts) of the photodetector 51
To do. That is, the reflected light r₁Is the reference of the scanning photodetector 51
It is incident on the pixel portion (n) points away from the position 51b,
Reflected light r₂Is (n + m) points away from the reference position 51b.
Incident on the broken pixel portion. Also, the registration mark 6
If the height of the surface is different, for example, from the surface 6a
When there is a high surface portion 6b, the irradiation light s is
Reflected light r reflected at point C of b₃And the height of its reflective surface
Reach a predetermined position of the scanning photodetector 51 corresponding to
It That is, the reflected light r₃Is from the reference position 51b to (n + m +
l) It is incident on a pixel that is apart by a point.

As described above, the position where the reflected light reaches the scanning type photodetector 51 changes depending on the height of the surface on which the irradiation light s is reflected. As a result, even if the registration mark is of the same color as the conveyor belt (black registration mark in this example), the reflected light of the mark reaches a photodetector position different from the reflected light on the surface of the conveyor belt. The mark can be reliably identified and detected. If the conveyor belt 2 is light-transmissive, the irradiation light s from the illumination means 50 will pass through the belt 2 as it is, as indicated by the dotted line in FIG. There is no reflected light, only the reflected light from the resist mark.

In the present embodiment, in order to prevent the vertical movement of the conveyor belt 2 at the time of detecting the mark, as shown in FIG. A motion preventing roll support member 43 is provided. As a result, it is possible to prevent the occurrence of mark detection errors due to the vertical movement of the belt.

The detection data of the registration mark thus detected is then sent to the measuring means 52. The operation of the measuring means 52 will be described with reference to FIG. 6 based on the case of detecting the registration mark 6 having the surface portions 6a, 6b, 6c having different heights as shown in FIG.

FIG. 6 shows the respective output signals obtained as the scans 1 to 5 of the scanning photodetector 51 corresponding to the detection time points (t = t _{1 to} t ₅ ) shown in FIGS. FIG. That is, the output signal of the scan 1 is that immediately before the detection of the mark 6 (t = t ₁ ) as shown in FIG.
The output signal of the scan 2 is when the surface 6a of the mark 6 is detected (t = t ₂ ) as shown in FIG. 7B, and the output signal of the scan 3 is as shown in FIG. When detected (t
= T ₃ ), the output signal of the scan 4 is the one when the surface 6c of the mark 6 is detected (t = t ₄ ) as shown in FIG. 7D, and the output signal of the scan 5 is shown in FIG. Immediately after the detection of the mark 6 (t = t ₄ ). The alternate long and short dash line in FIG. 6 indicates the reference voltage set to the voltage v ₀ .

That is, in the measuring means 52, as shown in FIG. 6, the time required for the voltage signal for each scan to reach the reference voltage v ₀ from the position of the reference signal (vertical axis portion in the drawing) ( Δt) is measured respectively.

Next, the required time (Δt) data obtained by the measuring means 52 is temporally converted into a predetermined voltage by the voltage converting means 53, and a signal waveform as voltage information as shown in FIG. 7 is obtained. can get. Although the required times Δt _{1 to} Δt ₅ shown in FIG. 6 are entered in FIG. 7,
This is for convenience, and therefore the signal waveforms in FIG. 7 do not correspond to the contents shown in FIG.

Next, the voltage information obtained by the voltage converting means 53 is sent to the calculating means 54, and by the calculating means 54,
As shown in FIG. 7, the times T ₁ and T _{2 at} which the reference voltage v ₁ is reached are measured, and after a simple average of both times T ₁ and T ₂ is obtained to obtain the average value as the mark detection position, The mark detection position data is multiplied by the process speed of the conveyor belt or the like, and the result is output to the signal processing means 40 as the position information of the registration mark.

Finally, the positional deviation information obtained from the signal processing means 40 based on the positional information of the registration mark is sent to the correcting means 41, and the correcting means 41 corrects the image forming position according to the positional deviation information. To be done. After this correction is completed, the registration mark 6 is erased by the cleaning device 24.

By performing such alignment,
As described above, the image formation can be satisfactorily performed without causing the positional deviation.

In the above-described embodiment, the sheet conveying belt is exemplified as the conveying member 2, but the present invention has the same operation even when the conveying member is configured as the intermediate transfer member 2a as shown in FIG. The effect is obtained. When the conveying member is the intermediate transfer body 2a, the recording sheets that pass between the backup roll 25 and the intermediate transfer body 2a after all the images from the respective photosensitive drums 1a to 1d are once transferred onto the intermediate transfer body 2a. 3 is transferred at once.

Further, although the full-color image forming apparatus is exemplified in the above embodiment, the present invention may be a single-color image forming apparatus. Further, the image forming method on the image bearing member is not limited to the electrophotographic method, and in the present invention, any method can be applied as long as it is a method using a conveying member, for example, inkjet, thermal transfer, etc. It may be a recording method.

[0039]

As described above, according to the present invention,
Regardless of the conditions of the transport member, the mark detection can be reliably performed even when the registration mark has the same color as the transport member, and thus the registration mark detection information is reliable and stable. Is required, it becomes possible to form a high-quality image with very little misalignment.

[Brief description of drawings]

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

FIG. 2 is a perspective view of a main part showing a configuration around a mark detection unit.

FIG. 3 is an explanatory diagram showing a configuration of mark detection means.

FIG. 4 is an explanatory diagram showing the principle of detection by a mark detecting means.

FIG. 5 is an explanatory diagram showing a mark detection state.

FIG. 6 is an output signal waveform diagram from the scanning photodetector for explaining the function of the measuring unit.

FIG. 7 is a voltage waveform diagram from the voltage converting means for explaining the function of the calculating means.

FIG. 8 is a schematic configuration diagram showing an image forming apparatus according to another embodiment of the present invention.

[Description of Reference Signs] 1a to d ... Photosensitive drum, 2 ... Paper transport belt, 2a ...
Intermediate transfer member, 4 ... Registration device, 5 ... Mark detecting means, 6 ... Registration mark, 40 ... Signal processing means,
41 ... Correction means, 50 ... Illumination means, 51 ... Scanning photodetector, 52 ... Measuring means, 53 ... Voltage conversion means, 54 ... Arithmetic means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Sakamaki 2274 Hongo, Ebina, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Satoshi Usui 2274, Hongo Ebina, Kanagawa Prefecture, Fuji Xerox Co., Ltd. 72) Inventor Kibun Sato 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Takeshi Noguchi 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Minoru Kasama Kanagawa Prefecture Fuji Xerox Co., Ltd., 2274 Hongo, Ebina City (72) Inventor Kiichiro Iijima 2274 Hongo, Ebina, Ebina City, Kanagawa

Claims (1)

[Claims] 1. An image carrier on which an image is formed according to image information, a carrier member for transferring and carrying an image on the carrier while moving in synchronization with the rotation of the image carrier, and the carrier. Mark detection means for detecting a registration mark transferred and formed on a member and outputting position information of the mark, signal processing means for outputting positional deviation information based on the positional information of the registration mark, and image based on the positional deviation information In an image forming apparatus provided with a registration correction device including correction means for correcting the formation position, the mark detection means in the registration correction device is oblique to the area surface of the conveyance member on which the registration mark is transferred and formed. The illuminating means for irradiating the light from the illuminating means and the reflected light from the conveying member or the registration mark by the illuminating light of the illuminating means are identified according to the arrival position. A scanning photodetector that receives light, a measuring unit that measures the time required for the output signal for each scan obtained by the scanning photodetector to reach a predetermined voltage from the reference signal position, and the measuring unit Position information of the registration mark is calculated based on voltage conversion means for outputting a voltage according to each required time obtained with time and voltage information of a range exceeding a predetermined voltage among voltage information obtained by the voltage conversion means. An image forming apparatus comprising: