JPH08211693A - Image forming device - Google Patents

Abstract

PURPOSE: To precisely detect the mark of an intermediate transfer belt though it is soiled by toner as for a color image forming device detecting the mark of the intermediate transfer belt and taking timing between a belt-like photoreceptor and the intermediate transfer belt. CONSTITUTION: The plural magnetic marks 26 are provided on the outside surface of the intermediate transfer belt 10 along in the circumferential direction thereof. Besides, the marks 26 are dividedly formed at equal intervals in a vertical direction with respect to the advancing direction of the belt. A mark detector 27 converting a signal from the marks 26 to an encoder signal and executing the feedback of the encoder signal to a rotation driving motor 25 is provided closely to the marks 26. By the motor 25, a rotation control action such as a PLL control action is executed by using the inputted encoder signal so as to compensate the fluctuation of the torque of a turning roller 2 or the fluctuation of frictional force and the like between the roller 2 and the belt 10.

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 such as a color copying machine, a color printer, a facsimile, etc. The present invention relates to an image forming apparatus that determines by detecting a mark.

[0002]

2. Description of the Related Art An example of a conventional color image forming apparatus is shown in FIG.
1, shown in FIG. This apparatus is a color laser printer, and reference numeral 1 in FIG. 11 is a flexible belt-shaped photosensitive member which is a belt-shaped image carrier, and the belt-shaped photosensitive member 1 is stretched between rotating rollers 2 and 3. Therefore, the rotation roller 2 is driven to rotate clockwise in the drawing. 4 in the figure
Is a charging member which is a charging means, 5 is a laser writing optical system unit which is an image exposing means, and 6 to 9 are a plurality of developing devices each containing a developer of a specific color. The charging member 4 and the photoconductor cleaning device 15 are provided in proximity to one roller 2 of the plurality of rollers that bridge the belt-shaped photoconductor 1.

The laser writing optical system unit 5 is incorporated in the main body of the apparatus by being housed in a holding case having a slit-shaped exposure opening on the upper surface. In addition to the illustrated optical system, the laser writing optical system unit 5 also uses an optical system in which a light emitting portion and a converging optical transmission body are integrated.

The developing units 6, 7, 8 and 9 respectively contain respective developing agents such as yellow, magenta, cyan, black, etc., and develop at a predetermined position in proximity to or in contact with the belt-shaped photoreceptor 1. Each has a sleeve and has a function of visualizing the latent image on the belt-shaped photoreceptor 1 by non-contact development or contact development.

Reference numeral 10 in the drawing denotes an intermediate transfer belt which is a transfer image carrier, and is stretched between rotating rollers 11 and 12, and is rotated counterclockwise in the drawing by driving the rotating roller 11. It is supposed to do. This intermediate transfer belt 10
Comes into contact with the belt-shaped photosensitive member 1 at the part of the rotating roller 3,
The bias roller 13 provided inside transfers the visible image on the belt-shaped photoreceptor 1. When forming a color image, as is well known, a visible image corresponding to each color image is repeatedly transferred onto the intermediate transfer belt 10 so as not to cause a positional deviation.

Further, in the figure, reference numeral 14 is a transfer roller, which is provided so as to come into contact with and separate from the intermediate transfer belt 10, and 16 is a cleaning device for the intermediate transfer belt 10, which is a blade 16A
Is kept at a position apart from the surface of the intermediate transfer belt 10 during image formation, and is brought into pressure contact with the surface of the intermediate transfer belt 10 as shown in the figure only during cleaning after image transfer.

A process of forming a color image, that is, a process of forming a multicolor image by the color image forming apparatus having such a structure will be described. First, using a separate image reading device, calculate the color image data obtained by scanning the original image with the image sensor to create image data, save it by storing it in the image memory, etc. and record it. Then, it is taken out and input to the color image forming apparatus of FIG. 11 which is a recording unit.

That is, when a color signal output from an image reading device separate from the printer is input to the laser writing optical system unit 5, it is generated by a semiconductor laser (not shown) in the laser writing optical system unit 5. The laser beam is rotationally scanned by the polygon mirror 5B which is rotationally driven by the drive motor 5A, the optical path is bent by the mirror through the f.theta. The peripheral surface of the body 1 is exposed to light to form an electrostatic latent image. The image pattern to be exposed is a monochromatic image pattern when a desired image, for example, a full-color image is separated into yellow, magenta, cyan, and black. Then, each formed electrostatic latent image is developed with a yellow, magenta, cyan, and black developing device by a rotary developing device and visualized to form a monochromatic image. The monochromatic image formed on the belt-shaped photoreceptor 1 is transferred onto the intermediate transfer belt 10 which rotates counterclockwise while contacting the belt-shaped photoreceptor 1. Then, the yellow, magenta, cyan, and black single-color images formed on the belt-shaped photoreceptor 1 are sequentially superposed on the surface of the intermediate transfer belt 10, and the paper feed table 17 is provided.
The image is transferred by the transfer roller 14 to the transfer sheet conveyed from the sheet to the transfer section through the sheet feeding roller 18 and the registration roller 19.
After the transfer is completed, the image is fixed on the transfer paper by the fixing device 20 to complete a full-color image.

FIG. 2 is an enlarged perspective view of the main part of the color image forming apparatus of FIG. As shown in the figure, in this apparatus, the rotary roller 2 is rotationally driven by the rotary drive motor 25, and the belt-shaped photoconductor 1 is driven by the rotary roller 2 to rotate at a constant speed. In addition, the rotary drive motor 25
A pulley 22 is coaxially arranged between the rotary roller 2 and the rotary roller 2, and the pulley 22 rotationally drives the timing belt 23.
A pair of gears 2 provided at one end of the timing belt 23
Drive 4 The gear 24 is connected to the rotary roller 11 via a rotary shaft to rotationally drive the rotary roller 11, and the rotary roller 11 rotates the intermediate transfer belt 10 at a constant speed.

As described above, it is necessary to superimpose and transfer a plurality of single color images on the intermediate transfer belt 10. However, the belt-shaped photosensitive member 1 and the intermediate transfer belt 10 are driven at the same speed by the same rotary drive motor 25. Even when the belt-shaped photoconductor 1 is rotated, the belt-shaped photoconductor 1 and the belt-shaped photoconductor 1 are affected by torque fluctuations generated in the rotary rollers 2 and 11 and frictional forces between the rotary rollers 2 and 11 and the belt-shaped photoconductor 1 and the intermediate transfer belt 10. The rotation speed of the intermediate transfer belt 10 may fluctuate, and this speed fluctuation causes color misregistration during transfer and distortion of a transferred image. Therefore, it is necessary to rotate the belt-shaped photoconductor 1 and the intermediate transfer belt with timing. Therefore, a mark 53 having a reflectance different from that of the intermediate transfer belt 10 is provided on the intermediate transfer belt 10, and the mark 53 is detected by an optical detection device to be used as a writing start signal to the intermediate transfer belt 10. There is. As a conventional image forming apparatus that uses an optical method for mark detection, for example, there is one disclosed in Japanese Patent Laid-Open No. 2-130567.

[0011]

However, when the optical mark detection as described above is used, there is a problem that accurate mark detection cannot be performed when the intermediate transfer belt 10 is soiled with toner or the like. Therefore, an object of the present invention is to provide an image forming apparatus capable of performing accurate detection regardless of toner stains on marks.

[0012]

In order to achieve the above object, an image forming apparatus according to the present invention reflects an exposure beam of a photosensitive member and an electrostatic latent image corresponding to a plurality of image forming signals on a rotating polygon mirror. And a latent image forming means for forming on the photoreceptor,
A plurality of developing units each having a developer carrying member that visualizes the latent image of the photoreceptor, an intermediate transfer body that transfers the developer image on the photoreceptor, and a fixing that fixes an unfixed developer after transfer. An image forming apparatus that includes a device and drives the photoconductor and the intermediate transfer member by the same drive motor to determine an image forming timing by detecting a mark on the intermediate transfer member. The mark to be provided is a magnetic body, and means for detecting the mark of the magnetic body is provided.

In the image forming apparatus according to the present invention, a plurality of marks are arranged on the intermediate transfer body at equal intervals, and a speed detecting means for detecting the moving speed of the intermediate transfer body based on the detection result of these marks. Can be provided.

In the image forming apparatus according to the present invention, the intermediate transfer member is provided with a magnetic recording portion made of a strip-shaped magnetic material, and the predetermined magnetic recording of the magnetic recording portion is used as the mark, and based on the detection result of the mark. It is also possible to adopt a structure including a speed detecting means for detecting the moving speed of the intermediate transfer member.

The image forming apparatus according to the present invention may be arranged such that the writing start position in the magnetic recording portion is the mark portion or the joint portion of the magnetic recording portion.

In the image forming apparatus according to the present invention, a pair of mark detecting devices for detecting the marks recorded in the magnetic recording portion are arranged so as to be displaced in the moving direction of the intermediate transfer member, and the mark detecting devices of the mark detecting devices are arranged. It is possible to adopt a configuration having means for controlling the speed of the intermediate transfer member or the photosensitive member based on the deviation time of the result.

In the image forming apparatus according to the present invention, the mark and the mark detecting device may be arranged on the side opposite to the surface for transferring the visible image.

The image forming apparatus according to the present invention comprises means for controlling the speed of the photosensitive member and the intermediate transfer member by feeding back the moving speed detected by the speed detecting means to the drive motor. You can also do it.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that, in the following, the portions common to the conventional ones will be denoted by the same reference numerals, and overlapping description will be omitted.

FIG. 1 shows a first embodiment of the present invention. As shown in the figure, the intermediate transfer belt 10 of this embodiment is provided with a plurality of magnetic material marks 26 along the circumferential direction on the outer surface thereof. The magnetic marks 26 are formed at equal intervals in a direction perpendicular to the belt traveling direction. Also, this magnetic mark 2
A magnetic material detector (hereinafter referred to as a mark detector) 27 is provided in the vicinity of 6. The mark detector 27 converts the signal from the magnetic mark 26 into an encoder signal and feeds the encoder signal back to the rotary drive motor 25.

The rotary drive motor 25 uses a phase-locked PLL (Phase Locked) by using the input encoder signal.
The rotation control such as Loop control is performed, but detecting the encoder mark on the intermediate transfer belt in this way is to detect the rotation (movement) speed of the intermediate transfer belt 10, and the detection of the intermediate transfer belt 10 is performed. When the rotation of the rotary drive motor 25 is drive-controlled based on the speed, the intermediate transfer belt 10 is compensated so as to compensate for torque fluctuations generated in the rotating roller 2 and fluctuations in frictional force between the rotating roller 2 and the intermediate transfer belt 10. Can be rotationally driven at a constant speed.

Although the drive control device for the rotary drive motor 25 is not specifically shown, it may have a circuit configuration as shown in FIG. 2, for example. FIG. 3 shows the signal states of the circuit of FIG. That is, the output signal voltage V1 from the mark detector 27
Is input to the comparator 37, and a predetermined threshold voltage VT is input in advance.
Is compared with the output signal voltage V1 from the mark detector 27, and the comparison result is the voltage V1.
2 is output, and this voltage V2 is fed back to the drive control means of the rotary drive motor 25 as an encoder signal to perform PLL control and the like.

When the voltage V2 is frequency / voltage converted by the frequency / voltage converter 38, the rotational speed of the intermediate transfer belt 10 can be obtained. Therefore, the detected speed is fed back to control the rotation of the rotary drive motor 25. You can also do it.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, a magnetic recording layer 39 is provided on the intermediate transfer belt 10,
The magnetic recording data recorded on the magnetic head 28
Is read out, and this signal is fed back to the rotary drive motor 25 for drive control. FIG. 5 shows a magnetic recording example 41 of the magnetic recording layer 39. 50 in FIG.
Is a magnetic recording portion, and 51 is a portion without magnetic recording. Such a magnetic recording layer 39 can be realized by attaching a magnetic tape to the intermediate transfer belt 10. For example, as shown in FIG. 6, when a recording signal is displaced like a seam portion 42 of the magnetic recording layer 39, This portion 42 can be used as a write start signal. Further, a portion where the magnetic recording portion is wider than the other portion is provided, and the signal portion 52 corresponding thereto may be used as the write start signal as shown in FIG. If the mark using magnetism is used as described above, even if the intermediate transfer belt 10 is contaminated with toner, it is not affected.

FIG. 8 shows a third embodiment of the present invention. In this embodiment, the mark detection device (magnetic head 28) is arranged inside the intermediate transfer belt 10, that is, on the side opposite to the transfer surface of the visible image. By arranging in this way, it becomes easy to secure the place of arrangement.

FIG. 9 shows a fourth embodiment of the present invention. In this embodiment, a magnetic mark 55 perpendicular to the rotation (movement) direction is provided on the intermediate transfer belt 10, and the pair of magnetic heads 2 is provided.
8, 8 and 29 are arranged so as to be displaced in the traveling direction of the intermediate transfer belt 10. FIG. 10 is an enlarged plan view of the mark detection device portion. Although only one magnetic mark 55 is shown in the drawing, a plurality of magnetic marks 55 are provided at equal intervals. With this arrangement, the moving speed of the intermediate transfer belt 10 can be obtained by detecting the rising portion of the same magnetic mark 55 and obtaining the deviation time of the detection at this time. Further, the moving speed of the intermediate transfer belt 10 can be accurately obtained even if the interval between the magnetic marks 55 or the mark width is slightly deviated. Further, when used in combination with each of the embodiments described above, even if there is a signal shift due to the seam portion of the magnetic recording layer 39, this can be compensated.

In the embodiment described above, the mark detection is performed and the detection result is fed back to the rotary drive motor driving the intermediate transfer belt. However, the laser writing timing is controlled by the detection result. Therefore, it is also possible to provide a device that compensates for color shift.

[0028]

As described above, in the image forming apparatus according to the first aspect of the present invention, the mark to be attached to the intermediate transfer member is the mark of the magnetic material, so that the accurate mark detection can be performed regardless of the dirt of the mark. There is an effect that.

The image forming apparatus according to the second aspect of the invention detects the moving speed of the intermediate transfer member based on the detection result of the marks arranged at equal intervals on the intermediate transfer member.
In addition to the common effects described above, there is an effect that it becomes possible to compensate for transfer deviation and transfer image distortion.

In the image forming apparatus according to the third aspect of the present invention, the predetermined magnetic recording of the magnetic recording portion formed of the belt-shaped magnetic body provided on the intermediate transfer member is used as a mark, and the moving speed of the intermediate transfer member is determined based on the detection result. Since the detection is performed, in addition to the common effects described above, there is an effect that it becomes possible to compensate the transfer deviation and the transfer image distortion.

In the image forming apparatus according to the fourth aspect, the writing start position to the magnetic recording portion is set to the mark portion or the joint portion of the magnetic recording portion. Therefore, in addition to the common effect, the writing start control is performed. The speed control can be performed by the same magnetic recording unit, and the write start control device and the speed control device can be simplified.

In the image forming apparatus according to a fifth aspect of the present invention, a pair of mark detecting devices for detecting marks recorded in the magnetic recording portion are arranged so as to be displaced in the moving direction of the intermediate transfer member, and based on the deviation time of the mark detection result. Since the speed of the intermediate transfer member or the photoconductor is controlled, the effect of the seam portion of the magnetic recording portion can be compensated for in addition to the common effect described above.

In the image forming apparatus according to the sixth aspect of the present invention, the mark and the mark detecting device are arranged on the side opposite to the surface on which the visible image is transferred. Therefore, in addition to the common effects described above, it is easy to secure a place for disposing the mark detecting device. Has the effect of becoming.

In the image forming apparatus according to the seventh aspect of the invention, the moving speed detected by the speed detecting means is fed back to the drive motor to control the speed of the photosensitive member and the intermediate transfer member. In addition, it is easy to drive the photoconductor and the intermediate transfer member at a constant speed, and it is possible to eliminate transfer deviation and transfer image distortion.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing an example of an electric circuit configuration of the mark detector of FIG.

FIG. 3 is a diagram showing signal states of the circuit of FIG.

FIG. 4 is a perspective view showing a second embodiment of the present invention.

5 is a diagram showing an example of magnetic recording on a magnetic recording layer of the apparatus of FIG.

6 is a diagram showing an example of magnetic recording on a magnetic recording layer of the device of FIG. 4 having a seam portion.

FIG. 7 is a diagram showing an example in which a write start signal is set in a magnetic recording layer of the device of FIG. 4 in which a magnetic recording portion is wider than other portions.

FIG. 8 is a perspective view showing a third embodiment of the present invention.

FIG. 9 is a perspective view showing a fourth embodiment of the present invention.

10 is an enlarged plan view of a mark detection device portion of the device of FIG.

FIG. 11 is a cross-sectional view showing an example of a color printer as a conventional image forming apparatus.

12 is an enlarged perspective view of a main part of the color printer of FIG.

[Explanation of symbols]

 1 Photoconductor Belt 2, 3 Rotating Roller 4 Charging Roller 5 Laser Writing Optical System Unit 5A Drive Motor 5B Polygon Mirror 5C fθ Lens 6 to 9 Developing Unit 10 Intermediate Transfer Belt 11, 12 Rotating Roller 13 Bias Roller 14 Transfer Roller 15 , 16 Cleaning device 16A Cleaning blade 17 Paper feed table 18 Paper feed roller 19A Upper registration roller 20 Fixing device 22 Pulley 23 Timing belt 24 Gear 25 Rotational drive motor 26 Magnetic mark 27 Mark detector 28, 29 Magnetic head 37 Comparator 38 Frequency / Voltage converter 39, 40 Magnetic recording layer 41 Magnetic recording signal example 42 Magnetic recording layer seam portion 50 Magnetic recording portion 51 No magnetic recording portion 52 Writing start mark 53 Mark 54 Optical mark detection device 55 Magnetic Mark V1 Mark detector output signal V2 Comparator output voltage VT Threshold voltage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Sasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Yutaka Shio 10-3 Kitamura, Tottori, Tottori Prefecture Ricoh Micro Electronics Co., Ltd. In the company

Claims (7)

[Claims] 1. A photoconductor, latent image forming means for forming an electrostatic latent image corresponding to a plurality of image forming signals on the photoconductor by reflecting an exposure beam on a rotary polygon mirror, and a latent image forming means for the photoconductor. A plurality of developing units each having a developer carrying member that visualizes an image, an intermediate transfer member that transfers the visible image on the photoconductor, and a fixing device that fixes the unfixed developer after transfer, In an image forming apparatus in which the photosensitive member and the intermediate transfer member are driven by the same drive motor and the image forming timing is determined by detecting the mark on the intermediate transfer member, the mark provided on the intermediate transfer member is made of a magnetic material. And an image forming apparatus comprising means for detecting the mark of the magnetic material. 2. The image forming apparatus according to claim 1, wherein a plurality of the marks are arranged on the intermediate transfer body at equal intervals, and a moving speed of the intermediate transfer body is detected based on a detection result of the marks. An image forming apparatus comprising a detecting unit. 3. The image forming apparatus according to claim 1, wherein the intermediate transfer member is provided with a magnetic recording portion made of a belt-shaped magnetic material,
An image forming apparatus, characterized in that a predetermined magnetic recording of the magnetic recording section is used as the mark, and a speed detecting means for detecting a moving speed of the intermediate transfer member based on a detection result of the mark is provided. 4. The image forming apparatus according to claim 3, wherein a write start position to the magnetic recording portion is the mark portion or a joint portion of the magnetic recording portion. 5. The image forming apparatus according to claim 3, wherein a pair of mark detecting devices for detecting marks recorded on the magnetic recording portion are arranged so as to be displaced in a moving direction of the intermediate transfer member, and these mark detecting devices are detected. A color image forming apparatus comprising means for controlling the speed of the intermediate transfer member or the photosensitive member based on the deviation time of the mark detection result of the device. 6. The image forming apparatus according to claim 3, wherein the mark and the mark detecting device are arranged on the side opposite to the transfer surface of the visible image. 7. The image forming apparatus according to claim 1, further comprising means for performing speed control of the photosensitive member and the intermediate transfer member by feeding back the moving speed detected by the speed detecting means to the drive motor. A color image forming apparatus characterized by the above.