JP2001215857A - Image forming apparatus, transfer material transport control method, transfer device and belt device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus enabling suppression of the misregistration of an image on a transfer paper even when the perimeter of an intermediate transfer belt changes, and to provide a transfer material transport control method in the device and a transfer device. SOLUTION: Transportation conditions of a copying paper to a secondary transfer position are changed according to the perimeter change of an intermediate transfer belt 11. For example, a mark 71 provided on the intermediate transfer belt 11 is detected twice by a mark sensor 70, and then the variation of the perimeter of the intermediate transfer belt 11 is determined from the time interval of the mark detection signal. The delivery start time Ts of the copying paper 100 by the delivery transportation roper (a paper feeding roller 51, resist roller 52) is changed according to the variation of the perimeter of the intermediate transfer belt 11. An electromagnetic clutch 55 for transmitting rotary driving force to the delivery transportation roller is turned on at the timing when the delivery start time Ts has passed since the time point when the second mark has been detected.

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 copying machine, a printer, a facsimile, etc., a transfer material transfer control method in the apparatus, and a transfer apparatus and a belt apparatus applicable to the apparatus. An image is formed on the surface of an image carrier such as an endless photoreceptor belt and an intermediate transfer belt, and the transfer material is transported to a transfer position facing the image carrier,
The present invention relates to an image forming apparatus for transferring an image on the image carrier to the transfer material, a transfer material transport control method in the device, and a transfer device and a belt device applicable to the device.

[0002]

2. Description of the Related Art As an image forming apparatus of this type, an image formed on a photosensitive member is primarily transferred onto an intermediate transfer member as an endless belt-shaped image carrier so as to be superposed a plurality of times. There is known a color image forming apparatus for secondary transfer of a superimposed image onto a transfer material. In this apparatus, a transfer material is sent out at a preset timing by a transfer material transporting unit configured using a registration roller, and is transported toward a secondary transfer position facing the intermediate transfer body. By sending and transferring the transfer material in this manner, the image can be transferred to the transfer material by aligning the tip of the image on the intermediate transfer member with the tip of the transfer material.

[0003]

In an image forming apparatus using an intermediate transfer member like the above-mentioned conventional apparatus, the transfer start timing of the transfer material is adjusted so that the leading end of the image on the intermediate transfer member and the leading end of the transfer material are aligned. In addition, the transport speed and the like when the transfer material is transported toward the secondary transfer position are set. However,
The circumferential length of the intermediate transfer body may change due to environmental fluctuations such as the temperature in the apparatus and changes over time in the material properties of the intermediate transfer body. When the circumferential length of the intermediate transfer member changes in this way, the distance from the image leading end position to the secondary transfer position on the surface of the intermediate transfer member when the transfer material is started to be changed changes from a preset reference distance. . Due to this change, the alignment between the leading end of the image and the leading end of the transfer material becomes insufficient, and the image transferred to the transfer material deviates from a predetermined position, and the leading edge and the trailing edge of the transfer paper have "white spots" or "edges". Dirt "
There was a problem that occurs. For example, if the leading edge of the transfer paper reaches the secondary transfer position before the leading edge of the image on the surface of the intermediate transfer member, "white spots" may occur in the image transfer scheduled portion at the leading end of the transfer material, or the intermediate transfer member When the upper image comes into contact with the rear end of the transfer material, there is a possibility that “stain on the edge surface” may occur at the rear end. Conversely, when the leading end of the image on the surface of the intermediate transfer member reaches the secondary transfer position before the leading end of the transfer paper, "white spots" may occur in the image transfer scheduled portion at the rear end of the transfer material. When the image on the intermediate transfer member comes into contact with the leading end of the transfer material, there is a possibility that "edge contamination" may occur at the leading end. Further, due to a positional shift between the leading end of the image on the intermediate transfer body and the leading end of the transfer material, the toner constituting the image on the intermediate transfer body adheres to the transfer roller without passing through the transfer material, or the fixing roller There was also a problem that it adhered to the surface.

[0004] In particular, when a belt member made of a material such as resin or rubber is used as the intermediate transfer member, the material easily expands over time due to a creep phenomenon and greatly expands and contracts due to environmental fluctuations. The amount of the “white spots” tends to increase, and the “dirt on the edge side” tends to be severe. Also, the degree of toner adhesion to the transfer roller and the like tends to be severe.

When a thick paper mode using a thick paper as the transfer material or a magnification mode is selected, the primary transfer from the photosensitive member to the intermediate transfer member is completed while the intermediate transfer member is moved at a normal speed. After that, the transfer speed of the intermediate transfer body and the transfer material may need to be reduced to perform the secondary transfer in some cases. For example, when the thick paper mode or the magnification mode is selected, prior to the secondary transfer, by switching the moving speed of the intermediate transfer body and the transfer material to reduce the speed of the thick paper passing through the fixing device, the heat capacity is higher than that of the normal paper. Sufficient heat is applied to the large cardboard to ensure that the image on the cardboard is fixed. When the moving speed of the intermediate transfer member and the transfer material is reduced prior to the secondary transfer after the completion of the primary transfer, the leading end of the image on the intermediate transfer member is moved upstream from the secondary transfer position in the intermediate transfer member moving direction. Side, the image on the intermediate transfer body cannot be secondarily transferred immediately after passing through a position that is as far back as the distance Lc between the secondary transfer position and the transfer paper sending position. It is necessary to further rotate the intermediate transfer member idly by one turn. Further, after the moving speed of the intermediate transfer member is decreased, the intermediate transfer member may be idlely rotated one or more times in order to stabilize the moving speed of the intermediate transfer member.

Further, in a color image forming apparatus for forming a color image, there is a case where color discrimination is performed based on an image signal read by an image reading section (scanner) and automatic color setting for selecting a mode corresponding to the color determination is performed. In the case of performing the automatic color setting, it is determined whether the document is a monochrome document or a color document after the scanning of the document is completed. If this determination is made, the leading end of the image of the first color on the intermediate transfer member is located upstream of the secondary transfer position in the intermediate transfer member moving direction by the distance Lc between the secondary transfer position and the transfer sheet sending position. If the intermediate transfer member has passed through the position, the image on the intermediate transfer member cannot be immediately transferred to the secondary transfer member, and the intermediate transfer member must be further idled one turn.

In a mode in which the idling operation of the intermediate transfer member is likely to enter, such as the cardboard mode, the magnification mode, and the mode for executing the automatic color setting, the idling is performed after idling from the reference time for the secondary transfer. During the period before the actual start of the secondary transfer, an error due to a shift of one circumference of the intermediate transfer body (a change in circumference due to expansion) is further added, and the image shift is more likely to occur than in the normal mode. .

The problem that the displacement of the image transferred from the image carrier to the transfer material due to the change in the circumference of the image carrier occurs only when the image carrier is a belt-shaped intermediate transfer body. However, it can also occur in the case of a drum-shaped intermediate transfer member. Further, even when the image bearing member is a belt-shaped photosensitive member or a belt-shaped photosensitive member, and the image is directly transferred from the image bearing member to a transfer material, the same can occur.

The present invention has been made in view of the above problems, and a first object of the present invention is to suppress displacement of an image on a transfer material even when the circumference of an image carrier changes. An object of the present invention is to provide an image forming apparatus, a transfer material transport control method and a transfer apparatus in the image forming apparatus.
Further, a second object of the present invention is to provide an image forming apparatus as described above, wherein the amount of change in the circumference of the belt member can be obtained more accurately than in the case of indirectly obtaining the result from the detection result of the environmental temperature. It is an object of the present invention to provide a belt device suitable for the above.

[0010]

According to a first aspect of the present invention, there is provided an image carrier having a surface capable of endlessly moving, and an image carrier having a surface endlessly movable. Image carrier driving means for driving the image carrier, image forming means for forming an image on the surface of the image carrier, and a transfer material for transferring an image on the image carrier at a transfer position facing the image carrier. A transfer material transferring means for transferring the transfer material to a transfer position, and a transfer material transferring means for transferring the transfer material at a preset timing and transferring the transfer material to the transfer position. The transfer condition of the transfer material in the transfer material transfer means is changed according to the condition.

In this image forming apparatus, an image is formed on the surface of the image carrier by the image forming means, and the image on the image carrier is transferred to the transfer position by the transfer material transferring means by the transfer material transferring means. Transfer to a transfer material. Prior to the transfer to the transfer material, the transfer condition of the transfer material in the transfer material transfer means is changed according to the change in the circumference of the surface of the image carrier. Even when the circumference of the image carrier changes due to a change in environmental temperature or a change in material characteristics of the image carrier due to the change in the transport conditions, the transfer is performed in accordance with the leading edge of the image on the image carrier. The transfer material can be transported to the position.

The image carrier includes an endless belt-shaped intermediate transfer member and a latent image carrier (photoconductor), a drum-shaped intermediate transfer member and a latent image carrier (photoconductor), and the like. Examples of the transfer material transport conditions to be changed include the transfer material delivery timing in the transfer material transport unit, the transport speed and the transport path length when the transfer material is delivered and transported to the transfer position.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a mark for position detection is provided on the image carrier, and mark detecting means for detecting a mark on the image carrier; Transfer material transport control means for controlling the transfer material transport means so as to change the transfer material transport conditions based on a detection time interval of a plurality of detection signals detected at least twice by the detection means. It is assumed that.

In this image forming apparatus, the mark on the image carrier is detected at least twice by the mark detecting means.
Based on the detection time intervals of the plurality of detection signals, the amount of change in the circumference of the image carrier can be directly obtained under the condition that the moving speed of the image carrier is constant. Therefore, according to the change in the circumference of the image carrier, the transfer material transporting means can be controlled by the transfer material transport control means, and the transfer condition of the transfer material can be changed.

According to a third aspect of the present invention, there is provided a latent image carrier, a latent image forming means for forming a latent image on the latent image carrier, and developing the latent image on the latent image carrier to form an image. Developing means, an intermediate transfer body as the image carrier having a mark for position detection, an intermediate transfer means for transferring an image on the latent image carrier to the intermediate transfer body, 2. The image forming apparatus according to claim 1, further comprising: mark detection means for detecting a mark; and latent image formation control means for controlling a start timing of forming a latent image on the latent image carrier based on a detection result of the mark detection means. A transfer material transport control means for controlling the transfer material transport means so as to change the transfer material transport conditions based on detection time intervals of a plurality of detection signals detected at least twice by the mark detection means; Is provided.

In this image forming apparatus, the mark detecting means detects the position detecting mark on the intermediate transfer member as the image carrier. Based on the detection result of the mark, the latent image forming means starts to form a latent image on the latent image carrier. The latent image on the latent image carrier is developed by a developing unit and transferred to a predetermined position on the intermediate transfer body by an intermediate transfer unit. The image on the intermediate transfer body is transferred by the transfer material transfer means onto the transfer material transported to the transfer position by the transfer material transport means. Here, before the transfer to the transfer material, the mark on the intermediate transfer body is detected at least twice by the mark detection means. As one of the plurality of mark detections, the mark detection for the latent image formation start timing can be used. Then, based on the detection time intervals of the plurality of detection signals, the amount of change in the circumference of the intermediate transfer body can be directly obtained under the condition that the moving speed of the intermediate transfer body is constant. . Therefore, according to the change in the circumference of the intermediate transfer body, the transfer material transporting means can be controlled by the transfer material transport control means, and the transfer condition of the transfer material can be changed.

According to a fourth aspect of the present invention, after the mark on the image carrier is detected to transfer the image formed on the image carrier to the transfer material, the tip of the image on the image carrier is changed. The image carrier is driven idle so as to pass through the transfer position at least once, and then the image on the image carrier is transferred when the tip of the image on the image carrier reaches the transfer position. The image forming apparatus according to claim 2, wherein the image is transferred to a material.
Prior to the start of the transfer of the transfer material, the transfer condition of the transfer material is changed based on a detection time interval of a plurality of detection signals detected at least twice by the mark detection unit.

In this image forming apparatus, after the mark detection on the image carrier and the idle driving, when the leading end of the image on the image carrier reaches the transfer position, the image on the image carrier is removed. Transferred to transfer material. Here, before the transfer material is started to be sent out by the transfer / conveying means, the mark on the image carrier is detected at least twice by the mark detecting means. As one of the plurality of mark detections, the mark detection immediately before the idle driving can be used. Then, based on the detection time intervals of the plurality of detection signals, the amount of change in the circumference of the image carrier can be directly obtained under the condition that the moving speed of the image carrier is constant. . Therefore, according to the change in the circumference of the image carrier, the transfer material transporting means can be controlled by the transfer material transport control means, and the transfer condition of the transfer material can be changed.

According to a fifth aspect of the present invention, in the image forming apparatus of the second, third or fourth aspect, a plurality of the marks are provided at predetermined intervals in a circumferential direction of the image carrier.

In this image forming apparatus, by detecting a plurality of marks provided at predetermined intervals in the circumferential direction of the image carrier, a shorter moving distance of the surface of the image carrier as compared with the case where only one mark is provided. Thus, the amount of change in the circumference of the image carrier can be obtained.

According to a sixth aspect of the present invention, in the image forming apparatus according to the second, third or fourth aspect, the image carrier is an endless belt member supported by a plurality of support rollers including a tension roller. The detecting means is provided at a plurality of positions in the circumferential direction of the image carrier, which sandwich the tension roller.

In this image forming apparatus, the mark on the image carrier is detected by mark detecting means provided at a plurality of positions sandwiching the tension roller in the circumferential direction of the image carrier. By detecting the mark on the image carrier at a plurality of positions, even if there is only one mark on the image carrier, the change amount of the circumferential length of the image carrier at a shorter moving distance of the surface of the image carrier. Can be requested.

According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, the image carrier is an endless belt member supported by a plurality of support rollers including a tension roller. Tension roller movement amount detection means for detecting the movement amount, and transfer material conveyance control means for controlling the transfer material conveyance means to change the transfer material conveyance conditions based on the detection result of the tension roller movement amount detection means Are provided.

In this image forming apparatus, prior to the transfer to the transfer material, the amount of movement of the tension roller that moves in accordance with the expansion and contraction of the belt member as the image carrier is detected by the tension roller movement amount detecting means. Detect.
From this detection result, the amount of change in the circumference of the image carrier can be obtained. Therefore, according to the change in the circumference of the image carrier, the transfer material transporting means can be controlled by the transfer material transport control means, and the transfer condition of the transfer material can be changed.

According to an eighth aspect of the present invention, in the image forming apparatus of the first aspect, an environmental temperature detecting means for detecting an environmental temperature;
And a transfer material transfer control means for controlling the transfer material transfer means so as to change the transfer material transfer conditions based on the detection result of the environmental temperature detection means.

In this image forming apparatus, prior to the transfer to the transfer material, the environmental temperature detecting means detects the environmental temperature which is one of the factors of expansion and contraction of the belt member as the image carrier. From this detection result, the amount of change in the circumference of the image carrier can be obtained. Therefore, according to the change in the circumference of the image carrier, the transfer material transporting means can be controlled by the transfer material transport control means, and the transfer condition of the transfer material can be changed.

According to a ninth aspect of the present invention, there is provided a delivery conveyance roller for sandwiching the transfer material and sending and carrying the transfer material at a predetermined timing, and a rotation driving means for rotating the delivery conveyance roller. Claim 8 constituted by using
Wherein the rotation speed of the delivery conveyance roller is changed together with the rotation start timing of the delivery conveyance roller based on the detection result of the environmental temperature detection means.

In this image forming apparatus, the rotation start timing of the delivery conveyance roller, that is, the transfer start timing of the transfer material, is determined in accordance with a change in the circumference of the image carrier based on the detection result of the environmental temperature detection means. change. Further, based on the detection result of the environmental temperature detecting means, the rotation speed of the delivery conveyance roller is changed in accordance with a change in the diameter of the delivery conveyance roller, and the delivery conveyance speed of the transfer material is maintained constant.

The invention according to claim 10 is the invention according to claims 1, 2, 3,
In the image forming apparatus of any one of 4, 5, 6, 7, 8 and 9, the transfer condition changed by the transfer material transfer control means is a start timing of sending the transfer material to the transfer position. is there.

In this image forming apparatus, the transfer start timing of the transfer material, which is easier to control than when the length of the transport path from the transfer material transfer position to the transfer position is changed, is changed.

According to the eleventh aspect of the present invention, there is provided a transfer material transfer apparatus for controlling transfer material transfer conditions when a transfer material is sent out and transferred at a preset timing to a transfer position facing an image carrier whose surface moves endlessly. In the control method, the transfer condition of the transfer material may be changed in accordance with a change in the circumference of the surface of the image carrier.

In this transfer material transport control method, prior to the transfer of the image on the image carrier to the transfer material, the transport condition of the transfer material is changed according to a change in the circumferential length of the surface of the image carrier. change. Even when the circumference of the image carrier changes due to a change in environmental temperature or a change in material characteristics of the image carrier due to the change in the transport conditions, the transfer is performed in accordance with the leading edge of the image on the image carrier. The transfer material can be transported to the position.

According to a twelfth aspect of the present invention, in the transfer material transport control method of the eleventh aspect, the position detection mark provided on the image carrier is detected at least twice, and a plurality of detection signals obtained by the detection are detected. The transfer condition of the transfer material is changed based on the detection time interval.

In this transfer material transport control method, the condition that the moving speed of the image carrier is constant is determined based on the detection time intervals of a plurality of detection signals that detect the mark on the image carrier at least twice. First, the amount of change in the circumference of the image carrier is determined. Then, the transfer condition of the transfer material is changed according to the change in the circumference of the image carrier.

According to a thirteenth aspect of the present invention, the image carrier is an intermediate transfer member onto which an image formed on the latent image carrier formed by forming a latent image and developing the latent image is transferred. A transfer material transport control method, wherein a mark for position detection provided on the intermediate transfer body is detected at least twice, and based on a detection time interval of a plurality of detection signals obtained by the detection, the transfer material is detected. It is characterized in that the transfer conditions are changed.

In this transfer material transport control method, the condition that the moving speed of the intermediate transfer member is constant is determined based on the detection time intervals of a plurality of detection signals for detecting the mark on the intermediate transfer member at least twice. First, the amount of change in the circumference of the intermediate transfer body is determined. Then, the transfer condition of the transfer material is changed according to the change of the circumference of the intermediate transfer body.

According to a fourteenth aspect of the present invention, in the transfer material transport control method according to the eleventh, twelfth or thirteenth aspect, the transport condition to be changed is a timing to start sending the transfer material to the transfer position. Things.

In this transfer material transfer control method, the transfer material transfer start timing, which is easier to control than when the length of the transfer path from the transfer material transfer position to the transfer position is changed, is changed.

According to a fifteenth aspect of the present invention, there is provided a transfer material transferring means for transferring an image formed on the surface of an image carrier to a transfer material at a transfer position facing the image carrier having a surface that moves endlessly, A transfer material transporting means for delivering the material at a preset timing and transporting the material to the transfer position, wherein the transfer in the transfer material transporting means is performed in accordance with a change in the circumferential length of the surface of the image carrier. It is characterized in that the material transfer conditions are changed.

In this transfer device, prior to the transfer of the image on the image carrier to the transfer material, the transfer condition of the transfer material in the transfer material transport means is changed according to the change in the circumferential length of the surface of the image carrier. To change. Even if the circumference of the image carrier changes due to a change in the environmental temperature or a change in the material characteristics of the image carrier due to the change in the transport condition, the transfer position is adjusted to the leading end of the image on the image carrier. The transfer material can be conveyed to the printer.

According to a sixteenth aspect of the present invention, in the transfer device of the fifteenth aspect, a mark for position detection is provided on the image carrier, a mark detecting means for detecting a mark on the image carrier, and the mark detecting means. Transfer material transport control means for controlling the transfer material transport means so as to change the transfer material transport condition based on a detection time interval of a plurality of detection signals detected at least twice by the means. Is what you do.

In this transfer apparatus, the mark on the image carrier is detected at least twice by the mark detecting means. Based on the detection time intervals of the plurality of detection signals, the amount of change in the circumference of the image carrier can be obtained under the condition that the moving speed of the image carrier is constant. Therefore, according to the change in the circumference of the image carrier, the transfer material transporting means can be controlled by the transfer material transport control means, and the transfer condition of the transfer material can be changed.

The invention of claim 17 is the invention of claim 15 or 16
In the above transfer apparatus, the transfer condition changed by the transfer material transfer control means is a timing to start sending the transfer material to the transfer position.

In this transfer device, the transfer start timing of the transfer material, which is easier to control than when the length of the transport path from the transfer position of the transfer material to the transfer position is changed, is changed.

According to another aspect of the present invention, there is provided a belt having an endless belt member supported by a plurality of support rollers, and a belt driving means for driving the belt member. In the apparatus, a mark for position detection is provided on the belt member, and mark detection means for detecting a mark on the belt member is provided based on a detection time interval of a plurality of detection signals detected at least twice by the mark detection means. And calculating means for calculating the amount of change in the circumference of the belt member.

In this belt device, the mark on the endless belt member supported by the plurality of support rollers is detected at least twice by the mark detecting means. Based on the detection time intervals of the plurality of detection signals, the amount of change in the circumference of the belt member can be calculated and obtained by the calculation means.

A nineteenth aspect of the present invention is the belt device of the eighteenth aspect, wherein a plurality of the marks are provided at predetermined intervals in a circumferential direction of the belt member.

In this belt device, by detecting a plurality of marks provided at predetermined intervals in the circumferential direction of the belt member, the belt member can be moved at a shorter moving distance on the surface of the belt member than in the case of one mark. The amount of change in the circumference of the belt member can be obtained.

According to a twentieth aspect of the present invention, in the belt device according to the eighteenth aspect, one of the plurality of support rollers for supporting the belt member is a tension roller, and the mark detecting means is connected to the tension member in a circumferential direction of the belt member. It is characterized by being provided at a plurality of positions sandwiching the roller.

In this belt device, marks on the belt member are detected by mark detecting means provided at a plurality of positions sandwiching the tension roller in the circumferential direction of the belt member. By detecting the mark on the belt member at a plurality of positions, even if there is only one mark on the belt member, the amount of change in the circumferential length of the belt member can be obtained with a shorter moving distance on the surface of the belt member. Can be.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter, referred to as a copying machine) as an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. The copying machine includes a color image reading device (hereinafter, referred to as a scanner unit) and a color image recording device (hereinafter, referred to as a printer unit).

First, the configuration and operation of a scanner unit (not shown) in the above copying machine will be described. In this scanner unit, an image of a document placed on a contact glass is formed on a color sensor via an illumination / mirror optical system such as an illumination lamp, a mirror group and a lens, and color image information of the document is obtained. For example, it is read out for each color separation light of Blue (hereinafter, referred to as B), Green (the same, G), and Red (the same, R), and is converted into an electric image signal. The color sensor includes B, G, and R color separation means and a photoelectric conversion element such as a CCD, and can simultaneously read three colors. B, G, R obtained by this scanner unit
Each image signal is subjected to color conversion processing by the image processing unit based on the intensity level. By this color conversion processing,
Black (hereinafter, described as Bk), Cyan (the same,
C), Magenta (same, M), Yellow (same,
Y) color image data is obtained. Specifically, the illumination / mirror optical system scans a document upon receiving a start signal interlocked with the printer unit, and obtains color image data. In the present embodiment, since the image data of one color is obtained for each original scan in the illumination / mirror optical system, the color image data of four colors Bk, C, M and Y is obtained. In order to obtain it, the above document scanning is repeated four times in total.

Next, the schematic configuration and operation of the printer section will be described. A writing optical unit 5 as an exposure unit (not shown) is
And a photosensitive drum 1 as a latent image carrier. The writing optical unit 5 converts the color image data from the above-described scanner unit into an optical signal, and irradiates the uniformly charged negatively charged photosensitive drum 1 with light L corresponding to the original image to thereby form a negative image. Form a latent image. The writing optical unit 5 includes, for example, a semiconductor laser, a light emission drive control unit (not shown) for controlling light emission and drive of the semiconductor laser, a polygon mirror, and a rotation drive motor for rotating the same.
A lens composed of an f / θ lens and a reflection mirror can be used. The photosensitive drum 1 is rotationally driven in the direction of arrow A in FIG. 1, that is, counterclockwise.

Around the photosensitive drum 1, the writing optical unit, a photosensitive member cleaning device 2 as a cleaning unit, and a charging charger 3 as a charging unit
And a revolver developing unit 4 as a developing unit, and an intermediate transfer unit 10 as a transfer device (belt device). The photoconductor cleaning device 2 has a fur brush 2a and a photoconductor cleaning blade 2b, and cleans the surface of the photoconductor drum 1 after the primary transfer. The writing optical unit, the charger 3 and the like constitute a latent image forming means for forming a latent image on the photosensitive drum 1.

The revolver developing unit 4 has a Bk developing unit 4a, a C developing unit 4b, an M developing unit 4c, and a Y developing unit 4d, and rotates the revolver developing unit to develop each color. The developing position of the photoconductor drum 1 facing the photoconductor drum 1 can be determined. Each of these developing units includes a developing paddle as a stirring means (not shown) for pumping up and stirring the developer, a toner concentration detecting sensor as a toner concentration detecting means (not shown) for detecting the toner concentration of the developer, And a developing sleeve as a developer carrying member (not shown) for bringing the ear formed by the above into contact with the surface of the photosensitive drum 1. The internal structure of these four developing units (4a, 4b, 4c, 4d) is exactly the same.

These four developing units (4a, 4b, 4c,
The developer contained in 4d) uses a two-component developer, and the toner in the developer is negatively charged. When the toner is consumed by the development and the toner concentration of the developer in the developing device decreases, this information is detected by the toner concentration detecting sensor. In this case, toner for replenishment is supplied into the developing device from a toner bottle as a developer container of a toner replenishing device (not shown). Thus, the toner density in the developing device is kept at a predetermined density. Further, when the amount of toner is reduced by consumption, the remaining amount of toner can be detected by an optical sensor (not shown).

Although the rotary type revolver developing unit 4 is used in the present embodiment, a developing device having another structure may be used. For example, a developing device may be used in which the developing units of each color are arranged along the circumferential direction of the photosensitive drum 1.

The intermediate transfer unit 10 has a structure in which an intermediate transfer belt 11, which is an endless belt member as an intermediate transfer body (image carrier), is stretched over a plurality of rollers. The plurality of rollers 1
From the next transfer position B to the downstream side in the belt moving direction (direction C in the drawing), a primary transfer bias roller 12 as a charge applying means to which a primary transfer power source (not shown) is connected, and a predetermined tension on the intermediate transfer belt 11. Tension roller 15, a secondary transfer opposing roller 16 as a secondary transfer charge applying member, a driving roller 14 constituting a belt driving unit, and an earth roller 1 as a pre-primary transfer charge removing unit.
3. The drive roller 14 is connected to a drive motor (not shown), and the drive of the drive motor is controlled by a control unit (not shown). All the rollers that stretch the intermediate transfer belt 11 are formed of a conductive material, and each roller other than the primary transfer bias roller 12 is grounded.

The primary transfer bias roller 12
Is disposed adjacent to the primary transfer position B from the downstream side in the moving direction of the intermediate transfer belt. This one
The primary transfer bias is applied to the secondary transfer bias roller 12 by the primary transfer power supply. The ground roller 13 is disposed at a position adjacent to the primary transfer position B from the upstream side in the moving direction of the intermediate transfer belt. The intermediate transfer belt 11 is pressed against the photosensitive drum 1 by the primary transfer bias roller 12 and the ground roller 13 to form a primary transfer nip.

The intermediate transfer belt 11 has a multilayer structure including a surface layer, an intermediate layer, and a base layer. The surface layer is located on the outer peripheral surface in contact with the photosensitive drum 1, and the inner peripheral surface is It is arranged so that a base layer may be located.
Further, an adhesive layer for bonding the two layers is interposed between the intermediate layer and the base layer. This intermediate transfer belt 1
For No. 1, a medium resistance having a volume resistivity ρ _V of about 10 ¹¹ Ωcm according to the measurement method described in JIS K 6911 is used.

Around the intermediate transfer belt 11, a lubricant coating device 20, a belt cleaning device 30, and a paper transfer unit 40 as a transfer material transfer unit are provided. These can be brought into contact with and separated from the intermediate transfer belt 11, respectively.

The lubricant applying device 20 includes a lubricant applying brush roller 21 and a lubricant accommodating case 22. The lubricant containing case 22 contains a solid lubricant and a spring. As the solid lubricant, for example, zinc stearate composed of plate-shaped fine particles can be used. The solid lubricant is urged toward the lubricant applying brush roller 21 by the spring, and is in contact with the lubricant applying brush roller 21. After the secondary transfer, the lubricant applying brush roller 21 is rotationally driven by a drive unit (not shown) to scrape off the solid lubricant and apply the powdered lubricant to the intermediate transfer belt 11.

The belt cleaning device 30 includes a belt cleaning blade 31 as a cleaning member.
, An inlet seal member 32 as a sealing means, and a casing 33. The toner peeled off by the belt cleaning blade 31 is stored in the casing 33. The inlet seal 32 receives the toner and guides it into the casing 33 so that the peeled toner does not fly into the apparatus.

Further, the lubricant applying brush roller 21,
The cleaning blade 31 and the entrance seal 3
Each of the members 2 is controlled by a contact / separation mechanism 34 integrally formed by a spring, a cam, or the like so as to contact / separate from the surface of the intermediate transfer belt 11 at a predetermined timing.

The paper transfer unit 40 includes a secondary transfer bias roller 41 facing the secondary transfer facing roller 16 of the intermediate transfer unit 10 and a secondary transfer bias roller 4.
Cleaning blade 4 for cleaning the surface of 1
2. It is composed of a paper neutralization charger 43 and the like. 2
The secondary transfer power supply 42 supplies the secondary transfer bias roller 41 with
A next transfer bias is applied. The paper transfer unit 40 to which the secondary transfer bias roller 41 and the paper discharging charger 43 are attached is connected to the secondary transfer opposed roller 16 of the intermediate transfer belt 11 by a contact / separation mechanism constituted by a spring, an eccentric cam, or the like. It is swung so as to come in contact with and separate from the supported portion at a predetermined timing. FIG. 1 shows a state in which the paper transfer unit 40 is separated, but at the time of the secondary transfer, the paper transfer unit 40 is swung so as to approach the intermediate transfer belt 11, and the secondary transfer position indicated by D in the drawing is shown. , The secondary transfer bias roller 41 comes into pressure contact, thereby forming a secondary transfer nip portion. A transfer material transfer unit for transferring the toner image on the intermediate transfer belt 11 to a transfer paper 100 as a transfer material includes the secondary transfer bias roller 41, the secondary transfer power supply 42, and the like.

Further, the printer section is provided with a sheet feed registration section 50 as a transfer material conveying means for sending and conveying the transfer sheet 100 to the secondary transfer nip section. The paper feed registration unit 50 includes a pair of paper feed rollers 51 and a pair of registration rollers 52 (hereinafter, these four rollers are collectively referred to as “delivery conveyance rollers”), and the conveyance guide plate 5.
3, a paper sensor 54, a roller driving unit for driving each roller (not shown), and the like. The roller drive section is configured to drive the upper roller in the drawing of the pair of paper feed rollers 51 and the lower roller of the pair of registration rollers 52. The transfer paper 100 conveyed to the secondary transfer position is first supplied to the paper feed roller 5.
When the paper feed roller 51 is stopped at the timing when the leading edge of the transfer paper is detected by the paper sensor 54, the transfer paper is temporarily stopped immediately before the registration roller 52 and enters a standby state. When the rotation of the paper feed roller 51 and the registration roller 52 is started at a predetermined sending timing, the transfer paper 100 in the standby state is sent to the secondary transfer position.

Further, although not shown, the printer section includes a transfer paper cassette for storing transfer paper of various sizes, a manual paper feed tray for using OHP paper, thick paper, and the like, and a paper transporting tray. The unit includes a unit, a fixing device as a fixing unit for fixing the toner image on the transfer paper, and a copy tray (not shown). The transfer paper 100 that has passed through the secondary transfer position D is neutralized by the paper neutralization charger 43, and then conveyed by the conveyor belt unit 60 and guided to the fixing device.

Further, the above-mentioned 2 of the intermediate transfer unit 10
The inner surface (back surface) of the intermediate transfer belt 11 is located at a position adjacent to the next transfer position D from the upstream side in the moving direction of the intermediate transfer belt.
A mark sensor 70 for detecting a mark 71 for position detection provided in the device is attached. This mark sensor 7
As 0, a light reflection type sensor, a magnetic sensor, or the like can be used. For example, when a light reflection type sensor is used, a mark 71 having light reflection characteristics different from the inner surface of the intermediate transfer belt 11 is used. When a magnetic sensor is used, a mark 71 having magnetic properties different from those of the intermediate transfer belt 11 is used. The mark 71 is provided, for example, at the widthwise end of the back surface of the intermediate transfer belt 11.
The mark sensor 70 is arranged at a position where 1 passes. The mark 71 may be provided in a region on the surface of the intermediate transfer belt 11 that is outside the toner image carrying region.
The detection signal of the mark sensor 70 is sent to a control unit, which will be described later, and controls the formation of a latent image on the photosensitive drum 1 and the transfer paper 1
It is used for the control of sending / transporting 00.

Next, a description will be given of a color image forming operation of the copying machine when the order of development is Bk, C, M, and Y. The order of image formation is not limited to this. When the copy operation starts,
First, the Bk process starts, and the color image information of the document is read by the above-described scanner unit. Then, based on the Bk image data obtained from the image information, the laser beam L of the writing optical unit in the above-described printer unit is irradiated, and a Bk latent image is formed on the photosensitive drum 1. The start of the latent image formation is determined by the mark sensor 70
Is determined based on the detection signal. The Bk latent image is applied with Bk toner by the Bk developing device 4a,
It is developed by forming a toner image. The Bk toner image formed on the photosensitive drum 1 is primarily transferred onto the surface of the intermediate transfer belt 11 driven at the same speed as the photosensitive drum 1, and the Bk process is completed.

In parallel with the primary transfer of the Bk toner image,
The following C step is started on the photosensitive drum 1 side. That is, the color image information of the document is read again at a predetermined timing, and based on the C image data obtained from the image information, a C latent image is formed on the photosensitive drum 1 by laser light, and the C developing device 4b A C toner image is formed.
The C toner image formed on the photosensitive drum 1 is primarily transferred by being aligned with the image surface of the intermediate transfer belt 11 on which the Bk toner image has been transferred.

Thereafter, in the M step and the Y step, as in the above-mentioned C step, latent image formation, development and primary transfer are performed based on the respective image data. In this manner, Bk, C, M, and Y sequentially formed on the photosensitive drum 1 on the same image surface on the intermediate transfer belt 11.
Is primarily transferred, a toner image in which these four colors overlap is formed on the intermediate transfer belt.

Until the toner image is formed on the intermediate transfer belt 11, the primary transfer of the fourth color Y toner image after the primary transfer of the first color Bk toner image is performed. Until the end, the lubricant application brush roller 21 of the lubricant application device 20, the belt cleaning blade 31 and the entrance seal member 32 of the belt cleaning device 30, the secondary transfer bias roller 41 of the paper transfer unit 40, and the like. Is separated from the intermediate transfer belt 11.

The toner image primarily transferred on the intermediate transfer belt 11 as described above is sent to the secondary transfer position D for secondary transfer on the transfer paper 100. At this time,
Secondary transfer bias roller 41 of paper transfer unit 40
Usually, the toner image is pressed against the intermediate transfer belt 11 before the timing at which the toner image is transferred onto the transfer paper 100.
Thereafter, a predetermined 2
A secondary transfer bias is applied, and 2
A next transfer electric field is formed. Thus, the toner image on the intermediate transfer belt 11 is transferred onto the transfer paper 100. still,
The transfer paper 100 is conveyed in the direction of the registration roller 52 from a transfer paper cassette of a size designated by an operation panel (not shown) and fed to the secondary transfer nip. When the transfer paper 100 is fed, the transfer paper 100 is sent out at the timing when the leading end of the toner image on the intermediate transfer belt 11 reaches the secondary transfer position by the feed roller 51 and the registration roller 52. Conveyed. The transfer paper 100 on which the toner images formed by overlapping the four colors on the intermediate transfer belt 11 are collectively transferred is then transported to a fixing device by the paper transport unit 60, and the unfixed toner image on the transfer paper 100 is fixed. I do. Then, the transfer paper 100 is carried out to a copy tray and stacked.

The surface of the photosensitive drum 1 after the primary transfer is cleaned by the photosensitive member cleaning unit 2 and is uniformly discharged by a discharging lamp (not shown) as a discharging unit. The surface of the intermediate transfer belt 11 after the secondary transfer is cleaned by the cleaning blade 31 of the belt cleaning device 30 being pressed against the intermediate transfer belt 11 with a predetermined pressing force.

Next, the control of the transfer of the transfer sheet to the secondary transfer position, which is a feature of the present invention, will be described. When the toner image formed on the intermediate transfer belt 11 is transferred onto the transfer paper 100 in the copying machine having the above-described configuration, a predetermined sending start time Ts is set to a predetermined time from the time when the mark 71 on the back surface of the intermediate transfer belt 11 is detected. At the elapse of the timing, the transfer paper 100 that has been temporarily stopped at the registration roller 52 starts to be sent.

Here, the transmission start time T in the initial setting
so is represented by the following Equation 1. “To” in the expression is a “laser writing start time” from the detection of the mark to the start of laser writing on the fourth color toner image. In addition, as shown in FIG.
Indicates a laser writing position EX on the peripheral surface of the photosensitive drum 1.
From the first transfer position to the primary transfer position. “Lb” is a “toner image moving distance” from the primary transfer position on the peripheral surface on the intermediate transfer belt 11 to the secondary transfer position along the belt moving direction. “Lc” is a “transfer sheet feed distance” from a position at which transfer of the transfer sheet by the registration roller 52 is started to a position at the secondary transfer position. Also, "V
“a”, “Vb”, and “Vc” are the surface speed of the photosensitive drum, the speed of the intermediate transfer belt, and the surface speed of the delivery conveyance roller, respectively. “ΔTh” is a correction time based on machine variation.

[0077]

## EQU1 ## Transmission start time Tso = To + La / Va + Lb
/ Vb-Lc / Vc + ΔTh

In FIG. 2, the leading end position Ptop of the toner image on the intermediate transfer belt 11 is shifted from the secondary transfer position on the belt 11 to the upstream side in the belt moving direction by the transfer paper feeding distance L.
When the transfer sheet 100 reaches a position Pr (hereinafter, referred to as a “transfer sheet transfer corresponding position”) Pr, which is advanced by c, the transfer conveyance of the transfer sheet 100 is started.

In the conventional example, the distances La, L
The transmission start time Tso is determined using fixed values set in advance as b, Lc and the speeds Va, Vb, Vc. Further, since the position of each roller, the paper conveyance speed, and the like vary depending on the machine, there is a machine that corrects the correction time ΔTh in the above equation to change the transmission start time Ts.
However, in this type of machine, the sending start time Tso must be reset each time the circumferential length of the intermediate transfer belt 11 changes due to environmental temperature or aging.

Therefore, in the copying machine of the present embodiment, as shown by the following equation 2, the above-mentioned sending start time Ts is changed according to the circumferential length change amount ΔL of the intermediate transfer belt 11. With this change, even when the circumferential length of the intermediate transfer belt 11 changes due to environmental temperature or aging, the leading edge of the image and the predetermined position at the leading edge of the transfer paper 100 can be accurately aligned.

[0081]

## EQU2 ## Transmission start time Ts = Tso + ΔTs

Here, the above-mentioned “ΔTs” is a correction value based on a change in the circumference of the intermediate transfer belt, and can be obtained by the following equations (3) and (4). “ΔLb” in Expression 3 is a change amount of the change amount Lb of the toner image moving distance,
“L” is an initial setting value of the circumference of the intermediate transfer belt 11. “ΔL” is the amount of change in the circumference of the intermediate transfer belt 11.

[0083]

ΔTs = ΔLb / Vb = (Lb × ΔL / L) / Vb

ΔL = (Tm−Tmo) × Vb

The change amount ΔL of the circumference of the intermediate transfer belt 11 in the above equation 3 is at least 2 which is continuously detected.
Time interval T of the mark detection signal that has detected the mark 71 times
From m, it can be obtained by using the above equation (4). Note that “Tmo” in Equation 4 is the time interval of the mark detection signal on the intermediate transfer belt 11 in the initial non-expandable state.

By using the time interval Tm of the mark detection signal, the change amount of the circumferential length of the intermediate transfer belt 11 can be more accurately compared to the case where the time interval Tm is obtained indirectly from the detection results of environmental conditions such as temperature and humidity. Can be requested. When the time interval Tm of the mark detection signal is used, the intermediate transfer belt 11 is not caused by environmental conditions such as temperature and humidity, but is changed due to a temporal change in material characteristics of the intermediate transfer belt 11.
Even when the circumference of the intermediate transfer belt 11 changes, the amount of change in the circumference of the intermediate transfer belt 11 can be obtained.

FIG. 3 is a block diagram of a control system for controlling the timing at which the transfer rollers 51 and 52 start transferring the transfer paper in accordance with the change in the circumference of the intermediate transfer belt 11. This control system functions as transfer material (transfer paper) transport control means for controlling the transfer of the transfer material (transfer paper) in accordance with the change in the circumference of the intermediate transfer belt 11.
It is configured using a main control unit 200, a sensor control unit 210, and a clutch control unit 220.

The main control unit 200 includes a ROM 201 as a recording medium on which a program for controlling transfer paper transfer to the secondary transfer position is recorded, a RAM 202 for temporarily storing data used for the control, and the like. It is composed of an input / output interface. The sensor control unit 210 detects a voltage required for mark detection by the mark sensor 7.
0, or converts an analog signal output from the sensor 70 into a digital signal. The clutch control unit 220 controls the on / off operation of an electromagnetic clutch 55 provided in the middle of a drive device (not shown) that drives the delivery conveyance rollers 51 and 52 based on a control command from the main control unit 200. It is. In addition to the configuration using the electromagnetic clutch, the driving device that drives the delivery conveyance rollers 51 and 52 may be configured to directly control on / off of a driving motor as a driving source.

FIG. 4 is a flowchart showing an example of transfer paper transport control in the copying machine having the above-described configuration. In this control, first, a mark for forming a third color toner image on the intermediate transfer belt 11 is detected, and then the latent image corresponding to the third color image is driven while the intermediate transfer belt 11 is driven to rotate one revolution. Image formation, development, primary transfer, etc. are performed (S1, S
2). Next, mark detection for forming a fourth color (final color) toner image on the intermediate transfer belt 11 is performed (S
3). Then, while the latent image formation, development, primary transfer, and the like corresponding to the fourth color image are being performed, the circumferential length change amount ΔL of the intermediate transfer belt 11 is calculated based on Expression 4 (S4). Then, it is determined whether or not the perimeter change amount ΔL falls within a preset allowable range (S5).
If the above ΔL changes more than the allowable range, the transmission start time T is calculated based on the above equations (2) and (3).
s is changed (S6). Next, when the transmission start time Ts has elapsed from the mark detection in step S3,
When the electromagnetic clutch 55 is turned on, the delivery conveyance roller 51,
The rotation drive of 52 is started, and the transfer paper 100 is sent to the secondary transfer position (S7).

In the control shown in FIG. 4, the circumferential length change amount ΔL of the intermediate transfer belt 11 is calculated based on data of two consecutive mark detections immediately before the secondary transfer. If the moving speed of the intermediate transfer belt 11 is stable, data of a plurality of mark detections detected in other periods may be used. Alternatively, a plurality of circumferential length change amounts ΔL may be calculated using data of three or more mark detections, and the average value thereof may be used for the transfer and transfer control of the transfer paper.

In the control of FIG. 4, the control is performed such that the transmission start time Ts is changed only when the circumferential length change amount ΔL of the intermediate transfer belt 11 is out of the preset allowable range. Instead of setting the permissible range, the above-mentioned sending start time Ts may always be calculated based on the above formulas 2 and 3, and may be used for controlling the sending and transport of the transfer paper.

Further, two or more marks 71 on the intermediate transfer belt 11 may be provided at predetermined intervals in the circumferential direction. In this case, the change amount ΔL of the circumferential length of the intermediate transfer belt 11 can be obtained with a shorter moving distance of the intermediate transfer belt 11 than when only one mark 71 is provided. Also,
The mark sensor 70 may be provided at a plurality of positions sandwiching the tension roller 15 in the circumferential direction of the intermediate transfer belt 11. For example, in the configuration of FIG. 1 described above, an additional mark sensor is provided between the primary transfer bias roller 12 and the tension roller 15. In this case, the intermediate transfer belt 11
Even if there is only one upper mark 71, the intermediate transfer belt 1
The change amount ΔL of the circumference of the intermediate transfer belt 11 can be obtained with a shorter moving distance of 1.

As described above, according to the present embodiment, the environment (temperature,
Even when the circumferential length of the intermediate transfer belt 11 changes due to a change in humidity or the material characteristics of the intermediate transfer belt 11 over time, the secondary transfer position is adjusted to the leading end of the superimposed toner image on the intermediate transfer belt 11. Since the transfer paper 100 can be conveyed to the transfer paper 100, it is possible to suppress the displacement of the color image on the transfer paper 100. Therefore, it is possible to prevent "white spots" and "dirt on the edge surface" at the leading end and the trailing end of the transfer paper 100 due to the displacement.

In the copying machine of the above embodiment, when the thick paper mode, the magnification mode, and the automatic color setting mode are selected, after the primary transfer is completed as described above, the intermediate transfer belt is provided prior to the secondary transfer. 11 may be caused to make one round rotation. For example, after the primary transfer of the final color toner image is completed in the thick paper mode, when the moving speed of the intermediate transfer belt 11 is reduced, as shown in FIG.
r may pass through the top end position Ptop of the toner image. In this case, the operation of starting the transfer and conveyance of the transfer paper 100 cannot be made in time, and therefore, it is necessary to rotate the intermediate transfer belt 11 by one idle rotation.

FIG. 6 is a flowchart showing an example of transfer paper transport control in the case where the intermediate transfer belt 11 idles prior to the secondary transfer. In this control, a value obtained by adding the circumferential length L of the intermediate transfer belt 11 is used as the toner image moving distance Lb when obtaining the initial set value Tso of the transmission start time represented by the above equation (1). When the transmission start time Ts is changed in step S6, the following equation 5 is used instead of the above equation 3. Then, after idling of the intermediate transfer belt 11, when the sending start time Ts has elapsed from the mark detection in step S3, the electromagnetic clutch 55 is turned on to start rotating the sending transport rollers 51 and 52, and The transfer paper 100 is sent to the secondary transfer position (S7, S8).

[0095]

ΔTs = (ΔL + Lb × ΔL / L) / Vb

As described above, when the intermediate transfer belt 11 is idly rotated, the feeding and conveyance control of the transfer paper 100 is performed in consideration of the change in the circumferential length of the intermediate transfer belt 11, whereby the intermediate transfer belt 11 is rotated. Even after an idle rotation in which an image shift due to expansion and contraction is likely to occur, a position shift of the image on the transfer paper 100 can be reliably suppressed.

In the above embodiment, the change in the circumferential length of the intermediate transfer belt 11 is obtained based on the result of detecting the mark on the intermediate transfer belt 11 a plurality of times, but the position of the tension roller 15 is detected. Alternatively, the change in the circumference of the intermediate transfer belt 11 may be determined based on the amount of movement of the tension roller 15. As the tension roller position sensor for detecting the position of the tension roller 15, for example, a potentiometer attached to the shaft of the tension roller 15 can be used. Further, another position sensor such as an optical length measuring device using light reflection on a light reflecting plate attached to the shaft of the tension roller 15 can be used.

FIG. 7 is a block diagram of a control system for controlling the timing of starting the transfer paper transfer by the transfer rollers 51 and 52 based on the detection result of the tension roller position sensor. In this control system, the tension roller position sensor 72 is connected to the main controller 200 via the sensor controller 210. The main control 200 includes a tension roller position sensor 72 previously obtained by an experiment or the like.
And the data indicating the correspondence between the output of the intermediate transfer belt 11 and the circumference of the intermediate transfer belt 11 are stored. FIG. 8 is a flowchart showing transfer paper transport control based on the detection result of the tension roller position sensor. In this control, the position of the tension roller 15 is detected by the tension roller position sensor 72 at a predetermined timing, and the circumferential length change amount ΔL of the intermediate transfer belt 11 is calculated based on the detection result (S1, S2). The subsequent control is the same as the control in FIG.

Instead of detecting the mark on the intermediate transfer belt 11, a change in the circumference of the intermediate transfer belt 11 may be obtained based on environmental conditions such as temperature and humidity in the apparatus.
FIG. 9 is a block diagram of a control system for controlling the timing at which the transfer conveyance rollers 51 and 52 start transferring the transfer paper based on the detection result of the temperature and humidity sensor for detecting the temperature and humidity in the apparatus. In this control system, the temperature and humidity sensor 7
3 is connected to the main control unit 200 via the sensor control unit 210. The main control 200 stores data indicating the correspondence between the output of the temperature / humidity sensor 73 and the circumference of the intermediate transfer belt 11, which is obtained in advance through experiments or the like. FIG.
9 is a flowchart showing transfer paper transport control based on the detection result of the temperature and humidity sensor 73. In this control, the temperature and humidity in the apparatus are detected by the temperature / humidity sensor 73 at a predetermined timing, and based on the detection result, the circumference change amount ΔL of the intermediate transfer belt 11 is calculated (S1, S1).
2). The subsequent control is the same as the control in FIG.

Further, in the above-described embodiment, the image forming apparatus has been described in which the toner images of each color are sequentially formed on one photosensitive drum 1 and transferred to the intermediate transfer belt 11. As shown in FIG. 11, the present invention can be applied to a tandem type image forming apparatus having a plurality of photosensitive drums 1a to 1d. In this apparatus, an intermediate transfer belt 11 stretched around a driving roller 14, a tension roller 15, a secondary transfer opposing roller 16, and other support rollers 17a to 17e is used. The intermediate transfer belt 11 is stretched so as to partially wind around the peripheral surfaces of the photosensitive drums 1a to 1d. The mark 71 on the back surface of the intermediate transfer belt 11 is detected twice by the mark sensor 70, and the circumference of the belt 11 is obtained based on the detection result. Then, based on the amount of change in the circumference of the intermediate transfer belt 11, a registration roller 52 that feeds and conveys the transfer paper toward a secondary transfer start position where the secondary transfer facing roller 16 and the secondary transfer bias roller 41 face each other. Is started. In FIG. 11, members having the same functions as those of the apparatus in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The present invention is also applicable to an apparatus that does not use an intermediate transfer belt. For example, FIG.
As shown in FIG. 2, the photosensitive belt 30 stretched around the plurality of support rollers 301a to 301c and the tension roller 16
The present invention is also applicable to the case where the image data is directly transferred from 0 to the transfer paper. 12, a mark 71 on the back surface of the photoconductor belt 300 is detected by a mark sensor 70, and based on the detection result, toner images of a plurality of colors are formed on the photoconductor belt 300 in a superimposed manner. And the photoreceptor belt 3
The color image superimposed on the support roller 301
c at the transfer position where the paper transfer roller 302 and the paper transfer roller 302 are opposed to each other.
Is transferred to Further, based on the detection result of the mark sensor 70 that has detected the mark 71 on the back surface of the photosensitive belt 300 twice, the amount of change in the circumference of the belt 300 is obtained. Then, based on the amount of change in the circumference of the photoreceptor belt 300,
The drive start timing of the registration roller 52 is controlled.

Further, according to the present invention, as shown in FIG. 13, based on the detection result of the mark 71 on the photosensitive drum 1, a plurality of toner images are formed on the photosensitive drum 1 in a superimposed manner. 1 on the transfer paper 100
The present invention can also be applied to a case where the image is directly transferred to a sheet. FIG.
In 3, the color image superimposed on the photosensitive drum 1 is transferred to the transfer paper 100 sent and conveyed by the registration roller 52 at a transfer position where the surface of the drum and the paper transfer roller 302 face each other. Also, the photosensitive drum 1
The amount of change in the circumference of the drum 1 is obtained based on the detection result of the mark sensor 70 that has detected the mark 71 on the back surface of the drum 2 twice. Then, the drive start timing of the registration roller 52 is controlled based on the amount of change in the circumference of the photosensitive drum 1.

Further, in the above embodiment, the transfer sheet transfer start timing is changed in accordance with the change in the circumference of the intermediate transfer belt 11, but other transfer sheet conveyance conditions may be changed. For example, the transport speed at which the transfer paper is transported to the secondary transfer position by the transport rollers (the feed roller 51 and the registration roller 52) may be changed. Further, the transport path length between the registration roller 52 where the transfer paper is temporarily on standby and the secondary transfer position may be changed.

Further, in the above-described embodiment, the apparatus in which the toner image is superimposed and transferred on the surface of the intermediate transfer belt 11 as the image carrier and the toner image is transferred to the transfer paper has been described. If the transfer paper is delivered and conveyed at the timing when the delivery start time has elapsed from a certain reference time, the present invention can be applied to a case where the image is not superimposed on the surface of the image carrier.

In the above embodiment, the case of a copying machine has been described. However, the present invention can be applied to other image forming apparatuses such as a printer and a facsimile.

[0106]

According to the present invention, the transfer material can be conveyed to the transfer position in accordance with the leading edge of the image on the image carrier even when the peripheral length of the image carrier changes. Therefore, there is an excellent effect that it is possible to suppress the displacement of the image on the transfer material.

In particular, according to the second, twelfth and sixteenth aspects, the amount of change in the circumference of the image carrier can be directly obtained by detecting the mark on the image carrier. There is an excellent effect that the transfer material transfer condition can be accurately changed according to the change in the circumference of the carrier.

In particular, according to the third and thirteenth aspects of the present invention, the amount of change in the circumference of the intermediate transfer member can be directly obtained by detecting the mark on the intermediate transfer member. There is an excellent effect that the transfer material transfer condition can be accurately changed according to the change in the circumference of the body.

According to the fourth aspect of the present invention, the interval between the time when the mark on the image carrier is detected and the time when the image on the image carrier is transferred to the transfer material, the empty space of the image carrier. When driving, it is possible to accurately change the transfer material transport condition according to the change in the circumference of the image carrier. Therefore, even after the above-mentioned idle driving in which the image shift due to the expansion and contraction of the image carrier easily occurs, there is an excellent effect that the position shift of the image on the transfer material can be surely suppressed.

According to the fifth aspect of the present invention, the circumferential length of the image carrier changes with a shorter moving distance of the surface of the image carrier than in the case where only one mark is formed on the image carrier. There is an excellent effect that the amount can be determined.

According to the sixth aspect of the present invention, even if there is only one mark on the image carrier, the circumferential length of the image carrier changes with a shorter moving distance of the surface of the image carrier. There is an excellent effect that the amount can be determined.

According to the seventh aspect of the present invention, the amount of movement of a tension roller, which is one of a plurality of rollers for supporting the image carrier, is detected, so that a change in the circumferential length of the image carrier can be obtained. Accordingly, there is an excellent effect that the transfer condition of the transfer material can be changed.

In particular, according to the eighth and ninth aspects of the present invention, by detecting the environmental temperature, the transfer condition of the transfer material is changed according to the change in the circumference of the image carrier depending on the environmental temperature. There is an excellent effect that you can.

According to the ninth aspect of the present invention, since the conditions for the transfer start timing and the transfer speed for the transfer material are simultaneously changed as the transfer condition for the transfer material, the displacement of the image on the transfer material can be reduced. There is an excellent effect that the suppression can be surely performed.

According to the tenth, fourteenth, and seventeenth aspects of the present invention, there is an excellent effect that control for changing the transfer condition of the transfer material is facilitated.

According to the eighteenth to twentieth aspects of the present invention, by detecting the mark formed on the image carrier, the circumference of the belt member can be more accurately compared with the case where the mark is indirectly obtained from the detection result of the environmental temperature. There is an excellent effect that the amount of change in length can be obtained.

In particular, according to the invention of claim 19, the amount of change in the circumference of the belt member can be obtained with a shorter moving distance of the surface of the belt member as compared with the case where only one mark is on the belt member. There is an excellent effect that can be.

According to the twentieth aspect of the present invention, even if there is only one mark on the belt member, the amount of change in the circumferential length of the belt member can be obtained with a shorter moving distance on the surface of the belt member. There is an excellent effect that you can.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a copying machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing parameters used for calculating a sending start time in the copying machine, and a relationship between a toner image front end position Ptop on an intermediate transfer belt and a transfer paper sending corresponding position Pr.

FIG. 3 is a block diagram of a control system of transfer paper transport control in the copying machine.

FIG. 4 is a flowchart of the transfer paper transport control.

FIG. 5 is a diagram illustrating a tip end position Ptop of a toner image on an intermediate transfer belt and a transfer paper transfer corresponding position Pr in a thick paper mode of the copying machine.
FIG.

FIG. 6 is a flow chart of transfer paper transport control in a thick paper mode of the copying machine.

FIG. 7 is a block diagram of a control system of transfer paper transport control according to another embodiment.

FIG. 8 is a flowchart of the transfer paper transport control.

FIG. 9 is a block diagram of a control system of transfer paper transport control according to still another embodiment.

FIG. 10 is a flowchart of the transfer paper transport control.

FIG. 11 is a schematic configuration diagram of an image forming apparatus according to still another embodiment.

FIG. 12 is a schematic configuration diagram of an image forming apparatus according to still another embodiment.

FIG. 13 is a schematic configuration diagram of an image forming apparatus according to still another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Photoconductor cleaning device 3 Charger 4 Revolver developing unit 5 Writing optical unit 10 Intermediate transfer unit 11 Intermediate transfer belt 12 Primary transfer bias roller 13 Earth roller 14 Drive roller 15 Tension roller 16 Secondary transfer counter roller Reference Signs List 20 lubricant application device 30 belt cleaning device 40 paper transfer unit 41 secondary transfer bias roller 50 paper feed registration unit 51 paper feed roller 52 registration roller 55 electromagnetic clutch 70 mark sensor 71 mark for position detection 72 tension roller position sensor 73 temperature Humidity sensor 200 Main controller 210 Sensor controller 220 Clutch controller

Claims (20)

[Claims] An image carrier having a surface that can move endlessly, image carrier driving means that drives the image carrier so that the surface of the image carrier moves endlessly, and an image formed on the surface of the image carrier. Image transfer means for transferring an image on the image carrier to a transfer material at a transfer position facing the image carrier, and sending the transfer material at a preset timing to transfer the image. An image forming apparatus comprising: a transfer material transport unit that transports the transfer material to a transfer position; wherein a transfer condition of the transfer material in the transfer material transport unit is changed according to a change in a circumferential length of a surface of the image carrier. Image forming apparatus. 2. An image forming apparatus according to claim 1, wherein a mark for detecting a position is provided on said image carrier, and mark detecting means for detecting a mark on said image carrier; An image forming apparatus comprising: a transfer material transport control unit that controls the transfer material transport unit so as to change the transfer material transport condition based on detection time intervals of a plurality of detection signals that have been detected twice. . 3. A latent image carrier, a latent image forming means for forming a latent image on the latent image carrier, a developing means for developing a latent image on the latent image carrier to form an image, and a position. An intermediate transfer member as the image carrier having a mark for detection, an intermediate transfer means for transferring an image on the latent image carrier to the intermediate transfer member, and a mark for detecting the mark on the intermediate transfer member 2. The image forming apparatus according to claim 1, further comprising: a detection unit; and a latent image formation control unit configured to control a start timing of forming a latent image on the latent image carrier based on a detection result of the mark detection unit. 3. Transfer material transport control means for controlling the transfer material transport means so as to change the transfer material transport condition based on a detection time interval of a plurality of detection signals detected at least twice by the mark detection means. Characteristic image forming apparatus. 4. The method according to claim 1, wherein after detecting the mark on the image carrier to transfer the image formed on the image carrier to the transfer material, the leading end of the image on the image carrier sets the transfer position at least. Driving the image carrier so that the image carrier passes once, and then transferring the image on the image carrier to the transfer material when the leading end of the image on the image carrier reaches the transfer position. Item 2. The image forming apparatus according to Item 2 or 3, wherein the transfer condition of the transfer material is changed based on a detection time interval of a plurality of detection signals detected at least twice by the mark detection unit before the start of the transfer material transfer. An image forming apparatus. 5. The image forming apparatus according to claim 2, wherein a plurality of the marks are provided at predetermined intervals in a circumferential direction of the image carrier. 6. An image forming apparatus according to claim 2, wherein said image bearing member is an endless belt member supported by a plurality of support rollers including a tension roller. An image forming apparatus provided at a plurality of positions sandwiching the tension roller in a circumferential direction of the image carrier. 7. The image forming apparatus according to claim 1, wherein said image carrier is an endless belt member supported by a plurality of support rollers including a tension roller. Tension roller movement amount detection means; and transfer material conveyance control means for controlling the transfer material conveyance means to change the transfer material conveyance conditions based on the detection result of the tension roller movement amount detection means. An image forming apparatus comprising: 8. An image forming apparatus according to claim 1, wherein said transfer material is changed so as to change a transfer condition of said transfer material based on a detection result of said environmental temperature detector. An image forming apparatus, comprising: a transfer material transport control unit that controls a transport unit. 9. The transfer material transporting means comprising a delivery transport roller for sandwiching the transfer material and delivering the transfer material at a preset timing, and a rotary drive means for rotating the delivery transport roller. 8. The image forming apparatus according to claim 8, wherein the rotation speed of the delivery conveyance roller is changed together with the rotation start timing of the delivery conveyance roller based on a detection result of the environmental temperature detection means. 10. The method of claim 1, 2, 3, 4, 5, 6, 7, or 8.
In the image forming apparatus according to the ninth aspect, the transfer condition changed by the transfer material transfer control means is a timing to start sending the transfer material to the transfer position. 11. A transfer material transfer control method for controlling transfer condition of a transfer material when sending and transferring a transfer material to a transfer position opposite to an image carrier whose surface moves endlessly at a preset timing. A transfer material transfer control method, wherein the transfer condition of the transfer material is changed according to a change in the circumference of the surface of the image carrier. 12. The transfer material transport control method according to claim 11, wherein the mark for position detection provided on the image carrier is detected at least twice, and a detection time interval of a plurality of detection signals obtained by the detection is detected. A transfer material transfer control method based on the transfer condition. 13. The transfer material transport control method according to claim 11, wherein said image carrier is an intermediate transfer member onto which an image on the latent image carrier formed by forming a latent image and developing the latent image is transferred. Detecting a position detection mark provided on the intermediate transfer body at least twice, and changing a transfer condition of the transfer material based on a detection time interval of a plurality of detection signals obtained by the detection. A transfer material transport control method, comprising: 14. The transfer material transport control method according to claim 11, wherein the changed transport condition is a start timing of sending the transfer material to the transfer position. . 15. A transfer material transferring means for transferring an image formed on the surface of an image carrier to a transfer material at a transfer position opposite to the image carrier having an endlessly moving surface, and the transfer material is preset. A transfer material transporting means for delivering the transfer material to the transfer position at a timing, wherein a transfer condition of the transfer material in the transfer material transporting means is changed according to a change in a circumferential length of a surface of the image carrier. A transfer device characterized by changing. 16. A transfer device according to claim 15, wherein a mark for position detection is provided on said image carrier, and mark detecting means for detecting a mark on said image carrier, and at least two times by said mark detecting means. A transfer material transfer control unit that controls the transfer material transfer unit so as to change a transfer condition of the transfer material based on detection time intervals of the plurality of detected detection signals. 17. The transfer device according to claim 15, wherein the transfer condition changed by the transfer material transfer control means is a start timing of sending the transfer material to the transfer position. 18. A belt device comprising: an endless belt member supported by a plurality of support rollers; and belt driving means for driving the belt member, wherein a mark for position detection is provided on the belt member. Mark detecting means for detecting a mark on the belt member,
A belt device comprising: a calculating means for calculating an amount of change in circumference of the belt member based on a detection time interval of a plurality of detection signals detected at least twice by the mark detecting means. 19. The belt device according to claim 18, wherein a plurality of the marks are provided at predetermined intervals in a circumferential direction of the belt member. 20. The belt device according to claim 18, wherein one of the plurality of support rollers for supporting the belt member is a tension roller, wherein the mark detecting means is provided at a plurality of positions sandwiching the tension roller in a circumferential direction of the belt member. A belt device provided in the belt device.