JP2003029543A - Image forming device and method for deciding timing to carry transfer material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a transfer position where a toner image is transferred to transfer material from being deviated from a specified transfer position even when the peripheral length of an intermediate transfer body is changed with time or even when there is an individual difference at the time of manufacturing in the peripheral length of the intermediate transfer body. SOLUTION: When the peripheral length of the intermediate transfer body is elongated because of secular change or when there is the individual difference at the time of manufacturing in the peripheral length of the intermediate transfer body, timing to start carrying the transfer material is corrected by a carrying start timing correction means (step S6) in accordance with the elongation and the individual difference of the peripheral length, whereby a situation that the transfer position where the toner image is transferred to the transfer material is deviated from the specified transfer position caused by the elongation of the peripheral length because of the secular change of the intermediate transfer body or the individual difference at the time of manufacturing in the peripheral length of the intermediate transfer body is prevented.

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 and a facsimile using an intermediate transfer member and a method for determining a transfer material conveying timing.

[0002]

2. Description of the Related Art Conventionally, two methods are known as a method of transferring a toner image onto a transfer material in a color image forming apparatus.

First, each color (yellow, magenta, cyan, black) formed on a photoconductor is obtained by holding a transfer material such as a sheet of paper on a transfer material carrier such as a transfer drum and rotating the same.
Is a method of sequentially transferring the toner image of No. 1 to the transfer material. By completing the transfer of toner images of all colors,
A color toner image is formed on the transfer body. The transfer material on which the color toner image is formed is peeled from the transfer material carrier and is conveyed to the fixing unit to be fixed.

The other one is transfer (primary transfer) in which toner images of respective colors formed on a photoconductor are sequentially superposed on an intermediate transfer body.
After completing the primary transfer of the toner images of all colors onto the intermediate transfer body, the toner images (color toner images) on the intermediate transfer body are collectively transferred (secondary transfer) onto the transfer material. Is the method. The transfer material to which the color toner image has been secondarily transferred is conveyed to a fixing unit and subjected to a fixing process.

According to the transfer method using the intermediate transfer member, since it is not necessary to hold the transfer material on the transfer member carrier,
Image can be formed on various transfer materials such as thin paper (40 g / m ² or less), thick paper (200 g / m ² or more), postcards, envelopes, etc., and has the advantage that the transfer material that can be used is highly versatile. . An intermediate transfer drum and an intermediate transfer belt are generally used as the intermediate transfer member.

Here, the timing of the primary transfer and the secondary transfer when the intermediate transfer member is used is controlled as follows.

First, a reference position mark provided on the intermediate transfer member is detected by a sensor, and based on the detection result,
The electrostatic latent image is formed on the photoconductor, the toner image is formed by developing the electrostatic latent image, and the formed toner image is primarily transferred onto the intermediate transfer body.

On the other hand, the transfer material stands by at the position of the conveying means (for example, the registration roller), and this transfer material has passed a predetermined time after the reference position mark provided on the intermediate transfer member is detected by the sensor. After that, the transportation is started by driving the transportation unit, and the toner image on the intermediate transfer body is secondarily transferred onto the transfer material.

As described above, on the basis of the fact that the reference position mark provided on the intermediate transfer member is detected by the sensor,
Since the toner image is formed on the photosensitive member, the toner image formed is primarily transferred onto the intermediate transfer member, and the transfer material on which the toner image on the intermediate transfer member is secondarily transferred is conveyed, basically, The toner image is always secondarily transferred to a predetermined position on the transfer material.

[0010]

However, the intermediate transfer member,
In particular, in the intermediate transfer belt, there are variations in the intervals between the reference position marks and individual variations in the circumferential length of the intermediate transfer belt, that is, variations in the circumferential length. When the conveyance of the material is started, the relative position between the toner image primarily transferred on the intermediate transfer body and the transfer body conveyed by the conveying means is displaced, and the toner image secondarily transferred on the transfer body is displaced. There may be a problem that the position deviates from the predetermined position.

In order to solve such a problem, Japanese Patent Laid-Open No.
In Japanese Patent Application Laid-Open No. 00-98852, of the plurality of reference position marks provided, the elapsed time from the reference position mark serving as an image forming reference to the reference position mark for starting paper feeding is counted, and the difference between the count value and the theoretical value is calculated. It has been proposed that the sheet feeding start timing be corrected based on the obtained difference.

However, with this method, although it is possible to correct the variation in the interval between the plurality of reference position marks, the variation in the circumferential length of each intermediate transfer belt (individual difference) and the variation in the diameter of each registration roller (individual). However, it is impossible to correct the dimensional variation from the position of the registration roller to the secondary transfer position in each image forming apparatus.
In particular, when the peripheral length of the intermediate transfer belt is extended due to aging, or when the intermediate transfer belt is replaced, proper correction cannot be performed.

An object of the present invention is to provide a predetermined transfer position of a toner image on a transfer material even when the circumference of the intermediate transfer member changes with time or when there are individual differences in the circumference of the intermediate transfer member during manufacturing. The transfer position should not be shifted.

Another object of the present invention is to provide a toner image on the transfer material even if there are variations in the size of the transport means for transporting the transfer material or in the dimensions from the position of the transport means to the secondary transfer position. This is to prevent the transfer position of 1 from shifting from the desired transfer position.

[0015]

An image forming apparatus according to a first aspect of the present invention includes an image carrier which is rotationally driven in a predetermined direction,
A toner image forming unit that forms a toner image on the image carrier, an intermediate transfer member that is rotationally driven in a predetermined direction, and a toner image that is formed on the image carrier are primarily transferred onto the intermediate transfer member. At least one reference provided on the intermediate transfer body; a primary transfer means; a secondary transfer means that contacts the back surface of the transfer material to secondarily transfer the toner image on the intermediate transfer body to the transfer material; A position mark, a reference position mark detecting means for detecting the reference position mark, an intermediate transfer body one cycle measuring means for measuring one cycle of the intermediate transfer body by detecting the reference position mark, and a secondary transfer material for the transfer material. From the difference between the conveying means for conveying to the transfer position, the one cycle measured by the one cycle of the intermediate transfer body and the predetermined theoretical value of one cycle of the intermediate transfer body, Transport start timing Has a conveyance start timing correction means for correcting the grayed, the.

Therefore, when the circumference of the intermediate transfer member is extended due to a change with time, or when the circumference of the intermediate transfer member has individual differences at the time of manufacture, the transfer is performed according to the individual differences in the elongation and the peripheral length. The timing at which the material starts to be conveyed is corrected. For this reason, the transfer position of the toner image on the transfer material is deviated from the predetermined transfer position due to the circumferential length extension of the intermediate transfer member due to aging and individual differences in the peripheral length of the intermediate transfer member during manufacturing. Is prevented.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the correction by the conveyance start timing correction means is Y = (T1−T0) × Q , T1: One cycle measurement value of the intermediate transfer body T0: The theoretical value Q1 of one cycle of the intermediate transfer body: It is performed based on the correction coefficient.

Therefore, the conveyance start timing can be easily corrected based on the correction value Y.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the intermediate transfer member is an endless intermediate transfer belt.

Therefore, the intermediate transfer belt is liable to have an increase in the circumferential length due to aging and individual differences in manufacturing. Even when such an intermediate transfer belt is used, the circumferential length of the intermediate transfer belt and the intermediate length are increased. It is possible to prevent the transfer position of the toner image on the transfer material from being deviated from a predetermined transfer position due to individual differences in the circumference of the transfer belt during manufacturing.

The invention according to claim 4 is the invention according to claims 1 to 3.
In the image forming apparatus according to any one of the above, the reference position mark is a reflection mark attached to the front surface or the back surface of the intermediate transfer member.

Therefore, it is possible to easily attach such a reflection mark to the intermediate transfer member, and it is possible to accurately detect such a reflection mark by the reference position mark detecting means.

The invention as defined in claim 5 is defined by claim 1 through claim 3.
In the image forming apparatus described in any one of the above, the reference position mark is a transmission hole formed at an end portion of the intermediate transfer member.

Therefore, since no dedicated part as the reference position mark is required, the cost can be reduced by reducing the number of parts. Further, the detection accuracy does not deteriorate due to the attachment of dirt such as toner to the transmission hole, and the detection accuracy of the transmission hole can be maintained semipermanently.

The invention according to claim 6 is the invention according to claims 1 to 5.
In the image forming apparatus described in any one of the above 1 to 3, a conveyance start timing adjusting unit that adjusts a conveyance start timing of the conveying unit is provided.

Therefore, if there is a machine-to-machine difference such as a variation in the size of the transporting means for transporting the transfer material or a variation in the size from the position of the transporting means to the secondary transfer position, depending on the variation. The transport start timing can be adjusted. Therefore, the transfer position of the toner image on the transfer material is caused by the machine-to-machine difference such as the size variation of the transporting means that transports the transfer material and the dimension variation from the position of the transporting means to the secondary transfer position. Is prevented from deviating from a predetermined transfer position.

According to a seventh aspect of the present invention, an image forming apparatus for primarily transferring a toner image formed on an image bearing member onto an intermediate transfer member and secondarily transferring the toner image on the intermediate transfer member onto a transfer material. In the method for determining the transfer material transport timing of, the one cycle of the intermediate transfer body is measured by detecting the reference position mark provided on the intermediate transfer body, and the measured one cycle is determined as the predetermined intermediate period. It is characterized in that the difference from the theoretical value of one cycle of the transfer body is obtained, and the transfer timing of the transfer material is corrected based on this difference.

Therefore, when the peripheral length of the intermediate transfer member is extended due to aging, or when there are individual differences in the peripheral length of the intermediate transfer member at the time of manufacture, depending on the individual differences in the elongation and the peripheral length. The timing at which the transfer material starts to be conveyed is corrected. For this reason, the transfer position of the toner image on the transfer material is deviated from the predetermined transfer position due to the circumferential length extension of the intermediate transfer member due to aging and individual differences in the peripheral length of the intermediate transfer member during manufacturing. Is prevented.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
Or, it demonstrates based on FIG. FIG. 1 is a cross-sectional view showing the schematic structure of a color printer which is an image forming apparatus, and FIG. 2 is a conveyance of a sheet (transfer material) by a registration roller (conveying means) from detection of a reflection mark (reference position mark) in this color printer. FIG. 3 is a schematic diagram illustrating the time until the timing, and FIG. 3 is a flowchart illustrating the correction of the conveyance start timing of the sheet (transfer material).

First, the structure of the color printer will be described. This color printer includes a photoconductor belt 1 which is an image carrier, an intermediate transfer belt 2 which is an intermediate transfer body, a paper tray 4 which stores and holds a paper 3 which is a transfer material, a fixing unit 5,
A control unit (not shown) having a microcomputer structure, which includes a paper discharge unit 6, a CPU, a ROM, a RAM and the like, and controls each unit of the color printer, is provided.

The photosensitive belt 1 includes three rollers 7a, one of which is rotationally driven by a motor (not shown).
It is wound around 7b and 7c and is rotationally driven in the direction of arrow A.

Around the photosensitive belt 1, as a toner image forming means for forming a toner image on the photosensitive belt 1, a charging roller 8, a laser writing unit 9, a yellow developing device 10Y, a magenta developing device. 10M, a cyan developing device 10C, a black developing device 10K, a cleaning unit 11 and the like are arranged.

The charging roller 8 is used to uniformly charge the surface of the photosensitive belt 1. The laser writing unit 9 is used to perform exposure according to image data, and an electrostatic latent image is written on the photosensitive belt 1 by this exposure. Developing devices for each color 10Y, 10M, 10C, 10
K is used to supply toner to the electrostatic latent image on the photosensitive belt 1, and the supply of this toner visualizes the electrostatic latent image on the photosensitive belt 1 to form a toner image. .
The cleaning unit 11 is used to remove the toner remaining on the photosensitive belt 1 after the toner image on the photosensitive belt 1 is primarily transferred to the intermediate transfer belt 2.

The intermediate transfer belt 2 is wound around a driving roller 12, a primary transfer bias roller 13 which is a primary transfer means, a driven roller 14, a secondary transfer counter roller 15 and a tension roller 16. It is driven to rotate in the direction of arrow B.

The primary transfer bias roller 13 is used to apply a bias voltage, and by applying this bias voltage, the toner image on the photosensitive belt 1 is primarily transferred onto the intermediate transfer belt 2. The tension roller 16 applies tension to the intermediate transfer belt 2, and the tension application keeps the intermediate transfer belt 2 slack.

The intermediate transfer belt 2 is made of PVDF (vinyl fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate) or the like, and a conductive material such as carbon black. Dispersed, and its volume resistivity is 10 ⁸ to 10 ¹² Ωcm, and
The surface resistivity is adjusted to be in the range of 10 ⁸ to 10 ¹⁵ Ωcm. A release layer may be coated on the surface of the intermediate transfer belt 2 if necessary. Materials used for coating include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinyldenfluoride), PEA (perfluoroalkoxyfluorine resin), FEP (tetrafluoride). Ethylene
A fluorinated resin such as a propylene hexafluoride copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.

A reflection mark 17, which is a reference position mark, is attached to the end of the outer peripheral surface of the intermediate transfer belt 2. Around the intermediate transfer belt 2, a light reflection type mark sensor 18 which is a reference position mark detecting means for detecting the reflection mark 17, a secondary transfer bias roller 19 which is a secondary transfer means, a cleaning unit 20 and the like are arranged. Has been done.

The mark sensor 18 is used to detect the reflection mark 17 that moves with the rotation of the intermediate transfer belt 2, and the detection result is transmitted to the control unit. The secondary transfer bias roller 19 is used for applying a bias voltage,
By applying this bias voltage, the toner image on the intermediate transfer belt 2 is secondarily transferred onto the sheet 3 conveyed between the intermediate transfer belt 2 and the secondary transfer bias roller 19. The secondary transfer bias roller 19 is movably provided to a position in contact with and away from the intermediate transfer belt 2, and moves to a position in contact with the intermediate transfer belt 2 at the timing of performing secondary transfer. . Cleaning unit 2
0 is used to remove the toner remaining on the intermediate transfer belt 2 after the toner image on the intermediate transfer belt 2 is secondarily transferred to the sheet 3. The cleaning unit 20 is movably provided to a position in contact with and away from the intermediate transfer belt 2, and moves to a position in contact with the intermediate transfer belt 2 at the timing of cleaning.

A paper transport path 21 for transporting the paper 3 is formed between the paper tray 4 and the paper discharge section 6, and a paper feed roller 22 and a transport means are provided on the paper transport path 21. Registration roller 23, secondary transfer bias roller 1
9, the fixing unit 5 and the like are arranged.

The registration roller 23 temporarily stops the sheet 3 fed by the sheet feeding roller 22 and is driven at a predetermined timing to cause a bias roller 1 for the secondary transfer.
The sheet 3 is conveyed to the secondary transfer position by 9. The sheet 3 to which the toner image has been transferred at the secondary transfer position is subjected to a fixing process in the fixing unit 5, and is discharged to the paper discharge unit 6 after the fixing process.

In such a structure, the basic operation of this color printer is as follows. The photosensitive belt 1 is operated a predetermined time after the reflection mark 17 is detected by the mark sensor 18.
Writing of the electrostatic latent image on the upper side is started, and after a lapse of a predetermined time, primary transfer is performed on the intermediate transfer belt 2, and the above operation or the image of each color is performed. After a lapse of a predetermined time after the transfer is performed, the registration roller 23 is turned on and the conveyance of the sheet 3 is started, and after a lapse of the predetermined time after that, the secondary transfer is performed.

Here, from the detection of the reflection mark 17 in this color printer to the sheet 3 by the registration roller 23.
The conveyance start timing and the time until the secondary transfer are described with reference to FIG.

First, the mark sensor 18 is operated by the reflection mark 17
From the timing at which the latent image is written to the photosensitive belt 1, the distance from the latent image writing position to the primary transfer position, and the distance from the temporary transfer position to the secondary transfer position are defined as the process speed. The time "TA" obtained by adding the divided time is obtained as an initial value. This time "TA" is
It is the time from the detection of the reflection mark 17 to the arrival of the front end of the toner image primarily transferred to the intermediate transfer belt 2 at the secondary transfer position.

Next, the transfer start timing of the paper 3 by the registration roller 23 necessary for transferring the toner image on the intermediate transfer belt 2 to a predetermined position of the paper 3 is determined. The conveyance start timing is the time “T” obtained by subtracting the time “TB” until the paper 3 reaches the secondary transfer position from the position of the registration roller 23 from the above “TA”.
It becomes A '".

During this time "TA '", the mark sensor 18
Is the time from the detection of the reflection mark 17 to the start of conveyance by the registration roller 23, and there is no extension of the circumferential length of the intermediate transfer belt 2 or variation in the circumferential length at the time of manufacture of each intermediate transfer belt 2. If anything, this time "TA '"
By starting the conveyance of the sheet 3 at, the toner image is secondarily transferred to the predetermined position of the sheet 3 with high accuracy. Conversely, if there is an increase in the circumferential length of the intermediate transfer belt 2 or a variation in the circumferential length at the time of manufacturing each intermediate transfer belt 2,
If the sheet conveyance by the registration roller 23 is started at this time “TA ′”, the toner image secondarily transferred onto the sheet 3 may be displaced from a predetermined transfer position.

Therefore, in the present embodiment, by providing a conveyance start timing correction means for correcting the timing of the conveyance start by the registration rollers 23, the circumferential length of the intermediate transfer belt 2 is extended and each intermediate transfer belt 2 is manufactured. Even if there is a variation in the circumferential length, the toner image is secondarily transferred to the predetermined position of the paper 3 with high accuracy.

The carrying start timing correction means is a process executed by the control unit, and the carrying start timing correction means will be described in detail with reference to the flowchart of FIG.

First, at the time of image formation by the color printer, the photosensitive belt 1 and the intermediate transfer belt 2 are rotated, and the mark sensor 18 detects the reflection mark 17 for the first time (step S1). At a predetermined timing, writing of the electrostatic latent image for the image of the first color is started, and the electrostatic latent image is visualized as a toner image, and the toner image is primarily transferred onto the intermediate transfer belt 2. . After that, the reflection mark 17 by the mark sensor 18
Is detected for the second time (step S2), and writing of the electrostatic latent image on the image of the second color is started at a predetermined timing according to the detection result. From these two detection results of the reflection mark 17, the measurement value "T1" for one cycle of the intermediate transfer belt 2 is measured (step S3), and the one cycle measurement unit of the intermediate transfer member is executed.

After that, the theoretical value "T0" for one cycle of the intermediate transfer belt 2, which is a value obtained by dividing the theoretical circumference of the intermediate transfer belt 2 by the process speed, and the measured value "for one cycle" of the intermediate transfer belt 2 described above. T = "and Y = (T1−T0) × Q
The correction value “Y” is calculated by the correction formula (step S
4) Further, a time "Ty" obtained by dividing the correction value "Y" by the process speed is calculated (step S5). Then, the calculated time "Ty" is added to "TA '" (step S6), and the transport start timing correction means is executed here.

As can be seen from the correction formula of Y = (T1−T0) × Q, when the intermediate transfer belt 2 extends and its circumference becomes long (when T1> T0), the correction value "Y" is obtained. ”
Becomes positive and is corrected so that the value of "TA '" becomes large. That is, the timing when the registration roller 23 is turned on and the conveyance of the sheet 3 is started is delayed. At this time, since the value of “TB” does not change, the value of “TA” shown in FIG. 2 increases by “Ty”.

On the other hand, when the circumference of the intermediate transfer belt 2 is shorter than the theoretical circumference, the correction value "Y" becomes negative,
It is corrected so that the value of "TA '" becomes smaller. That is, the timing at which the registration roller 23 is turned on and the conveyance of the sheet 3 is started is advanced.

The correction coefficient "Q" is a value obtained from an experimental result using a plurality of intermediate transfer belts 2, and the measured value "T1" for one cycle of each intermediate transfer belt 2 is transferred to a sheet. It is obtained from the relationship with the amount of deviation of the toner image from a predetermined transfer position. In the present embodiment, when the theoretical value “T0” for one cycle of the intermediate transfer belt 2 is 2960 msec, “Q” is 0.15 mm / msec.

Further, in the present embodiment, a conveyance start timing adjusting means for adjusting the timing of the conveyance start by the registration rollers 23 is provided. In this conveyance start timing adjusting means, when the operator operates the operation panel, the mark sensor 18 causes the reflection mark 1 to move.
This is a means for varying the value of "TA '" from the time 7 is detected to the start of the conveyance of the sheet 3 by the registration roller 23, and the timing of the conveyance start is adjusted.

By carrying out the adjustment by the conveyance start timing adjusting means, there are machine-to-machine differences such as the diameter variation of the registration roller 23 and the dimension variation from the position of the registration roller 23 to the secondary transfer position in each color printer. Even in this case, the sheet 3 conveyed by the registration rollers 23 can be accurately aligned with the toner image on the intermediate transfer belt 2 at the secondary transfer position, and the transfer position of the toner image on the sheet 3 is predetermined. Can be prevented from being displaced from the transfer position.

The adjustment by the transport start timing adjusting means is such that the toner actually transferred onto the paper 3 when the image is formed so that the distance from the front end of the paper 3 to the image has a predetermined size (for example, 5 mm). It is performed so that the distance of the image from the front end of the sheet 3 is within a predetermined dimension (for example, 5 ± 0.5 mm).

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. The same parts as those described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The basic structure of the present embodiment is the same as that of the first embodiment, and is provided with the carrying start timing correcting means and the carrying start timing adjusting means which are the features of the present invention.

This embodiment is different from the first embodiment in the reference position mark provided on the intermediate transfer belt 2, and in the first embodiment, it is the reflection mark 17, whereas the present embodiment is different from the first embodiment. In the embodiment, the point is the transmission hole 24.
The transmission holes 24 are formed so as to penetrate the front and back surfaces of the intermediate transfer belt 2, and in order to prevent the transfer of the toner image onto the intermediate transfer belt 2, the end portions of the intermediate transfer belt 2 are formed. Is formed in.

Further, the transmission hole 24 is used as a reference position mark.
Due to the provision of the above, a light transmission type mark sensor 25 having a light emitting portion and a light receiving portion is used as the reference position mark detecting means.

In the above-described embodiment, the case where one reflection mark 17 or the transmission hole 24 as the reference position mark is provided in the intermediate transfer belt 2 has been described as an example.
You may provide more than one. By providing a plurality of reference position marks, any one of the reference position marks can be promptly detected by the reference position mark detecting means at the start of image formation, and the image formation can be started promptly.
When a plurality of reference position marks are provided, it is necessary to detect the same reference position mark twice in order to measure one cycle of the intermediate transfer belt 2. Therefore, the reference position detected by the reference position mark detecting means is detected. Means are provided for counting the number of marks.

Further, in the above-described embodiments, the case where the photoconductor belt 1 is used as the image carrier has been described as an example, but other forms of the image carrier such as the photoconductor drum may be used. .

[0062]

According to the image forming apparatus of the first aspect of the present invention, when the peripheral length of the intermediate transfer member is extended due to aging, or when the peripheral length of the intermediate transfer member has individual differences during manufacturing. The transfer start timing of the transfer material can be corrected according to the individual difference in the elongation and the perimeter. It is possible to prevent the transfer position of the toner image on the transfer material from being displaced from the predetermined transfer position due to the difference, and it is possible to improve the accuracy of the secondary transfer position of the toner image on the transfer body.

According to the second aspect of the invention, in the image forming apparatus according to the first aspect, the correction by the transport start timing correcting means is a correction value Y obtained by a correction equation of Y = (T1−T0) × Q. However, T1: measured value of one cycle of the intermediate transfer member T0: theoretical value of one cycle of the intermediate transfer member Q: Since it is performed based on the correction coefficient, it is easy to correct the transport start timing based on the correction value Y. It can be carried out.

According to the third aspect of the invention, in the image forming apparatus according to the first or second aspect, the intermediate transfer member is an endless intermediate transfer belt. Even when using an intermediate transfer belt that tends to cause individual differences in time, the toner image on the transfer material may be different due to the increase in the peripheral length of the intermediate transfer belt and the individual difference in the manufacturing of the peripheral length of the intermediate transfer belt. It is possible to prevent the transfer position from deviating from the predetermined transfer position, and it is possible to improve the accuracy of the secondary transfer position of the toner image on the transfer body.

According to a fourth aspect of the invention, in the image forming apparatus according to any one of the first to third aspects, the reference position mark is a reflection mark attached to the front surface or the back surface of the intermediate transfer member. Therefore, it is possible to easily attach such a reflection mark to the intermediate transfer member, and it is possible to accurately detect such a reflection mark by the reference position mark detecting means.

According to the invention of claim 5, in the image forming apparatus according to any one of claims 1 to 3, the reference position mark is a transmission hole formed at the end of the intermediate transfer member. Since a dedicated part as a reference position mark is not required, it is possible to reduce the cost by reducing the number of parts, and the detection accuracy does not deteriorate due to dirt such as toner adhering to the transmission hole. Therefore, the detection accuracy of the transmission hole can be maintained semipermanently.

According to the invention of claim 6, in the image forming apparatus according to any one of claims 1 to 5, since the carrying start timing adjusting means for adjusting the carrying start timing of the carrying means is provided. If there are machine-to-machine differences, such as variations in the size of the transport unit that transports the transfer material, and variations in the size from the position of the transport unit to the secondary transfer position, adjust the transport start timing according to those variations. It is possible to prevent the toner image from being transferred onto the transfer material due to machine-to-machine differences such as the size variation of the transport means that transports the transfer material and the dimension variation from the position of the transport means to the secondary transfer position. It is possible to prevent the transfer position from deviating from the predetermined transfer position.

According to the transfer material conveying timing determining method of the invention described in claim 7, there is an individual difference at the time of manufacturing when the circumference of the intermediate transfer body is extended due to a change with time or the circumference of the intermediate transfer body is increased. In this case, the timing at which the transfer material starts to be conveyed can be corrected according to the individual difference in the elongation and the circumference, and the elongation of the circumference due to the aging of the intermediate transfer body or the manufacturing of the circumference of the intermediate transfer body can be performed. It is possible to prevent the transfer position of the toner image on the transfer material from being deviated from the predetermined transfer position due to the individual difference of the above, and it is possible to improve the accuracy of the secondary transfer position of the toner image on the transfer body. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic structure of a color printer which is an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a time period from detection of a reflection mark to timing at which a registration roller starts conveying a sheet.

FIG. 3 is a flowchart illustrating correction of a sheet conveyance start timing.

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

[Explanation of symbols]

1 image carrier 2 intermediate transfer member, intermediate transfer belt 3 transfer materials 8, 9, 10Y, 10M, 10C, 10K, 11 toner image forming means 13 primary transfer means 17 reference position mark, reflection mark 18 reference position mark detecting means 19 Secondary transfer means 23 Conveying means 24 Reference position mark, transmission hole 25 Reference position mark detecting means Step S3 Intermediate transfer member 1 cycle measuring means Step S6 Conveyance timing correcting means

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H027 DA21 DA38 DE02 DE07 EB06                       EC06 ED17 ED24 EE02 EE07                       EF06                 2H030 AA01 AD05 AD17 BB42 BB44                       BB56                 2H072 AA32 AB03 AB07 AB19 BA03                       BA12 CA01                 2H200 FA02 GA24 GA47 HA02 HB12                       HB22 JB49 JC03 JC19 JC20                       PA10 PB15 PB35 PB39

Claims (7)

[Claims] 1. An image carrier that is rotationally driven in a predetermined direction, a toner image forming unit that forms a toner image on the image carrier, an intermediate transfer member that is rotationally driven in a predetermined direction, and the image carrier. Primary transfer means for primary transfer of the toner image formed on the intermediate transfer member, and secondary transfer for secondary transfer of the toner image on the intermediate transfer member to the transfer material by contacting the back surface of the transfer material. Means, at least one or more reference position marks provided on the intermediate transfer member, reference position mark detecting means for detecting the reference position mark, and one cycle of the intermediate transfer member by detecting the reference position mark. Intermediate transfer member one cycle measuring means for measuring, conveying means for conveying the transfer material to the secondary transfer position, one cycle measured by the intermediate transfer member one cycle measuring means, and a predetermined first half One round of the transfer body And a transport start timing correction unit that corrects the transport start timing of the transport unit based on the difference from the theoretical value of the period. 2. A correction value Y obtained by the correction formula of Y = (T1−T0) × Q, where T1 is a measured value of one cycle of the intermediate transfer member T0 is an intermediate transfer. The image forming apparatus according to claim 1, wherein the theoretical value Q of one cycle of the body is performed based on a correction coefficient. 3. The image forming apparatus according to claim 1, wherein the intermediate transfer member is an endless intermediate transfer belt. 4. The image forming apparatus according to claim 1, wherein the reference position mark is a reflection mark attached to the front surface or the back surface of the intermediate transfer member. 5. The image forming apparatus according to claim 1, wherein the reference position mark is a transmission hole formed at an end of the intermediate transfer member. 6. The image forming apparatus according to claim 1, further comprising a transport start timing adjusting unit that adjusts a transport start timing of the transport unit. 7. A transfer material conveyance timing of an image forming apparatus for primary-transferring a toner image formed on an image carrier to an intermediate transfer body and secondarily transferring the toner image on the intermediate transfer body to a transfer material. In the determination method, one cycle of the intermediate transfer body is measured by detecting a reference position mark provided on the intermediate transfer body, and one cycle of the measured one cycle and a predetermined one cycle of the intermediate transfer body is determined. A method for determining a transfer material conveyance timing, which is characterized in that a difference from a theoretical value is obtained, and the conveyance start timing of the transfer material is corrected based on this difference.