JPH06282178A - Transfer device - Google Patents

Abstract

PURPOSE:To obtain an excellent full color image without the occurrence of color slippage caused by a deviation in the position of each color toner image transferred on a transfer material, at the time of moving the transfer material held on a transfer belt extended between rotary rollers by their rotations and leading the transfer material to a transfer position opposite to an image carrier, to superimpose/transfer each color toner image formed on the image carrier onto the transfer material. CONSTITUTION:The rotary rollers 11 and 12 are rotated to carry the transfer material 1 held on the transfer belt 13 extended between the rotary rollers 11 and 12, the rotational speeds of the rotary rollers 11 and 12 are controlled before the transfer material 1 is detected by a position detecting sensor 15 and the transfer material 1 is detected by the position detecting sensor 15 in this state and then, led to the transfer position facing oppositely the image carrier 2, to transfer the toner image from the image carrier 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for transferring a toner image formed on an image bearing member onto a transfer material such as transfer paper, and more particularly to an endless transfer which is spread between rotating rollers. While the transfer material is held on the belt, the rotating roller is rotated to drive the transfer belt, and the transfer material held on the transfer belt is guided to the transfer position facing the image carrier to carry the image. The present invention relates to a transfer device adapted to transfer a toner image from a body onto a transfer material.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus such as a copying machine or a printer, a toner image formed on an image carrier is transferred onto a transfer material such as transfer paper by various transfer devices. Was there.

Further, in recent years, a full-color electrophotographic apparatus has been developed, and in such an electrophotographic apparatus, toner images of different colors are repeatedly superposed on a transfer material such as transfer paper from an image carrier. The image was transferred to form a full-color image on the transfer material.

Here, as a transfer device for transferring the toner images of different colors from the image carrier to the transfer material many times as described above, conventionally, the transfer device is generally arranged so as to face the image carrier. The transfer drum is arranged so that the transfer material is wound around the transfer drum and held, and in this state, the transfer drum is rotated many times to transfer the transfer material onto the transfer material held on the transfer drum. In addition, the one in which toner images of different colors are repeatedly superposed and transferred from the image carrier has been used.

However, in the case where the transfer material is wound around the transfer drum and held in this way, when the transfer material is a card such as a postcard, the transfer material is well wound around the transfer drum. However, there is a problem that an image cannot be formed on such a thick paper transfer material, and a large transfer material such as B4 plate or A3 plate should not overlap the outer circumference of the transfer drum along its longitudinal direction. Since it is wound around, it is necessary to use a transfer drum having a large diameter, the position at which this transfer drum is provided is limited, and the electrophotographic apparatus as a whole becomes large.

Therefore, in recent years, in order to solve the above-mentioned problems, as shown in FIG. 1, an endless transfer belt 13 is laid between rotating rollers 11 and 12 provided at a required interval. , Transfer paper 1 on this transfer belt 13
In the state where the transfer belt 13 is held, the rotating rollers 11 and 12 are rotated to drive the transfer belt 13,
The transfer material 1 held above is guided to a transfer position facing the image carrier 2, and the toner images of the respective colors formed on the image carrier 2 are transferred onto the transfer material 1 by the transfer device 14 in an overlapping manner. Transfer device was developed.

Further, in such a transfer device, generally, the rotating rollers 11 and 12 are rotated in forward and reverse directions to reciprocate the transfer material 1 held on the transfer belt 13 and thereby, What is used is that the transfer material 1 is repeatedly guided to a transfer position facing the image carrier 2 and the toner images of respective colors are repeatedly transferred from the image carrier 2 onto the transfer material 1. It was

Here, in such a transfer device,
The transfer material 1 held on the transfer belt 13 is repeatedly guided to a transfer position facing the image carrier 2 so that the toner images of the respective colors formed on the image carrier 2 are transferred onto the transfer material 1 in an overlapping manner. In order to ensure that the toner image formed on the image carrier 2 is accurately transferred to an appropriate position on the transfer material 1, the timing at which the transfer material 1 is guided to the transfer position and the time when the transfer material 1 is formed on the image carrier 2 are formed. It is necessary to always match the timing at which the formed toner image is guided to the transfer position.

As a method of always matching the timing at which the transfer material 1 is guided to the transfer position and the timing at which the toner image formed on the image carrier 2 is guided to the transfer position, the transfer after the transfer is performed. It is conceivable that the material 1 is returned to a predetermined forward movement start position and always moved from a constant position, but it is very difficult to always return the transfer material 1 to the predetermined forward movement start position accurately. Yes, for this reason
Conventionally, the transfer belt 13 is moved forward to move the transfer material 1
A margin is provided in the timing setting for guiding the transfer material to the transfer position so that the timing at which the transfer material 1 is guided to the transfer position coincides with the timing at which the toner image formed on the image carrier 2 is transferred to the transfer position. .

However, even in this case,
In order to shorten the transfer time for transferring the toner image formed on the image carrier 2 onto the transfer material 1, as shown in FIG. 2, the rotating rollers 11 and 12 are rotated in opposite directions at a high speed to transfer the transfer belt. If 13 is moved back at a high speed and the transfer material 1 is quickly returned, the position of the returned transfer material 1 may be largely displaced. As described above, the timing setting for guiding the transfer material 1 to the transfer position may be performed. Even if a margin is provided, the timing at which the transfer material 1 is next guided to the transfer position does not coincide with the timing at which the toner image formed on the image carrier 2 is transferred to the transfer position. When toner images of different colors are repeatedly transferred from the carrier 2, the positions of the respective toner images transferred to the transfer material 1 may be displaced, resulting in color misregistration in the formed image. There was a problem.

Therefore, conventionally, as shown in FIG. 1, a position detecting sensor 15 for detecting the position of the transfer material 1 is provided before the transfer material 1 is guided to the transfer position by the transfer belt 13, and this position is provided. The timing at which the transfer material 1 is guided to the transfer position is measured by the detection sensor 15, and the timing at which the toner image formed on the image carrier 2 is guided to the transfer position and the timing at which the transfer material 1 is guided to the transfer position are measured. I was trying to synchronize.

However, even in such a transfer device,
In order to reduce the transfer time for transferring the toner image formed on the image carrier 2 onto the transfer material 1, the above-mentioned rotating roller 1
When the rotational speeds of 1 and 12 are increased and the transfer material 1 held on the transfer belt 13 is moved rapidly, the position of the transfer material 1 is detected by the position detection sensor 15 as described above,
Based on this, in order to synchronize the timing at which the transfer material 1 is guided to the transfer position and the timing at which the toner image formed on the image carrier 2 is guided to the transfer position, it is necessary to perform high-speed sampling processing. However, there is a problem in that the cost of the apparatus is high because such high speed processing is performed.

Further, when the transfer material 1 is rapidly moved in this way, an error also occurs in the detection of the position of the transfer material 1 by the position detection sensor 15, and as a result, the timing at which the transfer material 1 is guided to the transfer position is changed. When the toner images of the respective colors formed on the image carrier 2 do not coincide with the timing of being guided to the transfer position, and when toner images of different colors are repeatedly transferred from the image carrier 2 onto the transfer material 1 In addition, there is a problem in that the positions of the toner images transferred to the transfer material 1 are displaced, resulting in color misregistration in the formed image.

[0014]

SUMMARY OF THE INVENTION According to the present invention, while the transfer material is held on an endless transfer belt spanned between rotating rollers, the rotating roller is rotated to drive the transfer belt. The transfer medium held on the transfer belt is guided to a transfer position facing the image carrier to transfer the toner image from the image carrier onto the transfer material, thus causing various problems as described above. The problem is to solve.

That is, according to the present invention, in the above-mentioned transfer device, even if the transfer material held on the transfer belt is moved fast by increasing the rotation speed of the rotating roller, the transfer material is guided to the transfer position. The position of the transferred transfer material can be accurately detected, and the timing at which this transfer material is guided to the transfer position can be set to the transfer position of the toner image formed on the image carrier without the need for high-speed sampling processing as in the past. Can be easily and accurately synchronized with the timing at which the transfer material is guided to the image carrier, and the rotating roller is rotated in the forward and reverse directions to reciprocate the transfer material held on the transfer belt so that the transfer material faces the image carrier. When repeatedly transferring the toner images of the respective colors formed on the image bearing member onto the transfer material, the positions of the toner images of the respective colors superimposed on the transfer material are Is it, without that the color misregistration in the image to be formed or occur, it is an object to make it the image of a good full color is obtained.

[0016]

According to the present invention, in order to solve the above-mentioned problems, the rotating roller is held in a state where the transfer material is held on an endless transfer belt which is stretched between the rotating rollers. Is rotated to drive the transfer belt, guide the transfer material held on the transfer belt to a transfer position facing the image carrier, and transfer the toner image from the image carrier onto the transfer material. In the transfer device, a position detection sensor for detecting the position of the transfer material is provided before the transfer material is guided to the transfer position by the transfer belt, and the transfer belt is moved before the transfer material is detected by the position detection sensor. A speed control means for controlling the rotation speed of the driven rotating roller is provided.

In the transfer device according to the present invention, when the rotational speed of the rotary roller for driving the transfer belt is controlled by the speed control means, generally, the transfer material is guided to the position detection sensor by the transfer belt. This is detected by an appropriate detection means, and based on this, the rotation speed of the rotating roller is reduced to decrease the speed of the transfer material conveyed by the transfer belt before being guided to the position detection sensor. The position of the transfer material is detected by the position detection sensor in such a slowed state.

Here, when the rotating roller is rotated in the forward and reverse directions to reciprocate the transfer material held on the transfer belt, the rotation speed of the rotating roller for driving the transfer belt by the above speed control means is set. In the case of control, for example, as shown in FIG. 3A, the rotation speed of the rotating roller is slowed down until the transfer material conveyed by the transfer belt is detected by the position detection sensor. The speed of the transferred transfer material is slowed down, and after the position of the transfer material is detected by the position detection sensor, the rotation speed of the rotating roller is accelerated to a predetermined rotation speed, as shown in FIG. As described above, until the transfer material conveyed by the transfer belt approaches the position detected by the position detection sensor, the rotating roller is rotated at a predetermined rotation speed to move the transfer material quickly. Before the transfer material reaches the detection position by the position detection sensor, down the rotational speed of the rotating roller, to the transfer material is detected by the position detection sensor,
The rotation speed of the rotating roller is decreased to decrease the speed of the transfer material conveyed by the transfer belt, and after the position detection sensor detects the position of the transfer material, the rotation speed of the rotating roller is changed to a predetermined rotation speed again. Try to accelerate to.

Further, when the rotating roller is rotated in a fixed direction to convey and circulate the transfer material held on the transfer belt in the fixed direction, the rotation of the rotating roller for driving the transfer belt by the speed control means described above. When controlling the speed, as shown in FIG. 4, the rotating roller is rotated at a predetermined rotation speed until the transfer material conveyed by the transfer belt approaches the position detected by the position detection sensor, and the transfer material is moved to the position. Before reaching the detection position by the detection sensor, the rotation speed of the rotation roller is decreased and rotation of the rotation roller is performed until the transfer material is detected by the position detection sensor, as in the case shown in FIG. 3B. After the speed is slowed down to slow down the speed of the transfer material conveyed by the transfer belt, and the position of the transfer material is detected by the position detection sensor, The rolling speed so as to accelerate to a predetermined rotational speed.

However, it is not always necessary to control the rotational speed of the rotating roller by the speed control means as described above. For example, the rotating roller is rotated in the forward and reverse directions to transfer the transfer material held on the transfer belt. The rotational speed of the rotary roller may be controlled by this speed control means only when reciprocating.

[0021]

In the transfer device according to the present invention, while the transfer material is held on the endless transfer belt spanned between the rotating rollers, the rotating roller is rotated to drive the transfer belt. When the transfer material held on the belt is guided to the transfer position facing the image carrier, the rotation speed of the rotating roller is adjusted by the speed control means before the transfer material is guided to the position detection sensor by the transfer belt. Are trying to control.

In controlling the rotational speed of the rotary roller by the speed control means in this manner, the rotational speed of the rotary roller is controlled before the transfer material conveyed by the transfer belt is detected by the position detection sensor. By slowing down, the speed of the transfer material conveyed by the transfer belt is slowed down, and the position of the transfer material is detected by the detection sensor in such a slowed state.

By doing so, the position of the transfer material conveyed by the transfer belt and guided to the transfer position facing the image carrier can be accurately detected by the above position detection sensor, and the transfer can be performed as in the conventional case. In order to synchronize the timing when the material is guided to the transfer position and the timing when the toner image formed on the image carrier is guided to the transfer position, it is not necessary to perform high-speed sampling processing, and the transfer material is guided to the transfer position. It is possible to easily and accurately synchronize the timing at which the toner image formed on the image carrier is guided to the transfer position, and transfer the toner images of the respective colors formed on the image carrier onto the transfer material in an overlapping manner. In doing so, there is no chance of color misregistration.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the transfer device according to the present invention will be specifically described below with reference to the accompanying drawings.

Also in the transfer device according to this embodiment, as shown in FIG. 5, an endless transfer belt 13 is stretched between a pair of rotating rollers 11 and 12 provided at a required interval, and this transfer is performed. While the transfer paper (transfer material) 1 is held on the belt 13, the rotating rollers 11 and 12 are rotated to drive the transfer belt 13, and the transfer paper 1 held on the transfer belt 13 is carried as an image. The toner image formed on the image carrier 2 is guided to the transfer position facing the body 2 and transferred to the transfer device 1.
It is adapted to be transferred onto the transfer paper 1 via the sheet 4.

Here, as described above, the rotating rollers 11, 1
When rotating the roller 2, as shown in the figure, one rotating roller 11 located on the downstream side of the transfer paper 1 in the feeding direction at the time of transfer is rotated by the stepping motor 16.

Then, the above stepping motor 16
Is controlled by the main controller 17b in the electrophotographic apparatus or the like via the servo controller 17a, and the number of pulses generated by driving the stepping motor 16 is controlled by the main controller 17b via the servo controller 17a. I am trying to output.

Further, as described above, the rotary rollers 11, 12 are
Of the transfer paper 1 held on the transfer belt 13 by rotating the
In order to measure the timing at which the transfer paper 1 is guided to the transfer position facing the image carrier 2, the position detection sensor 15 for detecting the transfer paper 1 is located at the upstream position before the transfer paper 1 is guided to the transfer position.
The position detecting sensor 15 detects the leading end of the transfer paper 1 in the feeding direction, and determines the timing at which the transfer paper 1 is guided to the transfer position.

Here, in the transfer device according to this embodiment, the servo control device 17a is automatically operated by the main control device 17b according to the size of the transfer paper 1 and the number of copies.
The rotation of the stepping motor 16 is controlled via the stepping motor 16. The stepping motor 16 causes the rotating rollers 11 and 12 to rotate in a fixed direction to move the transfer belt 13 in a fixed direction. The transfer paper 1 held above is circulated, the transfer paper 1 is guided to the transfer position facing the image carrier 2 many times, and the toner images of the respective colors formed on the image carrier 2 are transferred by the transfer device 14. The first mode in which the transfer paper 1 is overlaid and transferred, and the rotating rollers 11 and 12 are moved forward by the stepping motor 16 described above.
The transfer belt 13 is reciprocated by rotating in opposite directions, and the reciprocating movement of the transfer belt 13 guides the transfer paper 1 to the transfer position facing the image carrier 2 many times, and each color formed on the image carrier 2 is moved. The toner image of
The mode is automatically switched to the second mode in which the image is transferred and superposed on the upper side.

In the transfer device of this embodiment, the rotary rollers 11 and 12 are rotated in both the forward and reverse directions to reciprocate the transfer belt 13 as described above, whereby the transfer belt 13 is held. In the second mode in which the transfer paper 1 is repeatedly guided to the transfer position facing the image carrier 2, the above-mentioned step is performed before the transfer material 1 conveyed by the transfer belt 13 is detected by the position detection sensor 16. The rotation speed of the rotating rollers 11 and 12 by the swing motor 16 is controlled by the main controller 17b.
Control is performed via the servo control device 17a, and the timing at which the transfer paper 1 held on the transfer belt 13 is guided to the transfer position facing the image carrier 2 and the toner image formed on the image carrier 2 Is synchronized with the timing at which is transferred to the transfer position.

Here, as described above, the rotating rollers 11, 1
2 is rotated in both the forward and reverse directions to reciprocally move the transfer belt 13, whereby the transfer paper 1 is repeatedly guided to the transfer position facing the image carrier 2 and the toner of each color formed on the image carrier 2. When the image is transferred onto the transfer paper 1 via the transfer device 14 in a superimposed manner, first, the stepping motor 16 causes the rotating rollers 11 and 12 to rotate in the forward direction to move the transfer belt 13 forward to transfer the image. After the paper 1 is guided to a transfer position facing the image carrier 2 and the first toner image is transferred from the image carrier 2 onto the transfer paper 1, as shown in FIG.
The transfer rollers 1 and 12 are rotated in the opposite directions to move the transfer belt 13 back, and the transfer paper 1 is returned.

Then, the transfer belt 13 is moved back in this way to return the transfer paper 1, and as shown in FIG. 7, the rear end of the transfer paper 1 in the returning direction (the front end in the feeding direction) is the position detecting sensor. When detected by the step 15, the stepping motor 16 decelerates the rotation speeds of the rotating rollers 11 and 12 to stop them, whereby the transfer paper 1 held on the transfer belt 13 is appropriately moved as shown in FIG. While stopping at the position, the number of pulses of the stepping motor 16 until the transfer paper 1 stops after the rear end in the return direction of the transfer paper 1 is detected by the position detection sensor 15 is controlled by the servo control device 17a. Output to the main controller 17b, and based on this, the approximate position where the transfer paper 1 is stopped is obtained, and the position where the transfer paper 1 is stopped and the position detection sensor 1 are detected.
Try to find the approximate distance between and 5.

Next, the rotating rollers 11 and 12 are again rotated in the forward direction to move the transfer belt 13 forward so that the transfer paper 1 is guided to a transfer position facing the image carrier 2 and the transfer paper 1 is transferred. The next toner image is transferred from the image carrier 2 to the top.

Here, in this embodiment, as shown in FIG. 8, the transfer belt 13 is based on the distance between the stop position of the transfer sheet 1 and the position detection sensor 15 obtained as described above. Until the front end of the transfer sheet 1 conveyed in the feeding direction is detected by the position detection sensor 15, as shown in FIG. 3A, the main control device 17b passes through the servo control device 17a. The rotation of the rotating rollers 11 and 12 by the stepping motor 16 is slowed down to slow down the transfer speed of the transfer paper 1 by the transfer belt 13, and the transfer direction front end of the transfer paper 1 is detected at the above-mentioned position when the transfer speed is slow. Detected by the sensor 15, then
The rotating roller 1 is driven by the stepping motor 16 described above.
The rotational speeds of 1 and 12 are accelerated to a predetermined speed so that the timing at which the transfer sheet 1 is guided to the transfer position and the timing at which the next toner image formed on the image carrier 2 is guided to the transfer position are synchronized. I have to.

In this way, the transfer paper 1 is guided to the transfer position facing the image carrier 2 and the next toner image formed on the image carrier 2 is transferred onto the transfer paper 1 via the transfer device 14. After that, the above-described operation is repeated to transfer the toner images of the respective colors formed on the image carrier 2 on the transfer paper 1 in order.

In this embodiment, when the transfer paper 1 on which the toner image has been transferred and returned is guided to the transfer position facing the image carrier 2 again, the front end of the transfer paper 1 in the feeding direction is detected. The rotation of the rotating rollers 11 and 12 is delayed until the transfer belt 13 is detected by the sensor 15.
Although the transfer speed of the transfer paper 1 is slowed down and the leading edge of the transfer paper 1 in the feed direction is detected by the position detection sensor 15 when the transfer speed is slow, the stop position of the transfer paper 1 and the position detection sensor 15 are If the distance is long, transfer paper 1
In order to shorten the transfer time by shortening the time until the front end of the feeding direction of the sheet is detected by the position detection sensor 15, as shown in FIG.
It is preferable to control the rotation speed.

That is, when the distance between the stop position of the transfer paper 1 and the position detection sensor 15 is long, when the transfer paper 1 is again guided to the transfer position facing the image carrier 2, the transfer obtained previously is transferred. Based on the distance between the stop position of the paper 1 and the position detection sensor 15, the rotating rollers 11, 12 are rotated at a predetermined rotation speed until the leading end of the transfer paper 1 in the feeding direction approaches the position detected by the position detection sensor 15. The transfer speed of the transfer paper 1 by the transfer belt 13 is increased by rotating the transfer belt 13 at a position immediately before the leading end of the transfer paper 1 in the feeding direction reaches the detection position of the position detection sensor 15.
By means of the servo control device 17a, the rotation speed of the rotating rollers 11 and 12 by the stepping motor 16 is reduced to slow down the transfer speed of the transfer paper 1 by the transfer belt 13, and the transfer paper 1 is fed in the low transfer speed. The leading edge in the direction is detected by the position detection sensor 15, and thereafter, similarly to the above case, the stepping motor 16 accelerates the rotational speed of the rotary rollers 11, 12 to a predetermined speed, and the transfer paper 1 is guided to the transfer position. Timing and image carrier 2
The timing at which the next toner image formed in 1 is guided to the transfer position is synchronized.

Further, in this embodiment, the transfer rollers 13 and 12 are rotated in both the forward and reverse directions to reciprocate the transfer belt 13 as described above, whereby the transfer belt 13 is held on the transfer belt 13. Only when the paper 1 is guided to the transfer position facing the image carrier 2 many times, the above control is performed so that the leading end of the transfer paper 1 in the feeding direction is detected by the position detection sensor 15 in a state where the transfer speed is slow. However, the rotating rollers 11 and 12 are rotated in a fixed direction to circulate the transfer paper 1 held on the transfer belt 13, and the transfer paper 1 is repeatedly moved to a transfer position facing the image carrier 2. Even in the case of guiding, it is possible to control the rotation speeds of the rotation rollers 11 and 12 as shown in FIG. Can .

Next, a case where the above-mentioned transfer device is mounted on the full-color copying machine A as shown in FIG. 10 to form a full-color image on the transfer paper 1 will be specifically described.

Here, the full-color copying machine A shown in FIG.
In FIG. 1, an endless belt photosensitive member 2 having a photosensitive layer formed on the outer peripheral surface is used as the image bearing member 2, and the belt photosensitive member 2 is provided with a photosensitive member driving roller 32 having a rotation detection sensor 31 and others. The belt photosensitive member 2 is wound around the two rotating rollers 33 and 34, and the belt photosensitive member 2 is moved in the direction of arrow a based on the rotation of the photosensitive member driving roller 32.

Further, as described above, the photoconductor driving roller 32 is
A charging charger 3 for charging the belt photosensitive member 2 around the belt photosensitive member 2 wound around the other two rotating rollers 33, 34, and yellow, magenta, cyan, black for the belt photosensitive member 2. Developing device 4 provided with four developing devices 4a, 4b, 4c, 4d for individually supplying the developer of each color, and the toner image remains on the belt photoconductor 2 after being transferred to the transfer paper 1. A cleaning device 5 for removing toner and an eraser lamp 6 for irradiating the belt photosensitive member 2 after cleaning with light to eliminate residual potential on the belt photosensitive member 2 are arranged. In addition,
Each of the developing devices 4a to 4d described above includes the belt photosensitive member 2
It is possible to switch between a developing state in which the development is performed and a non-development state in which the development is not performed.

Further, in this full-color copying machine A, in order to read a document to be copied, a document illumination lamp 53 is provided below a document table glass 52 covered by an upper cover 51, and the document illumination lamp 53 is provided. While moving in the direction of arrow b, the original illumination lamp 53 irradiates light on an original (not shown) placed on the original table glass 52, and the light reflected by the original is reflected by the mirror system 54 and the lens system 55.
It is guided to the CCD licensor 56 via the, and is read as color signals of the three primary colors in this CCD licensor 56.

Then, the color signals of the three primary colors read by the CCD licensor 56 are output to the image processing circuit 57, and in the image processing circuit 57, the four developing devices 4 are connected.
After being converted into four-value signals of yellow, magenta, cyan, and black, which are the colors of the developers accommodated in a to 4d, the signals thus converted are transferred from the image processing circuit 57 to below the belt photoreceptor 2. The laser beam is output to the laser emitting device 58 provided.

Further, in the laser emitting device 58, the laser beam is emitted from the charging charger 3 and the developing device on the basis of the four-valued signals of yellow, magenta, cyan and black output from the image processing circuit 57 as described above. The belt photosensitive member 2 charged by the charging charger 3 is irradiated with the laser beam from the position 4 to the laser beam. First, the laser beam corresponding to the yellow image, then the laser beam corresponding to the magenta image, The belt photoconductor 2 is irradiated with laser light corresponding to a cyan image and finally laser light corresponding to a black image at appropriate timings, and the belt photoconductor 2 is subjected to yellow, magenta, cyan, and black images. The electrostatic latent images corresponding to are sequentially formed.

Then, in this way, yellow, magenta,
For each latent image formed on the belt photosensitive member 2 corresponding to the cyan and black images, the developing device 4 described above is then used.
The developer of each color is supplied from each of the developing devices 4a to 4d in FIG. 1 to form a toner image of each color on the belt photoreceptor 2.

Further, in this full-color copying machine A, when the transfer device of the above-mentioned embodiment is provided, the transfer belt 13 is placed at the position of the above-mentioned photosensitive member driving roller 32.
Of the pair of rotating rollers 11 and 12 provided in the vertical direction with a required space therebetween so as to be close to the belt photosensitive member 2.
Although not shown, the transfer belt 13 is spanned between the rotating roller 11 and the stepping motor 16 so that the rotating roller 11 provided above is rotated. A tension roller 18 is provided on the circumferential side, and the tension roller 1
8, the tension of the transfer belt 13 is adjusted.

When the transfer paper 1 is supplied to the transfer belt 13, the transfer paper 1 of an appropriate size is supplied from each paper supply unit 60 provided at the bottom of the full-color copying machine A, and the transfer paper 1 is transferred. The paper 1 is supplied to the transfer belt 13 by a timing roller 61 in synchronism with the toner image formed on the belt photoconductor 2.

In order to hold the transfer paper 1 thus supplied to the transfer belt 13 on the transfer belt 13, the transfer belt 13 is cleaned by a belt cleaner 19 provided near the lower rotating roller 12. rear,
The transfer belt 13 is charged by the transfer belt charging charger 20 provided below the rotating roller 12, and the transfer paper 1 is charged on the transfer belt 13 thus charged.
Are attracted to the rotary roller 12 in this state.
Is guided between a pair of assist rollers 21 provided above the transfer roller 13, and the transfer belt 13 to which the transfer paper 1 is adsorbed is pinched between the assist rollers 21, and thereby the transfer paper 1 is more securely held on the transfer belt 13. I am trying to let you.

Further, in order to transfer the toner image formed on the belt photosensitive member 2 onto the transfer paper 1 held on the transfer belt 13 in this way, at a position facing the above-mentioned photosensitive member driving roller 32, The transfer roller 14 is provided on the inner peripheral side of the transfer belt 13 as the transfer device 14, and the transfer roller 14 is a roller 3 for driving the photoconductor.
It is provided so that it can move forward and backward toward 2.

When the toner image formed on the belt photosensitive member 2 is transferred onto the transfer paper 1, the transfer roller 14 is moved to the photosensitive member driving roller 32 side and held on the transfer belt 13. The transferred transfer paper 1 is brought into contact with the belt photosensitive member 2, while after transfer, the transfer roller 14 is moved in a direction away from the photosensitive member driving roller 32, and such an operation is repeated, and the belt is transferred. The toner images of the respective colors formed on the photoconductor 2 are sequentially superposed and transferred on the transfer paper 1.

Here, in transferring the toner images of the respective colors formed on the belt photoconductor 2 to the transfer paper 1 held on the transfer belt 13 as described above, the belt photoconductor 2
Of the transfer paper 1 held on the transfer belt 13 and the transfer speed of the transfer paper 1 held on the transfer belt 13 are the same, and the toner image formed on the belt photoreceptor 2 and the transfer paper 1 held on the transfer belt 13 are the same.
In this full-color copying machine A, the position detection sensor 15 for detecting the position of the transfer paper 1 is provided below the transfer roller 14 on the inner peripheral side of the transfer belt 13 in order to determine the timing at which and are guided to the transfer position. It is provided at the position.
Here, in the full-color copying machine A, the position detection sensor 1 provided on the inner peripheral side of the transfer belt 13 as described above.
In order to detect the position of the transfer paper 1 by means of 5, the transfer belt 13 is provided with a hole or the like for detecting the position of the transfer paper 1, and is held on the transfer belt 13 and guided to the transfer position. The leading end of the transfer sheet 1 in the feeding direction is detected by the position detection sensor 15 through the hole of the transfer belt 13 or the like. The method for detecting the position of the transfer paper 1 is not limited to the above-described method. For example, when the transfer paper 1 is always held at a predetermined position on the transfer belt 13, Alternatively, a pattern for position detection may be provided at a predetermined position on the transfer belt 13, and the position of the transfer paper 1 may be estimated by detecting the pattern for position detection.

Further, in order to separate the transfer paper 1 on which the toner images of the respective colors have been transferred in the above-described manner from the transfer belt 13, an antistatic charger 25 and a separation claw 26 are provided in the vicinity of the upper rotary roller 11. The charge removing charger 25 charges the transfer belt 13 charged as described above to facilitate the separation of the transfer paper 1 from the transfer belt 13, and the separation claw 26 allows the transfer paper 1 to be separated.
Is separated from the transfer belt 13.

Further, a fixing device 7 is provided above the separating claw 26, and the toner image on the transfer paper 1 separated from the transfer belt 13 by the fixing device 7 is fixed on the transfer paper 1 in this way. The transfer paper 1 on which is fixed is discharged onto a discharge tray 8 by a discharge roller 9.

Next, the operation of forming a full-color image on the transfer paper 1 by the full-color copying machine A will be specifically described.

First, the original to be copied is placed on the original table glass 52, the open / close cover 51 is covered on the original, and a print switch (not shown) is turned on.

As a result, the document illumination lamp 53 illuminates the document while moving in the direction of arrow b. Then, the light emitted from the document illumination lamp 53 and reflected by the document is transferred to the CCD via the mirror system 54 and the lens system 55.
It is guided to the licensor 56 and read as color signals of the three primary colors by the CCD licensor 56. Then, the color signals of the three primary colors read by the CCD licensor 56 are converted into four-value signals of yellow, magenta, cyan, and black in the image processing circuit 57, and output to the laser emitting device 58.

On the other hand, in the above belt photoreceptor 2,
At the position where the belt photosensitive member 2 moves in the direction of arrow a as the photosensitive member driving roller 32 rotates and faces the charging charger 3, a charge of a predetermined potential is applied from the charging charger 3 to the belt photosensitive member 2. It is applied and charged.

Then, as described above, the laser emitting device 5 is applied to the belt photoreceptor 2 which is charged and moves.
At an appropriate timing from 8, the laser light corresponding to the yellow image, the laser light corresponding to the magenta image, the laser light corresponding to the cyan image,
Finally, a laser beam corresponding to a black image is sequentially irradiated, and the charged belt photosensitive member 2 receives yellow, magenta,
Electrostatic latent images corresponding to cyan and black images are sequentially formed at appropriate timings.

Here, in irradiating the belt photoconductor 2 that is charged and moves as described above with laser light from the laser emitting device 58 at an appropriate timing, the photoconductor drive for moving the belt photoconductor 2 is driven. A pulse signal is generated each time the roller 32 makes one rotation, and the rotation detection sensor 31 detects the movement of the belt photosensitive member 2 based on this pulse signal, whereby the laser emitting device 58 produces an image of each color. The belt photosensitive member 2 is irradiated with the corresponding laser light at an appropriate timing.

Then, for each electrostatic latent image corresponding to the yellow, magenta, cyan, and black images formed on the belt photosensitive member 2 in sequence at appropriate timing as described above, the above-described developing device is used. At positions 4, the developers of the corresponding colors are supplied from the developing devices 4a to 4d containing the developers of the corresponding colors, and the toner images of the respective colors are sequentially formed on the belt photoconductor 2.

On the other hand, in the transfer device of this embodiment for transferring the toner images of the respective colors sequentially formed on the belt photosensitive member 2 on the transfer paper 1 in this manner, the stepping motor 16 rotates the upper direction. The roller 11 rotates in the forward direction to guide the transfer paper 1 to the transfer position, and the transfer belt 13 moves in the direction of arrow c accordingly. After the surface of the transfer belt 13 is cleaned by the belt cleaner 19, the transfer belt charging charger 20 charges the transfer belt 13 to a predetermined potential.

Next, the transfer belt 1 thus charged.
3, the transfer paper 1 fed from the appropriate paper feed unit 60 is supplied at an appropriate timing by the timing roller 61, and the transfer paper 1 is electrostatically adsorbed on the charged transfer belt 13, and in this state. The transfer paper 1 moves with the transfer belt 13 and is guided between the assist rollers 21, and the assist roller 21 securely holds the transfer paper 1 on the transfer belt 13.

The transfer sheet 1 thus held on the transfer belt 13 is moved by the arrow c as the transfer belt 13 moves.
When the front end of the transfer paper 1 in the feeding direction is detected by the position detection sensor 16 provided below the transfer roller 14, the transfer roller 14 moves to the photosensitive member driving roller 32 side. The transfer belt 13 comes into contact with the belt photosensitive member 2, and in this state, the transfer paper 1 held on the transfer belt 13 is guided to a transfer position facing the belt photosensitive member 2 and transferred via the transfer roller 14. First, the yellow toner image formed on the belt photoreceptor 2 is transferred onto the paper 1.

Further, after the yellow toner image is transferred in this manner, the trailing edge of the transfer paper 1 is placed between the transfer roller 14 and the photosensitive member driving roller 32 depending on the number of pulses from the stepping motor 16. When it is detected that the transfer belt 14 has passed through, the transfer roller 14 moves in the direction away from the photoconductor driving roller 32, the transfer belt 13 separates from the belt photoconductor 2, and The pair of assist rollers 21 are also separated from each other.

After that, the main control unit 17 of the full-color copying machine A automatically controls the rotation of the stepping motor 16 via the servo control unit 16 according to the size of the transfer paper 1 and the number of copies as described above. Controlled,
By rotating the rotating rollers 11 and 12 in the above-mentioned fixed direction,
The first mode in which the transfer paper 1 is conveyed in the direction of the arrow c as the transfer belt 13 moves,
Either of the second mode in which the transfer paper 1 is rotated in the opposite directions to reciprocate in the directions c and c'with the transfer belt 13 is automatically selected.

When the above-mentioned first mode is selected, the transfer belt 13 subsequently moves in the direction of arrow c, and the transfer paper 1 on which the yellow toner image has been transferred is circulated and the belt photosensitive member 2 is circulated. Is guided near the transfer position opposite
After that, in the same manner as described above, the next magenta toner image formed on the belt photosensitive member 2 is transferred onto the transfer paper 1 onto which the yellow toner image has been transferred via the transfer roller 14 in an overlapping manner. Further, in the same manner, the cyan toner image and the black toner image formed on the belt photosensitive member 2 are sequentially transferred and superposed on the transfer paper 1.

On the other hand, when the second mode is selected, the yellow toner image is transferred as described above, and the rear end of the transfer paper 1 is transferred to the transfer roller 14 and the photosensitive member driving roller 3.
When it is detected that the number of pulses has passed between the stepping motor 16 and the stepping motor 16, the rotation of the stepping motor 16 is stopped, the transfer belt 13 is temporarily stopped, and then the stepping motor 16 is used. The rotating rollers 11 and 12 rotate in opposite directions at high speed,
The transfer belt 13 is moved at a moving speed faster than the direction of the arrow c.
Moves in the direction of arrow c ′, and the transfer paper 1 is quickly returned.

When the transfer paper 1 is returned in this way and the rear end of the transfer paper 1 in the return direction (front end in the feed direction) is detected by the position detection sensor 15, the stepping motor 16 is operated as described above. The rotating rollers 11, 12
Then, the transfer paper 1 is decelerated and stopped, the transfer paper 1 is stopped at an appropriate position, and an approximate distance between the position of the transfer paper 1 stopped in this way and the position detection sensor 15 is obtained.

Next, the rotating roller 1 stopped in this way
The rotating rollers 11 and 12 rotate at a slow speed until the stepping motor 16 starts to rotate in the positive direction and the leading end of the transfer sheet 1 in the feeding direction is detected by the position detection sensor 15 as described above. When the transfer belt 13 conveys the transfer paper 1 at a slow speed, the leading end of the transfer paper 1 in the feeding direction is detected by the position detection sensor 15 and thereafter the stepping motor 16 causes the rotation rollers 11, 12 to rotate. The transfer paper 1 is guided to the transfer position in synchronization with the timing when the rotation speed is accelerated to a predetermined speed and the next magenta toner image formed on the belt photosensitive member 2 is guided to the transfer position. The magenta toner image is superposedly transferred onto the paper 1 via the transfer roller 14, and thereafter, the above operation is repeated to repeat the operation of the belt. The cyan toner image formed on the optical body 2, a black toner image is to be transferred superimposed on the transfer sheet 1 in turn.

In this way, the position of the transfer paper 1 conveyed by the transfer belt 13 is set to the position detection sensor 1 described above.
5, the transfer paper 1 is accurately guided to the transfer position in synchronization with the timing when the toner images of the respective colors formed on the belt photosensitive member 2 are guided to the transfer position.
The toner image of each color formed on the belt photoconductor 2 is transferred onto the transfer paper 1.
It will be accurately superimposed and transferred to the appropriate position above,
Even when the toner images of the respective colors are transferred onto the transfer paper 1 in a superimposed manner, the color shift does not occur.

Then, as described above, the first mode or the second mode
After the toner images of all colors have been transferred to the transfer paper 1 by the mode, the transfer belt 13 charged by the charge removing charger 25 provided in the vicinity of the upper rotating roller 11 is discharged, The transfer paper 1 is easily separated from the transfer belt 13, and then the transfer paper 1 is separated from the transfer belt 13 by the separating claw 26.
The transfer paper 1 thus separated is guided to the upper fixing device 7, and the toner images transferred and superposed on the transfer paper 1 are fixed in the fixing device 7, and then the transfer paper 1 is discharged. The rollers 9 discharge the paper to the paper discharge tray 8.

When a full-color image is formed on the transfer paper 1 in this way, when the toner images of the respective colors are transferred from the belt photosensitive member 2 onto the transfer paper 1 in a superimposed manner, the position of the transferred toner image is displaced. A good full-color image was obtained without causing color misregistration.

[0073]

As described above in detail, in the transfer device according to the present invention, the rotating roller is rotated while the transfer material is held on the endless transfer belt that is stretched between the rotating rollers. Drive the transfer belt, and before the transfer material held on the transfer belt is guided to the transfer position facing the image carrier, the position of the transfer material is detected by the position detection sensor and is conveyed by the transfer belt. Before the transfer material to be detected is detected by the position detection sensor, the rotation speed of the rotating roller is slowed down by the speed control means to slow down the speed of the transfer material transported by the transfer belt. Since the position detection sensor detects the position of the transfer material when the transfer speed is slow, the position detection sensor detects the transfer material conveyed at a high speed. Compared with the conventional one, the position of the transfer material conveyed by the transfer belt can be detected more accurately, and the timing at which the transfer material is guided to the transfer position is determined by the transfer of the toner image formed on the image carrier. It is now possible to easily and accurately synchronize with the timing of being guided to a position.

As a result, in the transfer device according to the present invention, when the position of the transfer material is detected by the position detection sensor, it is not necessary to perform high-speed sampling processing as in the conventional case, and the cost required for the device is low. There is no difference between the timing when the transfer material is guided to the transfer position and the timing when the toner image formed on the image carrier is guided to the transfer position, and the toner image of each color formed on the image carrier is not deviated. Is transferred to an appropriate position on the transfer material, and a good full-color image can be obtained without causing color misregistration.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a conventional transfer device configured to transfer a transfer material, which is held on a transfer belt spanning between a pair of rotating rollers, to transfer a toner image from an image carrier. is there.

FIG. 2 is a diagram showing a change in rotation speed of a rotating roller when a transfer material held on a transfer belt is reciprocated to transfer a toner image from an image carrier in a conventional transfer device.

FIG. 3 is a diagram showing a state in which, in the transfer device of the present invention, when the transfer material held on the transfer belt is reciprocated, the rotation speed of a rotating roller that drives the transfer belt is controlled by a speed control unit. .

FIG. 4 is a diagram showing a state in which the rotation speed of a rotating roller that drives the transfer belt is controlled by a speed control unit when the transfer material held on the transfer belt is circulated in the transfer device of the present invention.

FIG. 5 is a schematic explanatory view showing a configuration of a transfer device according to an embodiment of the present invention.

FIG. 6 shows a transfer device according to an embodiment of the present invention,
FIG. 6 is a schematic diagram showing a state in which the transfer belt is moved back and the transfer material after transfer is returned.

FIG. 7 shows a transfer device according to an embodiment of the present invention,
FIG. 6 is a schematic diagram showing a state in which the position detection sensor detects the trailing end of the transfer material that is returned by the return movement of the transfer belt.

FIG. 8 shows a transfer device according to an embodiment of the present invention.
FIG. 6 is a schematic view showing a state in which the transfer material returned by the backward movement of the transfer belt is separated from the position detection sensor and stopped.

FIG. 9 shows a transfer device according to an embodiment of the present invention.
FIG. 6 is a schematic diagram showing a state in which a transfer belt is moved forward to convey a transfer material, and a front end of the transfer material in a feeding direction is detected by a position detection sensor.

FIG. 10 is a schematic explanatory view showing a state of a full-color copying machine equipped with a transfer device according to an embodiment of the present invention.

[Explanation of symbols]

 1 Transfer Material (Transfer Paper) 2 Image Carrier (Belt Photosensitive Member) 11, 12 Rotating Roller 13 Transfer Belt 14 Transfer Device (Transfer Roller) 15 Position Detection Sensor 16 Stepping Motor 17a Servo Control Device 17b Main Control Device 20 Transfer Belt Charger 21 for assist roller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshihisa Terasaka 2-3-13 Azuchi-cho, Chuo-ku, Osaka Osaka International Building Minolta Camera Co., Ltd. (72) Masami Yamada 2-chome, Azuchi-cho, Chuo-ku, Osaka 3-13 No. 13 Osaka International Building Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A transfer belt is driven by rotating the rotary roller while holding the transfer material on the endless transfer belt spanned between the rotary rollers, and the transfer held on the transfer belt. In a transfer device that guides a material to a transfer position facing the image carrier to transfer a toner image from the image carrier onto the transfer material, the transfer belt is configured to transfer the toner image to the transfer position before the transfer material is guided to the transfer position. A position detection sensor for detecting the position of the transfer material is provided, and speed control means for controlling the rotation speed of the rotating roller that drives the transfer belt before the transfer material is detected by the position detection sensor is provided. A transfer device characterized by the above.