JP3193735B2 - Conveyor for color image forming equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus having a registration roller and a transfer unit.

[0002]

2. Description of the Related Art In a conventional multi-color image forming apparatus such as a color copying machine, a transfer material fed from a paper feeding section, passes through a transfer section and a fixing section in order, and is transferred to the outside of the machine. In order to discharge the transfer material, a transfer device that transfers the transfer material along the series of transfer paths is provided. The transport device includes a plurality of transport members adjacent to each other along the transport path, for example, a paper feed roller of a paper feed member, a registration roller, a transfer transport belt, a fixing roller, a paper discharge roller, and the like. . In this case, in particular, if there is a `` speed difference '' in the transport speed of transporting the transfer material between the registration roller and the transfer transport belt, image blur or rubbing occurs, which deteriorates image quality. In addition, uneven color tone and color misregistration occur, and the color image quality is remarkably deteriorated.

Generally, the motors for driving the transfer belt and the registration roller of the transfer unit are controlled by PLL control or the like. However, uneven rotation caused by the drive transmission system, the transfer unit transfer belt drive roller and the registration A transport speed difference occurs due to a speed difference or the like due to a diameter error with the roller.

In consideration of such a problem, a method of providing a surface speed detecting means of the transfer belt and controlling a drive motor by a signal of the detecting means is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-242.
Although disclosed in Japanese Patent Application Publication No. 964, however, a speed difference is unavoidable due to the rotation accuracy of the motor and the accuracy of the registration roller diameter. Therefore, in order to prevent such a linear velocity difference, a means for providing an adsorption charger upstream of the transfer portion of the transfer belt, adsorbing the transfer material to the transfer belt in advance, and conveying the transfer material at the same speed as the transfer belt is also available. It has been devised.

Here, as a specific example, an example of a conventional transport device of a color image forming apparatus will be described with reference to FIG.
First, the overall configuration of the color image forming apparatus will be described. The apparatus includes a scanner unit 1 for reading a document, an image processing unit 2 for electrically processing an image signal output as a digital signal from the scanner unit 1, and an image recording unit for each color from the image processing unit 2. It is roughly divided into a printer unit 3 that forms an image on a transfer material based on information. In the scanner section 1, a document (not shown) is placed on a document table 4, and reflected light from the document when illuminated by a fluorescent lamp 5 thereunder is sequentially reflected by mirrors 6, 7, and 8. And the dichroic prism 1
It is imaged at 0. Thus, for each wavelength, for example, R
(Red) to the receiver 11R, G (green) to the receiver 11G,
B (blue) is respectively incident on the light receiver 11B. In addition,
These light receivers are composed of CCDs. The light incident on each of these light receivers is converted into a digital signal and output, and the output is subjected to necessary electrical processing in the image processing unit 2, and then the recording color signal of each color, Bk (black), Y (Yellow), M (magenta), and C (cyan) are converted into recording signals of respective colors. The signal from the image processing unit 2 is input to the printer unit 3 and sent to the laser light output devices 12Bk, 12C, 12M, and 12Y for the respective colors.

In the printer unit 3, the signals output from the laser light output devices 12Bk, 12C, 12M, and 12Y, that is, the laser beams are respectively recorded by the recording device 13B.
k, 13C, 13M, and 13Y. Here, the recording device 13Y is provided with a photosensitive drum 14Y to which the emitted laser beam is irradiated.
A charging charger 15 is provided around the photosensitive drum 14Y.
Y, a developing device 16Y, a transfer charger 17Y, and the like are provided. The photosensitive drum 14Y uniformly charged by the charging charger 15Y is connected to the laser light output device 1
After the latent image of the cyan light image is formed by the laser beam from 2Y, the latent image is developed by the developing device 16Y to form a visible image. In addition, similarly to the recording device 13Y, various devices are provided for the other recording devices 13Bk, 13C, and 13M to perform the same processing, but the description is omitted here.
The same reference numerals are given to the same names.

[0007] Copy paper as a transfer material supplied from a paper feed cassette 19 as a paper feed unit disposed corresponding to each of the two paper feed rollers 18 is fed by a pair of registration rollers 20 to the leading end thereof. The sheets are fed onto a transfer belt 21 as a transfer section conveying device at a timing when the sections are uniformly aligned. The copy paper conveyed onto the transfer belt 21 is a photosensitive drum 14Bk on which a visible image is formed, respectively.
The images are sequentially sent to 14C, 14M, and 14Y, and a visual image is transferred under the action of the transfer chargers 17Bk, 17C, 17M, and 17Y. Thereafter, the transferred copy sheet is fixed by a pair of fixing rollers 22 and discharged from a pair of discharge rollers 23. The conveyed copy paper is conveyed with high precision at the speed of the transfer belt 21 by being electrostatically attracted onto the transfer belt 21.

In this case, in the printer section 3, members adjacent to the conveyance path from the paper feed roller 18 in contact with the paper feed cassette 19 to the paper discharge roller 23, for example, a registration roller 20, a transfer belt 21, a photosensitive drum 14Bk, 14
C, 14M, 14Y, transfer charger 17Bk, 17
The conveying device is constituted by members such as C, 17M, 17Y, and the fixing roller 22.

[0009]

In the above-described conventional conveying apparatus, the transfer voltage is required to transfer the image on the latent image carrier in order to charge the transfer material (copy paper described above) in advance. It is necessary to increase the transfer voltage, especially when transferring a plurality of times as in the case of a color image, and it is necessary to increase the transfer voltage each time. Further, since the attraction force for attracting the transfer material to the transfer belt by charging is proportional to the contact area, the nipping and conveying force of the registration roller 18 is larger than the attraction force at the leading end of the transfer material, and the transfer material speed is reduced. It depends on the transport speed of the paper feeding unit. In particular, when the paper thickness is large, the paper has a strong stiffness, and thus tends to depend on the transport speed of the paper feeding unit. To prevent this, the distance from the adsorption charger to the transfer unit may be increased, but there is a problem that the machine itself becomes large.

Further, the registration roller 20 and the transfer belt 2
If there is a “linear velocity difference” with the transfer device 1 (transfer unit transport device),
The following problems occur. That is, when the registration linear velocity> the transfer linear velocity, the transfer material sags between the registration roller 20 and the transfer portion. In particular, when the transfer material has a weak stiffness, a displacement occurs at the transfer portion. And
As a result, transfer blur occurs, or the state of close contact between the photosensitive drum and the transfer material becomes unstable, resulting in transfer omission. When the registration linear velocity is smaller than the transfer linear velocity, slippage occurs between the transfer device and the transfer material due to the clamping force of the registration roller 20 , or the running state of the transfer device becomes unstable. This causes a problem that color misregistration occurs in multicolor superposition. Further, the various inconveniences described above are more likely to occur because the larger the transfer material size (length in the feeding direction), the larger the amount of slack or the amount of tension.

[0011]

According to the first aspect of the present invention, a registration roller for transferring a transfer material to an image transfer unit at a predetermined timing, and a transfer material for transferring the transfer material at the image transfer unit.
A transfer unit transporting device provided with a transfer belt , wherein the transfer roller transports a plurality of color images onto the transfer material in an overlapping manner. A linear speed switching means for switching the linear speed of the transfer from the first linear speed equal to the linear speed of the transfer unit transport device to a second linear speed lower than the linear speed of the transfer unit transport device.

[0012]

According to a second aspect of the present invention, in the first aspect of the invention, the linear speed of the registration roller is switched according to the size of the transfer material.

According to a third aspect of the present invention, in the first aspect of the invention, the linear speed of the registration roller is switched based on a detection result of a registration sensor after a lapse of a predetermined time from the start of the transport operation.

According to a fourth aspect of the present invention, in the first aspect of the invention, the first linear velocity and the second linear velocity of the registration roller can be set to predetermined values.

[0016]

According to the first aspect of the present invention, the transfer of the transfer material is performed.
Between the entrance of the transfer unit and the state where the transfer belt is weakly attracted
Is good because there is no load due to the registration roller clamping force
Transfer condition is obtained, and the effect of subtle linear velocity
Transfer near the trailing edge of the transfer material
Stable running and transfer state due to sufficient suction force of belt
It is possible to obtain a state.

[0017]

According to the second aspect of the present invention, since the registration roller linear speed is switched in accordance with the size of the transfer material, the optimum switching timing can be set for each size of the transfer material. It is possible to prevent an unnecessary load from being applied from the registration roller.

According to the third aspect of the present invention, since the linear speed of the registration roller is switched in accordance with the detection result of the registration sensor, when the size of the transfer material is unknown such as when manual feeding is used. However, the linear speed of the registration roller can be switched.

According to the fourth aspect of the present invention, the first linear velocity and the second linear velocity can be set to predetermined arbitrary values, respectively. It is possible to respond according to the speed difference
As a result, it is possible to obtain an optimum conveyance state, and thus a good image can be obtained.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. Since the outline of the overall configuration of the color image forming apparatus has been described with reference to FIG. 6 described above, the description is omitted here, and the same parts are denoted by the same reference numerals.

First, in the transfer device of the color image forming apparatus, the basic configuration of the pulse motor drive circuit for driving the registration roller 20 and the transfer belt 21 as the transfer portion transfer device and the basic operation will be described with reference to FIGS. A description will be given based on FIG. The pulse motor drive circuit includes a pulse motor driver 24 and a pulse motor 25 as shown in FIG.
It is composed of The pulse motor driver 2
4 comprises a distribution circuit 26 and a driver 27.
The distribution circuit 26 receives a drive clock signal a, a rotation direction signal b, and an on / off signal c from a control unit (not shown). The distribution circuit 26 generates four-phase drive signals 28 to 31 synchronized with the drive clock signal a as shown in FIG.
, The registration roller 20 and the transfer belt 21 can be rotated in a predetermined direction.

Next, the configuration of the pulse motor drive circuit according to the present invention based on the above-described basic configuration will be described with reference to FIGS. Here, a counter 32 as a linear speed switching means for switching the linear speed of the registration roller 20 from the first linear speed to the second linear speed during the transfer operation of one transfer material.
Are provided before the distribution circuit 26.

In this case, the first linear speed of the registration roller 20 is set equal to the linear speed of the transfer belt 21, and the second linear speed of the registration roller 20 is set lower than the linear speed of the transfer belt 21. Switching of the linear speed of the registration roller 20 is performed according to the size of the transfer material.

In such a configuration, the counter 32 receives a count setting signal d and a reset signal e in addition to the drive clock signal a. That is, when the driving clock signal a is input to the counter 32, the frequency is divided according to the count value set by the count setting signal d, and the divided clock signal f is divided by the distribution circuit 26.
Is input to In this case, the drive clock signal a is set to a frequency sufficiently higher than the input clock of the pulse motor 25. For example, in the relationship between the driving clock signal a and the clock signal f as shown in FIG.
The input clock to the distribution circuit 26 is H every 100 pulses
i and Lo are repeated. When the pulse motor 25 rotates in this state, the linear speed of the registration roller is set to be equal to the linear speed of the transport speed.

If the set value of the counter 32 is changed to 102 during the operation in this state, that is, during the transfer of the transfer material, the input clock to the distribution circuit 26 is changed every 102 pulses of the drive clock signal a from that point. Hi and Lo are repeated. As a result, the number of rotations of the pulse motor 25 is reduced by 2%, and the linear velocity of the registration roller <the linear velocity of the conveying speed is satisfied. As described above, the set value of the counter 32 is set by a method such as being stored in advance by a digital SW on a board (not shown) or an input from an operation panel, and the set value is changed during operation. become.

In addition, as described above, the problem due to the speed difference between the linear speed of the registration roller and the linear speed of the conveying device is more likely to occur for large-size paper. For this reason, if it is determined from the signal from the paper size detecting unit (not shown) provided in the paper feed cassette 19 that the registration linear speed is to be switched according to the transfer material size, the registration linear speed switching is performed only in the case of the large size, or
By setting the switching timing in accordance with the size of the transfer paper, finer control becomes possible.

Further, in this embodiment, the first linear velocity and the second linear velocity can be set to arbitrary values, respectively, so that the linear velocity of the registration roller due to the variation in the tolerance of parts can be increased.
It becomes possible to respond according to the mechanical difference of the linear speed of the transfer device. Thereby, an optimal conveyance state can be obtained, so that a good image can be obtained.

Next, a modification of the above embodiment will be described with reference to FIG. Here, an example is shown in which the size (length) of the transfer material is unknown, such as when paper is fed by a manual feed mechanism. On the upstream side of the registration roller 20, a pre-registration sensor 33 as a registration sensor is provided. In this case, the linear speed of the registration roller 20 can be switched according to the detection result of the pre-registration sensor 33 after a predetermined time has elapsed from the start of the transport operation.

That is, the pre-registration sensor 33 detects the entry of the transfer material 34 into the registration roller 20 and stops the registration roller 20 so that the transfer material 34 is stopped.
Of the registration roller 20 and the transfer of the transfer material 34 at the same time as the image forming timing.
The presence / absence of the transfer paper 34 after the start of the transfer operation is continuously detected. If the detection of the transfer material 34 is still continued after a lapse of a predetermined time after the start of the transfer operation, the registration linear speed is switched. Accordingly, even if the size of the transfer material is unknown, if the length of the transfer material 34 is equal to or more than a predetermined value, the registration linear speed can be switched to prevent a problem due to a difference in linear speed between the registration roller 20 and the transport device.

The driving motor of the registration roller 20 is not limited to the pulse motor 25 as described above,
For example, it can be implemented by varying the reference clock using a DC motor that is PLL controlled.

[0032]

According to the first aspect of the present invention, there is provided a registration roller for conveying a transfer material to an image transfer section at a predetermined timing;
And a transfer portion conveying apparatus having a transfer roller for conveying the transfer material at the image transfer unit, in a color image forming apparatus for superimposing transfer an image of a plurality of colors onto a transfer material, the registration roller
Line one linear velocity of the registration roller in the conveying operation of the transfer material switching from a linear velocity equal to the first line speed of the transfer portion conveying device to a second line speed slower than the linear velocity of the transfer section conveyor apparatus according Since the speed switching means is provided, during the period when the transfer material enters the transfer section and the transfer belt is in a state where the attraction force is weak, no load is generated due to the registration roller holding force, and a good transfer state is obtained. In the vicinity of the rear end of the transfer material where a problem due to a slight linear velocity difference is likely to occur, a stable traveling and transfer state can be obtained by a sufficient suction force of the transfer belt.

[0033]

According to the second aspect of the present invention, the linear speed of the registration roller is switched in accordance with the size of the transfer material, so that the optimum switching timing can be set for each transfer material size. Therefore, it is possible to prevent an unnecessary load from the registration roller from being applied to the transfer unit transport device.

According to the third aspect of the present invention, the linear speed of the registration roller is switched based on the detection result of the registration sensor after a lapse of a predetermined time from the start of the conveyance operation. Even when the size of the transfer material is unknown, the linear speed of the registration roller can be switched.

According to a fourth aspect of the present invention, the first linear velocity and the second linear velocity of the registration roller can be set to predetermined values, respectively. It is possible to cope with mechanical differences in the linear velocities, and thereby to obtain an optimum conveyance state, so that a good image can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a pulse motor drive circuit according to one embodiment of the present invention.

FIG. 2 is a timing chart showing waveforms of various driving signals of FIG.

FIG. 3 is a side view illustrating a state of a sheet feeding control mechanism when a transfer material size is unknown.

FIG. 4 is a block diagram showing a basic configuration of a pulse motor drive circuit.

FIG. 5 is a timing chart showing waveforms of various driving signals of FIG. 4;

FIG. 6 is a side view illustrating the overall configuration of the color image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 20 registration roller 21 transfer unit transfer device 32 linear speed switching means 33 registration sensor 34 transfer material

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/00 G03G 15/01 G03G 15/16 G03G 21/00-21/04 G03G 21/14 B65H 9 / 00-9/20 B65H 5/02-5/22

Claims (4)

(57) [Claims] An image transfer unit that transfers a transfer material to the image transfer unit at a predetermined timing; and a transfer unit transfer device that includes a transfer belt that transfers the transfer material at the image transfer unit. in color color image forming apparatus for transferring overlapped images of the registration roller, the resist roller first line speed equal to the linear speed of the linear velocity of the transfer section conveying device during the conveyance operation of a sheet of the transfer material by A linear speed switching means for switching from a first linear speed to a second linear speed lower than the linear speed of the transfer unit transport device. 2. The conveying device of a color image forming apparatus according to claim 1, wherein the switching of the linear speed of the registration roller is performed according to the size of the transfer material. 3. The conveying device of the color image forming apparatus according to claim 1, wherein switching of the linear speed of the registration roller is performed based on a detection result of a registration sensor after a lapse of a predetermined time from the start of the conveyance operation. 4. The conveying device of a color image forming apparatus according to claim 1, wherein the first linear speed and the second linear speed of the registration roller can be set to predetermined values, respectively.