JP3518285B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus using an intermediate transfer member.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a toner image is temporarily transferred from an image carrier to an intermediate transfer member (primary), and the toner image is transferred to a recording material (secondary). There is an image forming apparatus that forms a permanent image of toner on a recording material by transferring and fixing.

In an image forming apparatus for forming an image using an intermediate transfer member, a latent image or a toner image is formed on the image carrier or the intermediate transfer member before the recording material is fed. Therefore, it is necessary to accurately detect the size and direction of the recording material and to control the size and direction of the toner image formed on the image carrier or the intermediate transfer member according to the detected size and direction. In response to such a request, conventionally, the size and the direction of the recording material stored in advance in the recording material tray are detected, and the size of the image formed according to the size and the direction of the conveyed recording material is detected. It is common practice to limit the direction and. However, it is structurally difficult to provide a sensor for detecting the size and direction of the recording material in advance for a tray in which recording materials of different sizes and directions are frequently inserted, such as a manual feed tray. .

Therefore, in the conventional paper feeding from the manual feed tray, only the size in the width direction of the carrying direction which is relatively easy to detect is detected, the size in the carrying direction is predicted from the size in the width direction, and the detected width direction. The size of the toner image formed on the image carrier or the intermediate transfer member is controlled based on the size of the toner image and the expected size in the transport direction.

In such a conventional image forming apparatus,
A process when the predicted size of the recording material in the transport direction is different from the actual size will be described with reference to the flowchart of FIG. First, the width detection sensor detects the size of the recording material in the conveyance width direction (S101). This is usually performed when setting the recording material on the manual feed tray. Next, the size of the recording material in the conveyance direction is predicted from the size of the recording material in the conveyance width direction (S102). This is predicted based on the assumption that, for example, the recording material has a standard size and a short side is in the conveyance width direction (short edge feed: SEF). Therefore, for example, for a recording material of A4 size, the long side is conveyed in the conveyance width direction (long edge feed: L
When set to the bypass tray as EF), A3
I would expect the size recording material to be set as SEF.

Based on this prediction, the size of the electrostatic latent image formed on the exposure device is set (S103). In the previous example,
It is set so as to form a latent image of A3 size SEF. Based on the setting, a toner image is formed on the image carrier (S104), the primary transfer is performed on the intermediate transfer member (S105), and the recording material is fed at a predetermined timing (S106), and then on the intermediate transfer member. Second toner image is secondarily transferred onto the recording material (S107). That is, the A3 size SEF toner image is about to be transferred to the A4 size LEF recording material.

Here, when the registration sensor provided at a predetermined position of the recording material conveyance path detects that the rear end of the recording material has passed the registration sensor (S108), it takes time for the rear end to reach the secondary transfer position. Considering this, after waiting for a certain time (S109), the transfer roll pair that performs the secondary transfer is retracted to release the nip (S110).

By carrying out such a treatment, the secondary transfer roll on the recording material side is prevented from coming into direct contact with the toner image formed on the intermediate transfer member.

[0009]

However, the toner image secondarily transferred onto the recording material by such a process causes an image of the rear end portion due to a slight shift in the timing of releasing the nip of the secondary transfer roll. Becomes thin. Further, the toner image may slightly adhere to the secondary transfer roll on the recording material side, which may cause the recording material to be soiled during the next image formation. Further, a large amount of toner adhered on the intermediate transfer member is removed by a cleaning blade or the like on the downstream side, but at that time, it may diffuse into the image forming apparatus and may become a factor to contaminate the inside of the apparatus. Further, the toner that is not secondarily transferred to the recording material is wasted.

The present invention has been made in view of the above problems, and an object of the present invention is to form the recording material at the rear end portion of the recording material even if the size of the recording material is unknown when the recording material is fed. It is an object of the present invention to provide an image forming apparatus in which a formed image does not become thin and waste toner is not diffused in the image forming apparatus.

[0011]

SUMMARY OF THE INVENTION The present invention is directed to an image forming portion for forming a toner image on an image bearing member by an electrophotographic process, an intermediate transfer member for holding the toner image formed on the image bearing member, and an image bearing member. The primary transfer means for transferring the toner image formed on the body to the intermediate transfer body, the secondary transfer means for transferring the toner image held on the intermediate transfer body to the recording material, and the secondary transfer of the recording material at a predetermined timing. A conveying means for conveying the recording material, a width detecting means for detecting the conveying width direction size of the recording material, a recording material detecting means for detecting the presence or absence of the recording material at a predetermined position of the conveying means, and a recording material according to the size and the direction of the recording material. hand
Controls the size and direction of the toner image formed by the image forming unit
In the image forming apparatus having a control unit for controlling
The width detection means detects the size of the recording material in the conveyance width direction.
After allowed to, to determine the transport direction size of the recording material by causing detecting the presence or absence of the recording material at a predetermined position of the transport means after a predetermined time to convey the recording material by the conveying means in the recording material detecting means, these transport width Direction size and transport direction size
It is to determine the size and direction of the recording material and a's. The present invention also provides image bearing by an electrophotographic process.
The image forming unit that forms a toner image on the body and the image carrier
An intermediate transfer body that holds the formed toner image and an image carrier
Transfer that transfers the toner image formed on the intermediate transfer body
And the toner image held on the intermediate transfer member onto the recording material.
The secondary transfer means for copying and the recording material are copied at a predetermined timing.
Conveyance means for conveying to the next transfer means, and conveyance width direction of recording material
Width detection means to detect the size and the predetermined position of the conveyance means
Recording material detection means for detecting the presence or absence of recording material in the
Toner formed by the image forming unit according to the size and direction of the material
-Images with control means for controlling image size and orientation
In the forming apparatus, the control means records with the width detection means.
The size of the material in the width direction is detected, and the recording material is
At the specified position of the transporting means while transporting and waiting
The presence or absence of the recording material
The size of the recording material in the conveying direction is determined by
Size and direction of recording material
It is to judge the direction. Also, the predetermined position is a single location
May be

By configuring the image forming apparatus in this way, for example, even if the recording material is fed from a manual feed tray that does not have a recording material size detection means, the size and Since the toner image formation control is performed after accurately determining the direction, the sizes of the toner image formed on the image carrier and the intermediate transfer body and the recording material on which the toner image is actually transferred are the same, An image defect such as a thin image formed on the trailing edge of the recording material does not occur, and a large amount of untransferred toner does not remain on the intermediate transfer body after the secondary transfer.

[0013]

DETAILED DESCRIPTION OF THE INVENTION

Examples Next, preferred embodiments of the present invention will be described based on examples. FIG. 1 shows the entire image forming apparatus according to this embodiment. The image forming apparatus includes an image forming unit 1 that forms a toner image on an image carrier by an electrophotographic process, an intermediate transfer member 2 that holds the toner image formed on the image carrier, and an image carrier. Primary transfer means 3 for transferring the toner image onto the intermediate transfer body, and secondary transfer means 4 for transferring the toner image held on the intermediate transfer body onto the recording material.
A conveyance means 5 for conveying the recording material to the secondary transfer means at a predetermined timing, a width detection means 51 for detecting the conveyance width direction size of the recording material, and the presence or absence of the recording material at a predetermined position of the conveyance means. Jam detection means (recording material detection means) 5
In the image forming apparatus having the second recording medium, the recording material is conveyed by the conveying means 5, the size and the direction of the recording material conveyed by the width detecting means 51 and the jam detecting means 52 are determined, and the determined recording material is determined. The control unit 6 controls the size and the direction of the toner image formed by the image forming unit 1 according to the size and the direction.

The image forming section 1 comprises a photosensitive drum 11, which is an image bearing member, a charging device 12, an exposing device 13, a developing device 14, a cleaning blade 15, and the like. Toner is formed on the photosensitive drum by a well-known electrophotographic method. It forms an image. Note that the present invention is not limited to the configuration of the image forming unit according to the present embodiment. For example, the image carrier 11 is not limited to a drum shape and may be an endless belt shape, and the developing device is a rotary type. However, the tandem system may be used.

The intermediate transfer member 2 comprises an intermediate transfer belt 21, a driving roll 22, a stretching roll 23, etc., and a toner image formed on the photosensitive drum 11 by the primary transfer means 3 described later is once transferred. Is. The toner image formed on the intermediate transfer belt rotates together with the intermediate transfer belt 21 by the rotation of the driving roll 22 and the tension roll 23, and moves to the secondary transfer position. In this embodiment, the intermediate transfer member 2 has a belt shape, but may have a drum shape.

The primary transfer means 3 applies a voltage opposite to that of the toner image to the primary transfer roll 31 to transfer the toner image formed on the photosensitive drum 11 to the intermediate transfer belt 21.
Is to be transferred to. The primary transfer means 3 is
For example, a non-contact member such as a corotron may be used.

The secondary transfer means 4 transfers the toner image transferred on the intermediate transfer belt 21 to a recording material by applying a voltage opposite to that of the toner image to the secondary transfer roll . Further, this secondary transfer roll has a retract function of releasing contact with the intermediate transfer belt 21 when forming a color image. The secondary transfer means 4 may also be composed of a non-contact member such as a corotron.

The conveying means 5 is composed of a plurality of conveying roll pairs (not shown) and registration roll pairs 53 provided from a tray for storing recording materials or a manual feed tray (neither shown) to a secondary transfer position. Then, the recording material is conveyed from each tray to the secondary transfer position at a predetermined timing.

The width detecting means 51 detects the size of the recording material in the conveying width direction, and detects the conveying width direction by an analog sensor by setting the recording material on a manual feed tray (not shown). is there.

The jam detecting means 52 detects the presence / absence of a recording material at a predetermined position in the conveyance path from the manual feed tray to the secondary transfer position.

The control means 6 detects the conveyance width direction size of the recording material by the width detecting means 51 and conveys the recording material by the conveying means 5 to determine the presence or absence of the recording material at a predetermined position of the conveying means after a predetermined time has elapsed. Jam detection means 52
The size and direction of the recording material are determined by detecting the size and direction of the recording material, and the size and direction of the toner image formed by the image forming unit 1 according to the determined size and direction of the recording material. (Not shown).

FIG. 2 is a block diagram showing the relationship between the transport means 5, the image forming section 1 and the like and the control means 6. The control unit 6 sends a signal indicating the size of the recording material in the conveyance width direction from the width detection unit 51 and the jam detection unit 52.
Receives a signal indicating the presence or absence of a recording material at a predetermined position for a predetermined time. Based on these signals, the control unit 6 determines the size of the recording material and the conveying direction, and the image forming unit 1 is determined based on the determined size and the conveying direction of the recording material.
The setting signal of the image size to be formed is transmitted. Further, a control signal for controlling the rotational driving of the registration rolls is transmitted to the registration roll pair 53 so that the conveyed recording material is conveyed to the secondary transfer position at a predetermined timing.

FIG. 3 is a flowchart for explaining the image forming process of the image forming apparatus according to the present embodiment.

First, the width detecting means detects the size of the recording material in the conveying width direction (S201). This is performed by setting a recording material on a manual feed tray or the like and detecting it by an analog sensor provided on the manual feed tray. Then, the recording material is conveyed by the conveying means 5 without waiting for image formation (S202). Then, when the pair of transport rolls provided on the transport path is “off”, that is, when the leading edge of the recording material reaches the pair of registration rolls 53 and is in the standby state (S203), the control unit 6
Determines the size of the recording material being conveyed and the conveying direction (S204).

The control means 6 sets the image size in the image forming section 1 based on the determined size of the recording material and the conveying direction (S205), and starts forming a toner image (S20).
6). At this time, the recording material conveyed is the control means 6
Since the rotation of the registration roll pair 53 is stopped by the above, it is kept on standby before the registration roll pair. By the control unit 6 performing such control, the size and direction of the toner image and the recording material match, and the transfer is not interrupted during the secondary transfer, so that the toner image is formed on the rear end portion of the recording material. Since the formed image does not become thin and the toner image does not become larger than the recording material, useless toner does not diffuse into the image forming apparatus.

The toner image formed on the photosensitive drum 11 is primarily transferred onto the intermediate transfer belt 21 by the primary transfer means 3 (S207). When the toner image formed on the intermediate transfer belt 21 approaches the secondary transfer position along with the rotation of the intermediate transfer belt 21, the registration roll pair 53 is rotationally driven at a predetermined timing (S208), and the secondary transfer means performs the operation. The toner image held on the intermediate transfer belt is secondarily transferred to the recording material (S209).

FIG. 4 is a timing chart for explaining the timing (S204) at which the control means of the image forming apparatus according to the present embodiment determines the size of the recording material and the conveying direction thereof. The presence or absence of the toner image held on the secondary transfer position, the presence or absence of rotational drive of the registration roll pair 53, the presence or absence of rotational drive of the transport roll pair, and the presence of the recording material at the position installed in front of the registration roll pair 53. The output of a registration sensor for determining the presence / absence and the output of a recording material detection unit installed at a predetermined position of the conveyance path and determining the presence / absence of the recording material at that position are shown.

At time T1, the leading edge of the recording material reaches the jam detecting means 52, but does not reach the registration sensor. Further, the recording material is conveyed, and at time T2, the recording material is present at both the position of the recording material detection unit and the position of the registration sensor. Time T
3, the rotation of the pair of transport rolls is temporarily stopped to sandwich the leading end of the recording material between the pair of registration rolls 53,
Before that, the recording material stands by while forming a loop. In this state, the control unit 6 receives the output of the jam detection unit 52 to determine the size and direction of the recording material.

That is, the size of the conveyed recording material in the conveying width direction is detected by the width detecting means, and if the recording material has a standard size, the recording material detecting means has to detect. , The recording material conveyed is SEF
Or LEF only. Therefore, when LEF is performed while the recording material is on standby, the recording material does not exist and S
At the time of EF, the jam detecting means 5 is provided at the position where the recording material exists.
By installing 2, it is possible to detect that the recording material being conveyed is SEF or LEF.

For example, as shown in FIG. 5, the front end of the recording material is in a state where it is nipped by the registration roll pair 53, and the recording material is in a standby state to determine whether the recording material is A4 (LEF) or A3 (SEF). In this case, the jam detecting means 52 may be installed at the portion A on the left diagonal line in FIG. In addition, for example, B5 (LE
In order to determine whether it is F) or B4 (SEF), the jam detecting means 52 may be similarly installed at the right diagonal line B portion. In addition, both (A4 (LEF) or A3 (SEF), B5
In order to determine (LEF) or B4 (SEF), the jam detecting means 52 may be installed at the overlapping portion of the left diagonal line A portion and the right diagonal line B portion in FIG. In this example, the case of the side registration method in which the recording material is conveyed along the end of the conveyance path is shown, but the same idea is applied to the case of the center registration method in which the recording material is conveyed along the center of the conveyance path. The installation position of the recording material detection means may be determined by.

Focusing on the output of the jam detecting means 52 in FIG. 4, the output is "OFF" at the time T3 in the standby state, so that it can be determined that this recording material is LEF. By more accurately determining the size and the conveying direction of the recording material in this manner, the size and the conveying direction of the toner image to be formed and the conveyed recording material match.

At time T4, when the toner image held on the intermediate transfer belt 21 approaches the secondary transfer position, both the registration roll pair 53 and the transport roll pair start rotational driving, and the secondary transfer from the standby state. The recording material is conveyed to the position at a predetermined timing.

In this embodiment, the size of the recording material in the conveying direction is judged by judging the presence or absence of the paper at the predetermined position while the recording material is in the standby state. It is not limited, for example,
It is also possible to measure the time during which the jam detecting unit 52 is “on” and determine the size of the recording material in the transport direction from the transport speed of the recording material and the measured time. If the size of the recording material in the carrying direction is detected in this manner, the size of the recording material in the carrying direction can be accurately detected even for a non-standard size recording material. Further, in the case of detecting the size in the conveyance direction as described above, the installation position of the jam detection unit 52 is set such that the trailing edge of the recording material always passes when the recording material is conveyed from the manual feed tray to the standby position. It should be installed in a position where

[0034]

As described above, according to the present invention, the size of the recording material fed in an unclear size is detected during conveyance, and the toner image formed based on the detection result is detected. Since the image is formed by setting the size and the direction thereof, it is possible to prevent an image defect in which the image at the rear end portion of the image formed on the recording material becomes thin. In addition, the toner image slightly adheres to the secondary transfer roll on the recording material side, and the recording material is not contaminated during the next image formation, and the inside of the machine is not contaminated with a large amount of toner images. Also, the toner can be used without waste.

[Brief description of drawings]

FIG. 1 shows an entire image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating the relationship between the control unit of the image forming apparatus according to the embodiment, various detection units, and the control target.

FIG. 3 illustrates an image forming process of the image forming apparatus according to the embodiment with reference to a flowchart.

FIG. 4 illustrates the timing of each process of the image forming apparatus according to the embodiment with reference to a timing chart.

FIG. 5 illustrates an installation position of a recording material detection unit.

FIG. 6 illustrates a process of a conventional image forming apparatus using a flowchart.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming part, 2 ... Intermediate transfer body, 3 ... Primary transfer means,
4 ... Secondary transfer means, 5 ... Conveying means, 51 ... Width detecting means,
52 ... Jam detecting means (recording material detecting means), 6 ... Control means

Continuation of the front page (56) Reference JP-A-4-82765 (JP, A) JP-A-9-240914 (JP, A) JP-A-6-156773 (JP, A) JP-A-5-112055 (JP , A) JP 4-338983 (JP, A) JP 4-42167 (JP, A) JP 9-230751 (JP, A) JP 7-253735 (JP, A) JP 9-230648 (JP, A) JP 7-49636 (JP, A) JP 64-9251 (JP, A) JP 61-72265 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/36 G03G 15/00 510 G03G 21/00 370-512

Claims (3)

(57) [Claims] 1. An image forming unit for forming a toner image on an image bearing member by an electrophotographic process, an intermediate transfer member for holding the toner image formed on the image bearing member, and a toner image formed on the image bearing member. A primary transfer means for transferring to the intermediate transfer body, a secondary transfer means for transferring the toner image held on the intermediate transfer body to the recording material, and a conveying means for conveying the recording material to the secondary transfer means at a predetermined timing, A width detection unit that detects the size of the recording material in the conveyance width direction, a recording material detection unit that detects the presence or absence of the recording material at a predetermined position of the conveyance unit ,
Toner image formed by the image forming unit according to size and direction
Formation having control means for controlling the size and direction of the image
In the apparatus, the control means is recorded after detected the conveyance width direction size of the recording material at a width detecting means, the presence or absence of the recording material at a predetermined position of the transport means after a predetermined time to convey the recording material by the conveying means determining the transport direction size of the recording material by causing sensed by wood detecting means, conveying these conveyance width direction size
An image forming apparatus characterized by determining the size and direction of a recording material from the direction size . 2. An image forming unit for forming a toner image on an image bearing member by an electrophotographic process, an intermediate transfer member for holding the toner image formed on the image bearing member, and a toner image formed on the image bearing member. A primary transfer means for transferring to the intermediate transfer body, a secondary transfer means for transferring the toner image held on the intermediate transfer body to the recording material, and a conveying means for conveying the recording material to the secondary transfer means at a predetermined timing, A width detection unit that detects the size of the recording material in the conveyance width direction, a recording material detection unit that detects the presence or absence of the recording material at a predetermined position of the conveyance unit ,
Toner image formed by the image forming unit according to size and direction
Formation having control means for controlling the size and direction of the image
In the apparatus, the control means causes the sensing of the conveyance width direction size of the standard recording material at a width detecting means, to convey the standard recording material by the conveying means waiting
Constant by causing detecting the presence or absence of the standard recording material in a predetermined position of the transfer means in a state of being machine by the recording material detecting means
Determining the transport direction size of the type recording material, these conveying width direction
An image forming apparatus characterized by determining the size and direction of a standard recording material from the size and the size in the transport direction . 3. The predetermined position is a single position.
Or the image forming apparatus according to 2 .