JPH0777875A - Paper holding device - Google Patents

Abstract

PURPOSE:To provide a paper holding means capable of detecting the fact that a clip fails to nip a paper sheet by detecting the presence of the paper again, after its leading edge is detected and a specified time lapses. CONSTITUTION:When the clip 2 fails to nip the paper 9 fed from a carrying path 12 and further, the paper 9 passes between transmission sensors, the paper 9 leaves from a transfer drum 1, but the paper 9 is ejected from the carrying path 12 by the carrying action of a resist roller 11 still continued after that, to be sent to the downstream side, enters between the transmission sensors 1a and 3b and never moves in this state. When the sensor detects the leading edge of the paper 9 and a specified time lapses, the sensor detects the presence of the paper, in such a manner that light is emitted from the light emitting element 3a, again. In this state, a control part recognizes that the paper 9 is not wound on the transfer drum 1, because an electric signal is not inputted from the light receiving element 3b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet holding device for holding a sheet on a transfer drum, which is used in a color copying machine, a printer, a facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, for example, some color copying machines use a transfer drum for winding and transferring paper.
As shown in FIG. 5, such a transfer drum is provided with a clipper 2 as a paper holding means for holding the leading edge of the fed paper by nipping it, and the transfer drum 1 is also provided.
Has a cylindrical cage shape composed of both side portions provided with a pair of circular frames, a stay provided between the circular frames, and a transfer sheet that electrostatically adsorbs a sheet (that is, the periphery of the transfer drum 1). The central part of the surface has a structure that allows light to pass through through a transparent transfer sheet). In addition, in and around the periphery of the transfer drum 1, the paper conveyance direction (transfer drum 1
The transfer drum 1 from the upstream side with respect to
Registration roller 11 to be fed to and a conveyance path 12 for conveying the sheet, a transmission type sensor 3 for detecting by light whether the sheet is held by the clipper 2 and wound around the transfer drum 1, and an electrostatic latent image is formed by exposure. A photosensitive drum 14 on which the electrostatic latent image is developed to form a toner image, a transfer charger 13 for transferring the toner image on the photosensitive drum 14 to a sheet, and the sheet after transfer is separated from the transfer drum 1. Separation Charger 1 for
5, a separation claw 16 for separating the paper separated by the separation charger 15 from the transfer drum 1, a separation switch 18 for detecting by an actuator whether or not the separated paper should pass at a time to be passed, and the like. The transmissive sensor 3 is mounted on the body frame 17 so as to be close to the transfer drum 1 and emits light. The light emitting element 3a is provided inside the transfer drum 1.
The light receiving element 3b receives the light emitted by a.

In the above-described structure, the sheet sent out by the registration roller 11 and sent through the conveying path 12 is held by the front end of the sheet being sandwiched by the clipper 2 of the transfer drum 1, and in that state. It is wound around the transfer drum 1 as it rotates. When the paper wound around the transfer drum 1 passes through the transmissive sensor 3, the light of the light emitting element 3a is blocked and it is detected that the paper is wound around the transfer drum 1. Here, when the paper is not fed from the registration roller 11, there is no paper that blocks the light of the light emitting element 3a even when the transfer drum 1 rotates by a predetermined amount, and therefore the paper is not wound around the transfer drum 1. Can be detected.

[0004]

However, in such a method, as shown in FIG.
When the paper 9 is pinched by the clipper 2 due to insufficient opening of the clipper 2 or the like, the feeding operation of the paper 9 by the registration roller 11 is continued as it is. The sheet 9 is conveyed toward the transmissive sensor 3 while being separated from the transfer drum 1. As a result, the leading edge of the sheet 9 may be carried between the light emitting element 3a and the light receiving element 3b of the transmissive sensor 3. Therefore, the paper 9 blocks the light of the light emitting element 3a, and the same operation as when the paper 9 is wound around the transfer drum 1 is performed. Therefore, until the separation switch 18 detects that the transferred sheet has not passed at the time when it should pass, it is not possible to detect the pinching failure of the sheet 9. As a result, although the sheet 9 is not held, the image forming operation is performed, and four color toners (in the case of full color) are transferred to the transfer drum 1 to cause mechanical damage such as dirt. There is a problem that it takes time to detect the pinch failure of 9 and is inconvenient for the user.

In view of such problems of the conventional transfer drum, the present invention can solve the inconvenience that all four color toners are transferred to the transfer drum because the paper is not normally held on the transfer drum. An object of the present invention is to provide a sheet holding device.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a transfer drum around which a transfer sheet is wound, a sheet holding means provided on the transfer drum for holding an incoming sheet, and a normal sheet. If the paper is not held and conveyed, it detects the presence or absence of the paper in the place where the paper continues to exist. Is a sheet holding device provided with a sheet holding detection unit that operates at a timing when no sheet can exist.

[0007]

According to the present invention, when the paper holding means holds the sent paper on the transfer drum, the paper holding detection means, when the paper is normally held and conveyed, completes passing through the place. The presence / absence of paper is detected at a timing when the paper cannot exist. Therefore, when the sheet is normally held and conveyed, if it is detected at that timing, the sheet should not exist, so the sheet is not detected.

When the sheet is not normally held, the sheet holding detection means detects the presence of the sheet at the place where the sheet continues to exist when the sheet cannot be held as described above.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view of a sheet holding device used in a copying machine, which is a first embodiment of the present invention. That is, the transfer drum 1 is provided with the stay 5,
A clipper 2 that can be opened and closed is attached to the stay 5 so as to sandwich the leading edge of the sheet 9. The transfer drum 1 is
Similar to the conventional example, both side portions provided with a pair of circular frames,
A cylindrical cage shape is formed by stays and the like provided between the circular frames. That is, from the upstream side with respect to the conveyance direction of the paper 9, inside and outside of the peripheral surface of the transfer drum 1,
A registration roller 11 for feeding the paper 9 to the transfer drum 1, a registration switch 6 for controlling the drive of the registration roller 11, a transport path 12 for transporting the paper 9, and a paper path 9 for transporting the paper 9 are provided. A timing switch 30 for detecting arrival at that position, a photosensitive drum 14 on which an electrostatic latent image is formed by exposure and the electrostatic latent image is developed to form a toner image, and the photosensitive drum 14
A transfer charger 13 for transferring the above toner image onto the sheet 9, a separation charger 15 for separating the sheet 9 that has been transferred and is electrostatically attracted to the transfer drum 1, and a sheet 9 separated by the separation charger 15. Separation claw 16 for separating the sheet from the transfer drum 1 and the separated sheet 9
Is provided with a separation switch 18 or the like for detecting whether or not the vehicle should pass by using an actuator. In addition, between the photosensitive drum 14 and the transport path 12, a light beam is provided near the clip position where the clipper 2 sandwiches the leading edge of the paper 9 (that is, this is the initial holding position of the clipper 2). A transmissive sensor 3 for detecting the presence or absence of the sheet 9 is provided. The transmissive sensor 3 is attached to the body frame 17 so as to be close to the transfer drum 1.
And a light receiving element 3b provided inside the transfer drum 1 for receiving the light emitted by the light emitting element 3a. Further, the paper 9 is placed on the upstream side of the registration roller 11 with the registration roller 11
A paper feed roller for continuously feeding paper to the paper, and a paper cassette for feeding a fixed amount of paper 9 are provided.
In addition, the paper detection sensor 20 for detecting the paper size
Is connected to the size instruction button (not shown) of the copying machine. In addition, inside the body frame 17, the transmission type sensor 3
A control unit 21 is provided for controlling the driving of the. The control unit 21 is the timing setting unit 2
2 and the control unit 23. The timing setting unit 22 is means for setting the timing information 22a that is the time interval t according to the paper size information 20a detected by the paper size detection sensor 20. The control unit 23 is means for controlling the operation of the transmissive sensor 3 based on the timing information 22a set by the timing setting unit 22 and the time information 30a indicating the time when the timing switch 30 detects the paper 9.

Next, the operation of the above embodiment will be described with reference to FIGS. 2, 3 and 4.

First, the case where the paper 9 is normally sandwiched by the clippers 2 and wound around the transfer drum 1 will be described. That is, the operator presses the paper size button to select a desired paper size. Therefore, the paper size detection sensor 20 detects the paper size and outputs the result to the timing setting unit 22. The timing setting unit 22 outputs timing information 22a indicating a predetermined time interval t corresponding to the paper size information 20a detected by the paper size detection sensor 20 to the control unit 23.

When the operator presses the start button, the transfer drum 1 is rotated as shown in FIG. 2, the clipper 2 is sent to the clip position where the tip of the paper 9 is pinched, and the tip of the clipper 2 is lifted. . That is,
The tip of the clipper 2 opens. On the other hand, the sheet 9 supplied from the paper cassette is detected by the registration switch 6, and the registration roller 11 starts driving. And then
The sheet 9 sent by the registration rollers 11 passes through the conveyance path 12 and enters while the clipper 2 is open. Furthermore, after the leading edge of the paper 9 has entered between the clippers 2,
The clipper 2 is closed and the front end of the paper is sandwiched and held by the stay 5. Next, as the transfer drum 1 rotates, the paper 9
Is wound around the transfer drum 1. At the same time, the stay 5 passes between the passage sensors 3, and thereafter, the further wound paper 9 completes the passage between the transmission sensors 3 normally.

By the way, as described above, when the sheet 9 passes through the transport path 12, the timing switch 30 detects the leading edge of the sheet 9 (the time is set to T). The sheet detection information 30a is input to the control unit 23. Therefore, the control unit 23 drives the light emitting element 3a after the time interval t of the timing information 22a input in advance as described above has elapsed from the input time T, that is, at the (T + t) time. At the time interval t, after the leading edge of the sheet 9 has passed the timing switch 30, the sheet 9 is normally clipped, wound around the transfer drum 1 and conveyed, and the trailing edge of the sheet 9 passes between the transmissive sensors 3. A predetermined time interval that is longer than the time interval until the passage is completed is predetermined. Therefore, the light emitted from the light emitting element 3a driven by the control unit 23 is not blocked by the paper 9, and is thus received by the light receiving element 3b and converted into an electric signal. The electric signal is further input to the control unit 23. Therefore, the control unit 23 can recognize that the paper 9 is reliably wound around the transfer drum 1.

On the other hand, a laser beam corresponding to an original image is irradiated onto the photosensitive drum 14 to form an electrostatic latent image, and the electrostatic latent image is developed by a developing device (not shown) to form a toner image. Is formed. The toner image thus formed contacts the surface of the sheet 9 as the photosensitive drum 14 and the transfer drum 1 rotate, because the sheet 9 is normally wound around the transfer drum 1, and the transfer charger 13 transfers the toner image on the transfer drum 1. And is transferred to the paper 9. In the case of full-color copying, the transfer drum 1 rotates four times until four color toner images are transferred. The sheet 9 after the fourth transfer is electrically separated from the transfer drum 1 by the corona discharge of the separation charger 15, is further separated from the transfer drum 1 by the separation claw 16, and is fixed by the conveyor belt (not shown). The sheet is conveyed to (not shown).

On the other hand, the case where the sheet 9 is damaged by the clipper 2 will be described. That is, as shown in FIG. 3, the paper 9 from which the clipper 2 is sent from the transport path 12
If the paper 9 happens to pass between the transmissive sensors 3 when the paper 9 is caught by the transfer drum 1
The registration roller 1 which is separated from, but continues
The sheet is discharged from the conveying path 12 by the conveying operation No. 1 and is sent to the downstream side, and does not move while being inserted between the transmission type sensors 3. Therefore, the time (T
Also in + t), the paper 9 exists between the transmissive types 3. As a result, the light emitted from the light emitting element 3a is emitted from the paper 9 even after the time (T + t) (which is a timing that cannot exist when the paper 9 is normally wound around the transfer drum 1). Is blocked by. Therefore, the control unit 23
Since no electric signal is input from the light receiving element 3b, the paper 9
It is possible to recognize that is not wound around the transfer drum 1.

Next, a second embodiment of the present invention will be described.

By the way, in the first embodiment, as shown in FIG. 4, when the clipper 2 does not pinch the paper 9 sent from the transport path 12 and does not enter between the transmissive sensors 3. The paper 9 is separated from the transfer drum 1, and is discharged from the conveyance path 12 to the downstream side by the conveyance operation of the registration roller 11 which continues thereafter, without passing through the detection position of the transmissive sensor 3 as it is. It remains stagnant on the upstream side of the transmissive sensor 3. Therefore, when light is emitted from the light emitting element 3a at the timing of the time (T + t), the light is received by the light receiving element 3b without being blocked, and the same as when the sheet 9 is wound around the transfer drum 1, There is a possibility that it may not be possible to detect the pinching failure of the paper 9 until it is detected by the separation switch 18 that the paper 9 after transfer has not passed at the time when it should pass.

Therefore, in the second embodiment, in order to prevent such an inconvenience, when the sheet 9 is normally held and conveyed, it is in the process of passing the detection position of the transmissive sensor 3. The presence / absence of the sheet 9 can be detected at the timing when the sheet 9 should be present at the detection position. The timing to be present is the time interval t ′ until the time when the front end of the sheet 9 passes through the timing switch 30 and then the sheet 9 is normally conveyed and is present at the transmissive sensor 3 and the light can be blocked. Is obtained in advance, and it is the timing when t ′ has elapsed from the T.

Therefore, the t'is also set in the timing setting section 22, and the control section 23 can drive the transmissive sensor 3 and detect the presence or absence of the sheet 9 even at the time when t'is elapsed from the T. It is like this.

In this way, the paper 9 as shown in FIG.
In the conveyance state of No. 3, since there is no sheet 9 that blocks the light emitted from the light emitting element 3a, the light is received by the light receiving element 3b and the sheet 9 is not wound around the transfer drum 1.
It can be detected immediately. Note that when the sheet 9 is normally held and conveyed, the light emitted from the light emitting element 3a at the timing when it should exist is blocked by the sheet 9 and is not received by the light receiving element 3b, and thus is shown in FIG. It can be clearly distinguished from the paper transport state.

Although the paper holding detection means of the present invention is a transmissive optical sensor in the above embodiment, it is possible to detect the presence or absence of the paper 9 in short, for example, a reflective optical sensor or a limit switch. All you have to do is

Further, the paper holding means of the present invention uses the clipper 2 in the above embodiment, but the invention is not limited to this, and an electrostatic adsorption device or the like may be used.

Further, although the sheet holding detecting means of the present invention is attached to the place near the downstream of the clip position of the clipper in the above-mentioned embodiment, the present invention is not limited to this, and the place of the sheet at that place is not limited to this. The attachment position may of course be another place as long as the presence or absence can be detected.

Further, although the paper holding detection means of the present invention detects the presence or absence of paper at a location near the downstream of the clipper 2 position in the above-mentioned embodiment, the present invention is not limited to this, and it is not limited to the downstream of the clip position. If the sheet is not normally held and conveyed such as a position slightly upstream of the photosensitive drum, the presence or absence of the sheet at the place where the sheet continues to exist may be detected.

Further, in the above embodiment, the timing at which the paper of the present invention cannot exist is calculated based on the paper detection information from the timing switch, but the present invention is not limited to this. The timing is detected based on another time such as detecting the time when the leading edge of the paper passes using the transmissive sensor 3 according to the example and using the time as a reference, or the time when the registration switch detects the paper. May be determined.

Further, the sheet holding device of the present invention is used in the copying machine in the above-mentioned embodiment, but is not limited to this, and can be applied to a device for holding other sheets such as a facsimile and a printer.

[0028]

As is apparent from the above description,
The present invention according to claim 1 has an advantage in that it is possible to reliably detect the paper jam and to solve the inconvenience that all the four color toners are transferred to the transfer drum even when the four color color copy is used. Have.

Further, in addition to the above advantages, the present invention according to claim 2 can reliably detect the pinch failure of the sheet even when the sheet is pinched and the sheet is largely deviated from the sheet holding detection means. It also has advantages.

[Brief description of drawings]

FIG. 1 is a side view of a sheet holding device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a sheet conveyance state of the embodiment.

FIG. 3 is a diagram for explaining a sheet conveyance state of the embodiment.

FIG. 4 is a diagram illustrating a sheet conveyance state of the embodiment.

FIG. 5 is a side view of a conventional paper holding device.

FIG. 6 is a diagram illustrating a sheet conveyance state in a conventional sheet holding device.

[Explanation of symbols]

 1 transfer drum 2 clipper 3 transmissive sensor 3a light emitting element 3b light receiving element 6 registration switch 9 paper 18 separation switch

Claims (3)

[Claims] 1. A transfer drum around which a sheet for transfer is wound, a sheet holding unit provided on the transfer drum for holding a sheet sent thereto, and the sheet is not normally held and is not conveyed. In the case where the sheet continues to exist, the presence or absence of the sheet is detected, and when the sheet is normally held and conveyed, the timing at which the sheet cannot exist by completing the passage of the sheet. A sheet holding device including a sheet holding detection unit that operates in accordance with the above. 2. The sheet detecting means can detect the presence / absence of a sheet at a timing when the sheet should be present since the sheet is passing through the place when the sheet is normally held and conveyed. The sheet holding device according to claim 1, wherein 3. The sheet holding device according to claim 2, wherein the place where the sheet continues to exist is near the downstream of the correct initial holding position of the leading edge of the sheet by the sheet holding means.