JPH10104966A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a transfer failure such as transfer slippage and prevent a trouble of damaging the surface of a photoreceptor drum by providing a guide vertically moving means for determining the vertical movement of a guide member to the sheet surface of a transfer paper according to the kind of the transfer paper detected by a paper kind detecting means. SOLUTION: A paper kind detecting part 4 detects the kind of transfer papers P within a feed cassette 9. A guide member 3 vertically movable to a transfer paper passing line (λ) is provided in a lower proper position between a transfer equipment 2 and a carrying guide plate 8. When the detecting part 4 detects the transfer paper P of a predetermined kind, the guide member 3 is moved up to guide the transfer paper P upward, whereby the close fitting property between the transfer paper and a photoreceptor drum 1 is satisfactorily kept over the whole transfer paper area, so that the quality of image is never lost. Further, when a transfer paper other than the predetermined kind is detected, the member 3 is moved down so that it is not excessively closely fitted to the drum 1, whereby a trouble of damaging the drum 1 surface is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
Regarding image forming devices such as laser printers and facsimile machines, especially when transferring a toner image on a photoreceptor onto a transfer paper by a corona discharge type transfer unit, it is possible to prevent the transfer paper from coming into contact with the photoreceptor sufficiently. And an image forming apparatus with improved transfer performance.

[0002]

2. Description of the Related Art In recent years, the development of image forming apparatuses such as copying machines, laser printers, and facsimile machines has been remarkable, and in particular, progress has been remarkable in terms of high performance, high speed, and downsizing. Here, in order to reduce the size of the apparatus, an image carrier such as a photosensitive drum must be small in size and small in diameter. Therefore, there is a problem in transferability of a transfer sheet fed to a transfer position. For example, while the registration roller pair is nipping the transfer paper, the transfer paper can maintain a state of being in proper contact with the surface of the photoconductor, but once the rear end of the transfer paper separates from the registration roller pair and the conveyance guide, Transfer stability of the transfer paper is impaired, slippage occurs, and the adhesion between the transfer paper and the photosensitive drum is impaired, making the transfer from the photosensitive drum to the transfer paper by the transfer unit more unstable. This causes a problem that image quality is impaired. Therefore, actual Kaihei 2-1
In the technique described in Japanese Patent No. 36269, when the rear end portion of the transfer paper leaves the conveyance guide member, the angle and position of the rear side conveyance guide member are changed so that the transfer paper is hard to separate from the cylindrical photoconductor, and the transfer is performed. It prevents transfer defects such as omissions,
In the technique described in JP-A-63-8159, two paper guides which can move up and down are provided on both sides of a transfer device.
By moving the two paper guides upward to bring the transfer paper into close contact with the photosensitive drum, slippage of the transfer paper and peeling of the transfer paper from the photosensitive drum are eliminated, thereby preventing image quality from being impaired. ing.

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Utility Model Laid-Open No. 2-13
In the transfer paper guide method described in Japanese Patent Application Laid-Open No. 6269 and Japanese Patent Application Laid-Open No. 63-8159, as long as the standard for setting the transport guide member and the paper guide is set to that of plain paper, the slip of the transfer paper and the photoconductor In terms of peeling from the drum, plain paper has some effect, but
When a thick transfer paper is used, a problem arises that the surface of the photoconductor drum is damaged due to excessively close contact with the photoconductor drum. Therefore, an object of the present invention is to provide a paper type detecting means for detecting the type of transfer paper, and to move the guide member upward for plain paper transfer paper so that the adhesion between the transfer paper and the photosensitive drum is improved. The guide member is moved downward so that it is not damaged, and the transfer member of thick paper does not become too close, so that transfer failure such as transfer omission is prevented.
An object of the present invention is to provide an image forming apparatus in which a problem of damaging the surface of a photosensitive drum is prevented.

[0004]

In order to achieve the above object,
The invention according to claim 1 is an image carrier that forms a toner image corresponding to a document image through a process of an electrostatic process, a transfer device that transfers the toner image formed on the image carrier to transfer paper,
A guide member downstream of the transfer unit in the transfer paper transport direction and movable up and down with respect to a paper passing surface of the transfer paper; and a paper type detection unit for detecting a type of the transfer paper; The image forming apparatus further includes a guide vertical movement unit that determines the vertical movement of the guide member with respect to the paper passing surface of the transfer paper according to the type of the transfer paper detected by the detection unit. According to a second aspect of the present invention, when the guide vertical moving means moves the guide member upward with respect to the paper passing surface of the transfer paper, the guide vertical movement means moves after the leading end of the transfer paper has passed over the guide member. Is performed. According to a third aspect of the present invention, when the paper type detection means detects a thick paper transfer sheet, the guide member is retracted downward with respect to the paper passing surface of the transfer paper, and the paper type detection means transfers the plain paper. When the paper is detected, the guide member is moved upward with respect to the paper passing surface of the transfer paper.

[0005]

According to the first aspect of the present invention, when the paper type detecting means detects a transfer paper of a predetermined paper type (size and thickness), the guide vertical moving means moves the guide member upward to make the transfer paper and Improving the adhesion to the photoconductor drum and detecting transfer paper of a paper type other than the predetermined type,
The guide member can be moved downward so as not to make too much contact with the photosensitive drum. According to a second aspect of the present invention, in addition to the image forming apparatus according to the first aspect, the guide up / down moving means determines the up / down movement after the leading edge of the transfer paper has passed over the guide member. Since the guide member is moved downward in the initial state before the transfer of the transfer paper, the leading end of the transfer paper does not hit the guide member and the transfer is not disturbed. According to a third aspect of the present invention, in addition to the invention of the image forming apparatus configured as in the first or second aspect, when the plain paper transfer sheet is detected by the paper type detecting means, the guide is provided. The member is moved upward with respect to the paper passing surface of the transfer paper, and when the thick paper is detected, the guide member is moved downward with respect to the paper passing surface of the transfer paper. This improves the adhesiveness of the photosensitive drum, and eliminates the problem that the transfer paper of thick paper is too closely adhered to the photosensitive drum and damages the surface of the photosensitive drum.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a side view showing a main part of an electrophotographic copying machine (hereinafter, referred to as a copying machine). Since the detailed configuration and functions of the copying machine are known, only an outline will be given. In FIG. 1, transfer paper P stored in a paper feed cassette 9 is fed one by one by a pickup roller 10, and is conveyed to a stopped registration roller 12 by the action of a paper feed roller (not shown). Stop. On the other hand, the photosensitive drum 1 serving as the image carrier 1
An electrostatic latent image corresponding to the document image is formed on the upper surface through the process of the electrostatic process, and a toner image is formed by the operation of the developing device 13 as the photosensitive drum 1 rotates clockwise. . Further, the registration roller 12 starts driving in synchronization with the rotation of the photosensitive drum 1 and sends the transfer paper P to the photosensitive drum 1. The transfer paper P travels along a transport path including the transfer entrance guide 6 and the lower cover of the developing device, and comes into close contact with the photosensitive drum 1 on the transfer device 2. In the transfer device 2,
A transfer process by corona discharge is performed, and the toner image on the photosensitive drum 1 is transferred to the transfer paper P. Further, the transfer paper P is discharged by the discharging needle 7 and the transfer paper P is separated from the photosensitive drum 1 and advances along a transfer paper passing line indicated by a dotted line (a) in FIG. 8 is conveyed. Subsequently, the transfer paper P is transported along the transport guide plate 8 by transport rollers (not shown), and is heated by the induction of the fixing entrance guide plate 16 by the fixing roller 14.
The toner image on the transfer paper P is thermocompression-bonded and fixed between the pressurizing rollers pressed against each other.

In the above-described drawings, the paper feed cassette 9 and the transfer paper P are drawn smaller than other components for the sake of illustration and description. The transfer paper P sent out by the registration roller 12 is bent in the direction of a dotted line (a) by hitting the photosensitive drum 1 at the leading end, and is closely adhered to the photosensitive drum 1 while being fed by the registration roller 12. It is transported in the state where it is. However, when the rear end of the transfer paper P leaves the registration roller 12,
The adhesion between the transfer paper P and the photosensitive drum 1 changes significantly. In particular, when the paper has a soft stiffness, the rear end portion of the transfer paper P separates from the photosensitive drum 1 due to its own weight, thereby deteriorating the adhesion and causing poor transfer. Therefore, in the present embodiment, a guide member 3 that can move up and down with respect to the transfer paper passage line (a) is provided at an appropriate lower position between the transfer unit 2 and the conveyance guide plate 8, and the guide member 3 is provided when necessary. By moving the transfer paper 3 upward (see FIG. 2) to guide the transfer paper P upward, the adhesion between the transfer paper P and the photosensitive drum 1 can be maintained satisfactorily over the entire area of the transfer paper P. Quality can be prevented from being impaired.

Next, the operational relationship between the transfer sheet P and the guide member 3 will be described with reference to FIGS. In FIG. 1, a guide member 3 is rotatable up and down around a support 3a, and when a solenoid 5a is OFF, a spring 5
c pulls in the direction of the arrow (b) as shown in the figure,
The guide member 3 is placed at a position retracted downward with respect to the transfer paper passing line (a). The paper type detection unit 4 can determine the paper type of the transfer paper P in the paper cassette 9. Depending on the type of the transfer paper, there is also a type that does not require the guide member 3 to be moved upward. At that time, the solenoid 5a is not operated, and the guide member 3 remains in the lower retracted position as shown in FIG. It is. When it is necessary to move the guide member 3 upward as a result of detecting the paper type by the paper type detection unit 4, the detection result of the paper type detection unit 4 is transmitted to the solenoid control unit 5d, and the solenoid is transmitted through the solenoid control unit 5d. Work 5a. When the plunger of the solenoid 5a is sucked into the solenoid 5a, the guide member 3 is attracted through the joint 5b, and a force is applied to the guide member 3 in the direction of arrow (c) (projection direction) as shown in FIG. The guide member 3 moves upward with respect to the paper passing line (a). The state is shown in FIG.

However, if the guide member 3 is moved upward before the transfer paper P reaches the guide member 3, the leading end of the transfer paper P collides with the guide member 3, and the transfer paper P is shifted. As a result, transfer failure such as transfer omission occurs.
For this reason, the solenoid 5a is operated after a predetermined time period in which the transfer paper P is considered to reach the guide member 3 after the registration roller 12 is driven to rotate. This operation command is issued from the solenoid control unit 5d.
In the figure, a dashed line drawn between the registration roller 12 and the solenoid control unit 5d is a signal line for receiving a signal for knowing a driving start state of the registration roller 12. further,
The timing of returning the guide member 3 moved above the line (a) to below the initial position is performed after the rear end of the transfer paper P has completely passed over the guide member 3.
Therefore, after the trailing edge of the transfer sheet P is detected by the trailing edge detecting element 11 set near the registration roller 12, a time period in which the trailing edge of the transfer sheet P completely passes over the guide member 3 elapses. Then, the solenoid 5a is turned from ON to OFF. Although a signal line at this time is not shown, the solenoid control unit 5d receives a detection signal from the rear end detection element 11, and the solenoid control unit 5d stops the operation of the solenoid 5a after a predetermined time. The guide vertical moving means 5 for determining the vertical movement of the guide member 3 includes a solenoid 5a, a joint 5b, a spring 5c, a solenoid control unit 5d, and the like in the figure.

FIG. 3 is an explanatory diagram for discriminating the paper type of the transfer paper P. The transfer paper P stored in the paper feed cassette 9 is shown in FIG.
Is detected by the paper size detection sensor 4a and the paper thickness detection sensor 4b, and the result is transmitted to the solenoid control unit 5d. The solenoid control unit 5d turns on the solenoid 5a if necessary based on the result. Here, the paper type detection unit 4
Although it is described that the paper size detection sensor 4a and the paper thickness detection sensor 4b are configured, the paper thickness detection sensor 4b
You can just do it. Note that the paper size detection sensor 4a
Can be detected, for example, by detecting a mark or the like provided on the cassette 9, and as the paper thickness detection sensor 4b, means for detecting the paper thickness based on the transmitted light amount of one transfer paper can be used. It is.

FIG. 4 is a flowchart showing the main operation of the guide member 3 according to the present invention in the vertical movement. The paper type of the transfer paper is detected by the paper type detection unit 4 (Step S)
1). It is determined whether or not the detected paper type is plain paper (S2).
. If the paper type is not plain paper (S2 No), it is determined that the paper is thick paper, and the routine exits. Returning to step S2, if the detected paper type is plain paper (Yes in S2)
Wait until the registration roller 12 is rotationally driven (S3 No), and if the registration roller 12 is rotationally driven (S3 Yes),
A delay timer for generating a timing for turning on the solenoid 5a is started (S4). It is asked whether the delay timer has reached the set time (S5). If the set time has not been reached, the process returns to step S5 and waits for the set time (S5 No). Therefore, if the set time has been reached (S
5 Yes), the solenoid 5a is turned on through the solenoid control unit 5d, and the guide member 3 is moved upward (S6).

Next, in order to generate a timing to turn off the solenoid 5a, the transfer paper P is detected by the trailing end detecting element 11 set near the registration roller 12.
It is asked whether or not the trailing edge has been detected (S7). If the rear end has not been detected, the process returns to step S7 and waits until the rear end is detected (S7 No). If the rear end is detected in step S7 (S7 Yes), the solenoid 5a
Then, a delay timer for generating a timing for turning OFF is started (S8). Furthermore, it is asked whether the delay timer has reached the set time (S9). If the set time has not been reached, the process returns to step S9 and waits for the set time (S9N).
o). If the set time has been reached (S9 Yes), the solenoid 5a is turned off, the guide member 3 is returned below the initial state (S10), and this routine ends.

[0013]

As described above, according to the first aspect of the present invention,
When a transfer paper of a predetermined paper type is detected, the guide up / down moving means moves the guide member upward to improve the adhesion between the transfer paper and the photosensitive drum, thereby transferring a paper type other than the predetermined paper type. When the paper is detected, the guide member is moved downward so as not to make too much contact with the photoconductor drum, and the problem of damaging the photoconductor drum surface can be prevented. It has become possible to provide an image forming apparatus in which defects are eliminated and the reliability of the photosensitive drum is improved.

According to the second aspect of the present invention, the guide vertical moving means determines the vertical movement after the transfer paper has passed over the guide member, and the leading end of the transfer paper hits the guide member to convey the paper. Since the sheet is not disturbed, the guide member can be made high enough to realize the effect of the adhesion between the transfer sheet and the photosensitive drum. An image forming apparatus with no defects can be provided.

According to the third aspect of the present invention, when the transfer paper of the thick paper is detected, the guide member is retracted downward with respect to the paper passing surface of the transfer paper, and when the transfer paper of the plain paper is detected. Since the guide member is moved upward with respect to the paper passing surface of the transfer paper, the adhesion to the photosensitive drum is improved, and transfer defects such as transfer omissions are eliminated regardless of the paper type. An image forming apparatus with improved reliability of the photosensitive drum can be provided.

[Brief description of the drawings]

FIG. 1 is a side view of a main part before operation of a guide member of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a side view of a main part after operation of a guide member of the image forming apparatus according to the exemplary embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a paper type detecting unit of the image forming apparatus according to the exemplary embodiment of the present invention.

FIG. 4 is a flowchart showing a main operation of the guide member according to the present invention in the vertical movement.

[Explanation of symbols]

1 image carrier or photosensitive drum, 2 transfer device, 3
Guide member, 4 paper type detecting section, 5 guide vertical moving means, 5a solenoid, 5b connecting hand, 5c spring, 5d solenoid control section, 6 transfer entrance guide, 9
Paper feed cassette, 11 Rear end detection element, 12 Registration roller, 13 Developing device

Claims (3)

[Claims] An image carrier for forming a toner image corresponding to a document image through a process of an electrostatic process; a transfer device for transferring the toner image formed on the image carrier to transfer paper; and the transfer device A guide member, which is located on the downstream side in the transfer paper transport direction and can move up and down with respect to the paper passing surface of the transfer paper, and paper type detection means for detecting the type of the transfer paper. An image forming apparatus comprising: a guide vertical moving unit that determines the vertical movement of the guide member with respect to the paper passing surface of the transfer paper according to the type of the detected transfer paper. 2. The apparatus according to claim 1, wherein the guide vertical moving unit moves the guide member upward with respect to a paper passing surface of the transfer paper.
2. The image forming apparatus according to claim 1, wherein the guide member is moved after the leading edge of the transfer paper has passed over the guide member. 3. When the paper type detecting means detects thick transfer paper, the guide member is retracted downward with respect to the paper passing surface of the transfer paper, and the paper type detecting means removes plain paper transfer paper. 3. The image forming apparatus according to claim 1, wherein when the detection is performed, the guide member is moved upward with respect to a sheet passing surface of the transfer sheet.