JPH0895325A - Image forming device - Google Patents

Abstract

PURPOSE: To excellently carry a transfer material by making attracting force act on the transfer material in a guiding member and making the attracting force different among the respective parts of the guiding member. CONSTITUTION: The transfer material which passes through a transfer part and on which a developer image is carried is fed to a fixing device along a carrying guide (guiding member) 8, and heated and pressured by a nip between a fixing roller and a pressure roller, so that the developer image is permanently fixed on the transfer material. Thereafter, the transfer material is ejected to a paper ejection tray. The carrying guide 8 is constituted by attaching a sheet metal member 8a for attraction electrically grounded to a member having a rib 8b. The transfer material 6 passing through the transfer part advances by force for pushing out the guide 8 from the transfer part first, and then it advances by the stiffness of the transfer paper 6. Therefore, since the attracting force of the guide 8 is set weaker on the fixing part side, the frictional force of the rib 8b and the transfer material 6 becomes weaker than the transfer part side, thereby allowing the transfer material 6 to smoothly enter the fixing part.

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.

[0002]

2. Description of the Related Art FIG. 8 is a vertical sectional view of a conventional electrophotographic image forming apparatus. 106 is a transfer material such as paper,
It is supplied from the paper cassette 111 into the apparatus by the paper feed roller 112 through the registration device 113.

Reference numeral 101 denotes an image bearing member such as a photosensitive drum. The surface of the image bearing member is cleaned by a cleaning device 102 and then charged to a desired potential by a charging member 103. The exposure device 104 exposes the image according to image information to form an image. Carrier 101
An electrostatic latent image corresponding to image information is formed on the surface of the.

The electrostatic latent image is developed by the developer moved by the developing device 105. A transfer member 107 abuts on the image carrier 101, the transfer material 106 is supplied to the transfer portion, electric charges are supplied to the back surface of the transfer material 106, and the developer is transferred to the surface of the transfer material 106.

The transfer material 106 on which the image of the developer that has passed through the transfer portion is placed is sent to a fixing device 109 along a conveyance guide 108 (see FIG. 9) and heated and pressed by a nip between the fixing roller and the pressure roller. Then, the developer image is permanently fixed to the transfer material 106. Then, the paper is discharged to the paper discharge tray 110.

FIG. 9 shows the structure of a conventional conveyance guide 108.

In FIG. 9, the conveyance guide 108 is ABS.
It is constituted by a sheet metal member 108a made of resin such as zinc coated steel. The sheet metal member 108a is the transfer material 1 being conveyed.
It has a function of adsorbing 06, and stably conveys the transfer material 106 to the fixing portion. Reference numeral 108b denotes a resin rib, which prevents the transfer material 106 and the sheet metal member 108a from coming into contact with each other and disturbing the developer image on the transfer material 106.

[0008]

However, in the above-mentioned conventional example, it is possible to obtain a structure capable of stably feeding the transfer material in a low speed machine or an image forming apparatus having a small number of paper sizes. High speed machines and image forming apparatuses with many types of paper sizes have the following problems.

Generally, an image forming apparatus that passes large-sized paper needs to pass not only large-sized paper but also normal-sized or small-sized paper. Since the paper may have horizontal or vertical grain in the manufacturing process, the strength of the strainer of the paper in the image forming apparatus changes depending on the type of paper size, the paper passing direction and the like.

Transfer material 106 extruded from the transfer nip
When the sheet is conveyed along the conveyance guide 108, if the suction force is too strong on the fixing portion side of the conveyance guide 108, the transfer material 1
The transport speed of the leading end of 06 becomes slow or stops, and when it is sent to the fixing device 109, it is delayed or incomplete, and the image forming apparatus detects it and stops. It was easy to get up on paper.

Further, when the suction force is weakened by the transport guide 108 in order to prevent the delay of the transfer material 106, the rear end of the transfer material 106 immediately after passing through the transfer portion is splashed to the opposite side of the transport guide 108, and the transfer material before fixing is fixed. There is a problem that the image of the developer on 106 is disturbed.

It is difficult to realize the image forming apparatus at a low cost because the setting range in which the above-mentioned conveyance delay and the trailing edge splash do not occur is small.

Further, in the image forming apparatus having the double-sided printing function, the transfer material 10 which has once passed through the fixing device 109 is used.
6 has a weaker paper strain, and the state of paper conveyance differs between single-sided printing and double-sided printing. Therefore, the range of the above-mentioned setting that does not cause delay in conveyance and the trailing edge splashing is considerably smaller. , The fixing device 109, the transfer member 107, the conveyance guide 108, etc. need to be considerably high in positional accuracy.
It was a cause of cost increase.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an image forming apparatus capable of favorably carrying a transfer material.

[0015]

In order to achieve the above object, in the present invention, an image carrier, a transfer unit in the vicinity of the image carrier, and a fixing unit for fixing an image on a transfer material. ,
In an image forming apparatus provided with a guide member for conveying the transfer material from the transfer means side to the fixing means side, the guide member exerts a suction force on the transfer material, and the suction force is applied to each part of the guide member. Are different in.

The attraction force of the guide member is preferably weak on the fixing means side.

The attraction force of the guide member is preferably strong on the transfer means side.

The guide member may include an insulating rib and a sheet metal made of a conductor.

The sheet metal forming the guide member preferably has a large area on the transfer means side and a small area on the fixing means side.

In the guide member, the distance between the rib and the surface of the sheet metal may be small on the transfer means side and large on the fixing means side.

The sheet metal forming the guide member may be divided into a plurality of pieces.

The sheet metal forming the guide member may be divided into a transfer means side and a fixing means side, and a bias voltage may be applied thereto.

It is preferable that the sheet metal having the double-sided printing function and applied to the sheet metal constituting the guide member have different bias voltages when the transfer material for the first side printing is conveyed and when the transfer material for the second side printing is conveyed.

[0024]

In the image forming apparatus constructed as described above, the guide member exerts a suction force on the transfer material, and this suction force is different in each part of the guide member, so that the transfer material is conveyed in each part. Adsorption force is obtained.

Since the attracting force of the guide member is weak on the fixing means side, the frictional force with the transfer material on the fixing means side is weakened, and the transfer material can be smoothly fed to the transfer means side.

Since the attracting force of the guide member is strong on the transfer means side, the trailing edge of the transfer material is conveyed without fluttering, so that the developer image on the transfer material is not disturbed.

Since the guide member is composed of an insulating rib and a sheet metal made of a conductor, the guide member can be obtained with a simple structure.

Since the sheet metal forming the guide member has a large area on the transfer means side and a small area on the fixing means side, it is easy to make a difference in the attraction force to the transfer material.

In the guide member, since the distance between the rib and the surface of the sheet metal is small on the transfer means side and large on the fixing means side, it is easy to make a difference in the attraction force to the transfer material.

Since the sheet metal constituting the guide member is divided into a plurality of pieces, the attraction force for the transfer material can be set by each sheet metal.

The sheet metal constituting the guide member is divided into the transfer means side and the fixing means side, and by applying a bias voltage, the attraction force can be differentiated with a simple structure.

Since the bias voltage applied to the sheet metal constituting the guide member having the double-sided printing function is different between when the transfer material for the first-side printing is conveyed and when the transfer material for the second-side printing is conveyed, each of the transfer material is conveyed. The bias voltage is set according to.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 6 denotes a transfer material such as paper, which is supplied from the paper cassette 11 to the inside of the apparatus through the registration device 13 by the paper feed roller 12.

Reference numeral 1 denotes an image bearing member such as a photosensitive drum. The surface of the image bearing member is cleaned by the cleaning device 2 and then charged to a desired potential by the charging member 3, and the exposure device 4 exposes the image in accordance with image information to form an image. An electrostatic latent image corresponding to image information is formed on the surface of the carrier 1.

The developing device 5 moves the developer to the electrostatic latent image to develop it. A transfer member (transfer means) 7 is brought into contact with the image carrier 1, the transfer material 6 is supplied to the transfer member 7, electric charges are supplied to the back surface of the transfer material 6, and a developer is applied to the surface of the transfer material 6. Is transcribed to.

The transfer material 6 on which the image of the developer passed through the transfer portion is placed is sent to a fixing device (fixing means) 9 along a conveyance guide (guide member) 8 and heated by a nip between the fixing roller and the pressure roller. , And the developer image is permanently fixed to the transfer material 6. After that, the paper is discharged to the paper discharge tray 10.

(First Embodiment) FIG. 2 shows only the conveyance guide 8 of FIG.

In FIG. 2, the conveyance guide 8 is a sheet metal member (sheet metal) for suction that is electrically grounded to a member having a rib 8b.
8a is attached.

The height of the ribs 8b is kept constant at 3 mm from the surface of the sheet metal member 8a, and the ribs 8b have a width of 2 mm and are arranged at intervals of 16 mm.

The suction sheet metal member 8a has a width which is narrower on the fixing portion side and is 8 mm in this embodiment.

In the present embodiment, since the negative developer is used, the positive charge is applied to the back surface of the transfer material 6 by the transfer member 7 so that the transferred developer image is stable and the surface of the transfer material 6 is stable. It is designed to be adsorbed on.

The transfer material 6 that has passed through the transfer first advances by the force of pushing the conveyance guide 8 out of the transfer portion, and then advances by a strainer of the transfer material 6. Conventionally, the suction force of the transport guide 8 may be too strong and delayed at the portion where the paper is advanced.

However, in this embodiment, since the suction force of the transport guide 8 can be set weaker on the fixing portion side, the frictional force between the rib 8b and the transfer material 6 is smaller than that on the transfer portion side, and the transfer is smoothly performed on the fixing portion. Material 6 can be put in. On the contrary, when the suction force of the transport guide 8 is stronger on the fixing unit side than on the transfer unit side, a loop may occur during the transport of the transfer material 6, and the developer on the transfer material 6 is disturbed. Will end up.

However, if the suction force is too weak, the conveyance guide 8
Since the transfer material 6 floats from above, it is desirable that the width of the suction sheet metal member 8a on the fixing portion side is 4 to 12 mm in order to obtain stable conveyance of the transfer material 6.

Of course, the shape of the sheet metal member 8a is not limited to this embodiment, and the same effect can be obtained even if the width is gradually narrowed from the transfer portion side to the fixing portion side.

(Second Embodiment) FIG. 3 is a view showing a conveyance guide (guide member) 81 of an image forming apparatus according to a second embodiment of the present invention.

In the figure, the conveyance guide 81 is a rib 81.
A sheet metal member (sheet metal) 81a that is electrically grounded is attached to the member having b.

The height of the rib 81b is kept constant at 3 mm from the surface of the sheet metal member 81a, and the rib 81b has a height of 2 mm.
, And are arranged at intervals of 16 mm.

The sheet metal member 81a is provided with a plurality of holes on the fixing unit side. By doing so, the suction force that the transfer material 6 receives from the transport guide 81 is reduced by the amount of the hole portion, so that the suction force on the fixing portion side can be weakened and the same effect as in the first embodiment can be obtained. The frictional force between the rib 81b and the transfer material 6 is smaller than that on the transfer portion side, and the transfer material 6 can be smoothly inserted into the fixing portion.

However, if the suction force is too weak, the conveyance guide 8
Since the transfer material 6 floats from No. 1, the size of the holes on the fixing portion side of the sheet metal member 81b is φ1 to 3 mm, and the number of the holes is 4 to 10 pieces / cm ^{2 in} order to obtain stable transfer of the transfer material 6.
Is desirable.

Of course, the shape of the sheet metal member 81b is not limited to this embodiment. For example, the density of holes may be gradually increased from the transfer section side to the fixing section side, or may not be holes. If the area of the sheet metal member 81b is reduced, the attraction force to the transfer material 6 is weaker on the fixing portion side than on the transfer portion side, and the same effect can be obtained.

(Third Embodiment) FIG. 4 is a drawing showing a conveyance guide (guide member) 82 of an image forming apparatus according to a third embodiment of the present invention.

In the figure, the conveyance guide 82 is a rib 82.
It has a structure in which a sheet metal member (sheet metal) 82a for electric attraction that is electrically grounded is attached to a member having b. The present embodiment is characterized in that the height of the rib 82b from the surface of the sheet metal member 82a is low on the transfer portion side and high on the fixing portion side.

When the height of the rib 82b from the sheet metal member 82a is low, the transfer material 6 receives a large suction force, and on the contrary, the rib 8b.
When the height of 2b is high, the suction force is small. Therefore, in the present invention, the suction force is strong on the transfer portion side where the height (h ₂ ) of the rib 82b is low, and the suction force is weak on the fixing portion side where the height (h ₁ ) of the rib 82b is high.

By doing so, the first embodiment and the second embodiment
Similar to the embodiment, the transfer material 6 has a weak adsorption force on the fixing portion side.
Can be smoothly inserted into the fixing portion without being hindered by the friction with the rib 82b.

Further, the problem that the developer image on the transfer material 6 is shaken and disturbed due to the trailing edge of the transfer material 6 bouncing immediately after leaving the transfer portion side has a strong suction force on the transfer portion side. Because it does not occur.

If the height of the ribs 82b is too low on the transfer portion side, the back surface of the transfer material 6 may come into contact with the sheet metal member 82a, and the image may be disturbed. Also, the ribs 82b on the fixing portion side are too high, and the ribs 82b are attracted. If the force becomes too weak, the transfer material 6 may float on the transfer portion side, which may disturb the conveyance.

Therefore, the height of the rib 82b on the transfer portion side is 1
˜2 mm is desirable, and the height on the fixing section side is desirably 2-5 mm.

(Fourth Embodiment) FIGS. 5 and 6 show a fourth embodiment of the present invention.
Conveyance guide (guide member) 8 of the image forming apparatus according to the embodiment
It is a drawing showing 4.

In the figure, the conveyance guide 84 is a rib 84.
The sheet metal member (sheet metal) 82a for adsorption, which is electrically grounded, and the sheet metal member 84c biased by the DC bias power source 84d are attached to the member having b.

The present embodiment is characterized in that the DC bias power source 84d applies a DC bias to the sheet metal member 84c to increase the attraction force on the transfer portion side.

By doing so, the rear end spring of the transfer material 6 can be prevented, so that the transfer material 6 can be stably transported.

(Fifth Embodiment) FIG. 7 is a drawing showing a conveyance guide (guide member) 85 of an image forming apparatus according to a fifth embodiment of the present invention.

In the figure, the conveyance guide 85 is a rib 85.
The sheet metal member (sheet metal) 85c for adsorption biased by the DC bias power source 85d and the sheet metal member (sheet metal) 85a for adsorption biased by the DC bias power source 85e are attached to the member having b. .

In this embodiment, a bias voltage is applied to the sheet metal member 85a for suction and the sheet metal member 85c, and a bias applied to the sheet metal member 85a on the transfer portion side is applied to the sheet metal member 85c on the fixing portion side. It is also characterized by increasing.

By doing so, the suction force on the transfer portion side can be strengthened and the suction force on the fixing portion side can be weakened. Therefore, it is possible to stably carry the paper as in the first to fourth embodiments.

Further, according to the present invention, in the image forming apparatus (not shown) having the double-sided printing function, the suction force on the fixing portion side of the second side is set to be weak for the first side and the second side, The transfer material 6 at the time of printing on the second side where the strain of the paper has weakened through the fixing device could be stably conveyed without any problem.

The bias voltage applied to the attracting sheet metal members 85a and 85c is, for example, -300 V for the sheet metal member 85a and -500 for the sheet metal member 85c during one-side printing.
V, -200V on the sheet metal member 85a during double-sided printing,
-450V was applied to the sheet metal member 85c.

In this embodiment, the suction sheet metal member is divided into two parts, that is, the transfer part side and the fixing part side. However, the present invention is not limited to this. For example, three, four, or more May be divided into a plurality of parts.

(Other Embodiments) By appropriately combining the above-described first to fifth embodiments, a conveyance guide with higher performance can be provided, and this conveyance guide can be applied to an image forming apparatus. it can.

[0073]

As described above, in the present invention, the guide member exerts an adsorbing force on the transfer material, and this adsorbing force is different in each part of the guide member, so that the transfer material is conveyed in each part. Adsorption force is obtained, and the transfer material can be stably conveyed.

Since the attracting force of the guide member is weak on the fixing means side, the frictional force with the transfer material is weakened on the fixing means side, and the transfer material can be conveyed smoothly. That is, unlike the case where the fixing unit has a large frictional force, a loop does not occur in the transfer material and the developer on the transfer material is not disturbed. Further, on the transfer means side, the rear end of the transfer material passes through the transfer means and is adsorbed by a strong adsorption force, so that the developer is not disturbed and disturbed.

Since the guide member is composed of the insulating rib and the sheet metal made of a conductor, the guide member can be obtained with a simple structure and the cost can be reduced.

Since the area of the sheet metal constituting the guide member is large on the transfer means side and small on the fixing means side, it is easy to make a difference in the attraction force for the transfer material, and the performance of the guide member is improved.

In the guide member, since the distance between the rib and the surface of the sheet metal is small on the transfer means side and large on the fixing means side, it is easy to make a difference in the attraction force to the transfer material, and the performance of the guide member is improved.

Since the sheet metal constituting the guide member is divided into a plurality of pieces, the attraction force for the transfer material can be set by each sheet metal, and a highly accurate guide member can be obtained.

The sheet metal constituting the guide member is divided into the transfer means side and the fixing means side, and by applying the bias voltage, the attraction force is made different with a simple structure, and the cost is reduced.

Since the bias voltage applied to the sheet metal which has the double-sided printing function and which constitutes the guide member is different between when the transfer material for the first side printing is conveyed and when the transfer material for the second side printing is conveyed, each of the transfer material is conveyed. Bias voltage can be set according to
Stable transfer material transfer is obtained for both the first-side printing and the second-side printing.

[Brief description of drawings]

FIG. 1 is a schematic view showing an image forming apparatus which is an embodiment of the present invention.

FIG. 2 is a perspective view showing a conveyance guide applied to the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a conveyance guide applied to an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a conveyance guide applied to an image forming apparatus which is a third embodiment of the present invention.

FIG. 5 is a perspective view showing a conveyance guide applied to an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing a conveyance guide applied to an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view showing a conveyance guide applied to an image forming apparatus which is a fifth embodiment of the present invention.

FIG. 8 is a schematic view showing a conventional image forming apparatus.

FIG. 9 is a schematic view showing a conveyance guide applied to a conventional image forming apparatus.

[Explanation of symbols]

1, 101 image carrier 6, 106 transfer material 7, 107 transfer member (transfer means) 8, 81, 82, 84, 85, 108 transport guide (guide means) 9, 109 fixing device (fixing means) 8a, 81a, 82a, 84a, 85a, 108a Sheet metal member (sheet metal) 8b, 81b, 82b, 84b, 85b, 108b Rib 85c Sheet metal member (sheet metal) 84d, 85d, 85e Bias power supply

Front Page Continuation (72) Inventor Kazuro Ono 3-30-2 Shimomaruko, Ota-ku, Tokyo In Canon Inc. (72) Inventor Norio Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo In Canon Co., Ltd. (72) Inventor Yasunari Ohara, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Masaharu Okubo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Invention Person Takayasu Yukinochi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (9)

[Claims] 1. An image carrier, a transfer means near the image carrier, a fixing means for fixing an image on a transfer material, and a guide for conveying the transfer material from the transfer means side to the fixing means side. In the image forming apparatus, the guide member exerts a suction force on the transfer material, and the suction force is different in each portion of the guide member. 2. The image forming apparatus according to claim 1, wherein the attraction force of the guide member is weak on the fixing unit side. 3. The image forming apparatus according to claim 1, wherein the attraction force of the guide member is strong on the transfer unit side. 4. The image forming apparatus according to claim 1, wherein the guide member includes an insulating rib and a sheet metal made of a conductor. 5. The image forming apparatus according to claim 4, wherein the sheet metal forming the guide member has a large area on the transfer unit side and a small area on the fixing unit side. 6. The image forming apparatus according to claim 4, wherein in the guide member, the distance between the rib and the surface of the sheet metal is small on the transfer unit side and large on the fixing unit side. 7. The sheet metal forming the guide member is divided into a plurality of pieces.
The image forming apparatus according to item 1. 8. The image forming apparatus according to claim 4, 5, 6 or 7, wherein the sheet metal forming the guide member is divided into a transfer unit side and a fixing unit side, and a bias voltage is applied thereto. apparatus. 9. A double-sided printing function is provided, and the bias voltage applied to the sheet metal constituting the guide member is different between when the transfer material for the first side printing is conveyed and when the transfer material for the second side printing is conveyed. Image forming apparatus.