JP3232887B2 - Paper transport mechanism of image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying mechanism of an image forming apparatus, and more particularly, to a sheet conveying mechanism of an image forming apparatus including a plurality of sheet guide members.

[0002]

2. Description of the Related Art A sheet guide member for guiding a sheet is provided at various places in a sheet conveying path of a copying machine or the like. Such a paper guide member has a problem in that when the potential increases due to friction with the paper or the like, the floating toner adheres to the paper guide and soils the paper. Also,
Particularly, in a paper guide member that guides a sheet to an opposing portion of a photoreceptor and a transfer charger, the transfer current flows into the sheet guide member due to a decrease in sheet resistance in a high-humidity environment, causing transfer failure. There was a problem.

For this reason, a technique for grounding a sheet guide member via a resistor has been proposed. In such a device, the potential of the paper guide member changes according to the environment due to the action of the resistance, and the potential is low at low humidity and normal humidity, and high at high humidity. Is resolved.

Further, when the potential of the paper guide member suddenly becomes extremely high due to the contact of a person with the paper guide member and the leakage of static electricity or the like, a slight discharge is generated between the paper guide member and the frame or the like. This may occur as signal noise in the CPU and cause the device to malfunction.
For this reason, there has been conventionally provided a device in which a paper guide member is grounded by using a constant voltage element such as a varistor in parallel with a resistor so that the paper guide member is not charged to a potential exceeding the rating of the constant voltage element. I have.

[0005] The grounding technique of the paper guide member as described above is
When applied to a paper transport mechanism composed of a plurality of paper guide members, each paper guide member is electrically connected to conduct,
It is often configured to be grounded at several places via a resistor or a constant voltage element. With this configuration, the number of resistors and constant voltage elements is reduced as compared with the case where each paper guide member is grounded, which is advantageous in terms of cost.

[0006]

However, in the paper transport mechanism configured as described above, when the paper transport path is opened, for example, for a paper jam, the electrical connection with the grounding point is cut off and the electrical connection is made. The paper guide member floats on the paper guide member. At this time, when an operator or the like during a paper jam process touches the paper guide member, the potential of the paper guide member temporarily becomes extremely high as described above, and noise may enter the CPU.

In view of such a problem, the present invention relates to a paper transport mechanism of an image forming apparatus including a plurality of paper guide members, and in any state of the paper transport mechanism, for example, in a state where the paper transport path is opened. It is an object of the present invention to provide a paper transport mechanism of an image forming apparatus in which each paper guide member is grounded without being electrically floated.

[0008]

As a specific means for achieving the above object, the present invention relates to a paper feeding mechanism of an image forming apparatus comprising a plurality of paper guide members provided in a paper feeding path. At this time, a conducting means for electrically connecting each sheet guide member to conduct electricity, a grounding means for grounding the sheet guide member conducted by the conducting means via a resistor or a constant voltage element, and a sheet transport path are opened. An auxiliary grounding unit that grounds the paper guide member that is insulated from the grounding unit when the conduction between the paper guide members is released, and an insulating unit that insulates the auxiliary grounding unit from each of the paper guide members during paper passing. With.

[0009]

When a sheet is passed, each sheet guide member provided in the sheet conveyance path is conducted and grounded via a resistor or a constant voltage element, while the sheet conveyance path is opened and the conduction between the sheet guide members is released. In this case, the paper guide member, which is insulated from the grounding point, is auxiliaryly grounded.

[0010]

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

[1. FIG. 1 is a diagram showing a state of a sheet transport mechanism when a copying machine to which the present invention is applied passes a sheet. In FIG. 1, reference numeral 10 denotes a vertical transport door. Vertical transfer door 1
A mounting plate 11 is provided inside 0. Mounting plate 11
Are attached to a ground terminal (not shown) via a varistor 6 and are grounded.

On the right side of the mounting plate 11 (inside of the main body of the copying machine), paper guide members 44 and 45 and transport rollers 46 and 47 are provided.
Is provided. The paper guide member 45 is in contact with the paper guide member 44 at point A, and is electrically connected to the mounting plate 11 by the leaf spring 13.

The multi-manual feed unit 20 is provided above the paper guide member 44. The multi manual feed unit 20 includes paper guide members 22 and 23 and transport rollers 24,
25. The paper guide members 22 and 23 are electrically connected to each other by being attached to a conductive frame or the like, and are electrically connected to the mounting plate 11 by the leaf spring 12. That is, the paper guide members of the multi manual feed unit 20 are electrically connected to the paper guide members 44 and 45 via the mounting plate 11. A paper guide member 21 made of a non-conductive material such as polyethylene or polypropylene is provided at a position facing the paper guide member 22. In addition, all the sheet guide members (including those described below) other than the sheet guide member 21 are formed of a conductive material.

A front transport unit 30 is provided on the right side of the multi manual feed unit 20. Front transport unit 30
Is composed of sheet guide members 31, 32, 33, 34, 35 and transport rollers 36, 37, 38, 39. Each paper guide member of the front transport unit 30 is electrically connected to each other in the same manner as in the case of the multi-manual feed unit 20, and is connected to a ground terminal (not shown) via the resistor 4 and the varistor 5, and is grounded. 26 is electrically connected to each sheet guide member of the multi manual feed unit 20.

At the upper right of the front transport unit 30, the photosensitive member 1
Are provided, and a transfer charger 2 and a separation charger 3 are provided at a position facing the lower portion of the photoconductor 1.
A sheet guide member 4 is provided between the photoconductor 1 and the front conveyance unit 30.
0 and 41 are provided, and a leaf spring 42 and a lead wire 4 are provided, respectively.
3, it is electrically connected to each paper guide member of the front transport unit 30. That is, in the paper transport mechanism of the copying machine of the present embodiment, each paper guide member is conductive when the paper is passed, and is grounded via the resistor 4 and the varistors 5 and 6. In the present embodiment, the sheet guide members are electrically connected to each other by a plate spring, a lead wire, and an attachment plate to conduct electricity.
What is necessary is just to use what is suitable according to a structure, space, etc. of an apparatus. Further, the varistors 5 and 6 may be other constant voltage elements such as Zener diodes.

In the above-described paper transport mechanism, the paper is transported according to the following procedure. When the paper is fed from a paper storage unit (not shown) in the copying machine main body (automatic paper feeding), the paper passes through a paper transport path formed by the paper guide members 44 and 45 and the paper guide members 21 and 22 and is forwarded. After reaching the transport unit 30 and passing through a paper transport path formed by the paper guide members 31, 32 and 33, 34, 35, the paper guide members 40,
At 41, it is guided to the opposing portion of the photoconductor 1 and the transfer charger 2. At such a position, corona discharge is performed by the transfer charger 2 from the back of the sheet, and the toner image on the photoconductor 1 is transferred to the sheet.

On the other hand, when the paper is manually fed from the outside of the copying machine main body (manual paper feeding), the paper is pre-conveyed through the paper conveyance path formed by the paper guide members 22 and 23 of the multi manual feeding unit 20. It reaches unit 30. Thereafter, the sheet is sent to the transfer position in the same manner as in the case of the automatic sheet feeding, and the transfer is performed.

In the paper transport mechanism of the copying machine of the present embodiment, as described above, each paper guide member is grounded via the resistor 4 and the varistors 5 and 6 when the paper is passed. Therefore, the potential of the sheet guide member is low enough to prevent the floating toner from adhering in a low humidity and normal humidity environment due to the action of the resistor 4, and high enough not to allow the transfer current to flow in the high humidity environment. Is prevented,
The action of the varistors 5 and 6 prevents the potential of the paper guide member from suddenly rising and noise from entering the CPU. In addition, since the paper guide members are electrically connected, the number of grounding portions can be reduced, so that the number of resistors and varistors is reduced, which is advantageous in terms of cost.

[2. At the time of paper jam processing (vertical transport door 10 is open)] In the copying machine of the present embodiment, the vertical transport door 10 is openable and closable. The road can be opened. FIG. 2 is a diagram illustrating a state of the paper transport mechanism when the vertical transport door 10 is opened. When the vertical transport door 10 is opened, the multi manual feed unit 20 moves with the vertical transport door 10 and separates from the front transport unit 30. At this time, multi-bypass unit 2
Each of the sheet guide members 0 is electrically connected to the mounting plate 11 via the leaf spring 12 and is grounded via the varistor 6. Each paper guide member of the front transport unit 30 is grounded via the resistor 4 and the varistor 5. However, the sheet guide members 44 and 45 are moved by the leaf spring 13
And the paper guide member 45 are separated from each other, so that any of the above-mentioned grounding points is not grounded.

FIG. 3 is a diagram showing the operation of the paper guide members 44 and 45 when the vertical transport door 10 is opened. In FIG. 3, what is indicated by a two-dot chain line is when paper is passed (the vertical conveyance door 10
In the closed state. 1 (see FIG. 1). When the vertical transport door 10 is opened, the paper guide member 45 is released from the pressing force of the leaf spring 13, falls down in the direction indicated by the arrow in FIG. 3 by its own weight, and comes into contact with the mounting plate 50 and stops. At the time of paper passing, the leaf spring 49 regulated by the protrusion 15 of the vertical transport door 10 (see FIG. 1) comes into contact with the mounting plate 48 of the paper guide member 44. The mounting plate 50 and the leaf spring 49 are each connected to a ground terminal (not shown) and grounded, whereby the paper guide members 44 and 45 are auxiliary grounded. That is, even when the vertical transport door 10 is opened, each paper guide member is grounded without being in an electrically floating state.

Therefore, even if an operator during paper jam processing touches the paper guide member and static electricity leaks, the potential of the paper guide member does not suddenly rise and noise does not enter the CPU.

As described above, the mounting plate 50 and the leaf spring 49 are insulated from the paper guide members 44 and 45 when paper is passed, and are connected only when paper is not passed (when the vertical conveyance door 10 is opened). Alternatively, it can be directly grounded without passing through a varistor. For this reason, the aforementioned cost advantage is not impaired.

Although the present embodiment has been described with reference to a copying machine as an example, the present invention can be applied to an image forming apparatus having a plurality of paper guide members, such as a printer, in addition to the embodiments.

[0024]

According to the present invention, in a sheet transport mechanism of an image forming apparatus provided with a plurality of sheet guide members, each sheet guide member is conductive when paper is passed, and is grounded via a resistor or a constant voltage element. Therefore, transfer failure due to paper contamination due to the adhesion of the floating toner and inflow of the transfer current is prevented.
In addition, since each sheet guide member is conductive, the number of resistances or constant voltage elements can be reduced as a result of minimizing the number of grounding points, which is advantageous in terms of cost.

On the other hand, when the sheet conveying path is opened and the conduction between the sheet guide members is released, the sheet guide member insulated from the grounding point at the time of sheet passing is connected to the auxiliary grounding point. For example, even if an operator or the like during a paper jam process touches the paper guide member and the static electricity leaks, the potential of the paper guide member does not suddenly rise and noise does not enter the CPU. Further, since the auxiliary grounding portion is insulated from the paper guide member when the paper is passed, it can be directly grounded without passing through a resistor or a constant voltage element, and the above-described cost advantage is impaired. Absent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a sheet transport mechanism of a copying machine according to an embodiment when a sheet is passed.

FIG. 2 is a cross-sectional view of a sheet transport mechanism of the copying machine of the present embodiment during a paper jam process.

FIG. 3 is a cross-sectional view illustrating an operation of a part of the sheet transport mechanism of the copying machine according to the present exemplary embodiment during a paper jam process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Transfer charger, 4 ... Resistance, 5.6
... Varistor, 10 ... Vertical transfer door, 20 ... Multi manual feed unit, 30 ... Front transfer unit, 11 ... Mounting plate, 12.1
3 ・ 26 ・ 42 ・ 49 ... leaf spring, 21 ・ 22 ・ 23.3
1, 32, 33, 34, 35, 40, 41, 44, 45
… Paper guide member

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B65H 5/00-5/38

Claims (1)

(57) [Claims] A conductive means for electrically connecting and guiding each of the sheet guide members during sheet passing in a sheet conveying mechanism of an image forming apparatus comprising a plurality of sheet guide members provided in a sheet conveying path; Grounding means for grounding the sheet guide member conducted by the conducting means via a resistor or a constant voltage element, and when the sheet conveyance path is opened and conduction between the sheet guide members is released, the sheet guide member is insulated from the grounding means. A sheet transport mechanism of an image forming apparatus, comprising: an auxiliary grounding means for grounding a paper guide member; and an insulating means for insulating the auxiliary grounding means and each paper guide member when paper is passed.