JP2000206799A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a toner from scattering in the case of transferring by discharging a transfer material well before the transferring with a simple constitution, without using a power source. SOLUTION: When a transfer material P is supplied from a paper supplying cassette 8, and triboelectricity is generated in the part of the material P due to the friction of a paper supplying roller 9, so that the toner on this part easily scatters in the case of toner image transfer. When humidity detected by a humidity sensor 17 is <=50%, a control means 16 makes a discharging brush 14 protrude in a transfer material carrying path 10 by a moving mechanism 15 so as to come into contact with the material P in the middle of being carried, and discharges the material P, so that the toner scattering in the case of toner image transfer can be prevented. When humidity is 50% or higher, a brush 14 is retreated from the path 10, the brush 14 is not brought into contact with the material P in the middle of being carried, and the material P is not discharged, so that a transfer charging current is prevented from being grounded through the material P, and the transfer omission can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a transfer material (for example, paper) to which a toner image formed on a photosensitive drum is transferred is loaded on a paper feed cassette and fed. The rollers are brought into contact with each other, and the sheets are sequentially fed one by one from the uppermost one by a predetermined frictional force and sent out to the transfer material transport path. The transferred transfer material is transported by a plurality of transport rollers and reaches a pair of registration rollers. In the pair of registration rollers, the leading edge of the transfer material is abutted against the nip portion of the two registration rollers to ensure parallelism between the nip portion and the leading edge, thereby preventing skew in the transfer direction of the transfer material. The toner is sent to the transfer charger while taking timing with the toner image on the photosensitive drum.

The toner image on the photosensitive drum is transferred to the transfer material sent at the proper timing by a transfer charger.
Thereafter, the toner image is fixed on the surface by the fixing device, whereby the copying (image formation) is completed.

[0004]

By the way, in an image forming apparatus which performs reversal development, various problems due to frictional charging are likely to occur. Unnecessary friction, especially in low humidity environments,
Toner scattering easily occurs. As described above, in this type of image forming apparatus, the transfer material is rubbed using the frictional force of the paper feed roller.
In such a case, the transfer material is strongly frictionally charged, and toner may be scattered at the contact portion during transfer.

[0005] In particular, in an image forming apparatus that performs normal development, in an apparatus that performs reversal development, a toner image is formed on a light portion (exposed area) of a photosensitive drum. Although the bonding force between the transfer material and the toner is weak and the charging current of the transfer charge is small, the transfer material is very susceptible to the unnecessary frictional charge of the transfer material as described above.

In order to prevent such a problem, it is conceivable to neutralize the transfer material on the upstream side of the transfer charger in the transfer direction of the transfer material. However, if the grounded neutralizing brush is simply kept in contact with the transfer material at all times, the transfer current escapes through the transfer material absorbed in high humidity and the grounded brush, resulting in transfer omission.

Therefore, conventionally, there has been proposed a method using a static elimination needle for the purpose of non-contact static elimination. However, a large static elimination effect cannot be obtained only by grounding the static elimination needle, and a bias must be applied. Therefore, there is a problem that a separate power supply is required, the configuration becomes complicated and the cost increases. Also, with respect to the bias output, an excessive voltage causes a leak, and an excessively low voltage does not satisfy the static elimination performance, and the latitude for achieving the static elimination performance is extremely narrow. According to the examination by the present applicant, it has been found that the best effect can be obtained when the transfer material is directly rubbed with a grounded brush.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a simple structure without using a power supply, which can satisfactorily remove electricity from a transfer material before transfer and prevent toner from scattering at the time of transfer. It is an object of the present invention to provide an image forming apparatus according to the present invention.

[0009]

According to a first aspect of the present invention, a toner image formed on a surface of an image carrier is transferred between the image carrier and a transfer unit. In an image forming apparatus for electrically transferring a transfer material fed to a transfer unit, a sheet feeding unit for feeding a transfer material stored in a storage unit toward the transfer unit by frictional force caused by rubbing A transfer material transporting path provided between the paper feeding unit and the transfer unit; and a charge removing member capable of contacting a transfer material transported in the transfer material transporting path. Switching means for switching between static elimination and non-static elimination of the material, a humidity sensor for detecting humidity, and control means for switching between static elimination and non-static elimination of the switching means in accordance with an output of the humidity sensor, I do.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the switching unit includes the movably disposed static elimination member and the static elimination member in the transfer material conveyance path. A moving mechanism that protrudes and makes contact with the transfer material in the transfer material conveyance path, and a movement mechanism that retreats from the transfer material conveyance path and moves it to a position that does not make contact with the transfer material in the transfer material conveyance path. , Characterized in that.

[0013] According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the switching unit is configured to constantly contact the transfer material conveyed in the transfer material conveyance path, and the charge elimination member; And a switch member for switching between grounding and non-grounding of the member.

According to a fourth aspect of the present invention, there is provided the first and second aspects.
In the image forming apparatus of the third aspect, the control unit performs charge elimination of the transfer material by the switching unit when the humidity detected by the humidity sensor is equal to or lower than a predetermined humidity, and performs transfer by the switching unit when the humidity exceeds the predetermined humidity. The material is not discharged.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the predetermined humidity is set within a range of 30 to 60%.

According to a sixth aspect of the present invention, there is provided the first and second aspects.
The image forming apparatus according to any one of 3, 4, or 5, wherein the charge removing member is a conductive charge removing brush.

According to a seventh aspect of the present invention, there is provided the first and second aspects.
A charging unit configured to uniformly charge the surface of the image carrier, an exposure unit configured to expose the charged surface of the image carrier to form an electrostatic latent image, Developing means for attaching toner to the electrostatic latent image to develop the toner image as a toner image, wherein the developing means is a developing means for performing reversal development with toner of the same polarity as the charged surface of the image carrier. It is characterized by the following.

[0016]

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

Embodiment 1 FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG.
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a laser beam printer.

The image forming apparatus shown in FIG. 1 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") 1 as an image carrier. The photosensitive drum 1 is supported rotatably in the direction of arrow R1. Around the photosensitive drum 1, a primary charger (charging means) 2 for uniformly charging the photosensitive drum 1 in order along the rotation direction, emits a laser beam corresponding to a document image to expose the photosensitive drum 1, Exposure device (exposure means) 3 for forming electrostatic latent image, developing device (developing means) for forming toner image by attaching toner to electrostatic latent image
4. A transfer charger 5 as a transfer means for transferring the toner image on the photosensitive drum 1 to a transfer material P such as paper, a charge elimination needle 6 for removing electricity from the back surface of the transfer material after transfer, and a residue on the photosensitive drum 1 after transfer. A cleaner 7 and the like for removing toner are arranged.

In FIG. 1, reference numeral 17 denotes a humidity sensor, and reference numeral 16 denotes a CPU (control means), which is arranged on a substrate of a DC controller (not shown). The humidity information of the humidity sensor 17 is sent to the CPU 16, and the CPU 16 controls the switching unit 13 for controlling the charge elimination state of the transfer material P.

On the other hand, on the upstream side of the photosensitive drum 1 in the transport direction of the transfer material P, a paper feed cassette 8 for loading and storing the transfer material P on which an image is to be formed is mounted. A paper supply roller (paper supply means) 9 is disposed above the front side of the paper supply cassette 8, and an electrically insulated transfer material transport path 10 is provided downstream thereof. Transfer material transfer path 10
A grounded neutralization brush (static elimination member) 14 for contacting the surface of the transfer material P to neutralize the transfer material P;
Rollers (not shown) for nipping and transporting the sheet P from the front and back, a registration sensor (not shown) for detecting the leading end of the transfer material P, a pair of registration rollers 11 including a metal roller and a rubber roller, and the transfer material P. A transfer entrance guide 12 that leads to the transfer area and is grounded via a resistor is sequentially provided.

Here, the configuration of the charge removing brush 14 will be described in detail. FIGS. 3A and 3B are schematic views of the static elimination brush of the present embodiment, wherein FIG. 3A is a front view and FIG. 3B is a side view. The static elimination brush 14 has a large number of wires 14a and an aluminum plate 14b holding the wires 14a. The wire 14a has a diameter of 1
Electrodes formed by bundling 100 stainless steel fibers of 2 μm into one electrode are appropriately arranged in parallel (for example, at a pitch of 1.6 mm), and attached to the aluminum plate 14b with a conductive tape. The aluminum plate 14b is grounded via a lead wire. Aluminum plate 14b of wire 14a
And the width W of the neutralizing brush in the longitudinal direction is at least equal to or longer than the length of the sheet feeding roller 9. In the present embodiment, a transfer material having a length of 300 mm that satisfies the maximum width of the transfer material is used. Further, the charge removing brush 14 is configured to be able to enter and exit the transfer material transport path 10, and the movement is performed by a moving mechanism 15 as switching means.
When the transfer mechanism 15 causes the charge removing brush 14 to protrude into the transfer material transport path 10 and contact the transfer material P,
It is desirable that the transfer material P be contacted at a predetermined angle so as not to hinder the conveyance of the transfer material P.

Now, when a print signal is input from the host computer (not shown) to the image forming apparatus, the photosensitive drum 1 starts rotating in the direction of arrow R1, and the surface of the photosensitive drum 1 is given a predetermined polarity (for example, by the primary charger 2). , Minus) at a predetermined potential. At this time, the paper feed roller 9 rotates, and the transfer material P is fed from the paper feed cassette 8. The fed transfer material P is nipped and transported by a transport roller (not shown), sent to the position of the registration sensor, reaches the registration roller 11, and temporarily stops. On the other hand, the charged surface on the surface of the photosensitive drum 1 is irradiated with a laser beam modulated by an image signal, and the charge on the irradiated portion is removed to form an electrostatic latent image. Next, the electrostatic latent image is reversely developed. That is, toner (minus charge) is attached to this electrostatic latent image by the developing roller 4a of the developing device 4, and is developed as a toner image. The registration roller 11 is driven again so as to synchronize with the toner image,
The transfer material P is transferred to the photosensitive drum 1 by the transfer charger 5 in the transfer region via the transfer entrance guide 12. After that, the transfer material P is fixed to a toner image by a fixing device (not shown) and is discharged outside the apparatus. On the other hand, the toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image is removed by the cleaner 7 to prepare for the next image forming cycle.

Hereinafter, the present embodiment will be described in more detail.

According to the study by the present applicant, the relationship between the humidity and the occurrence of toner scattering does not occur at about 30% or more at all, and starts to occur at 30% or less when there is no grounded neutralizing brush 14. If it is less than 10%, it surely occurred.

On the other hand, the grounded neutralizing brush 14 is transferred to the transfer material P
The relationship between the humidity and the state of occurrence of transfer omission did not occur at 60% or less, started to occur at 60% or more, and certainly occurred at 80% or more.

From the above, it can be understood that there is no problem in controlling the switching means 13 by the humidity sensor 17 if the humidity is set within the range of 30 to 60%.

Therefore, in the present embodiment, the humidity of the humidity sensor 17 for controlling the switching means 13 for switching between the charge elimination of the transfer material P and the charge elimination is set to 50%.

First, when the humidity sensor 17 detects that the humidity is lower than a predetermined humidity (for example, 5%), an output signal of the humidity sensor 17 is sent to the CPU 16 on the DC controller, and the signal is output to the CPU 16.
The PU 16 controls the switching unit 13 so that the discharging brush 14 projects into the transfer material transport path 10 before the transfer material P is fed (solid line in FIG. 1). Therefore, the static elimination brush 14
Is in contact with the transfer material P fed from the paper feed cassette 8 by the frictional force of the paper feed roller 9 and conveyed through the transfer material conveyance path 10. For this reason, the transfer material P, which has been rubbed by the paper feed roller 9 during paper feeding and has been strongly frictionally charged, is subjected to charge elimination by the charge elimination brush 14 on the downstream side.
When the toner image on the photosensitive drum 1 is transferred to the transfer material P, the toner does not scatter.

When the humidity sensor 17 detects that the humidity is equal to or higher than a predetermined humidity (for example, 90%), similarly, before the transfer material P is fed, the switching means 13 causes the CPU 16 to switch the neutralization brush 14 to the transfer material. Transfer material transport path 1 so as to be in contact
1 is retracted by retracting the neutralizing brush 14 (dotted line in FIG. 1). Therefore, the transfer material P is not in contact with the charge removing brush 14 (that is, the charge is not removed), so that the transfer charging current does not escape to the ground via the absorbed transfer material P. Therefore, transfer failure does not occur.

<Second Embodiment> In the first embodiment, the switching unit 1 switches between the charge elimination and the non-charge elimination of the transfer material P.
Control 3 was performed by moving the grounded neutralizing brush 14 so as to be in contact with or non-contact with the transfer material P. However, the present invention is not limited to this.

FIG. 2 shows another example. As shown in the figure,
The charge removing brush 14 always projects into the transfer material transport path 10 so as to always contact the transported transfer material P, while a switch (switch member) 1 as a switching unit.
8, the charge removing brush 14 may be switched to be electrically grounded or insulated.

In Embodiments 1 and 2 described above, an image forming apparatus that performs reversal development has been described. However, the present invention is applicable to an image forming apparatus that performs regular development, although there are differences in the degree of effect. Of course, it can also be applied.

[0033]

As described above, according to the present invention,
In accordance with the humidity detected by the humidity sensor, the control unit switches between static elimination and non-static elimination of the transfer material by the switching unit. When the value exceeds a predetermined value, the transfer material is not discharged, so that there is no transfer omission.

Further, since no bias is applied at the time of removing the charge of the transfer material, no additional power source is required and the configuration can be simplified accordingly.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment.

FIG. 3A is a front view of a static elimination brush. (B) is a side view of a static elimination brush.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Charging means (primary charger) 3 Exposure means (exposure apparatus) 4 Developing means (developing apparatus) 5 Transfer means (transfer charger) 9 Paper supply means (paper feed roller) 10 Transfer material Transport path 13 Switching means 14 Static elimination member (static elimination brush) 15 Moving mechanism 16 Control means (CPU) 17 Humidity sensor 18 Switch member (switch) P Transfer material

Claims (7)

[Claims] 1. A toner image formed on the surface of an image carrier,
An image forming apparatus for electrically transferring a transfer material fed to a transfer portion between the image bearing member and the transfer means, wherein the transfer material stored in the storage portion is rubbed by frictional force caused by rubbing. Paper feeding means for feeding paper toward the transfer section; a transfer material transport path provided between the paper feed means and the transfer section; and a transfer material transported in the transfer material transport path. Switching means for switching between static elimination and non-static elimination of the transfer material by the static elimination member; a humidity sensor for detecting humidity; and performing static elimination and non-static elimination of the switching means in accordance with an output of the humidity sensor. Switching means for controlling the image forming apparatus. 2. The switching unit comprises: a movably disposed static elimination member; and a position where the static elimination member is protruded into the transfer material transport path and comes into contact with the transfer material in the transfer material transport path. 2. The image forming apparatus according to claim 1, further comprising: a moving mechanism that retreats from the transfer material transport path and moves the transfer material to a position in the transfer material transport path that does not contact the transfer material. 3. The switching unit includes: a static elimination member that constantly contacts a transfer material conveyed in the transfer material conveyance path; and a switch member that switches the static elimination member between ground and non-ground. The image forming apparatus according to claim 1, wherein: 4. The control unit performs charge elimination of the transfer material by the switching unit when the humidity detected by the humidity sensor is equal to or lower than a predetermined humidity, and eliminates the charge of the transfer material by the switch unit when the humidity exceeds the predetermined humidity. The image forming apparatus according to claim 1, wherein the image forming apparatus does not perform the following. 5. The image forming apparatus according to claim 4, wherein the predetermined humidity is set within a range of 30% to 60%. 6. The image forming apparatus according to claim 1, wherein the discharging member is a conductive discharging brush. 7. A charging unit for uniformly charging the surface of the image carrier, an exposure unit for exposing the charged surface of the image carrier to form an electrostatic latent image, and attaching toner to the electrostatic latent image. And developing means for developing the toner image as a toner image, wherein the developing means is a developing means for performing reversal development with toner having the same polarity as the charged surface of the image carrier. 7. The image forming apparatus according to 2, 3, 4, 5, or 6.