JPH07261564A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of preventing the occurrence of the re-transfer of a toner or a cleaner jam of paper by applying the proper charge removing current to the paper in response to the type of the paper and the environment. CONSTITUTION:This image forming device is provided with a photoreceptor drum (image carrier) 1, a transfer electrifier 10 transferring the developed image carried on the photoreceptor drum 1 to the paper 9, a separating charge remover 11 removing the charges of the paper 9, a paper sensor (constituted of a light transmitter 18 and a light receiver 19) detecting the time when the paper 9 passes through a conveyance section, and a control means controlling the current (separating/charge removing current) of the separating charge remover 11 based on the passing time of the paper 9 detected by the paper sensor. The separating/ charge removing current value is increased as the passing time of the paper 9 becomes longer, and the proper separating/charge removing current can be applied to the paper in response to the type of the paper 9 and the environment.

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 or a laser beam printer which uses an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, paper separation in an electrophotographic process in an image forming apparatus is carried out by removing a charge charged on the paper by a separation charger when transferring the toner to the paper which is a transfer material. The static elimination current of the separation charger was always fixed.

[0003]

However, if the static elimination current of the separation charger is set to a constant value as described above, the static elimination current is too strong when the paper type or environment (particularly humidity) changes. As a result, the toner again moves to the photosensitive drum side, retransfer occurs, or the charge removal current is insufficient, the paper does not separate from the photosensitive drum, and a cleaner thrust jam occurs.

The present invention has been made in view of the above problems, and an object of the present invention is to retransfer toner or to remove paper by applying an appropriate discharging current to the paper according to the type and environment of the paper. An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of a cleaner thrust jam or the like.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides an image carrier, a transfer charger for transferring a developed image carried on the image carrier to a paper, and charge removal for the paper. An image forming apparatus including a separation static eliminator controls a current of the separation static eliminator according to a paper sensor that detects a time when the paper passes through a conveyance unit and a paper passage time detected by the paper sensor. It is characterized in that a control means for controlling is provided.

[0006]

According to the present invention, the time required for the paper to pass through the transport section is detected by the paper sensor, and the longer the passing time, the more the separation current value is controlled. Therefore, the proper separation current is always set. It

That is, when the paper is difficult to separate from the image carrier and is detoured in the direction of the separation claw and separated, the paper passage time is long, and when the paper passes straight from the separation static eliminator to the conveyance section. Since the paper passage time is short, the paper separation time can be judged based on the paper passage time, and an optimum separation current can be applied to the paper.As a result, retransfer of toner or paper cleaner jam Occurrence is effectively prevented.

[0008]

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

FIG. 1 is a block diagram of a main part of an image forming apparatus according to the present invention.

In FIG. 1, reference numeral 1 denotes a photosensitive drum which is an image carrier, and the photosensitive drum 1 is rotationally driven in a direction indicated by an arrow at a predetermined speed, around which a primary charger 2, a developing sleeve 4, A pair of registration rollers 5 and 6, guide plates 7 and 8, a transfer charger 10, a separation charger 11, and a conveyance unit 1.
2, a separation claw 13 and a cleaner unit 14 are provided.

In addition, a fixing device 17 composed of a pair of heat rollers 15 and 16 is disposed near the transport section 12.

The primary charger 2 uniformly charges the photosensitive drum 1 in a negative charge. When the original image 3 is exposed on the photosensitive drum 1 by an original reading means (not shown),
An electrostatic latent image corresponding to the original image 3 is formed on the photosensitive drum 1. Then, the electrostatic latent image is developed by the toner carried on the developing sleeve 4 and visualized as a toner image.

On the other hand, the paper 9 as the transfer material is sent out along the guide plates 7 and 8 so as to come into contact with the photosensitive drum 1 by the pair of registration rollers 5 and 6 which are driven and controlled by a signal from a controller (not shown). Be done. Then, the transfer charger 10 transfers the toner image on the photosensitive drum 1 onto the paper 9 by corona discharge having a polarity opposite to that of the toner of the toner image formed on the photosensitive drum 1.

The paper 9 on which the toner image has been transferred as described above
, The charge charged by the transfer charger 10 is removed by the separation charger 11, and the attraction force with the photosensitive drum 1 is weakened. As a result, the paper 9 is caused by the strength of the waist of the paper 9 or by the action of the separating claw 13 to cause the photosensitive drum 1
And is sent to the transport unit 12.

The toner remaining on the photosensitive drum 1 which has been transferred is removed and cleaned by the cleaner unit 14 to prepare for the next image formation.

Then, the paper 9 on which the toner image has been transferred is
The toner image is fixed by heat and pressure by being conveyed between the heat rollers 15 and 16 by being conveyed to the fixing device 17 by the conveying unit 12, and the paper 9 on which the toner image is fixed is finally out of the apparatus. Is discharged.

The above is a description of a general electrostatographic process, but the construction in which the charge elimination current of the separation static eliminator 11 is controlled to an optimum value for the paper 9 by the separation delay of the paper 9 which is the gist of the present invention is described below. Will be described.

In this embodiment, a paper sensor for detecting the paper 9 is provided, and this paper sensor is composed of a light emitter 18 and a light receiver 19. The angle α formed by the traveling direction of the paper 9 and the optical axis of the light L emitted from the light emitter 18 is set to 30 ° to 75 °.

By the way, when the paper 9 is difficult to separate from the photosensitive drum 1 and detours toward the separating claw 13,
The leading edge of the paper 9 starts the registration rollers 5 and 6 (registration rollers 5 and 6 ON) and then passes the paper sensor (light L
(Hereinafter, referred to as paper passage time) becomes longer, and when the paper 9 goes straight from the separation static eliminator 11 to the transport unit 12, the paper passage time becomes shorter.

FIG. 2 shows the relationship between the paper passing time T and the separation charge-eliminating current I.

In FIG. 2, t ₁ is the passage time of the paper 9 when the paper 9 contacts the separation claw 13 and is separated from the photosensitive drum 1. Also, in curves A, B, and C, the paper 9 is thin paper,
Passage time T and separation static elimination current I for medium and thick paper
It shows the relationship of. Further, I _A , I _B , and I _C are allowable current values that do not cause retransfer of the toner to the photosensitive drum 1 again due to separation and charge elimination of the respective paper types.

Generally, as the transfer current is larger, the toner is more easily transferred from the photosensitive drum 1 to the paper 9, but at the same time, the paper 9 is strongly charged and attracted to the photosensitive drum 1. The charge of the paper 9 is eliminated by an AC current superposed with a DC current of opposite polarity.
If this DC current component is too strong, the toner on the paper 9 returns to the photosensitive drum 1 again, so-called retransfer occurs.

However, when the paper 9 comes into contact with the separation claw 13 (time t ₁ ), image rubbing by the separation claw 13 has already occurred. Since the plunging jam of 9 occurs, the separation charge-eliminating current I is set to the maximum value I _M.

Further, when the first sheet of paper 9 is used, the time t ₀ shown in FIG. 2 is set by the controller 21 (see FIG. 3) described later.
Is set. In FIG. 2, i _A , i _B , and i _C represent current values at time t ₀ .

Now, the operation of controlling the separation current in the image forming apparatus according to the present invention will be described with reference to the block diagram of FIG.

The controller 21 controls all the signals of the image forming apparatus and outputs the registration roller control signal necessary for controlling the separation current. Then, the motor control unit 2
2 is the registration rollers 5 and 6 according to the registration roller signal
The drive motor 23 for driving the

On the other hand, the registration roller control signal turns on the lamp in synchronization with the driving of the registration rollers 5 and 6 through the light emitter control section 24 which controls the light emitter 18, and drives the registration rollers 5 and 6 in synchronization. Turn off the lamp in synchronization.
Further, this registration roller control signal starts a timer 26 for measuring the paper passing time T via the timer ON gate signal converter 25.

The light from the light emitter 18 is received by the light receiver 19, and the output of the light receiver 19 is input to the timer OFF gate signal converter 27.

Then, the paper 9 conveyed in the image forming apparatus
When the light from the light emitter 18 is blocked, the timer OF
F gate signal converter 27 is turned off for timer 26
A signal is issued and the timer 26 is stopped.

The paper passing time T measured by the timer 26 is controlled by the controller 21 to be 9
The trailing end of the trailing edge passes through the separation charger 11 and is stored in the memory 28.

The data stored in the memory 28 is converted into a current control signal by the time / current value converter 29, and this current control signal determines the current value of the separation charger 11 via the separation current controller 30. To do.

On the other hand, the paper information input by the paper type input section 32 is input to the paper type conversion current curve selection section 31, and the conversion curves A, B, C shown in FIG. Is selected, and the separation static elimination current is set according to the selected conversion curve (A, B, C).

Although the control of the separation charge-eliminating current depending on the thickness of the paper 9 has been described above, similar control can be performed depending on the environment and the quality of the paper.

[0034]

As is apparent from the above description, according to the present invention, the image carrier, the transfer charger for transferring the developed image carried on the image carrier to the paper, and the paper are discharged. An image forming apparatus including a separation static eliminator controls a current of the separation static eliminator according to a paper sensor that detects a time when the paper passes through a conveyance unit and a paper passage time detected by the paper sensor. By providing the control means for controlling, it is possible to apply an appropriate static elimination current to the paper according to the type and environment of the paper, and it is possible to prevent the retransfer of toner and the occurrence of paper cleaner jams. To be

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between a separation charge-eliminating current I and a paper passage time T using a paper thickness as a parameter.

FIG. 3 is an operation block diagram of separation current control in the image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 9 Paper 10 Transfer charger 11 Separation charger 18 Light emitter (paper sensor) 19 Light receiver (paper sensor)

Claims (1)

[Claims] 1. An image forming apparatus comprising an image carrier, a transfer charger for transferring a developed image carried on the image carrier to paper, and a separation charge eliminator for discharging the paper. An image forming apparatus comprising: a paper sensor for detecting a time for the paper to pass through a conveyance unit; and a control unit for controlling a current of the separation static eliminator according to a paper passage time detected by the paper sensor. .