JPH10340015A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image without faulty attraction and faulty transfer even in the case of the sudden change of atmospheric environment which exerts an influence on the moisture content of recording material. SOLUTION: The moisture content of the recording material detected by a sensor 19 detecting the moisture content of the recording material is stored in a memory 22, and attraction bias and transfer bias are respectively impressed on an attraction electrifier 7 and a transfer electrifier 10 from an attraction bias power source 102 and a transfer bias power source 101 through a control means 18 variably adjusting a feed quantity based on the moisture content stored in the memory 22. Thus, even when the atmospheric environment is suddenly fluctuated, the change of the moisture content of the recording material to be used is grasped and power is optimally fed to the electrifiers 7 and 10, so that the high-quality image is always obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an electrophotographic or electrostatic recording type image forming apparatus.
For example, a visible image (toner image) formed on an image carrier by electrostatically attracting and holding a recording material on a recording material holding means such as a transfer sheet and applying an electric field to the recording material. The present invention is suitably embodied in a color image forming apparatus such as a multicolor electrophotographic copying machine or a color printer which obtains a color image by superimposing and transferring the image on the recording material.

[0002]

2. Description of the Related Art For example, a multicolored electron is obtained by superimposing a visible image (toner image) formed on an image carrier onto a recording material such as transfer paper carried on a transfer sheet to obtain a color image. In a color image forming apparatus such as a photocopier or a color printer, an attraction / charging unit is used so that a stable state of adsorption of a recording material onto a transfer sheet is obtained, and furthermore, stable and good transfer can be performed. In addition, the amount of power supplied to the transfer charging unit is controlled.

[0003]

However, in such a conventional apparatus, a temporal change in physical properties of the recording material due to a temporal change in an environment in which the recording material is accommodated, particularly, a resistance value, a dielectric constant, etc. The temporal change has been overlooked. For example, in a case where the atmosphere environment in which the recording material is accommodated changes rapidly from high humidity to low humidity, the apparatus body side determines that the humidity is low, and performs adsorption charging and transfer charging according to the low humidity. As described above, the amount of power supply to be applied to the adsorption charging unit and the transfer charging unit is controlled.

On the other hand, in the case of the recording material, the water content does not change abruptly, that is, the water does not rapidly evaporate from the recording material. Even if it changes to, the recording material, for the time being,
The same physical properties as those on the high humidity side, that is, the same resistance and dielectric constant are shown. In addition, the change in the amount of water is different between the contained recording materials at the upper end portion, the middle portion, and the lower end portion. It has a gradual change in water content.

Further, even when a recording material that has just been opened from a packaging material or a recording material brought in from a different atmosphere environment is used immediately, the condition of the recording material differs from the atmosphere environment sensed by the apparatus body. That can happen.

[0006] In such a case, a problem occurs between the suction charging or the transfer charging and the recording material, and unexpected suction failure, transfer failure, etc. occur to cause a paper jam or a defective image. Is output.

Accordingly, it is an object of the present invention to set the conditions for adsorption and transfer charging while monitoring the moisture content of a recording material, thereby achieving good adsorption and transfer failure even in a sudden change in the atmospheric environment. An object of the present invention is to provide an image forming apparatus capable of obtaining an image.

[0008]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image carrier on which a visible image is formed, and a recording material carrier for carrying a recording material onto which the visible image formed on the image carrier is transferred by electrostatic adsorption and transporting the recording material to a transfer position of the image carrier Means, an adsorption charging means operable to adsorb the recording material to the recording material holding means, a transfer charging means operable to transfer the visible image onto the recording material, and detecting a water content of the recording material. Detecting means, storing means for storing information on the amount of moisture detected by the detecting means, and variably adjusting the amount of power supplied to the adsorption charging means and the transfer charging means based on the information on the amount of moisture stored in the storing means. An image forming apparatus comprising: a control unit.

It is preferable that the power supply amount of the transfer charging means is determined in accordance with the power supply amount of the attraction charging means. The charging characteristics of the developer for obtaining the visible image vary depending on the amount of water in the developer. In this case, it is preferable that the amount of power supplied to the transfer charging unit is variably adjusted by detecting the amount of water in the developer.

The water content detecting means is a detecting means for detecting the water content by measuring the absorption of infrared or microwave light by the water contained in the recording material. It is preferable that the storage unit stores the moisture content information for a predetermined time. It is preferable that paper type and / or paper thickness data is fed back to the water content detection means.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIGS.

In the color electrophotographic image forming apparatus of this embodiment shown in FIG. 1, an electrophotographic photosensitive drum 3 as an image carrier is rotated in the direction of an arrow, and is uniformly charged by a charger 4. Next, image exposure is performed by a laser beam E modulated by a yellow image signal of a document (not shown), and an electrostatic latent image is formed on the photosensitive drum 3.

On the other hand, a rotary developing device 1 is arranged adjacent to the photosensitive drum 3 in this embodiment. The rotary developing device 1 includes a yellow developing device 1Y, a magenta developing device 1M, a cyan developing device 1C, and a black developing device 1BK mounted on a rotating body 1a. Is transported to a position facing the. Further, each developer is supplied with a developer from the yellow hopper 2Y, the magenta hopper 2M, the cyan hopper 2C, and the black hopper 2BK of the developer (toner) replenishing device 2, respectively.

The latent image formed on the photosensitive drum 3 is developed by the yellow developing device 1Y stopped at the developing position in advance, and a visible image, that is, a toner image is formed on the photosensitive drum 3. On the other hand, a recording material such as transfer paper, which has progressed from the paper feed cassette 20a or the paper feed cassette 20b via the paper feed guide 5a, the paper feed roller 6, and the paper feed guide 5b, is transferred to the transfer drum 9 at a predetermined timing. Is sent.
At this time, the recording material is electrostatically attracted to the transfer drum 9 by the attraction charger 7 serving as the attraction / charging means and the contact roller 8, and is wound around the transfer drum 9.

The transfer drum 9 has a recording material holding means on its surface,
That is, the transfer sheet 9 a is wound and configured to rotate in the direction of the arrow in synchronization with the photosensitive drum 3. The toner image developed by the yellow developing device 1Y is transferred to a recording material by a transfer charger 10 which is a transfer charger in a transfer section. The transfer drum 9 continues to rotate and prepares for the transfer of the next color, magenta in this embodiment.

After the transfer, the photosensitive drum 3 is cleaned by the cleaner 12, and then charged again by the charger 4, and is exposed by the next magenta image signal in the same manner as described above. During this time, the developing device 1 rotates, and the magenta developing device 1M is fixed at a predetermined developing position and performs a predetermined magenta development.

Subsequently, images are formed for cyan and black by the same operation as described above, and the transfer of toner images of four colors is performed. When the superimposition transfer of the four color toner images is completed in this way, the four color toner images on the recording material are discharged by the chargers 13 and 14, separated from the transfer drum 9 by the separation claws 15, and fixed by the transport belt 16. Vessel 1
7, a series of full-color printing operations is completed,
A full-color print image is formed.

The apparatus is provided with a moisture sensor 19 as moisture detecting means for detecting the moisture content of the recording material fed and conveyed from the sheet cassettes 20a and 20b containing the recording material. Then, the detection information is notified to the control means 18 described later.

FIG. 2 is a block diagram for briefly explaining the control configuration of the color electrophotographic image forming apparatus shown in FIG. In FIG. 1, a transfer bias power supply 101 for supplying power to the transfer charger 10 and a suction bias power supply 102 for supplying power to the suction charger 7 are connected to control means 18 such as a microcomputer for controlling the output value of the power supply. Have been. The control means 18 is connected to the moisture sensor 19 and also to a memory 22 as storage means.

In the image forming apparatus configured as described above, when the moisture content of the recording material is detected by the moisture content sensor 19, this information is stored in the storage means, that is, the memory 22,
The control means 18 variably adjusts the amount of power supply to the adsorption charger 7 and the transfer charger 10 based on the stored moisture amount information, and determines the amount of power supply corresponding to the amount of water in the recording material, while controlling the amount of electricity supplied to the adsorption charger 7 and transfer. Optimal power supply to the charger 10 is performed.

FIG. 3 shows that when the adsorption current of a certain value is applied to the adsorption charger 7, the water content of the recording material flows on the horizontal axis, and actually flows in the direction of the contact roller 8 as a counter electrode. 5 is a graph showing the relationship between the two with the attraction current as the vertical axis. Here, the suction current actually flowing to the contact roller 8 is
The figure shows the difference between the attraction bias current applied to the attraction charger 7 and the shield current flowing into the shield of the attraction charger 7.

As can be seen from FIG. 3, when the moisture content of the recording material increases, the resistance value decreases, so that the discharge load in the direction of the recording material, that is, the direction of the contact roller 8 decreases in the attraction charging. Then, the suction current in the direction of the contact roller 8 when a certain current flows in the suction charger 7 increases. On the other hand, if the amount of water in the recording material decreases, the suction current in the direction of the contact roller 8 decreases, contrary to the above.

Next, in the graph of FIG. 4, the water content is 6.5%.
4 shows the relationship between the attracting current (horizontal axis) in the direction of the contact roller 8 and the attracting force (vertical axis) of A4 size transfer paper as the recording material when the recording material is attracted.

The above-described suction force is obtained by using a polyvinylidene fluoride resin film as the transfer sheet 9a of the transfer drum 9, pulling the A4-size recording material adsorbed on the transfer sheet 9a by a spring, and applying a force to the recording material. It was determined by measuring the critical tension when sliding out.

From the above, it can be seen that a constant attracting force can be always obtained by changing the bias current applied to the attracting charger in accordance with the amount of water in the recording material.

FIG. 5 shows the water content of the recording material when the transfer current of a certain value is applied to the transfer charger 10 on the horizontal axis.
7 is a graph showing the relationship between the current actually flowing in the direction of the photosensitive drum 3 as the counter electrode and the vertical axis. Here, the transfer current actually flowing to the photosensitive drum 3 includes a transfer bias current applied to the transfer charger 7 and a transfer bias current applied to the transfer charger 7.
The figure shows the difference from the shield current flowing into the shield of FIG.

As can be seen from FIG. 5, as the water content of the recording material increases, the resistance value decreases.
In the transfer charging, the discharge load in the recording material direction, that is, in the direction of the photosensitive drum 3 decreases, and the transfer current in the direction of the photosensitive drum 3 when a certain current flows to the transfer charger 10 increases. On the other hand, if the amount of water in the recording material is reduced, the transfer current in the direction of the photosensitive drum 3 is reduced, contrary to the above.

Next, in the graph of FIG. 6, the water content is 6.5%.
5 shows the relative relationship between the attracting current (horizontal axis) in the direction of the photosensitive drum 3 and the transfer efficiency (vertical axis) when the image is transferred onto the recording material.

As shown in this figure, for each water content of the recording material,
There is a transfer current in the direction of the photosensitive drum 3 at which the maximum transfer efficiency can be obtained. That is, by changing the bias current applied to the transfer charger 10 in accordance with the amount of water in the recording material, high transfer efficiency can always be obtained.

The water content sensor 19 as a means for detecting the water content of the recording material can detect light in a short time, that is, absorb the light (such as infrared rays and microwaves) by the water contained in the recording material. It is desirable to use a type that can be detected.

In this embodiment, the position of the water content sensor 19 is set at a portion where the recording material is fed and conveyed, and the water content of the passing recording material is measured. Alternatively, it may be installed in the vicinity of the paper feed tray to measure the moisture content of the recording material in a stacked state.

Further, a moisture sensor 19 of a type for detecting the moisture content of the recording material by absorbing light by the moisture contained in the recording material.
Since the light absorption rate differs depending on the weighing, material, color, etc. of the recording material, in order to accurately detect the water content, information on the paper type and paper thickness input by the user in advance, paper It is desirable that information from a thickness sensor (not shown) or the like be fed back to the water content sensor 19 so that the water content can be accurately detected for various types of recording materials.

In the above description, the necessity of changing the bias power supply applied to the attraction charger 7 and the bias power supply applied to the transfer charger 10 according to the water content of the recording material has been described. They cannot be set independently and have a close correlation with each other. More specifically, the transfer bias current value is dependently determined by the attraction bias current value. The details are shown below.

FIGS. 7A and 7B schematically show the transfer sheet 9a after passing through the adsorption charging and the state of the electric charge adhering to the recording material P. FIG. The (+) charge given by the suction bias and the (-) charge induced by the contact roller 8 are in a stable suction state.

As described above, the transfer sheet 9a is made of polyvinylidene fluoride and has a volume resistivity of 10 ¹⁵ Ω ·
cm, and the time constant is several hours, so that the charges (+) and (-) are held until the transfer charge is received.

Next, in the case of transfer charging, as shown in FIG. 7 (C), when charging is performed with the same output I1 as the _first charging, (+) charge by the previous adsorption charging becomes a barrier,
The released (+) charge hardly moves in the direction of the photosensitive drum 3, that is, does not adhere to the transfer sheet 9a. However, FIG.
As shown in (D), I _2> case of performing a transfer charging in I ₁ becomes the output current I _2, and adhered to move to (+) beyond the barrier due to the charge (+) charge transfer sheet 9a , And attracts ions such as nitrogen and oxygen in the air and forms a stable state. That is, good transfer is performed. Here, when setting the output bias current, the potential change ΔV (the difference between the surface potential of the recording material immediately before and immediately after the recording material passes through the transfer portion) is a current setting value ΔV ≧ 0.5 kV It is experimentally known that it is sufficient to set.

Furthermore, in a full-color multiple transfer system, in particular, the transfer is repeated four times in addition to the adsorption charging, and the above description applies to each transfer. That is,
The transfer bias current is set to secure a potential difference of 0.5 kV or more. In this case, if the bias current is increased unnecessarily, the saturation charge potential is reached before the transfer of the final color, and the transfer of the second half, such as the third color and the fourth color, becomes defective. Therefore, it is usually preferable to set the transfer belt current such that ΔV = 0.5 kV.

As can be seen from the above description, if the attraction current is determined, the subsequent transfer current is also determined experimentally.

As described above, according to the present embodiment, by setting the suction bias current value and the transfer bias current value while monitoring the moisture content of the recording material with the moisture content sensor, the sudden change in the atmospheric environment can be achieved. Also poor suction,
A good image without transfer failure can be obtained.

Embodiment 2 Next, Embodiment 2 of the present invention will be described with reference to FIG. In the first embodiment, a one-drum type color image forming apparatus has been described, but in the present embodiment, the present invention is applied to a four-drum side-by-side color image forming apparatus. Hereinafter, this embodiment will be described.

In the image forming apparatus of FIG. 8, each of the image forming units I to IV has the same configuration, and those having the same configuration and operation as those of the image forming apparatus shown in FIG. It is.

In this embodiment, each of the image forming units I to IV includes a primary charger 4a, 4b, 4c, 4d around a photosensitive drum 3a, 3b, 3c, 3d, and an exposure unit Ea,
Eb, Ec, Ed, developing units 1a, 1b, 1c, 1d, transfer chargers 10a, 10b, 10c, 10d, discharging units 13a, 13b, 13c, 13d; 14a, 14b, 14
c, 14d and cleaners 12a, 12b, 12c, 1
2d.

A recording material holding means 99 is disposed below the photosensitive drums 3a to 3d in the form of an endless conveyance belt penetrating the image forming units I to IV, and conveys the recording material P at a predetermined speed. .

The recording material P is accommodated in a paper feed cassette 20, and a water content sensor 19 is disposed near the paper feed conveyance path to notify a print control unit PCON (not shown) of the water content. Has become.

After the recording material P is fed by the feed roller 6, each of the image forming units I to IV is transported by the transport belt 99.
Are transferred through a transfer section in which transfer chargers 10a to 10d are disposed.

In the image forming apparatus having the above-described configuration, the bias power supply output for the transfer charging is controlled by the print control unit PCO based on the information on the water content of the recording material in the same manner as in the above embodiment.
Even when the atmosphere environment is changed suddenly, good adsorption and transfer can always be performed, and a good color image without transfer failure or the like can be formed.

Example 3 A change in charging characteristics due to a change in the environment of a developer used for image formation, ie, a toner, greatly affects transfer.

In particular, the charging characteristics vary greatly depending on the environment.
For example, characteristics as shown in FIG. 9, that is, the amount of water (g / kg)
In the case of using a toner whose charge amount (μC / g) and the charge amount (μC / g) are inversely proportional, substantially the same as in the first embodiment described above,
Stable image formation can be performed by directly detecting the water content of the toner in the hopper or the developing device by the water content sensor and controlling the transfer charging condition.

This is also effective when the dried toner is suddenly supplied to the main unit in a humid environment.

In the description of each embodiment, the adsorption charging means and the transfer charging means have been described as corona chargers. However, it is not possible to use a device for charging, such as a charging roller or a charging brush. It is not against the spirit of the invention.

[0052]

As is apparent from the above description, the image forming apparatus according to the present invention has a detecting means for detecting the water content of the recording material and a storage means for storing the information on the water content detected by the detecting means. And adjusting means for variably adjusting the amount of power supplied to the adsorbing means and the transfer charging means based on the amount of water stored by the storing means. Thus, it is possible to perform the optimal power supply to the adsorption charging unit and the transfer charging unit by capturing the change in the amount of water, and to always obtain a high quality image.

As described above, according to the present invention, it is possible to obtain a good image without defective adsorption and poor transfer even if the ambient environment changes suddenly and a defect occurs between the transfer charging and the physical properties of the recording material. It is possible to achieve an excellent effect such as the formation of

[Brief description of the drawings]

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

FIG. 2 is a control block diagram for explaining a control configuration of the apparatus of FIG. 1;

FIG. 3 is a graph showing a relationship between a water content of a recording material and a current flowing in a direction of a contact roller.

FIG. 4 is a graph showing a relationship between a current flowing in a contact roller direction and a suction force when a recording material having a water content of 6.5% is suctioned.

FIG. 5 is a graph showing the relationship between the amount of water in the recording material and the current flowing in the direction of the photosensitive drum.

FIG. 6 is a graph showing a relationship between a current flowing in the direction of the photosensitive drum during transfer to a recording material having a water content of 6.5% and transfer efficiency.

FIG. 7 is a model diagram showing electric charges generated on the recording material carrier and the recording material during adsorption and transfer.

FIG. 8 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 9 is a graph showing an example of the amount of water in air and the amount of toner charge according to the third embodiment.

[Explanation of symbols]

 3 Image Carrier (Photosensitive Drum) 7 Adsorption Charging Unit (Adsorption Charging Unit) 9 Transfer Drum 9a Recording Material Support Unit (Transfer Sheet) 10 Transfer Charging Unit (Transfer Charging Unit) 18 Control Unit 19 Water Content Detection Unit 22 Storage Unit ( memory)

Claims (7)

[Claims] An image carrier on which a visible image is formed and a recording material on which the visible image formed on the image carrier is transferred are electrostatically attracted to a transfer position of the image carrier. A recording material carrying unit that conveys, an adsorption charging unit that operates to adsorb the recording material to the recording material holding unit, a transfer charging unit that operates to transfer the visible image onto the recording material, Detecting means for detecting the amount of water, storage means for storing information on the amount of water detected by the detecting means, and power supply to the adsorption charging means and the transfer charging means based on the information on the amount of water stored in the storing means An image forming apparatus comprising: a control unit that variably adjusts an amount. 2. The image forming apparatus according to claim 1, wherein the power supply amount of the transfer charging unit is determined in accordance with the power supply amount of the attraction charging unit. 3. The image forming apparatus according to claim 1, wherein a charge characteristic of the developer for obtaining the visible image varies depending on a water content of the developer. 4. An image forming apparatus according to claim 3, wherein the amount of power supply to said transfer charging means is variably adjusted by detecting the amount of water in the developer. 5. The apparatus according to claim 1, wherein the water content detecting means is a detecting means for detecting a water content by measuring absorption of infrared or microwave light by water contained in the recording material. Image forming device. 6. The image forming apparatus according to claim 1, wherein the storage unit stores the moisture content information for a predetermined time. 7. An image forming apparatus according to claim 5, wherein data of paper type and / or paper thickness is fed back to said moisture amount detecting means.