JP2001092278A - Image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain an satisfactory image by performing appropriate transfer to small size recording material, without being influenced by the material values of an image carrier, a recording material carrier and recording material and the like even when the installation environment of a device and the standing environment of the recording material are changed and the material values are changed. SOLUTION: A plural color toner image, superimposed and primarily transferred from a photoreceptor drum, is transferred secondarily to the recording material by applying secondary transfer bias to a transfer roller 2, abutting on an intermediate transfer belt through the recording material in this image- forming device. At this time, the allotted voltage of a secondary transfer roller is made high, and the allotted voltage of the intermediate transfer belt is made low so that a sufficient transfer current is secured by making the resistance ratio of a paper passing part and a paper non-passing part at a secondary transfer part small, even when the small size recording material passes.

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, a facsimile, and a printer for obtaining a hard copy by forming an image on a recording material using an electrophotographic method.

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming units are provided, and each image forming unit forms a toner image of a different color, and the toner images are successively superimposed on the same recording material to a color image. Various image forming apparatuses have been proposed.

[0003] Under such circumstances, an electrophotographic color copying machine using an intermediate transfer member has been developed. An example of a color electrophotographic recording apparatus will be described with reference to FIG. 6. In the apparatus, first, second, third, and fourth image forming units Pa, Pb, Pc, and Pd are provided side by side. Forming part Pa
Through Pd, toner images of different colors are formed through the processes of latent image formation, development, and transfer.

The image forming units Pa, Pb, Pc, and Pd each have a dedicated image carrier, in this embodiment, an electrophotographic photosensitive drum 3.
a, 3b, 3c, 3d.
A toner image of each color is formed on b, 3c and 3d. A belt-shaped intermediate transfer member, that is, an intermediate transfer belt 130 is installed adjacent to each of the photosensitive drums 3a, 3b, 3c, and 3d.
The toner images of the respective colors formed on the photosensitive drums 3a, 3b, 3c, and 3d are primarily transferred onto the intermediate transfer belt 130, and then secondarily transferred onto the recording material P. The recording material P to which the toner images of the respective colors have been transferred is fixed to the toner image by heating and pressurizing in a fixing device 9 and then discharged out of the device as a color recorded image.

[0005] Drum chargers 2a, 2b, 2c, 2d are provided on the outer periphery of the photosensitive drums 3a, 3b, 3c, 3d, respectively.
d, developing devices 1a, 1b, 1c, 1d, primary transfer chargers (charging blades) 24a, 24b, 24c, 24d, and cleaners 4a, 4b, 4c, 4d, which are not further shown above the apparatus A light source device is installed.

The laser light emitted from the light source device is scanned by a rotating polygon mirror, the light beam of the scanning light is deflected by a reflection mirror, and collected by an fθ lens in the generatrix direction of each of the photosensitive drums 3a, 3b, 3c and 3d. By performing light exposure, an electrostatic latent image corresponding to an image signal is formed on each of the photosensitive drums 3a, 3b, 3c, and 3d.

The developing devices 1a, 1b, 1c, and 1d are filled with a predetermined amount of cyan, magenta, yellow, and black toners, respectively, by a supply device (not shown). The developing devices 1a, 1b, 1c, and 1d develop the latent images on the photosensitive drums 3a, 3b, 3c, and 3d, respectively, and visualize the latent images as cyan, magenta, yellow, and black toner images.

The obtained cyan toner image, magenta toner image, yellow toner image and black toner image are respectively transferred to primary transfer chargers 1a, 1b, 1c and 1d at respective primary transfer portions.
Is temporarily transferred onto the intermediate transfer belt 130 to form a full-color toner image.
The secondary transfer unit 11 collectively transfers the recording material P to the recording material P conveyed to the secondary transfer unit 30 by the secondary transfer charger 11 (transfer roller).

The recording material P is accommodated in a recording material cassette 10 and is supplied to the intermediate transfer belt 130 through a plurality of transport rollers and registration rollers 12 so that four color toner images on the intermediate transfer belt 130 are formed. The secondary transfer is performed.

The intermediate transfer belt 130 is made of a sheet of a dielectric resin such as polyethylene terephthalate resin (PET), polyvinylidene fluoride resin, or polyurethane resin. Or seamless (seamless) belts.

As the primary transfer charger 24 (24a to 24d) and the secondary transfer charger 11, a non-contact charger such as a corona discharge or a charging member such as a conductive blade, roller, or brush is used. Use the contact charger. The non-contact charger has problems such as generation of ozone, and susceptibility to fluctuations in the temperature and humidity environment of the atmosphere due to charging through air, resulting in unstable image formation. The contact charger has no such problems, and has advantages such as ozonelessness, resistance to environmental changes in temperature and humidity, and high image quality.

The recording material P after the secondary transfer is conveyed to the fixing device 9. The fixing device 9 includes a fixing roller 51, a pressure roller 52,
A heat-resistant cleaning member (not shown) for cleaning each of them; a heater installed in rollers 51 and 52; an application roller for applying a release agent oil such as dimethyl silicone oil to fixing roller 51; It comprises a reservoir and a thermistor that detects the temperature of the surface of the pressure roller 52 and controls the fixing temperature.

The recording material P to which the four color toner images have been transferred is
By the fixing, the color mixture of the toner image and the fixation to the recording material P are performed to form a full-color copy image, and the image is discharged to the paper discharge tray 63.

The photosensitive drums 3a, 3b, 3 after the transfer is completed
c and 3d are the respective cleaners 4a, 4b, 4c and 4d
Thus, the transfer residual toner is cleaned and removed, and the apparatus is ready for the formation of the next latent image. Toner and other foreign matter remaining on the intermediate transfer belt 130 are wiped off by bringing a cleaning web (nonwoven fabric) 19 into contact with the surface of the intermediate transfer belt 130.

Next, the secondary transfer section will be described in detail. Conventionally, it has been known that the image is stabilized when the secondary transfer charger 11 makes the current contributing at the time of transfer constant at an appropriate current. Therefore, it is general to perform constant current control so that a constant current can be obtained even when the volume resistivity changes depending on the type (thickness, material, etc.) of the recording material, moisture absorption conditions, and the like.

As shown in FIG. 7, the transfer current at the transfer portion is I
[ΜA], the recording material width is W [cm], and the process speed is v [cm / sec], the surface charge density ρ on the recording material P
“ΜC / cm ² ” is: ρ = I / (W × v) As described above, transfer is stably performed by applying a charge having a constant surface charge density to the recording material.

The secondary transfer charger, that is, the transfer roller 11 is a charging roller having a metal core as a shaft and having a conductive rubber provided on a surface layer thereof. Since the conductive rubber layer plays the role of an electrode, it has a sufficiently low resistance as compared with the intermediate transfer belt, and the conductive rubber layer is a conductor having a volume resistance of about 10 ⁶ Ωcm.

On the other hand, the intermediate transfer belt 130 is generally
It consists of films of engineering plastics such as ET and PC. These plastic films are usually 1
It has a volume resistivity of about 0 ¹⁶ Ωcm and a relative dielectric constant of 3 to 4.
Dielectric of the order.

The intermediate transfer belt 130 is an insulator, and can be regarded as a capacitor from that viewpoint. Then
When the intermediate transfer belt 130 is not rotating, no transfer current flows. However, the rotation causes empty capacitors to come to the transfer roller 11 one after another, and the transfer roller charges the intermediate transfer belt. Can be seen.

That is, when the intermediate transfer belt 130 is not rotating, it is a capacitor. However, it can be considered that a constant current flows as the intermediate transfer belt 130 rotates and becomes an electric resistance.

At this time, a constant voltage is applied to the transfer power supply (high-voltage power supply) through which the transfer current flows. This is the transfer voltage. FIG. 8A shows the vicinity of the secondary transfer unit, and FIG. 8B shows an equivalent circuit of the secondary transfer unit. In general, the electric resistance sharing the transfer voltage is higher in the intermediate transfer belt 13
0, the recording material P, the secondary transfer roller 11, and the secondary transfer opposing roller 14 (however, the order is different depending on the image forming apparatus and the type of the recording material). By applying the transfer voltage, a voltage is applied to this resistor, and each part shares the transfer voltage.

Now, let the volume resistance value of the secondary transfer roller 11 be ρ
a2, the thickness of the conductive layer is 1 and the transfer nip is d, the resistance Ra2 of the transfer roller at the time of transfer is Ra2 = ρa2 · l / d.

Similarly, the resistance of the intermediate transfer belt 130 is set to R
b, if its volume resistivity is ρb and its thickness is t, then Rb = ρb · t / d.

However, actually, since the transfer roller 11 and the intermediate transfer belt 130 are rotating, the resistance of the rotating intermediate transfer belt is lower than that during the stop. Assuming that the impedance during rotation during image formation is Z and the secondary transfer voltage is V2, Z = V2 / I using the secondary transfer current I.

[0025]

Generally, in this type of apparatus, recording materials of various sizes can be used.
In order to perform proper transfer even when a small-size recording material is passed, the surface charge density on the recording material must be the same as when the maximum-size recording material has passed. That is, as shown in FIG. 9A, the current flowing through the paper passing portion is represented by Iw [μ
A], the current flowing in the non-sheet passing portion is Iu [μA], the recording material width is w [cm], the width of the non-sheet passing portion is u [cm], and the width of the transfer roller 11 is G, and the transfer current I , Ρ = Iw / (w × v) = I / (G × v) using the process speed v. Here, W (the large-sized recording material width in FIG. 7) ≒ G.

However, since the resistance of the recording material itself exists in the paper passing portion, the impedance is higher than that in the non-paper passing portion. Therefore, the current per unit area flowing through the paper passing portion is smaller than that of the non-paper passing portion, and the surface charge density on the recording material is also smaller than that of the non-paper passing portion. For this reason, the surface charge density on the recording material becomes insufficient, the transfer efficiency decreases, and a sufficient image density cannot be obtained.

That is, in reality, Iu / (u × v)> I / (G × v)> Iw / (w × v), and the paper passing portion has an insufficient charge density and the non-paper passing portion has an excess charge density. .

FIG. 9B shows an equivalent circuit when small-size paper is passed. The ratio between the current 1w flowing to the paper passing portion and the current Iu flowing to the non-paper passing portion is inversely proportional to the resistance ratio between the paper passing portion and the non-paper passing portion. That is, the resistance of the paper passing portion is Rw,
Assuming that the resistance of the non-sheet passing portion is Ru, Iw: Iu = Ru: Rw.

This problem is particularly problematic in low humidity environments (for example, 2
This is likely to occur when transferring to a recording material that has been dried at 3 ° C., 5% RH) and has increased resistance. Generally, the volume resistivity of the recording material is about 10 ⁷ to 10 ¹⁴ Ωcm depending on the type and temperature and humidity conditions.
Vary to the extent. However, the intermediate transfer belt is made of a dielectric resin sheet, and its volume resistivity changes only by about 1 to 3 digits depending on temperature and humidity conditions. This phenomenon is more likely to occur in an intermediate transfer belt of a low volume resistance whose resistance is adjusted by an additive.

When small-sized paper is passed in this way, a large amount of current flows in the non-paper passing portion having a small resistance, and the current flowing in the paper passing portion becomes insufficient, resulting in transfer failure. The recording material has a very high volume resistivity under a low humidity environment, but even in such a case, if the surface charge density is not the same as the surface charge density on the maximum size recording material, a transfer failure occurs.

When the resistance of the intermediate transfer member is low, an overcurrent may flow through a member in contact with the intermediate transfer member. When the secondary transfer current flows to the photosensitive drum through the intermediate transfer member, primary transfer failure and image failure such as a drum memory occur.

The object of the present invention is affected by changes in the physical properties of the image carrier, the recording material carrier, the recording material, etc. due to changes in the environment in which the apparatus is installed, the environment in which the recording material is left, and the like. An object of the present invention is to provide an image forming apparatus capable of performing a proper transfer to a small-sized recording material without any trouble and stably obtaining a good image without a transfer failure.

[0033]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
In an image forming apparatus including an image carrier on which a visible image is formed, and a transfer unit that transfers the visible image formed on the image carrier to a recording material, a sharing voltage applied to the transfer unit at the time of the transfer is controlled. An image forming apparatus is characterized in that the voltage is higher than a shared voltage applied to the image carrier.

The present invention also provides an image carrier on which a visible image is formed, an intermediate transfer member on which the visible image formed on the image carrier is primarily transferred, and a visible image transferred on the intermediate transfer member. In an image forming apparatus provided with a transfer unit that performs a secondary transfer of an image onto a recording material, the shared voltage applied to the secondary transfer unit during the secondary transfer is set to be higher than the shared voltage applied to the intermediate transfer body. The image forming apparatus is a feature.

According to the present invention, there is provided a recording material carrier for carrying the recording material and transporting the recording material to the intermediate transfer member, wherein the shared voltage applied to the secondary transfer means during the secondary transfer and the recording material carrier The total amount of the shared voltage applied to the intermediate transfer member is set to be larger than the total amount of the shared voltage applied to the intermediate transfer member. Further, the intermediate transfer member is a belt-shaped intermediate transfer member, and an opposing roller is opposed to the secondary transfer member with the intermediate transfer member interposed therebetween, and the shared voltage applied to the secondary transfer member during the secondary transfer and the opposing roller are opposed to each other. The total amount of the voltage applied to the roller was set to be larger than the voltage applied to the intermediate transfer member. A recording material carrier that carries the recording material and conveys the recording material to the intermediate transfer member; and a shared voltage applied to the secondary transfer unit, a shared voltage applied to the opposed roller, and the recording material carrier during the secondary transfer. The total amount of the shared voltage applied to the intermediate transfer member is set to be larger than the total amount of the shared voltage applied to the intermediate transfer member. The intermediate transfer member is a drum-shaped intermediate transfer member.

[0036]

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

Embodiment 1 A feature of the present invention is that, at the time of the secondary transfer, the shared voltage of the secondary transfer charger is increased, and the shared voltage of the intermediate transfer belt and the like is reduced, so that even the small-sized transfer material is not in contact with the paper passing portion. That is, a sufficient transfer current is ensured by reducing the resistance ratio of the sheet passing portion, and good transfer is performed.

This embodiment is applied to the image forming apparatus shown in FIG. The mechanical configuration of the image forming apparatus and the operation thereof have been described above, and the following description will be directed to the parts related to the present invention. FIG. 6 and the like are referred to as necessary.

In FIG. 6, the intermediate transfer belt 130 is
As a dielectric sheet material, PET, polyacetal, polyamide, polyvinyl alcohol, polyether ketone, polystyrene, polybutylene terephthalate, polymethylpentene, polypropylene, polyethylene, polyphenylene sulfide, polyurethane, silicone resin, polyamide imide, polycarbonate, polyphenylene oxide Generally, a film-shaped sheet of an engineering plastic such as polyether sulfone, polysulfone, aromatic polyester, polyetherimide, and aromatic polyimide is used.

In this embodiment, the intermediate transfer belt 130 is
A 100 μm-thick seamless type was formed using a polyimide resin sheet in terms of mechanical properties, electrical properties, flame retardancy, and the like. The resin sheet had a volume resistivity of 10 ¹³ Ωcm by adding a conductive filler to the resin.

The secondary transfer roller 11 is made of a metal having an outer diameter of 8 mm.
With a volume resistivity of 10 ^TenΩcm, thickness 4m
m and a surface layer of conductive foamed urethane rubber.
EPDM and silicone rubber are used as the rubber for the conductive rubber layer.
Rubber such as rubber and NBR can be used.
The solid type is also commonly used.

As shown in FIG. 8A, the transfer roller 11 transfers the recording material P conveyed to the transfer portion during the secondary transfer.
Is pressed so as to contact the intermediate transfer belt 130. A secondary transfer power supply HV is connected to the core of the transfer roller 11 via a power supply unit (not shown). FIG. 8B
Is an equivalent circuit diagram of the secondary transfer unit at this time.

In the above-mentioned contact state, a negative charging bias having a polarity opposite to that of the toner (positive in this example) is applied to the core of the transfer roller 11 from the power supply HV to the transfer roller 11 from the back side of the recording material P. By performing the negative charging, the toner images of four colors on the intermediate transfer belt 130 are electrostatically transferred collectively to the surface of the recording material P.

In this embodiment, the process speed is 100 m
m / sec, and the transfer current was controlled at a constant current of 10 μA to perform secondary transfer. Transfer roller 11 and intermediate transfer belt 130
Was 50 μm.

In this embodiment, as shown in FIG. 1A, at the time of the secondary transfer, the shared voltage of the secondary transfer roller 11 is increased, and the shared voltage of the intermediate transfer belt 130 is decreased. As a result, the resistance ratio between the sheet passing portion and the non-sheet passing portion is reduced, so that a sufficient transfer current can be ensured even when a small-sized transfer material is passed, and good transfer can be performed. conventionally,
As shown in FIG. 1B, the shared voltage of the secondary transfer roller 11 is higher than that of the intermediate transfer belt 130, so that the resistance ratio between the sheet passing portion and the non-sheet passing portion is large, and the small transfer material When the paper was used, the transfer current was small and good transfer was not possible.

In this embodiment, the shared voltage of the secondary transfer roller 11 and the intermediate transfer belt 130 having the above-described configuration was measured.

As shown in FIG. 2A, the intermediate transfer belt 130 is removed from the secondary transfer portion, and the secondary transfer facing roller 14 is removed.
Is grounded, a voltage is applied to the secondary transfer roller 11 from the power supply HV under constant current control of 10 μA. 2 at this time
The equivalent circuit of the next transfer unit is as shown in FIG. 2B, and the shared voltage of the transfer roller 11 can be measured.

To measure the shared voltage of the intermediate transfer belt 130, as shown in FIG. 3A, the secondary transfer roller 11 and the opposing roller 14 come into contact with each other via the intermediate transfer belt 130 as usual. In this state, the opposing roller 14 is grounded, and a voltage is applied to the transfer roller 11 under the same conditions as described above. The equivalent circuit of the secondary transfer unit at this time is as shown in FIG.
Since the shared voltage of the combined transfer roller 11 and intermediate transfer belt 130 can be measured,
The shared voltage of the intermediate transfer belt 130 was obtained by subtracting the shared voltage measurement value of No. 1.

With the secondary transfer roller 11 and the intermediate transfer belt 130 of this embodiment, shared voltages of 1.2 kV and 1.0 kV were obtained from the above measurements.

At this time, the postcard (with a thrust width of 100) left in a low humidity environment, which is the most severe environmental condition for transferability, is used.
mm) was passed through the secondary transfer section, the resistance R
The resistance ratio between w and the resistance Ru of the non-sheet passing portion was Rw: Ru = 3: 1. The resistance was measured by connecting a power source to a metal roller pair having a thrust width of 100 mm and passing the metal roller pair.

In such a state, the secondary transfer is performed on the postcard,
When an image was formed, sufficient transferability was obtained with a transfer current and voltage lower than those in the related art, and an image without transfer failure was obtained.

In the above description, the secondary transfer roller 11 is a conductive rubber roller, and the opposing roller 14 is a metal roller. Conversely, the secondary transfer roller 11 may be a metal roller and the opposing roller 14 may be a conductive rubber roller. . Although the secondary transfer power supply HV is connected to the secondary transfer roller 11, it may be connected to the secondary transfer opposing roller 14.

As described above, in this embodiment, the shared voltage of the secondary transfer roller 11 is increased and the shared voltage of the intermediate transfer belt 130 is reduced. The resistance ratio of the intermediate transfer member, the secondary transfer roller, the recording material, and the like may change due to the installation environment of the image forming apparatus, the leaving environment of the recording material, etc.
Irrespective of this, it is possible to stably secure an appropriate transfer current (electric charge amount) necessary for transfer to a recording material having a width equal to or less than the maximum size width, and perform good transfer.

Embodiment 2 FIG. 4 is a sectional view showing another embodiment of the image forming apparatus of the present invention.

In the first embodiment, the secondary transfer roller 11 abuts on the intermediate transfer belt 130 via the recording material P. However, in the present embodiment, as shown in FIG. Is provided with a transfer belt 140 at a secondary transfer portion, and a secondary transfer roller 11 is provided inside the transfer belt 140, and the secondary transfer roller 11 is provided via the transfer belt 140 and the recording material P.
Is brought into contact with the intermediate transfer belt 130. The recording material P is conveyed to a secondary transfer unit while being carried on the transfer belt 140, and the toner image on the intermediate transfer belt 130 is transferred.

In the present embodiment, the total amount of the shared voltage of the transfer belt 140 and the shared voltage of the secondary transfer roller 11 is set so that the resistance ratio between the sheet passing portion and the non-sheet passing portion can be reduced even with a small-size recording material. The voltage is higher than the shared voltage of the intermediate transfer belt 130.

More specifically, the transfer belt 140 uses an endless belt made of an EPDM rubber sheet having a volume resistivity of 10 ¹⁰ Ωcm and a thickness of 300 μm, and the secondary transfer roller 11 has a volume resistivity of a conductive rubber layer. The thickness was 10 ⁸ Ωcm and the thickness was 4 mm. The same intermediate transfer belt 130 as that of the first embodiment was used.

The shared voltage of the intermediate transfer belt 130, the transfer belt 140, and the secondary transfer roller 11 in this embodiment was measured by applying a constant current control voltage of 10 μA as in the first embodiment. 0 kv, 1.0 kV, 0.7
kV was obtained. The total amount of the shared voltage of the transfer belt 140 and the secondary transfer roller 11 is larger than the shared voltage of the intermediate transfer belt 130.

As described above, according to the present embodiment, the transfer ratio between the paper-passing portion and the non-paper-passing portion is reduced, the necessary transfer current is secured, and the transfer is performed with sufficient transferability for the postcard left in a low humidity environment. As a result, a good image without transfer failure was obtained.

Embodiment 3 FIG. 5 is a sectional view showing still another embodiment of the image forming apparatus of the present invention.

In the first and second embodiments, the intermediate transfer belt is used as the intermediate transfer member. In this embodiment, the intermediate transfer drum 150 is used.

In FIG. 5, reference numerals 1a, 1b, and 1c represent
Cyan, magenta, and yellow developing units 1d, which are rotary developing units, are black developing units, which are fixed developing units.
Reference numeral 2 denotes a primary charging roller, 3 denotes a photosensitive drum, 4 denotes a cleaner, and 9 denotes a fixing device. The image forming process of the image forming apparatus according to the present embodiment is basically the same as that of the image forming apparatus according to the first embodiment, and a description thereof will be omitted.

In this embodiment, the total amount of the shared voltage of the transfer belt 140 and the shared voltage of the secondary transfer roller 11 is set so that the resistance ratio between the sheet passing portion and the non-sheet passing portion can be reduced even with a small-size recording material. The voltage is higher than the shared voltage of the intermediate transfer drum 150.

According to this embodiment, the intermediate transfer drum 150
Is an intermediate layer of EDDM rubber having a thickness of 5 mm and a volume resistivity of 10 ¹¹ Ωcm on a cylindrical aluminum substrate having an outer diameter of 185 mm, and a thickness of 10 μm and a volume resistivity of 10 ¹⁶ Ωc
m high resistance surface layer. At this time, the total volume resistivity of the intermediate layer and the surface layer was 10 ¹³ Ωcm. The secondary transfer roller 11 and the transfer belt 140
Same as Example 2.

The voltage applied to the intermediate transfer drum 150, the transfer belt 140, and the secondary transfer roller 11 in this embodiment was measured by applying a constant current control voltage of 10 μA as in the first embodiment. 0 kv, 1.0 kV, 0.7
kV was obtained. The total amount of the shared voltage of the transfer belt 140 and the secondary transfer roller 11 is larger than the shared voltage of the intermediate transfer drum 150.

According to this embodiment, it is possible to transfer a postcard left in a low-humidity environment by reducing the resistance ratio between the paper-passing portion and the non-paper-passing portion, securing a necessary transfer current, and having sufficient transferability. A good image without defects was obtained.

As described above, in the first to third embodiments, the case where the transfer current is controlled by the constant current has been described. However, the present invention is not limited to this.
The present invention can be applied to the case where constant voltage control is performed. The width of the recording material may be input by the operator from the operation unit of the image forming apparatus main body, a host computer, or the like, or may be automatically determined using a mechanical sensor or an optical sensor.
Although the position of the recording material with respect to the intermediate transfer belt and the like is arranged with an end, it may be arranged with reference to the center of the thrust. Further, the image carrier is not limited to the electrophotographic photosensitive member, and may be a dielectric in electrostatic recording.

As a developing method, generally, a non-magnetic toner is coated on a developing sleeve with a blade or the like, and a magnetic toner is coated by a magnetic force. Develop 1
A component non-contact development method, a one-component contact development method in which the image carrier is developed in a contact state, and a mixture of toner and a magnetic carrier are used as a developer, which is carried on a developing sleeve by magnetic force. And a two-component non-contact development method in which the toner is conveyed to the image carrier and developed in a non-contact state, and a two-component contact development method in which development is performed in a contact state. In the present invention,
Any of them can be employed, but the two-component contact development method is often used from the viewpoint of high quality and stability of image quality.

[0069]

As described above, according to the present invention,
Even if the environment in which the image forming apparatus is installed or the environment in which the recording material is left is changed, it is not affected by changes in the physical properties of the image carrier, the recording material carrier, the recording material, and the like. In addition, it is possible to stably obtain a good image without transfer failure by performing appropriate transfer.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a magnitude relationship between shared voltages of a transfer roller and an intermediate transfer belt at the time of secondary transfer in an embodiment of the image forming apparatus of the present invention and a conventional example.

FIG. 2 is an explanatory diagram showing a method of measuring a shared voltage of a transfer roller in the embodiment of FIG. 1 and an equivalent circuit at that time.

FIG. 3 is an explanatory diagram showing a method of measuring a shared voltage of the intermediate transfer belt and an equivalent circuit at that time in the embodiment of FIG. 1;

FIG. 4 is a sectional view showing another embodiment of the image forming apparatus of the present invention.

FIG. 5 is a sectional view showing still another embodiment of the image forming apparatus of the present invention.

FIG. 6 is a cross-sectional view illustrating a conventional image forming apparatus.

FIG. 7 is a sectional view illustrating a secondary transfer unit of the image forming apparatus of FIG. 6;

FIG. 8 is an explanatory diagram showing the vicinity of a secondary transfer portion in FIG. 7 and an equivalent circuit thereof.

FIG. 9 is an explanatory diagram showing a secondary transfer unit and its equivalent circuit when a small-size recording material is passed.

[Explanation of symbols]

 3, 3a-3d Photosensitive drum 11 Secondary transfer roller 14 Secondary transfer opposing roller 130 Intermediate transfer belt 140 Transfer belt 150 Intermediate transfer drum HV Secondary transfer power supply P Recording material

Claims (6)

[Claims] 1. An image forming apparatus comprising: an image carrier on which a visible image is formed; and a transfer unit for transferring the visible image formed on the image carrier to a recording material. Wherein the shared voltage is higher than the shared voltage applied to the image carrier. 2. An image carrier on which a visible image is formed, an intermediate transfer member on which the visible image formed on the image carrier is primarily transferred, and a visible image transferred on the intermediate transfer member are recorded. An image forming apparatus provided with a transfer unit for performing secondary transfer onto a material, wherein a shared voltage applied to the secondary transfer unit during the secondary transfer is set to be higher than a shared voltage applied to the intermediate transfer body. Image forming device. 3. A recording material carrier for carrying the recording material and transporting the recording material to the intermediate transfer body, wherein the recording material carrier is used during the secondary transfer.
3. The image forming apparatus according to claim 2, wherein a total amount of a shared voltage applied to a next transfer unit and a shared voltage applied to the recording material carrier is larger than a shared voltage applied to the intermediate transfer body. 4. The intermediate transfer member is a belt-shaped intermediate transfer member, and an opposing roller is opposed to the secondary transfer member with the intermediate transfer member interposed therebetween. The image forming apparatus according to claim 2, wherein a total amount of a voltage and a shared voltage applied to the opposed roller is larger than a shared voltage applied to the intermediate transfer body. 5. A recording material carrier for carrying the recording material and transporting the recording material to the intermediate transfer member, wherein the recording material carrier is used during the secondary transfer.
5. The image forming apparatus according to claim 4, wherein a total amount of a shared voltage applied to a next transfer unit, a shared voltage applied to the opposed roller, and a shared voltage applied to the recording material carrier is larger than a shared voltage applied to the intermediate transfer body. . 6. The image forming apparatus according to claim 2, wherein said intermediate transfer member is a drum-shaped intermediate transfer member.