JP2001296759A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set an optimum transfer condition in an image forming device where a toner image is formed on an image carrier provided with electrification, exposure and developing means in its periphery, primarily transferred to an intermediate transfer body and then is secondarily transferred from the intermediate transfer body to a recording medium. SOLUTION: This device is provided with a sensor A detecting humidity and/or temperature in the vicinity of the intermediate transfer body, and a sensor B detecting the humidity and/or the temperature of atmosphere in which the device is put or the atmosphere of a paper supply part. Then, a primary transfer current value or voltage value is corrected according to output from the sensor A, and a secondary transfer current value or voltage value is corrected according to the information of output from the sensors B and A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus used as a printer or a copying machine, and more particularly, to a method for forming a toner image on an image carrier and transferring the toner image via an intermediate transfer member. And an image forming apparatus for transferring an image onto a recording medium to record an image.

[0002]

2. Description of the Related Art A toner image is formed on an image carrier having charging, exposure, and developing means around it, and the toner image is electrostatically transferred (primary transfer) to an intermediate transfer member, and then transferred paper or the like. There is known an image forming apparatus that electrostatically transfers (secondarily transfers) a toner image from an intermediate transfer member to a recording medium.

In such an image forming apparatus, the electrical resistance of the intermediate transfer member or the recording medium changes depending on the temperature and / or humidity (hereinafter simply referred to as temperature and humidity) of the atmosphere in which the intermediate transfer member and the recording medium are present, so that primary transfer or secondary transfer is performed. If you set to fixed transfer conditions (constant current control or constant voltage control) in transfer,
The transfer performance of the transfer rate fluctuates with the change in the temperature and humidity of the atmosphere, and a stable and good transfer image cannot be obtained.

There have been many proposals for correcting the transfer performance in response to such changes in the temperature and humidity of the atmosphere. The proposals in JP-A-5-94099, JP-A-11-161052 and JP-A-11-167239 have a sensor for detecting the vicinity of the transfer material, the atmosphere outside the apparatus, and the temperature and humidity. And / or to correct secondary transfer conditions. However, since the apparatus has a heat source such as a thermal fixing device, the temperature and humidity A around the intermediate transfer member and the temperature and humidity B in the external environment around the sheet feeding unit or the apparatus where the paper is placed may be significantly different. is there. Naturally, the resistance value of the intermediate transfer member changes depending on the temperature and humidity A inside the apparatus, and the resistance value of the recording medium such as paper changes depending on the temperature and humidity B around the apparatus and the paper feeding unit.
The primary transfer related to the resistance value of the intermediate transfer body is temperature and humidity A,
Secondary transfer involving the resistance value of a recording medium such as paper is affected by temperature and humidity B. Therefore either detected temperature and humidity by the primary transfer, in the case of the secondary transfer both correction, it is difficult to perform optimum correction. Japanese Patent Application Laid-Open No. 9-2
No. 36964 proposes a method of controlling primary transfer or secondary transfer or other process conditions without a temperature / humidity sensor. However, a method for controlling resistance changes of an intermediate transfer belt, a primary transfer roller, and a secondary transfer roller is described. Is not set to the optimum secondary transfer condition because it does not pay attention to the resistance fluctuation of the recording medium.

A toner image is formed on an image carrier, the toner image is transferred onto an intermediate transfer member by a primary transfer means, and the toner image on the intermediate transfer member is further transferred from a paper cassette by a secondary transfer means. In an image forming apparatus in which a toner image is transferred onto a conveyed recording medium and the recording medium holding the toner image is fixed by a heat fixing device, the primary transfer is performed in order to stably obtain a good print image. It is necessary that optimum transfer conditions are set for each of the means and the secondary transfer means.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus in which optimal transfer conditions are set for both primary transfer means and secondary transfer means. By providing temperature and humidity sensors in the vicinity of the primary transfer means and in the vicinity of the sheet feeding section, the first and second means for achieving the above object are provided.
Third and fourth inventions that achieve the above object by making it possible to set optimum transfer conditions for the secondary transfer means by using a temperature and humidity sensor provided near the primary transfer means. An intermediate transfer type image forming apparatus that forms a toner image on an image carrier and transfers the formed toner images by superimposing and transferring the formed toner images onto an intermediate transfer body by primary transfer means provided for each of the toner images. It is an object of the present invention to set an optimum transfer condition for any of a plurality of primary transfer means and to achieve the above-mentioned object, and to provide a first invention to a fifth invention.

[0007]

A first aspect of the present invention for achieving the above object is as follows.
According to the invention, a toner image is formed on an image carrier having charging, exposure, and developing means around the toner image, and the toner image is electrostatically transferred (primary transfer) to an intermediate transfer member, and then intermediately transferred to a recording medium. In an image forming apparatus for electrostatically transferring (secondarily transferring) a toner image from a body, at least one sensor A for detecting humidity and / or temperature is provided near the intermediate transfer body, and the apparatus is placed. Humidity of the atmosphere or the atmosphere of the paper feeding unit and / or
Alternatively, a sensor B for detecting the temperature is provided, and the primary transfer current value or the voltage value is corrected by the output of the sensor A.
It is an object of the present invention to provide an image forming apparatus wherein the next transfer current value or voltage value is corrected by the output of the sensor B.

According to a second aspect of the present invention, there is provided a photoreceptor having a charging, exposing, and developing means on its periphery, forming an electrostatic latent image on the photoreceptor by charging and exposing, and developing the electrostatic latent image by the developing means. Forming a toner image corresponding to the image, electrostatically transferring the toner image to the intermediate transfer member (primary transfer), and then electrostatically transferring the toner image from the intermediate transfer member to the recording medium (secondary transfer) ), At least one sensor C for detecting the temperature and / or humidity of the atmosphere around the intermediate transfer body and the photoreceptor and the developing means is provided, and the atmosphere in which the apparatus is placed or the atmosphere of the paper feeding unit is provided. A sensor B for detecting humidity and / or temperature is provided, the primary transfer current value or voltage value and the process conditions around the photoconductor are corrected by the output of the sensor C, and the secondary transfer current value or voltage value of the sensor B is corrected. Correct by output An image forming apparatus comprising (claim 5
Invention) is provided.

A third aspect of the present invention for achieving the above object is to form a toner image on an image carrier having charging, exposure, and developing means around it, and electrostatically transfer the toner image to an intermediate transfer member (primary transfer). Then, the toner image is electrostatically transferred from the intermediate transfer member to the recording medium (secondary transfer), and the secondary-transferred toner image is heated by a heat fixing device and fixed on the recording medium. In the apparatus, at least one sensor A for detecting humidity and / or temperature is provided in the vicinity of the intermediate transfer member, and a primary transfer current value or a voltage value is constantly determined by an output α (t) of the sensor A which fluctuates over time. The power of the device
When the output of the temperature sensor E for detecting the temperature in the thermal fixing device is equal to or lower than a predetermined temperature at the time when the thermal fixing device is turned on or when the thermal fixing device is turned on, the atmosphere near the intermediate transfer body is changed to the device. Judging that it is almost equal to the surrounding atmosphere,
The image forming apparatus according to claim 3, wherein the output β of the sensor A at that time is stored and the secondary transfer current value or the voltage value is corrected by the output β of the sensor A. is there.

According to a fourth aspect of the present invention, there is provided a photoreceptor having charging, exposure, and developing means around it, forming an electrostatic latent image on the photoreceptor by charging and exposing, and developing the electrostatic latent image by the developing means. Forming a toner image corresponding to the image, electrostatically transferring the toner image to the intermediate transfer member (primary transfer), and then electrostatically transferring the toner image from the intermediate transfer member to the recording medium (secondary transfer) )
In an image forming apparatus in which a secondary-transferred toner image is heated and fixed on a recording medium by a heat fixing device, at least one sensor C for detecting the temperature and / or humidity of the atmosphere around the intermediate transfer body and the photoconductor is provided. The primary transfer current value or voltage value and the process conditions around the photoconductor are constantly corrected by the output γ (t) of the sensor C, which changes over time, and at the time when the power of the apparatus is turned on or When the output of the temperature sensor E for detecting the temperature inside the thermal fixing device is lower than or equal to a predetermined temperature at the time when the thermal fixing device is turned on, the atmosphere around the intermediate transfer body and the photoreceptor is substantially equal to the atmosphere around the apparatus. The image forming apparatus according to claim 7, wherein it is determined that they are equal, the output δ of the sensor C at that time is stored, and the secondary transfer current value or voltage value is corrected by the output δ of the sensor C. It is intended to provide a bright).

According to a fifth aspect of the present invention, there is provided a photoreceptor having a plurality of photosensitive members having charging, exposing, and developing means disposed therearound, and forming an electrostatic latent image on each of the photoreceptors by charging and exposing. To form a toner image corresponding to the electrostatic latent image, and each toner image is electrostatically superposed and transferred (primary transfer) to an intermediate transfer member, and then the toner image is statically transferred from the intermediate transfer member to a recording medium. In an image forming apparatus for electrically transferring (secondary transfer), one sensor D for detecting the temperature and / or humidity of the atmosphere around the intermediate transfer body and the photoconductor is provided, and the primary transfer current value or voltage value and When the process conditions around the photoconductor are corrected by the output ε (t) of the sensor D, the process conditions around each photoconductor and ε (t) of each primary transfer condition are used.
The present invention provides an image forming apparatus (invention of claim 9) characterized in that the correction level is changed.

[0012]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Further, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning or technical scope of the terms of the present invention.

An image forming process and each mechanism of an embodiment of an image forming apparatus common to the claims of the present invention will be described.
This will be described with reference to FIG. FIG. 1 is a cross-sectional view of a main part of a color image forming apparatus showing an embodiment of an image forming apparatus common to the claims of the present invention.

According to FIG. 1, 10 is a photosensitive drum as an image carrier for each color, 11 is a charging roller as charging means for each color, 12 is an exposure optical system as image writing means for each color, Reference numeral 13 denotes a developing device as a developing unit for each color, 14a an intermediate transfer belt as an intermediate transfer member, and 14c a first transfer unit for transferring a toner image on an image carrier for each color to the intermediate transfer member. A secondary transfer roller 14g, a secondary transfer roller as a second transfer unit for retransferring the toner image on the intermediate transfer member onto a recording material; a fixing device 17 as a thermal fixing unit;
Reference numeral 190 denotes a photoconductor cleaning device as an image carrier cleaning unit for each color, and reference numeral 190a denotes an intermediate transfer member cleaning device as an intermediate transfer member cleaning unit.

In this embodiment, a photosensitive drum 10 as an image carrier for each color, a charging roller 11 as a charging unit for each color, and an exposure optical system 1 as an image writing unit for each color.
2. Developing device 13 as a developing device for each color and photoconductor cleaning device 190 as an image carrier cleaning device
Are provided as a set, four image forming units 100 are provided for each color of yellow (Y), magenta (M), cyan (C), and black (K), and counterclockwise indicated by an arrow in FIG. Are arranged in the order of Y, M, C, and K on the upper side of the intermediate transfer belt 14a with respect to the rotation direction of the intermediate transfer belt 14a according to the color to be formed and the order.

Photoconductor drum 10 as an image carrier for each color
Is formed by forming an organic photoreceptor layer (OPC) having an overcoat layer (protective layer) on the outer periphery of a cylindrical metal substrate formed of, for example, an aluminum material on the outer periphery of the metal substrate. In the grounded state, the photosensitive drum 10 for each color is rotated in a clockwise direction indicated by an arrow in FIG. 1 by a photosensitive member drive motor (not shown).

A charging roller 11 as charging means for each color
Is formed by coating a peripheral surface of a conductive core metal (not shown) such as stainless steel with a semiconductive elastic rubber (not shown) having a volume resistance of about 10 ⁵ to 10 ⁷ Ω · cm. 10
At the time of charging, the charging operation (minus charging in the present embodiment) is performed by applying a charging bias of a DC voltage with the same polarity (minus polarity in the present embodiment) as the toner used (toner at the time of development), A uniform potential is applied to the photosensitive drum 10. In addition, as a charging unit, a charging brush of a contact charging type, a charging blade, a non-contact corona discharger, or the like can be used.

Exposure optical system 1 as image writing means for each color
2 is arranged around the photosensitive drum 10 such that the exposure position on the photosensitive drum 10 is located on the downstream side in the rotation direction of the photosensitive drum 10 with respect to the charging roller 11 for each color described above. . The exposure optical system 12 rotationally scans a laser beam emitted from a laser light source (not shown) with a rotary polygon mirror (not shown), and comprises an fθ lens (not shown), a reflection mirror (not shown), and the like, and is separate. Exposure (image writing) of the photoreceptor layer of the photoreceptor drum 10 in accordance with the image data of each color read by the image reading device and stored in the memory.
Then, an electrostatic latent image is formed on the photosensitive drum 10 for each color.

The developing device 13, which is a developing means for each color,
One-component developer or toner (in this embodiment, negative polarity) and carrier using yellow (Y), magenta (M), cyan (C), and black (K) toners in this embodiment using negatively charged toner in this embodiment. , Each of which contains a two-component developer, and which rotates in the developing position in the forward direction with respect to the rotation direction of the photosensitive drum 10 in contact with or non-contact with the peripheral surface of the photosensitive drum 10, for example, aluminum, stainless steel, etc. It is made of non-magnetic material such as steel.
A developing roller 131, which is a developer carrier that is rotatably supported with a roughened surface of 0.5 to 5 μm as indicated by a 10-point average roughness (JIS-B0610),
By applying a developing bias of a DC voltage or a DC voltage superimposed on an AC voltage to the developing roller 131, contact or non-contact reversal development is performed, and the toner image is formed on a latent image portion on the photosensitive drum 10. To form

The intermediate transfer belt 14a, which is preferably an intermediate transfer member using a belt shape, has a volume resistance of 10 ⁶ to 1.
An endless belt of 0 ¹² Ω · cm, for example, polycarbonate (PC), polyimide (PI), polyamide imide (PAI), polyvinylidene fluoride (PVD)
F), Etrafluoroethylene-ethylene copolymer (E
A resin material such as TFE) or a rubber material such as EPDM, NBR, CR, or polyurethane in which a conductive filler such as carbon is dispersed or an ionic conductive material is contained is used. 50-20 for material
The setting is preferably about 0 μm, and in the case of a rubber material, about 300 to 700 μm. Intermediate transfer belt 14a
Are stretched in contact with roller members such as a driving roller 14d, a driven roller 14e, a cleaning opposing roller 14f, a secondary transfer opposing roller 14j, and a tension roller 14i which are grounded. The drive roller 14d is rotated by the drive from M1, and the intermediate transfer belt 14a is rotated in the counterclockwise direction indicated by the arrow in FIG. The drive roller 14d is, for example, a rubber or resin material such as polyurethane, EPDM, silicone, etc.
Conductive or semiconductive (with no sign) coated with a conductive filler such as carbon is used. A drum-shaped intermediate transfer member can be used.

A primary transfer roller 14c, which is a first transfer means for each color, is formed on a peripheral surface of a conductive core (not shown) made of, for example, stainless steel having an outer diameter of 8 mm by using polyurethane, EPDM, or the like.
By dispersing a conductive filler such as carbon or containing an ionic conductive material in a rubber material such as silicone or the like, a solid state having a volume resistance of about 10 ⁵ to 10 ⁹ Ω · cm or a foamed sponge state is obtained. And a semiconductive elastic rubber (not shown) having a thickness of 5 mm and a rubber hardness of about 20 to 70 ° (Asker-C). The primary transfer roller 14c for each color faces the photosensitive drum 10 for each color with the intermediate transfer belt 14a interposed therebetween, and the intermediate transfer belt 14a
To form a transfer area (no symbol) for each color between the intermediate transfer belt 14a and the photosensitive drum 10 for each color, and transfer the toner image to the intermediate transfer belt 14a. At this time, the toner image on the photosensitive drum 10 for each color is transferred onto the intermediate transfer belt 14a by applying a DC voltage primary transfer bias having the opposite polarity to the toner (positive polarity in the present embodiment). . As the first transfer means, the above-mentioned contact method is preferably used, but it is also possible to use a non-contact corona transfer device.

A secondary transfer roller 14 as a second transfer means for retransferring the color toner image on the intermediate transfer member onto a recording material.
g is, for example, a conductive filler such as carbon dispersed in a rubber material such as polyurethane, EPDM, or silicone, or a conductive filler such as ionic conductive material on a peripheral surface of a conductive core (not shown) such as stainless steel having an outer diameter of 8 mm. Including materials,
In a solid state or foamed sponge state having a volume resistance of about 10 ⁵ to 10 ⁹ Ω · cm, a thickness of 5 mm and a rubber hardness of 2
It is formed by covering a semiconductive elastic rubber (not shown) of about 0 to 70 ° (Asker-C). Secondary transfer roller 14
Since g is different from the primary transfer roller 14c and is in contact with the toner, the surface may be covered with a material having good releasability such as semiconductive fluororesin or urethane resin. Secondary transfer roller 14
g is opposed to the secondary transfer opposing roller 14j, which is grounded across the intermediate transfer belt 14a, and is provided in contact with (contact with) the intermediate transfer belt 14a.
A transfer area (no sign) is formed between the transfer roller 14j and the next transfer opposing roller 14j. At the time of re-transfer of the color toner image, the toner has the opposite polarity (positive polarity in this embodiment) to DC voltage of 2
By applying the next transfer bias, the superimposed color toner images on the intermediate transfer belt 14a are collectively transferred onto the recording paper P. As the second transfer means, the above-mentioned contact method is preferably used, but it is also possible to use a non-contact corona transfer device.

The heat fixing device 17 as a heat fixing means includes a fixing roller 17a having a heat source such as a halogen heater and a pressure roller 17a inside at least one of the rollers.
b, and applies heat and pressure between the fixing roller 17a and the pressure roller 17b to fix the toner image on the recording material.

The photoconductor cleaning device 190, which is an image carrier cleaning unit for each color, provided on the downstream side in the rotation direction of the photoconductor drum 10 from the transfer area of the primary transfer roller 14c for each color, The transfer residual toner on the photoconductor drum 10 for each color is cleaned by a photoconductor cleaning blade 191 which is a provided photoconductor cleaning member.

An intermediate transfer member cleaning device 190a, which is an intermediate transfer member cleaning means provided downstream of the transfer area of the secondary transfer roller 14g in the traveling direction of the intermediate transfer belt 14a, is a cleaning device that is grounded across the intermediate transfer belt 14a. The transfer residual toner on the intermediate transfer belt 14a is cleaned by an intermediate transfer member cleaning blade 191a which is provided opposite to the opposing roller 14f and is an intermediate transfer member cleaning member provided in the intermediate transfer member cleaning device 190a.

Next, the image forming process (image forming step) will be described. By starting a photoconductor drive motor (not shown) at the start of image recording, the photoconductor drum 10 of the yellow (Y) image forming unit 100 is rotated clockwise as indicated by an arrow in FIG. The application of a potential to the Y photoconductor drum 10 is started by the charging action.

After the Y photoreceptor drum 10 is applied with a potential, the Y exposure optical system 12 starts image writing with a first color signal, that is, an electric signal corresponding to the Y image data, and the Y photoreceptor drum 10 starts writing. Y of the original image on the surface of the body drum 10
An electrostatic latent image corresponding to the image is formed.

The latent image is reversely developed in a contact or non-contact state by a developing roller 131 of a Y developing device 13, and yellow (Y) is formed on the photosensitive drum 10 in accordance with the rotation of the Y photosensitive drum 10. ) Is formed.

The Y toner image formed on the Y photoreceptor drum 10 as the image carrier by the above-described image forming process is transferred to the Y transfer area (no symbol) in the Y transfer area (no symbol). The image is transferred onto the intermediate transfer belt 14a by the primary transfer roller 14c.

Next, the intermediate transfer belt 14a is synchronized with the Y toner image, and is given a potential by the charging operation of the M charging roller 11 by the magenta (M) image forming unit 100. The image writing is performed by the second color signal, that is, the electric signal corresponding to the M image data, and the developing roller 131 of the M developing device 13 is used.
The contact or non-contact reversal development of M causes the M toner image on the M photoreceptor drum 10 to be transferred to the M transfer area (no symbol) by the M primary transfer roller 14c as the first transfer means. The M toner image is formed by being superimposed on the Y toner image of FIG.

By a similar process, the image is synchronized with the superposed toner images of Y and M, and is formed by the third color signal formed on the photosensitive drum 10 of C by the image forming unit 100 of cyan (C). The C toner image corresponding to the C image data is transferred from above the Y and M toner images by the C primary transfer roller 14c, which is the first transfer unit, in the C transfer area (no symbol). A toner image of C is formed on the photosensitive drum 10 of K by the black (K) image forming unit 100 in synchronism with the toner image of Y, M, and C. The K toner image corresponding to the K image data based on the fourth color signal is represented by K
In the transfer area (no symbol), the above-mentioned Y, M, and C are transferred by the K primary transfer roller 14c as the first transfer unit.
Are formed on top of each other, and a superposed color toner image of Y, M, C and K is formed on the intermediate transfer belt 14a.

The untransferred toner remaining on the peripheral surface of the photoconductor drum 10 for each color after the transfer is brought into contact with the photoconductor drum 10 of the photoconductor cleaning device 190 which is an image carrier cleaning means for each color. Contact) state, the photosensitive member cleaning blade 191 which is a photosensitive member cleaning member
Is mechanically cleaned.

The recording paper P separated and conveyed one by one from the paper feed cassette 21 as the recording material storage means in synchronization with the formation of the superimposed color toner image on the intermediate transfer belt 14a is used as the recording material feeding means. The recording paper P is conveyed to the transfer area (no symbol) of the secondary transfer roller 14g as the second transfer means via the timing roller 15b, and a DC voltage of the opposite polarity (positive polarity in the present embodiment) to the toner is applied. The intermediate transfer belt 1 is driven by the applied secondary transfer roller 14g.
The superimposed color toner images on 4a are collectively retransferred onto the recording paper P.

The recording paper P on which the color toner image has been transferred is
The charge is removed by a charge removing electrode 16b, which is a separating means formed of a sawtooth electrode plate, conveyed to a heat fixing device 17, and heat and pressure are applied between a fixing roller 17a and a pressure roller 17b, so that the recording paper P After the toner image is fixed, the toner image is discharged to a tray (not shown) outside the apparatus.

The untransferred toner remaining on the peripheral surface of the intermediate transfer belt 14a after the transfer is an intermediate transfer member cleaning means which is an intermediate transfer member cleaning means provided opposite to the cleaning opposing roller 14f with the intermediate transfer belt 14a interposed therebetween. The apparatus 190a is mechanically cleaned by an intermediate transfer member cleaning blade 191a, which is an intermediate transfer member cleaning member that is brought into contact (contact) with the intermediate transfer belt 14a.

(Embodiment 1) The first invention (the invention of claim 1) and the second invention (the invention of claim 5) will be described. FIG. 2 is a block diagram showing the control of the transfer condition in the first invention. First, description will be made from the first invention.

A sensor S (A) for detecting temperature and humidity is provided in the vicinity of the intermediate transfer belt 14a located near the center of the image forming apparatus.
Alternatively, a sensor S (B) for detecting the temperature and humidity near the sheet cassette 21 located at the lower corner of the image forming apparatus is provided.

The controller (ROM) stores the output (temperature and humidity) of the sensor S (A) and the primary transfer current value or voltage value applied to the primary transfer roller 14c as the optimal transfer condition at that temperature and humidity. Is stored as a table.

Further, based on the output (temperature and humidity) of the sensor S (B) and the output (temperature and humidity) of the sensor S (A), the sensor S
The secondary transfer current value or voltage value applied to the secondary transfer roller 14g is stored as a table in the ROM (B) as the optimal transfer condition at the temperature and humidity of (B) and the temperature and humidity of the sensor S (A). In the secondary transfer, the change in the resistance of the recording sheet is not so affected, but the change in the resistance of the intermediate transfer member also affects the transfer performance.
(B) By performing correction based on both information, it is possible to secure optimal transfer performance.

In forming an image, the control unit controls the sensor S
From the detection output that changes over time in (A), the primary transfer condition as the optimum transfer condition is called by the ROM (A),
The constant current value or constant voltage value to be applied to the primary transfer roller 14c is controlled by constantly correcting. The sensor S
From the detection output of (B) and the detection output of sensor S (A), R
OM (B) calls a secondary transfer condition which is an optimal transfer condition, and changes over time in image formation.
The constant current value or constant voltage value applied to the next transfer roller 14g is controlled.

To explain a specific example of the transfer current value control for performing the constant current control, the primary transfer current value increases as the detection temperature X (relative humidity% RH) detected by the sensor S (A) increases. Perform control. For example, when the primary transfer is a constant current transfer, the current value is 20 (1 + X / 50) μ.
By performing control using a table so as to achieve A, the optimal primary transfer condition is always maintained. Further, control is performed such that the higher the detected humidity X detected by the sensor S (A) and the detected humidity Y (relative humidity% RH) of the sensor S (B) are, the higher the secondary transfer current value is. However, in the secondary transfer, the output of the sensor S (B) has a stronger effect than the output of the sensor S (A). Therefore, for example, when the secondary transfer is a constant current transfer, the current value is 30 ( 1 + X / 100) × (1
By performing control using a table so as to be + Y / 50) μA, the optimal secondary transfer condition is always maintained.

Next, the second invention will be described. The second invention is different from the first invention in that the sensor S (A) is provided near the intermediate transfer belt 14a in the first invention.
While the correction control of the primary transfer condition is performed based on the detection output of (A), in the second invention, the temperature of the atmosphere around the intermediate transfer belt 14a and the photosensitive drum 10 is replaced with the sensor S (A). A sensor S (C) for detecting humidity is provided, and the detection output of the sensor S (C) performs not only correction control of primary transfer conditions, but also a charging voltage of a charging roller 11 provided around the photosensitive drum 10 as a process unit. The correction control of the value or the current value and the correction control of the developing bias applied to the developing device 13 are performed. In addition to the first invention, the correction control of the process condition around the photoconductor is performed. FIG. 3 is a block diagram showing the control of the transfer conditions and the process conditions of the second invention, and mainly the differences from the first invention will be described.

Since the photosensitive characteristics of the photosensitive drum 10 fluctuate depending on the temperature and humidity of the environment, in order to correct this and always obtain a stable and good toner image on the photosensitive member, constant voltage or constant current control is required. The voltage value or the current value applied to the charging roller 11 for uniformly charging the photosensitive member needs to be set high when the temperature and humidity of the environment are high. Must be set higher when is higher.

The control section outputs the output (temperature and humidity) of the sensor S (C), the bias voltage or current condition applied to the charging roller 11 at the optimum temperature and humidity, and the optimum voltage applied to the developing device 13 at the temperature and humidity. The bias condition and the transfer condition applied to the primary transfer roller 14c at the optimum temperature and humidity are stored as a table in the ROM (C).

In forming an image, the control unit controls the sensor S
From the detection output of (C), the optimum applied voltage or applied current to the charging roller 11 is called by the ROM (C), and the setting of the charging condition of the charging roller 11 is controlled, and the developing device 13 which is similarly optimized Is applied to the developing device 13 to perform development. The setting of the optimum transfer condition of the primary transfer roller 14c is determined by the sensor S.
(C) is performed based on the output situation, and the secondary transfer roller 14
The setting of the optimal transfer condition of g based on the output of the sensor S (B) and the output of the sensor S (C) is the same as in the first invention.

According to the first or second aspect of the present invention, even when the environmental temperature and humidity fluctuate or the temperature and humidity in the image forming apparatus fluctuate due to continuous use for a long time, they are always stable. As a result, good image formation is performed.

(Embodiment 2) The third invention (the invention of claim 3) and the fourth invention (the invention of claim 7) will be described. In the first embodiment, the sensor S (A) or the sensor S (C) is provided near the intermediate transfer member 14a,
A sensor S (B) is provided in the vicinity of the paper feed cassette 21, the temperature and humidity of the recording sheet are detected by the sensor S (B), and the optimum transfer conditions for the secondary transfer are set based on the output of the sensor S (B). Was. In this embodiment, the optimum transfer conditions can be set for the secondary transfer only by the sensor S (A) or the sensor S (C) without providing the sensor S (B).

FIG. 4 is a block diagram showing the control of the transfer condition in the third invention. In the present embodiment, a temperature sensor S (E) for detecting the temperature of the heating element is provided in the heat fixing device 17. This temperature sensor S (E) may be shared with a sensor used for controlling the temperature of thermal fixing of the thermal fixing device 17.

When the power switch of the image forming apparatus is turned on, or when the heating unit of the heat fixing device 17 is turned on after the apparatus has been in a standby state for a long time, the control unit detects the temperature sensor S (E). Check the temperature. The detected temperature is preset and stored at a predetermined temperature, for example, 4
When the detected temperature is lower than the predetermined temperature as compared with 0 ° C., the temperature and humidity β detected by the sensor S (A) or the sensor S (C) at that time are substantially equal to the temperature and humidity near the sheet cassette 21. It is determined that the vehicle is in the temperature / humidity state, and the temperature / humidity β is stored in the RAM.

In the image formation, as in the first embodiment, the primary transfer condition as well as the charging condition and the developing condition, which are the process conditions around the photosensitive member, are determined by the sensor S (A).
Alternatively, the correction is always performed by the output α (t) of the sensor S (C) which fluctuates with time.

For the secondary transfer condition, the stored temperature and humidity β and the output α of the sensor S (A) or the sensor S (C) are used.
It is always corrected by (t).

The correction including the primary and secondary transfer conditions described above is maintained while image formation is continuously performed. The control unit checks the temperature detected by the temperature sensor S (E) when the power switch is once turned off and turned on again, or when the heating unit of the heat fixing device 17 is turned off and turned on again. I do.

When the detected temperature is higher than the predetermined temperature, for example, higher than 40 ° C., the previously stored temperature and humidity β are maintained as they are, and the correction control of the secondary transfer condition is continuously performed.

When the detected temperature is lower than the predetermined temperature, the temperature / humidity β 'detected by the sensor S (A) or S (C) at that time is the temperature / humidity near the paper feed cassette 21 at that time. Is determined to be substantially equal to β, and β previously stored in the RAM is stored in place of β ′. Then, the temperature and humidity β ′ and the sensor S updated and stored for the secondary transfer condition are stored.
(A) or the output α (t) of the sensor S (C) always corrects the secondary transfer condition.

According to the present embodiment, it is possible to secure optimal primary and secondary transfer conditions without increasing the temperature and humidity sensor and reducing it compared to the first embodiment. Further, according to the fourth aspect of the present invention, in which not only transfer but also process conditions around the photoreceptor are corrected by the output of the temperature and humidity from the sensor S (C), a better image as a whole can be secured with a smaller number of sensors. .

(Embodiment 3) A fifth invention (an invention of claim 9) will be described with reference to a block diagram in FIG. 5 showing control of transfer and process conditions. The image forming apparatus to which the present invention is applied is the tandem intermediate transfer type image forming apparatus described with reference to FIG.

The image forming apparatus has a heat fixing device 17 and other heating elements such as the exposure optical system 12. In particular, since the heat fixing device 17 performs heat fixing of a recording medium at a high temperature of 100 ° C. or more, a large amount of heat is radiated from the heat fixing device 17 during image formation. An exhaust means such as a fan is provided in the image forming apparatus to prevent the internal temperature from becoming extremely high. Even if an air flow is formed in the apparatus by the fan, it is difficult to keep the inside of the apparatus under uniform temperature and humidity conditions due to local stagnation of air, for example, in FIG. The temperature and humidity conditions near the image forming unit 100 (Y) near the thermal fixing device 17 and the temperature and humidity conditions at the image forming unit 100 (K) located far away are considerably different. Therefore, if common corrections are made to the process conditions and primary transfer conditions of all the image forming units by the output of the temperature and humidity detecting means provided at one location, unsatisfactory process conditions and primary transfer conditions are set. Will occur.

According to the present invention, when correction is performed by one sensor S (D) for detecting the temperature and humidity around the intermediate transfer member and the photosensitive member, the process conditions around each photosensitive member and each one of the sensors S (D) are corrected.
The control is performed by changing the correction level of the next transfer condition, and a specific example will be described.

A case in which a sensor S (D) is provided near the image forming unit 100 (C) near the intermediate transfer belt 14a will be described. Regarding the target image forming apparatus, the temperature of the image forming apparatus before shipment is temporarily set near the image forming units 100 (Y), 100 (M), and 100 (K) in the vicinity of the sensor S (D). A sensor for detecting humidity is provided, and the image forming apparatus is installed in a room under standard temperature and humidity conditions. While forming an image, outputs from four sensors for detecting temperature and humidity are recorded. Y, M, based on the output ε (t) of the sensor S (D)
A correction amount for the output ε (t) for K is obtained.

For the output ε (t) that fluctuates and outputs while the sensor S (D) moves from the low temperature / humidity condition to the high temperature / humidity condition, the variation of the correction amount for Y, M, and K is obtained. As a result, the following corrected humidity function is obtained.

Y: ε + Δf _Y (ε) M: ε + Δf _M (ε) C: ε K: ε + Δf _K (ε) Here, Δf (ε) can be either positive or negative, and the above value is obtained. The relationship between the corrected temperature and humidity among Y, M, C, and K is recorded in the ROM as a table.

In forming an image, the control unit controls the sensor S
Output ε of (D)₁Is detected. The control unit first charges Y
Setting of charging bias to roller 11 (Y), developing device 1
3 (Y) development bias setting, primary transfer roller 14c
The bias recorded in the ROM for setting the applied bias
Corrected temperature and humidity ε of Y from the table of positive temperature and humidity₁+ Δf_Y(Ε
₁), And then use the ROM (D) table to
Temperature and humidity after ε₁+ Δf _Y(Ε₁) Compatible charged via
Control of the bias application to the charging roller 11 (Y).
I will do it. Similarly, the corrected temperature and humidity ε₁+ Δf_Y(Ε₁)
A primary transfer applying bias corresponding to the primary transfer roller 1 is determined.
Control of bias application to 4c (Y) is performed. M, K
The bias control is similarly performed using the corrected temperature and humidity.
Control was performed, and C was output from the sensor S (D).
ε₁Is used as it is to perform bias control.

In the present invention, the relationship between the temperature and humidity among Y, M, C and K is recorded in a ROM,
Exactly the same effect can be obtained when four temperature / humidity sensors are provided by one temperature / humidity sensor.

[0064]

As described in the first aspect, a humidity and / or temperature detecting sensor A is provided around the intermediate transfer member, and the humidity and / or the temperature of the atmosphere where the apparatus is placed or the atmosphere of the paper feeding section are provided. A temperature detection sensor B is provided to correct the primary transfer current or voltage value by the output of the sensor A,
Correcting the primary transfer and the secondary transfer can be performed accurately by correcting the secondary transfer current or the voltage value based on the output of the sensor B.

Further, in the secondary transfer, the change in the resistance value of the intermediate transfer member does not influence as much as the change in the resistance of the paper, but naturally also affects the transfer performance.

For this reason, as described in claim 2, the secondary transfer current or voltage value is supplied to the sensor A and the sensor B.
By correcting with both information, a more optimal 2
Next transfer performance can be ensured.

In contrast to the known examples, those described in claims 1 and 2 increase the cost due to the addition of the sensor. However, as described in claims 3 and 4, the sensor A uses the intermediate transfer member. When the ambient temperature / humidity fluctuation is always fed back to the primary transfer condition, and it is determined that the temperature / humidity around the intermediate transfer member is close to the temperature / humidity around the apparatus (for example, the temperature of the thermal fixing device is sufficiently low and the The heating means is OF
In the state F, when it is determined that the temperature and humidity in the apparatus are almost close to the atmosphere around the apparatus, the detection output of the sensor A is stored as the temperature and humidity around the apparatus (the stored value is β
), The feedback of the secondary transfer condition only by the value of β, or both the values α (t) and β constantly detected by the sensor A, so that the optimum temperature and humidity sensor can be obtained without adding a temperature and humidity sensor. Primary and secondary transfer conditions can be ensured.

As described in the fifth to eighth aspects, the information of the temperature and humidity sensor for detecting the atmosphere around the intermediate transfer member is used to calculate
If not only the transfer but also other process conditions around the photoconductor can be corrected, a better image as a whole can be secured with a smaller number of sensors.

Further, in the case of the tandem type as described in claim 9, since the inside of the apparatus partially has a heat source such as a heat fixing unit and an exhaust means, the temperature and humidity inside the apparatus are kept low for each photosensitive member and for one. Many cases are different in the next transfer unit, and the output ε (t) of the temperature / humidity detection unit at one location does not apply a common correction to each photoconductor and the primary transfer unit, but a different correction for ε (t). By applying a level, better correction is possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a main part of a color image forming apparatus.

FIG. 2 is a block diagram showing control of transfer conditions in the first invention.

FIG. 3 is a block diagram showing control of transfer conditions and process conditions according to a second invention.

FIG. 4 is a block diagram showing control of transfer conditions according to the third invention.

FIG. 5 is a block diagram showing control of transfer conditions and process conditions according to a fifth invention.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 charging roller 12 exposure optical system 13 developing device 14a intermediate transfer belt 14c primary transfer roller 14g secondary transfer roller 17 heat fixing device 100 image forming unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA12 DA13 DA14 DE07 EA01 EA03 EA05 EB04 EF09 2H030 AB02 BB02 BB21 BB42 BB54 2H032 AA05 BA09 BA21 CA02 CA12 CA14

Claims (9)

[Claims] 1. A toner image is formed on an image carrier having charging, exposure, and developing means around it, and the toner image is electrostatically transferred (primary transfer) to an intermediate transfer member, and then transferred to a recording medium. In an image forming apparatus for electrostatically transferring (secondarily transferring) a toner image from an intermediate transfer member, at least one image is provided near the intermediate transfer member.
Sensor A for detecting humidity and / or temperature, and a sensor B for detecting humidity and / or temperature of the atmosphere where the apparatus is placed or the atmosphere of the paper feeding unit, and the primary transfer current value or voltage value is determined. An image forming apparatus, wherein the correction is performed by the output of the sensor A and the secondary transfer current value or the voltage value is corrected by the output of the sensor B. 2. The image forming apparatus according to claim 1, wherein the secondary transfer current value or the voltage value is corrected based on information on both the output of the sensor A and the output of the sensor B. 3. A toner image is formed on an image carrier having charging, exposure, and developing means around it, and the toner image is electrostatically transferred (primary transfer) to an intermediate transfer member, and then transferred to a recording medium. In an image forming apparatus in which a toner image is electrostatically transferred (secondary transfer) from an intermediate transfer body and the secondary-transferred toner image is heated by a heat fixing device and fixed on a recording medium, A sensor A for detecting at least one humidity and / or temperature is provided in the vicinity, and the primary transfer current value or the voltage value is constantly corrected by the output α (t) of the sensor A which fluctuates over time, and the power supply of the apparatus is changed. When the output of the temperature sensor E for detecting the temperature inside the thermal fixing device is equal to or lower than a predetermined temperature at the time when the thermal fixing device is turned on or when the thermal fixing device is turned on, the atmosphere near the intermediate transfer body is changed to the device. Judging that it is almost equal to the surrounding atmosphere Stores the output β of the sensor A at that time, the image forming apparatus characterized by a secondary transfer current value or voltage value is corrected by the output β of the sensor A. 4. The image forming apparatus according to claim 3, wherein the secondary transfer current value or the voltage value is corrected based on information on both the output α (t) and the output β of the sensor A. 5. A photoreceptor having charging, exposing, and developing means around the photoreceptor, forming an electrostatic latent image on the photoreceptor by charging and exposing, and forming a toner image corresponding to the electrostatic latent image by the developing means. In an image forming apparatus, the toner image is electrostatically transferred (primary transfer) to an intermediate transfer member, and then the toner image is electrostatically transferred (secondary transfer) from the intermediate transfer member to a recording medium. The temperature of the atmosphere around the transfer member and the photosensitive member, and the developing means, and / or
Alternatively, at least one sensor C for detecting the humidity is provided, and a sensor B for detecting the humidity and / or temperature of the atmosphere in which the apparatus is placed or the atmosphere of the paper feeding unit is provided. An image forming apparatus, wherein a process condition around the body is corrected by an output of a sensor C, and a secondary transfer current value or a voltage value is corrected by an output of a sensor B. 6. The image forming apparatus according to claim 5, wherein the secondary transfer current value or the voltage value is corrected based on information on both the output of the sensor C and the output of the sensor B. 7. An electrostatic latent image is formed on a photoconductor by charging, exposing, and developing means, and a toner image corresponding to the electrostatic latent image is formed by the developing means. Then, after the toner image is electrostatically transferred (primary transfer) to the intermediate transfer member, the toner image is electrostatically transferred (secondary transfer) from the intermediate transfer member to the recording medium, and the secondary transfer is performed. In an image forming apparatus in which a toner image is heated by a heat fixing device and fixed on a recording medium, at least one sensor C for detecting the temperature and / or humidity of the atmosphere around the intermediate transfer body and the photosensitive body is provided.
The output γ (t) of the sensor C, which fluctuates the primary transfer current value or voltage value and the process conditions around the photoconductor over time.
And a temperature sensor E for detecting the temperature inside the thermal fixing device when the power of the apparatus is turned on or when the thermal fixing device is turned on.
Is lower than the predetermined temperature, it is determined that the atmosphere around the intermediate transfer body and the photoconductor is substantially equal to the atmosphere around the apparatus, and the output δ of the sensor C at that time is stored and
An image forming apparatus wherein a next transfer current value or a voltage value is corrected by an output δ of a sensor C. 8. The image forming apparatus according to claim 7, wherein the secondary transfer current value or the voltage value is corrected based on information on both the output γ (t) and the output δ of the sensor C. 9. An electrostatic latent image is formed on each photosensitive member by charging and exposing, and a plurality of photosensitive members having charging, exposing and developing means around the photosensitive element are formed, and the developing means corresponds to the electrostatic latent image. After a toner image is formed, each toner image is electrostatically superposed and transferred (primary transfer) to an intermediate transfer member, and then the toner image is electrostatically transferred from the intermediate transfer member to a recording medium (secondary transfer). In the image forming apparatus, the sensor D for detecting the temperature and / or humidity of the atmosphere around the intermediate transfer body and the photoreceptor is provided with one sensor.
When the primary transfer current value or the voltage value and the process condition around the photoconductor are corrected by the output ε (t) of the sensor D, the process condition around each photoconductor and ε of each primary transfer condition are corrected. An image forming apparatus wherein the correction level according to (t) is changed.