JP2001318538A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out image formation where there is no influence due to cleaving during image formation by not being restricted by the material or hardness, etc., of an intermediate transfer body in an image forming device where a toner image formed on an image carrier is transferred to transfer paper, etc., through the intermediate transfer body. SOLUTION: In the device, the intermediate transfer body is rotated for equal to or more than a specified time (t1) during warming up or before the image formation. The specified time (t1) is varied according to temperature and humidity detected in the device.

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 for forming an image by an electrophotographic method, and more particularly to an image forming apparatus for transferring a toner image formed on an image carrier onto a recording medium via an intermediate transfer member. About.

[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 transferred to an intermediate transfer member (primary transfer) and then transferred onto a recording medium such as transfer paper. 2. Related Art An image forming apparatus that transfers a toner image from an intermediate transfer member (secondary transfer) is known. In such an image forming apparatus,
As an intermediate transfer member, a belt-shaped intermediate transfer member is described in JP-A-62-206567 and the like. As a belt-shaped intermediate transfer body, polycarbonate, polyamide imide, polyimide, polyvinylidene fluoride, those based on various types of rubbers such as resin-based ones such as ethylene tetrafluoroethylene are known, In the image apparatus, the belt is supported and stretched by a plurality of rollers including a driving roller and a tension roller.

[0003]

A considerable tension is applied to the intermediate transfer belt supported and stretched by the plurality of rollers so that no slip occurs between the intermediate transfer belt and the drive roller. It is in contact with a considerable winding angle. If tension is applied to the intermediate transfer belt in a stopped state and the belt is kept in contact with the roller, a crease occurs at a portion where the belt is stretched around the roller. If the belt is stretched by the roller and has a cleave habit, the image will be adversely affected, or the resistance value at the cleave position will fluctuate, adversely affecting the image.

In order to reduce such a phenomenon as much as possible, conventionally, as described in Japanese Patent Application Laid-Open No. 10-240025, a belt material or the like is devised so as not to cleave, or the diameter of a supporting roller is increased. And reducing the tension applied to the belt. However, these measures impose great restrictions on the belt material, the diameter of the support roller, and the setting of the tension. Also, JP-A-8-305123, JP-A-9-22280
No. 2, Japanese Patent Application Laid-Open No. 10-142963, an image forming position on the intermediate transfer belt and a belt stop position are defined so that an image is not formed at the cleave occurrence position. There is a disadvantage that an image can be formed only on a specific portion of the belt. Even if the intermediate transfer member has a drum-shaped elastic layer, the elastic layer may cleave at the contact portion with the image carrier or the secondary transfer member, which may adversely affect the image. In order to prevent the occurrence of the problem, the material and hardness of the elastic layer are devised to cope with the problem. However, these countermeasures place great restrictions on the material of the intermediate transfer member.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus having an intermediate transfer member which does not suffer from the above-described restrictions and does not cause adverse effects due to cleave on an image.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to form a toner image on an image carrier having charging, exposure and developing means around it, transfer the toner image to an intermediate transfer member, and then transfer the toner image to a recording medium. An image forming apparatus for transferring a toner image from a transfer body, wherein the intermediate transfer body is rotated for a predetermined time (t1) or more during warm-up of the apparatus or prior to image formation. Image formation in which a toner image is formed on an image carrier having charging, exposure, and development means around it, the toner image is transferred to an intermediate transfer member, and then the toner image is transferred from the intermediate transfer member to a recording medium An image forming apparatus (invention of claim 2), wherein the apparatus detects that the apparatus is in a stop state for a predetermined time (t2) and rotates the apparatus for a predetermined time (t3) or more. Developing means An image forming apparatus that forms a toner image on an image carrier having the surroundings, transfers the toner image to a belt-shaped intermediate transfer body, and then transfers the toner image from the belt-shaped intermediate transfer body to a recording medium, includes at least an apparatus. If the apparatus is in a stop state for a predetermined time (t4) or longer, or
This is achieved by an image forming apparatus (the invention of claim 4), which reduces the tension for stretching the intermediate transfer belt when the FF is performed.

[0007]

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.

[0008] 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.

A photosensitive 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 a 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.

A 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 -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. The intermediate transfer belt 14a has a driving roller 14d, a driven roller 14e, an intermediate roller 14f, and a secondary transfer opposing roller 14j, each of which is grounded.
A roller member such as a tension roller 14i is stretched in contact with the intermediate transfer member driving motor M during image formation.
1, the drive roller 14d is rotated, and the intermediate transfer belt 14a is rotated counterclockwise as indicated by the arrow in FIG. The drive roller 14d is formed of, for example, polyurethane or EP on a peripheral surface of a conductive core metal (no symbol) such as stainless steel.
A material in which a conductive filler such as carbon or the like is dispersed in rubber or a resin material such as DM or silicone and which is coated with a conductive or semiconductive material (no symbol) 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 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 device 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 driven by the intermediate transfer belt 14a and is grounded. An intermediate transfer member cleaning blade 191 that is provided to face the roller 14e and is an intermediate transfer member cleaning member provided in the intermediate transfer member cleaning device 190a.
By a, the transfer residual toner on the intermediate transfer belt 14a is cleaned.

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 a potential is applied to the Y photosensitive drum 10, 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. 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 reference numeral). 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 a potential is applied by the charging operation of the M charging roller 11 by the magenta (M) image forming unit 100, and the M exposure optical system 12 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 the same 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 photosensitive drum 10 for each color after the transfer is brought into contact with the photosensitive drum 10 of the photosensitive member cleaning device 190 which is the 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.

In synchronization with the formation of the superimposed color toner image on the intermediate transfer belt 14a, the recording paper P is fed from a paper feed cassette (not shown) as a recording material storage means via a timing roller 15b as a recording material feeding means. The toner is conveyed to a transfer area (no symbol) of a secondary transfer roller 14g, which is a second transfer unit, and a secondary transfer roller 14g to which a DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. Then, the superimposed color toner images on the intermediate transfer belt 14a are collectively re-transferred 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.

In the image forming apparatus of the present invention, the deformation history of the intermediate transfer belt, which is an intermediate transfer member stretched between a plurality of rollers provided inside, is wound around the rollers while the belt is stopped. Cleave), which eliminates the deterioration of the image quality at the corresponding portion of the belt during the subsequent image formation, and comprises the following invention.

(1) The intermediate transfer member is rotated for a predetermined time (t1) or more at the time of warm-up performed prior to image formation of the apparatus or prior to image formation (claim 1). Is rotated for a predetermined time (t1) or more to restore the deformation habit (cleave) generated in the intermediate transfer body to a level that does not affect the image during the long stop, and then image formation is performed. Thus, the cleave phenomenon can be eliminated without being restricted by the material and the like of the intermediate transfer member.

(2) When the control section detects that the apparatus is in a stopped state such as standby for a predetermined time (t2), the control section rotates the intermediate transfer member for a predetermined time (t3) or more. When the intermediate transfer member is in a stop state for a predetermined time (t2), the cleave phenomenon generated during the intermediate transfer member is removed by rotating the intermediate transfer member for a predetermined time (t3) or more. In addition, a high-quality image can be obtained without being restricted by the material of the intermediate transfer member.

(3) Although the above-mentioned intermediate transfer member is effective even if it is in the form of a roller, a remarkably excellent effect is exhibited for a belt-shaped intermediate transfer member such as the intermediate transfer belt 14a in FIG. .

(4) The apparatus is operated for at least a predetermined time (t4)
When the apparatus is in the stop state or when the apparatus is turned off, the intermediate transfer belt 14a is stretched, for example, by a means such as reducing the pressing force for pressing the belt from the inside to the outside by the tension roller 14i. The present invention is characterized in that the tension for tensioning the transfer belt is reduced (Claim 4), wherein the generation of cleave is prevented by weakening the belt tension, and the material of the intermediate transfer belt 14a is restricted. And a high-quality image is obtained.

(5) A sensor S (A) for detecting humidity and / or temperature is provided in the apparatus, and the control unit includes the sensor S (A)
(T1), (t2), (t3), (t)
Control is performed so as to change each of 4) (claim 5).
The intermediate transfer belt 14a is provided with a sensor S (A) for detecting humidity and / or temperature in the apparatus since the susceptibility to cleave changes depending on the surrounding temperature and humidity.
The control unit obtains a relationship between the temperature and humidity detected in (A) and the state of occurrence of cleave, and sets the predetermined time using a relationship table created based on the obtained result (t1).
(T2), (t3), and (t4) are changed, whereby the intermediate transfer belt 14a is prevented from being affected by cleave by a minimum rotation according to the temperature and humidity so that a high-quality image can be obtained. It was made.

(6) The sensor S (A) for detecting the humidity and / or temperature is arranged near the intermediate roller 14f, which is the smallest roller among the rollers in contact with the intermediate transfer belt 14a. I have. By arranging in the vicinity of the roller where the cleave is most likely to occur among the rollers that support the intermediate transfer belt in this way, it is possible to measure the appropriate temperature and humidity at the place where the cleave is likely to occur, and to minimize the belt The rotation prevents the effect of the cleave and provides a high quality image.

(7) The sensor S (A) for detecting the temperature and humidity is disposed near the drive roller 14d, which is the roller having the largest winding angle among the rollers that come into contact with the intermediate transfer belt 14a, and where the cleave is most likely to occur. Is performing accurate temperature and humidity detection. Cleave is strongly generated at the roller where the diameter is small and the winding angle is large among the rollers that come into contact with the belt. Therefore, the sensor S (A) is provided in the vicinity of the belt contacting the roller where the cleave is strongly generated.

(8) When the intermediate transfer belt 14a is rotated for the purpose of erasing cleave, control is performed such that contact between the belt and the photosensitive drum 10 as an image carrier is released. As a result, the intermediate transfer belt 14a
And the abrasion of the photoreceptor drum 10 and improper aging are prevented.

(9) In the case where the transfer of the toner image from the intermediate transfer belt 14a to the recording medium is performed while the secondary transfer roller 14g is being pressed, when the intermediate transfer belt 14a is rotated for the purpose of eliminating the cleave. , Secondary transfer roller 1
4 g is controlled to be separated from the belt. This prevents the belt and the rollers from being stained or worn.

(10) The intermediate transfer member cleaning blade 191a, which comes into contact with the intermediate transfer belt 14a and removes transfer residual toner adhered to the belt, contacts the intermediate transfer belt 14a when the intermediate transfer belt 14a is rotated for elimination of cleave. Is controlled to be released and separated. As a result, the intermediate transfer belt 14a and the intermediate transfer member cleaning blade 191a are prevented from abrasion and undue aging.

(11) When rotating the intermediate transfer belt 14a, the phases of the intermediate transfer belt 14a in the stopped state before and after the rotation do not match, or the support roller contacts the intermediate transfer belt 14a before the rotation. The rotation time is controlled so that the position does not contact another support roller after the rotation. This prevents the cleave from being emphasized due to the phase matching before and after the rotation of the belt or the overlapping of the contact positions of the belt with the rollers.

FIG. 2 shows the contact interval between the intermediate transfer belt 14a stretched by the support roller and the support roller. The total length D of the intermediate transfer belt 14a is D = Σ (d1
d5). Assuming that the belt rotation speed is v, the time from when the belt starts rotating until it stops is n
If (D / v) (where n is a positive integer), the phases of the belt and the support roller before and after rotation match, so that control is performed so as not to stop the belt at this time.

Further, the time from the start of rotation of the belt to the stop thereof is

[0045]

(Equation 1)

In this case, since the contact position of the belt before rotation with the roller overlaps with the contact position of the belt with the other roller after rotation, control is performed so as not to stop the belt at this time. Do.

The control unit has a time measuring means, which stores in advance a time period during which the stop of the belt after the start of rotation is prohibited, and controls the intermediate transfer belt so as to stop during this time period. It is possible to avoid a phase match between before and after the rotation of 14a or an overlap between the contact positions of the belt and the roller.

(12) At least one reference mark M is provided at the end of the intermediate transfer belt 14a, and a photo sensor S (B) for detecting the reference mark M is provided on the apparatus main body side. B) detects the reference mark M so that the phases of the intermediate transfer belt 14a in the stopped state before and after the rotation of the belt do not match, or the contact position of the support roller on the intermediate transfer belt 14a before rotation is different from that after rotation. The rotation stop position is controlled so as not to come into contact with the supporting roller. This prevents the phases from being matched before and after the rotation of the belt, or the contact position between the belt and the roller from being emphasized.

FIG. 3 shows a reference mark M and a photosensor S.
It is explanatory drawing which shows the relationship with (B). The control unit has a timing unit. Further, the control unit has a table of a prohibition time period for prohibiting the belt stop in advance as a memory in order to avoid a phase match or an overlap of the stop position of the belt and the roller. When the table is called up and the photo sensor S (B) detects the reference mark M, time counting is started, and the control of the belt stop time is performed using the prohibited time zone table to avoid the prohibited time zone.

(13) An optical sensor S (C) or S (D) for detecting the flatness of the intermediate transfer belt 14a is provided, and the intermediate transfer belt 14a is rotated for elimination of cleave when the apparatus warms up. At this time, the control is performed so that the rotation is continued until the cleave amount becomes equal to or less than a predetermined value by the detection of the optical sensor S (C) or S (D). This ensures that the curl is less than a certain amount that is permissible, and a good image can be obtained with the curl corrected.

FIG. 4 is an explanatory view showing the structure of the optical sensor S (C). The light sensor S (C) 1 comprises a light emitting element S (C) 1 and a light receiving element S (C) 2. It emits light and irradiates the surface of the intermediate transfer belt 14a with an inclination of θ (for example, 50 °), and the light receiving element S (C) 2 is set at a regular reflection position with respect to the intermediate transfer belt 14a at a regular position. Have been. When the intermediate transfer belt 14a is displaced or tilted from the normal position, the light receiving position of the reflected light with respect to the light receiving element S (C) 2 moves. By setting the allowable light receiving range of the light receiving element S (C) 2 in advance, the control unit can control the reflected light from the light emitting element S (C) 1
The control is performed so that the rotation of the intermediate transfer belt 14a is continued while it is present at a place where the projection is out of the allowable range of 2 (where the cleave exists).

FIG. 5 shows another optical detection method for detecting the flatness of the intermediate transfer belt 14a, and the amount of reflected light received by the optical sensor S (D) varies depending on the distance. I'm using The received reflected light amount is converted into a voltage value or a current value and detected, but the control is performed so that the rotation of the intermediate transfer belt 14a is continuously performed until the detected light amount difference ΔRL becomes equal to or less than an allowable predetermined value. Done.

As described above with reference to (1) to (13), all of them have the effect of preventing image defects due to cleave, but by combining any of (1) to (13), the effect is further reduced. Ensure the effect. Next, a combination example of a few will be shown.

According to the output X of the sensor S (A) for detecting the temperature and humidity, the rotation of the intermediate transfer belt 14a is started when the intermediate transfer belt 14a is stopped for a predetermined time f1 (X), and stopped after the elapse of f2 (X) ( 5). Primary transfer roller 1 during belt rotation
4c, the secondary transfer roller 14g and the intermediate transfer body cleaning blade 191a release the pressure contact with the belt (8), (9), and (10).

At this time, the higher the humidity and the higher the temperature, the higher the f
The value of 1 is set to be small, and the value of f2 is set to be large.

When the intermediate transfer belt 14a is in a stop state for a predetermined time f1 (X), the tension roller 14i moves in the direction of weakening the tension based on the output X of the sensor S (A) for detecting the temperature and humidity (4). ) (5).

During warm-up, the intermediate transfer belt 1
4a is rotated, and rotation is stopped upon detecting that the cleave amount has become equal to or less than a predetermined value by the detection output of the optical sensor S (C). At this time, by detecting the reference mark M by the photo sensor S (B), the belt portion which is in contact with the intermediate roller 14f where the cleave is most likely to occur before the warm-up is changed to the drive roller 14d and the intermediate roller 14d.
f, secondary transfer opposed roller 14j, tension roller 14
i, The stop position is controlled so as not to come into contact with the portion corresponding to the driven roller 14e (1) (12).

[0058]

According to the present invention, there is provided an image forming apparatus which is not restricted by the material, hardness and the like of the intermediate transfer member and which does not cause deterioration in image quality due to cleave.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a main part of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a contact interval between an intermediate transfer belt and a support roller.

FIG. 3 is an explanatory diagram showing a relationship between a reference mark and a photosensor.

FIG. 4 is an explanatory diagram showing a configuration of an optical sensor.

FIG. 5 is an explanatory diagram showing the configuration and operation of another optical sensor.

[Explanation of symbols]

 Reference Signs List 10 Photoconductor drum 14a Intermediate transfer belt 14c Primary transfer roller 14d Drive roller 14e Follower roller 14f Intermediate roller 14g Secondary transfer roller 14i Tension roller 14j Secondary transfer opposed roller S (A) Sensor S (B) Photo sensor S (C) ) Optical sensor S (C) 1 Light emitting element S (C) 2 Light receiving element M Reference mark

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA11 DA14 DA38 DE02 EC06 ED24 EF01 EF06 2H032 BA09 BA23 BA30 CA01 CA13 CA14

Claims (13)

[Claims] 1. A method for forming a toner image on an image carrier having charging, exposure and developing means around the image carrier, transferring the toner image to an intermediate transfer member, and then transferring the toner image from the intermediate transfer member to a recording medium. In the image forming apparatus, the intermediate transfer body is moved for a predetermined time (t) when the apparatus is warmed up or prior to image formation.
1) An image forming apparatus characterized by being rotated as described above. 2. A toner image is formed on an image carrier having charging, exposure, and developing means around it, and the toner image is transferred to an intermediate transfer member, and then the toner image is transferred from the intermediate transfer member to a recording medium. In the image forming apparatus, the apparatus is operated for a predetermined time (t2).
An image forming apparatus which detects that the apparatus is in a stop state during a predetermined period of time and rotates the apparatus for a predetermined time (t3) or more. 3. The image forming apparatus according to claim 1, wherein the intermediate transfer member has a belt shape. 4. A toner image is formed on an image carrier having charging, exposure, and developing means around the toner carrier, and the toner image is transferred to a belt-shaped intermediate transfer member. In an image forming apparatus for transferring an image, when the apparatus is in a stopped state for at least a predetermined time (t4),
Alternatively, when the apparatus is turned off, the tension for stretching the intermediate transfer belt is reduced. 5. A humidity and / or temperature detection sensor is provided in the apparatus, and the predetermined time is set based on a detection result (t).
The image forming apparatus according to any one of claims 1 to 4, wherein (1), (t2), (t3), and (t4) are changed. 6. The humidity and / or temperature detection sensor,
The image forming apparatus according to claim 5, wherein the image forming apparatus is disposed near a roller having the smallest diameter among rollers that contact the intermediate transfer belt. 7. The humidity and / or temperature detection sensor,
The image forming apparatus according to claim 5, wherein the image forming apparatus is disposed near a roller having the largest winding angle among rollers that contact the intermediate transfer belt. 8. The image forming apparatus according to claim 1, wherein when the intermediate transfer body is rotated, the contact between the image carrier and the intermediate transfer body is released. An image forming apparatus according to claim 1. 9. When the transfer from the intermediate transfer member to the recording medium is performed by a contact member, releasing the contact between the intermediate transfer member and the contact transfer member when rotating the intermediate transfer member is performed. The image forming apparatus according to claim 1, wherein the image forming apparatus includes: 10. A cleaning member, which is in contact with the intermediate transfer member and removes transfer residual toner, on the downstream side in the rotation direction of the intermediate transfer member from a position where the transfer from the intermediate transfer member to the recording medium is performed. The image forming apparatus according to claim 1, wherein when the body rotates, the contact between the intermediate transfer body and the cleaning member is released. 11. When rotating the intermediate transfer member, the phase of the intermediate transfer member in a stopped state before and after rotation is not matched, or the contact position of the support roller on the intermediate transfer belt before rotation is rotated. The image forming apparatus according to any one of claims 1 to 3, wherein the rotation time is controlled so as not to come into contact with another support roller later. 12. At least one reference mark is provided at an end of the intermediate transfer member, and a sensor for detecting the mark is provided. When the intermediate transfer member is rotated by detecting the reference mark during rotation, it is rotated before and after rotation. The rotation stop position should be controlled so that the phase of the intermediate transfer body in the later stop state does not match, or the support roller contact position on the intermediate transfer belt before rotation does not contact another support roller after rotation. The image forming apparatus according to claim 1, wherein: 13. An optical sensor for detecting the flatness of the intermediate transfer member, wherein the rotation is continued until the cleave amount becomes equal to or less than a predetermined value by the detection of the optical sensor. The image forming apparatus according to claim 1.