JP2001331045A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a problem that a transfer current is not successively controlled 6 optimally because it is made different by external parameter (environment, resistance, change with the lapse of time and the material characteristic of a part). SOLUTION: This device is provided with transfer bias varying means 8A and 14 to vary transfer bias in accordance with a detected value by detecting at least either of the bias application variation of the resistance of a contact transfer member 6 and the time variation of the resistance of the contact transfer member 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and a contact transfer device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, and a facsimile, a transfer belt, a transfer roller, and the like are used as a transfer device for transferring a toner image on an image carrier such as a drum-shaped photosensitive member onto a sheet such as transfer paper. There is an apparatus using a contact transfer device having the above contact transfer member. This contact transfer device applies a transfer bias to a contact transfer member from a transfer bias power supply to transfer a toner image on the image carrier to a sheet between the contact transfer member and the image carrier, and removes the sheet from the contact transfer member. The transfer current flowing to the image carrier through the control unit is controlled by a differential constant current method or a constant current method.

In the differential constant current method, a target current value is determined, a feedback current from the contact transfer member is detected, and an output current from the transfer bias power supply to the contact transfer member is determined by adding the target current value to the feedback current. (The output current of the transfer bias power supply is controlled so that the current value obtained by subtracting the feedback current from the output current of the transfer bias power supply becomes the target current value.) This differential constant current method can cope with uneven resistance of the contact transfer member. In the constant current method, an output current from a transfer bias power supply to a contact transfer member is set as a target current value.

Japanese Patent Application Laid-Open No. Hei 9-15994 discloses that an electrostatic latent image formed on an image carrier by an electrostatic photographic process is developed into a toner image by a developing means, and a pre-transfer charge removing means forms a toner image under the toner image. The charge of the electrostatic latent image is removed, the toner image is transferred to a transfer sheet sandwiched between the image carrier and the transfer belt by a transfer unit, the transfer sheet is separated from the transfer belt, and fixed by a fixing unit. An image forming apparatus in which an image is formed by fixing, based on at least one of a resistance value of the transfer belt and a toner density,
There is described an image forming apparatus including a static elimination control unit that controls an output of the pre-transfer static elimination unit.

Japanese Patent Application Laid-Open No. Hei 10-3235 discloses an image carrier for carrying a toner image, and an endless transfer as a contact transfer means for carrying a sheet and transferring the toner image on the image carrier to the carried sheet. A belt, a first electrode that contacts a surface on a side facing the transfer belt and applies a transfer bias to the transfer belt, a second electrode that contacts the transfer belt, and a transfer bias that is applied to the first electrode. Power supply and
The current value output from the power supply is I ₁ , and the current value flowing from the power supply to the second electrode via the transfer belt is I ₂
And when, so as to maintain a constant target current value the output value Iout = I ₁ -I ₂ have been established transfer current, and transfer control means for variably controlling the current value I1, the setting condition of the target current value A target current value control unit that controls the discharge of the residual image on the image carrier after the transfer of the toner image to the sheet; and a control unit that controls the post-transfer charge removal unit according to a set condition. A post-transfer static elimination controller, an image carrier temperature detector for detecting the temperature of the image carrier, a belt resistance detector for detecting a resistance value of the transfer belt, and a size of the sheet In the image forming apparatus provided with the sheet size detecting means, the post-transfer static elimination control means controls the post-transfer static elimination means to the image carrier based on the temperature of the image carrier detected by the image carrier temperature detecting means. Variable output Is described an image forming apparatus characterized by.

[0006] Japanese Patent Application Laid-Open No. 10-123845 discloses that a predetermined nip is formed by a transfer belt wound around a driving roller and a driven roller and movable by driving the driving roller, and a photosensitive member carrying a toner image. In a state where the transfer paper is sandwiched in the area, the photosensitive member and the transfer belt are driven, and by applying a transfer bias from a power supply to the transfer belt by a transfer unit disposed in contact with the transfer belt, In the transfer device for transferring the toner image on the photoconductor to the transfer paper, of the current output from the power supply,
Transfer current control means for controlling a current output from the power supply so that a current flowing into the photoconductor becomes a preset target value; and a transfer current in the nip area between the transfer means and the driven roller. A transfer device is described, comprising a potential lowering unit that is disposed in contact with the transfer belt at a position near the upstream of the movement of the belt and that lowers the potential of the transfer belt.

Japanese Patent Application Laid-Open No. 5-297735 discloses that a multicolor toner image is formed by superposing a toner image on an image carrier by repeating charging, image exposure and development steps, and transferring the multicolor toner image to a transfer material. A power supply for applying a transfer electric field to the transfer material of the transfer belt device, wherein the transfer material or the transfer material is provided. A detection unit for detecting a current value that varies according to the resistance value of the material and the transfer member of the transfer belt device, and when the detection unit operates, the output current or output voltage of the power supply is fixed to a constant value, Before the transfer material enters the transfer area, the current value or the voltage value of the power supply is changed to a value selected based on a result detected by the detection unit. It is.

Japanese Unexamined Patent Publication No. 6-35337 discloses that charging,
The process of image exposure and development is repeated to form a multicolor toner image by superimposing the toner image on the image carrier and transferring the multicolor toner image to a transfer material by stretching and rotating between holding rollers. In an image forming apparatus having a belt device, a transfer power supply for applying a transfer electric field to the transfer material of the transfer belt device, and a resistance value of the transfer material or a resistance value of the transfer material and a transport member of the transfer belt device. An image forming apparatus is provided which includes a detecting unit for detecting a paper charging current value to be applied, and turns on the transfer power supply after the detection of the paper charging current by the detecting unit is completed.

Japanese Patent Application Laid-Open No. 7-248687 discloses a transfer belt in contact with an image carrier, a voltage applying member for applying a voltage to the transfer belt, a power supply for applying a voltage, and a transfer belt for contacting the transfer belt. And a grounding member for returning a current to the power supply, comprising: a driving unit for moving the grounding member back and forth in the rotation direction on the transfer belt. Is described.

Japanese Patent Application Laid-Open No. 8-339127 discloses an endless transfer belt stretched over a plurality of rollers so as to form a transfer portion in contact with or close to an image carrier on which an image to be transferred is formed. And a charge supply means for supplying a transfer charge to a surface of the transfer belt opposite to the image carrier side, wherein the transfer belt supports a transfer material and conveys the transfer material to the support, and the charge supply means A transfer device that transfers an image to be transferred on the image carrier to a transfer material by the transfer charge supplied in the step (a), on the downstream side of the transfer unit in the transfer material transport direction, and on the transfer material passing through the transfer unit. A corona charger facing a part thereof; an AC power supply for applying an AC voltage to the corona charger; and a transfer detecting a DC current flowing between the AC power supply and the transfer material via the corona charger. Material current detecting means, and a small number of the transfer belt and the plurality of support rollers. At least one of a support roller current detecting means for detecting a direct current flowing between the transfer roller and the other, and a setting of an output current amount of the charge supply means based on detection results of the transfer material current detecting means and the support roller current detecting means. And a control unit for changing the image quality.

JP-A-8-339127 discloses a transfer belt for bringing a transfer material into contact with the surface of an image carrier on which an image to be transferred is formed, a belt support for supporting the transfer belt,
A charge supply unit for supplying a transfer charge to the transfer belt; and a difference current between an output current amount from the charge supply unit and a current amount flowing from the transfer belt to the belt support becomes a predetermined current amount. A constant current control means for controlling the charge supply means, a potential detection means for detecting a potential of a charge supply area on the transfer belt to which charges are supplied by the charge supply means; The potential detection means detects the potential of the charge supply area when the difference current reaches the predetermined current amount when the transfer material is not present at the position, and the difference current when the transfer material is present at the transfer position. Comparing means for comparing the potential of the charge supply region when the current reaches the predetermined current amount with the result detected by the potential detecting means, and the predetermined voltage based on the comparison result by the comparing means. Transfer apparatus characterized by comprising a correction means for correcting the amount is described.

Japanese Patent Application Laid-Open No. Hei 10-198195 discloses that a transfer material is introduced along a transfer guide into a transfer portion which is an opposing portion of an image carrier and a transfer means, and a bias is applied to the transfer means to transfer the image. In an image forming apparatus for transferring an image formed on a body surface to a transfer material, a varistor having a predetermined resistance value when an applied voltage exceeds a threshold value v1 is installed between a transfer guide and ground, and a resistance value of a transfer unit is set. The image forming apparatus is characterized in that the threshold value v1 is changed according to.

JP-A-10-207262 discloses that
"A contact transfer type image forming apparatus for transferring a transferable image on an image carrier side to a recording medium side by passing a recording medium between an image carrier and a transfer member which is brought into contact with and applied with a voltage. A voltage output means for outputting a voltage value to be applied to the transfer member; a current detection means for monitoring a current flowing through the transfer member based on the voltage output by the voltage output means; and detection information from the current detection means. Based on
An image forming apparatus, comprising: voltage control means for controlling an output voltage of the voltage output means, wherein the voltage control means has the following first voltage control mode and second voltage control mode. A first voltage control mode: in a non-passing period in which the recording medium does not pass between the image carrier and the transfer member, the current detecting means determines a predetermined target current from the low output state of the voltage output means. The voltage is sequentially increased until the value is detected, and from the voltage output value when it is determined that the predetermined target current has been reached, when the recording medium passes between the image carrier and the transfer member, A voltage control mode for determining an output voltage value of the voltage output means when the recording medium does not pass between the image carrier and the transfer member and does not pass therethrough. Second voltage control mode: during a non-passing period in which the recording medium does not pass between the image carrier and the transfer member, the recording medium is determined between the image carrier and the transfer member in the first voltage control mode. The output voltage at the time of non-passage not passing through is compared with the information from the current detection means at the time of output and the target current, and based on the result, at least the recording medium passes between the image carrier and the transfer member. A voltage control mode for correcting the output voltage value of the voltage output means during the passing. Is described.

[0014]

In the above-described differential constant current method, the output current of the transfer bias power supply is sequentially changed in accordance with the resistance of the contact transfer member. Are sequentially controlled. However, the optimal transfer current to be targeted depends on external parameters (environment, resistance, aging, and material properties of parts), but the transfer bias depends on external parameters (environment, resistance, aging, material properties of parts). The output current of the power supply cannot be controlled sequentially (feedback control).

It is ideal that the transfer current is controlled by sequentially detecting the target transfer current value. However, in detecting the resistance of the contact transfer member, a constant bias voltage or bias current must be applied to the contact transfer member each time, and the current or voltage of the contact transfer member must be detected and converted to the resistance value of the contact transfer member. It is necessary to always apply a bias to the contact transfer member, and it takes time to detect the resistance of the contact transfer member.

Further, since it is not known how the resistance of the contact transfer member behaves, a simple feedback that the temperature and humidity are directly detected by a temperature and humidity sensor or the like and the transfer current is immediately controlled by the detected value is used. No control.
That is, at present, the transfer current is controlled by detecting only the resistance of the contact transfer member, but there is a problem that if the resistance of the contact transfer member fluctuates rapidly with time or environment, it cannot follow the change.

For example, when a material whose resistance fluctuates greatly due to environmental fluctuations is used for the contact transfer member, the transfer current cannot be quickly set to an optimum value when the environment changes. If a method of complicating the detection of the resistance of the contact transfer member is adopted in order to solve the above problem, the user cannot be satisfied in terms of machine productivity.

If the transfer of the toner image is performed with the transfer current set in the environment before the change, there is a problem that an abnormal image is generated when the environment changes significantly. In particular,
In a contact transfer member made of a material whose resistance varies depending on the environment such as an ion conductive system, when the temperature changes from high temperature and high humidity (hereinafter, referred to as H / H) to low temperature and low humidity (hereinafter, referred to as L / L), H becomes high. If the electrophotographic current is set at / H, L / L
Causes an abnormal image.

In the case where the ratio suddenly changes from L / L to H / H, the transfer charge becomes insufficient. Furthermore, sheet transportability such as transfer paper (separability from image carrier such as photoreceptor)
Is not secured, and a sheet jam occurs. The sheet is separated from the image carrier by the nail even if the environmental change is such that the jam does not occur, so that there is also a problem that the mark of the nail is generated on the image on the sheet. In addition, the contact transfer member made of a material whose resistance fluctuates with time has a large change in resistance in an initial state such as when the apparatus is loaded or when the contact transfer member is replaced. Control is required.

It is an object of the present invention to provide an image forming apparatus capable of performing optimal transfer current control according to the characteristics of a contact transfer member. The invention according to claim 2 provides an image forming apparatus capable of performing optimal transfer current control according to the characteristics of the contact transfer member, and performing optimal transfer current control more accurately with respect to the environment and time. The purpose is to provide.

According to a third aspect of the present invention, there is provided an image forming apparatus capable of performing optimum transfer current control in accordance with the characteristics of a contact transfer member and performing more stable and optimum transfer current control. With the goal. An object of the present invention is to provide an image forming apparatus capable of performing optimal transfer current control according to the characteristics of a contact transfer member and performing more stable optimal transfer current control. I do.

A fifth object of the present invention is to provide a contact transfer device capable of performing optimal transfer current control according to the characteristics of the contact transfer member. The invention according to claim 6 provides a contact transfer device capable of performing optimal transfer current control in accordance with the characteristics of the contact transfer member and capable of performing optimal transfer current control more accurately with respect to the environment and aging. The purpose is to provide.

[0023]

According to a first aspect of the present invention, there is provided an image bearing member for carrying a toner image and a sheet passing between the image bearing member. In an image forming apparatus having a contact transfer member for transferring the upper toner image and a bias applying unit for applying a transfer bias to the contact transfer member, a bias application change amount of a resistance of the contact transfer member and The apparatus further comprises a transfer bias varying means for detecting at least one of the time change amounts of the resistance and varying the transfer bias according to the detected value.

According to a second aspect of the present invention, there is provided an image carrier for carrying a toner image, a contact transfer member for transferring the toner image on the image carrier to a sheet passing between the image carrier, An image forming apparatus having a bias applying unit for applying a transfer bias to the contact transfer member, wherein at least one of a bias application change amount of the resistance of the contact transfer member and a time change amount of the resistance of the contact transfer member is detected. A transfer bias varying means for varying the transfer bias at least in the environment and / or with time according to the detected value is provided.

The invention according to claim 3 is the invention according to claim 1 or 2
In the above-described image forming apparatus, the transfer bias varying unit varies a correction amount of the transfer bias.

According to a fourth aspect of the present invention, there is provided an image carrier for carrying a toner image, a contact transfer member for transferring the toner image on the image carrier to a sheet passing between the image carrier, In an image forming apparatus having a bias applying unit for applying a transfer bias to a contact transfer member, a bias application change amount of a resistance of the contact transfer member, a time change amount of a resistance of the contact transfer member, and a resistance of the contact transfer member are determined. The image forming apparatus further includes a transfer bias varying unit that detects and varies the transfer bias according to the detected value.

According to a fifth aspect of the present invention, there is provided a contact transfer device of an image forming apparatus having an image carrier for carrying a toner image and transferring the toner image on the image carrier to a sheet. A contact transfer member for transferring a toner image on the image carrier to a sheet passing between the contact transfer member, a bias applying unit for applying a transfer bias to the contact transfer member, and a bias application change amount of a resistance of the contact transfer member. A transfer bias varying means for detecting at least one of the temporal changes in the resistance of the contact transfer member and varying the transfer bias in accordance with the detected value.

According to a sixth aspect of the present invention, there is provided a contact transfer device of an image forming apparatus having an image carrier for carrying a toner image and transferring the toner image on the image carrier to a sheet. A contact transfer member for transferring a toner image on the image carrier to a sheet passing between the contact transfer member, a bias applying unit for applying a transfer bias to the contact transfer member, and a bias application change amount of a resistance of the contact transfer member. A transfer bias varying means for detecting at least one of a time change amount of the resistance of the contact transfer member and varying the transfer bias at least in the environment and / or with time according to the detected value.

[0029]

FIG. 3 shows a first embodiment of the present invention, and FIGS. 1 and 2 show a part of the first embodiment during non-transfer and during transfer. The first embodiment is an embodiment of the invention according to claims 1 and 2, and is an example of an image forming apparatus having a contact transfer device according to one embodiment of the inventions according to claims 5 and 6. In the first embodiment, as shown in FIG.
Are detachably supported on the image forming apparatus main body 1A.

The belt unit 2 transfers the toner image on the drum-shaped photosensitive member 3 as an image carrier to a transfer sheet S as a sheet.
A transfer belt 6 as a contact transfer member for transferring the toner image onto the transfer belt 6, a driving roller 5 and a driven roller 4 around which the transfer belt 6 is wound, a contact / separation lever 9 for bringing the transfer belt 6 into and out of contact with the photosensitive member 3, DC for rotating the contact / separation lever 9
It has a solenoid 8, a bias roller 11 as an electrode that contacts the inner peripheral surface of the transfer belt 6 and applies a transfer bias to the transfer belt 6, and a contact plate 13 as an electrode that contacts the transfer belt 6. The photoconductor 3 is configured by, for example, providing a photosensitive layer on a conductor, and the conductor is grounded.

A cleaning device 16 having a cleaning blade 16A for scraping off residual toner and paper dust on the transfer belt 6, and a high-voltage power supply 12 for applying a transfer bias to the bias roller 11 are provided in the main body 1A of the image forming apparatus. The drive roller 5 has a gear 5b (see FIG. 4) interlocked with a belt drive motor 22 (see FIG. 9) as a drive unit (not shown).
Is driven to rotate. The transfer belt 6 is rotationally driven by the drive roller 5 and moves in the transfer paper transport direction A at a position facing the photoconductor 3.

As shown in FIG. 5, the transfer belt 6 is composed of two layers 6a and 6b, and the electrical resistance measured according to JIS K6911 is determined by applying a DC voltage of 100 V to the surface layer 6a.
The surface resistance of the surface b is set in a wide range from 1 × 10 8 Ω to 1 × 10 12 Ω in the order of 1 to 2 and the inner layer 6 a
The surface resistivity of the transfer belt 6 is set in a wide range of about 1 to 2 orders from 1 × 10 7 Ω to 1 × 10 9 Ω. Is set to The surface layer 6b is a coating layer having a low coefficient of friction and has a large elongation until cracks occur.

The rollers 4 and 5 are rotatably supported by a support 7. The support member 7 can swing about the support shaft 5 a of the roller 5, which is located downstream of the transfer position of the toner image from the photoconductor 3 to the transfer sheet S in the transfer sheet transport direction A, among the rollers 4 and 5. It has become. The support 7 is moved by the rotation of the contact / separation lever 9 to move the transfer belt 6 toward and away from the photosensitive member 3, and the contact / separation lever 9 is driven by a DC solenoid (SOL) 8 to transfer and transfer the belt 6. Rotate the position side. That is, a contact / separation lever 9 is connected to the DC solenoid 8, and the contact / separation lever 9 is driven by a signal from a control plate 8A as a control means to rotate and move the support 7, thereby causing the support 7 to move. 7 moves the transfer belt 6 toward and away from the photoconductor 3.

The transfer paper S is fed from a paper feeding device (not shown) to the registration roller 10 and is sent out to the transfer belt 6 by the registration roller 10 so that the leading end of the toner image is aligned with the toner image on the photoconductor 3. When the DC solenoid 8 is driven by the control plate 8A and the contact / separation lever 9 approaches the photoconductor 3 side, the support 7 makes the transfer belt 6 contact the photoconductor 3 and the transfer belt 6 and the photoconductor 3 are connected. A transfer nip B is formed.

As shown in FIG. 4, both ends 4a and 4a of the driven roller 4 are tapered in the axial direction to prevent the transfer belt 6 from being shifted. The driven roller 4 is a conductive roller made of metal or the like, but only supports the transfer belt 6 having the electric resistance as described above, and is electrically connected directly to another conductive member. This is an example in the case where it has not been performed. Further, the driven roller 4 can be grounded. When the driven roller 4 is grounded, the driven roller 4 is connected to the transfer control plate 14 so that current is fed back from the transfer belt 6 to the transfer control plate 14 as control means via the driven roller 4.

Since the driving roller 5 has a function of increasing the gripping force on the transfer belt 6 when driving the transfer belt 6, a material such as EPDM rubber, chloroprene rubber or silicone rubber is selected. Further, the driving roller 5 may be a conductive roller without using rubber. Further, the feedback current from the roller 5 can be returned to the transfer control plate 14. In this case, the drive roller 5 is connected to the transfer control plate 14 so as to return a feedback current from the transfer belt 6 to the transfer control plate 14 via the drive roller 5.

The bias roller 11 is provided so as to contact the inside of the transfer belt 6 on the downstream side of the roller 4 in the moving direction of the transfer belt 6. The bias roller 11 constitutes a contact electrode for applying a charge having a polarity opposite to the charge polarity of the toner on the photoconductor 3 to the transfer belt 6, and is connected to a high voltage power supply 12 as a bias applying unit. You. The contact plate 13 is disposed in contact with the inner surface near the driven roller 4 on the lower side of the transfer belt 6 which is not the transfer paper transport surface, and suppresses charge injection to the transfer paper S upstream from the transfer nip portion. The contact plate 13 is an electrode for detecting a current flowing in the transfer belt 6 as a feedback current, and is connected to a transfer control plate 14. The transfer control plate 14 is a feedback current from the contact plate 13 (the rollers 4 and 5 are connected). In this case, a feedback current from the rollers 4 and 5) is detected to control a supply current or an applied voltage from the high voltage power supply 12 to the bias roller 11.

As shown in FIG. 2, the transfer plate 1 controls the DC solenoid 8 in accordance with the transfer of the transfer paper S from the registration roller 10 so that the support 7 moves the transfer belt. 6 is brought close to the photoconductor 3,
A transfer nip portion B having a width of 4 to 8 mm corresponding to a predetermined length is formed between the photoreceptor 3 and the transfer belt 6 along the transfer direction of the transfer paper S.

On the other hand, in the case of the present embodiment (analog copying machine), the surface of the photoconductor 3 is uniformly charged to, for example, -800 V by a charging unit (not shown), and then exposed to light by an exposing unit (not shown). Is formed, and this electrostatic latent image is developed by the developing device 18 as shown in FIG. 6 to become a toner image. That is, the photoconductor 3 electrostatically attracts the positively charged toner 19 from the developing device 18, so that the electrostatic latent image becomes a toner image.

Before the photosensitive member 3 reaches the transfer nip portion B, the pre-transfer discharging lamp 1 as a pre-transfer discharging device is provided.
5, the charge on the surface is weakened. In FIG. 6, the height of the charge is represented by the size of a circle.
The transfer paper S fed from the registration roller 10 is conveyed by the transfer belt 6 and passes through the transfer nip portion B. In the transfer nip portion B, the toner on the photoconductor 3 is transferred from the high-voltage power supply 12 via the bias roller 11 to the transfer belt 6.
When a transfer bias is applied to the transfer belt 6
The image is transferred to the upper transfer sheet S.

The transfer bias is 1.5 KV to -6.5.
The voltage is applied to the bias roller 11 from the high voltage power supply 12 in the range of KV. Since the transfer bias current is controlled as described below, the transfer bias is variably set. That is, the current output from the high voltage power supply 12 and I _1, if the current detected by the transfer control board 14 flows to the ground side from the transfer belt 6 was I _2, the transfer control board 14 is I ₁ -I ₂ = Iout (where, Iout constant value) for controlling the I ₁ by controlling the high voltage source 12 so as to (1). This is to stabilize the surface potential on the transfer sheet S to eliminate the change in transfer efficiency, regardless of changes in environmental conditions such as temperature and humidity and variations in the manufacturing quality of the transfer belt 6.

That is, the current flowing to the photoconductor 3 through the transfer belt 6 and the transfer paper S is viewed as Iout, so that the current to the transfer belt 6 due to the reduction or increase in the surface resistance of the transfer paper S is obtained. This is to prevent the change in the ease of flow from affecting the separation performance and transfer performance of the transfer paper S.

When the image is transferred from the photosensitive member 3 to the transfer paper S, the transfer paper S is charged at the same time.
Therefore, the transfer paper S is electrostatically attracted onto the transfer belt 6 and separated from the photoconductor 3 after the transfer, due to the relationship between the true charge of the transfer belt 6 and the separated charge generated on the transfer paper S side.
This separation is promoted by the peeling operation of the transfer paper S using the stiffness of the transfer paper S using the curvature separation of the photoconductor 3.

In such electrostatic attraction, when the humidity becomes high due to a change in environmental conditions, the current easily flows through the transfer sheet S, and the transfer sheet S cannot be separated properly. Therefore, the resistance value of the surface layer 6b of the transfer belt 6 is set slightly higher to delay the transfer of the true charges to the transfer paper S in the transfer nip portion B. Further, since the bias roller 11 is located on the downstream side of the transfer nip portion B in the transfer paper transport direction, the transfer of the true charge from the transfer belt 6 to the transfer paper S is delayed, and the transfer paper S and the photosensitive member 3 Thus, the electrostatic attraction relationship between them is avoided.

In this case, to delay the transfer of the true charge means
This means that charge injection to the transfer paper S does not occur upstream of the transfer paper S until the transfer paper S reaches the transfer nip portion B on the photoconductor 3 side. For this reason, the winding of the transfer paper S around the photoconductor 3 is prevented, and the separation failure of the transfer paper S from the photoconductor 3 is also prevented.

Further, as the transfer paper S, it is better to select one having a small change in resistance due to environmental changes. As a conductive material for controlling the resistance, an appropriate amount of carbon or zinc oxide is added, and a rubber belt is used as an elastic belt. In the case where is used, it is desired to select a material having low hygroscopicity and a stable resistance value, such as chloroprene rubber, EPDM rubber, silicone rubber, and epichlorohydrin rubber.

It should be noted that the value of the current Iout flowing to the photosensitive member 3 is not unique and can be reduced when the transfer paper transport speed is low, and conversely when the transfer paper transport speed is high or before transfer. When the static elimination lamp 15 is not used, the number is increased. When the transfer paper S is not separated from the photoconductor 3, the transfer paper S is separated from the photoconductor 3 by the separation claw 20.

On the other hand, the transfer paper S passing through the transfer nip portion B
Is transported in accordance with the movement of the transfer belt 6 while being electrostatically attracted to the transfer belt 6, and the curvature separation is performed at the drive roller 5. For this reason, the diameter of the driving roller 5 is set to 16 mm or less. When such a driving roller 5 is used, high quality 45K paper (rigidity 21 mm in width) is used.
(Cm ^3/100)) experimental result that separation is possible of is obtained.

The transfer paper S separated from the transfer belt 6 at the driving roller 5 is guided by a guide plate and conveyed between a heating roller 17a and a pad roller 17b constituting a fixing section 17, and a toner image is formed. Be established. After the transfer of the image from the photoreceptor 3 to the transfer paper S and the separation of the transfer paper are completed, the excitation of the DC solenoid 8 is released by the control plate 8A, and the contact / separation lever 9 and the support 7 return to the original positions. As a result, the photosensitive member 3 is separated from the photosensitive member 3 and the surface is cleaned by the cleaning device 16.

The cleaning device 16 includes a cleaning blade 16A which rubs against the transfer belt 6 and moves from the surface of the photoreceptor 3 to the transfer belt 6, a toner which is not transferred to the transfer paper S and adheres to the transfer belt 6, Debris of the transfer paper S is scraped off the transfer belt 6 by the cleaning blade 16A.

The transfer belt 6 rubbed by the cleaning blade 16A has a low frictional resistance on the surface so as to prevent a phenomenon such as an increase in driving force due to an increase in rubbing resistance or a turning-up of the cleaning blade 16A. Resin material, for example, polyvinylidene fluoride, ethylene tetrafluoride and the like. The toner or paper dust scraped off from the surface of the transfer belt 6 by the cleaning blade 16A is stored from the image forming apparatus main body 1A into a waste toner collector (not shown) by the collection screw 16B. The cleaning means is the cleaning blade 16A, but may be a cleaning roller to which a bias is applied.

In this embodiment, the transfer belt 6 uses a plurality of types of transfer belts each made of a material having a different tendency. 2. Description of the Related Art Conventionally, in an image forming apparatus having a contact transfer device, control of a transfer current is performed only in accordance with a contact transfer member made of one kind of material. It is difficult to use the plurality of types of the contact transfer members thus obtained.

If the material of the contact transfer member is one type, the transfer current can be controlled by detecting the resistance inside the apparatus. However, several materials with different characteristics (for example, carbon dispersion system, ion conduction system, hybrid system)
Is to be used as the material of the contact transfer member in one image forming apparatus, it is indispensable to grasp the tendency of the material of the currently mounted contact transfer member.

If you know what kind of system the material is,
Since it is possible to grasp the behavior of the resistance of the material due to the temporal change and the environmental change, it becomes easy to perform the transfer current control corresponding to each system. For this purpose, it is necessary to detect the material of the contact transfer member. In addition, there is also a merit in terms of cost if a transfer belt composed of a plurality of different materials can be used. Therefore, in this embodiment,
The change amount of the resistance of the transfer belt 6 as a contact transfer member over time is detected to grasp the characteristics of the transfer belt 6, and the transfer bias control is performed based on the result.

As a method for detecting the amount of change in the resistance of the transfer belt 6 over time, for example, the following method is available. The first method is a method in which a constant voltage is applied to the transfer belt 6 and a current flowing through the transfer belt 6 is detected from immediately after the voltage is applied until after a certain period of time to detect a change amount. The second method is a method in which a constant current is supplied to the transfer belt 6 and the amount of change in the voltage of the transfer belt 6 is detected from a time immediately after the current is supplied to a time after a predetermined time.

Here, the time change amount of the resistance of the contact transfer member is the rate of change or difference between the current value immediately after the voltage application of the contact transfer member and the current value after the same voltage application for a certain period of time, or
This is the rate of change or difference between the voltage value immediately after the current supply of the contact transfer member and the voltage value after the same current supply for a certain period of time.
In the present embodiment, the time variation is set as in the following equation. (Current value of the contact transfer member one minute after voltage application-current value of the contact transfer member immediately after application of the same voltage) / (current value of the contact transfer member immediately after application of the same voltage) This is an example of the rate of change of the current value. It is. In addition, for a certain time,
Instead of one minute, two minutes, three minutes, or the like may be used.

The rate of change of the current value ΔIt is ΔIt = (current value of one minute after application of voltage to contact transfer member−current value of contact transfer member immediately after application of same voltage) / (application of same voltage of contact transfer member) (Current value immediately after). FIG. 7 shows an example of a time change amount of the resistance of the transfer belt 6. (A) of FIG.
FIG. 7C is a typical example of the time change amount of the resistance of the transfer belt 6 formed of the carbon dispersion system, and FIG. 7C is a representative example of the time change amount of the resistance of the transfer belt 6 formed of the ion conductive system. FIG. 7B is a typical example of the amount of change over time in the resistance of the transfer belt 6 made of a hybrid material in which an ion conductive system and a carbon dispersion system are mixed.
By detecting the time change amount of the resistance of the transfer belt 6 from FIG. 7, the rate of change of the resistance of the transfer belt 6 in each environment can be determined.

That is, it is possible to know how much the resistance of the transfer belt 6 changes in each environment, and to determine whether the material of the transfer belt 6 is an ion conductive material, a carbon dispersed material, or a mixture thereof. It can be understood whether the material is a hybrid material or a material closer to the ion conductive system or the carbon dispersion system. Therefore, it is possible to accurately control the transfer current in each environment by detecting the time change amount of the resistance of the transfer belt 6.

The present invention is not limited to the method of controlling the transfer current by dividing the material of the transfer belt 6 into three material systems as described above. For example, taking a carbon dispersion system as an example, comparing the case where a material having a polar group to a polymer is used as the material of the transfer belt 6 and the case where a normal polymer is used as the material of the transfer belt 6, Even if the amount and type of the conductive material are the same, the behavior of the material may be different. When a polymer having a large polarity is used as the material of the transfer belt 6, the transfer belt 6 may be closer to an ion conductive system.

The ion conductive material has a very large change in resistance environment compared to the carbon dispersed material, and it is very difficult to control the transfer current in each environment. On the other hand, the amount of change in resistance over time (resistance change rate over time)
There is almost no. If the amount of change in resistance with time is large, it can be considered that the material of the transfer belt 6 is a carbon-dispersed material. Carbon dispersion materials have a large resistance change over time (resistance change rate over time), making it very difficult to control the transfer current over time.

For example, in the case of a transfer belt made of an ion conductive material, conventionally, the transfer current must be controlled by detecting the resistance of the transfer belt every time there is an environmental change. However, in the present embodiment, once the resistance of the transfer belt 6 is detected, it is possible to know how much the resistance of the transfer belt 6 is changed in each environment. It is clear whether the system is a dispersion system or a hybrid system).
It is not necessary to control the transfer current by detecting the resistance of the transfer current. The temperature and humidity are detected by the temperature and humidity detecting means, and the sequential transfer belt 6 is detected.
Can be controlled.

FIG. 8 shows temperature and humidity (here, L / L, normal temperature and normal humidity N / N, and H / H), the amount of change in resistance of the transfer belt 6 (the amount of change in resistance with time), and the amount of transfer current. Show the relationship. This is an example, and the temperature and humidity (L / L, N / N,
Data on the relationship between the transfer current and the resistance change amount (time change amount of the resistance) of the transfer belt 6 composed of a plurality of types of materials and the transfer belt 6 are stored in advance in the ROM. Thus, it is possible to detect the resistance change amount (time change amount of the resistance) of the transfer belt 6 and control the transfer current based on the data in the ROM. In particular, it is very advantageous when there is a sudden environmental change. That is, here, as shown in FIG. 9, the environment (temperature and humidity) is detected by the temperature / humidity detecting means 21, and the transfer current can be sequentially changed by the transfer control plate 14 by the control plate 8A. This is advantageous. The control plate 8A is a CPU
23, the ROM 24, the RAM 25, the timer 26, and the I / Os 27 and 28, which are connected to the operation unit 29.

Next, the material of the carbon dispersion system will be described. This material has a greater change in resistance over time than the change in resistance in the environment, and it is essential to focus on controlling the transfer current over time. 10 to 12 show the relationship between the amount of change in resistance of the transfer belt over time T (the amount of change in resistance with time) and the transfer current. Also in this case, the data of this relation is stored in the ROM 24. Therefore, it is possible to detect the resistance change amount (time change amount of the resistance) of the transfer belt 6 and control the transfer current by referring to the data in the ROM based on the resistance change amount. In particular, when there is a change in resistance due to stretching as well as a change with time as in the transfer belt 6, an optimal transfer current can be controlled with time. It is to be noted that the resistance change amount is in the order of 7 or more in FIG. 10, FIG. 11 is in the order of 8 to 9 power, and FIG. 12 is in the order of 10 or more power. FIG. 13 shows the resistance change rate of the transfer belt 6 over time. The rate of change in resistance of the carbon dispersion system as shown in FIG. 13D is greater than the rate of change in resistance of the ion conductive system as shown in FIG. 13E.

FIG. 14 shows a flow from the detection of the resistance of the transfer belt 6 and the detection of the amount of change in the resistance with time to the transfer current control. The control plate 8A first detects the resistance of the transfer belt 6 from the output voltage and output current of the high-voltage power supply 12 via the transfer control plate 14, and detects the time change amount of the resistance of the transfer belt 6 to detect the resistance. Transfer belt 6 based on time variation
Is determined whether the material is ion conductive or carbon dispersed.

When the detected value (the amount of change in resistance with time) is 0.5 or less, the control plate 8A controls the transfer current in the environment, that is, the input signal from the temperature / humidity detecting means 21 and the time of the resistance. The data (temperature and humidity (L / L, N / L) in the ROM 24 as shown in FIG.
The transfer current is transferred to the transfer control plate 14 with reference to the N, H / H (3 environments) and the data on the relationship between the transfer current and the resistance change amount of the transfer belt 6 composed of a plurality of types of materials. (Temperature / humidity) and the transfer current according to the time change amount (resistance change amount) of the resistance, and the operation time of the apparatus (use time of the transfer belt 6) is measured by a time measuring means. The transfer current is transferred to the transfer control plate 14 with reference to the data in the ROM 24 as shown in FIGS. 10 to 12 based on the time change amount of the resistance (resistance change amount). The transfer current is changed according to the operation time of the apparatus (use time of the transfer belt 6).

When the detected value (the amount of change in resistance with time) is greater than 0.5, the control plate 8A controls the transfer current over time, that is, the operation time of the apparatus (the use time of the transfer belt 6). ) And the time change amount of the resistance (resistance change amount), referring to data in the ROM 24 as shown in FIGS. Amount) and the transfer current according to the operation time of the apparatus (use time of the transfer belt 6).

FIG. 15 shows a flow for detecting the resistance of the transfer belt 6. This flow corresponds to ☆ in FIG. The control plate 8A causes the transfer control plate 14 to set I ₁ -I ₂ = Iout to 40 μA to detect the output voltage V of the high-voltage power supply 12 (transfer voltage applied to the transfer belt 6).
Is determined to be 2.0 kV or less. Control board 8A
If the voltage V is 2.0 kV or less, it is further determined whether or not the voltage V is 1.0 kV or less.
If the voltage V is less than 1.0 kV, it is determined that the resistance of the transfer belt 6 is very low.
Is determined to be low.

If the voltage V is not less than 2.0 kV, the control plate 8A causes the transfer control plate 14 to set I ₁ -I ₂ = Iout to 50 μA to detect the output voltage V of the high voltage power supply 12, When this voltage V is higher than 2.0 kV and is 3.2 kV
It is determined whether it is smaller than. If the voltage V is higher than 2.0 kV and lower than 3.2 kV, the control plate 8A determines that the resistance of the transfer belt 6 is medium, and determines that 2.0 kV <V.
If not <3.2 kV, I ₁ −
The output voltage V of the high-voltage power supply 12 is detected by setting I ₂ = Iout to 60 μA.

The control plate 8A detects that the voltage V is equal to 3.2.
It is determined whether or not kV <V ≦ 6.0 kV, and 3.2 kV
If <V ≦ 6.0 kV, it is determined that the resistance of the transfer belt 6 is high, and if 3.2 kV <V ≦ 6.0 kV, it is determined that the resistance of the transfer belt 6 is extremely high. The transfer belt has a high resistance in an initial state and tends to decrease with time. Therefore, if it is determined that the resistance of the transfer belt 6 is extremely high, the output voltage of the high-voltage power supply 12 may be abnormally high and a leak may occur from the transfer belt 6 to the photoconductor 3.
Therefore, when the control plate 8A determines that the resistance of the transfer belt 6 is extremely high, the process proceeds to the flow shown in FIG. 16 and causes the transfer control plate 14 to switch from constant current control to constant voltage control. The constant voltage applied to the transfer belt 6 is 6.3 k
V to about 6.8 kV is desirable.

That is, the control plate 8A is connected to the transfer control plate 14
The time change of the resistance of the transfer belt 6 is detected from the output voltage and output current of the high-voltage power supply 12 via the interface, and based on the time change of the resistance, whether the material of the transfer belt 6 is ion conductive or carbon dispersed Judge. When the detected value (the amount of change in resistance with time) is 0.5 or less, the control plate 8A determines whether or not the environment is L / L based on an input signal from the temperature / humidity detecting means 21. If it is L, the flow proceeds to * in the flow shown in FIG. 14. If the environment is not L / L, the transfer control board 14 is caused to control the output voltage of the high-voltage power supply 12 to a constant voltage of 6 kV.

When the detected value (time change amount of the resistance) is larger than 0.5, the control plate 8A sets the operation time (use time of the transfer belt 6) T of the device measured by the timer means to 50 hours ( hr) It is determined whether or not T is less than or equal to 50.
If the time is not less than the time, the process proceeds to * 1 in the flow shown in FIG. 14. If T is less than 50 hours, the output voltage of the high voltage power supply 12 is controlled by the transfer control plate 14 to a constant voltage of 6 kV.

In the above-described resistance detection of the transfer belt 6, the transfer belt 6 when a constant current is supplied to the transfer belt 6 is used.
Although the resistance of the transfer belt 6 is detected by detecting the voltage of the transfer belt 6, the resistance of the transfer belt 6 may be obtained by detecting the current of the transfer belt 6 when a voltage is applied to the transfer belt 6.

According to the first embodiment, the control plate 8A as a transfer bias varying means for detecting a time change amount of the resistance of the transfer belt 6 as a contact transfer member and varying a transfer bias according to the detected value. In addition, since the transfer control plate 14 is provided, optimal transfer current control (transfer bias control) can be performed according to the characteristics of the contact transfer member, and sequential control of the transfer bias can be performed. In particular, by detecting the amount of change in resistance of the contact transfer member with time, it is possible to know how much the contact transfer member is an ion conductive system or a carbon dispersion system, and to obtain a more accurate transfer bias. Control becomes possible.

Further, according to the first embodiment, the transfer bias variable which detects the time change amount of the resistance of the contact transfer member 6 and changes the transfer bias at least in the environment and / or with time according to the detected value. Since the control plate 8A and the transfer control plate 14 are provided as means, optimal transfer current control (transfer bias control) can be performed according to the characteristics of the material of the contact transfer member. In particular, when a contact transfer member made of an ion conductive material is used, the transfer bias control can be more accurately performed to stabilize the transfer bias control in the environment. H / H makes it possible to stabilize the sheet transportability. In addition, when a contact transfer member made of a carbon dispersion material is used, the transfer bias control can be more accurately performed to stabilize the transfer bias control over time, and the resistance of the contact transfer member over time can be improved. Can be accommodated.

Next, a second embodiment of the present invention will be described. The second embodiment is an embodiment of the invention according to claims 1 and 2, and is an example of an image forming apparatus having a contact transfer device according to one embodiment of the inventions according to claims 5 and 6. This second
In this embodiment, the transfer bias is controlled by detecting the amount of change in the bias applied to the resistance of the contact transfer member in the first embodiment.

The bias application change amount of the resistance of the contact transfer member is a difference or a change rate of the resistance of the contact transfer member detected when at least two or more biases are applied to the contact transfer member. In the second embodiment, since the transfer bias is controlled by detecting the amount of change in the bias applied to the resistance of the contact transfer member, two parameters are detected, and more precise transfer bias control is performed than in the first embodiment. be able to.

Here, a constant voltage is applied as a bias to the contact transfer member to make the transfer current constant. For example, a current value when a constant voltage of 1 KV is applied to the contact transfer member as a bias is detected, and a constant voltage of 2 KV is further detected.
Is applied to the contact transfer member, and the current value at that time is detected. The rate of change of these current values is calculated and the rate of change is detected. In this case, when the current value is detected, the bias is applied for a fixed time, and the current value is kept constant regardless of the applied voltage. For example,
The predetermined time is set in advance as one minute.

FIG. 17 shows the transfer belt 6 in the second embodiment.
4 shows a flow from detection of a bias application change amount of a resistor to transfer current control. The control plate 8A sequentially applies the output voltage (transfer bias) of the high-voltage power supply to the transfer control plate 14 by 100,5.
00, 1 KV, and 2 KV, the current flowing through the transfer belt 6 when each transfer bias is applied is detected, and these currents are converted into the resistance of the transfer belt 6. Then, the bias of the resistance of the transfer belt 6 is applied from these resistances. Change rate Δ as change amount
Calculate Iv.

Next, the control plate 8A recognizes the type of the material of the transfer belt 6 based on the difference in the change rate.
That is, it recognizes whether the material of the transfer belt 6 is an ion conductive system or a carbon dispersion system, and varies the transfer current Iout for the transfer control plate 14 for each material system. That is, when ΔIv is smaller than 0.5, the control plate 8A sets the correction coefficient to L
/ L is set to 0.8, H / H is set to 1.2,
The environment is H / H by the input signal from the temperature / humidity detecting means 21.
Or L / L. When the environment is H / H, the control plate 8A corrects the transfer current Iout to 1.2 times by the correction coefficient to the transfer control plate 14 and outputs the transfer bias from the high voltage power supply 12, and the environment is L / H. In the case of L, the transfer control plate 1
4, the transfer current is corrected to 0.8 times by the correction coefficient, the transfer bias is output from the high voltage power supply 12, and the environment is H / H.
If neither H nor L / L, the transfer current is not corrected.

When ΔIv is 0.5 or more, the control plate 8A sets the correction coefficient to 0.9 in L / L and sets H / H
Then, it is set to 1.1, and it is determined whether the environment is H / H or L / L based on an input signal from the temperature / humidity detecting means 21. Control board 8
A indicates that when the environment is H / H, the transfer current is corrected to 1.1 times by the correction coefficient with respect to the transfer control
2, the transfer bias is output from the high voltage power supply 12, and the transfer bias is output from the high voltage power supply 12 when the environment is L / L. However, if it is not L / L, the transfer current is not corrected.

According to the second embodiment, the control plate as the transfer bias variable means for detecting the amount of change in the bias applied to the resistance of the transfer belt 6 as the contact transfer member and changing the transfer bias in accordance with the detected value. 8A and transfer control plate 14
Therefore, optimal transfer current control (transfer bias control) can be performed according to the characteristics of the contact transfer member, and sequential control of the transfer bias can be performed. In particular, by detecting the amount of bias applied change in the resistance of the contact transfer member, it is possible to grasp how much the contact transfer member is an ion conductive system or a carbon dispersed system,
According to the second embodiment, it is possible to more accurately control the transfer bias. According to the second embodiment, the amount of change in the bias applied to the resistance of the contact transfer member 6 is detected, and the transfer bias is set to at least the environment and (/ Or) since the control plate 8A and the transfer control plate 14 are provided as transfer bias variable means that varies with time, optimal transfer current control (transfer bias control) can be performed according to the characteristics of the material of the contact transfer member. . In particular, when a contact transfer member made of an ion conductive material is used, the transfer bias control can be more accurately performed to stabilize the transfer bias control in the environment. H / H makes it possible to stabilize the sheet conveyance. In addition, when a contact transfer member made of a carbon dispersion material is used, the transfer bias control can be more accurately performed to stabilize the transfer bias control over time, and the resistance of the contact transfer member over time can be improved. Can be accommodated.

Next, a third embodiment of the present invention will be described. The third embodiment is an embodiment of the invention according to claims 1 and 2, and is an example of an image forming apparatus having a contact transfer device according to an embodiment of the inventions according to claims 5 and 6. This third
In this embodiment, in the above-described first embodiment, the transfer bias is controlled over the environment and over time by detecting the bias application change amount ΔIv of the resistance of the contact transfer member and the time change amount ΔIt of the resistance of the contact transfer member.

FIGS. 18 to 21 show the relationship between the time T of the transfer belt of each material system, the environment, and the transfer current. Data relating to this relationship is stored in the ROM 24. The material system of the rubber resistance constituting the transfer belt 6 is divided into four cases. (1) Ion conductive system when ΔIv <0.5 and ΔIt <0.5 (2) When IIV <0.5 and ΔItT ≧ 0.5 Is a hybrid system (3) ΔIv ≧ 0.5, ΔItT <0.5 is a hybrid system (4) ΔIv ≧ 0.5 ΔIt ≧ 0.5 is a carbon dispersion system.

FIG. 22 shows a transfer belt 6 according to the third embodiment.
5 shows the flow from the detection of the amount of change in the bias applied to the resistor and the change in the resistance of the transfer belt 6 with time to the transfer current control. The control plate 8A causes the transfer control plate 14 to sequentially set the output voltage (transfer bias) of the high-voltage power supply 12 to 100, 500, 1 KV, and 2 KV, and to detect the current flowing through the transfer belt 6 when each transfer bias is applied. After these currents are converted into the resistance of the transfer belt 6, a change rate ΔIv as a bias application change amount of the resistance of the transfer belt 6 is calculated from these resistances.

Further, the control plate 8A applies a transfer bias of 2 kV to the transfer belt 6 from the high-voltage power supply 12 via the transfer control plate 14 for a fixed time of 30 sec, 60 sec, and 90 sec, respectively. After the current flowing through the transfer belt 6 after the application is detected and these currents are converted into the resistance of the transfer belt 6, a change rate ΔI as a time change amount of the resistance of the transfer belt 6 is obtained from these resistances.
Calculate t.

Next, the control plate 8A determines the rate of change ΔIv,
The transfer belt 6 recognizes the type of the material of the transfer belt 6 based on the difference of ΔIt, that is, recognizes whether the material of the transfer belt 6 is an ion conductive type, a carbon dispersed type, or a hybrid type. The transfer current Iout is varied for each material system. That is, the control plate 8A
It is determined whether Iv is 0.5 or more and whether ΔIt is 0.5 or more.

In the case of ΔIv <0.5 and ΔIt <0.5, the control plate 8A determines that the material of the transfer belt 6 is an ion conductive system, and the input signal from the temperature / humidity detecting means 21 and the time counting by the timing means are performed. By referring to data in the ROM 24 as shown in FIG. 21 according to the operation time of the apparatus (the use time of the transfer belt 6), the transfer current to the transfer control plate 14 is changed to the environment (temperature and humidity) and the operation time of the apparatus (operation time). (The use time of the transfer belt 6).

Further, the control plate 8A has ΔIv <0.5, ΔIt
If ≧ 0.5, it is determined that the material of the transfer belt 6 is a hybrid system, and based on the input signal from the temperature / humidity detecting means 21 and the operation time of the apparatus (time of use of the transfer belt 6) measured by the time measuring means. ROM 24 as shown in FIG.
The transfer current is changed to the transfer control plate 14 according to the environment (temperature and humidity) and the operation time of the apparatus (use time of the transfer belt 6) with reference to the data in the above.

Further, the control plate 8A is provided with: ΔIv ≧ 0.5, ΔIt
In the case of <0.5, it is determined that the material of the transfer belt 6 is a hybrid system, and based on the input signal from the temperature / humidity detecting means 21 and the operation time of the apparatus (time of use of the transfer belt 6) measured by the time measuring means. ROM 24 as shown in FIG.
The transfer current is changed to the transfer control plate 14 according to the environment (temperature and humidity) and the operation time of the apparatus (use time of the transfer belt 6) with reference to the data in the above.

Further, the control plate 8A is provided with: ΔIv ≧ 0.5, ΔIv ≧ 0.5
If t ≧ 0.5, it is determined that the material of the transfer belt 6 is a carbon dispersion system, and the input signal from the temperature and humidity detecting means 21 and the operation time of the apparatus measured by the time measuring means (the time during which the transfer belt 6 is used) ), The ROM 24 as shown in FIG.
The transfer current is changed to the transfer control plate 14 according to the environment (temperature and humidity) and the operation time of the apparatus (use time of the transfer belt 6) with reference to the data in the above.

According to the third embodiment, the amount of change in the bias of the resistance of the transfer belt 6 as the contact transfer member and the amount of the time change in the resistance of the transfer belt 6 as the contact transfer member are detected and the detected values are obtained. The control plate 8A and the transfer control plate 14 as transfer bias varying means for varying the transfer bias according to the transfer bias can perform optimum transfer current control (transfer bias control) according to the characteristics of the contact transfer member. ,
The transfer bias can be sequentially controlled. In particular, by detecting the amount of bias applied change of the resistance of the contact transfer member and the amount of time change of the resistance of the contact transfer member, how much the contact transfer member is an ion conductive system, or whether it is a carbon dispersed system, It is possible to determine whether the system is a hybrid system, and it is possible to more accurately control the transfer bias.

Further, according to the third embodiment, the amount of change in the bias of the resistance of the contact transfer member 6 and the amount of the time change in the resistance of the transfer belt 6 as the contact transfer member are detected, and according to the detected value. Since the control plate 8A and the transfer control plate 14 are provided as transfer bias varying means for varying the transfer bias at least in the environment and / or over time, optimal transfer current control (transfer) is performed according to the characteristics of the material of the contact transfer member. Bias control). In particular, when a contact transfer member made of an ion conductive material is used, the transfer bias control can be more accurately performed to stabilize the transfer bias control in the environment. H
At / H, the sheet transportability can be stabilized. In addition, when a contact transfer member made of a carbon dispersion material is used, the transfer bias control can be more accurately performed to stabilize the transfer bias control over time, and the resistance of the contact transfer member over time can be improved. Can be accommodated.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment is an embodiment of the present invention. In the fourth embodiment, in the third embodiment,
The transfer bias is controlled over time in the environment by detecting the bias application change amount ΔIv of the resistance of the contact transfer member, the time change amount ΔIt of the contact transfer member resistance, and the resistance of the contact transfer member.

FIG. 23 to FIG. 26 show the relationship between the time T of the transfer belt of each material system, the environment, and the transfer current. Data relating to this relationship is stored in the ROM 24. The material system of the rubber resistor constituting the transfer belt 6 is divided into four cases as in the third embodiment. FIG. 27 shows the flow from the detection of the bias application change amount of the resistance of the transfer belt 6, the time change amount of the resistance of the transfer belt 6 and the resistance of the contact transfer member to the transfer current control in the fourth embodiment.

The control plate 8A sequentially applies the output voltage (transfer bias) of the high voltage power supply 12 to the transfer control plate 14 by 100,5.
00, 1 KV, the current flowing through the transfer belt 6 when each transfer bias is applied is detected, and these currents are converted into the resistance of the transfer belt 6. Rate of change ΔIv as
Is calculated.

The control plate 8A applies a transfer bias of 1 kV to the transfer belt 6 from the high-voltage power supply 12 via the transfer control plate 14 for a fixed time of 30 sec, 60 sec and 90 sec, respectively. After the current flowing through the transfer belt 6 after the application is detected and these currents are converted into the resistance of the transfer belt 6, a change rate ΔI as a time change amount of the resistance of the transfer belt 6 is obtained from these resistances.
Calculate t. Further, the control plate 8A is a transfer control plate 1
A transfer bias of 2 kV is applied to the transfer belt 6 from the high-voltage power supply 12 via 4, a current flowing through the transfer belt 6 is detected, and this current is converted into a resistance R of the entire transfer belt 6.

Next, the control plate 8A determines whether or not the resistance R of the entire transfer belt 6 is smaller than 10 ¹⁰ Ω. If the resistance R of the entire transfer belt 6 is smaller than 10 ¹⁰ Ω, then the control board 8A shown in FIG. Move to the processing of. If the resistance R of the entire transfer belt 6 is equal to or greater than 10 ¹⁰ Ω, the control plate 8A recognizes the material of the transfer belt 6 based on the difference in the change rates ΔIv and ΔIt. It recognizes whether the material is an ion conductive system, a carbon dispersed system, or a hybrid system, and makes the transfer control plate 14 vary the transfer current Iout for each material system. That is, the control plate 8A
Determines whether ΔIv is greater than or equal to 0.5 and whether ΔIt is greater than or equal to 0.5.

When ΔIv <0.5 and ΔIt <0.5, the control plate 8A determines that the material of the transfer belt 6 is an ion conductive system, and inputs the signal from the temperature / humidity detecting means 21 and measures the time by the time measuring means. Referring to the data in the ROM 24 as shown in FIG. 26, the transfer current is transferred to the transfer control plate 14 based on the operation time of the apparatus (use time of the transfer belt 6) and the environment (temperature and humidity) and the operation time of the apparatus (operation time). (The use time of the transfer belt 6).

Further, the control plate 8A has ΔIv <0.5, ΔIt
If ≧ 0.5, it is determined that the material of the transfer belt 6 is a hybrid system, and based on the input signal from the temperature / humidity detecting means 21 and the operation time of the apparatus (time of use of the transfer belt 6) measured by the time measuring means. ROM 24 as shown in FIG.
The transfer current is changed to the transfer control plate 14 according to the environment (temperature and humidity) and the operation time of the apparatus (use time of the transfer belt 6) with reference to the data in the above.

Further, the control plate 8A is provided with: ΔIv ≧ 0.5, ΔIt
In the case of <0.5, it is determined that the material of the transfer belt 6 is a hybrid system, and based on the input signal from the temperature / humidity detecting means 21 and the operation time of the apparatus (time of use of the transfer belt 6) measured by the time measuring means. ROM 24 as shown in FIG.
The transfer current is changed to the transfer control plate 14 according to the environment (temperature and humidity) and the operation time of the apparatus (use time of the transfer belt 6) with reference to the data in the above.

Further, the control plate 8A is provided with: ΔIv ≧ 0.5, ΔIv ≧ 0.5
If t ≧ 0.5, it is determined that the material of the transfer belt 6 is a carbon dispersion system, and the input signal from the temperature and humidity detecting means 21 and the operation time of the apparatus measured by the time measuring means (the use time of the transfer belt 6) ), The ROM 24 as shown in FIG.
With reference to the data in the above, the transfer current is changed to the transfer control plate 14 according to the environment (temperature and humidity) and the operation time of the apparatus (use time of the transfer belt 6).

According to the fourth embodiment, the amount of change in the bias of the resistance of the transfer belt 6 as the contact transfer member, the amount of change in the resistance of the contact transfer member 6 with time, and the resistance of the entire contact transfer member 6 are detected. Since the control plate 8A and the transfer control plate 14 are provided as transfer bias varying means for varying the transfer bias in accordance with the detected value, not only the same effects as in the first to third embodiments can be obtained, but also By detecting the resistance of the entire contact transfer member, stable and precise transfer bias control can be performed irrespective of time and environment.

Next, other embodiments of the present invention will be described. These embodiments are embodiments of the invention according to claim 3. In these embodiments, the first to fourth embodiments are described.
In the embodiments, the correction amount of the transfer bias is varied. The correction of the transfer bias refers to the correction of the transfer bias (change of the transfer current) in the above-described first to fourth embodiments, and further varies the correction amount of the transfer bias as described below.

That is, when the width of the transfer sheet S becomes small, the control plate 8A corrects the transfer bias to obtain an optimum transfer current by a signal from a sensor for detecting the width of the transfer sheet S. The amount is increased (corrected) according to the width of the transfer sheet S. Here, the control plate 8A may be configured to vary the correction amount with the environment and with time. When forming an image on the back surface of the transfer sheet S and correcting the transfer current at that time, the control plate 8A uses the transfer bias to correct the transfer current when forming the image on the back surface of the transfer sheet S. The correction may be performed by changing the correction amount. Further, the control plate 8A corrects the transfer current when forming an image on the back surface of the transfer sheet S by changing the correction amount of the transfer bias, and outputs a signal from a sensor that detects the width of the transfer sheet S. Accordingly, the correction amount of the transfer bias may be corrected according to the width of the transfer sheet S.

In these embodiments, in the first to fourth embodiments, the control plate 8A and the transfer control plate 14 as the transfer bias variable means change the correction amount of the transfer bias, so that only the transfer current is used. In addition, by varying the correction amount, more stable transfer current control becomes possible.

Although the above embodiment uses a contact transfer device having a transfer belt as a contact transfer member, the present invention can be applied to a case where a contact transfer device having a contact transfer member such as a transfer roller is used. The above embodiment is an example in which differential transfer current control is performed as transfer current control.
The present invention is also applicable to a case where simple constant current control or constant voltage control is performed as transfer current control. Further, the present invention is applicable even if the mechanical configuration and the transfer current control method are other than those in the above embodiment.

[0107]

As described above, according to the first aspect of the present invention, optimal transfer current control can be performed according to the characteristics of the contact transfer member, and transfer bias can be sequentially controlled. In particular, by detecting at least one of a bias application change amount of the resistance of the contact transfer member and a time change amount of the resistance of the contact transfer member, the degree of the ion transfer system of the contact transfer member or the carbon dispersion system It is possible to know whether there is, and more accurate control of the transfer bias becomes possible.

According to the second aspect of the present invention, optimal transfer current control can be performed according to the characteristics of the material of the contact transfer member. In particular, when a contact transfer member made of an ion conductive material is used, the transfer bias control can be more accurately performed, and the transfer bias control in an environment can be stabilized. In addition, when a contact transfer member made of a carbon dispersion material is used, the transfer bias control can be more accurately performed to stabilize the transfer bias control over time, and the resistance of the contact transfer member over time can be improved. Can be accommodated.

According to the third aspect of the present invention, more stable transfer current control becomes possible. According to the fourth aspect of the present invention, not only the same effects as those of the image forming apparatus according to the first and second aspects, but also stable and precise transfer bias control can be performed regardless of time and environment.

According to the invention of claim 5, optimal transfer current control can be performed according to the characteristics of the contact transfer member, and successive control of the transfer bias can be performed. In particular, by detecting at least one of a bias application change amount of the resistance of the contact transfer member and a time change amount of the resistance of the contact transfer member, the degree of the ion transfer system of the contact transfer member or the carbon dispersion system It is possible to know whether there is, and more accurate control of the transfer bias becomes possible.

According to the invention of claim 6, optimal transfer current control can be performed according to the characteristics of the material of the contact transfer member. In particular, when a contact transfer member made of an ion conductive material is used, the transfer bias control can be more accurately performed, and the transfer bias control in an environment can be stabilized. In addition, when using a contact transfer member made of a carbon dispersion material, the transfer bias control can be performed more accurately, and the stability of the transfer bias control over time can be improved, and the resistance of the contact transfer member over time can be improved. Can be accommodated.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a state at the time of non-transfer of a part of a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state of a part of the first embodiment at the time of transfer.

FIG. 3 is a perspective view showing the first embodiment.

FIG. 4 is a schematic view showing a part of the first embodiment.

FIG. 5 is a sectional view showing a part of the transfer belt in the first embodiment.

FIG. 6 is a diagram for explaining the operation of the first embodiment.

FIG. 7 is a diagram showing a time change rate of the resistance of the transfer belt in the first embodiment.

FIG. 8 is a diagram showing a relationship between temperature and humidity, a resistance change amount of a transfer belt, and a transfer current in the first embodiment.

FIG. 9 is a block diagram showing a control system of the first embodiment.

FIG. 10 is a diagram showing the relationship between the amount of change in resistance of the transfer belt over time T and the transfer current in the first embodiment.

FIG. 11 is a diagram showing the relationship between the amount of change in resistance of the transfer belt over time T and the transfer current in the first embodiment.

FIG. 12 is a diagram showing the relationship between the amount of change in resistance of the transfer belt over time T and the transfer current in the first embodiment.

FIG. 13 is a diagram showing a resistance change rate of the transfer belt over time in the first embodiment.

FIG. 14 is a flowchart showing a flow from detection of the resistance of the transfer belt and detection of the amount of change in the resistance with time to transfer current control in the first embodiment.

FIG. 15 is a flowchart showing a flow for detecting the resistance of the transfer belt in the first embodiment.

FIG. 16 is a flowchart showing a part of a transfer current control flow in the first embodiment.

FIG. 17 is a flowchart illustrating a flow from detection of a bias application change amount of a resistance of a transfer belt to transfer current control according to a second embodiment of the present invention.

FIG. 18 is a diagram showing the relationship between the time T of the transfer belt of each material system, the environment, and the transfer current in the third embodiment of the present invention.

FIG. 19 is a diagram showing the relationship between the time T of the transfer belt of each material system, the environment, and the transfer current in the third embodiment.

FIG. 20 is a diagram showing the relationship between the time T, the environment, and the transfer current of the transfer belt of each material system in the third embodiment.

FIG. 21 is a diagram showing the relationship between the time T, the environment, and the transfer current of the transfer belt of each material system in the third embodiment.

FIG. 22 is a flowchart showing a flow from detection of a bias application change amount of the transfer belt resistance and a time change amount of the transfer belt resistance to transfer current control in the third embodiment.

FIG. 23 is a diagram showing the relationship between the time T, the environment, and the transfer current of the transfer belt of each material system in the fourth embodiment of the present invention.

FIG. 24 is a diagram showing the relationship between the time T, the environment, and the transfer current of the transfer belt of each material system in the fourth embodiment.

FIG. 25 is a diagram showing the relationship between the time T, the environment, and the transfer current of the transfer belt of each material system in the fourth embodiment.

FIG. 26 is a diagram showing the relationship between the time T, the environment, and the transfer current of the transfer belt of each material system in the fourth embodiment.

FIG. 27 is a flowchart showing the flow from the detection of the bias application change amount of the transfer belt resistance, the time change amount of the transfer belt resistance and the resistance of the entire contact transfer member to the transfer current control in the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transfer conveyance device 3 Photoconductor 6 Transfer belt 8A Control plate 11 Bias roller 12 High voltage power supply 14 Transfer control plate 21 Temperature and humidity detecting means

Claims (6)

[Claims] An image carrier for carrying a toner image; a contact transfer member for transferring the toner image on the image carrier to a sheet passing between the image carrier; and a transfer bias to the contact transfer member. And applying at least one of a bias application change amount of the resistance of the contact transfer member and a time change amount of the resistance of the contact transfer member, and according to the detected value. An image forming apparatus comprising: a transfer bias varying unit that varies the transfer bias. 2. An image carrier for carrying a toner image, a contact transfer member for transferring a toner image on the image carrier to a sheet passing between the image carrier, and a transfer bias to the contact transfer member. And applying at least one of a bias application change amount of the resistance of the contact transfer member and a time change amount of the resistance of the contact transfer member, and according to the detected value. An image forming apparatus comprising: a transfer bias varying unit that varies the transfer bias with at least the environment and / or the passage of time. 3. An image forming apparatus according to claim 1, wherein said transfer bias varying means varies a correction amount of said transfer bias. An image carrier for carrying the toner image; a contact transfer member for transferring the toner image on the image carrier to a sheet passing between the image carrier; and a transfer bias to the contact transfer member. And a bias applying means for applying a bias voltage, the amount of change in bias applied to the resistance of the contact transfer member, the amount of change in time of the resistance of the contact transfer member, and the resistance of the contact transfer member. An image forming apparatus comprising: a transfer bias varying unit that varies the transfer bias in accordance with the transfer bias. 5. A contact transfer device of an image forming apparatus having an image carrier for carrying a toner image and transferring the toner image on the image carrier to a sheet, wherein a sheet passing between the image carrier and the image carrier is provided. A contact transfer member for transferring a toner image on the image carrier, a bias applying unit for applying a transfer bias to the contact transfer member, a bias application change amount of a resistance of the contact transfer member, and a resistance of the contact transfer member. A transfer bias varying means for detecting at least one of the time variations of the transfer bias and varying the transfer bias in accordance with the detected value. 6. A contact transfer device of an image forming apparatus having an image carrier for carrying a toner image and transferring the toner image on the image carrier to a sheet, wherein a sheet passing between the image carrier and the image carrier is provided. A contact transfer member for transferring a toner image on the image carrier, a bias applying unit for applying a transfer bias to the contact transfer member, a bias application change amount of a resistance of the contact transfer member, and a resistance of the contact transfer member. And a transfer bias varying unit that varies at least one of the transfer bias with time and at least the environment and / or time according to the detected value.