JPH1138799A - Transfer-control device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly have a transfer control over a whole transfer control means, and to easily realize a high qualification of a transferred picture, without being affected by a resistance change of one circuit of an intermediate transfer belt or a resistance change of one circuit of a transfer roller or a backing-up roll. SOLUTION: This image-forming device, by which a visible image on an image carrier 1 is transferred on an intermediate transfer belt 2 for a while and afterwards collectively transcribed on a recording material 5, is equipped with a resistance-measuring means 6, by which a resistance information, including a resistance value of one circuit of the intermediate transfer belt 2 and at least a resistance value of one circuit of the roll having a larger resistance change between a transfer roller 3 and a backing-up roll 4 as a whole transcribing means, is measured, and also with a transfer-condition control means 7, by which a transfer conditions of the transfer roller 3 are changed within the period of one circuit of the intermediate transfer belt 2, based on the resistance information of this resistance-measuring means 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a laser printer, and other image forming apparatuses employing an electrophotographic system, an electrostatic recording system, or the like, and more particularly, to a charged color material formed on an image carrier. The present invention relates to a transfer control device of an image forming apparatus of a type in which a visible image formed by a toner or the like is once transferred to an intermediate transfer belt and then collectively transferred to a recording material.

[0002]

2. Description of the Related Art Conventionally, as an intermediate transfer type image forming apparatus of this type, each color component toner image formed on a photoreceptor or the like is primarily transferred sequentially to an intermediate transfer belt, and a multicolor toner image on the intermediate transfer belt is formed. A device in which a secondary transfer device (batch transfer device) is used to transfer a batch transfer to paper is known (Japanese Patent Publication No.
No. 120117). A batch transfer device used in this type of image forming apparatus includes, for example, a transfer roll that is disposed in pressure contact with the front side of the intermediate transfer belt via a sheet and that collectively transfers the multicolor toner image on the intermediate transfer belt to the sheet. A backup roll that is arranged in pressure contact with the back side of the intermediate transfer belt facing the transfer roll and forms a transfer nip area of a predetermined width with the transfer roll, and forms a transfer electric field between the transfer roll and the backup roll. By doing so, the multicolor toner image on the intermediate transfer belt is collectively transferred to the paper side.

In the conventional intermediate transfer type image forming apparatus, the resistance of the intermediate transfer belt, the transfer roll, and the backup roll changes with environmental fluctuations and aging. If the voltage applied to the transfer roll becomes inappropriate due to the change or the resistance change of the transfer roll and the backup roll, there is a possibility that image quality defects may occur. Specifically, if the applied voltage is too high, a discharge mark (image quality defect due to discharge occurring between the paper and the intermediate transfer belt and a toner image missing at that portion) or a retransfer phenomenon (an intermediate image from the paper side) When the applied voltage is too low, insufficient density occurs due to poor transfer. In order to solve such a technical problem, in the above-described prior art, a resistance measuring device of an intermediate transfer belt is provided near a batch transfer device, and a batch transfer device is provided based on resistance information from the resistance measurement device. A technique of controlling the transfer current value is disclosed.

[0004]

However, in this type of transfer control device of an image forming apparatus, although the resistance change of the intermediate transfer belt is measured, only the partial resistance measurement of the intermediate transfer belt is performed. Since the measurement error is large, it is difficult to realize accurate transfer control for the batch transfer apparatus, and it is difficult to completely prevent the image quality defect.
In particular, in the case of a type using a batch transfer device including a transfer roll and a backup roll, not only the intermediate transfer belt, but also the resistance value around the backup roll and the transfer roll easily fluctuates. Since the resistance value fluctuation is large, unless the resistance distribution of the intermediate transfer belt, the transfer roll, and the backup roll for one round is accurately grasped, the maximum and minimum resistance values as a whole that affect the batch transfer device The technical problem that a large difference is generated between them and that the transfer control for the batch transfer device is likely to be insufficient is very remarkable.

The present invention has been made to solve the above technical problems, and is not affected by a resistance change of one rotation of the intermediate transfer belt or a resistance change of one rotation of the transfer roll and the backup roll. Another object of the present invention is to provide a transfer control device of an image forming apparatus, which can accurately perform transfer control on a batch transfer unit and easily realize high quality of a transferred image.

[0006]

That is, as shown in FIG. 1, the present invention relates to one or a plurality of image carriers 1 on which a visible image is formed and supported by a charged color material, and on this image carrier 1 An intermediate transfer belt 2 on which the visible image is intermediately transferred and carried;
A transfer roll 3 which is pressed against the surface of the intermediate transfer belt 2 via a recording material 5 and collectively transfers the visible image on the intermediate transfer belt 2 to the recording material 5; In an image forming apparatus provided with a backup roll 4 which is arranged in pressure contact with the back side of the belt 2 and forms a transfer nip area of a predetermined width between itself and the transfer roll 3, a resistance value for one rotation of the intermediate transfer belt 2, and Transfer roll 3
And a resistance measuring means 6 for measuring resistance information including at least a resistance value of one round of the roll having a large resistance change among the backup rolls 4, and a transfer condition of the transfer roll 3 based on the resistance information of the resistance measuring means 6. And a transfer condition control means 7 for changing the length of the intermediate transfer belt 2 during one rotation.

In such technical means, an image forming method of an image forming apparatus to be covered by the present invention may be appropriately selected from an electrophotographic method, an electrostatic recording method, and the like.
In addition, one image carrier 1 may be used to form a visible image using a charged coloring material such as toner,
Alternatively, a plurality of image carriers 1 may be used. Further, if a transfer electric field can be formed between the transfer roll 3 and the backup roll 4, power may be supplied to any of the transfer roll 3 and the backup roll 4.
Further, the power supply method may be appropriately selected, but from the viewpoint of stably supplying the current to the transfer roll 3 or the backup roll 4 to be supplied with power,
It is preferable to use a power supply roll that uniformly contacts the outer peripheral surface of the transfer roll 3 or the backup roll 4 along the axial direction.

Further, the circumference of the intermediate transfer belt 2 may be appropriately selected in consideration of the synchronism with the image carrier 1, but it is easy to handle the resistance information from the resistance measuring means 6. Therefore, it is preferable that the circumferential length of the intermediate transfer belt 2 is an integral multiple of the circumferential length of at least the roll having a large resistance change among the transfer roll 3 and the backup roll 4. Here, in a case where the resistance change of one of the transfer roll 3 and the backup roll 4 is measured, the circumference of the intermediate transfer belt 2 can be adjusted to an integral multiple of the circumference of the one roll 3 or 4. However, in a mode in which the resistance change of both the transfer roll 3 and the backup roll 4 is measured, it is not necessary to adjust the circumference of the rolls 3 and 4 to an integer multiple.

The resistance measuring means 6 receives the resistance information including the resistance value of one rotation of the intermediate transfer belt 2 and the resistance information including the resistance value of at least one rotation of the transfer roll 3 and the backup roll 4 having a large resistance change. The required resistance information may be measured as a whole, or the required resistance information described above may be individually measured, or the required resistance information described above may be appropriately separated and measured. You may do so.

Further, the resistance measuring means 6 includes not only those capable of directly measuring resistance information but also those capable of indirectly measuring resistance information by measuring current or voltage. As such a resistance measuring means 6, for example, a constant voltage is applied to the transfer roll 3, measurement is performed with a return current, a constant current is applied to the transfer roll 3, measurement is performed with a return voltage, and special electric resistance value measuring means (for example, The resistance of the intermediate transfer belt 2 is measured. However, the measurement is also performed by measuring any one of the current and the voltage and indirectly measuring the resistance). The resistance measuring means 6 is normally arranged in contact with the member to be measured, but may be arranged in a non-contact manner as long as the resistance can be measured.

Further, the execution timing of the resistance value measuring cycle by the resistance measuring means 6 is appropriately selected according to the situation where the transfer condition control means 7 needs to control the transfer conditions. In addition, the operation start timing of the resistance measuring means 6 may be set as appropriate, but from the viewpoint of increasing the measurement accuracy by the resistance measuring means 6, a predetermined time has elapsed after the member to be measured has started operation. It is preferable to execute a measurement cycle of the resistance value when the stable state is reached. The “stable state” here means
Generally, the intermediate transfer belt 2 and the transfer roll 3 remain elastically deformed immediately after the start of the operation from the standby state.
It refers to a state in which this elastic deformation disappears. That is, the resistance value at the elastically deformed portion of the intermediate transfer belt 2 or the transfer roll 3 may become an abnormal value, and this indicates a state in which the occurrence of the abnormal value disappears.

In controlling the transfer condition of the transfer roll 3 for batch transfer, the transfer condition control means 7
The transfer output with respect to the total resistance value measured by the resistance measuring means 6 can be appropriately selected as long as the transfer output is calculated for one rotation of the intermediate transfer belt 2. Here, as a method of calculating the transfer output, for example, an optimum transfer output is applied to the average value, a minimum transfer output is applied to the minimum value,
Applying the maximum value of transfer that is optimal to the maximum value, applying the median value in an analog manner, and the like can be mentioned. Which one of these transfer output calculation methods is to be used may be appropriately selected depending on the environment, use conditions of the image forming apparatus, and the like.

Further, the transfer condition control means 7 controls the transfer condition of the transfer roll 3 for batch transfer, and the resistance change for one rotation of the intermediate transfer belt 2 changes the visible image on the image carrier 1. This also affects the primary transfer device 8 that is primary-transferred to the intermediate transfer belt 2, so that the transfer condition control means 7
It is preferable that the transfer condition of the primary transfer device 8 is also changed during one rotation of the intermediate transfer belt 2. In this embodiment, as the primary transfer device, a transfer roll, a transfer corotron and the like are intended,
In the type in which the primary transfer device 8 is provided with a transfer roll having a large resistance change, the resistance measuring means 6 preferably measures the resistance value of one round of the transfer roll constituting the primary transfer device 8. .

Further, the transfer condition control means 7 can be provided with additional functions as appropriate. For example, from the viewpoint of responding to an environmental change, the transfer condition of the transfer roll 3 is changed for one rotation of the intermediate transfer belt 2 based on the resistance information from the resistance measurement unit 6 and the environment information from the environment detection unit. Preferably, it is changed. From the viewpoint of checking the quality and life of each component, the transfer condition control unit 7 determines whether or not the resistance information from the resistance measuring unit 6 is abnormal, and determines the state of each component (component failure). It is preferable to perform the determination and the life determination.

Next, the operation of the above technical means will be described. In FIG. 1, a resistance measuring unit 6 measures the resistance value for one rotation of the intermediate transfer belt 2 and the resistance information including the resistance value of at least one rotation of the transfer roll 3 and the backup roll 4 having a large resistance change. .
Then, the transfer condition control unit 7 changes the transfer condition of the transfer roll 3 for one rotation of the intermediate transfer belt 2 based on the resistance information of the resistance measurement unit 6. For this reason, the visible image on the intermediate transfer belt 2 is in a state where variations in resistance values, environmental changes, and changes over time with respect to the entire area of the intermediate transfer belt 2 and the collective transfer device (transfer roll 3, backup roll 4) are accurately corrected. Then, the batch transfer device collectively transfers the recording material 5 to the recording material 5.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a schematic configuration of a color image forming apparatus to which the present invention is applied. In the same figure, reference numeral 11 denotes a photosensitive drum (latent image carrier), which has a charging device 12 and an exposure device (not shown in FIG. An electrostatic latent image corresponding to image information is formed by a known electrophotographic process such as that shown in FIG. Around the photosensitive drum 11, developing units 14 to 17 corresponding to black (Bk), yellow (Y), magenta (M), and cyan (C) are provided. The toner image T is formed by developing the electrostatic latent image formed on the developing unit 11 by one of the developing units 14 to 17.
Therefore, if the electrostatic latent image written on the photosensitive drum 11 corresponds to yellow image information, the electrostatic latent image is developed by the developing device 15 containing yellow (Y) toner, and A yellow toner image T is formed on the body drum 11.

Reference numeral 20 denotes an intermediate transfer belt arranged so as to be in contact with the surface of the photosensitive drum 11;
A plurality (in the present embodiment) of four rolls 21 to 24 are stretched and rotated in the direction of arrow B. Here, in the present embodiment, reference numeral 21 denotes the intermediate transfer belt 20.
Is a driven roll, 22 is a driven roll, 23 is a tension roll for controlling the tension of the intermediate transfer belt 20 to be constant, and 24 is an opposing roll (backup roll) for secondary transfer. Further, in the present embodiment, the intermediate transfer belt 20 is made of polyimide, polycarbonate,
Polyester, polypropylene, polyethylene terephthalate and other resins or various rubbers are formed to contain an appropriate amount of carbon black or the like so that the volume resistivity is 10 ⁶ to 10 ¹⁵ Ω · cm, and the thickness is set to, for example, 0.1 mm. Is done. Further, in the present embodiment, the intermediate transfer belt 2
The circumference of 0 is set to an integral multiple of the circumference of the backup roll 24.

The toner image T formed on the photosensitive drum 11 is transferred from the photosensitive drum 11 to the surface of the intermediate transfer belt 20 at a primary transfer position where the photosensitive drum 11 contacts the intermediate transfer belt 20. At this primary transfer position, a primary transfer device (transfer roll in the present embodiment) 18 is provided on the back side of the intermediate transfer belt 20, and a voltage having a polarity opposite to the polarity of the charged toner is applied to the transfer roll 18. By applying the voltage, the toner image T on the photosensitive drum 11 is electrostatically attracted to the intermediate transfer belt 20.

When a single-color image is formed, the toner image T primarily transferred to the intermediate transfer belt 20 is immediately transferred to a sheet 30.
When a color image is formed by superposing toner images of a plurality of colors, the photosensitive drum 1
The steps of forming the toner image on the surface 1 and primary transferring the toner image T are repeated for the number of colors. For example, when a full-color image is formed by superimposing four color toner images, black, black,
Yellow, magenta and cyan toner images T are formed,
These toner images T are sequentially primary-transferred onto the intermediate transfer belt 20. On the other hand, the intermediate transfer belt 20 rotates at the same cycle as the photosensitive drum 11 while holding the black toner image T that has been primarily transferred first, and the yellow, magenta and Cyan toner image T
Is transferred. Reference numeral 19 denotes a drum cleaner for removing residual toner on the photosensitive drum 11.

The toner image T primarily transferred to the intermediate transfer belt 20 in this manner is conveyed to a secondary transfer position facing the conveyance path of the paper 30 as the intermediate transfer belt 20 rotates. A secondary transfer device 40 is provided at the secondary transfer position. In the present embodiment, as shown in FIGS. 2 and 3, the secondary transfer device 40 is pressed against the toner image bearing surface of the intermediate transfer belt 20. Secondary transfer roll 25 and intermediate transfer belt 20
And a counter roll (backup roll) 24 which is disposed on the back side of the transfer roll 25 and forms a counter electrode of the transfer roll 25. In the present embodiment, the secondary transfer roll 25 is grounded, and a bias having the same polarity as the charged polarity of the toner is stably applied to the backup roll 24 via the power supply roll 26. In addition, the secondary transfer roll 2
5 is provided with a cleaning blade 28 made of, for example, urethane rubber.

In the present embodiment, the backup roll 24 uses a two-layer EPDM in which a foamed elastic material layer and an outer conductive layer are coated on the outer periphery of a metal core material. The outer conductive layer is a semiconductive EPDM (ethylene propylene diene rubber) foam rubber in which carbon black is dispersed at 15 to 35% by weight, and the thickness of the surface layer is 0.5 to 1.5.
mm. Surface resistivity is 10 ⁷ to 10 ¹⁰ Ω
/ □ is controlled in the resistance region. Also, the secondary transfer roll 2
Reference numeral 5 denotes a core layer made of a carbon black-dispersed foamed EPDM material fixed around the core bar and coated with a carbon black-dispersed fluororesin-based material having a thickness of 5 to 20 μm via a skin layer. the volume resistivity of the coating layer becomes 10 ⁴ [Omega] cm to 10 ⁶ [Omega] cm, roll hardness is 45 ° to 20 ° in Asker C hardness. In the present embodiment, the secondary transfer roll 25 is made up of the same components as the primary transfer roll 18.

At such a secondary transfer position, the following operation is performed. The paper 30 in the paper cassette 50 is
It is carried out by the feed roll 51 at a predetermined timing,
It is sequentially supplied to the secondary transfer device 40 via the transport roll 52. At this time, when the secondary transfer roll 25 nips the sheet 30 with respect to the backup roll 24, the secondary transfer roll 25 is carried on the intermediate transfer belt 20 by the action of a transfer electric field formed between the secondary transfer roll 25 and the backup roll 24. The transferred toner image T is electrostatically transferred to the sheet 30 at the secondary transfer position. At this time, since the secondary transfer roll 25 is driven to rotate with respect to the intermediate transfer belt 20, dirt attached to the secondary transfer roll 25 by the cleaning blade 28 is removed over the entire circumference of the transfer roll 25. The stain on the back surface of the paper 30 is effectively avoided.

The paper 30 on which the toner image T is transferred
Is a sheet 30 that has been separated from the intermediate transfer belt 20 and has been separated.
Is sent to the fixing device 54 by the transport belt 53, and the fixing process of the toner image is performed. On the other hand, the intermediate transfer belt 2
As shown in FIG. 2, a belt cleaner 41 is provided on the downstream side of the secondary transfer device 40 for removing the residual toner on the intermediate transfer belt 20 after the secondary transfer of the toner image is completed. It has become. The secondary transfer roll 25 and the belt cleaner 41 are disposed so as to be able to contact and separate from the intermediate transfer belt 20. When a color image is formed, the toner image before the final color is transferred to the secondary transfer roll 25, These members are separated from the intermediate transfer belt 20 until they pass through the belt cleaner 41.

Further, in the present embodiment, the resistance value of the same part of the intermediate transfer belt 20 and the backup roll 24 within one circumference varies widely, and the resistance value changes with the environment and with time. In addition, backup roll 2
4 has a tendency to increase with time, and conversely,
The resistance value of the intermediate transfer belt 20 tends to decrease with time. Further, both the primary transfer roll 18 and the secondary transfer roll 25 vary in resistance value within one circumference of the same component.
However, since the primary transfer roll 18 and the secondary transfer roll 25 have lower resistance values than the backup roll 24, there is little variation in resistance value within one circumference of the same component. Therefore, unless the resistance distribution of each of the intermediate transfer belt 20, the primary transfer roll 18, the secondary transfer roll 25, and the backup roll 24 is grasped, a large difference occurs between the maximum value and the minimum value of the resistance value as a whole. As a result, appropriate transfer control cannot be performed.

Therefore, in this embodiment, as shown in FIGS. 3 and 4, a transfer control system for controlling the transfer conditions of the primary transfer device 18 and the secondary transfer device 40 is provided. The transfer control system includes a first current detecting unit 131 for measuring a resistance value of the intermediate transfer belt 20 and one round of the primary transfer roll 18 in the primary transfer unit, and an intermediate transfer belt 20 in the secondary transfer unit. , A secondary transfer roll 25, and a second current detector 132 for measuring the resistance value of one round of the backup roll 24. In the present embodiment, the first current detection unit 131
The second current detector 132 measures a return current from the photoconductor drum 11 when a constant voltage is applied to the secondary transfer roller 8. This is to measure the return current when a constant voltage is applied via the roll 24).

The current information (corresponding to the resistance information) detected by each of the current detectors 131 and 132 is sequentially transmitted to the controller 14.
It is taken into 0. Here, the control unit 140 includes a CPU 141, a ROM 142, a RAM 143, as shown in FIG.
The transfer condition control program in the ROM 142 is executed in accordance with the execution timing (details will be described later) of the resistance value measurement cycle, and the current detection units 131 and 132 perform the measurement. With respect to the obtained resistance information, the information on the circumferential direction of the intermediate transfer belt 20 from a certain reference (for example, a predetermined belt mark location) is
The data is sequentially stored in the AM 143. Thereby, it is possible to always grasp the fluctuation of the resistance value and its value in the primary transfer section and the secondary transfer section within one round of the intermediate transfer belt 20.

"IBT belt + BUR + BTR" in FIG.
Shows an example of the resistance value fluctuation in the secondary transfer section,
This is the sum of resistance value fluctuations in the IBT belt (intermediate transfer belt 20), BUR (backup roll 24), and BTR (secondary transfer roll 25). In particular, in the present embodiment, the circumferential length of the intermediate transfer belt 20 is an integral multiple of the circumferential length of the backup roll 24. Therefore, unless the intermediate transfer belt 20 or the like is replaced, the periodic fluctuation of the resistance value does not change. It is always constant. Although the resistance change in the primary transfer unit is not shown in FIG. 5, the IBT belt (intermediate transfer belt 20), BTR (secondary transfer roll 2)
5: the same as the primary transfer roll 18).

Thereafter, the control unit 140 controls the primary transfer roll 1 against the total resistance measured in the primary transfer unit and the secondary transfer unit according to the transfer condition control program.
8. The transfer output of the secondary transfer roll 25 is calculated, and the primary transfer power supply 151, the secondary transfer power supply 1
52, each transfer bias is controlled. Here, as a method of calculating the transfer output, an optimum transfer output is applied to the average value,
One of four methods of applying the optimum minimum output of the transfer to the minimum value, applying the maximum value of the optimum transfer to the maximum value, and applying the median value in an analog manner is used.

When the transfer conditions of the primary transfer device 18 and the secondary transfer device 40 were controlled in such a transfer condition control process, the intermediate transfer belt 20, the backup roll 24,
It was confirmed that a high-quality transfer image was always obtained without being affected by the variation of the resistance value of one round of the transfer rolls (primary and secondary) 18 and 25, the environment of the resistance, and the variation over time.

When the primary transfer roll 18 and the secondary transfer roll 25 are made of the same material and have the same resistance value as in the present embodiment, the intermediate transfer belt 2 is used in the primary transfer section.
0 and the resistance value between the primary transfer roll 18 and the intermediate transfer belt 20 and the backup roll 2 at the secondary transfer portion.
It is possible to easily calculate the resistance value of the backup roll 24 by monitoring the resistance value of the secondary transfer roll 25 and the resistance value of the secondary transfer roll 25 and subtracting both. For this reason, in particular, when the secondary transfer condition is controlled, if the resistance value fluctuation of the backup roll 24 is also taken into consideration, the secondary transfer condition can be realized with higher accuracy.

Embodiment 2 FIG. 6 shows Embodiment 2 of a transfer control device of an image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the transfer control device according to the present embodiment is substantially the same as that of the first embodiment, but is different from the first embodiment.
A belt resistance measuring device 60 for measuring resistance with respect to 0 is added. Note that components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted here. In the figure, a belt resistance measuring device 60 is configured such that, for example, a pair of electrode rolls 61 sandwiches an intermediate transfer belt 20 located downstream of a secondary transfer unit, and applies a predetermined voltage between the pair of electrode rolls 61. The current detector 133 detects the current flowing through the intermediate transfer belt 20. Then, in the present embodiment, as shown in FIG.
The resistance information from 31 to 133 is taken in, and the intermediate transfer belt 20, the backup roll 24, and the transfer roll (primary,
After obtaining the respective resistance value fluctuations of (secondary) 18 and 25, each transfer bias of the primary transfer power supply 151 and the secondary transfer power supply 152 is controlled.

Therefore, according to the present embodiment, the current detectors 131 and 132 always keep track of the resistance fluctuations and the values thereof in the primary transfer unit and the secondary transfer unit within one round of the intermediate transfer belt 20. In addition to the above, it is possible to grasp the fluctuation of the resistance value and the value thereof for one rotation of the intermediate transfer belt 20 from the current detection unit 133. At this time, by subtracting the resistance change of the intermediate transfer belt 20 from the resistance change of the primary transfer section, the resistance change of the primary transfer roll 18 (secondary transfer roll 25) is obtained, and the resistance value of the secondary transfer section is determined. By subtracting the fluctuation in the resistance value of the intermediate transfer belt 20 and the fluctuation in the resistance value of the primary transfer roll 18 (secondary transfer roll 25) from the fluctuation, the fluctuation in the resistance value of the backup roll 24 is obtained. For this reason, it is possible to grasp the resistance value for one round for all the components of the intermediate transfer belt 20, the backup roll 24, the primary and secondary transfer rolls 18 and 25, and accordingly, the accuracy is higher than that of the first embodiment. Is controlled.

In particular, in the present embodiment, the circumferential length of the intermediate transfer belt 20 is set to an integral multiple of the circumferential length of the backup roll 24. Although it is always constant, even if the circumference of the intermediate transfer belt 20 is not an integral multiple of the circumference of the backup roll 24, the intermediate transfer belt 2
0, backup roll 24, primary and secondary transfer roll 1
Since the resistance value of one part of each of the components 8 and 25 is known, it is possible to always appropriately control the transfer conditions.

In this embodiment, the control unit 140
The above-mentioned resistance value measurement is performed periodically, the resistance value change of each part in the primary transfer part and the secondary transfer part is grasped over time, and when each part becomes a certain or more resistance value When an abnormal resistance value is detected in one round of each component, the life of each component or the occurrence of component failure is displayed on the life indicator 153 (see FIG. 4).

In the present embodiment, the execution timing of the resistance value measurement cycle is as follows: when power is turned on, when an environmental change is detected, when returning from the standby mode, when a certain time interval elapses, and when Transfer belt 20, transfer rolls (primary and secondary) 18, 25,
This is performed in each of the five cases when the backup roll 24 is replaced. In FIG. 6, reference numeral 70 denotes an environment sensor for detecting environmental information such as humidity and temperature.

Further, in the present embodiment, it is necessary to pay attention to the following points regarding the starting point of the execution timing of the resistance value measuring cycle. That is, the secondary transfer roll 25 and the intermediate transfer belt 20 usually remain elastically deformed immediately after the start of the operation from the standby state. More specifically, in the case of the secondary transfer roll 25, the deformation is caused by the biting of the cleaning blade 28, and the intermediate transfer belt 20 is deformed by the drive roll 21 and the idle rolls 22 to 24. Thereby, the resistance value at the deformed portion shows an abnormal value. However, this outlier should decrease over time. So, the result of the resistance measurement is
It is necessary to store these abnormal values in the RAM 143 after they have disappeared.

As described above, the abnormal value of the resistance value due to the elastic deformation of the intermediate transfer belt 20 and the secondary transfer roll 25 should disappear after a certain period of time (if the elastic deformation disappears). If the abnormal value of the resistance value is always detected, the control unit 140 determines that the intermediate transfer belt 20, the primary and secondary transfer rolls 18 and 25, and the backup roll 24 have defective parts and reach the life. Is determined, and the information is displayed on the life indicator 153.

Third Embodiment FIG. 7 shows a third embodiment of the transfer control device of the image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the transfer control device according to the present embodiment is substantially the same as that of the second embodiment, but is different from the second embodiment.
In addition to the belt resistance measuring device 60 for measuring the resistance to zero,
A roll resistance measuring device 63 for measuring the resistance to the primary transfer roll 18 and a roll resistance measuring device 66 for measuring the resistance to the secondary transfer roll 25 are further added. Note that components similar to those of the second embodiment are denoted by the same reference numerals as those of the second embodiment, and a detailed description thereof will be omitted.

In the same figure, the roll resistance measuring device 63
The primary transfer roll 18 is provided so as to be retractable from the intermediate transfer belt 20, and a predetermined voltage from, for example, the primary transfer power supply 151 is applied via the power supply roll 64 in a state where the primary transfer roll 18 is separated from the intermediate transfer belt 20. As a result, the current for one round of the primary transfer roll 18 is supplied to the current detecting unit 1
34, it is detected. Further, the roll resistance measuring device 66 applies a predetermined voltage from an arbitrary power supply 153 to the intermediate transfer belt 20 via the power supply roll 68 in a state where the secondary transfer roll 25 is retractable from the intermediate transfer belt 20. The current detection unit 132 detects the current for one round of the secondary transfer roll 25 by applying the current.

Therefore, according to the present embodiment, the belt resistance measuring device 60 measures the change in the resistance value for one rotation of the intermediate transfer belt 20 and the roll resistance measuring devices 63 and 66 measure the change in the resistance of each transfer roll 1.
Since the change in resistance value for one round of 8,25 can be directly taken in, even if the change in resistance value of each of the transfer rolls 18, 25 is significantly different, the change in resistance value for one round of each of the transfer rolls 18, 25 is more accurate. Therefore, the transfer condition can be more accurately controlled.

In the present embodiment, the change in the resistance value for one rotation of the backup roll 24 is determined by, for example, the secondary transfer roller 2 on the intermediate transfer belt 20 in the secondary transfer section.
5 is contacted and arranged, a predetermined voltage is applied to the backup roll 24 to determine the total resistance change of the intermediate transfer belt 20, the backup roll 24, and the secondary transfer roll 25. It is determined by subtracting the change in the resistance value of the transfer roll 25.

Incidentally, it is a matter of course that a dedicated roll resistance measuring device may be provided to measure a change in the resistance value for one round of the backup roll 24.

Fourth Embodiment FIG. 8 shows a fourth embodiment of a color image forming apparatus to which the present invention is applied. In the figure, the color image forming apparatus according to the present embodiment is different from the first to third embodiments in that, for example, a plurality of image forming units 100 (specifically, a plurality of image forming units 100 in which respective color component toner images are formed by an electrophotographic method). 100K, 100
Y, 100M, and 100C) are arranged in parallel, and the respective color component toner images formed by the respective image forming units 100 are primary-transferred sequentially to the intermediate transfer belt 110.
The secondary transfer of the respective color component toner images on the intermediate transfer belt 110 to the paper 117 supplied from the supply tray 116 is performed, and the toner image is guided to the fixing device 119 via the transport belt 118.

In this embodiment, the image forming unit 100 for each color component is a latent image carrier 101 such as a photosensitive drum.
Charger 1 around which the latent image carrier 101 is charged
02, a laser exposure device 103 for writing an electrostatic latent image on the latent image carrier 101, and a developing device 104 for containing each color component toner and visualizing the electrostatic latent image on the latent image carrier 101 ,
An electrophotographic device such as a primary transfer roll 105 for transferring each color component toner image on the latent image carrier 101 to the intermediate transfer belt 110 and a cleaner 106 for removing residual toner and the like on the latent image carrier 101 are sequentially arranged. It was established. Reference numeral 111 denotes a belt cleaner that removes residual toner and the like on the intermediate transfer belt 110, 112 denotes a static eliminator that removes residual charges of the intermediate transfer belt 110, and 11
Reference numeral 4 denotes the intermediate transfer belt 1 facing the secondary transfer roll 113.
10, a backup roll pressed against the back side of 1
Reference numeral 15 denotes a power supply roll.

In particular, in the present embodiment, the intermediate transfer belt 110 in the primary transfer portion is substantially similar to the first embodiment.
And the resistance change of the primary transfer roll 105 is measured. In the secondary transfer unit, the resistance change of the intermediate transfer belt 110, the secondary transfer roll 113, and the backup roll 114 is measured, and based on these resistance change. Thus, the conditions for the transfer to the primary transfer roll 105 and the secondary transfer roll 113 are controlled. In addition, the primary transfer roll 1
In the example, one of the four primary transfer portions is selected and the change in the resistance value is measured because the same component is used in 05.

Therefore, in the present embodiment, the toner images on each latent image carrier 101 of each image forming unit 100 are sequentially transferred to the intermediate transfer belt 110 and then collectively transferred to a sheet. In such an image forming process, the transfer conditions of the primary transfer roll 105 and the secondary transfer roll 113 are determined in consideration of the resistance value change of the intermediate transfer belt 110, the primary transfer roll 105, the secondary transfer roll 113, and the backup roll 114. As a result, the intermediate transfer belt 110, the primary transfer roll 10
5. Secondary transfer roll 113, backup roll 114
It has been confirmed that a high-quality transfer image can always be obtained without being affected by the variation of the resistance value for one round, the environment of the resistance, and the variation over time. In the present embodiment, it goes without saying that the transfer control device used in the second and third embodiments may be employed.

[0047]

As described above, according to the present invention, the resistance distribution of one round of the intermediate transfer belt, one round of the transfer roll as a batch transfer device, and one round of the backup roll having a large resistance change is determined. Since the transfer conditions of the transfer roll are controlled over one rotation of the intermediate transfer belt based on the resistance distribution, the resistance value for the entire area of the intermediate transfer belt and the batch transfer device (transfer roll, backup roll) is controlled. It is possible to collectively transfer the visible image to the recording material under good transfer conditions at all times without being affected by the variation of the environment, environmental change, and aging.
As a result, it is possible to easily realize high quality of the transferred image.

Further, in the present invention, if the transfer conditions of the primary transfer device are controlled in consideration of the resistance change for one rotation of the intermediate transfer belt (if necessary, the resistance change of the primary transfer device), the intermediate transfer The transfer conditions of the primary transfer device can be optimized without being affected by variations in the resistance value of the entire belt (and the primary transfer device), environmental changes, and changes over time. Image quality can be improved.

Further, in the present invention, an intermediate transfer belt,
By monitoring the resistance change of the batch transfer device (transfer roll, backup roll) and, if necessary, the resistance change of the primary transfer device, it is possible to determine the abnormality of the resistance change of the component that is the resistance measurement target, It is possible to determine the defect and the life of each component (intermediate transfer belt, batch transfer device, and primary transfer device as necessary).

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a transfer control device of an image forming apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of Embodiment 1 of the image forming apparatus to which the present invention is applied.

FIG. 3 is an explanatory diagram illustrating a transfer control device used in the first embodiment.

FIG. 4 is an explanatory diagram illustrating a specific configuration example of a control unit illustrated in FIG. 3;

FIG. 5 is a graph showing resistance changes of an intermediate transfer belt, a transfer roll, and a backup roll according to the first embodiment, and a combined resistance change thereof.

FIG. 6 is an explanatory diagram illustrating a transfer control device used in a second embodiment.

FIG. 7 is an explanatory diagram illustrating a transfer control device used in a third embodiment.

FIG. 8 is an explanatory diagram showing Embodiment 4 of the image forming apparatus to which the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Intermediate transfer belt, 3 ... Transfer roll,
4 backup roll, 5 recording material, 6 resistance measuring means, 7 transfer condition control means, 8 primary transfer device

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Fumio Furusawa 2274 Hongo, Fuji Xerox Co., Ltd., Ebina City, Kanagawa Prefecture (72) Inventor Osamu Handa 2274 Hongo, Hongo Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Masao Okubo 2274 Hongo, Ebina City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd.

Claims (9)

[Claims] 1. An image carrier on which a visible image is formed and carried by a charged color material, an intermediate transfer belt on which a visible image on the image carrier is intermediately transferred and carried, and A transfer roll that is pressed against the front surface of the transfer belt via a recording material and transfers the visible image on the intermediate transfer belt to the recording material at once, and is pressed against the rear surface of the intermediate transfer belt that faces the transfer roll; And a backup roll that forms a transfer nip area with a predetermined width between the transfer roll and the transfer roll, wherein the resistance value of one rotation of the intermediate transfer belt, and at least a large change in resistance among the transfer roll and the backup roll A resistance measuring means for measuring resistance information including a resistance value for one rotation of the roll; and a transfer condition of the transfer roll for one rotation of the intermediate transfer belt based on the resistance information of the resistance measurement means. Transfer control device of the image forming apparatus is characterized in that a transfer condition control means for changing between. 2. The transfer control device for an image forming apparatus according to claim 1, wherein a peripheral length of the intermediate transfer belt is an integral multiple of a peripheral length of at least a roll having a large resistance change among the transfer roll and the backup roll. And a transfer control device of the image forming apparatus. 3. The transfer control device for an image forming apparatus according to claim 1, wherein the resistance measuring means includes a resistance value for one rotation of the intermediate transfer belt, and a resistance value of at least one rotation of a transfer roll and a backup roll having a large resistance change. A transfer control device for the image forming apparatus, wherein the resistance information including the resistance values of the above is measured as a whole. 4. The transfer control device for an image forming apparatus according to claim 1, wherein the resistance measuring means includes a resistance value for one rotation of the intermediate transfer belt, and a resistance value of at least one rotation of a transfer roll and a backup roll having a large resistance change. A transfer control device for an image forming apparatus, which individually measures resistance information including the resistance values of the above. 5. The transfer control device for an image forming apparatus according to claim 1, wherein the resistance measuring means measures the resistance value when a member to be measured for resistance reaches a stable state after a predetermined time has elapsed from the start of operation. A transfer control device for an image forming apparatus, which executes a cycle. 6. The transfer control device for an image forming apparatus according to claim 1, wherein the transfer condition control means determines a transfer condition of a primary transfer device for primary-transferring a visible image on the image carrier to an intermediate transfer belt. A transfer control device for an image forming apparatus, wherein the transfer control device changes the rotation for one rotation of the intermediate transfer belt. 7. A transfer control device for an image forming apparatus according to claim 6, wherein the primary transfer device includes a transfer roll having a large resistance change, wherein the resistance measuring means is provided around the transfer roll constituting the primary transfer device. A transfer control device for an image forming apparatus, wherein the transfer control device also measures a minute resistance value. 8. The transfer control device for an image forming apparatus according to claim 1, wherein the transfer condition control unit determines a transfer condition of the transfer roll based on resistance information from the resistance measurement unit and environment information from the environment detection unit. A transfer control device for an image forming apparatus, wherein the transfer control device changes the rotation for one rotation of the intermediate transfer belt. 9. The transfer control device for an image forming apparatus according to claim 1, wherein the transfer condition control means determines whether or not the resistance information from the resistance measurement means is abnormal, and also determines the state of each component. A transfer control device for an image forming apparatus.