JP3823578B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that employs an electrophotographic system, and more particularly to an improvement in an image forming apparatus that includes a contact transfer unit that transfers a toner image to a transfer material, and a charge removal unit that neutralizes the transferred transfer material.
[0002]
[Prior art]
An image forming apparatus employing an electrophotographic system generally includes a contact transfer unit that transfers a toner image formed on an image carrier onto a transfer material such as paper, and a charge removal unit that neutralizes the transfer material onto which the toner image is transferred. It has.
Of these, the contact transfer means is composed of a contact transfer roller that sandwiches a transfer material with an image carrier, and a toner image is transferred to the sandwiched transfer material by applying a predetermined transfer bias to the contact transfer roller. To do.
The neutralizing means is usually composed of a large number of needle-like electrodes arranged along the axial direction of the image carrier. By applying a predetermined static elimination voltage to the needle-like electrodes, the contact transfer means applies a transfer material to the transfer material. Remove the accumulated charge.
On the other hand, in this image forming apparatus, when the transfer material is peeled off from the image carrier, a peeling discharge may occur between the transfer material and the image carrier. When this peeling discharge occurs, the image carrier is originally charged. The charge having the opposite polarity to the remaining electric potential remains on the image carrier, and this portion cannot be charged to the original charged potential even after the charging process by the contact charging means, and is developed in some cases, and the transfer material A black line may occur from the position of the rear end to the position after one round of the image carrier (hereinafter referred to as peeling memory).
[0003]
Therefore, in the conventional image forming apparatus, in order to prevent this peeling memory as much as possible, a high voltage removal voltage is applied to the charge removal unit.
[0004]
However, when a high static elimination voltage is applied to the static elimination means, if the transfer material such as paper contains a lot of moisture, the resistance of the transfer material decreases, and the current flowing through the contact transfer means passes through the transfer material. This may flow into the charge eliminating unit, and a transfer current may not be supplied from the contact transfer unit to the transfer material, resulting in a transfer failure.
Therefore, in the conventional image forming apparatus, as in the image forming apparatus disclosed in JP-A-9-43996, a transfer material moisture content measuring means which is an independent device for measuring the moisture content of the transfer material is disposed. Based on the moisture content of the transfer material measured by the transfer material moisture content measuring means, the neutralization voltage applied to the static elimination means is controlled to prevent transfer failure with a transfer material having a high moisture content.
[0005]
[Problems to be solved by the invention]
By the way, according to the above-described conventional image forming apparatus, in order to prevent a transfer failure with a transfer material such as paper having a high water content, the transfer material water content measurement is an independent device for measuring the water content of the transfer material. Since the means were provided, there was a problem that the number of parts was large and the manufacturing cost was high.
[0006]
In view of the above-described circumstances, the first to fourth inventions of the present application have an object to provide an image forming apparatus that has a small number of parts, is inexpensive, and has high image quality.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the first invention of the present application is directed to an image carrier, a contact transfer unit that transfers a toner image formed on the surface of the image carrier to a transfer material, and a transfer bias applied to the contact transfer unit. An image forming apparatus comprising: a transfer bias applying unit to be applied; a neutralizing unit that neutralizes the transfer material onto which the toner image has been transferred; and a neutralizing voltage applying unit that applies a high voltage to the neutralizing unit. A neutralization current detection unit for detecting a neutralization current flowing in the unit; a current detection unit for detecting a current flowing between the image carrier and the contact transfer unit before transfer to the transfer material by the contact transfer unit; A static elimination voltage changing means for changing the static elimination voltage which is the high voltage, the static elimination voltage changing means, based on the current detected by the current detection means, the static elimination voltage and a threshold of the static elimination current And when the static elimination current detected by the static elimination current detection means that is the static elimination current of the static elimination means to which the set static elimination voltage is applied does not exceed the threshold value, the static elimination voltage is set to It is characterized in that it is made to increase above the set static elimination voltage.
The second invention of the present application provides an image carrier, contact transfer means for transferring a toner image formed on the surface of the image carrier to a transfer material, and transfer bias applying means for applying a transfer bias to the contact transfer means. An image forming apparatus comprising: a charge eliminating unit that performs charge removal on the transfer material onto which the toner image has been transferred; and a charge eliminating voltage applying unit that applies a high voltage to the charge removing unit. A neutralizing current detecting means for detecting; a current detecting means for detecting a current flowing between the image carrier and the contact transfer means before transfer to the transfer material by the contact transfer means; and a static elimination that is the high voltage. A static elimination voltage changing means for changing the voltage, and the static elimination voltage changing means, based on the current detected by the current detection means, a first static elimination voltage and a second higher than the first static elimination voltage. With static elimination voltage And setting a first threshold value of the static elimination current corresponding to the first static elimination voltage and a second threshold value of the static elimination current corresponding to the second static elimination voltage, If the static elimination current of the static elimination means to which the first static elimination voltage is applied and the static elimination current detected by the static elimination current detection means does not exceed the first threshold value, the first static elimination voltage is While changing to the second static elimination voltage, the static elimination current of the static elimination means to which the second static elimination voltage is applied and the static elimination current detected by the static elimination current detecting means is the second threshold value. In the case of exceeding the above, the second static elimination voltage is changed to the first static elimination voltage.
The third invention of the present application is an image carrier, contact transfer means for transferring a toner image formed on the surface of the image carrier to a transfer material, and transfer bias applying means for applying a transfer bias to the contact transfer means. An image forming apparatus comprising: a charge eliminating unit that performs charge removal on the transfer material onto which the toner image has been transferred; and a charge eliminating voltage applying unit that applies a high voltage to the charge removing unit. A neutralizing current detecting means for detecting; a current detecting means for detecting a current flowing between the image carrier and the contact transfer means before transfer to the transfer material by the contact transfer means; and a static elimination that is the high voltage. A static elimination voltage changing means for changing the voltage, and the static elimination voltage changing means, based on the current detected by the current detection means, a first static elimination voltage and a second higher than the first static elimination voltage. With static elimination voltage And setting a first threshold value of the static elimination current corresponding to the first static elimination voltage and a second threshold value of the static elimination current corresponding to the second static elimination voltage, In the case where a second static elimination voltage is applied to the static elimination means, the static elimination current detected by the static elimination current detection means when the leading edge of the transfer material reaches the static elimination means is the second current. When the threshold value is exceeded, the second static elimination voltage is changed to the first static elimination voltage, and the static elimination current detected by the static elimination current detecting means when the substantially central portion of the transfer material reaches the static elimination means. When the current does not exceed the first threshold value, the first static elimination voltage is changed to the second static elimination voltage when the rear end of the transfer material reaches the static elimination means. It is characterized by that.
The fourth invention of the present application is the image forming apparatus of the first invention of the present application, further comprising a transfer material storage tray change detection means for detecting whether or not the transfer material storage tray for storing the transfer material has been changed, The static elimination voltage changing means changes the high voltage to a predetermined static elimination voltage when the transfer material accommodation tray change detecting means detects that the transfer material accommodation tray has been changed. .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The image forming apparatus according to the present invention will be described in detail below.
[0009]
An image forming apparatus 1 according to a first embodiment of the present invention includes a photosensitive drum 2 as an image carrier, a contact transfer roller 3 as a contact transfer means, and a charge eliminating device, as shown in FIG. It comprises a large number of needle-like electrodes 4 which are means and control means 11 (FIG. 2) for controlling them.
[0010]
Among these, the control means 11 includes a transfer bias applying means 12 comprising a voltage output circuit, a current detection means 13 comprising a current detection circuit, and a CPU (center) as shown in FIG. The static elimination voltage changing means 14 comprising a processing device), the static elimination voltage applying means 15 comprising a static elimination voltage output circuit, and the static elimination current detecting means 16 comprising a static elimination current detection circuit.
[0011]
Among them, the transfer bias applying unit 12 applies a predetermined voltage VB0 to the contact transfer roller 3 before the transfer to the transfer material 8 by the contact transfer roller 3, and the transfer bias VT is set by the charge removal voltage changing unit 14. Thereafter, a transfer bias VT is applied to the contact transfer roller 3.
[0012]
In addition, the current detection unit 13 detects a current IB0 flowing between the contact transfer roller 3 to which the predetermined voltage VB0 is applied and the photosensitive drum 2, and sends the current IB0 to the neutralization voltage changing unit 14.
[0013]
Further, in the static elimination voltage changing means 14, based on the input current IB0, the transfer bias VT, the first static elimination voltage VD1, the second static elimination voltage VD2 (VD1 <VD2), and the first static elimination voltage VD1. Is set to the threshold value IDmax1 of the static elimination current corresponding to.
[0014]
Further, at this time, the first static elimination voltage VD1 and the second static elimination voltage VD2 are applied to the peeling memory as much as possible regardless of whether the transfer material 8 is a transfer material having a high water content or a transfer material having a low water content. The voltage is sufficiently high to prevent it, and is set to a potential sufficient to prevent transfer failure as much as possible when transferring to the transfer material 8 by the contact transfer roller 3. The threshold IDmax1 of the static elimination current indicates whether the transfer material 8 is a transfer material having a high water content or a low transfer material when the first static elimination voltage VD1 is applied to a large number of needle-like electrodes 4. This is a threshold value for judgment.
[0015]
The static elimination voltage application means 15 applies the first static elimination voltage VD1 or the second static elimination voltage VD2 set by the static elimination voltage changing means 14 to the many needle-like electrodes 4.
[0016]
Further, the static elimination current detecting means 16 detects the static elimination current ID flowing through the many needle-like electrodes 4 to which the first static elimination voltage VD1 is applied, and sends the current ID to the static elimination voltage changing means 14.
[0017]
Further, in the static elimination voltage changing means 14, when the static elimination current ID detected by the static elimination current detecting means 16 does not exceed the threshold value IDmax1, the static elimination voltage VD applied to the many needle electrodes 4 is used as the first static elimination voltage. The voltage is changed from VD1 to the second static elimination voltage VD2.
[0018]
Next, the processing procedure of the control means 11 of the image forming apparatus 1 according to the first embodiment will be described with reference to the flowchart of FIG.
[0019]
The control means 11 applies a predetermined voltage VB0 to the contact transfer roller 3 by the transfer bias applying means 12 before transfer to the transfer material 8 by the contact transfer roller 3 (step 101), and the contact transfer roller 3 and the photosensitive member. The current IB0 flowing between the drum 2 is detected by the current detection means 13 (step 102). Next, the static elimination voltage changing unit 14 determines the environment such as whether or not the environment in which the image forming apparatus 1 is installed is hot and humid based on the predetermined voltage VB0 and the detected current IB0. Based on the determined environment, the transfer voltage VT, the first static elimination voltage VD1, the second static elimination voltage VD2 (VD1 <VD2), and the static elimination current threshold IDmax1 corresponding to the first static elimination voltage VD1 are set. (Step 103).
[0020]
Next, the control means 11 applies the first static elimination voltage VD1 to the multiple needle-like electrodes 4 by the static elimination voltage application means 15 (step 104), and the static elimination current ID flowing through the multiple needle-like electrodes 4 is detected as the static elimination current. Detection is performed by means 16 (step 105). Then, whether or not the detected static elimination current ID exceeds the threshold IDmax1 of the static elimination current is judged by the static elimination voltage changing means 14 (step 106). The first transfer voltage VD1 is maintained by determining that the transfer material is high.
[0021]
The first static elimination voltage VD1 has a potential sufficient to prevent a transfer failure as much as possible when transferring to the transfer material 8 by the contact transfer roller 3, and prevents the peeling memory as much as possible. If the transfer material 8 is determined to be a transfer material having a high water content, if the first static elimination voltage VD1 is maintained in this way, the transfer material after the transfer material 8 is determined. When transfer is performed, the risk of transfer failure is prevented as much as possible, and the possibility of peeling memory is prevented as much as possible.
[0022]
On the other hand, if it is determined in step 106 that the detected static elimination current ID does not exceed the threshold IDmax1 of the static elimination current, the static elimination voltage changing means 14 determines that the transfer material 8 is a transfer material having a low moisture content. When the transfer material 8 after the transfer material 8 to be transferred next to the transfer material 8 is subjected to charge removal, the charge removal voltage VD is changed from the first charge removal voltage VD1 to the second charge removal voltage VD2.
[0023]
As described above, when the charge removal voltage VD is increased from the first charge removal voltage VD1 to the second charge removal voltage VD2, the transfer material after the transfer material to be transferred next to the transfer material 8 is a transfer material having a low water content. In some cases, it is possible to further prevent the possibility that a peeled memory is generated.
When the static elimination voltage VD is increased from the first static elimination voltage VD1 to the second static elimination voltage VD2 in this way, the transfer to a transfer material having a low water content is prevented from causing a transfer failure as much as possible. It goes without saying that it is done.
Even when the transfer material to be transferred after this transfer material 8 has a high water content, the second static elimination voltage VD2 is transferred to the transfer material 8 by the contact transfer roller 3 as described above. Since the voltage is sufficient to prevent transfer defects as much as possible, the possibility of transfer defects being prevented as much as possible.
[0024]
As described above, in the image forming apparatus 1 according to the first embodiment, the static elimination current detection unit 16 that detects the static elimination current ID that flows through the many needle-like electrodes 4, and the static elimination current ID detected by the static elimination current detection unit 16. Therefore, the transfer material moisture content measuring means, which is an independent device for measuring the moisture content of the transfer material 8 as in the prior art, is provided. Without being provided, it is possible to prevent transfer defects on the transfer material 8 such as paper having a high water content as much as possible.
[0025]
Accordingly, in the image forming apparatus 1 of the first embodiment, the number of parts can be reduced and the manufacturing cost can be reduced by the amount of the transfer material moisture content measuring means not provided.
[0026]
Further, in the image forming apparatus 1 according to the first embodiment, the transfer current leaking through the transfer material 8 is directly detected and the transfer condition / discharge condition is set. The transfer current leaking through the transfer material is predicted from the relationship between the moisture content measured by the rate measuring means and the resistance of the transfer material, and the moisture content of the transfer material 8 is set compared to indirectly setting the transfer condition / static discharge condition. It is possible to respond quickly to the state, and thereby improve the image quality.
[0027]
Further, in the image forming apparatus 1 of the first embodiment, the current detection for detecting the current IB0 flowing between the photosensitive drum 2 and the contact transfer roller 3 before the transfer to the transfer material 8 by the contact transfer roller 3 is further performed. The neutralization voltage changing unit 14 includes a unit 13 and sets the transfer bias VT, the first neutralization voltage VD1, and the threshold IDmax1 of the neutralization current based on the current IB0 detected by the current detection unit 13. At the same time, when the static elimination current ID of a large number of needle-like electrodes 4 to which the set first static elimination voltage VD1 is applied does not exceed the threshold IDmax1, the static elimination voltage VD is set higher than the first static elimination voltage VD1. Therefore, when the transfer material 8 to be determined is a transfer material having a low water content, there is a further possibility that a peeling memory may occur in the transfer material subsequent to the transfer material 8 after the transfer material 8. In It is possible to stop.
[0028]
Further, when the static elimination voltage VD is increased from the first static elimination voltage VD1, the static elimination voltage VD is sufficiently high to prevent the peeling memory as much as possible, like the second static elimination voltage VD2. In addition, when transferring to the transfer material 8 by the contact transfer roller 3, if the potential is set to a potential sufficient to prevent transfer failure as much as possible, transfer after the transfer material transferred next to the transfer material 8 is performed. Even when the material has a high water content, it is possible to prevent as much as possible the possibility of transfer failure during transfer to the transfer material.
[0029]
Further, in the image forming apparatus 1 according to the first embodiment, when it is determined that the transfer material 8 is a transfer material having a low water content, the charge-removing voltage of the transfer material subsequent to the transfer material 8 is determined. Although VD is increased, the present invention is not limited to this. For the transfer material 8 to be determined, the static elimination voltage VD may be changed based on the determination result.
[0030]
In the image forming apparatus 1 according to the first embodiment, after the static elimination voltage VD is changed from the first static elimination voltage VD1 to the second static elimination voltage VD2, the static elimination voltage VD is maintained at the second static elimination voltage VD2. However, the image forming apparatus of the present invention is not limited to this. For example, the static elimination voltage VD is changed from the first static elimination voltage to the second static elimination voltage VD2, and then the first static elimination voltage VD1. It may be something that can be changed to.
[0031]
Next, the image forming apparatus according to the second embodiment will be described with respect to an image forming apparatus capable of changing the static elimination voltage VD from the first static elimination voltage VD1 to the second static elimination voltage VD2 and then further to the first static elimination voltage VD1. The image forming apparatus 31 according to the third embodiment and the image forming apparatus 41 according to the fourth embodiment will be described.
[0032]
In the image forming apparatus 21 of the second embodiment, the control means 11 of the image forming apparatus 1 of the first embodiment is configured in the control means 28 as shown in FIG. Instead of the static elimination voltage changing means 14, the static elimination voltage changing means 24 is provided, and the transfer material position detecting means 27 is provided.
[0033]
Among these, the transfer material position detecting means 27 detects the tip 8 a (FIG. 1) of the transfer material 8 passing through the needle electrode 4, and sends the detection result to the static elimination voltage changing means 14.
[0034]
The static elimination current detection means 16 detects the static elimination current ID when the transfer material position detection means 27 detects that the tip 8a of the transfer material 8 has passed through the needle electrode 4.
[0035]
Further, the static elimination voltage changing means 24 is based on the current IB0 detected by the current detection means 13, and the transfer bias VT, the first static elimination voltage VD1, and the second static elimination voltage larger than the first static elimination voltage VD1. VD2 is set, and a first threshold value IDmax1 of the static elimination current corresponding to the first static elimination voltage VD1 and a second threshold value IDmax2 of the static elimination current corresponding to the second static elimination voltage VD2 are set. To do.
[0036]
At this time, the first threshold value IDmax1 of the static elimination current is a value corresponding to the threshold IDmax1 of the static elimination current of the image forming apparatus 1 of the first embodiment, and the first threshold value IDmax1. IDmax1, transfer bias VT, first charge removal voltage VD1, and second charge removal voltage VD2 are set in the same manner as in image forming apparatus 1 of the first embodiment.
[0037]
Further, the second threshold value IDmax2 of the static elimination current is that the transfer material 8 is a transfer material having a high moisture content or a low transfer material when the second static elimination voltage VD2 is applied to a large number of needle-like electrodes 4. It is a threshold value for judging whether or not there is.
[0038]
Further, in the static elimination voltage changing means 24, when the static elimination current ID of the static elimination means to which the first static elimination voltage VD1 is applied does not exceed the first threshold value IDmax1, the first static elimination voltage VD1 is changed to the second static elimination voltage. When the static elimination current ID of the static elimination means to which the second static elimination voltage VD2 is applied exceeds the second threshold value IDmax2, the second static elimination voltage VD2 is changed to the first static elimination voltage VD1. Change to
[0039]
Next, the processing procedure of the control means 28 of the image forming apparatus 21 according to the second embodiment will be described with reference to the flowchart of FIG.
[0040]
The controller 28 applies a predetermined voltage VB0 to the contact transfer roller 3 by the transfer bias applying unit 12 before the transfer to the transfer material 8 by the contact transfer roller 3 (step 201). The current IB0 flowing between the body drum 2 is detected by the current detection means 13 (step 202). Next, the static elimination voltage changing unit 24 determines whether or not the environment in which the image forming apparatus is installed is high-temperature and high-humidity based on the predetermined voltage VB0 and the detected current IB0. Based on this, the transfer voltage VT, the first charge removal voltage VD1, the second charge removal voltage VD2 (VD1 <VD2), the charge removal current first threshold IDmax1, and the charge removal current second threshold IDmax2 are set. (Step 203).
[0041]
Next, the control means 28 applies the first static elimination voltage VD1 to the multiple needle-like electrodes 4 by the static elimination voltage application means 15 (step 204), and the transfer material position detection means 27 applies the leading end 8a of the transfer material 8. Is detected by the static elimination current detecting means 16 when the static elimination current ID flowing through the multiple needle-like electrodes 4 is detected.
(Step 205). Next, it is determined by the neutralization voltage changing means 24 whether or not the neutralization voltage VD applied to the many needle-like electrodes 4 is the first neutralization voltage VD1 (step 206), and the first neutralization voltage VD1. If it is determined that there is, the neutralization voltage changing means 24 determines whether or not the detected neutralization current ID exceeds the set neutralization current threshold IDmax1 (step 207). When it is determined that the static elimination current ID detected by the static elimination voltage changing unit 24 exceeds the threshold IDmax1 of the static elimination current, it is determined that the transfer material 8 is a transfer material having a high water content, and the first static elimination is performed. The voltage VD1 is maintained, and the charge removal voltage of the transfer material next to the transfer material 8 is set to the first charge removal voltage VD1 (step 208).
[0042]
As described above, when the transfer material 8 is determined to be a transfer material having a high water content, if the first static elimination voltage VD1 is maintained, the transfer material 8 and the transfer material next to the transfer material 8 are transferred. At this time, it is needless to say that the possibility of occurrence of transfer failure is prevented as much as possible, and the possibility of occurrence of peeled memory is prevented as much as possible.
[0043]
Further, after step 208, the control means 27 determines whether or not there is a transfer material 8 to be transferred next by a detection means (not shown) (step 209). On the other hand, if it is determined that there is a transfer material 8 to be transferred next, the processes in and after step 205 are repeated.
[0044]
On the other hand, if it is determined in step 207 that the detected static elimination current ID does not exceed the threshold IDmax1 of the static elimination current, the static elimination voltage changing unit 14 determines that the transfer material 8 is a transfer material having a low moisture content. When the transfer material to be transferred next to the transfer material 8 is subjected to charge removal, the charge removal voltage VD is changed from the first charge removal voltage VD1 to the second charge removal voltage VD2 (step 210).
[0045]
As described above, when the static elimination voltage VD is increased from the first static elimination voltage VD1 to the second static elimination voltage VD2, when the transfer material 8 next to the transfer material 8 is a transfer material having a low moisture content, Needless to say, it is possible to further prevent the possibility of the peeled memory from occurring.
[0046]
Further, after step 210, the control means 28 repeats the processing from step 209 onward.
[0047]
On the other hand, if it is determined in step 206 that the static elimination voltage VD applied to the many needle electrodes 4 is not the first static elimination voltage VD1, it is judged that the static elimination voltage VD is the second static elimination voltage VD2. Then, it is judged by the static elimination voltage changing means 24 whether or not the detected static elimination current ID does not exceed the second threshold IDmax2 of the static elimination current (step 211). When it is determined that the detected static elimination current ID does not exceed the second threshold IDmax2 of the static elimination current, it is determined that the transfer material 8 is a transfer material having a low water content, and the steps after step 210 are performed. Repeat the process.
[0048]
As described above, when it is determined that the transfer material 8 is a transfer material having a low water content, if the charge removal voltage VD is maintained at the second charge removal voltage VD2, the transfer material 8 and the transfer material next to the transfer material 8 are transferred. Therefore, it is possible to prevent as much as possible the possibility of the peeling memory.
[0049]
Needless to say, the transfer material 8 by the contact transfer roller 3 and transfer of the transfer material 8 to the next transfer material can be prevented as much as possible from occurrence of transfer failure.
[0050]
If it is determined in step 211 that the detected static elimination current ID exceeds the second threshold IDmax2 of the static elimination current, the static elimination voltage changing means 24 uses the transfer material 8 having a high water content. It is determined that there is, and the processing from step 208 is repeated.
[0051]
As described above, when it is determined that the transfer material 8 is a transfer material having a high water content, if the charge removal voltage VD is decreased from the second charge removal voltage VD2 to the first charge removal voltage VD1, the next transfer of the transfer material 8 is performed. When transferring to the material, it is possible to prevent the possibility of transfer failure as much as possible.
[0052]
Needless to say, the transfer material 8 and the transfer material next to the transfer material 8 can prevent as much as possible the occurrence of peeling memory.
[0053]
As described above, the image forming apparatus 21 according to the second embodiment includes the current detection unit 27 and the neutralization voltage changing unit 24, and the neutralization voltage changing unit 24 is applied with the first neutralization voltage VD 1. When the static elimination current ID of the needle electrode 4 does not exceed the first threshold value IDmax1, the static elimination voltage VD is increased from the first static elimination voltage VD1 to the second static elimination voltage VD2, and the second static elimination voltage When the static elimination current ID of the many needle-like electrodes 4 to which VD2 is applied exceeds the second threshold value IDmax2, the static elimination voltage VD is decreased from the second static elimination voltage VD2 to the first static elimination voltage VD1. Therefore, the moisture content is determined for each transfer material 8, and based on this determination, the static elimination voltage VD for the transfer material to be transferred next can be changed. Judgment is possible It is possible to prevent manner.
[0054]
Therefore, according to the second image forming apparatus 21, it is possible to further prevent the possibility of transfer failure and the occurrence of peeling memory when the toner image is transferred to the transfer material 8.
[0055]
In the image forming apparatus 21 of the second embodiment, when it is determined that the transfer material 8 is a transfer material having a low water content, the charge removal voltage of the transfer material 8 to be transferred next to the transfer material 8 is determined. Although the VD is changed, the present invention is not limited to this, and the charge removal voltage VD may be changed when the transfer material 8 to be determined is discharged.
[0056]
In the image forming apparatus 21 according to the second embodiment, the static elimination current ID is detected when it is detected that the tip 8a of the transfer material 8 has passed through the needle electrode 4. For example, it may be performed when it is detected that the substantially central portion 8 b of the transfer material 8 has passed through the needle electrode 4.
[0057]
Further, the static elimination current ID may be detected from the time when the front end 8a of the transfer material 8 passes through the needle electrode 4 until the time when the rear end 8c passes. At this time, based on the detection result. The static elimination voltage VD may be changed immediately.
[0058]
In this way, the static elimination voltage VD can be applied in accordance with the water content of each part of the transfer material 8, so that there is a further possibility that a transfer failure may occur during transfer of the toner image to the transfer material 8 and a peeling memory may occur. Can be prevented.
[0059]
At this time, if the thresholds IDmax1 and IDmax2 of the static elimination current are set taking into consideration that the distance between the needle-like electrode 4 and the transfer material 8 changes with time depending on the conveying posture of the transfer material 8, the transfer material Since the static elimination voltage VD applied to the needle-like electrode 4 can be changed in accordance with the time-dependent change in the transport posture of FIG. 8, there is a risk of transfer failure when transferring to the transfer material 8 by the contact transfer roller 3, and peeling. The possibility that a memory is generated can be further prevented as much as possible.
[0060]
In addition, the detection of the static elimination current ID takes into consideration that the distance between the needle-like electrode 4 and the transfer material 8 changes with time depending on the conveying posture of the transfer material 8, and the transfer material 8 is heated by the fixing means 5 (FIG. 1). It may be performed when it is pinched by a certain fixing roller or the like.
[0061]
Next, in consideration of the fact that the distance between the needle electrode and the transfer material changes depending on the posture of the transfer material, an image forming apparatus that detects the static elimination current ID when the transfer material is sandwiched between the heating and fixing means will be described. The image forming apparatus according to the third embodiment will be described.
[0062]
In the image forming apparatus 31 of the third embodiment, the control means of the image forming apparatus 21 of the second embodiment is added to the control means 38 as shown in FIG. Instead of the static elimination voltage changing means 24 and the transfer material position detecting means 27 which are configured, a static elimination voltage changing means 34 and a transfer material position detecting means 37 are provided.
[0063]
Among these, the transfer material position detecting means 37 detects when the leading end portion 8a, the substantially central portion 8b, and the rear end portion 8c of the transfer material 8 have passed through the needle electrode 4, and the detection result is indicated as a static elimination voltage. It is sent to the changing means 34.
[0064]
Further, when the transfer material position detection unit 37 detects that the front end portion 8a and the substantially central portion 8b of the transfer material 8 have passed through the needle electrode 4, the neutralization current detection unit 16 detects the neutralization current ID. .
[0065]
Based on the current IB0 detected by the current detection means 13, the static elimination voltage changing means 34 is based on the transfer bias VT, the first static elimination voltage VD1, and the second static elimination voltage VD2 that is greater than the first static elimination voltage VD1. Is set, and a first threshold value IDmax1 of the static elimination current corresponding to the first static elimination voltage VD1 and a second threshold value IDmax2 of the static elimination current corresponding to the second static elimination voltage VD2 are set.
[0066]
At this time, the transfer bias VT, the first static elimination voltage VD1, the second static elimination voltage VD2, the first threshold IDmax1 of the static elimination current, and the second threshold IDmax2 of the static elimination current are the second implementation. Settings are made in the same manner as the image forming apparatus 21 in the example.
[0067]
Further, when the transfer material position detecting unit 37 detects that the substantially central portion 8b of the transfer material 8 has passed through the needle-like electrode 4, the static elimination voltage changing unit 34 causes the tip 8a of the transfer material 8 to be heated and fixed. 5 is determined to be held by a fixing roller or the like.
[0068]
Further, the static elimination voltage changing means 34 is a case where the second static elimination voltage VD2 is applied to the needle electrode 4 and the static elimination current detection means when the tip 8a of the transfer material 8 reaches the needle electrode 4. When the static elimination current ID detected by 16 exceeds the second threshold IDmax2 of the static elimination current, the second static elimination voltage VD2 is changed to the first static elimination voltage VD1, and the substantially central portion 8b of the transfer material 8 is changed. When the static elimination current ID detected by the static elimination current detecting means 16 when the voltage reaches the needle electrode 4 does not exceed the first threshold IDmax1 of the static elimination current, the rear end 8c of the transfer material 8 is Is reached, the first static elimination voltage VD1 is changed to the second static elimination voltage VD2.
[0069]
Next, the processing procedure of the control means 38 of the image forming apparatus 31 of the third embodiment will be described with reference to the flowchart of FIG.
[0070]
The control means 38 applies a predetermined voltage VB0 to the contact transfer roller 3 by the transfer bias applying means 12 before the transfer to the transfer material 8 by the contact transfer roller 3 (step 301). The current IB0 flowing between the body drum 2 is detected by the current detection means 13 (step 302). Next, the static elimination voltage changing unit 34 determines whether or not the environment in which the image forming apparatus is installed is high-temperature and high-humidity based on the predetermined voltage VB0 and the detected current IB0. Based on this, the first threshold value IDmax1 and the second threshold value IDmax2 for the transfer voltage VT, the static elimination voltages VD1, VD2 (VD1 <VD2) static elimination current are set (step 303).
[0071]
Next, the control means 38 applies the first static elimination voltage VD1 to the multiple needle-like electrodes 4 by the static elimination voltage application means 15 (step 304), and the transfer material position detection means 37 causes the leading end 8a of the transfer material 8 to be applied. Is detected by the static elimination current detection means 16 (step 305). Next, whether or not the static elimination voltage VD applied to the many needle-like electrodes 4 is the first static elimination voltage VD1 is judged by the static elimination voltage changing means 34 (step 306), and the first static elimination voltage VD1. Is determined by the transfer material position detecting means 37 whether or not the substantially central portion 8b of the transfer material 8 has passed through the needle electrode 4. When it is detected that the substantially central portion 8 b of the transfer material 8 has passed through the needle-like electrode 4, the static elimination voltage changing means 34 is a fixing roller or the like in which the front end portion 8 a of the transfer material 8 is the heating and fixing means 5. Therefore, the static elimination current ID flowing through the many needle electrodes 4 is detected by the static elimination current detecting means 16 (step 307).
[0072]
Next, whether or not the detected static elimination current ID exceeds the set static elimination current threshold IDmax1 is judged by the static elimination voltage changing means 34 (step 308). It is determined that the transfer material has a high water content, and it is then determined whether or not there is a transfer material 8 to be transferred next (step 309). If it is determined that there is no transfer material 8 to be transferred next, the process is terminated. If it is determined that there is a transfer material 8 to be transferred next, the processes in and after step 305 are repeated.
[0073]
In step 308, when the static elimination voltage changing unit 34 determines that the detected static elimination current ID does not exceed the set static elimination current threshold IDmax 1, the transfer material 8 is a transfer material having a low moisture content. When the transfer material position detecting means 37 detects that the rear end 8c of the transfer material 8 has passed through the needle electrode 4 (step 310), the static elimination voltage VD is changed from the static elimination voltage VD1 to the static elimination voltage VD2. Then, the static elimination voltage VD2 is applied to the position corresponding to the rear end of the transfer material 8 (step 311), and the processing after step 309 is repeated.
[0074]
As described above, in the image forming apparatus according to the third embodiment, when the transfer material position detecting unit 37 detects that the substantially central portion 8b of the transfer material 8 has passed through the needle electrode 4, the transfer material 8 is heated. When it is sandwiched by a fixing roller or the like as the fixing means 5, the static elimination current ID is detected and a determination is made as to whether the moisture content of the transfer material is high or low. It is possible to prevent as much as possible the possibility of misjudgment about the level of the moisture content of the transfer material 8 by changing the distance to the transfer material 8.
[0075]
Therefore, at this time, if the static elimination voltage VD is increased from the first static elimination voltage VD1 to the second static elimination voltage VD2, it is possible to further prevent the possibility that a peeling memory is generated on the transfer material 8 as much as possible.
[0076]
Further, since the peeling memory is particularly likely to occur at the rear end portion 8c of the transfer material 8, the second charge removal voltage VD2 having a higher potential than the first charge removal voltage VD is applied to the position corresponding to the rear end of the transfer material 8 in this way. This is particularly effective.
[0077]
On the other hand, when it is determined in step 306 that the static elimination voltage VD applied to the many needle-like electrodes 4 is not the first static elimination voltage VD1, it is judged that the static elimination voltage VD is the second static elimination voltage VD2. Next, it is determined by the static elimination voltage changing means 24 whether or not the detected static elimination current ID does not exceed the second threshold IDmax2 of the static elimination current (step 312). If it is determined that the detected static elimination current ID does not exceed the second threshold IDmax2 of the static elimination current, it is determined that the transfer material 8 is a transfer material having a low moisture content, and the steps after step 309 are performed. Repeat the process.
[0078]
If it is determined in step 312 that the detected static elimination current ID exceeds the second threshold IDmax2 of the static elimination current, the static elimination voltage changing means 24 uses the transfer material 8 having a high water content. It is determined that there is, and the static elimination voltage VD is immediately changed from the second static elimination voltage VD2 to the first static elimination voltage VD1 (step 313), and the processing after step 307 is performed.
[0079]
If it is determined that the transfer material 8 has a high water content, the transfer voltage 8 is transferred from the second discharge voltage VD2 to the first discharge voltage VD1 immediately. Also during application, transfer defects can be further prevented as much as possible.
[0080]
The image forming apparatus according to the present invention may further include a transfer material accommodation tray change detecting means in addition to the configuration of the image forming apparatus 31 of the third embodiment.
[0081]
Next, an image forming apparatus according to the fourth embodiment will be described with respect to an image forming apparatus further comprising a transfer material accommodation tray changing means in addition to the configuration of the image forming apparatus according to the third embodiment.
[0082]
In the image forming apparatus 41 of the fourth embodiment, as shown in FIG. 8 where the same parts as those in FIG. 6 are denoted by the same reference numerals, the control means 38 of the image forming apparatus 31 of the third embodiment is configured as the control means 48. In addition to the neutralizing voltage changing means 34, the neutralizing voltage changing means 44 is provided, and the transfer material accommodation tray change detecting means 49 is further provided.
[0083]
This transfer material accommodation tray change detecting means 49 is arranged to determine whether or not the next transfer material to be transferred is the same tray as the transfer material accommodation tray that accommodates the transfer material currently being transferred. Then, it is detected whether or not the transfer material accommodation tray has been changed, and the detection result is sent to the static elimination voltage changing means.
[0084]
Further, when the charge removal voltage changing means 44 detects that the transfer material accommodation tray has been changed by the transfer material accommodation tray change detection means 49, the transfer material to be transferred next is the transfer material currently being transferred. It is determined that the transfer material storage tray is different from the transfer material storage tray to be stored, and the static elimination voltage VD is always changed to the first static elimination voltage VD1.
[0085]
Next, the processing procedure of the control unit 48 of the image forming apparatus 41 of the fourth embodiment described above will be described with reference to the flowchart of FIG. 9. This control unit 48 controls the image forming apparatus 31 of the third embodiment. Since the processing from step 301 to step 309, the processing from step 308 to step 310, the processing from step 311 and the processing from step 306 to step 312 described in the processing procedure of the means 38 are performed, the description of this processing is omitted. To do. In FIG. 9, the same processes as those in FIG. 7 are denoted by the same reference numerals.
[0086]
Further, in the control means 48 of the image forming apparatus 41 of the fourth embodiment, in the same way as the processing in the image forming apparatus 31 of the third embodiment, in step 309, the transfer that performs the transfer next to the transfer material 8 is performed. It is determined whether or not there is a material (step 309), but if the control unit 48 determines that there is a transfer material to be transferred next, the transfer material storage tray change detection unit 49 causes the transfer material storage tray to be transferred. It is detected whether or not the transfer material has been changed (step 401). If it is determined that the transfer material storage tray has not been changed, the transfer material to be transferred next is the transfer material that stores the transfer material 8 that is currently being transferred. It judges that it is accommodated in the same tray as a material accommodation tray, and repeats the process after step 304. FIG.
[0087]
On the other hand, if it is determined in step 401 that the transfer material accommodation tray has been changed, the transfer material to be transferred next is in a different tray from the transfer material accommodation tray that accommodates the transfer material 8 currently being transferred. It is determined that it is accommodated, and the processing after step 303 is repeated.
[0088]
The image forming apparatus 41 according to the fourth embodiment includes a transfer material accommodation tray change detection unit 49, and the charge removal voltage change unit 49 changes the transfer material accommodation tray by the transfer material accommodation tray change detection unit 49. When the transfer material is detected, it is determined that the transfer material to be transferred next is stored in a different tray from the transfer material storage tray for storing the transfer material 8 currently being transferred, and the charge removal voltage VD is set. Since the first static elimination voltage VD1 is changed, even if the second static elimination voltage VD2 is applied to the needle-like electrode 4, the transfer material 8 to be transferred next is transferred to the second static elimination voltage VD2. The charge removal is performed with the first charge removal voltage VD1 having a lower potential.
[0089]
That is, when the transfer material to be transferred next is stored in a different tray from the transfer material storage tray for storing the transfer material 8 currently being transferred, the transfer material 8 has a moisture content. Even in the case of a high transfer material, since the first static elimination voltage VD1 having a potential lower than the second static elimination voltage VD2 is applied, the transfer defect is further made possible when the toner image is transferred to the transfer material. Can be prevented.
[0090]
As described above, when the transfer material to be transferred next is stored in a different tray from the transfer material storage tray for storing the transfer material 8 currently being transferred, the charge removal voltage is set to the second level. The neutralization voltage VD2 can be returned to the first neutralization voltage VD1 so that when the transfer material in the transfer material storage tray runs out, the transfer material is continuously supplied from different trays in advance. This type of image forming apparatus is particularly effective.
[0091]
【The invention's effect】
As described above, according to the present invention, the image carrier, the contact transfer unit that transfers the toner image formed on the surface of the image carrier to the transfer material, and the transfer bias application that applies the transfer bias to the transfer transfer unit. In the image forming apparatus, comprising: a discharging means for discharging the transfer material onto which the toner image has been transferred; and a discharging voltage applying means for applying a high voltage to the discharging means. And a static elimination voltage changing means for changing the high voltage based on the static elimination current detected by the static elimination current detection means. Without providing a transfer material moisture content measuring means which is an independent device for measuring the rate, transfer defects on a transfer material such as a paper with a high moisture content can be prevented as much as possible.
[0092]
Therefore, in the image forming apparatus according to the present invention, the number of parts can be reduced and the manufacturing cost can be reduced because the transfer material moisture content measuring means is not provided.
[0093]
Further, in the image forming apparatus of the present invention, since the transfer current leaking through the transfer material is directly detected and the transfer condition / static charge condition is set, it is measured by the transfer material moisture content measuring means as in the conventional image forming apparatus. Compared to predicting the transfer current that leaks through the transfer material from the relationship between the moisture content and the resistance of the transfer material, and indirectly setting the transfer condition / static charge condition, it can respond quickly to the moisture content of the transfer material. As a result, the image quality can be improved.
[0094]
Therefore, according to the present invention, it is possible to provide an image forming apparatus that has a small number of parts, is inexpensive, and has high image quality.
[Brief description of the drawings]
FIG. 1 is a conceptual configuration diagram showing an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a conceptual configuration diagram showing a configuration of an image forming apparatus according to a first embodiment of the present invention.
FIG. 3 is a flowchart showing the processing operation of the image forming apparatus according to the first embodiment of the present invention;
FIG. 4 is a conceptual configuration diagram showing a configuration of an image forming apparatus according to a second embodiment of the present invention.
FIG. 5 is a flowchart showing the processing operation of the image forming apparatus according to the second embodiment of the present invention;
FIG. 6 is a conceptual configuration diagram showing the configuration of an image forming apparatus according to a third embodiment of the present invention.
FIG. 7 is a flowchart showing the processing operation of the image forming apparatus according to the third embodiment of the present invention;
FIG. 8 is a conceptual configuration diagram showing the configuration of an image forming apparatus according to a fourth embodiment of the present invention.
FIG. 9 is a flowchart showing the processing operation of the image forming apparatus according to the fourth embodiment of the present invention;
[Explanation of symbols]
1, 21, 31, 41 ... Image forming apparatus
2 ... Image carrier
3 ... Contact transfer means
4 ... Static elimination means
8 ... Transfer material
8a ... tip
8b: substantially central part
8c ... rear end
12: Transfer bias applying means
13 ... Current detection means
14, 24, 34 ... Static elimination voltage changing means
15: Static elimination voltage application means
16 ... Static elimination current detection means
49. Transfer material accommodation tray change detection means
IB0 ... Current
ID: Static elimination current
IDmax1 ... Threshold
IDmax1 ... 1st threshold value
IDmax1 ... second threshold
VD, VD1, VD2 ... Static elimination voltage
VD1: First static elimination voltage
VD2 ... second static elimination voltage
VT ... Transfer bias

Claims (4)

An image carrier, contact transfer means for transferring a toner image formed on the surface of the image carrier to a transfer material, transfer bias applying means for applying a transfer bias to the contact transfer means, and the toner image transferred In an image forming apparatus comprising a charge removing unit for removing charge from the transfer material, and a charge removing voltage applying unit for applying a high voltage to the charge removing unit,
A static elimination current detecting means for detecting a static elimination current flowing in the static elimination means;
Current detection means for detecting a current flowing between the image carrier and the contact transfer means before transfer to the transfer material by the contact transfer means;
A static elimination voltage changing means for changing the static elimination voltage which is the high voltage,
The static elimination voltage changing means includes
Based on the current detected by the current detection means, the static elimination voltage and a threshold of the static elimination current are set,
When the static elimination current of the static elimination unit to which the set static elimination voltage is applied and the static elimination current detected by the static elimination current detection unit does not exceed the threshold value, the static elimination voltage is determined from the set static elimination voltage. The image forming apparatus according to claim 1, wherein the image forming apparatus is also increased. An image carrier, contact transfer means for transferring a toner image formed on the surface of the image carrier to a transfer material, transfer bias applying means for applying a transfer bias to the contact transfer means, and the toner image transferred In an image forming apparatus comprising a charge removing unit for removing charge from the transfer material, and a charge removing voltage applying unit for applying a high voltage to the charge removing unit,
A static elimination current detecting means for detecting a static elimination current flowing in the static elimination means;
Current detection means for detecting a current flowing between the image carrier and the contact transfer means before transfer to the transfer material by the contact transfer means;
A static elimination voltage changing means for changing the static elimination voltage which is the high voltage,
The static elimination voltage changing means includes
Based on the current detected by the current detection means, a first static elimination voltage and a second static elimination voltage larger than the first static elimination voltage are set, and the static elimination corresponding to the first static elimination voltage Setting a first threshold of current and a second threshold of the static elimination current corresponding to the second static elimination voltage;
The first static elimination voltage when the static elimination current of the static elimination means to which the first static elimination voltage is applied and the static elimination current detected by the static elimination current detection means does not exceed the first threshold value To the second static elimination voltage,
When the static elimination current of the static elimination means to which the second static elimination voltage is applied and the static elimination current detected by the static elimination current detection means exceeds the second threshold value, the second static elimination voltage Is changed to the first static elimination voltage. An image carrier, contact transfer means for transferring a toner image formed on the surface of the image carrier to a transfer material, transfer bias applying means for applying a transfer bias to the contact transfer means, and the toner image transferred In an image forming apparatus comprising a charge removing unit for removing charge from the transfer material, and a charge removing voltage applying unit for applying a high voltage to the charge removing unit,
A static elimination current detecting means for detecting a static elimination current flowing in the static elimination means;
Current detection means for detecting a current flowing between the image carrier and the contact transfer means before transfer to the transfer material by the contact transfer means;
A static elimination voltage changing means for changing the static elimination voltage which is the high voltage,
The static elimination voltage changing means includes
Based on the current detected by the current detection means, a first static elimination voltage and a second static elimination voltage larger than the first static elimination voltage are set, and the static elimination corresponding to the first static elimination voltage Setting a first threshold of current and a second threshold of the static elimination current corresponding to the second static elimination voltage;
In the case where a second static elimination voltage is applied to the static elimination means, the static elimination current detected by the static elimination current detection means when the leading end of the transfer material reaches the static elimination means is the second static elimination voltage. When the threshold value is exceeded, the second static elimination voltage is changed to the first static elimination voltage,
When the neutralization current detected by the neutralization current detection unit when the substantially central portion of the transfer material reaches the neutralization unit does not exceed the first threshold value, the trailing end of the transfer material is the neutralization unit. An image forming apparatus characterized in that, when reaching the means, the first static elimination voltage is changed to the second static elimination voltage. A transfer material storage tray change detecting means for detecting whether or not the transfer material storage tray for storing the transfer material has been changed,
The static elimination voltage changing means is configured to change the high voltage to a predetermined static elimination voltage when the transfer material accommodation tray change detecting means detects that the transfer material accommodation tray has been changed. The image forming apparatus according to claim 1.

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