JP6759931B2 - Secondary transfer device, image forming device, and control program - Google Patents

Description

The present invention relates to a secondary transfer device, an image forming device, and a control program.

Patent Document 1 describes a carrier on which a toner image is supported, a transfer belt that transfers the toner image supported on the carrier to a recording material, cleaning means for cleaning the surface of the transfer belt, and the above. In the transfer region from the carrier to the recording material, the carrier is arranged so as to press the carrier with the transfer belt in between, and functions as a counter electrode of the cleaning means and also has a drive roller for driving the transfer belt. An image forming apparatus including is described.

Japanese Unexamined Patent Publication No. 2005-315987

The present invention is a secondary transfer device that suppresses deterioration of image quality due to secondary transfer as compared with the case where the transfer member is not charged with the same polarity as the detection bias prior to detecting the combined resistance. , An image forming apparatus, and a control program.

In order to achieve the above object, the secondary transfer device according to claim 1 is provided with a transfer member which is provided at a position facing the intermediate transfer body and transfers a toner image formed on the intermediate transfer body to a recording medium. The support member that supports the intermediate transfer body from the side opposite to the side facing the transfer member, the detection unit that detects the combined resistance between the intermediate transfer body and the support member, and the support member. On the other hand, an application unit that applies a transfer bias when transferring the toner image from the intermediate transfer body to the recording medium, and applies a detection bias when the detection unit detects the combined resistance. The detection unit includes a charging unit that charges the transfer member with the same polarity as the detection bias prior to detecting the combined resistance.

Further, the secondary transfer device according to claim 2 also has a function of cleaning the side of the transfer member facing the intermediate transfer body in the secondary transfer device according to claim 1. Have.

Further, the secondary transfer device according to claim 3 is the secondary transfer device according to claim 1 or 2, wherein the application unit transfers the toner image from the intermediate transfer body to the recording medium. Except for the case where the detection unit detects the combined resistance and the case where the detection unit detects the combined resistance, in a predetermined case, a bias having a polarity different from the detection bias is applied to the support member.

Further, the secondary transfer device according to claim 4 is in contact with the side of the transfer member facing the intermediate transfer body in the secondary transfer device according to any one of claims 1 to 3. A cleaning member for cleaning the transfer member is further provided.

Further, the secondary transfer device according to claim 5 is the secondary transfer device according to claim 4, wherein the application unit applies a bias having a polarity opposite to the detection bias to the cleaning member.

On the other hand, in order to achieve the above object, the image forming apparatus according to claim 6 includes an intermediate transfer body, a forming portion for forming a toner image on the intermediate transfer body, and any one of claims 1 to 5. The secondary transfer apparatus according to item 1 is provided.
Further, the image forming apparatus according to claim 7 further includes a control unit that controls a charging portion of the secondary transfer apparatus in the image forming apparatus according to claim 6.

Further, in order to achieve the above object, the control program according to claim 8 is for causing the computer to function as a control unit of the image forming apparatus according to claim 7.

According to the inventions of claims 1, 6, 7, and 8, as compared with the case where the transfer member is not charged to the same polarity as the detection bias prior to detecting the combined resistance. , It is possible to suppress deterioration of image quality due to secondary transfer.

According to the invention of claim 2, the charging member and the cleaning member can be used in combination.

According to the third aspect of the present invention, deterioration of image quality due to secondary transfer can be suppressed regardless of the polarity of the support member.

According to the fourth aspect of the present invention, the transfer member can be cleaned as compared with the case where the cleaning member is not provided.

According to the fifth aspect of the present invention, the transfer member can be cleaned more cleanly than when a bias having the same polarity as the detection bias is applied.

It is a breaking front view (partial block diagram) which shows an example of the structure of the image forming apparatus of an embodiment. It is a breaking front view which shows an example of the structure of the secondary transfer apparatus of embodiment. It is explanatory drawing for demonstrating the relationship between each mode, cleaning bias and transfer bias in the secondary transfer apparatus of embodiment. It is a graph which showed an example of the time change of the charged state of a transfer belt at the time of changing from the transfer belt dirt prevention mode to the synthetic resistance detection mode in a general secondary transfer apparatus and the secondary transfer apparatus of embodiment. It is a time chart which shows an example of the time change of a cleaning bias and a transfer bias in the case of shifting from the transfer belt stain prevention mode to the synthetic resistance detection mode in the secondary transfer apparatus of the embodiment. It is a flowchart which shows an example of the flow of the precharge control processing executed by the control part of embodiment. As another example of the configuration of the secondary transfer device of the embodiment, the fracture front surface showing the configuration when the cleaning device in the secondary transfer device shown in FIG. 2 is provided with a conductive cleaning blade instead of the fur brush and the recovery roller. It is a figure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the configuration of the image forming apparatus of the present embodiment will be described with reference to FIG. FIG. 1 is a broken front view showing a configuration of an example of the image forming apparatus 10 of the present embodiment. As shown in FIG. 1, the image forming apparatus 10 of the present embodiment is a so-called tandem type image forming apparatus.

The image forming apparatus 10 of the present embodiment includes image forming units 12Y, 12M, 12C, and 12K, an intermediate transfer body 21, a secondary transfer device 30, and a fixing device 50. In the following description, when distinguishing each color of yellow (Y), magenta (M), cyan (C), and black (K) for the image forming unit, the symbols "Y", "M", which distinguish each of them, are used. Explained with "C" and "K", and when individual is not distinguished, the description of the above reference numerals is omitted.

Each image forming unit 12 includes an image holder 14 that is rotationally driven in the direction of arrow A shown in FIG. Then, when the light beam Bm is irradiated from the corresponding exposure apparatus 18 to each image holder 14, an electrostatic latent image is formed on each image holder 14.

Around each image holder 14, a charging device 16 for charging the image holder 14, a developing device 20 for developing an electrostatic latent image formed on the image holder 14 by the exposure device 18 with toner, and a developing device 20 after transfer. A removing device 24 for removing the toner remaining on the image holder 14 of the above is provided. The charging device 16, the developing device 20, and the removing device 24 are arranged in this order from the upstream side to the downstream side in the rotation direction of the image holding body 14 so as to face the surface of the image holding body 14.

Further, a primary transfer device 26 is provided under each image forming unit 12. The primary transfer device 26 includes an annular intermediate transfer body 21 that contacts each image holder 14 and a primary transfer roll 22 that multiplexes the toner image formed on each image holder 14 onto the intermediate transfer body 21. There is.

The intermediate transfer body 21 is wound around a drive roll 52 driven by a motor (not shown), a tension applying roll 54, and a backup roll 48, and is wound in one direction (arrow B in FIG. 1) by the drive roll 52. Circularly moved in the direction). The backup roll 48 of the present embodiment is an example of the support member of the present invention.

Each primary transfer roll 22 is arranged so as to face the image holder 14 of each image forming unit 12 with the intermediate transfer body 21 interposed therebetween. Further, the primary transfer roll 22 is subjected to a transfer bias having a polarity opposite to that of the toner by a power feeding unit (not shown).

On the downstream side of the backup roll 48, a cleaning device 56 for removing residual toner, paper dust, and the like on the intermediate transfer body 21 is provided.

Below the primary transfer device 26, a recording medium accommodating section 60 accommodating a recording medium P, which is an example of a recording medium such as paper, is provided. Above one end side (left side in front view in FIG. 1) of the recording medium accommodating unit 60, a pickup roll 62 for sending the recording medium P from the recording medium accommodating unit 60 to the transport path 65 is provided.

A plurality of transport rolls 64 for transporting the recording medium P are provided on the downstream side of the pickup roll 62 in the transport path 65 in the recording medium transport direction.

The transport path 65 transports the recording medium P from the recording medium accommodating unit 60 toward the transfer region X (so-called “transfer nip”) of the secondary transfer device 30.

Although details will be described later, the secondary transfer device 30 of the present embodiment includes a cleaning device 32, a cleaning device 34, a transfer belt 36, a drive roll 38, a driven roll 39, a backup roll 48 described above, and a power supply roll 49. ..

The transfer belt 36 is wound around the drive roll 38 and the driven roll 39. The transfer belt 36 of the present embodiment is an example of the transfer member of the present invention. The drive roll 38 is arranged in the transfer region X at a position facing the intermediate transfer body 21 and the backup roll 48 with the transfer belt 36 interposed therebetween, and is secondarily transferred to the recording medium P conveyed on the transfer belt 36. Functions as a secondary transfer roll for applying. A cleaning device 32 and a cleaning device 34 are arranged on the secondary transfer device 30 in contact with the intermediate transfer body 21 on the transfer belt 36. The cleaning device 32 includes a conductive fur brush 40 and a recovery roller 42. The cleaning device 34 includes a conductive fur brush 44 and a recovery roller 46. The fur brushes 40 and 44 are arranged in contact with the transfer belt 36 to remove stains adhering to the transfer belt 36. The collection rollers 42 and 46 are arranged adjacent to the fur brushes 40 and 44, and collect the dirt removed by the fur brushes 40 and 44.

Further, as shown in FIG. 1, the image forming apparatus 10 of the present embodiment includes each of the above-described devices and a control unit 100 that controls the operation of each unit. The control unit 100 includes a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 104, and a RAM (Random Access Memory) 106. The CPU 102 controls the overall operation of the image forming apparatus 10. Various programs including a control program 105, which will be described in detail later, and various parameters are stored in the ROM 104 in advance. The RAM 106 is used as a work area or the like when the CPU 102 executes various programs.

Next, the image forming step by the image forming apparatus 10 will be described.

The image data obtained by performing image processing on the image data supplied from an external device such as a computer is sent to each exposure device 18. Each exposure device 18 emits each light beam Bm according to the image data to expose each image holder 14 charged by the charging device 16 to form an electrostatic latent image.

The electrostatic latent image formed on the image holder 14 is developed by the developing apparatus 20, and toner images of each color of Y, M, C, and K are formed.

As shown in FIG. 1, the toner images of each color formed on the image holders 14 of the image forming units 12Y, 12M, 12C, and 12K are sequentially multiplex-transferred to the intermediate transfer body 21 by the four primary transfer rolls 22. Toner.

The toner images of each color multiplex-transferred to the intermediate transfer body 21 are secondary-transferred by the secondary transfer device 30 onto the recording medium P conveyed from the recording medium storage unit 60. The recording medium P on which the toner image is transferred is conveyed toward the fixing device 50 by the transfer belt 66.

The toner images of each color on the recording medium P are fixed to the recording medium P by being heated and pressurized by the fixing device 50. The recording medium P on which the image is fixed is discharged to the outside of the image forming apparatus 10 by a discharge roll (not shown). After the transfer to the recording medium P is completed, the residual toner remaining on the intermediate transfer body 21 is conveyed along with the movement of the intermediate transfer body 21, and is removed from the intermediate transfer body 21 by the cleaning device 56.

Next, the configuration of the secondary transfer device 30 of the present embodiment will be described in detail.

FIG. 2 is a broken front view showing an example of the configuration of the secondary transfer device 30 provided in the image forming device 10 of the present embodiment. As shown in FIG. 2, the drive roll 38 for driving the transfer belt 36 sandwiches the intermediate transfer body 21 in the transfer region X and presses the backup roll 48 to hold the toner image on the intermediate transfer body 21. Functions as a transfer roller for secondary transfer to the recording medium P. Further, the drive roll 38 and the driven roll 39 are both grounded, and the drive roll 38 adjacent to the fur brushes 40 and 44 also functions as a counter electrode for the cleaning devices 32 and 34.

In the secondary transfer device 30 of the present embodiment, the transfer bias applying device 72 applies the transfer bias to the feeding roll 49, the cleaning bias applying device 74 applies the cleaning bias to the fur brush 40 and the recovery roller 42, and the cleaning bias is applied. The device 78 applies a second cleaning bias to the fur brush 44 and the recovery roller 46. In the following, the bias applied by the transfer bias applying device 72 is referred to as “transfer bias”, and the bias applied by each of the cleaning bias applying device 74 and the cleaning bias applying device 78 is referred to as “cleaning bias”. And cleaning bias are collectively referred to as "bias".

As shown in FIG. 2, the transfer bias applying device 72 of the present embodiment includes a power supply 73, and the polarity of the applied transfer bias is switched by the control unit 100 controlling the power supply 73. The transfer bias application device 72 of the present embodiment is an example of the application unit of the present invention.

Further, a combined resistance detection unit 70 is provided between the transfer bias applying device 72 and the feeding roll 49, and when the transfer bias is applied, the feeding roll 49, the backup roll 48, the intermediate transfer body 21, and the transfer belt are provided. The secondary transfer current flowing through the 36 and the drive roll 38 is detected. In the combined resistance detection unit 70, the control unit 100 derives the combined resistance based on the detected secondary transfer current and outputs the combined resistance to the control unit 100. The control unit 100 derives a bias according to the combined resistance derived by the combined resistance detecting unit 70. The combined resistance detection unit 70 of the present embodiment is an example of the detection unit of the present invention. Needless to say, the combined resistance detection unit 70 may not derive the combined resistance, but the control unit 100 may derive the combined resistance based on the secondary transfer current detected by the combined resistance detection unit 70.

On the other hand, the cleaning bias applying device 74 includes a power source 75 and a power source 76, and the polarity of the applied cleaning bias is switched by the control unit 100 controlling the power source 75 and the power source 76. Further, the cleaning bias applying device 78 includes a power source 79 and a power source 80, and the polarity of the applied cleaning bias is switched by the control unit 100 controlling the power source 79 and the power source 80.

The secondary transfer device 30 of the present embodiment applies a bias according to each mode in any one of the toner image transfer mode, the transfer belt stain prevention mode, and the combined resistance detection mode. The transfer belt stain prevention mode is an example of a predetermined case of the present invention.

The toner image transfer mode is a mode used when transferring a toner image to the recording medium P. Further, the transfer belt stain prevention mode is a mode used to prevent toner from adhering to the transfer belt 36 when the transfer belt stain prevention mode is not set. In the toner image transfer mode and the transfer belt stain prevention mode, an electric field having a substantially constant potential gradient is stably formed, so that it can be applied to various recording media P.

When the toner image is transferred (secondary transfer) to the recording medium P, the toner remaining on the transfer belt 36 after the transfer has a variation in electric charge. Therefore, the cleaning device 32 and the cleaning device 34 have different polar cleaning biases. Is applied. In the secondary transfer device 30 of the present embodiment, a positive polarity cleaning bias is applied to the cleaning device 32 by the cleaning bias applying device 74 in order to adsorb the negatively charged toner, and the cleaning device 34 is subjected to a positive polarity cleaning bias. A cleaning bias of negative polarity is applied by the cleaning bias applying device 78 in order to adsorb the positively charged toner.

The polarity of the cleaning bias applied in the cleaning device 32 is positive, and the magnitude of the cleaning bias applied to the recovery roller 42 is larger than the magnitude of the cleaning bias applied to the fur brush 40. Further, the polarity of the cleaning bias applied in the cleaning device 34 is negative, and the magnitude of the cleaning bias applied to the recovery roller 46 is larger than the magnitude of the cleaning bias applied to the fur brush 44. In this way, by setting the cleaning bias applied to the collection rollers 42 and 46 to a cleaning bias larger than the bias applied to the fur brushes 40 and 44, the toner collected by the fur brushes 40 and 44 is collected by the collection rollers 42. , 46 is smoothly transferred, and the cleaning ability of the fur brushes 40 and 44 is maintained.

On the other hand, the combined resistance detection mode is a mode used when the recording medium P does not exist in the transfer region X, and is a mode implemented when the combined resistance detection unit 70 detects the combined resistance in the transfer region X. ..

In the secondary transfer device 30 of the present embodiment, in the combined resistance detection mode, the control unit 100 applies the transfer bias from the backup roll 48 side by the transfer bias applying device 72. Further, the control unit 100 applies a cleaning bias having the same polarity as the transfer bias applied by the transfer bias applying device 72 by the cleaning bias applying device 74 and the cleaning bias applying device 78. Then, the control unit 100 causes the combined resistance detecting unit 70 to detect the combined resistance of the backup roll 48, the intermediate transfer body 21, the transfer belt 36, and the drive roll 38. In the secondary transfer device 30 of the present embodiment, the cleaning bias applied to the fur brushes 40 and 44 is determined by the control unit 100 based on the combined resistance derived by the combined resistance detecting unit 70.

By controlling the bias applied in this way, the optimum bias is applied according to the resistance of the drive roll 38, so that the surface of the transfer belt 36 is cleaned by the fur brushes 40 and 44.

The timing for setting the combined resistance detection mode (detecting the combined resistance) is not only when the image is formed (secondary transfer) for each predetermined number of images (for example, 200), but also when the temperature is set by a sensor (not shown). And at least one of the humidity is monitored, for example, the timing when the temperature changes by a predetermined threshold value or more, the timing when the humidity changes by a predetermined threshold value or more, and the like can be considered.

As described above, the secondary transfer device 30 of the present embodiment applies a bias according to each mode in any one of the toner image transfer mode, the transfer belt stain prevention mode, and the combined resistance detection mode. To do. As shown in FIG. 3, in the toner image transfer mode, the cleaning device 32 applies a cleaning bias having a positive polarity, the cleaning device 34 applies a cleaning bias having a negative polarity, and the transfer bias applying device 72 has a negative polarity. Transfer bias is applied.

Further, in the transfer belt stain prevention mode, the cleaning device 32 applies a cleaning bias having a positive polarity, the cleaning device 34 applies a cleaning bias having a negative polarity, and the transfer bias applying device 72 applies a toner image transfer having a positive polarity. Apply a transfer bias that is weaker (smaller in magnitude) than the mode. Further, in the combined resistance detection mode, the cleaning device 32 applies a negative cleaning bias or does not apply a cleaning bias, the cleaning device 34 applies a cleaning bias having a negative polarity, and the transfer bias applying device 72 has a polarity. Apply a negative transfer bias.

As described above, when the mode is switched from the other mode to the combined resistance detection mode, the cleaning bias and the transfer bias may change. At this time, in general, the charged state of the transfer belt is affected by the offset voltage generated by the change from the bias applied in the other modes. As an example, FIG. 4 shows an example of time change of the charged state of the transfer belt when the transfer belt stain prevention mode is switched to the combined resistance detection mode.

As an example, as shown by the voltage A in FIG. 4, in a general secondary transfer device, when the transfer belt stain prevention mode is switched to the combined resistance detection mode due to the influence of the offset voltage, the voltage is immediately referred to. It does not reach the voltage and changes stepwise according to the rotation cycle of the transfer belt. If the combined resistance is detected in the combined resistance detection mode in the state where the voltage of the transfer belt is changing stepwise in this way, the voltage of the transfer belt is stable at the reference voltage as compared with the case where the voltage is stable at the reference voltage. The derived combined resistance value is also incorrect, and as a result, the derived bias value is also incorrect. Further, when the bias value becomes improper, uneven transfer of the toner image, poor cleaning of the transfer belt, and the like occur, so that the quality of the image deteriorates due to the secondary transfer.

On the other hand, in the secondary transfer device 30 of the present embodiment, unlike the general secondary transfer device showing the change shown by the voltage A, as an example, as shown as the voltage B in FIG. 4, the offset voltage is Since the influence is suppressed, the voltage of the transfer belt 36 does not change stepwise as described above, but quickly reaches the reference voltage.

That is, as illustrated as the voltage B in FIG. 4, in order to change the charged state of the transfer belt 36, the secondary transfer device 30 of the image forming device 10 of the present embodiment shifts to the combined resistance detection mode. Prior, in the combined resistance detection mode, a bias having the same polarity as the bias applied to the transfer belt 36 is precharged by applying it to the transfer belt 36 in advance.

Next, the operation of the secondary transfer device 30 in the image forming device 10 of the present embodiment will be described.

The operation for performing the pre-charging in the secondary transfer device 30 of the present embodiment will be described. FIG. 5 shows a time chart of an example of the time change of the cleaning bias and the transfer bias when shifting from the transfer belt stain prevention mode to the combined resistance detection mode. The secondary transfer device 30 of the present embodiment precharges the transfer belt 36 during the period T1 and the period T2 shown in FIG. 5 as an example under the control of the control unit 100.
Even when the toner image transfer mode is switched to the combined resistance detection mode, it is preferable to perform precharging in the same manner as described above.

In the image forming apparatus 10 of the present embodiment, in the period T1 and the period T2, the region of the transfer belt 36 located in the transfer region X when the combined resistance detection mode is entered is the cleaning bias applying device 74 and the cleaning bias applying device 78. It is determined to be precharged with. Specifically, the period T1 is a value obtained by dividing the distance from the position where the fur brush 40 contacts the position where the fur brush 44 contacts on the transfer belt 36 by the moving speed of the transfer belt 36. .. Further, the period T2 is a value obtained by dividing the distance from the position where the fur brush 44 contacts the transfer region X on the transfer belt 36 by the moving speed of the transfer belt 36.

For example, when the main power switch of the image forming apparatus 10 is turned on, the control unit 100 executes the precharge control process shown in FIG. 5 by the CPU 102 executing the control program 105 stored in the ROM 104. To do.

In step S100, the control unit 100 determines whether or not the timing is the timing obtained by subtracting the period T1 and the period T2 from the timing of the above-mentioned combined resistance detection mode (hereinafter, referred to as “combined resistance detection mode transition timing”). If the timing is not the timing obtained by subtracting the period T1 and the period T2 from the combined resistance detection mode transition timing, the determination in step S100 becomes a negative determination, and the standby state is set. On the other hand, when the timing obtained by subtracting the period T1 and the period T2 from the combined resistance detection mode transition timing is reached, the determination in step S100 becomes an affirmative determination, and the process proceeds to step S102.

In step S102, the control unit 100 applies a cleaning bias as shown in FIG. 5 by the cleaning bias applying device 74 to precharge the cleaning device 32, more specifically, the fur brush 40. In the present embodiment, as shown in FIG. 5, the bias applied in the precharging has the same magnitude as the bias applied in the combined resistance detection mode, but if the polarities are the same, the magnitude may be different. Good. As in the present embodiment, it is preferable that the magnitude of the bias is the same.

In the next step S104, the control unit 100 determines whether or not the period T2 is subtracted from the combined resistance detection mode transition timing. If the timing is not the timing obtained by subtracting the period T2 from the combined resistance detection mode transition timing, the determination in step S104 is a negative determination, and the standby state is set. On the other hand, when the timing obtained by subtracting the period T2 from the combined resistance detection mode transition timing is reached, the determination in step S104 becomes an affirmative determination, and the process proceeds to step S106.

In step S106, the control unit 100 applies a cleaning bias by the cleaning bias applying device 78 as shown in FIG. 5, and precharges the cleaning device 34, more specifically, the fur brush 44. In the present embodiment, as shown in FIG. 5, the bias applied in the precharging has the same magnitude as the bias applied in the combined resistance detection mode, but if the polarities are the same, the magnitude may be different. Good. As in the present embodiment, it is preferable that the magnitude of the bias is the same.

In the next step S108, the control unit 100 determines whether or not it is the combined resistance detection mode transition timing. If it is not the combined resistance detection mode transition timing, the determination in step S108 is a negative determination, and the standby state is set. On the other hand, when the combined resistance detection mode transition timing is reached, the determination in step S108 becomes an affirmative determination, and the process proceeds to step S110.

In step S110, the control unit 100 shifts the secondary transfer device 30 to the combined resistance detection mode. By executing this step, the mode shifts to the combined resistance detection mode, and the secondary transfer device 30 performs the above-mentioned combined resistance detection and processing based on the detection result under the control of the control unit 100.

In the next step S112, the control unit 100 determines whether or not to end the pre-charge control process. For example, when a predetermined termination condition is satisfied, such as when the main power switch of the image forming apparatus 10 is turned off, the determination in step S112 becomes an affirmative determination, and the preliminary charging control process ends. On the other hand, if the end condition is not satisfied, the determination in step S112 becomes a negative determination, the process returns to step S100, and the pre-charge control process is repeated.

As described above, the secondary transfer device 30 of the image forming apparatus 10 of the present embodiment is provided at a position facing the intermediate transfer body 21, and the toner image formed on the intermediate transfer body 21 is transferred to the recording medium P. A backup roll 48 that supports the transfer belt 36 and the intermediate transfer body 21 from the side opposite to the side facing the transfer belt 36, and a composite resistor that detects the combined resistance between the intermediate transfer body 21 and the backup roll 48. A transfer bias for transfer is applied to the detection unit 70 and the backup roll 48 in the toner image transfer mode in which the toner image is transferred from the intermediate transfer body 21 to the recording medium P, and the composite resistance detection unit 70 detects the composite resistance. In the combined resistance detection mode, the transfer bias applying device 72 that applies the transfer bias for detection and the combined resistance detecting unit 70 charge the transfer belt 36 with the same polarity as the transfer bias for detection prior to detecting the combined resistance. A fur brush 40 and a fur brush 44 are provided.

As described above, according to the secondary transfer device 30 of the present embodiment, the transfer belt 36 is applied by the fur brush 40 and the fur brush 44 in the combined resistance detection mode prior to the transition to the combined resistance detection mode. Charge with the same polarity as the bias. Therefore, when the mode shifts to the combined resistance detection mode, the charged state of the transfer belt 36 changes as shown by the voltage B shown in FIG. 5, and quickly reaches the reference voltage.

Therefore, the combined resistance detection unit 70 can detect an appropriate combined resistance, and as a result, the derived bias value is also appropriate. As described above, according to the secondary transfer device 30 of the present embodiment, the transfer unevenness of the toner image, the cleaning failure of the transfer belt 36, and the like can be suppressed by making the bias value appropriate. Therefore, according to the secondary transfer device 30 of the present embodiment, it is caused by the secondary transfer as compared with the case where the transfer belt 36 is not charged with the same polarity as the transfer bias for detection prior to detecting the combined resistance. Suppresses deterioration of image quality.

The voltage of the transfer belt may be increased as the particle size of the toner is reduced for the purpose of improving the image quality. The higher the voltage of the transfer belt, the more prominent the phenomenon that the voltage of the transfer belt shown as the voltage A in FIG. 5 changes stepwise. Therefore, when the image forming apparatus 10 (secondary transfer apparatus 30) of the present embodiment is applied when the transfer belt 36 has a high voltage in this way, a more remarkable effect can be obtained.

In the present embodiment, the mode in which the secondary transfer device 30 includes the cleaning device 32 and the cleaning device 34, and each of the fur brush 40 and the fur brush 44 functions as a charging portion of the present invention has been described. It goes without saying that it is not limited. For example, the charging portion that precharges the transfer belt 36 and the cleaning member that cleans the transfer belt 36 are not limited to the fur brush, and may be, for example, other rolls or blades. For example, FIG. 7 shows a case where the cleaning device 34 includes a conductive cleaning blade 45 instead of the fur brush 40 and the recovery roller 42. In the example shown in FIG. 7, the cleaning bias applying device 78 provided with the power supply 80 applies the cleaning bias to the cleaning blade 45 under the control of the control unit 100. In the example shown in FIG. 7, the cleaning blade 45 is used for precharging the transfer belt 36.

Further, the charged portion of the transfer belt 36 may be a conductive film or the like.

Needless to say, the charged portion of the transfer belt 36 and the cleaning member may be provided separately. In this case, it is preferable that the charged portion is provided at a position closer to the transfer region X than the cleaning member.

Further, in the present embodiment, the cleaning device 32 and the cleaning device 34 are provided as the cleaning members, but the number of the cleaning members is not limited to the present embodiment and may be one or three or more. Needless to say, it's good.
Further, the “plus” and “minus” in the polarity of the bias described in the present embodiment are examples, and are not limited to the present embodiment. In this embodiment, the polarity when the polarity of the toner transferred to the intermediate transfer body 21 is negative has been described. Therefore, if the polarity of the toner is positive, the polarity of the bias may be different from that of the present embodiment. Needless to say.

It goes without saying that the above embodiment is an example of the present invention and can be changed depending on the situation within a range not deviating from the gist of the present invention.

10 Image forming device 21 Intermediate transfer device 30 Secondary transfer device 32, 34 Cleaning device 36 Transfer belt 40, 44 Fur brush 42, 46 Recovery roller 48 Backup roll 70 Combined resistance detector 72 Transfer bias application device 74, 78 Cleaning bias application Device 100 Control unit 102 CPU
105 control program

Claims (8)

A transfer member provided at a position facing the intermediate transfer body and transferring a toner image formed on the intermediate transfer body to a recording medium.
A support member that supports the intermediate transfer body from a side opposite to the side facing the transfer member, and
A detection unit that detects the combined resistance between the intermediate transfer body and the support member,
A transfer bias is applied to the support member when the toner image is transferred from the intermediate transfer body to the recording medium, and a detection bias is applied when the detection unit detects the combined resistance. Applying part and
A charging unit that charges the transfer member to the same polarity as the detection bias prior to the detection unit detecting the combined resistance.
Secondary transfer device equipped with. The secondary transfer device according to claim 1, wherein the charged portion also has a function of cleaning the side of the transfer member facing the intermediate transfer body. The application unit is a support member when predetermined, except for two cases where the toner image is transferred from the intermediate transfer body to the recording medium and the detection unit detects the combined resistance. A bias having a polarity different from that of the detection bias is applied.
The secondary transfer device according to claim 1 or 2. Further provided with a cleaning member which comes into contact with the side of the transfer member facing the intermediate transfer body and cleans the transfer member.
The secondary transfer device according to any one of claims 1 to 3. The application unit applies a bias having a polarity opposite to that of the detection bias to the cleaning member.
The secondary transfer device according to claim 4. With the intermediate transcript,
A forming portion that forms a toner image on the intermediate transfer body,
The secondary transfer apparatus according to any one of claims 1 to 5.
An image forming apparatus equipped with. A control unit for controlling the charging unit of the secondary transfer device is further provided.
The image forming apparatus according to claim 6. Computer,
A control unit for the image forming apparatus according to claim 7.
Control program.