JP2021128244A - Image forming apparatus - Google Patents

Abstract

To normally execute high voltage trouble detection processing and prevent the generation of streaks on printing paper in a transfer preparation stage.SOLUTION: A transfer device comprises: a transfer member that is arranged at a transfer position where a photoreceptor drum and a surface of a transfer belt are in contact with each other and transfers a toner image to a recording medium conveyed to the transfer position; a transfer voltage application unit that applies a transfer voltage to the transfer member; a transfer preparation unit that executes transfer preparation processing including high voltage trouble detection processing and transfer adsorption processing before the toner image is transferred to the recording medium; and an actual transfer voltage control unit that applies, to the transfer member, an actual transfer voltage necessary for transferring the toner image to the recording medium.SELECTED DRAWING: Figure 4

Description

The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a function of transporting printing paper using a transfer belt having a seam formed therein and transferring a toner image to the printing paper.

In a conventional image forming apparatus, a toner image corresponding to an electrostatic latent image is produced by developing an electrostatic latent image formed on the surface of the charged photoconductor drum by using the toner supplied to the photosensitive drum. The toner image formed and formed on the surface of the photoconductor drum is transferred onto the printing paper by the transfer device.
When the printing paper is conveyed and is in a position where the photoconductor drum and the transfer belt come into contact with each other (referred to as a transfer position or a nip position), the toner image of the photoconductor drum is transferred onto the printing paper at that position.

Further, in the transfer step, after the toner image is transferred to the printing paper, the residual toner that remains attached to the photoconductor drum is adsorbed on the transfer belt in a state where the photoconductor drum and the transfer belt are in direct contact with each other to cause the photoconductor. Removal from the drum is done.
Further, the residual toner adsorbed on the transfer belt is removed by a predetermined cleaning mechanism, and the residual toner is prevented from adhering to the back surface of the printing paper that is subsequently conveyed.

For example, in Patent Document 1, a transfer device that transfers a toner image of a photoconductor drum to paper, a transfer belt that is a transfer material that conveys the paper, a drive roller that rotates the transfer belt, and a static eliminator that removes static electricity from the paper. The static eliminator is provided at a position facing the drive roller, and the toner transferred to the transfer belt remains when the photoconductor drum and the transfer belt are in contact with each other when the paper does not pass through the transfer position. When the transferred cover toner passes between the drive roller and the static eliminator, a high voltage is applied to the static eliminator to ground the drive roller, so that the cover toner is removed. A transfer device that removes from the transfer belt and cleans the transfer belt has been proposed.

Further, in Patent Document 2, the transport belt for transporting the recording material, the cleaning web for removing the toner adhering on the transport belt, the pressing roller for pressing the cleaning web against the surface of the transport belt, and the transport belt rotate. A high-voltage DC bias is applied while the belt is in contact with the back surface of the transport belt, and the inner static eliminator roller is provided. An image forming apparatus has been proposed in which image defects are prevented by removing the electric charge of the transport belt by a DC bias.

Japanese Unexamined Patent Publication No. 2003-122134 Japanese Unexamined Patent Publication No. 7-44079

By the way, today, as a transfer belt for transporting printing paper to a transfer position, a transfer belt manufactured by an injection molding method is used.
The transfer belt manufactured by the injection molding method can be produced at low cost, but when it is molded as a belt, a convex line (referred to as a parting line (PL)) is formed at the seam portion.
When a transfer belt manufactured by such an injection molding method is used, there is a problem that the following streaks are generated on the printing paper.

Conventionally, a process of detecting a high-voltage trouble has been performed in order to output a constant output to a transfer device before transferring to printing paper. In order to detect this high voltage trouble, for example, a high current transfer output of about 30 V or more is performed.

When high-pressure trouble detection is executed before transfer to printing paper is performed, printing is performed when the photoconductor drum and the parting line (PL) of the transfer belt come into contact with each other at the timing when the printing paper passes the transfer position. On the paper, streaks may occur due to the residual toner (hereinafter referred to as fog toner) remaining on the photoconductor drum after the previous transfer, and the print quality deteriorates.
This is because a high current for detecting high-voltage trouble flows to the transfer member at the transfer position, but when the photoconductor drum and the parting line (PL) of the transfer belt come into contact, the photoconductor immediately before transfer is at that contact position. This is because the overcurrent is concentrated on a part of the drum and the potential fluctuation of the photoconductor drum cannot be canceled.

If the current value of the transfer output is lowered, the occurrence of streaks can be suppressed, but if the current value is too low, erroneous detection will occur in the high-voltage trouble detection process due to insufficient current, and normal detection processing will occur. May not be possible.

Therefore, the present invention has been made in consideration of the above circumstances, and in the transfer process of the image forming apparatus, high-pressure trouble is detected in the transfer preparation stage before the toner image is transferred to the printing paper. An object of the present invention is to enable the processing to be normally executed and to prevent streaks from being generated on the printing paper when the photoconductor drum and the parting line (PL) of the transfer belt come into contact with each other.

The present invention comprises a photoconductor drum on which a toner image to be transferred to a recording medium is formed, a transfer belt, and a transfer device for transferring a toner image formed on the surface of the photoconductor drum to the recording medium. The transfer device is arranged so as to come into contact with the back surface of the transfer belt at a transfer position where the photoconductor drum and the front surface of the transfer belt come into contact with each other, and the toner is placed on a recording medium conveyed to the transfer position. It includes a transfer member that transfers an image, a transfer voltage application unit that applies a predetermined transfer voltage to the transfer member, and a high-pressure trouble detection process and a transfer adsorption process before transferring the toner image to the recording medium. A transfer preparation unit that executes a transfer preparation process, and an actual transfer voltage control unit that controls the transfer voltage application unit so as to apply the actual transfer voltage required for transferring the toner image to the recording medium to the transfer member. The present invention provides an image forming apparatus comprising the above.

Further, the high-pressure trouble detection process is a process for detecting whether or not the transfer output given to the transfer member is normal, and the transfer adsorption process transfers the toner remaining on the photoconductor drum. This is a process for adsorbing to the belt, and the transfer preparation unit executes the high-pressure trouble detection process before the recording medium is conveyed to the transfer position, and then executes the transfer adsorption process to perform the transfer. After the adsorption process, during the transfer output period when the recording medium passes through the transfer position, the actual transfer voltage control unit applies the actual transfer voltage to the transfer member by the transfer voltage application unit. The toner image is transferred to the recording medium.

Further, a detection voltage control unit that controls the transfer voltage application unit so that the transfer preparation unit applies a voltage required for executing the high voltage trouble detection process to the transfer member.
In the transfer adsorption process, the adsorption voltage control that controls the transfer voltage application unit so that the voltage required for adsorbing the toner remaining on the photoconductor drum to the transfer belt is applied to the transfer member. It is characterized in that the current value of the adsorption current flowing through the transfer member in the transfer adsorption process is lower than the current value of the trouble detection current flowing through the transfer member in the high voltage trouble detection process.

Further, the transfer member is a transfer roller that comes into contact with the back surface of the transfer belt and rotates in the transport direction of the recording medium. The transfer roller is rotated to rotate the transfer belt, and in the transfer adsorption process. By applying a predetermined transfer voltage to the transfer roller, the transfer voltage applying unit generates a charge having a polarity opposite to that of the toner remaining on the photoconductor drum on the surface of the transfer belt, and the photosensitivity is generated. It is characterized in that the toner remaining on the body drum is adsorbed on the transfer belt.

Further, when a plurality of recording media are continuously conveyed to the transfer position, after the transfer of the toner image to the first recording medium among the two adjacent recording media is completed, 2 In the inter-paper waiting period until the transfer of the toner image to the first recording medium is started, the transfer preparation unit performs the transfer before the second recording medium is conveyed to the transfer position. It is characterized by performing an adsorption process.

Further, in the case where the transfer to the front surface of the recording medium and the transfer to the back surface of the recording medium are continuously performed in order to transfer a predetermined toner image to the front surface and the back surface of one recording medium, respectively, the above-mentioned case. After the transfer of the toner image to the front surface of the recording medium is completed, the transfer preparation unit moves to the back surface of the recording medium during the inter-paper waiting period until the transfer of the toner image to the back surface of the recording medium is started. It is characterized in that the transfer adsorption process is executed before the recording medium is conveyed to the transfer position in order to start the transfer of.

Further, the photoconductor drum is a cylindrical member in which the toner image is formed on the side surface of the cylinder and is rotationally driven around the cylindrical axis. It is characterized in that it is executed only for the transfer adsorption period corresponding to.

Further, the transfer belt is an endless belt in which a convex line is formed at a seam portion.

Further, in the present invention, the toner image is arranged so as to come into contact with the back surface of the transfer belt at the transfer position where the photoconductor drum formed on the surface and the surface of the transfer belt come into contact with each other, and is conveyed to the transfer position. A transfer member that transfers the toner image to the recording medium, a transfer voltage application unit that applies a predetermined transfer voltage to the transfer member, and high-pressure trouble detection processing and transfer before transferring the toner image to the recording medium. The transfer preparation unit that executes the transfer preparation process including the adsorption process and the transfer voltage application unit are controlled so as to apply the actual transfer voltage required for transferring the toner image to the recording medium to the transfer member. The high-pressure trouble detection process is a process for detecting whether or not the transfer output given to the transfer member is normal, and the transfer adsorption process is performed on the photoconductor drum. This is a process for adsorbing the remaining toner to the transfer belt. The transfer preparation unit executes the high-pressure trouble detection process before the recording medium is conveyed to the transfer position, and then the transfer. The actual transfer voltage control unit applies the transfer voltage to the transfer voltage during the transfer output period after the adsorption process is executed and the recording medium passes through the transfer position. The present invention provides a transfer apparatus characterized in that the toner image is transferred to the recording medium by applying it to a transfer member.

Further, the present invention is a transfer method of an image forming apparatus, wherein the image forming apparatus comprises a photoconductor drum on which a toner image to be transferred to a recording medium is formed on the surface, a transfer belt, and the photoconductor drum. The transfer device includes a transfer device that transfers a toner image formed on the front surface to the recording medium, and the transfer device contacts the back surface of the transfer belt at a transfer position where the photoconductor drum and the surface of the transfer belt come into contact with each other. A transfer member that transfers the toner image to a recording medium that is arranged so as to be transferred to the transfer position, a transfer voltage application unit that applies a predetermined transfer voltage to the transfer member, and the toner image are recorded. Before transferring to a medium, a transfer preparation unit that executes a transfer preparation process including a high-pressure trouble detection process and a transfer adsorption process, and a transfer member that applies an actual transfer voltage required for transferring the toner image to the recording medium. A transfer voltage control unit that controls the transfer voltage application unit is provided so that the transfer voltage is applied to the transfer member. A step of executing a high-pressure trouble detection process for detecting whether or not is normal, and then a step of executing a transfer adsorption process for adsorbing the toner remaining on the photoconductor drum to the transfer belt. After the transfer adsorption process, during the transfer output period when the recording medium passes through the transfer position, the actual transfer voltage control unit applies the actual transfer voltage to the transfer member by the transfer voltage application unit. Provided is a transfer method of an image forming apparatus, which comprises a step of transferring the toner image to a recording medium passing through the transfer position.

According to the present invention, the high-pressure trouble detection process and the transfer adsorption process are executed before the recording medium is transferred to the transfer position to transfer the toner image to the recording medium, so that the transfer before the transfer to the printing paper is performed. In the preparatory stage, it is possible to prevent streaks from being generated on the printing paper when the photoconductor drum and the transfer belt come into contact with each other without causing an electrical high-pressure trouble.

It is a block diagram of one Example of the transfer apparatus in the image forming apparatus of this invention. It is explanatory drawing of the schematic structure of one Example of the image forming apparatus of this invention. It is a schematic explanatory drawing of an Example of toner adsorption near the transfer position of the image forming apparatus of this invention. It is explanatory drawing of one Example of the change of the transfer current value in the transfer process of this invention. It is explanatory drawing of one Example of the change of the transfer current value at the time of continuously transferring a plurality of printing papers in the transfer process of this invention. It is explanatory drawing of one Example of the detection process in the high pressure trouble detection period of the transfer process of this invention. It is explanatory drawing of one Example of the detection process in the high pressure trouble detection period of the transfer process of this invention. In the present invention, it is a flowchart of an Example of transfer preparation and transfer processing in a transfer step. In the present invention, it is a flowchart of one Example of transfer preparation and transfer processing in a transfer process in the case of printing a plurality of printing papers. In the present invention, it is a flowchart of one Example of transfer preparation and transfer processing in a transfer process in the case of printing on the front surface and the back surface of printing paper.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the description of the following examples does not limit the present invention.

<Structure of image forming device and transfer device>
FIG. 1 shows a block diagram of an embodiment of a transfer device in the image forming device of the present invention.
The image forming apparatus is an apparatus for processing image data, and in particular, an apparatus for reading a document on which an image, characters, etc. are described as image data and printing the image data on printing paper.
Further, for example, there is also an image forming apparatus (MFP: Multifunction Peripheral, also referred to as a multifunction device) having a copying function, a printing function, a document reading function (scanning function), a document editing function, a fax function, a communication function, and the like.

(Structure of transfer device)
The image forming apparatus of the present invention includes a transfer apparatus for printing image data on printing paper. The printing paper corresponds to the recording medium described above.
The transfer device is a device that transfers a toner image (hereinafter, also simply referred to as a toner image) corresponding to image data formed on the surface of a photoconductor drum to printing paper.
As shown in FIG. 1, the transfer device mainly includes a transfer processing unit 10 and a transfer member 11.
The transfer member 11 includes a transfer belt, a transfer roller, a transfer brush, etc., so that the transfer member 11 contacts the back surface of the transfer belt at a position where the photoconductor drum and the surface of the transfer belt come into contact with each other (hereinafter referred to as a transfer position). It is a member that transfers a toner image formed on the surface of a photoconductor drum to a printing paper that has been arranged and conveyed to a transfer position.
When the printing paper is conveyed to the transfer position, a predetermined transfer voltage (actual transfer voltage) is applied to the transfer member 11 and a high current is applied to the transfer member 11 to apply a high current to the toner formed on the surface of the photoconductor drum, as will be described later. The image is transferred to the printing paper.

Further, the transfer processing unit 10 performs the necessary preparatory processing in the transfer step before actually transferring the toner image to the printing paper, and then, when transferring the toner image to the printing paper, the transfer member 11 is predetermined. This is the part that controls the application of the transfer voltage.
The preparatory process includes, for example, a high-voltage trouble detection process and a transfer adsorption process, which will be described later.
The transfer processing unit 10 mainly includes a transfer voltage application unit 12, a detection signal acquisition unit 13, a high-voltage trouble detection unit 14, a transfer preparation unit 20, an actual transfer voltage control unit 30, and a storage unit 50.
Here, the transfer preparation unit 20 includes a detection voltage control unit 21, an adsorption voltage control unit 22, and a paper-to-paper voltage control unit 23.

The transfer voltage application unit 12 is a portion that applies a predetermined transfer voltage to the transfer member 11.
For example, when transferring a toner image to printing paper, a high voltage of about 500 volts is applied.

The detection signal acquisition unit 13 is a portion that detects a current flowing through the transfer member 11 and uses the detected current to acquire a detection signal (also referred to as a trouble detection signal) used in high-voltage trouble detection processing.

The high-voltage trouble detection unit 14 is a part that executes a high-voltage trouble detection process for checking whether or not a high-voltage trouble has occurred by using the acquired detection signal.
The high-voltage trouble detection process mainly detects whether or not the output (transfer output) given to the transfer member 11 is normal in the transfer process, in other words, gives a normal transfer output to the transfer member 11. This is a process for detecting whether or not a trouble that cannot be performed has occurred.
High-voltage troubles include, for example, troubles such as transfer output and charged output.
Since the high-voltage trouble detection process itself is a process that has been performed conventionally, detailed description of the process content will be omitted.

The transfer preparation unit 20 is a portion that performs a preparation process necessary for the transfer step before actually transferring the toner image to the printing paper, and executes a transfer preparation process including a high-pressure trouble detection process and a transfer adsorption process.
The transfer step of the present invention includes a transfer preparation step of performing a preparatory process (also referred to as a transfer preparatory process) and a transfer output step of actually transferring the toner image to printing paper.
Further, the transfer preparation step of the present invention includes a high-pressure trouble detection process and a transfer adsorption process performed immediately after that.
The transfer adsorption process is a process for adsorbing the toner remaining on the photoconductor drum to the transfer belt. The toner remaining on the photoconductor drum is also called a fog toner.

In the present invention, the transfer preparation process is executed after the printing process is required and the rotation of the photoconductor drum is started.
In the transfer preparation process, the transfer preparation unit 20 executes the high-voltage trouble detection process within a predetermined high-voltage trouble detection period before the printing paper is conveyed to the transfer position, and then transfers the print paper within a predetermined transfer adsorption period. Perform the adsorption process.

In the high-voltage trouble detection process, a relatively high current is passed through the transfer member 11, and a predetermined high-voltage trouble detection is performed.
In the transfer adsorption process, a current having a current value lower than the current flowed during the high-voltage trouble detection process is passed through the transfer member 11, and the fog toner remaining on the photoconductor drum is adsorbed on the transfer belt. Is done. The reason why a current having a relatively low current value is passed through the transfer member 11 is to prevent streaks from being generated on the printing paper.
After the transfer adsorption process, the printing paper is conveyed in the direction of the transfer position, and the toner image is transferred to the printing paper during the transfer output period.

The detection voltage control unit 21 is a part that controls the voltage applied to the transfer member 11 in the high voltage trouble detection process. In particular, the transfer voltage application unit 12 is controlled so that the voltage required for executing the high voltage trouble detection process is applied to the transfer member 11 within the high voltage trouble detection period.
For example, as will be described later, the transfer voltage application unit 12 is controlled so that a current of about 40 μA flows through the transfer member 11 within a high voltage trouble detection period of about 200 msec.
The current flowing through the transfer member 11 during the high-voltage trouble detection period is called a trouble detection current.

The adsorption voltage control unit 22 is a portion that controls the voltage applied to the transfer member 11 in the transfer adsorption process.
In particular, in the transfer adsorption process, the transfer voltage is applied so that the voltage required for adsorbing the toner (fog toner) remaining on the photoconductor drum 4 on the transfer belt is applied to the transfer member 11 within the transfer adsorption period. The application unit 12 is controlled.
This applied voltage is a voltage at which a current that does not cause streaks on the printing paper can be passed through the transfer member 11.

For example, as will be described later, the transfer voltage application unit 12 is controlled so that a current of about 10 μA flows through the transfer member 11 within a transfer adsorption period of about 1200 msec.
The current flowing through the transfer member 11 during the transfer adsorption period is called an adsorption current.
The current value of the adsorption current flowing through the transfer member 11 in this transfer adsorption process is lower than the current value of the trouble detection current flowing through the transfer member 11 in the high-voltage trouble detection process.
Further, as will be described later, it is preferable that the transfer adsorption process is executed only for the transfer adsorption period corresponding to, for example, the time required for the photoconductor drum 4 to make two rounds.
However, the period for executing the transfer adsorption treatment depends on the size of the drum diameter of the photoconductor drum and the rotation speed of the photoconductor drum, and is not limited to the time required for two rounds.

The inter-paper voltage control unit 23 can be used between two printing sheets when printing on a plurality of printing sheets continuously or when printing continuously on the front surface and the back surface of one printing sheet. This is a portion that controls the voltage applied to the transfer member 11 during a period during which transfer is not actually performed on printing paper (waiting period between sheets).

A relatively high voltage is applied to the transfer member 11 in order to transfer to the first printing paper, but streaks do not occur even in the inter-paper waiting period after the transfer of the first printing paper is completed. It is preferable to apply the voltage of the above to the transfer member 11.
This is because when the potential difference between the voltage applied to the first printing paper at the time of transfer and the applied voltage during the standby period between sheets becomes large, and when the potential difference causes the transfer to subsequent printing papers, This is because a defect may occur in the printed image.

In order to prevent defects in the printed image, it is preferable to apply a relatively high voltage to the transfer member 11 during the inter-paper standby period so that the potential difference becomes small.
However, during the inter-paper standby period, it is necessary to perform a process of adsorbing the fog toner on the transfer belt so that streaks do not occur, so it is not preferable to continue applying a relatively high voltage to the transfer member 11.
Therefore, as will be described later, even in the inter-paper standby period, a period similar to the high-voltage trouble detection process and the transfer adsorption process is provided, and the transfer member 11 is subjected to the two-step voltage application process.
Further, in order to suppress the occurrence of streaks in the inter-paper standby period, at least a transfer adsorption period for performing the transfer adsorption process is provided, a relatively low voltage is applied to the transfer member 11, and the current flowing through the transfer member 11 is applied. It is preferable to lower the value.

The actual transfer voltage control unit 30 is a unit that controls the transfer voltage application unit 12 so as to apply the actual transfer voltage required for transferring the toner image to the printing paper to the transfer member 11.
The toner image is transferred to the printing paper after the transfer preparation is performed as described above, but the actual transfer voltage control unit 30 transfers the toner image to the printing paper after the transfer adsorption process and during the transfer output period when the printing paper passes through the transfer position. The actual transfer voltage is applied to the transfer member 12 by the voltage application unit 12, so that the toner image is transferred to the printing paper.

In order to actually transfer the toner image to the printing paper, it is necessary to control the transfer voltage application unit 12 so that a relatively high current flows through the transfer member 11 as in the high voltage trouble detection process.
For example, as will be described later, the transfer voltage application unit 12 is controlled so that a current of about 20 μA to 40 μA flows through the transfer member 11 during the transfer output period.
The time of the transfer output period varies depending on the size of the printing paper and is not a fixed time.

The storage unit 50 is a part that stores information and programs necessary for executing the functions of the transfer device of the present invention, and is a semiconductor storage element such as ROM, RAM, flash memory, a storage device such as HDD, SSD, and the like. Storage medium is used.
Further, the storage unit 50 does not have to be provided in the transfer device 1, and a storage device or the like that stores information or a program for executing each function of the image forming device may be used as the storage unit 50. ..

In the storage unit 50, for example, high voltage detection set time 51, high voltage current set value 52, detected high voltage information 53, high voltage comparison information 54, adsorption processing set time 55, adsorption current set value 56, transfer processing set time 57, transfer current The set value 58 and the like are stored.

The high-voltage detection set time 51 (t1) is a time in which the high-voltage trouble detection period for performing the high-voltage trouble detection process is preset.
The high-voltage detection set time t1 is set in advance as the time for executing a predetermined high-voltage trouble detection process. For example, a time of about 100 msec to 400 msec may be set.

The high-voltage current set value 52 (a1) is a numerical value in which the current value of the current flowing through the transfer member 11 is preset when the high-voltage trouble detection process is performed.
As the high-voltage current setting value a1, for example, a current value of about 10 μA to 50 μA may be set.

The detected high-voltage information 53 (a0) is information on the detection signal acquired by the detection signal acquisition unit 13, and is information used in high-voltage trouble detection. The detected high-voltage information a0 is, for example, information on the voltage level of the detection signal, which is low level (0V) when normal and high level (+ 5V) when abnormal.

The high pressure comparison information 54 (as) is information to be compared with the detected high pressure information a0, and is information set and stored in advance. The high-voltage comparison information as is, for example, a threshold voltage, and when the acquired detected high-voltage information a0 is lower than the threshold voltage, it is determined that the detection state by the detection signal is normal and there is no trouble. Will be done. On the other hand, when the acquired detected high-voltage information a0 is higher than the threshold voltage, the detection state by the detection signal is abnormal, and it is determined that a trouble has occurred.

However, the number of detection judgments is not limited to once. For example, when the detection judgment is made at regular time intervals (50 msec) and the abnormal state continues for about 4 times or more continuously within the high-voltage trouble detection period. , It is preferable to judge that a trouble has occurred.
The time interval for detection determination and the number of continuous times for determining an abnormality are not limited to 50 msec or 4 times, and an appropriate time interval and continuous number of times may be set in advance for each high-voltage trouble detection signal.

The adsorption treatment set time 55 (t2) is a time in which the transfer adsorption period for performing the transfer adsorption treatment is preset.
As the adsorption process setting time t2, the time for executing the predetermined transfer adsorption process is set in advance. For example, a time of about 1000 msec to 1500 msec may be set.
Further, in order to suppress the phenomenon of streaks (also referred to as drum memory), it is preferable to set at least the time corresponding to the time for the photoconductor drum to make two rounds as the adsorption processing setting time t2.

Even if the potential of a part of the photoconductor drum remains high due to the overcurrent of the previous transfer output, the surface potential of the photoconductor drum is long after the time has passed for the photoconductor drum to make two rounds. Can be improved to a state close to uniform, and the generation of streaks (drum memory) can be suppressed.
Therefore, if the adsorption processing set time t2 is set to a time corresponding to the time required for the photoconductor drum to make two rounds, or a time equal to or longer than the time required to make two rounds, the streaks do not occur within the transfer adsorption period. The fog toner can be adsorbed on the transfer belt.

The adsorption current set value 56 (a2) is a numerical value in which the current value of the current flowing through the transfer member 11 is set in advance when the transfer adsorption process is performed.
As the adsorption current set value a2, a current value lower than the high voltage current set value a1, for example, a current value of about 10 μA may be set.
Further, the adsorption current set value a2 is set lower than the high voltage current set value a1, but for example, the adsorption current set value a2 is set to a current value of about 5% or more and 25% or less of the high voltage current set value a1. It is preferable to do so.
Further, in order to suppress the occurrence of streaks, it is preferable that the upper limit value of the adsorption current set value a2 is set to about 10 μA and the lower limit value of the adsorption current set value a2 is set to a current value of about 2 μA.

The transfer processing set time 57 (t3) is a time in which the transfer output period for actually performing the transfer process on the printing paper is set in advance. However, since the time required for the transfer process differs depending on the size of the printed paper to be conveyed, a different transfer output period is set for each size of the printing paper.
As the transfer processing set time t3, for example, when the printed paper to be conveyed is A4 size, a time of about 1200 msec is set.

The transfer current set value 58 (a3) is a numerical value in which the current value of the current flowing through the transfer member 11 is preset when the printing paper is actually subjected to the transfer process.
As the transfer current set value a3, for example, a current value of about 20 μA to 40 μA may be set.

(Configuration of image forming apparatus)
FIG. 2 shows an explanatory diagram of a schematic configuration of an embodiment of the image forming apparatus of the present invention.
The image forming apparatus converts the image data input by the image reading apparatus (scanner) or the like into information that can be printed.
For example, when printing image data on a recording medium (printing paper), generally, each step of charging, exposure, development, transfer, cleaning, static elimination, and fixing is continuously performed to record the image data on the recording medium. To form.
As shown in FIG. 2, the image forming apparatus mainly includes a photoconductor drum 4, a charging device 71, an exposure device 72, a developing device 73, a transfer device 1, a transfer belt 2, a fixing device 74, a cleaning device (not shown), and static elimination. Equipped with a device.

The photoconductor drum 4 is a cylindrical member composed of a conductive substrate and a photosensitive layer formed on the surface thereof, and is responsible for forming a latent image by charging and exposure. A toner image is formed on the side surface of the cylinder, and the circumference of the cylindrical axis is formed. It is a cylindrical member that is driven to rotate.
The photoconductor drum 4 exhibits conductivity when irradiated with light, and an electrical image called an electrostatic latent image is formed on the surface of the photoconductor drum 4. Further, the photoconductor drum 4 is supported by a driving means (not shown) so that the photoconductor drum 4 can be rotationally driven around the axis.

A charging device 71, an exposure device 72, a developing device 73, a transfer device 1, and the like are arranged around the photoconductor drum 4. After performing the charging step, the exposure step, and the developing step, a toner image to be transferred to the printing paper is formed on the surface of the photoconductor drum 4.

The charging device 71 is a device that uniformly charges the surface of the photoconductor drum 4 to a predetermined potential. As the charging device 71, a contact roller type, a contact brush type, a non-contact charger type, or the like is used.

The exposure device 72 irradiates the surface of the charged photoconductor drum 4 with light corresponding to the image data from between the charging device 71 and the developing device 73 to expose the surface of the photoconductor drum 4. It is a device that forms an electrostatic latent image according to the image data.
The exposure apparatus 72 is composed of, for example, a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror.

The developing apparatus 73 mainly has a developing roller arranged so as to face the photoconductor drum 4 in a developing tank containing a developer containing toner and a magnetic carrier, and the developing roller causes the photoconductor drum 4 to have a developing roller. This is a device that supplies toner to the surface to develop an electrostatic latent image formed on the surface of the photoconductor drum 4. By developing the electrostatic latent image, a toner image is formed on the surface of the photoconductor drum 4.

As described above, the transfer device 1 is a device that transfers the toner image formed on the surface of the photoconductor drum 4 to the printing paper, and includes a transfer member 11 and a transfer processing unit 10.
The transfer member 11 is mainly composed of a transfer roller, and the transfer roller is rotatably supported near the transfer position and is provided so as to come into contact with the back side of the transfer belt 2 in the same direction as the transfer direction of the printing paper 6. It is a rotating member.
Further, the transfer belt 2 is also rotated by the rotation of the transfer roller.
To transfer the toner image from the photoconductor drum 4 to the printing paper 6 at the transfer position, the transfer roller in contact with the back side of the transfer belt 2 is pressed against the transfer belt 2, the printing paper 6, and the photoconductor drum 4 to rotate. It is done by.

For the transfer of the toner image, a transfer bias for transferring the toner image onto the printing paper 6 is applied to the transfer roller when the printing paper 6 is present at the transfer position (transfer output period).
That is, in order to transfer the toner image onto the printing paper 6, a high voltage transfer bias having a polarity (+) opposite to the charging polarity (−) of the toner is applied to the transfer roller.

Further, in the transfer adsorption process, the transfer voltage application unit 12 applies a predetermined transfer voltage to the transfer roller to apply a charge having a polarity opposite to that of the toner remaining on the photoconductor drum 4 on the surface of the transfer belt 2. The toner generated and remaining on the photoconductor drum 4 is attracted to the transfer belt 2.

The transfer roller is formed based on a metal (for example, stainless steel) shaft having a diameter of, for example, 8 mm to 10 mm, and its surface is covered with a conductive elastic material (for example, urethane foam). With this conductive elastic material, the transfer roller can uniformly apply a high voltage to the transfer belt 2.
As the transfer member 11, a transfer brush or the like can be used as the transfer electrode in addition to the roller-shaped transfer roller.

The transfer belt 2 is stretched between three rollers (belt drive roller 3a, belt driven roller 3b, cleaning opposing roller 3c) by a transfer belt tension mechanism (not shown) and is provided so as to come into contact with the photoconductor drum 4. , The above three rollers are rotationally driven in the direction of the arrow in FIG.
Further, by rotationally driving the transfer belt 2, the printing paper 6 conveyed from the paper feed tray (not shown) is conveyed in the direction of the transfer position between the photoconductor drum 4 and the transfer device 1.
In the following embodiment, the transfer belt 2 is a transfer belt produced by injection molding and having a convex line (parting line) formed at a seam portion, and an endless belt is used.
The transfer step of the present invention may also be carried out when a transfer belt produced by extrusion molding is used.

The cleaning device removes and recovers the toner remaining on the surface of the photoconductor drum 4 after the development and image transfer steps. Further, the static eliminator removes static electricity remaining on the photoconductor drum 4 and the transfer belt 2.

Further, when the printing paper 6 is not conveyed to the transfer position, the transfer belt 2 and the photoconductor drum 4 come into direct contact with each other, so that the toner 5 remaining on the surface of the photoconductor drum 4 is adsorbed on the transfer belt 2. Perform the processing to be performed.
FIG. 3 shows a schematic explanatory view of an embodiment of toner adsorption near the transfer position.
Toner adsorption causes the photoconductor drum 4 and the transfer belt 2 to rotate when the printing paper 6 is not conveyed to the transfer position, and applies a transfer voltage to the transfer member 11 (transfer roller, transfer brush) to the extent that streaks do not occur. And do it.

Due to this transfer voltage, as shown in FIG. 3, the toner 5 remaining on the surface of the photoconductor drum 4 moves from the photoconductor drum 4 onto the transfer belt 2 when it reaches the transfer position, and the photoconductor drum 4 is moved. Removed from 4.
The toner 5 adsorbed on the transfer belt 2 is removed and recovered by a cleaning device (not shown) that cleans the surface of the transfer belt because it causes image defects or the like in the next step.

The fixing device 74 is a device for fixing a toner image transferred to printing paper, and is mainly composed of a heat roller and a pressure roller that rotate in opposite directions, and a toner image is placed between the heat roller and the pressure roller. The printing paper to which the toner is transferred is conveyed.
The heat roller is heated to a predetermined fixing temperature, and when the printing paper passes between the heat roller and the pressure roller, the transferred toner is melted and the toner image is fixed on the printing paper. ..

<Explanation of transfer process of the present invention>
As described above, the transfer step of the present invention includes a transfer preparation step and a transfer output step.
In the transfer preparation step, a high-pressure trouble detection period for executing the high-pressure trouble detection process and a transfer adsorption period for executing the transfer adsorption process are provided after that.
In the high-pressure trouble detection period, a preset transfer voltage is applied to the transfer member 11 to check whether or not a trouble related to transfer has occurred, and then in the transfer adsorption period, a streak does not occur in advance. The set transfer voltage is applied to the transfer member 11 to attract the fog toner remaining on the photoconductor drum to the transfer belt to prevent the back surface of the printing paper from becoming dirty.

In the present invention, since the period for executing the high-voltage trouble detection process and the period for executing the transfer adsorption process are separated, erroneous detection is performed in the high-voltage trouble detection process due to insufficient current flowing through the transfer member 11. Further, when a transfer belt having a convex line (parting line) formed at the seam is used, the fog toner can be adsorbed on the transfer belt so that streaks do not occur on the printing paper.

Hereinafter, an embodiment of a change in the current value (transfer current value) of the current flowing through the transfer member 11 in the transfer step will be described.
(Example 1)
FIG. 4 shows an explanatory diagram of an embodiment of a change in the transfer current value in the transfer step of the present invention.
Here, an embodiment of a change in the transfer current value when the toner image is transferred to only one sheet of printing paper will be described.

FIG. 4 shows an example of a graph of changes in the transfer current value in the transfer step.
The vertical axis is the current value TRi (transfer current value) of the current flowing through the transfer member 11, and the horizontal axis is time.
The time on the horizontal axis in the transfer process consists of four periods (t1, t2, ta, t3).
The high-voltage trouble detection period t1 is a period during which the high-voltage trouble detection process is performed.
The transfer adsorption period t2 is a period during which the transfer adsorption process is performed.
The transfer output period t3 is the period during which the transfer is actually performed on the printing paper.
The waiting period ta is a period from the completion of the transfer adsorption process to the transfer to the printing paper.

Of the transfer current value TRi on the vertical axis, the trouble detection current value a1 is the current value of the current flowing through the transfer member 11 during the high-voltage trouble detection period t1.
The adsorption current value a2 is the current value of the current flowing through the transfer member 11 during the transfer adsorption period t2.
The actual transfer current value a3 is the current value of the current flowing through the transfer member 11 during the transfer output period t3.
During the standby period ta, no current is passed through the transfer member 11.
Here, since the toner image is transferred to only one sheet of printing paper, the transfer process is completed after the transfer output period t3 is completed, and the transfer current value TRi becomes zero.

In the transfer step of FIG. 4, when the transfer preparation process is activated, the high-voltage trouble detection period t1 is started.
That is, the transfer voltage application unit 12 is controlled so that the current having the trouble detection current value a1 (trouble detection current) is passed through the transfer member 11 at the start of the high voltage trouble detection period t1. Until the high-voltage trouble detection period t1 elapses, a current having the trouble detection current value a1 is passed, and within the high-voltage trouble detection period t1, the high-voltage trouble detection unit 14 executes a predetermined high-voltage trouble detection process.

The high-voltage trouble detection period t1 is a time preset in the high-voltage detection set time 51, for example, about 200 msec.
Further, the trouble detection current value a1 is a current value preset in the high voltage current set value 52, and is, for example, a current value of 10 μA or more and 40 μA or less.
The reason why the upper limit value and the lower limit value of the trouble detection current value a1 have a range as described above is mainly because it depends on the development conditions (conditions for latent image of the toner on the photoconductor drum).
For example, when the development bias (development potential) is low, the trouble detection current is set low, and a current having a lower limit value of the trouble detection current value a1 is passed. Further, when the development bias (development potential) is high, the trouble detection current is set high, and the current of the trouble detection current value a1 which is the upper limit value is passed.

In the high-voltage trouble detection process, it is determined whether or not any trouble has been detected by using the acquired detection signal.
When a trouble is detected, the content of the trouble detection is notified to the user by means such as display.
On the other hand, if no trouble is detected, the next transfer adsorption period t2 is started.

In the transfer adsorption period t2, the transfer voltage application unit 12 is controlled so that a current (adsorption current) having an adsorption current value a2 is passed through the transfer member 11. Until the transfer adsorption period t2 elapses, a current having an adsorption current value a2 is passed, and within the transfer adsorption period t2, the photoconductor drum 4 and the transfer belt 2 are rotated to remove the toner 5 remaining on the photoconductor drum 4. , The transfer adsorption process of adsorbing to the transfer belt 2 is executed.

The transfer adsorption period t2 is a time preset in the adsorption process set time 55, for example, about 1200 msec.
Further, the adsorption current value a2 is a current value preset to the adsorption current set value 56, and is, for example, a current value of about 10 μA.
During the transfer adsorption period t2, the toner 5 remaining on the photoconductor drum 4 is adsorbed on the transfer belt 2 and the surface of the photoconductor drum 4 is cleaned.
Further, since the current value of the adsorption current flowing through the transfer member 11 within the transfer adsorption period t2 is lower than the trouble detection current value a1, the printing paper conveyed in the next transfer output period may have streaks. Can be suppressed.

When the transfer adsorption period t2 ends, the transfer output period t3 shifts to the transfer output period t3 after the elapse of the predetermined waiting period ta.
The waiting period ta is the time until the printing paper is conveyed in the direction of the transfer position, and is preferably as short as possible, but is, for example, about 300 msec.
Further, since the transfer voltage is not applied to the transfer member 11 within this standby period ta, the current value of the current flowing through the transfer member 11 becomes almost zero.

At the start of the transfer output period t3, the tip of the printing paper is conveyed to the transfer position, and a current having an actual transfer current value a3 is used to transfer the toner image formed on the photoconductor drum 4 to the printing paper 6. The transfer voltage application unit 12 is controlled so that (transfer current) is passed through the transfer member 11.
The actual transfer current value a3 is a current value preset to the transfer current set value 58, and is, for example, a current value of 20 μA or more and 40 μA or less.
The reason why the upper limit value and the lower limit value of the actual transfer current value a3 have a range as described above is the same reason that the upper limit value and the lower limit value of the trouble detection current value a1 have a range as described above.

Since the size of the printing paper conveyed to the transfer position is already known in the image forming apparatus, the transfer processing setting time 57 corresponding to the size of the printing paper is set as the transfer output period t3.
In the transfer output period t3, the photoconductor drum 4 and the transfer belt 2 are rotated, and the toner image formed on the photoconductor drum 4 is transferred to the printing paper 6.
At the end of the transfer output period t3, the rear end of the printing paper passes through the transfer position, and the transfer of the toner image to the printing paper 6 is completed.

FIG. 8 shows a flowchart of an embodiment of transfer preparation and transfer processing in the transfer step of the present invention.
As shown in FIG. 4, the flowchart of the transfer preparation and the transfer process here shows the case where the toner image is transferred to only one sheet of printing paper.

As a premise, for example, the user selects the copy function of the image forming apparatus, places the original to be copied on the platen, sets and inputs setting items such as resolution and number of copies, and sets the original size manually or automatically. Suppose you typed it.
After that, when the user inputs an operation to execute the copy function, the control device of the image forming apparatus is assigned to a mechanism for executing the copy function (for example, a charging device, a developing device, a photoconductor drum, a transfer device, etc.). , Sends a signal to start operation.
When the transfer device 1 receives this operation start signal, the process shown in FIG. 8 is executed.

In step S1 of FIG. 8, the transfer processing unit 10 activates the transfer preparation process.
When the transfer preparation process is started, first, the detection voltage control unit 21 or the like executes a high-voltage trouble detection step.
In step S2, the detection voltage control unit 21 reads out the high voltage detection set time 51 stored in advance in the storage unit 50, sets the high voltage trouble detection period t1, and activates the timer t1.

In step S3, the transfer voltage application unit 12 applies a voltage to the transfer member 11 for high-voltage trouble detection processing, and outputs the trouble detection current of the current value corresponding to the high-voltage current set value a1 to the transfer member 11 ( Shed).
In step S4, the high-voltage trouble detection unit 14 executes the high-voltage trouble detection process.
In the high-voltage trouble detection process, a predetermined trouble detection signal is acquired to check whether or not a high-voltage trouble has occurred.
Examples of the trouble detection signal include an MHV-T signal and a THV-T signal.

If the timer t1 has not timed out in step S5, the process returns to step S3 and the high-voltage trouble detection process is executed until the timer t1 times out.
If the timer t1 times out, the process proceeds to step S6.

The above high-voltage trouble detection process checks the voltage level of the trouble detection signal to determine whether or not trouble detection has occurred, but the voltage level check shows the ON state, which is the state with trouble detection (abnormal state), and the trouble. The OFF state, which is a no-detection state (normal state), is the detection high-voltage information 53 (a0) acquired by the detection signal acquisition unit 13 and the high-voltage comparison information 54 (as), which is a preset threshold voltage. It is judged by comparing.
In high-voltage trouble detection, the voltage level of the trouble detection signal at a fixed determination interval is checked as a change in the voltage level of the trouble detection signal during the high-voltage trouble detection period t1.
The constant determination interval is, for example, set in advance for a time of about 50 msec, and is repeated a predetermined number of times (multiple times). When the specified number of times is detected as the ON state, it is determined that the trouble associated with the trouble detection signal has occurred (with trouble detection).
In addition, if the first half of the specified number of times is detected as the ON state and the remaining second half is detected as the OFF state, the trouble associated with the trouble detection signal has not occurred (no trouble detection). judge.

6 and 7 show explanatory views of an embodiment of the high-voltage trouble detection process in the high-voltage trouble detection period t1 of the transfer process.
FIG. 6 shows an embodiment in which the voltage level of the trouble detection signal is checked and it is determined that the trouble is detected.
FIG. 7 shows an embodiment in which the voltage level of the trouble detection signal is checked and it is determined that no trouble is detected.

In FIGS. 6 and 7, the vertical axis indicates the voltage level of the acquired trouble detection signal.
Here, the trouble detection signal is assumed to indicate either of two voltage levels, an ON state and an OFF state.
The horizontal axis of FIGS. 6 and 7 shows the time Tm, and the graph of the figure shows the change in the voltage level of the trouble detection signal during the high-voltage trouble detection period t1.

Depending on the determination result of such trouble detection, it is determined whether to perform subsequent transfer output to printing paper or to notify that a trouble has occurred.
The judgment criteria of the judgment interval, the number of judgments, and 5 consecutive times shown in FIGS. 6 and 7 are merely examples, and the judgment criteria are not limited to these, and different judgment times and judgment criteria may be used depending on the trouble detection signal. It may be set.

In step S6, the high-voltage trouble detection process is terminated and the output of the trouble detection current is stopped. In addition, the determination result of the above-mentioned high-voltage trouble detection process is acquired to determine the presence or absence of trouble detection.
If it is determined in step S7 that there is a trouble detection, the process proceeds to step S8, and if it is determined that there is no trouble detection, the process proceeds to step S9.
In step S8, the trouble detection content is displayed or a warning sound is sounded to notify the user that a trouble has occurred. After that, although not shown, the printing process of the image forming apparatus is interrupted and the process is terminated.

In step S9, in order to start the transfer adsorption process, the adsorption voltage control unit 22 reads out the adsorption process set time 55 stored in advance in the storage unit 50, sets the transfer adsorption period t2, and sets the timer t2. Start it.
In step S10, the adsorption voltage control unit 22 executes the transfer adsorption process.
In the transfer adsorption process, the transfer voltage application unit 12 applies a voltage for performing the transfer adsorption process to the transfer member 11, and outputs (flows) an adsorption current having a current value corresponding to the adsorption current set value a2 to the transfer member 11. ).
Further, the photoconductor drum 4 and the transfer belt 2 are rotated to adsorb the cover toner 5 adhering to the photoconductor drum 4 to the transfer belt 2.

If the timer t2 has not timed out in step S11, the process returns to step S10, and the transfer adsorption process is executed until the timer t2 times out.
If the timer t2 times out, the process proceeds to step S12.
The transfer adsorption process is carried out during the transfer adsorption period t2, but the fog toner 5 may be adsorbed on the transfer belt 2 only for a time such that the photoconductor drum 4 is rotated twice as described above.

In step S12, the transfer adsorption process is completed and the output of the adsorption current is stopped.
In step S13, a transfer process of transferring the toner image formed on the photoconductor drum to the printing paper is executed.
In the transfer process, the transfer belt 2 is driven in synchronization with the rotation of the photoconductor drum 4 on which the toner image is formed, and the printing paper 6 is conveyed in the direction of the transfer position.
Further, the actual transfer voltage control unit 30 applies a voltage for performing the transfer process to the transfer member 11 until the entire printing paper passes through the transfer position, and the current value corresponding to the transfer current set value a3 is applied to the transfer member 11. Outputs (flows) the transfer current of.

By outputting the transfer current in this way, the toner image formed on the photoconductor drum is transferred to the printing paper.
The transfer process is executed only for the transfer output period t3 corresponding to the transfer process set time 57 corresponding to the size of the printed paper to be conveyed.

If the transfer process has not been completed in step S14, the process returns to step S13.
In this embodiment, printing is performed on only one sheet of printing paper. Therefore, when the transfer processing on one sheet of printing paper is completed, the processing of this flowchart is completed.

(Example 2)
FIG. 5 shows an explanatory diagram of an embodiment of a change in the transfer current value when a plurality of printing sheets are continuously transferred in the transfer step of the present invention.
Here, an embodiment of a change in the transfer current value when the toner image is transferred to two sheets of printing paper that are continuously conveyed will be described.

When a plurality of printing sheets are continuously conveyed to the transfer position, the second sheet is printed after the transfer of the toner image to the first printing sheet is completed among the two adjacent printing sheets. In the inter-paper waiting period until the transfer of the toner image to the paper is started, the transfer preparation unit 20 executes the high-pressure trouble detection process before the second printing paper is transferred to the transfer position, and then the transfer preparation unit 20 executes the high-pressure trouble detection process. Perform the transfer adsorption process.

FIG. 5 shows an example of a graph of changes in the transfer current value in the transfer step, as in FIG. Again, the vertical axis is the current value TRi (transfer current value) of the current flowing through the transfer member 11, and the horizontal axis is time.
In FIG. 5, when the toner image is transferred to the first printing paper, the period on the horizontal axis of the transfer process is the high pressure trouble detection period t1, the transfer adsorption period t2, and the waiting period ta1 as in FIG. And the first transfer output period t3.

Similarly to FIG. 4, the current value of the current flowing through the transfer member 11 in the three periods (t1, t2, t3) is also the trouble detection current value a1 in the high-voltage trouble detection period t1 and the trouble detection current value a1 in the transfer adsorption period t2. It is the adsorption current value a2, and is the first actual transfer current value a3 in the transfer output period t3.
The transfer preparation and transfer process performed in the transfer step for the first printing paper are the same as those shown in Example 1, and thus the description thereof will be omitted.

When transferring to two printing papers in succession, the second printing paper is conveyed in the direction of the transfer position after the first transfer output period t3 of the first printing paper is completed. An inter-paper waiting period occurs until the transfer is actually performed on the second sheet of printing paper (until the second sheet transfer output period t32 starts). The inter-paper waiting period varies depending on the length and configuration of the paper transport path, the transport speed, and the like.
In FIG. 5, the inter-paper waiting period is the total period of the four periods (ta2, t12, t22, ta3).

As described above, it is preferable to apply a predetermined voltage to the transfer member 11 in order to prevent image defects from occurring even during the inter-paper standby period. Therefore, the inter-paper voltage control unit 23 informs the transfer member 11. Control the applied voltage.
Therefore, in the second embodiment, as shown in FIG. 5, even in the inter-paper waiting period, after a certain waiting period ta2, the high-voltage trouble detection period t12 and the transfer adsorption period t22 are the same as in the first printing paper. And a waiting period ta3.

That is, in the inter-paper standby period, the inter-paper voltage control unit 23 executes a two-step voltage application process on the transfer member 11 in preparation for transfer to the second printing paper.
First, in the high-voltage trouble detection period t12, a current having a trouble detection current value a12 is passed through the transfer member 11.
Although it depends on the length of the paper-to-paper standby period, the length of the high-voltage trouble detection period t12 may be set to be substantially the same as the initial high-voltage trouble detection period t1.
Further, the trouble detection current value a12 may be set to a value substantially equal to that of the first trouble detection current value a1.

In this way, by applying a relatively high voltage in the first half of the inter-paper standby period, the potential difference does not suddenly increase during the inter-paper standby period, so that image defects can be prevented. can.
Since the trouble detection process has already been performed during the high-voltage trouble detection period t1 as the preparation for transferring the first printing paper, it is not necessary to perform the trouble detection process during the high-voltage trouble detection period t12. However, the trouble detection process may be performed again during the high-voltage trouble detection period t12.

Then, in the transfer adsorption period t22, a current having an adsorption current value a22 is passed through the transfer member 11.
The transfer adsorption period t22 also depends on the length of the inter-paper waiting period, but may be set to be substantially the same length as the initial transfer adsorption period t2.
Further, the adsorption current value a22 may be set to a value substantially equal to the initial adsorption current value a2.
Even in this transfer adsorption period t22, the fog toner adhering to the photoconductor drum 4 is adsorbed on the transfer belt 2 by rotating the photoconductor drum 4 and the transfer belt 2.
As described above, by applying a relatively low voltage in the latter half of the inter-paper standby period, it is possible to suppress the occurrence of streaks on the second printing paper.

After the transfer adsorption period t22 ends and the waiting period ta3 elapses, the second transfer output period t32 starts in synchronization with the timing at which the second printing paper is conveyed to the transfer position.
In the second sheet transfer output period t32, the current of the second sheet actual transfer current value a32 is passed through the transfer member 11, and the toner image formed on the photoconductor drum 4 is transferred to the second sheet of printing paper. ..
The length of the waiting period ta3 may be set to the same length as the first waiting period ta1.
The length of the second sheet transfer output period t32 is set to a numerical value corresponding to the size of the second sheet of printing paper. If the size of the second printing paper is the same as that of the first printing paper, the second transfer output period t32 is set to the same value as the first transfer output period t3.
The second sheet actual transfer current value a32 may be set to a value substantially equal to that of the first sheet actual transfer current value a3.

After the second sheet transfer output period t32 is completed, the toner image formed on the photoconductor drum 4 is transferred to the second sheet of printing paper and conveyed to the fixing device side.
If there are two sheets of printing paper for continuous printing, the transfer process is completed, but if there are three or more sheets of printing paper for continuous printing, after the second transfer output period t32, the high-pressure trouble as described above An inter-paper waiting period including the detection period t12 and the transfer adsorption period t22 may be provided, and the transfer process may be performed on the third printing paper during the subsequent transfer output period for the third printing paper. The same applies when there is a transfer process on the fourth and subsequent printing papers.

FIG. 9 shows a flowchart of an embodiment of transfer preparation and transfer processing in the transfer step when printing a plurality of printing papers.
In the flowchart of FIG. 9, the same step number is assigned to the step that performs the same processing as the step shown in the flowchart of FIG.
Here, for example, when a user places two originals on an automatic document feeder and prints (copies) a copy of each original, or when one original is placed on a platen and five copies of the original are printed. Corresponds to processing such as printing.
The number of sheets to be printed (copied) shall be set and input by the user.

Similar to FIG. 8, when the transfer device 1 receives the signal for starting the operation for executing the copy function, the process shown in FIG. 9 is executed.
In step S1 of FIG. 9, the transfer preparation process is started in the same manner as in FIG.
Next, in step S21, the number of prints set and input by the user is set (temporarily stored) in the number of print sheets n.

After that, the processes from step S2 to step S14 are performed in the same manner as in FIG.
In steps S2 to S14, as described above, a transfer preparation process including a high-voltage trouble detection process and a transfer adsorption process is performed, and then a transfer process to the first printing paper is performed.
When the transfer process to the first printing paper is completed in step S14, the process proceeds to step S22.

In step S22, 1 is subtracted from the number of printing papers n to update the number of printing papers n (n = n-1).
In step S23, when the number of printing papers n is not n> 0, that is, when the number of printing papers n is zero and printing on all printing papers is completed, the transfer process is terminated.

On the other hand, when the number of printing papers n is n> 0, the printing paper to be printed still remains, so the process returns to step S2, the processes from step S2 to step S14 are executed, and the second printing paper is executed. The transfer preparation and transfer process for the paper are performed.
After that, similarly, the processes from step S2 to step S14 are repeatedly executed until printing on a plurality of preset printing sheets is completed.

However, although not shown in the flowchart of FIG. 9, as shown in the explanation of FIG. 5, the high-pressure trouble detection process has already been performed in the process of preparing the transfer for the first printing paper, so that the second and subsequent sheets are processed. In the process of preparing for transfer to the printing paper, it is not necessary to perform the high-voltage trouble detection process in step S4.
That is, for the second and subsequent printing sheets, steps S4 and S6, S7, and S8 may be omitted, and if the timer times out in step S5, the process may proceed to step S9.
The above is an example of transfer preparation and transfer processing in the transfer process when printing a plurality of printing papers.

(Example 3)
Here, in the case of double-sided printing, a case where the toner image is transferred to the front surface of one printing paper and then the toner image is continuously transferred to the back surface of the same printing paper will be described.
When the transfer to the front surface of the printing paper and the transfer to the back surface of the printing paper are continuously performed in order to transfer a predetermined toner image to the front surface and the back surface of one printing paper, the printing paper After the transfer of the toner image to the front surface is completed, the transfer preparation unit 20 starts the transfer to the back surface of the printing paper during the inter-paper waiting period until the transfer of the toner image to the back surface of the printing paper is started. Therefore, before the printing paper is conveyed to the transfer position, the high-pressure trouble detection process is executed, and then the transfer adsorption process is executed.

In double-sided printing, when the toner image is continuously transferred to the front surface and the back surface of one printing sheet, the transfer current value may be changed as in the second embodiment.
The continuous transfer treatment to the front surface and the back surface of one printing paper in this double-sided printing is similar to the continuous transfer treatment to two printing papers in Example 2.

FIG. 10 shows a flowchart of an embodiment of transfer preparation and transfer processing in the transfer step when printing on the front surface and the back surface of the printing paper.
In the flowchart of FIG. 10, the same step number is assigned to the step that performs the same processing as the step shown in the flowchart of FIG.
In FIG. 10, in order to distinguish between the front surface and the back surface of the printing paper to be transferred, the print surface information is temporarily stored, and when the front surface is transferred, the “front surface” is set and stored in the print surface information, and the back surface is transferred. When this is done, the "back side" shall be set and stored in the print side information. However, it is not always necessary to temporarily store the print surface information.

In addition, the user shall place the original to be printed on the platen, input the settings for double-sided printing, and input to start the copy function. In double-sided printing, two originals may be printed on both sides of one printing paper, or the information written on the front and back sides of one original may be printed on both sides of one printing paper. ..

Similar to FIG. 8, when the transfer device 1 receives the signal for starting the operation for executing the copy function, the process shown in FIG. 10 is executed.
In step S1 of FIG. 10, the transfer preparation process is started in the same manner as in FIG.
Next, in step S31, it is assumed that the front surface is printed first, and the "front surface" is set (temporarily stored) as the print surface information.

After that, as in FIG. 8, the timer t1 is started in step S2, and the trouble detection current is output (flowed) to the transfer member 11 in step S3.
Next, in step S32, it is checked whether or not the print surface information is set on the surface. If the print surface information is set to "front side", the process proceeds to step S4, the high-voltage trouble detection process is executed, and the process proceeds to step S5.
On the other hand, if the print side information is set to "back side", the process proceeds to step S5.
In step S5, if the timer t1 has not timed out, the process returns to step S3, and if the timer t1 has timed out, the process proceeds to step S33.

In step S33, as in step S32, it is checked whether or not the print surface information is set to the front surface, and if the print surface information is set to "front surface", the process proceeds to step S6 and the print surface information is set. If is set to "Back", proceed to step S9.
Steps S6, S7, and S8 are the same as those in FIG. 8, and when a trouble is detected, for example, the trouble content is displayed and the process ends.
If no trouble is detected in step S7, the process proceeds to step S9.

After that, from step S9 to step S14, the same process as in FIG. 8 is performed, and the transfer adsorption process and the transfer process to the surface of the printing paper are executed.
When the transfer process to the surface of the printing paper is completed in step S14, the process proceeds to step S34.
In step S34, it is checked whether or not the printing process on the back side of the printing paper is completed, and if the printing process on the back side is completed, the process is ended.
On the other hand, if the printing process on the back surface is not completed again, the process proceeds to step S35.

In step S35, the back side is printed next, so the “back side” is set (temporarily stored) as the print side information.
In step S36, the printing paper transfer process is executed in order to print the back side.
Here, the printing paper whose front surface has been printed is guided to a predetermined transfer path, and the printing paper is conveyed in the direction of the transfer position so that the toner image can be transferred to the back surface.

After step S36, the process returns to step S2 to perform transfer preparation and transfer processing on the back surface of the printing paper.
Here, too, the processes of steps S2 to S14 of FIG. 10 are executed, but since the “back side” is set as the print surface information, the processes of steps S4 and steps S6, S7, and S8 are executed. Instead, the process proceeds to step S9, and the transfer adsorption process of step S10 is further executed.
After that, in step S13, the transfer process on the back surface of the printing paper is executed, and when the transfer process on the back surface is also completed in step S34, the transfer process on both sides of one printing paper is completed.

Note that FIG. 10 shows a case where transfer preparation and transfer processing are performed on both sides of one printing paper, but when double-sided printing is performed on both sides of a plurality of printing papers, FIG. By combining the processes shown in FIG. 10, transfer preparation and transfer processing for both sides of one printing paper as shown in FIG. 10 may be repeated for the number of printing papers preset and input.

(Example 4)
In Examples 2 and 3 described above, a high-voltage trouble detection period and a transfer adsorption period are provided in the inter-paper standby period.
However, in order to suppress the occurrence of streaks on the printing paper to be transferred after the inter-paper waiting period elapses, at least a transfer adsorption period is provided in the inter-paper waiting period, and a current sufficient to allow the fog toner to be adsorbed on the transfer belt. A current having a relatively low current value may be allowed to flow through the transfer member 11.
That is, in the inter-paper standby period, only the transfer adsorption period may be provided without providing the high-voltage trouble detection period. As a result, it is possible to suppress the occurrence of streaks on the printing paper.

1 Transfer device,
2 Transfer belt,
3a belt drive roller,
3b belt driven roller,
3c Cleaning facing roller,
4 Photoreceptor drum,
5 toner,
6 Printing paper,
10 Transfer processing unit,
11 Transfer member,
12 Transfer voltage application part,
13 Detection signal acquisition unit,
14 High-voltage trouble detector,
20 Transcription Preparation Department,
21 Detection voltage control unit,
22 Adsorption voltage control unit,
23 Paper-to-paper voltage control unit,
30 Actual transfer voltage control unit,
50 storage,
51 High voltage detection set time (t1),
52 High voltage current set value (a1),
53 Detection high voltage information (a0),
54 High pressure comparison information (as),
55 Adsorption processing set time (t2),
56 Adsorption current set value (a2),
57 Transfer processing set time (t3),
58 Transfer current set value (a3),
71 Charging device,
72 exposure equipment,
73 Developer,
74 Fixing device

Claims (10)

It includes a photoconductor drum on which a toner image to be transferred to a recording medium is formed, a transfer belt, and a transfer device that transfers a toner image formed on the surface of the photoconductor drum to the recording medium.
The transfer device
A transfer member that is arranged so as to contact the back surface of the transfer belt at a transfer position where the photoconductor drum and the front surface of the transfer belt come into contact with each other and transfers the toner image to a recording medium conveyed to the transfer position.
A transfer voltage application unit that applies a predetermined transfer voltage to the transfer member,
A transfer preparation unit that executes a transfer preparation process including a high-pressure trouble detection process and a transfer adsorption process before transferring the toner image to the recording medium.
An image forming feature is provided with an actual transfer voltage control unit that controls the transfer voltage application unit so that the actual transfer voltage required for transferring the toner image to the recording medium is applied to the transfer member. Device. The high-voltage trouble detection process is a process for detecting whether or not the transfer output given to the transfer member is normal.
The transfer adsorption process is a process for adsorbing the toner remaining on the photoconductor drum to the transfer belt.
The transfer preparation unit executes the high-voltage trouble detection process before the recording medium is conveyed to the transfer position, and then executes the transfer adsorption process.
After the transfer adsorption process, during the transfer output period when the recording medium passes through the transfer position, the actual transfer voltage control unit applies the actual transfer voltage to the transfer member by the transfer voltage application unit. The image forming apparatus according to claim 1, wherein the toner image is transferred to the recording medium. The transfer preparation unit
A detection voltage control unit that controls the transfer voltage application unit so as to apply a voltage required for executing the high-voltage trouble detection process to the transfer member.
In the transfer adsorption process, the adsorption voltage control that controls the transfer voltage application unit so that the voltage required for adsorbing the toner remaining on the photoconductor drum to the transfer belt is applied to the transfer member. With a department
The invention according to claim 1 or 2, wherein the current value of the adsorption current flowing through the transfer member in the transfer adsorption process is lower than the current value of the trouble detection current flowing through the transfer member in the high-voltage trouble detection process. Image forming device. The transfer member is a transfer roller that comes into contact with the back surface of the transfer belt and rotates in the transport direction of the recording medium. The transfer roller rotates to rotate the transfer belt.
In the transfer adsorption process, the transfer voltage application unit applies a predetermined transfer voltage to the transfer roller to apply a charge having a polarity opposite to that of the toner remaining on the photoconductor drum on the surface of the transfer belt. The image forming apparatus according to any one of claims 1 to 3, wherein the toner generated and remaining on the photoconductor drum is adsorbed on the transfer belt. When a plurality of recording media are continuously conveyed to the transfer position,
Wait between sheets until the transfer of the toner image to the first recording medium is completed and the transfer of the toner image to the second recording medium is started among the two adjacent recording media. In the period
The image forming apparatus according to claim 1 or 2, wherein the transfer preparation unit executes the transfer adsorption process before the second recording medium is conveyed to the transfer position. When the transfer to the front surface of the recording medium and the transfer to the back surface of the recording medium are continuously performed in order to transfer a predetermined toner image to the front surface and the back surface of one recording medium, respectively.
In the inter-paper waiting period from the completion of the transfer of the toner image to the front surface of the recording medium to the start of the transfer of the toner image to the back surface of the recording medium.
According to claim 1 or 2, the transfer preparation unit executes the transfer adsorption process before the recording medium is conveyed to the transfer position in order to start the transfer of the recording medium to the back surface. The image forming apparatus according to the description. The photoconductor drum is a cylindrical member in which the toner image is formed on the side surface of a cylinder and is rotationally driven around a cylindrical axis.
The image forming apparatus according to claim 1 or 2, wherein the transfer adsorption process is performed at least for a transfer adsorption period corresponding to the time required for the photoconductor drum to make two rounds. The image forming apparatus according to any one of claims 1 to 7, wherein the transfer belt is an endless belt in which a convex line is formed at a seam portion. The toner image is placed on a recording medium that is arranged so as to come into contact with the back surface of the transfer belt at a transfer position where the photoconductor drum formed on the surface of the toner image and the surface of the transfer belt come into contact with each other. And the transfer member that transfers
A transfer voltage application unit that applies a predetermined transfer voltage to the transfer member,
A transfer preparation unit that executes a transfer preparation process including a high-pressure trouble detection process and a transfer adsorption process before transferring the toner image to the recording medium.
It is provided with an actual transfer voltage control unit that controls the transfer voltage application unit so that the actual transfer voltage required for transferring the toner image to the recording medium is applied to the transfer member.
The high-voltage trouble detection process is a process for detecting whether or not the transfer output given to the transfer member is normal.
The transfer adsorption process is a process for adsorbing the toner remaining on the photoconductor drum to the transfer belt.
The transfer preparation unit executes the high-voltage trouble detection process before the recording medium is conveyed to the transfer position, and then executes the transfer adsorption process.
After the transfer adsorption process, during the transfer output period when the recording medium passes through the transfer position, the actual transfer voltage control unit applies the actual transfer voltage to the transfer member by the transfer voltage application unit. A transfer device for transferring the toner image to the recording medium. It is a transfer method of an image forming apparatus.
The image forming apparatus transfers the photoconductor drum on which the toner image to be transferred to the recording medium is formed on the surface, the transfer belt, and the toner image formed on the surface of the photoconductor drum to the recording medium. Including equipment
The transfer device
A transfer member that is arranged so as to contact the back surface of the transfer belt at a transfer position where the photoconductor drum and the front surface of the transfer belt come into contact with each other and transfers the toner image to a recording medium conveyed to the transfer position.
A transfer voltage application unit that applies a predetermined transfer voltage to the transfer member,
A transfer preparation unit that executes a transfer preparation process including a high-pressure trouble detection process and a transfer adsorption process before transferring the toner image to the recording medium.
It is provided with an actual transfer voltage control unit that controls the transfer voltage application unit so that the actual transfer voltage required for transferring the toner image to the recording medium is applied to the transfer member.
Before the recording medium is delivered to the transfer position
A step in which the transfer preparation unit executes a high-pressure trouble detection process for detecting whether or not the transfer output given to the transfer member is normal, and
After that, a step of executing a transfer adsorption process for adsorbing the toner remaining on the photoconductor drum to the transfer belt, and
After the transfer adsorption process, during the transfer output period when the recording medium passes through the transfer position, the actual transfer voltage control unit applies the actual transfer voltage to the transfer member by the transfer voltage application unit. A transfer method of an image forming apparatus, which comprises a step of transferring the toner image to a recording medium passing through the transfer position.

Images