JP7312372B2 - Transfer device and image forming device - Google Patents

Description

The present invention relates to a transfer device and an image forming apparatus.

2. Description of the Related Art Conventionally, there has been known a transfer device provided with control means for switching on or off the charge removing function of a charge removing means for a member in contact with a sheet material in the vicinity of a transfer area where an image is transferred from an image bearing member to a sheet material by applying a transfer bias.
For example, Patent Document 1 discloses a transfer apparatus of this type, which is installed in the vicinity of a transfer position facing a conveying path of a sheet material, and among a plurality of members near the conveying path that are in contact with the sheet material or within a certain distance range when a transfer bias is applied, at least one of the members is provided with a neutralizing mechanism and is grounded by a conductive material. It is disclosed that the transfer current is prevented from leaking, and the static electricity accumulated in the member near the conveying path is grounded and discharged by turning on for a predetermined time at a time other than when the transfer bias is applied.

However, in the conventional transfer device, since static electricity is not removed when the transfer bias is applied, there is a problem that the unfixed toner image is disturbed by the contact between the member near the transfer path and the transfer paper charged during printing and the discharge, resulting in an abnormal image such as dust and blur.

In order to solve the above-described problems, the present invention provides a transfer apparatus comprising control means for switching ON/OFF of the charge removing function of the charge removing means for a member in contact with the sheet material in the vicinity of a transfer area where an image is transferred from an image bearing member to the sheet material by applying a transfer bias, wherein the control means uses information regarding the sheet material as information for ON/OFF switching.The information is the electrical resistance of the sheet material, and when the electrical resistance is within a high range, the static elimination function is turned on, and when the electrical resistance is within a range lower than the high range, the static elimination function is turned off, and information on the number of sheets continuously fed in a print job is also used as the on/off switching information.It is characterized by

According to the present invention, there is an effect that abnormal images such as dust and blur can be reduced compared to the conventional art.

1 is an explanatory diagram of the overall configuration of an image forming apparatus according to the embodiment; FIG. FIG. 10 is an explanatory diagram of the overall configuration of an image forming apparatus according to a modification; FIG. 2 is an enlarged view of the vicinity of a transfer position in the image forming apparatus of FIG. 1; FIG. 4 is an explanatory diagram of an example of a switchable configuration; 4 is an operation flow according to Operation Example 1; FIG. 11 is an operation flow according to Operation Example 2; FIG. FIG. 11 is an operation flow according to Operation Example 3; FIG.

An embodiment in which the present invention is applied to an electrophotographic image forming apparatus will be described. FIG. 1 is a diagram for explaining the overall configuration of an image forming apparatus according to this embodiment. The image forming means 100 has a drum-shaped photoreceptor 1 as a first image carrier that rotates counterclockwise.

A writing device 11 is provided on the left side of the image forming means 100 in FIG. A toner bottle 13 is provided above the image forming means 100 . The toner bottle 13 supplies toner to the image forming means 100 by being rotationally driven.

At the transfer position, a transfer roller 5 is pressed against the photoreceptor 1 by an urging member so as to be in contact with the photoreceptor 1, and is in contact with the toner image bearing surface of the photoreceptor 1 to form a pressure contact portion, which is a transfer nip. A transfer bias is applied to the transfer roller 5 by a power supply, and a transfer electric field is formed in the transfer nip positioned between the roller 5 and the grounded photoreceptor 1 . Examples of the transfer roller 5 include a metallic roller or a roller in which a core bar is covered with a conductive elastic layer having a volume resistivity of 1×10 ⁵ Ω·cm to 1×10 ¹² Ω·cm, a thickness of 2 mm to 10 mm, and a rubber hardness of 10 degrees to 100 degrees. This elastic layer is preferably made of a foaming material.

In FIG. 1, a contact type transfer roller is shown as the bias applying section, but the bias applying section may be of a transfer belt type as shown in FIG. 2 instead of the transfer roller. In the transfer belt system, the transfer belt 4 is wound around a driving roller 17, a driven roller 18, and a transfer roller 5 so as to be able to travel clockwise in the figure. A cleaning device 9 for cleaning the surface of the transfer belt 4 is provided opposite the driven roller 18 .

A paper feed tray 20 is provided in the lower part of the main body of the image forming apparatus, and a transfer paper P, which is a sheet material fed from the paper feed tray 20 by a paper feed roller 21, reaches a registration roller pair 19, where the skew is corrected and then conveyed to a transfer position by the registration roller pair 19 at a predetermined timing. The toner image is transferred while passing through this transfer position. The transfer paper on which the toner image has been transferred is conveyed to the fixing device 8 . A temperature/humidity sensor 22 is also provided as an environment sensor for measuring the environment in the vicinity of the transfer position near the upstream of the pair of registration rollers 19 in the conveying direction. Note that the temperature/humidity sensor 22 may be located near the downstream of the pair of registration rollers 19 in the conveying direction.

The fixing device 8 includes a heating roller 14, a pressure roller 16, and a pressure roller cleaning roller 15. The heating roller 14 and the pressure roller 16 form a fixing nip. The toner image is fixed by the fixing device 8 on the transfer paper P to which the toner image has been transferred, and an image is formed.

FIG. 3 is an enlarged view of the vicinity of the transfer position in the image forming apparatus of FIG. The neutralization mechanism will be described by exemplifying the case of the transfer method using the transfer roller in FIG. 1, but the operation of the neutralization mechanism is the same in the case of the transfer belt method in FIG. As shown in FIG. 3, a conveying member 7, which is a member that contacts the transfer paper (sheet material) P, is provided in the vicinity of the transfer position upstream in the conveying direction. The conveying member 7 is a sheet attached to the entire conveying surface of the developing device 3 in the longitudinal direction for the purpose of conveying the transfer paper P smoothly. Polyethylene is used as the raw material for the material to give it more slidability. A guide plate made of metal may be used as long as it does not interfere with the transportation of the transfer paper. The conveying member 7 may be located downstream of the pair of registration rollers 19 in the conveying direction.

During printing, the conveying member 7 comes into contact with the transfer paper, rubs against it, and is electrified. Therefore, when static electricity is accumulated during printing and becomes a high potential, before the toner image is transferred to the transfer paper, the transfer paper is partially charged due to contact between the conveying member 7 and the transfer paper and discharge, which causes deterioration of image quality such as dust and unevenness. Therefore, the neutralization mechanism 30 is provided to neutralize the charge on the conveying member 7 that has been charged during printing.

The neutralizing mechanism 30 according to the embodiment is configured to ground the conveying member 7 to the side plate of the main body, and includes a configuration 31 capable of switching between grounding and non-grounding. FIG. 4 is an explanatory diagram of one configuration example of the switchable configuration 31 . For example, by turning on and off a driving device 32 such as a solenoid to rotate the earth plate 33 around the fulcrum 34, the ground plate 33 can be selectively taken between a posture in contact with the main body side plate 35 and a posture separated from the main body side plate 35.例文帳に追加This ground plate 33 is electrically connected to the conveying member 7 . This is a mechanism for switching between ON and OFF of the neutralization function for the conveying member 7 .

[Switching operation example 1]
The ON/OFF switching operation of the static elimination function of the static elimination mechanism 30 will be described. At the time of printing, it is possible to judge whether the transfer paper is low-resistance paper or high-resistance paper, and to change whether the conveying member 7 is grounded or not. Specifically, when the transfer paper is determined to be low-resistance paper, the transfer current from the transfer roller 5 tends to flow to the transfer paper, so the grounding of the conveying member 7 is turned off by separating the grounding plate from the main body side plate (grounding) by the driving device. On the other hand, when the transfer paper is determined to be a high-resistance paper, the transfer current from the transfer roller 5 is difficult to flow to the transfer paper, so that the grounding of the conveying member 7 is turned on by bringing the grounding plate into contact with the main body side plate (grounding) by the driving device. The earth is turned ON for the purpose of eliminating static electricity from the conveying member 7 except when printing.

Table 1 is a table showing an example of the resistance range of low-resistance paper and high-resistance paper, and the relationship between the resistance value and ground ON/OFF (on/off of the neutralization function).

As shown in Table 1, low resistance paper is used for less than 10 ¹⁰ Ω (range of relatively low electrical resistance values), and high resistance paper is used for 10 ¹² Ω or more (range of relatively high electrical resistance values). In the resistance value range of 10 ¹⁰ Ω to 10 ¹² Ω (intermediate range of electrical resistance values), the ground is turned off to prevent transfer leakage during printing. In addition, since low resistance paper is difficult to electrify the conveying member and conversely high resistance paper is easy to electrify the conveying member, the above configuration is adopted from the above point of view. Note that the threshold value of electrical resistance may be changed as appropriate.

The resistance value of the transfer paper can be obtained as follows. As a method of applying a transfer voltage to the transfer roller 5 during printing, a constant current control method is used in which the current during printing is maintained at a predetermined current by adjusting the voltage with a power supply device. In this case, the resistance value of the transfer paper can be calculated by Ohm's law from the fluctuation of the transfer voltage during printing by constant current control. Alternatively, a resistance measuring device may be provided for directly measuring the resistance of the transfer paper in the transport path. Alternatively, the user may select the paper type to be used from the operation panel used for operation, and retrieve the corresponding resistance value from a data table storing the resistance value for each paper type.

FIG. 5 is an operation flow of ground ON/OFF according to the resistance value during printing according to Operation Example 1. FIG. First, a copy or printer Job signal is acquired (S1). The job number is determined from the acquired job information (S2), and if the job is determined to be a one-off job, printing is performed with the earth OFF (S3). If the job is determined to be a continuous job of two or more sheets, the ground is turned off, the first sheet is printed, and the resistance value is calculated at that time (S4). It is determined whether or not this resistance value is 10 ¹² Ω or more (S5). If it is determined to be 10 ¹² Ω or more, the earth is turned ON (S6). If it is determined to be less than 10 ¹² Ω, the earth is turned off (S7), and the next printing is performed (S8). Next, at the end of printing, it is determined whether or not there is a next job (S9), and if there is a next job, continue printing.

[Switching operation example 2]
Table 2 is a table showing the relationship between the resistance value and ground ON/OFF (on/off of the neutralization function) according to another operation example.

In this operation example 2, temperature and humidity information is used in addition to the resistance value in operation example 1 as the ground ON/OFF operation condition. When the absolute humidity detected and calculated by the temperature/humidity sensor 22 (see FIGS. 1 and 2) is less than 1.9 g/m3 (low-temperature, low-humidity environment), the conveying member 7 is likely to be electrified due to ^friction during conveyance with the transfer paper. If the resistance is less than 10 ¹⁰ Ω, the transfer bias may leak, so the ground is turned off. Note that the absolute temperature threshold may be changed as appropriate.

FIG. 6 is an operation flow of ground ON/OFF according to resistance value and temperature/humidity information during printing according to operation example 2. FIG. First, a copy or printer Job signal is acquired (S1). The job number is determined from the acquired job information (S2), and if the job is determined to be a one-time job, printing is performed with the ground OFF (S3). If the job is determined to be a continuous job of two or more sheets, the ground is turned off, the first sheet is printed, and the resistance value is calculated at that time (S4). When this resistance value is determined to be 10 ¹² Ω or more, the ground is turned ON (S6) and the next printing is performed (S8). If it is determined to be less than 10 ¹² Ω, it is further determined whether it is ^{10 10} Ω or more (S20). If it is determined to be 10 ¹⁰ Ω or more, it is determined that the absolute humidity is <1.9 g/m3 (S21). If Yes, the ground is turned on (S6), and if No, the ground is turned off (S7), and the next printing is performed (S8). When the next job finishes printing, it is determined whether or not there is a next job (S9). If there is, continue printing. If not, stop the machine (S10), turn the ground ON (S11), and wait for the next job.

[Switching operation example 3]
Table 3 is a table showing the relationship between the resistance value and ground ON/OFF (on/off of the neutralization function) according to still another operation example.

In this operation example 3, in addition to the resistance value in operation example 1, job information for printing is used as the ground ON/OFF operation condition. In the case of a job of printing a predetermined number of sheets, for example, 100 sheets or more in succession, the transfer member 7 continuously rubs against the transfer paper and is more likely to be charged. For this reason, as shown in Table 3, when the number of printed sheets reaches 100 or more even when the resistance value is 10 ¹⁰ Ω or more, the earth is turned ON in jobs from the 101st sheet in order to prevent charging of the conveying member 7 . If the resistance is less than 10 ¹⁰ Ω, the transfer bias may leak, so the ground is turned off. It should be noted that the ground ON/OFF operation may be corrected in consideration of both the temperature/humidity information and the job information of printing in Operation Example 2. FIG. Note that the threshold for the number of consecutive jobs may be changed as appropriate.

FIG. 7 is an operation flow of ground ON/OFF according to resistance value during printing and job information of printing according to operation example 3. FIG. First, a copy or printer Job signal is acquired (S1). Based on the acquired job information, the number of jobs is determined (S2), and if it is determined that the job is a one-time job, printing is performed with the earth OFF (S3). If the job is determined to be a continuous job of two or more sheets, the ground is turned off, the first sheet is printed, and the resistance value is calculated at that time (S4). When this resistance value is determined to be 10 ¹² Ω or more, the ground is turned ON (S6) and the next printing is performed (S8). If it is determined to be less than 10 ¹² Ω, it is further determined whether it is ^{10 10} Ω or more (S30).

If it is determined to be 10 ¹⁰ Ω or more, it is determined whether the job is 100 sheets or more (S31). If it is determined that the job is not 100 sheets or more, the earth is turned off (S7), and the next printing is performed (S8). If it is determined that the number of sheets in the job is 100 or more, the next printing is performed with the ground OFF as it is (S32), and it is determined whether the total number of printed sheets (the number of sheets continuously passed) in the job determined to be 100 or more is 100 (S33). If the judgment of whether the total number of prints≧100 is NO, the next printing with the ground OFF and the judgment of whether the total number of prints≧100 after printing are repeated until the judgment is YES. At the end of printing of the next job in S8, it is determined whether or not there is a next job (S9), and if there is, printing is continued, and if there is not, the machine is stopped (S10), the ground is turned on (S11), and the next job is waited for.

Reference Signs List 1 : Photoreceptor 2 : Charging roller 3 : Developing device 4 : Transfer belt 5 : Transfer roller 6 : Cleaning device 7 : Conveying member 8 : Fixing device 11 : Writing device 13 : Toner bottle 14 : Heating roller 15 : Pressure roller Cleaning roller 16 : Pressure roller 17 : Drive roller 18 : Driven roller 19 : Registration roller pair 20 : Paper feed tray 21 : Paper feed roller 22 : Temperature and humidity sensor 30 : Eliminating mechanism 31 : switchable configuration 32 : drive device 33 : earth plate 35 : main body side plate 100 : image forming means P : transfer paper

JP 2009-128481 A

Claims (3)

A transfer device comprising control means for switching on/off a charge removing function of the charge removing means for a member in contact with the sheet material upstream in the sheet material conveying direction from a transfer position for applying a transfer bias to transfer an image from an image bearing member to the sheet material,
The control means uses information about the sheet material as information for switching on and off,
On/off switching using the information is switching between on and off of the static elimination function during printing,
the information is the electrical resistance of the sheet material;
turning on the static elimination function when the electrical resistance is within a high range, and turning off the static elimination function when the electrical resistance is within a range lower than the high range;
The transfer device is characterized in that information on the number of sheets continuously passed in a print job is also used as the on/off switching information . The transfer device of claim 1,
When the electrical resistance is within a predetermined range, the static elimination function is turned on when the number of sheets continuously passed is equal to or greater than a predetermined number, and the static elimination function is turned off when the number of sheets continuously passed is less than the predetermined number. In an image forming apparatus equipped with a transfer device,
3. An image forming apparatus, wherein the transfer device according to claim 1 is used as the transfer device.

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