JP2010249864A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic copying device that is not complicated for state measuring of a recording medium, does not cause transfer omission also in a highly wet state, and does not cause jam of the recording medium. <P>SOLUTION: The image forming apparatus includes: a recording medium-feeding means 42 for feeding the recording medium P stored in a recording medium storing means 40 sequentially from the uppermost layer; a measuring means 46 for measuring leaving period of the recording medium in the recording medium storing means; and a setting means 49 for setting type and material of the recording medium P. A transfer device has a transfer power source for supplying transfer voltage. The transfer device constant-current-controls the transfer current supplied from the transfer power source based on the set recording medium and the measured leaving period, and secures the optimal transferability. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or the like that supplies a large quantity or various types of recording media from a mass feeding apparatus called a paper feeding bank.

In general, an image forming apparatus using an electrophotographic method charges and exposes a photoconductive photosensitive member to form an electrostatic latent image on the photosensitive member, and then the electrostatic latent image contains a colorant and the like. The toner image is developed with fine particle toner, and the obtained toner image is transferred and fixed on a recording medium to obtain a recorded image.
As a method for developing the toner, a magnetic brush development method using a two-component developer composed of a toner capable of high-speed and high-quality development and a magnetic carrier is often used. In recent years, for the purpose of developing electrostatic latent images that have become finer due to the demand for higher image quality, the particle size of toner and carrier has also been reduced, fine particle toner having a volume average particle size of 10 μm or less, and weight average particle size of 100 μm or less. Application of fine particle carriers is underway.
In an image forming apparatus that requires a color image, a visible image formed on a photoconductor is usually transferred to an intermediate transfer member by using yellow, magenta, cyan, and black toner filled in the developing device. Then, the superimposed visible images are collectively transferred to a recording medium by a transfer device, thereby forming a toner image on the recording medium, and then fixing the toner image by a fixing device.

As a method for fixing a toner image, a heat roller fixing method that has high thermal efficiency and enables high-speed fixing is often used. In the heat roller fixing method, a toner image is directly brought into contact with a metal heating roller having a heat source inside and heated to a temperature sufficient to melt the toner, and at the same time, pressure is applied by a pressure roller to both the rollers. In this method, fixing is performed by passing a recording medium in between.
In an image forming apparatus using such an electrophotographic system, a sheet cut into a predetermined size, a so-called cut sheet, is usually used as a recording medium made of plain paper, high-quality paper, or the like. A so-called paper feed unit is installed in which a sheet as a recording medium is loaded into a part of the image forming apparatus and is sent to the image forming unit for each sheet.
2. Description of the Related Art In recent years, in an image forming apparatus, a paper feeding unit is separated from an image forming unit and the paper feeding device is installed independently due to the expansion of the POD (Print On Demand) market, which is a method for printing according to demand. The paper feeding device is characterized in that it can feed a large amount of recording media on the order of several thousand sheets. In the paper feeding device, there are many cases where almost all of the recording media fed in large quantities, that is, the loaded amount is almost used up.

In general, a bundle of recording media wrapped with coated paper or plastic film is taken out from the package, and this bundle of recording media is loaded into a paper feeding device, and this is fed one by one to the image forming unit. Image formation has been performed by transporting the recording medium to a transfer unit, a fixing unit, and the like of the image forming unit by sending out by means using air.
Conventionally, plain paper or high-quality paper has been used as the recording medium, and since the adhesive force between the overlapping recording media is low and the air permeability is low, the recording medium bundle is loaded when the recording medium is loaded into the paper feeding unit as a bundle. However, it was easy to become familiar with the installation environment of the paper feeding unit, and at the time of image formation, high image quality could be ensured according to the image formation conditions for plain paper and high-quality paper that matched the installation environment.
However, in recent years, it has become necessary to transport various types of recording media, including those with high surface smoothness. In particular, with the progress of colorization technology, whiteness has increased and gloss has been achieved. Coated paper (a recording medium coated with a coat layer for the purpose of improving printability on both sides or one side of a sheet) is used.

In such an image forming apparatus, the resistance value of a recording medium as a sheet has a great influence when electrostatically transferring a toner image. That is, if the resistance value of the recording medium is too higher than the allowable range, a discharge or the like occurs during electrostatic transfer, resulting in an image quality defect. It is known that the moisture content of the recording medium has a great influence on the resistance value of the recording medium.
Therefore, a heater for reducing the moisture content of the recording medium (increasing the resistance value of the recording medium) and the moisture content of the recording medium are increased (recording) in the paper feeding device that supplies the recording medium to the transfer device. 2. Description of the Related Art An image forming apparatus has been proposed in which a humidifier for reducing a medium resistance value is attached and a recording medium can be set to a desired moisture content (resistance value) (see Patent Documents 1 to 3). .
However, the above-described prior art apparatus is a serious problem in terms of power consumption and apparatus cost. In addition, it is known that these coated papers have strong adhesion between overlapping recording media. As the quality of coated paper increases, the coating amount increases and the white glossiness increases, and the unevenness of the paper surface decreases and the smoothness increases.
When the smoothness of the surface becomes high, it becomes difficult for air to pass through the gaps between the stacked papers, and if you try to peel the papers that touch each other, negative pressure is maintained, and the recording medium (paper) strongly adheres and pulls. It becomes difficult to peel off. As a method for eliminating such close contact with the recording medium during feeding, Japanese Patent Application Laid-Open No. 2004-228561 proposes a technique of blowing air from the side surface of the loaded recording medium.

Of course, such a recording medium having strong adhesion between the recording media has a very strong adhesion not only with the adsorbing force between the recording media but also with a member with which the recording medium comes into contact. On the other hand, regarding the adhesion of the recording medium, the amount of water contained in the recording medium, that is, the water content is greatly affected, and as the moisture content of the recording medium increases, the degree of adhesion increases, and it is difficult to peel off from the contact partner member. It has been. Therefore, it is difficult to ensure the separation performance from the image carrier under the conditions set in the room temperature environment.
In addition, some measure humidity and feed it back to the separation current, but after measuring the humidity, the humidity is uniformly defined as such separation current, and attention is paid to the stack position of the recording medium. However, if the paper is passed continuously at a high humidity of 20 sheets or more, an excessive current causes a problem of transfer repelling on the image quality as described above.
By the way, in the prior art, measures against moisture absorption of the recording medium were taken from the viewpoint of preventing paper jams and double feeding. However, image defects or separation failures occurred in the recording medium that is the fed printing paper. However, due to lack of consideration for the recording medium, the specific image forming conditions are not set for the recording medium that has absorbed moisture and increased the water content, and depending on the condition of the recording medium, it may cause serious image loss or jamming. May cause disability.
Further, according to the configuration for detecting the resistance value of the recording medium disclosed in Patent Document 3, it is possible to execute the transfer process satisfactorily to some extent without being affected by the environmental temperature and humidity in which the image forming apparatus is installed. .

However, in the technique of Patent Document 3, the device configuration of the paper feed system from the paper feed cassette to the transfer device is complicated, and the control for synchronizing the paper feed timing and the voltage application timing is complicated. In addition, there are cases where transfer residuals and separation failures are caused by the charge remaining on the transfer paper.
Furthermore, measuring the resistance value of the recording medium (transfer paper) one by one is not preferable because the mechanism becomes large and, further, jamming of the recording medium occurs. Similarly, it is not preferable to measure the water content one by one because the operation is complicated. Further, jams due to poor separation of recording media in the image forming apparatus tend to occur frequently once they occur, and countermeasures for this have become important.
As a result of repeated studies focusing on the relative humidity of the atmosphere inside the recording medium storage unit in the recording medium stored in the recording medium storage unit of the image forming apparatus, the present inventor has determined that the moisture content of the stored recording medium and the recording medium It has been found that there is a close relationship with the relative humidity inside the storage means. Further, it has been found that the humidity is influenced in order from the uppermost layer stacked depending on the time of being left in the environment inside the recording storage means, which changes with the passage of time, and that the change occurs in a very short time.

If the recording medium storage time inside the recording medium storage means is not within the predetermined range, paper feeding is prohibited, so that a paper jam or a paper jam that occurs when a recording medium with an unstable moisture content is fed can be obtained. It has been found that image defects can be prevented.
Since the relationship between the surface resistance of the recording medium and the moisture content of the recording medium varies depending on the method of surface processing of the recording medium, information on the method of surface processing of the recording medium, that is, the type of the recording medium is also important. It has become. Therefore, it has been found that it is important to reflect the information of the type of the recording medium.
In view of the above circumstances, the object of the present invention is to make the recording medium jam without complicating the apparatus for measuring the state of the recording medium and without causing transfer omission even in a high humidity state. It is an object of the present invention to provide an electrophotographic copying apparatus that does not cause any trouble.
Another object is to suppress the occurrence of image quality defects due to moisture absorption when forming an image on a recording medium, and to prevent the occurrence of poor separation from the image carrier due to moisture absorption when the recording medium is separated from the image carrier. .

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a toner image is formed on an image carrier using an electrophotographic method, and the toner is transferred to the recording medium, and then the recording medium is transferred to the recording medium. In an image forming apparatus to be separated from an image carrier, a recording medium accommodating unit that stacks and accommodates the recording medium, and a recording medium sending unit that sequentially feeds the recording medium accommodated in the recording medium accommodating unit from the uppermost layer. Measuring means for measuring the recording medium storage time in the recording medium housing means, and setting means for setting the type and material of the recording medium, and the image on the image carrier is recorded on the recording medium. A transfer power supply for supplying a transfer voltage, and the transfer device transfers the transfer power based on the recording medium set by the setting means and the standing time measured by the measurement means. The transfer current supplied to the constant current control from, and wherein the image forming apparatus to ensure the optimum transfer properties.
According to a second aspect of the present invention, there is provided the image according to the first aspect, wherein the transfer condition of the recording medium in the transfer device is changed based on the leaving time of the recording medium in the recording medium accommodating means. Features a forming device.
According to a third aspect of the present invention, there is provided a static elimination / separation power source for separating the recording medium from the image carrier, wherein the static elimination / separation device supplies a separation voltage for separating the recording medium from the image carrier. And the static elimination / separation device performs constant voltage control on the static elimination / separation voltage supplied from the static elimination / separation power source based on the set recording medium and the measured standing time, The image forming apparatus according to claim 1, wherein separability is ensured.

  According to the present invention, the humidity measuring unit at the place where the image forming apparatus main body is installed, the unit for measuring the elapsed time left after being left in the mass feeding device for the recording medium set in a predetermined place, Since the control means for determining whether or not the recording medium can be sent out based on the measurement result of the measuring means, the state of the recording medium can be predicted, and the image can be stabilized. In addition, it is not necessary to dry the recording medium, and it is possible to save power waste without using a recording medium drying heater or the like, and it is possible to minimize the running performance of the recording medium and the temperature rise of the image carrier.

1 is a schematic diagram illustrating a configuration of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic block diagram illustrating a control circuit in the image forming apparatus according to the present invention. FIG. 6 is a graph showing the relationship between the storage time of a recording medium and the water content in a mass feeding device. FIG. 6 is a graph showing the relationship between the recording medium leaving time and the deformation degree of the recording medium in the mass feeding device. It is a figure which shows the data of the leaving time in the mass paper feeder of the coated paper, the presence or absence of the image defect | deletion at that time, and the presence or absence of jam.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of an embodiment of an image forming apparatus according to the present invention. In the image forming apparatus 100 of FIG. 1, a photosensitive drum 1 is disposed as a drum-shaped image carrier at the center, and rotates in the direction of arrow A in FIG.
Around the photosensitive drum 1, a charging device 2, an exposure device 8, a developing device 3, a transfer device 5, and a charge eliminating / separating device 6 are arranged. After the surface of the photosensitive drum 1 is uniformly charged by the charging device 2, an electrostatic latent image is formed on the surface of the photosensitive drum 1 by the laser light irradiated according to the image signal from the exposure device 8. The developing device 3 develops toner on the electrostatic latent image to form a visualized image.
A mass feeding device 40, which is a recording medium storage means for storing recording media in a stacked manner, includes a humidity sensor 41 on the side wall thereof, for example, on the upper side wall on the left side of the drawing. A paper feed sensor 43 is provided at a predetermined distance outside the mass paper feed device 40 from a paper feed roller 42 provided in the vicinity of the side wall facing the humidity sensor 41 in the paper feed direction of the mass paper feed device 40. It is configured to detect the loading sequence by detecting the passage.

Thereafter, the registration roller pair 44 conveys the recording medium P to the nip between the registration roller pair 44 at an appropriate timing for aligning the toner image on the photosensitive drum 1 and the recording medium P.
The toner image formed on the surface of the photosensitive drum 1 is transferred by the transfer device 5 to the recording medium P that has been conveyed in the direction of arrow B in FIG. The transfer device 5 superimposes the recording medium P on the toner image electrostatically carried on the photosensitive drum (OPC) 1 and injects a charge onto the recording medium P by injecting electric charge from the back side of the recording medium P. Transcript.
The transfer device 5 is preferably a corotron, but is not limited to this, and any device that transfers electrostatically, such as a transfer roller, may be used. The neutralization / separation device 6 separates the recording medium P from the photosensitive drum 1 by neutralizing the recording medium P electrostatically attracted to the photosensitive drum 1. The neutralization / separation device 6 may be anything such as a corotron or a neutralization needle. Thereafter, the image is fixed on the surface of the recording medium P by the fixing device 7 and the image formation is completed.

In general, when the image forming operation is continuously performed, the large amount of paper feeding device 40 is configured to stack recording media P packed with wrapping paper, in this case, recording media as paper in a bundle state. . The door (not shown) of the mass feeding device 40 is opened, the recording media taken out from the pack are stacked inside the mass feeding device 40 (P1 to Pn), and then the door is closed.
The stacked recording media (P1 to Pn) wait for an image formation instruction that is instructed to the control means (CPU) 20 from a host device such as a client computer, and wait for the timing to be sequentially sent from the uppermost recording medium P1. Yes. Until it is sent out, the recording media (P1 to Pn) are held in the mass feeding device 40 and wait.
The inside of the mass feeding device 40 is usually exposed as it is to the environment where the mass feeding device 40 is installed. When the loaded recording media (P1 to Pn) are left in a high humidity environment for a long time, the moisture content of the upper layer of the loaded layer that directly contacts the surrounding atmosphere increases.
In the figure, reference numeral 9 denotes a toner supply hopper for supplying toner to the developing device 3, 31 denotes a developing roller for supplying toner to form a toner image on the surface of the photosensitive drum 1, and 32 denotes toner to the developing roller 31. A supply conveyance roller 45 to be supplied is a recording medium information input unit for inputting information of the recording medium P to the control unit 20.

FIG. 2 is a schematic block diagram showing a control circuit in the image forming apparatus according to the present invention. In FIG. 2, the main body control device 30 includes a photosensitive drum 1 constituting an image forming unit, a transfer device 5, a charge eliminating / separating device 6, a large amount paper feeding device 40, a paper feeding roller 42 serving as a recording medium feeding unit, and the like. Also connected is a control unit (CPU) 20 that waits for an image formation instruction from a host device such as a client computer, that is, the main body control device 30.
The control unit 20 includes a recording medium information input unit 45, a recording medium storage unit 40, or a leaving time measuring unit 46 that measures a leaving time of a recording medium that has been loaded and left in the image forming unit, a transfer power supply 47, a static elimination unit. A separation power source 48, a recording medium setting means 49 for setting the type and material of the recording medium, and the like are connected.

Referring to FIGS. 1 and 2, as described above, the moisture content of the recording medium P stored in the mass feeding device 40 serving as the recording medium housing means of the image forming apparatus 100 and the inside of the mass feeding device 40 are described. Therefore, the humidity sensor 41 measures the humidity.
The recording medium P is influenced by the humidity in order from the top of the stacked layers depending on the time left in the environment inside the mass feeding device 40, and changes with time, and the change occurs in a very short time. Then, the elapsed time when the recording medium P is left in the large-volume sheet feeding device 40 or the image forming unit is measured by the clock counter 46 which is a leaving time measuring means.
The recording medium P sent out from the mass paper feeding device 40 in accordance with the image forming instruction waits for the timing to be sent to the next process by the registration roller pair 44 through the recording medium sending means 42 which is sent out in order from the uppermost layer.
The recording medium P synchronized with the image formation passes through the registration roller pair 44 and is placed on the photosensitive drum 1 between the photosensitive drum 1 on which the toner image is formed using the electrophotographic method and the transfer device 5. Is transferred to the nip between the photosensitive drum 1 and the transfer device 5 in order to transfer the image of the image to the recording medium P.

The control unit 20 is connected to a transfer power supply 47 of a transfer device 5 that supplies a transfer voltage for transferring an image on the photosensitive drum 1 to the recording medium P, and a transfer current supplied from the transfer power supply 47 is determined. Control the current. Here, since the transfer configuration shown in FIG. 1 is constant current control, the transfer power source 47 is set to transfer current-constant current control. However, the same effect can be obtained by another configuration, for example, constant voltage control with a transfer roller. Become.
The control unit 20 is connected to a separation power supply 48 that supplies a separation voltage of the charge removal / separation device 6 in order to separate the recording medium P from the photosensitive drum 1, and the separation voltage supplied from the separation power supply 48 is supplied. Constant voltage control.
Since the relationship between the surface resistance of the recording medium P and the moisture content of the recording medium varies depending on the surface processing method of the recording medium P, information on the surface processing method of the recording medium P, that is, the type of the recording medium P is also available. It becomes important.

Therefore, the recording medium information input means 45 is connected to the control means 20, and the recording medium setting means 49 connected to the control means 20 for setting the type and material of the recording medium P is controlled via the main body control device 30. The type and material of the recording medium P are set according to information from the recording medium information input means 45 connected to 20.
Accordingly, the optimum type of recording medium P is determined based on the elapsed time measured by the clock counter 46, which is a leaving time measuring means after the recording medium P is loaded into the large-volume sheet feeding device 40. The transfer device 5 is controlled in order to ensure the transfer property, and the static elimination / separation device 6 is controlled in order to ensure the optimum separation property.
As described above, since the control means 20 for setting the recording medium transfer condition and the separation condition is provided, the time point when the predetermined recording medium P is loaded into the large-volume sheet feeding device 40 that is the sheet feeding bank in the target humidity range. Since the transfer condition and separation condition of the image forming apparatus can be set for each sheet until the standing time information reaches a predetermined range, the state of the recording medium P can be predicted and the image can be stabilized. . In addition, it is not necessary to dry the recording medium P, use of a recording medium drying heater or the like can be performed, power waste can be saved, and running performance of the recording medium P and temperature rise of the photosensitive drum 1 can be minimized. it can.

FIG. 3 is a graph showing the relationship between the storage time of the recording medium and the moisture content in the mass feeding device. FIG. 3 shows the transition of the moisture content of a certain recording medium left in a high humidity environment over time, with the vertical axis representing the moisture content (%) and the horizontal axis representing the paper feeding device. 40 is the time (minutes) since the recording medium (P1 to Pn) was loaded into 40. P1, P2, P3,... Pn are indicated as P1, P2, P3,... Pn for each sheet from the upper part of the recording medium P stacked on the mass feeding device 40. From the graph, each recording medium P converges to a constant moisture content.
The recording medium P held in the mass feeding device 40 is affected by the environment in the mass feeding device 40 from around the mass of the recording media P. For example, when the apparatus is left in an environment of 27 ° C./80%, the mass of the recording medium P in the large-volume sheet feeding apparatus 40 that is a sheet feeding bank begins to absorb moisture from the surroundings, and in many cases, recording is performed. The bottom surface and side surface of the mass of the medium P may be surrounded by the components of the mass feeding device 40, side plates, and the like, and the influence of moisture absorption from the uppermost recording medium P1 in the mass of the recording medium P is significant. I understood that it was supposed to appear.

FIG. 4 is a graph showing the relationship between the storage time of the recording medium and the degree of deformation of the recording medium in the mass feeding device. In FIG. 4, next, 3000 sheets were left in the large-volume paper feeder 40, which is a paper feed bank, in a 27 ° C./80% environment with respect to a certain coated paper (coated paper A) in FIG. The degree of deformation of the uppermost recording medium P1 of the recording medium bundle over time is shown.
The degree of deformation of the recording medium bundle referred to here is an amount of deformation in the vertical direction when the recording medium P is projected with a length of 100 mm, and is an original index for determining the expansion of the recording medium P due to moisture absorption. According to this, it was found that the degree of deformation of the recording medium P left in the large-volume sheet feeding device 40 increased with the standing time, and entered the stable region after 10 minutes. In addition, when leaving time was less than 5 minutes, it turned out that a deformation | transformation degree becomes the maximum in 3 minutes vicinity, and the variation | change_quantity is large with progress of time.
This is because the moisture absorption of the recording medium P is partially started on the surface of the recording medium P, so that the deformation of the recording medium P proceeds locally, and as a result, the deformation of the entire recording medium P is unstable. It was found that the degree of deformation changed greatly. Although this phenomenon seems to have a correlation with the moisture content data shown in FIG. 3 of the recording medium, the form of change is different. At least, the moisture content shown in FIG. 3 does not reach its maximum value within 5 minutes.

The same evaluation was performed on the second and subsequent recording media from the top of the recording media bundle. The recording medium below the third sheet P3 was hardly affected by moisture absorption and tended to exhibit almost the same characteristics. As a result, with respect to the recording medium P made of coated paper, in order to form an image under optimum image forming conditions, one of the recording media to be sent out according to the leaving time in the mass feeding device 40. It has been found that it is effective to change the image forming conditions for the second, third and subsequent sheets.
The change of the image forming conditions is performed by mapping the information of the humidity sensor 41, the leaving time after loading the recording medium P from the CPU 20 into the mass feeding device 40, and the result of the recording medium information input means 45. It is effective to individually set transfer conditions and separation conditions for the first, second, third and subsequent sheets of the recording medium.
In addition, although it did not describe about the recording medium which consists of another coated paper in inventor's evaluation, it turned out that there exists a tendency similar to the result shown in FIG. As characteristics of the recording medium P, there is a large correlation with the air permeability of the recording medium measured in a normal temperature environment (for example, 23 ° C./50%), and the air permeability is 0 to 5000 seconds, 5000 to 10,000 seconds, 10,000 to 10,000. When the image forming conditions were switched under the conditions of 15000 seconds and 15000 seconds or more, it was effective.

FIG. 5 is a table showing data on whether the coated paper is left in the large-volume feeding device, whether there is an image defect, and whether there is a jam. From the result of FIG. 5, it was found that if the leaving time in the large-volume sheet feeding device 40 is within 5 minutes, image loss and jamming occur.
As a result, when the image formation is performed in the region where the standing time is 5 minutes or less, the moisture absorption condition of the recording medium P is unstable, and when the transfer or separation is performed, the recording medium P is localized in one recording medium. In other words, it is easy to develop as an image defect or separation defect due to a transfer defect. In particular, the standing time was unstable for 2 to 4 minutes.
Based on the above examination results, it is possible to simultaneously measure the measurement unit 46 for measuring the leaving time of the recording medium P in the large-volume sheet feeding device 40 and the leaving environment for the recording medium P in the large-volume sheet feeding device 40. It was found that this is effective for the countermeasures.
Therefore, in the present invention, the humidity sensor 41 is arranged on the side plate of the mass feeding device 40 to measure the humidity in the mass feeding device 40, and the mass feeding is performed by the clock count of the leaving time measuring means 46 which is a clock counter of the CPU 20. The standing time after the recording medium P was loaded in the paper device 40 was measured. This time may be measured by installing a separate counter or timer, and any means can be used as long as it can be measured.

Therefore, in the present invention, when the time is 5 minutes or less, the recording media P stacked in the large-volume paper feeding device 40 are ordered in order from the uppermost recording media after an image formation instruction from a host computer or the like. Sent out. At this time, the transfer current and separation voltage were mapped from the coated paper condition, the standing time value, and the humidity sensor detection value, and the optimum conditions were set. Thereby, it was confirmed that there was no image defect such as image omission in the transfer device 5 due to the difference in moisture content in one sheet of recording medium, and the subsequent separation was achieved without any defects.
In copiers used in general offices, the first print time is regarded as important, and it is not acceptable to wait several minutes after loading the recording medium. However, in the case of a production printer, the reason for ensuring the stability of print quality In many cases, operations such as color correction and print position correction are performed at the time of starting up the apparatus and before starting printing, and several minutes may elapse before starting printing. In many cases, permission to send a recording medium is issued after several minutes.
Therefore, the present invention is extremely effective for an apparatus that requires stability of image quality, such as a production printer. Note that a printer generally used as a production printer is A4, and a printer with 30 pages or more per minute is often used. In addition, since the transfer condition and the separation condition are different depending on the type of the recording medium, the basis weight, and the like, an image forming apparatus that does not cause image loss is provided by making it possible to change depending on the paper type based on the experimental verification result. be able to.

The present invention has the same effect in an electrophotographic apparatus using an intermediate transfer method, and the same effect can be obtained even in a configuration in which a transfer roller is used as a secondary transfer member and a static elimination needle is used for separating a recording medium. It goes without saying that there is.
Further, in this embodiment, the humidity sensor for detecting the humidity in the mass feeding device is installed on the side plate of the feeding device. Even if judging from information from a humidity sensor arranged for process control, there was no significant difference in the detection of the environment in which the apparatus is installed, so it was confirmed that the same effect was obtained. The present invention can be utilized for all apparatuses that require paper feed such as a printing press.

  DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum), 5 Transfer device, 6 Auto transmission / separation device, 20 Control means (CPU), 30 Main body control device, 40 Recording medium accommodation means (mass feeding device), 41 Humidity sensor, 42 Recording Medium feeding means (paper feed roller), 43 paper feed sensor, 45 recording medium information input means, 46 standing time measuring means (clock counter), 47 transfer power supply, 48 static elimination / separation power supply, 49 recording medium setting means

JP-A-11-5543 JP-A-4-345447 JP-A-53-57042

Claims (3)

In an image forming apparatus that forms a toner image on an image carrier using an electrophotographic method, transfers the toner to the recording medium, and then separates the recording medium from the image carrier.
Recording medium accommodating means for accommodating the recording medium in a stacked manner, recording medium sending means for sequentially sending the recording medium accommodated in the recording medium accommodating means from the uppermost layer, and the recording in the recording medium accommodating means A transfer device for transferring the image on the image carrier to the recording medium, comprising: a measuring unit for measuring the medium leaving time; and a setting unit for setting the type and material of the recording medium. A transfer power supply
The transfer device performs constant current control on the transfer current supplied from the transfer power source based on the recording medium set by the setting unit and the standing time measured by the measurement unit, thereby ensuring optimum transfer performance. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the transfer condition of the recording medium in the transfer apparatus is changed based on the leaving time of the recording medium in the recording medium accommodation unit.   The static eliminator / separator for separating the recording medium from the image carrier has a static eliminator / separation power source for supplying a separation voltage for separating the recording medium from the image carrier, The neutralization / separation voltage supplied from the neutralization / separation power supply is controlled at a constant voltage based on the set recording medium and the measured standing time, and optimal separability is ensured. Item 3. The image forming apparatus according to Item 1 or 2.

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