JP2002023562A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an image forming device which transfers a toner image formed on a photoreceptor to the surface of a transfer material by a transfer electrostatic charging member applied with a voltage to transfer the toner image to the surface of the transfer material under suitable transfer conditions even when an image is formed on the reverse surface of the transfer material. SOLUTION: When an image presence/absence detection sensor 28 detects the image being formed on the reverse surface of the transfer material, a current having a value suitable thereto is supplied to the transfer electrostatic charging member 7 to transfer the toner image on a photoreceptor 2 to the surface of the transfer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for transferring an image formed on an image carrier to a transfer material by the action of a transfer charging member to which a voltage is applied.

[0002]

2. Description of the Related Art An image forming apparatus of the above-described type having at least two functions of an electronic copying machine, a printer, a facsimile, and the like has been well known. This type of image forming apparatus can be broadly classified into an image forming apparatus having a double-sided function capable of automatically forming an image on both sides of a transfer material and an image forming apparatus having no such function.

When an image is formed on both sides of a transfer material by an image forming apparatus having no double-sided function, an image is first formed on one surface of the transfer material, and the transfer material discharged to a paper discharge unit is discharged. May be manually set again in the paper feeding section, and the transfer material may be fed again to form an image on the other surface. However, control conditions suitable for each of the first image formation for forming an image on one surface of the transfer material and the second image formation for forming an image on the other surface are different. The image quality of the image formed on the other surface of the transfer material may be degraded. The following points can be considered as one of the causes.

[0004] During the first image formation, the transfer material passes through the fixing device. Therefore, the transfer material having an image formed on one surface and the transfer material having no image formed on any surface are different. The water content is different, and the former transfer material has a lower water content and a higher volume resistivity. When a toner image on an image carrier is transferred to each transfer material having a different water content, that is, a different volume resistivity, a voltage having the same value is applied to the transfer charging member. The transfer efficiency at the time decreases, thereby deteriorating the image quality of the formed image.

On the other hand, in an image forming apparatus having a double-sided function capable of automatically forming an image on each side of a transfer material,
Since the control conditions can be made different between the first image formation and the second image formation, it is possible to prevent the above-described problem from occurring (see Japanese Patent Application Laid-Open No. H7-19967).
No. 9).

In an image forming apparatus having a double-sided function, a transfer material having an image formed on one side is once discharged to a paper discharge section, and then the transfer material is manually set in a paper supply section. By pressing the print start key after pressing the second side selection key, an image is formed on the other side of the transfer material. In this case, by pressing the second side selection key, the control conditions for the second image formation are switched to those suitable for image formation on the other side of the transfer material. Thus, also in this case, it is possible to prevent the image quality of the image formed on each surface of the transfer material from deteriorating. However, prior to the start of the second image formation, the user
If the operation of the face selection key is forgotten, the control conditions cannot be switched to those suitable for the second image formation, and the image quality of the image formed on the other surface of the transfer material deteriorates.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus of the type described at the beginning, which can eliminate the above-mentioned conventional disadvantages with a simple structure.

[0008]

According to the present invention, in order to achieve the above object, an image forming apparatus of the type described at the beginning has an image formed on a transfer material surface opposite to a surface on which an image is to be transferred. Different control conditions between when an image is formed on the transfer material surface and when it is detected that an image is not formed. An image forming apparatus comprising a control unit for setting the image forming apparatus (claim 1).

In this case, it is advantageous that the control condition is a current value supplied to the transfer charging member.

Further, in the image forming apparatus according to claim 1 or 2, the transfer material carrier for carrying and transferring the transfer material onto which the image is transferred, and separating the transfer material from the transfer material carrier. And a separate charging member to which a voltage is applied,
Advantageously, the control condition is a current value supplied to the separated charging member (claim 3).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing an example of an image forming apparatus with a double-sided function capable of forming images on both sides of a transfer material. In the main body 1 of the image forming apparatus shown here, a drum-shaped photoconductor 2 as an example of an image carrier is arranged, and when the photoconductor 2 rotates clockwise, the surface of the photoconductor is charged by the charging device 3. Is charged to a predetermined polarity. The charged surface is irradiated with a light-modulated laser beam L emitted from a laser writing unit 4 which is an example of an exposure device, whereby an electrostatic latent image is formed on the surface of the photoconductor. The electrostatic latent image is visualized as a toner image by the developing device 5, and the toner image is formed on one surface of a transfer material fed from a paper feeding unit 6 disposed at a lower portion of the image forming apparatus main body 1. Is transferred by the action of the transfer charging member 7. The transfer residual toner adhering to the photoreceptor surface after the transfer of the toner image is removed by the cleaning device 8.

The paper supply section 6 is provided with a paper supply cassette 9 containing a transfer material P made of, for example, sheet-like transfer paper.
Due to the rotation of the paper feed roller 11, the uppermost transfer material P is sent out from the paper feed cassette 9 in the direction of arrow A1. The transferred transfer material is moved by the rotation of the registration roller pair 12 as shown by an arrow A2 to the photosensitive member 2 and the transfer charging member 7.
And the toner image on the photoconductor 2 is transferred to one surface of the transfer material as described above.

The transfer material onto which the toner image is transferred and conveyed in the direction of arrow A3 subsequently passes through the fixing device 13, and at this time, the toner image on the transfer material is fixed by the action of heat and pressure. When the one-sided mode in which an image is formed only on one side of the transfer material is selected, the transfer material that has passed through the fixing device 13 is directly discharged from the discharge tray 14 outside the apparatus as indicated by an arrow A4. It is discharged to paper.

When the duplex mode for forming images on both sides of the transfer material is selected, the first switching claw 15 provided on the downstream side of the fixing device 13 in the transfer material transport direction is switched to the position indicated by the chain line. As a result, the transfer material exiting the fixing device 13 is guided by the first switching claw 15 and fed into the reversing path 16 as shown by the arrow A5. Next, the transfer material is sent to a reversing tray 17 as shown by an arrow A6, and the reversing roller 18 is continuously rotated in the reverse direction.
As shown by an arrow A7, the transfer material is guided to the intermediate tray 20 by the second switching claw 19 switched to the position indicated by the dashed line, with the rear end up to that point as the leading end.

The transfer material which has been turned over and sent to the intermediate tray 20 as described above is again sent to the registration roller pair 12 as shown by an arrow A8 by the rotation of the intermediate paper feed roller 21. By the rotation of the registration roller pair 12, the sheet passes through the transfer position between the photoconductor 2 and the transfer charging member 5. At this time, the photoconductor 2 rotating clockwise
On the top, a toner image is formed in the same manner as described above, and the toner image is transferred to the other surface of the transfer material by the action of the transfer charging member 5. Next, the transfer material passes through the fixing device 13 again, and at this time, the toner image transferred to the other surface is fixed on the transfer material by the action of heat and pressure. The transfer material that has passed through the fixing device 13 is discharged onto a discharge tray 14.

In the image forming apparatus shown in FIG. 1, the transfer charging member 7 is constituted by a transfer roller, and the transfer charging member 7 is supplied by a high voltage power supply 22 with a polarity opposite to the charging polarity of the toner on the photosensitive member. Is applied, whereby the toner image on the photoconductor 2 is electrostatically transferred to the transfer material. Instead of a transfer charging member consisting of a transfer roller, a transfer charging member consisting of a transfer brush, a transfer blade or a charge wire is used, and a voltage having a polarity opposite to the charge polarity of the toner is applied to these members to transfer the toner image on the photoconductor. It can also be configured to transfer onto a material. As described above, the image forming apparatus is configured to transfer the image formed on the image carrier to the transfer material by the action of the transfer charging member to which the voltage is applied.

FIG. 2 is a block diagram schematically showing a control system of the image forming apparatus shown in FIG. 1, and an operation unit 23 (not shown in FIG. 1) provided in the image forming apparatus main body 1 shown in FIG. When the automatic double-side selection key 24) is pressed, the above-described double-side mode is selected. Next, when the print start key 26 is pressed, the image forming operation in the above-described duplex mode is executed. Thereby, an image is automatically formed on both sides of the transfer material. At this time, the current supplied to the transfer charging member 7 is different between the first image formation for forming the toner image on one surface of the transfer material and the second image formation for forming the toner image on the other surface. The values are different. That is, a control signal is sent from the CPU 27 shown in FIG. 2 to the high-voltage power supply 22 to supply a current to the transfer charging member 7. However, the transfer is more frequent during the second image formation than during the first image formation. Charging member 7
Is increased. As a result, during the second image formation, the volume resistivity of the transfer material is higher than at the time of the first image formation for the reason described above, but the transfer efficiency of the toner image is prevented from lowering. You.

On the other hand, when the user selects the automatic
Without pressing the face selection key 25, the print start key 2
When 6 is pressed, the image forming operation in the single-sided mode is performed. At this time, the transfer material that has been copied on one side and discharged to the paper output tray 14 is manually turned with the image surface facing upward.
When the user again sets the paper cassette 9 or a paper feed unit such as a manual feed table (not shown), presses the second side selection key 25 of the operation unit 23, and then presses the print start key 26, the second image forming operation is started. Is executed, a toner image is formed on the other surface of the transfer material, and the transfer material is
Is discharged on top. Also in this case, by pressing the second-side selection key 25, a higher current is supplied to the transfer charging member 7 than in the first image formation, and the transfer efficiency is prevented.

As described above, the transfer material having an image formed on one surface at the time of the first image formation is manually set again in the paper feed unit, and the second image formation is performed. A series of operations or operations for forming an image on a surface is referred to as a manual two-sided operation. Before the second image forming operation of the manual two-sided operation is performed, by operating the second-side selection key 25, It is possible to prevent image quality deterioration of an image formed on the other surface of the transfer material.

However, in this type of conventional image forming apparatus, if the user forgets to operate the second side selection key 25 during the manual double-sided operation, the first image forming The toner image is transferred to the other surface of the transfer material under the same transfer conditions as at the time, and the image quality deteriorates.

Therefore, in the image forming apparatus of this embodiment,
It is determined whether an image is formed on the transfer material surface opposite to the surface on which the image is to be transferred, at an appropriate position between the paper supply unit 6 and the transfer position where the transfer of the toner image on the photoconductor is performed. An image presence / absence detection sensor 28 to be detected is provided. As the image presence / absence detection sensor 28, for example,
A reflection type optical sensor similar to the sensor described in Japanese Patent No. 927 can be used.

When the user forgets to press the second-side selection key 25 and presses the print start key 26 prior to the second image formation during the manual double-sided operation, the single-sided copy sent out from the paper feed cassette 9 is completed. When the transfer material passes through the image presence / absence detection sensor 28, light emitted from the image presence / absence detection sensor 28 is applied to one surface of the transfer material on which an image has already been formed, and the amount of light reflected from the one surface It is detected that an image is formed on the one surface. The detection signal is taken into the CPU 27,
A control signal is sent from the CPU 27 to the high-voltage power supply 22, and a higher current is supplied from the high-voltage power supply 22 to the transfer charging member 7 than during the first image formation. Thereby, when the toner image on the photoconductor 2 is transferred to the other surface of the transfer material, it is possible to prevent the transfer efficiency from being lowered. As described above, even when the user forgets to operate the second side selection key during the manual double-sided operation, a high-quality image can be formed on the other side of the transfer material.

Further, since it is possible to detect that an image is formed on one surface of the transfer material by the image presence / absence detection sensor 28, even if the second surface selection key 25 is abolished, it is optimal for the other surface of the transfer material. The toner image can be transferred under the conditions. Thus, by eliminating the second-side selection key 25, the configuration of the image forming apparatus can be simplified. In addition, the user does not need to operate the second side selection key 24, and the operability of the image forming apparatus can be improved.

On the other hand, when the transfer material passes through the image presence / absence detection sensor 28 during the first image forming operation in the one-sided mode or the manual two-sided operation, no image is normally formed on the other side. Therefore, the amount of light reflected on the other surface and incident on the image presence / absence detection sensor 28 increases, whereby it is detected that no image is formed on the other surface. When the detection signal is taken into the CPU 27, a control signal is sent from the CPU 27 to the high voltage power supply 22, and the high voltage power supply 22 supplies a lower current to the transfer charging member 7 than in the second image formation. Thus, the toner image can be transferred to one surface of the transfer material under a transfer condition suitable for a transfer material having a low high product resistivity.

As described above, the image forming apparatus of the present embodiment operates when the image presence / absence detection sensor 28 detects that an image is formed on the transfer material surface opposite to the surface to which the image is to be transferred. And control means for setting different control conditions when it is detected that no image is formed on the transfer material surface. In the illustrated example, the CPU 27 constitutes a control unit, and the control condition is a current value supplied to the transfer charging member 7.

The configuration of the image presence / absence detection sensor 28 and the control means described above can also be applied to an image forming apparatus having no double-sided function. The image forming apparatus having no double-sided function does not include the intermediate tray 20, the automatic double-sided selection key 24, the second-sided selection key 25, and components related thereto. When the above-described manual double-sided operation is performed by such an image forming apparatus, during the second image formation, the image presence / absence detection sensor 28 detects that an image is formed on one surface of the transfer material, and the detection result By making the current value supplied to the transfer charging member 7 higher than that at the time of the first image formation, the quality of the image formed on any surface can be improved.

Further, the transfer material having an image formed on one surface is not distributed, and the unnecessary transfer material after reading the image information is not discarded, and the image is formed on the other surface by the image forming apparatus. Is also commonly performed. When forming an image on the other side of an old transfer material having an image formed on one side in this way, it is different from forming an image on one side of a new transfer material having no image formed on both sides. Although some control conditions may be imposed, this requirement can be satisfied by the above-described configuration. That is, when an old transfer material is set on the paper feed cassette 9 of the image forming apparatus shown in FIG.
Detects that an image is formed on one surface of the transfer material, and supplies a current having a value suitable for the old transfer material to, for example, the transfer charging member 7 based on the detection result. Can be.

In the example described above, the control condition set by the control means is the current value supplied to the transfer charging member 7, but the control condition set by whether or not an image is formed on the transfer material surface is set. Other conditions may be used. For example, as shown in FIG. 3, the transfer material P sent from the paper feed cassette 9 of the paper feed unit 6 is wound around the peripheral surface of the transfer material carrier 29 formed in a drum shape and clamped. While rotating the carrier 29 in the counterclockwise direction, the toner images of different colors sequentially formed on the photoconductor 2 are
For example, by the action of the transfer charging member 7 composed of a transfer brush, the image is sequentially transferred onto the transfer material carried on the transfer material carrier 29, and after the transfer is completed, a voltage is applied to the separation charging member 30 composed of, for example, a charge wire of a corona discharger. In the image forming apparatus that separates the transfer material from the transfer material carrier 29 as indicated by the arrow A9 while applying the image, an image is formed on the surface of the transfer material sent to the transfer material carrier 29 by the image presence / absence detection sensor 28. It is detected whether or not the transfer is performed, and depending on the presence or absence of the image, a current of an appropriate value is supplied to the separation charging member 30 to prevent the toner image from scattering when the transfer material is separated. In this case, it is needless to say that the transfer charging member 7 may be supplied with a current having a value suitable for the presence or absence of an image.

As described in Japanese Patent Application Laid-Open No. 7-199679, an image forming apparatus capable of inverting a transfer material separated from a transfer material carrier 29 and forming an image on the other surface is also provided. The configuration of the image presence / absence detection sensor 28 and the control means can be adopted.

As described above, in the image forming apparatus exemplified above, the transfer material carrier 29 that carries and transports the transfer material on which an image is formed, and separates the transfer material P from the transfer material carrier 29. Therefore, the control condition set by the above-described control means is a current value supplied to the separation charging member 30.

Although the preferred embodiments of the present invention have been described above, the present invention should not be limited to the configurations of these embodiments.

[0033]

According to the first aspect of the present invention, when an image is formed on the other surface of a transfer material having an image formed on one surface, the presence of the image on one surface is determined by the presence or absence of the image. An image can be formed on the other surface of the transfer material under the control conditions suitable for the detection by the detection sensor.

According to the second aspect of the invention, it is possible to prevent the occurrence of image deterioration due to a decrease in transfer efficiency.

According to the third aspect of the present invention, it is possible to prevent a problem that the image is scattered when the transfer material is separated from the transfer material carrier.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view schematically showing an image forming apparatus.

FIG. 2 is a control block diagram of the image forming apparatus shown in FIG.

FIG. 3 is a schematic view illustrating an example of another image forming apparatus.

[Explanation of symbols]

 7 Transfer charging member 28 Image presence / absence detection sensor 29 Transfer material carrier 30 Separation charging member P Transfer material

Claims (3)

[Claims] 1. An image forming apparatus for transferring an image formed on an image carrier to a transfer material by the action of a transfer charging member to which a voltage is applied, wherein a transfer material surface opposite to a surface on which the image is to be transferred is provided. An image presence / absence detection sensor for detecting whether an image is formed on the
A control unit that sets different control conditions when it is detected that an image is formed on the transfer material surface and when it is detected that an image is not formed. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the control condition is a current value supplied to a transfer charging member. 3. A transfer material carrier for carrying and transferring a transfer material onto which an image is transferred, and a separation charging member to which a voltage is applied to separate the transfer material from the transfer material carrier, The image forming apparatus according to claim 1, wherein the control condition is a current value supplied to the separated charging member.