JP2000047438A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the fluctuation of image density according to the fluctuation of humidity within a device and to prevent the toner scattering or photographic fog, for example, at a high humidity. SOLUTION: This image forming device is provided with a toner density sensor 261 provided within a processing device, a humidity sensor 262 for detecting the absolute humidity within the device, a toner supplying motor 263 for supplying toner from a toner cartridge to the processing device, and a transfer voltage application part 264 for applying a transfer voltage to a transfer roller. In this device, the target T/D value for operating the toner supplying motor 263 is corrected on the basis of the absolute humidity detected by the humidity sensor 262, and the transfer voltage from the transfer voltage application part 264 is also corrected.

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, and more particularly, to a transfer apparatus in which an electrostatic latent image formed on a peripheral surface of a photosensitive drum is visualized into a toner image by a developing device and a high voltage is applied. The present invention relates to an image forming apparatus that attracts a toner image on a photosensitive drum from the back side of a sheet and transfers the toner image to the sheet.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus, a document is placed on a document table provided on an upper surface of the apparatus, and the document image is irradiated with light and reflected from the document. The document image is read based on the. Based on the read document image, an electrostatic latent image is formed on the surface of the photosensitive drum. The photoreceptor drum is charged to a predetermined polarity by the main charging device, and when light is irradiated based on a document image, the charge at that portion is removed to form an electrostatic latent image.

Around the photosensitive drum, a developing device, a transfer device, a separating device, a cleaning device and the like are arranged. The developing device contains therein toner charged to the same polarity as the photosensitive drum. The toner stored in the developing device is adsorbed to a portion of the photosensitive drum where there is no charge at a position close to the developing device and the photosensitive drum. Therefore, the electrostatic latent image formed on the peripheral surface of the photosensitive drum is visualized as a toner image.

The transfer device applies a voltage having a polarity opposite to that of the toner from the back surface of the paper to the paper conveyed between the photosensitive drum and attracts the toner on the peripheral surface of the photosensitive drum onto the paper. To transfer the toner image. A separation device is disposed downstream of the transfer device in the sheet conveyance direction. This separation device prevents the paper from wrapping around the photoconductor drum.
The sheet is sucked from the back side, and for example, a separation needle to which a predetermined voltage is applied is employed.

The cleaning device is for removing the toner remaining on the peripheral surface of the photosensitive drum, and includes a cleaning blade that comes into contact with the peripheral surface of the photosensitive drum and scrapes off the toner. A fur brush for weakening the binding force, a toner transport device for transporting the toner separated from the peripheral surface of the photosensitive drum to a collection unit, and the like are provided.

[0006]

In an image forming apparatus using a two-component toner, a developing material containing a carrier and a toner is stored in the developing device. When the electrostatic latent image on the peripheral surface of the photosensitive drum is visualized, only the toner in the developing device moves to the peripheral surface of the photosensitive drum, and the carrier remains in the developing device. A magnetic sensor is provided in the developing device. The magnetic sensor detects the magnetic permeability of the stored contents, detects the toner concentration with respect to the developing material, so-called T / D, and detects the consumed toner. The amount has been determined.

The toner can be supplied to the developing device via a toner cartridge or a toner hopper, and the T / D value in the developing device is set to a predetermined target T / D value based on the detection result of the magnetic sensor. Is supplied so that When the humidity in the device increases, the charge amount of the carrier in the developing device decreases, and the toner is easily scattered. As a result, the toner is easily transferred from the developing device to the peripheral surface of the photosensitive drum, and the formed image density tends to increase. Further, when the humidity increases, the output of the magnetic sensor built in the developing device is detected higher than the actual value, and the T / D value obtained based on the detection signal of such a magnetic sensor is lower than the actual value. Will be. For this reason, control is performed such that toner is further supplied from the toner cartridge or the toner hopper into the developing device, and the formed image density is further increased.

For this reason, a humidity sensor for detecting the absolute humidity in the image forming apparatus is provided, and based on the detection result of the humidity sensor, when the humidity increases, the target T / D value is reduced. It is possible. In this case,
As the humidity in the image forming apparatus rises, T
Since the / D value decreases, scattering of toner can be suppressed.

However, if the T / D in the developing device is reduced in the above case, there is a possibility that an appropriate image density cannot be maintained. This is because the charge amount of the carrier is reduced due to the increase in the humidity, and the toner concentration is reduced. Therefore, the ratio of the toner to the carrier is reduced, and the uniform toner concentration cannot be maintained. This is considered to be due to the occurrence of density unevenness in the image.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress a change in image density due to a change in humidity in the apparatus, for example, to prevent toner scattering and fogging when the humidity becomes high.

[0011]

An image forming apparatus according to the present invention develops an electrostatic latent image formed on the peripheral surface of a photosensitive drum into a toner image by a developing device, and applies a high voltage to the transfer device. An image forming apparatus for attracting a toner image on a photosensitive drum from the back side of a sheet and transferring the toner image to the sheet, comprising: a toner density detecting unit; a toner replenishing unit; a transfer voltage applying unit; a humidity detecting unit; Density control means. The toner concentration detecting means measures the toner concentration for the developer in the developing device. The toner replenishing means replenishes the toner based on the detection result of the toner density detecting means so that the toner density in the developing device becomes a predetermined target T / D value. The transfer voltage applying means applies a voltage to the transfer device. The humidity detecting means detects the absolute humidity in the device. The image density control means corrects the target T / D value of the toner replenishing means based on the absolute humidity detected by the humidity detecting means, and corrects the voltage applied to the transfer device by the voltage applying means.

Here, the image density control means can be configured to set the target T / D value low and set the applied voltage value to the transfer device high with an increase in the absolute humidity detected by the humidity detection means. . Accordingly, the target T / D of the toner replenishing unit is changed according to the absolute humidity detected by the humidity detecting unit.
Even if the correct image density cannot be obtained when the value is corrected, the transfer voltage value is corrected to make the image density transferred on the paper appropriate, and toner scattering, fogging, or density Problems such as unevenness can be eliminated.

[0013]

FIG. 1 is a longitudinal sectional view of a copying machine to which an embodiment of the present invention is applied. The copying machine 1 has a main body 10 and a document holder 11 mounted on the upper part of the main body 10 so as to be openable and closable. An original platen 15 on which an original is placed is disposed on the main body 10 at an upper portion thereof. Inside the main body 10, an image forming unit 16 is provided at the left end as viewed from the front and substantially at the center in the vertical direction.
Further, a paper supply unit 17 for supplying paper to the image forming unit 16 is provided at a lower portion.

The paper supply unit 17 is detachably attached to the main body 10 and stores paper supply cassettes 18 and 19 for storing paper.
And a stack bypass 20 provided thereabove. An optical system 21 for reading image information of a document placed on the document table 15 is provided below the document table 15. The optical system 21 includes a light source 22 for irradiating light to the surface of the document placed on the document table 15 and mirrors 23, 24, and 2 for deflecting light reflected from the surface of the document.
5 and a lens 2 for converging the light from the mirror 25
6 and an image sensor 27 such as a CCD sensor that receives light converged by the lens 26 and generates an image data signal corresponding to an original image.

The image forming section 16 has a photosensitive drum 30 on the surface of which an electrostatic latent image is formed.
0, a main charging device 31, a developing device 32,
It has a transfer roller 33 and a cleaning device 34. The main charging device 31 is a device for charging the surface of the photoconductor drum 30, and is disposed diagonally above and to the right of the photoconductor drum 30. The photosensitive drum 3 is disposed diagonally below and to the right of the photosensitive drum 30 with a predetermined gap from the main charging device 31.
A developing device 32 for forming a toner image on the image sensor 0 is disposed. The developing device 32 stores toner inside, and visualizes the electrostatic latent image formed on the photosensitive drum 30 by the toner. The transfer roller 33 is a device for transferring the toner image on the photosensitive drum 30 to a sheet, and is disposed on the left side of the photosensitive drum 30. The cleaning device 34 is a device for removing residual toner and the like on the surface of the photoconductor drum 30.
0.

On the right side of the photosensitive drum 30, a laser unit 35 for forming an electrostatic latent image on the peripheral surface of the photosensitive drum 30 is provided. The laser unit 35 forms an electrostatic latent image on the peripheral surface of the photosensitive drum 30 based on an image data signal obtained from the image sensor 27. The paper feed unit 17 includes a vertical transport path 41 for transporting paper from each of the paper cassettes 18 and 19 toward the image forming unit 16 and a bypass transport path for transporting paper from the stack bypass 20 to the image forming unit 16. 42 are provided. Each paper cassette 1
Pickup rollers 43, 4 for taking out the stored paper are provided in the stack bypasses 8, 19 and the stack bypass 20.
4, 45 and a pair of paper feed rollers 46, 47, 48 for feeding the paper one by one to the transport path. The vertical transport path 41 is provided with pairs of transport rollers 49 and 50, and the bypass transport path 42 is provided with a pair of transport rollers 51. The vertical transport path 41 and the bypass transport path 42 join below the transfer position where the photosensitive drum 30 and the transfer roller 33 face each other. At the confluence, a registration roller 52 for stopping the conveyed sheet at a predetermined position is provided.

Above the photosensitive drum 30 and the transfer roller 33, a fixing device 53 for fusing and fixing the toner transferred onto the paper is provided. The fixing device 53
A heating roller 54 having a built-in heater and a pressure roller 55 pressing the heating roller 54 are provided. The sheet is nipped between the rollers and transported, and the toner image formed on the surface of the sheet is heated and fixed. Things.

Further above the fixing device 53, a branch 5
6 are provided. On the right side of the branch portion 56, a discharge tray 57 for discharging sheets via a discharge roller pair 60 is provided.
And a discharge roller pair 6 disposed above the discharge tray 57.
1 and a sub-eject tray 58 from which sheets are ejected. A switchback unit 59 for reversing the sheet at the time of double-sided copying is provided at the lower left of the branch unit 56.
Is arranged. The branching portion 56 is provided with a branching claw 62 for switching the sheet conveying direction between the direction of the discharge tray 57 and the direction of the switchback portion 59. Branch claw 62
Two branch claws 63 and 64 are provided on the left side of. Below the two branch claws 63 and 64, a switchback transport path 65 for guiding a sheet to a switchback section 59 is provided.
A sub-tray conveyance path 66 for guiding the sheet to the sub-discharge tray 58 is provided above, and a sheet is conveyed to a finisher (not shown) such as a sorter or a staple sorter between the two branch claws 63 and 64. A finisher transport path 67 is provided. Branch claws 63, 64
Switches the transported paper to the switchback transport path 65,
It is possible to switch so as to guide to either the sub-tray conveyance path 66 or the finisher conveyance path 67. [Toner Conveying Mechanism] The cleaning device 34 is for removing toner remaining on the peripheral surface of the photosensitive drum 30. The toner removed from the peripheral surface of the photosensitive drum 30 is transferred to the toner conveying device via the toner conveying device. The developer is conveyed to the developing device 32. This toner conveying device will be described with reference to FIG.

The cleaning device 34 includes a cleaning blade (not shown) that presses against the peripheral surface of the photosensitive drum 30 in order to scrape off the toner remaining on the peripheral surface of the photosensitive drum 30, and a cleaning blade that scrapes off the toner. Spiral 70 that conveys the discharged toner to one end in the width direction
And The toner conveying device 71 is provided at one end in the width direction of the cleaning device 34. The toner conveying device 71 includes a toner conveying container 72 having a hollow inner tube shape, and a conveying member 73 rotatably disposed in the toner conveying container 72.

The toner conveying container 72 has an opening 74 communicating with one end in the width direction of the cleaning device 34 and a developing device 3.
2 is provided with a discharge port 75 for discharging toner. The transport member 73 includes a rotating shaft 76 and a contact member 77 provided in a spiral shape around the rotating shaft 76. The contact member 77 is made of a fiber made of a synthetic resin material,
6 and is provided so as to be in contact with the inner wall of the toner transport container 72.

The rotating shaft 76 is supported by bearings 78 and 79 provided at both ends in the length direction of the toner carrying container 72, and is rotated by driving means (not shown).
The residual toner scraped off from the peripheral surface of the photosensitive drum 30 by the cleaning blade is conveyed by the spiral 70 to the toner conveying device 71 side, and falls onto the conveying member 73 in the toner conveying container 72 from the opening 74.

Here, the conveying member 73 is driven to rotate, and the toner conveyed by the spiral 70 is conveyed in the toner conveying container 72 rightward in FIG. The toner is further discharged into the developing device 32. At this time, the contact member 77 of the transport member 73 is formed of a brush made of an elastic synthetic resin material, and transports the toner while rubbing the inner wall of the toner transport container 72. Therefore, the tip of the contact member 77 always cleans the inner wall of the toner transport container 72, and the toner does not stick to the inner wall of the toner transport container 72. Further, since the contact member 77 has elasticity, the contact member 77 is always elastically deformed by rotating.
It is difficult for the toner to adhere to the surface, and even if the toner adheres, the toner is easily separated by elastic deformation, so that the adhered toner does not become a large lump and does not block the inside of the toner transport container 72. Therefore, the toner conveying device 71
Can be prevented from lowering. [Developing Apparatus] The developing apparatus 32 has a casing 85 as shown in FIGS. In this casing 85, two spirals 81 and 82 and a stirring paddle 83
And a developing roller 84 are provided.

The spirals 81, 8 are provided in the casing 85.
Grooves 86 and 87 in which 2 are arranged are formed. The grooves 86 and 87 form a transport path in which the carrier and the toner are stirred and transported by the spirals 81 and 82. In the groove 86, the spiral 81 is driven to rotate, so that the carrier and the toner are transported upward from the bottom in FIG. Further, in the groove 87, the carrier 82 and the toner are transported downward from above in FIG. 3 by rotating the spiral 82. Between the groove 86 and the groove 87, a partition wall 88 for isolating both transport paths is formed. This partition wall 88
Has notches 89 and 90 at both ends in the length direction, and the notches 89 and 90 connect the groove 86 and the groove 87. From this, spiral 8
The carrier and toner conveyed by 1, 82
Circulation is performed along the groove 86 and the groove 87 while being stirred.

The developing device 32 has a detachable toner cartridge 91 for storing toner therein and replenishing the developing device 32 with toner. The toner cartridge 91 has a casing 94 in which a spiral 92 and a stirring paddle 93 are built. Casing 94
Is provided with a toner outlet 95 for discharging toner.

In the casing 85 of the developing device 32, a toner supply port 96 is provided at a position corresponding to the toner discharge port 95 of the toner cartridge 91. The toner supply port 96 is provided above the groove 86 in which the spiral 81 is arranged. In the casing 85 of the developing device 32, a collected toner supply port 97 is provided at a position corresponding to the discharge port 75 of the toner conveying device 71. The recovered toner supply port 97 is provided above the groove 87 in which the spiral 82 is disposed and near the notch 90.

As a result, the collected toner conveyed by the toner conveying device 71 is supplied to the collected toner supply port 9.
7, falls on the spiral 82. The position where the collected toner falls is the lower end position of the spiral 82 in FIG. Since the conveying direction of the spiral 82 is downward from above in FIG. 3, the collected toner dropped on the spiral 82 is immediately conveyed to the groove 86 in which the spiral 81 is arranged via the cutout 90. .

Here, the toner is mixed with the toner supplied from the toner cartridge 91 through the toner supply port 96,
While being stirred with the carrier by the spiral 81,
It is transported upward from the bottom in FIG. The carrier and the toner conveyed upward by the spiral 81 are conveyed to the groove 87 via the notch 89, further stirred by the spiral 82, and conveyed in the groove 87.

A part of the carrier and toner transported in the groove 87 overflows to the stirring paddle 83 side, and the stirring paddle 83
Is transported to the developing roller 84 side. Developing roller 8
Due to the toner attached to 4, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 30 is visualized as a toner image. As described above, since the collected toner collected by the cleaning device 34 is directly conveyed to the developing device 32 and recycled, the resources can be effectively used. In the developing device 32, two spirals 8 are provided.
1 and 82 are disposed, and by dropping the collected toner collected from the cleaning device 34 onto the spiral, the mixing of the carrier and the toner can be suitably performed. In particular, since the collected toner supply port 97 is provided upstream of the supply port 96 for supplying new toner from the toner cartridge 91 in the carrier and toner transport paths formed by the spirals 81 and 82, each of the spirals 81 , 82, the carrier, the recovered toner and the new toner can be sufficiently stirred, and the image quality does not deteriorate. [Toner replenishing section] The toner cartridge 91
3 can be moved between a set position (FIG. 3) where the toner supply port 96 overlaps the toner supply port 96 of the developing device 32 and a retreat position located rightward from the set position in FIG. It is configured to slide.

As shown in FIG. 4, the toner cartridge 9
A first slide plate 101 that is slidable is attached to 1, and is urged by a spring 102 in a direction of blocking the discharge port 95. The right end portion of the first slide plate 101 has an operating projection 1 that can contact a part of the developing device 32.
03. A second slide plate 1 slidable near the toner supply port 96 of the developing device 32.
The toner supply port 04 is urged by a spring 105 in a direction of blocking the toner supply port 96. The left end portion of the second slide plate 104 forms an operating projection 106 that can abut a part of the toner cartridge 91.

The left outer surface of the discharge port 95 of the toner cartridge 91 constitutes a position restricting portion 107 which abuts on the operating projection 106 of the second slide plate 104 and slides the second slide plate 104. The right outer surface of the toner supply port 96 of the developing device 32 is
A position restricting portion 108 that comes into contact with the first operating projection 103 and slides the first slide plate 101 is configured.

When the toner cartridge 91 is not set at the set position, as shown in FIG. 4, the first slide plate 101 is urged leftward by a spring 102 to shield the discharge port 95. I have. The second slide plate 104 is also urged rightward in the figure by a spring 105 to shield the toner supply port 96. Toner cartridge 91
Is slid to the left in the figure and set to the set position, as shown in FIG. 5, the operating projection 103 of the first slide plate 101 comes into contact with the position regulating portion 108 of the developing device 32, and the urging force of the spring 102 is applied. To the right in the figure, and the discharge port 95 of the toner cartridge 91 is opened.
At the same time, the operating projection 106 of the second slide plate 104 comes into contact with the position regulating portion 107 of the toner cartridge 91, and moves to the left in the drawing against the urging force of the spring 105.
The second toner supply port 96 is opened. As a result, the discharge port 95 of the toner cartridge 91 and the developing device 3
The second toner supply port 96 is in communication with the second toner supply port 96, and toner can be supplied from the toner cartridge 91 to the developing device 32.

When the toner cartridge 91 is to be moved to the retreat position in order to replace the toner cartridge 91 or to perform another process, the toner cartridge 91 is moved rightward in the drawing from the state shown in FIG. At this time, the first slide plate 101 is released from the regulation of the position regulating unit 108, moves to the left in the figure by the urging force of the spring 102, and blocks the discharge port 95 of the toner cartridge 91. At the same time, the second slide plate 104
After being released from the regulation of the position regulating unit 107, the urging force of the spring 105 moves rightward in the figure, and blocks the toner supply port 96 of the developing device 32.

As a result, the toner cartridge 91
Is moved from the predetermined set position, the discharge port 95 of the toner cartridge 91 is blocked by the first slide plate 103, and the toner supply port 96 of the developing device 32 is
Since the toner is shielded by the slide plate 104, the toner can be prevented from scattering to the outside. In particular, when performing a maintenance operation, a large amount of toner may remain inside the toner cartridge 91, and even if the toner cartridge 91 is moved to the retreat position, the remaining toner may be scattered to the outside. Can be prevented.

It is also possible to separately provide a position regulating member for contacting the operation projection 103 of the first slide plate 101 in the developing device 32, and the operation projection 106 of the second slide plate 104.
A position regulating member that comes into contact with the toner cartridge 91 is separately provided.
Can also be provided. Further, the case where the toner cartridge 91 is directly attached to the developing device 32 has been illustrated. However, the toner cartridge 91 is provided with a toner hopper for supplying toner to the developing device, and the toner cartridge is detachably attached to the toner hopper. Even so, a similar configuration is possible. [Imaging Unit] As shown in FIG. 6, the photosensitive drum 30, the main charging device 31, the developing device 32, the cleaning device 34, and the toner conveying device 71 are composed of a casing 1
Imaging unit 11 integrally housed in 11
0. The lower surface of the casing 111 is a bottom surface 11 serving as a horizontal surface when housed inside the copying machine 1.
Two. Guided grooves 113 and 114 are provided on the bottom surface 112 in a direction perpendicular to the plane of FIG. Copier 1
On the side, guide members 115 and 116 extending in a direction perpendicular to the plane of FIG. 6 are formed. Guided grooves 113 and 114 of the imaging unit 110 are fitted in guide members 115 and 116, respectively, so that the imaging unit 110 can move in a direction perpendicular to the plane of FIG.

The imaging unit 110 is guided by guide members 115 and 116 and can be pulled out to the front of the copying machine 1 (vertically upward in FIG. 6). The imaging unit 110 pulled out of the copying machine 1 uses the bottom surface 112 of the casing 111 to
Can be placed on a horizontal surface. As a result, when the imaging unit 110 is pulled out of the copying machine 1,
The printer can be placed on a horizontal surface while maintaining the state of being stored in the copying machine 1, and the developer and the toner stored therein can be stably maintained. Further, the peripheral surface of the photosensitive drum 30 exposed to the outside is not damaged.
Furthermore, since there is no need to provide any parts that project downward or other parts outward, the work of attaching and detaching the imaging unit 110 is facilitated, and other parts and workers are not damaged. [Control Unit] A control unit 251 is provided inside the copying machine 1 as shown in FIG. The control unit 251 controls the CP
It is constituted by a microcomputer system including U, RAM, ROM, various drivers and the like. Control unit 251
Includes an operation panel 252 for issuing various operation instructions.
Is connected. The operation panel 252 includes an input key unit including numeric keys and other command keys, a liquid crystal display element, and an L key.
It includes a display unit such as an ED, and also includes a start key for instructing the start of a copying operation.

The control unit 251 further includes an image reading unit 2
53 are connected. The image reading unit 253 includes the above-described optical system 21 and the like, irradiates light to a document placed on the document table 15, reads light reflected from the document by the image sensor 27, and converts the light into an image data signal. . Control unit 2
An image processing unit 254 that receives an image data signal output from the image sensor 27 and performs image processing is connected to 51.

An exposure unit 255 including a laser unit 35 is connected to the control unit 251. The exposure unit 255 irradiates a laser beam from the laser unit 35 based on the image information processed by the image processing unit 254, and forms an electrostatic latent image on the peripheral surface of the photosensitive drum 30. Further, the control unit 251 includes the image forming unit 16 including the photosensitive drum 30, the developing device 32, the transfer roller 33, and the like.
6, a paper feed unit 17 for transporting the paper, and a fixing device 53 for heating and fusing and fixing the toner image transferred to the paper surface in the image forming unit 16 are connected. The T of the developing material provided in the developing device 32 and housed in the developing device 32
A toner density sensor 261 for detecting / D is connected to the control unit 251. Further, a humidity sensor 262 for detecting the absolute humidity in the apparatus is connected to the control unit 251. Further, a toner replenishing motor 2 for replenishing toner from the toner cartridge 91 into the developing device 32 is provided.
63 is connected to the control unit 251. Further, a transfer voltage applying unit 2 for applying a transfer voltage to the transfer roller 33
64 is connected to the control unit 251.

As shown in FIG. 3, the toner cartridge 91 is provided with a rotatable stirring paddle 93 for stirring the toner contained therein. The rotating shaft of the stirring paddle 93 extends above the discharge port 95,
A spiral (not shown) that conveys the toner from right to left in the figure with the rotation of the rotating shaft is provided near the discharge port 95. The toner supply motor 263 is configured to rotationally drive the rotation shaft of the stirring paddle 93 so that toner is supplied from the toner cartridge 91 to the developing device 32 according to the drive time of the toner supply motor 263. It is configured.

In the control unit 251, the toner density sensor 26
T / D of the developing material in the developing device 32 based on the output signal of
, The ON / OFF duty ratio of the drive signal supplied to the toner supply motor 263 is determined, and the toner supply amount from the toner cartridge 91 so that the T / D in the developing device 32 becomes a predetermined target T / D value. To adjust. Further, the control unit 251 applies a predetermined transfer voltage value to the transfer roller 33 via the transfer voltage application unit 264 to transfer an image from the photosensitive drum 30 to a sheet.

The control unit 251 controls the target T / D based on the absolute humidity in the apparatus detected by the humidity sensor 262.
Correct the value. At the same time, the transfer voltage application unit 264 corrects the transfer voltage value.

[0041]

[Table 1]

For example, as shown in Table 1, a temperature of 20 ° C. /
Under a normal environment with a humidity of 45%, the target T
Density sensor 261 for setting / D value to 4.5%
Is 3.0V. At this time, the transfer voltage value by the transfer voltage application unit 264 is set to 5 kV. When the temperature becomes 20 ° C./humidity 85% from this state, the output of the toner density sensor 261 becomes 4.0 V even if the T / D value in the developing device 32 is the same. As the output of the toner density sensor 261 varies with humidity, the target T /
The D value fluctuates to about 5.5%. Therefore, the control unit 251 controls so as to lower the target T / D value. Since the humidity is rising, the target T under normal environment
Even if it is set to 4.5%, which is the / D value, there is a risk of toner scattering. Here, it is preferable to set it lower than 4.5%, for example, it is set to 4.0%. .
This makes it difficult to obtain an appropriate image density. However, by increasing the transfer voltage applied to the transfer roller 33, a sufficient image density can be obtained. In this case, as shown in Table 1, the transfer voltage value is set to 5.5 kV.

With this setting, the image density formed on the paper is not affected by the absolute humidity in the apparatus. For example, even if the humidity rises, the scattering or fogging of the toner And the occurrence of uneven density can be prevented. Instead of correcting the transfer voltage value in accordance with the absolute humidity, the voltage applied to the main charging device 31 is changed in accordance with the absolute humidity, and the surface potential of the photosensitive drum 30 is corrected. Can be obtained.

[0044]

According to the present invention, the target T / D value is corrected on the basis of the absolute humidity in the apparatus, and the applied voltage value applied to the transfer apparatus is corrected, so that the image density to be formed can be reduced. By maintaining the temperature appropriately, it is possible to prevent toner scattering, fogging, density unevenness, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a copying machine employing an embodiment of the present invention.

FIG. 2 is an explanatory view of a main part.

FIG. 3 is an explanatory diagram of a main part.

FIG. 4 is an explanatory diagram illustrating an operation of a toner supply unit.

FIG. 5 is an explanatory diagram illustrating an operation of a toner supply unit.

FIG. 6 is a longitudinal sectional view of the imaging unit.

FIG. 7 is a control block diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier 30 Photoconductor drum 31 Main charging device 32 Developing device 33 Transfer roller 34 Cleaning device 251 Control unit 252 Operation panel 253 Image reading unit 254 Image processing unit 255 Exposure unit 261 Toner density sensor 262 Humidity sensor 263 Toner supply motor 264 Transfer Voltage application section

Claims (2)

[Claims] An electrostatic latent image formed on the peripheral surface of a photosensitive drum is visualized into a toner image by a developing device, and a toner on the photosensitive drum is transferred from a back surface of a sheet by a transfer device to which a high voltage is applied. An image forming apparatus that attracts an image and transfers the image to a sheet, comprising: a toner concentration detecting unit configured to measure a toner concentration of a developer in the developing device; Toner supply means for replenishing toner so that the toner concentration becomes a predetermined target T / D value; transfer voltage application means for applying a voltage to the transfer apparatus; humidity detection means for detecting absolute humidity in the apparatus; The target T / D value of the toner replenishing unit is corrected based on the absolute humidity detected by the humidity detecting unit, and the voltage applied to the transfer device by the voltage applying unit is corrected. Image forming apparatus and an image density control means for correcting the. 2. The image forming apparatus according to claim 1, wherein said image density control means is adapted to increase the absolute humidity detected by said humidity detecting means.
The image forming apparatus according to claim 1, wherein a value is set to be low and a voltage value applied to the transfer device is set to be high.