JP2002174962A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which problems such as machine inside soiling and the back staining of a recording material are eliminated by preventing toner overflow due to the excessive stacking of toner to a cleaning member for a recording material carrier, an intermediate transfer body and a transfer member. SOLUTION: In the image forming device capable of both-side printing, a toner image is directly formed to a recording material feeding member 30 at regular intervals, so that the toner is supplied to the cleaning blade 8a of the recording material feeding member 30.

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 capable of forming a double-sided image by forming an image on one side of a recording material and then forming an image on the back surface of the same recording material using an electrophotographic method.

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming units using an electrophotographic method are provided, and toner images of different colors are formed in each image forming unit, and the toner images are sequentially superimposed on the same recording material. Various image forming apparatuses for forming a color image on a recording material by transferring the image have been proposed. A color copying machine for performing color high-speed recording, which includes a transfer belt as a recording material conveying member in the form of an endless belt and in which a plurality of image forming units are linearly arranged along the transfer belt, has been proposed.

An example of this color copier will be briefly described with reference to FIG. 1. First, second, third, and fourth image forming units Pa, Pb, Pc, and Pd are arranged in the apparatus. The image forming section includes electrophotographic photosensitive drums 3a, 3b, 3c, and 3d each serving as a dedicated image carrier, and a toner image of each color is formed on each photosensitive drum. A transfer belt (belt-shaped recording material transporting member) 30 is installed adjacent to each photosensitive drum, and a recording material on which each color toner image formed on each photosensitive drum 3 is carried on the transfer belt 30 and transported. It is superimposed and transferred onto P. The recording material P to which the toner images of the respective colors have been transferred is fixed to the toner image by heating and pressurizing in the fixing device 9 and then discharged out of the apparatus as a color recorded image.

In such an image forming apparatus, in order to prevent the toner on the recording material from adhering to the fixing roller 51 of the fixing device 9 as a fixing means, a release agent oil such as dimethyl silicone oil is filled in the oil reservoir 53. The release agent oil is stored and applied to the surface of the fixing roller 51 by the application roller 50.

[0005] Further, on the transfer belt 30 after the transfer, toner stains (mainly transfer residual toner transferred from the photosensitive drum onto the transfer belt (referred to as fog toner))
, A part of which includes paper dust, etc.), and a cleaning blade 8a made of an elastic material such as rubber provided on a transfer belt cleaner 8 as cleaning means is brought into contact with the transfer belt to scrape off toner stains. Are collected in the transfer belt cleaner 8.

In the configuration shown in FIG. 1, the cleaning blade 8a is arranged such that the edge surface of the cleaning blade (the surface parallel to the blade thickness direction from the blade contact portion to the transfer belt) faces upward with respect to the direction of gravity. Is arranged.

Such an arrangement of the cleaning blade makes it easy to hold the toner on the blade edge surface, and by this toner holding, a stable slidability is obtained at the contact portion with the transfer belt, and a polishing effect of the toner is added. Thus, the cleaning performance can be improved.

[0008]

However, in such an image forming apparatus, when an image is formed on both sides of a recording material, excessive toner is accumulated on the edge of the cleaning blade 8a, and the accumulated toner is removed by the cleaner. 8
A problem of overflowing from above. The overflowed toner adheres to the back surface of the recording material and becomes a back stain, or scatters in the apparatus to stain the inside of the apparatus.

As a result of investigations by the present inventors, the reason that toner builds up on the edge of the cleaning blade 8a is as follows.
The following reasons were found. That is, after the image is formed on one side of the recording material and is fixed by the fixing device 9, the recording material is turned upside down so as to form an image on the back surface (second surface) and is again carried on the transfer belt 30. The fixing oil adhered to the surface (first surface) of the recording material adheres to the transfer belt 30 and is carried to the cleaning blade 8a. Therefore, when the contaminated toner on the transfer belt 30 is carried to the cleaning blade 8a, the toner is mixed with the powdered toner to form a clay, and is accumulated on the edge surface of the cleaning blade 8a.

[0010] The above-described problem is caused by an intermediate transfer type image forming apparatus in which a toner image on a photosensitive drum is once transferred to an intermediate transfer member and then transferred from the intermediate transfer member to a recording material. In the case where the cleaning device having the above-described configuration is used, the same occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent toner overflow due to excessive accumulation of toner on a cleaning member with respect to a recording material carrier, an intermediate transfer member, and a transfer member, and to prevent problems such as contamination inside the apparatus and back contamination of the recording material. An object of the present invention is to provide a lost image forming apparatus.

[0012]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image forming unit for forming a toner image, a recording material conveying member for carrying and conveying the recording material, a cleaning unit including a cleaning blade in contact with a surface of the recording material conveying member, and a fixing member coated with a release agent. An image forming apparatus capable of forming an image on a surface opposite to a toner image transfer surface on a recording material that has undergone a fixing operation by the fixing unit. The cleaning blade is arranged in such a manner that the surface of the cleaning blade, which is close to the contact portion and faces upstream from the contact portion in the recording material transporting member transport direction, has a normal to the surface of the blade substantially in the direction of gravity. The toner image to be supplied to the cleaning unit, which is disposed and formed by the image forming unit, is directly transferred onto the recording material conveying member, and the recording material conveying member is conveyed to transfer the toner image onto the recording material conveying member. Turn An image forming apparatus, characterized in that the supplying toner image comprises control means, for controlling to supply to the cleaning means.

According to another aspect of the present invention, there is provided an image forming means for forming a toner image, an intermediate transfer member for carrying the toner image formed by the image forming means, and a toner carried on the intermediate transfer member. A transfer unit that transfers an image to a recording material, a cleaning unit that includes a cleaning blade that abuts on the surface of the intermediate transfer body, and a fixing unit that includes a fixing member coated with a release agent. In the image forming apparatus capable of forming an image on the surface opposite to the toner image transfer surface with respect to the recording material that has undergone the fixing operation, the image forming apparatus is close to the contact portion with the intermediate transfer body, and is more intermediate than the contact portion. The cleaning blade is disposed such that the surface of the cleaning blade facing the upstream side in the transfer body transport direction is directed to the direction of gravity substantially in the direction of gravity, and the cleaning unit is formed by the image forming unit. Companion Control means for carrying the toner image for use on the intermediate transfer body, and controlling the supply of the carried supply toner image to the cleaning means by transporting the intermediate transfer body. An image forming apparatus is provided.

According to still another aspect of the present invention, there is provided an image forming means for forming a toner image, a transfer member for transferring the toner image formed by the image forming means to a recording material, and a transfer member for contacting a surface of the transfer member. Cleaning means having a cleaning blade in contact therewith;
A fixing unit having a fixing member coated with a release agent; and an image capable of forming an image on a surface opposite to a toner image transfer surface on a recording material subjected to a fixing operation by the fixing unit. In the forming apparatus, the surface of the cleaning blade that is close to the contact portion with respect to the transfer member and faces upstream from the contact portion in the transfer member transport direction is such that the normal line of the blade surface is substantially in the direction of gravity. The cleaning blade is disposed, and the toner image for supply to the cleaning unit formed by the image forming unit is directly transferred to the transfer member,
An image forming apparatus comprising: a control unit configured to control the supply of the supply toner image to the cleaning unit by conveying the transfer member.

According to the present invention, in an image forming apparatus capable of performing double-sided printing, a toner image is periodically formed directly on a recording material conveying member, an intermediate transfer member or a transfer member, and the toner is transferred to the recording material conveying member. To the cleaning blade of the intermediate transfer body and the cleaning blade of the transfer member, so that the oil adhering to the recording material at the time of fixing is transferred to the recording material transporting member, the intermediate transfer body and the transfer member at the time of double-sided printing. Caused by
The accumulation of toner on the cleaning blade can be prevented, and problems such as contamination in the apparatus and back contamination of the recording material can be prevented.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus according to the present invention, which is configured as a four-color full-color copying machine.

In this copying machine, a plurality of image forming units Pa,
Pb, Pc, Pd, and the image forming units Pa, Pb, P
c and Pd rotatably have photosensitive drums (drum-shaped electrophotographic photosensitive members) 3a, 3b, 3c and 3d as image carriers, and have chargers 2a, 2b and 2 around them.
c, 2d, potential sensors 113a, 113b, 113
c, 113d, developing devices 1a, 1b, 1c, 1d, transfer chargers (blades) 24a, 24b, 24c, 24d, and drum cleaners 4a, 4b, 4c, 4d are provided.
A light source device (not shown) and a polygon mirror 117 are installed above the device.

The photosensitive drums 3a to 3d are charged to a predetermined potential by respective chargers 2a to 2d. Then
The laser light emitted from the light source device is converted to a polygon mirror 1
Scanning is performed by the rotation of 17, and the light beam of the scanning light is deflected by a reflection mirror, and is condensed and exposed to the generatrix of the photosensitive drums 3a to 3d by an f.theta. An electrostatic latent image corresponding to the image is formed.

The developing devices 1a, 1b, 1c, and 1d are filled with a predetermined amount of cyan, magenta, yellow, and black toners by a supply device (not shown). The developing devices 1a, 1b, 1c, and 1d develop the latent images on the photosensitive drums 3a, 3b, 3c, and 3d, respectively, and visualize the latent images as cyan, magenta, yellow, and black images.

At the lower portion of the apparatus, a recording material cassette 10 containing a recording material P is installed. The recording material P is conveyed from the cassette 10 to the registration roller 12 through a conveyance path 65 by a plurality of conveyance rollers, supplied from the registration roller 12 onto the transfer belt 30, and carried thereon.
, And are sequentially sent to the transfer units facing the photosensitive drums 3a, 3b, 3c, and 3d.

The transfer belt 30 is made of a dielectric sheet such as polyimide, polyethylene terephthalate (PET), polyvinylidene fluoride, and polyurethane.
Either end portions thereof are overlapped and joined to form an endless shape, or a seamless (seamless) belt is used. The volume resistivity of such a transfer belt is generally 10 ¹³ to 10 ¹⁸ Ωcm. In this embodiment, a polyimide resin sheet is used.

The transfer belt 30 is supported and installed by the driving roller 13 and the stretching roller 15. Transfer belt 3
0 is rotated by the driving of the drive roller 13, and when it is confirmed that the recording material P is at a predetermined position, the recording material P is sent out from the registration roller 12 to the transfer belt 30 and carried thereon, and the first recording material P is carried.
The sheet is conveyed toward the transfer section of the image forming section Pa. At the same time, the image writing signal is turned on, and an image is formed on the photosensitive drum 3a of the image forming unit Pa at a certain timing based on the signal. The first color toner image obtained on the photosensitive drum 3a is transferred onto the recording material P by the transfer charger 24a in the lower transfer section of the photosensitive drum 3a applying an electric field or charge.

By this transfer, the recording material P is transferred to the transfer belt 3
On the other hand, the sheet P is firmly held by the electrostatic attraction force and is conveyed to the second image forming portion Pb and thereafter. Thus, instead of electrostatically adsorbing the recording material P onto the transfer belt 30 at the same time as the transfer, the adsorption charger 5 is provided at a position on the upstream side of the first image forming unit Pa. It may be adsorbed.

As the attraction charger 5, a non-contact charger such as a corona charger or a contact charger using a charging member such as a blade, a roller, or a brush is used.

Similarly, as the transfer charger 24 (24a to 24d), a non-contact charger such as a corona charger or a contact charger using a charging member such as a blade, a roller, or a brush is used. The non-contact charging device has problems such as generation of ozone, and susceptibility to fluctuations in the temperature and humidity environment of the atmosphere due to charging through air, resulting in unstable image formation. On the other hand, the contact charger has advantages such as ozonelessness, resistance to environmental changes in temperature and humidity, and high image quality.

In some cases, static elimination needles 7a to 7d are provided for stabilizing transferability. The static elimination needles 7a to 7d are connected to the transfer belt 30.
Has a role of discharging a part of the transfer current to escape. Thereby, it is possible to prevent the toner image from being disturbed due to the peeling discharge when the photosensitive drum and the recording material are peeled off.

Image formation and transfer of the second to fourth image forming units Pb to Pd are performed in the same manner as in the first image forming unit Pa. The recording material P on which the toner images of four colors are superimposedly transferred in this manner.
Then, at the downstream side of the transfer belt 30 in the transport direction, the charge is removed by the separation charge remover 32, and the electrostatic attraction force is attenuated, thereby separating from the end of the transfer belt 30. In particular, in a low humidity environment, the recording material is also dried and the electric resistance is high, and the attraction force with the transfer belt is large. Therefore, a separation static eliminator is necessary for separating the recording material. Normally, a non-contact charger is used for the separation charge eliminator 32 because the toner image is charged to the recording material P on which the toner image is not fixed, which is opposite to the adsorption charge.

The detached recording material P is conveyed by the guide member 64 and the conveying section 62 to the fixing device 9 as fixing means.

The fixing device 9 includes a fixing roller 5 serving as a fixing member.
1. Pressure roller 52, heat-resistant cleaning members 54 and 55 for cleaning each of them, and rollers 51 and 52
Heaters 56 and 57 installed inside the fixing roller 5
1, an application roller 50 for applying a release agent oil such as dimethyl silicone oil, an oil storage tray 53 for storing the oil, and a thermistor 58 for detecting the temperature of the surface of the pressure roller 52 and controlling the fixing temperature. And

The recording material P to which the four color toner images have been transferred is
The color of the toner image is mixed and fixed to the recording material P by the fixing, and a full-color copy image is formed.

The photosensitive drums 3a, 3b, 3 after the transfer is completed
c, 3d are the respective cleaners 4a, 4b, 4c, 4
d removes the transfer residual toner by cleaning, and prepares for the formation of the next latent image. Toner and other stains remaining on the transfer belt 30 are removed by a urethane rubber cleaning blade 8a in contact with the transfer belt 30 of the transfer belt cleaner 8 as cleaning means.
It is collected in the cleaner 8. After the cleaning, the transfer belt 30 is cleaned of residual charges on the surface thereof by the charge removing rollers 21 and 22 to prepare for the next transfer step.

It is known that the transfer charger 24 stabilizes an image when the current contributing at the time of transfer is fixed to an appropriate value. Therefore, it is general to perform constant current control so that a constant current can be obtained even when the volume resistivity changes depending on the type (thickness, material, etc.) of the recording material, moisture absorption conditions, and the like.

Further, the image forming apparatus includes a control unit 100 for controlling the operation of the image forming apparatus.

The single-sided printing process is performed in the recording material cassette 10
The toner image is transferred onto the recording material P conveyed from the printer, fixed, and immediately discharged to the paper discharge tray 63. On the other hand, in the double-sided printing process, the recording material P, which has been fixed in the single-sided printing process, is sent to the conveyance path 67 without being discharged, then is switched back and sent to the double-sided conveyance path 66, and then again via the conveyance path 65. The sheet is conveyed to the transfer belt 30. The transfer material P is placed so that the surface (first surface) of the transfer belt 30 on which the toner image is fixed is in contact with the transfer belt 30, and thereafter, the toner image is transferred to the back surface (second surface) of the recording material P in the same manner as in the single-sided printing process. Transcribed,
It is fixed and discharged.

At the time of fixing, the recording material P comes into contact with the fixing roller 51 to which the fixing oil has been applied, so that the fixing oil adheres to the surface of the recording material P, and at the time of printing on the back surface of the recording material P, the recording material P The fixing oil is transferred to and adhered to the transfer belt 30 because the surface on which the fixing oil has adhered is placed on the transfer belt 30.

When paper is used as the recording material P, the fixing oil adhering to the white background where there is no toner image on the paper is almost absorbed into the paper, and the amount of oil remaining on the paper surface is small. However, as for the oil adhering to the portion where the toner image is present, only a part of the adhering oil is absorbed into the paper, and most of the oil remains on the surface of the toner image. Become. Therefore, the larger the area occupied by the toner image on the paper and the higher the density of the toner image, the more the amount of oil adhering to the transfer belt 30 tends to increase.

Next, the transfer belt cleaner will be described with reference to FIG.

The transfer belt cleaner 8 has the cleaning blade 8a as described above, and the cleaning blade 8a is, as shown in FIG.
And more specifically, for example, at a position corresponding to approximately 9 o'clock in the clockwise hand on the circumference of the drive roller 13 at a position corresponding to approximately 9 o'clock.
0, the contact pressure is 500 gf, and the angle between the tangent at the contact and the blade 8a is about 10 degrees. Thus, the cleaning blade 8a
Are arranged such that the blade edge surface A facing the upstream side in the transport direction of the transfer belt 30 has a normal line of the blade edge surface A substantially in the direction of gravity.

The cleaner 8 has a container 8c, and the cleaning blade 8a has a sheet metal 8 fixed in the container 8c.
b.

As described above, by providing a configuration in which the cleaning blade abuts on the portion where the transfer belt 30 is hung on the drive roller, there is no need to provide a dedicated member as a backup member in the blade abutment portion. By increasing the pressure contact force with the transfer belt, the belt can be transported more stably.

The fog toner R on the transfer belt 30 is conveyed to the cleaning blade 8a by the rotation of the transfer belt 30, is scraped off by the cleaning blade 8a, and is collected in the container 8c. Here, the fog toner means the photosensitive drum 3 (3a to 3d) and the transfer belt 3
The toner adhering to the non-image area of the photosensitive drum is transferred to the transfer belt 30 when 0 is in direct contact with the recording medium without passing through the recording material.

The toner collected in the container 8c moves along the inner wall of the container as shown by oblique lines W, and is sent to a collection box (not shown) by the transport screw 8d installed in the container 8c. An upper portion of the cleaning blade 8a is provided with a shielding plate 8e fixed to an end of the container 8c.
(a) prevents the toner scraped off from scattering upward.

In the image forming apparatus provided with such a transfer belt cleaner 8, when double-sided printing was continuously performed, the image was formed along the belt 30 on the outer peripheral surface of the drive roller 13 from the blade edge surface A of the cleaning blade 8 a. When the toner accumulation T is increased and the toner accumulation T is increased, the toner overflows from a gap between the driving roller 13 and the guide member 64, separates from the transfer belt 30 and passes over the guide member 64. An image defect that adheres to the lower surface of the recording material and stains the recording material occurs.

After studying the cause of the occurrence of stacking, the fixing oil F adhered to the transfer belt 30 was examined.
It has been clarified that the fogging toner R is cleaned by the cleaning blade 8a, accumulates at the upper end of the cleaning blade 8a, and mixes there, and the viscosity of the fogging toner R is increased to accumulate.

FIG. 3 shows the results of measuring the toner accumulation height by changing the mixing ratio (weight ratio) between the fixing oil adhering to the recording material and the fogging toner on the transfer belt. Here, the toner accumulation height is the distance X shown in FIG. 2, that is, the toner accumulation T which comes into contact with the transfer belt 30 from the upper end of the cleaning blade 8a on which the toner is accumulated.
Is the distance to the top of

As can be seen from FIG. 3, the toner stacking height is such that the ratio of the oil weight to the fogging toner weight is 0.1%.
When the value is 5 to 1.5, the maximum value is 8 mm or more, and when the value is smaller or larger than this, the toner accumulation height is low.

This is because, when the amount of the oil is a very small amount of 0.5 or less, the toner mixed with the oil has a shape close to that of the dried powder, and the toner collapses on the cleaning blade 8a and the container is broken. 8c. In particular, when only one-sided printing is performed, the amount of oil adhering to the transfer belt is zero, and the stacking height is as low as 2 mm. If the weight ratio is 1.5 or more and the oil is contained in a large amount, the toner in which the oil is mixed becomes fluid and flows down from the cleaning blade 8a.

The cleaning blade 8a in the present apparatus
The normal weight ratio of the amount of oil and the amount of toner supplied to
0.5 to 1.5 is measured, so that the toner accumulation is as large as 8 mm or more. This is because the distance S from the upper end of the cleaning blade 8a to the upper surface of the guide member 64 shown in FIG.
Therefore, an image defect occurs due to toner adhesion on the lower surface (first surface) of the recording material.

In order to prevent the occurrence of image defects, it is sufficient to reduce the toner accumulation height on the cleaning blade 8a. To this end, the amount of oil adhering to the transfer belt 30 must be reduced, and therefore, it adheres to the recording material. It is conceivable to reduce the amount of oil. However, when the amount of oil applied to the fixing roller 51 was reduced to reduce the amount of oil applied to the recording material, no significant change was observed in the toner accumulation height, while the amount of oil applied was small.
The releasability between the fixing roller and the recording material is reduced, and a new problem occurs in that the recording material is wound around the fixing roller.

The reason why the accumulation height of the toner does not change is that even if the amount of oil on the transfer belt 30 is reduced, the cleaning blade 8a always abuts on the belt to block the oil. This is because oil accumulates on the blade and mixes with the toner. Therefore, a method of reducing the amount of oil applied to the fixing roller has not been effective.

Therefore, when the toner accumulates on the cleaning blade edge surface A so that the toner does not overflow from the cleaning device, a toner image is formed on the photosensitive drum 3 and the toner image is transferred to the transfer belt 30. do it,
By forming a toner image directly on the transfer belt 30,
This toner image is supplied to the cleaning blade 8a,
When the mixing ratio of the oil to the toner was reduced, it was confirmed that the accumulated toner collapsed. This is because the oil accumulated on the cleaning blade 8a is absorbed by the supplied toner image, and the mixing ratio of the oil is reduced.

Further, by supplying the toner image, the toner image enters between the accumulated toner T on the cleaning blade 8a and the transfer belt 30, and the accumulated toner is easily released from the transfer belt or supplied. There is also an effect that the accumulated toner image presses the accumulated toner to drop from the cleaning blade.

FIG. 4 shows a toner image for forming an image directly on the transfer belt. The recording material P is conveyed while being adsorbed substantially at the center of the transfer belt 30 in a direction perpendicular to the running direction of the transfer belt 30. The directly formed toner image Q is a rectangular pattern having a width t in the vertical direction and a width r in the running direction. The vertical width t is the maximum width m of the recording material to be used, and the width b of the cleaning blade 8a. The length is set to satisfy m ≦ t ≦ b. Further, the pattern toner image Q, the recording material P, and the cleaning blade 8a are arranged symmetrically with respect to the center axis E in the width direction of the transfer belt 8, respectively. Transfer belt 30
The width to which the oil adheres is the same as the recording material width m. Therefore, the width at which the oil is mixed on the cleaning blade 8a is substantially the same as the recording material width m.

As described above, the width t of the pattern toner image Q is made longer than the width m of the recording material so that the width direction of the pattern toner image Q covers the width direction of the recording material P.
The oil mixture ratio of the toner accumulated on the cleaning blade 8a could be reduced uniformly regardless of the location. Further, the width t of the toner image Q is adjusted by the cleaning blade 8.
By making the width a of the transfer belt 30 smaller than the width b, the pattern toner image Q on the transfer belt 30 is scraped by the cleaning blade 8a over the entire area in the width direction.
No cleaning residual toner was generated on the top.

As a result of examining the toner amount of the pattern toner image Q, it was found that there was an optimum toner amount. 5 will be described with reference to FIG. 5. FIG. 5 is a result obtained by examining the stacking height of the toner when a pattern toner image is supplied for every fixed number of double-sided prints while changing the density level of the pattern toner image. is there.

The pattern toner image has a high density regardless of the location.
A solid image or a halftone image having a uniform degree was used. Patter
The total amount of toner in the toner image is determined in terms of toner consumption.
Since it is preferable to use as little as possible, the pattern toner image
1mg / cm ^TwoAnd change the concentration.
While changing the width r in the transfer belt running direction
Was. The width t in the vertical direction is constant at 300 mm. This
Then, the solid image has a total toner amount of 1 mg / cm.^Two, R =
12.5 mm and t = 300 mm. The density level is 0
To 256 levels. 0 level is white background
The image at 256 levels corresponds to a solid image.

As shown in FIG. 5, if the density of the pattern toner image is too low, there is no effect of disturbing the accumulated toner, and the accumulated height is minimized at the halftone 64 level (r = 50 mm). It was found that the height of the pile gradually increased when the level of was increased. The reason why the accumulation height of the toner increases on the high density side is because the toner layer of the pattern toner image is thick, so that the toner in the upper layer does not sufficiently mix with the accumulation toner on the blade edge portion, and the oil in the cleaner container is not absorbed. 8c, and it was found that a sufficient toner accumulation removing effect could not be obtained. From these results, in the case of this configuration, setting the density of the pattern toner image to 64 levels was effective in reducing the stacking height and in reducing the toner consumption.

FIG. 6 shows the operation timing of each unit for forming a pattern toner image of a toner image on the transfer belt. This operation timing is determined by the transfer charger 24a in FIG.
The transfer position of any transfer charger of 24b, 24c, and 24d is viewed as a reference. Each area I is a timing at which a toner image to be recorded on a recording material is continuously formed on a photosensitive drum and these come to a transfer position. The recording material is sent to the transfer position by the transfer belt in synchronization with each of the toner images. The transfer bias applied to the transfer charger is turned on shortly before the recording material reaches the transfer position, and the rotation of the transfer belt is turned on in synchronization with the previous rotation start of the photosensitive drum.

The number of image forming sheets is counted by a counter which forms a part of the control means 100, and a pattern toner image for supplying toner to the cleaning unit is formed every fixed number of sheets. When the number of image formations reaches n, a pattern toner image Q1 is formed on the transfer belt between the nth and (n + 1) th toner images. The pattern toner image is formed on the transfer belt in the same manner as in the normal toner image formation. After the pattern toner image is formed on the photosensitive drum through charging, exposure, and development, the transfer bias is applied at the timing when the recording material does not exist at the transfer position. To transfer the image directly onto the transfer belt.

The counter is reset to zero when the pattern toner image is formed, then counts the number of image formation again, is reset to zero again at the next pattern toner image formation, and thereafter repeats the same operation. In addition, as a timing for forming a pattern toner image, the pattern toner image may be inserted during the rotation of the belt immediately before the end of the job that has reached n sheets without being inserted in the middle of the job (image formation in which a plurality of sheets are continuously formed) ( Q2 in FIG. 6). Alternatively, it may be inserted during the rotation of the belt immediately before the start of image formation for the job following the job that has reached n sheets.

FIG. 7 shows the change of the toner accumulation height on the cleaning blade 8a when the two-sided printing is continuously performed in the apparatus described above. The dashed line A in FIG. 7 indicates the transition in the case of the conventional example, that is, when the direct image formation of the pattern toner image on the transfer belt is not performed, and the stacking height increases as the number of image formation increases. When the number of sheets exceeded 200, the image defect exceeded the limit value of 8 mm.

On the other hand, the zigzag solid line B indicates that in this embodiment, the image formation of the pattern toner image directly on the transfer belt is performed every 100 image formations (every 50 double-sided recording materials). The stacking height increased immediately before the pattern toner image was inserted, but immediately after the pattern toner image was inserted, the height decreased, and the height was suppressed to the allowable height L or less, and no image defects occurred. However, the allowable height L is a distance from the upper end of the cleaning blade 8a to the shielding plate 8e shown in FIG. 2, and is a value with a margin for the limit value S = 8 mm.

Embodiment 2 FIG. 8 is an overall configuration diagram showing another embodiment of the image forming apparatus of the present invention.

In the first embodiment, an example in which the present invention is applied to an image forming apparatus using a transfer belt has been described. However, the present invention can also be applied to an image forming apparatus using an intermediate transfer member as shown in FIG. . 8, members having the same functions as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the image forming apparatus has a belt-like intermediate transfer member, that is, an intermediate transfer belt 140,
The intermediate transfer belt 140 is an endless belt made of polyimide resin or the like, like the transfer belt, and rotates in the direction of the arrow in the figure. Each photosensitive drum 3 (3a to 3
d) The toner images of each color formed thereon are transferred by the transfer chargers 24 (24a to 24d) at the respective primary transfer positions.
The toner image is sequentially transferred onto the intermediate transfer belt 140 in a superimposed manner (primary transfer), and then transported to the secondary transfer position 70 as the intermediate transfer belt 140 rotates. The recording material P is sent to the secondary transfer position from the recording material cassette 10 in synchronization with the movement of the toner image on the intermediate transfer belt, and the transfer bias is applied to the transfer charger 80 at the same time when the toner image contacts the recording material P. Is applied to transfer the toner image to the recording material P.
As the secondary transfer charging unit 80, a transfer roller made of conductive or semiconductive rubber was used.

The image forming apparatus has a control unit 100 for controlling the operation of the image forming apparatus.

The recording material after the transfer is sent to the fixing unit 9 by the transport unit 62, and the toner image is fixed by the fixing unit 9.
At the time of double-sided printing, the recording material on which the first surface (front surface) of one side has been fixed is sent again to the secondary transfer position 70 via the conveyance paths 67 and 66, and the toner image is transferred to the second surface (back surface) of the recording material. The image is fixed by the fixing device 9.

The fixing oil adheres to the transfer roller 80 of the secondary transfer means from the recording material in order to come into contact with the first surface of the recording material to which the fixing oil has adhered. Also, the transfer roller 80
The fogging toner on the intermediate transfer belt 140 adheres to contact the intermediate transfer belt 140. This transfer roller 8
In order to remove oil and fog toner attached to 0,
The cleaning blade 81 is in contact with the transfer roller 80.

In the cleaning blade 81, too, the oil and the fogging toner were mixed, excessive toner accumulation on the blade edge surface occurred, overflowed the cleaner, and toner stains on the recording material.

Therefore, in this embodiment, the intermediate transfer belt 1
A pattern toner image is formed on the sheet 40 at regular intervals, and is transferred to the transfer roller 80 without secondary transfer to the recording material, and supplied to the edge of the cleaning blade, thereby suppressing the toner accumulation height. As a result, it was possible to prevent image stains.

On the other hand, the cleaning blade 90 is attached to the intermediate transfer belt 140 in order to remove the secondary transfer residual toner remaining on the intermediate transfer belt 140 after the secondary transfer.
Is in contact. The intermediate transfer belt 140 is a transfer roller 8
As a result, a part of the oil that has slipped from the cleaning blade 81 is transferred to the intermediate transfer belt 140 and sent to the cleaning blade 90.

For this reason, the oil and the toner are also mixed in the cleaning blade 90, and the toner is aggregated near the edge. However, since the edge of the blade 90 is in contact with the intermediate transfer belt 140 such that the edge of the blade 90 faces downward in the direction of gravity, the accumulation is performed. Part of the toner fell into the waste toner container 92 of the blade 90, and the pile height was small. However, since the viscosity of the toner collected in the container 92 is increased by containing oil,
There is a problem that the sheet is attached to the discharge screw 91 and is not conveyed.

Therefore, in this embodiment, the intermediate transfer belt 1
A pattern toner image is formed directly on the sheet 40 at regular intervals, and the toner is supplied to a cleaning blade 90 without secondary transfer to a recording material, and is placed in a container 92. Was lowered with the supplied toner. As a result, the recovered toner discharging screw 91
, And good transport was possible.

In this case, in order to prevent the pattern toner image on the intermediate transfer belt from being secondarily transferred, the secondary transfer bias is turned off while the pattern toner image is passing through the secondary transfer position, or the intermediate transfer is performed while the pattern toner image is passing therethrough. The secondary transfer roller 80 may be configured to be separated from the belt.

Embodiment 3 FIG. 9 shows another configuration of an image forming apparatus using an intermediate transfer member. The present invention can also be applied to a configuration having a cleaning blade in contact with the transfer belt in the present embodiment.

The transfer belt 211, which is an intermediate transfer member, is stretched over rollers 213 and 212 and is conveyed in the direction of the arrow in the figure. In this embodiment, the roller 212 is a driving roller. Image forming portions Pa, Pb, Pc, and Pd capable of forming images of different colors are arranged on the side surface of the transfer belt 211. In the image forming unit Pa, a developing device 202a, a cleaning device 204a, and a charging device 205a are arranged around a photosensitive drum 203a as an image carrier. Photosensitive drum 2 uniformly charged by charging device 205a
Exposure is performed on the surface of the substrate 03a by the exposure unit 201a to form a latent image. This latent image is developed by the developing device 202a.
Is developed into a toner image. The toner image is transferred to the transfer belt 2 by a transfer roller 206a as a primary transfer unit.
11 is transferred. The image forming units Pb, Pc, and Pd also
The configuration is similar to that of the image forming unit Pa.

The images formed by the image forming units Pa to Pd are sequentially transferred onto the transfer belt 211 in a superimposed manner to form a color image.

The recording material fed from the cassette 210
The image is conveyed to a secondary transfer section formed between the roller 213 and the secondary transfer roller 218, and the image on the transfer belt 211 is transferred onto a recording material. The recording material to which the image has been transferred is fixed by a fixing unit 209 having a fixing roller 209a and a pressure roller 209b. An oil application member 20 for applying oil as a release agent is applied to the fixing roller 209a.
9c is provided.

The image forming apparatus includes a control unit 100 for controlling the operation of the present image forming apparatus.

In the case of double-sided printing, the fixed recording material is once guided to a reversing path 215 and then re-fed
The sheet passes through 16 and joins the sheet feeding path, and is guided again to the secondary transfer section.

In this embodiment, the cleaning blade 214a of the cleaning device 214 contacts the portion where the transfer belt 211 is
Cleans transfer residual toner and the like. Also in this embodiment, since the blade edge surface is arranged facing upward, toner is easily accumulated at the edge portion.
Therefore, when the oil is supplied to the blade edge, excessive toner accumulation at the blade edge occurs,
In some cases, toner overflow may occur.

Therefore, in the present embodiment, in order to prevent this problem from occurring, for example, a pattern toner image is formed on the transfer belt 211 every fixed number of sheets, and this toner is not secondary-transferred to the recording material. Cleaning blade 214
a, and the viscosity of the toner containing oil collected at the edge portion was reduced by the supplied toner. As a result, it was possible to prevent the toner from being excessively loaded on the blade edge portion, and to prevent the toner from overflowing.

Embodiment 4 In this embodiment, a method for reducing the supply amount of the pattern toner image will be described. Reducing the supply amount is preferable from the viewpoint of suppressing the toner consumption, and has an effect of reducing the running cost of the toner.

In the image forming apparatus shown in FIG. 1, the height of the accumulated toner on the cleaning blade 8a sharply rises particularly during double-sided printing in which oil is constantly supplied to the cleaning blade 8a. On the other hand, at the time of single-sided printing after the completion of double-sided printing, the supply of oil to the transfer belt 30 is stopped, and the oil on the transfer belt is absorbed by the pattern toner image, and is removed and collected together with the pattern toner image by the cleaning blade 8a. Therefore, the oil mixture ratio gradually decreases, and the pile height also decreases.

FIG. 10 shows the stacking for one-sided printing when a sufficient number of double-sided printings are performed while supplying the pattern toner image, and after the supply of the pattern toner image is completed, and then the single-sided printing is continuously performed. This is a change in height. The supply interval of the pattern toner image was set to every 100 sheets as in the first embodiment.

As shown in FIG. 10, the rising gradient of the pile height gradually decreases, and the final pile height is almost constant (2 mm, which is the same as the pile height when there is no oil on the transfer belt). Began to change. As can be seen from this result, during one-sided printing, the ascending gradient is reduced, so that the supply interval can be set longer than in both-sided printing. further,
Since the stacking height decreases, it is possible to gradually extend the supply interval and finally stop the supply.

FIG. 11 shows a method of setting the toner supply interval for one-sided printing after performing a predetermined number of double-sided printings.

After 100 sheets of double-sided printing, the toner supply point for single-sided printing is 300
The number of sheets is 600, and the number of sheets is 1000, and the toner supply interval gradually widens as the number of single-sided prints increases. That is, the actual toner supply amount is reduced. At the time of the 100th sheet immediately after the start of the one-sided printing, the double-sided printing has been performed before that, and the amount of oil accumulated at the edge of the cleaning blade is still large. Supply. Thereafter, since one-sided printing continues and there is no oil supply, toner accumulation is reduced and the toner supply interval can be extended. Then, as the number of single-sided prints further increases, the toner accumulation is further reduced, and the toner supply interval can be further increased. When the toner supply interval is 400
After toner supply is performed at the time of 1000 single-sided prints, the toner loading height at the blade edge is:
Since the level no longer causes a problem, the subsequent toner supply is unnecessary.

Further, the smaller the number of double-sided prints before the single-sided printing, the smaller the oil accumulation amount at the edge of the cleaning blade, so that the toner supply interval can be increased accordingly, as in the following example.

The toner supply points for single-sided printing after performing 50 double-sided prints are 200, 500, and 900 sheets. Toner supply is not performed after 900 sheets.

Further, the toner supply point at the time of single-sided printing after performing ten double-sided printings is as follows.
At the time of 00 sheets, toner supply is not performed after 700 sheets.

The above is a method for reducing the supply amount.
The supply interval was set long. Alternatively, for example, the supply interval may be fixed every 100 sheets as in the case of double-sided printing, and the toner supply amount per time may be reduced according to the number of single-sided prints.

FIG. 12 shows a method of setting the toner supply amount (the density level of the pattern toner image) at the time of single-sided printing after a predetermined number of double-sided printings have been performed.

When toner is supplied every 100 sheets during single-sided printing after 100 sheets of double-sided printing, the density level of the pattern toner image gradually decreases from the 64 level shown in the previous embodiment as the number of printed sheets increases. Let me. After the toner is supplied at the density of 16 levels at the time of 600 sheets, the toner is not supplied.

After 50 sheets of double-sided printing, the density starts at a level of 56. After the toner is supplied at a level of 16 at the time of 500 sheets, the toner is not supplied.

After 10 sheets of double-sided printing, the density starts at 48 levels, and after 6 levels of toner are supplied at 400 sheets, no toner is supplied.

As described above, the smaller the number of double-sided prints before the single-sided printing, the smaller the amount of toner accumulated at the blade edge portion. Therefore, it is possible to reduce the toner supply amount per 100 sheets and the total toner supply amount. it can.

In this embodiment, the image forming apparatus having the structure shown in FIG. 1 has been described. However, the same effects can be obtained in the image forming apparatuses shown in FIGS.

Embodiment 5 In this embodiment, another method for reducing the supply amount of the pattern toner image will be described.

As described above, the toner accumulation height depends on the amount of oil adhering to the transfer belt.
It was found that this oil amount changed with humidity.
That is, as the humidity becomes lower, the low molecular weight components of the dimethyl silicone oil used as the release agent oil evaporate, and the amount of oil on the recording material, the transfer belt and the cleaning blade decreases. For this reason, it has been found that even when the same number of double-sided prints are performed, the toner accumulation height does not increase in a low humidity environment as compared with a high humidity environment. By utilizing this phenomenon, it is possible to reduce the toner amount of the pattern toner image in a low humidity environment.

FIG. 13 shows the setting of the density level of the pattern toner image with respect to the moisture content (absolute moisture content, that is, the weight of water contained in 1000 cc of air) of the atmosphere in the image forming apparatus during double-sided printing.

In a high humidity environment with a water content of 18 g or more, the same density (64
Level) pattern toner image is required. On the other hand, in a low humidity environment with a water content of 5 g or less, half the concentration (32 levels)
However, it was possible to suppress the toner accumulation height. 5g and 1
In an environment with an intermediate humidity of 8 g, an effect was obtained with a setting in which the concentration was linearly interpolated.

In this embodiment, an environment sensor 60 for detecting temperature and relative humidity is provided near the transfer belt 30 of the image forming apparatus shown in FIG. The amount of water was calculated from the temperature and the relative humidity thus obtained, and the concentration level was switched based on FIG. 13 according to the result of the amount of water.

As a result, the height of the accumulated toner can be suppressed in accordance with the change in the amount of water in the atmosphere in the image forming apparatus, and at the same time, the minimum amount of toner consumption can be maintained.

In the above description, an example in which the density level of the supplied toner is changed according to the detected amount of water has been described. However, a similar effect can be obtained by changing the toner supply interval according to the detected amount of water. . That is, control is performed to increase the toner supply interval as the water content decreases.

For example, when the amount of water is 18 g or more, the toner is easily deposited. Therefore, the toner is supplied every 100 sheets. When the amount of water is 5 g or less, the toner is supplied every 200 sheets.
In the case of an intermediate water content of 8 g, the setting may be made by linear interpolation.

The specific numerical values such as the toner supply interval, the supplied toner concentration level, and the detected water content shown in the above embodiments are merely examples, and optimum values exist depending on the apparatus configuration. It is not limited to these values.

In this embodiment, the image forming apparatus having the structure shown in FIG. 1 has been described. However, similar effects can be obtained in the image forming apparatuses shown in FIGS.

[0110]

As described above, according to the present invention,
In an image forming apparatus capable of performing double-sided printing, a toner image is periodically formed directly on a recording material conveying member, an intermediate transfer body, and a transfer member, and the toner is cleaned with a cleaning blade of the recording material conveying member and a cleaning of the intermediate transfer body. Since the blades and the transfer member are supplied to the cleaning blade, these cleaning blades are generated because oil adhering to the recording material at the time of fixing is transferred to the recording material conveying member, the intermediate transfer body or the transfer member at the time of double-sided printing. It is possible to prevent toner from accumulating on the recording medium, and to prevent problems such as contamination in the apparatus and stains on the back of the recording material.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a cross-sectional view illustrating a cleaner of a transfer belt installed in the image forming apparatus of FIG.

FIG. 3 is a graph showing a relationship between a toner accumulation height on a cleaning blade of the cleaner of FIG. 2 and an oil mixing ratio of the toner.

FIG. 4 is a schematic diagram showing a dimensional relationship between a pattern toner image directly formed on a transfer belt and a cleaning blade, a recording material, and the like in the embodiment of FIG. 1;

FIG. 5 is a graph showing the relationship between the density of the pattern toner image of FIG. 4 and the height of the accumulated toner;

FIG. 6 is a diagram showing the operation timing of the pattern toner image formation of FIG.

FIG. 7 is a graph showing a change in toner accumulation height with respect to the number of image formations.

FIG. 8 is an overall configuration diagram showing another embodiment of the image forming apparatus of the present invention.

FIG. 9 is an overall configuration diagram showing another embodiment of the image forming apparatus of the present invention.

FIG. 10 is a graph showing a change in the height of accumulated toner with respect to the number of formed images during single-sided printing.

FIG. 11 is a diagram illustrating a change in a toner supply interval during single-sided printing after double-sided printing.

FIG. 12 is a diagram illustrating a change in supplied toner density during one-sided printing after two-sided printing.

FIG. 13 is a graph showing a method of setting a density of a pattern toner image with respect to a water content.

[Explanation of symbols]

Pa to Pd Image forming unit 3a to 3d Photosensitive drum 8 Transfer belt cleaner 8a Cleaning blade (cleaning unit) 9 Fixing unit (fixing unit) 24a to 24d Transfer charger 30 Transfer belt (recording material conveying member) 64 Guide member 80 Secondary Transfer roller (transfer member) 8a, 81, 90, 214a Cleaning blade 91 Discharge screw 140, 211 Intermediate transfer belt (intermediate transfer member)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinya Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 2H027 DA14 DA46 DE04 DE07 EC03 ED16 ED24 ED30 EE02 FA13 FA35 2H200 FA08 GA23 GA34 GA44 GA47 GB11 GB22 GB25 HA02 HA12 HB03 HB12 HB14 HB48 JA02 JA28 JB06 JB25 JB31 JB41 JB42 JC03 JC07 JC11 JC12 KA07 LB02 LB09 LB13 LB35 MA03 MA20 NA16 3F101 AB09 AB19 LA02 LA07 LB03

Claims (22)

[Claims] An image forming means for forming a toner image; a recording material transporting member for carrying and transporting a recording material; a cleaning means having a cleaning blade in contact with the surface of the recording material transporting member; An image forming apparatus that can form an image on a surface opposite to a toner image transfer surface on a recording material that has been subjected to a fixing operation by the fixing unit. The surface of the cleaning blade that is close to the contact portion with respect to the recording material transporting member and faces upstream from the contact portion in the recording material transporting member transport direction so that the normal of the blade surface is substantially directed in the direction of gravity. The cleaning blade is disposed, and the toner image for supply to the cleaning unit formed by the image forming unit is directly transferred onto the recording material conveying member, and the recording is performed by conveying the recording material conveying member. An image forming apparatus comprising: a control unit configured to control the supply toner image transferred onto the material conveying member to be supplied to the cleaning unit. 2. An image forming means for forming a toner image, an intermediate transfer body for carrying the toner image formed by the image forming means, and a transfer for transferring the toner image carried on the intermediate transfer body to a recording material Means, a cleaning means having a cleaning blade in contact with the surface of the intermediate transfer member, and a fixing means having a fixing member coated with a release agent, and the recording material having undergone a fixing operation by the fixing means. On the other hand, in an image forming apparatus capable of forming an image on a surface opposite to the toner image transfer surface, the image forming apparatus is arranged so as to be close to a contact portion with respect to the intermediate transfer member and to be upstream of the contact portion in the intermediate transfer member transport direction The cleaning blade is arranged so that the surface of the cleaning blade facing the surface of the blade is substantially normal to the direction of gravity, and the toner image for supply to the cleaning unit, which is formed by the image forming unit, is Is supported during the transfer member, the image forming apparatus, wherein a supply toner image obtained by said supported by conveying a control means for controlling so as to supply to the cleaning means the intermediate transfer body. 3. An image forming means for forming a toner image, a transfer member for transferring the toner image formed by the image forming means to a recording material, and a cleaning means comprising a cleaning blade in contact with a surface of the transfer member. A fixing unit having a fixing member coated with a release agent; and an image capable of forming an image on a surface opposite to a toner image transfer surface with respect to the recording material subjected to the fixing operation by the fixing unit. In the forming apparatus, the surface of the cleaning blade that is close to the contact portion with respect to the transfer member and that faces upstream from the contact portion in the transfer member transport direction is such that the normal of the blade surface is substantially in the direction of gravity. The cleaning blade is disposed, and the toner image for supply to the cleaning unit formed by the image forming unit is directly transferred onto the transfer member, and the transfer toner is conveyed by transferring the transfer member. An image forming apparatus comprising: control means for controlling supply of an image to the cleaning means. 4. The recording material conveying member is a belt body,
The image forming apparatus according to claim 1, wherein a roller member for hanging the belt member is provided, and the cleaning blade contacts an area where the belt member is hung on the roller member. 5. The image forming apparatus according to claim 1, wherein the intermediate transfer member is a belt member, a roller member for hanging the belt member is provided, and the cleaning blade contacts an area where the belt member is hung on the roller member. The image forming apparatus according to claim 2. 6. The image forming apparatus according to claim 4, wherein the roller member is a driving roller. 7. The maximum length m in a direction perpendicular to the conveying direction of the recording material, the length t in the direction perpendicular to the recording material conveying direction of the supply toner image, and the direction perpendicular to the recording material conveying direction of the cleaning blade. Where b is the length of
2. The relationship of m ≦ t ≦ b is satisfied.
7. The image forming apparatus according to any one of claims 1 to 6, wherein 8. The image forming apparatus according to claim 1, wherein the operation of supplying the supply toner image is performed intermittently. 9. The image forming apparatus according to claim 8, wherein the supply operation is performed every time a predetermined number of images are formed on a recording material. 10. When the image formation is performed on a plurality of recording materials as a series of operations and the predetermined number of sheets is reached during the series of operations, the supply operation is performed after the series of operations is completed. The image forming apparatus according to claim 9, wherein: 11. The image forming apparatus according to claim 9, wherein the value of the predetermined number of sheets is larger when forming a single-sided image on a recording material than when forming a double-sided image on a recording material. 12. The method according to claim 9, wherein, when forming a single-sided image on a recording material, the toner supply interval is increased by increasing the value of the predetermined number of sheets as the number of image formations increases. Image forming device. 13. The value of the predetermined number of sheets when a single-sided image is formed on a recording material thereafter, according to the number of recording materials on which double-sided images are formed.
4. The image forming apparatus according to claim 1. 14. The image forming apparatus according to claim 13, wherein the value of the predetermined number is smaller as the number of recording materials on which the double-sided image is formed is larger. 15. As the number of single-sided images formed increases,
15. The image forming apparatus according to claim 14, wherein a toner supply interval is widened by increasing the value of the predetermined number of sheets. 16. The image forming apparatus according to claim 9, wherein as the number of single-sided images formed on the recording material increases, the toner supply amount per one supply operation is reduced. 17. The image forming apparatus according to claim 16, wherein the toner supply amount is reduced by lowering the density of the supply toner image. 18. A toner supply amount per one supply operation when a single-sided image is formed on a recording material thereafter, according to the number of recording materials on which a double-sided image has been formed. Item 10. The image forming apparatus according to Item 9. 19. The image forming apparatus according to claim 18, wherein the larger the number of recording materials on which the double-sided image is formed, the greater the toner supply amount. 20. As the number of single-sided images formed increases,
20. The image forming apparatus according to claim 19, wherein the toner supply amount is reduced. 21. Humidity detecting means for detecting humidity,
The image forming apparatus according to claim 9, wherein the value of the predetermined number is determined according to a detection result of the humidity detecting unit. 22. The image forming apparatus according to claim 21, wherein the value of the predetermined number of sheets decreases as the detection result becomes higher in humidity.