JPH06186886A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of excellently maintaining cleaning properties even if the quantity of toner inputted to a cleaning blade cleaning a transfer rotary body is changed. CONSTITUTION:When an actual toner image on a photosensitive drum 14 is transferred on a transfer paper, a cleaning device 26 having the cleaning blade 42 is arranged opposite to a transfer belt 21 carrying the transfer paper. When the transfer ratio of the toner from the photosensitive drum 14 to the transfer belt 21 is high, a cleaning blade press-contact force variable device is constituted to connect with the cleaning blade 42, so that the press-contact force of the cleaning blade 42 with the transfer belt 21 is increased.

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 having a structure for forming a pattern image for toner density detection on the surface of a photoconductor.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a facsimile or a printer, which forms an electrostatic latent image on the surface of a photoconductor, the electrostatic latent image is visualized as a toner image by a predetermined developing device. It has been visualized. As a developing device,
For example, in a developing device that uses a dry two-component developer,
The concentration of toner in the developer decreases with time.
Therefore, the concentration is detected by some method. As one of the methods, there is a method in which a pattern image for toner density detection is formed on a photoconductor and the density is detected by a detection means such as a reflection type sensor.

On the other hand, in this type of image forming apparatus, a recording medium such as transfer paper is carried on an endless belt-shaped or drum-shaped transfer rotator and conveyed, while a toner image on a photoreceptor is recorded. There are some that are designed to be transferred to. In the image forming apparatus having such a configuration, the toner remaining on the surface of the transfer rotator is scraped and removed by a cleaning member such as a cleaning blade or a cleaning brush after the transfer process.

By the way, the pattern visible image formed on the photosensitive member is transferred to a surface portion between recording media on the surface of the transfer rotator, and the toner of the transferred pattern visible image is As a matter of course, it is removed by the above-mentioned cleaning member.

The environment in which this type of image forming apparatus is put into operation is various, and the conditions of use are also different. For example, when the image forming apparatus is used in an environment of high temperature and high humidity, the charge amount of the toner becomes small, so that the latent image adheres to the pattern latent image (the pattern visible image is formed by developing the latent image). The amount of toner to be used increases.

Further, even when the charging property of the developer is deteriorated due to deterioration of the developer over time, the amount of toner attached to the pattern latent image increases. In this case, the amount of toner transferred to the transfer rotary member also increases, and accordingly, the amount of toner removed by the cleaning member also increases.

In the prior art, since the contact pressure of the cleaning blade for cleaning the transfer rotary member and the rotation speed of the cleaning brush for cleaning the transfer rotary member were set to be constant, the amount of toner input to the cleaning member was set. However, the toner removal capability cannot keep up with the increase, resulting in poor cleaning and back stain on the recording medium.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of maintaining good cleaning performance even if the amount of toner input to a cleaning blade for cleaning a transfer rotary member changes. To provide.

[0009]

According to the present invention, in order to achieve the above object, a toner image can be formed in an image forming area on the surface, and a toner pattern image for toner density detection can be formed outside the area. And a transfer rotator that conveys the recording medium so that the recording medium moves while being in contact with the photosensitive member, and a transfer unit where the recording medium is in contact with the photosensitive member. To a recording medium, first detecting means for detecting the density of the pattern image before reaching the transfer portion, and density of the pattern image remaining on the surface of the photoconductor after passing through the transfer portion. From the detection output values of the first and second detection means, the second detection means for detecting, the cleaning blade for pressing the transfer rotation body and removing the toner remaining on the transfer rotation body after the transfer process, are detected. The obtained transfer rate is set in advance When the large compared with the constant reference values, it is to propose an image forming apparatus including a cleaning blade contact pressure variable control means for setting a high pressure contact force of the cleaning blade.

Similarly, in order to achieve the above object, a photoreceptor capable of forming a toner image in the image forming area of the surface and a pattern image of toner for detecting the toner density outside the area, respectively, A transfer rotary member that conveys the recording medium so that the recording medium moves while being in contact with the photoconductor;
A transfer unit in which the recording medium is in contact with the photosensitive member, a transfer unit that transfers the toner visible image on the photosensitive member to the recording medium, and a first detection unit that detects the density of the pattern visible image before reaching the transfer unit;
On the transfer rotator, the second detecting means for detecting the density of the pattern image remaining on the surface of the photoconductor after passing through the transfer part and the transfer rotator, which is rotated so as to rub against the transfer rotator and remains after the transfer step When the transfer rate obtained from the cleaning brush that removes the toner and the detection output values of the first and second detection units becomes large as compared with a preset reference value, the rotation speed of the cleaning brush is An image forming apparatus is proposed which is provided with a means for rotating and driving the cleaning brush so as to increase the height.

Similarly, in order to achieve the above object, a photoreceptor capable of forming a toner image in the image forming area of the surface and a pattern image of toner for detecting the toner density outside the area, respectively. A transfer rotator that conveys the recording medium so that the recording medium moves while contacting the photoreceptor.
A transfer unit in which the recording medium is in contact with the photosensitive member, a transfer unit that transfers the toner visible image on the photosensitive member to the recording medium, and a first detection unit that detects the density of the pattern visible image before reaching the transfer unit;
Second detection means for detecting the density of the pattern visible image remaining on the surface of the photoconductor after passing through the transfer portion and the transfer rotator are pressed to remove the toner remaining on the transfer rotator after the transfer step. A cleaning blade for cleaning, a cleaning brush that rotates so as to rub against the transfer rotary member, and removes toner remaining on the transfer rotary member after the transfer process;
When the transfer rate obtained from each detection output value of the detection means becomes large as compared with a preset reference value, the cleaning blade pressure contact force variable control means for setting the pressure contact force of the cleaning blade high, similarly to the above. When the transfer rate obtained from each detection output value of the first and second detection means becomes large as compared with a preset reference value, the cleaning brush is rotated so that the rotation speed of the cleaning brush becomes high. An image forming apparatus including a driving unit is proposed.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

This image forming apparatus is a digital type image forming apparatus, and includes a scanner section 1 for reading a document and an image processing section for electrically processing an image signal output as a digital signal from the scanner section 1. 2 and a printer unit 3 that forms an image on a transfer sheet based on image recording information from the image processing unit 2.

The scanner unit 1 has a lamp (for example, a fluorescent lamp) 5 for illuminating and scanning an original (not shown) on the original table 4. The reflected light from the document when illuminated by the lamp 5 is reflected by the mirrors 6, 7, 8 and enters the imaging lens 9, passes through this lens, and then enters the light receiver 11. The light receiver 11 is composed of, for example, a CCD, which converts incident light into a digital signal and outputs the digital signal. The output is subjected to necessary processing in the image processing section 2 and converted into a signal for recording formation. .

A signal for recording formation is input to the printer unit 3 and sent to the laser light emitting device 12. A photoconductor drum 14, which is an example of the configuration of the photoconductor, is driven to rotate in the direction of the arrow shown in the figure. The surface of the photoconductor drum 14 is uniformly charged by a charging charger 15 and then exposed by a laser beam emitting device 12. As a result, a predetermined electrostatic latent image is formed on the surface of the photoconductor drum 14. Next, the electrostatic latent image is developed by the developing device 16, and a toner visible image is formed on the surface of the photoconductor drum 14. The developing device 16 stores a two-component developer having toner and carrier, and the toner of the developer visualizes the electrostatic latent image. The toner visible image is formed in the image forming area on the photosensitive drum 14.

The transfer paper supplied from the paper supply unit 19, for example, one of the two paper supply cassettes, by the paper supply roller 18 is aligned at the leading edge by the registration roller pair 20 and directed toward the transfer rotary member 21 at the same timing. Sent.

In this embodiment, the transfer rotary member 21 is made of polyester film or the like and has an endless belt shape. Hereinafter, the transfer rotator 21 will be referred to as a “transfer belt” in accordance with this example. The above-mentioned transfer paper forms an example of a recording medium, and the transfer belt 21 is stretched between the belt driving roller 24 and the driven roller 25 so that the transfer paper moves while being in contact with the photosensitive drum 14. Works to convey paper. In addition,
The present invention can also be applied to a device that uses a transfer drum as a transfer rotary member.

A transfer charger 17, which is an example of the constitution of the transfer means, is provided inside the transfer belt 21 at a portion facing the photoconductor drum 14.
The toner image on the photoconductor drum 14 is transferred to the transfer paper conveyed on the transfer belt 21 by the transfer unit 10.

The transfer paper on which the toner image has been transferred is fixed by the fixing roller pair 22 and discharged onto the tray 29 by the paper discharge roller pair 23. The transfer paper is conveyed to the transfer belt 21 with high accuracy by being electrostatically attracted to the transfer belt 21.

A unitized cleaning device 26 is provided so as to face the portion of the transfer belt 21 that is stretched around the driven roller 25.
Is equipped with a cleaning blade 42 made of polyurethane rubber or the like. The cleaning blade 42 is pressed against the transfer belt 21 to scrape off and remove the toner remaining on the transfer belt 21 after the step of transferring the toner image.

Here, in FIG. 1, exposure is performed by the laser light emitting device 12, and a pattern latent image for toner density detection is formed on the photoconductor drum 14 in addition to the above electrostatic latent image. . 2 (a), (b), (c), and (d) show such pattern latent images for various examples.
The digital image forming apparatus shown in FIG. 1 performs area gradation on a basic matrix in a size of 4 × 4, and a pattern latent image is formed by repeating this 4 × 4 pattern. Which of the 4 × 4 = 16 dots is black (hatched portion) or white is determined by the detection sensitivity. Note that FIG. 2A shows a concentrated latent image with an area ratio of 50%, FIG. 2B shows a 50% concentrated pattern latent image, FIG. 2C shows a 25% concentrated concentrated pattern latent image, and FIG.

Such a pattern latent image is developed by the image processing section 2 with a normal developing bias. That is, it is developed as a pattern visible image by the developing device 16, and this pattern visible image is formed on the photosensitive drum portion outside the image forming area where the previous toner visible image is formed.

In FIG. 1, between the developing device 16 and the transfer portion (the portion where the transfer paper on the transfer belt 21 contacts the photosensitive drum 14), the transfer portion is provided so as to face the photosensitive drum 14. The first detection means 27 for detecting the density of the pattern visible image 30 before reaching 10 is provided closely.

The detecting means 27 is composed of, for example, a reflection type photo sensor, and the emitted light is applied to the pattern visible image 30, and the light reflected from the pattern visible image is received. When the density of the pattern image 30 is high, the amount of reflected light decreases, and when the density is low, the amount of reflected light increases. Due to this difference
The density of the pattern image is detected. When the concentration is low, the toner is supplied from the toner hopper 13 into the two-component developer in the developing device 13, and the concentration of the toner in the developer in the developing device 16 is maintained within a certain range. The first detection means 27 will be hereinafter referred to as a "first detection sensor" in accordance with this embodiment.

The above-mentioned toner visible image is transferred onto the transfer paper conveyed on the transfer belt 21, and the pattern visible image 30 is transferred onto the transfer belt portion before the leading end of this transfer paper. To be done. After this transfer, the photosensitive drum 1
There is a pattern visible image left on the surface 4 without being transferred. Hereinafter, this is referred to as "pattern afterimage".

Here, a cleaning device 41 is provided on the opposite side of the photoconductor drum 14 from the developing device 16. The cleaning device 41 removes the toner remaining on the surface of the photoconductor drum after the transfer process, Clean the surface. Between the cleaning device 41 and the transfer unit 10, a second detection unit 28 for detecting the density of the pattern afterimage after passing through the transfer unit 10 is provided.
It is deployed in close proximity to face.

The second detecting means 28 is the first detecting sensor 2
Similar to the reference numeral 7, it is composed of a reflection type photo sensor, receives the reflected light from the pattern afterimage, and detects the density of the pattern afterimage by the difference in the amount of received light. The second detection means will be described below.
In accordance with this embodiment, it will be called a "second detection sensor".

Here, the first detection sensor 27 detects the density of the pattern image 30, and the detection output value is set to V ₁ . The second detection sensor 28 detects the density of the pattern afterimage, and the detection output value is set to V ₂ . Here, the transfer rate η (%) of the pattern visible image from the photosensitive drum 14 to the transfer belt 21 is given by the absolute value of the value obtained from the following equation. {(V ₁ −V ₂ ) / V ₁ } × 100

When the absolute value of the value obtained from such an equation is large, the transfer rate η is large, and in this case, the amount of toner transferred from the photosensitive drum 14 to the transfer belt 21 is large.

Here, FIG. 3 is a perspective view showing the structure of the cleaning device 26 for cleaning the transfer belt 21.
In this figure, a cleaning blade 42 facing the transfer belt 21 is provided between the pair of side plates 31, 31.
And the cleaning brushes 4 on both side plates.
3 is rotatably supported. Cleaning brush 4
One end of the shaft 43A of No. 3 extends from the side plate 31, and a coupling 45 is fixedly attached to the extending end.

The cleaning blade 42 is in pressure contact with the transfer belt 21 to remove the toner adhering to the transfer belt 21. The removed toner includes, of course, the toner of the pattern visible image transferred from the photosensitive drum 14 to the transfer belt 21. FIG. 4 shows the cleaning blade 4.
FIG. 3 is a detailed diagram showing a configuration example of a variable control unit of the pressure contact force with respect to the transfer belt 21 of FIG.

As described above, when the image forming apparatus is used, for example, in a high temperature and high humidity environment, the toner charge amount becomes small and the toner amount attached to the pattern latent image becomes large. . Further, even if the developer deteriorates with time, the chargeability thereof deteriorates, and the amount of toner attached to the pattern latent image also increases. In this case, the amount of toner of the pattern image also increases, and the amount of the toner transferred to the transfer belt 21 also increases. If this amount becomes too large, cleaning failure will occur, but a transfer rate that does not cause such cleaning failure is predetermined.

This transfer rate becomes the set reference value η ₀ (%), but the transfer rate η obtained from each detection output value of both sensors 27, 28 is the same as the set reference value η ₀ , or If it is less than this, as shown in FIG. 6, the cleaning blade 42 is brought into contact with the photosensitive drum 14 at a pressure P ₀ . In this contact state, the toner of the pattern image transferred onto the transfer belt 21 is transferred to the cleaning blade 4.
It is removed by 2.

Incidentally, FIG. 6 shows the cleaning blade 42.
6 is a diagram showing how the toner removing ability changes when the pressure contacting force with respect to the transfer belt 21 is changed. When the pressure contacting force is increased, the toner removing ability is improved.

As the environmental conditions change, the detection sensor 2
The transfer rate η obtained from the detection output values of 7 and 28 becomes larger than the set reference value η ₀ , and the toner of the pattern image on the photoconductor drum 14 is transferred to the reference transfer amount (the transfer rate is set to the set reference value). η transition amount when ₀₎ greater than, the so moves on the transfer belt 21, a solenoid 81 shown in FIG. 4 is adapted to be excited.

Then, the plunger 82 is pulled, and along with this, the link 83 whose one end is connected to the plunger 82 rotates around the shaft 85 that pivotally supports it, and the other end 83a is lifted. A pin 86 fixedly implanted in the other end portion 83a and a pin 89 fixedly implanted in the blade mounting member 88
A spring 87 for applying a blade pressure contact force between
Is hung.

The blade mounting member 88 is swingable around a pivot 90. When the other end 83a of the link rod 83 is lifted, the spring 87 is pulled and the cleaning blade 42 is pressed against the transfer belt 21. Is set to be high. That is, as shown in FIG. 6, the pressure contact force can be changed from P ₀ to P ₁ .

According to this embodiment, the transfer rate η at an arbitrary time point becomes larger than the set reference value η ₀ , and the transfer belt 2
When the amount of the toner of the pattern visible image that moves to 1 is increased, the pressure contact force of the cleaning blade 42 is increased, so that the toner can be sufficiently removed without being left behind. That is, even if the amount of toner input to the cleaning blade 42 for cleaning the transfer belt 21 changes, the cleaning property can always be kept good.
As a result, it is possible to suppress the occurrence of stains on the back of the transfer paper.

If the transfer rate is less than or equal to the set reference value, the pressing force of the cleaning blade is reduced as compared with the case where the cleaning blade exceeds the set reference value.
The life of the cleaning blade, the transfer belt, or the like can be extended as compared with a structure in which the cleaning blade is brought into contact with the transfer belt at a high pressure.

The cleaning device 2 shown in FIGS. 1 and 3.
As described above, the cleaning brush 43 is also attached to the reference numeral 6, but the cleaning brush 43 faces the transfer belt 21 and rotates so as to rub against the belt 21, and after the toner image transfer step. Transfer belt 2 that remains
Remove the toner on 1. At the same time, the cleaning brush 43 also removes the toner of the pattern visible image that has moved onto the transfer belt 21.

Here, instead of variably controlling the pressure contact force of the cleaning blade 42 according to the magnitude of the transfer rate η as described above, the above-mentioned transfer rate η at an arbitrary time is set to a preset reference value η. A means for rotationally driving the cleaning brush 43 may be provided so that the rotation speed of the cleaning brush 43 becomes higher when the _{value is} greater than ₀ . That is, the rotation speed of the cleaning brush 43 is variable.

The rotation driving means for achieving such a function is
As shown in FIG. 5, it is composed of a speed controllable motor 35, a gear 36 directly connected to the motor 35, a gear 37 meshing with the gear 36, and the like.

A shaft 38 having a coupling 44 fixed to one end and a gear 37 fixed to the other end is rotatably supported by a side plate 40 via a bearing 39. The coupling 44 is engaged with the coupling 45 (FIG. 3) attached to the shaft 43A of the cleaning brush 43. The rotation of the motor 35 is transmitted to the cleaning brush 43 by such coupling.

Here, FIG. 7 shows the cleaning brush 43.
FIG. 6 is a diagram showing how the toner removing ability changes when the number of rotations is changed.

The transfer rate η at an arbitrary time point is the set reference value η.
_When it is equal to ₀ or smaller than the set reference value, the motor 35 rotates so that the cleaning brush 43 is rotationally driven at the rotation speed of N ₀ . Where N ₀
That is, when the transfer rate is η ₀ or less, the number of rotations does not cause cleaning failure.

Here, the transfer rate η obtained from the respective detection output values of the detection sensors 27, 28 due to changes in environmental conditions and the like.
Becomes larger than the set reference value η ₀ , and the photosensitive drum 14
When the toner of the upper pattern visible image is transferred to the transfer belt 21 by a larger amount than the reference transfer amount (transfer amount when the transfer rate is the set reference value η ₀ ), the cleaning brush 4
The motor 35 is accelerated so that the rotation speed of _No. 3 becomes N ₀ (N ₁ ) (FIG. 7) larger than this. Here, N ₁ is the number of rotations of the cleaning brush 43 so that cleaning failure does not occur even if the transfer rate increases.

Also in the above-mentioned configuration, the transfer belt 2 is also similarly to the configuration for controlling the pressure contact force of the cleaning blade.
Even if the amount of toner input to the cleaning brush 43 for cleaning No. 1 is changed, good cleaning performance can be maintained at all times. As a result, it is possible to suppress the occurrence of stains on the back of the transfer paper. If the transfer rate is less than or equal to the setting reference value, the cleaning brush 43
Since the rotation speed of the cleaning brush 43 is low, the life of the cleaning brush, the transfer belt, or the like can be extended as compared with a structure in which the cleaning brush 43 is constantly rubbed against the transfer belt 21 at a high rotation speed. . Further, the toner scattering from the cleaning brush 43 can be suppressed, and the inside of the image forming apparatus is not contaminated with the toner.

When the transfer rate η is larger than the set reference value η ₀ , the pressing force of the cleaning blade 42 is set high and the cleaning brush 43 is set as described above.
The number of rotations may be set to be high as well. That is, both the configuration in which the pressure contact force of the cleaning blade is variably controlled as described above and the configuration in which the rotation speed of the cleaning brush 43 is variably controlled are adopted depending on the magnitude of the transfer rate. Even with such a configuration, it is possible to obtain the same effects as those of the series of embodiments described above.

[0050]

According to the first aspect of the present invention, even if the amount of toner input to the cleaning blade for cleaning the transfer rotator changes, the cleaning property can always be maintained in a good condition. It is possible to prevent back stains from occurring easily. Further, the life of the cleaning blade, the transfer rotary member, etc. can be extended.

According to the second aspect of the invention, even if the amount of toner input to the cleaning brush that cleans the transfer rotary member changes, the cleaning performance can always be kept good. It is possible to reduce the occurrence of such. Further, the life of the cleaning brush, the transfer rotary member, etc. can be extended. Further, the scattering of toner from the cleaning brush is also minimized, and there is no risk of the inside of the image forming apparatus being soiled with toner.

According to the third aspect of the present invention, even if the amount of toner input to the cleaning blade or the cleaning brush for cleaning the transfer rotary member changes, the cleaning property can always be kept good, so that the recording medium can be maintained. It is possible to make it difficult for stains on the back of the sheet to occur. Further, the life of the cleaning blade, the cleaning brush, the transfer rotator, etc. can be extended. Further, the scattering of toner from the cleaning brush is also minimized, and there is no risk of the inside of the image forming apparatus being soiled with toner.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing various specific examples of pattern latent images formed on a photoconductor.

FIG. 3 is a perspective view showing the structure of a transfer belt cleaning device.

FIG. 4 is a perspective view showing a cleaning blade pressure contact force variable control mechanism unit included in the same cleaning device.

FIG. 5 is a configuration diagram showing an example of a rotation driving unit of a cleaning brush.

FIG. 6 is a diagram showing a correlation characteristic between a pressure contact force of a cleaning blade and a toner removing ability.

FIG. 7 is a diagram showing a correlation characteristic between the number of rotations of the cleaning brush and the toner removing ability.

[Explanation of symbols]

 10 Transfer Part 14 Photosensitive Drum as Photosensitive Member 21 Transfer Belt as Transfer Rotating Body 27 Detection Sensor as First Detection Means 28 Detection Sensor as Second Detection Means 30 Pattern Image 42 Cleaning Blade 43 Cleaning Brush

Claims (3)

[Claims] 1. A photoconductor on which a toner image is formed in an image forming area on the surface, and a pattern image with toner for toner density detection can be formed outside the area, and a recording medium is in contact with the photoconductor. A transfer rotary member that conveys the recording medium so that the recording medium moves while moving, a transfer unit that transfers the toner image on the photosensitive member to the recording medium by a transfer unit in which the recording medium contacts the photosensitive member, and before the transfer unit. First detecting means for detecting the density of the pattern visible image, the second detecting means for detecting the density of the pattern visible image remaining on the surface of the photoconductor after passing through the transfer portion, and a pressure contact with the transfer rotating body. Then, the cleaning blade for removing the toner remaining on the transfer rotary member after the transfer process and the transfer rate obtained from the respective detection output values of the first and second detecting means are compared with a preset reference value. Cleaning blur An image forming apparatus comprising: a cleaning blade pressure contact force variable control means for setting a high pressure contact force of a card. 2. A photoreceptor in which a toner image can be formed on an image forming area on the surface and a pattern image by toner for toner concentration detection can be formed outside the area, and a recording medium is in contact with the photoreceptor. A transfer rotary member that conveys the recording medium so that the recording medium moves while moving, a transfer unit that transfers the toner image on the photosensitive member to the recording medium by a transfer unit in which the recording medium contacts the photosensitive member, and before the transfer unit. First detecting means for detecting the density of the pattern visible image of No. 1, second detecting means for detecting the density of the pattern visible image remaining on the surface of the photoconductor after passing through the transfer portion, and sliding on the transfer rotating body. The cleaning brush that rotates so as to remove the toner on the transfer rotator that remains after the transfer process and the transfer rate obtained from the detection output values of the first and second detection means are set to a predetermined setting criterion. When it becomes large compared to the value, An image forming apparatus, comprising: a unit that rotationally drives a cleaning brush so that the number of rotations of the brush is high. 3. A photoreceptor in which a toner image is formed on an image forming area on the surface, and a pattern image by toner for toner concentration detection can be formed outside the area, and a recording medium is in contact with the photoreceptor. A transfer rotary member that conveys the recording medium so that the recording medium moves while moving, a transfer unit that transfers the toner image on the photosensitive member to the recording medium by a transfer unit in which the recording medium contacts the photosensitive member, and before the transfer unit. First detecting means for detecting the density of the pattern visible image, the second detecting means for detecting the density of the pattern visible image remaining on the surface of the photoconductor after passing through the transfer portion, and a pressure contact with the transfer rotating body. A cleaning blade for removing the toner remaining on the transfer rotator after the transfer step, and a cleaning brush for removing the toner remaining on the transfer rotator after the transfer step by sliding to rub against the transfer rotator. And the first and the first When the transfer rate obtained from the respective detection output values of the second detecting means becomes large as compared with the preset reference value, the cleaning blade pressure contact force variable control means for setting the pressure contact force of the cleaning blade high, , The cleaning brush is set so that the number of rotations of the cleaning brush becomes high when the transfer rate obtained from the respective detection output values of the first and second detecting means becomes large as compared with a preset reference value. An image forming apparatus having a means for rotationally driving.