JPH07175282A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of restraining the change of the density and the line width of a developed image even when a gap between a developer carrier and an image carrier is changed in an image forming device where oscillating bias voltage is impressed on the developer carrier. CONSTITUTION:The bias voltage including an AC voltage component is impressed on a developing sleeve 6. When the sleeve 6 is opposed to the non-image area of a photosensitive drum 1, reference bias voltage including a constant- current AC voltage component or reference bias voltage including a constant- voltage AC voltage compoment is impressed on the sleeve 6. In such a case, an AC voltage value or an AC current value applied to the sleeve 6 is detected. An image forming factor is controlled based on the detected AC voltage value or AC current value.

Description

Detailed Description of the Invention

[0001]

The present invention relates to carrying and carrying a developer,
The present invention relates to an image forming apparatus that applies a vibration bias voltage to a developer carrying member applied to an electrostatic latent image carrying member in a developing area.

[0002]

2. Description of the Related Art It is known to apply a vibration bias voltage, in which a DC voltage component is superposed with an AC voltage component such as a sine wave, a rectangular wave or a triangular wave, to a developer carrying member such as a developing sleeve or a developing roller.

The DC voltage component contributes to preventing fogging, improving the density of a developed image, and optimizing the line width of a line image. The AC voltage component activates the motion of the developer in the developing area, It contributes to improving the density and gradation of the developed image and preventing the line width of the line image from becoming thin.

On the other hand, in order to maintain a gap between the image bearing member and the developer bearing member, spacer rollers are provided at both ends of the developer bearing member, and the spacer rollers are pressed against the image bearing member. .

[0005]

By the way, when the spacer roller and / or the pressure contact portion of the image carrier with the spacer roller gradually wears as the apparatus is used repeatedly,
The gap between the image bearing member and the developer bearing member in the developing area changes from the initial value.

Then, since the oscillating electric field strength in the developing area changes from the initial value, the line width of the developed line image,
There is an inconvenience that the density of the developed solid image changes from the initial density.

There is also known an image forming apparatus in which a so-called process cartridge integrally holding an image carrier and a developing device, if necessary, a charging device, and / or a cleaner is attached and detached.

By the way, the gap between the image carrier and the developer carrier may vary from cartridge to cartridge due to manufacturing errors or the like. In such a case, since the oscillating electric field strength varies from cartridge to cartridge, there arises a disadvantage that the line width and density of the developed image differ from cartridge to cartridge.

An object of the present invention is to provide an image forming apparatus for applying a vibration bias voltage to a developer bearing member, which can reduce the density and line width of a developed image even if the gap between the developer bearing member and the image bearing member changes. An object is to provide an image forming apparatus that can suppress changes.

Another object of the present invention is an image forming apparatus in which a process cartridge having at least an image carrier and a developing device is detachably mounted, and a process in which a gap between the image carrier and the developer carrier is different from a reference value. An object of the present invention is to provide an image forming apparatus capable of suppressing changes in density and line width of a developed image even if a cartridge is used.

[0011]

The above objects are achieved by the image forming apparatus according to the present invention. In summary, the present invention is
An image bearing member; a latent image forming means for forming an electrostatic latent image on the image bearing member; arranged to face the image bearing member, and carry and convey a developer in the developing area. A developer carrier for developing the latent image; a power supply for applying a bias voltage containing an AC voltage component to the developer carrier; the developer carrier facing the non-image area of the image carrier When
The power supply is controlled to apply a reference bias voltage including a constant current AC component to the developer carrying member, and the AC voltage value applied to the developer carrying member is detected by applying the reference bias voltage, An image forming apparatus comprising: a control unit that controls at least one image forming factor corresponding to the detected AC voltage value.

According to another aspect of the present invention, an image carrier;
Latent image forming means for forming an electrostatic latent image on the image carrier; arranged to face the image carrier, and carry and convey a developer to develop the latent image in a developing area. A developer carrier; a power supply for applying a bias voltage containing an AC voltage component to the developer carrier; and the developer when the developer carrier faces a non-image area of the image carrier. The power supply is controlled so as to apply a reference bias voltage including a constant voltage AC component to the agent carrier, and the AC current value applied to the developer carrier is detected by applying the reference bias voltage. An image forming apparatus is provided, which comprises: a control unit that controls at least one image forming factor corresponding to the AC current value.

[0013]

The image forming apparatus according to the present invention will be described in more detail with reference to the drawings. FIG. 1 illustrates an image forming apparatus to which the present invention can be applied.

In this example, the main body 30 of the image forming apparatus is such that the following optical device, transfer material conveying device, transfer device, fixing device, power supply 100, which will be described later, control device 118 and process cartridge P are attached to and detached from the main body 30. It has a guide member 31 for guiding.

The process cartridge P is a cylindrical or drum-shaped electrophotographic photosensitive member 1 that rotates in the direction of the arrow, a charger 2 that uniformly charges the photosensitive member 1, and an electrostatic latent image formed on the photosensitive member 1. It has a developing device D for developing an image and a cleaning means C for removing the developer remaining on the surface of the photoconductor 1 after the transfer of the developed image, that is, a cleaning container 7 having a cleaning blade 8. The means are integrally supported in a molded synthetic resin frame 32. Then, the process cartridge P slides in and out of the main body 30 by sliding along the guide member 31. As a result, when the developer in the developing device D is exhausted, the process cartridge P is taken out of the main body 30 by the operator, and instead of this, the developing device D is replaced.
The process cartridge P, which is filled with the developer in advance, is attached to the main body 30. Alternatively, the process cartridge P accommodating the developer of the desired color is the apparatus main body 30.
It can also be loaded inside, thereby outputting an image of the desired color.

On the outer surface of the frame 32 of the process cartridge P, an electric contact 9 for transmitting a developing bias voltage to the developing sleeve 6 of the developing device D is provided. When mounted in the main body 30, the main body 30 is connected to the output contact 10 of the power source 100, which allows the vibration bias voltage from the power source 100 to be transmitted to the developing sleeve 6.

The developing device D is provided with a toner container 3 containing a developer T, a stirring member 4 rotatably provided in the container 3, a developing chamber 5, and a developing chamber 5. Developer carrier, that is, developing sleeve 6 having a magnet inside
And are equipped with.

The stirring member 4 rotates in the direction of the arrow to rotate the container 3
The developer T therein is agitated, and the developer T is conveyed to the developing chamber 5 through the opening 33 provided in the wall of the container 3. The developing sleeve 6 carries the developer carried into the developing chamber 5, rotates in the direction of the arrow and conveys it to the developing region 13, and applies the developer to the electrostatic latent image formed on the photosensitive drum 1 to To develop.

In the unused process cartridge P, the seal member 20 is releasably adhered to the side wall of the container 3, and the opening 33 of the seal member 20 is sealed to prevent the developer from being exposed outside the container 3. This prevents the developer from leaking and polluting the inside and outside of the cartridge, resulting in unnecessary loss of the developer. At the start of use of the cartridge P, the operator removes the seal member 20 from the position of the opening 33 and opens the opening 33 before or after loading the cartridge P into the apparatus main body 30, and the developer T is developed from the container 3. The chamber 5 is set to be movable. Further, the seal member 20 may be configured to openably seal the opening of the developing chamber 5 in which the developing sleeve 6 is arranged.

Next, the image forming operation will be described.
The photosensitive drum 1 is first charged by the charger 2 and then scanned and exposed by the exposure means A, that is, the laser beam 34 modulated corresponding to the recorded image information signal to form an electrostatic latent image. The laser beam 34 is formed by a known optical device 35 including a semiconductor laser, a rotary polygon mirror, an f-θ lens, and the like, and is reflected by a mirror 36 toward the photosensitive drum 1.

This electrostatic latent image is developed by the developing device D as described above.
Reverse development is performed by. The developed image thus obtained, that is, the toner image is transferred to a transfer material such as paper by the action of the transfer charger 37, and then the transfer material is separated from the photosensitive drum 1 by the action of the separation charge eliminator 38.

The transfer material conveying device conveys the transfer material to the transfer area in synchronization with the cassette 39 containing the transfer material, the pickup roller 40 for feeding the transfer material from the cassette 39, and the movement of the toner image. It has a registration roller 41 and conveyance guides 42, 43, 44.

The transfer material separated from the photosensitive drum 1 is sent to a fixing means E, a roller fixing device 45 in this example, via a guide 44, where the toner image is fixed on the transfer material.
The transfer material after fixing is discharged onto the tray 46.

In this example, the exposure device exposes the laser beam to the photosensitive drum 1, but the photosensitive drum 1 may be exposed by the radiation light of the light emitting diode array driven by the image signal. Furthermore, the image of the original document may be directly exposed to the photosensitive drum 1 through the lens, and the electrostatic latent image obtained by the exposure may be normally developed by the developing device D.

The above-mentioned cartridge P is a cartridge having a cleaning device 7 and a charging device 2 in addition to the drum-shaped electrophotographic photosensitive member 1 and the developing device D. Although the present invention has a photosensitive member and a developing device, The present invention can also be applied to an image forming apparatus using a cleaning device and / or a process cartridge having no charging device.

The developing device D will be described in more detail with reference to FIG.

In order to avoid complication, the toner container 3 is shown in a simplified manner compared to FIG. In FIG. 2, A is a latent image forming means including the charger 2 and the exposure optical systems 35 and 36, B is a transferring means including the chargers 37 and 38, and C is a cleaning means including the blade 8 and the container 7. is there.

In this embodiment, the developing device D contains a developer containing no carrier particles, that is, an insulating one-component magnetic developer (toner) T in a toner container 3.

The toner T is charged to a polarity for developing the electrostatic latent image, mainly by friction with the developing sleeve 6. The magnetic toner T contains, for example, 60% by weight of magnetite in a binder resin containing styrene-acrylic copolymer as a main component and 1% by weight of a metal complex salt of a monoazo dye as a negative charge control agent and has a volume resistance of about 10 ^13. An insulating magnetic toner of Ωcm is basically used, and silica fine particles hydrophobized in order to improve fluidity are externally added to the toner in an amount of 0.4% by weight based on the weight of the toner. The toner T is negatively charged by friction with the sleeve 6.

The toner T is carried out of the toner container 3 by a non-magnetic sleeve (cylindrical body) 6 made of aluminum, stainless steel or the like which rotates in the direction of the arrow which is the opposite direction to the direction of rotation of the photosensitive drum 1, and goes to the developing area 13. Be transported.
The sleeve 6 is made of, for example, aluminum and has a diameter of 1
The outer diameter of 6 mm is sandblasted with Alundum abrasive grains (Morundum A # 400 manufactured by Showa Denko KK) in a range of 220 mm facing the drum, and the center is described in JIS B-0601. Line average roughness (R
A material having a thickness of about 0.5 μm can be used in a).

In the developing area 13, the photosensitive drum 1 and the developing sleeve 6 are opposed to each other with a minimum gap of 50 to 500 μm. Then, in the developing area 13, the toner T is applied to the electrostatic latent image and developed.

In order to maintain a gap between the photosensitive drum 1 and the sleeve 6, spacer rollers 11 provided coaxially with the sleeve 6 are provided at both ends of the sleeve 6, and the spacer roller 11 is used as the photosensitive drum 1. It is pressed against both ends.

The thickness of the toner layer T'conveyed to the developing area 13 is regulated by the developer regulating member, that is, the blade 16. The blade 16 is a magnetic substance such as iron,
A magnetic pole N _{1 of} a magnet 15 which is stationary arranged in the sleeve 6,
They are opposed to each other with the sleeve 6 in between. Therefore, magnetic force lines from the magnetic pole N ₁ are concentrated on the blade 16, and a strong magnetic curtain is formed between the blade 16 and the sleeve 6. Due to this magnetic curtain, a toner layer T ′ thinner than the gap between the blade 16 and the sleeve 6 is formed on the sleeve 6.

The gap between the blade 16 and the sleeve 6 is
The thickness of the formed toner layer T ′ is set to a gap that can be made thinner than the minimum gap between the sleeve 6 and the drum 1 in the developing region 13. (In this specification, the minimum gap between the sleeve and the drum is referred to as an SD gap.) An elastic blade pressed against the developing sleeve 6 is used instead of the blade 16 to regulate the toner layer thickness. May be.

As described above, the apparatus shown in FIG. 2 performs so-called non-contact development. That is, since the thickness of the developer layer T ′ conveyed to the developing area 13 is thinner than the minimum gap between the sleeve 6 and the drum 1, the toner flies through the air gap from the sleeve 6 and reaches the drum 1.

A vibration bias voltage is applied to the sleeve 6 from a power supply 100, which will be described later, in order to improve the development efficiency, form a high density, clear, and fogging-reduced developed image. This oscillating bias voltage is a DC voltage DC voltage superposed with an AC voltage AC voltage. And
This oscillating bias voltage is a voltage such that the dark part potential and the light part potential of the latent image exist between the maximum value and the minimum value, and the DC voltage is between the dark part potential and the light part potential of the latent image. A voltage such that a value is present is preferred. The frequency of the AC component of the vibration bias voltage is 0.6 to 2.4 kHz, and the peak-to-peak voltage (the difference between the maximum value and the minimum value, which is also called the peak-to-peak value) Vpp is 0.4 to 2. 0kV, AC
The current value is preferably 0.2 to 3.0 mA, and a rectangular wave, sine wave, triangular wave or the like is used as the waveform. By such a bias voltage, the sleeve 6 is applied to the developer in the developing area 13.
From the electric field in the direction of urging the force from the drum to the drum 1,
The electric field in the direction of applying a force in the direction from the drum 1 to the sleeve 6 acts alternately. As a result, the toner vibrates reciprocally in the developing area 13, and thus a good developed image can be obtained.

The value of the DC voltage component of the vibration bias voltage is set to a value between the value of the light portion potential and the value of the dark portion potential of the latent image, but in the case of reversal development, the dark portion potential is higher than the light portion potential. In the case of regular development, it is preferable to set the values closer to the light potential than the dark potential in the case of regular development, from the viewpoints of fog prevention, image density improvement, line image thinning prevention, and the like.

The term "reversal development" means development in which a toner charged to the same polarity as the latent image is attached to the bright area potential area (area exposed to light) of the latent image to visualize it. on the other hand,
The development in which the toner charged in the opposite polarity to the latent image is made visible in the dark potential region (the region not exposed to light) of the latent image is called "regular development".

In the developing device D of the present embodiment, the magnetic pole S ₁ of the magnet 15 forms a magnetic field in the developing area 13 to prevent fog and enable clear development of a line image. Further, the magnetic poles N ₂ and S ₂ contribute to the toner conveyance.

Next, SD, which is a characteristic used in the present invention,
The dependence of the size of the gap and the AC current value will be described with reference to FIG.

In FIG. 3, when the developing sleeve 6 faces the area of the photosensitive drum 1 where the electrostatic latent image is not formed, that is, the non-image area (dark portion potential −700 V), the five sleeves 6 shown in FIG. The results are obtained by applying a rectangular wave AC voltage whose constant voltage is controlled to each value. The AC frequency is 1.8 kHz in each case.

In FIG. 3, the alternating current value (effective value) is a value obtained by plotting an alternating current ammeter in series between the constant voltage alternating current power source and the sleeve 6, and plotting the sleeve 6 several times. The average value when doing is that point. The ammeter used is the FLUKE 8062A TRUE RM.
It was S METER.

The horizontal axis of FIG. 3 indicates the SD gap (unit: μ
m), and the horizontal axis is the alternating current value (effective value: mA). The SD gap holding member (spacer roller 11) used here was made with a deflection accuracy of about 10 μm.

As can be seen from this graph, when a constant alternating voltage is applied, the alternating current value changes due to a change in the SD gap due to a cartridge difference or the like. In other words, the size of the SD gap can be known by measuring the alternating current value.

In FIG. 4, the AC current value (effective value) is 2 mA.
SD gap when set to (constant) and alternating voltage (Vpp)
Shows the relationship. This is created from the graph of FIG. As can be seen from the figure, when a constant-current controlled AC voltage is applied to the sleeve, the AC voltage value (Vpp) changes according to the size of the SD gap.

FIG. 4 shows that if the AC current value is kept constant and the alternating voltage at that time is obtained, the size of the SD gap at that time can be obtained uniquely.

The present invention utilizes the above characteristics to control the image forming factor in response to a change or difference in the SD gap to control a change in line width and a change in image density.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Embodiment 1 FIG. 5 shows a control device 118 constructed according to the present invention, and FIG. 6 shows a control sequence.

First, when the main motor is turned on and the pre-rotation of the photosensitive drum 1 is started, the charging of the photosensitive drum 1 is started by the charger 2 (FIG. 1), and the surface of the photosensitive drum 1 is charged to a dark potential of -700V. To be done. At this time, CPU1
Reference numeral 09 controls the switching circuit 111 to connect the constant current control circuit 104 to the AC power supply 101. Constant current control circuit 104
Is receiving a feedback of the output AC current value of the AC power supply 101 detected by the current detection circuit 103, and sets the AC current value of the output of the AC power supply 101 to a target value, for example, 2 mA.
Maintain (effective value).

The output A of the AC power source 101 at this time
The C voltage value V _DO is detected by the voltage detection circuit 105. As can be seen from FIG. 4, the detected AC voltage value V _DO is S
Corresponds to the D gap. Then, the detected AC voltage value V _DO is held in the hold circuit 110 via the AD conversion circuit 107 and the CPU 109. (Note that the above A
Since the C voltage value V _DO corresponds to the size of the SD gap,
In other words, detecting the AC voltage value V _DO means S
It is also to detect the size of the D gap. Note that the above operation is performed during the period between images.

Next, the charged surface of the photosensitive drum 1 is irradiated with the laser beam modulated by the image signal, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. Before the latent image comes to the developing area 13 when the photosensitive drum 1 rotates, the CPU 10
9 controls the switching circuit 111 to disconnect the connection between the AC power supply 101 and the constant current control circuit 104, and also connects the constant voltage control circuit 106 to the AC power supply 101.

The constant voltage control circuit 106 includes the drum 1
The detection voltage V _DO held in the hold circuit 110 during the pre-rotation is applied as a target voltage value via the CPU 109 and the DA conversion circuit 108. Further, the AC voltage value of the output of the AC power supply 101 detected by the voltage detection circuit 105 is fed back to the constant voltage control circuit 106.
As a result, the constant voltage control circuit 106 maintains the AC voltage value of the output of the AC power source at the target voltage value V _DO during latent image development, in other words, during printing.

Therefore, during development of the latent image, the sleeve 6 has
A vibration bias voltage in which a constant-voltage-controlled DC voltage (for example, −500 V) that is the output of the constant-voltage DC power supply 102 is superimposed on the AC voltage that is controlled to the target voltage value is applied. The potential is −700 V, for example, and the bright part potential is −100 V, for example.
That is, even if the SD gap changes, the change in the strength of the oscillating electric field is prevented. (Note that the constant voltage DC power supply 102 is energized both during the pre-rotation period and during the image-to-image period, so that the sleeve is not limited to the developing time and the AC power supply 101 operates during these periods. A voltage in which the output of the DC power supply 102 is superimposed is applied to the output.) As described above, in the present embodiment, the AC constant current value is 2 mA, A
Since the C frequency is set to 1.8 kHz, the AC voltage value Vpp corresponding to each SD gap value is as shown in the graph of FIG.

Therefore, for example, the dark potential is -700V,
When the SD gap is set to 300 μm in an apparatus for reversal development at a process speed of 47.1 mm / s, using a toner negatively charged with a latent image having a light portion potential of −100 V, the detection voltage (peak-to-peak voltage) ) V _DO becomes 1600V. Therefore, the latent image is an AC voltage (frequency 1.8 kH) which is constant voltage controlled so that the peak-to-peak voltage Vpp becomes 1600V.
In z), the development is performed by the sleeve 6 to which the vibration bias voltage on which the DC voltage controlled to the constant voltage of −500 V is superimposed is applied.

In the present embodiment, the SD gap was changed from 250 to 350 μm for the sake of explanation.
The gap is similarly established in the range of 50 to 500 μm, and the electric field strength during development can be kept constant regardless of the size of the SD gap, so that the line width and the density are substantially constant. It was also confirmed that the same effect can be achieved at an alternating frequency of 600 to 2400 Hz.

In the conventional example, the SD gap is set to 250.
When the thickness was changed to ˜350 μm, the line width and the density changed. This state is shown in the graphs of FIGS. 7 and 8.

The term "pre-rotation period" means that the photosensitive drum 1 is rotated and the charging devices and developing devices are turned on by the time the latent image is formed on the photosensitive drum 1 after the print switch is turned on. It is a period during which the sensitivity of the photosensitive drum and the operation of the charging device and the developing device are stabilized by operating the photosensitive drum.

The term "inter-image period" means the time from the end of development of one latent image when a plurality of latent images are continuously formed, that is, when printing is continuously performed on a plurality of sheets of paper. It refers to the period until the development of the next latent image is started.

During the pre-rotation period and the image-to-image period, the developing sleeve 6 faces the area of the photosensitive drum 1 where the latent image is not formed, that is, the non-image area. Even if a bias voltage is applied to the sleeve 6 during the period, toner is not substantially consumed on the drum 1.

Embodiment 2 In Embodiment 2, the target AC voltage for constant voltage control is based on the AC voltage value V _DO detected while the non-image area of the photosensitive drum 1 is passing through the developing area. The value V _DT is calculated by the CPU 109.

That is, the CPU 109 substitutes the detected AC voltage value V _DO into a predetermined function V _DT = f (V _DO ), and calculates the target AC voltage value V _DT corresponding to the detected value V _DO. . Then, the target value V _DT is held by the hold circuit 110.

When the image area of the photosensitive drum 1 passes through the developing area 13, the CPU 109 controls the AC voltage value V _{DT held} by the hold circuit 110 as a target AC voltage value via the D-A conversion circuit. It is given to the circuit 106.

The control circuit 106 maintains the voltage value of the AC voltage applied to the sleeve 6 at the voltage value V _DT . The other points are the same as in the first embodiment.

FIG. 9 shows the relationship between the SD gap and the AC voltage during development. The dotted line is the case of the first embodiment, and the solid line is the case of the second embodiment.

As can be seen from the above, a linear function is adopted as the function in the present embodiment.

Assuming that the function f in this embodiment is V _DT = f (V _DO ) = αV _DO + β, when 250 μm ≦ SD ≦ 350 μm,
When α = 1 SD ≦ 250 μm, 350 μm ≦ SD,
α = 1.5. β is a constant determined in each case.

That is, the SD gap is 250 μm or more and 350 μm.
Below m, the same as in Example 1, but below 250 μm or above 350 μm, the inclination α = 1.5, and as shown in FIGS. 10 and 11, in the case of this example, Is better.

That is, referring to FIG. 10, according to the present embodiment,
Further, the line width can be made constant. This is SD
When the gap is 350 μm or more, the alternating electric field is made stronger than in Example 1, and when the SD gap is 250 μm or less, the weakening is effective. FIG. 11 shows the relationship between the SD gap and the solid black density. In this embodiment, the SD gap is effective in preventing the density reduction when the SD gap is 350 μm or more.

As described above, by substituting the detection voltage into the predetermined function to determine the alternating voltage at the time of development, it was possible to obtain a stable image in a wider SD gap.

The above α and β are examples used for explaining the present invention, and are not limited to the above values, and in the present embodiment, the expression of f (V _DO ) is a linear expression. However, it is naturally possible to use an expression other than the linear expression according to the gist of the present embodiment.

Embodiment 3 Another embodiment of the control device 118 according to the present invention is shown in FIG. During the pre-rotation, the time between images, CPU 109, as the output of the AC power supply 101 is kept at a predetermined constant voltage value V _R, and controls the constant voltage control circuit 106. The AC current value i _O at this time is applied by the current detection circuit 103, and the detected value i _O is transmitted to the CPU 109 via the AD conversion circuit 107.

The CPU 109 uses the detected value i _O as a predetermined function V
Substituting into _DT = f (i _O ), the AC voltage value V _DT corresponding to the detected value i _O is calculated. This value V _DT is the hold circuit 110.
Is held at.

At the time of development, the CPU 109 uses the AC voltage value V _DT as the target AC voltage value and the DA conversion circuit 108.
It is applied to the constant voltage control circuit 106 via. As a result, the output AC voltage of the AC power source during development is maintained at the above voltage value V _DT .

In this embodiment, the output of the AC power source 101 is V
Constant voltage control with _R (peak-to-peak voltage) set to 800V
The alternating current i _O at that time is detected. According to FIG. 3, the size of the SD gap is uniquely determined by the value of i _O. Therefore, the alternating voltage at the time of development corresponds to the size of the SD gap at that time, and the size of the SD gap of the second embodiment shown in FIG. Line or Example 1
As it becomes similar to a line, defining a function _{V DT = g (i O)} .

As a result, even in the present embodiment, as shown in FIG.
0, it was possible to obtain the same effect as that of the second embodiment or the first embodiment shown in FIG.

By the way, it has been conventionally known that a leak phenomenon occurs when an alternating voltage is applied to the SD gap at a voltage higher than the voltage according to Paschen's law.

When the leak phenomenon occurs, white spots occur when printing solid black on the entire surface when it is slight, and elliptical leak marks occur when it is severe.

According to the present invention, since the alternating voltage value changes according to the SD gap, the leak phenomenon is unlikely to occur, but a leak rarely occurs during constant current control.
Leak prevention becomes more reliable by limiting the maximum value of the C voltage.

Therefore, in the graph of FIG. 4, it is preferable to provide a limiter so that the AC voltage does not momentarily exceed the voltage obtained by adding 200 V to the Vpp value at each SD gap. This completes leak prevention. However, when the current is detected using the AC voltage controlled by the constant voltage, it is sufficient to select a voltage that can prevent the leakage, and thus the limiter is not necessary.

Embodiment 4 Another embodiment of the control device 118 according to the present invention is shown in FIG.
FIG. 14 shows the operation sequence.

In this example, C at the time of pre-rotation and at the time of image interval, C
The PU 109 controls the variable power source 112 to apply a reference voltage (for example, −700V) to the grid 2b of the charger 2. (For example, −5 KV is applied to the corona discharger 2a.) As is well known, the surface potential (dark part potential V _D ) of the photosensitive drum 1 becomes substantially equal to the voltage applied to the grid 2b.

On the other hand, the CPU 109 connects the constant current control circuit 104 to the AC power source 101 via the switching circuit 111. As a result, the output of the AC power supply 101 is, for example, 2 mA.
Constant current is controlled to (effective value).

The AC voltage value V _DO of the output of the AC power supply 101 at this time is detected by the voltage detection circuit 105, and the CPU 109
Is the target surface potential V corresponding to the detected AC voltage value V _DO
DP , that is, the voltage value V _DP to be applied to the grid 2b is determined, and this voltage value V _DP is held in the hold circuit 110.

Next, at the time of development, the CPU 109 sets the output voltage of the power source 112 to the above V _DP . As a result, the surface potential (dark portion potential) of the photosensitive drum 1 becomes V _DP .

On the other hand, the CPU 109 connects the constant voltage control circuit 106 to the AC power source 101 by the switching circuit 111. As a result, the output of the AC power supply 101 is subjected to constant voltage control to a predetermined voltage, for example, 1700V (peak-to-peak voltage).

The output of the AC power supply 101 is a rectangular wave having a frequency of 1.8 kHz, for example. As described above, the output DC voltage of the DC power supply 102 (for example, -500V) is superimposed on the output AC voltage of the AC power supply 101.

The detected AC voltage value V _DO corresponds to the size of the SD gap, as shown in FIG.

On the other hand, in order to prevent the fluctuation of the electric field strength when the constant voltage controlled AC voltage is used, the relationship shown in FIG. 15 is required between the photoconductor surface potential V _D and the SD gap. Become.

Therefore, based on FIG. 4 and FIG.
From the C voltage V _DO to the photoconductor surface potential corresponding to the SD gap,
That is, the voltage V _DP to be applied to the grid 2b can be obtained.

Thus, for example, when the latent image on the photosensitive drum 1 is subjected to reversal development at a process speed of 47.1 mm / s using negatively charged toner, if the SD gap is 300 μm, Under this condition, a good image can be output in the image area.

Photoelectric drum charging potential −700 V (dark portion potential) (value determined by the above detection voltage when SD gap is 300 μm) Development bias alternating voltage (constant voltage) 1700 V (peak to peak value) Frequency 1.8 kHz DC voltage −500 V In this embodiment, the AC voltage during development is maintained at the same constant voltage regardless of the size of the SD gap.

In this embodiment, for example, the SD gap is 100 μm.
m is V _D = -800 V, SD gap is 300 μm, V _D = -700 V, SD gap is 500 μm, V _D =
The line width and density are set to be approximately constant at -600V.

In the conventional example, the SD gap is 250 to
When the thickness was changed to 350 μm, the line width and the density changed. This state is shown in the graphs of FIGS. 16 and 17.

Fifth Embodiment In this embodiment, the output voltage of the DC power supply 102 is controlled based on the detected AC voltage value V _DO described in the fourth embodiment, not the dark portion potential of the photosensitive drum 1. Therefore, the dark portion potential of the photosensitive drum 1 is constant (for example, -70) regardless of the size of the SD gap.
On the other hand, the DC voltage component of the vibration bias voltage applied to the sleeve 6 at the time of developing the latent image, that is, the value of the output voltage of the DC power supply 102 is changed according to the size of the SD gap. The other points are similar to those of the fourth embodiment.

FIG. 18 shows the control device 118 of this embodiment. The CPU 109 controls the DC power supply 102 so as to output a DC voltage having a constant value (for example, −500 V) that does not depend on the size of the SD gap during the pre-rotation and during the image.

On the other hand, the CPU 109 causes the detected A
Based on the C voltage V _DO, it determines the DC voltage value V _DC during development and holds this value V _DC to the hold circuit 110.

Then, the CPU 109 maintains the output voltage of the DC power source 102 at the above value V _DC during development.

The graph of FIG. 19 shows the relationship between the SD gap size and the developing bias DC component V _DC in this embodiment.

In the fifth embodiment, since V _D is constant, V _D
L (light part potential) is also constant. Therefore, the line width and the density correspond to the developing bias DC voltage. When this voltage is low (-350 to -500 V), the contrast with _VL is small, the line width is thin, and the density is low. If this DC voltage is high (-650 to -500V),
The contrast with V _L is large, the line width is thick, and the density is high. Therefore, in Example 5, when the SD gap was 100 μm, _VDC = −350 V, when the SD gap was 300 μm the median value was _VDC = −500 V, and when the SD gap was 500 μm, _VDC = −650 V.

Also in the fifth embodiment, the same effect as that of the fourth embodiment can be achieved, and the results of FIGS. 16 and 17 are directly applied.

Sixth Embodiment By the way, in the fourth embodiment, the dark potential V _D of the photosensitive drum 1 is controlled according to the size of the SD gap, and in the fifth embodiment, the DC voltage component V _DC is controlled according to the size of the SD gap. . In these cases, due to the change in the SD gap, the difference (contrast) between the DC voltage and the bright portion potential V _L of the latent image changes, although slightly.

Therefore, it is more preferable to combine the fourth embodiment and the fifth embodiment in order to suppress the change in the contrast to a smaller extent.

In this case, on the basis of the detected AC voltage value V _DO , the charging voltage of the photosensitive drum 1 is controlled to the value shown in FIG. 15, and at the same time, the voltage value of the DC component of the developing bias is changed to that shown in FIG. Printing is performed by controlling the constant voltage to the value shown in. For example, when the SD gap is 300 μm, V _D =
-700V, _VDC = -500V.

Example 7 In Example 7, the voltage applied to the grid 2b of the charger 2 is controlled using the AC current value i _O detected in the same manner as in Example 3. That is, the dark potential V _D of the photosensitive drum 1 is controlled. Then, during development, the output of the AC power supply 101 is controlled to a predetermined voltage (for example, peak value 1700 V) by a constant voltage regardless of the size of the SD gap. Others are the same as in the third embodiment.

FIG. 20 shows the controller 118 of this embodiment, and FIG. 21 shows the operation sequence.

The dark portion potential V _D corresponding to the detected AC current value i _O can be obtained from FIGS. 4 and 17.

For example, the AC voltage at the time of detection has a peak-to-peak value of 80.
If the detected AC current value i _O is 1.1 mA when the constant voltage is controlled to 0 V, the dark portion potential V _D is set to −700 V. This has an SD gap of 300 μm
Because it was. Also in this example, the effects shown in FIGS. 16 and 17 were obtained.

Example 8 In Example 8, using the detected AC current value i _O , D
The output voltage V _D of the C power supply 102 is controlled. The other points are the same as in Example 7.

DC corresponding to the detected AC current value i _O
The voltage value V _DC can be obtained from FIGS. 4 and 19.

FIG. 22 shows a control device 118 according to the eighth embodiment. Also in this example, the effects shown in FIGS. 16 and 17 were obtained.

When the seventh and eighth embodiments are combined, the effect of preventing the line width change and the image density change is further improved.

Embodiment 9 In this embodiment, the light emission intensity of the light source of the exposure optical system, that is, the semiconductor laser 35a is controlled. That is, the exposure amount of the photosensitive drum 1 is controlled. That is, the AC power supply 101 outputs a constant-current-controlled AC voltage at a constant current (for example, 2 mA) during forward rotation and between images, and the AC applied to the sleeve 6 at that time.
The voltage value V _DO is detected. The CPU 109 uses the AC voltage value V _DO to apply the drive current I _D to the laser 35a.
Is determined and held in the hold circuit 110.

During development, the CPU 109 controls the laser driver 113 to apply a drive current having a value I _D to the laser 35a.

In this example, the dark portion potential of the photoconductor 1 is constant regardless of the size of the SD gap. Others are the same as those in the fourth embodiment.

The control device 118 of the ninth embodiment is shown in FIG. The relationship between the SD gap and the AC voltage is shown in FIG. 4, and the SD gap and the laser light intensity are shown in FIG.
It was shown to. From these, the laser light intensity corresponding to the detected AC voltage, that is, the laser drive current _ID can be obtained.

According to FIG. 24, the amount of laser light on the photosensitive drum surface is 2.4 when the SD gap is 300 μm.
μJ / cm ² . Small SD gap 100-200
In case of μm, the line width becomes thicker as it is,
The amount of laser light on the drum surface is small, for example 100 μm
And 2.0μJ / cm ² when, on the contrary, in the case of SD gap is large 400~500μm, line width is narrow,
Since the density also decreases, the amount of laser light is increased, for example, 5
When it was 00 μm, it was 2.8 μJ / cm ² . Here, when the laser light amount is increased, the line width is thicker and the density is higher, and when the laser light amount is weaker, the line width is thinner and the density is thinner.

In this embodiment, the SD gap is small (100
～200Myuemu) If, in order to prevent thickening of the line width, although small amount of laser light, so as not occur concentrations decrease, there is the order of about 15% reduction of 2.4μJ / cm ^2.

In order to investigate the effect of the present invention, an experiment was conducted in this example while changing the SD gap. The results are shown in FIGS. 25 and 26.

In FIG. 25, the SD gap is 100 to 500 μm.
The line width when changed to, due to the effect of the present invention,
The line width is almost constant at about 200 μm regardless of the change in the SD gap.

FIG. 26 shows an SD gap of 100 to 500 μm.
When the concentration is changed to, the concentration is almost constant due to the effect of the present invention.

Example 10 In Example 10, AC detected in the same manner as in Example 3
The emission intensity of the laser 35a is controlled using the current value i _O. At the time of development, the output of the AC power source 101 is set to a predetermined voltage (for example, a peak-to-peak voltage of 1
The constant voltage is controlled to 700 V). Others are the same as those in the third and ninth embodiments.

The laser drive current corresponding to the detected AC current value i _O can be obtained from FIGS. 3 and 24. The correspondence between the SD gap size and the laser power may be set in the same manner as in the ninth embodiment.

FIG. 27 shows the controller 118 of the tenth embodiment.

Eleventh Embodiment In the eleventh embodiment, when the SD gap is particularly large and particularly small, not only the laser light amount on the photosensitive drum surface but also the DC voltage of the developing bias is changed. It is a feature. The other points are the same as those in Example 9 or 10 above.
The control of the laser light amount is the same as in Example 9 or 1.
The same as 0.

The relationship between the SD gap and the DC component of the developing bias in the eleventh embodiment is as shown in FIG. That is, when the SD gap is 200 μm or less, the line width tends to be slightly thick even if the amount of laser light is reduced. Therefore, the developing bias DC voltage is lowered to −500 to −450.
It was set to V. As a result, the output DC voltage of the power source 102 and the photoconductor light portion potential corresponding to the character portion (about -100 to -120).
The contrast with V) is reduced, and the line width can be reduced.

On the other hand, when the SD gap is 400 μm or more, the line width tends to be narrow even if the laser light amount is increased. Therefore, the output DC voltage of the power supply 102 is increased to −5.
It was set to 00 to -550V. As a result, the developing bias D
The contrast between the C voltage and the photoconductor light portion potential (about -80 to -100 V) is increased, and the line width can be thickened.

As described above, in the eleventh embodiment, by controlling not only the laser light amount but also the DC voltage component of the developing bias in accordance with the size of the SD gap, the same or more than in the 26th and 27th embodiments is obtained. It was possible to obtain the line width and the concentration stability.

The control of the DC power supply 102 is performed by using the detected AC voltage V _DO (which corresponds to the SD gap) or the detected AC current i _O (which corresponds to the SD gap). It suffices if the relationship shown in FIG. 28 is satisfied.

In the above embodiments, the drum sensitivity of about 2.4 μJ / cm ² is used as an example, but the present invention is not limited to this, and according to the present invention, a high sensitivity drum, For example, 0.3 μJ / cm ² can be used.

In the ninth, tenth and eleventh embodiments, the laser beam optical device 35 is used as the exposing means for the photosensitive drum, but the exposing means is not limited to this, and for example, an LED,
Exposure means such as a liquid crystal shutter array may also be used.

In each of the above embodiments, the duty ratio of the AC voltage is 50%.

The duty ratio is the ratio of the time length of the urging electric field forming phase in one cycle of the AC voltage.

Here, the urging electric field is an electric field that applies a force to the toner in the direction from the developing sleeve to the photosensitive drum. On the other hand, an electric field that applies a force to the toner in the direction from the photosensitive drum toward the developing sleeve is referred to as a reverse biasing electric field.

Thus, assuming that the time length of the energizing electric field forming phase in one cycle is T ₁ and the time length of the reverse energizing electric field forming phase is T ₂ , the duty ratio is T ₁ / (T ₁ + T ₂ )

The following embodiments control the duty ratio of the AC voltage during development.

Twelfth Embodiment FIG. 29 shows the control device of the twelfth embodiment, and FIG. 30 shows the operation sequence.

In the present embodiment, the CPU 109 connects the constant current control circuit 104 to the AC power supply 101 by the switching circuit 111 during the pre-rotation, during the image-to-image conversion, and the AC power supply 10
A predetermined duty ratio, for example 50%, is set in the duty ratio control circuit 114 that controls the duty ratio of the output of 1.

As a result, the AC power supply 101 outputs a constant-current-controlled AC voltage having a predetermined duty ratio and a predetermined current value, for example, 2 mA.

At this time, the AC voltage value V _DO applied to the sleeve 6 is detected by the voltage detection circuit 105. This detected voltage value V _DO corresponds to the size of the SD gap as described above.

The CPU 109 uses the detected AC voltage value V _DO.
The duty ratio DR of the AC voltage component to be applied to the sleeve at the time of development is calculated based on the above, and held in the hold circuit 110.

During development, the CPU 109 sets the calculated duty ratio DR in the duty ratio control circuit 114, and connects the constant voltage control circuit 106 to the AC power supply 101 by the switching circuit 111. As a result, the AC power supply outputs a predetermined peak-to-peak voltage, for example, an AC voltage whose constant voltage is controlled to 1600 V and whose duty ratio is the value DR.

The DC power source outputs a predetermined voltage, for example, a DC voltage of -500 V, during pre-rotation, between images, and during development.

The frequency of the output of the AC power supply 101 is
Pre-rotation, between images, during development, a predetermined value, for example 1.8
kHz.

As described above, the detected AC voltage V _DO corresponds to the size of the SD gap as shown in FIG.
The D gap and the duty ratio DR are associated as shown in FIG. Therefore, the CPU 109 can calculate the duty ratio DR based on the detection voltage V _DO .

More specifically, for example, when the SD gap is 100 μm, the line width is thick and the characters are crushed in the conventional example. Therefore, in this embodiment, the duty ratio is 40%.
As a result, the formation time of the biasing electric field was shortened and the formation time of the reverse biasing electric field was lengthened. The time average value of the developing bias voltage at this time is -340V. SD gap 10
The thickening of the line width at 0 μm was prevented.

Further, when the SD gap is 500 μm, the line width becomes narrow in the conventional example, and the density lowers. Therefore, in this embodiment, the duty ratio is set to 60%, the forming time of the biasing electric field is long, and the reverse bias is applied. The time for forming the pulsating electric field was shortened. The time average value of the developing bias voltage at this time is -660V. As a result, even when the SD gap was 500 μm, the line width was reduced and the density was prevented from decreasing.

FIG. 32 shows SD gaps of 100 μm and 300 μm.
One cycle of the developing bias voltage waveform for m and 500 μm is shown.

FIG. 31 shows the relationship between the SD gap and the duty ratio control value in this embodiment. By performing such control, in this embodiment, the SD gap is 100 μm to 5 μm.
The line width could be kept almost constant in the range of 00 μm. This is shown in FIG.

As for the density, the SD gap 100 as shown in FIG. 34 is obtained by performing the control in this embodiment.
It could be kept almost constant in the range of ˜500 μm.

The thirteenth embodiment differs from the thirteenth embodiment in that, in the thirteenth embodiment, a predetermined voltage V _R, for example, a peak is applied to the AC power supply 101 during the pre-rotation and the image-to-image similar to the third embodiment. AC with a duty ratio of 50% that is constant voltage controlled so that the interval value becomes 800V
A voltage is output, and the AC current i _O flowing through the sleeve at that time
Is detected by the detection circuit 103, and the CPU 109 controls the duty ratio DR of the output of the AC power supply 101 during development based on the detected current value i _O. The other points are similar to those of the twelfth embodiment.

The relationship between the SD gap and the AC current for an AC voltage having a predetermined peak-to-peak value is as shown in FIG. 3, and the relationship between the SD gap and the duty ratio is shown in FIG.
As shown in 1.

Therefore, the CPU 109 can calculate the duty ratio DR corresponding to the AC current value i _O.

In this example, A is detected when the AC current value i _O is detected.
The output of the C power supply 101 has a peak-to-peak value of 800V,
At the time of development, it is set to 1600V, for example.

FIG. 35 shows the control device of the thirteenth embodiment.

Also in this example, the same effect as that shown in FIGS. 33 and 34 can be obtained.

Example 14 In Example 14, not only the duty ratio of the AC voltage but also the maximum value and the minimum value of the AC voltage are controlled based on the detected AC voltage or the detected AC current.

That is, in this embodiment, the maximum value and the minimum value are changed so that the time average value of the vibration bias voltage applied to the sleeve is kept constant even if the duty ratio changes. Therefore, in this embodiment, the vibration bias voltage of 1
The integrated value of the voltage for the period is the output voltage of the DC power supply 102,
That is, the CPU 109 controls the maximum value and the minimum value of the vibration bias voltage according to the duty ratio so that it becomes equal to the value of the DC component of the vibration bias voltage.

FIG. 36 shows the SD gap 10 in the fourteenth embodiment.
One cycle of the developing bias (rectangular wave) in the case of 0, 300 and 500 μm is shown. For example, SD gap is 100 μm
In the case of, the duty ratio is set to 70%, the biasing electric field to the bright portion potential region is weakened, and the reverse biasing electric field in the bright portion potential region is strengthened. Also, the SD gap is 50
In the case of 0 μm, the duty ratio is set to 30%, the biasing electric field to the bright portion potential region is strengthened, and the reverse biasing electric field in the bright portion potential region is weakened.

In other words, in this embodiment, the line width is kept constant by controlling the strength of the biasing electric field (which corresponds to the minimum value of the vibration bias voltage), while the image density is controlled by controlling the duty ratio. Keep constant.

Therefore, in this embodiment, the relationship between the SD gap and the duty ratio is as shown in FIG. As shown in FIG. 37, the slope of the line is opposite to the slope of the line in FIG. 31 corresponding to Examples 12 and 13.

In the twelfth and thirteenth embodiments, since the line width is controlled by the energizing electric field forming time length, for example, when the SD gap is small, the duty is increased in order to prevent the line width from becoming thick in the past. Reduced the ratio.

On the other hand, in the fourteenth embodiment, for example, S
When the D gap is small, the energizing electric field is made small in order to prevent the line width from becoming thick. If this is done, the image density will drop, so in the fourteenth embodiment, the duty ratio is increased in order to prevent this.

In any case, since the time average value of the vibration bias voltage (the integrated value of the voltage for one cycle) is constant in the fourteenth embodiment, it is abnormal that the latent image is charged in the opposite polarity (minus). Even if the toner is mixed in the developer, it is possible to prevent the abnormal toner from being fogged to the dark potential region.

By the way, in the embodiment described above, the AC voltage or the AC current is detected not only during the pre-rotation but also between the images, but the AC voltage or the AC current is detected only during the pre-rotation, and based on the detection. The image forming conditions may be controlled.

Further, in the above-described embodiment, the timing of switching from the developing bias control for SD gap detection to the developing control is the same as the timing of changing from the non-image area to the image area. Switching may take several to several hundreds of milliseconds, and it is also possible to switch to control for development earlier by the time required for this switching.
Naturally, included in the present invention.

Further, in the above-mentioned embodiments, the negative latent image is reversely developed with the negatively charged toner, but the present invention is an apparatus for reversely developing the positive latent image with the positively charged toner. Can also be applied to. Further, the present invention can be applied to an apparatus for developing a latent image normally.

The present invention can also be applied to an apparatus using a non-magnetic one-component developer and an apparatus using a two-component developer.

Further, the present invention can be applied to an apparatus using a belt-shaped or solid columnar developer carrier and a belt-shaped developer carrier.

Furthermore, the present invention can be applied to a so-called contact development type apparatus in which the developer layer carried on the developer carrying member is brought into contact with the image carrying member in the developing area.

Further, the present invention is particularly useful for an image forming apparatus of the type in which a process cartridge is attached and detached, but it is also applicable to an image forming apparatus in which a photoconductor and a developing device can be attached and detached separately. Further, although the rectangular wave AC voltage is used in each of the above embodiments, the present invention can be applied to a device using a sine wave AC voltage or a triangular wave AC voltage.

Further, the present invention uses the vibration bias voltage such that the maximum value and / or the minimum value of the vibration bias voltage are between the value of the dark portion potential and the value of the light portion potential of the electrostatic latent image. It can also be applied to a developing device.

[0173]

As described above, in the image forming apparatus of the present invention, the bias voltage including the AC voltage component is applied to the developer carrier, and the developer carrier faces the non-image area of the image carrier. During the operation, the reference bias voltage including the constant current AC voltage component or the reference bias voltage including the constant voltage AC voltage component is applied to the developer carrier, and at that time, the AC voltage value or the AC current applied to the developer carrier. The value is detected and the image forming factor is controlled based on the detected AC voltage value or AC current value. Therefore, even if the gap between the developer carrying member and the image carrying member is changed, the development is performed. It is possible to suppress changes in image density and line width, and further, even in a device configuration in which a process cartridge having at least an image carrier and a developing device is attached and detached, the gap between the image carrier and the developer carrier is set to a reference value. Is different If the Seth cartridge is also used, it is possible to suppress the change in density and line width of the developed image can be stably obtain a high quality image.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of an image forming apparatus to which the present invention can be applied.

FIG. 2 is an explanatory diagram of an example of a developing device that can be used in the present invention.

FIG. 3 is an explanatory diagram of a correlation between an SD gap and an AC current.

FIG. 4 is an explanatory diagram of a correlation between an SD gap and an AC voltage.

FIG. 5 is an explanatory diagram of a control device according to the first and second embodiments.

FIG. 6 is an explanatory diagram of an operation sequence of Examples 1 and 2.

FIG. 7 is an explanatory diagram of an effect of the first embodiment.

FIG. 8 is an explanatory diagram of another effect of the first embodiment.

FIG. 9 is an explanatory diagram of a relationship between an AC voltage and an SD gap in the second embodiment.

FIG. 10 is an explanatory diagram of an effect of the second embodiment.

FIG. 11 is an explanatory diagram of another effect of the second embodiment.

FIG. 12 is an explanatory diagram of a control device according to a third embodiment.

FIG. 13 is an explanatory diagram of a control device according to a fourth embodiment.

FIG. 14 is an explanatory diagram of an operation sequence of the fourth embodiment.

FIG. 15 is an explanatory diagram of a relationship between an SD gap and a photoconductor dark part potential in Example 4.

FIG. 16 is an explanatory diagram of an effect of the fourth embodiment.

FIG. 17 is an explanatory diagram of another effect of the fourth embodiment.

FIG. 18 is an explanatory diagram of a control device according to a fifth embodiment.

FIG. 19 is an explanatory diagram of the relationship between the SD gap and the DC voltage in the fifth embodiment.

FIG. 20 is an explanatory diagram of a control device according to a seventh embodiment.

FIG. 21 is an explanatory diagram of an operation sequence of the seventh embodiment.

FIG. 22 is an explanatory diagram of a control device according to an eighth embodiment.

FIG. 23 is an explanatory diagram of a control device according to a ninth embodiment.

FIG. 24 is an explanatory diagram of the relationship between the SD gap and the laser light amount on the drum surface in Example 9.

FIG. 25 is an explanatory diagram of an effect of the ninth embodiment.

FIG. 26 is an explanatory diagram of another effect of the ninth embodiment.

FIG. 27 is an explanatory diagram of the control device according to the tenth embodiment.

FIG. 28 is an explanatory diagram of the relationship between the SD gap and the DC voltage in the eleventh embodiment.

FIG. 29 is an explanatory diagram of a control device according to a twelfth embodiment.

FIG. 30 is an explanatory diagram of an operation sequence of the twelfth embodiment.

FIG. 31 is an explanatory diagram of the relationship between the SD gap and the duty ratio in the twelfth embodiment.

FIG. 32 is an explanatory diagram of the waveform of the developing bias voltage according to the twelfth embodiment.

FIG. 33 is an explanatory diagram of an effect of the twelfth embodiment.

FIG. 34 is an explanatory diagram of another effect of the twelfth embodiment.

FIG. 35 is an explanatory diagram of a control device according to a thirteenth embodiment.

FIG. 36 is an explanatory diagram of a developing bias voltage waveform according to the fourteenth embodiment.

FIG. 37 is an explanatory diagram of a relationship between the SD gap and the duty ratio in the fourteenth embodiment.

[Description of Reference Signs] 1 image carrier (photosensitive drum) 2 charger 6 developer carrier (developing sleeve) 7 cleaning device 35, 36 exposure optical system

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location G03G 15/04 15/06 101 15/08 115 (72) Inventor Kazuro Ono 3 Shimomaruko, Ota-ku, Tokyo C. 30-2 Canon Inc. (72) Inventor Akihiko Takeuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (20)

[Claims] 1. An image bearing member; a latent image forming means for forming an electrostatic latent image on the image bearing member; a latent image forming unit arranged opposite to the image bearing member, and carrying and carrying a developer for development. A developer carrier for developing the latent image in a region; a power supply for applying a bias voltage including an AC voltage component to the developer carrier; and a non-image of the developer carrier being the image carrier. The developer carrier, the power source is controlled to apply a reference bias voltage containing a constant current AC component to the developer carrier, and the developer carrier is applied by applying the reference bias voltage. An image forming apparatus including: a control unit configured to detect an AC voltage value, and control at least one image forming factor corresponding to the detected AC voltage value. 2. The controlled imaging factor is
The image forming apparatus according to claim 1, which is a peak-to-peak value of an AC voltage component of a bias voltage applied to the developer carrying member during development of the latent image. 3. The power source applies a bias voltage including a DC voltage component and the AC voltage component to the developer carrier, and a controlled image forming factor is applied to the developer carrier during development of the latent image. The image forming apparatus according to claim 1, wherein the bias voltage is a voltage value of a DC voltage component of the bias voltage. 4. The controlled imaging factor is
The bias voltage A applied to the image carrier at the time of developing the latent image
The image forming apparatus according to claim 1, wherein the duty ratio is the C voltage component. 5. The latent image forming means has a charging means for charging the image carrier and an exposing means for exposing the image carrier charged by the charging means with image information light, and is controlled. The image forming apparatus according to claim 1, wherein the image forming factor is a charging potential of the image carrier by the charging unit. 6. The latent image forming means has a charging means for charging the image carrier and an exposing means for exposing the image carrier charged by the charging means with image information light, and is controlled. The image forming apparatus according to claim 1, wherein the image forming factor is the intensity of the image information light. 7. The process cartridge according to claim 1, further comprising cartridge supporting means for detachably supporting the process cartridge, wherein the image carrier and the developer carrier are provided in the process cartridge. The image forming apparatus according to item 1. 8. The image forming apparatus according to claim 7, wherein the process cartridge is further provided with a cleaning unit for cleaning an image carrier. 9. A spacer is provided at an end portion of the developer carrier, and the spacer is pressed against the image carrier to form a gap between the image carrier and the developer carrier. The image forming apparatus according to any one of 1 to 6. 10. A spacer is provided at an end portion of the developer carrier, and the spacer is pressed against the image carrier to form a gap between the image carrier and the developer carrier. 7 image forming apparatus. 11. An image bearing member; a latent image forming means for forming an electrostatic latent image on the image bearing member; a latent image forming unit disposed opposite to the image bearing member, and carrying and carrying a developer for development. A developer carrier for developing the latent image in a region; a power supply for applying a bias voltage including an AC voltage component to the developer carrier; and a non-image of the developer carrier being the image carrier. The developer carrier, the power source is controlled to apply a reference bias voltage including a constant voltage AC component to the developer carrier, and the developer carrier is applied by applying the reference bias voltage. And a control means for detecting at least one image forming factor corresponding to the detected AC current value, and an image forming apparatus. 12. The image forming apparatus according to claim 11, wherein the controlled image forming factor is a peak-to-peak value of an AC voltage component of a bias voltage applied to the developer carrier during development of the latent image. 13. The power supply applies a bias voltage including a DC voltage component and the AC voltage component to a developer carrier, and a controlled image forming factor is applied to the developer carrier during development of a latent image. The image forming apparatus according to claim 11, which is a voltage value of a DC voltage component of the bias voltage. 14. The image forming apparatus according to claim 11, wherein the controlled image forming factor is a duty ratio of an AC voltage component of a bias voltage applied to the image carrier at the time of developing the latent image. 15. The latent image forming means has a charging means for charging the image carrier and an exposing means for exposing the image carrier charged by the charging means with image information light, and is controlled. The image forming apparatus according to claim 11, wherein the image forming factor is a charging potential of the image carrier by the charging unit. 16. The latent image forming means has a charging means for charging the image carrier and an exposing means for exposing the image carrier charged by the charging means with image information light, and is controlled. The image forming apparatus according to claim 11, wherein the image forming factor is the intensity of the image information light. 17. The process cartridge according to claim 11, further comprising a cartridge supporting means for detachably supporting the process cartridge, wherein the image bearing member and the developer bearing member are provided in the process cartridge. The image forming apparatus according to item 1. 18. The process cartridge is further provided with cleaning means for an image carrier.
7 image forming apparatus. 19. A spacer is provided at an end portion of the developer carrier, and the spacer is pressed against the image carrier to form a gap between the image carrier and the developer carrier. The image forming apparatus according to any one of 11 to 16. 20. A spacer is provided at an end of the developer carrier, and the spacer is pressed against the image carrier to form a gap between the image carrier and the developer carrier. 17 image forming apparatuses.