JPH06202459A - Image forming device - Google Patents

Abstract

(57) [Summary] [Purpose] To increase the reliability of the developing action and control the maximum development density and development density gradient. A charge amount of toner t is estimated by detecting a current flowing between a charging blade 42 and a developing roller 41, and a motor 50 is controlled by the result to control a motor 50 through a worm gear 49 and a worm wheel 48. The charging blade holder 44 is rotated about the shaft 46 by the eccentric cam 47 that is interlocked with the charging blade holder 44.
Developing roller 41 of charging blade 42 attached to
The amount of charge of the toner t is adjusted by controlling the pressing force against.

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 such as an electronic copying machine using a developing device.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine, a latent image corresponding to an original is formed on a photosensitive drum, and a toner is applied to the latent image by a developing device to visualize the latent image. The transferred toner image is transferred onto a sheet by using a transfer device, and then the toner image on the sheet is fixed by using a fixing device.

For example, in the conventional developing device shown in FIG.
Developing roller 91 which is a rubber roller coated
A charging blade 93 having a rubber tip 92 attached to its tip is pressed against the toner to charge the toner t which is drawn out along with the rotation of the developing roller 91. The scraping roller 94 scrapes off the toner t that has gone around the developing roller 91 once to reduce the memory effect due to the development.

In the conventional developing device, the charging blade 93 is mounted and adjusted at the time of assembling and shipping the product. Therefore, the pressing force of the charging blade 93 against the developing roller 91 is constant, and the toner t is charged corresponding to this pressing force.

However, in such a method, the maximum density and the so-called γ value are required when the color balance of the developing device for the color printer or the like is required or when the halftone is required as in the PPC copying machine or the like. There is a drawback in that the ratio of the image density to the original density, which is referred to as "original density", cannot be adjusted, and the change in the properties of the toner cannot be dealt with.

[0006]

As described above, when the color balance of the developing device for the color printer or the like is required, or when the halftone is required as in the PPC copying machine or the like, the maximum density and There is a problem that the reliability of the developing action is low because the ratio of the image density to the original density, which is the so-called γ value, cannot be adjusted and the change in the property of the toner cannot be dealt with. Therefore, an object of the present invention is to provide an image forming apparatus capable of increasing the reliability of the developing action and controlling the maximum developing density and the developing density gradient.

[0007]

SUMMARY OF THE INVENTION In an image forming apparatus using a non-magnetic one-component developing device for electrophotography, an image forming apparatus of the present invention includes a developer supplying body for supplying a developer and the developer supplying body. A charging unit that charges the developer on the body, a detection unit that detects the charging state of the developer charged by the charging unit, and a control unit that controls the charging state of the developer according to the detection result of the detection unit. It consists of and.

The image forming apparatus of the present invention is an image forming apparatus using a non-magnetic one-component developing device for electrophotography, which includes a developer supplying body for supplying a developer and a developer on the developer supplying body. Contact charging means for pressingly contacting and charging, detecting means for detecting the charged state of the developer charged by the contact charging means, and the developer on the developer supply body according to the detection result of the detecting means. And a control means for controlling the charged state of the developer, which includes a moving means for moving the position of the contact charging means in the direction in which the pressing force on the developer changes.

[0009]

The developer on the developer supplying body for supplying the developer is pressed into contact with the developer and charged by the contact charging means, the charged state of the charged developer is detected, and the above-mentioned development is performed according to the detected charged state. The charging state of the developer is controlled by including a moving unit that moves the position of the contact charging unit in the direction in which the pressing force on the developer on the agent supply body changes.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows the internal structure of a copying machine as an image forming apparatus of the present invention. That is, reference numeral 1 is a main body of a copying machine, and an original table (transparent glass) 2 for supporting an original is fixed to the upper surface of the main body 1. This manuscript table 2
₁ is provided with a fixed scale 21 serving as a reference for setting a document, and an openable and closable document cover 1 ₁ is provided near the document table 2.

The original placed on the original table 2 is reciprocally moved along the lower surface of the original table 2 in the direction of arrow a by the scanning system including the exposure lamp 4 and the mirrors 5, 6 and 7. Exposure scanning is performed during the reciprocation.
In this case, the mirrors 6 and 7 move at half the speed of the mirror 5 so as to maintain the optical path length. The reflected light from the original by the scanning of the scanning system, that is, the reflected light from the original by the irradiation of the exposure lamp 4 passes through the lens block 8 for zooming after being reflected by the mirrors 5, 6 and 7. The light is reflected by the mirrors 9 ₁ , 9 ₂ , and 9 ₃ and guided to the photoconductor drum 10, and the image of the original is formed on the surface of the photoconductor drum 10. The exposure lamp 4, the mirrors 5, 6, and 7, the variable magnification lens block 8, the mirrors 9 ₁ and 9
_The optical system 3 is composed of ₂ and 9 ₃ .

The photosensitive drum 10 rotates in the direction of the arrow b in the figure, and the surface is first charged by the charging charger 11, and then the image is slit-exposed at the exposure section Ph to electrostatically charge the surface. A latent image is formed. The electrostatic latent image is visualized by the toner attached by the developing device 12. The developing device 12 is detachable from the copying machine main body 1.

On the other hand, the paper (image forming medium) is sent from the selected upper paper feed cassette 13 ₁ or lower paper feed cassette 13 ₂ to the feed rollers 14 ₁ and 14 ₂ and the roller pair 1.
5 ₁ ,

The sheet is picked up one by one by 15 ₂ and guided to the registration roller pair 17 through the paper guide paths 16 ₁ and 16 ₂ and is guided to the transfer section by the registration roller pair 17. Here, the paper feed cassettes 13 ₁ and 13 ₂ are detachably provided at the lower right end of the main body 1, and either one can be selected on an operation panel (not shown).

Further, each of the above-mentioned paper feed cassettes 13 ₁ and 13 ₂
Are cassette size detection switches 30 ₁ and 30 respectively.
₂ detects the cassette size. The cassette size detection switches 30 ₁ and 30 ₂ are composed of a plurality of micro switches that are turned on / off according to the insertion of cassettes of different sizes. Further, a manual feed guide 13a is provided on the upper surface of the paper feed cassette 13 ₁ , and a sheet manually inserted through the manual feed guide 13a is guided to the roller pair 15 ₁ by a delivery roller 14a. After that, the sheet is conveyed similarly to the sheet fed from the sheet feeding cassette 13 ₁ .

On the other hand, the sheet sent to the transfer portion is brought into close contact with the surface of the photoconductor drum 10 at the transfer charger 18, so that the toner image on the photoconductor drum 10 is formed by the action of the charger 18. Transcribed. The transferred sheet P is electrostatically peeled from the photosensitive drum 10 by the action of the peeling charger 19, is conveyed by the conveying belt 20, and is sent to the fixing device 21 provided at the end portion thereof. The transferred image is fixed by passing through.

Then, the sheet after fixing is sent out by a pair of delivery rollers 2.
2 is discharged to the tray 25 outside the main body 1. After the transfer, the photosensitive drum 10 is returned to the initial state by removing the residual toner on the surface by the cleaner 26 and erasing the residual image by the charge eliminating lamp 27.

Reference numeral 29 is a cooling fan for preventing the temperature inside the main body 1 from rising. In addition, the exposure lamp 4,
The mirror 5 is provided on the first carriage 31 ₁ , the mirrors 6 and 7 are provided on the second carriage 31 ₂ , and the mirrors 9 ₁ and 9 ₂ are provided on the third carriage 31 ₃ .

The developing device 12 is constructed as shown in FIG. That is, a developing roller 41 which is a coated rubber roller, a charging blade 42 having a rubber tip in contact with the developing roller 41 at the tip thereof, and a scraping roller 4 for scraping off the toner that has made a round of the developing roller 41.
3, a charging blade holder 44 to which the charging blade 42 is attached, a holder support shaft 45 that supports the charging blade holder 44 and serves as a rotation shaft, an eccentric cam 47 that is rotated around a fulcrum (axis) 46, and an eccentric cam 47. The shaft 46 includes a motor 50 that rotates via a worm wheel 48 and a worm gear 49, a toner storage unit 51 that stores the toner t, and a toner stirrer 52 that stirs the toner t in the toner storage unit 51. The operation of such a configuration will be described.

In this embodiment, the charging blade holder 44 has a rotation control mechanism, that is, an eccentric cam 47, a shaft 46, a worm wheel 48, a worm gear 49, and a rotating motor 5.
0 is provided, the charged state of the toner t is detected, the detected charged state is fed back, and the toner t on the developing roller 41 is always controlled to a desired charge amount.
In order to detect the charged state of the toner t, it is preferable to detect the current flowing between the charging blade 42 and the developing roller 41.

That is, in FIG. 1, the charging blade 4
Assuming that the current i (A) flowing between the developing roller 41 and the developing roller 41 is equal to the charge carried away by the toner t, the charging amount per one toner t is q (coul / unit), the developing roller 4
The toner adhesion amount per unit area on 1 is N (pieces / cm ² ),
With the length of the developing roller 41 being 1 (cm) and the peripheral velocity of the developing roller 41 being v (cm / sec), the electric charge i carried away by the toner t in a unit time is considered to be i = qNlv.
However, since triboelectric charging also contributes from the developing roller 41 side, i = kqNlv when the contribution rate from the charging blade 42 side is k. Therefore, if the current i and the peripheral velocity v are measured, the length l and the toner adhesion amount N are known, so that the charge amount q of the toner t can be estimated. Therefore, the current flowing between the charging blade 42 and the eccentric cam 47 can be estimated. To measure.

As shown in FIG. 3, in the CPU 60, i / v is calculated from the measured current i and the peripheral speed v by the calculation unit 61, and the toner t is calculated from the known length l and the toner adhesion amount N.
The charge amount q of is estimated. The blade position control unit 62 controls the position of the charging blade 42 (developing roller 4) so that the desired charge amount q of the toner t is obtained by the charge amount q of the toner t.
The pressing force to 1) is feedback-controlled via the motor 50.

The rotation of the motor 50 controlled by the blade position control unit 62 rotates the eccentric cam 47 about a fulcrum (axis) 46 via a worm gear 49 and a worm wheel 48. By the eccentric cam 47 rotated around the fulcrum (axis) 46, the charging blade holder 44
Rotates around the holder support shaft 45, and the position of the charging blade 42 attached to the charging blade holder 44, that is, the pressing force of the charging blade 42 against the developing roller 41 is adjusted.

By adjusting the pressing force of the charging blade 42 in this manner, the toner t on the developing roller 41 can be controlled to a desired charge amount. In addition, in the present embodiment, by using the worm transmission mechanism, the motor 5
The eccentric cam 47 is prevented from returning even when the current to 0 stops flowing, so that the pressing force of the charging blade 42 does not change.

Further, the length l of the developing roller 41 is known,
The peripheral speed v is fixed, the relationship between the charge amount q and the toner adhesion amount N is predicted in advance, and the charge amount q is determined only by measuring the current i.
It is also possible to estimate As the timing of measurement, it is appropriate from the time the print button on the operation panel (not shown) is pressed until the time when the developing device is actually used for image development.

FIG. 4 shows a developing device 70 having another structure. The same parts as those of the developing device 12 of FIG. 1 are designated by the same reference numerals. That is, the developing device 70 includes the developing roller 41, the charging blade 42, the scraping roller 43, the shaft 45, the charging roller 71, the charging blade support body 72, the sliding block 73, the rail 74, the toner storage portion 51, and the agitator 52. It is configured.

In the developing device 70, the developing roller 41 is independent and the scraping roller 43 is opposed to the charging roller 71. Further, the sliding block 73 is moved in the axial direction b by the screw 75 being rotated by the motor 50 as shown in FIG. When the slide block 73 moves with respect to the rail 74 that is skewed and attached to the charging blade holder 72, the charging blade holder 72 connected thereto rotates about the shaft 45 as a fulcrum, and the charging blade 42
The pressing force on the charging roller 71 changes. In this case, the current i measured for input to the CPU 60 is
Detects a current flowing between the charging blade 42 and the charging roller 71.

In the developing device 70 having such a structure, the toner t on the developing roller 41 can be controlled to a desired charge amount by controlling the motor 50 by the CPU 60 described above.

FIG. 6 shows a developing device 80 having another structure. The same parts as those of the developing device 12 of FIG. 1 are designated by the same reference numerals. That is, the developing device 80 includes the developing roller 41, the charging blade 42, the holder support shaft 45, the shaft 46, and the eccentric cam 4.
7, toner storage portion 51, agitator 52, charging roller 81,
The charging blade holder 82, the scraping roller 83, and the conveying roller 84 are included. In the main developing device 80, only a charging roller 81, a scraping roller 83, and a conveying roller 84 are added to the developing device 12 of FIG. . The transport roller 84 transports the toner t in the toner storage portion 51 to the developing roller 41.

In the developing device 80 having this structure, the above-mentioned C
The current i measured for input to the PU 60 detects the current flowing between the charging blade 42 and the charging roller 81. Even in the developing device 80 having such a configuration, the toner t on the developing roller 41 can be controlled to a desired charge amount by the control of the motor 50 by the CPU 60 described above.

Here, the blade current flowing between the charging blade 42 and the charging roller 81 in the developing device 80 is measured for each rotation angle of the eccentric cam 47 (that is, the pressing force of the charging blade 42 against the developing roller 41). The results obtained are shown in FIG. 7. At the time of this measurement, a bias of −100 V is applied to the developing roller 41 with respect to the charging roller 81.

When the setting of FIG. 6 is checked by CAD, it is as follows in the drawing. When the eccentric cam 47 rotated about the fulcrum (axis) 46 is rotated 30 degrees from the point A to the point B, the holder support shaft 45 and the charging roller 8 are rotated.
The length 1 to the contact point 1 is 9.4 mm, and the charging blade 4
The tip deflection y of 2 is 1.25 mm. The pressing force W of the charging blade 42 in this case is calculated as follows.

First, since the charging blade 42 has a rectangular cross section, the second moment of area I = bh ³ / 12 is required. Here, long side h = 10 mm, short side b = 0.1
It is 5 mm. Also, tip deflection y = Wl ³ The formula of the cantilever of / 3 EI is established, and when the above-mentioned second moment of area I is included, it becomes the following formula. y = Wl ³ / (3Ebh ³ / 12)

Here, tip deflection y = 1.25 mm, length l = 9.4 mm, longitudinal elastic modulus E = 10550 kgf / m.
m ² , The width b = 10 mm and the thickness h = 0.15 mm to obtain the pressing force W. W = y3Ebh ³ / 12 x l ³ = 1.25 × 3 × 105
50 x 10 ³ × 10 × 0.15 ³ / 12 x 9.4 ³ = 1
34 g / cm The pressing force W is 134 g / cm.

The charging current when the eccentric cam 47 is rotated by 30 degrees is about 0.3 μA at a peripheral speed of 250 mm / sec in FIG. 7, but when the contribution rate k = 1 is calculated from the above equation i = kqNlv. It becomes as follows. Charge amount per toner q = 10 μq / g, developing roller 41
Toner adhesion amount per unit area above N = 1 mg / c
m ² , The developing roller 41 length l = 20.4 cm, and the developing roller 41 peripheral velocity v = 25 (cm / sec), i = kqNlv = 1 × 10 × 10 ⁻⁶ × 1 × 10 ⁻³ × 2
0.4 × 25 = 5 μA.

Since the charging current is therefore about 5 μA,
When the contribution ratio is calculated from this, k = 0.3 / 5 = 0.06
Is an abnormally small value. Charging roller 81 at this time
The current flowing between the developing roller 41 and the developing roller 41 was 3 μA. In the apparatus of FIG. 6, it is better to use the current flowing from the charging roller 81 to the developing roller 41 as a standard rather than the blade current as a standard.

In this case, it is considered that the charging of the toner t on the developing roller 41 is more contributed by the frictional charging at the contact portion between the charging roller 81 and the developing roller 41 than that by the charging blade 42. It is not possible to control the charge amount q of the toner t on the developing roller 41 only by the pressing force of.

Although there is the problem of the above-mentioned contribution rate, it is possible to estimate the charge amount q of the toner t from the blade current i. That is, when the pressing force of the charging blade 42 is actually increased, the blade current i continues to increase despite the decrease in the adhesion amount N of the toner t on the developing roller 41.

When the pressing force of the charging blade 42 is increased, the toner adhesion amount N is shown in FIG. 4, and the toner t is conveyed by the length l ₂ of the tip of the charging blade 42 and the surface roughness of the charging roller 71. Since it converges to a certain value determined by the force, the blade current i is given data which is directly proportional to the charge amount q of the toner t. FIG. 8 shows a measurement example of the relationship between the charge amount of the toner t and the pressing force of the charging blade 42 in this case.
Shown in. It should be noted that this measurement is simpler than the method of measuring the developing current for the reference pattern, since it does not require the reference pattern.

As described above, according to the above embodiment,
By controlling the pressing force of the charging blade of the developing device, it is possible to increase the reliability of the developing action and set the toner charge amount to a certain value. Therefore, the maximum development density and the development density gradient can be controlled.

[0042]

As described above in detail, according to the present invention,
It is possible to provide an image forming apparatus capable of increasing the reliability of the developing action and controlling the maximum developing density and the developing density gradient.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a configuration of a developing device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the overall configuration of a copying machine according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of the CPU.

FIG. 4 is a diagram showing another configuration of the developing device.

FIG. 5 is a diagram for explaining the operation of the sliding block and the rail.

FIG. 6 is a diagram showing another configuration of the developing device.

FIG. 7 is a diagram showing a measurement example of blade current.

FIG. 8 is a diagram showing an example of measurement of a toner charge amount with respect to a pressing force of a charging blade.

FIG. 9 is a diagram for explaining a conventional developing device.

[Explanation of symbols]

 12 ... Developing device 41 ... Developing roller 42 ... Charging blade 44 ... Charging blade holder 47 ... Eccentric cam 48 ... Worm wheel 49 ... Worm gear 50 ... Motor

Claims (2)

[Claims] 1. An image forming apparatus using a non-magnetic one-component developing device for electrophotography, a developer supply body for supplying a developer, and a charging means for charging the developer on the developer supply body. An image forming apparatus comprising: a detection unit that detects the charging state of the developer charged by the charging unit; and a control unit that controls the charging state of the developer according to the detection result of the detection unit. apparatus. 2. In an image forming apparatus using a non-magnetic one-component developing device for electrophotography, a developer supply body for supplying a developer and the developer on the developer supply body are pressed to be charged. Contact charging means, detection means for detecting the charged state of the developer charged by the contact charging means, and the pressing force of the developer supply member on the developer changes according to the detection result of the detection means. An image forming apparatus, comprising: a control unit that controls a charging state of the developer, the control unit including a moving unit that moves the position of the contact charging unit in a direction of moving.