JPH01280774A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent sticking of a carrier to an image, toner fogging and the deterioration of resolution and to form the image with high quality by individually controlling the number of the developing sleeve rotations of plural developing means in response to each developing condition. CONSTITUTION:When image density is manually set, density information specified in an operation part 21 is sent to a control part 22 and the control part 22 reads the number of the developing sleeve rotations of the developing means 9Y, 9M, 9C and 9Bk in response to specified density from a storing part 23. Secondly, out of clutches 1Y, 1M, 1C and 1Bk connected with the developing means, only the clutch connected with the developing means performing a developing action is made into a connected state and a clutch action signal 30 is sent. At the same time, a rotation number control signal rotating developing sleeves the number of times read from the storing part 23 is sent to a motor driver 24. As a result, a motor 25 rotates only the developing sleeve of the developing means, which is connected with the clutch in the connected state the number of times read from the storing part 23 so as to stick the specified amount of toner to the latent image of an image carrier.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus having a plurality of developing devices, in which the amount of toner deposited from each developing device onto a latent image on an image bearing member (hereinafter referred to as "toner adhesion") This invention relates to improvements in means for controlling

(Background of the Invention) Conventionally, an image forming apparatus having a plurality of developing devices controls the amount of adhesion from 1 to 4 by changing the developing bias voltage of each developing device. That is, if the toner adhesion amount is to be increased, the developing bias voltage is increased, and if the number of adhering stars is to be decreased, the toner adhering amount is controlled by lowering the developing bias voltage. ing.

In the case of color images, color reproduction is determined by the amount of toner adhering to the photoreceptor and the order of development. In particular, when overlapping is performed using reversal development on a photoreceptor, it is necessary to satisfy various development constraints such as image coverage, resolution, and image density. In particular, in the case of two-component development, conditions for carrier adhesion must also be satisfied.

Furthermore, when full color reproduction is to be achieved by overlapping one henna on another, it is particularly difficult to control the developing bias so as not to satisfy the above constraints.

(Problem to be Solved by the Invention) However, in the toner adhesion amount control means of the conventional image forming apparatus described above, when the developing bias voltage exceeds a certain value in an attempt to increase the toner adhesion amount, carriers are removed from the formed image. The surface of the image may become rough due to adhesion of toner, or excess toner may adhere to the image (hereinafter referred to as toner fog), for example, areas of the image that should be white may become slightly smudged. Problems may arise when the image becomes opaque or when the resolution decreases.

In the case of full-color images, in addition to the above problems, there is also the problem that the color reproduction range becomes narrower.

FIG. 4 shows the relationship between the amount of toner adhering to the first layer and the amount of toner adhering to the second layer. The fourth quadrant of this figure shows the amount of toner adhering to the first layer when recharging and re-exposure are performed on top of the toner (first layer toner) that has adhered to the photoreceptor after charging, exposure, and development. This shows the amount of change in potential due to The amount of potential drop in the figure is the difference between the charging potential and the surface potential of the re-exposed area. The third quadrant shows the amount of potential drop, the development potential (the difference between the DC voltage of the development bias and the surface potential of the re-exposed area). The second quadrant shows the relationship between the development potential and the amount of the second layer attached. This becomes a characteristic curve for determining the toner adhesion amount of the second layer when toners are superimposed on the photoreceptor.

In the case of a full-color image, the amount of toner adhesion is an important parameter that determines the color reproduction range.61 In order to control the amount of toner adhesion, it is good to change the characteristic curve in the second quadrant. However, the potential of the re-exposed portion, which is a parameter that determines the development potential, is determined by the characteristics of the photoreceptor, the amount of charge held by the toner, and the like. On the other hand, the DC voltage of the developing bias is a fixed condition in order to prevent toner scattering, carrier adhesion, and a decrease in resolution. Under such circumstances, in order to control the amount of toner (4), another parameter must be used.

) What is required to control the amount of color applied is the color reproduction range and the image density in a single color as shown in FIG. Therefore, it is preferable to use the product at a concentration exceeding a certain level, and this point must be taken into consideration when controlling the amount of 1-20% coverage.

In the present invention, when the rotational speed of the developing sleeve of each developing device is individually changed to obtain an image density of a certain level or higher when monochromatic, and when color reproduction is performed by overlapping toner and toner, the color reproduction is widely stable. Controls the amount of I/ner that adheres to the photoreceptor so that it can be removed easily. It is an object of the present invention to provide an image forming apparatus in which the amount of toner adhesion can be controlled without causing carrier adhesion to the image, toner fogging, or reduction in resolution, which are likely to occur when changing the developing bias voltage.

(Means for Solving the Problems) The image forming apparatus of the present invention has the following means configuration in order to achieve the above object.

That is, the image forming apparatus of the present invention includes a plurality of developing devices,
a rotational drive means for rotating the developing sleeve of the developing device; a rotational speed control means for controlling the rotational speed of each developing sleeve to a predetermined rotational speed determined according to each developing condition;
It is characterized by comprising the following.

(Function) The function of the image forming apparatus of the present invention having the above means configuration will be explained below.

A developing sleeve included in each of the plurality of developing devices is rotated by a rotation driving means. Under a constant development bias voltage, the amount of toner adhesion increases as the rotation speed of the developing sleeve increases within a certain range of rotation speed. By changing the rotational speed of each developing sleeve while keeping it at a constant value, it is possible to control the amount of toner deposited from each developing device. The rotation speed control means is
Since the rotational speed of each developing sleeve is individually controlled to a rotational speed corresponding to a predetermined toner adhesion amount determined by each developing condition, each developing device carries an image with a predetermined amount of toner determined by each developing condition. Attach to the latent image of the body.

As explained above, the image forming apparatus of the present invention can control the amount of 1-ner adhering to a predetermined amount according to each developing condition by individually controlling the rotation speed of the developing sleeve of each developing device. High-quality images can be formed without causing carrier adhesion to images, toner fogging, or deterioration in resolution, which tend to occur with other image forming apparatuses.

(Example) An example of the image forming apparatus of the present invention will be described below with reference to the drawings.

When you press the copy button of the image forming device shown in Figure 1, φ180m
The phthalocyanine-based OPC photoreceptor drum 3 rotates in the direction of the arrow, and the surfaces of the photoreceptors 1 to ram 3 that have been cleaned by the cleaning device 4 are uniformly irradiated by a pre-charging exposure device 10 using a red LED. The charger 5 is uniformly charged to 1800 cm. In addition, the document mounting table 1 or the document reading means 6 reciprocates, and in the forward movement, the document exposure lamp 6a scans and exposes the document, and the reflected light from the document surface is sent to the color image sensor via a mirror and an imaging lens. 6b. The color image sensor 6b separates the original image into colors, such as blue (B).

Analog signals corresponding to green (G) and red (R) images are input to an image signal processing circuit (not shown).

The image signal processing circuit converts the toner colors yellow (Y), magenta (M), cyan (C), and black (BK) from the B, G, and R signals.
) to create a digital image signal.

In order to perform sufficient color reproduction in this image forming apparatus, the image signal processing circuit is
The signal is output to the image light beam scanning device 8. The image light beam scanning device 8 inputs a laser beam modulated by a Y signal from a laser light source through a beam diameter changing means such as a photoacoustic element to a deflector such as a rotating polygon mirror, and is deflected and scanned by the deflector. The laser beam L is incident on the uniformly charged surfaces of the photoreceptors 1 to rams 3 through an imaging lens such as an f-theta lens.

As a result, an electrostatic image is formed on the charged surface of the photoreceptor l-ram 3, consisting of the distribution to the low potential spots 1.

A developing device 9Y uses Y toner as a developer for this electrostatic image.
to form a Y toner image.

The surface of the photoreceptor tram 3 on which the Y l-ner image is formed is exposed to the developing units 9M and 9C which are placed in an inoperative state.

9BK, transfer device 11, separator 12, cleaning device 4
, and is uniformly charged again by the charger 5. When this charged surface reaches the incident position of the laser beam L, the image signal processing circuit outputs the M signal to the image light beam scanning device 8 in the second document scanning exposure. A laser beam L modulated by an M signal from 8 is incident. This forms f
A developing device 9M using M1 to toner as the developer develops the S 6% electric image into an M + -toner image. As a result, Y and M toner images are formed on the photoreceptor 1' ram 3;

The surface with the M+-ner image is exposed to the laser beam L as before.
When the image light beam scanning device 8 reaches the position where the C signal is incident, the laser beam L modulated by the C signal is incident thereon. The electrostatic image thus formed is developed by a developing device 9C using C toner as a developer. As a result, Y and M are printed on the photoreceptor drum 3.

A color image is formed by combining C1 to color images.

When the surface on which this color image is formed reaches the position where the laser beam L is incident as before, the image light beam scanning device 8
This time, the laser beam L modulated by the BN signal is incident. The electrostatic image thus formed is developed by a developing device 9BK using BK)ner as a developer. As a result, a color image with excellent contrast and last is formed on the photoreceptor drum 3 by combining Y, M, C, and BK toner images.

Note that the developing devices 9Y, 9M, 9C, and 9BK are either the developing screens magnetized according to the pattern shown in FIG.
It is commonly used for each developing unit shown in the figure.

1 to 28 φ6 mm magnetic stainless steel rods are attached to the S1 pole.
It is pressed with a load of f/mm, thereby making the developer layer thick so that it does not come into contact with the photoreceptor 1-ram 3, so that the height of the spike is 03 to 0.
4 mm), and non-contact development is performed in which the developer layer is made to fly and deposit on the electrostatic image.

The developing conditions shown in Table 1 should be used (Example)
〉. The developers used are a coach ink ferrite carrier with a particle size of 40 μm and a polynisder type l.
Two-component developer (1-toner concentration 7% Q /
M −-10 to −1,5 μc/g) is used. The pigments contained in each 1-ner are shown in Table 2.

By this, Y, M, C, B H, Blue, G
When a green and red toner image is formed, an amount of toner as shown in Table 3 adheres to the photoreceptor.

The color image formed on the photoreceptor drum 3 through the above steps is transferred by the transfer device 11 onto the transfer material P fed by the paper feeder 14. The transfer material P onto which the color image has been transferred is separated from the photoreceptor drum 3 by a separator 12, the color image is fixed by a fixing roller 15, and the transfer material P is discharged outside the machine.

The obtained solid image is Y, M, C, B x, B
lue.

It was sufficient to distinguish between Green and Red.

<Example 2> Using the developing sleeve rotational speed shown in Table 4, the amount of toner of the first layer and second layer adhering to the fourth photosensitive surface was controlled, and Y, M, C were prepared in the same manner as in Example 1. , B x, Blue, G
When solid images of reen and red were formed, the resulting images were sufficient to distinguish seven colors as in Example 1.

<Example 3> Example 1. As in Example 2, when a solid image was formed by changing the rotational speed of the developing sleeve and changing the amount of toner in the first and second layers adhering to the photoconductor, 1 as shown in Example 1
-Y, M if the variation in the amount of toner adhesion is within the range shown in Table 5.

It was possible to distinguish seven colors: C, B, (, Blue, Green, and Red).

<Comparative Example 1> As shown in Table 6, the rotational speed of the developing sleeve was set to 300 rpm for Y, M, C, and Bo to form rough images. In this case, the sleeve rotation speeds stored in the storage section 23 shown in FIG. 2 are each 30 Orpm.

The resulting dark image has a higher image density than that of Example 1, Table 5, Table 6, Table 5, in which the number of rotations of the developing sleeve was controlled and the adhesion amount was set to a predetermined amount. is also low and Bl
The color reproduction of UE and Re+I was poor.

FIG. 2 is a diagram showing the configuration of the apparatus in which Examples 1, 2, and 3 of the image forming apparatus of the present invention and comparative examples were conducted. Second
In the figure, a Y toner developer 9Y containing yellow toner (hereinafter abbreviated as Y l-ner), an M + -ner developer 9M containing magenta toner (hereinafter abbreviated as M1 toner), and a cyan 1 hener (hereinafter abbreviated as CI-ner), the CI-toner developing device 9C and the black toner developing device 98 housing black I-toner have developing sleeve rotation shafts 2Y, 2M, 2C, and 28K, respectively. have.

On the other hand, the rotation of the shaft 26 connected to the motor 25 is controlled by the coupling of the clutches IY, Clutches IY, Clutches IC, and Clutches IBK.
, 2C and 2BK. The storage unit 23 is composed of, for example, a non-volatile memory, and the memory stores the number of rotations of each developing sleeve corresponding to the amount of 1-toner attached (in other words, the density) for performing good development. It is memorized for each device. The motor 25 is
Before any of the developing units in the stand starts a developing operation, the control unit 22 starts rotating in response to an ON signal sent to the motor driver 24, and after all of the four developing units stop performing the developing operation, the control unit 22 Rotation is stopped by an OFF signal issued from the motor driver 24 to the motor driver 24. Operation unit 21
has a manual concentration button and an automatic concentration button.
When the user presses the manual setting button, the operator 21 subsequently specifies the density according to the developing conditions for each of the four developing units. Density designation information specifying the density is sent from the operating section 2 to the control section 22, and the control section 22 reads from the storage section 23 the number of rotations of the developing sleeve of each developing device corresponding to the specified density. The control unit 22 is
A clutch operation signal 30 is sent to connect only the clutch connected to the developing unit that performs the developing operation, and the developing sleeve of the developing unit that performs the developing operation is rotated at the rotation speed read from the storage unit 23. A rotation speed control signal for rotation is sent to the motor driver 24 at the same time as the crudge operation signal 30 described above.

As a result, the motor 25 rotates only the developing sleeve of the developing device connected to the clutch in the engaged state at the rotation speed read from the storage section 23, and the developing device is operated. In section 21, a predetermined amount of 1-hener is applied to the latent image on the image carrier to achieve a specified density according to development conditions.

When the user presses the automatic setting button, patch development corresponding to each developing device is performed on the image carrier, density information obtained from the result of the development is sent to the control section 22, and The control unit 22 compares the density set in advance according to the development conditions with the density of the patch development for each developing device.

According to the result of the comparison, if the amount of toner adhesion is to be increased, a rotation speed control signal is sent from the control unit 22 to the motor driver 24 to rotate the developing sleeve at a predetermined rotation speed higher than the current one, and the amount of toner adhesion is increased. If the rotation speed does not decrease, a rotation speed control signal is sent from the control unit 22 to the motor driver 24 to rotate the developing sleeve at a predetermined rotation speed lower than the current rotation speed.

This rotation speed control signal is applied to each developing device that performs a developing operation.
It is output at the same time as the clutch operation signal 30 that causes only the clutch connected to the developing unit to be in the engaged state. As a result,
The motor 25 controls only the developing sleeve of the developing device connected to the clutch that is in the engaged state.
The developing device is rotated at a predetermined rotational speed outputted by No. 2, and the developing device attaches a predetermined amount of Hener 1 to the latent image on the image carrier to achieve a preset density according to the developing conditions.

In the above embodiment, in order to separately rotate each developing sleeve of the four developing units using one motor 25, the clutch IY,
LM, IC, and IBK, and whether the clutch operation signal 30 is issued to select and engage the clutch, or by coupling one motor to each of the four developing units, the clutch and the clutch can be activated. A configuration in which the operation signal is eliminated is also possible.

Further, for example, the first motor rotates the developing sleeves of the first and second developing devices, and the second motor rotates the developing sleeves of the third and fourth developing devices. .

(Effects of the Invention) As explained hereinafter, the image forming apparatus of the present invention can adjust the toner adhesion amount to a predetermined value corresponding to each developing condition by individually controlling the rotational speed of the developing sleeve of each developing device. Since it is possible to control the amount of toner, it has the advantage of being able to form high-quality images without causing carrier adhesion or toner fogging that tends to occur with conventional image forming apparatuses.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the arrangement of each component of an embodiment of an image forming apparatus to which the present invention is applied, FIG. 2 is a block diagram of the configuration of an embodiment of the image forming apparatus of the present invention, and FIG. Figure 4 is a characteristic diagram showing the relationship between the amount of toner deposited in the second layer and the amount of toner deposited in the first layer, Figure 5 is a diagram of the magnetization pattern of the developing sleeve, and Figure 6 is the photoreceptor. FIG. 3 is a layout diagram of a drum and a plurality of developing devices. ] Original table, ], Y, I M, ],
C, I BM...clutch, 2Y, 2M, 2C, 2B
K...Developing sleeve rotation shaft, 3...Photoconductor drum,
4...Cleaning device, 5...Charger, 6.Pa.Document reading means, 6a...Document exposure lamp, 611...Color image sensor date, 8...
・Image light beam scanning device, 9Y...Yl~l Lunar device, 9M Ml-ner developing device, 9C・C1~
Toner developer, 98K...Black toner developer, 1
0...Pre-charging exposure device, 11...Transfer device,
12...Separator, 14...Paper feeding device,
15 fixing roller, 21...operation unit, 22...
Control unit, 23... Storage unit, 24... Motor driver, 25... Motor, 26... Axis,
30...Clutch operation signal. Agent Patent Attorney Yoshihiro Yahata No. 5 Figure N9 51~S4-1-600±100G N1~Ns --600±100G Nu --500G Kujin] and 36'As vehicle 1 fiyn Shto Morikata () No. g Figure 31 2nd drum γ toner Hamura Ryojiki 9Y ○ ○ M toner present and control to C toner present 7

Claims (1)

[Claims] a plurality of developing devices; a rotational drive means for rotating a developing sleeve of the developing device; a rotational speed control means for controlling the rotational speed of each developing sleeve to a predetermined rotational speed determined according to each developing condition; An image forming apparatus comprising: