JPH06314018A - Electrophotographic recorder - Google Patents

Abstract

PURPOSE:To facilitate the adjusting image density by varying the rotational speed itself of a developing roller, which supplies toner to a photoreceptor by a rotational speed varying means. CONSTITUTION:The developing roller 64 and supply 65 of a developing device 60 are rotated and driven by a motor 80 for use in development, the rotating speed of this motor 80 is determined by the rotational speed varying means 81, and an order is given to the means 81 by a main control part 82. As an amount of toner in a toner sensor 63 decreased, the main control part 82 orders the means 81 to increase the rotational speed of the motor 80. Also, by the operation of an operation means 85 by an operator, the order for the rotational speed of the motor 80 to be increased/reduced is given to the means 81 through the main control part 82. Thus, when the rotational speed of the motor 80, that is, of the roller 64 is varied to arbitrary speed by the means 81, image density can be made stable at requested set-density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus having a developing roller which develops an electrostatic latent image on a photoconductor by rotating the photoconductor in contact with the photoconductor or keeping a certain distance.

[0002]

2. Description of the Related Art A conventional process from charging to development in an electrophotographic recording apparatus will be described with reference to FIG.

The surface of the photosensitive member 1 is charged to about -500 V by applying a negative voltage of the high voltage power source 3 to the charging device 2. Next, the surface of the photoconductor is selectively exposed by the exposure device 5 according to the image to be recorded, and the surface of the photoconductor 1 has a recorded portion (exposed portion) of about -50V to -100V and a non-recorded portion (non-recorded portion). An electrostatic latent image having an exposed portion) of about -500V is formed.

On the other hand, the toner 9 stored in the toner hopper 8 of the developing device 7 is a toner friction means (developing blade 11 or developing roller 12 for one-component development and two-component development for one-component development). Carrier becomes friction means)
Are charged by the same polarity (negative in this example) as the charging potential of the photoconductor 1. Further, a negative developing bias voltage of about −200 V is applied to the developing roller 12 from the high voltage power source 14 for developing.

Therefore, as shown in FIG. 5, the toner 9 on the developing roller 12 moves to the surface of the photoconductor 1 at the exposed portion of the surface of the photoconductor 1 where the electric potential is from -50 to -100V, whereby the electrostatic latent image is generated. The image is toner imaged.

By the way, as a means widely used for controlling the image density of the electrophotographic apparatus, there is a method of increasing or decreasing the exposure energy intensity (laser intensity) of the exposure apparatus or the exposure time per pixel. However, these methods are effective in moving the image density to the low density side, but when the image density is moved to the low density side due to deterioration of the photoconductor or the developing device with time (for example, toner by the developing roller). However, the supply capacity itself could not be returned to the high concentration side.

As another means for controlling the image density, there is a method of making the set value of the developing bias variable. FIG. 6 is a diagram showing the relationship between the developing bias and the image density in the two-component development and the non-magnetic one-component development. still,
The two-component development and the non-magnetic one-component development are different in the rising due to the influence of the difference in the developing method.

As shown in this figure, the developing bias voltage is set to V _B3 in the two-component development and V _B1 in the non-magnetic one-component development, so that both images have the most stable image density IDa (A , B), the density is generally set.

In this case, the image density characteristic may change with time and, for example, the image density IDa may not be obtained with the voltages V _B3 and V _B1 , but in the two-component development, the developing bias is increased by V _B31 . Image density IDa (A1)
Obtainable. On the other hand, in the non-magnetic one-component development, since the toner particles are formed on the developing roller 1 by the developing blade 11 in about one layer, and the electrostatic latent image on the photoconductor 1 is developed by this, the image density is reduced. The maximum value of is determined by the density of the toner formed on the developing roller. For this reason, when the fluidity of the toner deteriorates with time, the toner layer itself on the developing roller 12 becomes thin, and the image density cannot be increased no matter how large the developing bias is.

FIG. 7 shows an example in which this problem appears prominently. This figure shows the result of measuring the black solid followability before toner replenishment and the black solid followability after toner replenishment. It can be seen that the black solid followability is getting worse. In addition, as shown in FIG.
A black solid band pattern 17 having a predetermined length is formed on the paper 16, and the difference between the density of the leading end portion A and the density of the trailing end portion B of the band pattern 17 is used as a measured value.

Further, in FIG. 6, when the image density is set to IDb which is slightly lighter than IDa, the developing bias voltage is V _B2 (point C) in the two-component development, and the non-magnetic 1
In component development, V _B4 (point D) may be set, but in the non-magnetic one-component development method, the image density characteristics rise rapidly, so if the characteristics of other processes change even slightly due to changes in temperature and humidity, There was a problem that the concentration changed extremely. Therefore, it is difficult to set a stable concentration at a concentration lower than IDa.

[0012]

As described above, in the conventional electrophotographic recording apparatus, particularly in the electrophotographic recording apparatus using the non-magnetic one-component developing system, firstly, as the toner replenished in the developing apparatus is consumed. There is a problem that the image density becomes low, and second, there is a problem that it is difficult to obtain a desired image density in a stable state.

The present invention has been made to solve the above-mentioned conventional drawbacks, and a first object thereof is to provide an electrophotographic recording apparatus capable of easily setting an image density, and it is always stable regardless of toner consumption. A second object is to provide an electrophotographic recording device capable of obtaining image density.

[0014]

SUMMARY OF THE INVENTION The present invention provides an electrophotographic recording apparatus having a developing roller that carries toner and rotates while contacting a photoconductor to develop an electrostatic latent image on the photoconductor. The rotation speed changing means for changing the rotation speed of the roller is provided.

Further, a toner amount detecting means for detecting the amount of toner stored in the toner hopper for supplying the toner to the developing roller is provided, and the rotation speed varying means is provided in the toner hopper based on the information of the toner amount detecting means. The rotational speed of the developing roller may be increased as the toner amount decreases.

Further, it is preferable that the rotation speed varying means is configured to increase or decrease the rotation speed of the developing roller according to the information of the operator operating means to which the information is input by the operation of the operator.

[0017]

In the present invention, since the rotation speed of the developing roller for supplying toner to the photosensitive member can be changed by the rotation speed varying means, the desired image density can be easily set by changing the rotation speed of the developing roller.

If the rotation speed of the developing roller is increased as the amount of toner in the toner hopper decreases,
A decrease in the amount of toner on the photoconductor caused by a decrease in the fluidity of the toner over time can be compensated by an increase in the rotation speed of the developing roller.

Further, if the rotation speed of the developing roller is changed by the information of the operator operating means, the operator can obtain a desired image density in a stable state.

[0020]

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

FIG. 1 is a diagram showing the configuration of an electrophotographic recording apparatus according to the present invention. The process from charging to transfer of this electrophotographic recording device will be described with reference to FIG.

The surface of the photosensitive member 51 having photosensitivity is uniformly charged to about -500V by the charging device 52. Next, the surface of the photoconductor 51 is exposed by the exposure device 55 according to the image to be recorded, and an electrostatic latent image of about −50 V to −100 V on the recorded portion and about −500 V on the non-recorded portion is formed. .

The developing device 60 for converting the electrostatic latent image formed on the surface of the photoconductor 51 into a toner image is composed of a toner hopper 62 in which the toner 61 is stored and a toner sensor (toner amount detection) for detecting the toner amount in the toner hopper 62. 63), a developing roller 64 that rotates in contact with the photoconductor 51 to attach toner onto the photoconductor 51, a supply roller 65 that conveys the toner 61 in the toner hopper 62 to the developing roller 64, and a toner layer on the surface of the developing roller 64. And toner 61
And a developing blade 66 for triboelectrifying. Then, the toner 61 on the developing roller 64 that is negatively charged is
The developing roller 64, to which a developing bias voltage of about −200 V is applied, moves to the exposed portion (recording portion) of the photoconductor 51, and the electrostatic latent image is formed into a toner image.

The recording paper P is conveyed from the right side in the drawing between the photoconductor 51 and the transfer device 73 by the paper feed roller 70 and the registration roller 71, and the toner image on the photoconductor 51 is transferred by the transfer device 73 to the recording paper. After being transferred to P, the toner image is fixed on the recording paper by the fixing device 75. Further, the transfer residual toner on the photoconductor 51 that has not been transferred is removed from the photoconductor surface by the cleaner device 77.

In the above recording apparatus, the developing roller 64 and the supply roller 65 of the developing device 60 are rotationally driven by the developing motor 80. The rotation speed of the developing motor 80 is determined by the rotation speed varying means 81, and an instruction to the rotation speed varying means 81 is issued by the main control section 82. Also,
The toner sensor 63 is connected to the main controller 82, and the main controller 82 can receive information on the amount of toner in the toner sensor 63. Then, the main control unit 82 sends to the rotation speed varying unit 81 a command to increase the rotation speed of the developing motor 80 as the toner amount in the toner sensor 63 decreases.

An operator operating means 85 is connected to the main control section 82. This operator operating means 85
Is composed of various switches through which the operator can input information.
By operating 5, the rotation speed varying means 81 is given a command to increase or decrease the rotation speed of the motor 80 via the main control portion 82.

The main control unit 82 is connected to a main motor 87 that rotationally drives the photoconductor 51, the paper feed roller 70, the registration roller 71, and the fixing device 75, and a paper feed clutch 88 of the paper feed roller 70 and the like. The registration clutch 89 of the registration roller 71 is also connected to the photosensitive member 51,
The paper feed roller 70 and the like rotate in a predetermined manner under the control of the main controller 82.

As described above, in the electrophotographic recording apparatus of this embodiment, firstly, the developing motor 80, and thus the developing roller 6
Since the rotation speed of No. 4 can be changed to an arbitrary speed by the rotation speed changing unit 81, the image density can be stabilized at a desired set density. FIG. 2 is a diagram showing the relationship between the developing bias voltage and the image density when the rotation speed v _DEV of the developing roller is changed. As is apparent from this figure, even if the developing bias voltage V _B1 is the same, as the developing roller speed v _DEV becomes faster, the stable image density value shifts to the darker side. Here, v _DEV3 > v _DEV2 > v _DEV1 .

Secondly, since the developing roller rotation speed v _DEV is increased as the toner 61 in the toner hopper 62 decreases, the amount of toner on the photosensitive member 51 caused by the deterioration of the fluidity of the toner over time. Can be compensated by increasing the developing roller rotation speed. FIG. 3 is a diagram showing a change in black solid followability from one toner replenishment to the next toner replenishment, in comparison with a conventional recording apparatus. As is clear from the figure, it can be more stable than the conventional black solid tracking performance.

Thirdly, since information can be input to the operator operating means 85 and the setting of the rotation speed varying means 81 can be changed, the operator can easily set a desired image density. For example, when it is desired to reduce the toner consumption amount as much as possible, the developing roller rotation speed v _DEV can be slowed to meet the demand. In an electrophotographic recording device such as a digital copying machine or a facsimile device, for example, a "character image" switch and a "photographic image" switch are provided on the operation panel surface as the operator operating means 85, and the "photo image" If the switch is pressed,
It is _advisable to set the developing roller rotation speed v _DEV to be slightly slower. This is because if the solid black density is suppressed when copying a photographic image, it is possible to prevent the influence (crushing) of the black pixel on the white pixel, so that a clearer halftone image can be recorded. In this case, the facsimile apparatus preferably has a configuration in which the information of the operator operating means 85 is transmitted from the transmitting station side to the receiving station side and the image density of the receiving station side can be designated. With such a configuration, the density of the received image can be set to an image density suitable for the original image.

[0031]

As described above, in the electrophotographic recording apparatus of the present invention, the rotation speed of the developing roller for supplying the toner to the photosensitive member can be changed by the rotation speed varying means.
The desired image density can be easily set by changing the rotation speed of the developing roller.

If the rotation speed of the developing roller is increased as the amount of toner in the toner hopper decreases,
A decrease in the amount of toner on the photoconductor caused by a decrease in the fluidity of the toner over time can be compensated by an increase in the rotation speed of the developing roller.

Further, if the rotation speed of the developing roller is changed by the information of the operator operating means, the operator can obtain a desired image density in a stable state.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrophotographic recording apparatus showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a developing roller rotation speed and image density in the electrophotographic recording apparatus of FIG.

FIG. 3 is a diagram showing a relationship between toner consumption and black solid followability in the electrophotographic recording apparatus of FIG.

FIG. 4 is a partial configuration diagram of a conventional electrophotographic recording apparatus.

FIG. 5 is a model diagram of a photoreceptor surface potential.

FIG. 6 is a diagram showing image density characteristics of non-magnetic one-component development and two-component development.

FIG. 7 is a diagram showing a relationship between a conventional toner consumption amount and black solid followability.

FIG. 8 is a diagram showing a black solid followability evaluation pattern.

[Explanation of symbols]

51 Photoreceptor 61 Toner 62 Toner Hopper 63 Toner Sensor 64 Developing Roller 81 Rotational Speed Variable Means 85 Operator Operation Means

Claims (3)

[Claims] 1. An electrophotographic recording apparatus having a developing roller that carries toner and that is adjacent to a photosensitive member and that develops an electrostatic latent image on the photosensitive member. A rotational speed variable that changes the rotational speed of the developing roller. An electrophotographic recording apparatus comprising means. 2. A toner amount detecting means for detecting an amount of toner stored in a toner hopper for supplying toner to a developing roller, wherein the rotation speed varying means is provided in the toner hopper according to information of the toner amount detecting means. 2. The electrophotographic recording apparatus according to claim 1, wherein the rotation speed of the developing roller is increased as the toner amount of the toner decreases. 3. The electrophotographic recording apparatus according to claim 1, wherein the rotation speed varying means increases or decreases the rotation speed of the developing roller according to the information of the operator operating means to which the information is input by the operation of the operator. .