JP2003255704A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device and an image forming apparatus in which the occurrences of abnormal images caused by the developing device is suppressed and the long life of a developer carrier is promoted. <P>SOLUTION: Drive and stop of the developer carrier 7a is repeated before or after an image is output or after a power source is turned on. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for forming an electrostatic latent image on an image bearing member and converting the electrostatic latent image into a visible image (toner image) by a developer bearing member, and such a developing device. The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus such as a copying machine, a laser beam printer, a facsimile, an electrostatic recording apparatus, etc.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image is formed on an image bearing member such as an electrophotographic photosensitive member by an electrophotographic process, and a developing sleeve as a developer bearing member that carries and conveys a developer (toner), There is an electrophotographic image forming apparatus such as a copying machine or a laser beam printer, which is provided with a developing device for converting the electrostatic latent image into a visible image (toner image).

In such an image forming apparatus, in order to prevent deterioration of the developer accommodated in the developing device, the developing sleeve has a drive motor ON / OFF or rotation speed switching, or a gear train and a clutch. There is a combination that enables the presence or absence of rotation or switching of the number of rotations.

That is, in the simplest structure, the drive motor and the gear train are used to rotate the developing sleeve only when outputting an image. Further, as a complicated structure, a structure in which the rotation speed of a drive motor is controlled or a plurality of rotation speeds are set by a combination of a gear train and a clutch has been adopted in recent years.

Further, since the number of revolutions of the developing sleeve changes the amount of toner adhered to the opposing image bearing member, the environmental characteristics and the degree of deterioration of the developer in the developing device and the toner in the two-component developer. Any speed can be selected so that the optimum speed can be obtained depending on the difference in carrier ratio and the like.

[0006]

By the way, the developing device has a blade for regulating the thickness of the toner layer coated on the developing sleeve, and the toner layer is kept in contact with the image bearing member from several times. It is regulated by the developing device to have a unique gap up to a state of being separated by about mm.

However, in some cases, the toner layer thickness is not properly regulated, and the toner layer on the developing sleeve may have a non-uniform thickness.

For example, due to a phenomenon called blotch in a low-humidity environment, the toner layer causes wavy or dot-like abnormality,
The image may be uneven. Alternatively, streaky unevenness may occur in the toner layer in a high-humidity environment or the like, and unpleasant streaks may occur on the image. To make things worse,
The roughness of the developing sleeve surface is correlated with blotch and uneven streak, and when the roughness of the developing sleeve surface decreases with the lapse of time, the above-mentioned image abnormality tends to occur, which hinders the extension of the life of the developing sleeve. .

Therefore, the present inventor has solved this problem by paying attention to the number of rotations of the developing sleeve as a means for reducing these blotches or uneven streaks.

That is, as a result of many researches and experiments, the inventor of the present invention has found that, in a developing device having a developing sleeve having a second rotational speed, the rotational speed of the developing sleeve is changed in a short cycle before output of an image to generate pulsation. , It has been found that the blotches or streaks that occur once are reduced. Moreover, it has been found that this effect is also effective in the developing device in which the rotation of the developing sleeve can only be turned ON / OFF.

Further, the present inventor has found that the pulsation or ON / OFF of the rotation of the developing sleeve is effective not only before the output of the image but also when the rising time after the power is input or after the image is output. It was

The present invention is based on the novel findings of the present inventor.

An object of the present invention is to provide a developing device and an image forming apparatus which can suppress image abnormalities caused by the developing device and can prolong the life of the developer carrying member. is there.

[0014]

The above object is achieved by the developing device and the image forming apparatus according to the present invention. In summary, according to an aspect of the present invention, in a developing device including a developer carrying member that carries and conveys a developer, and a driving unit that drives the developer carrying member, before image output, or A developing device is provided which is characterized in that the developer carrier is repeatedly driven and stopped after image output, or after power is turned on.

According to another aspect of the present invention, there is provided a developing device comprising a developer carrying member carrying and carrying a developer, and a driving means for driving the developer carrying member, wherein the developer carrying member is provided. Is capable of being driven at a plurality of drive speeds, and the drive speed of the developer carrier is repeatedly changed before the image output, after the image output, or after the power is turned on, to the drive speed of the developer carrier. Provided is a developing device characterized by giving pulsation.

According to one embodiment of the present invention, since blotches and streaks may or may not occur depending on the environment, an environment sensor for detecting the temperature or humidity of the outside air is provided,
Depending on the detection result of the environment sensor, whether or not to execute the driving stop for the developer carrier is changed,
Alternatively, whether or not the pulsation is applied to the developer carrier is changed or changed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A developing device and an image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 shows a schematic configuration of a laser beam printer as an embodiment of an image forming apparatus according to the present invention.

In the present embodiment, the laser beam printer is provided with a cylindrical electrophotographic photosensitive member, that is, a photosensitive drum 2 as an image bearing member, at approximately the center of the apparatus main body 1. The photosensitive drum 2 is rotatably supported by the apparatus main body 1 in the direction of the arrow R1, and around the photosensitive drum 2, a static eliminator 3 for erasing the potential on the photosensitive drum 2 in order along the rotation direction thereof. A primary charger 4 as a charging means for uniformly charging the surface of the photosensitive drum 2, an exposing means 5 for exposing the surface of the photosensitive drum 2 to form an electrostatic latent image, and a potential for measuring the potential on the photosensitive drum 2 after exposure. The toner is carried on the sensor 6 and a developing sleeve 7a as a developer carrying member, and the toner image is formed on the transfer device P as the developing device 7 as a developing means for forming a toner image by adhering the toner to the electrostatic latent image. A transfer charger 8 for transferring, a separation charger 9 for separating the transfer material P from the photosensitive drum 2, and a cleaner 10 for removing residual toner on the photosensitive drum 2 are arranged.

The transfer material P, which is the transfer destination of the toner image, is supplied from the paper feed deck 11. Below the photosensitive drum 2, that is, below the inside of the apparatus main body 1, a paper feed deck 11 for accommodating the transfer material P is arranged.

The transfer material P in the paper feed deck 11 is fed by the paper feed roller 12, and is supplied between the photosensitive drum 2 and the transfer charger 8 via the transport roller 13 and the registration roller 15.

A toner image is transferred from the photosensitive drum 2 to the transfer material P, and the transfer belt P is fixed by the transport belt 16 to the fixing device 17.
Be transported to. The transfer material P on which the toner image is fixed by the heat and pressure applied by the fixing device 17 is discharged onto the paper discharge tray 20 by the paper discharge roller 19 as a final output image.

In the above printer, the exposure means 5
Is scanned by a polygon mirror 31 with a laser beam emitted from the semiconductor laser 30 according to an image signal,
It is guided to the photosensitive drum 2 via the imaging lens 32 and the reflection mirror 33.

FIG. 2 is a diagram schematically illustrating the electrical configuration around the control board that constitutes the control means in the image forming apparatus of this embodiment.

In the control board 100 shown in FIG. 2, a ROM in which a control program is described and a RAM which is a temporary storage element for necessary data on the program are connected to a CPU which is a central element of processing.

I / O which is an interface element
Then, the A / D converter and the D / A converter, which are data conversion elements, are connected to external peripheral devices, and information is input / output to / from the control board 100.

In this embodiment, a drive motor M for the developing sleeve 7a is connected as a peripheral device. In this embodiment, the drive motor M starts to rotate in response to an image output signal from the image forming apparatus as a basic operation, and stops rotating when image output ends.

FIG. 3 shows the developing sleeve 7 in this embodiment.
It is the schematic explaining the drive path of a.

Drive unit 200 constituting drive means
Has a drive motor M, gear trains 201 and 202 for speed conversion until driving of the developing sleeve, and a clutch CL, and is configured to drive the developing sleeve 7a by turning on the drive motor M.

FIG. 4 shows the developing sleeve 7 in this embodiment.
It is a flow chart explaining the drive sequence of a.

When the image output is executed by the image output signal in the image forming apparatus, the present embodiment adopts a sequence in which the developing sleeve 7a is repeatedly turned on and off a predetermined number of times.

That is, the number of times is counted and it is confirmed whether it is a predetermined number (S1). If the predetermined number is not reached, the rotation of the sleeve 7a is turned on for a predetermined time t1 (S2) and the sleeve 7a is rotated for a predetermined time t2. Turn off (S
3). Specifically, the predetermined number of times is 10 times, and t1 =
The sleeve 7a is repeatedly rotated and stopped within a short time with 0.2 seconds and t2 = 0.1 seconds.

Then, immediately before the image output, the developing sleeve 7a is rotated again (S4), the image is output (S5), and the developing sleeve 7a is stopped after the output (S6).

FIG. 5 shows the number of rotations of the developing sleeve 7a in the sequence shown in FIG. When the time axis is plotted on the horizontal axis, the rotation speed of the sleeve 7a is basically turned on for t1 seconds and turned off for t2 seconds. Strictly speaking, it is often impossible to make a clear cut due to the rise time and fall time, but as is clear from the figure, the sleeve 7
It can be seen that the number of rotations of a repeats rotation and stop. Of course, the normal image output is executed after the rotation and stop are repeated a predetermined number of times.

As described above, in this embodiment, the following effects are obtained by repeatedly rotating and stopping the developing sleeve 7a before outputting an image.

Table 1 shows a sleeve blotch in a low humidity environment and a developing device in which uneven streaks occur in a high humidity environment.
The effect when this sequence is input is shown. If blotches and streaks have already occurred, there is no change in the sequence in normal image output that is a conventional example, so naturally blotches
Although it does not disappear with streak, suppression has started in this example. The fact that the suppression starts means that it does not occur if this sequence is used constantly or with a certain frequency. Therefore, it can be seen that the repeated rotation and stop of the developing sleeve 7a according to the present invention is effective.

[0037]

[Table 1]

In this embodiment, the sequence of rotating the developing sleeve 7a immediately before the image output is explained, but it is not always necessary to execute it, and therefore it may be executed every predetermined time or every predetermined number of output sheets.

Since streaks and the like are likely to occur on the first sheet after the power is turned on, it is also useful to perform it while the image forming apparatus is starting up when the power is turned on. further,
Since there is a time constraint immediately before the image output, it may be executed after the image output. What is important is to repeat the rotation and stop of the developing sleeve at times other than image output.

Embodiment 2 FIG. 6 is a diagram schematically illustrating the electrical configuration around the control board in the image forming apparatus of this embodiment.

In the control board 100 shown in FIG. 6, a ROM in which a control program is described and a RAM which is a temporary storage element for necessary data on the program are connected to a CPU which is a central element of processing.

I / O which is an interface element
Then, the A / D converter and the D / A converter, which are data conversion elements, are connected to external peripheral devices, and information is input / output to / from the control board 100.

In this embodiment, as a peripheral device, the drive motor M of the developing sleeve 7a, the clutch CL1 and the clutch CL2 are connected. In this embodiment, the drive motor M starts to rotate in response to an image output signal from the image forming apparatus as a basic operation, and stops rotating when image output ends. The clutch CL1 and the clutch CL2 are used to switch the sleeve rotation speed.

FIG. 7 shows the developing sleeve 7 in this embodiment.
It is the schematic explaining the drive path of a.

The drive path is composed of a drive unit 200 as drive means and a rotation speed conversion unit 300,
The drive unit 200 includes a drive motor M and a gear train 201.
The rotation speed conversion unit 300 has two clutches CL1 and CL2 and gear trains 301, 302, 303. Clutch CL1 in the rotation speed conversion unit 300
CL2 and CL2 are not in the sequence to turn on the clutch at the same time.
It will be configured as follows.

FIG. 8 shows the developing sleeve 7 in this embodiment.
It is a flow chart explaining the drive sequence of a.

When the image output is executed by the image output signal in the image forming apparatus, first, in this embodiment, the sequence is such that the pulsation is given to the rotation speed of the developing sleeve a predetermined number of times.

That is, the number of times is counted and it is confirmed whether it is a predetermined number (S11). If the predetermined number is not reached, the clutch CL1 is turned on and the clutch CL2 is turned off for a predetermined time t1 to rotate the developing sleeve 7a on the high speed side ( S
12), the clutch CL1 is turned off and the clutch CL2 is turned on for a predetermined time t2, and the developing sleeve 7a is set at the low speed side
Is rotated (S13). Specifically, the predetermined number of times is 10
A pulsation is generated in the rotation of the sleeve 7a within a short time with t1 = 0.1 seconds and t2 = 0.1 seconds.

Then, immediately before image output, again on the high speed side, that is, the clutch CL1 is turned on and the clutch CL2 is turned off.
As a result, the developing sleeve 7a is rotated (S14), an image is output (S15), and the developing sleeve is stopped after the output (S16).

FIG. 9 shows the number of rotations of the developing sleeve 7a in the sequence shown in FIG. When the time axis is taken on the horizontal axis, the rotation speed of the sleeve 7a is basically on the high speed side for t1 seconds and on the low speed side for t2 seconds. Strictly speaking, it is often impossible to make a clear distinction depending on the engagement time of the clutch and the inertia of rotation, but as is clear from the figure, it can be seen that the rotational speed of the sleeve repeats pulsations of high speed rotation and low speed rotation. Of course, the normal image output is executed after the predetermined number of times.

As described above, in this embodiment, the following effects are obtained by imparting the pulsation to the rotation speed of the developing sleeve 7a before the image output.

Table 2 shows a sleeve blotch in a low humidity environment and a developing device in which uneven streaks occur in a high humidity environment.
The effect when this sequence is input is shown. If blotches and streaks have already occurred, there is no change in the sequence in normal image output that is a conventional example, so naturally blotches
Although it does not disappear with streak, it disappears or is suppressed in this example. The fact that the suppression starts means that it does not occur if this sequence is used constantly or with a certain frequency. Therefore, it can be said that pulsating the rotation of the developing sleeve according to the present invention is effective. Also,
In this embodiment, since the pulsation is imparted to the rotation speed of the sleeve, the pulsation cycle can be shortened depending on the selection of the rotation speed, and it is particularly advantageous in terms of time when executed immediately before image output. become. This is because the number of pulsations of the sleeve peripheral speed is considered to be effective against blotches and streaks.

[0053]

[Table 2]

In this embodiment, the sequence for rotating the sleeve 7a immediately before the image output is explained.
Since it need not always be executed, it may be executed every predetermined time or every predetermined number of output sheets. In addition, since uneven streaks and the like are likely to occur on the first sheet after the power is turned on, it is also useful to execute it while the image forming apparatus is starting up when the power is turned on. Further, since there is a time constraint immediately before the image output, it may be executed after the image output. What is important is to give pulsation to the rotation speed of the developing sleeve during the time other than image output.

Embodiment 3 FIG. 10 is a diagram schematically illustrating the electrical configuration around the control board in the image forming apparatus of this embodiment.

In the control board 100 shown in FIG. 10,
A ROM in which a control program is written and a RAM, which is a temporary storage element for necessary data on the program, are connected to a CPU, which is a central element of processing.

I / O which is an interface element
Then, the A / D converter and the D / A converter, which are data conversion elements, are connected to external peripheral devices, and information is input / output to / from the control board.

As peripheral equipment of this embodiment, the drive motor M for the developing sleeve 7a, the clutch CL1 and the clutch CL are used.
2 is connected. In this embodiment, the drive motor M is
As a basic operation, rotation is started by an image output signal of the image forming apparatus, and rotation is stopped when image output is completed.
The clutch CL1 and the clutch CL2 are used to switch the sleeve rotation speed.

Also in this embodiment, similarly to the second embodiment shown in FIG. 7, the developing unit drive path can be constituted by including the drive unit 200 and the rotation speed conversion unit 300 as the drive means.

Further, in this embodiment, the image forming apparatus has an environment sensor S for detecting the temperature and humidity of the outside air around the image forming apparatus.

FIG. 11 is a flow chart for explaining the driving sequence of the developing sleeve 7a in this embodiment.

When the image output is executed by the image output signal in the image forming apparatus, the detection result of the environment sensor S is first read in this embodiment (S21), and only when the absolute humidity is low or high (S22). Execute the sequence of.

That is, the number of times is counted and it is confirmed whether or not it is a predetermined number (S23). If the predetermined number is not reached, the clutch CL1 is turned ON and the clutch CL2 is turned OFF for a predetermined time t1 (S24), and the clutch CL is held for a predetermined time t2.
1 is turned off and clutch CL2 is turned on (S2
5). Specifically, the predetermined number of times is 10 times, and t1 =
0.1 second and t2 = 0.1 second, the pulsation is generated in the rotation of the sleeve 7a within a short time.

Immediately before the image output, the developing sleeve is rotated again at the high speed side (S26), and the image is output (S2).
7) After the output, the developing sleeve is stopped (S28).

As described above, in this embodiment, the absolute humidity in which the image forming apparatus is placed is detected, and in an environment where sleeve blotches and uneven streaks are not generated, unnecessary ON / OFF of the sleeve rotation or pulsation of the rotation speed is detected. It is possible to suppress the deterioration of the developer due to unnecessary rotation of the sleeve, although it is a slight difference, and it is possible to save the time.

It should be noted that the detection result of the environment sensor S as shown in this embodiment may be temperature or relative humidity instead of absolute humidity.

The drive control of the developing sleeve 7a in consideration of the detection result of the environment sensor S described in the present embodiment is also applied to the drive sequence described in the first embodiment to rotate the developing sleeve 7a. It goes without saying that the stop can be carried out and the same effect can be achieved.

[0068]

As described above, according to the present invention, in a developing device provided with a developer carrying member for carrying and conveying a developer and a driving means for driving the developer carrying member, before image output, Alternatively, after the image is output, or after the power is turned on, the developer carrier is repeatedly driven and stopped, or the developer carrier can be driven at a plurality of driving speeds before the image output,
Alternatively, after the image is output or after the power is turned on, the driving speed of the developer carrying member is repeatedly changed to give a pulsation to the driving speed of the developer carrying member. It can be suppressed, and the extension of the life of the developer carrier can be promoted.

[Brief description of drawings]

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

FIG. 2 is a diagram illustrating an electrical configuration around a control board according to the first exemplary embodiment.

FIG. 3 is a schematic diagram illustrating a drive path of a developing sleeve according to the first exemplary embodiment.

FIG. 4 is a flowchart illustrating a driving sequence of the developing sleeve according to the first exemplary embodiment.

FIG. 5 is a graph showing the rotation speed of the developing sleeve in the first embodiment.

FIG. 6 is a diagram illustrating an electrical configuration around a control board according to a second embodiment.

FIG. 7 is a schematic diagram illustrating a drive path of a developing sleeve according to the second exemplary embodiment.

FIG. 8 is a flowchart illustrating a driving sequence of the developing sleeve according to the second exemplary embodiment.

FIG. 9 is a graph showing the rotation speed of the developing sleeve in the second embodiment.

FIG. 10 is a diagram illustrating an electrical configuration around a control board according to a third exemplary embodiment.

FIG. 11 is a flowchart illustrating a developing sleeve driving sequence according to a third exemplary embodiment.

[Explanation of symbols]

2 Photosensitive drum (image carrier) 4 Primary charger 7 Developing device 7a Developing sleeve (developer carrier) 100 control board 200 drive unit 300 rpm conversion unit M developing sleeve drive motor CL1 Clutch 1 CL2 Clutch 2

Claims (5)

[Claims] 1. A developing device comprising a developer carrying member for carrying and carrying a developer, and a driving unit for driving the developer carrying member, before or after image output or after power supply. After input,
A developing device characterized in that driving and stopping of the developer carrying member are repeated. 2. An environmental sensor for detecting the temperature or humidity of the outside air, wherein whether or not to stop driving the developer carrier is changed or changed according to the detection result of the environmental sensor. Item 1 of the developing device. 3. A developing device comprising: a developer carrying body carrying and carrying a developer; and a driving means for driving the developer carrying body, wherein the developer carrying body can be driven at a plurality of driving speeds. Before image output, after image output, or after power-on,
A developing device characterized in that the driving speed of the developer carrying member is repeatedly changed to give a pulsation to the driving speed of the developer carrying member. 4. An environment sensor for detecting the temperature or humidity of the outside air, and whether or not the pulsation is applied to the developer carrier is changed or changed depending on the detection result of the environment sensor. Item 3. The developing device. 5. The electrostatic latent image is formed on the image carrier,
An image forming apparatus, wherein the developing device described in any one of (1) to (4) makes the electrostatic latent image a visible image.