JP2909319B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device which is applied to, for example, an electrophotographic recording device and visualizes an electrostatic latent image formed on an image carrier such as a photosensitive drum.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a configuration example of a conventional developing device. In the figure, reference numeral 1 denotes a developing device, which includes a hopper 11, a developing roller 12, a supply roller 13, a blade 14, an agitator 15, a developing power source 16, a switch 17, and a DC.
The motor 18 is provided.

The hopper 11 stores a non-magnetic one-component toner (not shown). The developing roller 12 is made of, for example, conductive rubber and is in contact with the photosensitive drum 2, and a part of the developing roller 12 is formed in the opening of the hopper 11.
1 are arranged in a state located inside. The transport roller 13 is made of, for example, a conductive sponge, and
1 is disposed in parallel with and in contact with the developing roller 12. The blade 14 is for thinning the toner carried on the developing roller 12 and guided to the outside of the hopper 11 and for frictionally charging the toner. The agitator 15 rotates in the hopper 11 and scrapes toner toward the supply roller 13. The developing power source 16 applies a developing bias of a predetermined voltage (for example, −200 V) to the developing roller 12. The switch 17 turns on / off the application of the developing bias to the developing roller 12. DC motor 18
Rotates the developing roller 12 at a constant peripheral speed.

In the developing device 1, the toner stored in the hopper 11 moves to the vicinity of the supply roller 13 by its own weight or the agitator 15, and is supplied to the development roller 12 by the rotation of the supply roller 13. Developing roller 12
Carries the supplied developer, guides the developer to the outside of the hopper 11, and contacts the surface of the photosensitive drum 2. At this time, the toner carried on the developing roller 12 is thinned by the blade 14 and is triboelectrically charged. The toner in contact with the photosensitive drum 2 is electrostatically charged according to the electrostatic latent image by the action of the charged charge, the electrostatic latent image formed on the photosensitive drum 2, and the developing bias applied to the developing roller 12. It adheres to the drum 2. Thus, the electrostatic latent image formed on the photosensitive drum 2 is visualized by the toner.

Incidentally, the photosensitive drum 2 and the developing roller 12
If the peripheral speed ratio (the peripheral speed of the developing roller 12 / the peripheral speed of the photosensitive drum 2) is 1 or less, the amount of contact toner per unit area of the surface of the photosensitive drum 2 is reduced, and the image density is reduced. Will come. For this reason, the peripheral speed of the developing roller is set so that the peripheral speed ratio with the photosensitive drum 1 is 1 or more. FIG. 6 is a diagram showing an example of the relationship between the peripheral speed ratio between the photosensitive drum 2 and the developing roller 12 and the density. As can be seen from this figure, the concentration increases in proportion to the peripheral speed ratio.

When the peripheral speed ratio is close to 1, the charge amount of the toner is reduced as shown in FIG. this is,
The charging of the toner is not limited to the friction caused by the blade 14,
Since the friction is also caused by the friction by the photosensitive drum 2 and the friction by the supply roller 13, the friction by the photosensitive drum 2 is small near the peripheral speed ratio of 1, and the charge amount is reduced. When the charge amount of the toner is reduced in this way, the toner easily adheres to the photosensitive drum 1, and fog increases in a recorded image. FIG. 8 shows an example of the relationship between the peripheral speed ratio and fog. For this reason, the peripheral speed of the developing roller is set so that the peripheral speed ratio with the photosensitive drum 1 does not become close to 1.

However, when the rotation of the developing roller 14 is started and stopped, the rotation of the developing roller 14 is gradually accelerated or decelerated, so that a period in which the peripheral speed ratio becomes close to 1 can be prevented. Absent. Therefore, during this period, toner adheres to the photosensitive drum 2. When the toner adheres to the photosensitive drum 2, the toner adhered to the photosensitive drum 2 is collected by a cleaning device (not shown) and becomes waste toner, so that the toner is wasted. If a transfer device (not shown) such as a roller or a brush is used as a transfer device, the toner adhered to the photosensitive drum 2 adheres to the transfer device and stains the back surface of the recording paper. Further, there has been a problem that transfer efficiency is reduced and transfer failure occurs.

[0008]

As described above, in the conventional developing device, when the rotation of the developer carrier is started and stopped, the peripheral speed ratio between the photosensitive member and the developer carrier is close to one. There is a problem in that there is a period during which the developer becomes unnecessary, and wasteful developer adhesion to the photoconductor occurs.

The present invention has been made in view of such circumstances, and an object of the present invention is to minimize wasteful adhesion of a developer to a photoreceptor, thereby achieving economical and high-quality recording. An object of the present invention is to provide a developing device that enables the developing device.

[0010]

According to the present invention, there is provided an endless developer carrier such as a developing roller for carrying a developer and contacting the surface of a photoconductor such as a photosensitive drum.
It rotates at the number of rotations according to the frequency of the supplied drive signal,
A pulse motor for rotating the developer carrier , for example,
And a control means such as control unit, the control means, during the rotation start and stop of the rotation of the pulse motor, the path
The motor should be slewed up and down.
Control for gradually increasing and decreasing the frequency of the drive signal.
It performed as in A, and the other frequency range is a predetermined frequency range peripheral speed ratio rotating said developer carrying member at a peripheral speed which is a predetermined range of near 1 between the photosensitive member and the developer carrying member
The frequency of the drive signal is changed more steeply than
Caught.

[0011]

By taking such measures, when the rotation of the pulse motor is started and stopped, the rotation speed of the pulse motor is reduced so that the peripheral speed ratio between the photosensitive member and the developer carrier is close to 1. The pulse motor is subjected to through-up control and through-down control using a drive signal having a frequency other than the frequency that is the number of rotations of the developer carrier at a peripheral speed within a predetermined range. Therefore, the developer carrier is rotated at a peripheral speed at which the peripheral speed ratio between the photoconductor and the developer carrier does not fall within a predetermined range near 1.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a main configuration of an electrophotographic recording apparatus configured by applying the developing device according to the present embodiment. Around the photosensitive drum 2 along its peripheral surface,
Charging device 3, exposure device 4, developing device 5, and transfer device 6
Is provided.

The charging device 3 comprises a well-known scorotron charger, for example, and uniformly charges the surface of the photosensitive drum 2 to a predetermined potential. The exposure device 4 is a well-known laser scanner or the like that turns ON / OFF according to image data of an image to be recorded, for example, although a specific configuration is omitted in the drawing.

The developing device 5 includes a hopper 11, a developing roller 12, a supply roller 13, a blade 14, and an agitator 1.
5, developing power supply 16, switch 17, and developing roller 12
Is provided with a pulse motor 51 for rotating.

The transfer device 6 includes a transfer roller 61 in contact with the photosensitive drum 2, a transfer power source 62 for applying a predetermined positive transfer voltage to the transfer roller 61, and a transfer roller 6
Switch 63 for turning on / off the application of the transfer voltage to 1
It is composed of

Reference numeral 7 denotes a photosensitive drum drive system including, for example, a motor and a gear, which rotates the photosensitive drum 2 at a constant peripheral speed. Reference numeral 8 denotes a registration roller for adjusting the timing of conveying the recording paper P to the timing of the electrophotographic process, and is rotated by the pulse motor 51 in synchronization with the development roller 12. Reference numeral 9 denotes a control unit that controls the electrophotographic recording apparatus as a whole.

Next, the operation of the electrophotographic recording apparatus configured as described above will be described according to the control procedure of the control unit 9. First, when starting up the operation of the present electrophotographic recording apparatus, the control unit 9
Instructs the photosensitive drum drive system 7 to start rotating the photosensitive drum 2. In response to this, the photosensitive drum drive system 7
The rotation drive of the photosensitive drum 2 is started, and the photosensitive drum 2 rotates (at time T1 in FIG. 2). At the same time, the control unit 9
Instruct the charging device 3 to start operation. In response, the charging device 3 starts discharging, and uniformly charges the surface of the photosensitive drum 2 to a predetermined potential (for example, -500 V).

Subsequently, the control unit 9 determines the time TA from the time T1.
At a point in time (time required for an arbitrary point on the photosensitive drum 2 to move from the charging position A by the charging device 3 to the developing position B by the developing device 5) (time T2 in FIG. 2),
The switch 17 is turned on to start applying the developing bias generated by the developing power supply 16 to the developing roller 12.

Next, the control unit 9 starts supplying the recording paper P from a paper feeding system (not shown). After a certain period of time after the recording paper P reaches the registration roller 8, the control unit 9 starts the rotation of the pulse motor 51 and starts the rotation of the developing roller 12 and the registration roller 8 (T4 in FIG. 2).
Time). The control unit 9 rotates the pulse motor 51 until the trailing edge of the recording paper P has completely passed through the registration roller 8 (TB period in FIG. 2), and then stops the rotation of the pulse motor 51 ( (Time T5 in FIG. 2).

On the other hand, when the leading end of the recording paper P reaches the transfer position C by the transfer device 6, the control unit 9 controls the exposure device so that the exposure start point is located slightly closer to the developing position B than the transfer position C. 4 is instructed to start exposure. In response, the exposure device 4 starts exposure based on separately provided image data (time T3 in FIG. 2). Then, the control unit 9 operates the exposure device 4 while the exposure device 4 performs exposure for one page (TC period in FIG. 2),
The exposure by the exposure device 4 is stopped (time T6 in FIG. 2). Thereafter, if it is necessary to record the next page, the control unit 9 drives the exposure device 4 and the pulse motor 51 at the same timing as described above. In this state, the image is recorded on the recording paper P by a well-known operation.

The rotation of the pulse motor 51 is turned on / off as described above. When the rotation of the pulse motor 51 rises and falls, the control unit 9 performs the through-up control and the through-down control. Do. However, the through-up control and the through-down control are performed as follows without using a frequency in which the peripheral speed ratio between the photosensitive drum 2 and the developing roller 12 is in a predetermined range near 1.

The peripheral speed of the developing roller 12 is controlled by a pulse motor 51.
, And the rotation speed of the pulse motor 51 is proportional to the frequency of the drive signal supplied from the control unit 9. Therefore, the peripheral speed of the developing roller 12 is proportional to the frequency of the drive signal output from the control unit 9. Since the peripheral speed of the photosensitive drum 2 is constant, the peripheral speed ratio between the photosensitive drum 2 and the developing roller 12 is proportional to the frequency of the drive signal output from the control unit 9 as shown in FIG. From this relationship, the peripheral speed ratio is within a predetermined range near 1 (the peripheral speed ratio Ra to the peripheral speed ratio R in FIG. 3).
b (range of frequency fa to frequency fb in FIG. 3). The predetermined range near 1 varies depending on various conditions. For example, when the relationship between the peripheral speed ratio and the fog has the characteristics shown in FIG.
It is about 0.9 to 1.2 (more preferably 0.8 to 1.4).

As shown in FIG. 4, the control unit 9 relatively gradually increases the frequency of the drive signal at a predetermined increase rate. When the frequency of the drive signal reaches fa, the control unit 9 rapidly increases the frequency of the drive signal to fb. Further, thereafter, the control unit 9 returns the frequency of the drive signal to the predetermined increase rate until the peripheral speed ratio reaches a frequency (for example, fc in FIG. 3) at which the peripheral speed ratio reaches a predetermined value suitable for the developing operation, and the control unit 9 is relatively gently controlled. When the frequency of the drive signal becomes fc, the frequency is stabilized at fc. Although the through-up control has been described here, the through-down control also reduces the frequency of the drive signal at a timing opposite to that of the through-up control.

As described above, according to the present embodiment, the pulse motor 51 is used to rotate the developing roller 12, and the control unit 9 gives the pulse motor 51 a rotation when the pulse motor 51 starts or stops. The frequency of the drive signal is changed from the lower limit frequency to the upper limit frequency of the frequency range corresponding to the peripheral speed of the developing roller 12 in which the peripheral speed ratio between the photosensitive drum 2 and the developing roller 12 is in a predetermined range near 1. From the lower frequency to the lower limit frequency, and increase or decrease relatively slowly in other frequency ranges. For this reason, the peripheral speed of the developing roller 12 is a period in which the peripheral speed ratio is from the peripheral speed at the lower limit of the predetermined range to the peripheral speed at the upper limit, or from the peripheral speed at the upper limit to the peripheral speed at the lower limit. It increases and decreases sharply during the period, and relatively slowly increases and decreases during the other periods.

Therefore, the peripheral speed ratio does not fall within the predetermined range near 1 even during the through-up or the through-down. However, in practice, a change in the rotation speed of the pulse motor 51 and a change in the peripheral speed of the developing roller 12 require some time. Therefore, in this transition period, the peripheral speed ratio falls within a predetermined range of around 1; Since this period is very short, the charge amount of the toner does not decrease. For this reason,
The occurrence of fog on the photosensitive drum 2 is reduced, and waste of toner and dirt on the transfer roller 61 and the back surface of the recording paper P are prevented.

Since the range in which the rotation speed of the pulse motor 51 (peripheral speed of the developing roller 12) is sharply increased or decreased is small, no step-out of the pulse motor 51 occurs.
It does not hinder the through-up operation and the through-down operation.

Although the effect of reducing fog increases as the predetermined range increases, the range in which the rotational speed of the pulse motor 51 sharply increases and decreases becomes large. The through-down operation may be hindered. For this reason, the above-mentioned predetermined range needs to be set optimally in consideration of various conditions. Further, the increase / decrease of the rotation speed (peripheral speed of the developing roller 12) of the pulse motor 51 outside the predetermined range is determined by the pulse motor 5
It is desirable that the developing roller 12 be as steep as possible as long as the developing roller 12 can be rotated smoothly without step-out or the like.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0029]

According to the present invention, an endless developer carrier such as a developing roller, which carries a developer and is brought into contact with the surface of a photoconductor such as a photosensitive drum, and a driving signal supplied thereto A pulse motor that rotates at a rotation speed according to a frequency and rotates the developer carrier , for example, a control unit, etc.
And a control means, the control means, during the rotation start and stop of the rotation of the pulse motor, the pulse motor
Drive to drive through and through down
Controls the frequency of the signal to gradually increase and decrease.
And a predetermined frequency range in which the developer carrier is rotated at a peripheral speed in which a peripheral speed ratio between the photoconductor and the developer carrier is a predetermined range near 1 compared to other frequency ranges.
The frequency of the drive signal is changed steeply.
In this case, the peripheral speed ratio between the photosensitive member and the developer carrying member is within a predetermined range near 1.
By shortening the enclosing period, wasteful adhesion of the developer to the photoreceptor is suppressed to the utmost, whereby the developing apparatus can record economically and with high image quality.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a main configuration of an electrophotographic recording apparatus configured by applying a developing device according to an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation timing of each unit in FIG. 1;

FIG. 3 is a diagram showing a relationship between a peripheral speed ratio between a photosensitive drum 1 and a developing roller 12 in FIG. 1 and a frequency of a drive signal of a pulse motor 51.

FIG. 4 is a diagram showing a change in the frequency of a drive signal output by a control unit 9 in FIG. 1;

FIG. 5 is a diagram illustrating a conventional technique.

FIG. 6 is a diagram illustrating a conventional technique.

FIG. 7 is a diagram illustrating a conventional technique.

FIG. 8 is a diagram illustrating a conventional technique.

[Explanation of symbols]

2 photosensitive drum, 5 developing device, 12 developing roller, 5
1 ... pulse motor, 9 ... control unit.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/08

Claims (1)

(57) [Claims] A developing device that develops an electrostatic latent image formed on the surface of the photoconductor by bringing a charged developer into contact with the surface of the photoconductor rotating at a predetermined peripheral speed; And an endless developer carrier that contacts the surface of the photoconductor, and rotates at a rotation speed according to the frequency of the supplied drive signal,
A pulse motor for rotating the developer carrying member, during the rotation start and stop of the rotation of the pulse motor, before
Make the pulse motor slew up and down
System for gradually increasing and decreasing the frequency of the drive signal as much as possible
Be one performing control, and other frequencies in a predetermined frequency range peripheral speed ratio rotating said developer carrying member at a peripheral speed which is a predetermined range of near 1 between the photosensitive member and the developer carrying member
The frequency of the drive signal is changed steeply compared to a number range.
And a control unit.