JPH06236109A - Development device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To agitate a large amount of toner replenished in the developing tank. [Structure] When printing of a sheet is started, the toner in the developing tank 1 is consumed and the toner density is reduced. Permeability sensor 4
When low printing is performed in which the maximum change width of the output voltage is 0.1 V or less, the toner is slightly replenished by the toner replenishing roller 22. The replenished toner is sufficiently stirred by the stirring roller 3. When high printing is performed in which the maximum change width of the output voltage of the magnetic permeability sensor 4 exceeds 0.1 V, a large amount of toner is replenished by the toner replenishing roller 22. When high printing is completed, the stirring roller 3 is rotated for a certain period of time to sufficiently stir the toner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an electrophotographic image forming mechanism such as a laser printer, a copying machine and a laser facsimile.

[0002]

2. Description of the Related Art In a conventional developing device such as a laser printer or a copying machine, when printing is performed, the toner in the developing tank is consumed, and the output voltage of the toner density sensor for detecting the toner density in the developing tank increases. The toner is replenished by the toner replenishing roller until the output voltage returns to the reference value when the toner concentration in the developing tank is optimum. Then, unless the output voltage of the toner concentration sensor returns to the reference value, the next printing cannot be performed.

When high printing is performed in which the printing portion is large and the toner consumption is large, a large amount of toner is replenished by the time the output voltage of the toner concentration sensor reaches the reference value, and the upper portion of the developing tank has a sufficient amount of toner. Insufficient charging without stirring (uncharged)
There was a large amount of toner. When low-printing was performed with few printed portions, the amount of toner consumed was small and the amount of replenished toner was small, so that sufficient stirring was possible and almost no uncharged toner was present.

[0004]

Conventionally, when high printing is performed and then the next high printing is performed in a state where there is a large amount of unstirred toner in the upper portion of the developing tank, unstirred toner will be developed. When the toner is solidified on the photosensitive drum (toner concentration is high), development is performed.
As a result, toner scattering and spot-like unevenness due to uncharged toner occur on the printed paper.

Further, if high printing is performed and then low printing (for example, white solid) is performed, uncharged toner easily adheres to the white solid portion of the photosensitive drum, resulting in background fog on the white solid portion. Occur. This means that in the case of uncharged toner, for example, a small amount of + charged toner is present in the toner that has been agitated and becomes −charged (see FIG. 26), and this + charged toner is a white solid on the photoconductor drum. It adheres to the area corresponding to the part. In addition, all the sufficiently charged toners are negatively charged (see FIG. 27).

Further, when high printing is continuously performed, it is necessary to replenish a large amount of toner, it takes time to replenish the toner by the toner replenishing roller, and the printing speed (sheets / minute) becomes slow.

In view of the above, it is an object of the present invention to provide a developing device capable of preventing defective stirring of the toner replenished in the developing tank and shortening the toner replenishment time.

[0008]

According to a first aspect of the present invention, there is provided a developing tank 1 in which a developing roller 2 and an agitating roller 3 are rotatably mounted, and toner for detecting the toner concentration in the developing tank 1 is provided. A density detecting means 4, a toner replenishing section 5 for replenishing the toner in the developing tank 1 until the output value of the toner density detecting means 4 reaches a reference value, and a change in the output value of the toner density detecting means 4 during development. If the width is larger than the preset value, the stirring roller 3 is
And a stirring extension means for rotating the same for a certain period of time.

According to a second aspect of the present invention, a stirring promoting means for increasing the rotation speed of the stirring roller 3 when the change width of the output value of the toner concentration detecting means 4 at the time of development becomes larger than a preset set value. Is provided.

According to a third aspect of the present invention, the toner replenishing section 5 replenishes the toner within a fixed time when the variation range of the output value of the toner concentration detecting means 4 during development becomes larger than a preset set value. A toner replenishment promoting means for increasing the amount is provided.

According to a fourth aspect of the present invention, there is provided a means for solving a problem in the toner density detecting means 4 when the change width of the output value of the toner density detecting means 4 is larger than a preset value during development.
The reference value changing means for increasing the reference value is provided.

The means for solving the problem according to the fifth aspect is provided with a toner replenishment stopping means for stopping the toner replenishment by the toner replenishing section 5 for a certain period from the start of printing.

According to a sixth aspect of the present invention, when the toner replenishing time by the toner replenishing section 5 during development is longer than a preset time, the toner concentration detecting means 4 is used.
The reference value changing means for increasing the reference value is provided.

The means for solving the problem according to the seventh aspect is provided with a toner replenishment stopping means for stopping the toner replenishment by the toner replenishing section 5 for a certain period from the start of printing.

According to an eighth aspect of the present invention, the stirring and replenishing means for rotating the stirring roller 3 for a certain period of time after completion of printing when the toner replenishing time by the toner replenishing section 5 during development is longer than a preset time. Is provided.

According to a ninth aspect of the present invention, there is provided a means for strengthening agitation for increasing the rotation speed of the agitation roller 3 when the toner replenishment time by the toner replenishing section 5 becomes longer than a preset time during development. It is a thing.

According to a tenth aspect of the present invention, when the toner replenishing time by the toner replenishing section 5 during development is longer than a preset time, the toner replenishing section 5 increases the toner replenishing amount within a fixed time. A means for strengthening toner replenishment is provided.

According to the eleventh aspect of the present invention, the means for solving the problem is provided with reference value correcting means for increasing the reference value of the toner concentration detecting means 4 in accordance with the toner replenishing amount per predetermined time in the toner replenishing portion 5 during development. .

[0019]

In the means for solving the problems according to the first aspect, when the printing of the paper is started, the developing roller 2 and the stirring roller 3 rotate. Then, the toner in the developing tank 1 is consumed, the toner density is reduced, and the toner replenishment section 5 starts the toner replenishment.

Here, when low printing with a small amount of toner consumption is performed, the change width of the output value of the toner density detecting means 4 is less than or equal to the set value. Then, the toner replenishing unit 5 slightly replenishes the toner. The toner replenished in the developing tank 1 is sufficiently stirred by the stirring roller 3.

Further, when performing high-printing with a large amount of toner consumption, if the output value of the toner concentration detecting means 4 changes greatly and the change width exceeds the set value, a large amount of toner is replenished by the toner replenishing section 5. It When high printing is completed, the stirring roller 3 is rotated for a certain period of time to sufficiently stir the replenished toner.

In the problem solving means according to the second aspect, when high printing is performed and the variation width of the output value of the toner concentration detecting means 4 exceeds the set value, the rotation speed of the stirring roller 3 is increased to improve stirring efficiency. Raise the toner and agitate the replenished toner sufficiently.

In the problem solving means according to the third aspect, when the high-printing is performed and the variation width of the output value of the toner concentration detecting means 4 exceeds the set value, the toner replenishing amount by the toner replenishing section 5 is changed within a predetermined time. The time until the output value of the toner density detecting means 4 increases and returns to the reference value is shortened. This reduces the time required to replenish a large amount of toner.

In the problem solving means according to claim 4, when the high-printing is performed and the variation width of the output value of the toner density detecting means 4 exceeds the set value, the reference value of the toner density detecting means 4 is increased. As a result, the output value of the toner concentration detecting means 4 returns to the reference value with a smaller amount than the normal toner replenishment amount, so that the time required for toner replenishment is shortened.

In the means for solving the problems according to claims 5 and 7, the toner replenishing section 5 is stopped for a certain period from the start of printing to stop the toner replenishment, and the sufficiently stirred toner is supplied onto the developing roller 2. . After a certain period of time, the replenished toner is supplied onto the developing roller 2. This allows
It is less likely that toner with poor stirring is supplied onto the developing roller 2.

In the problem solving means according to the sixth aspect, when high printing is performed and the toner replenishing time by the toner replenishing section 5 exceeds the set time, the reference value of the toner density detecting means 4 is increased. As a result, the output value of the toner concentration detecting means 4 returns to the reference value with a smaller amount than the normal toner replenishment amount, so that the time required for toner replenishment is shortened.

In the problem solving means according to the eighth aspect, when high toner printing is performed, if the toner replenishing time by the toner replenishing section 5 exceeds the set time, the agitating roller 3 is rotated for a certain period of time after the printing is finished to replenish the toner. Is thoroughly stirred.

In the means for solving the problems according to the ninth aspect, when high printing is performed, if the toner replenishing time by the toner replenishing section 5 exceeds the set time, the rotating speed of the agitating roller 3 is increased to improve agitating efficiency, and a large amount is obtained. Stir well the toner replenished in.

In the problem solving means according to claim 10,
When high-printing is performed, if the toner replenishment time by the toner replenishment unit 5 exceeds the set time, the toner replenishment amount by the toner replenishment unit 5 is increased within a certain time, and the output value of the toner density detection means 4 becomes the reference value. Shorten the time to return.
This reduces the time required to replenish a large amount of toner.

In the problem solving means according to claim 11,
The reference value of the toner concentration detecting means 4 is increased according to the toner replenishment amount per predetermined time. As a result, even if the toner replenishment amount per predetermined time decreases, the time until the output value of the toner concentration detecting means 4 returns to the reference value does not change, and the toner replenishment time becomes constant.

[0031]

【Example】

(First Embodiment) As shown in FIG. 2, a developing device for a laser printer according to the first embodiment of the present invention has a developing tank 1 in which a developing roller 2 and a stirring roller 3 are rotatably mounted. Toner concentration detecting means 4 for detecting toner concentration
And a toner replenishing section 5 for replenishing the toner T into the developing tank 1, and drive control of the developing roller 2, the agitating roller 3 and the toner replenishing section 5 in accordance with a change in the output value of the toner concentration detecting means 4. A control unit 6 is provided.

The developing roller 2 has an opening 1a in the developing tank 1.
It is arranged in the vicinity so as to face the photosensitive drum 7, and is driven by the main motor 8. The stirring roller 3 is arranged at the bottom of the developing tank 1 and driven by a stirring motor 9.

As shown in FIG. 3, the driving force of the main motor 8 is applied to the developing roller 2 through the first stirring gear 11 and the idle gear 12 which are rotatably supported by the roller shaft 3a of the stirring roller 3 from the motor gear 10. It is transmitted to the developing gear 13 fixed to the roller shaft 2a. The driving force of the stirring motor 9 is transmitted from the motor gear 14 to the second stirring gear 15 fixed to the roller shaft 3 a of the stirring roller 3.

The toner concentration detecting means 4 is a magnetic permeability sensor which converts the magnetic permeability of the developer D into a voltage and outputs the voltage, and is attached to the tank wall of the developing tank 1 so as to face the stirring roller 3. The magnetic permeability sensor 4 has a characteristic that its output voltage increases when the toner consumption in the developing tank 1 increases and the toner concentration decreases.

As shown in FIG. 2, the toner replenishing section 5 includes a toner hopper 20 mounted in the developing tank 1 and a toner agitator 21 rotatably mounted in the toner hopper 20.
The toner replenishing roller 22 arranged at the toner replenishing port 20a of the toner hopper 20 communicating with the developing tank 1 and the toner agitator 21 and the toner motor 23 for driving the toner replenishing roller 22.

The control unit 6 is a microcomputer as shown in the block diagram of FIG. 4, until the output voltage of the magnetic permeability sensor 4 returns to the reference value when the toner density in the developing tank 1 is optimum during development. When the toner replenishment function of driving the toner motor 23 to replenish the toner and the change width of the output voltage of the magnetic permeability sensor 4 at the time of development are larger than a preset value (0.1 V), stirring is performed after printing is completed. Laura 3
It is equipped with a stirring extension function that rotates the machine for a certain period of time.

Here, the change width of the output voltage of the magnetic permeability sensor 4 is the difference between the reference value and the output voltage when the toner is consumed by printing. For example, when the ratio of the portion printed on the paper surface to the entire surface of the paper is taken as the print ratio, as shown in FIG. 5A, when the print ratio is about 4%, the output voltage of the magnetic permeability sensor 4 changes little. When the printing rate shown in (b) is about 30%, the maximum change width of the output voltage of the magnetic permeability sensor 4 is about 0.1 V. When the printing rate shown in (c) is 50%, the magnetic permeability is The maximum change width of the output voltage of the sensor 4 is about 0.16V. Therefore, when the change width of the magnetic permeability sensor 4 is larger than the set value (0.1 V), it is understood that the printing rate is high and the output voltage of the magnetic permeability sensor 4 is high. The printing rate can be determined from the change width of.

As shown in FIG. 6, the developing device is detachably mounted as a cartridge 30 on the laser printer main body 31. In the figure, 32 is an optical unit such as a semiconductor laser, 33 is a photoconductor 7, a charging device 3
4, a process unit in which the cleaning device 35 is integrated, 36 is a paper feed cassette, 37 is a paper feed roller, 38 is a PS roller, 39 is a fixing roller, and 40 is a paper discharge roller, and these are driven by the control unit 6. Controlled.

The printing cycle including the image forming process and the sheet conveying process of the laser printer is shown in FIG.
Since it is a known one, the detailed description will be omitted.

In the above structure, when the printing of the paper is started, the developing roller 2 and the agitating roller 3 rotate, and the toner on the developing roller 2 adheres to the electrostatic latent image on the photosensitive drum 7. Then, the toner in the developing tank 1 is consumed, the toner density is reduced, and the toner supply by the toner supply roller 22 is started.

When printing with a printing rate of about 4%, the amount of toner consumed is small and the output voltage of the magnetic permeability sensor 4 rises slightly. Then, the toner replenishing roller 22 rotates to slightly replenish the toner. Then, the output voltage of the magnetic permeability sensor 4 returns to the reference value. As shown in FIG. 8, the toner replenished in the developing tank 1 is sufficiently agitated by the agitating roller 3, and there is no uncharged toner.

For printing up to a printing rate of about 30%,
Even if toner is replenished until the output voltage of the magnetic permeability sensor 4 increased due to the decrease in toner concentration returns to the reference value, the toner is sufficiently agitated by the agitating roller 3, so that the background fog or the like on the next printed sheet due to agitation failure. Is unlikely to occur.

However, when the printing rate becomes high such that the printing rate exceeds about 30% and reaches about 50%, the toner in the developing tank 1 is rapidly consumed, and the output voltage of the magnetic permeability sensor 4 largely changes and becomes the maximum. The change width exceeds 0.1V. In order to replenish the toner until the output voltage returns to the reference value, a large amount of toner needs to be replenished in the developing tank 1. As shown in FIG. Development tank 1
Exists in the upper part of.

At this time, as shown in FIG. 1, the stirring roller 3 is rotated for a certain period of time before high printing is completed and printing of the next sheet is started. Then, the replenished toner is sufficiently agitated to be sufficiently charged, and the next paper is printed.

As described above, when high printing is performed such that the maximum change width of the output voltage of the magnetic permeability sensor 4 exceeds 0.1 V, the toner is kept for a certain period of time by the stirring roller 3 before the printing of the next sheet is started. Stirring is performed to prevent poor stirring of toner that has been replenished in large amounts. Therefore, when the next sheet of paper is printed, it is possible to prevent printing defects such as toner scattering and background fogging due to defective stirring.

(Second Embodiment) In the second embodiment, instead of the agitation extension function of the first embodiment, the control unit controls the change width of the output value of the magnetic permeability sensor 4 at the set value (0. 1
When V is larger than V), a stirring promotion function for increasing the rotation speed of the stirring motor 9 is added.

As a result, as shown in FIG. 10, when high printing is performed and the variation range of the output voltage of the magnetic permeability sensor 4 exceeds 0.1 V, the stirring motor 9 from that time is more than the normal stirring. Only by increasing the rotation speed to increase the stirring efficiency,
The toner replenished in a large amount is sufficiently agitated. Other configurations and operations are similar to those of the first embodiment.

(Third Embodiment) In the developing devices of the first and second embodiments, as shown in FIG. 11, when the printing rate is up to about 30%, the output of the magnetic permeability sensor 4 within the printing cycle. The voltage returns to the reference value. However, the printing rate is 30
In the case of high printing of about 50% exceeding 50%, the output voltage of the magnetic permeability sensor 4 returns to the reference value by the end of the printing cycle because the output voltage of the magnetic permeability sensor 4 has a large variation range and a large amount of toner needs to be replenished. There are things you can't do. For this reason, printing of the next sheet cannot be performed until the toner replenishment by the toner replenishing roller 22 is completed, the start of printing of the next sheet is delayed, and the printing speed (sheets / minute) becomes slow.

In the third embodiment, the change width of the output value of the magnetic permeability sensor 4 is set to the set value (0.1
V) is larger than V), a toner replenishment promoting function is added to increase the rotation speed of the toner motor 23 as compared with normal toner replenishment to increase the toner replenishment amount within a fixed time.

Then, as shown in FIG. 12, when the printing cycle of high printing is started and the toner on the developing roller 2 begins to adhere to the electrostatic latent image on the photosensitive drum 7, the toner is consumed. The change width of the output voltage of the magnetic permeability sensor 4 is 0.
When it becomes 1 V or more, the number of rotations of the toner motor 23 becomes 5
Change from rpm to 10 rpm. For this reason, the toner supply amount increases within a certain period of time, and the output voltage of the magnetic permeability sensor 4 returns to the reference value by the end of the printing cycle. In this way, when high printing is performed, the toner replenishment amount within a certain period of time is increased and the toner replenishment time is shortened, so that it is possible to replenish a large amount of toner consumed during the printing cycle, and the printing speed is increased. It won't be late.
Other configurations and operations are similar to those of the first or second embodiment.

(Fourth Embodiment) In the fourth embodiment, when the change width of the output value of the magnetic permeability sensor 4 at the time of development is larger than the set value (0.1 V), the control unit of the third embodiment is A reference value changing function for increasing the reference value of the magnetic permeability sensor 4 is added.

The normal reference value of the magnetic permeability sensor 4 is 1 count = 1 in the reference output value (the output voltage of the magnetic permeability sensor 4 after the toner in the developing tank 1 is stirred for one minute in the new developing tank 1). ÷ 256 × 5 (V) ≈0.02V is a voltage value added, and is stored in the control unit 6 as a toner density detection level. For example, if the reference output value is 1.8V,
As shown in FIG. 13, the normal reference value (toner density detection level) stored in the control unit 6 is 1.8 to 1.82V.
(92 to 93 counts).

When the toner density detection level is increased by controlling the count number added to the reference output voltage of the magnetic permeability sensor 4 during development, the output voltage of the magnetic permeability sensor 4 returns to the reference value (toner density detection level). The time can be shortened. That is, the time required to replenish the toner consumed in printing can be shortened. Therefore, even when a large amount of toner is consumed in high printing in which the variation range of the output voltage of the magnetic permeability sensor 4 is large, the printing speed does not slow down.

FIG. 14 shows the influence on the printing speed when the toner density detection level is changed. According to this, by increasing the count number added to the reference output value, the printing speed becomes constant regardless of the printing rate. That is, in order to keep the printing speed constant, the number of counts to be added may be increased as the printing rate increases. Table 1 shows the number of counts added according to the printing rate when the printing speed is set to 8 sheets / min.

[0055]

[Table 1]

Therefore, as shown in FIG. 15, in order to keep the printing speed constant (8 sheets / min) regardless of the printing rate, the maximum change width of the output voltage of the magnetic permeability sensor 4 is 0.1 V or less. When the print ratio is about 30%, the count number to be added is 1 (1 ÷ 256 × 5V), and the maximum change width is larger than 0.1V and smaller than 0.16V.
When it is about 0%, the number of counts to be added is 3 (3 ÷ 256 ×
5V), and when the maximum change width is larger than 0.16V and the printing rate is about 70%, the number of counts to be added is 5 (5/2
56 × 5V).

As described above, if the toner density detection level is increased by controlling the count number to be added according to the printing rate, that is, the variation width of the output voltage of the magnetic permeability sensor 4, the printing speed can be made constant regardless of the printing rate. In particular, the printing speed does not slow down in high printing. If the toner density detection level is raised, the amount of toner replenishment will decrease by that amount,
After printing is completed, the toner density detection level is returned to the normal level before it is raised, and the insufficient toner is replenished. Other configurations and operations are similar to those of the third embodiment.

(Fifth Embodiment) In the fifth embodiment, a toner replenishment stop function for stopping the toner replenishment by the toner replenishment unit 5 for a certain period from the start of printing is added to the control unit of the fourth embodiment. This is intended to delay the time until the replenished toner that has not been sufficiently stirred reaches the developing roller 2 at the start of printing, thereby suppressing the possibility of defective printing due to poor stirring. .

In the first to fourth embodiments, when the printing is started and the toner in the developing tank 1 is consumed and the output voltage of the magnetic permeability sensor 4 rises, the toner supply is immediately started. In the printing time ta to tb required to print one sheet of paper shown in 16, the time for the toner replenished on the developing roller 2 to reach is te. Therefore, te to t
During b, printing may be performed by the replenished toner that has not been sufficiently stirred, and printing may be defective. Particularly, in the small-sized developing tank 1 having a small capacity, the replenished toner reaches the developing roller 2 immediately, so that the replenished toner is not sufficiently agitated, and the agitation failure is more likely to occur.

Therefore, a fixed time (ta-
tc) When the toner motor 23 is stopped to stop the toner replenishment, and the toner is replenished between tc and tb, the ta-
Since there is no toner replenishment during the time tc, there is no unstirred toner and sufficiently stirred toner is supplied onto the developing roller 2, and printing defects do not occur. Further, when the toner replenishment is started at tc, the time taken for the replenished toner to reach the developing roller 2 is td. Therefore, unstirred toner still exists in the developing tank 1 between tc and td. It is not supplied onto the roller 2 and no printing failure occurs. As a result, there is a possibility of printing failure in a short time between td and tb, that is, in a small range on the printed paper. It is also possible to further delay the time for starting the toner replenishment so that the toner replenishment time is set between the time when one sheet is printed and the time when the next sheet is printed.

As described above, if the toner replenishment is prohibited for a certain time from the start of printing, the printing speed may slow down. As shown in FIG. 17, the toner replenishment stop function is changed to the reference value described in the fourth embodiment. By combining the functions, the occurrence of defective printing due to defective stirring is suppressed as much as possible, and the printing speed does not slow down. The other configurations and operations are the same as those in the fourth embodiment.

(Sixth Embodiment) In the sixth embodiment, instead of the reference value changing function of the fourth embodiment, the toner replenishing time by the toner replenishing unit 5 at the time of development is preset in the control unit. A reference value changing function for increasing the reference value of the magnetic permeability sensor 4 when the set time is longer than 2 seconds is added. In the fourth embodiment, the reference value of the magnetic permeability sensor 4 is increased according to the change width of the output voltage of the magnetic permeability sensor 4, whereas the toner motor driven based on the output of the magnetic permeability sensor 4 is used. Permeability sensor 4 according to the drive time of 23
Has raised the standard value of.

Here, the driving time of the toner motor 23 is
As shown in FIG. 18, when the printing rate is about 4% (a), the driving time is short, and when the printing rate is about 30%, the driving time is 2 seconds and the printing rate is about 50%. In case of (c), the driving time is 3 seconds, and the toner motor 2
The printing rate is known from the driving time of 3. The drive time of the toner motor 23 is set by a timer or the like.
Measured from the start of driving.

Therefore, as shown in FIG. 19, in order to keep the printing speed constant (8 sheets / min) regardless of the printing rate, the reference output value of the magnetic permeability sensor 4 is set when the driving time is 2 seconds or less. The number of counts to be added is 1, and the number of counts to be added is 3 when the driving time is greater than 2 seconds and less than 3 seconds,
The number of counts to be added when the driving time is longer than 3 seconds is 5. As a result, similar to the fourth embodiment, the printing speed does not slow down even when a large amount of toner is consumed in high printing in which the output voltage variation of the magnetic permeability sensor 4 is large.

When the toner replenishing time by the toner replenishing unit 5 during development is longer than a preset time (2 seconds) as shown in FIGS. A stirring replenishment function of rotating the stirring roller 3 for a predetermined time and a stirring enhancement function of similarly increasing the rotation speed of the stirring roller 3 are added. As a result, similarly to the first and second embodiments, the toner in the developing tank 1 is sufficiently agitated even when high printing is performed, and printing defects can be prevented.

Further, as shown in FIG. 22, when the toner replenishing time by the toner replenishing unit 5 is longer than the preset time (2 seconds) at the time of development, as shown in FIG.
A toner replenishment strengthening function is added to increase the amount of toner replenished by the toner replenishing unit 5 within a fixed time. As a result, as in the third embodiment, even when high printing is performed, a large amount of toner consumed during the printing cycle can be replenished and the printing speed does not slow down.

Further, as shown in FIG. 23, the control section is provided with a toner replenishment stop function for stopping the toner replenishment by the toner replenishment section for a certain period from the start of printing. As a result, as in the fifth embodiment, the possibility of defective printing due to defective stirring can be minimized. The other configurations and operations are the same as those in the fourth embodiment.

(Seventh Embodiment) In the seventh embodiment, instead of the reference value changing function of the fourth embodiment, the control unit is controlled according to the toner replenishing amount per predetermined time in the toner replenishing unit 5 during development. A reference value correction function for increasing the toner concentration detection level of the magnetic permeability sensor 4 is added.

In the case of a large-capacity toner hopper 20, the toner replenishing roller 2 is initially used when there is a large amount of toner in the hopper 20.
Although the toner is sufficiently conveyed onto the second hopper 20, the toner is not sufficiently conveyed onto the toner replenishing roller 22 in the final stage when the toner in the hopper 20 is low. Therefore, as shown in FIG. 24, the toner replenishment amount (toner drop amount) per predetermined time decreases with the lapse of time. In particular, in the final stage, it takes a long time for the output voltage of the magnetic susceptibility sensor 4 to return to the reference value, and the printing speed may slow down. The amount of toner replenished per predetermined time depends on the amount of toner in the hopper 20, and the amount of toner in the hopper 20 is related to the total drive time of the toner motor 23 from the initial state of the hopper 20. is doing.

By the way, in order to always keep the amount of toner replenished per predetermined time constant regardless of the amount of toner in the hopper 20, the rotation speed of the toner agitator 21 is increased so that the amount of toner on the toner replenishing roller 22 is sufficient. May be transported. However, in this case, since the amount of toner is large in the initial stage, it is necessary to use a high torque motor for the toner motor 23 that drives the toner agitator 21, resulting in a very high cost.
Therefore, the rotational speed of the toner agitator 21 is slowed down to increase the torque, and the toner motor 23 having a low torque is used to reduce the cost.

Further, as disclosed in Japanese Patent Application Laid-Open No. 62-25778, when the number of copies after the replacement of the developer, that is, the total usage time of the developer increases, the reference level of the toner density sensor is changed. To regulate toner replenishment, maintain a normal toner density, and keep the image density constant. However, in this case, since the time when the developer is replaced and the time when the hopper 20 is in the initial state do not match,
The total use time of the developer does not match the total drive time of the toner motor 23, and if the toner replenishment amount per predetermined time decreases, the printing speed may slow down.

However, when developing, the count number to be added to the reference output value of the magnetic permeability sensor 4 is controlled according to the toner replenishment amount per predetermined time, that is, the total driving time of the toner motor 23, and the toner density detection of the magnetic permeability sensor 4 is detected. By increasing the level, it is possible to make the toner supply time constant regardless of the toner supply amount per predetermined time.

FIG. 25 shows the toner replenishment amount per second (1 g / min, when changing the added count number).
Changes in printing speed at 0.8 g / min and 0.6 g / min) are shown. Now, the hopper 20 is added to the control unit.
The amount of toner in the inside, that is, the toner replenishment amount per second with respect to the total drive time of the toner replenishment roller 22 from the time when the hopper 20 is in the initial state is stored, and the accumulated drive time of the toner replenishment roller 22 is stored. By determining the toner replenishment amount per second and changing the added count number according to this replenishment amount, it is possible to make the printing speed constant regardless of the toner replenishment amount per predetermined time. As shown in Table 2, in order to set the printing speed to 8 sheets / min regardless of the toner replenishment amount, the count number to be added when the toner replenishment amount is 1 g / min is 1 (1 ÷ 256 × 5V). , 0.8 g / min
The number of counts to be added at 3 is 3 (3/256 × 5V), and the number of counts to be added at 0.6 g / min is 5
(5 ÷ 256 × 5V).

[0074]

[Table 2]

As described above, when the toner replenishment amount per predetermined time decreases, the count number to be added is controlled to raise the toner density detection level. Therefore, even if the toner replenishment amount per predetermined time is small, the output value of the magnetic permeability sensor 4 immediately returns to the reference value, so that the printing speed can be made constant regardless of the toner replenishment amount per predetermined time. The printing speed does not slow down at the end of the hopper 20. The other configurations and operations are the same as those in the fourth embodiment.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention. For example, the reference value correction function of the seventh embodiment may be added to the sixth embodiment.

[0077]

As is apparent from the above description, according to claims 1 and 8 of the present invention, a large amount of replenished toner is agitated for a certain period of time after the completion of printing to prevent the agitation of the following paper. When printed, it is possible to prevent printing defects such as toner scattering and background fog caused by poor stirring.

According to claims 2 and 9, the rotation speed of the stirring roller is increased to stir a large amount of the replenished toner to prevent stirring failure. It is possible to prevent printing defects such as toner scattering and background fog.

According to the third and tenth aspects, the toner replenishment amount within a fixed time can be increased, and the time required for replenishing a large amount of toner can be shortened. The time runs out and toner supply can be completed within the print cycle.

According to the fourth and sixth aspects, by increasing the reference value of the toner density detecting means, the replenishment time of the toner replenished in a large amount at the time of development can be shortened, and the printing speed does not slow down.

According to the fifth and seventh aspects, since the supplied toner is delayed in reaching the developing roller, the supply of the supplied toner to the developing roller is delayed, and printing defects can be suppressed as much as possible. The speed does not slow down.

According to the eleventh aspect, when the toner replenishment amount per predetermined time in the toner replenishing unit decreases, the reference value of the toner concentration detecting means is raised, so that there is an excellent effect that the printing speed does not slow down.

[Brief description of drawings]

FIG. 1 is a flowchart for rotating a stirring roller after printing according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a developing device.

FIG. 3 is a diagram showing a drive system of a developing roller and a stirring roller.

FIG. 4 is a block diagram of a control unit.

FIG. 5 is a diagram showing changes in output voltage of a magnetic permeability sensor,
(A) when the printing rate is 4%, (b) when the printing rate is 30%, (c) when the printing rate is 50%

FIG. 6 is a configuration diagram of a laser printer including the developing device of the present invention.

FIG. 7 is a diagram showing a printing cycle of a laser printer.

FIG. 8 is a diagram showing a state of the developer in the developing tank after the low print is completed.

FIG. 9 is a diagram showing a state of the developer in the developing tank after completion of high printing.

FIG. 10 is a flowchart for increasing the rotation speed of the stirring roller of the second embodiment.

FIG. 11 is a comparison diagram of a change in output voltage of a magnetic permeability sensor and a printing cycle. (A) shows a printing rate of 4%, (b) shows a printing rate of 30%, and (c) shows a printing rate of 50%. When

FIG. 12 is a flowchart for changing the rotation speed of the toner motor according to the third embodiment.

FIG. 13 is a diagram showing a toner concentration detection level of a magnetic permeability sensor.

FIG. 14 is a diagram showing the influence on the printing speed when the toner concentration detection level is changed.

FIG. 15 is a flowchart for changing the toner concentration detection level of the magnetic permeability sensor according to the fourth embodiment.

FIG. 16 is a diagram showing a temporal transition when a sheet passes through a developing roller.

FIG. 17 is a flowchart for changing the toner concentration detection level of the magnetic permeability sensor after stopping the toner supply according to the fifth embodiment.

FIG. 18 is a diagram showing a driving time of the toner motor, (a) shows a printing rate of 4%, (b) shows a printing rate of 30%,
(C) is when printing rate is 50%

FIG. 19 is a flowchart for changing the toner concentration detection level of the magnetic permeability sensor according to the sixth embodiment.

FIG. 20 is a flow chart when the stirring roller is rotated after printing as well.

FIG. 21 is a flowchart for similarly increasing the rotation speed of the stirring roller.

FIG. 22 is a flowchart when changing the rotation speed of the toner motor.

FIG. 23 is a flowchart for changing the toner concentration detection level of the magnetic permeability sensor after the toner supply is stopped.

FIG. 24 is a diagram showing changes over time in the toner replenishment amount per second in the toner hopper.

FIG. 25 is a diagram showing the influence on the printing speed when the toner concentration detection level in the toner supply amount per second is changed.

FIG. 26 is a diagram showing a charge amount distribution of uncharged toner.

FIG. 27 is a diagram showing a charge amount distribution of a sufficiently charged toner.

[Explanation of symbols]

 1 developing tank 2 developing roller 3 stirring roller 4 toner concentration detecting means 5 toner replenishing section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sachishi Ando 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (11)

[Claims] 1. A developing roller and a stirring roller are rotatably mounted in a developing tank, and a toner concentration detecting means for detecting a toner concentration in the developing tank and an output value of the toner concentration detecting means become a reference value. In a developing device provided with a toner replenishing unit for replenishing toner in the developing tank, when the change width of the output value of the toner concentration detecting means is larger than a preset set value at the time of development, printing is completed. A developing device comprising a stirring extension means for rotating the stirring roller for a predetermined time later. 2. A developing roller and an agitating roller are rotatably installed in a developing tank, and a toner density detecting means for detecting a toner density in the developing tank, and an output value of the toner density detecting means become a reference value. In a developing device provided with a toner replenishing section for replenishing toner in the developing tank, when the change width of the output value of the toner concentration detecting means during development becomes larger than a preset set value, the stirring is performed. A developing device, characterized in that stirring means for increasing the rotation speed of the roller is provided. 3. A developing roller and an agitating roller are rotatably installed in the developing tank, and a toner density detecting means for detecting the toner density in the developing tank, and an output value of the toner density detecting means become a reference value. In a developing device provided with a toner replenishment section for replenishing toner in the developing tank, when the change width of the output value of the toner concentration detecting means during development becomes larger than a preset set value, the toner A developing device, comprising: a toner replenishment promoting means for increasing the amount of toner replenished by a replenishing unit within a fixed time. 4. A developing roller and an agitating roller are rotatably mounted in a developing tank, and a toner density detecting means for detecting the toner density in the developing tank and an output value of the toner density detecting means become a reference value. In a developing device provided with a toner replenishing section for replenishing toner in the developing tank, when the change width of the output value of the toner concentration detecting means during development becomes larger than a preset set value, the toner A developing device comprising a reference value changing means for increasing the reference value of the density detecting means. 5. The developing device according to claim 4, further comprising a toner replenishment stopping means for stopping the toner replenishment by the toner replenishing unit for a certain period from the start of printing. 6. A developing roller and a stirring roller are rotatably mounted in the developing tank, and toner concentration detecting means for detecting the toner concentration in the developing tank and an output value of the toner concentration detecting means become a reference value. In a developing device provided with a toner replenishing section for replenishing toner in the developing tank, when the toner replenishing time by the toner replenishing section during development is longer than a preset set time, the toner concentration detecting means And a reference value changing means for increasing the reference value. 7. The developing device according to claim 6, further comprising a toner replenishment stopping means for stopping the toner replenishment by the toner replenishing section for a certain period from the start of printing. 8. A developing roller and an agitating roller are rotatably installed in a developing tank, and a toner density detecting means for detecting a toner density in the developing tank and an output value of the toner density detecting means become a reference value. In a developing device provided with a toner replenishing section for replenishing toner in the developing tank, when the toner replenishing time by the toner replenishing section during development is longer than a preset time, the agitation is performed after printing is completed. A developing device comprising a stirring and replenishing means for rotating the roller for a predetermined time. 9. A developing roller and an agitating roller are rotatably mounted in the developing tank, and a toner density detecting means for detecting the toner density in the developing tank and an output value of the toner density detecting means become a reference value. In a developing device provided with a toner replenishing section for replenishing toner in the developing tank, when the toner replenishing time by the toner replenishing section during development is longer than a preset set time, the stirring roller is rotated. A developing device, characterized in that stirring means for increasing the speed is provided. 10. A developing roller and an agitating roller are rotatably installed in a developing tank, and a toner density detecting means for detecting a toner density in the developing tank, and an output value of the toner density detecting means become a reference value. In a developing device provided with a toner replenishing section for replenishing toner in the developing tank, when the toner replenishing time by the toner replenishing section during development becomes longer than a preset set time, the toner replenishing section keeps a constant value. A developing device comprising a toner replenishment strengthening means for increasing a toner replenishment amount within a time period. 11. A developing roller and an agitating roller are rotatably mounted in a developing tank, and a toner density detecting means for detecting a toner density in the developing tank and an output value of the toner density detecting means become a reference value. In a developing device provided with a toner replenishing section for replenishing toner in the developing tank, a reference value for increasing the reference value of the toner concentration detecting means in accordance with the toner replenishing amount per predetermined time in the toner replenishing section during development. A developing device provided with a correction means.