JP2001183894A - Developing device and image forming device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the irregularity of toner concentration in two-component developer. SOLUTION: The inside of a developing unit housing 12 is divided into a developing roller chamber 13 being near to a developing roller 11 and a stirring chamber 14 being distant from the roller 11 so that the two-component developer is stirred and made to circulate by stirring rollers 15 and 16 arranged at the respective chambers. Then, the supply of toner from plural sub-toner charging ports 19a-19d arranged on the chamber 13 side by side are individually controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device using a two-component developer and an image forming apparatus such as an electrophotographic printer, a facsimile or a copying machine using the developing device.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a surface of a photoreceptor is uniformly charged by a charger, and then the charge is selectively removed by light to adsorb toner onto an electrostatic latent image formed. A toner image is formed on the recording paper, and the toner image is transferred to a recording sheet, and the toner is melted and fixed by heat in a fixing device.

A developing device for adsorbing toner to an electrostatic latent image uses a two-component developer in which toner and carrier are mixed, a stirring chamber and a stirring roller for stirring toner and carrier, and a developer from a toner inlet. A transport roller for transporting to the developing roller is provided, and a developing roller for forming a magnetic brush with a two-component developer by magnetic force to develop an electrostatic latent image is provided.

The developing device replenishes the toner periodically or when the toner density decreases to a predetermined value or less because the toner adheres to the photoreceptor and is consumed in the developing process in accordance with the image formation. There is a need. The supplied toner is configured to be mixed with a carrier and then carried to the photoreceptor surface. If the toner concentration in the developer is non-uniform, the toner image developed on the photoreceptor has uneven density, and the image quality is significantly deteriorated. Therefore, the toner concentration in the developer is
It must be kept uniform.

Conventionally, as described in Japanese Patent Application Laid-Open No. 5-165328, a developer transport means for transporting a two-component developer comprising a toner and a carrier in a container to an electrostatic latent image carrier, and the container A two-component developing device comprising: a stirring unit for stirring the toner and the carrier in the toner supply unit; and a toner supply unit for supplying the toner in the toner storage unit into the container. A variable toner supply unit is provided, and control means for detecting the toner consumption and controlling the toner supply unit is provided, and controlling the toner supply amount per unit time of the toner supply unit according to the toner consumption. The way to do it.

[0006]

However, a plurality of inlets for supplying toner are provided, and a stable print result is obtained by changing the amount of toner supply per unit time regardless of the printing rate. Since the developing device obtains the detection of the toner consumption amount due to the difference in the printing rate as the toner consumption amount per page, if the printing area printed in one page is biased, Since the distribution of the toner density is uneven in the axial direction of the developing roller, there is a problem that the image quality is deteriorated due to the uneven printing.

An object of the present invention is to maintain the toner density of a developer in a developing device at a constant level even when the toner in the developer is partially consumed, and to maintain the toner density in the developer. An object of the present invention is to provide a developing device and an image forming apparatus that reduce unevenness and fluctuation by reducing unevenness in printing.

[0008]

According to the present invention, a two-component developer in which a toner and a carrier are mixed is accommodated in a housing of a developing device.
In the developing device, the two-component developer is attracted to a developing roller while being stirred to develop an electrostatic latent image, and when the toner concentration of the two-component developer in the developing device housing becomes insufficient, toner is supplied. The means for replenishing toner in the developing device housing has a plurality of toner inlets arranged in parallel in the axial direction of the developing roller, and means for independently controlling the amount of toner supplied from each toner inlet independently. .

The toner inlet is arranged parallel to the axial direction of the developing roller.

Further, in the developing device housing, a developing roller chamber near the developing roller and a stirring chamber far from the developing roller are partitioned by a partition wall, and a two-component developer is circulated by a stirring roller provided in each chamber. The plurality of toner inlets are provided above the developing roller chamber.

Further, a toner inlet having a larger toner replenishing capacity than the plurality of toner inlets is provided above the stirring chamber.

A means for estimating a partial toner consumption in the developing device housing based on the print image data; and a means for controlling a toner supply amount from a plurality of toner inlets based on the estimated toner consumption. Was provided.

Further, a plurality of toner concentration sensors, a toner concentration distribution monitoring device for monitoring the toner concentration distribution in the developing device, and toner supply from a plurality of toner input ports based on the monitoring result by the toner concentration distribution monitoring device. Means for controlling the amount were provided.

The toner inlet having a large toner replenishing capacity is used for toner replenishment for adjusting the overall toner concentration of the two-component developer.

[0015]

FIG. 1 is a schematic diagram showing an embodiment of an image forming apparatus using a developing device of the present invention.

The image forming apparatus includes a photosensitive drum 1 having a drum surface coated with a material whose electrical characteristics change when irradiated with light of a specific wavelength. The surface of the photosensitive drum 1 is first cleaned with a cleaner 2 while rotating, and then uniformly charged using a charger 3.

Next, the surface of the photoreceptor drum 1 is scanned and exposed with light of a specific wavelength using a laser exposure device 4 based on the print image data, thereby erasing the electric charge at the light irradiation. By erasing the charge in this way, a difference is generated in the charged potential of the photosensitive drum 1 to form an electrostatic latent image.

The developing device 5 contains a two-component developer in which a toner and a carrier are mixed, and a stirring chamber and a stirring roller for stirring the toner and the carrier; a stirring roller for transporting the two-component developer to the developing roller; And a developing roller for performing the following. The developing roller includes a magnet and a non-magnetic sleeve surrounding the outer periphery of the magnet, and forms a magnetic brush by attracting the two-component developer around the sleeve by magnetic force.

The developing device 5 selectively applies toner to the electrostatic latent image formed on the photosensitive drum 1 by approaching or rubbing the magnetic brush formed on the developing roller with the photosensitive drum 1. The toner image is formed on the photosensitive drum 1 by being adhered.

The toner image is transferred from the photosensitive drum 1 to the sheet 7 by the transfer device 6. The toner image transferred to the sheet 7 is heated and melted using a heat fixing device 8 and fixed on the sheet 7. Then, the toner remaining on the surface of the photosensitive drum 1 without being transferred to the sheet 7 is removed by the cleaner 2.

Next, an embodiment of the developing device 5 in the image forming apparatus will be described with reference to FIGS. FIG. 2 is a cross-sectional plan view of the developing device in the developing device 5, and FIG. 3 is a vertical sectional side view of the developing device and a block diagram of a control system.

The developing device 9 of the developing device 5 contains a two-component developer 10 and a developing roller 1 having a magnetic brush formed thereon.
The developing device housing 12 includes a part of the developing device 1 that is exposed to the outside. In the developing device housing 12, a partition wall 12 a that partitions a developing roller chamber 13 on the side close to the developing roller 11 and a stirring chamber 14 on the side far from the developing roller 11 is formed.
And stand in parallel. By separating both ends of the partition wall 12a from the inner side wall of the developing device housing 12, the two-component developer 10
To allow the developer to circulate through the developing roller chamber 13 and the stirring chamber 14.

The developing roller chamber 13 and the stirring chamber 14
Screw-shaped stirring rollers 15 and 16 for conveying the developing agent chamber 13 and the stirring chamber 14 in the direction of the arrow while stirring the component developer 10 are provided.

A toner hopper 18 for stocking the toner 17 is provided on the developing device housing 12, and a plurality of sub-toner inlets 19a to 19a to supply the toner 17 from the toner hopper 18 into the developing device housing 12. 19d and a main toner inlet 20 are provided. The auxiliary toner input ports 19 a to 19 d are positioned above the stirring roller 15 in the developing roller chamber 13 so that the developing roller 1 is parallel to the developing roller 11.
1, the main toner inlet 20 is
It is provided so as to be located on the stirring roller 16 of the stirring chamber 14.

Normally, toner is supplied from the main toner inlet 20. The main toner inlet 20 increases the amount of toner that can be replenished per unit time when compared with the sub toner inlets 19a to 19d. On the other hand, the amount of toner that can be replenished per unit time in the sub-toner inlets 19a to 19d is small. The auxiliary toner inlets 19a to 19a
9d is used so that toner is intensively supplied to a place where the toner concentration in the two-component developer 10 is partially reduced. The amount of toner supplied from each of the toner inlets 19a to 19d and 20 is individually controlled according to conditions. The control of the toner replenishment amount is performed by controlling the toner supply ports
d, toner supply roller 2 installed corresponding to 20
This is performed according to steps 1 and 22.

The toner 17 replenished in a large amount from the main toner inlet 20 into the stirring chamber 14 is sufficiently stirred in the stirring chamber 14 by the stirring roller 16,
, The unevenness in the toner concentration of the two-component developer 10 adsorbed on the developing roller 11 is suppressed.

FIG. 4 is a perspective view showing the toner hopper 18 and the toner supply rollers 21 and 22 in a see-through manner.

The toner replenishing roller 21 is composed of sponge rollers 21a to 21d divided so as to correspond to the respective sub toner input ports 19a to 19d, and the toner replenishing roller 22 is a single sponge roller corresponding to the main toner input port 20. Is constituted by the sponge roller 22. The sponge roller 22 is integrally driven by an external driving device (not shown) by a gear 23.
a to 21d are configured to be independently driven individually.

FIG. 5 is a vertical sectional side view of a drive mechanism for independently driving the sponge rollers 21a to 21d of the toner supply roller 21 individually.

Toner supply into the developing roller chamber 13 by the toner supply roller 21 is performed by the developing roller chamber 13.
Within the area where the toner density has decreased. Accordingly, the toner replenishing roller 21 includes a plurality of sponge rollers 21 a to 21
d can be driven independently and individually.

The drive shafts 24 for driving the sponge rollers 21a to 21d are four hollow shafts 24a to 24 having different thicknesses which are arranged concentrically and can be relatively rotated.
d. The innermost shaft 24a
Need not be hollow. Sponge roller 21a
Is attached to the innermost hollow shaft 24a, and the sponge roller 2
1b is attached to the outer hollow shaft 24b, the sponge roller 21c is further attached to the outer hollow shaft 24c, and the sponge roller 21d is attached to the outermost hollow shaft 24d. A gear 25a is mounted on the hollow shaft 24a, a gear 25b is mounted on the hollow shaft 24b, a gear 25c is mounted on the hollow shaft 24c, a gear 25d is mounted on the hollow shaft 24d, and each hollow shaft 24a to 24d is externally mounted. , So that the sponge rollers 21a to 21d can be independently rotated by being independently driven to rotate.

The overall toner concentration of the two-component developer 10 in the developing device housing 12 is determined by the two-component developer 10 in the stirring chamber 14.
Is detected by a toner concentration sensor 26 installed so as to detect the toner concentration of the toner, and a detection signal of the toner concentration sensor 26 is monitored by a toner concentration distribution monitoring device 27. The toner 17 in the toner hopper 18 is supplied from the main toner inlet 20 into the stirring chamber 14 by controlling the clutch control device 28 in such a manner. Then, due to bias in the print density of the image data, etc.,
When the toner in the component developer 10 is partially consumed and the toner density is partially reduced, the partial decrease in the toner density is detected by the toner density sensor 29, and the detection signal of the toner density sensor 29 is output. Is monitored by the toner concentration distribution monitoring device 27 to select the optimal sub-toner inlets 19a to 19d for toner replenishment for restoring the toner concentration in the portion where the toner concentration has decreased, and the selected optimum sub-toner inlet 19a The toner controller 17 controls the clutch control device 30 so as to rotate the sponge rollers 21a to 21d located at positions 19 to 19d to replenish the toner 17 in the toner hopper 18 to the developing roller chamber 13.

The toner concentration sensor 29 is located close to the developing roller 11 so as to detect the toner concentration of the two-component developer 10 in the developing roller chamber 13 at a plurality of places, and is arranged in parallel to the axial direction of the developing roller 11. A plurality of toner concentration sensors are arranged in a distributed manner, and a toner concentration distribution monitoring device 2
Reference numeral 7 selects the optimum sub-toner inlets 19a to 19d for recovering the toner density in the portion where the toner density has decreased based on the detection signals of these toner density sensors. In this selection, a plurality of sub-toner inlets 19a to 19d may be selected.

In this way, when the toner is partially consumed in a large amount and the toner density is partially reduced, the toner is partially replenished so that the two-component developer 1
It is possible to recover the bias of the toner concentration by replenishing the toner only in the region where the toner has been consumed without raising the toner concentration of 0 as a whole.

The toner supplied to the developing roller chamber 13 and the stirring chamber 14 is stirred by the stirring rollers 15 and 16 with the carrier. The stirring rollers 15 and 16 circulate the two-component developer 10 while stirring the carrier and the toner and make the two-component developer adhere to the developing roller 11 to form a magnetic brush on the surface of the developing roller 11 and form the magnetic brush on the photosensitive drum 1. The developed electrostatic latent image is developed.

The timing of toner supply and the selection of the toner inlets 19a to 19d and 20 are determined based on the positions of the toner density sensors 26 and 29 and the detection signals. FIG.
Is a dotted line A of the developing roller 11 of the developing device 9 shown in FIG.
3B illustrates the toner concentration distribution of the two-component developer 10 in FIG. Considering the case where the toner density partially decreases due to the rapid consumption of a part of the toner in the two-component developer 10, the toner density distribution at AB on the developing roller 11 is as shown in FIG. The toner concentration curve 31 shown in FIG. In such a state, when a portion where the toner density is lower than the control threshold value 32 occurs and the toner replenishment is performed by rotating the toner replenishing roller 22 to recover the toner density, the toner density after the toner replenishment becomes As shown by the toner density curve 33, the toner density rises uniformly, and the toner density distribution on the developing roller 11 becomes excessive in some areas.

Therefore, the toner concentration distribution monitoring device 27 in this embodiment monitors individual detection signals of a plurality of toner concentration sensors 29 installed in the vicinity of the developing roller 11 in an axially dispersed manner, and sets a threshold value. 32, the sub-toner inlets 19a to 19d most suitable for replenishing toner for restoring the toner density of the portion where the toner density sensor 29 which has output the detection signal below 32 are selected, and the corresponding sponge rollers 21a to 21d are selected. The toner 17 is replenished by rotating the 21d.

By executing such toner replenishment, the toner density on the developing roller 11 after toner replenishment is increased only in a portion where the density is reduced as shown by a toner density curve 34 in FIG. 5B. And can be adjusted uniformly.

FIG. 7 is a cross-sectional plan view of a developing device and a block diagram of a control system showing another embodiment of the developing device. The developing device 9 in this developing device is provided with a toner hopper 18 (not shown) on the developing device housing 12 similarly to the above-described embodiment, and the inside of the developing device housing 12 includes a developing roller chamber 13 and a stirring chamber 14. A developing roller 11 and stirring rollers 15 and 16 are provided, and a two-component developer 10 in which a toner and a carrier are mixed is accommodated in a developing device housing 12. The plurality of auxiliary toner inlets 19a to 19d are
The main toner inlet 20 is arranged above the agitating chamber 14 while being arranged above the developing roller chamber 13 in parallel with respect to 1. The developing device 5 includes a region-divided toner consumption calculating device 35 that calculates the toner consumption from the transferred print image data.

The region-divided toner consumption calculating device 35 calculates (predicts) the amount of toner consumption for each region from the print image data 36 and, based on the calculated toner consumption, the toner supply amount and the toner supply ports 19a to 19d for replenishment. , 20 are selected. The amount of toner consumed per dot is the development conditions such as the development bias and toner concentration of the developer, the environmental conditions around the development device such as temperature and humidity, and the print image data such as solid black and halftone dots. Fluctuates depending on the type. Therefore, the toner consumption amount M is set by the user or the controller and the environmental information E (T, H) such as the number of dots N in consideration of the printing state of the solid portion and the edge portion, the temperature T and the humidity H around the developing device, and the like. Using the developing condition C (Vb, Tc) such as the developing bias Vb and the toner concentration Tc, the value can be calculated from the relational expression of M = N × E (T, H) × C (Vb, Tc).

In this embodiment, the toner consumption M taking into account the type of print image data is calculated using pattern matching. Refer to the pattern
A template of n × n dots around the reference dot is used.
For the matching data, it is determined whether the reference dot is a solid dot or an edge dot, and the information for weighting the toner consumption in accordance with the determination is stored as consumption pattern data. Then, the amount of toner consumed to print the print image data 36 is calculated based on the information on the consumption pattern data and the environment information around the developing device such as temperature and humidity read by the environment sensor.

In this embodiment, as an example of a method of deriving the toner consumption M in consideration of the type of print image data, an example using pattern matching will be described. However, the present invention is not limited to this.

In order to calculate the toner consumption by such a pattern matching method and to perform the toner replenishment control, the region-divided toner consumption calculation device 35 uses the print image data 3
6 is divided into the same number or more as the number of sub toner inlets 19a to 19d, an area dividing unit 37, a consumption pattern data ROM 38 storing pattern information for calculating toner consumption, and a temperature around the developing device. Sensor 39 that captures environmental information such as temperature and humidity, and toner consumption calculation unit 40 that calculates toner consumption for each area
And a toner supply control buffer unit 41 for storing the calculated total amount of toner consumption for each divided area and issuing a toner supply instruction.

The area dividing unit 37 divides the sent print image data 36 into a plurality of areas in the axial direction of the developing roller 11. Toner consumption calculation unit 40
Calculates the toner consumption for each area of the divided print image data. This toner consumption is calculated using pattern matching that refers to information in the consumption pattern data ROM 38. The calculated toner consumption is accumulated by the toner replenishment control buffer unit 41 for each area, and when a predetermined amount or more of toner is consumed and the amount of toner is insufficient, the auxiliary toner input port 19a in the area where the amount of toner is insufficient is used. ~ 1
The sponge rollers 21a to 21d are rotationally driven by controlling the clutch control devices 28a to 28d so as to distribute the toner amount to be supplied to the 9d and the auxiliary toner inlets 19a to 19d around the 9d and supply the toner. After toner supply,
The accumulated toner consumption of the replenished area is returned to zero. If a situation occurs in which the toner is consumed almost uniformly in all areas, the sponge roller 22 is driven to rotate by controlling the clutch control device 39 so as to replenish the toner using the main toner inlet 20. Also at this time, if necessary, the toner is supplementarily supplied from the auxiliary toner inlets 19a to 19d to adjust the toner density distribution.

In the two embodiments described above, a method of actually measuring using a plurality of toner density sensors and a method of calculating based on print image data are separately described as a toner density detecting method for replenishing toner. However, the toner concentration in the two-component developer 10 is detected by combining the two methods in a complex manner.
More precise and stable toner density control can be performed.

[0046]

As described above, according to the present invention, the toner concentration of the two-component developer in the developing device is maintained within a predetermined concentration range even when the toner in the developer is partially rapidly consumed. Variations can be suppressed, and a developing device and an image forming device with less printing unevenness can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an image forming apparatus using a developing device of the present invention.

FIG. 2 is a cross-sectional plan view of a developing device of the developing device in the image forming apparatus shown in FIG.

FIG. 3 is a vertical sectional side view of the developing device shown in FIG. 2 and a block diagram of a control system.

FIG. 4 is a perspective view showing a toner hopper and a toner supply roller in the developing device shown in FIGS. 2 and 3 in a see-through manner;

5 is a vertical sectional side view of a driving mechanism of a toner supply roller in the developing device shown in FIG.

FIG. 6 is a characteristic diagram of a change in toner density distribution due to toner replenishment.

7 is a vertical sectional side view of a developing device and a block diagram of a control system showing another embodiment of the developing device in the image forming apparatus shown in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Cleaner, 3 ... Charger, 4 ...
Laser exposure device, 5: developing device, 9: developing device, 10
... two-component developer, 11 ... developing roller, 12 ... developing device housing, 13 ... developing roller chamber, 14 ... stirring chamber, 15, 16
... Agitating roller, 17 ... Toner, 18 ... Toner hopper, 19a-19d ... Sub toner inlet, 20 ... Main toner inlet, 21, 22 ... Toner supply roller, 21a-2
1d: sponge roller, 26, 29: toner concentration sensor, 27: toner concentration distribution monitoring device, 28, 30: clutch control device.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Susumu Edo 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Akira Shimada 7-1 Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 F term in Hitachi Research Laboratory, Hitachi, Ltd. (Reference) 2H077 AC04 AD06 BA08 DA10 DA42 DA78 DB01 EA03

Claims (8)

[Claims] A two-component developer in which a toner and a carrier are mixed is accommodated in a developing device housing, and the two-component developer is attracted to a developing roller while stirring to develop an electrostatic latent image. In a developing device that replenishes toner when the toner concentration of the two-component developer in the body is insufficient, the means for replenishing toner in the developing device housing includes a plurality of toner inlets arranged in the axial direction of the developing roller. And a means for independently controlling the amount of toner to be supplied from each toner input port. 2. A developing device according to claim 1, wherein said plurality of toner inlets are arranged in parallel with an axial direction of a developing roller. 3. The stirring roller according to claim 1, wherein the inside of the developing device housing is partitioned by a partition wall into a developing roller chamber near the developing roller and a stirring chamber far from the developing roller. Wherein the plurality of toner inlets are provided above a developing roller chamber. 4. A developing device according to claim 3, wherein a toner inlet having a larger toner supply capacity than said plurality of toner inlets is provided above said stirring chamber. 5. A method according to claim 1, further comprising means for estimating a partial toner consumption in the developing device housing based on the print image data, and supplying a plurality of toners based on the estimated toner consumption. A developing device provided with a means for controlling a toner supply amount from a mouth. 6. A toner concentration distribution monitoring device according to claim 1, wherein the plurality of toner concentration sensors, a toner concentration distribution monitoring device for monitoring the toner concentration distribution in the developing device, and a monitoring result of the toner concentration distribution monitoring device. A means for controlling the amount of toner supplied from a plurality of toner inlets. 7. The developing device according to claim 4, wherein the toner inlet having a large toner replenishing capacity is used for toner replenishment for adjusting the overall toner concentration of the two-component developer. 8. An image forming apparatus comprising the developing device according to claim 1.