JPH09106169A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the precise control of toner concentration and improvement in image quality by controlling the toner concentration, based on the peak value of the output ripple of a magnetic permeability sensor. SOLUTION: The toner concentration is controlled, based on the top (peak value) of the output ripple of the magnetic permeability sensor 14. By using the peak value of the output ripple as control data in such a way, it does not drop below a reference value even if the level of developer in a developing device 5 becomes low due to a temporary toner concentration decrease, therefore toner is supplied from a toner bottle 16 and proper toner concentration is maintained. Where the number of the rotations of a carrying member 10 is (r), (rpm), the data of the magnetic permeability sensor 14 divided at regular intervals, equal to or longer than 60/r(sec), is the peak value of each interval, and it is preferable that an average value in a fixed period of time be used as the control data. Thus, the toner concentration can be controlled more precisely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer or a fax machine, and more particularly to a type using a two-component developer and a magnetic permeability sensor for controlling the toner density. Image forming apparatus.

[0002]

2. Description of the Related Art In this type of image forming apparatus, there is a demand for downsizing and cost reduction, and accordingly, a developing device as a part thereof is also required to be small. From this point of view, in the developing device, two conveying members 32 with the blade-shaped members 30 as shown in FIGS. It has a compact structure that conveys and circulates while mixing and stirring in different directions. In addition, a magnetic permeability sensor is provided in the middle of the conveyance of the developer to output the magnetic permeability of the developer as a voltage, and the toner is replenished based on the difference between the reference voltage and the average value of the detected voltage. The toner density is controlled.

[0003]

By the way, in an image forming apparatus having such a compact developing device,
Due to its compact structure, it is not possible to secure a sufficient amount of developer in the developing device, so the up-down fluctuation of the developer surface (developer volume) accompanying image output is large. When the above-described transport member 32 is used, the developer is transported in only one direction, so the developer is in a dense state on the front side F of the blade-shaped member 30 and the back side R.
Then it will be in a rough state. The output value of the magnetic permeability sensor at this time is represented as a ripple having a peak portion H and a valley portion L as shown in FIG. The peaks H of the ripple correspond to the state where the developer is dense, and the valleys L correspond to the state where the developer is coarse.

However, when the toner density is temporarily low, that is, when images having a high image area ratio are continuously output, the bulk of the developer is reduced and the magnetic permeability sensor is used. The amount of developer in the area is reduced. As a result, normally, the sensor output as shown in FIG.
The ripple becomes large as shown in. This is because when the developer is sufficiently present, it is detected that the toner concentration is low, and when the amount of the developer is small, it is detected that the toner concentration is high. A ₁ becomes a level when the toner concentration is high and falls below the reference value A _0, and as a result, toner is not replenished even though it is in a state where it is necessary to replenish toner in the developing device. As described above, in the conventional case, it is difficult to accurately control the toner density by the magnetic permeability sensor.

An object of the present invention is to provide an image forming apparatus capable of controlling the toner density with high accuracy even when the toner density is temporarily lowered, and thus contributing to the improvement of image quality. To do.

[0006]

According to the present invention, since the valley portion of the output ripple is in a rough state in which a gap of air is generated in the developer due to the rotation of the conveying member, the output value of the magnetic permeability sensor is It is difficult to say that the toner density of the developer is correctly represented because it has decreased, and it is not correct to control the toner density by using the average value of the output data of the valley portion and the mountain portion as data. Is based on. Based on this idea, in the invention according to claim 1, the toner density is controlled by replenishing the toner according to the output of the magnetic permeability sensor attached to the developing device, while having the toner recycling mechanism. In an image forming apparatus having a conveying member for stirring, mixing, and conveying the developer in one direction above the sensor, the toner concentration is controlled based on the peak value of the output ripple of the magnetic permeability sensor. , Is adopted.

According to a second aspect of the present invention, in the structure of the first aspect, when the number of revolutions of the conveying member is r (rpm), the data of the magnetic permeability sensor is 60 / r (s).
ec) A configuration is adopted in which the peak value at each interval when divided at constant intervals above and the average value thereof at a certain constant time are used as control data for toner concentration control.

[0008]

An embodiment of the present invention will be described below with reference to FIG. The image forming apparatus 2 includes a photoconductor 4 and a developing device 5. The developing device 5 includes a developing sleeve 6 for supplying toner to the photoconductor 4 and two developing sleeves 6 extending along the developing sleeve 6. The transport members 8 and 10 are arranged side by side on a horizontal plane. A partition plate 12 partitions the space between the transport members 8 and 10 to divide the transport path. Further, a magnetic permeability sensor 14 for measuring the magnetic permeability of the two-component developer is provided at an intermediate position of the conveying member 10, and the toner concentration is controlled based on the detection data of the magnetic permeability sensor 14. It has become. A toner bottle 16 extending along the conveying member 10 is provided beside the conveying member 10, and the toner is supplied to the front side of the conveying member 10 based on the control of the toner concentration. Reference numeral 18 is a charger, 19 is a doctor blade, 20 is a cleaning blade, and 21 is a cleaning blade.
Indicate transfer devices, respectively. Further, reference numeral 22 denotes a cleaning toner carrying screw which constitutes a part of the toner recycling mechanism, and the residual toner sent to the front side of the apparatus by the cleaning toner carrying screw 22 is carried by the carrying belt mechanism (not shown). It is designed to be supplied to the front side of.

The image forming operation of the image forming apparatus 2 will be briefly described. First, the photoconductor 4 is neutralized by the neutralization light, and the surface potential is averaged to the reference potential. Next, after being charged by the charger 18, it is exposed at the exposure portion, and the surface potential of the image portion not irradiated with light is maintained, so that the toner on the developing sleeve 6 adheres to the image portion. The photoconductor 4 on which the toner image is formed is rotationally moved, and the transfer paper is sent from a paper feeding unit (not shown) at a timing such that the front end of the paper and the front end of the image are aligned by the transfer device 21, and the photoconductor 4 is transferred by the transfer device 21. The toner image on the surface 4 is transferred to the transfer paper. The transfer sheet is sent to a fixing unit (not shown), the toner is fused to the transfer sheet by heat and pressure, and is ejected as a copy. On the other hand, the residual toner remaining on the photoconductor 4 is scraped off by the cleaning blade 20, and then the residual charge is eliminated by the elimination light, leaving a toner-free state and moving to the next image forming step again. .

The conveying members 8 and 10 each have a stirring blade as shown in the conventional example, and are driven so as to convey the developer in different directions. A communication path for circulating the developer is formed on the front side and the depth side of the partition plate 12. The developer is conveyed while being stirred and mixed in the depth direction by the conveyance member 10, and is supplied to the conveyance member 8 side via the depth communication path. The developer is conveyed in the front direction while being stirred and mixed by the conveying member 8, and at this time, the toner is supplied to the developing sleeve 6. Further, the developer carried by the carrying member 8 is supplied to the carrying member 10 side via the communication path on the front side.

The toner concentration is controlled based on the peak portion (peak value) of the output ripple from the magnetic permeability sensor 14. If the peak value of the output ripple is used as the control data in this way, as shown in FIG. 6, even if the toner concentration temporarily decreases and the volume of the developer in the developing device 5 decreases, the reference value A0 falls below the reference value A0. Therefore, the toner is supplied from the toner bottle 16 and the proper toner concentration is maintained.

FIG. 2 shows another embodiment. In the above embodiment, the peak value of the output ripple is simply used as the control data. However, as shown in FIG. 2, when the number of revolutions of the conveying member 10 is r (rpm), the data of the magnetic permeability sensor 14 is 60 /. The peak value of each interval when the interval is divided by a constant interval of r (sec) or more, and the average value thereof in a certain constant time is used as control data for toner concentration control. For example, the rotation speed of the transport member 10 is 300
In the case of rpm, the data of the magnetic permeability sensor 14 is set to a peak value when the data is divided at regular intervals of 0.2 sec, and the average value of all 15 data when it is performed for 3 sec is used to control the toner density. Control data for In this way, the error in the peak value can be optimized, and the toner density can be controlled with high accuracy.

[0013]

According to the present invention, the toner density is controlled based on the peak value of the output ripple of the magnetic permeability sensor. Therefore, even if the toner density is temporarily lowered, the current toner density can be maintained. It is possible to perform a correct control that is suitable for the image, and thus it is possible to improve the image quality. Further, when the total average value of the peak values in the cycle divided for each fixed period within a fixed period is used as the data, the toner density can be controlled with higher accuracy.

[Brief description of the drawings]

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

FIG. 2 is a graph showing a usage model of a peak value of output ripple.

FIG. 3 is a side view of a transport member.

FIG. 4 is a perspective view of a transport member.

FIG. 5 is a graph showing normal output ripple.

FIG. 6 is a graph showing an output ripple when the toner density is temporarily lowered.

[Explanation of symbols]

 5 Developing Device 14 Permeability Sensor 8 and 10 Conveying Member

Claims (2)

[Claims] 1. A toner recycling mechanism is provided, and
The toner density is controlled by supplying toner according to the output of the magnetic permeability sensor attached to the developing device,
In an image forming apparatus having a conveying member for stirring, mixing, and conveying the developer in one direction above the magnetic permeability sensor, the toner concentration of the toner concentration is determined based on the peak value of the output ripple of the magnetic permeability sensor. An image forming apparatus characterized by performing control. 2. When the number of revolutions of the conveying member is r (rpm), the data of the magnetic permeability sensor is 60 / r (se).
c) The peak value for each interval when the above-described intervals are divided, and the average value for a certain fixed time is used as control data for toner concentration control. Image forming apparatus.