JPH1195537A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain, in the image forming device equipped with a developing device of a two-component development system, a defect-free, satisfactory image every time by correctly detecting the concentration of toner even in case an amount of the electrification of the toner and its volume change, and accurately controlling the concentration of the toner. SOLUTION: The image forming device has a toner replenishment device 18 for replenishing the developing device 2 with the toner, toner-concentration detection means for detecting the concentration of the toner of the two- component developer in the developing device, and a toner concentration control means 25 which controls the toner replenishment device 18 based on the value of the output of the toner concentration detection means. In the image forming device, toner concentration detection sensors 19A and 19B, as the toner concentration detection means, are provided in two areas, one above the center of a stir member 4 which stirs the developer and the other below. By computing for the comparison of the outputs of the upper and lower sensors with each other, the concentration of the toner can be detected correctly even in case the amount of the electrification of the toner and the volume of it change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art Image forming apparatuses such as copying machines, printers, and facsimile machines generally rotate an image carrier such as a photoreceptor by a driving means such as a motor, and form an electrostatic image on the image carrier by a latent image forming means. A latent image is formed, and the electrostatic latent image is developed by a developing device into a toner image. The toner image is transferred to a transfer material such as transfer paper by a transfer unit, and then the toner image on the transfer material is fixed by a fixing device. The image is fixed and output as an image.

As a developing device of the image forming apparatus, for example, a developing device of a two-component developing system for developing an electrostatic latent image on an image carrier with a two-component developer composed of toner and carrier is known. In the developing device of the two-component developing system, the toner and the carrier are charged by stirring by a stirring member or the like, and then conveyed to a position facing the image carrier by the developer carrier, and the toner in the developer is transferred onto the image carrier. The electrostatic latent image is developed and visualized by electrostatically adhering to the electrostatic latent image. By repeating this developing operation, only the toner in the developing device is consumed. Therefore, the developing device is provided with a toner replenishing device, and the toner replenishing device is used to keep the toner concentration in the developing device constant. Is replenished.

In recent years, a developing device in which a plurality of developer stirring / conveying members for stirring and conveying a two-component developer and a developer carrying member are arranged in a horizontal direction has been widely used. This is because the developing device can be manufactured at a low cost with a simple configuration and can be downsized.
A toner replenishing device for replenishing toner to the developing device is often configured to replenish toner from an end on a developer stirring and conveying member side in order to take advantage of downsizing of the unit.

In the image forming apparatus, the toner density of the two-component developer is detected by detecting the magnetic permeability of the two-component developer in the developing device by a toner density detection sensor, and the toner density control means is provided. Controls toner supply by the toner supply device based on the output value of the toner density detection sensor.

[0006]

In an image forming apparatus such as a copying machine, a printer, a facsimile, or the like, when a developer is left unused for a long time from manufacture to use, particularly, two components are used. In the case of a developer in a developing device using a developing method, a phenomenon in which the charge amount and the bulk of the toner are reduced due to being left for a long time may occur. On the other hand, when used continuously, the charge amount of the toner increases.

In the small-sized developing device described above, since the amount of developer in the device is small, when the charge amount of the toner is reduced as described above, the toner easily falls and the background is stained. Conversely, if the charge amount of the toner increases, the density decreases. Furthermore, the output value of the toner density detection sensor also fluctuates depending on the charge amount. This causes a phenomenon in which the output value of the toner concentration detection sensor changes due to a decrease in the charge amount and bulk of the toner, although the toner concentration of the initial developer is constant. This is because the output value of the toner density detection sensor should be constant if the toner concentration of the developer at the time of shipment is constant, but the output value of the toner density detection sensor is reduced due to the decrease in the charge amount. Changes to a lower output value, the toner concentration control means determines that the amount of toner is small, and causes the toner replenishing device to replenish the toner.
When the toner concentration becomes higher than the target, the background smear and the toner drop become serious.

The present invention has been made in view of the above circumstances, and it is possible to accurately detect the toner density even when the charge amount or bulk of the toner fluctuates, to stabilize the image density, and to prevent background contamination. It is an object of the present invention to provide an image forming apparatus capable of always obtaining a good image without an abnormal image such as toner dust and toner scattering.

[0009]

According to a first aspect of the present invention, there is provided an image carrier, a latent image forming means for forming an electrostatic latent image on the image carrier, and A developing device for developing the electrostatic latent image on the carrier with a two-component developer to make it visible, a toner replenishing device for replenishing toner to the developing device, and a two-component developer in the developing device. A toner density detecting means for detecting the toner density, and a toner density controlling means for controlling the toner replenishing device based on an output value of the toner density detecting means, wherein the toner image on the image carrier is transferred by the transferring means. In an image forming apparatus that transfers an image onto a transfer material to form an image and outputs the image, a toner concentration detecting unit that detects a toner concentration of a two-component developer in the developing device is provided at a center of a stirring member that stirs the developer. 2 above and below It is obtained characterized by including at. As described above, the toner concentration detecting means is provided at two positions: the upper position and the lower position from the center of the stirring member for stirring the developer.
Provision at multiple locations enables accurate detection of toner density even when the charge amount or bulk of the toner fluctuates, stabilizes image density, and eliminates abnormal images such as background contamination, toner dust, and toner scattering. It is possible to always obtain a proper image.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the toner density control means includes a toner density control unit provided at two positions above and below the center of the stirring member. The amount of toner replenishment is determined by calculating the output of the detecting means. By calculating the outputs of the two toner density detecting means in this way, a change in bulk can be properly detected and the toner density can be accurately determined. Good control can be achieved.

The invention according to claim 3 is the invention according to claim 1 or 2
In the above-described image forming apparatus, the two toner density detecting units are attached at positions substantially facing the developing device. By mounting at the facing position, it is possible to appropriately control the change in bulk and accurately control the toner concentration.

According to a fourth aspect of the present invention, in the image forming apparatus of the first, second or third aspect, the toner density detecting means below the center of the stirring member is a developer among the two toner density detecting means. And the upper toner concentration detecting means is not in contact with the developer. Thus, one of the toner concentration detecting means is provided at a position always in contact with the developer, and the other By providing the density detecting means at a position not in contact with the developer, it is possible to appropriately control the change in bulk and accurately control the toner density.

The invention according to claim 5 is the invention according to claims 1, 2, 3
5. The image forming apparatus according to claim 4, wherein a stirring blade of a stirring member is not provided between said two toner concentration detecting means. By not providing the stirring blade of the stirring member in between, it is possible to suppress the variation in the bulk depending on the position of the stirring blade, and it is possible to appropriately control the change in the bulk and more accurately control the toner concentration.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a schematic structural view of an image forming apparatus showing an embodiment of the present invention. This image forming apparatus charges a drum-shaped photosensitive member 1 as an image carrier and the photosensitive member 1. A charging roller 14 as an example of a charging unit, a latent image forming unit that irradiates the charged photoconductor 1 with light 15 (or light corresponding to a document image) 15 according to image information, and forms an electrostatic latent image. A developing device 2 for developing the electrostatic latent image on the photoreceptor 1 with a two-component developer to visualize the toner; a toner replenishing device 18 for replenishing the developing device 2 with toner; Toner concentration detection sensor 1 for detecting the toner concentration of a component developer
9A and 19B, and the toner concentration detecting sensors 19A and 1B.
And a control unit 25 for controlling the toner replenishing device 18 based on the output value of the toner image 9B. After the toner image on the photoreceptor 1 is transferred onto a transfer material by a transfer roller 16 as a transfer unit,
The image is fixed by a fixing device (not shown), formed as an image, and output. Hereinafter, a more specific configuration of the image forming apparatus according to the present invention will be described.

FIG. 2 is a schematic sectional view of a developing device portion of the image forming apparatus according to the present invention. 1 and 2, a drum-shaped photosensitive member 1 as an image carrier is rotated in the direction of an arrow by a driving unit such as a motor during image formation.
A developing device 2 covered with a casing is provided at a predetermined portion around the photoconductor 1. The developing device 2 has a predetermined length in a direction penetrating the paper surface in accordance with the photoconductor 1, and a developing sleeve 5 which is a developer carrier is disposed closer to the photoconductor 1 than the opening of the developing device 2. It is rotatably supported.

Further, a first stirring member 3 and a second stirring member 4 for stirring and transporting the developer are sequentially disposed adjacent to the developing sleeve 5 and are supported by the shaft. The first stirring member 3 and the second stirring member 4 Are provided with a large number of stirring blades each having a function of stirring and transporting a two-component developer composed of a toner and a carrier. The first stirring member 3 and the second stirring member 4 are
The two-component developer composed of toner and carrier is rotated and driven by a drive unit such as a motor to stir and transport the two-component developer, and the two-component developer is circulated in the developing device 2 via the developing sleeve 5.

The first stirring member 3 and the second stirring member 3 in the developing device 2
A long opening 6 is formed in a portion above the specific region that straddles the stirring member 4 in a direction penetrating the paper, and an elongated box-shaped developer container 7 is provided detachably with respect to the developing device 2 in accordance with the opening 6. ing. The attaching / detaching means for attaching / detaching the developer container 7 to / from the developing device 2 is such that the locking convex portion 7a of the locking convex portions 7a and 7b protruding from the side of the developing container 7 is formed on the developing container 2 side. Locking portion 2a of locking portions 2a, 2b
The developer container 7 is detachably attached to the developing device 2 by adopting a structure in which the developer container 7 is attached to the developing device 2 by inserting the developer container 7 into the developing device 2 by inserting the engaging convex portion 7b on the engaging portion 2b. .

FIG. 2 shows a state immediately after the developer container 7 is mounted on the developing device 2. The opening of the developer container 7 is set downward, and the opening is a heat seal 9 as a sealing member. The developer container 7 is hermetically closed by being closed. Inside the developer container 7, a developer 10 and a dehumidifier 11 are enclosed. In this enclosed state, the developer 10 can flow in the developer container 7 while being simply filled in the developer container 7, but the dehumidifier 11 is provided on the side of the opening 6 provided with the heat seal 9. Since it is fixed to a portion corresponding to the bottom on the opposite side by bonding or the like, it does not drop when mounted in the state of FIG.

The heat seal 9 can be easily pulled out with the developer container 7 attached to the developing device 2 as shown in FIG. When the heat seal 9 is pulled out, the developer container 7 and the developing device 2 are in communication with each other, and the developing container 7
The developing agent 10 falls into the developing device 2 but the dehumidifying agent 11
Remain in the developer container 7. Thus, the developer container 7
Until the heat seal 9 is pulled out, the developer 10 and the dehumidifier 11 are sealed in the developer container 7.

Of the developer that has fallen into the developing device 2, the toner is consumed at each development, and new toner is supplied from the toner bottle of the toner replenishing device (not shown) into the developing device 2 to supplement the consumed toner. Is replenished. Since the developer container 7 communicates with the inside of the developing device 2, after the heat seal 9 is pulled out, the dehumidifying agent 11 performs the dehumidifying function in the developing device 2, and the developer 10 in the developing device 2 has a charging characteristic due to humidity. Is prevented from being reduced.

FIG. 3 is a schematic sectional view showing a more specific configuration example of the image forming apparatus according to the present invention. The developing device 2 is integrally formed with a photoconductor case 13 that supports the photoconductor 1, and these constitute a photoconductor unit 22. The photoconductor 1 rotating in the clockwise direction is first uniformly charged by a charging roller 14 as a charging unit, and is intensified according to image information from a writing unit (writing unit using laser light, LED light, or the like) as an exposure device (not shown). The modulated exposure light 15 is irradiated and exposed, whereby image information is written and an electrostatic latent image is formed. The exposure device may be of a type that exposes a document image to a photoconductor.

The electrostatic latent image on the photoreceptor 1 is
Is developed by the developer carried by the developing sleeve 5 and is visualized to form a toner image. A transfer bias is applied from a power supply (not shown) to the transfer roller 16 as a transfer unit, and the transfer paper fed from a paper supply device (not shown) is exposed to light when passing through a nip portion between the transfer roller 16 and the photoconductor 1. The toner image on the body 1 is transferred by the transfer roller 16,
After the transfer paper on which the toner image has been transferred is separated from the photoreceptor 1, the toner image is fixed by a fixing device (not shown) and is discharged to a discharge tray or the like.

On the other hand, the residual toner is removed from the photoreceptor 1 by the cleaning blade 17a of the cleaning device 17 after the transfer of the toner image, and the photoreceptor 1 is discharged by a discharge light 220 from a discharger (not shown). Cleaning blade 1
The residual toner scraped off from the photoreceptor 1 by the device 7 or the like falls into a collection container provided in a part of the photoreceptor case 13 and is sent to the axial end of the transport screw 20 by the rotation of the transport screw 20. Recycled belt 21
To the developing device 2. The toner sent to the developing device 2 is mixed with the developer, and the developer includes:
The new toner supplied from the toner bottle 18a of the toner supply device 18 by the first stirring member 3 and the second stirring member 4 is mixed and sent to the developing sleeve 5.

The developing device 2 has the developing container 7 as described above.
Are provided detachably. FIG. 3 shows a state before the heat seal 9 is pulled out. In this state, the developer 10 is still in the developing container 7. From the developing container 7 to the heat seal 9
, The developer 11 in the developing container 7 falls into the developing device 2, and the developer 11 is stirred by the first stirring member 3 and the second stirring member 4 and is conveyed through the developing sleeve 5. This circulates through the developing device 2. The dehumidifier 11 has a function of dehumidifying the inside of the developing device 3 after the heat seal 9 is pulled out.

The toner in the toner bottle 18a is supplied from the toner replenishing device 18 to the opening of the developing device 2 formed above the second stirring member 4 via a path shown by an arrow.
The toner consumed by the developing operation is supplemented. Toner density detection sensors 19A and 19 as toner density detection means
B detects the toner concentration of the two-component developer in the developing device 2 and, for example, detects the toner concentration of the two-component developer by detecting the magnetic permeability of the two-component developer in the developing device 2; The amount of toner supplied from the toner bottle 18a is controlled based on the detection information of the toner concentration detection sensors 19A and 19B as described later.

FIGS. 4 and 5 show the appearance of the photosensitive unit 22. FIG. FIG. 4 shows a state in which the developer container 7 is mounted on the developing device 2, and FIG. 5 shows a state in which the developer container 7 of the developing device 2 is removed. As described above, the locking protrusions 7a and 7b are formed on the developer container 7, while the locking portions 2a and 2b combined with the locking protrusions 7a and 7b are formed on the developing device 2. With these combinations, the developer container 7 is made detachable from the developing device 2.

As shown in FIG. 6, the second stirring member 4 is
A screw is formed at a portion longer than the stirring member 3 (on the front side) and longer than the first stirring member 3.
The second stirring member 4 is provided with a number of stirring blades 4h having a shape obtained by cutting an elliptical plate into approximately half at a position inside the portion where the screw is formed, and provided obliquely with respect to the axis. Is agitated in accordance with the rotation of the second agitating member 4 and is simultaneously conveyed. The developer conveying direction due to the rotation of the second stirring member 4 is the direction of arrow A. Similarly, the first stirring member 3
A similar stirring blade 3h is formed corresponding to the arrangement area of the stirring blade 4h formed on the second stirring member 4. The inclination of the stirring blade 3h formed on the first stirring member 3 is opposite to the inclination of the stirring blade 4h of the second stirring member 4, and the developer is moved by the first stirring member 3 according to the rotation of the arrow B in accordance with its rotation. Sent in the direction.

A partition plate 24 is provided between the first stirring member 3 and the second stirring member 4, and the partition plate 24 separates the first stirring member 3 from the second stirring member 4. The developing sleeve 1 has a fixed shaft in which five-pole magnets are arranged,
The non-magnetic pipe material covering the outer peripheral surface is rotationally driven by a driving unit (not shown). The developer is sent to the developing sleeve 1 by the magnetic attraction of the developing sleeve 1 while being sent in the direction of arrow B according to the rotation by the first stirring member 3.

The remaining developer moves to the second stirring member 4 side from the gap on the near side that is separated from the partition plate 24, is sent in the direction of arrow A by the second stirring member 4, and is It moves to the first stirring member 3 from the gap. As described above, basically, the developer is circulated in a loop by the first stirring member 3 and the second stirring member 4 with the partition plate 24 interposed therebetween. The developing sleeve 1 magnetically attracts the developer by an internal magnet and conveys the developer along with the rotation. The developer on the developing sleeve 1 is regulated to a fixed amount by a doctor blade 8, and the developing sleeve 1 The electrostatic latent image on the photoreceptor 1 is developed when the electrostatic latent image passes between them.

Here, the toner in the toner bottle 18a is replenished into the developing device 2 with the opening / closing lid 23 opened as shown in FIGS. Toner supply position 1 of developing device 2
Numeral 8 denotes a screw portion formed on the second stirring member 4 as shown in FIG. 6, that is, on a screw portion 4a outside a portion where the partition plate 24 and the stirring blade 4h are formed. Screw portion 4b axially outside of screw portion 4a
The waste toner scraped off from the photoreceptor 1 is sent by the recycling belt 21 for reuse.

Therefore, the screw portion 4 of the second stirring member 4
b, the waste toner is fed into the screen portion 4a, and the new toner is mixed with the waste toner. The waste toner and the new toner are fed into the developer in the loop circulation path and stirred by the stirring blade 4h. Conveyed. The toner is in an insufficiently charged state at the initial stage of stirring, and it is not preferable that the insufficiently charged toner crosses the partition plate 24 and is subjected to development. Is set higher than other parts.

As shown in FIG. 1, the toner replenishing device 18 replenishes toner from the toner bottle 18a to the developing device 2 by the operation of a toner replenishing drive portion 18b composed of a motor or a clutch.
Is controlled by an image forming apparatus control circuit 25 which is a control means configured by using The operation panel 27 has an operation unit and a display unit including a number of keys operated by the user. The image forming apparatus control circuit 25 controls each part of the image forming apparatus using input signals from the toner density detection sensors 19A and 19B, various other sensors, and the operation panel 27, and performs image forming operation and the like as described above. Is performed.

The configuration example of the image forming apparatus according to the present invention has been described above. However, in the above-described two-component developing apparatus, the case where the toner density is maintained at a high level or the case where magnetic toner is used is used. When a magnetic permeability sensor is used as the toner density detection sensor, the detection value of the toner density detection sensor may be greatly affected by the bulk of the toner due to the influence of the toner charge amount and the toner magnetic force.
If the developer is not used for a long time after being manufactured and used, the charge of the toner will be discharged, and the phenomenon that the charge amount of the toner decreases and the bulk density increases will occur. . When the bulk density of the toner is increased as described above, there is a case where the toner concentration detection sensor is provided only in the lower portion as in a conventional developing device generally used (in a conventional two-component developing device, the lower side of FIGS. Only the toner density detection sensor 19A) is provided, the output value Vt of the toner density detection sensor detects the toner density lower than the actual value due to the decrease in the bulk of the toner. On the other hand, when continuous paper passing is performed, the stirring of the developer by the stirring member is performed continuously, and excessive frictional charging increases the toner charge amount and increases the bulk. The toner density is detected to be higher than that.

Therefore, in the present invention, as shown in FIGS. 1, 2 and 3, the toner concentration detecting means is provided at two positions above and below the center of the second stirring member 4 which is a developer stirring means. Are provided with the toner concentration detection sensors 19A and 19B, thereby correcting variations in measured values due to changes in the bulk of the toner. Hereinafter, embodiments of the claimed invention will be described.

(Embodiment 1) In an embodiment of the present invention, as shown in FIGS. 1, 2 and 3, magnetic permeability is detected at two locations above and below a second stirring member 4 for stirring and transporting a developer. There are provided toner concentration detection sensors 19A and 19B, which are sensors. These two toner density detection sensors 19A and 19B
Are installed at the same position in the axial direction of the second stirring member 4 so as to face each other. Here, the toner concentration detection sensor 19A provided below the center position of the second stirring member 4 is referred to as a toner concentration detection sensor A, and the toner concentration detection sensor 19B provided above is referred to as a toner concentration detection sensor B. The sensitivities of these toner density detection sensors A and B are determined by the layout, and the two sensors used this time have different sensitivities. These toner concentration detection sensors A and B are both set to output 2.0 V at a target toner concentration of 5 wt% and a toner charge amount of 25 μC / g.

FIGS. 7A and 7B show the relationship between the toner densities of the toner density detection sensors A and B and the sensor outputs. As is clear from FIG. 7, when the toner charge amount decreases, the toner density detection is performed. The output of the sensor A increases, and the output of the toner density detection sensor B decreases. Conversely, when the toner charge amount increases, the output of the toner density detection sensor A decreases and the output of the toner density detection sensor B increases. As described above, since the change in the output with respect to the change in the toner charge amount has the opposite characteristic between the sensor A and the sensor B, the change in the output of the toner density detection sensor A and the change in the output of the toner density detection sensor B can be detected. Thus, a change in the toner charge amount can be detected. Therefore, the toner density control means (the image forming apparatus control circuit 25 shown in FIG. 1) detects a change in the output of the toner density detection sensor A and a change in the output of the toner density detection sensor B to detect a change in the toner charge amount, and By properly controlling the toner density while appropriately detecting the change in the toner density, it is possible to maintain a good image without an abnormal image.

(Embodiment 2) A toner concentration control means for determining a toner supply amount based on a calculation result of the output of the toner concentration detection sensor A and the output of the toner concentration detection sensor B and replenishing the toner. It is about. FIG. 8 is a flow chart showing a part of the control operation by the toner density control means according to an embodiment of the present invention. Hereinafter, an example of a process performed by the toner density control unit in the present embodiment will be described. 1 and 8, the image forming apparatus control circuit 25 serving as a toner density control unit stores the output values of the toner density detection sensor A (19A) and the toner density detection sensor B (19B) for each image forming operation. Execute The stored output values are obtained by first sampling the output values Vta and Vtb of the toner density detection sensors A and B during operation and taking in the data at a plurality of points (n points), and then averaging these n points Vta 'and Vtb'. And calculate the average value Vt
a 'and Vtb' are stored in the internal memory of the control circuit 25 (S1, S2). This value is updated every time an image forming operation is performed. Then, a value Vt '= Vta' + Vtb 'obtained by calculating the sum of the average value Vta' of the output of the sensor A and the average value Vtb 'of the output of the sensor B is calculated (S
3) By comparing the value Vt 'with the reference value Vref of toner supply, the presence or absence of toner supply is determined (S4, S4).
5). That is, ΔVt = Vt′−Vref is obtained, and ΔVt>
When it is 0, the amount of toner replenishment is estimated according to the value of ΔVt,
The toner is supplied (S6, S7). When ΔVt <0, the process ends without performing toner supply.

According to this toner density control method, as shown in FIG. 7, the toner density detection sensors A and B increase the output of the sensor A and decrease the output of the sensor B when the toner charge amount decreases. Conversely, when the toner charge increases, the output of the sensor A decreases, and the output of the sensor B increases, so that the sum of the outputs is substantially constant. Can be accurately detected and toner can be supplied. Therefore, by using the two toner concentration detection sensors A and B in this manner, a change in bulk can be properly captured and the toner concentration can be accurately controlled, so that a good image without an abnormal image can be maintained. Can be.

(Embodiment 3) FIG. 9 is a view showing one embodiment of the third aspect, and is an explanatory view of the installation positions of two toner density detecting sensors. FIG. 9 schematically shows a cross section of the sensor installation position of the developing device when viewed from two directions.
(A) is a cross section perpendicular to the axis of the stirring member, and (b) is a cross section parallel to the axis of the stirring member. In the third embodiment, FIG.
As shown in (2), toner concentration detection sensors A (19A) and B (19B) provided at two locations above and below the second stirring member 4 are attached at positions substantially facing each other. This is because by providing the two toner density detection sensors A and B at positions substantially facing each other, the change in bulk can be detected most efficiently. That is, when the two sensors A and B do not face each other, a case may occur where the output of the sensor B does not change even if the output of the sensor A changes, and in such a case, the toner This causes the concentration to vary. Therefore, in this embodiment, by installing the sensors A and B facing each other as shown in FIG. 9, it is possible to appropriately control a change in bulk and accurately control the toner density, and to obtain a good image without any abnormal image. Can be maintained.

(Embodiment 4) FIG. 10 is a view showing an embodiment of claim 4 and is an explanatory view of the relationship between the installation positions of two toner density detection sensors and the developer. FIG. 10 schematically illustrates a cross section of the sensor installation position of the developing device as viewed from two directions, where (a) is a cross section perpendicular to the axis of the stirring member.
(B) is a cross section parallel to the axis of the stirring member. In the embodiment of FIG. 4, as shown in FIG. 10, the toner concentration detection sensors A (19) provided at two places above and below the second stirring member 4 are provided.
A) and B (19B), the lower toner concentration detection sensor A is provided in the developer so as to always contact the developer, and the upper toner concentration detection sensor B is normally in contact with the developer. It is provided at a position where it does not. This is because the sensor A detects the toner density in a state where the bulk density is increased by being left alone, and the sensor B detects the change in the height of the bulk. This is for efficient detection. By installing the toner concentration detection sensors A and B in this manner, a change in the bulk of the toner can be appropriately captured, the toner concentration can be accurately controlled, and a good image without an abnormal image can be maintained. .

(Embodiment 5) FIG. 11 is a view showing one embodiment of the fifth aspect, and is an explanatory view of the relationship between the installation positions of two toner concentration detection sensors and the stirring blades of the stirring member.
FIG. 11 schematically shows a cross section of the sensor installation position of the developing device when viewed from two directions, where (a) is a cross section perpendicular to the axis of the stirring member, and (b) is a cross section parallel to the axis of the stirring member. It is a cross section. In the embodiment of FIG. 5, as shown in FIG. 11, a portion of the second agitating member 4 which is provided between the toner concentration detection sensors A (19A) and B (19B) provided above and below the second agitating member 4 is provided. Is not provided with the stirring blade 4h. This is because if there is a stirring blade 4h between the toner concentration detection sensor A and the toner concentration detection sensor B,
Since the height of the developer changes depending on the position of h, by eliminating the stirring blade 4h, although the shaft 4c of the stirring member 4 is located between the sensor A and the sensor B, the stirring blade 4h
The difference in the sensor output due to the difference in the positions can be eliminated, so that the variation in the volume can be suppressed and the accurate toner density can be detected. As a result, even if the degree of deterioration of the toner changes, the toner is sufficiently stirred and returns to the target charge amount.
It is possible to control the toner concentration accurately by appropriately capturing the change in the bulk, and to maintain a good image without any abnormal image.

[0043]

As described above, according to the first aspect of the present invention, an image carrier, a latent image forming means for forming an electrostatic latent image on the image carrier, and a static image on the image carrier are provided. A developing device for developing the latent image with a two-component developer to make it visible, a toner replenishing device for replenishing toner to the developing device, and detecting a toner concentration of the two-component developer in the developing device And a toner density control means for controlling the toner replenishing device based on an output value of the toner density detection means, wherein the toner image on the image carrier is transferred onto a transfer material by a transfer means. In the image forming apparatus which forms and outputs the image as an image, the toner concentration detecting means for detecting the toner concentration of the two-component developer in the developing device is provided at a position above the center of the stirring member for stirring the developer. Lower position 2
By providing them at different locations, the toner density can be accurately detected even when the charge amount or bulk of the toner fluctuates, and the toner density can be controlled accurately, so that the image density is stable and the density is insufficient. It is possible to maintain a good image without an abnormal image such as image, background dirt, toner dust, and toner scattering.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the toner density control means includes a toner density control unit provided at two positions above and below the center of the stirring member. By determining the toner replenishment amount by calculating the output of the detection means, it is possible to appropriately control the change in bulk and accurately control the toner concentration.
A good image without abnormal images such as insufficient density, background contamination, toner dust, and toner scattering can be maintained.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the two toner concentration detecting means are mounted at positions substantially facing the developing device, thereby increasing the bulk of the image forming apparatus. Since the toner density can be controlled with high accuracy by appropriately capturing the change, it is possible to maintain a good image free from abnormal images such as insufficient density, background contamination, toner dust, and toner scattering.

According to a fourth aspect of the present invention, in the image forming apparatus of the first, second or third aspect, of the two toner density detecting means, the toner density detecting means below the center of the stirring member is a developer. Because the upper toner concentration detecting means is not in contact with the developer, the change in the bulk can be properly captured and the toner concentration can be controlled accurately. A good image without an abnormal image such as toner scattering can be maintained.

In the invention according to claim 5, claims 1, 2,
5. In the image forming apparatus according to 3 or 4, by not providing a stirring blade of a stirring member between the two toner concentration detecting means, it is possible to suppress a variation in bulk due to the position of the stirring blade, and Since the toner density can be controlled with higher accuracy by appropriately capturing the change, it is possible to maintain a good image free from abnormal images such as insufficient density, background contamination, toner dust, and toner scattering.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view of a developing device portion of the image forming apparatus according to the present invention.

FIG. 3 is a schematic sectional view illustrating a more specific configuration example of the image forming apparatus according to the present invention.

FIG. 4 is a perspective view illustrating an appearance of a photoconductor unit of the image forming apparatus according to the present invention.

5 is a partially cutaway perspective view showing a state in which a developing container of the photoconductor unit shown in FIG. 4 is removed.

6 is a perspective view showing a state in which a developing container and an upper case of the photoconductor unit shown in FIG. 4 are removed.

FIG. 7 is a diagram illustrating a relationship between toner concentrations of two toner concentration detection sensors A and B and sensor outputs.

FIG. 8 is a flow chart showing a part of the control operation by the toner density control means according to one embodiment of the present invention.

FIG. 9 is a view showing one embodiment of the third embodiment, and is an explanatory view of installation positions of two toner density detection sensors.

FIG. 10 is a view showing one embodiment of claim 4, and is an explanatory view of a relationship between an installation position of two toner density detection sensors and a developer.

FIG. 11 is a view showing one embodiment of claim 5, and is an explanatory view of a relationship between an installation position of two toner concentration detection sensors and a stirring blade of a stirring member.

[Explanation of symbols]

Reference Signs List 1 photoconductor (image carrier) 2 developing device 3 first stirring member 4 second stirring member 4c shaft of stirring member 4h stirring blade 5 developing sleeve (developer carrier) 14 charging roller (charging unit) 15 from exposure device Light (latent image forming means) 16 Transfer roller (transfer means) 17 Cleaning device 18 Toner replenishing device 18a Toner bottle 18b Toner replenishing drive unit 19A Toner density detecting sensor A (toner density detecting means) 19B Toner density detecting sensor B (toner density Detecting means) 22 photoreceptor unit 25 image forming apparatus control circuit (toner density control means)

Claims (5)

[Claims] An image carrier, a latent image forming means for forming an electrostatic latent image on the image carrier, and a developing device for developing the electrostatic latent image on the image carrier with a two-component developer. A developing device for forming an image, a toner replenishing device for replenishing toner to the developing device, a toner concentration detecting device for detecting a toner concentration of a two-component developer in the developing device, and an output value of the toner concentration detecting device A toner density control means for controlling the toner replenishing device based on the image forming apparatus, wherein the toner image on the image carrier is transferred to a transfer material by a transfer means to form an image and output the image. The toner concentration detecting means for detecting the toner concentration of the two-component developer in the developing device is provided at two positions above and below the center of the stirring member for stirring the developer. Image forming device. 2. An image forming apparatus according to claim 1, wherein said toner density control means calculates an output of toner density detection means provided at two positions above and below the center of said stirring member. An image forming apparatus for determining a toner replenishment amount by using the image forming apparatus. 3. An image forming apparatus according to claim 1, wherein said two toner density detecting means are mounted at positions substantially facing the developing device. 4. The image forming apparatus according to claim 1, wherein, of the two toner density detecting means, a toner density detecting means below a center of a stirring member is always in contact with a developer, An image forming apparatus, wherein the upper toner density detecting means is not in contact with the developer. 5. An image forming apparatus according to claim 1, wherein no stirring blade of a stirring member is provided between said two toner density detecting means. .