JP2005164827A - Developing apparatus and image forming apparatus provided with the developing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing apparatus which hardly causes a ripple of output variation of a toner concentration detection voltage Vt detecting a toner concentration in a developing vessel, is capable of forming a high quality toner image and is small-size and low-cost, and to provide an image forming apparatus provided with the developing apparatus. <P>SOLUTION: The developing apparatus comprises a developing roller 2 which is retained by an opening part 1a of a developing container 1 storing developer consisting of a carrier containing a magnetic body and toner and supplies the toner to an image carrier 51 by rotation, a conveyance screw shaft 3 which is retained in the developing container 1 and conveys the developer to be supplied to the developing roller 2 and a toner concentration detection means 4 which detects a mixing ratio of the carrier and toner of the conveyed developer and outputs it as the toner concentration detection voltage Vt. Therein, the toner concentration detection means 4 is arranged on the position where the extent of output variation of the toner concentration detection voltage Vt detected and outputted by the toner concentration detection means 4 comes to ≤10% of the maximum value of the toner concentration detection voltage Vt. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device and an image forming apparatus including the developing device, and more specifically, includes a developing device that supplies toner by an electrophotographic method to visualize a latent image, and the developing device. The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a complex machine for forming a toner image by an electrophotographic method.

2. Description of the Related Art Conventionally, in a developing device and an image forming apparatus including the developing device, a developing unit composed of a developing roller, a developing sleeve, a doctor blade, a conveying screw, and the like is used to maintain the output image quality of a copying machine or the like. Control is performed so as to keep the toner concentration of the developer in the developer container at a constant value.
A two-component developer consisting of a toner and a carrier is developed by monitoring the toner concentration of the developer to be developed using a toner concentration detection device that detects a change in the magnetic permeability of the developer and outputs it as a voltage value. It is known to keep the toner density of the developer in the developing container of the unit at a constant value (Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, (See Patent Document 7).
Furthermore, in recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their applications have been expanded to various types, and demands for high definition and high image quality are increasing.
Therefore, the toner of the developer is synthesized by dispersion polymerization or the like, and is easily manufactured. Since it is spherical, the fluidity is excellent, and there is little variation in individual characteristics of the toner. It is also known to achieve high image quality by using a toner having a small particle size as a polymerization toner (see Patent Document 8, Patent Document 9, Patent Document 10, Patent Document 11 and the like).

By the way, this toner concentration detecting device is generally attached to a location where the toner concentration of the developer in the developing unit can be obtained accurately and stably.
If a developer that is not sufficiently stirred is detected, the sensitivity of the toner density detection voltage (Vt) is reduced with respect to the actual change in toner density, so that the toner density cannot be accurately controlled.
If the development unit is composed of hard members, the predetermined mechanical accuracy can be maintained, so that the conveyance screw can reach the vicinity where it does not come into contact with the container wall, and the developer in the development unit can be smoothly conveyed. I can do it.
However, a developing unit that is composed of an inexpensive and relatively soft member that is actually used may be bent or distorted, causing the conveyance screw and the container wall to come into contact with each other, causing problems such as toner sticking. is there.
Therefore, in order to provide a margin between the instrument wall and the conveying screw, a distance for avoiding contact is provided.
However, since the conveying screw reaches only a position away from the container wall, the developer near the container wall is stagnated.
When the toner density detector is attached to the developing unit to control the toner density, if mechanical accuracy such as bending of the developing unit cannot be maintained, the developer in the vicinity of the detecting surface is sufficiently stirred. A system in which a stirring member is locally attached and a sufficiently well-stirred developer can be detected is used.
The member for stirring the developer on the toner concentration detection surface of the toner concentration detection device is a resin such as urethane, which is durable and can be sufficiently stirred without causing toner fixation. Below, it is attached to the development unit.

In the gap generated after the developer is stirred by the stirring member, the new developer is transported by the transport screw, so that not only the part scraped by the stirring member but also the developer before and after the developer The developer flow occurred in a layer near the container wall.
When the toner density of the developing unit using the stirring member for the conveying screw is detected, a ripple of output fluctuation occurs in the toner density detection voltage (Vt) of the toner density detection device.
When a toner concentration detection device that outputs a low detection voltage (Vt) when the toner concentration is high and a high detection voltage (Vt) when the toner concentration is low is used, the detection voltage (Vt) immediately before the developer is scraped off by the stirring member. Immediately after being scraped, there is no developer on the detection surface, so that the detection voltage (Vt) is output high, and the toner concentration detection voltage (Vt) of the conventional developing device has a large output fluctuation. Ripple has occurred (see Figure 2).
This output value is processed on the software of the image forming apparatus, and is used for toner density control as a predetermined toner density detection voltage (Vt).
However, a ripple of large output fluctuation occurs, and an error from the true toner concentration detection voltage (Vt) increases, and the toner concentration of the developer in the developing container of the developing unit can be maintained at a constant value. As a result, the quality of the formed toner image was deteriorated.
Therefore, in the conventional developing device and the image forming apparatus including the developing device, when the toner concentration in the developing container of the developing unit using the stirring member for the conveying screw is detected, the toner concentration detection voltage (Vt) is obtained. A large output fluctuation ripple occurs, and an error from the true toner concentration detection voltage (Vt) increases, so that the toner concentration of the developer in the developing container of the developing unit cannot be maintained at a constant value and formed. There has been a problem that the quality of the toner image is degraded.
JP 2000-112221 A Japanese Patent Laid-Open No. 5-289499 JP-A-8-248774 JP 2002-296236 A JP 2002-296240 A JP 2002-296890 A JP 2002-296893 A JP 2002-244355 A Japanese Patent Laid-Open No. 5-188443 Japanese Patent Laid-Open No. 6-180512 JP 2002-328551 A

In a conventional developing device and an image forming apparatus including the developing device, when the toner concentration in the developing container of a developing unit using a stirring member as a conveying screw is detected, a large output is generated in the toner concentration detection voltage (Vt). A fluctuation ripple occurs, and an error from the true toner density detection voltage (Vt) increases, so that the toner density of the developer in the developing container of the developing unit cannot be maintained at a constant value, and the formed toner There was a problem that the quality of the image deteriorated.
Therefore, an object of the present invention is to solve such problems. That is, the ripple of the output fluctuation of the toner density detection voltage (Vt) for detecting the toner density in the developing container is small, the error from the true toner density detection voltage (Vt) is small, and the toner density in the developing container is constant. An object of the present invention is to provide a small-sized and low-cost developing device capable of forming a high-quality toner image while maintaining the value, and an image forming apparatus including the developing device.

In order to achieve the above object, the present invention described in claim 1 is a developing device for developing a latent image by supplying toner by an electrophotographic method, and a developer comprising a carrier containing magnetic material and toner. A developing container to be accommodated, a developing roller held in the opening of the developing container and contacting the image carrier or rotating at the time of image formation while maintaining a small interval, and supplying toner; and in the developing container A toner density detection voltage (Vt) by detecting a mixing ratio of a conveying screw shaft that conveys developer that is rotatably held and that is supplied to the developing roller, and a carrier and toner of the developer conveyed by the conveying screw shaft. The toner density detection means that outputs the toner density, and the magnitude of the output fluctuation of the toner density detection voltage (Vt) that is detected and output by the detection surface of the toner density detection means is the value of the toner density detection voltage (Vt). The most important feature that at the position of 10% or less Daine a developing device arranged above the detection surface of the toner concentration detecting means.
According to a second aspect of the present invention, in the developing device according to the first aspect, the developer contained in the developing container is made of a small particle diameter toner having an average particle diameter of 4 μm to 8 μm. The main feature is that the developing device.
According to a third aspect of the present invention, there is provided the developing device according to the first or second aspect, wherein the agitating member that conveys the developer in the vicinity of the container wall in the developing container of the conveying screw shaft is a toner concentration detecting means. The main feature is that the developing device does not stir the detection surface.
According to a fourth aspect of the present invention, in the developing device according to the first, second, or third aspect, the detection surface of the toner concentration detection means is a developer that is conveyed to the stirring member of the conveying screw shaft. The main feature is that the developing device is arranged to be shifted upstream in the transport direction.
According to a fifth aspect of the present invention, there is provided the developing device according to the first, second, third or fourth aspect, wherein the detection surface of the toner concentration detection means is a development conveyed to a stirring member of a conveyance screw shaft. The main feature is that the developing device is arranged to be shifted to the downstream side in the transport direction of the agent.
According to a sixth aspect of the present invention, in the developing device according to the first, second, third, fourth, or fifth aspect, the toner concentration detecting means is a developing device that does not protrude from the wall surface of the developing container. Is the main feature.

According to a seventh aspect of the present invention, there is provided the developing device according to the first, second, third, fourth, fifth or sixth aspect, wherein the detection surface of the toner density detecting means is a flat developing device. Main features.
Further, the present invention described in claim 8 is the developing device according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the detection surface of the toner density detecting means is for transporting the developer to be transported. The main feature is that the developing device has a longer conveying direction length in the conveying direction of the developer to be conveyed than the vertical length perpendicular to the direction.
According to a ninth aspect of the present invention, there is provided the developing device according to the first, second, third, fourth, fifth, sixth, seventh or eighth aspect, wherein the toner concentration detecting means is a nonmagnetic fixed member made of a nonmagnetic member. The main feature is that the developing device is fixed to the developing container with a member.
According to a tenth aspect of the present invention, in an image forming apparatus for forming a toner image by an electrophotographic method, an image carrier that is rotatably held and carries a toner image, and a surface of the image carrier. A charging unit that charges uniformly, a latent image forming unit that forms a latent image on the surface of the image carrier uniformly charged by the charging unit, and a latent image formed by the latent image forming unit An image forming apparatus comprising: the developing device according to any one of claims 1 to 9; and a transfer unit that transfers a toner image formed by the developing device to a transfer target. The most important feature is to be.

Since the present invention is configured as described below, according to the first aspect of the present invention, the ripple of the output fluctuation of the toner concentration detection voltage (Vt) for detecting the toner concentration in the developing container is small and true. An error from the toner concentration detection voltage (Vt) is reduced, and the developing device capable of forming a high-quality toner image by maintaining the toner concentration in the developing container at a constant value can be provided. .
According to the invention of claim 2, the ripple of the output fluctuation of the toner density detection voltage (Vt) for detecting the toner density in the developing container is small, and the error from the true toner density detection voltage (Vt) is reduced, and the developing container is reduced. It is now possible to provide a developing device in which the toner density is maintained at a constant value and a high-quality toner image is formed at a low cost.
According to the invention of claim 3, the ripple of the output fluctuation of the toner concentration detection voltage (Vt) for detecting the toner concentration in the developing container by preventing the stirring member from stirring right above the detection surface of the toner concentration detection means. Therefore, it is possible to provide a developing device in which a high-quality toner image is formed by reducing the error from the true toner concentration detection voltage (Vt) and reducing the error and maintaining the toner concentration in the developing container at a constant value. It became so.
According to the fourth aspect of the present invention, the toner density detecting means is arranged such that the detection surface of the toner density detecting means is shifted to the upstream side in the conveying direction of the developer conveyed with respect to the stirring member of the conveying screw shaft. The toner density detection voltage (Vt) detecting the output fluctuation has less ripple of the output fluctuation and the error with the true toner density detection voltage (Vt) is reduced, and the toner density in the developing container is kept at a constant value, and the high quality It is now possible to provide a developing device capable of forming the toner image.
According to the fifth aspect of the present invention, the toner density detecting means is arranged such that the detection surface of the toner density detecting means is shifted to the downstream side in the conveying direction of the developer conveyed with respect to the stirring member of the conveying screw shaft. The toner density detection voltage (Vt) detecting the output fluctuation has less ripple of the output fluctuation and the error with the true toner density detection voltage (Vt) is reduced, and the toner density in the developing container is kept at a constant value, and the high quality It is now possible to provide a developing device capable of forming the toner image.

According to the sixth aspect of the present invention, the flow of the developer in the developing container is not hindered by the toner density detecting means, and the output fluctuation of the toner density detecting voltage (Vt) for detecting the toner density in the developing container is further prevented. There is provided a developing device in which a high-quality toner image is formed by reducing an error from a true toner concentration detection voltage (Vt) with little ripple and maintaining a constant toner concentration in a developing container. I can do it now.
According to the seventh aspect of the present invention, the toner concentration detection voltage (Vt) for detecting the toner concentration in the developing container is further prevented without obstructing the flow of the developer in the developing container by the detection surface of the toner concentration detecting means. Providing a developing device that forms a high-quality toner image with little ripple of output fluctuation and a small error from the true toner concentration detection voltage (Vt), keeping the toner concentration in the developing container at a constant value. I can do it now.
According to the invention of claim 8, the ripple of the output fluctuation of the toner density detection voltage (Vt) for detecting the toner density in the developing container is small, and the error from the true toner density detection voltage (Vt) is reduced, and the developing container is reduced. It is possible to provide a small-sized developing device in which the toner density in the inside is maintained at a constant value and a high-quality toner image is formed.
According to the ninth aspect of the present invention, the member that affects the magnetic permeability detection of the toner concentration detecting means is eliminated, and the ripple of the output fluctuation of the toner concentration detection voltage (Vt) for detecting the toner concentration in the developing container is further eliminated. Therefore, it is possible to provide a developing device in which a high-quality toner image is formed by reducing the error from the true toner concentration detection voltage (Vt) and reducing the error and maintaining the toner concentration in the developing container at a constant value. It became so.
According to the invention of claim 10, the ripple of the output fluctuation of the toner density detection voltage (Vt) for detecting the toner density in the developing container is small, and the error from the true toner density detection voltage (Vt) is reduced. It is possible to provide an image forming apparatus having a small and low-cost developing device in which the toner density in the inside is maintained at a constant value and a high-quality toner image is formed.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2, a developing device 0 that supplies toner by an electrophotographic method to visualize a latent image includes a developing container 1 that contains a carrier including a magnetic material and a developer composed of toner, and the developing container. A developing roller 2 that is held in one opening 1a and abuts against the surface 51a of the drum-shaped photosensitive drum of the image carrier 51, or rotates at the time of image formation while maintaining a minute interval; A conveyance screw shaft 3 that conveys a developer that is rotatably held in the developing container 1 and that is supplied to the developing roller 2, and detects a mixing ratio of the carrier and toner of the developer conveyed by the conveyance screw shaft 3. And a toner density detecting means 4 for outputting the toner density detecting voltage (Vt), and a change in the output fluctuation of the toner density detecting voltage (Vt) detected and outputted by the detection surface 4a of the toner density detecting means 4. Since the detection surface 4a of the toner concentration detecting means 4 is disposed at a position where the size of the toner (Vtr) is 10% or less of the maximum value (Vt0) of the toner concentration detection voltage (Vt), the inside of the developing container 1 The toner density detecting means 4 for detecting the toner density of the toner density detecting voltage 4 on the detecting surface 4a has less ripples in the output fluctuation of the toner density detecting voltage (Vt), and the error from the true toner density detecting voltage (Vt) is reduced. The toner density in the container 1 is maintained at a constant value, and a high-quality toner image is formed.
Further, since the developer contained in the developer container 1 is a small particle diameter toner having an average particle diameter of 4 μm to 8 μm, it is easily manufactured by being synthesized by dispersion polymerization or the like, and has a spherical shape. Therefore, it is possible to provide the developing device 0 that is excellent in fluidity, has little variation in individual toner characteristics, and further forms a high-quality toner image.
In the toner density detecting means 4 using the magnetic permeability detecting method, it is considered that the ease of movement of the developer, that is, the fluidity of the developer contributes to the detection, but not the movement of the developer itself but the carrier itself. It detects the state of distribution of the magnetic material, such as when there are many or few.
The toner concentration detection means 4 is disposed at a position where the developer is agitated in the developing container 1 where the distribution changes significantly, and is not detected by the detection surface 4a. Therefore, the toner concentration detection voltage (Vt ) Output fluctuation ripple does not increase.

3 and 4, the developing device 0 is illustrated by the stirring member 3a of the conveying screw 3 rotating the developer on the detection surface 4a of the toner density detecting means 4 in the direction of the arrow (A). If the detection surface 4a of the (XY) line is agitated, the ripple of the output fluctuation of the toner concentration detection voltage (Vt) detected by the detection surface 4a becomes large. The stirring member 3a does not stir the detection surface 4a directly above the (XY) line shown in the drawing, but rather develops the detection surface 4a in the direction indicated by the arrow (B). Of the agitating member 3a _{1 of} the agitating member 3a that agitates a little upstream in the conveying direction of the agent, or of the agitating member 3a that agitates a little downstream in the conveying direction of the developer in the direction of the arrow (B) shown in the figure mounting position on the downstream side stirring member 3a ₂ , The shifting direction of the arrow (C) direction shown, are staggered respectively, as shown in FIG.
The developing device 0 includes the upstream stirring member 3a ₁ that stirs the slightly upstream side of the stirring member 3a in the direction of the arrow (B) of the developer illustrated in FIG. The downstream stirring member 3a ₂ that stirs the downstream side of the developer in the direction B) slightly promotes the flow of the developer in the vicinity of the container wall 1b where the transport screw 3b does not reach. Therefore, the flow of the developer can be ensured even if it is not directly above the (XY) line of the detection surface 4a shown in the drawing, and the flowing developer can be detected.
That is, in the developing device 0, the developer stirred by the upstream stirring member 3a ₁ or the downstream stirring member 3a _{2 of the} stirring member 3a moves remarkably, but the developer moves before and after that. Since it is transported at a speed by the transport screw 3b in the developing container 1, the upstream stirring member 3a _{1 of} the stirring member 3a or the illustrated (X--) of the downstream stirring member 3a ₂ is illustrated. If the detection is performed directly below the Y) line, it is directly affected by the agitation, so that the ripple of the output fluctuation of the obtained toner concentration detection voltage (Vt) becomes large, but before and after the (XY) line shown in the figure. By detecting the developer, it is possible to obtain a toner concentration detection voltage (Vt) in which a direct stirring state is avoided and a ripple of output fluctuation is small.

The attachment position of the detection surface 4a of the toner density detection means 4 is moved from the position immediately below the (XY) line of the stirring member 3a to the downstream side in the developer conveyance direction in the direction of the arrow (B). An example of the result of detection sensitivity characteristics when shifted is shown (see FIG. 4).
The detection surface 4a of the toner density detection means 4 has a length in the direction of developer conveyance in the direction of arrow (B) shown in the figure, which is 15 mm, and is perpendicular to the direction of developer conveyance in the direction of arrow (B) shown in the figure. The evaluation was performed with the length in the vertical direction (the width of the detection surface 4a) being 10 mm and the distance between the conveying screw 3b of the developing container 1 and the container wall 1b being 1.5 mm.
The detection sensitivity at a position where the detection surface 4a of the toner density detection means 4 is shifted by 10 mm from the position immediately above the (XY) line shown in the drawing is only reduced by 15%, and the detection sensitivity at a position shifted by 15 mm. Decreased to 25%.
It has been found that if the position is shifted beyond that, the sensitivity is greatly reduced, and accurate toner density control cannot be performed.
That the sensitivity sufficient to control the toner density is maintained means that the developer on the detection surface 4a including the vicinity of the container wall 1b is being conveyed properly.
However, when the predetermined distance or more is shifted from the position directly above the (XY) line in the figure, sufficient sensitivity cannot be obtained, so the upstream stirring member 3a _{1 of} the stirring member 3a, or The distance that the developer stirred by the downstream stirring member 3a ₂ is transported is limited.

Various factors such as internal friction between developer particles, developer fluidity, and pitch (p) of the conveying screw 3b shown in the figure are involved, and the upstream stirring member 3a _{1 of} the stirring member 3a, or When the distance by which the developer stirred by the downstream stirring member 3a ₂ is conveyed is (L) and the distance between the illustrated conveying screw 3b and the container wall 1b is (D), (L) = b / (A + (D) + c...) (Where a, b, and c are coefficients.) (Equation 1).
The toner density detection at a position beyond a predetermined distance (L) in which the developer stirred by the upstream stirring member 3a ₁ or the downstream stirring member 3a ₂ of the stirring member 3a shown in the figure is conveyed. If the detection surface 4a of the means 4 is attached, it can be explained that the sensitivity cannot be obtained because the developer in that portion is not conveyed.
Further, in the developing container 1 in which the distance (D) between the conveying screw 3b and the container wall 1b is small, when the detection surface 4a of the toner concentration detecting means 4 is attached, the agitated developer is easily conveyed. Therefore, the detection surface 4a of the toner concentration detection means 4 is shifted from the upstream agitating member 3a _{1 of} the agitating member 3a or just below the (XY) line of the downstream agitating member 3a _2. The range where it can be expanded.
When the linear velocity condition for developer conveyance in the direction of the arrow (B) shown in the figure changes, the toner concentration detection voltage (Vt) value detected and output by the detection surface 4a of the toner concentration detection means 4 changes. .
The state in which the toner density detection voltage (Vt) changes even though the actual toner density has not changed is considered to be caused by the change in the developer transport speed in the developer container 1.
When the developer stirring speed is high, the developer distribution in the developer container 1 becomes sparse, and the gap becomes large.
In this faint state, the detection surface 4a of the toner concentration detection means 4 determines that the carrier is low and outputs an output indicating that the toner concentration is high. This is a shift of the toner density detection voltage (Vt) due to the linear velocity difference.

The detection surface 4a of the toner concentration detection means 4 contributes to the distribution state of the magnetic material of the developer. Therefore, when a location where the distribution of the magnetic material varies significantly is detected, the output of the toner concentration detection voltage (Vt) is output. The fluctuation ripple is large and the output accuracy is also lowered.
Therefore, the toner density detecting means 4 is slightly shifted from the upstream stirring member 3a _{1 of} the stirring member 3a or just below the illustrated (XY) line of the downstream stirring member 3a _2. The detection of the toner density on the detection surface 4a reduces the degree of change when the linear speed condition changes, and effectively acts to detect the true toner density.
Therefore, from the above (Equation 1) and the experimental results of FIG. 4 and the like, the flow of the developer by the upstream stirring member 3a ₁ or the downstream stirring member 3a ₂ of the stirring member 3a is maintained, and The toner density detection means for detecting the toner density in the developing container 1 by attaching the detection surface 4a of the toner density detection means 4 within a predetermined range in which the ripple of output fluctuation of the toner density detection voltage (Vt) becomes small. 4, the ripple of the output fluctuation of the toner density detection voltage (Vt) on the detection surface 4 a is small, and the error from the true toner density detection voltage (Vt) is small, so that the toner density in the developing container 1 becomes a constant value. Thus, it is possible to provide the developing device 0 in which a high-quality toner image is formed.
Further, the detection surface 4a of the toner density detection means 4 in the developing device 0 has a vertical length (4a ₁ ) perpendicular to the developer conveyance direction in the direction indicated by the arrow (B), and the arrow shown in the drawing. Since the transport direction length (4a ₂ ) in the developer transport direction in the (B) direction is long, a wider detection area can be secured.
Therefore, the developing device 0 is downsized, and each component constituting the developing device 0 is also downsized.
The same applies to the toner density detecting means 4, but the developing container 1 to which the toner density detecting means 4 is attached is also reduced in size.
For this reason, the vertical length (4a ₁ ) perpendicular to the developer conveying direction shown by the arrow (B) in the figure and the width of the toner density detecting means 4 are limited, so that a wide detection area is provided. In order to ensure this, it is advantageous for reducing the size of the developing device 0 by extending the detection region in the direction (4a ₂ ) of the developer conveying direction in the direction of the arrow (B) shown in the figure.
Therefore, the ripple of the output fluctuation of the toner density detection voltage (Vt) for detecting the toner density in the developer container 1 is small, and the error from the true toner density detection voltage (Vt) is reduced, so that the toner in the developer container 1 is reduced. It is possible to provide the developing device 0 having a reduced size in which the density is maintained at a constant value and a high-quality toner image is formed.

In FIG. 5, the toner concentration detecting means 4 in the developing device 0 is configured not to protrude a convex portion from the surface of the container wall 1 b in the developing container 1.
However, if there is a convex portion in the developer transport path, the presence of the convex portion obstructs the flow of the developer in the developer container 1, and a problem such as toner sticking is likely to occur. It will be.
In order to perform accurate toner density detection, it is desirable that the developer is uniformly distributed, and unnecessary movement of the developer adversely affects the toner density detection voltage (Vt).
Further, the toner concentration detecting means 4 in the developing device 0 is arranged to develop the developer in order to effectively transport the developer to the upstream stirring member 3a ₁ or the downstream stirring member 3a ₂ of the stirring member 3a. The detection surface 4a also does not protrude from the surface of the vessel wall 1b in the container 1.
Further, since the detection surface 4a of the toner concentration detection means 4 is not in contact with the developer, it can be externally attached to the developer container 1 and is easy to handle.
Therefore, the developing device 0 can prevent the developer from flowing smoothly and unnecessary stagnation because the container wall 1b in the developing container 1 has no convex portion.
Further, the toner density detection means 4 in the developing device 0 can detect the toner density more accurately and stably because the detection surface 4a is flat and can be detected without contact with the developer because it is sufficiently wide. You can also do it.
The toner concentration detecting means 4 in the developing device 0 is fixed to the developing container 1 by a nonmagnetic fixing member 5 made of a nonmetallic nonmagnetic member.
Magnetic materials such as metal may change the permeability of the developer, and in order to detect the change in permeability due to pure developer alone, from the vicinity of the toner concentration detecting means 4, Members that affect the magnetic permeability detection of the toner concentration detecting means 4 are excluded.

  In FIG. 6, an image forming apparatus 50 that forms a toner image by an electrophotographic method includes a drum-shaped photosensitive drum of the image carrier 51 that is rotatably held and carries a toner image, and the image carrier 51. A charging means 52 for uniformly charging the surface 51 a of the drum-shaped photosensitive drum, and a latent image on the surface 51 a of the drum-shaped photosensitive drum of the image carrier 51 uniformly charged by the charging means 52. The latent image forming means 53 for forming the toner image and the developing device according to any one of claims 1 to 9, wherein the latent image formed by the latent image forming means 53 is visualized to form a toner image storage. 0 and a transfer means 54 for transferring the toner image formed by the developing device 0 onto a transfer sheet (P), and a toner concentration detection voltage (Vt) for detecting the toner concentration in the developing container 1 Of output fluctuation Ripple becomes error is small and less real toner density detection voltage (Vt), the toner concentration of the developing container 1 is kept at a constant value, is a small high-quality toner image is formed.

A copying machine that forms a toner image by the electrophotographic method of the image forming apparatus 50 is provided with a document image reading unit 61 that reads a document image of a document (O) at the top.
On the other hand, a paper feeding device 60 for placing the image forming unit 59 and supplying the transfer material (P) transfer paper is disposed in the lower part.
The charging means 52 is made uniform by causing the laser diode of the latent image forming means 53 to emit light by an electrophotographic method for forming a toner image with image data of the original image of the original (0) read by the original image reading unit 61. Then, a latent image is formed on the surface 51a of the drum-shaped photosensitive drum of the image carrier 51 that is charged in the negative direction.
The electrostatic latent image formed by emitting the laser diode of the latent image forming means 53 is visualized by the developing device 0 to form a toner image.
The toner image visualized by the developing unit 0 is transferred and recorded by the transfer unit 54 on the transfer sheet of the transfer medium (P) conveyed from the paper feeding device 60.
The toner image transferred and recorded on the transfer sheet (P) by the transfer means 54 is heated and pressed by the fixing means 55, and the transfer sheet of the transfer body (P) is discharged by the paper discharge roller 56. Thus, the sheet is discharged onto the discharge tray 57 and stored.
On the other hand, the surface 51a of the drum-shaped photosensitive drum of the image carrier 51 is formed on the surface of the drum-shaped photosensitive drum of the image carrier 51 after the toner image is transferred to the transfer sheet of the transfer medium (P). Residual toner adhering to the surface 51a is scraped off and cleaned by the cleaning means 58 to prepare for image formation in the next process.
Therefore, the ripple of the output fluctuation of the toner density detection voltage (Vt) for detecting the toner density in the developer container 1 is small, and the error from the true toner density detection voltage (Vt) is reduced, so that the toner in the developer container 1 is reduced. To provide the image forming apparatus 50 which is provided with the developing device 0 which is downsized so that a high-quality toner image is formed while maintaining a constant density, and forms a high-quality toner image storage. I can do it now.

It is explanatory drawing explaining the developing device which shows the embodiment of this invention. FIG. 7 is a graph illustrating characteristics of toner concentration detection voltage (Vt) and time (t) of main parts of a developing device and a conventional developing device according to an embodiment of the present invention. It is a perspective view explaining the other main part of the image development apparatus which shows the embodiment of this invention. It is a figure explaining the characteristic of the shift amount (mm) of the attachment position of the other main part of the developing device which shows the embodiment of this invention, and a sensitivity fall (%). It is explanatory drawing explaining the other principal part of the image development apparatus which shows the embodiment of this invention. 1 is an explanatory diagram for explaining an image forming apparatus including a developing device according to an embodiment of the present invention.

Explanation of symbols

0 Development device 1 Developer container,
1a opening,
1b Device wall 2 Developing roller 3 Conveying screw shaft,
3a stirring member,
3a ₁ upstream stirring member,
3a ₂ downstream stirring member,
3b conveying screw 4 toner density detecting means,
4a detection surface,
4a ₁ vertical length,
4a ₂ Length in conveyance direction 5 Non-magnetic fixing member 50 Image forming apparatus
51 image carrier,
51a Surface 52 Charging unit 53 Latent image forming unit 54 Transfer unit 55 Fixing unit 56 Paper discharge roller 57 Paper discharge tray 58 Cleaning unit 59 Image forming unit 60 Paper feeding device 61 Document image reading unit

Claims (10)

  In a developing device that visualizes a latent image by supplying toner by an electrophotographic method, a carrier containing a magnetic material and a developer container containing toner, and an image carrier held in the opening of the developer container A developing roller that contacts the body or rotates at the time of image formation while maintaining a small interval and supplies toner, and a conveyance that conveys the developer that is rotatably held in the developing container and is supplied to the developing roller The toner density detecting means comprises a screw shaft and a toner density detecting means for detecting a mixing ratio of the carrier and toner of the developer conveyed by the conveying screw shaft and outputting the detected toner density detection voltage (Vt). The toner density detecting means is located at a position where the magnitude of the output fluctuation of the toner density detecting voltage (Vt) detected and output on the surface is 10% or less of the maximum value of the toner density detecting voltage (Vt) Developing apparatus is characterized in that a said detection surface.   2. The developing device according to claim 1, wherein the developer contained in the developing container is made of a small particle toner having an average particle diameter of 4 to 8 [mu] m.   3. The developing device according to claim 1, wherein the agitating member that conveys the developer in the vicinity of the container wall in the developing container of the conveying screw shaft does not agitate immediately above the detection surface of the toner concentration detecting means. Developing device.   4. The developing device according to claim 1, wherein the detection surface of the toner density detecting means is arranged so as to be shifted upstream in the transport direction of the developer transported with respect to the stirring member of the transport screw shaft. A developing device.   5. The developing device according to claim 1, wherein the detection surface of the toner density detecting means is arranged to be shifted downstream in the transport direction of the developer transported with respect to the stirring member of the transport screw shaft. A developing device.   6. The developing device according to claim 1, wherein the toner density detecting means does not protrude from a wall surface in the developing container.   7. The developing device according to claim 1, wherein the detection surface of the toner density detecting means is a flat surface.   8. The developing device according to claim 1, wherein the detection surface of the toner density detecting means is transported from a vertical direction perpendicular to a transport direction of the transported developer. A developing device characterized in that the transport direction length of the developer to be transported is long.   9. The developing device according to claim 1, wherein the toner density detecting means is fixed to the developing container by a nonmagnetic fixing member made of a nonmagnetic member. Development device.   In an image forming apparatus for forming a toner image by an electrophotographic method, an image carrier that is rotatably held and carries a toner image, a charging unit that uniformly charges the surface of the image carrier, and the charging unit The latent image forming means for forming a latent image on the surface of the uniformly charged image carrier, and the latent image formed by the latent image forming means is visualized to form a toner storage. 10. An image forming apparatus comprising: the developing device according to claim 1; and a transfer unit that transfers a toner image formed by the developing device to a transfer target.

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