JPH02127668A - Developing device - Google Patents

Abstract

PURPOSE:To supply a stable toner thin film by dividing the leading angle of a thin film forming member into two stages such as acute and obtuse angles and setting the length of a wedge space 1 to 50 times the diameter of toner grains. CONSTITUTION:The toner advancing direction of the leading edge of the thin film forming member 4 and the pressing direction of the thin film forming member 4 brought into contact with a toner holding member 6 make an acute angle theta and an obtuse angle (pi/2+theta ; theta is in the range of 45 deg. to 65 deg.). The length of the part forming the wedge space between the leading edge of the thin film forming member 4 and the toner holding member 6 is set 1 to 50 times the diameter of toner grains. Consequently, the strength of the top brought into contact with a developer holding member in the thin film forming member is increased, and a stable, uniform toner layer can be formed for a long time, thereby improving picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device that performs -component toner (magnetic toner and non-magnetic toner) development.

[Conventional technology]

Conventionally, there has been a thin layer blade that is a thin layer forming member that is pressed against the rotating direction of a developing roller that is a toner holding member in a counter direction and forms a uniform thin layer of toner on the surface of the developing roller. The developing device is manufactured by Japanese Patent Application Laid-Open No. 1986-1996.
This method is known from Japanese Utility Model Publication No. 981, Japanese Utility Model Application Publication No. 62-71643, and the like.

[Problem to be solved by the invention]

In the above-mentioned conventional device, especially when there is no toner between the developing roller and the thin layer blade, the tip edge of the thin layer blade may be distorted due to the coefficient of friction between them, the pressing force, the material strength of the thin layer blade, etc. A phenomenon of being caught in the rotational direction of the developing roller may occur.

For this reason, when toner is replenished next time to form a toner thin layer, a good uniform thin layer cannot be formed, and there is a problem in that image density unevenness appears on the image.

An object of the present invention is to provide a developing device that can stably supply a thin toner layer.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention is configured to pressurize the toner in a counter direction against a toner holding member that rotatably conveys a thin layer of toner to a latent image carrier, and to uniformly spread the toner on the surface of the toner holding member. In a developing device having a thin layer forming member that forms a thin toner layer, the shape of the tip edge portion of the thin layer forming member in the toner entry direction is such that the tip angle of the thin layer forming member that contacts the toner retaining member is a thin layer. Acute angle θ and obtuse angle ((π/2+θ)±2.0°) with respect to the pressing direction of the forming member
However, θ should be in the range of 45'' to 65°), and the length of the part that forms a wedge-shaped space with the toner holding member at the tip of the thin layer forming member should be set to 1 to 65° of the toner particle diameter. 5
It is characterized by being configured so that it is 0 times.

[Effect]

By adopting the above means and making the tip angle of the thin layer forming member two steps, acute angle and obtuse angle as described above, strength can be improved, and the straightness of the contact surface of the thin layer forming member to the toner holding member can be improved. The precision of the tip surface is improved, the uniformity of the toner thin layer is improved, and the length of the wedge space formed by the tip of the thin layer forming member and the toner holding member is 1 to 50 times the toner particle diameter. It does not impede the fluidity of toner particles.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view showing the relationship between the thin layer forming member and the toner holding member of the present invention, and FIG. 2 is a front sectional view showing the outline of the overall configuration of this embodiment.

In FIG. 2, 1 is a toner hopper, 2 is a toner hopper agitator, 3 is a toner supply roller, 4 is a thin layer blade made of an elastic material and is a thin layer forming member, 5 is a spring for applying pressure to the thin layer blade, and 6 is a toner supply roller. A developing roller 7, which is a holding member, is toner.

In the figure, toner 7 in a toner hopper 1 is agitated by a toner hopper agitator 2 and adhered to the surface of a developing roller 6 by a toner supply roller 3. As shown in FIG. 1, the thin layer blade 4 is brought into contact with the surface of the developing roller 6 in a counter direction with respect to its rotational direction with a pressing force P0 under the elastic force of a spring 5. As shown in FIG.
Foreign matter in the toner 7 such as paper powder, paper waste, toner lumps, etc. is retained in the toner pool A just before, or by catching the foreign matter with the thin layer blade 4, the toner thin layer T is formed.
This prevents white smudges from appearing on the image, and forms a uniform thin toner layer T on the surface of the developing roller 6.

Incidentally, θI: Wedge angle d at the tip of Fi 1-layer blade 4: Gap P at the tip of thin-layer blade 4: Blade pressure μB applied to toner 7 particles: Coefficient of friction between toner 7 and thin-layer blade 4 μR: Toner 7 and developing roller Assuming that the friction coefficient 2r between 6 and 6 is the average particle diameter of toner 7 particles, the tip of the thin layer blade 4 that contacts in the counter direction is as shown in the explanatory diagram showing an enlarged model of the thin layer blade tip shown in FIG. In order for the toner 7 particles to enter the thin layer blade 4, the gap d at the tip of the thin layer blade 4 must be
The condition d>2r should be satisfied, and in order for the seven toner particles to be conveyed, it is necessary that the relationship μ8>μ8 holds true.

At this time, between the blade pressure P and the wedge angle θ at the tip of the thin layer blade 4, the toner particle entry condition at the blade tip as shown in FIG. 4 is derived from a mechanical model.

That is, when the values of the friction coefficient μ8 of the thin layer blade 4 and the friction coefficient μ of the developing roller 6 are determined, as shown in the table of FIG. In the case of , it is hardly affected by the blade pressure P,
The toner 7 particles enter the inside from the tip of the thin layer blade 4 to form a thin toner layer T. The specific size of the gap d is from several tens of micrometers to several hundred micrometers, which is sufficiently smaller than the foreign matter in the toner 7. Therefore, there is no chance of foreign matter getting caught, and the formation of white sushi can be prevented.

The material of the thin layer blade 4 is related to wettability with the toner 7 to prevent toner particles from sticking, frictional charging characteristics with the toner particles, lifespan of the thin layer blade 4, mechanical system mechanism, and mass productivity. Materials containing silicone resins, fluorine-based polymer materials, and fluorine-based polymer materials can be cited by satisfying multifaceted composite functions such as cost.Specifically, PFA, polytetrafluoroethylene ( T F E
), tetrafluoroethylene-\xafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrichloroethylene (CTFE), polyvinylidene fluoride (P
There are U, DF). In addition, an inorganic filler (fine silica powder, 5tcl) is added to these materials as a charge control agent with the toner 7.
t powder, magnesium oxide, zinc oxide, aluminum oxide, etc.), carbon black, carbon fiber, etc. for imparting conductivity.

Using a thin layer blade member made of the above-mentioned material, the developing roller 6 can be made of the material alone or in combination with a metal holder.
A thin layer of toner is formed by applying pressure to the toner.
The dimensional accuracy of the thin layer blade 4 at the contact surface of the developing roller 6 is required to have a highly accurate straightness of 50 μm or less in the entire width direction of the thin layer blade 4. In order to satisfy this precision, the tip of the thin layer blade 4 is processed by high precision cutting and polishing.

By the way, as shown in FIG. 6, the shape of the thin layer blade 4 is such that the contact surface with the developing roller 6 is processed straight, and when a thin layer of toner is formed, the toner supply onto the developing roller 6 disappears. In the toner end state, the toner 7 particles interposed between the thin layer blade 4 and the developing roller 6 disappear, and due to the increase in the coefficient of friction due to direct contact between the thin layer blade 4 and the developing roller 6, the tip of the thin layer blade 4 The cutting edge X of the developing roller 6 is pulled in the rotational direction of the developing roller
To explain this using the model shown in FIG. 3, the decrease in the gap d at the tip of the thin layer blade 4 makes it impossible for the toner 7 particles to enter. The material of the thin layer blade 4 is often an elastic material as described above, but in the part where the retraction occurs,
Application that exceeds the elastic limit of the material concentrates on the tip end X of the thin-layer blade 4, causing plastic deformation and making it impossible to recover to the original shape. As a result, even if the toner hopper 1 is replenished with the next toner 7, the straightness and other shapes of the thin layer blade 4 change, resulting in thin layer unevenness and image unevenness.

In this way, in order to maintain a uniform toner thin layer on the surface of the developing roller 6 in a stable state over a long period of time, it is necessary to maintain the straightness of the contact surface of the thin layer blade 4 with respect to the developing roller 6, and to It is necessary to maintain the tip shape of the thin layer blade 4 within appropriate conditions as shown.

The present invention has been made in view of the above-mentioned points, and has a shape as illustrated in FIG. The tip angle of the part that contacts the RWi blade 4 is an acute angle θa (=θ) with respect to the pressing direction P of the RWi blade 4,
Obtuse angle θb (=(π/2+θ)±20°) (However, θ
It has a two-stage shape with 456 to 656), which makes the cutting edge H of the thin layer blade 4 the strongest, satisfies the entry conditions of the toner 7, and also stabilizes the processing of the thin layer blade 4. It is in a shape that can be done.

The thin layer blade 4 of this embodiment can have a structure in which the thickness of the blade edge H is increased by forming the blade edge H into the two-stage shape.
The strength of the developing roller 6 of the thin blade 4 is increased, and the phenomenon of the blade tip being drawn in is reduced.
Because the straightness of the contact surface and the precision of the leading edge surface have been improved, the uniformity of the toner thin layer has been improved and the image quality has been improved.

In addition, in the above-mentioned two-stage portion of the thin layer blade 4,
The length L (Fig. 3) of the wedge-shaped space S formed by the thin layer blade 4 and the developing roller 6 is 1 to 5 of the particle diameter of the toner 7.
Make it about 0 times.

The reason for this is that the toner 7 supplied by the toner supply roller 3 is stored in the wedge-shaped space S area at the tip of the thin-layer blade 4, and the overflowing toner 7 is discharged to the toner hopper 1 side. As shown in the explanatory diagram shown in the figure, if the length of the space S is too long (500 μm or more),
This is because the fluidity of the toner 7 particles is hindered, and the toner 7 aggregates or sticks B to the surface of the thin layer blade 4 forming the space S, which may disturb the toner thin layer T. Therefore, the length L was set in consideration of the fluidity of the toner particles and the external environment under usage conditions.

As a result of actually running this example under the initial conditions within the above-mentioned setting range, the tip of the thin-layer blade 4 was completely worn out at a level of IOK to 20. The leading edge of the thin layer blade 4 is a stick-slip operation of the thin layer blade 4,
A stable worn shape was exhibited by polishing with toner particles and rotation of the developing roller 6, and the tip was worn while maintaining a smooth curved surface with a radius of about 25 μm. In this way, the thin toner layer T on the surface of the developing roller 6 maintains a stable level.
We were able to obtain a long lifespan of several hundred thousand sheets or more.

Here, as shown in FIG. 7, we will consider a case where the wedge angle θ1 of the thin layer blade 4 is increased (for example, 30" upward with respect to the horizontal axis X). According to the toner particle entry conditions in FIG. , wedge angle θ.

When , the toner 7 cannot enter unless the blade pressure of the thin layer blade 4 is made very small.

However, in order to control the blade pressure with a very small pressure, it is difficult to control the blade pressure with a very small pressure due to variations in the sliding friction force between the thin layer blade 4 and the mechanical system of the developing device, or the developing roller with which the thin layer blade 4 comes into contact. There is a limit due to the need to improve the straightness, dimensional accuracy, etc. of 6. Furthermore, an excessively concentrated stress is generated on the tip (edge) Y of the contact point between the thin layer blade 4 and the developing roller 6, and the tip (edge) of the thin layer blade 4 having a straight tip shape as shown in FIG. As with the blade edge) X, the tip Y is wound up in the rotational direction of the developing roller 6, causing a change in the straightness of the thin layer blade 4, causing unevenness in the toner thin layer and resulting in image unevenness.

〔Effect of the invention〕

As explained above, according to the present invention, the strength of the tip of the contact portion of the thin layer forming member with the developer holding member is increased;
It is possible to provide a developing device that can stably form a uniform tray thin layer over a long period of time and improve image quality.

[Brief explanation of the drawing]

FIG. 1 is a front view of an embodiment showing the relationship between the thin layer forming member and the toner holding member of the present invention, FIG. 2 is a front cross-sectional view schematically showing the overall configuration of this embodiment, and FIG. An explanatory diagram showing an enlarged model of the tip of the layer forming member, FIG.
FIGS. 6 and 7 are explanatory diagrams showing the state of adhesion, and are explanatory diagrams of the contact portion between the thin layer forming member and the toner holding member shown for comparison with this embodiment. 4... Thin layer forming member, 6... Toner holding member, 7...
...Toner, L...Length of wedge-shaped space, S...Wedge-shaped space, θ,...Wedge angle. 1999 1999 1999 1999 1999

Claims (1)

[Claims] a thin layer forming member that is pressurized in a counter direction against a toner holding member that rotatably conveys the thinned toner to the latent image carrier, and forms a uniform thin layer of toner on the surface of the toner holding member; In the developing device, the shape of the tip edge portion of the thin layer forming member in the toner entrance direction is such that the tip angle of the thin layer forming member that contacts the toner holding member is an acute angle θ with respect to the pressing direction of the thin layer forming member. and obtuse angle {(π/2+θ)
±20°} (however, θ is in the range of 45° to 65°)
A developing device characterized in that the length of the portion forming a wedge-shaped space with the toner holding member at the tip of the thin layer forming member is 1 to 50 times the toner particle diameter. .