JPH0434529Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a developing device for developing an electrostatic latent image with a developer such as toner.

(Prior Art) A developing device is known that develops an electrostatic latent image on a latent image carrier with a developer carried on the circumferential surface of a roller-shaped developer carrier. The developer carried on the circumferential surface of the developer carrier is thinned to an appropriate thickness, and conventionally, as a means for thinning the layer, an elastic plate is attached to a plate member. A structure was adopted in which this elastic plate was brought into contact with the developer carrier, but
With this configuration, it is necessary to increase the contact setting accuracy as much as possible, and since it causes wear at the contact end, the amount of developer attached per unit area and the amount of charge per unit weight of developer change greatly. This makes it difficult to obtain a stable thin layer of developer and an appropriate amount of charge per unit weight of developer. Furthermore, there is a drawback that the cost of the device increases due to the increase in assembly time in order to increase the precision of parts or the precision of installation.

(Objective) An object of the present invention is to provide a low-cost developing device that can uniformly and stably form a thin layer of developer to obtain high-quality images.

(Structure) In order to achieve the above object, the present invention arranges the developer regulating member at an obtuse angle to the tangent at the position of contact with the developer carrier, and then moves it in this arrangement direction. It is characterized in that it is freely supported and urged to move in the abutment direction.

Hereinafter, an explanation will be given based on one embodiment of the present invention.

In FIG. 1, the reference numeral 1 indicates a drum-shaped photoreceptor which is an example of a latent image carrier, and the reference numeral 2 indicates a developing device according to the above embodiment. Toner, which is an example of a developer, is stored in a hopper 3 of the developing device 2, and this toner is transported to a toner supply member 5 by an agitator 4. The toner supply member 5 is a sponge roller in this embodiment. Hereinafter, such a member will be referred to as a toner supply roller.

Reference numeral 6 indicates a developer carrier. This developer carrier 6 is a rubber roller in this embodiment. Hereinafter, such a developer carrying member will be referred to as a toner carrying roller.

The toner replenishing roller 5 and the toner carrying roller 6, which can also be called a developing roller, are driven to rotate in the directions of the arrows, and due to the friction between them at this time,
The toner is electrically charged so that the toner adheres to the toner carrying roller 6.

Reference numeral 7 indicates a developer layer thickness regulating member whose lower end is brought into contact with the circumferential surface of the toner carrying roller 6. Since this embodiment uses toner as the developer, the developer layer thickness regulating member described above will be used as follows.
It is called a toner layer thickness regulating member.

The toner carried on the circumferential surface of the toner carrying roller 6 and charged as described above is carried to the toner layer thickness regulating member 7, and the amount of charge is adjusted at the end of the member 7 that contacts the roller 6. It is triboelectrically charged so as to further increase the amount of water, and is transported to the development area 8 in the form of a uniform thin layer.

In the development area 8 , a part of the carried toner is used for developing the electrostatic latent image on the photoreceptor 1 , and the remaining toner that does not contribute to the development is carried on the roller 6 and transferred to the toner replenishing roller 5 . Come back to the part. The returning residual toner is scraped off by the toner supply roller 5, and toner is again supplied to the scraped surface by the toner supply roller 5.

In this embodiment, the toner layer thickness regulating member 7 is made of an elastic plate, and has a lower contact end with respect to a tangent 1 at the contact position with the toner carrying roller 6.
The arrangement thereof is determined so that the angle θ formed between the tangent 1 and the regulating member 7 is an obtuse angle when viewed from the rotational direction of the roller 6.

The toner layer thickness regulating member 7 is slidable in the direction of its disposed position by a guide member 9 held in an immovable state, and is biased by an extensible spring 11 to the roller 6 . is urged to move in the direction of contact with the That is, the regulating member 7 is supported so as to always maintain the obtuse angle θ even if it moves up and down.

Now, if the angle θ is not an obtuse angle but an acute angle, and the regulating member 7 is movable, if the coefficient of friction between the regulating member 7 and the toner carrying roller 6 is large, the This may cause a situation in which a large amount of toner escapes, which hinders the uniform thinning of the toner layer.

An obtuse angle will help prevent such situations from occurring, and will also help prevent debris from clogging.
It also achieves the function of repelling toner to prevent excessive toner from entering. Furthermore, setting an obtuse angle (Fig. 5) that repels toner,
Compared to an acute angle (FIG. 6) that grips the toner, it is possible to improve the fluidity of the toner.

FIG. 5 shows the case where the angle θ is an obtuse angle, and FIG. 6 shows the case where the angle θ is an acute angle. In the former obtuse case, the vertical force F _N from the roller 6 in the moving direction A of the regulating member 7, The force in the direction of the tangent l (frictional resistance force of the abutting part) and the composite component of the _force is the force that is the composite component of the force in the direction of the tangent l
Another force that is balanced with the load in the swinging direction and that is obtained by further decomposing the composite component force into a vector acts as a force that causes the regulating member to bite into the roller.

On the other hand, in the latter acute case, F _N and F _S
The resultant force is not directed in the above-mentioned swinging direction, but the tip of the regulating member acts in the direction of escaping from the roller, and the toner is caught between the regulating member 7 and the roller 6, resulting in uneven toner distribution. It becomes difficult to thin the layer.

In this type of developing device, an elastic plate that is elastically deformed by the load is used as the toner layer thickness regulating member 7, and the toner gripping action is largely due to the elastic deformation accompanying the load. Therefore, when the toner carrying roller 6 is made of an elastic material, or when the creep of the toner layer thickness regulating member 7 itself is taken into consideration, the obtuse angle setting is more advantageous because it requires a smaller set load.

On the other hand, the toner layer thickness regulating member 7 of this embodiment is movable in the direction of load application (direction A), and the reason for this movement is that the regulating member 7 is worn and used as a toner thinning means. This is due to the fact that it has been adopted as a method.

The reason why the toner layer thickness regulating member 7 is worn out is to prevent the toner from sticking to the regulating member contact surface, which occurred in the conventional example, and to prevent white lines and black lines appearing on the image. This is to stabilize the amount of toner charge per unit weight by constantly supplying a new surface by abrading the surface.

Furthermore, due to the guiding action of the guide member 9,
Since the regulating member 7 does not always change its position as shown in FIG. 1, even if the contact end of the regulating member 7 is worn, the amount of toner adhering to the roller 6 per unit area can be stabilized. Further, this layer thinning means is characterized in that it can reduce fluctuations in the amount of toner adhering per unit area with respect to fluctuations in pressure.

Here, the configuration regarding the support of the toner layer thickness regulating member 7 by the guide member 9 will be described in more detail.

The toner layer thickness regulating member 7 moves in relative contact with the guide member 9, but in this case, unless the coefficient of frictional resistance μ between the two members is small, the regulating member 7 cannot move smoothly. In this embodiment, Teflon (trade name) is used as the guide member 9, and aluminum is used as the holding portion 7a of the regulating member 7, and μ in this case is about 0.04 to 0.15.

However, the value of μ itself changes depending on conditions including differences in materials, loads, and the materials of the regulating member 7 and the toner carrying roller 6, but the value of μ varies from 0.04 to 0.04. By setting it to about 0.3, the regulating member 7 can be smoothly moved.

Also, the clearance between the regulating member 7 and the guide member 9 should be 0.2 m/m or less, preferably 0.1 m/m.
By setting the angle θ to a certain degree, the obtuse angle θ described above can be maintained with high precision regardless of the movement of the restriction member 7, and the movement of the restriction member 7 in the abutment direction can also be performed smoothly. As a result, the toner layer is uniformly and stably made thinner.

The toner layer thickness regulating member 7 thins the toner layer while being worn out over time, and has an edge portion on the toner entry side of the abutting end of the toner layer thickness regulating member that achieves this function. The angle α is an acute angle as shown in FIG. And the angle α is (π−
θ). Here, θ is of course the angle formed by the tangent 1 and the regulating member 7, and is an obtuse angle.

The angle α is set in the vicinity of (π-θ), that is, (π-θ-β). Here, β is
It is 0° or more and 10° or less. Now, if the angle α is set larger than (π-θ) from the beginning, the left edge portion will come into contact with the right edge portion earlier than the right edge portion at the initial stage of assembly. As a result, a wedge-shaped space is formed between the roller 6 and the toner, which is guided more than necessary, making it difficult to thin the toner layer in the early stages of using the developing device. Become. That is,
It is difficult to uniformly thin the toner layer until it reaches a state of wear where (π-θ). On the other hand, if we set it as (π-θ-β),
Even if there is some play in the installation, the right edge portion will be in contact with the roller 6 from the beginning, and the toner thinning function can be performed from the beginning. In other words, even until it wears down to (π-θ),
The layer thinning function can be achieved without changing the amount of toner adhered per unit area (relative to the roller 6).

Although the embodiments described above apply a contact development method in which the toner carrying roller 6 is brought into contact with the photoreceptor 1, the present invention can also be applied to a non-contact development method. Further, the present invention can also be applied to a developing method using a thinning means having a medium between a latent image carrier and a developer carrier.

In the embodiments shown in FIGS. 3 and 4, the developing device is placed above and below the photoconductor 1, respectively. There are no restrictions on location.

In FIG. 2, a toner layer thickness regulating member 7 is attached to a hook-shaped portion 12a of an arm 12, and an elastic spring 14 is applied to the arm 12, which is made swingable about a fulcrum shaft 13, and the regulating member 7 is attached to a toner carrying roller 6. This shows an embodiment in which it is brought into contact with. In addition, arm 12
has a sufficient length so as not to change the obtuse angle position of the regulating member 7. The present invention can also be applied to a pressurizing method having such a fulcrum. In this embodiment, there is no problem in changing the position of the fulcrum to the left by bringing the arm 12 to the chain line position.

(Effects) As described above, according to the present invention, since a thin layer of developer can always be formed uniformly and stably, high-quality images can always be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of an embodiment in which the toner layer thickness regulating member is pressurized by a different method, and Figs. 3 and 4 are diagrams of another embodiment. 5 is a diagram for explaining the toner layer regulating effect when the toner layer thickness regulating member is set at an obtuse angle position, and FIG. 6 is a diagram showing the toner layer when the regulating member is set at an acute angle position. FIG. 7, which is a diagram for explaining the layer regulating effect, is a diagram showing the manner in which the regulating member contacts the toner carrying roller. 2...Developing device, 6...Developer carrier, 7...
Developer layer thickness regulating member.

Claims (1)

[Scope of utility model registration request] Developer layer thickness regulation for regulating the developer layer thickness in a developing device that develops an electrostatic latent image on a latent image carrier with a developer carried on the circumferential surface of a roller-shaped developer carrier. The member is moved and biased so that this one end comes into contact with the circumferential surface of the developer carrier, and the tangent line and the developer layer thickness are The arrangement position of the developer layer thickness regulating member is determined so that the angle formed with the regulating member is an obtuse angle θ when viewed from the rotation direction of the developer carrier, and the developer is not allowed to enter at one end of the regulating member. The angle of the side edge portion is set to an angle near (π-θ), the regulating member is supported movably by a guide member in the direction of the arrangement position, and the guide member and the regulating member are The frictional resistance coefficient between 0.04
A developing device characterized in that the clearance between the two members is set to 0.2 m/m or less.