JP2002023491A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high quality image by optimally controlling layer thickness of one-component developer and electrification. SOLUTION: In the image forming device in which, on the downstream side from a developer supply starting point in the carrying direction, contact members abut on a developer carrier (2) which supplies developer to an image carrier (1) to develop an image, a relationship of μc<μd<μr is established, wherein μr, μc, and μd represent friction factors of a upstream contact member (4), the downstream contact member (5), and the developer carrier (2), respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a regulating blade and a charging member are brought into contact with a developer carrier.

[0002]

2. Description of the Related Art Conventionally, in a developing device which supplies toner to a photoreceptor on which an electrostatic latent image is formed and develops the toner, in the case of a one-component developing toner, the toner is compared with a two-component developing toner in which toner and carrier are mixed. Is not stable. Therefore, a plurality of elastic blades are brought into contact with the developing roller, and the developer is charged while adjusting the layer thickness of the developer with the first-stage elastic blade disposed on the upstream side (toner supply starting point side). (Japanese Patent Application Laid-Open No. 62-278578) has been proposed in which the toner is recharged by an elastic blade disposed on the downstream side to stabilize the charging of the one-component toner. In this proposal, the antinode of the elastic blade is brought into contact with the developing roller to provide a protruding portion toward the upstream side, and the length of the protruding portion (protrusion length) of the upstream elastic blade is set to the protruding length of the downstream elastic blade. By making the length shorter than the length, the layer thickness of the upstream elastic blade is regulated, and the downstream elastic blade is recharged so that all the toner whose layer thickness is regulated can pass through.

[0003]

However, in the above-mentioned proposal, since the layer thickness and charging of the toner are controlled only by the shape and the load of the elastic blade, the toner adheres to the elastic blade, and the portion is removed. Filming due to melting and hardening due to frictional heat, and uneven transport such as transport streaks are likely to occur.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to form a high-quality image by appropriately controlling the layer thickness and charging of a one-component developer.

[0005]

According to a first aspect of the present invention, a plurality of abutments are provided on a developer carrying member for supplying and developing a developer to an image carrying member on a downstream side in a transport direction from a developer supply starting point. In an image forming apparatus in which members are brought into contact with each other, when the friction coefficients of the upstream contact member, the downstream contact member, and the developer carrier with respect to the developer are μr, μc, and μd, respectively, μc <μd < μr. The invention according to claim 2 is characterized in that, when the friction coefficient of the supply member for supplying the developer to the developer carrying member with respect to the developer is represented by μs, there is a relation of μd <μs.

[0006]

Embodiments of the present invention will be described below. The image forming apparatus of the present invention is applicable to both mono-color and full-color. First, the configuration of the developing device according to the present invention will be described with reference to FIGS.

FIG. 1 is a schematic view showing an example of a developing device used in the present invention. The developing device is required to convey the toner to a developing position (a portion where the photoconductor 1 and the developing roller 2 are opposed), and at the same time, impart a predetermined layer thickness, a conveying amount, and a charging amount to the toner and perform the development. The developing device includes a developing roller 2 for supplying the toner contained in the housing to the photoreceptor 1, a supply roller 3 for supplying the toner transferred from the agitator to the developing roller 2, and a developing roller which is pressed against the developing roller 2. The upstream contact member (regulating member) 4 and the downstream contact member (charging member) 5 for regulating the layer thickness and the transport amount of the toner above, and the lower seal 6 for preventing leakage of the toner in the housing. Have.

The developing roller 2 is formed of a metal material such as iron, SUS or A1 having a diameter of 15 to 25 mm, and its surface is given a roughness by blasting or chemical polishing to improve the printing durability. Hardening treatment such as plating and alumite is performed. The developing roller holds the toner due to surface roughness or electrostatic force, carries the toner to a developing position opposite to the photoconductor, and rotates in the same direction at a contact portion with the photoconductor. The speed is 1.5 to 2.5 times the peripheral speed of the photoconductor.

The supply roller 3 is made of a porous elastic material made of a foam material such as urethane or silicon, and carries the toner on the surface thereof and supplies the toner by rubbing against the developing roller 2. By setting the peripheral speed of the supply roller 3 to about 50 to 80% of that of the developing roller 2, it is possible to ensure the supply of the toner to the developing roller and to prevent the deterioration of the toner. Further, the development history is suppressed by peeling off the toner from the developing roller after the development and supplying the toner at the same time.

The upstream contact member 4 functions as a regulating blade by contacting an elastic body such as urethane or silicon rubber provided at the tip of the support member with the toner on the developing roller by a tension coil spring or the like. The conveyance amount is determined without causing conveyance unevenness such as a conveyance line in the upper toner, and conveyance failure such as filming does not occur through durability. At this time, the toner is also charged. However, if the charge is strong, the toner adheres to the regulating blade and causes filming. Therefore, it is necessary to suppress the charging.

The downstream contact member 5 contacts the toner on the developing roller by pressing a sheet material such as urethane or nylon or a sheet material coated with urethane paint with the compressive force of an elastic body. Without restricting the toner, the toner is passed between the contact member and the developing roller to a charge amount suitable for development (in this embodiment, negative charge), the transfer surface is adjusted, and a transfer failure such as filming does not occur through durability.

The lower seal 6 makes the antinode of the sheet material such as urethane or PET abut against the developing roller so that the tip protrudes in the direction of rotation of the developing roller. Seal to prevent toner inside the body from leaking outside. Preferably, the charge on the toner on the developing roller after the development is removed, and the reset by the supply roller (stripping off the toner on the developing roller) and the resupply of the toner are assisted.

In FIG. 1, the upstream contact member 4 and the downstream contact member 5 are connected to each other by a support member through an elastic member 7 made of foam, soft rubber or the like. The contact member 5 can move independently to contact the developing roller, and there is no possibility that one contact abuts the other. The upstream contact member 4 is formed by the elastic member 7.
Since the and the downstream contact member 5 are connected, it is difficult to independently control the contact pressure between them, but since they do not interfere with each other, they can be uniformly contacted, Further, the degree of freedom in selecting the material of the contact member is large.

FIG. 2 is a schematic view showing another example of the developing device used in the present invention. The same reference numerals as in FIG. 1 denote the same contents, and only the structure of the contact member is different. Will be described only. The downstream contact member 5 'is formed by attaching a leaf spring to the upstream contact member 4' functioning as a regulating blade. A sheet material such as urethane is adhered to the surface of the leaf spring that comes into contact with the developing roller, as in the case of FIG. 1, but any material that can be adhered to the leaf spring may be used. In this example, one abutment affects the other, and the abutment of the downstream abutment member reduces the regulated load on the upstream side, making stable abutment difficult. There is an advantage that space can be achieved.

FIG. 3 is a schematic diagram showing another example of the developing device used in the present invention. The same reference numerals as those in FIGS. 1 and 2 denote the same contents, and only the structure of the contact member is different. Therefore, only this point will be described. The downstream contact member 5 ″ is provided separately from the upstream contact member 4 ″ to contact the developing roller, and although the configuration is relatively complicated, the downstream and upstream sides are completely independent. Because of the contact, there is no interference between the two, and the desired contact conditions are obtained.In addition, since the holding of the downstream contact member is of the holder type, the elastic material of the backing has a very high degree of freedom, and the foam Solid rubber can be used as desired.

Next, a mechanism for determining the thickness of the toner layer on the developing roller and the transport amount will be described. The layer thickness and the transport amount of the toner on the developing roller are determined by the relationship between the transporting force of the developing roller for transporting the toner and the regulating force of the contact member.

The transporting force of the developing roller refers to the toner holding force of the developing roller, and depends on the surface morphology, roughness, coefficient of friction with toner, and tackiness of the developing roller. By making the surface of the developing roller a form and roughness suitable for holding the toner, specifically, a roughness of about 0.5 to 2 times the toner particle diameter, the conveying force is improved. As for the coefficient of friction with the toner, the higher the toner conveying force, the higher the coefficient of friction.
It is desirable to have the above. If the tackiness is present, the conveying force is increased, but on the other hand, there is a problem that the release of the toner from the developing roller is deteriorated.

The regulating force of the contact member depends on the contact pressure, the shape of the entrance, the surface roughness, the coefficient of friction, and the tackiness. The contact pressure is determined by the contact load and the area (nip area) of the contact portion between the contact member and the developing roller, and the higher the higher, the greater the regulating force. However, 2 g is required for stable contact in high-speed development.
/ Mm ² or more is required. On the other hand, if the contact pressure is too high, the abrasion of the contact portion is accelerated, the stress on the toner is increased, and filming occurs, so that 100 g / mm.
It is desirable to set it to ² or less. The contact pressure of the upstream and downstream contact members determines the transport amount on the upstream side and does not change the transport amount on the downstream side, so that the upstream side is larger than the downstream side.
The entrance shape refers to a form of a portion where toner enters the contact portion, and is represented by a contact R (curvature of roundness of the contact portion), a protrusion length, and a contact angle. The smaller the contact R and the smaller the protruding length, the closer the edge contact, the higher the regulating force. However, when the R portion is contacted, the regulating force is too high if the R is smaller than the toner particle diameter. It is desirable to make the above. Further, the friction coefficient of the contact member is set larger on the upstream side than the developing roller in order to determine the transport amount, and is set smaller on the downstream side so as not to restrict the toner. However, when the ratio exceeds 0.8, the toner is held by the contact member, which causes filming, which is not preferable. By making the surface roughness of the contact member smaller than that of the developing roller, the toner can be carried on the developing roller and transported. Conversely, if the surface roughness of the contact member is increased, the toner is carried on the contact member, causing filming. On the other hand, by making the surface roughness of the downstream-side contact member smaller than that of the upstream side, the toner layer is made more uniform and does not disturb. The tackiness tends to be the same as that of the developing roller. If the tackiness is larger than necessary, it causes filming, which is not preferable.

As described above, the conveying force and the regulating force are determined not only by one characteristic but also by a combination of a plurality of elements. However, by giving priority to the main characteristics,
The conveying force and the regulating force can be set in a desirable relationship.

Next, the relationship between the desired friction coefficient between the contact member and the developing roller will be described. As described above, the toner conveying force increases as the friction coefficient of the developing roller increases, while the upstream contact member determines the conveyance amount and the downstream contact member does not change the conveyance amount. Is required to be larger on the upstream side than on the developing roller and smaller on the downstream side than the developing roller so as not to restrict toner. The upstream contact member that overcomes the toner carrying force of the developing roller and determines the conveyance amount is 2 g / g as described above.
It should be regulated with a relatively low load of mm ^{2 to} 100 g / mm ² .

FIG. 4 shows the relationship between the change in the friction coefficient of the abutting member with respect to the toner and the toner conveyance amount when the friction coefficient of the developing roller with respect to the toner is 0.5. The toner transport amount sharply increases when the friction coefficient of the contact member is smaller than 0.5, and decreases when it is larger than 0.5. As can be seen from this relationship, when the friction coefficient for the toner is the upstream contact member μr, the developing roller μd, and the downstream contact member μc, respectively, μc <μd <μr. With this configuration, the upstream contact member can overcome the force of the developing roller to carry the toner, regulate the toner layer thickness, and determine the transport amount. on the other hand,
If the regulating force on the toner in the upstream contact member is strong, a conveying streak is likely to occur due to the surface shape of the regulating blade. Therefore, the transport surface can be adjusted by suppressing the toner layer without regulating the toner layer with a downstream contact member having a smaller coefficient of friction than the developing roller. The toner can be rubbed, so that the charge of the toner is improved.

FIG. 5 is a view showing a state of restricting toner conveyance at a contact portion of the upstream contact member with the developing roller. The developing roller is moved in the direction of the arrow (from right to left in the figure).
The toner is rotated, and the numbers in the circles are the numbers assigned to explain the behavior of the individual toners. Since the friction coefficient μr of the upstream contact member 4 with respect to the toner is larger than the friction coefficient μd of the developing roller,
As shown in the figure, the toner which is not in direct contact with the surface of the developing roller is regulated and is not conveyed.

FIG. 6 is a view showing a state in which the downstream contact member regulates the toner conveyance at the contact portion with the developing roller, and the developing roller is moved in the direction of the arrow (from right to left in the figure).
It rotates and moves, and the numbers in the circles are the numbers assigned to explain the behavior of the individual toners, and are numbered 1 to 7 in the figure. Since the friction coefficient μc of the downstream contact member 5 with respect to the toner is smaller than the friction coefficient μd of the developing roller, as shown in FIG.
Everything is conveyed, and only functions as a charging member without changing the conveyance amount.

Next, the relationship between the desired coefficient of friction between the supply roller and the developing roller will be described with reference to FIGS. As described above, the supply roller is formed of a porous elastic material, and supplies the toner by holding the toner on the surface and rubbing the toner against the developing roller, peeling the toner from the developing roller after development (reset), and simultaneously supplying the toner. By doing so, generation of a development history is suppressed. FIG. 7 is a diagram illustrating a state of toner supply from the supply roller to the developing roller. Supply roller 3
And the developing roller 2 rotate so as to move in opposite directions at the contact portion. As shown in the drawing, the residual toner conveyed after development is peeled off from the developing roller by the supply roller 3 and is conveyed as it is, or once dropped off from the supply roller and mixed with other toner and conveyed by the supply roller, It is again rubbed against the developing roller.

FIG. 8 is a diagram showing a state in which residual toner is peeled off from the developing roller by the supply roller. The supply roller 3 elastically presses against the developing roller 2 and moves in a direction opposite to the developing roller at the press contact portion, so that the supply roller 3 cannot enter the press contact portion and is peeled off. 3 and is transported. As described above, the toner on the developing roller after development is removed by the lower seal (in the present embodiment, the toner is negatively charged, so that the toner is charged to the positive side by friction with the toner). As a result, the residual toner is easily peeled off.

FIG. 9 is a diagram showing how toner is rubbed from the supply roller to the developing roller. This is the opposite phenomenon to the case where the residual toner is peeled off from the developing roller, and the supply roller 3 is elastically pressed against the developing roller 2,
Since the toner is transported in the direction opposite to the developing roller at the pressure contact portion, the toner transported by the supply roller cannot enter the pressure contact portion, but is peeled off from the supply roller and transported by the developing roller.

[0027]

According to the first aspect of the present invention, since the upstream contact member has a higher coefficient of friction than the developing roller, the toner carried on the developing roller in the supply portion overcomes the force of the developing roller to carry the toner. The amount of conveyance can be determined by regulating the load with a low load using the upstream contact member. Also, if the upstream contact member has a strong regulating force on the toner, conveyance streaks are likely to occur depending on the surface shape of the contact member. However, the downstream contact member is provided to suppress the toner layer to adjust the conveyance surface. be able to. Since the downstream contact member has a lower coefficient of friction than the developing roller, it does not regulate the toner layer. Further, since the downstream contact member can rub the toner against the developing roller without disturbing the toner layer, the charging of the toner is improved, and the fog and the development history can be improved.

According to the second aspect of the present invention, the layer thickness of the developing roller after development is different between the portion where the toner is consumed by the development and the remaining portion, and when the toner is resupplied in that state, the layer thickness becomes small. Different toner is supplied to the developing position, causing image unevenness. By making the friction coefficient of the supply roller larger than that of the developing roller, the ability to reset the toner from the developing roller is improved. At the same time, by supplying the toner, a uniform image can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a developing device used in the present invention.

FIG. 2 is a schematic view showing another example of the developing device used in the present invention.

FIG. 3 is a schematic view showing another example of the developing device used in the present invention.

FIG. 4 shows a friction coefficient of the developing roller with respect to the toner of 0.
5 is a diagram illustrating a relationship between a change in a friction coefficient of a contact member with respect to toner and a toner conveyance amount when the number is set to 5. FIG.

FIG. 5 is a diagram illustrating a state of regulating toner conveyance at a contact portion of an upstream contact member with respect to a developing roller.

FIG. 6 is a diagram illustrating a state of restricting toner conveyance at a contact portion of a downstream contact member with a developing roller.

FIG. 7 is a diagram illustrating a state of toner supply from a supply roller to a developing roller.

FIG. 8 is a diagram illustrating a state in which residual toner is peeled off from a developing roller by a supply roller.

FIG. 9 is a diagram illustrating a state in which toner is rubbed from a supply roller to a developing roller.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor 2 developing roller 3 supply roller 4 upstream contact member 5 downstream contact member 6 lower seal 7
... elastic body.

Claims (2)

[Claims] An image forming apparatus in which a plurality of contact members are brought into contact with a developer carrier that supplies a developer to an image carrier and develops the developer at a downstream side in a transport direction with respect to a developer supply start point. , The friction coefficients of the upstream contact member, the downstream contact member and the developer carrier with respect to the developer are μr and μ, respectively.
An image forming apparatus, wherein c and μd have a relationship of μc <μd <μr. 2. The image forming apparatus according to claim 1, wherein a relation of μd <μs is satisfied when a friction coefficient of the supply member for supplying the developer to the developer carrier with respect to the developer is μs.