JPH05257376A - Developing device - Google Patents

Abstract

PURPOSE:To stably form a toner layer where there is small toner which is not electrostatically charged and which has desired electrostatic charge quantity on a developing roller and to supply it to a latent image carrier. CONSTITUTION:The developing roller 4 is constituted so that a dielectric part 41 and an electrical conductive part 42 are made to coexist and exposed on the surface thereof with fine areas. A toner supply roller 5 is arranged so as to be made to be in press-contact with the roller 4. Then, both rollers 4 and 5 are driven so that the mutual surfaces thereof are moved in an identical direction at the contact part of both of them. Besides, a layer thickness smoothing member 8 is provided so as to be made to be in press-contact with the surface of the roller 4 which is passed through a press-contact part with the roller 5 by the linear pressure of 10-50gf/cm being comparatively low. Thus, the dielectric part 41 of the roller 4 is charged by the friction on toner or the surface of the roller 5 and electric charge is held. Then, a fine closed electric field is formed between the dielectric part 41 and electrical conductive part 42. By the electric field, the large amount of only the toner which is passed through the press-contact part of both rollers 4 and 5 and electrostically charged is carried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile machine, a printer, etc., and more particularly to stabilizing toner charging in a developing device using a one-component developer. It is about.

[0002]

2. Description of the Related Art In an image forming apparatus in which an electrostatic latent image is formed on a latent image carrier and visualized by a developer, one component is used in view of downsizing, cost reduction and high reliability of the developing apparatus. A developing device using a system developer (hereinafter referred to as toner) is advantageous. In addition, it is advantageous to use a non-magnetic toner because it has high transparency for colorization. And
A developer carrier that is driven so that the surface of the toner moves toward the surface facing the latent image carrier so as to supply a predetermined charge to the toner and supply the toner to the developing area that faces the latent image carrier. There is known a developing device having a developer supplying member for supplying toner to the surface of the developer carrying member. For example, JP-A-61
No. 42672 discloses that a medium resistance (10 ⁹ to 10 ¹¹ Ωcm) developing roller having a float electrode as a developer carrying member and a sponge roller made of, for example, polyurethane as a developer supplying member are brought into pressure contact with each other. It is disclosed that they are arranged and rotated so that the surfaces of each of them are moved in opposite directions at the pressure contact portions of both. This developing device is also provided with a blade as a layer forming member that presses against the developing roller with a predetermined contact force in order to regulate the toner adhesion amount on the developing roller to a predetermined amount. In this developing device, the toner conveyed to the pressure contact portion of both by the rotation of the sponge roller is frictionally charged at the pressure contact portion and adhered to the surface of the developing roller. Then, the layer thickness of the toner layer made of toner adhered to the surface is regulated by the blade to form a predetermined amount of toner layer on the developing roller. Then, by rotating the developing roller, the toner layer is conveyed to a contact portion with the photoconductor as a latent image carrier to develop the electrostatic latent image on the photoconductor.

[0003]

The optimum toner charge amount and toner adhesion amount in the one-component developing system, for example, the non-magnetic one-component developing system will be described below. The toner charge amount is preferably 5 to 10 μc / g as an average charge amount, and the toner charge amount distribution is desired to be a stable distribution in which there are few relatively low-charged toners that cause sharpness and deterioration of resolution and scumming. .. On the other hand, the amount of toner deposited on the developing roller, image bearing member at 0.6~1.0mg / cm ² about the toner adhesion amount, 0.5~0.7mg / cm ² of about toner adhesion on paper transfer It is desirable that the amount can be obtained. The toner adhesion amount on the latent image carrier and the transfer sheet depends not only on the toner adhesion amount on the developing roller but also on the relative speed between the latent image carrier and the developing roller in the developing area.

However, according to the conventional developing device, since the toner layer on the developing roller is one layer and the adhesion amount is small, the charge amount of the toner conveyed to the developing area is 5 to 5 on average.
Although it is about 15 μc / g, the toner adhesion amount on the developing roller is 0.2 to 0.8 mg / cm ² , and in order to obtain the desired toner adhesion amount on the latent image carrier, etc. It is necessary to set the speed of the developing roller to 2 to 4 times the speed of the latent image carrier. In this way, when the rotation of the developing roller is set high in order to cover the insufficient toner adhesion amount on the developing roller, not only it is difficult to increase the image forming speed, but also when the solid portion is developed. There is also a phenomenon called "toner trailing edge shift" in which the density of the trailing edge of the image becomes high. This phenomenon is not a big problem in a black and white image, but in a color image there is a problem that the color is transmitted through the toner and the color is visualized, so that the density is high at the rear end portion, and in the case of a superimposed image, a color difference occurs. ..

Therefore, in order to obtain a desired toner adhesion amount on the latent image carrier or the like without causing such a phenomenon of "toner trailing edge", the speed of the developing roller is set to the latent image carrier. It is necessary to approach the speed of the body, that is, to approach constant-velocity development, and increase the amount of toner adhered on the developing roller as compared with the conventional method. Specifically, a sufficient toner adhesion amount on the latent image carrier or transfer paper is
In order to ensure almost constant speed development, the toner adhesion amount on the developing roller should be at least 0.8 mg / cm ² in the contact development method with good development efficiency and at least 1.0 mg / cm ^{2 in} the non-contact development method with poor development efficiency. Must be cm ² . In order to obtain such toner adhesion amount on the developing roller, the toner layer thickness must be two or more layers.

Here, the contact pressure of the blade may be set to be weak only for the purpose of making the toner layer thickness of two or more layers. However, in the developing device according to the above conventional example,
Since the surface of the developing roller and the sponge roller move in opposite directions at the pressure contact portions of the developing roller and the sponge roller, the surface of the developing roller passing through the pressure contact portions also contains uncharged toner from the toner accommodating portion. Supplied with a sponge roller. Therefore, a large amount of uncharged toner is contained in the upper layer portion of the toner layer on the developing roller that enters the blade contact portion. Therefore, the distribution of the charge amount of the toner on the developing roller that has passed through the blade contact portion is in the range of 10 μc / g or less, and includes uncharged toner and reversely charged toner. This non-charged toner or the like has a poor development transfer, and causes background stains and resolution deterioration.

As described above, all the toner in the upper layer of the toner layer on the developing roller is fully charged, and there is no uncharged toner. Forming on the developing roller is the most important issue in increasing the image forming speed and enabling constant speed development for preventing "from the trailing edge of the toner".

The amount of toner adhered on the developing roller is
Even if there are too many, problems will occur. That is, when the amount of the adhered toner is 2.0 mg / cm ² or more, problems such as background stain and deterioration of resolution occur regardless of the toner charge amount. In addition, the surrounding environment changes and low humidity environment (for example,
At 5% RH), the toner charge amount rises compared to normal (normal temperature and humidity) and the toner adheres strongly to the developer carrier, so the toner supply amount becomes excessive and the adhered amount on the roller increases, It is easy to exceed the appropriate amount above. Therefore, image fluctuation due to the environment becomes a big problem. Further, in the conventional configuration, the layer regulating member that abuts the developer carrying member has a relatively high abutment pressure, so that the material that can be used as the layer forming member is limited in terms of strength and releasability. ..

The present invention has been made in view of the above problems, and an object of the present invention is to provide an appropriate amount of a uniform toner layer having a desired amount of uncharged toner with a developer. It is an object of the present invention to provide a one-component developing device that can be stably formed on a carrier and supplied to the latent image carrier.

[0010]

In order to solve the above-mentioned problems, the present invention is directed to a developer carrier which is driven so that the surface moves, and the surface moves in contact with the surface of the developer carrier. And a developer supply member driven by the developer supply member, wherein the developer supplied to the developer carrier by the developer supply member visualizes the latent image on the latent image carrier. As the agent carrier, one capable of selectively retaining an electric charge on the surface to form a large number of minute electric fields is used, and the moving directions of the surface of the developer supplying member are set to the same direction at the contact portion with the surface of the developer carrier. A layer regulating member, which is set so as to move and uniformizes the layer of the developer on the surface of the developer carrier that has passed through the contact portion, has a free end downstream from the base end in the developer carrier surface moving direction. And the free end is provided on the surface of the developer carrying member by 10 to 0 g is characterized in that is pressed against at a linear pressure of the heavy / centimeter.

[0011]

In the present invention, the developer supplying member conveys the one-component developer from the developer storage means to the contact portion with the developer carrying member, and the developer is frictionally charged at the contact portion. At this time, the moving direction of the surface of the developer supply member and the surface of the developer carrier is such that both surfaces move in the same direction at the contact portions of both, so that the surface of the developer carrier passing through the contact portions The developer supplying member does not directly supply the uncharged developer from the toner containing portion. Therefore, on the surface of the developer carrying member which has passed through the contact portion, only the developer sufficiently charged by the triboelectric charging at the contact portion is carried in a laminated state on the surface by the minute electric field near the surface of the developer carrying member. .. Then, the developer layer on the developer carrying member that has passed through the contact portion is made uniform by a layer regulating member whose free end is pressed against the surface of the developer carrying member with a linear pressure of 10 to 50 gf / cm. As a result, even when the amount of the developer on the developer carrier that has passed through the contact portion is increased due to a change in the surrounding environment or the like, the proper amount of the attached developer can be obtained. Here, the reason why the pressure contact force of the layer regulating member with respect to the developer carrying member can be set to a relatively low pressure such as 10 to 50 gf / cm is that the developer carrying member and the developer supplying member are in contact with each other. By driving so that the surface moves in the same direction in the part, the absolute amount of the developer supply amount by the developer supply member to the developer carrying member is relatively reduced, and the charge amount distribution is relatively uniform. This is because the developer layer is formed. As described above, since the pressing force of the layer regulating member against the developer carrying member is relatively low, the strength and releasability are not required as much as the layer regulating member in the conventional developing device.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of an electrophotographic copying machine will be described below. FIG. 1A is a front view showing a schematic configuration of the developing device according to this embodiment. The photosensitive drum 1 as a latent image carrier has a peripheral speed of 120 mm, for example.
With / Sec, it is driven to rotate clockwise by the arrow. A developing device 2 is arranged on the right side of the photosensitive drum 1. Around the photosensitive drum 1, a known charging device, an exposure optical system, a transfer / separation device, a cleaning device, and a destaticizing device (none of which are shown) are arranged to carry out an electrophotographic process. The developing device 2 of this embodiment includes a casing 3 having an opening facing the surface of the photoconductor drum 1, and a developing roller which is partially exposed from the opening and is rotationally driven counterclockwise in the arrow direction at a predetermined peripheral speed. 4, a toner supply roller 5 as a developer supply member that is rotationally driven in the clockwise direction of the arrow in a state of being pressed against the right side portion of the developing roller 4, and a hopper portion configured on the right side portion inside the casing 3. The non-magnetic toner (hereinafter referred to as toner) accommodated in the supply roller 5
The agitator 6 that supplies the toner to the surface and agitates the toner in the hopper, and the rotation of the developing roller 4 makes the thickness of the toner layer on the developing roller 4 that is conveyed to the developing area, which is the portion facing the photosensitive drum 1, uniform. It has a smoothing layer thickness smoothing plate 8.

The casing 3 has a shape such that the inner surface portion below the toner supply roller 5 maintains a predetermined gap with the surface of the toner supply roller 5.

The developing roller 4 may be arranged with a predetermined gap from the surface of the photosensitive drum 1 as shown in FIG.
Contact development may be performed by disposing the upper toner layer so as to contact the surface of the photosensitive drum 1. In any case, in order to prevent the above-mentioned phenomenon that the trailing edge of the toner is deviated, the developing roller 4 is rotated such that the surface moving direction in the developing area is the same direction as the photosensitive drum 1 and the peripheral speed thereof is the same. The peripheral speed of the photosensitive drum 1 is approximately equal to the peripheral speed, that is, about 120 mm / sec in this example. However, in the contact development, if the development is completely constant speed, there is no difference in speed between the surface of the photosensitive drum 1 and the surface of the developing roller 4, so that the physical development is performed regardless of the potential of the surface of the photosensitive drum 1. Toner may adhere. In order to prevent this, the peripheral speed of the developing roller 4 is set to be slightly higher. For example, the peripheral speed ratio (1 peripheral speed of the photosensitive drum: 4 peripheral speed of the developing roller) is preferably 1: 1.05 to 1.1. With such a speed ratio, the above-mentioned trailing edge toner deviation is not noticeable. Further, an appropriate developing bias voltage, for example, direct current, alternating current, alternating current of direct current superposition, pulse voltage or the like is applied to the developing roller 4. In particular, in the case of non-contact development, it is desirable to apply a voltage having an alternating component with good flight conditions (AC, AC with superimposed DC, or pulse voltage).

The developing roller 4 of this example is shown in FIG. 2A for the purpose of increasing the amount of adhered toner.
As shown in (c) to (c), the dielectric portion 41 and the conductor portion 42 are configured to be exposed in a mixed manner on the surface in a minute area. FIG. 2A is an explanatory view showing the surface of the developing roller 4, FIG. 2B is its cross section, and FIG. 2C is a toner layer forming state on the surface. The size of the dielectric portion 41 is, for example, about 50 to 200 μm in diameter. It is arranged that such dielectric portions 41 are dispersed randomly or according to a certain rule. The area ratio of both parts is the dielectric part 41.
The area is preferably in the range of 40 to 70%. As the material of the dielectric portion 41, a material having a resistance value such that electric charges are not accumulated by frictional charging by the toner supply roller 5 is used. To form the surface layer portion shown in the figure, for example, knurling the surface of the cored bar roller to form a predetermined groove, coating an insulating resin, for example, and then cutting the surface to form a cored bar. And the resin in the groove is the dielectric part 4
1 can be formed by exposing each surface. The surface structure shown in FIGS. 3A and 3B may be replaced with the surface structure shown in FIGS. 2A to 2C. FIG. 3A is the surface of the developing roller, and FIG.
FIG. 3 is an explanatory diagram showing a toner layer formation state on the surface thereof. In the surface portion of this example, after a surface layer made of a conductive material in which dielectric particles having a particle size of, for example, 50 to 100 μm are dispersed is formed on a cored roller, the surface layer is slightly cut if necessary. Can be formed by

The toner supply roller 5 preferably has a structure such as a roller provided with a sponge layer and a roller having a large number of fur brushes planted therein so that the toner can be retained inside the vicinity of the surface. Further, at least the surface material is in the middle of the toner material and the developing roller 4 material in the triboelectrification series so that the toner and the developing roller 4 can be contacted with the developing roller 4 and desired triboelectrification can be given. To adopt. Then, the toner supply roller 5
Is rotated in the forward direction in which the surface moves in the same direction as the surface of the developing roller 4 at the contact portion B with the developing roller 4. The peripheral speed is, for example, about 0.5 to the peripheral speed of the developing roller 4.
It is desirable to set it to 1.5 times. Further, the same voltage as that applied to the developing roller 4 may be applied to the core metal of the toner supply roller 5.

The agitator 6 supplies the toner contained in the hopper to the surface of the toner supply roller 5 and agitates the toner. However, the agitator 6 uses the weight of the toner due to the shape of the hopper and the fluidity of the toner. When it is possible to supply to the surface of the supply roller 5,
You may omit it.

In the layer-thickness leveling plate 8, the free end is located downstream of the base end in the direction of movement of the surface of the developing roller 4, and the free end is in contact pressure of about 10 to 50 gf / cm. Is arranged so as to contact the developing roller 4. The layer-thickness leveling member 8 can be made of, for example, an organic or inorganic material.

In the above structure, the toner contained in the hopper is supplied to the surface of the toner supply roller 5 on the hopper side by the agitator 6. The toner supplied to the toner supply roller 5 adheres to the voids and the surface of the sponge or brush and is conveyed toward the contact portion between the toner supply roller 5 and the developing roller 4 by the clockwise rotation of the toner supply roller 5. On the other hand, in the contact portion B with the toner supply roller 5, the surface portion of the developing roller 4 which has passed through the developing area by the counterclockwise rotation of the developing roller 4 also enters.

At this contact portion B, the surface of the toner supply roller 5 and the surface of the developing roller 4 move with a relative speed difference, so that they do not adhere to the surface of the photosensitive drum 1 when passing through the developing area and remain on the surface of the developing roller 4. The residual toner in the non-image area is scraped mechanically and electrically by the toner supply roller 5 (for example, a sponge roller), and
The electric charge on the developing roller 4 is also made constant by the triboelectric charging by the toner supply roller 5, whereby the surface of the developing roller 4 is initialized. Then, due to the friction between the developing roller 4, the toner and the toner supplying roller 5, the developing roller 4
The charge of the opposite polarity to the desired toner charging polarity is applied to the dielectric portion 41 (in the normal development (P / P), the charge has the same polarity as the photoconductor charge, and in the reversal development (N / P), the photoconductor charge is charged). (Charging of opposite polarity) is applied, and a microfield (closed electric field) is created on the developing roller 4 as shown by electric force line E in FIG. On the other hand, since the toner supply roller is rotating in the forward direction with respect to the developing roller 4, the toner attached to the toner supply roller 5 is slid between the developing roller 4 and the toner supply roller 5, and most of the toner has a desired polarity (regular). In development, it has a polarity opposite to that of the photoreceptor charge, and in reversal development, it has the same polarity as the photoreceptor charge. Then, the charged toner on the toner supply roller 5 is electrostatically attracted by the electric field of the microfield on the developing roller 4 and adheres to the surface of the developing roller 4 in multiple layers. As a result, the developing roller 4 exits the contact portion B in a state where the sufficiently charged toner is carried in multiple layers. In this embodiment, since the toner supply roller 5 and the developing roller 4 are rotated in the forward direction, unlike the developing device according to the conventional example described above, the toner supply roller 5 rotates to pass through the contact portion B. No uncharged toner is supplied from the hopper onto the developing roller 4. This point will be described in detail later.

The thickness of the toner layer on the developing roller 4 that has passed through the contact portion B is uniformly controlled by the layer leveling member 8 that is in light contact with the developing roller 4. Here, since the contact force of the layer-thickness leveling member 8 to the developing roller 4 in this embodiment is set to be about 10 to 50 gf / cm as described above, the contact force is relatively high even if the environment changes. It is possible to form two or more toner thin layers having a stable adhesion amount. This point will be described in detail later.

The toner layer that has passed through the layer thickness leveling member 8 is conveyed to the developing area. In the developing area, the development is performed while the surface of the developing roller 4 to which the optimum developing bias is applied by the contact or non-contact developing method and the surface of the photosensitive drum 1 move at substantially the same speed. In this developing area, the electric conductor portion 42 of the developing roller 4 exerts an electrode effect to form an electric field in which the toner on the developing roller 4 easily adheres to the photosensitive drum 1.

Here, stabilization of the toner charge distribution of the toner layer carried by the developing roller 4 by the forward rotation of the toner supply roller 5 and the developing roller 4 will be described in detail. FIG. 4 and FIG. 5 show the toner adhesion and charging status on the developing roller 4 when the toner supply roller 5 (sponge roller in the illustrated example) and the developing roller 4 respectively rotate forward and reverse. It is a schematic representation. In the figure, ◯ indicates toner, and only those that are charged are marked with a + in the circle to indicate whether or not they are charged. As shown in FIG. 4, when the toner supply roller 5 and the developing roller 4 rotate in the forward direction, the charged toner already attached to the toner supply roller 5 and the uncharged toner newly supplied from the hopper unit are detected. Both of them are conveyed to the contact portion with the developing roller 4 by the toner supply roller 5, and at this contact portion, all the toner is charged by the friction between the rollers 4 and 5 and adheres onto the developing roller 4. Since the toner supply roller 5 and the developing roller 4 are rotated in the forward direction, the rotation of the toner supply roller 5 does not supply uncharged toner from the hopper to the developing roller 4 that has passed through this contact portion. .. Therefore, the amount of toner adhering to the developing roller 4 that has passed through the contact portion is relatively stable because it is determined by the electric field of the developing roller 4, the porosity of the sponge roller as the toner supply roller 5, and the like. On the other hand, as shown in FIG. 5, even when the toner supply roller 5 and the developing roller 4 rotate in reverse, the charged toner already attached to the toner supply roller 5 and the uncharged toner newly supplied from the hopper unit Both of them are conveyed to the contact portion with the developing roller 4 by the toner supply roller 5. In particular, as in the illustrated example, new toner (a blank arrow indicates a supply path to the surface of the toner supply roller 5) supplied from the hopper portion remains on the toner supply roller 5 and the developing roller 4 In the case where the toner is conveyed to the contact portion with, the relatively large amount of uncharged toner is conveyed to the entrance of the contact portion.
Then, the toner that has entered this contact portion and is sufficiently charged by the friction between the rollers 4 and 5 is positively charged to the developing roller 4.
It adheres to the surface and is carried out from this contact part. In addition, the insufficiently charged toner carried on the toner supply roller 5 to the entrance of the contact portion is also contacted by electrostatic force (gradient force) due to the electric field on the developing roller 4 or toner cohesive force. Adheres on the developing roller 4 after passing through the part. The amount of toner physically attached due to the toner cohesive force and the like greatly changes depending on the environment. In particular, when a microfield electric field is formed on the surface to form a multi-layer toner like the developing roller 4 of this embodiment,
The attachment of the uncharged toner leads to unstable toner sticking too much.

FIGS. 6A and 6B show the developing roller 4 at a position before passing through the layer thickness leveling member 8 when the toner supply roller 5 and the developing roller 4 rotate forward and reverse, respectively. 6 is a diagram showing the distribution of the charge amount of toner in the upper toner layer. As shown in FIG. 7, the distribution of the charge amount of the toner is obtained by suctioning the toner carried on the developing roller 4 by the suction nozzle 9 while changing the distance from the surface of the developing roller 4 and sampling the toner a plurality of times. 9 is a graph in which the charge amount and the adhesion amount of the suction toner captured by the filter 91 in 9 are obtained, and this is graphed as the charge amount distribution in the carried toner on the developing roller 4. From this graph as well, in the case of reverse rotation (Fig. 6)
(B) It can be seen that the amount of uncharged toner is large, whereas the amount of uncharged toner is drastically reduced during forward rotation. Figure 8
(A) and (b) show the case where the toner supply roller 5 and the developing roller 4 rotate forward and the case where they rotate reversely, respectively.
6 shows the distribution of the charge amount of toner in the toner layer on the developing roller 4 at the position after passing through the layer leveling member 8.
From this, it can be seen that the amount of uncharged toner is large in the reverse rotation (FIG. 8B), whereas the amount of the uncharged toner is drastically reduced in the forward rotation.

As described above, when the toner supply roller 5 and the developing roller 4 rotate in the forward direction, the developing roller 4
The amount of toner adhered to the toner is unlikely to be affected by environmental fluctuations, and a charge amount distribution of toner containing less uncharged toner can be obtained, which is extremely advantageous for stability of developing characteristics.

Next, the layer thickness leveling member 8 of this embodiment will be described in detail. In the conventional developing device of this type, in order to make the layer thickness of the toner adhered on the developing roller 4 and conveyed to the developing region appropriate, the contact pressure of the layer thickness leveling member to the developing roller 4 is set. It had to be set relatively high. Further, when the toner charge amount changes due to the change of the surrounding environment, the toner supply amount may change and the image density may change. On the other hand, in this embodiment, by rotating the developing roller 4 and the toner supply roller 5 in the forward direction as described above, the absolute amount of toner supply is reduced, and the charge amount distribution becomes uniform as will be described later in detail. With the layer-thickness leveling member 8, no extra contact pressure is required, and a uniform toner layer can be formed with a low linear pressure of 50 gf / cm or less. Further, even if the amount of toner supplied by the toner supply roller 5 is increased, the linear pressure of the layer-thickness leveling member 8 is set within the range of 10 gf / cm or more, so that the toner to the contact portion between the layer-thickness leveling member 8 and the developing roller 4 is Sufficient regulating force can be exerted against the pressure fluctuation when the inflow amount increases, and a stable and uniform toner layer can be formed.

In FIG. 9, the horizontal axis represents the temperature of the surrounding environment, and the vertical axis represents the toner adhesion amount (M / A) per unit area on the developing roller 4 after passing through the layer thickness leveling member 8. 3 shows the relationship between the ambient temperature and the toner adhesion amount. Unlike the present embodiment, a in the figure shows experimental data when the toner supply roller 5 is rotated so that the surface moves in the opposite direction at the contact portion with the developing roller 4. It can be seen that the toner adhesion amount greatly varies depending on the temperature of the surrounding environment, and particularly at low temperatures, it deviates greatly from the optimum toner adhesion amount range of 1 to 2 mg / cm ² . In the figure, b, c, and d all rotate the toner supply roller 5 in the same manner as in the present embodiment, but under the condition that the pressing force of the layer thickness leveling member 8 against the developing roller 4 is different from each other. It is the result of the experiment. That is, b is the experimental data under the condition that the pressure contact force is less than 10 gf / cm, c is within the range of 10 to 50 gf / cm, and d is greater than 50 gf / cm. is there. Only c of these b, c and d had the toner adhesion amount within the optimum range regardless of the temperature change. Further, in the case of this c, a stable toner layer having a small amount of uncharged toner and an average charge amount of 5 to 8 μc / g can be obtained. Also from the above, in the present embodiment, since both conditions of the toner supply characteristic of the toner supply roller 5 and the layer regulation characteristic of the layer thickness leveling member 8 are proper, a uniform toner layer is easily formed. I know what I can do.

As described above, according to this embodiment, the developing roller 4
As a dielectric part 41 and a conductor part 42 grounded
And the toner supply roller 5 frictionally electrify the dielectric portion 41 to form a large number of microelectrodes, whereby the surface of the developing roller 4 is formed. Since a large amount of sufficiently charged toner can be easily sucked, a sufficiently charged multi-layered toner layer can be easily formed on the developing roller 4. Further, the toner supply roller 5 and the developing roller 4
Are rotated in the forward direction, so that the uncharged toner from the hopper is not supplied onto the developing roller 4 which has passed through the contact portion B by the rotation of the toner supply roller 5, so that the toner to the developing roller 4 is not supplied. It is possible to obtain a toner charge amount distribution in which the amount of adhered is less likely to be affected by environmental changes, and which has less uncharged toner, and to stabilize the developing characteristics. Therefore, since a multi-layered toner layer having a small amount of uncharged toner and a desired charge amount can be stably formed on the developing roller 4, constant speed development is also possible.

Further, the developing roller 4 of the layer thickness leveling member 8
Since the pressure contact force to the can be set to a lower pressure than the conventional one, the material of the layer-thickness leveling member is not limited to the conventional material having excellent releasability and strength such as PFA. ..
Therefore, a resin material such as elastic rubber such as polyurethane rubber, fluorine rubber, and silicon rubber, or a metal material such as SUS can be used, and the range of material selection is widened. For example, conventional A
Even when a blade made of metal in which toner sticking occurs and vertical streaks are generated on an image after approximately 1000 copies of 4 copies, according to this embodiment, the blade can be pressed against the developing roller 4 at a relatively low pressure. As a result, it was possible to form an image similar to that at the initial stage without toner adhesion even after copying 20,000 sheets.

Further, since the developing roller 4 is rotated so as to move at substantially the same speed as the photosensitive drum 1 in the developing area, "toner trailing edge shift" does not occur, and even in the color image, the trailing edge portion does not appear. It is possible to obtain a good image without problems such as excessive density and different colors of superimposed images.

Further, since the toner layer on the developing roller 4 contains no uncharged toner, it is possible to obtain a good image quality without background stains and resolution deterioration.

Further, the contact portion B with the toner supply roller 5
A layer-thickness leveling member 8 that comes into light contact with the surface portion of the developing roller 4 that has passed through is provided, thereby uniformly controlling the toner thickness on the roller and making the thickness of the toner layer conveyed to the developing area uniform. Therefore, it is possible to improve the density uniformity of the developed image and obtain a good quality solid image. In particular, since the developing roller 4 is configured such that the dielectric portion 41 and the grounded conductor portion 42 are mixed in a minute area on the surface, the developing roller 4 has a small amount of adhesion. There is a possibility that unevenness may occur, and it is effective in preventing the deterioration of the image quality due to this uneven adhesion amount.

A more specific aspect of this embodiment will be described below. (1) Developing roller 4-By knurling on the surface of a core metal roller having a diameter of 25 mm, a groove having a depth of 0.1 mm and a groove width of 0.13 mm is formed with a pitch of 0.
The iris was formed at 3 mm and an angle of 45 degrees.・ Fluorine resin (Asahi Glass Lumiflon L
F200) was coated and dried at 100 ° C. for about 30 minutes to apply a dielectric layer coating. The surface of this roller was cut to expose the cored bar portion as a conductor portion 42 on the surface, and the fluorine resin portion filled in the knurled groove and left was used as the dielectric portion 41. At this time, the area of the conductor portion 42 was 36% of the whole, and the area of the dielectric portion 41 was 64% of the whole. The surface roughness is R
3 to 20 μm, preferably about 5 to 10 μm. (2) Toner supply roller 5 ・ Resistance 1 on the surface impregnated with foamed polyurethane carbon
Sponge roller with a diameter of 0 ⁷ Ω and a diameter of 14 mm
It was placed in contact with the developing roller 4. The same voltage as that of the developing roller 4 or a voltage that causes a potential difference of 100 V to give an electrostatic force to the developing roller 4 side to the toner frictionally charged with a predetermined polarity between the core metal of the sponge roller and the developing roller 4 is applied. did. (3) Layer thickness leveling plate 8 An elastic plate made of urethane rubber having a thickness of 2 mm was placed in contact with the developing roller 4 at a contact pressure of 10 to 50 g / cm. (4) Development bias, development gap-DC-500V superimposed DC-500V peak-to-peak 1000V, 250HZ AC bias was applied (alternatively, DC bias of -50 to 150V was applied. Good) ・ The development gap was set to 150 μm. (5) Photoreceptor-OPC-Uniform charging potential was set to -900V. (6) Toner-Non-magnetic styrene acrylic positive charging toner-As a polarity control agent: Nigrosine was used, and 0.5 wt% of SiO ₂ fine powder was externally added as an external additive.

Under the above conditions, the amount of adhesion of the toner layer adhered and carried on the developing roller 4 was measured. As a result, the amount of adhesion and the average amount of charge were within the proper range, and the amount of charge of the uncharged toner was small. A toner layer having a distribution could be formed. In addition, contact development with a development gap of 0 mm was performed with peak-to-peak 50 with DC-250V superimposed as the development bias.
AC bias of 0V, 250HZ (Instead of this, -100 to 250V
DC bias may be applied) and other conditions are the same as above, and the adhesion amount of the toner layer adhered and carried on the developing roller 4 is measured. Could be formed. When contact development is performed in this manner, it is desirable to use a belt-shaped photosensitive member or an elastic roller having an elastic layer such as rubber as the developing roller 4.

Further, in the above specific example, a positive latent image (a latent image where a portion to which toner is to be attached has a larger potential than a background portion) on a negatively charged photosensitive member is normally developed with a positively charged toner (relatively). The present invention is applied to the case where toner is attached to a portion having a large electric potential), but the present invention uses the opposite polarity as the polarity of each charge, or a negative latent image (toner should be attached to toner) on the photoconductor. (The latent image has a smaller potential than the background part)
Can be applied to reversal development (development in which toner is attached to a portion having a relatively small potential).

Next, another embodiment of the present invention will be described. The present embodiment relates to an improvement of the layer thickness smoothing member 8. A metal plate is used as the layer-thickness leveling member 8, and a thin plate is required to obtain a low linear pressure on the developing roller 4. If a screw is used to attach such a thin metal plate to the support member that attaches to the casing 3 of the developing device, the metal plate is thin, so that bending tends to occur. In addition, in order to directly attach such a thin metal plate to the supporting member, even if an adhesive such as double-sided tape is used, it is necessary to use a highly accurate fixing member and a fixing method in order to prevent bending, which increases costs. Lead to When the metal thin plate serving as the layer-thickness leveling member 8 is bent, a uniform thin layer cannot be formed and streaks may occur on the image.

Therefore, in this embodiment, a metal thin plate such as SUS or phosphor bronze, which is advantageous as a material for the layer-thickness leveling member 8 in view of environmental characteristics over time (deformation is small), is formed so as not to cause bending. Used as a leveling member. Specifically, for example, the layer thickness leveling member 8 made of a thin plate of SUS is
As shown in FIGS. 10A and 10B, the elastic member 82 is attached to the support member 81. FIG. 10A is a schematic configuration diagram of a developing device having such a layer-thickness leveling member 8, and FIG. 10B is an enlarged view of a mounting portion of the layer-thickness leveling member 8. The developing device of this embodiment has the same structure as that of the above-described embodiment shown in FIG. 1 except for the method of attaching the layer-thickness leveling member 8. In the drawing, corresponding members are designated by the same reference numerals. is doing.

According to this, since the thin metal plate is adhered to the metal supporting member via the elastic body such as rubber having a constant thickness and a constant width, distortion is unlikely to occur, and the developer carrying member is uniform in the thrust direction. The blade thickness can be added, which eliminates the bending that occurs when the thin metal plate is directly bonded to the support member, and makes it possible to reproduce a certain concentration. Then 1
A uniform concentration could be obtained by adjusting the blade thickness to 0 to 30 gf / cm.

Further, instead of arranging the entire elastic body 82 so as to be sandwiched between the layer thickness leveling member 8 and the supporting member 81 as shown in FIG. 10 (b), as shown in FIG. A layer thickness leveling member 8 made of a thin metal plate is attached to the free end of an elastic body 82 made of a rubber plate having a certain thickness (for example, a thickness in the range of 3 to 5 mm) using an adhesive agent in a range where it does not occur. You may attach it by the etc.

FIG. 12 shows another embodiment for preventing the generation of streaks on the image due to the bending of the layer thickness leveling member 8 made of a thin metal plate. In this example,
For example, the tip of the metal thin plate 8 made of SUS is bent as shown in the drawing to make it difficult to bend, and is abutted against and abutted against the developing roller 5.

In each of the embodiments shown in FIGS. 10 to 12, a thin metal plate is used as the material for the layer thickness leveling member 8. However, deformation, creep, etc. occur due to the environment resistance and aging resistance. If not, the layer-thickness leveling member 8 is formed of a thin plate made of rubber or resin, and the layer-thickness leveling member 8 is formed on the layer thickness leveling member 8.
A method of attaching to the support member 81 similar to that shown in FIG.

Specific examples of the embodiments shown in FIGS. 10 to 12 will be described below. [Specific Example 1] (FIG. 10B) An ethylene propylene die material (EPDM) having a weather resistance of 3 to 5 mm and a thickness of 3 to 5 mm between a 0.1 mm-thick SUS blade as the layer-thickness leveling member 8 and the support member 81. ) A photosensitive member 1 having an elastic body 82 made of rubber or a silicon rubber plate is used as the photosensitive member 1.
Non-contact reversal development was performed using a pc drum and a negatively charged toner as a developer. The photoconductor 1 and the developing roller 4
A developing gap of 150μ is provided between the photoconductor 1 and VH (unexposed portion potential) of 1000V, V
In a device in which L (potential of exposed portion) is 100V, the developing roller 4 has a developing bias of DC 500V and AC (500
HZ1000V) was superimposed and applied. The toner supply roller 5 is rotated in the same direction at a linear velocity 1.2 times that of the developing roller 4, and the layer thickness leveling member 8 is moved to 15 gf /
Adhesion amount 1.2mg / cm by setting the line pressure to cm
2. A toner layer having a charge amount of 7 μc / g was obtained, and when developed, an image having excellent sharpness and a uniform solid portion could be obtained.

[Specific Example 2] (FIG. 11) Layer-thickness leveling member 8
As the elastic member 82 made of a rubber plate, a thin metal plate is attached to the tip of the elastic member 82, and the elastic member 82 is placed on the abdominal surface of the developing roller 4. Contact reversal development was performed using an opc drum as the photoreceptor 1 and a negatively charged toner as the developer. As the developing roller 4, a conductive member having elasticity is used.
It was brought into contact with the photoconductor 1. In this case, the developing potential of 600V is provided by applying 700V as the developing bias. The setting conditions were the same as those in the above-mentioned specific example 1, and when the development was carried out, a good image was reproduced without the background stain generally seen in the contact constant-velocity development.

[Specific Example 3] (FIG. 12) Layer-thickness leveling member 8
As a result, the tip of the thin metal plate was bent, and the inside was abutted against the developing roller 4. In other respects, a good image was obtained when the image was printed with the apparatus set under the same conditions as in Example 1.

Next, still another embodiment of the present invention will be described. This embodiment relates to the improvement of the size of the toner supply roller 5. When the developing device is configured such that the toner supply roller 5 has a smaller diameter than the developing roller 4 as in the embodiment shown in FIG. 1, the toner supply roller 5 has a sufficient amount of toner on the surface as the device is used for developing a solid image. May not be adhered, the amount of toner supplied to the developing roller 4 may be insufficient, and the density of the trailing edge may be lower than that of the leading edge on the image. In order to prevent such a problem, it is effective to accelerate the rotation of the toner supply roller 5 and maintain the toner supply amount. However, even in this case, the surface of the toner supply roller 5 that is repeatedly in sliding contact with the developing roller 4 is abruptly worn by accelerating the rotation of the toner supply roller 5, so that a minute electric field formed on the surface of the developing roller 4 is worn. Further, there is a possibility that a new problem may occur in that the charge amount of the toner cannot be maintained over time, the amount of toner supplied to the developing roller 4 decreases, and the torque of the entire developing device increases.

In view of this, in this embodiment, sufficient toner adheres to the surface of the toner supply roller 5 regardless of the usage conditions of the apparatus, without problems such as early wear of the toner supply roller 5 and torque increase of the entire developing device. By maintaining the above state, the toner supply to the developing roller 4 is prevented from being insufficient.

Therefore, in this embodiment, for example, as shown in FIG. 13, when the diameter of the toner supply roller 5 is d _S and the diameter of the developing roller 4 is d _D , both diameters are d _D ≤ The configuration is such that d _S ≦ 5 · d _D.

According to this, since the diameter of the toner supply roller 5 is larger than the diameter of the developing roller 4, the peripheral length of the toner supply roller 5 is longer and the surface area thereof is larger than before. Therefore, when the amount of the toner supply roller 5 slidingly contacting the developing roller 4 per unit time in order to supply a sufficient amount of toner to the developing roller 4 is kept constant, the portion of the toner supply roller 5 that has once made sliding contact is The time until the next sliding contact can be made longer than in the conventional example. Therefore, the toner is more likely to adhere to the toner supply roller 5 during the rotation in the toner reservoir than in the conventional example, and the insufficient supply to the developing roller 4 can be prevented. Note that the diameter of the toner supply roller 5 is set to 5 times or less the diameter of the developing roller 4 when the shape of the toner supply roller 5 is too large with respect to the attachment of the layer thickness leveling member 8 and the size of the entire developing device. This is because a problem will occur.

In each of the above embodiments, a point C on the surface of the developing roller 4 where the surface of the toner supplying roller 5 first contacts the surface of the developing roller 4 (hereinafter, referred to as C).
The contact start point C) (see FIG. 14A) is the tangent line m.
A point B on the surface moving path of the developing roller 4 which is an angle of repose α of the toner to be used, which is an angle β formed between _C and a horizontal line 1 (a horizontal line passing through the center of the developing roller in the figure) (hereinafter referred to as a rest point B). The toner supply roller 5 with respect to the developing roller 4 is positioned so as to be located below (see FIG. 14B).
It is desirable to set the arrangement.

The reason will be described below. Figure 15
FIG. 1A shows an example (hereinafter referred to as this example) in which the toner supply roller 5 is arranged in the above-described desirable manner, and FIG.
5B shows an example (hereinafter referred to as a comparative example) in which the toner supply roller 5 is arranged in an undesired manner. In any of the examples, the toner is in contact with the surface of the developing roller 4 before the contact start point C is reached by rotation.

In the comparative example of FIG. 15B, the toner supply roller 5 is arranged so that the contact start point C is above the rest point B, so that the surface of the developing roller 4 is By the time the contact start point C is reached, the toner contacts the toner even above the rest point B. In the contact between the toner and the surface of the developing roller 4 above the rest point B, no slip occurs between the two, so that even the uncharged toner is carried on the surface of the developing roller 4. In this way, the uncharged toner carried on the surface of the developing roller 4 before reaching the contact start point C continues to be supplied with the charged toner by the toner supply roller 5 on the surface of the developing roller 4 and the toner supply roller 5 Even if the toner enters the contacting portion with and is rubbed by the contacting portion, the amount of the toner entering the contacting portion is too large as compared with the triboelectrification ability, and the toner may be insufficiently charged. For this reason, a large amount of uncharged toner or low-charged toner is contained on the developing roller 4 that has passed through the contact portion, which causes a problem such as background smearing of an image and a decrease in the development transfer rate.

On the other hand, in the present example of FIG. 15A, since the toner supply roller 5 is arranged so that the contact start point C is below the rest point B, the surface of the developing roller 4 is The toner does not come into contact by the time it reaches the contact start point C, and thus the above-mentioned problems can be prevented. Therefore, together with the effect of attracting the charged toner by the numerous minute electric fields on the developing roller 4, the toner can be carried in the laminated state, and the toner layer having a stable charge amount without the uncharged toner can be stably formed.

For example, a roller having a diameter of 27 mm is used as the developing roller 4, a roller having a diameter of 16 mm is used as the toner supply roller 5, and a toner having a repose angle of 50 degrees is used, as shown in a comparative example of FIG. When the position of the toner supply roll-5 is above the point B where the angle of the tangent line is the angle of repose of 50 degrees, the toner is excessively supplied and the supplied toner contains a large amount of uncharged toner. However, FIG. 15 (a)
When the contact start point C was set lower than the point B as in this example, a good toner supply amount and charge amount could be obtained.

The example of the non-magnetic one-component developing device has been described above, but the present invention is also applicable to a one-component developing device using magnetic toner.

[0055]

According to the developing device of the present invention, the surface of the developer supplying member and the surface of the developer carrying member are moved in the same direction at the contact portions of the two members so that the surface of the developer supplying member is moved. The developer is made to adhere to the surface of the developer carrying member, so that the uncharged developer from the toner accommodating portion is not directly supplied to the surface of the developer carrying member that has passed through the contact portion by the movement of the surface of the developer supplying member. In addition, since only the developer sufficiently charged by the triboelectric charging at the contact portion is carried in a laminated state on the surface by the minute electric field in the vicinity of the surface of the developer carrier, there is little uncharged toner and the desired charge amount. It is possible to supply a latent image carrier by forming a multi-layered toner layer having a toner on the developer carrier. Therefore, by performing constant speed development,
It is possible to prevent "toner trailing edge" and obtain a good developed image even in a color image without excessive density at the trailing edge or color difference in the superimposed image. Further, since the uncharged toner and the like are not conveyed to the developing area, it is possible to obtain a good developed image without causing background stains and resolution deterioration.

Further, the developer layer on the developer carrying member is made uniform by a layer regulating member whose free end is pressed against the surface of the developer carrying member with a linear pressure of 10 to 50 g / cm 2. As a result, even when the amount of the developer on the developer carrying member that has passed through the contact portion increases due to the change in the surrounding environment, the amount of the attached developer becomes appropriate, so that the change in the image due to the change in the surrounding environment can be prevented. .

Further, by driving the developer carrying member and the developer supplying member so that the surfaces move in the same direction at their contact portions, the pressure contact force of the layer thickness regulating member with respect to the developer carrying member is conventionally. Since it is smaller than the above, strength and releasability are not required as much as the layer regulation member in the conventional developing device, and the degree of freedom in material selection is increased.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a developing device according to an embodiment.

2A is a plan view showing a part of the surface of the developing roller 4 of the developing device, FIG. 2B is a sectional view of the surface portion, and FIG.
Is an explanatory view of a toner layer formation state on the surface.

FIG. 3A is a plan view showing a part of the surface of a developing roller 4 according to a modification, and FIG. 3B is an explanatory view of a toner layer formation state on the surface.

FIG. 4 is an explanatory view for explaining a toner supply action of the toner supply roller 5 of the developing device to the developing roller 4.

FIG. 5 shows a case where the relationship between the rotation directions of the toner supply roller 5 and the developing roller 4 is different from that of the developing device,
FIG. 4 is an explanatory diagram illustrating a toner supply action of the toner supply roller 5 to the developing roller 4.

FIG. 6A shows the toner layer on the developing roller 4 when the toner supplying roller 5 is rotated so as to move in the opposite direction at the contact portion with the developing roller 4 before reaching the layer leveling member. FIG. 6B is a graph showing the toner charge distribution, and FIG. 6B is a graph showing the toner charge distribution of the toner layer on the developing roller 4 when the contact portion is rotated so as to move in the forward direction.

FIG. 7 is an explanatory diagram of a measuring device for obtaining a toner charge amount distribution of a toner layer on the developing roller 4.

FIG. 8A shows the toner layer on the developing roller 4 when the toner supplying roller 5 is rotated so as to move in the opposite direction at the contact portion with the developing roller 4 after passing through the layer-thickness leveling member. FIG. 7B is a graph showing the toner charge distribution, and FIG. 9B is a graph showing the toner charge distribution of the toner layer on the developing roller 4 when the contact portion is rotated so as to move in the forward direction.

FIG. 9 is a graph showing the relationship between temperature and the amount of toner charge on the developing roller.

FIG. 10A is a schematic configuration diagram of a developing device according to another embodiment, and FIG. 10B is a partially enlarged view of the developing device.

FIG. 11 is an explanatory diagram of a modified example of attachment of a layer thickness leveling member of the developing device.

FIG. 12 is an explanatory view of a layer thickness leveling member of a developing device according to still another embodiment.

FIG. 13 is a schematic configuration diagram of a developing device according to still another embodiment.

14A and 14B are explanatory views for explaining a desirable example of the arrangement of the toner supply roller of the developing device of FIG.

15A is an explanatory view showing a desirable example of the arrangement of the toner supply roller, and FIG. 15B is an explanatory diagram showing an undesirable example of the arrangement of the toner supply roller.

[Explanation of symbols]

 1 Photoconductor Drum 2 Developing Device 3 Casing 4 Developing Roller 5 Toner Supply Roller 6 Agitator 8 Layer Thickness Leveling Member 41 Dielectric Part 42 Conductor Part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Co., Ltd. (72) Akira Sawada 1-3-6 Nakamagome, Ota-ku, Tokyo Stocks Inside Ricoh Company (72) Inventor Umitsu Fujishiro 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (1)

[Claims] 1. A developer supply member having a developer carrier that is driven so that its surface moves, and a developer supply member that is driven so that its surface contacts and moves with the surface of the developer carrier. In a developing device for visualizing a latent image on a latent image bearing member by a developer supplied to a developer bearing member by a member, a large number of charge carriers are selectively retained on the surface as the developer bearing member. Of which the minute electric field can be formed, the moving directions of the surface of the developer supply member are set so as to move in the same direction at the contact portion with the surface of the developer carrier, and the developer carrier passing through the contact portion is used. A layer regulating member for uniformizing the layer of the developer on the body surface is provided so that the free end is on the downstream side in the developer moving body surface moving direction from the base end,
A developing device characterized in that the free end portion is brought into pressure contact with the surface of the developer bearing member at a linear pressure of 10 to 50 gf / cm.