JPH07140788A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a device which forms an excellently reliable, high quality image free of fog and a density change with time even in the use of one- component developer by setting an angle between the common tangent of a developer carrier and a developer supply part and a straight line passing through the front end of a developer-thin-layer formation part and the lower end of a developer return member to a specific range. CONSTITUTION:In a developing chamber 4, a supply roller 7 for supplying toner, carried by a toner carry means 6, to a developing sleeve 5 is housed so as to abut on the developing sleeve 5. Further, on the developing sleeve 5, a blade 8 for controlling the thickness of a layer of the toner supplied by the developing sleeve 5 is attached to the toner return member 9. Here, the sum of an angle between the horizontal line and the straight line connecting the front end of the blade 8 and the lower end of the toner return member 9 and an angle between the horizontal line and the common tangent of the developing sleeve 5 and the supply roller is set to 50 deg.-100 deg.. Thus, because a toner circulation snare is made optimum, concentration is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device having a means for forming a toner image on an electrostatic latent image carrier using a one-component developer and capable of obtaining a stable image density. is there.

[0002]

2. Description of the Related Art A developing device using a conventional one-component developer (hereinafter referred to as toner) is shown in FIG. In the apparatus shown in FIG. 6, an opening 103 is provided at a position facing the photosensitive drum 101, and a developing chamber 102 for containing toner is provided. The developing chamber 102 accommodates a conductive developing sleeve 110 that carries the toner toward the photosensitive drum 101 while carrying the toner, and the developing chamber 102 is configured such that a part of the outer peripheral surface thereof projects from the opening 103 to the outside. It is arranged in 102. Further, the developing sleeve 110 is held with a gap of 50 to 500 μm from the photosensitive drum 101, and a developing region for supplying the toner carried on the developing sleeve 110 toward the photosensitive drum 101 is formed. A developing bias in which alternating current is superimposed on direct current is applied to the developing sleeve 110 from the bias power source 106.

A blade 113 for regulating the layer thickness of the toner carried on the developing sleeve 110 is attached to the developing chamber 102 above the developing sleeve 110, and below the developing sleeve 110 there is a developing chamber. A blow-out prevention sheet 108 is provided to prevent the toner from being blown out from the lower portion of 102. Further, in the developing chamber 102 behind the developing sleeve 110, the conveying means 111
A supply roller 112 for supplying the toner conveyed by the above to the developing sleeve 110 is housed.

Both magnetic and non-magnetic toner can be used, but magnetic toner is styrene,
Since magnetite or the like is dispersed in a resin such as acrylic, when a color toner is made from a magnetic toner, only a dull color with low saturation can be obtained. Therefore, in order to form a color image with a one-component developer, a non-magnetic toner containing no magnetic substance in the toner is used.

When developing is performed in the developing device as described above, the conveying means 111 supplies the toner to the supply roller 11.
Then, the toner is applied to the developing sleeve 110 by the supply roller 112. The developing sleeve 110 is rotated in the direction shown by the arrow in the figure, and the toner carried on the developing sleeve 110 is sent to the developing area after being regulated by the blade 113 to a predetermined layer thickness. In the developing area, an electric field is formed by the developing bias, and the force of the electric field causes the toner to fly toward the portion of the photosensitive drum 101 where the latent image is formed.

The developing sleeve 11 is not used for development.
The toner remaining on the developing roller 110 is peeled off by the supply roller 112 that rotates in the same direction as the developing sleeve 110, and new toner is applied to the developing sleeve 110 by the procedure described above.

[0007]

However, in the above-mentioned conventional developing device, if the residual toner after development by the supply roller 112 is not sufficiently stripped off, toner with high tribo will remain on the surface layer of the developing sleeve 110. ,
If the high tribo toner accumulates as the developing sleeve 110 rotates, the charged toner prevents new toner from coming into contact with the developing sleeve 110, so that it is not possible to have sufficient tribo. As a result, toner that does not have enough tribo and toner that has been charged up are present on the developing sleeve 110, and a broad tribo distribution is formed, causing fog and density decrease due to low tribo toner, and high tribo. Problems such as blotch due to toner will occur. Further, a ghost phenomenon in which the previously formed image is formed again for about one round of the developing sleeve is also induced.

In the case of a magnetic toner, since a magnetic restraining force can be applied to the toner having a low tribo by including a magnet in the developing sleeve 110, fog prevention can be achieved, but non-magnetic. In the case of toner, most of the force applied to the toner is the electrostatic force, so that fogging due to the toner with low tribo occurs remarkably.

Further, when the toner circulation in the developing chamber is not properly performed, an initial thin density phenomenon called a density rising phenomenon as shown in FIG. 7 occurs. This is because the toner circulation in the developing chamber is slow, and the toner near the tip of the regulation blade accumulates, causing toner charge-up. This charge-up toner prevents the addition of tribo to new toner and holds sufficient tribo. This is because the concentration will decrease due to the failure. Then, the toner, which is prevented from being imparted with tribo by performing continuous image formation, gradually retains to have tribo, and the density is increased, and a phenomenon of density rise as shown in FIG. 7 occurs. Further, due to retention, when continuous image formation is performed for a long time, toner deterioration is promoted, which causes problems such as fog generation and density reduction.

For example, in US Pat. No. 4,992,832, the angle formed by the common tangent line of the developing sleeve and the toner supply roller with respect to the horizontal line is set to 20 ° to 40 °. However, when the angle is set to this value, it is sufficiently above the developing container. If a large toner circulation space is not taken up, the toner stays in the developing container, leading to a decrease in density due to charge-up.

Further, when the wedge forming member disclosed in Japanese Patent Application Laid-Open No. 61-165780 is used, the toner does not return from the tip of the regulating blade to the toner container, resulting in an excessive toner supply state. Problems such as a charge-up phenomenon and toner deterioration will occur.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to develop a developing device capable of forming a high-quality image with excellent reliability without causing fog and density change with time even when a one-component developer is used. To provide.

[0013]

According to the present invention, the above-described object is to provide a developer container for containing a one-component developer, a developer carrier disposed at an opening of the developer container, A developer supply member which is arranged so as to contact the developer carrier and supplies the developer in the developer container to the developer carrier, and a developer thin layer is formed on the surface of the developer carrier. And a developer returning member for returning the developer regulated by the developer thin layer forming member to the developer supply member side, the tip of the developer thin layer forming member Is located below the developer return member and has a common tangent to the developer carrying member and the developer supply member, and a straight line passing through the developer thin layer forming member tip and the developer return member lower end. The angle formed is 50 °
It is achieved by satisfying the relationship of 100 °.

[0014]

According to the present invention, the tip of the developer thin layer forming member is located below the developer returning member, and
The angle formed by the common tangent to the developer carrier and the developer supply member and the straight line passing through the tip of the developer thin layer forming member and the bottom of the developer return member satisfies the relationship of 50 ° to 100 °. By setting, the developer is retained in the vicinity of the tip portion of the developer thin layer forming member, and the excess developer at the time of developer regulation is returned to the developer container with the movement of the developer supply member, Prevent charge up,
It was found that problems such as a decrease in initial density, fog, and low density do not occur.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing the configuration of the image forming apparatus of this embodiment. In this embodiment, a non-magnetic one-component toner will be used for description.

The developing device shown in FIG. 1 is provided with an opening 2 at a position facing the photosensitive drum 1 and a toner storage container 3 for storing toner. The developing chamber 4 holds the toner in the developing chamber 4 while holding the toner. A conductive developing sleeve 5 made of aluminum, SUS, or the like, which is conveyed toward 1, is accommodated. The developing sleeve 5 is arranged in the developing chamber 4 such that a part of the outer peripheral surface thereof protrudes from the opening 2 to the outside, and is held at a distance of 50 to 500 μm from the photosensitive drum 1. A developing area for supplying the toner carried on the photosensitive drum 1 toward the photosensitive drum 1 is formed. A developing bias power source (not shown) applies a developing bias voltage on which a DC component is superposed to the developing sleeve 5. The developing sleeve 5 may be a solid roller, or may be one whose surface is coated with gold, carbon, platinum, ceramic or the like to reduce its resistance, or one whose coating material is directly formed. . To the developing sleeve 5, a developing bias power source (not shown) applies a developing bias voltage in which a DC component is superimposed.

Further, in the developing chamber 4, a supply roller 7 for supplying the toner conveyed by the toner conveying means 6 to the developing sleeve 5 is accommodated so as to contact the developing sleeve 5. The supply roller 7 is preferably subjected to sponge processing, knurling processing, or brush processing in order to favorably supply and apply toner.

Further, above the developing sleeve 5, a blade 8 for regulating the layer thickness of the toner supplied to the developing sleeve 5 is attached to the toner returning member 9. The blade 8 is based on an elastic metal material such as a phosphor bronze thin plate or a SUS thin plate or an elastic resin material such as a PET thin plate, and urethane rubber is provided at least in the contact portion of the developing sleeve 5.
A so-called tip blade shape having an elastic body such as silicone rubber is formed. The blade 8 may be composed only of an elastic body such as rubber without the base.

In the apparatus of this embodiment as described above, when the photosensitive drum 1 is rotated in the direction of the arrow, the surface thereof is uniformly charged by the charging roller 10 at about -700 V, and an image is formed by a light emitting element such as a laser or LED. Exposure 11 based on information is performed, and an electrostatic latent image is formed on the photosensitive drum 1. At this time, the surface potential of the electrostatic latent image portion is about -100V. Then, the developing sleeve 5 and the supply roller 7 rotate in the direction of the arrow while having a relative speed, and an electrostatic latent image is applied to the developing sleeve 5 from a developing bias power source (not shown) to form a visible image. Is done. The visible toner image on the photosensitive drum 1 is transferred to the transfer roller 1.
It is transferred onto the transfer material 13 by 2 and is fixed onto the transfer material by the fixing device 14 to obtain a permanent image. The residual toner on the photosensitive drum 1 after the transfer process is scraped off by the cleaner 15. In this embodiment, a process cartridge in which the developing device, the photosensitive drum 1, the cleaner 15, and the charging roller 10 are integrally contained in the outer frame 16 is used.

Next, experimental results of the developing device having the above-mentioned structure will be described with reference to FIGS. FIG. 2 illustrates an example in which the angle formed by the straight line connecting the tip of the blade 8 and the lower end of the toner return member 9 with respect to the horizontal line and the angle formed by the common tangent line of the developing sleeve 5 and the supply roller 7 with respect to the horizontal line are changed. is there. Table 1 shows the results of measuring changes in the number of prints and the image density in nine combinations by changing each corner in three ways as shown in FIG.

[0022]

[Table 1]

The symbols A, B, and C in Table 1 indicate that the patterns in the graph showing the transition of the image density with respect to the number of prints in FIG. A is the case where a good print image with stable density and no fog was obtained from the initial stage. In the case of B, a print with an initial density of 1.48, which is close to 1.5, was obtained, but the toner moving in the direction of the developing blade 8 could not return to the toner storage container side because the toner circulation space was small, and again. This is the case where the supply roller 7 is pushed back toward the developing blade side due to the rotation thereof, and as a result, the tip portion of the blade 8 is caused to stay and a defect such as a decrease in fog density occurs. In C, since the toner circulation space is wide, the movement of the toner in the vicinity of the tip of the developing blade 8 becomes slow, the toner is charged up, and this charge-up toner prevents the addition of tribo to new toner and can hold a sufficient tribo. However, this is a case in which the density rise phenomenon occurs from the initial stage, and since the toner in which the vicinity of the tribo is obstructed by performing continuous image formation also has the tribo during the retention, the density rising phenomenon occurs.

As a result of the above experiment, in Table 1, A
It was found that, in all cases, the sum of the angles formed by the horizontal line and the toner return member and the horizontal line and the common tangent line of the sleeve supply roller was 50 ° to 100 °.

Therefore, in the present embodiment, the sum of the angle formed by the straight line connecting the tip of the blade 8 and the lower end of the toner return member 9 with respect to the horizontal line and the angle formed by the common tangent line between the developing sleeve 5 and the supply roller 7 with respect to the horizontal line. Was set to be 50 ° to 100 °, and the toner circulation space was optimized to stabilize the density.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. In Embodiment 1, the lower surface of the toner return member is moved up and down to change the angle formed by the blade tip and the lower end of the toner return member with respect to the horizontal line to optimize the toner circulation space. When the lower surface of the toner return member is arranged at the maximum position, the pressure of the toner is directly applied to the back surface of the blade, which may change the contact pressure of the blade with the sleeve. When the contact pressure of the blade with respect to the sleeve changes, the tribo imparting ability at the nip between the blade and the sleeve changes, so that stable image density cannot be obtained.

Therefore, the present embodiment is characterized in that the lower surface of the toner return member is tapered as much as possible so as to be inclined toward the developing sleeve.

FIG. 4 shows a developing device of an image forming apparatus to which this embodiment is applied, and those having the same functions as those of the first embodiment are designated by the same reference numerals and description thereof will be omitted. In FIG. 4, the toner returning member 9 indicated by diagonal lines is tapered toward the developing sleeve so as to be inclined downward, and the angle formed by the straight line connecting the tip of the blade 8 and the lower end of the toner returning member 9 with respect to the horizontal line is The toner is not large in contact with the back surface of the blade 8 while being sufficiently large.

By adopting the configuration of this embodiment, it is possible to always maintain the contact pressure of the blade with the sleeve at a proper value while ensuring a sufficient toner circulation space, so that stable image density can be achieved.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. The components having the same construction and operation as those of the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is characterized in that in the developing device of the second embodiment, the taper angle provided on the lower surface of the toner returning member is larger at the end portion than at the central portion in the longitudinal direction of the developing device.

FIG. 5 is a view of the vicinity of the toner returning member of the developing device in this embodiment as seen from the direction of the toner container.
The toner return member 9 is tapered toward the developing sleeve in the same manner as in Embodiment 2 so as to be inclined.
Further, as shown by the hatched portion, the end portion is provided with a taper so that the inclination is larger than that in the central portion.

In FIG. 5, the toner sent by the toner carrying means 6 toward the supply roller 7 is sent toward the developing sleeve 5 by the supply roller 7, but is regulated by the blade 8. Therefore, the toner carried by the sleeve is small. ,
The remaining toner is pushed upward and sent back toward the toner container. At this time, the toner can escape not only in the upward direction but also in the lateral direction in the vicinity of the center in the longitudinal direction of the developing device, but in the vicinity of the end portion, the movement in the lateral direction is restricted, which not only hinders the circulation of the toner. The accumulated toner easily enters the gaps of the sleeve, the bearing of the supply roller, and the seal.

Therefore, in the present embodiment, as shown in FIG. 5, the taper provided on the toner return member 9 is made to have a larger angle near the end so that the toner conveyed near the end easily escapes upward. did.

As described above, by improving the circulation of the toner in the vicinity of the end portion in the developing device and forming a uniform toner flow over the entire surface in the longitudinal direction, the density unevenness in the lateral direction of the image can be prevented. It is possible to prevent the toner from being fused to the sleeve and the bearing of the supply roller.

[0036]

As described above, according to the present invention,
The tip of the developer thin layer forming member is located below the developer return member, a common tangent to the developer carrying member and the developer supplying member, the tip of the developer thin layer forming member, and the developer. By setting the angle formed by the straight line passing through the lower end of the return member to satisfy the relationship of 50 ° to 100 °, it is possible to prevent the phenomenon of rising of the density of the developer and to prevent the phenomenon of density decrease due to fog and toner deterioration. The problem can be solved. Furthermore, since a uniform toner flow is achieved over the entire surface in the longitudinal direction inside the developing device, not only a high-quality image having a uniform density can be formed over the entire image surface, but also the developing sleeve and the toner supply roller bearing portion. Since the toner is prevented from entering into the bearings and the like, the fusion of the toner in the bearing portion is also prevented, so that a high-quality color image without color change between prints can be achieved.

[Brief description of drawings]

FIG. 1 is a side sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an example of the first embodiment of the present invention, in which an angle formed by a straight line connecting the leading end of the developer thin layer forming member and the lower end of the developer return member with respect to the horizontal line and a common tangent line of the developer carrier and the developer supply member with respect to the horizontal line. It is a figure explaining the example which changed the angle which is formed.

FIG. 3 is a diagram for explaining the results of an experiment conducted by changing each angle as shown in FIG. 2 in Example 1 of the present invention.

FIG. 4 is a side sectional view of a developing device in Embodiment 2 of the present invention.

FIG. 5 is a diagram illustrating in detail a developer returning member according to a third embodiment of the invention.

FIG. 6 is a side sectional view of a conventional developing device.

FIG. 7 is a diagram illustrating a rise in density by a conventional developing device.

[Explanation of symbols]

 3 Toner Storage Container (Developer Container) 5 Development Sleeve (Developer Carrier) 7 Supply Roller (Developer Supply Member) 8 Blade (Developer Thin Layer Forming Member) 9 Toner Return Member (Developer Return Member)

Claims (3)

[Claims] 1. A developer container for accommodating a one-component developer, a developer carrying member arranged in an opening of the developer container, and a developer carrying member arranged so as to come into contact with the developer carrying member, A developer supply member for supplying the developer in the developer container to the developer carrier, a developer thin layer forming member for forming a developer thin layer on the surface of the developer carrier, and the developer thin layer. In a developing device having a developer returning member for returning the developer regulated by a forming member to the developer supplying member side, the tip of the developer thin layer forming member is located below the developer returning member and The angle formed by the common tangent line to the developer carrier and the developer supply member and the straight line passing through the tip of the developer thin layer forming member and the bottom end of the developer return member satisfies the relationship of 50 ° to 100 °. Developing device. 2. The lower surface of the developer return member is
The developing device according to claim 1, wherein the developing device is disposed so as to be inclined downward toward the developer carrying member. 3. The developer according to claim 1, wherein the inclination angle provided on the lower surface of the developer return member is arranged so as to be larger near the end portion than in the central portion in the longitudinal direction of the developing device. Developing device.