JPH0344667A - Developing device - Google Patents

Abstract

PURPOSE:To effectively remove a stagnating developer by stopping the supply of a developer to a developing roller when a pressure sensor provided between the developing roller and a blade detects more than a certain amount of the stagnating developer. CONSTITUTION:The pressure sensor 26 is fitted to a housing side wall 102 at a proper place and detects the stagnating developer between the developing roller 11 and blade. Further, one end of the bearing 15 of the developer supply roller 12 is fixed to the internal wall of a copying machine through a tension spring 19 and a wire 17 provided on the other end is fixed to the internal wall W while being wound around the driving shaft 231 of a motor 23. When the stagnating developer exceeds the certain amount, the pressure detected by the pressure sensor 26 exceeds a specific value, a motor 23 rotates clockwise through a controller 28 to move the roller 12 to the right along a long hole 103 and separate the roller 12, and development is carried out only with a developer on the roller 11, thereby decreasing the amount of the stagnating developer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device provided in an image forming apparatus such as a copying machine.

[Conventional technology]

Generally, in a developing device that uses a non-magnetic component type developer, a thin layer forming member such as a blade is pressed against the surface of a developer carrier such as a developing roller with a predetermined pressure, and frictional electrification occurs between the two. By imparting an electric charge to the developer, the developer adheres to a photoreceptor having a predetermined surface potential, thereby forming a developed image. That is, the amount of charge of the developer is determined by the contact pressure between the thin layer forming member and the developer carrier, which in turn determines the state of the image.

However, in such a developing device, as the developer gradually accumulates between the thin layer forming member and the developer carrier, the stagnant developer sticks to each other, and the solidified developer is damaged. Due to the interposition, a gap is created between the thin layer forming member and the developer carrier, which may reduce the contact pressure between the two. Since such a decrease in contact pressure directly leads to image deterioration, prevention has become a major issue.

Therefore, Japanese Utility Model Application Publication No. 63-101951 proposes a device in which a developer aggregation preventing member made of a bristle brush or the like is provided near the thin layer forming member.

Furthermore, in Japanese Patent Application Laid-open No. 58-37675, a thin layer forming member (layer thickness regulating means in the same publication) is configured to be able to approach and separate from a developer carrier, and when the number of copies exceeds a predetermined number, In this example, the thin layer forming member is largely separated from the developer carrier, and the accumulated developer is carried to another area while remaining on the developer carrier.

Furthermore, Japanese Patent Application Laid-Open No. 63-118170 discloses a device in which the developer carrier is reversely rotated for a certain period of time or by a certain angle after the end of the development process or before the start of the development process, thereby removing the accumulated developer. It is shown.

C Problems to be Solved by the Invention] In the Utility Model Application Publication No. 63-101951, an agglomeration prevention member is provided in the space formed by the ring 1 element carrier and the thin layer forming member, so that the aggregation prevention member is provided in the space formed by the ring 1 element carrier and the thin layer forming member. It can be applied to devices where the angles formed are obtuse or close to right angles, but it is difficult to apply to devices where the angles mentioned above are small because there is no space to install the agglomeration prevention member. . Furthermore, there is a possibility that the aggregation prevention member itself may disturb the flow of the developer.

In addition, the device disclosed in Japanese Patent Application Laid-open No. 58-37675 and the device disclosed in Japanese Patent Application Laid-open No. 6
In addition to the development process, the device disclosed in Japanese Patent Publication No. 3-118170 not only requires a separate process to remove the accumulated developer, but also processes the accumulated developer after a certain period of time has elapsed regardless of the amount of the accumulated developer. Since the processing is performed after a certain number of times (for example, after the development process has been performed a certain number of times), the processing operation may be executed even when there is not much developer accumulated, or the processing operation may be executed even though the developer has accumulated. may not be executed, making it difficult to process at the appropriate timing.

In addition, if a means for setting the contact pressure to be strong from the time of assembly and set-up is used, wear and tear of the thin layer forming member and the developer carrier will be accelerated, and the amount of charge of the developer will be excessive, causing the image to disappear. There is an inconvenience that fogging or the like tends to occur.

In view of these circumstances, it is an object of the present invention to provide a developing device that can effectively remove the developer accumulated between the photoreceptor carrier and the thin layer forming member at an appropriate timing. .

[Means to solve the problem]

The present invention includes a developer carrier disposed near a photoreceptor, a supply means for supplying developer to the developer carrier, and a supply unit that is pressed against the surface of the developer carrier, and a supply means that supplies the developer to the developer carrier. A developing device comprising: a thin layer forming member for forming a thin layer of developer on the surface of the developing device; The apparatus further includes a supply stop means for stopping the supply of developer to the developer carrier by the supply means when the detection means detects a certain amount of developer.

[For production]

According to the above configuration, when a certain amount of developer actually accumulates between the developer carrier and the thin layer forming member, the supply of the developer to the developer carrier by the supply means is stopped. . After that, as the retained developer is consumed during development processing, etc.
It is removed from its retention area.

〔Example〕

An embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a developing device installed in an image forming apparatus such as a copying machine, and this developing device includes a housing 10 containing a non-magnetic component developer. The housing 10 is made up of a hopper 13 that accommodates developer and a developer container 14. Inside the developer container 14, a developer roller (developer carrier) 11 and a supply roller 1 are in contact with each other.
2 are arranged.

As shown in FIGS. 2 and 3, rotating shafts 111 and 121 of both rollers 11 and 12 are rotatably supported by both side walls 102 of the housing 10. As shown in FIGS.

Of these, the rotating shaft 1 of the developing roller 11 shown in FIG.
One end of the developing roller 11 is connected to a drive source via a drive transmission mechanism (not shown), so that the developing roller 11 is rotated as appropriate. A gear 112 is fixed to the other end of the rotating shaft 111, and this gear 112 meshes with the middle 1Jff gear 21 supported by the housing side wall 102.

On the other hand, the rotation support structure of the supply roller 12 is
It is as shown in FIGS.

Specifically, bearings 15 are fitted to both ends of the rotating shaft 121 of the supply roller 12, and the bearing 15 is composed of a large-diameter inner part 151 and an outer part 153, and a small-diameter intermediate part 152, This intermediate portion 152 is connected to the housing side wall 102.
It is fitted into a horizontally extending elongated hole 103 provided in the. Therefore, the supply roller 12 is rotatably supported by the housing side wall 102 via both bearings 15, and is movable horizontally with respect to the housing side wall 102.

One side of both bearings 15 is connected to a wire 17 and a tension spring 19.
The supply roller 12 is fixed to the inner wall W of the copying machine via a tension spring 19, and the tension of the tension spring 19 normally holds the supply roller 12 in a position where it contacts the development roller 11. On the other hand, one end of the wire 17 is fixed to the other side of the bearing 15,
The wires 17 are each wound around a drive shaft 231 of a stepping motor (supply stop means) 23 installed in the copying machine, and the other end is fixed to the inner wall W of the copying machine.

Therefore, as the drive shaft 231 of the stepping motor 23 rotates clockwise in FIG. 4, the supply roller 12 is pulled to the right in the figure together with the bearing 15, and is separated from the developing roller 11, resulting in the state shown in FIG. ), the drive shaft 231 of the stepping motor 23 rotates counterclockwise in the figure from this state, so that the supply roller 12 is returned to its original position by the elastic force of the tension spring 19.

Further, the bearing 15 is provided at one end of the rotating shaft 121.
A gear 122 is fixed to the outer part of the
This gear 122 is configured to mesh with the intermediate gear 21 when the supply roller 12 is in the position shown in FIG. That is, this gear 122 and the gear 112.2
1 constitutes an interlocking mechanism for rotating the developing roller 11 and the supply roller 12 in the same direction.

Returning to the explanation of FIG. The developing roller 1] is disposed near the photoreceptor drum 16, and a blade (
A thin layer forming member) 18 is provided. This blade 1
8 is fixed to a thin flexible metal plate 20, and the end of this metal plate 20 is fixed to an inner plate 101 inside the developer container 14.

On the other hand, a stepping motor 2 is mounted on the housing side wall 102.
2 is fixed, and the cam 24 is connected to its drive shaft 221.
By pushing down the metal plate 20, the blade 1
The free end of 8 is pressed onto the circumferential surface of the developing roller 11. The contact pressure between the blade 18 and the developing roller 11 is adjusted by the rotation of the cam 24 driven by the stepping motor 22.

Further, in this device, a pressure sensor (developer detection means) 26 is incorporated in a proper position on one side wall 102 of the housing. This pressure sensor 26 faces a space surrounded by the circumferential surface of the developing roller 11 and the lower surface of the blade 18, and is located at a position where it comes into contact with the developer when a certain amount of developer has accumulated in this space. It is arranged in

The detection signal of this pressure sensor 26 is manually input to a control device (microcomputer; constitutes a supply stop means) 28 as shown in FIG. 4.5. The control device 28 controls the pressure P detected by the pressure sensor 26 to a predetermined value Po.
When the output voltage of the pressure sensor 26 exceeds a certain value, a control signal is output to the stepping motor 23, and the stepping motor 23 is rotated clockwise in FIG. It is configured.

Next, the operation of this developing device and the details of the $ control performed by the control device 28 will be explained with reference to the flow chart of FIG.

First, every time the copying machine performs a copying operation, a developing process is performed (step S1). Specifically, developing roller 1
1 and the supply roller 12 are both rotationally driven in the counterclockwise direction in FIG. A charge (a negative charge in this embodiment) is applied to the developer due to slight frictional charging at the contact portion between the developer roller 11 and the developer roller 11 .

This developer layer adheres to the circumferential surface of the developing roller 11 and is conveyed to the photosensitive drum 16 side, and this developer layer is formed into a thin layer at the contact area between the circumferential surface of the developing roller 11 and the blade 18. At the same time, it is even more strongly triboelectrically charged and adheres to the circumferential surface of the photoreceptor drum 16, which has been given a positive surface potential in advance, thereby forming a developed image on the photoreceptor drum 16.

When such a developing process is repeated many times, a developer accumulates between the blade 18 and the circumferential surface of the developing roller 11, as shown in FIG. 1, and the amount thereof gradually increases. and,
When the amount of retained developer exceeds a certain amount, this retained developer begins to contact the pressure sensor 26 (dotted chain line in Figure 1), the pressure P detected by the pressure sensor 26 increases, and the amount of the retained developer increases. The contact pressure between the blade 18 and the developing roller 11 begins to decrease due to the intervention of the roller.

Here, when the detected pressure P exceeds the predetermined value Po (YES in step S2), a control signal is output from the control device 28 to the stepping motor 23, so that the drive shaft 231 rotates clockwise in FIG. The supply roller 12 is pulled along the long hole 103 to the right in FIG. 4 together with the bearing 15, and is separated from the developing roller 11 (step S3). Due to this separation, the gear 122 on the supply roller 12 side and the intermediate gear 21 are also disengaged, so that
The driving of the supply roller 12 is stopped, and the supply of developer to the developing roller 11 is stopped.

By continuing the same developing process as described above in this state (step S4), only the developer accumulated between the blade 18 and the developing roller 11 is consumed, and the amount of accumulated developer decreases. , the detected pressure P of the pressure sensor 26
also begins to decrease. Then, the same pressure P is a predetermined value P1 (<
PO) (YES in step S5), a control signal is outputted to the stepping motor 23 again, and its drive shaft 231 is now rotationally driven in the counterclockwise direction in FIG. Therefore, the supply roller 12 is pulled together with the bearing 15 to the left in the figure by the tensile force of the compression spring 19, and returns to the position where it contacts the developing roller 11.
The gear 122 fixed to the rotating shaft 121 is again meshed with the intermediate gear 21, thereby restarting the rotational drive of the supply roller 12 (step Ss).

As described above, this device actually detects the developer accumulated between the blade 18 and the developing roller 11 and separates the supply roller 12 from the developing roller 11 at a timing based on the detection result. This developing roller 11
Since the supply of developer is stopped and the accumulated developer is consumed, the accumulated developer that causes image deterioration can be effectively removed at an appropriate timing.

Furthermore, by continuing the development process after stopping the developer supply, the developer can be removed in the normal copy mode, and the accumulated developer can be used as is for image formation. There is no waste in both processing time and developer residue can be removed efficiently.

Note that the present invention is not limited to such embodiments, and may take the following embodiments as examples.

(1> The present invention can achieve its effects by stopping at least the supply of developer by the supply means at an appropriate timing. Therefore, in the above embodiment apparatus, the supply roller 12 is separated from the developing roller 11. Instead of this, it is also possible to remove the accumulated developer by stopping only the rotation of the supply roller 12 by switching a clutch or the like while keeping both rollers 11 and 12 in contact with each other.

(2> ・Also, in the present invention, regardless of the specific structure of the supply means, in addition to the supply roller 12 as described above, the developer may be supplied by dropping the developer from above onto the developer carrier. A similar effect can be obtained even if the device is equipped with other means.

(3) In the present invention, other types of sensors such as a photosensor may be used in addition to the pressure sensor described above, regardless of the specific structure of the developer detection means. For example, when using a photosensor, as shown in FIG.
02, and the other housing side wall 1.
By incorporating the light-receiving element 32 into 02, it is possible to detect the presence or absence of developer accumulated between the two.

(4) In the embodiment described above, in order to confirm that the developer has been removed, the supply roller 12 is returned to its original position when the pressure P detected by the pressure sensor 26 falls below the predetermined value P1.
If confirmation is not required, control may be performed such that the removing operation is started and the developing operation is performed for a predetermined period of time, and then the resetting is performed.

(5) In the present invention, there is no particular need for the thin layer forming member to be configured to be able to adjust the contact pressure with respect to the developer carrier, and for example, the present invention can be applied to a structure in which the thin layer forming member is fixed in a fixed position. It is.

〔Effect of the invention〕

As described above, the present invention actually detects the developer accumulated between the thin layer forming member and the developer carrier, and stops the supply of developer to the developer carrier at a timing based on the detection result. This promotes the consumption of the staying developer, so that the staying developer, which causes image deterioration, can be effectively removed at an appropriate timing.

Furthermore, the above-mentioned staying developer can be removed in a normal image forming mode, and the staying developer can be used as it is for image formation, so the above-mentioned removal process can be carried out efficiently. can.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view of a developing device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a support structure for a supply roller provided in the developing device. FIG. 4 is a side view showing a state in which the developing roller and supply roller of the developing device are in contact with each other, and FIG. 5 is a side view showing a state in which the developing roller and supply roller of the developing device are separated. ,
FIG. 6 is a flowchart showing the developer removal operation performed in the developing device, and FIG. 7 is a sectional view of the developing device in another embodiment, corresponding to FIG. 2. D... Developer, 11... Developing roller (developer carrier) 12... Supply roller (supplying means), 16... Photosensitive drum, 18... Blade (thin layer forming member), 23
...Stepping motor (supply stop means), 26...
・Pressure sensor (developer detection means), 28...control device (supply stop means), 31...light emitting element (developer detection means) 2...light receiving element (developer detection means)

Claims (1)

[Claims] 1. A developer carrier disposed near the photoreceptor, a supply means for supplying developer to the developer carrier, and a developer carrier that is pressed against the surface of the developer carrier and develops the developer onto the developer carrier. A developing device comprising a thin layer forming member for forming a thin layer of developer, a developer detecting means for detecting developer accumulated between the thin layer forming member and the developer carrier, and the developer detecting means. A developing device comprising: a supply stop means for stopping the supply of developer to the developer carrier by the supply means when a certain amount of developer is detected.