JPH087495B2 - Developing device for electrophotographic device - Google Patents

Description

The present invention relates to a developing device for an electrophotographic apparatus such as an electrostatic transfer type copying machine.

[Conventional technology]

Conventionally, an electrophotographic apparatus such as an electrostatic transfer type copying machine is provided with a developing device 1 as shown in FIG. 4, and the toner supplied from a toner carrying box 2 on the developing device 1 is
The stirring rollers 3 and 4 stir and mix with a carrier such as iron powder, and the developer is sent to the magnet roller 5 as a developer. The magnet roller 5 is provided between, for example, three main poles N ₁ , N ₂ , N ₃ which are magnetized parts and the main poles N _{1 to} N ₃ so that the developer can be smoothly transported. It has two auxiliary poles S ₁ and S _{2 for} assisting. And, these main poles N ₁ ~
The developer is attracted to the outer peripheral portion of the magnet roller 5 by N ₃ and the auxiliary poles S ₁ and S _2, and is conveyed, and the toner is supplied to the photosensitive drum 6 by the magnetic brush formed by the main pole N ₁ . It has become.

Further, a doctor 7 as a developer regulating member is provided above the magnet roller 5, and the doctor 7
A DV cover (developer cover) 8 is provided on the developer conveying direction side in FIG. And the doctor 7
The tip portion is close to the outer peripheral portion of the magnet roller 5, and the amount of the developer attracted to the magnet roller 5 is regulated so that an appropriate amount of the developer is conveyed.

A developing device having the same structure as the above is disclosed in, for example, Japanese Patent Laid-Open No. 62-138879.

Further, in Japanese Utility Model Laid-Open No. 53-72940, the doctor blade has a stepped portion so that the distance between the doctor blade and the sleeve becomes gradually narrower toward the portion where the sleeve and the photosensitive member face each other. Japanese Patent Application Laid-Open No. 2004-242242 discloses a configuration in which a magnet / brush with uniform bristles can be formed, and a high-density visible image without development unevenness can be formed on a photoconductor.

[Problems to be solved by the invention]

However, in the above-described conventional structure, due to the pressure drop in the downstream side of the doctor 7 in the developer conveying direction, that is, the portion on the DV cover 8 side, the DV cover 8 is moved from the tip end of the doctor 7 to the DV cover 8.
The toner is blown out in the direction. Since the toner here is a dynamic powder, it is not held between the DV cover 8 and the magnet roller 5 and is ejected to the outside. Therefore, there is a problem that the toner cannot be appropriately supplied to the photosensitive drum 6.

[Means for solving problems]

In order to solve the above-mentioned problems, a developing device for an electrophotographic apparatus according to the present invention has a main pole and each magnetized portion as a complementary pole having a polarity different from that of the main pole. A magnetic roller that supplies the developer to the photoconductor by forming the magnetic brush by adsorbing the developer on the outer periphery and a developer regulation that regulates the amount of the developer adsorbed on the outer periphery of the magnet roller. In a developing device of an electrophotographic apparatus including a member and a guide member provided on the downstream side of the developer regulating member in the developer conveying direction, the guide member has a step portion on the surface facing the magnet roller. However, with the stepped portion as a boundary, the upstream side portion in the developer transport direction forms a separation surface that is farther from the magnet roller than the downstream side portion, and the downstream side portion is close to the magnet roller. While making a face, The proximity surface is formed such that the gap between the magnet roller and the magnet roller is substantially uniform over a predetermined length in the developer transport direction, while the magnet roller and the portion facing the tip of the developer regulating member and A magnetizing portion is provided in the middle of the portion facing the step portion of the guide member, and the spikes of the developer formed on the outer peripheral portion of the magnet roller by the magnetizing portion are separated from the separating surface of the guide member. It is the structure contact | abutted.

[Action]

According to the above configuration, the developer is attracted to the outer peripheral portion of the magnet roller by the magnetizing portion and is conveyed. Then, in the developer conveying process, the developer regulating member regulates the amount of the developer adsorbed on the outer peripheral portion of the magnet roller. At this time, a pressure drop occurs on the downstream side of the developer regulating member in the developer conveying direction, and the toner is blown out from the developer regulating member to the downstream side. However,
The toner is sealed by the magnetizing portion contacting the spikes of the developer formed on the outer peripheral portion of the magnet roller in the middle of the separating surface of the guide member, and the blowout is suppressed. Further, the guide member has a step portion on the surface facing the magnet roller, and with this step portion as a boundary, a separation surface is formed in which the upstream side portion in the developer transport direction is separated from the magnet roller more than the downstream side portion. And the downstream side portion is close to the magnet roller, so that the gap between the magnet roller and the separation surface of the guide member is between the spike of the developer and the stepped portion. An air pocket is formed, and the toner blown through the spikes becomes a turbulent flow, and the blowing force is suppressed. Further, the downstream side portion forms a proximity surface that is in proximity to the magnet roller, and this proximity surface is formed so that the gap with the magnet roller is substantially uniform over a predetermined length in the developer transport direction. As a result, the space between the adjacent surface and the magnet roller functions as a seal portion, and the blowing of the toner is suppressed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 2, in a copying machine which is an electrophotographic apparatus, a toner box 23, which is a toner supply source containing toner, and a toner sent from the toner box 23 are placed on a developing device 21. Toner hopper 22 provided with a toner transport box 24 that supplies the toner to the developing device 21 while reciprocally transporting the toner.
Is provided.

The toner box 23 has a toner stirring shaft 25 that stirs the toner inside, and a toner supply screw 26 that transports the toner and sends it to the toner transport box 24. On the other hand, the toner transport box 24 is parallel to each other, and a pair of toner transport screws 27 and 28 that circulate and uniformize the toner inside by rotating counter to each other in synchronization with each other at the same rotation speed. These toner transport screws
Slots 24a are provided in parallel with 27 and 28, and the toner in the toner transport box 24 is formed in the lower wall by rotating.
The toner replenishing roller 29 made of sponge is supplied to the developing device 21 through.

Further, the developing device 21 prepares a developer by stirring and mixing the toner supplied from the toner transport box 24 and a carrier made of iron powder or the like, and supplies the developer to the magnet roller 32 by stirring. It has rollers 30 and 31, and a magnet roller 32 which adsorbs the developer supplied from these agitating rollers 30 and 31 to the outer peripheral portion and conveys it, and supplies it to the photosensitive drum 33.

The magnet roller 32 has three main poles N ₁ , N ₂ ,
It has N ₃ and two commutating poles S ₁ and S ₂ for assisting the developer to be smoothly transported. These main poles N _{1 to} N ₃ and commutating poles S ₁ and S ₂ are Each constitutes a magnetized part. The above-mentioned auxiliary pole S ₁ is arranged between the main poles N ₁ and N ₂ , and the auxiliary pole S ₂ is the main pole N ₁
The main pole N ₁ is arranged between N ₃ and the portion corresponding to the photosensitive drum 33, and the auxiliary pole S ₁ is arranged at the portion corresponding to the spacing surface 35 a of the DV cover 35. Further, the magnet roller 32 has a rotatable sleeve (not shown) on the outer peripheral portion. Then, in the main pole N ₁ to N ₃ and the interpole S ₁ · S ₂ Prefecture, conveyed by adsorbing the developer on the outer peripheral surface of the sleeve, so as to supply the toner to the photosensitive drum 33 .

Above the magnet roller 32, a doctor 34, which is a developer regulating member, is provided. This doctor 34
The front end portion of is adjacent to the outer peripheral portion of the magnet roller 32 by projecting downward, and forms a regulation portion 34a for regulating the amount of the developer adsorbed on the magnet roller 32.

Between the doctor 34 and the photosensitive drum 33, that is, on the downstream side of the doctor 34 in the developer transport direction, a DV cover which is a guide member along the outer peripheral portion of the magnet roller 32.
35 are provided. The lower surface of the DV cover 35 is curved in an arc shape in section along the outer peripheral portion of the cylindrical magnet roller 32. A portion of the curved lower surface on the upstream side in the developer transport direction has a large diameter from the center of the magnet roller 32 and is separated from the magnet roller 32 by a separating surface 35a.
The diameter of the downstream side portion is smaller than the circle center of the magnet roller 32 and is a proximity surface 35b that is close to the magnet roller 32. The boundary between the separation surface 35a and the proximity surface 35b is a step. There is. Therefore, the gap between the proximity surface 35b and the outer peripheral portion of the magnet roller 32 is uniform in the developer conveying direction, that is, in the length direction of the proximity surface 35. It should be noted that the smaller the contact surface 35b system centering on the center of the magnet roller 32 without contacting the developer, the more the toner scattering prevention function described later can be improved. Further, the separating surface 35a on the lower surface of the DV cover 35 comes into contact with the spikes 36 formed by the developer being attracted to the outer peripheral portion of the magnet roller 32 by the commutating pole S ₁ . The portion where the spikes 36 abut is the step portion which is the boundary between the separating surface 35a and the adjacent surface 35b and the doctor 34.
The commutating pole S ₁ is arranged in the middle of the tip of the.

In the above configuration, when the amount of toner in the toner transport box 24 becomes equal to or less than an appropriate value, the toner supply screw 26 in the toner box 23 rotates, as shown in FIG.
The toner in the toner box 23 is supplied to the toner transport box 24. At the same time, the toner transport screw 27
28 rotates and the supplied toner is
The toner is reciprocally transported inside and is evenly supplied into the toner transport box 24.

On the other hand, when the toner concentration in the developing device 21 becomes equal to or lower than the appropriate value, the toner replenishing roller 29 and the toner conveying screws 27, 28 in the toner conveying box 24 rotate, and the toner replenishing roller 29 causes the developing device to pass through the slot 24a. 21 is replenished with toner.

The toner supplied to the developing device 21 is agitating rollers 30 and 31.
Then, the toner is mixed with the carrier by agitation and sent to the magnet roller 32 as a developer. The developer sent to the magnet roller 32 is attracted to the outer peripheral surface of the sleeve of the magnet roller 32 by the main poles N _{1 to} N ₃ and the auxiliary poles S ₁ and S ₂ .
At this time, the developer is concentratedly attracted to the portions corresponding to the main poles N _{1 to} N ₃ and the supplementary poles S ₁ and S _2, and the magnet roller is
The spikes 36 protruding in the radial direction of 32 are formed. And
When the sleeve rotates, the developer is conveyed together with the sleeve toward the photoconductor drum 33. In this process, the amount of the developer on the sleeve is restricted by the regulating portion 34a of the doctor 34.
Regulated by, and an appropriate amount of developer is conveyed.

Here, a portion on the developer transport direction side from the doctor 34, that is, the separation surface 35a of the DV cover 35 and the magnet roller 32.
A pressure drop occurs in the gap between the DV cover 35 and the space between the regulating portion 34a of the doctor 34 and the magnet roller 32.
The toner is blown out in the direction. However, since the spikes 36 are formed on the outer peripheral surface of the sleeve on the commutating pole S ₁ of the magnet roller 32 and the spikes 36 are in contact with the separating surface 35a, the blown-out toner is spiked. Sealed by 36 to prevent blowout to the outside. Further, even if the toner is blown out after passing through the seal of the spikes 36, the gap between the separating surface 35a and the magnet roller 32 is smaller than the gap between the proximity surface 35b and the magnet roller 32 on the downstream side of this gap. Since the gap is formed wider than the gap, the gap on the side of the separating surface 35a forms an air pocket, and the toner blown from the doctor 34 causes a turbulent flow in the air pocket, which makes it difficult to blow the toner. Further, since the gap formed by the adjacent surface 35b is formed to have a uniform width over a predetermined length, it has a function as a seal portion and toner is reliably prevented from being blown out.

〔The invention's effect〕

As described above, the developing device of the electrophotographic apparatus according to the present invention has the main pole and each magnetized portion as a complementary pole having a polarity different from that of the main pole. A magnet roller that supplies the developer to the photoreceptor by adsorbing the developer to form a magnetic brush, a developer regulating member that regulates the amount of the developer adsorbed on the outer peripheral portion of the magnet roller, and a developer. And a guide member provided on the downstream side of the developer regulating member in the transport direction of the developing device, the guide member has a step portion on the surface facing the magnet roller, and the step portion With the boundary as the boundary, the upstream side portion in the transport direction of the developer forms a separation surface that is farther away from the magnet roller than the downstream side portion, and the downstream side portion forms a proximity surface that is close to the magnet roller, Development of the adjacent surface Is formed so as to have a substantially uniform gap with the magnet roller over a predetermined length in the conveying direction, the magnet roller includes a portion facing the tip end portion of the developer regulating member and a step portion of the guide member. A structure in which a magnetized portion is provided in the middle of the facing portion, and the spikes of the developer formed on the outer peripheral portion of the magnet roller by the magnetized portion are in contact with the spacing surface of the guide member. Is.

Therefore, even when a pressure drop occurs on the downstream side of the developer regulating member in the developer conveying direction and the toner blows out from the developer regulating member to the downstream side, the separation surface of the guide member In the middle of the above, the magnetic brushing portion makes contact with the rising edge of the developer formed on the outer peripheral portion of the magnet roller, so that a sealing function is generated at this portion, and the blowing of the toner is suppressed. Further, an air pocket is formed between the developer and the stepped portion of the guide member in the gap between the separating surface of the guide member and the magnet roller, and the toner blown out through the developer spike is disturbed. As a result, the blowing force is suppressed, and at the same time, the gap between the adjacent surface of the guide member and the magnet roller functions as a seal portion, and the blowing of toner is suppressed. Therefore, such a sealing function of each part prevents the toner from being blown out to the outside,
The effect that the developer can be appropriately supplied to the photoconductor is obtained.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view showing an internal structure of a developing device, and FIG.
FIG. 3 is a vertical sectional view showing the internal structures of the toner hopper and the developing device, FIG. 3 is an explanatory perspective view showing the flow of toner in the toner hopper shown in FIG. 2, and FIG. 4 is a conventional example. FIG. 3 is a vertical cross-sectional view showing the internal structure of the developing device. 21 is a developing device, 22 is a toner hopper, 30 and 31 are agitating rollers, 32 is a magnet roller, 33 is a photoconductor drum (photoconductor), 34 is a doctor (developer regulating member), 34a is a regulating section, and 35 is a DV. The cover (guide member) 35a is a separation surface, 35b is a proximity surface, and 36 is a spike.

Claims (1)

[Claims] 1. A magnetic brush is formed by having a main pole and magnetized portions as a complementary pole having a polarity different from that of the main pole, and adsorbing a developer to the outer peripheral portion of these magnetized portions. The magnet roller that supplies the developer to the photoconductor, the developer regulating member that regulates the amount of the developer adsorbed on the outer periphery of the magnet roller, and the downstream side of the developer regulating member in the developer conveying direction. In a developing device of an electrophotographic apparatus including a guide member provided, the guide member has a step portion on a surface facing the magnet roller, and the upstream side in the developer conveying direction is a boundary of the step portion. The part forms a separation surface that is separated from the magnet roller more than the downstream part, and the downstream part forms a proximity surface that is closer to the magnet roller, and the proximity surface has a predetermined length in the developer transport direction. Magne The magnet roller is formed so as to have a substantially uniform gap, while the magnet roller has a middle portion between a portion facing the tip of the developer regulating member and a portion facing the step of the guide member. And a magnetizing portion formed on the outer peripheral portion of the magnet roller by the magnetizing portion, and the spikes of the developer are in contact with the spacing surface of the guide member. apparatus.