JPS6034110B2 - magnetic brush developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing device for developing an electromagnetic image surface in electrostatic recording or electrophotography, and is particularly suitable for use in high-speed development printers, copying machines, etc. The present invention relates to a magnetic brush developing device.

A developing device used in a magnetic brush developing method has been proposed. For example, a plurality of magnetic rollers configured to rotate a non-magnetic sleeve are arranged in close proximity to the outer periphery of a fixed magnet having a plurality of magnetic poles formed in a cylindrical shape,
The fixed magnet is set so that adjacent magnetic poles have a Z relationship of different polarities. Then, the developer, which is a mixture of magnetic carrier and toner (colored powder), is attracted to the circumferential surface of the sleeve by the magnetic force of the fixed magnet from the opening (or developer reservoir) near the bottom of the developer mixing section. As the sleeve rotates, the developer is conveyed to a developing magnetic pole located opposite to the recording medium forming an electrical latent image, and the brush-like spikes of developer at this developing magnetic pole form an electrical latent image on the recording medium. By lightly rubbing the toner, the toner is transferred from the magnetic carrier to the latent image side and is attracted and developed. After the development is completed, the developer whose developing ability has decreased is released from the last sleeve, enters the developer mixing section (or developer reservoir), where it is mixed with the developer that has developing ability, and is magnetically transferred again. It is attracted to the circumferential surface of the sleeve of the roller and transported. Since toner is consumed in the developer, a replenishment toner tank with an appropriate toner supply device is provided at the bottom, and an amount of toner approximately equal to the amount of toner consumed is provided.
is supplied to the developer at appropriate times to keep the mixing ratio of carrier and toner almost constant at all times. When using the conventional magnetic brush developing device as described above for high-speed development, the rotation speed of the sleeve is increased to increase the amount of developer conveyed to the developing magnetic pole, or the magnetic roller is added and the developing magnetic pole is It is necessary to increase the surface area of the developing surface.

In the latter case, the developing device is complicated and the weight increases.
The former method of increasing sleeve rotation is preferred. However, if development is continued continuously at a high speed, the temperature of the developer increases, and as a result, the fluidity of the developer decreases, especially when a heat-fixing toner is used, and the flow of the developer from the developer mixing section to the sleeve increases. There is a drawback that the amount of developer adsorbed to the peripheral surface decreases, and the amount of developer conveyed to the developing magnetic pole decreases. Furthermore, the rise in temperature of the developing agent also affects the toner in the replenishment toner tank, causing the toner to form bridges within the tank, making it impossible to supply the toner into the developer. Furthermore, there was a drawback that the life of the developer was significantly reduced. An object of the present invention is to provide a lightweight, high-speed magnetic brush developing device that is capable of constantly conveying a constant amount of developer with a constant toner concentration by improving the configuration of the developing device and reducing the temperature rise of the developer. There is something to do.

In the present invention, the main causes of temperature rise in the developer are slippage when the developer is attracted to the circumferential surface of the sleeve of the magnetic roller and conveyed, and reversal of carriers that occur when the developer passes through different magnetic poles. It has been confirmed through experiments that the developer temperature rises as the transport amount and sleeve rotation speed increase due to frictional heat caused by intense mutual motion, and the magnetic rollers for transport and development are placed in upper and lower positions, separated from each other. However, instead of the magnetic roller, a simple conveying plate is installed at an angle between the two rollers, and a shaping member is installed between the developing magnetic pole and the upstream magnetic pole to make the spikes of the magnetic brush constant. It is provided on the upstream side of the center between the two magnetic poles, and the thickness of the amount of developer conveyed to this portion is adjusted to an appropriate amount by adjusting the amount of developer flowing out from the developer mixing section opening, and as a result, A drop is provided in the positional relationship between the toner supply device and the developer mixing section, which improves the flow of the developer until it is attracted and conveyed by the conveying zero magnetic roller, reducing the temperature rise of the developer and reducing the weight of the device. It is something that

The drawing is a sectional view showing an embodiment of a magnetic brush developing device to which the present invention is applied.

The developer 1, which is a mixture of a magnetic carrier and a toner, is passed through two mixing rods that transport the developer 1 in opposite directions in a developer mixing section 2, which has an inclined bottom to prevent the developer 1 from stagnation. After the magnetic carrier and toner are uniformly mixed by the Azusa impellers 3 and 4 and frictionally charged, an opening formed by the outflow amount regulating section 5 in the lower part of the developer mixing section 2 along the axial direction. 6, the amount of outflow is regulated and flows out. The developer 1 that has flowed out is attracted to the circumferential surface of the rotating sleeve 9 by the magnetic force of the conveying magnetic pole 8a of the fixed magnetic roller 8 located on the line connecting the center of the conveying magnetic roller 7 and the approximate center of the gap of the gate 6, and the developer 1 is attracted to the circumferential surface of the rotating sleeve 9. The magnetic carrier is conveyed upward by the counterclockwise rotation of the magnetic carrier 9, and after passing through the conveying magnetic pole 8b, since there is no magnetic pole, the magnetic force on the magnetic carrier decreases by 4.0, and the magnetic carrier is released from the rotating sleeve 9. The liberated developer 1 is placed between the conveying magnetic roller 7 and the first developing magnetic roller 10 installed obliquely above the conveying magnetic roller 7 and the first developing magnetic roller 10 installed at a distance above the conveying magnetic roller 7, with one end of the developer close to the circumferential surface of the rotary sleeve 9 and conveying magnetic pole 8b. The other end extends beyond the transport magnetic pole 11a of the fixed magnet roller 11, which has a different magnetic pole relationship with the transport magnetic pole 8b, and is connected to the circumferential surface of the rotating sleeve 12. The shortest distance is 10-2
The object is further pushed upward along the conveyance member 13 installed at an inclination angle of 30 to 50 degrees (depending on the distance between the conveyance magnetic roller 7 and the first developing magnetic roller 10). Then, the magnetic force of the transport magnetic pole 11a acts, and the developer 1 is attracted and transferred to the circumferential surface of the rotating sleeve 12 as if jumping. The transferred developer 1 is transferred to the rotating sleeve 1
The developer 1 is transported upward as the developer 2 rotates clockwise, and the developer 1 is transported upward to a position in front of the first developing magnetic pole 11c, specifically between the first developing magnetic pole 11c and the previous transporting magnetic pole 11b, and furthermore, the developer 1 The magnetic brush is strongly attracted to the circumferential surface of the rotating sleeve 12 by the magnetic force, and the magnetic brush is placed at an arbitrary position between the transport magnetic poles 11b from approximately the center between the two magnetic poles in a lying state along the axial direction of the first developing magnetic roller 10. The ears of the magnetic brush are uniformly aligned by the installed shaping member 14 to form the first developing magnetic pole 1.
1c, and contacts the electrical latent image formed on the circumferential surface of the recording medium 15, which rotates in the opposite direction (or in any circumferential direction) to the rotating sleeve 12, and develops the first latent image. . By the way, when the shaping member 14 is installed within the above range, there is an effect that the spikes of the magnetic brush can be uniformly aligned under any conditions. 14, the magnetic brush is in a standing state, so if the gap between the shaping member 14 and the circumferential surface of the rotating sleeve 12 is reduced, or if the conveyance capacity is reduced due to the influence of temperature, etc., the developer 1 A problem arises in which the rotary sleeve 12 is peeled off from the circumferential surface of the rotating sleeve 12. Also,
The conveyance amount d of the developer 1 up to the front of the shaping member 14 (developer 1
layer thickness) is greater than the gap g between the shaping member 14 and the circumferential surface of the rotating sleeve 12. If this is the case, the ears of the magnetic brush cannot be uniformly aligned. However, if there is too much developer, the excess developer will be attracted to the circumferential surface of the rotating sleeve 12 in front of the shaping member 14 by the magnetic force of the conveying magnetic poles 11b and 11a, and will accumulate, resulting in severe slippage and at the same time the rotational torque of the rotating sleeve 12. However, since the conveying member 13 is placed apart from the rotating sleeve 12, it does not accumulate on the circumferential surface of the rotating sleeve 9. However, when the particles pass through different magnetic poles on the rotating sleeves 9 and 12, the mutual movement between the particles becomes intense due to reversal. There is a problem in that the temperature rise of the developer 1 increases due to the above development. According to experiments 1. By adjusting the outflow amount regulating member 5 so that d is approximately 1.3 g, the developer accumulates in front of the shaping section 14 and at the bottom of the transport roll. In addition to this, a certain level of ear standing was obtained, and the effect of reducing temperature rise was obtained. The gap between the sleeve 9 and the regulating member 6 may be adjusted to reduce the amount of accumulation at the bottom of the transport roll. The direction of rotation of the conveying roll and the developing roll is preferably the direction shown in the figure in view of the amount of developer retained. After development, the developer 1 conveyed to the conveying magnetic pole 11d is attracted to the circumferential surface of the rotating sleeve 18 by the magnetic force of the conveying magnetic pole 17a of the fixed magnetic roller 7 of the second developing magnetic roller 16, which has a different magnetic pole relationship, and is transferred to rotate. As the sleeve 18 rotates clockwise, it is transported to the second developing magnetic pole 17b, and as described above,
The electrical latent image formed on the circumferential surface of the recording medium 15 is developed a second time by magnetic brush development.

Developer 1 with reduced toner concentration (mixing ratio) after second development
Since there is no magnetic pole after passing the next transport magnetic pole 17c, the magnetic force on the magnetic carrier becomes weaker, and the magnetic carrier is released from the rotating sleeve 18 and flows down along the scraping member 19. After a part of the toner density is measured by the toner density detection device 20', the other part directly falls into the developer 1 having a high developing ability in the developer mixing section 2, is mixed, and then passes through the closing port 6 again. It is configured to flow out, be transported and circulated. However, the actual development of the electrical latent image on the recording medium 15 is performed in the order of the second and first developing magnetic rollers 8 and 10, opposite to the direction in which the developer 1 is conveyed. The amount of consumed toner in the developer 1 is determined by continuously measuring the toner concentration from the toner concentration detection device 2, and when the concentration falls below a certain level, the toner in the toner 21 is automatically replenished by an appropriate means based on the signal. At the same time as rotating the impeller 22 to prevent the toner 23 in the container 21 from forming a bridge, the toner replenishing member 24 (for example, a ratchet wheel) provided at the bottom opening of the replenishing toner tank 21 is rotated. Toner 23 rotates to prevent the amount of replenishment toner from becoming excessive.
is immediately dropped onto the developer 1 in the developer mixing section 2 and mixed by the mixing rope impellers 3 and 4. The structure is such that development can always be carried out with the developer 1 having an appropriate toner concentration. The case where one magnetic roller for conveyance and two magnetic rollers for development are used has been explained above, but the present invention can be applied to one or two or more magnetic rollers for development, and is particularly effective when there are one or two magnetic rollers for development. It is.

Note that the magnetic roller is not limited to the above embodiment, and may be one in which the sleeve is fixed and the magnetic roll rotates, or one in which the sleeve and the magnetic roll rotate. The magnet roll may be one in which a magnetic member is magnetized as in this embodiment, or one in which a magnet is embedded in a suitable holding part. Further, the position of the developer mixing section is not limited to that in the embodiment, and the present invention can also be applied to a configuration in which it is formed near the bottom of the conveying magnetic roller. According to the above invention, the developing magnetic roller is installed diagonally above and separated from the conveying magnetic roller,
An inclined conveying member is provided between the two, and the circumferential length of the developer conveying sleeve is shortened, and the amount of conveyance is adjusted to the amount of outflow from the developer mixing section closing, and between the developing magnetic pole and the magnetic pole on the upstream side thereof, and at the center. By regulating it with the shaping member provided on the more upstream side, there is an effect that the rise in developer temperature can be reduced.

Further, by providing the conveyance member, the device becomes vertically elongated, and there is an effect that the flow of the developer is improved in areas other than the conveyance sleeve, and the developer fly body and the toner replenishment mechanism can be organically connected and set.

[Brief explanation of the drawing]

The drawing is a sectional view of the magnetic brush developing device of the present invention. 1...Developer, 2...Developer mixing section,
6...Developer mixing section closed, 7, 10, 16...
...Rotating sleeve magnetic roller, 8, 11, IT...
...Fixed magnet.

Claims (1)

[Claims] 1. One magnetic roller consisting of a fixed magnet roller and a non-magnetic sleeve rotating around the fixed magnet roller is used for conveyance and at least one for development, and an opening is formed in a part. It has a developer mixing section, in which a developer mixing section in which a magnetic carrier and toner are mixed flows out from the opening of the developer mixing section, and the flowing developer is mixed with a non-magnetic material by the magnetic force of the fixed magnet roller of the conveying magnetic roller. In a magnetic brush developing device in which the developer is attracted to the circumferential surface of the sleeve and is used to develop an electrical latent image surface with a magnetic brush of a developing section of a conveying developing magnetic roller, at least a magnetic pole facing the opening of the developer mixing section and means for installing the conveying magnetic roller so that a magnetic pole facing the developing magnetic roller exists;
A different magnetic pole is located apart from above the conveying magnetic roller and opposite to the opposing magnetic pole of the conveying magnetic roller, and the developing magnetic pole is located in the developing section. means for installing a magnetic roller, one end of which is close to a non-magnetic sleeve at a position immediately after the magnetic pole provided on the conveying magnetic roller so as to face the developing magnetic roller; an inclined conveyance member installed such that the non-magnetic sleeve and the other end face each other at a constant interval at a position below the magnetic pole provided to face the magnetic conveyance roller; a shaping member installed so as to make the thickness of the developer layer constant on the upstream side of the center between the developing magnetic pole of the developing magnetic roller installed in a close position and the magnetic pole on the upstream side of the developing magnetic pole; A gap g between the shaping member and the non-magnetic sleeve of the developing magnetic roller, which is provided at the opening of the developer mixing section, and a developing image conveyed on the circumferential surface of the non-magnetic sleeve on the upstream side of the shaping member. The thickness d of the agent layer is 1.2g<d<2
A magnetic brush developing device further comprising means for regulating an amount of developer flowing out from the opening so that the amount of developer flowing out from the opening is set to .g.