JP2002328510A - Toner replenishing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner replenishing device and an image forming apparatus which always have satisfactory responsiveness regardless of a changeover in mode and can employ simplified control. SOLUTION: A powder pump 40 is driven by an exclusive motor 47 independent of a main motor 100 provided in an image forming apparatus main body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner replenishing device for replenishing toner contained in a toner container to a developing device, and an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art There is known an image forming apparatus of the above-mentioned type which includes a toner replenishing device for replenishing toner stored in a toner container to a developing device by a powder pump. As this powder pump, it is also known to use a single-axis eccentric screw pump having a stator having a through-hole formed therein and a rotatable rotor fitted into the through-hole of the stator. Is capable of continuous quantitative transfer at a high solid-gas ratio, and provides an accurate toner transfer amount according to the number of rotations of the rotor.

The present applicant has already proposed an image forming apparatus in which toner is supplied by the suction type single-axis eccentric screw pump. In such an image forming apparatus, as shown in FIG. 7, the powder pump is configured to be rotationally driven by a motor 100 that drives a sheet feeding device, a fixing device, and a developing device. Further, the developing device is a two-component developing device, and controls the toner replenishment so as to keep the toner density constant. Therefore, the toner replenishing device can follow the entire solid image of the maximum size even when it is printed. Is set to

[0004]

The single-axis eccentric screw pump has a rotor with a rotation speed of 125 rpm.
When the toner supply amount per unit time at 250 rpm and 400 rpm was examined, the results shown in the graph of FIG. 8 were obtained. In this experiment, the pump performance, toner transfer distance and head are all the same. As a result, the rotation speed of the single-shaft eccentric screw pump is 125 r.
pm, 250 rpm and 400 rpm, when the replenishment time becomes approximately 500 msec or more, the replenishment amount reaches approximately 50 mg / sec at all the rotation speeds under all the conditions, but the replenishment amount is large at the start up until the amount can be replenished. Differences were seen.

[0005] In the above-described image forming apparatus,
For example, there is a type in which the rotation speed of the motor 100 is changed by switching modes, such as a low-speed mode for thick paper and a high-speed mode in which speed is prioritized. If the rotation speed of the motor 100 changes, the rotation speed of the rotor of the powder pump naturally changes. Therefore, in the mode in which the number of rotations is low, the responsiveness of toner supply is reduced, and there is a possibility that all the solid images of the maximum size described above cannot follow the print.

Further, when a toner replenishing device using a powder pump is used in a full-color image forming apparatus for forming four-color images, for example, as shown in FIG.
M, 4C, 4Y, and 4Bk, toner transfer distances L1, L2, and L from toner container 20 to powder pump 40
3, L4 and lift (height difference) H1, H2, H3, H
4 is different, there is a problem that a difference in ability occurs in toner supply, and control is complicated.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a toner replenishing apparatus and an image forming apparatus which are always responsive without being affected by mode switching and which can simplify replenishment control. I have.

[0008]

In order to achieve the above-mentioned object, the present invention provides a method for removing toner stored in a toner storage container.
In a toner supply device for replenishing a developing device with a powder pump having a stator having a through hole and a rotatable rotor fitted into the through hole of the stator, the powder pump is provided in an image forming apparatus main body. It is characterized by being driven by a dedicated drive source independent of the drive source.

In the toner supply device of the present invention,
When the rotation speed of the powder pump by the dedicated drive source is 250
It is effective if the rotation speed is not less than rpm. Further, in order to achieve the above object, the present invention provides a station having a plurality of image forming stations, each of which is provided with a toner accommodated in a toner accommodating container, and a stator having a through-hole formed therein. In the image forming apparatus provided with a toner replenishing device for replenishing the developing device with a powder pump having a rotatably driven rotor fitted into the through hole, the powder pump of each of the stations is provided in a main body of the image forming device. It is characterized by being driven by a dedicated drive source independent of the source.

In the image forming apparatus of the present invention, it is effective if the number of rotations of the powder pump of each station is set in advance for each station. Further, in the image forming apparatus of the present invention, it is effective if the number of rotations of the powder pump in each station is set in accordance with the transfer distance and head of the toner.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a color laser printer as an example of an image forming apparatus using the toner supply device according to the present invention. This color laser printer has a configuration in which a paper feed unit 2 is disposed at a lower portion of an apparatus main body 1 and an image forming unit 3 is disposed above the paper feed unit 2. The image forming unit 3 is provided with a transfer belt device that is arranged so as to be inclined such that the side for receiving the fed sheet is at the bottom and the sheet discharge side of the sheet after image formation is at the top. The transfer belt device is
An endless transfer belt 12 is wound around a plurality of belt wheels 11, in this example, four belt wheels 11. On the upper running side of the transfer belt 12, magenta (M), cyan (C) ), Yellow (Y), and black (Bk) stations 4M, 4C, 4Y, and 4Bk are arranged in parallel.

Each station 4M, 4C, 4Y, 4Bk
Is provided with a photosensitive drum 5 as an image carrier, and the photosensitive drum 5 is driven to rotate clockwise by a driving unit (not shown). Around the photoreceptor drum 5, there are provided a charging roll 6 as a charging unit, an optical writing unit in which writing by laser light is performed by an optical writing unit 8, a developing unit 10 as a developing unit, and a cleaning unit 9 as a cleaning unit. I have. The developing device 10 is a two-component developing device including a toner and a carrier, and a toner corresponding to the consumed amount is replenished by a toner replenishing device described later so as to keep the toner concentration substantially constant.

Next, an image forming operation for performing full-color printing of the color printer shown in FIG. 1 will be described with reference to a magenta station 4M. A laser diode (not shown) is driven to irradiate the polygon mirror 8a with laser light on the photosensitive drum 5 charged by the charging roll 6, and reflected light is transmitted through the cylinder lens or the like to the photosensitive drum 5. The optical writing device 8 for guiding upward performs optical writing of an optical image to be developed with magenta toner. As a result of this writing, an electrostatic latent image is formed on the photosensitive drum 5 based on image data sent from a host machine such as a personal computer, and the latent image becomes a visible image of magenta toner by the developing device 10.

On the other hand, paper designated as a transfer material is supplied from the paper supply unit 2, and the supplied paper is transferred to a transfer belt 12.
Is once abutted against a registration roller 13 provided on the upstream side in the transport direction. Then, the sheet is fed onto the transfer belt 12 in synchronization with the visible image, and reaches the transfer position facing the photosensitive drum 5 by running of the belt.
At this transfer position, the visible image of the magenta toner is transferred to the sheet by the action of the transfer roll 14 disposed on the back side of the transfer belt 12.

Similarly to the above-described image forming operation, visible images are formed on the surfaces of the respective photosensitive drums 5 by the respective toners in the other stations 4C, 4Y, and 4Bk. Each time the conveyed sheet arrives at each transfer position, the sheet is superimposed and transferred. Therefore, in the present color printer, a full-color image is overprinted and transferred onto a sheet in almost the same short time as a monochrome image. The sheet after the transfer is separated from the transfer belt 20 and fixed by the fixing device 15. The sheet on which fixing has been completed is normally discharged outside the apparatus as it is, or at this time, the sheet is inverted and discharged on the back side to a discharge tray 16 provided on the upper surface of the apparatus main body 1. For the printer, backside discharge is an almost essential condition for arranging prints in page order.

Next, the toner replenishing device provided in the printer will be described. FIG. 2 is a sectional explanatory view of a toner replenishing device using the toner container according to the present invention.

In FIG. 2, a developing device 10 has a powder pump 4 as a toner suction means from a toner storage container 20.
The toner is supplied through the transfer tube 17 by the suction pressure of zero. The developing device 10 is provided with a powder pump 40 at an upper portion thereof. As the powder pump 40, a suction-type uniaxial eccentric powder pump 40 is used. The configuration of the powder pump 40 is such that a rotor 41 formed in an eccentric screw shape with a rigid material such as metal is used.
And a stator 42 which is made of a rubber or other elastic material and has a two-screw shape formed inside and fixed and installed, and a holder 43 made of a resin material or the like which wraps them and forms a powder conveyance path. Have.

On the other hand, the setting section 50 provided in the image forming apparatus main body 1 in which the toner container 20 is set is configured as a unit separate from the developing apparatus 10. A nozzle 51 having a circular cross section inserted into the toner storage container 20 is provided upright in the set section 50.
0 is set in the setting section 50 of the image forming apparatus main body 1 from above. The nozzle 51 provided in the set section 50 has a conical tip 52 formed in the upper part, and the inside of the nozzle 51 has a double pipe structure. The air inflow path 53 and the toner discharge path 54 are formed by partition walls. Is formed. The toner discharge path 54 extends to the lower end of the nozzle 51 and is bent leftward, and the above-described toner transfer tube 17 is fitted therein.

On the other hand, the air inflow path 53 is bent to the right in the figure above the toner path, and is connected to the air pump 30 via the air transfer pipe 31. When the air pump 30 operates, the air transfer pipe 3
1 and the toner container 20 via the air inflow path 53
Air is blown into the inside from the lower side. Then, the air blown into the toner storage container 20 is fluidized while stirring the toner by passing through the stored toner layer.

The powder pump 40 is capable of continuous constant-quantity transfer at a high solid-gas ratio, and can obtain an accurate toner transfer amount in proportion to the rotation speed of the rotor 41. This powder pump 4
3, a rotor 41 is connected to a tip end of a drive shaft 44 rotatably supported by a bearing 45 via a connection shaft 45a, and a gear 46 is fixed to the drive shaft 44, as shown in FIG. As shown in FIG. 4, the gear 46 is meshed with a drive gear 48 driven by a supply motor 47 provided as a drive source dedicated to the powder pump. Therefore, the driving of the powder pump 40 is separated from the sheet feeding device, the developing device, and the fixing device driven by the main motor 100.

With this configuration, even if the number of revolutions of the main motor 100 is changed by mode switching in the printer, the rotor 41 can be driven at a desired number of revolutions without any influence. . Accordingly, the toner supply by the powder pump 40 can sufficiently follow all solid images of the maximum size in printing in any mode. In the above embodiment, as shown by the dotted line in FIG. 3, the gear 46 is provided with the clutch 4 with the clutch 49 in consideration of the response speed of the supply motor 47.
It can be 6. When the gear 46 is replaced by the gear 46 with the clutch 49, it is not necessary to consider the time required for the motor to rise and fall.

In the configuration in which the rotor 41 is rotationally driven by a drive source dedicated to the powder pump as shown in FIG. 4, the rotor speed (the number of revolutions of the powder pump) is determined by the experimental results shown in FIG. Taking into account delays caused by play and delays due to backlash in the joints of the connection, the effective minimum replenishment time is 200 msec or more, and even at that replenishment time, 250 rpm or more can be supplied stably to the target value. Therefore, it is desirable to set the rotation speed of the powder pump to 250 rpm or more.

In the case of an image forming apparatus having four stations 4M, 4C, 4Y, and 4Bk as described above, a dedicated replenishing pump 47 is provided for each toner replenishing device of each of the stations 4M, 4C, 4Y, and 4Bk. Alternatively, the powder pump 40 of each station may be driven by one motor. In this case, the gear with the clutch described above may be adopted and driven only at the time of replenishment.

Even with this configuration, since the powder pump 40 is driven separately from the main motor, it is not affected by the mode change. By the way, in the above-described color printer, the transfer distance and the head of the toner differ for each station. Therefore, each station 4M, 4C, 4Y,
When the 4Bk powder pump 40 is driven under the same conditions (all at a rotational speed of 250 rpm), as shown in the graph of FIG.
The difference between each of M, 4C, 4Y, and 4Bk has been described above.

Therefore, each station 4M, 4C, 4
The rotation speed of the Y, 4Bk rotor 41 is set to the rotation speed in consideration of the length and the head of the toner transfer tube 17 for each station, and the stations 4M, 4C, 4Y, 4B are set.
It is configured such that there is no difference in the toner supply amount per unit time at k. The setting of the number of revolutions of the rotor is preferably performed by changing the gear ratio by a gear train (not shown).

Specifically, the station 4M is set at 250r
pm, station 4C at 280 rpm, station 4Y at 300 rpm, station 4Bk at 350 rpm
m, the replenishment amount characteristics of the stations 4M, 4C, 4Y, and 4Bk become almost the same as shown in the graph of FIG. Therefore, each station 4M, 4C, 4Y, 4
Bk can be replenished with the same control, and the control can be simplified. Note that the specific numerical value of the set number of rotations naturally changes when the length and the head difference of the toner transfer tube 17 between the stations 4M, 4C, 4Y, and 4Bk described above change.

[0027]

According to the first aspect of the present invention, the powder pump is driven by a dedicated drive source independent of the drive source provided in the image forming apparatus main body. Can be kept constant. If the rotation speed of the powder pump does not change, it is not necessary to cope with the supply characteristics for each rotation speed that changes in a short supply time, so that control can be simplified and the supply characteristics for each rotation speed vary. Control instability can also be reduced.
Further, for example, it is possible to easily cope with a change in the replenishing amount which changes in a range not related to the performance of the powder pump particularly in the development stage, such as a change in the characteristics of the toner to be fed. .

According to the second aspect of the present invention, the target replenishing amount can be achieved even with an effective short replenishing time by setting the rotation speed of the powder pump to 250 rpm or more. According to the configuration of claim 3, since the powder pump of each station is driven by a dedicated driving source independent of the driving source provided in the image forming apparatus main body, the rotation of the powder pump of each station is independent of the mode. The number can be kept constant.

According to the fourth aspect of the present invention, since the number of rotations of the powder pump in each station is preset for each station, conditions such as the length of the toner transport tube and the head which differ for each station are taken into consideration. To set an optimum rotation speed.

According to the fifth aspect of the present invention, the number of rotations of the powder pump of each station is set according to the transfer distance and head of the toner, so that the difference in the amount of supply per unit time between the stations is compensated. This simplifies the control and stabilizes the toner concentration of the developing device.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory sectional view showing a toner supply mechanism of the image forming apparatus.

FIG. 3 is a perspective view showing a drive system of the powder pump of the present invention.

FIG. 4 is a perspective view showing a driving system of an image forming apparatus and a powder pump according to the present invention.

FIG. 5 is a graph showing the toner supply amount when the powder pumps of the respective stations are driven at the same rotation speed.

FIG. 6 is a graph showing a toner supply amount when the powder pump of each station is driven according to the present invention.

FIG. 7 is a perspective view showing a drive system of a powder pump in a conventional image forming apparatus.

FIG. 8 is a graph showing a relationship between a rotation speed of a powder pump and a toner supply amount.

FIG. 9 is a perspective view illustrating an example of an arrangement of each station in the color image forming apparatus.

[Explanation of symbols]

 Reference Signs List 20 toner container 40 powder pump 41 rotor 42 stator 47 motor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhisa Sudo 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H030 AA06 AB02 BB02 BB23 BB33 BB38 BB44 2H077 AA01 AA12 AA14 AA25 AA34 AC11 AD06 BA01 GA13

Claims (5)

[Claims] 1. The toner stored in a toner storage container,
In a toner supply device for supplying toner to a developing device by a powder pump having a stator having a through hole and a rotatable rotor fitted into the through hole of the stator, the powder pump is provided in an image forming apparatus main body. A toner supply device driven by a dedicated drive source independent of a drive source. 2. The toner supply device according to claim 1, wherein a rotation speed of the powder pump by the dedicated drive source is 250 rpm or more. 3. A station for forming a plurality of images, wherein each of the stations receives a toner stored in a toner storage container and a stator having a through-hole formed therein, and a rotary drive fitted into the through-hole of the stator. An image forming apparatus including a toner replenishing device for replenishing a developing device with a powder pump having a rotor to be rotated, wherein the powder pump of each of the stations is driven by a dedicated driving source independent of a driving source provided in the image forming device main body. An image forming apparatus that is driven. 4. The image forming apparatus according to claim 3, wherein the number of rotations of the powder pump of each station is set in advance for each station. 5. The image forming apparatus according to claim 3, wherein the number of rotations of the powder pump in each of the stations is set in accordance with a toner transfer distance and a head.