JPH1152726A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make stirring effective by projectingly providing a suitable number of stirring pins in the inside surface of a casing for housing a stirring/carrying screw and notching a screw part, so as to prevent interference with the stirring pins. SOLUTION: A stainless steel rotary shaft serving as an axial center is arranged in such a manner that it is supported by a supporting pin, in a die cavity having a spiral machined cavity. The axial center is pressed by clamping by a mold, to be fixed by a pin and meltable resin of ABS resin/PC resin incorporating glass fiber is injected into a cavity. After cooling, molded goods are taken out to obtain the toner stirring/carrying screw 4 provided with a spiral screw part 2a whose outer periphery has notches and a driving shaft supporting part 3a and a shaft supporting part 3b at both ends. The toner stirring/carrying screw 4 is constituted in such a manner that the spiral screw part, 2a, a shaft part 1 for covering the axial center and the driving shaft supporting part 3a and the shaft supporting part 3b at the shaft ends are integrally molded from resin. Then, the notches 5 are formed in the screw part 2a, at regular intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, and more particularly, to a developing device for an electrophotographic apparatus, and more particularly, to a developing apparatus for a color electrophotographic apparatus.

[0002]

2. Description of the Related Art In a developing device of an electrophotographic apparatus, a developer obtained by conveying toner and a carrier while stirring the toner must be uniformly distributed over the entire length of the developing drum. For this reason,
As shown in FIG. 3, a toner agitating / conveying screw provided with a spiral screw portion 2 on the outer periphery of the shaft portion 1 is provided in the toner supply portion.

As shown in FIG. 3, the screw for conveying and stirring toner has a single spiral or two spirals (only one in the illustrated example), and thus the toner is fed in the axial direction. Although the toner can be supplied to the carrier at the start of the supply, the toner may be supplied without being sufficiently stirred and evenly mixed. In some cases, a thin layer of the developer mixed with the above may not be obtained. If the number of rotations of the screw is increased beyond a certain level in order to increase the stirring effect of the screw, the deflection of the shaft portion 1 increases, and the screw portion 2 may come into contact with the inner surface of the developing device. And the problem that power consumption increases due to the contact between the screw portion and the developing device.

Therefore, as shown in FIG. 4, a method of changing the helical pitch of the screw portion 2 (P ₁ > P ₂ > P ₃ >)
P ₄ ) has been proposed. However, the method of changing the helical pitch in this way has a problem that the manufacturing cost of the mold is increased and the shape design of the mold is complicated.

In order to uniformly disperse the toner in the carrier while the toner is being conveyed from the toner supply point to the other end of the screw, as shown in FIG.
In some cases, a fin F is provided between the two to use a toner stirring / conveying screw which enhances the stirring effect. However, FIG.
The fin-attached toner agitating and conveying screw described in (1) has a problem that the molding die becomes complicated and expensive. In addition, since the fin F faces at right angles to the rotation direction of the screw, it also becomes an obstacle for toner conveyance, the torque for rotating the screw becomes large, and the power consumption is increased, but the conveyance efficiency is significantly reduced. is there. Further, toner may adhere to the fins F, and the adhered toners may become obstacles for toner conveyance, and may cause problems such as breakage of the fins when a screw is attached to the developing device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object a stirring performance superior to that of a helical pitch variable screw or a finned screw, and the same level of stirring performance. An object of the present invention is to provide a developing device which has a conveying performance and is less likely to cause a decrease in the rotation speed of a toner stirring and conveying screw due to an increase in torque.

[0007]

According to the present invention, an appropriate number of stirring pins are provided on an inner surface of a casing accommodating a stirring and conveying screw so as to generate turbulent flow during toner conveyance. By protruding and notching the screw portion so as not to interfere with the stirring pin, the laminar flow state and the turbulent flow state are repeated at the time of toner conveyance, and the stirring effect can be improved.

[0008]

The gist of the present invention is to provide a developing device having a developing roller, a toner stirring / conveying screw and a casing for accommodating the developing roller, a helical screw around the shaft. On the inner surface of the casing accommodating the provided toner stirring and conveying screw,
A stirring pin is protruded at a predetermined position in the longitudinal direction of the screw shaft portion, and the screw portion is cut out so as not to interfere with the stirring pin.

In the present invention, the developing roller carries the toner in a thin layer on the outer periphery and supplies the toner to the photosensitive drum to perform development. The developing roller includes a magnet roller, a magnet-containing sleeve roller, and a conductive roller on the outer periphery of the rotating shaft. For example, a roller provided with an elastic layer. The screw for toner stirring and transport is
The toner is supplied at one end in the longitudinal direction and is uniformly mixed with the carrier or the circulating developer (mixture of the toner and the carrier) while being transported to the other end.

Preferably, the screw portion and the shaft portion covering the outer periphery of the shaft core are integrally formed of synthetic resin.
As the synthetic resin, a resin having low thermal deformation, excellent heat resistance and non-adhesiveness to toner, and excellent dimensional stability and strength is used. For example, acrylonitrile butadiene styrene resin (ABS resin), polycarbonate resin (PC resin), alloy of ABS resin and PC resin (ABS resin / PC resin), polyphenylene ether (PPE resin), polyphenylene oxide (PPO resin) or ABS resin, PC resin, ABS resin / PC resin, PPE resin or PPO resin, etc. are used, which are reinforced with glass fiber such as carbon or aramid,
Among them, ABS resin / PC resin (containing 30% of glass fiber) is inexpensive, has heat stability, and is preferably used.

In the present invention, the casing provided with the stirring pin is a part of the casing close to the outer diameter of the screw for conveying and stirring the toner, and an upper lid provided for checking the screw portion is preferably used. The stirring pins protruding from the inner surface of the casing are usually provided at regular intervals in the length direction of the screw, but may be provided more on the side to which the toner is supplied, and may be provided on the opposite side at longer intervals in the axial direction. In some cases, no stirring pin is provided on the opposite side. As the cross-sectional shape of the stirring pin, a circle, an ellipse, a rectangle, or the like can be used, but a circle, an ellipse, or a semicircle thereof is preferably used because the rise of the rotation torque is small. A pin having a cross-sectional diameter of 2 to 4 mm has good stirring efficiency and is preferable in terms of strength. The stirring pin is preferably formed integrally with the casing with a resin or the like, but may be fixed to the casing with a screw or an adhesive. The height of the stirrer pin should be 1.
The height is set so that a clearance of 0 to 1.5 mm can be obtained.

In the present invention configured as described above,
When the toner is conveyed by the spiral screw portion having no notch, the toner is conveyed in a laminar flow state, and in the portion where the stirring pin is provided, the flow of the toner is disturbed by the interference action of the stirring pin. By repeating the laminar flow state and the turbulent flow state, the stirring effect can be improved.

It is unavoidable that the cutting performance of the screw is slightly reduced by cutting the spiral screw portion. However, by adjusting the height of the protruding stirrer pins and the cutout amount of the screw portion, the stirring performance can be reduced. And the transfer performance can be well balanced.

[0014]

EXAMPLES Examples and comparative examples of the present invention will be described below.

[Embodiment] A stainless steel rotary shaft having a diameter of 6 mm and a length of 290 mm serving as a shaft center is supported by a support pin in the cavity of a mold (not shown) having a cavity formed into a spiral shape. And fix this shaft core with a holding pin by mold clamping.
A molten resin of S resin / PC resin is injected, and after cooling, a molded product is taken out and, as shown in FIG. 1 (a), a length of the shaft portion 1 provided with a spiral screw portion 2a having a notch on the outer periphery. 296.1 mm, drive shaft support 3a and shaft support 3b at both ends
A toner stirring and conveying screw 4 having a length of 16.7 mm was obtained. The toner stirring and conveying screw 4 has an outer diameter of 14 mm.
helical screw 2 mm
a, Shaft 1 Covering Shaft Core and Drive Shaft 3 at Shaft End
a, the shaft support 3b was integrally formed of resin, and the screw 2a was formed with notches 5 at regular intervals. The size of the notch 5 is determined according to the diameter and the protruding height of the stirring pin 7 provided on the inner surface of the casing 6 as shown in FIG. In this embodiment, the cutout width is 3.5 mm, corresponding to the outer diameter of the stirring pin 7 of 3 mm and the height of 2 mm.
The depth from the spiral outer diameter was 2 mm.

[Comparative Example 1] A molten resin of ABS resin / PC resin containing 30% glass fiber was injected into the cavity in the same manner as in Example except that a mold having a different cavity shape was used, and a molded product was taken out after cooling. In this way, a toner stirring and conveying screw 8 having no notch as shown in FIG. 3 was obtained corresponding to the casing without the stirring pin.

[Comparative Example 2] A molten resin of ABS resin / PC resin containing 30% glass fiber was injected into the cavity in the same manner as in Example except that a mold having a different cavity shape was used, and after cooling, a molded product was taken out. Thus, a screw 9 for toner agitation and conveyance was obtained in which the helical pitch was varied as shown in FIG. 4 corresponding to the casing without the agitation pin. The spiral pitch of the toner stirring and conveying screw 9 is P ₁ > P ₂ >
It was changed so that P ₃ > P ₄ . [Comparative Example 3] A casing having the same screw portion 2 as in Comparative Example 1 and providing fins F at intervals of 180 ° between the screw portions 2 and 2 as shown in FIG. Screw 10 for stirring and conveying toner with fins
Was molded using the same synthetic resin as in the example.

Next, the screws for toner stirring and transport of the examples and comparative examples obtained as described above were mounted on a test apparatus 11 shown in FIG. 6 which simulates a developing apparatus of an electrophotographic apparatus. The test apparatus 11 has test screws S, S supported biaxially in a casing 12. A motor 14 is connected to one screw S via a speed reducer 13, and the other screw S is The transmission is driven by one screw S via the attached belt 15. Then, the screws S, S of the test device 11
Is rotated at 150 rpm, a toner containing 5% by weight of the toner component and 95% by weight of the carrier component is supplied and circulated, and a toner equivalent to 2.5% by weight is supplied at the toner supply point 16 for a certain period of time. The mixture having been stirred and transported was collected at the mixture collection point 17, and the stirring performance was evaluated by the charge amount of the toner component in the mixture, and the transport performance was evaluated by the toner concentration in the mixture. In addition, when the screw S for toner agitation and conveyance is mounted, the lid 6 installed on the upper surface of the test apparatus is used.
In the embodiment, a semicircular groove having an inner diameter of 16 mm is provided corresponding to the outer diameter of the toner stirring and conveying screw accommodated in the inner surface of
A stirrer pin 7 'was provided at a position corresponding to every other pitch of the spiral, and in the case of the comparative example, a stirrer without a stirrer pin was used.

The charge amount was determined by extracting the toner component from the mixture by blow-off and measuring the charge amount. The larger the charge amount, the better the stirring. The toner concentration was obtained by washing the mixture with methanol to remove the carrier and determining the toner content. The higher the toner concentration, the better the transport performance. FIG. 7 shows the measurement result of the charge amount, and FIG. 8 shows the measurement result of the toner concentration. The meaning of each symbol is as follows.

＝= Example, Δ = Comparative Example 1, ● = Comparative Example 2, ＝= Comparative Example 3 As is apparent from FIGS. 7 and 8, the developing device of this embodiment
The stirring performance is the best, and the transporting performance is slightly inferior to the conventional developing device using a screw for toner stirring and transporting,
This is a level with no practical problems.

[0021]

According to the present invention, only by combining the stirring pin of the casing and the notch of the screw, it has excellent stirring performance as compared with the case of using the helical pitch variable screw or the screw with the fin, and the same degree as these. It is possible to provide a low-cost developing device having the above-described transfer performance and less likely to cause operational trouble.

[Brief description of the drawings]

FIG. 1 is a side view of a toner stirring and conveying screw used in a developing device of the present invention. FIG. 1A shows an example in which notches are provided at substantially equal intervals, and FIG. It is a figure showing the example which provided notch only in a part.

FIG. 2 is a combined sectional view of an example of the developing device of the present invention in which a stirring pin is provided in a casing (upper lid) that accommodates a toner stirring and conveying screw provided with a notch;
2A is a diagram illustrating an example of a deep combination used in a toner supply unit and the like, and FIG. 2B is a diagram illustrating an example of a shallow combination on the opposite side of the toner supply unit.

FIG. 3 is a side view of a conventional toner stirring and conveying screw.

FIG. 4 is a side view of another conventional screw for conveying and stirring toner.

FIG. 5 is a side view of another conventional screw for conveying and stirring toner.

FIG. 6 is a perspective view of a test device simulating a developing device of the electrophotographic apparatus.

FIG. 7 is a graph showing a test result of toner stirring performance.

FIG. 8 is a graph showing a test result of toner conveyance performance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Shaft part 2, 2a ... Screw part 3a ... Drive shaft support part 3b ... Shaft support part 4, 8, 9, 10 ... Screw for toner stirring and conveyance 5 ... Notch 6 ... Casing (upper lid) 7 ... Stirring pin

Claims (1)

[Claims] 1. A developing device comprising a developing roller, a toner agitating / conveying screw, and a casing accommodating them, wherein an inner surface of a casing accommodating a toner agitating / conveying screw provided with a helical screw portion on an outer periphery of a shaft portion is provided. A developing device comprising a stirrer pin protruding at a predetermined position in a longitudinal direction of a screw shaft portion, and the screw portion facing the stirrer pin notched so as not to interfere with the stirrer pin.