JP2002005571A - Apparatus and method for drying by heating and method for heating and burning carrier particles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent powder from staying in the vicinity of a feeding portion and achieve efficient heating and burning. SOLUTION: An outer cylinder 2 is provided therein with a rotary inner cylinder 3 which is provided with a core 4 having an agitating portion that spreads from the side of a powder feeding portion 7 so as to have a radial form. When the power to be heated is agitated, rotational acceleration imposed on the powder at the feeding side of the core 4 is increased in order to raise the agitation effect on the powder. Thus the powder is prevented from staying in the vicinity of the feeding portion 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating and drying apparatus for drying and baking fine powder such as carrier particles of toner used as a developer in an image forming apparatus such as an electrophotographic copying machine or printer. The present invention relates to a heating drying method and a heating and firing method for carrier particles.

[0002]

2. Description of the Related Art For example, carrier particles of a toner used as a developer in an image forming apparatus such as an electrophotographic copying machine or a printer are coated with a resin containing a silicone resin as a main component on the surface thereof. Dry and fired. Various heating and drying devices are used to dry and bake such wet powder or resin-coated powder. Among them, the continuous heating and drying apparatus can heat and dry efficiently.

There are various types of continuous heating and drying apparatuses such as a rotary type, a ventilation type, a flow type, a ventilation flow type, and a stirring and ventilation type. Each of these heating and drying apparatuses has problems such as drying efficiency, productivity, environmental pollution, and cost depending on the method. Some powders require strict quality control. Further, some of the powders to be processed are very expensive, and these processes require not only quality but also high efficiency (high yield) productivity. In order to respond to this demand, for example, a heating and drying apparatus of a type combining a rotary type and a ventilation type is used. The heating and drying equipment of this method is a heating method in which the powder to be treated is charged into a rotating cylindrical furnace that is inclined and heated while the charged powder is moved to the discharge side by the rotation of the cylindrical furnace while being ventilated. There are two types: a co-current type in which the powder is blown from the input side to the discharge side, and a counter-current type in which the powder is blown from the discharge side to the input side.

[0004]

SUMMARY OF THE INVENTION In a heating and drying apparatus combining a rotary type and a ventilation type, a co-current type requires simultaneous heating of introduced powder and introduced air and the like.
Not very good in terms of thermal efficiency. Further, when high-temperature hot air is blown, the high-temperature air and the powder before heating come into immediate contact with each other, so that only moisture on the surface of the powder is rapidly taken away, and drying and firing become uneven. In the counter-current method, the introduced air is heated by the heat source of the cylindrical furnace and heated by the heated powder, so the thermal efficiency is high.However, when the carrier particles of the toner are thermally dried, the layer of the powder is heated. Granulation occurs in the inside, and powder accumulation occurs near the powder input section. In addition, the granules may grow more than necessary, increasing the load in the next step of sieving, which may lead to a decrease in yield.

The present invention has been made to solve the above-mentioned disadvantages, and provides a heating / drying apparatus, a heating / drying method, and a heating / baking method of carrier particles which can prevent powder from staying in the vicinity of a charging section and can efficiently heat and bake. It is intended to provide.

[0006]

A heating and drying apparatus according to the present invention has an outer cylinder, a rotating inner cylinder rotatably held in the outer cylinder, and a core provided in the rotating inner cylinder. Both ends of the tube are sealed, and one end is connected to the powder input section of the feeder, and the other end is provided with a powder discharge section below. The upstream side having the powder input section has the powder input section. It is installed so as to be higher than the downstream side with the body discharge section, a heating section is provided on the outer peripheral surface, and the core has a stirring section formed in a shape radiating from the powder input section side radially , And rotates in synchronization with the rotating inner cylinder.

It is preferable that the stirring section of the core has a plurality of stirring blades. It is desirable that the installation angle of the stirring blade is 30 to 90 degrees from the surface of the core with respect to the rotation direction of the core.

It is desirable that the outer cylinder has an air supply port on the downstream side having the powder discharge section, and has an exhaust port on the upstream side having the powder input section.

The heating and drying method of the present invention uses the above-mentioned heating and drying apparatus, controls the inside of the outer cylinder to a negative pressure, and heats the powder by passing a constant amount of air through a downstream air supply port. It is characterized by.

The method for heating and firing carrier particles of the present invention is a method for heating and firing carrier particles coated with a resin used in an electrophotographic developer. Is controlled to be in the range of 101.3 kPa to 100.3 kPa, and dry air of a constant air volume is passed from the air supply port on the downstream side to heat the carrier particles coated with the resin.

It is desirable to control the temperature at which the carrier particles coated with the resin are heated to below the decomposition point of the coated resin.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The heating and drying apparatus of the present invention has an outer cylinder, a rotating inner cylinder housed in the outer cylinder, and a core provided in the rotating inner cylinder. The powder input section of the feeding device is connected to one end, and a powder discharge section is provided below the other end, and the upstream side having the powder input section is the downstream side having the powder discharge section. The heater is installed at an angle so as to be higher, and a heater is provided on the outer peripheral surface.
An air supply port is provided on the downstream side of the outer cylinder having the powder discharge section, and an exhaust port is provided on the upstream side having the powder input section. The rotating inner cylinder is rotatably held on the outer cylinder by a plurality of holding rollers, and is rotated by a rotation driving device. The core has a stirrer formed in a shape that spreads radially from the powder input unit side, and a coupling unit provided on the downstream side of the stirrer and locked to the rotating inner cylinder, in synchronization with the rotating inner cylinder. Rotate.

The heating and drying apparatus uniformly coats a resin containing a silicone resin as a main component on the surface of carrier particles of toner used as a developer in an image forming apparatus such as an electrophotographic copying machine or a printer. When coating, drying and firing, the rotating inner cylinder and the core are heated by the heater provided on the outer cylinder while rotating the rotating inner cylinder and the core. Then, air is exhausted from an exhaust port provided on the upstream side of the outer cylinder, the inside of the heating and drying apparatus is controlled to a negative pressure, and dehumidified dry air is ventilated from an air supply port on the downstream side. In this state, the carrier particles coated with the resin are supplied into the core from the powder input section of the feeding device. The carrier particles supplied into the core are heated while moving downstream due to gravity. When heating these carrier particles,
The carrier particles are stirred by the rotation of the core. When stirring the carrier particles, the stirring portion of the core is formed in a radially spread shape in which the input side is narrow and the downstream side is wide, so that the rotational acceleration applied to the carrier particles on the input side can be increased. Enhances the stirring effect of the carrier particles. Therefore, it is possible to prevent the carrier particles from staying near the powder charging section.
In addition, since dry air is supplied from the downstream air supply port and exhausted from the upstream exhaust port, an air flow is generated in the core toward the injection side, and the flow velocity of the air flow is input into the core stirring section. It becomes faster as going to the side, and the stirring efficiency of the carrier particles on the charging side can be further increased.

[0014]

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention. As shown in FIG.
And a rotating inner cylinder 3 housed in the outer cylinder 2 and a core 4 provided in the rotating inner cylinder 3. Both ends of the outer cylinder 2 are sealed, and one end is connected to a powder feeding section 7 of a feeding device 6 for feeding powder from a hopper 5, and a powder discharge section is located below the other end. A portion 8 is provided, and is inclined at a small angle so that the upstream side having the powder inputting section 7 is higher than the downstream side having the powder discharging section 8. A plurality of heaters 9 are provided on the outer peripheral surface of the outer cylinder 2, an air supply port 10 is provided on the downstream side having the powder discharge section 8, and an exhaust port 11 is provided on the upstream side having the powder input section 7. Have been. A dehumidifier 13 such as a dryer is provided in an air supply pipe 12 connected to an air supply port 10 of the outer cylinder 2.

The rotating inner cylinder 3 is rotatably held on the outer cylinder 2 by a plurality of holding rollers 14, and is rotated by a rotation driving device 15. The core 4 is heat-resistant like the rotary inner cylinder 3,
As shown in the perspective view of FIG. 2, the agitating unit 16 is formed of a material having excellent corrosion resistance, and is formed in a shape radially spread from the powder input unit 7 side, and provided on the downstream side of the agitating unit 16.
It has a connecting portion 17 that is locked to the rotating inner cylinder 3, and rotates in synchronization with the rotating inner cylinder 3. The inclination angle α of the radially widened shape of the stirring section 16 of the core 4 is 20 depending on the type of powder to be treated.
The angle range is set to 60 degrees. A plurality of stirring blades 18 are provided on the inner surface of the stirring section 16 of the core 4. When the core 4 is formed in a cylindrical shape, six to eight stirring blades 18 are preferable. When the core 4 is formed in a polygonal cylindrical shape, at least one stirring blade 18 is provided on each surface. The installation angle β of the stirring blade 18 is set in an angle range of 30 to 90 degrees from the surface of the core 4 with respect to the direction of rotation of the core 4 as shown in the sectional view of FIG. Further, the tip of the stirring blade 18 is slightly inclined on the inner surface side of the core 4 so as to easily cause shearing development.

In the heating and drying apparatus 1 configured as described above,
For example, when uniformly coating a resin containing a silicone resin as a main component on the surface of carrier particles of a toner used as a developer of an image forming apparatus such as an electrophotographic copying machine or a printer, and drying and baking, While rotating the inner cylinder 3 and the core 4, the inner cylinder 3 and the core 4 are heated by the heater 9 provided on the outer cylinder 2. Then, air is exhausted from the exhaust port 11 provided on the upstream side of the outer cylinder 2 to control the inside of the heating and drying apparatus 1 to a negative pressure, and dehumidified dry air is ventilated from the air supply port 10 on the downstream side to ventilate the heating and drying apparatus 1. The internal pressure is controlled in the range of 101.3 kPa to 100.3 kPa. In this state, the carrier particles coated with the resin are supplied into the core 4 from the powder charging section 7 of the feeding device 6. The carrier particles supplied into the core 4 are heated while moving downstream due to gravity. When the carrier particles are heated, the carrier particles are stirred by the rotation of the core 4.

When the carrier particles are agitated, the agitating section 16 of the core 4 is formed in a radially expanding shape in which the input side is narrow and the downstream side is wide, so that the rotational acceleration applied to the carrier particles on the input side is reduced. It can be large and enhance the stirring effect of the carrier particles. Therefore, it is possible to prevent the carrier particles from staying in the vicinity of the powder charging section 7. In addition, the downstream air supply port 10
Since the dry air is supplied from the exhaust port 11 and exhausted from the exhaust port 11 on the upstream side, an air flow is generated in the core 4 toward the input side, and the flow rate of this air flow is increased toward the input side by the stirring unit 16 of the core 4. As a result, the stirring efficiency of the carrier particles on the charging side can be further increased.

When the carrier particles are agitated by the agitating section 14, the carrier particles having a large amount of aggregate immediately after the introduction are broken by the plurality of agitating blades 18 so that the carrier particles can be decomposed into individual particles. Is further enhanced to prevent stagnation in the vicinity of the powder charging section 7. When the installation angle β of the stirring blade 18 for decomposing the aggregate of the carrier particles is 30 degrees or less, the lifting effect and the showering effect are reduced, and the carrier particles stay on the inner surfaces of the stirring blade 18 and the stirring unit 14. It is not preferable because it becomes easy. When the installation angle β of the stirring blade 18 is 90 degrees or more, the lifting effect is reduced, and the effect of disintegrating aggregates of the carrier particles immediately after introduction is reduced. Therefore, the setting angle β of the stirring blade 18 is set in an angle range of 30 to 90 degrees from the surface of the core 4 with respect to the direction of rotation of the core 4 to enhance the crushing effect of the aggregates of the carrier particles, Decomposes reliably.

The carrier particles stirred by the stirring section 14 of the core 4 sequentially move downstream. Since heated and dried air is supplied from the air supply port 10 to the moved carrier particles and heated in the apparatus at a constant flow rate, the carrier particles are generated when the resin coated on the carrier particles is heated and sintered. High-temperature gas containing low-molecular components in the resin, and resin falling powder generated during the showering action and the lifting action can be discharged. At this time, when the internal pressure of the core 4 is a positive pressure, the flow rate of the heated and dried air becomes slow, and the gas and the falling powder generated from the resin cannot be discharged efficiently and remain, and the quality of the carrier particles is reduced. Lower it. The internal pressure of core 4 is 100.3 kP
When the pressure becomes lower than a, the flow rate of the heated and dried air increases,
Carrier particles having a low specific gravity are exhausted from the exhaust port 11, which lowers the yield. Therefore, the heating and drying device 1
Is controlled in the range of 101.3 kPa to 100.3 kPa.

Further, by sending dry air from the air supply port 10, low molecular components generated from the resin coated with the carrier particles during heating react with moisture contained in the ventilation or lower the sintering temperature. To prevent the quality of the carrier particles from deteriorating, and stably discharge high-quality carrier particles.

When the carrier particles of the toner are heated and baked as described above, the heating temperature is set to be equal to or lower than the decomposition temperature of the material having the lowest decomposition point among the materials in the resin coated with the carrier particles. Generally, the resin that coats the carrier particles includes a crosslinking agent and a curing agent for the purpose of curing and binding the resin in addition to the silicone resin. Heating and baking are performed at a temperature higher than the decomposition point of these materials. For example, when the curing agent is decomposed, the curing does not proceed very much, and carrier particles having a high surface viscosity are discharged. In addition, when the cross-linking agent is decomposed, the binding effect between the resin and the carrier particles is reduced, and during the showering action, the lifting action, and the movement to the discharge side, the resin falls off and the uncoated carrier is developed. Particles are generated and the quality is degraded. Therefore, heating and baking are performed at a temperature at which these materials do not decompose.

[Specific Example] For example, ferrite carrier particles having an average particle diameter of 50 to 100 μm are used as carrier particles of the toner, and the carrier particles are coated with a silicone resin. The installation angle β of the stirring blade 18 and the internal pressure of the apparatus are set as follows. Heating and sintering were carried out by charging 100 kg per hour under the conditions shown in the table, and various characteristics of the baked carrier particles were examined.

[0023]

[Table 1]

As a comparative example, the same carrier particles as described above were heated and fired under various conditions shown in the following table.

[0025]

[Table 2]

The evaluation results of the carrier particles heated and fired in each of the specific example and the comparative example are shown in the following evaluation tables.

[0027]

[Table 3]

In this evaluation table, the amount remaining in the drying furnace indicates the amount of carrier particles remaining in the furnace after the treatment, and the amount of agglutination generated is based on the weight of the charged carrier particles before the treatment.
The ratio of the weight of the treated carrier particles remaining on the specific opening sieve is shown. In addition, the carrier resin shedding is observed by electron micrographs of the surface of the carrier particles after the treatment, and the degree is divided into five stages. Those having almost no shed resin powder are evaluated as double circles according to the degree of occurrence. Did.
The electric resistance and the charging characteristics are classified into five stages according to the degree of difference from the reference value (target value).
It was a heavy circle, and the evaluation was divided according to the difference from the reference value. Further, the yield indicates the ratio (wt%) of the weight of the carrier particles after the treatment that has passed through a sieve with a specific opening to the total input amount.
The comprehensive evaluation was divided into five levels, including product productivity and quality.

As shown in the evaluation table, in the case of the specific example, the carrier particles coated with the silicone resin could be fired stably and high quality carrier particles could be efficiently produced.

In the above embodiment, the case where the carrier particles coated with the silicone resin are heated and baked is described. However, other powder particles can be heated and dried in the same manner.

[0031]

As described above, according to the present invention, a core having a stirring portion formed in a shape radially spread from a powder charging portion side is provided in a rotating inner cylinder provided in an outer cylinder and heated. Since the powder is agitated, the rotational acceleration applied to the powder on the core input side can be increased, and the effect of agitating the powder is enhanced. Therefore, it is possible to prevent the powder from staying near the powder input section,
It can move smoothly and heat.

By providing a plurality of stirring blades in the stirring section of the core, the stirring effect of the stirring section can be further enhanced.

By setting the angle at which the stirring blade is set at 30 to 90 degrees from the surface of the core with respect to the direction of rotation of the core, it is possible to enhance the crushing effect of the powder aggregate immediately after the introduction. And can be reliably decomposed into individual powders.

An air supply port is provided on the downstream side of the outer cylinder having the powder discharge section, and an exhaust port is provided on the upstream side of the outer cylinder having the powder input section. By heating with the powder to heat the powder on the upstream side, the thermal efficiency can be increased.

When heating the powder, the inside of the outer cylinder is controlled to a negative pressure, and a constant air volume is ventilated from an air supply port on the downstream side, thereby discharging gas and falling powder generated by the heating. It can be efficiently discharged and can be stably heated.

When the carrier particles coated with the resin used in the electrophotographic developer are heated and calcined, the internal pressure in the outer cylinder is controlled to be in the range of 101.3 kPa to 100.3 kPa while the air is supplied from the downstream air supply port. By heating the carrier particles coated with resin by passing dry air with a constant air volume, high-temperature gas containing low molecular components in resin generated during sintering and generated during showering action and lifting action Resin falling powder can be efficiently discharged, and carrier particles having a low specific gravity can be prevented from being discharged from an exhaust port, so that heating and firing can be performed with a high yield.

Further, by controlling the temperature at which the carrier particles coated with the resin are heated to a temperature not higher than the decomposition point of the coated resin, high-quality firing can be achieved, and a homogeneous fired product of the carrier resin can be stably formed. can do.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of the present invention.

FIG. 2 is a perspective view showing a core of the embodiment.

FIG. 3 is a sectional view showing a stirring blade provided in a stirring unit of a core.

[Explanation of symbols]

1; heating and drying device; 2; outer cylinder; 3; rotating inner cylinder; 4; core; 5; hopper; 6; feeding device;
8; powder discharger, 9; heater, 10; air supply port, 11; exhaust port, 12; air supply pipe, 13; dehumidifier, 14; holding roller, 15; Connection part, 18; stirring blade.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F26B 21/10 F26B 21/10 Z G03G 9/113 G03G 9/10 351 (72) Inventor Yoshikazu Karada Tokyo 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Eiji Oba 1-3-6, Nakamagome, Ota-ku, Tokyo, Japan Ricoh Co., Ltd. (72) Kazumi Otaki, Ota-ku, Tokyo 1-3-6 Nakamagome F-term in Ricoh Co., Ltd. (Reference) 2H005 BA06 BA11 3L113 AA07 AB03 AB05 AC01 AC25 AC32 AC45 AC46 AC48 AC49 AC50 AC58 AC59 AC60 AC68 BA02 CA04 CA08 CA10 CB23 DA24

Claims (7)

[Claims] An outer cylinder, a rotating inner cylinder rotatably held in the outer cylinder, and a core provided in the rotating inner cylinder, wherein both ends of the outer cylinder are sealed, and one end of the outer cylinder is sealed. The powder input section of the feeding device is connected, and a powder discharge section is provided below the other end, and the upstream side having the powder input section is inclined so as to be higher than the downstream side having the powder discharge section. The core is provided with a heating section on the outer peripheral surface, and the core has a stirring section formed in a shape that spreads radially from the powder input section side, and rotates in synchronization with the rotating inner cylinder. Heating and drying equipment. 2. The heating and drying apparatus according to claim 1, wherein the stirring section of the core has a plurality of stirring blades. 3. The heating and drying apparatus according to claim 2, wherein the installation angle of the stirring blade is 30 to 90 degrees from the surface of the core with respect to the direction of rotation of the core. 4. The heating device according to claim 1, wherein the outer cylinder has an air supply port on a downstream side having a powder discharge section and an exhaust port on an upstream side having a powder input section. Drying equipment. 5. A heating / drying method using the heating / drying apparatus according to claim 1, wherein the inside of the outer cylinder is controlled to a negative pressure, and a fixed air volume is ventilated from a downstream air supply port. And heating the powder by heating. 6. A method for heating and baking carrier particles coated with a resin used for an electrophotographic developer, wherein the internal pressure in the outer cylinder is reduced by using the heating and drying apparatus according to claim 1. A method for heating and baking carrier particles, characterized in that the carrier particles coated with the resin are heated by passing a constant amount of dry air through a downstream air supply port while controlling the carrier particles in a range of 101.3 kPa to 100.3 kPa. 7. The method according to claim 6, wherein the temperature at which the carrier particles coated with the resin are heated is controlled to be equal to or lower than the decomposition point of the coated resin.