JPH0735052B2 - Microwave dryer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a microwave dryer.

(B) Prior art Japanese Utility Model Laid-Open No. 59-91592 discloses, for example, a microwave dryer that applies microwaves to a drying chamber into which granular material to be dried is supplied to dry the material to be dried. It is disclosed. The microwave dried material is then discharged from the drying chamber to a predetermined location, and the microwave supply to the drying chamber is stopped.

However, in this case, if the material to be dried previously discharged to the predetermined location remains accumulated, the material to be dried is immediately discharged to the predetermined location even if the material to be dried has just been dried in the drying chamber. The material to be dried, which cannot be dried, must be left in the drying chamber as it is.
Then, even if the material to be dried is dried, it absorbs moisture again while being left in the drying chamber.

In this respect, re-moisture absorption can be prevented if the microwave supply control is performed again during such standing to keep the dried material to be dried.

On the other hand, the material to be dried is configured to be agitated by a separately provided agitating means during drying so as not to cause unevenness in drying. Therefore, even in the case of the above-mentioned heat retention, the agitating means is driven to cause unevenness in heat retention. Suppressed.

However, when the material to be dried is stirred in this manner, the granular material to be dried is rubbed with each other along with the stirring to generate unnecessary fine powder.

Here, even if it is unavoidable that the material to be dried is agitated at the time of drying, it is desirable to suppress the agitation of the material to be dried as much as possible during the heat retention performed only when necessary.

(C) Problems to be Solved by the Invention In the present invention, when the granular dried object is kept warm after completion of microwave drying, stirring of the dried object for suppressing uneven heat retention is suppressed as much as possible, and unnecessary fine powder is generated. It is intended to suppress as much as possible.

(D) Means for Solving the Problems A microwave drying apparatus of the present invention supplies a drying chamber into which an object to be dried is supplied, and a microwave for microwave-drying the object to be dried into the drying chamber. Microwave supply means,
Drying control means for driving the microwave supply means to execute the drying operation of the material to be dried until a desired dry state is obtained,
Independent of the stirring means for continuously driving the material to be dried in the drying chamber by the drying control means during the drying operation, and the drying chamber for discharging and storing the material to be dried from the drying chamber after the completion of the drying operation. A spare chamber, a level sensor disposed in the spare chamber for detecting the presence of a material to be dried in the spare chamber, and based on the detection result of the level sensor, from the drying chamber to the spare chamber after completion of the drying operation. Determining means for determining whether or not the discharge of the material is allowed, discharge means for discharging the material to be dried from the drying chamber to the preliminary chamber based on the determination result of the determining means, and the above-mentioned determination means based on the determining means. A heat retention control means that drives the microwave supply means to perform heating operation to such an extent that the material to be dried does not absorb moisture in the drying chamber, and an intermittent drive of the stirring means while heating and heat retention by the heat retention control means (alternate between driving and stopping). If the level sensor detects that the material to be dried does not exist, the determination means performs discharge permission determination that permits discharge, and if the material to be dried is detected, The discharge non-permission judgment not permitting the discharge of the material to be dried into the preliminary chamber is made, and the discharge means is driven after the drying operation is completed only when the discharge allowance is judged by the judging means to reserve the material to be dried. Further, the temperature maintaining control means is driven after the drying operation is completed only when the discharge non-permissible judgment of the judging means is carried out to keep the material to be dried in the drying chamber warm, and the intermittent driving means controls the stirring means. It is a structure that is intermittently driven.

(E) Action When the granular dried object is kept warm after being dried, the stirring means is intermittently driven to suppress the stirring of the dried article to some extent, and thus unnecessary fine powder is maintained while suppressing the unevenness of keeping the dried object in the heat state. Is suppressed.

(H) Embodiment FIG. 1 shows the structure of a microwave drying apparatus according to an embodiment of the present invention, which comprises a drying apparatus main body (1) and its peripheral mechanism.

The drying device main body (1) is provided with a cylindrical drying chamber (3) having an upper lid (2) as a main part. A supply pipe (4) is connected to the upper left portion of the drying chamber, and a tip of the supply pipe reaches a storage tank (6) for storing the granular material to be dried (5). As such a material to be dried (5),
Examples include resin pellets and rice. The resin pellets are molded after being melted, but if the resin pellets are dried prior to such melt molding, the subsequent molding will be performed well. In this embodiment, resin pellets are selected as the material to be dried (5). Also, the drying room (3)
A suction hopper (7) is connected to the center of the upper lid (2). A filter paper (8) having a mesh smaller than the material diameter of the material to be dried (5) is arranged in the hopper,
Moreover, a poppet valve (9) is provided above the filter paper. The suction pipe (10) is attached to the suction hopper (7) above the poppet valve (9).
A suction blower (11) is connected via. In this case, when the blower (11) is driven with the poppet valve (9) being opened, the intake action of the blower (11) causes the intake pipe (10), the suction hopper (7), and the drying chamber (3). )
The material to be dried (5) in the storage tank (6) reaches the drying chamber (3) through the supply pipe (4). When the material to be dried (5) reaches the drying chamber (3), it falls by its own weight and accumulates therein.

In the drying chamber (3), microwaves are supplied from the magnetron (12) to the inside of the drying chamber (3) through the waveguide (13), and the bottom wall is driven by the motor (14) to be dried (5). A) is provided with a stirring body (15) corresponding to the stirring means of the present invention, and a level sensor (16) and a temperature sensor (17) such as a thermistor are arranged on the side wall. The level sensor (16) detects whether or not a predetermined amount of the material to be dried (5) has accumulated in the drying chamber (3), and the temperature sensor (17) detects the temperature of the material to be dried (5). . A compressor (19) is connected to the left bottom of the drying chamber (3) via an intake valve (18), and an exhaust valve (20) is provided on the upper lid (2) of the drying chamber (3). . The driving of the compressor (19) and the opening of the intake valve (18) and the exhaust valve (20) are performed when the material to be dried (5) is dried by microwaves, and the steam generated during the drying is compressed. (19)
Is discharged to the outside through the exhaust valve (20) together with the air from.

Further, a discharge valve (21) is provided on the right bottom portion of the drying chamber (3), and the discharge valve is opened when discharging the dried object (5) to be dried. The material to be dried (5) discharged based on the opening of the discharge valve (21) falls through the discharge pipe (22) into the preliminary chamber (23) serving as a lower discharge portion and accumulates therein. A heat insulation heater (24) is installed on the lower inclined wall of the spare chamber.
And a level sensor (26) having a rotating body (25) is provided in the preliminary chamber (23).
Such a level sensor (26) normally rotates the rotating body (25), and a slight predetermined amount of the material to be dried (5) accumulates in the preliminary chamber (23) to rotate the rotating body (25). However, when the object to be dried (5) becomes a load and the rotating body (25) cannot be rotated satisfactorily, a predetermined signal is output and the object to be dried (5) accumulates in a slight predetermined amount. Detect that there is.

The lower part of the spare chamber (23) is connected to another suction hopper (27) located higher than the spare chamber (23) through a transfer pipe (28). Similar to the suction hopper (7), the suction hopper (27) is also provided with a filter paper (29) having a mesh smaller than the material diameter of the material to be dried (5), and located above the filter paper. Then, a poppet valve (30) is provided. The suction blower (11) is also connected to the suction hopper (27) via the intake pipe (31) at the upper portion of the poppet valve (30). In this case, with the poppet valve (30) open, the blower (11)
When the blower (11) is driven, the intake action of the blower (11) passes through the intake pipe (31) and the suction hopper (27) to convey the pipe (28).
Up to this point, the material to be dried (5) accumulated in the preliminary chamber (23) reaches the suction hopper (27) through the transfer pipe (28). When the material to be dried (5) reaches the suction hopper (27), it falls into the hopper by its own weight. In the suction hopper (27), the heat retaining heater (32) is arranged on the lower inclined wall and the opening / closing valve (33) is provided on the lower end, and
Upper and lower limit level sensors (34) (35) are arranged at the bottom. When the on-off valve (33) is closed, the intake action acts to drop the material to be dried (5) in the suction hopper (27), and the material to be dried (5) accumulates in the suction hopper (27). When the opening / closing valve (33) is opened, the material to be dried (5) thus accumulated falls downward to reach the next-stage processing section, that is, the material to be dried (5) dried in the processing section, that is, Resin pellets are melt molded.

FIG. 2 shows a circuit of the microwave dryer, and a microcomputer (36) of product number LC-65PG23 manufactured by Sanyo Electric Co., Ltd. is provided as a main control unit, and the computer is the dryer main body (1). Information from the operation section (37) arranged on the front surface of the vehicle, temperature information from the temperature sensor (17), and various level sensors (16) (26) (34)
Based on the information from (35), etc., the magnetron (12), motor (14), intake valve (18), exhaust valve (20),
Compressor (19), discharge valve (21), heat insulation heater (24)
(32), suction blower (11), poppet valve (9) (30),
The on-off valve (33) is drive-controlled.

FIG. 3 shows a flow chart of an operation program incorporated in the microcomputer (36), and the operation of the microwave dryer will be described below with reference to the chart.

After turning on the power, go through the S1 step and then use the normal S2, S3, S3a
4 and S5 are cyclically executed. In step S1, initial setting operation is performed. That is, all the writable areas in the microcomputer (36) are cleared, and the magnetron (12), motor (14), compressor (19), heaters (24) (32), suction blower ( 11) is placed in the drive stopped state and the intake valve (1
8), exhaust valve (20), discharge valve (21), poppet valve (9)
(30) and the on-off valve (33) are placed in the closed state. In S2 step, the operation information from the operation section (37) is input, and in S3 step, the lower limit level sensor (35) determines whether or not the material to be dried (5) is accumulated in the suction hopper (27). , In the S3a step, the level sensor (2
Based on the detection of 6), it is determined whether or not the dried object (5) is accumulated in the preliminary chamber (23) in a slight predetermined amount. In step S4, it is checked whether or not the start flag is set in the computer (36), and in step S5, it is determined whether or not the start key is currently operated by the operation section (37) based on the input information in step S2. It

Thus, when the material to be dried (5), which is a resin pellet, is melt-molded and the material to be dried (5) is dried in advance so that such molding can be performed well, first, the operation part (37) is hand,
Within a range of 20 to 60 minutes and a range of 70 to 170 ° C., the drying time and the drying temperature at which the material to be dried becomes a desired dry state are set by key operation, and the continuous switch (38) is turned on. These operation information are input in step S2. After that, the operation part (3
When the start key is operated in 7), the information is similarly input in step S2, an affirmative judgment is made in step S5, the start flag is subsequently set in step S6, and the above-mentioned heat retention is performed in step S7. The drive control of the heaters (24) (32) is started. That is, each of the heat retaining heaters (24) (32) is intermittently driven at a desired ratio so that the insides of the preliminary chamber (23) and the suction hopper (27) are approximately maintained at the set drying temperature. The inside of (23) and the suction hopper (27) is kept at the above temperature.

Then, steps S8, S9, and S10 are sequentially executed. S8
In step, it is checked whether or not the transport flag in the computer (36) is set (in this case, it is checked that it is not set). In step S9, the operation of supplying the material to be dried (5) to the drying chamber (3) is executed. That is, the poppet valve (9) is opened and the suction blower (11) is driven,
The material to be dried (5) is supplied from the storage tank (6) into the drying chamber (3) by the suction action of the blower (11), and the motor (14) is driven to rotate the stirring body (15), The top surface of the material to be dried (5) supplied into the drying chamber (3) is aligned with a smooth horizontal surface. In step S10, whether or not the upper surface of the material to be dried (5) reaches the position of this sensor (16) by the detection of the level sensor (16) and the material to be dried (5) has accumulated in a predetermined amount in the drying chamber (3). Is determined (in this case, it is determined that the predetermined amount is not accumulated).

Then, the steps S2, S3, S3a, S4, S11, and S8 to S10 are cyclically executed. At this time, in step S11, it is checked whether or not the supply end flag in the computer (36) is set. Then, a predetermined amount of the material to be dried (5) is accumulated in the drying chamber (3), and if this is determined in step S10, then S12, S1
3 steps are executed. In step S12, the operation of supplying the material to be dried (5) to the drying chamber (3) executed in step S9 is ended. In step S13, the supply end flag is set.

Then, steps S2, S3, S3a, S4, S11, and S14 to S17 are cyclically executed. At this time, in step S14, it is checked whether or not the drying end flag is set in the computer (36), and in step S15, the drying operation is executed. That is, the magnetron (12) is intermittently driven depending on whether or not the temperature of the article to be dried (5) detected by the temperature sensor (17) reaches the set drying temperature, and the article to be dried (5) is dried at the drying temperature. Maintained in the microwave and dried, and the motor (14)
Is re-driven to rotate the agitator (15) and to be dried (5)
Is agitated so as to be evenly dried, and the compressor (19) is driven and the intake valve (18) and the exhaust valve (20) are opened so that water vapor generated from the material to be dried (5) is discharged to the outside. Is discharged. Further, in the step S15, the time of the drying elapsed time is started together with such a drying operation. In step S16, it is determined whether or not the drying elapsed time has reached the set drying time. In step S17, the setting of the transport flag is checked as in step S8. Therefore, S1
Steps 4 to S19 correspond to the drying control means of the present invention.

When the elapsed dry time reaches the set dry time, S1
After 6 steps, S18 and S19 steps are executed. In step S18, the time of the drying operation and the elapsed time of drying executed in step S15 is ended, and the time counted is reset. In step S19, the drying end flag is set.

Then, after steps S17, S2, S3, S3a, S4, S11, and S14, steps S20, S21, S22, S23, and S24 are sequentially executed. In step S20, it is checked whether or not the ejection flag in the computer (36) is set. The step S21 corresponds to the determination means of the present invention. In this step S21, whether or not the material to be dried (5) has already accumulated in the preliminary chamber (23) based on the detection of the level sensor (26) is slightly small. Is judged. In step S22, when a heat retention routine operation (described later) in the drying chamber (3) is being performed, this operation is ended and the discharge flag is set. The step S23 corresponding to the discharging means of the present invention is dried from the drying chamber (3) to the preliminary chamber (23) because the predetermined amount of the material to be dried (5) is not accumulated in the preliminary chamber (23) in the step S21. This is performed when it is permitted to newly discharge the dried material (5), and in this step S23, the dried material (5) is transferred from the drying chamber (3) to the preliminary chamber (23). The operation of discharging to is executed. That is, the discharge valve (21) is opened and the motor (14) is continuously driven to move the stirring member (1
5) is rotated, and with the rotation of the stirring body (15), the material to be dried (5) near the stirring body (15) is pushed to the surroundings, and the material to be dried (5) is discharged to the discharge valve (21). Through the discharge pipe (22) to the spare chamber (23). Since the preliminary chamber (23) is kept warm from the above step S7, the material to be dried (5) thus discharged is not naturally cooled, and the material to be dried (5) is naturally cooled. It is prevented from absorbing moisture again. Further, in step S23, the time counting of the elapsed time of such discharge is started. In step S24, the discharge elapsed time is a predetermined discharge time (this is sufficient time to discharge all the predetermined amount of material to be dried (5) stored in the drying chamber (3)). Is determined.

After that, S2, S3, S3a, S4, S11, S14, S20, S23, S24,
When each step of S17 is cyclically executed, and a small predetermined amount of the material to be dried (5) is accumulated in the preliminary chamber (23) due to the discharge, the steps S3a to S25, S26, S2 in this cycle are performed.
Steps S7 and S28 are sequentially executed. In step S25, the transport flag is set, and in step S26, when the material to be dried supply operation is being executed in step S9, the operation is stopped. In step S27, an operation of transporting the dried object (5) to the suction hopper (27) from the preliminary chamber (23) which is kept warm is executed. That is, the poppet valve (30) is opened, the suction blower (11) is driven, and the intake action of the blower (11) causes the auxiliary chamber (23)
The material (5) to be dried is conveyed from the suction hopper (27).
Since the suction hopper (27) keeps the temperature of the object (5) to be dried conveyed in this way from the above step S7, the object to be dried (5) is prevented from absorbing moisture again. To be done. In step S28, it is determined whether or not the material to be dried (5) has accumulated in the suction hopper (27) up to the position of the sensor by the detection of the upper limit level sensor (34) (in this case, it is determined to be no). ). Then S4,
Each step of S11, S14, S20, S23, S24, S17, S27, S28 is cyclically executed, during which the discharge operation to the preliminary chamber (23) and the transfer operation to the suction hopper (27) are performed in parallel. The material to be dried (5) discharged into the preliminary chamber (23) is immediately conveyed to the suction hopper (27).

Then, when the elapsed discharge time reaches a predetermined discharge time (all the material to be dried (5) is discharged from the drying chamber (3) to the preliminary chamber (23)), then S29, S30, and S31 are performed. Each step is sequentially executed. In step S29, the discharge operation and discharge elapsed time, which have been executed in step S23, have been timed, and the time measured has been reset. S30
In the step, all of the above-mentioned supply end flag, drying end flag, and discharge flag are reset. In step S31, it is determined whether or not the continuous switch (38) is turned on in the operation section (37).

In the present case, the continuous switch (38) is in the ON state, and after passing through the step S17, the steps S4, S11, S8, S27 and S28 are cyclically executed. Then, when the material to be dried (5) in the preliminary chamber (23) is transported and the material to be dried (5) is accumulated in the suction hopper (27) to the position of the upper limit level sensor (34), the steps S28 to S32 are performed. , S33 step is executed. S
In step 32, the carrying operation executed in step S27 is stopped, and in step S33, the carrying flag is reset.

Thus, the material to be dried (5) thus accumulated in the suction hopper (27) is melt-molded in the next-stage processing section. This is executed when an external command signal P for commanding melt molding is given to the computer (36) in a state where the material to be dried (5) is accumulated up to the position of 34). That is, at this time, the opening / closing valve (33) is opened by the computer (36), and the material to be dried (5) is discharged from the suction hopper (27) to the next stage processing section. The on-off valve (33) is closed again when all the material to be dried (5) in the suction hopper (27) has been discharged. The released material (5) to be dried is melt-molded in the next-stage treatment section. In this case, the resin pellets, that is, the material (5) to be dried is dried in advance, so that the molding is performed well. .

By the way, when the processing capacity of the next-stage processing unit for the melt-forming is slow, the suction hopper (27) and the auxiliary chamber (23) are stored in the suction hopper (27) because the operation of supplying the material to be dried to the conveying operation is repeated. The material to be dried (5) remains accumulated. Then, when the material to be dried (5) is accumulated in the preliminary chamber (23) and the material to be dried (5) is about to be discharged from the drying chamber (3), this is determined in step S21, That is, the spare room (2
It is determined that the material to be dried (5) is accumulated in the predetermined amount more than the predetermined amount in 3), and it is not allowed to newly discharge the material to be dried (5) from the drying chamber (3) to the preliminary chamber (23). Then, the dried object (5) is left in the drying chamber (3) as it is after being dried. If such leaving is simply performed, the material to be dried (5) is naturally cooled and absorbs moisture again even if it is dried, but in this case, step S34 is repeatedly executed to cope with this.

In such step S34, the heat retention routine corresponding to the heat retention control means and the intermittent driving means of the present invention shown in FIG. 4 is immediately entered, and the temperature of the article to be dried (5) is now 5 ° C. lower than the preset drying temperature. A1, A2, A3, A4 as long as it is between temperature
Each step of is executed. In step A1, it is checked whether the low temperature flag is set in the computer (36),
In step A2, it is determined whether or not the temperature of the article to be dried (5) detected by the temperature sensor (17) is not more than 5 ° C. lower than the set drying temperature. In step A3, it is checked whether or not the high temperature flag is set in the computer (36). In step A4, it is determined whether the temperature of the material to be dried (5) detected by the temperature sensor (17) is equal to or higher than the set drying temperature. Is determined.

Then, when the temperature of the material to be dried falls and becomes 5 ° C or less lower than the set drying temperature, the heat retention routine is started and A1, A2, A
Steps 5, A6 and A7 are executed. At this time, in the A5 step, the motor (14) is driven to stir the material to be dried (5) by the stirring body (15), in the A6 step, the on-delay timer in the computer (36) is activated, and in the A7 step. The low temperature flag, the high temperature flag, and the motor stop flag are set, reset, and reset, respectively.

Then, every time the warming routine is entered, A1, A8, A9,
Steps A3 and A4 are executed. At this time, it is determined in step A8 whether or not the oscillation flag is set, and in step A9 it is determined whether or not the on-delay timer is activated from step A6 to count a predetermined time (several seconds to several tens seconds). .

After that, when the on-delay timer measures a predetermined time, steps A1, A8, A9, A10, A3, and A4 are executed in the heat retention routine. In step A10, the magnetron (12) is driven to heat the material to be dried (5) by microwaves, the on-delay timer is stopped and reset, and the oscillation flag is set.

Then, every time the warming routine is entered, steps A1, A8, A3, A4 are executed, and when the temperature of the material to be dried (5) reaches or exceeds the set drying temperature, steps A1, A8, A3, A4, A11 are executed. To be done. At this time, in the A11 step, the magnetron (1
The driving of (2) is stopped and the off-delay timer in the computer (36) is operated, and the high temperature flag, the low temperature flag and the oscillation flag are set, reset and reset respectively.

Then, every time the warming routine is entered, A1, A2, A3,
The steps A12 and A13 are executed. At this time, in step A12, it is checked whether or not the motor stop flag in the computer (36) is set, and in step A7, the off-delay timer in the computer (36) operates and a predetermined time (from several seconds to several seconds).
It is judged whether or not the time has been measured (tens of seconds).

After that, when the off delay timer measures a predetermined time, the steps A1, A2, A3, A12, A13 and A14 are executed in the heat retention routine. In step A14, the motor (14) is turned off to stop the stirring of the material (5) to be dried by the stirring body (15),
In addition, the off delay timer is stopped and reset, and the motor stop flag is set.

Then, every time the warming routine is entered, the steps A1, A2, A3, A12 are executed, and when the temperature of the material to be dried (5) becomes lower than the set drying temperature by 5 ° C or less, A1, A2, A
The steps 5, A6 and A7 are executed, and the above-mentioned operation is repeated thereafter.

In this way, in the heat retention routine in step S34, the temperature of the material to be dried (5) is 5 below the set drying temperature.
The microwave heating is restarted when the temperature is lower than the temperature lower by ℃, and the microwave heating is stopped when the temperature of the material to be dried is equal to or higher than the set drying temperature. It is prevented that the dried product (5) absorbs moisture again in the drying chamber (3).

Further, at this time, the stirring body (15) is driven for a predetermined time period before the microwave heating is restarted and is stopped after a predetermined time delay after the microwave heating, so that the material to be dried (5) is restarted by the microwave heating, Driven intermittently in conjunction with the stop,
Stirring of the material to be dried (5) is suppressed to some extent while suppressing unevenness of heat retention as much as possible, and generation of unnecessary fine powder due to rubbing of the materials to be dried rubbing with stirring is suppressed.

While the warming routine operation is being performed, the compressor (19) is driven and the intake valve (18) and the exhaust valve (20) are opened.

In the heat retention routine operation, the ON delay timer,
Both off-delay timers may be deleted. In this case, the stirring operation is interrupted at the same time as the microwave heating is restarted and stopped.

The above series of operations is ended by turning off the continuous switch (38). That is, when the step S31 is executed at the time of turning off, the step S35 is then executed, the start flag is reset, and the heat retention heaters (24) (32) are stopped. Then S2, S3, S3a, S
4, S5 step is cyclically executed.

However, since the transport flag is set if the product to be dried is being transported, it is determined that the transport flag is set in step S17, and the transport operation in step S27 is performed, and in step S28, the suction hopper (27) is loaded into the product to be dried. Is continuously executed until it is judged whether or not is accumulated up to the position of the upper limit level sensor (34).

(G) Effect of the Invention According to the present invention, when the granular material to be dried is kept warm after the completion of microwave drying, stirring is intermittently performed, and accordingly, unnecessary fine powder is provided while suppressing unevenness of heat retention due to stirring of the dried material. It is possible to provide an extremely practical microwave drying device capable of suppressing the occurrence of the above-mentioned phenomenon as much as possible.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a sectional view, FIG. 2 is a circuit diagram, and FIGS. 3 and 4 are flowcharts of an operation program of a microcomputer. (3) ... drying room, (12) ... magnetron, (15) ...
… Agitator, (36) …… Microcomputer.

Claims (1)

[Claims] 1. A drying chamber to which a material to be dried is supplied, a microwave supply means for supplying a microwave for microwave-drying the material to be dried to the drying chamber, and a microwave supply means for driving the microwave supply means. And a drying control means for performing a drying operation of the material to be dried until a desired dry state is obtained, a stirring means for continuously driving the material to be dried in the drying chamber during the drying operation by the drying control means, and the drying. After the operation is completed, a preliminary chamber independent of the drying chamber for discharging and accumulating the dried substance from the drying chamber, a level sensor arranged in the preliminary chamber and detecting the presence of the dried substance in the preliminary chamber, Determination means for determining whether to permit discharge from the drying chamber to the preliminary chamber after the drying operation is completed based on the detection result of the level sensor; and the drying chamber based on the determination result of the determination means. Above the spare room A discharging means for discharging the material to be dried,
Based on the determination means, a heat retention control means that drives and heats the microwave supply means to such an extent that the material to be dried does not absorb moisture in the drying chamber, and the stirring means is intermittently turned on during the heat retention by the heat retention control means. Intermittent driving means for driving (alternately executing driving and stopping), and the determination means performs discharge permission determination that permits discharge if the level sensor detects that the material to be dried does not exist, and If it detects that there is a dry matter, it makes a discharge non-permission judgment that does not permit the discharge of the dried material into the preliminary chamber, and the discharge means is driven after the drying operation is completed only when the judgment means determines that discharge is allowable. To discharge the object to be dried to the preliminary chamber, and the heat retention control unit drives the object to be dried in the drying chamber after the drying operation is completed only when the determination unit determines that discharge is not permitted. By the intermittent driving means together with the temperature of causing the microwave drying apparatus is characterized in that by intermittently driving the stirring means.