JP2001241846A - Circulation type grain dryer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To circulate a grain in a period suitable for its properties in a circulating drying treatment. SOLUTION: First, a conveying speed of a feeding valve is set to a predetermined value. A motor and a synchronous motor of drive sources of a circulating system are driven (steps 100, 102), and the grain is circulated in the system. A drive current value of the synchronous motor is detected during the circulating operation of the grain (step 108). When the detected drive current value becomes a predetermined given current value or more and the state is continued for a predetermined time, the feeding speed of the valve is changed to a speed faster by a predetermined speed (steps 110 to 114).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating grain drying apparatus, and more particularly to a circulating grain drying apparatus for drying while circulating and flowing grains.

[0002]

2. Description of the Related Art In general, a circulating grain drying apparatus is provided with a drying section consisting of a plurality of downflow passages immediately below a grain tank, and water is removed from the cereal grains while naturally flowing down the downflow passages. I have. The grain that has flowed down the downflow path is fed downward from the downflow path by a delivery valve that is arranged at the lower part of the downflow path and is continuously rotated, and is further arranged at the lower part of the delivery valve to rotate and transport the grain by rotating. By the transport screw, the grain is transported to an elevator that is installed in front of the machine body and transports the grain to the upper part of the apparatus. After being transported to the upper part of the apparatus by the elevator, the grain is sent again to the grain tank. Grains are dried until water is gradually removed in this circulation and reaches a predetermined moisture content. After completion of the drying process, the grain is conveyed again to the upper part of the apparatus by the feed valve, the lower conveying screw, and the elevator, and is discharged out of the apparatus from a discharge port provided at the upper part of the elevator.

[0003] By the way, the conventional apparatus as described above adjusts the amount of grain to be delivered from the delivery valve and adjusts the cycle of grain circulation when the amount of grain filling is large or when the water content decreases. Is set to be short (that is, to increase the circulation speed of the grain).

[0004]

However, as the cycle of circulating the grains is shortened, the speed at which the grains are fed to the lower transport screw is increased, and the grains are fed before the lower transport screw portion is completely empty. The paddy falls from the valve and accumulates gradually, and a motor (hereinafter, referred to as a lower transport motor) as a power source of the lower transport screw may stop due to overload.

[0005] Such a phenomenon is likely to occur particularly when there are many pity. Pity is light, so it floats on the lower transport screw, is less likely to be transported, and tends to stay.

In addition, even when there are many small rice grains such as immature grains, the lower transport motor is likely to stop due to overload. This is because the small paddy is tightly packed and accommodated in the feeding valve, and the amount thereof becomes large.

The present invention has been made in order to solve the above-mentioned problem, and the feeding speed of the grain is changed as needed so that the circulation operation is not stopped by the overload due to the staying grain. It is an object of the present invention to obtain a circulating grain drying apparatus that can circulate grains at an optimal cycle for their properties.

[0008]

According to the present invention, there is provided a grain tub for storing cereals, a drying unit for drying cereals supplied from the cereal tub, and a cereal continuously supplied from the drying unit. A feeding section for feeding, a conveying means for conveying the grain fed from the feeding section to the grain tank, a load detecting means for detecting a load of the conveying means, and a load detected by the load detecting means being a predetermined value or more. And a feeding speed changing means for changing the feeding speed of the grain so that the feeding speed becomes slow when the state continues for a predetermined time or more.

According to the first aspect of the present invention, the cereal comprises:
The paper is continuously fed from the grain tub through the drying unit by the feeding unit to the transporting means, and is again transported to the grain tub by the transporting means, thereby being circulated in the apparatus. Further, the load of the conveying means is detected by the load detection means, and the feeding speed of the grain is changed by the feeding speed changing means so that the feeding speed of the grain is reduced when the detected load continues for a predetermined time or more for a predetermined time or more. You. Thereby, it is possible to make a change so that the feeding speed of the grain is reduced according to the load state of the transporting means and the load on the transporting means is reduced.

According to a second aspect of the present invention, in the first aspect of the invention, the load detecting means detects a load by detecting a drive current of a motor for driving the transporting means, and the delivery speed changing means includes: When the driving current of the motor for driving the conveying means is continuously equal to or higher than a predetermined value for a predetermined time, the feeding speed of the grain in the feeding section is changed to a speed lower by a predetermined speed.

According to the second aspect of the present invention, the load detecting means uses the drive current of the motor for driving the transporting means,
Detect the load on the transport means. The feeding speed changing means changes the feeding speed of the grain in the feeding portion to a speed lower by the predetermined speed when the detected driving current is equal to or more than a predetermined value for a predetermined time. As a result, the feed amount fed from the feeding section to the transport means becomes smaller than the transport amount transported from the transport means, so that the drive current of the motor driving the transport means decreases. Therefore, it is possible to prevent the drive current of the motor for driving the transport means from continuing to be longer than the predetermined time and to be in the state of being equal to or higher than the predetermined value, and to appropriately circulate grains.

According to a third aspect of the present invention, in the first aspect of the present invention, the load detecting means detects a load by detecting a drive current of a motor for driving the transport means, and the feeding speed changing means includes: When the driving current of the motor driving the conveying means is continuously equal to or more than a predetermined value for a predetermined time, after stopping the feeding unit, the feeding speed of the grain of the feeding unit is changed to a speed lower by a predetermined speed. It is characterized in that it is driven again.

According to the third aspect of the present invention, the drive current of the motor driving the transporting means is detected by the load detecting means. When the current value is equal to or more than the predetermined value for a predetermined time, the feeding speed changing unit stops the feeding unit and interrupts the feeding of the grain to the transporting unit. Further, the feeding speed changing means changes the feeding speed of the grain in the feeding section to a speed lower by a predetermined speed. Then, the feeding speed changing means drives the feeding portion again at a feeding speed lower by a predetermined speed after the change. The time point at which the feeding speed is changed may be, for example, at the same time as stopping the feeding portion or immediately after stopping the feeding portion. Further, after stopping the feeding portion, the feeding speed may be changed after a predetermined time elapses, and the feeding speed may be changed after the drive current of the motor driving the conveying means is reduced below a predetermined value. May be. Further, the time point at which the feeding portion is re-driven may be after a predetermined time elapses after changing the feeding speed, or after the driving current of the motor for driving the transport means is reduced to less than a predetermined value. May be. According to the third aspect of the present invention, since the feeding to the conveying means is stopped, the grain can be quickly conveyed when an overload occurs, so that the grain does not stay in the conveying means. It can circulate at a high feeding speed.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIGS. 1 to 3, a circulating grain drying apparatus 10 to which the present invention is applicable includes a grain tank 14 and a lower The drying unit 16 is provided.

The drying section 16 is provided with a flow-down passage 18 partitioned by a porous net-like partition wall.
The grain in 4 flows down. An air guide path 20 is formed inside the adjacent flow-down path 18, and an exhaust path 22 is formed outside the adjacent flow path 18. A burner 24 is connected to the air guide path 20, and a suction exhauster 27 is connected to the exhaust path 22. For this reason, the hot air generated by the burner 24 is sent to the air guide path 20 and flows from the air guide path 20 to the exhaust path 22 through the downflow path 18. Therefore, the grains in the downflow path 18 are dried by the hot air. Further, a temperature sensor 58 is provided near the burner 24. The temperature sensor 58 detects the temperature of the hot air sent from the burner 24.

In the vicinity of the discharge port 23 below the downflow path 18,
A delivery valve 30 continuously rotated by a motor 28 is provided. As shown in FIG. 4, the delivery valve 30 includes a plurality of wings 30B that protrude from the central axis in the radial direction, and a housing portion 30A is formed between the wings 30B. A motor 28 shown in FIG. 2 is connected to the delivery valve 30. The motor 28 is rotated in a direction indicated by an arrow A in FIG. It is fed out to a grain collection unit 31 arranged below 30.
A lower screw conveyor 34 driven by a synchronous motor 32 is disposed below the grain collecting unit 31, and transports the grain fed by the feed valve 30 to the front side of the machine body 12. A bucket conveyor 36 stands on the front side of the body 12.

The bucket conveyor 36 comprises an endless conveyor 39 driven by a synchronous motor 38 and a grain transport bucket 41 attached to the endless conveyor 39. The bucket conveyor 36 conveys the grains sent from the lower screw conveyor 34 to the uppermost part of the machine body 12. One end of an upper screw conveyor 40 corresponds to the upper end of the bucket conveyor 36, and a rotary equalizer 42 is connected to the other end of the upper screw conveyor 40.

The upper screw conveyor 40 and the rotary equalizer 42 are driven by a synchronous motor 38 together with the bucket conveyor 36, and disperse and distribute the grains lifted and conveyed by the bucket conveyor 36 to the grain tank 14 of the machine body 12. ing.

At the lower part of the bucket conveyor 36, a moisture sensor 44 for detecting the moisture value of the grain is disposed, and a part of the grain scooped up when the grain transport bucket 41 of the bucket conveyor 36 is inverted. It is designed to flow inside.

An operation section 60 for operating the circulating grain drying apparatus 10 is provided on the right side of the machine body 12 in FIG.

As shown in FIG. 5, the operation unit 60 includes a power switch 50 for supplying power to the circulating grain drying apparatus 10, a setting operation switch 52 for performing a setting operation described later, A drying operation switch 54 for performing an operation, a discharging operation switch 56 for performing a discharging operation described later, a stop switch 58 for stopping each operation, and an operation dial (not shown) for setting various operating conditions. ). In addition, the control circuit 48 disposed inside the body 12 includes a microcomputer 48A and a drive current detection unit 48B. The microcomputer 48A includes a CPU 64, a RAM 66, and an R connected by a bus 68 so that information can be mutually exchanged.
An OM 62 and an input / output (I / O) port 70 are provided. Each switch of the operation unit 60 is connected to an input / output (I / O) port 70 so that a signal can be transmitted to the microcomputer 48A. The ROM 62 stores an operation program for each device of the circulating grain drying apparatus 10 including a processing routine for controlling the grain feeding speed and the like, which will be described later.

The microcomputer 48A includes:
The above-described burner 24, suction blower 27, motor 28, synchronous motors 32 and 38, moisture sensor 44, and temperature sensor 5
8 is connected via an input / output (I / O) port 70 and an AC power supply 51 is connected via a power switch 50, and a predetermined voltage (for example, 10
0 V or 200 V) and a predetermined frequency (for example, 50 V
Hz or 60 Hz). Therefore, the operation of the burner 24, the suction blower 27, the delivery valve 30, the lower screw conveyor 34, the bucket conveyor 36, the upper screw conveyor 40, and the like can be operated by the switches of the operation unit 60.

The microcomputer 48A further includes a drive current detector 48B connected to the synchronous motor 32 so as to output a signal corresponding to the drive current value of the synchronous motor 32. The microcomputer 48A includes an input / output (I / O) port. 70. Thus, in the microcomputer 48A, a signal corresponding to the drive current value of the synchronous motor 32 can be obtained from the drive current detector 48B via the input / output (I / O) port 70. The drive current detector 48B
Can be configured by a current detector for detecting the current of the motor, a full-wave rectifier for rectifying the detected current, and an A / D converter for converting the rectified current to a digital signal.

Next, the operation of the present embodiment will be described.

The circulation type grain drying apparatus 1 according to the present embodiment.
At 0, a setting operation for setting the grain into the grain tank 14 in the body 12, a drying operation for circulating the set grain in the body 12 and drying, and discharging the dried grain to the outside of the body 12. Discharge operation is performed.

In the setting operation for setting the grain, first, the grain set in the machine body 12 from a setting port (not shown) on the lower side of the circulating grain drying apparatus 10 is fed to the grain collecting section. 31 and is conveyed by the lower screw conveyor 34 to the bucket conveyor 36 side. The transported grain is scooped by the grain transport bucket 41 of the bucket conveyor 36 and transported to the uppermost part of the machine body 12. Airframe 12
Is transported to the upper central portion of the machine body 12 by the upper screw conveyor 40, and stored in the grain tank 14 by the rotary equalizer 42.

In the drying operation performed after the filling operation, the grains in the grain tank 14 pass through the downflow path 18 and are delivered to the grain collecting section 31 by the continuous rotation of the delivery valve 30. At this time, the burner 24 is ignited and the suction air
Is driven. As a result, the drying air is supplied to the suction exhaust device 27
And is supplied directly to the grains in the downflow path 18 through the air guide path 20. Here, the grain is dried.
The drying wind after absorbing the moisture of the grain is discharged to the outside of the machine body 12 through the exhaust passage 22. On the other hand, the dried grain fed to the grain collection unit 31 is a lower screw conveyor 34,
The bucket conveyor 36, the upper screw conveyor 40, and the rotary equalizer 42 convey the wafer again to the grain tank 14. In the course of this conveyance, the moisture sensor 44 detects the moisture value of the grain. Based on the detected moisture value, the cereal is subjected to the above-described circulating action until the desired moisture content is obtained. When the grain reaches a desired moisture content and drying is completed, the operation of the circulating grain drying apparatus 10 automatically stops completely.

In the discharging operation performed after the drying process is completed, a switching valve (not shown) at the upper part of the bucket conveyor 36 is used.
Is switched to the discharge side, and the delivery valve 30, the lower screw conveyor 34, and the bucket conveyor 36 are driven. As a result, the grains remaining in the downflow path 18 and the like are fed out from the feed valve 30 to the grain collection unit 31, and are conveyed to the upper part of the machine body 12 by the bucket conveyor 36 via the lower screw conveyor 34. Then, the cereal transported to the upper part of the machine body 12 is discharged out of the machine body 12 from the cereal discharge port 13.

In this embodiment, the circulating grain drying apparatus 1
In the case of driving 0, the operator first operates the power switch 50 provided on the operation unit 60, and then operates the above-mentioned various operation dials to operate each operation condition (for example, the amount of stuffing in the grain or the water content). Rate). Then, when each operation switch is turned on, the above-described processing routine shown in FIG. 6 is executed, and the corresponding operation operation described above is started.

First, at step 100, the delivery valve 3
The feeding speed of the grain ₀ is set to the maximum speed V ₀ determined based on the water content and the amount of stuffing of the grain.

In the next step 102, the drive of the motor 28 as a drive source is started so that the feed valve 30 is continuously rotated at the set speed V ₀ , and the synchronous motor as a drive source of the lower screw conveyor 34 is started. 32, and the drive of the synchronous motor 38 which is the drive source of the upper screw conveyor 40 and the bucket conveyor 36 is started.

In the next step 104, the synchronous motor 32
Is reset, the timer for measuring the duration of the state in which the detected drive current value is equal to or greater than the predetermined current value i ₀ , that is, the state in which the load on the lower screw conveyor 34 is equal to or greater than the predetermined value, is reset.

In the next step 106, it is determined whether or not the stop switch 58 of the operation unit 60 has been turned on. If the determination is affirmative, the process proceeds to step 116, in which the driving of the motor 28 and the synchronous motors 32 and 38 is stopped. Then, this processing routine ends.

On the other hand, if a negative determination is made in step 106, the process proceeds to step 108, where the drive current detector 48B detects the drive current value i of the synchronous motor 32.

Here, a current value between a maximum current value and a minimum current value i _min during driving of the synchronous motor 32 is defined as a predetermined current value i ₀ as an allowable current value which can avoid driving stop due to overload. Then, when the transport operation is performed normally, as shown in FIG. 7A, the drive current value i of the synchronous motor 32 is between the predetermined current value i ₀ and the minimum current value i _min . It becomes a substantially constant value.

On the other hand, during the circulation operation, as the lower screw conveyor 34 gradually becomes clogged with rice, the drive current value i of the synchronous motor 32 gradually increases as shown in FIG. As the degree of clogging progresses, the drive current value i further increases (dotted line portion). Here, in order to avoid driving stop due to overload, in the next step 110,
It is determined whether or not the detected current value i is equal to or greater than the predetermined current value i ₀ . If a negative determination is made in step 110, the drive current value is a current value for normal driving, so the process returns to step 104. If a positive determination is made in step 110, the process proceeds to the next step 112.

Even if the drive current value of the synchronous motor 32 continuously exceeds the predetermined current value i ₀ , an allowable time period in which the drive stop due to overload can be avoided is set in advance as the predetermined time t ₀ , and step 112 Then, it is determined whether or not the continuation time of the state where the drive current value of the synchronous motor 32 exceeds the predetermined current value i ₀ has passed the predetermined time t ₀ . Step 112
If the determination is NO, the process returns to step 106, and if the determination is YES in step 112, the process proceeds to step 114.

Here, when the lower screw conveyor 34 is in the state of paddy clogging, as shown in FIG. 7B, the drive current value of the synchronous motor 32 exceeds the predetermined current value i _0. The continuation time of the state in which it is present exceeds the predetermined time t ₀ (so-called overload state). Therefore, in step 114, the rotational speed of the motor 28 by reducing the predetermined speed amount, the feeding speed of the crop feed-out valve 30, to change from the speed V ₀ to a predetermined speed component slower speed V _1, Step 1
04, and thereafter, the above processing is repeated. Here, as the speed V ₁ , an appropriate speed value that can obtain a sufficient time for conveying the grain remaining on the lower screw conveyor 34 is set. As a result, when an overload is detected, the feeding speed is changed so as to be reduced.
The transport amount is larger than the feed amount, and the overload state can be gradually avoided.

Also, in the present embodiment, step 114
May be modified to one of the three modifications shown in FIGS. 8A and 8B and executed.

First, the flow of the process of the first modified example of FIG. 8A will be described.

If an affirmative determination is made in step 112, that is, if an overload condition in the lower screw conveyor 34 is detected, the process proceeds to step 200, where the motor 2
8 is stopped, and the feeding of the grain from the feeding valve 30 to the lower screw conveyor 34 is interrupted. At this time, since the driving of the lower screw conveyor 34 is continued, the paddy clogging is gradually eliminated, and the synchronous motor 3
2, the driving current is reduced.

[0043] Then by executing the process of step 114, to change the feeding speed of the grain feeding valve 30 at a predetermined speed component slower speed V ₁ than the speed V _0, the process proceeds to step 208. In step 208, re-driven at a feeding speed V ₁ of the post-change motor 28 resumes the cyclic operation feeding grain to the lower screw conveyor 34 from the supply valve 30, returns to step 104 described above, the subsequent above-described processing repeat.

The processing for changing the payout speed in step 114 may be executed simultaneously with stopping the feeder in step 200. In the first modified example, the feeding is interrupted in the overload state, so that the overload state can be quickly avoided.

Next, the flow of processing in the second modification of FIG. 8B will be described.

If an affirmative determination is made in step 110, the process in step 200 is executed, and then step 11
The point that the processing of No. 4 is executed is the same as the processing procedure of the above (a). After executing the processing of step 114, the process proceeds to step 202. At step 202, it is determined whether the predetermined time t ₁ has elapsed. Here, the predetermined time t ₁ is
This is a predetermined time during which the operation of the lower screw conveyor 34 is continued and the state of paddy clogging can be gradually eliminated.

If an affirmative determination is made in step 202, the process proceeds to step 208, in which the motor 28 is changed to a new delivery speed V _1.
To drive again. Thereby, the grains are fed from the feed valve 30 to the lower screw conveyor 34, and the circulation operation is restarted. Then, the process returns to the above step 104, and thereafter, the above processing is repeated.

The processing for changing the feeding speed in step 114 may be executed simultaneously with stopping the feeding unit in step 200, or may be executed immediately before step 208 after a predetermined time t _{1 has} elapsed. In a second modification,
Since the grain is fed after the overload state is avoided, the overload state of the synchronous motor 32 can be minimized.

Next, the flow of the process of the third modified example of FIG. 8C will be described.

If an affirmative determination is made in step 110, the process in step 200 is executed, and then step 11
The point that the processing of No. 4 is executed is the same as the processing procedure of the above (a). After executing the processing of step 114, the process proceeds to step 204.

Here, by stopping the driving of the motor 28 in step 200, the feeding of the grain from the feeding valve 30 to the lower screw conveyor 34 is interrupted. At this time, the driving of the lower screw conveyor 34 is continued. , Paddy clogging is gradually eliminated, and the synchronous motor 32
And the driving current is reduced.

In step 204, a decreasing drive current value i of the synchronous motor 32 is detected.
In, it is determined whether or not the detected drive current value i has become less than the predetermined current value i ₁ . Here, the predetermined current value i ₁ is a predetermined current value that is equal to or more than the minimum current value i _min and equal to or less than the predetermined current value i ₀ .

If a negative decision is made in step 206,
Returning to step 204, on the other hand, in the case of an affirmative determination,
To step 208, and the feeding speed after changing the motor 28
Degree V ₁To drive again. As a result, the delivery valve 30
The circulation operation is carried out by feeding out the grains to the screw conveyor 34.
Will be resumed. Then, the process returns to step 104 described above.
Thereafter, the above processing is repeated.

[0054] Incidentally, feeding processing of changing the speed in step 114 may be executed on stopping feeding unit in step 200, the drive current value of the synchronous motor 32 is in a state of less than the predetermined current value i _1, step It may be executed immediately before 208. In the third modified example, since it is determined whether the overload state has been avoided by the drive current of the synchronous motor 32, the grain can be fed out after the overload state is reliably avoided.

As described above, in the circulating grain drying apparatus 10 according to the present embodiment, during the circulating operation of the grains in the machine body 12, the synchronous motor 32 is overloaded due to the paddy clogging of the lower screw conveyor 34. When the overload state of the synchronous motor 32 is detected so as not to stop, the feeding speed of the grain of the feeding valve 30 is changed to a speed lower by a predetermined speed, so that it is possible to avoid the grain from staying. As a result, the grains can be circulated appropriately.

In the present embodiment, the drive current detector 48A detects the motor drive current value only for the synchronous motor 32 which is the drive source of the lower screw conveyor 34, but is not limited to this. Only for the synchronous motor 38 which is the driving source of the upper screw conveyor 40,
Alternatively, the drive current values of both the synchronous motors 32 and 38 may be detected.

[0057]

As described above, according to the first to third aspects of the present invention, the overload state is determined and fed out so that the circulation operation is not stopped by the overload due to the staying grain. Since the feeding speed of the grain in the part is reduced, an excellent effect that the grain can be circulated at a cycle optimal for its properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an appearance of a circulating grain drying apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a circulating grain drying apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of the circulating grain drying apparatus according to the embodiment of the present invention, taken along line II-II of FIG.

FIG. 4 is a schematic sectional view of a delivery valve used in the circulating grain drying apparatus according to the embodiment of the present invention.

FIG. 5 is a block diagram of a circulating grain drying apparatus according to an embodiment of the present invention.

FIG. 6 is a flowchart showing a flow of a feeding speed control process according to the embodiment of the present invention.

FIG. 7A is a diagram for explaining how the motor drive current changes over time during normal operation, and FIG.
FIG. 4 is a diagram for explaining a state of a time change of a motor drive current when paddy clogging occurs.

FIGS. 8A, 8B, and 8C are flowcharts showing a flow of the payout speed control process, which is a part of the flow of the payout speed control process shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Circulation type grain drying device 14 Grain tank 16 Drying part 28 Motor 30 Feeding valve (feeding part) 32 Synchronous motor 34 Lower screw conveyor (transporting means) 36 Bucket conveyor (transporting means) 38 Synchronous motor 48A Microcomputer (delivery cycle changing means) ) 48B drive current detection unit (load detection means) 60 operation unit

Claims (3)

[Claims] 1. A grain tub for storing cereals, a drying unit for drying cereals supplied from the grain tub, a feeding unit for continuously feeding grains from the drying unit, and a grain fed from the feeding unit. Transport means for transporting the load to the grain tank, load detection means for detecting the load of the transport means, and when the load detected by the load detection means is equal to or more than a predetermined value for a predetermined time or more, payout of the grain A recirculation type grain drying device comprising: a feeding speed changing means for changing the speed to be lower. 2. The load detecting means detects a load by detecting a driving current of a motor driving the transporting means, and the feeding speed changing means determines that the driving current of the motor driving the transporting means continues for a predetermined time. The circulation type grain drying device according to claim 1, wherein when the value is equal to or more than a predetermined value, the feeding speed of the grain in the feeding section is changed to a speed lower by a predetermined speed. 3. The load detecting means detects a load by detecting a driving current of a motor driving the transport means, and the feeding speed changing means determines that a driving current of the motor driving the transport means continues for a predetermined time. 2. The circulating grain drying apparatus according to claim 1, wherein when the value is equal to or more than a predetermined value, after stopping the feeding part, the feeding speed of the grain in the feeding part is changed to a speed lower by a predetermined speed and re-driven.