JP2002046108A - Dryer for wood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely and quickly dry wood while an explosion and a fire of the wood are surely prevented by irradiating the wood with a microwave. SOLUTION: A dryer for wood is equipped with a shielded case 2 in which the wood 1 to be dryed is put; a microwave generator 3 wherein the, wood 1 in the shielded case 2 is irradiated with the microwave; a smoke sensor 22 for detecting the smoke generated in the shielded case 3; and a control circuit 5 which controls an output of the microwave generator 3 by a signal from the smoke sensor 22. For the dryer, when the smoke sensor 22 detects the smoke in the shielde case 2, the control circuit cuts off or decreases the output of the microwave generator 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for irradiating microwaves to a raw wood or a sawn timber.

[0002]

2. Description of the Related Art When wood is used in an undried state,
Various adverse effects such as a large deformation with time or a contraction to form a gap occur. This evil can be prevented by drying the wood. The most common method of drying wood is to leave the wood to dry naturally, but this method is extremely time-consuming. As a method of drying wood in a short time, a method of heating wood with steam or high frequency has been put to practical use. In the method of heating with steam, the wood is heated to 100 ° C. or more in order to boil and remove moisture contained in the wood in a short time. For this purpose, wood is put into a pressure tank and steam at 100 ° C. or higher is supplied. This method requires a pressure vessel in order to heat the wood to 100 ° C. or higher, and has a drawback that the equipment cost is extremely high.
In addition, since the method of heating wood with steam conducts heat from the surface of the wood and heats it, it takes a considerable time to heat the wood to the inside, and it is difficult to dry the wood efficiently in a short time . In particular, pillars, logs, etc., take a long time to heat the central part and cannot be dried in a short time. In addition, this method also has the disadvantage that the surface shrinks and breaks easily because the wood is dried from the surface.

[0003] As a device for heating wood from the inside, a device for heating and drying wood by sandwiching it between high-frequency electrodes has been put into practical use. This device heats the wood with the high frequency loss of the wood placed between the electrodes. This apparatus can dry a thin wood such as a plate material relatively efficiently. However, there is a drawback that wood having a large surface area such as a pillar or round wood such as a raw wood cannot be efficiently heated. that is,
This is because pillars and the like cannot be sandwiched between wide electrodes, and if a log is sandwiched between planar electrodes, wood cannot efficiently absorb high frequencies. In addition, this device has different ideal electrode shapes and sizes depending on the shape and size of the wood to be dried.
Another drawback is that it is difficult to dry various woods with the same equipment. In addition, there is also a problem that high-frequency waves are radiated to the surroundings between the electrodes as radio waves.

[0004] An apparatus for drying wood by irradiating it with microwaves has excellent features not found in an apparatus sandwiched between electrodes. In particular, since the drying device absorbs microwaves into wood and heats and dries the wood, it has the advantage that wood can be heated from the inside and the whole can be dried in a short time.

[0005]

An apparatus for drying wood with microwaves can effectively heat the interior of the wood, which takes a long time with a normal heating method, so that the microwave output is increased and the drying time is shortened. There are features that can be done. However, when the microwave output is increased, the wood may be overheated and the moisture content in the wood may be significantly reduced. In this state, if the microwaves are further irradiated, the overheated wood may be carbonized inside, and if further heated, a fire or explosion may be caused.

The present inventor has sought to eliminate this drawback.
We have developed a device that detects the temperature of the wood surface and controls the output of the microwave generator. The surface temperature of wood can be detected by infrared rays emitted from the surface. The device includes a plurality of temperature sensors for detecting temperatures at a plurality of points of the wood. The temperature sensor is connected to a control circuit that controls the output of the microwave generator. This device shuts off the output of the microwave generator when the temperature of a part of the wood becomes higher than a set temperature. However, this device cannot reliably prevent fire and explosion of wood. that is,
This is because the internal temperature becomes abnormally high compared to the surface temperature of the wood, and the wood is carbonized inside and explodes as a whole. When microwaves heat the wood from the inside and the moisture content inside decreases, the wood's internal temperature rises further and tends to rise above the boiling point of water. In this state,
Water is boiled inside the wood and the water content drops sharply.
However, even in this state, the surface of the wood is not overheated as in the interior, so the surface temperature is lower than the internal temperature, and the temperature of the surface of the wood does not rise to the boiling point of water. In this state, the moisture content inside the wood is extremely reduced while the wood surface contains moisture. Inside the dehydrated wood, the heat energy absorption effect by the heat of vaporization of the water is lost, and the wood temperature rises abnormally. The wood whose temperature has risen is overheated and carbonized, and when overheated, it ignites,
Explode. Immediately before this state, since the surface of the wood contains moisture, the heat energy of vaporization of the water absorbs the heat energy on the surface of the wood. Since the heat of vaporization of water is so great, the surface temperature of the wood does not rise very much. Therefore, with the surface temperature of the wood not rising to an abnormal temperature,
Wood may ignite instantaneously and explode.

This drawback is a particular disadvantage of the method of heating wood from inside with microwaves. Conventional drying methods, for example, a method in which wood is heated and dried with steam or hot water do not pose a problem. This is because steam or hot water does not raise the heating temperature of the wood to the carbonization temperature. For this reason, it is extremely difficult to control the microwave output to an ideal state while detecting the environment of the entire wood by the method of drying the wood with microwaves.

[0008] The present invention has been developed to overcome this disadvantage unique to microwave drying. An important object of the present invention is to provide a wood drying apparatus that can dry wood safely and quickly while irradiating the wood with microwaves to reliably prevent explosion and fire of the wood.

[0009]

The apparatus according to the present invention comprises a shield case 2 for storing wood 1 to be dried, a microwave generator 3 for irradiating the wood 1 in the shield case 2 with microwaves, and a shield case 2. The apparatus includes a smoke sensor 22 for detecting smoke generated in the inside, and a control circuit 5 for controlling an output of the microwave generator 3 based on a signal from the smoke sensor 22.
This drying device detects smoke that is ejected to the outside through the pipe of the wood 1 when a part of the wood 1 is overheated and carbonized. When the wood 1 is overheated until the inside is carbonized, smoke is generated inside. The smoke generated inside is transmitted to the outside through a gap such as a pipe of the wood 1. Smoke is not fog, which is water vapor and fine water droplets. Contains fine carbon particles that absorb light. Accordingly, by detecting this smoke, the internal state of the wood 1 can be accurately detected, and when the smoke is ejected from the wood 1, the output of the microwave generator 3 is cut off or reduced to cause ignition or fire. Prevent explosion.

[0010] Preferably, the smoke sensor 22 accurately detects only smoke using water droplets as gaseous water vapor. The smoke sensor 22 that achieves this is provided with a duct 23 that allows air in the shield case 2 to pass through, and a heater 24 that heats the air in the duct 23 and vaporizes water droplets that pass through the duct 23. This smoke sensor 2
2 can accurately detect the smoke contained in the air by heating the water droplets in the duct 23 and evaporating them into water vapor.

Further, the smoke sensor 22 extends the duct 23 in the vertical direction and circulates the air heated in the duct 23 by a convection action. Air can be supplied. However, the smoke sensor 22 can also connect the fan 26 to the duct 23 and allow the air in the shield case 2 to pass through the duct 23 with the fan 26. Duct 23
As the heater 24 for heating the air, a bulb 24A can be used. Since the bulb 24A emits both light and heat, it is possible to accurately determine a failure or disconnection by looking at the light. Further, since a large number of light bulbs 24A are commercially available, there is a feature that maintenance can be simplified.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. However, the following examples illustrate a wood drying apparatus for embodying the technical idea of the present invention, and the present invention does not specify a drying apparatus as follows.

Further, in this specification, in order to make it easy to understand the claims, the numbers corresponding to the members shown in the embodiments will be referred to as “claims” and “ In the column of “means”. However, the members described in the claims are not limited to the members of the embodiments.

The apparatus for drying wood shown in FIGS. 1 and 2 comprises a shield case 2 for carrying wood 1, a plurality of microwave generators 3 for irradiating the wood 1 in the shield case 2 with microwaves, a shield case. 2, a smoke sensor 22 for detecting the smoke inside, a dry sensor 4 for detecting the weight or moisture content of the wood 1 to be dried, a smoke sensor 22 and a dry sensor 4
And a control circuit 5 for controlling the output of each microwave generator 3 with a signal from

The shield case 2 has an elongated hollow cylindrical shape extending in the transport direction of the wood 1 so that the elongated wood 1 such as a pillar or a raw wood can be carried in. Made of shield material. The shield case 2 shown in the figure has a plurality of case units 6 connected in series to form an elongated tubular shape. Case unit 6
Is a rectangular cylindrical shape having both ends open, and is connected so that microwaves do not leak, thereby forming a shield case 2. The shield case 2 having this structure includes a case unit 6
The total length can be easily changed by adjusting the number of connected. The total length of the pillars and logs to be dried is 3-8m. A device for drying short wood reduces the number of connected case units, and a device for drying long wood increases the number of connected case units.

The shield case 2 has a transfer conveyor 7 at the bottom for loading and unloading the wood 1. Further, a wheel 8 for rotating the log is disposed between the rollers 7A of the transfer conveyor 7. As shown in FIG. 3, a plurality of pairs of the wheels 8 are provided with two wheels as a pair. The pair of wheels 8 are separated from each other by an interval at which the wood 1 can be placed and rotated therebetween. The transfer conveyor 7 is disposed in the shield case 2 so that it can be moved up and down by the cylinder 9.

The transfer conveyor 7 is raised above the wheels 8 when loading and unloading the wood 1. Therefore,
The transfer conveyor 7 is moved up and down in a horizontal posture by a vertical mechanism such as a cylinder. The transfer conveyor 7 transfers the wood 1 away from the wheels 8 in the raised position. When the wheel 8 rotates the wood 1, the transport conveyor 7 is lowered,
The wood 1 is put on the wheel 8. Shield case 2 of this structure
Can easily carry the wood 1 in and out, and furthermore, when irradiating the microwave, the wood 1 can be rotated to uniformly irradiate the microwave. Although not shown, the wheels 8 are connected to a motor via a chain or a belt, and are rotated by the motor. The motor preferably rotates the wheels 8 in the opposite direction. This is for uniformly irradiating the microwave to the wood 1.

Further, the transfer conveyer 7 can ascend and move the wood 1 in the vertical direction not only when loading or unloading the wood 1 but also in the step of irradiating the microwave. The transfer conveyor 7 ascends, places the wood 1 on the roller 7A, and rotates the roller 7A with a motor or the like (not shown) to move the wood 1 in the vertical direction. After the wood 1 is moved, the wood 1 is lowered and the wood 1 is rotated by the wheels 8.

The cylindrical wood 1 such as a raw wood is rotated by wheels 8, but the wood 1, which is a prism or a plate, cannot be rotated by being placed between the wheels 8. Wood 1 that cannot be rotated with wheels 8
In the step of irradiating microwaves, the wood 1 is placed on the transfer conveyor 7 and reciprocated. This transfer conveyor 7
Roller 7A of transfer conveyor 7 by motor (not shown)
Are rotated in the forward and reverse directions to reciprocate the wood 1 inside the shield case 2. The reciprocating wood 1 is uniformly irradiated with microwaves.

The plurality of microwave generators 3 are shown in FIGS.
As shown in (2), it is fixed to the upper part of the shield case 2 so as to be separated in the longitudinal direction. Each of the microwave generators 3 is arranged at an interval capable of uniformly irradiating the microwave to the long wood 1 placed in the shield case 2. The microwave radiated from the microwave generator 3 into the shield case 2 is reflected by the inner surface of the shield case 2 or is reflected and diffused by a diffusion plate (not shown) provided in the shield case 2 or the like. Heat the long wood 1 uniformly. Microwave generator 3
Is a waveguide 10 for radiating microwaves to the shield case 2.
Is, for example, 30 to 100 cm. When the distance between adjacent waveguides 10 is reduced, wood 1
Can be dried more uniformly. In addition, if the spacing between the waveguides 10 is widened, interference of microwaves radiated from the adjacent microwave generator 3 can be reduced.

As shown in FIG. 4, each of the microwave generators 3 includes a magnetron 11 for generating a microwave, a waveguide 10 for supplying the microwave generated by the magnetron 11 to the shield case 2, and a magnetron 11. A high-voltage power supply 12 for supplying a high-voltage DC to the plate 11 and a heater power supply 13 for heating the heater are provided. Each microwave generator 3 preferably comprises a magnetron 11, a high voltage power supply 12 and a heater power supply 13, but the heater power supply can also be designed to supply heater power to a plurality of magnetrons. . The heater power supply is, for example, common to all microwave generators, and one unit can supply heater power to all magnetrons.

A drying apparatus in which each microwave generator 3 includes a magnetron 11 and a high-voltage power supply 12 includes:
The average output of each microwave generator 3 can be adjusted independently. For this reason, the wood 1 can be dried in a more ideal environment. In particular, as shown in FIGS. 1 and 2, when the long wood 1 is dried, the wood 1 is dried from both ends first. This is because the water is removed not only from the periphery but also from the end faces of the both ends, so that the surface area from which the water is removed is substantially increased. Microwave generator 3 whose output can be controlled independently
For example, the output of the microwave generators 3 disposed at both ends of the wood 1 is controlled to be small, or the oscillation of the microwave generators 3 at both ends is stopped first, and Can be uniformly dried.

The magnetron 11 irradiates the wood 1 in the shield case 2 from above with microwaves having a frequency of, for example, 2 to 4 GHz via the waveguide 10. The waveguide 10 is opened downward on the upper surface of the shield case 2 and irradiates the wood 1 with microwaves. The high-voltage power supply 12 boosts the input 100 or 200 V commercial power supply with a transformer, and converts the secondary side AC of the transformer to 2000 to 4000 V.
And supply it to the magnetron 11. The heater power supply 13 includes a transformer that reduces the input AC to a heater voltage of the magnetron 11. The magnetron 11 oscillates microwaves and outputs from the waveguide 10 when a high voltage is input from the high-voltage power supply 12 in a state where the heater is heated by electric power supplied from the heater power supply 13.

The microwave generator 3 includes a high-voltage power supply 12
The output of the magnetron 11 can be controlled by the average voltage supplied to the magnetron 11 from. If you lower the average voltage,
The output of the magnetron 11 decreases, and when the average voltage is increased, the output of the magnetron 11 increases. High voltage power supply 12
Can adjust the average voltage of the high-voltage power supply 12 by the capacitance of a capacitor connected to the secondary side of the transformer. When the capacitance of the capacitor is increased, the average voltage increases, and when the capacitance is decreased, the average voltage decreases.

Further, as shown in FIG. 4, the magnetron 11 includes a switch 1 connected to the input side or the output side.
The average output can also be adjusted by the duty for switching 4 on and off. The switch 14 supplies a high voltage to the magnetron 11 in the ON state to oscillate the magnetron 11. When the switch 14 is turned off, the magnetron 11 stops oscillating and the output becomes zero. Therefore, the average output of the magnetron 11 can be adjusted by the duty at which the switch 14 is turned on and off. If the time for turning on the switch 14 is increased and the time for turning off the switch 14 is shortened, the average output of the magnetron 11 increases. Conversely, if the on time is shortened and the off time is increased, the average output of the magnetron 11 decreases. Become. The switch 14 is turned on and off by the control circuit 5 to control the output of the magnetron 11.

Each microwave generator 3 has a
Is irradiated with microwaves at regular intervals. The microwave radiated from each microwave generator 3 is applied to the waveguide 1
The wood 1 is strongly heated near zero. Therefore, the plurality of microwave generators 3 are fixed to the shield case 2 close to an interval at which the wood 1 can be uniformly heated.

The smoke sensor 22 is disposed inside the shield case 2 and detects smoke emitted from the wood 1.
FIG. 5 shows a cross-sectional view of the smoke sensor 22. The smoke sensor 22 includes a duct 23 that allows air in the shield case 2 to pass through, and heats the air in the duct 23 so that the duct 2
A heater 24 for evaporating water droplets passing through 3 and a duct 2
And a smoke detecting section 25 for detecting smoke contained in the air heated in 3. The duct 23 is provided to extend in the vertical direction, a heater 24 is provided at a lower portion, and the smoke detector 2 is provided at an upper portion.
5 are arranged.

As the heater 24, an electric bulb 24A which is turned on by a commercial power supply is used. The bulb 24A is a socket 24B
It is mounted upward or downward so that it can be attached and detached. The bulb 24A that is mounted upward is the socket 24
It is possible to use the socket 24B having no heat-resistant structure by preventing overheating of B, and efficiently heat air rising inside the duct 23. In a downward-facing light bulb, the socket is heated by the heat of the light bulb to be in a dry state, thereby effectively preventing the electric leakage. The light bulb 24A is, for example, an incandescent light bulb with power consumption of 100W. However, light bulbs have a power consumption of 40 to 2
What is set to 00W can also be used. This smoke sensor 22
Has a heater 24 disposed inside a duct 23. The air in the duct 23 passes between the light bulb 24A and the inner surface of the duct, is heated by the light bulb 24A, and vaporizes water droplets contained in the air into water vapor.

As the heater, an electric heater can be used instead of the electric bulb. The electric heater is disposed inside the duct,
Alternatively, the duct is heated from the outside to heat the air passing through the duct. The heater disposed inside the duct has a feature that air can be efficiently heated. A heater that heats the duct from the outside can smoothly pass air into the duct.

The smoke sensor 22 that heats the inside of the duct 23 by the heater 24 and convects the air does not require a fan for forcibly blowing the air in the shield case 2 to the duct 23. For this reason, failure can be reduced with a simple structure. However, as shown in FIG. 6, the smoke sensor 22 can also connect a fan 26 to the duct 23 and allow the air in the shield case 2 to pass through the duct 23 by the fan 26.

The smoke sensing section 25 includes a light source for irradiating light, and a light receiving element for receiving light emitted from the light source. If there is smoke between the light source and the light receiving element, the smoke scatters or absorbs the light. Therefore, the amount of light received by the light receiving element decreases. If there is a water droplet floating in the air between the light source and the light receiving element, the smoke sensing unit 25 may erroneously detect the smoke as smoke. This is because water droplets reflect light emitted from the light source and reduce the amount of light received by the light receiving element. Inside the shield case 2, water released from the wood 1 to the outside floats in the air as fine water droplets. The air in the shield case 2 is sufficiently ventilated, that is, fine water droplets released from the wood 1 are quickly exhausted to the outside of the shield case 2 to reduce the amount of water droplets floating in the air in the shield case 2. it can. Just wood 1
In an environment in which microwaves are irradiated to dry the air, sufficient ventilation of the air in the shield case 2 is not always an optimal environment for drying wood. The reason is that if the humidity of the air in the shield case 2 is too low, the wood is dried too quickly and the wood may be cracked. When the air inside the shield case 2 is made to be in a supersaturated state in order to dry quickly while preventing cracking of the wood, countless water droplets float in the air, causing a detection error of the smoke sensor.

However, as shown in FIGS. 5 and 6,
The smoke sensor 22, which heats the air in the duct 23 and evaporates the water droplets contained in the air into water vapor, can effectively prevent the water droplets contained in the air from being erroneously detected as smoke.
This is because the water droplets contained in the air are heated inside the duct 23 and vaporized from the water droplets into water vapor.
This is because the water that has been vaporized into water vapor does not scatter or absorb the light from the light source. Therefore, duct 2
The water droplets that flow into the 3 together with the smoke become steam, and only the smoke is detected by the smoke sensing unit 25.

The drying sensor 4 detects the weight of the wood 1 or the moisture content of the wood 1. The drying sensor 4 in FIG. 1 detects the weight of the wood 1. The drying sensor 4 measures the weight by lifting both ends of the wood 1 from the wheels 8 and the transfer conveyor 7. Therefore, the drying sensor 4 includes a support 15 for supporting and lifting the wood 1 from the lower surface, a lifting mechanism 16 for raising the support 15,
And a weight sensing unit 17 connected to the lifting mechanism 16.

The lifting mechanism 16 and the weight sensing unit 17 are disposed outside the shield case 2, and the support 15 penetrates the shield case 2 so as to slide and prevent microwaves from leaking. ing. The lifting mechanism 16 in the figure is a vertically disposed cylinder, and the lower end is fixed to the weight sensing unit 17. The drying sensor 4 having this structure includes a lifting mechanism 16.
When the cylinder is extended, the support 15 lifts the wood 1. In this state, the weight of the wood 1 is detected by the two weight sensors 17. The weight sensing unit 17 detects the weight by adding the weights of the lifting mechanism 16 and the support base 15. Therefore, the weight of the wood 1 is detected by subtracting the weight of the lifting mechanism 16 and the weight of the support 15 from the weight detected by the weight sensing unit 17.

The drying sensor 4 shown in FIG. 2 detects the moisture content of the wood 1. The drying sensor 4 is a moisture content sensor that measures the moisture content of the wood 1 by approaching or contacting the surface of the wood 1. As the moisture content sensor, a commercially available one can be used, for example, a sensor that detects the moisture content that measures the electrical resistance and dielectric constant of wood can be used. When the moisture content sensor approaches the surface of the wood 1 when measuring the moisture content of the wood 1 and does not measure the moisture content of the wood 1,
Stand by outside the shield case 2. This is to prevent the moisture content sensor from being broken down by microwaves.

The moisture content sensor is fixed to the tip of the access cylinder 18. The access cylinder 18 has a water content sensor fixed to the tip of the rod so that the water content sensor approaches the wood 1 from outside the shield case 2. Further, the shield case 2 is provided with a through hole in a portion where the moisture content sensor enters and exits, and an opening / closing lid 19 is provided here.

The drying sensor 4 detects the water content of the wood 1 as follows. (1) The oscillation of the microwave generator 3 is stopped. The microwave generator 3 stops the oscillation by turning off the high voltage power supply 12. (2) Open the opening / closing lid 19 of the shield case 2, and bring the moisture content sensor into contact with the surface of the wood 1 with the access cylinder 18. (3) The moisture content sensor detects the moisture content of the wood 1, and outputs a signal of the detected moisture content to the control circuit 5. (4) The access cylinder 18 is extended and retracted, and the moisture content sensor is pulled out of the shield case 2 away from the surface of the wood 1. (5) Close the opening / closing lid 19 of the shield case 2 and close the through-hole so that microwaves do not leak. (6) Thereafter, the microwave is irradiated on the wood 1 by the microwave generator 3.

As described above, the drying sensor 4 detects the weight of the wood 1 or measures the water content at predetermined time intervals. The time interval at which the drying sensor 4 detects the weight and moisture content of the wood 1 is, for example, 1 minute to 2 hours, preferably 3 minutes to 60 minutes, and more preferably 5 minutes to 60 minutes. The time interval at which the drying sensor 4 detects the weight or moisture content of the wood 1 is constant from the start of drying to the completion thereof, or is changed by the weight or moisture content. As a method of changing the detection time interval, for example, it is preferable that the detection time interval is lengthened when the weight of the wood 1 is heavy and the moisture content is large, and is shortened when the weight is reduced and the moisture content is reduced. This is because if the wood 1 having a reduced water content is overheated by microwaves, it becomes easy to ignite.

Reducing the time interval at which the drying sensor 4 detects the weight and the moisture content has the advantage that the wood 1 can be dried in a more favorable environment. However, in the method for detecting the water content, the microwave output is interrupted when the water content is detected. Therefore, if the time interval is shortened, the total time for drying the wood 1 becomes longer. Since the method of measuring the weight of the wood 1 can detect without interrupting the output of the microwave, the drying time is not lengthened. Further, since the wood 1 is raised and the microwave is irradiated to the wood 1 at a position different from the transfer conveyor 7 and the wheel 8, the wood 1 can be dried more uniformly. However, it goes without saying that the method of detecting the weight of the wood 1 and the output of the microwave can be interrupted when detecting the weight.

The signals from the smoke sensor 22 and the drying sensor 4 are input to the control circuit 5. The control circuit 5 includes the smoke sensor 2
The output of the microwave generator 3 is controlled by signals input from the drying sensor 4 and the drying sensor 4. When a signal indicating detection of smoke is input from the smoke sensor 22, the control circuit 5 ignores the signal from the drying sensor 4 and cuts off the output of the microwave generator 3 to 0. At this time, the control circuit 5 switches off the power switch of the microwave generator 3. The power switch is a switch connected to the primary side of the power transformer. When the power switch is turned off, both the heater voltage and the plate voltage of the magnetron 11 of the microwave generator 3 become 0, and the microwave generator 3 does not oscillate the microwave.

The state in which the smoke sensor 22 detects the presence of smoke in the shield case 2 is a state in which a portion of the wood 1 has a heated portion and the heated portion emits smoke to the outside. In this state, the control circuit 5 shuts off the output of the microwave generator 3 irrespective of the weight or moisture content of the wood 1. However, the control circuit can also control the output of the microwave generator to an extremely weak output based on the smoke detection signal from the smoke sensor.

Further, when the smoke sensor 22 does not detect the detection detection signal, the control circuit 5 determines that the weight of the wood 1, the weight reduction rate at which the weight of the wood 1 decreases, the moisture content of the wood 1, and the moisture content decrease. The microwave output of the microwave generator 3 is controlled using any one of the moisture reduction rates as a parameter.

FIGS. 7 and 8 show the characteristics of the control circuit 5 controlling the microwave output of the microwave generator 3 using the weight of the wood 1 as a parameter. FIG. 7 shows that the output of the microwave is linearly controlled when the weight of the wood 1 is within a predetermined range, and when the wood 1 is heavier than the predetermined weight, the microwave is set to the maximum output. At a predetermined weight, the microwave output is set to 0, that is, the microwave is not irradiated. FIG. 8 shows that the microwave output is controlled in a stepwise manner when the weight of the wood 1 is within a predetermined range, and the microwave is set to the maximum output when the wood 1 is heavier than the predetermined weight. When the predetermined weight is reached, the microwave output is set to 0, that is, the microwave is not irradiated.

When the control circuit 5 controls the microwave output to dry the wood 1 as shown in FIGS. 7 and 8, as shown in FIG. 9, the weight of the wood 1 decreases with time and the wood 1 is dried. You. At first, the microwave power is large, so the wood weight drops sharply. As the microwave power is reduced linearly or stepwise, the weight loss of the wood becomes progressively smaller. When the wood 1 is dried to a predetermined weight, the microwave output becomes zero and the weight of the wood 1 does not change.
The wood weight at which the microwave output is set to 0 is the weight of the wood dried to a predetermined moisture content.

As shown in FIG. 9, the control circuit 5 controls the weight of the wood so that the weight of the wood decreases first and then decreases gradually.
Alternatively, as shown in FIG. 10, the microwave output can be controlled so that the wood weight decreases linearly. In the method of reducing the weight of the wood 1 as described above, when the wood 1 is dried to a predetermined weight, the microwave output is set to 0 and the irradiation of the microwave is stopped.

As shown in FIGS. 9 and 10, the control circuit 5 for reducing the weight of the wood 1 has a function that the weight of the wood 1 is a function A or B.
When the value becomes larger than the value indicated by, the microwave output is increased to bring the wood weight closer to the function shown in the figure. Further, when the weight of the wood becomes smaller than the values indicated by the functions A and B, the microwave output is reduced to bring the weight of the wood closer to the functions A and B.

FIGS. 11 and 12 show characteristics in which the control circuit 5 controls the microwave output of the microwave generator 3 using the moisture content of the wood 1 as a parameter. FIG.
When the water content of the wood 1 is within a predetermined range, the microwave output is controlled linearly. When the water content of the wood 1 is larger than the predetermined water content, the microwave is set to the maximum output.
Is dried to a predetermined moisture content, the microwave output becomes zero.
, Ie, do not irradiate microwaves. Figure 1
2 controls the microwave output stepwise when the water content of the wood 1 is within a predetermined range, and sets the microwave to the maximum output when the water content of the wood 1 is higher than the predetermined water content. When 1 is dried to a predetermined moisture content, the microwave output is set to 0, that is, the microwave is not irradiated.

When the control circuit 5 controls the microwave output to dry the wood 1 as shown in FIGS. 11 and 12, the moisture content of the wood 1 decreases with time as shown in FIG. Is done. At first, the microwave output is large,
The water content of wood 1 decreases rapidly. When the microwave power is reduced linearly or stepwise, the water content of the wood 1 decreases gradually. When the wood 1 is dried and reaches a predetermined moisture content, the microwave output becomes 0 and the moisture content of the wood 1 does not change. The moisture content at which the microwave output is set to 0 is the moisture content of the wood 1 dried to a predetermined moisture content.

The control circuit 5 controls the moisture content of the wood 1 so that the moisture content of the wood 1 decreases first and gradually decreases as shown in FIG. 13, or the water content of the wood 1 decreases linearly as shown in FIG. It is also possible to control the microwave output so as to reduce the power. In the method of reducing the water content of the wood 1 as described above, the microwave output is set to 0 and the irradiation of the microwave is stopped when the wood 1 is dried to a predetermined water content.

As shown in FIGS. 13 and 14, the control circuit 5 for reducing the water content of the wood 1 increases the microwave output when the water content of the wood 1 becomes larger than the value indicated by the function A or B. Then, the moisture content of the wood 1 is brought close to the function shown in the figure. Further, when the water content of the wood 1 becomes smaller than the values indicated by the functions A and B, the microwave output is reduced, and the water content approaches the functions A and B.

The simplest control circuit 5 controls a plurality of microwave generators 3 so that the microwave outputs are the same. As shown in FIG. 1, a control circuit 5 that detects the weight of both ends of the wood 1 and controls the microwave output of the microwave generator 3 uses the output of the drying sensor 4 on the right side in FIG. The microwave output of the microwave generator 3 can be controlled, and the output of the drying sensor 4 on the left side can control the microwave output of the microwave generator 3 on the left half.

Further, as shown in FIG. 2, a drying apparatus provided with a moisture content sensor in a region where each microwave generator 3 irradiates a microwave is disposed near the microwave generator 3. With the moisture content sensor, the microwave output of the microwave generator 3 in the vicinity can be controlled. The drying apparatus having this structure has a feature that the wood 1 can be more uniformly dried by controlling the microwave output of each microwave generator 3 while detecting the partially dried state of the wood 1.

[0053]

The wood drying apparatus of the present invention is characterized in that it can be dried safely by irradiating the wood with microwaves and quickly preventing explosion or fire of the wood.
That is, the wood drying apparatus of the present invention includes a smoke sensor that detects smoke generated in the shield case, and a control circuit that controls the output of the microwave generator based on a signal from the smoke sensor, and the smoke sensor includes the shield case. This is because the control circuit cuts off or controls the output of the microwave generator when detecting smoke in the inside. This drying device can detect smoke generated when a part of wood is overheated and carbonized by a smoke sensor. The generated smoke contains fine carbon particles that absorb light, unlike fog, which is water vapor or fine water droplets. Therefore, by detecting this smoke, the internal state of the wood can be accurately detected, and when smoke is generated, the output of the microwave generator can be cut off or reduced to effectively prevent ignition and explosion. . This structure provides very good safety for such a device for drying wood with microwaves.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a wood drying apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a wood drying apparatus according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of the drying device shown in FIG.

4 is a schematic configuration diagram of a microwave generator of the drying device shown in FIG.

FIG. 5 is a schematic sectional view of a smoke sensor of the drying device shown in FIG. 1;

FIG. 6 is a schematic sectional view showing another example of the smoke sensor.

FIG. 7 is a graph showing an example of controlling microwave output by weight of wood.

FIG. 8 is a graph showing another example of controlling the microwave output by the weight of wood.

FIG. 9 is a graph showing a state in which the weight of wood decreases with time.

FIG. 10 is a graph showing another example of a state in which the weight of wood decreases with time.

FIG. 11 is a graph showing an example of controlling the microwave output by the water content of wood.

FIG. 12 is a graph showing another example of controlling the microwave output based on the water content of wood.

FIG. 13 is a graph showing a state in which the water content of wood decreases with time.

FIG. 14 is a graph showing another example of a state in which the water content of wood decreases with time.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wood 2 ... Shield case 3 ... Microwave generator 4 ... Drying sensor 5 ... Control circuit 6 ... Case unit 7 ... Transfer conveyor 7A ... Roller 8 ... Wheel 9 ... Cylinder 10 ... Waveguide 11 ... Magnetron 12 ... High voltage power supply DESCRIPTION OF SYMBOLS 13 ... Heater power supply 14 ... Switch 15 ... Support base 16 ... Lifting mechanism 17 ... Weight sensing part 18 ... In / out cylinder 19 ... Opening / closing lid 22 ... Smoke sensor 23 ... Duct 24 ... Heater 24A ... Light bulb 2
4B: Socket 25: Smoke detector 26: Fan

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Manabu Kamata 1-7 Kasuga, Tokushima City, Tokushima Prefecture F-term in Nagai Machinery Co., Ltd. (Reference) 2B230 AA15 BA01 EA30 EB12 EC30 3L113 AA01 AA02 AA03 AB07 AC12 AC25 AC31 AC35 AC52 AC54 AC63 AC67 AC75 AC76 AC77 AC81 BA05 CA02 CA03 CA20 CB07 DA21 DA25

Claims (5)

[Claims] 1. A shield case (2) for storing wood to be dried (1), a microwave generator (3) for irradiating microwaves to the wood (1) in the shield case (2), and a shield case ( 2) a smoke sensor (22) for detecting smoke generated in the apparatus; and a control circuit (5) for controlling the output of the microwave generator (3) based on a signal from the smoke sensor (22). 22) A wood drying device that, when detecting smoke in the shield case (2), shuts off or reduces the output of the microwave generator (3) by the control circuit (5). 2. The smoke sensor (22) includes a shield case (2).
A duct (23) that allows the air inside to pass through, a heater (24) that heats the air inside this duct (23) to vaporize water droplets passing through the duct (23), and heats inside the duct (23) The apparatus for drying wood according to claim 1, further comprising a smoke detecting section (25) for detecting smoke contained in the air. 3. A duct (23) extending vertically.
2. An apparatus for drying wood according to claim 1, wherein the air heated in the duct (23) is circulated by convection. 4. The drying of wood according to claim 1, wherein a fan (26) is connected to the duct (23), and the air in the shield case (2) passes through the duct (23) by the fan (26). apparatus. 5. The wood drying apparatus according to claim 1, wherein the heater is a light bulb disposed inside the duct.