1. Field of the Invention
The present invention relates to a drying apparatus that dries an object to be dried containing a solvent.
2. Description of the Related Art
Conventionally, a drying apparatus has been known, which includes a furnace body; a movable body configured to move in an interior space of the furnace body, with an object to be dried containing a solvent loaded thereon; an infrared heater disposed above the movable body in the interior space of the furnace body; and gas supply unit for supplying a gas having a regulated temperature and humidity to the interior space of the furnace body (see, e.g., Japanese Patent No. 3897456).
In the apparatus described in the foregoing document, the infrared heater mainly has the function of drying the object by applying infrared radiation thereto. The gas supplied to the interior space of the furnace body mainly has the function of making uniform, as much as possible, the temperature of, and the solvent concentration in, a gas containing the solvent evaporating from the object in a near-surface region of the object. The higher the gas temperature in the near-surface region of the object and the lower the solvent concentration, the faster the drying rate of the object. Therefore, when the gas temperature and the solvent concentration in the near-surface region of the object become uniform, local variation in the drying rate of the object becomes less likely to occur, and the occurrence of deformation of, and cracks in, the object after drying can be reduced.
In the apparatus described in the foregoing document, if the volume of space through which the gas passes in the interior space of the furnace body is large, it is difficult to regulate “the temperature of, and the solvent concentration in, the gas containing the solvent” in the near-surface region of the object. This often makes it difficult to reduce local variation in the drying rate of the object. Additionally, the amount of the gas that needs to be supplied increases. Therefore, the volume of space through which the gas passes is preferably set at a small value. For properly drying the object with infrared radiation, there is a proper value for the distance between the infrared heater and the object (hereinafter also referred to as “heater-object distance”). Therefore, it is preferable to set the heater-object distance at a proper value.
However, in the apparatus described in the foregoing document, the infrared heater is disposed in the space (i.e., the interior space of the furnace body) through which the gas passes and in which the movable body moving with the object loaded thereon is disposed. This makes it difficult to independently and individually regulate the volume of the space through which the gas passes and the heater-object distance. There has been a demand for a drying apparatus capable of independently and individually regulating the volume of the space through which the gas passes and the heater-object distance.
The present invention aims to provide a drying apparatus that dries an object to be dried containing a solvent, and is capable of independently and individually regulating the volume of the space through which the gas passes and the heater-object distance.
A drying apparatus according to the present invention includes a furnace body which is the same as that described above, a movable body which is the same as that described above, and an infrared heater which is the same as that described above.
The drying apparatus according to the present invention is characterized in that it includes “a division wall configured to divide the interior space of the furnace body into a first space including the movable body and a second space including the infrared heater, the division wall being partially or entirely made of a material that transmits infrared radiation”, and that a first gas having a regulated temperature and humidity is supplied to the first space defined by the division wall and the supplied first gas is discharged from the first space. An inert gas, such as nitrogen or argon, is preferably used as the first gas.
Thus, a space through which the first gas passes and in which the movable body moves with the object loaded thereon (first space) and a space in which the infrared heater is disposed (second space) are different spaces separated by the division wall. This makes it easier to independently and individually regulate the volume of the first space through which the first gas passes and the heater-object distance. Also, since the volume of the first space can be reduced by providing the division wall, it is easier to regulate “the temperature of, and the solvent concentration in, the gas containing the solvent” in the near-surface region of the object.
Additionally, the division wall that separates the infrared heater and the object is partially or entirely made of a material that transmits infrared radiation. Therefore, infrared radiation emitted from the infrared heater can pass through the division wall and reach the object. In other words, the presence of the division wall does not interfere with the infrared heater's “function of drying the object” described above.
In the drying apparatus according to the present invention, a plurality of infrared heaters are preferably arranged along a direction of travel of the movable body at a plurality of points spaced from each other in the second space. A plurality of first portions of the division wall, the first portions being located at positions corresponding to the respective infrared heaters in the direction of travel of the movable body, are preferably made of a material that transmits infrared radiation, whereas a plurality of second portions of the division wall, the second portions being located at positions corresponding to respective spaces between adjacent ones of the infrared heaters in the direction of travel of the movable body, are preferably made of a material that does not transmit infrared radiation.
Thus, even when the infrared heaters are spaced apart along the direction of travel of the movable body, the intensity of infrared radiation applied to the object can be made substantially uniform in the direction of travel of the movable body (the details will be described later on). As a result, by powering up each of the infrared heaters, it is possible to increase the distance between adjacent infrared heaters and decrease the number of infrared heaters.
The drying apparatus according to the present invention preferably further includes transmittance regulating unit for varying an infrared transmittance of the first portions of the division wall in accordance with a position in a direction (hereinafter also referred to as “width direction”) orthogonal to the direction of travel of the movable body.
In the near-surface region of the object, “the temperature of, and the solvent concentration in, the gas containing the solvent” inevitably have variation in the width direction. Therefore, the “variation in gas temperature and solvent concentration in the width direction” may cause variation in the drying rate of the object in the width direction. At the same time, the greater the intensity of infrared radiation applied to the object, the faster the drying rate of the object.
With the configuration described above, it is possible to regulate the “distribution of the intensity of infrared radiation applied to the object in the width direction” to compensate for the “variation in the drying rate of the object in the width direction” caused by the “variation in gas temperature and solvent concentration in the width direction”. Therefore, even when there is “variation in gas temperature and solvent concentration in the width direction”, the drying rate of the object can be made uniform as much as possible in the width direction. As a result, the thickness of the object after drying can be made uniform as much as possible in the width direction.
The greater the thickness of the object, the more noticeably the differences in drying rate appear as variation in the thickness of the object, due to a larger amount of contraction of the object in the thickness direction. This means that the greater the thickness of the object, the greater the “effect of making the thickness uniform” achieved by the transmittance regulating unit.
(Configuration)
An embodiment of a drying apparatus according to the present invention will now be described with reference to
As illustrated in
The object to be dried (hereinafter referred to as “object”) is typically a film-shaped compact of a “slurry containing ceramic powder or metal powder, a binder, and a solvent” extending in the longitudinal direction. The object is subjected to the drying process of the present embodiment, so that the solvent in the object is vaporized and removed to dry the object. Then, the dried object is fired (i.e., the binder is vaporized and removed) to form a final product (fired body).
The present embodiment includes an “infrared drying furnace” corresponding to the first half of the drying process, and a “hot-air drying furnace” corresponding to the second half of the drying process. First, the configuration of the infrared drying furnace will be described. Note that the drying process may be carried out by the “infrared drying furnace” alone.
The infrared drying furnace includes a furnace body 10. As illustrated in
As illustrated in
As illustrated in
As illustrated in
In the division wall 50, the first portions 51 are arranged at positions corresponding to the respective infrared heaters 40 in the longitudinal direction, whereas the second portions 52 are arranged at positions corresponding to respective spaces between adjacent infrared heaters 40 in the longitudinal direction.
Quartz glass is suitable as the material of the first portions 51. Quartz glass has the property of transmitting infrared radiation (near-infrared radiation) with a dominant wavelength of 3.5 μm or less at a high transmittance. Stainless steel is suitable as the material of the second portions 52. Stainless steel has the property of not transmitting infrared radiation (near-infrared radiation) with a dominant wavelength of about 6 μm or less. At the same time, stainless steel has the property of absorbing infrared radiation (near-infrared radiation) at a given rate, and thus has the effect of retaining heat in the division wall 50.
Aluminum alloy is also suitable as the material of the second portions 52. Aluminum alloy not only has the property of not transmitting infrared radiation (near-infrared radiation) with a dominant wavelength of about 6 μm or less, but also has a lower level of absorption of infrared radiation (near-infrared radiation) than stainless steel. This can reduce overheating of the division wall 50. Therefore, aluminum alloy is suitable for use in drying the object at relatively low temperatures.
In the present embodiment, as illustrated in
As illustrated in
Similarly, an inlet 14 and an outlet 15 for air are provided in the space S3 of the furnace body 10. From the inlet 14, temperature-regulated air is ejected in the negative direction of the x-axis (see a thin arrow). The conveyor belt 20 is temperature-regulated by being exposed to the ejected air. The ejected air is discharged to the outside through the outlet 15 (see a thin arrow). The temperature and the flow rate of air ejected from each nozzle 60 and the inlet 14 are regulated by an air supply controller 300.
As illustrated in
The configuration of the “infrared drying furnace” has been described. Next, the configuration of the “hot-air drying furnace” will be described.
As illustrated in
As illustrated in
The operation of the embodiment configured as described above will now be briefly described. In the present embodiment, as illustrated in
The conveyor belt 20 carrying the object moves horizontally and parallel in the positive direction of the x-axis at a predetermined speed. Infrared radiation (near-infrared radiation) is emitted from each of the infrared heaters 40 at a predetermined intensity. The emitted infrared radiation (near-infrared radiation) passes through the corresponding first portion 51 of the division wall 50 to reach the object, which is thus dried.
From the nozzle 70, a nitrogen gas having a regulated temperature and humidity is ejected in the positive direction of the x-axis toward the interior of the space S1. Thus, the nitrogen gas flows in the space S1 in the positive direction of the x-axis. By the flow of nitrogen gas in the space S1, the temperature of, and the solvent concentration in, the “gas containing the solvent evaporating from the object” are made uniform as much as possible in the near-surface region of the object. As a result, local variation in the drying rate of the object becomes less likely to occur, and the occurrence of deformation of, and cracks in, the object after drying can be reduced. As described above, the greater the thickness of the object, the greater the action and effect described above.
From each of the nozzles 60, temperature-regulated air (e.g., air at room temperature) is ejected toward the inside of the space S2. At the same time, from the inlet 14, temperature-regulated air (e.g., air at a temperature slightly higher than room temperature) is ejected toward the inside of the space S3. As a result, the temperature of the division wall 50 and the temperature of the conveyor belt 20 (i.e., the temperature of the object) are set and maintained at proper temperatures. As described above, the temperature of air ejected from the nozzles 60 is set to be lower than that of air ejected from the inlet 14. This is because the air ejected from the nozzles 60 is slightly warmed in the space S2 by infrared radiation emitted from the infrared heaters 40. Thus, the temperature of the air that reaches the division wall 50 after being ejected from the nozzles 60 can be substantially the same as the temperature of the air that reaches the conveyor belt 20 after being ejected from the inlet 14.
Thus, the object that moves with the conveyor belt 20 in the “infrared drying furnace” is dried by the action of infrared radiation while being kept at a temperature slightly higher than room temperature, with little local variation in drying rate because of the action of flow of nitrogen gas in the space S1. As a result, the object can be obtained, which is dried to some extent without cracks and significant variation in thickness.
The object is then moved from the “infrared drying furnace” to the “hot-air drying furnace”. In the furnace body 80 of the hot-air drying furnace, air heated to a high temperature (hot air) is ejected from each of the nozzles 90 toward the inside of the space S4. As a result, the object that moves with the conveyor belt 20 in the “hot-air drying furnace” is further dried under high temperature by the action of the ejected air (hot air). Thus, at the stage when the object is discharged from the exit 81 of the furnace body 80, the drying of the object is completed, that is, a dry body is obtained. The object is sufficiently dried at the stage of being discharged from the “infrared drying furnace”. Therefore, even when the object is further subjected to a high temperature after this stage, the occurrence of cracks and significant variation in thickness can be avoided.
(Action and Effect)
The action and effect of the present embodiment will now be described. In the present embodiment, the “space through which nitrogen gas passes and in which the conveyor belt 20 moving with the object loaded thereon is disposed” (space S1) and the space in which the infrared heaters 40 are arranged (space S2) are different spaces separated by the division wall 50. This makes it easier to independently and individually regulate the “volume of the space S1 through which nitrogen gas passes” and the “heater-object distance”. Also, since the volume of the space S1 can be reduced by providing the division wall 50, it becomes easier to regulate “the temperature of, and the solvent concentration in, the gas containing the solvent” in the near-surface region of the object.
Additionally, in the division wall 50, as illustrated in
Thus, by regulating the distance between adjacent infrared heaters 40 and the length of the first portions 51 of the division wall 50 in the longitudinal direction as illustrated in
The present invention is not limited to the embodiments described above, and can adopt various modifications within the scope thereof. For example, although a nitrogen gas is used as a gas that flows in the space S1 in the embodiments described above, any inert gas, such as argon, may be used.
Although the division wall 50 is formed by the first portions 51 (portions transmitting infrared radiation) and the second portions 52 (portions not transmitting infrared radiation) in the embodiments described above, the division wall 50 may be formed entirely by the first portions 51 (portions transmitting infrared radiation).
In the embodiments described above, the lower surfaces of both ends of each second portion 52 of the division wall 50 in the width direction slightly overlap both ends of the upper surface of the conveyor belt 20 in the width direction. Thus, the space S1 is divided into the “space S1 corresponding to the upper side of the conveyor belt 20” and the “space S3 corresponding to the lower side of the conveyor belt 20”. Alternatively, the space S1 may be a single space in which the “space on the upper side of the conveyor belt 20” is continuous with the “space on the lower side of the conveyor belt 20”.
In the embodiments described above, “the temperature of, and the solvent concentration in, the gas containing the solvent” in the near-surface region of the object inevitably have variation in the width direction in the space S1. Therefore, the “variation in gas temperature and solvent concentration in the width direction” may cause variation in the drying rate of the object in the width direction. At the same time, the greater (smaller) the intensity of infrared radiation applied to the object, the faster (slower) the drying rate of the object.
By regulating the “distribution of the intensity of infrared radiation applied to the object in the width direction” on the basis of the findings described above, it is possible to compensate for “variation in the drying rate of the object in the width direction” caused by “variation in gas temperature and solvent concentration in the width direction”. For example, if the solvent concentration in the “gas containing the solvent” is higher in the center of the space S1 in the width direction than at both ends of the space S1 in the width direction, the drying rate of the object is greater at both ends than in the center in the width direction. In this case, the thickness of the object tends to be greater at both ends than in the center in the width direction.
In such a case, for example, as illustrated in
In the example illustrated in
In the example illustrated in
Also, in the example illustrated in
The present application claims priorities from Japanese patent application No. 2013-035924 filed on Feb. 26, 2013, and Japanese patent application No. 2013-218253 filed on Oct. 21, 2013, the entire contents of both of which are incorporated herein by reference.
Number | Date | Country | Kind |
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2013-035924 | Feb 2013 | JP | national |
2013-218253 | Oct 2013 | JP | national |
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Entry |
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Number | Date | Country | |
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20150354892 A1 | Dec 2015 | US |
Number | Date | Country | |
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Parent | PCT/JP2014/054467 | Feb 2014 | US |
Child | 14832196 | US |