JP3981576B2 - Exhaust type oven - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust type oven.
[0002]
[Prior art]
In a general batch oven, the inside is heated with a heater and hot air is circulated to uniformize the internal temperature and heat the workpiece.
However, in the debinding process of a ceramic molded body formed into a specific shape using a binder, the degassing (binder) is flammable, and the generated flammable gas may circulate and ignite or explode by the heater. is there.
[0003]
In order to prevent the flammable gas from circulating and igniting by the heater, Japanese Patent Laid-Open No. 2001-12857 discloses that a heater is provided separately from the hot air circulation path so that heated outside air is supplied to the hot air circulation path. Thus, a technique (hereinafter simply referred to as “prior art”) is disclosed in which flammable gas generated from an object to be processed does not flow to a heater.
[0004]
[Problems to be solved by the invention]
However, even in the prior art, the pressure on the hot air circulation path side is higher than that on the heater side due to insufficient exhaust from the hot air circulation path, and air flows backward from the hot air circulation path toward the heater. There is a risk. When such a backflow occurs, the flammable gas generated from the object to be processed comes into contact with the heater and ignites.
[0005]
The present invention has been made in view of such circumstances, and its problem is to exhaust air of a type in which air taken from outside is heated by a heater provided outside the hot air circulation path and hot air is supplied to the hot air circulation path. In the mold oven, the problem is that the gas generated from the object to be processed flows back to the heater and ignites.
[0006]
In the prior art, the air supplied to the hot air circulation path is sucked from the outside, and is configured as an atmospheric oven having only a filter at the air inlet. For this reason, for example, clean heat treatment cannot be performed in a highly purified environment of class 100.
Therefore, another object of the present invention is to perform clean heat treatment in an exhaust type oven in which air taken from outside is heated by a heater provided outside the hot air circulation path to supply hot air to the hot air circulation path. Is to do.
[0007]
[Means for Solving the Problems]
An exhaust oven according to the present invention includes a heating tank in which a hot air circulation path through which hot air circulates is formed , a supply path serving as a path for supplying air sucked from the outside to the hot air circulation path, and from the outside A heater provided in the supply path for heating the intake air to supply the hot air to the hot air circulation path, and an exhaust port for exhausting a part of the hot air circulating in the hot air circulation path . In the exhaust type oven,
A reverse flow detection means for detecting that a flow from the hot air circulation path toward the heater is generated, and the reverse flow detection means detects a pressure difference between the upstream side of the heater and the downstream side of the heater in the supply path. It is characterized by being a differential pressure gauge .
[0008]
According to such a configuration, it is possible to detect that the flow from the hot air circulation path toward the heater is generated by the backflow detection means, so that it is understood that the flammable gas generated from the object to be processed is directed to the heater, and there is a risk of ignition. You can make predictions.
[0009]
The backflow detection means is preferably a differential pressure gauge that detects a pressure difference between the heater upstream side and the heater downstream side of the intake airflow. In a normal state, a flow (intake flow) from the heater side toward the hot air circulation path is generated, so the pressure on the upstream side of the heater in the intake flow is higher than that on the downstream side. The pressure on the upstream side is lower than that on the downstream side. As described above, when a back flow occurs, a change occurs in the pressure difference between the upstream side and the downstream side of the heater. Therefore, the back flow can be detected by measuring the pressure difference.
[0010]
And it is preferable that the said heater stops heat_generation | fever, if the backflow of air is detected by the said backflow detection means. Since the heater stops generating heat, the risk of ignition can be suppressed even if a backflow occurs.
[0011]
Further, the present invention from the viewpoint of performing a clean heat treatment is an exhaust type oven that heats and supplies air sucked from outside to a hot air circulation path through which hot air circulates, and is sucked from the outside and supplied to the hot air circulation path. And a second particulate collection filter for purifying hot air sent to the object to be treated in the hot air circulation path. It is characterized by.
[0012]
By providing the first particulate collection filter, the air sucked from the outside is purified, clean hot air is supplied to the hot air circulation path, and clean heat treatment can be performed.
In addition, by providing the second particulate collection filter, the circulating hot air is further cleaned and then sent to the object to be processed, so that further cleaning can be achieved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an internal cross-sectional view of the exhaust oven 1. The oven 1 is configured as an exhaust type clean oven so that an object to be processed that generates flammable gas can be processed during heat treatment of a ceramic molded body formed using a binder, and clean heat treatment can be performed. ing.
[0014]
The exhaust type clean oven 1 is a batch type and includes an oven body 5 having a heating tank 3 in which an inner tank 2 in which an object to be processed is stored is installed. The oven body 5 is provided with an air inlet 7 for taking in air from the outside, and a clean air unit 9 is attached to the air inlet 7. A supply path 11 is formed as a path from the air inlet 7 to the heating tank 3, and a heater 13 is disposed in the supply path 11. The air sucked from the outside by the heater 13 is heated and supplied as hot air to the heating tank 3.
[0015]
The clean air unit 9 includes a fan (not shown) and a HEPA filter (first particulate collection filter) 15. The intake air is cleaned by the HEPA filter 15 and sent to the heater 13 side. In the heater 13, the air is heated to become hot air and is sent toward the hot air inlet 17 of the heating tank 3.
A sirocco fan 19 is provided at the hot air inlet 17 of the heating tank 3. The sirocco fan 19 is rotationally driven by a motor 20, blows air in the centrifugal direction, and introduces hot air into the heating tank 3 from the supply path 11.
[0016]
The hot air supplied to the heating tank 3 is further purified by passing through a HEPA filter (second fine particle collecting filter) 21 attached to the inner tank 2 in which the object to be processed is accommodated, and the inside of the inner tank 2. Then, the workpiece is heated in a clean environment with a cleanliness class of about 100 in the tank.
[0017]
When hot air comes into contact with the object to be processed and is heated, a flammable gas such as a binder of the object to be processed is generated from the object to be processed, and this flammable gas is formed in the inner tank 2 together with the hot air. Go out of the inner tank 2 through (not shown). Hot air (including flammable gas) that has flowed out of the inner tank 2 returns from the side passage 23 of the inner tank 2 to the vicinity of the hot air inlet 17 through the lower passage 24 and is again returned to the inner tank 2 by the sirocco fan 19. Enter inside. As described above, the hot air is circulated through the path including the inner tank 2 and the HEPA filter 21 in the heating tank 3, and a hot air circulation path is formed in the heating tank 3.
[0018]
An exhaust mechanism 28 having an exhaust port 26 and an exhaust amount adjustment valve 27 is provided in the upper part of the heating tank 3, and all the hot air coming out from the inner layer 2 is not recirculated but partially (about half ) Is exhausted to the outside. FIG. 2 conceptually shows the path through which the hot air flows in this manner. In addition to the circulation flow F1 circulating in the heating tank 3, the intake air flow F2 for supplying hot air to the circulation flow F and There is an exhaust stream F3 to be exhausted.
[0019]
Since a new hot air is supplied as an intake air flow F2 from the sirocco fan 19 which is also a hot air supply means to the heating tank 3, the pressure in the heating tank 3 is increased. A part of the hot air can be naturally exhausted as an exhaust flow F3. By exhausting a part of the circulating flow F1 and replacing it with new hot air F2 from the outside, it is possible to prevent the concentration of the flammable gas contained in the circulating flow F1 from increasing. Moreover, a part of the circulating flow F1 is exhausted and new hot air F2 is supplied, so that the temperature change in the heating tank 3 is small even when exhausting.
[0020]
Here, the hot air is circulated by the sirocco fan 19 as the circulating air generating means. The sirocco fan 19 circulates the hot air F2 sent from the heater 13 side through the supply path 11. This also serves to prevent hot air circulating in the hot air circulation path from flowing back into the supply path 11.
In addition, since the heater 13 is provided in the supply path 11 outside the hot air circulation path, even if the circulated hot air contains flammable gas, the flammable gas is not heated in the heater 13 unless the hot air flows back through the supply path 11. There is no contact.
[0021]
Further, a fine differential pressure gauge 30 is provided as a backflow detecting means for monitoring the backflow of hot air in the supply path 11. This fine differential pressure gauge 30 is located in the middle of the supply path 11, which is a path from the intake port 7 to the heating tank 3, and is positioned upstream of the heater 13 (between the clean unit 9 and the heater 13 in the direction of the intake air flow). ) A and a downstream position of the heater 13 (between the heater 13 and the sirocco fan 19) B are provided with pressure measurement terminals, respectively, and sense the pressure difference between the positions A and B. The pressure measuring terminal can be provided at another position in the supply path 11.
In a normal state, since the intake air flow from the heater 13 toward the heating tank 3 is generated, the upstream position A is at the pressure High and the downstream position B is at the pressure Low. When the pressure increases and a back flow from the heating tank 3 toward the heater 13 occurs, the position A becomes the pressure Low and the position B becomes the pressure High. When backflow occurs and the pressure at position B increases, the heater 13 automatically turns off, stops heat generation, and prevents ignition. Here, in order to stop the heat generation, the heater 13 does not need to be completely turned off, and the heater 13 may be put in the sleep state by reducing the supply voltage to the heater so that the heat generation hardly occurs. That is, even if there is slight heat generation from the heater 13, if the temperature is low, the heat generation is substantially stopped, and ignition can be prevented.
Further, when a reverse flow is detected, an alarm is issued, and the operator can immediately recognize the abnormality of the oven 1.
[0022]
Further, an explosion vent 32 is provided in the upper part of the heating tank 3 so that the explosion pressure can be released. Furthermore, an emergency power supply (not shown) for driving the fan of the clean air unit 9 is provided in order to prevent the flammable gas in the heating tank 3 from flowing back to the heater 13 during a power failure. Even in this case, the fan of the clean air unit 9 is driven to generate an intake air flow, thereby preventing a back flow of gas.
[0023]
The present invention is not limited to the above embodiment. For example, as a countermeasure when detecting the backflow to the heater, in addition to stopping the heat generation of the heater, the output of the fan that generates the intake air flow is increased to increase the pressure on the upstream side of the heater, The opening degree can be automatically increased to facilitate exhaust from the heating tank 3 to reduce the pressure in the heating tank 3.
[0024]
Further, as the particulate collection filter, a filter that can be cleaned more than a HEPA filter may be employed. For example, if a ULPA filter is employed, further cleaning is possible.
[0025]
【The invention's effect】
According to the present invention, it can be detected by the backflow detection means that the flow from the hot air circulation path to the heater is generated, so that it can be seen that the flammable gas generated from the object to be processed is directed to the heater, and there is a risk of ignition. You can make predictions.
Further, if the heater is configured to stop heat generation when the backflow detecting means detects the backflow of air, the risk of ignition can be suppressed even if backflow occurs.
[0026]
In addition, a first particulate collection filter for cleaning air that is sucked from the outside and supplied to the hot air circulation path, and a second that cleans the hot air sent to the object to be processed in the hot air circulation path. When a clean oven is provided with a particulate collection filter, clean heat treatment can be performed.
[Brief description of the drawings]
FIG. 1 is an internal cross-sectional view of an exhaust type oven.
FIG. 2 is a route diagram of hot air in an exhaust type oven.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exhaust type oven 2 Inner tank 3 Heating tank 7 Intake port 11 Supply path 13 Heater 15 HEPA filter (1st particle collection filter)
21 HEPA filter (second particulate collection filter)
26 Exhaust port 30 Differential pressure gauge (Backflow detection means)

Claims (3)

A heating tank in which a hot air circulation path through which hot air circulates is formed;
A supply path serving as a path for supplying air sucked from outside to the hot air circulation path;
A heater provided in the supply path for heating the air sucked from outside and supplying hot air to the hot air circulation path;
In an exhaust type oven comprising: an exhaust port for exhausting a part of hot air circulating in the hot air circulation path ;
A reverse flow detection means for detecting that a flow from the hot air circulation path toward the heater is generated, and the reverse flow detection means detects a pressure difference between the upstream side of the heater and the downstream side of the heater in the supply path. An exhaust type oven characterized by being a differential pressure gauge . The exhaust-type oven according to claim 1, wherein the heater stops heat generation when a backflow of air is detected by the backflow detection means . A first particulate collection filter for cleaning air that is sucked in from the outside and supplied to the hot air circulation path, and a second particulate collection filter that cleans the hot air sent to the object to be processed in the hot air circulation path. The exhaust-type oven according to claim 1, wherein the exhaust-type oven includes a collecting filter and is configured as a clean oven.

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