JPH08199232A - Gas heating tempering furnace - Google Patents

Abstract

PURPOSE: To obtain a gas heating tempering furnace having extremely narrow temp. range in the furnace in a low cost by guiding a combustion exhaust gas to a specific distance to an axis with a duct in the tempering furnace arranging a centrifugal fan. CONSTITUTION: An inner case 12 opened at the upper and the lower parts is arranged at almost center part in the tempering furnace covering the surroundings with a heat insulating material and a material 31 to be treated is arranged therein. A gas burner 21 is arranged at out of the furnace and the combustion exhaust gas is introduced into the furnace through a duct 22 and circulated in the furnace with the centrifugal fan 26 arranged at the upper part to treat the material 31 to be treated. In the gas heating tempering furnace, at the time of using (r) for the radius of the centrifugal fan 26, the combustion exhaust gas is introduced to the distance of 1/2r-(r) from this axis 30 desirably about 2/3r at the lower part of the centrifugal fan 26 through the duct 22. At this time, the position of the upper end of the duct 22 is desirable to be the range of 30-60mm from the lower end of the centrifugal fan 26. By this method, the temp. range in the furnace is made to be within about 10 deg.C and the required time for raising temp. of the tempering furnace can drastically be shortened.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a gas heating tempering furnace.

[0002]

2. Description of the Related Art Automotive engines and various gears, especially gears for automobile transmissions, are heat treated after molding, but in the process, they are treated in a tempering furnace that uniformly heats the whole, and their wear resistance It is necessary to increase The heating temperature of the tempering furnace varies depending on the type of the object to be heated, and is 150 to 350
Some of them are relatively low as ℃, but the temperature range in the furnace is small and it is necessary to keep the temperature within 10 deg. Therefore, as shown in FIG. 7, a tempering furnace 1 used conventionally has a heating wire 3 attached to a side wall 2 and a centrifugal fan 4 provided at the upper portion of the tempering furnace 1 removes furnace air from an inner case 5 accommodating an object to be processed. It is an electric heating device that sucks air, sends it to the surroundings as indicated by arrows, heats this air by the heating wire 3 attached to the side wall 2, and circulates from the lower part of the inner case 5.

Since the heating wire 3 is uniformly attached to the side wall 2, the temperature range in the tempering furnace 1 becomes relatively uniform within 10 deg, but there is a problem that it takes time to raise the temperature. Further, the unit price per calorie is twice as high as electricity as compared with gas, so that there is a problem that running cost is high. In order to deal with this, various gas heating tempering furnaces have been trial-produced. However, in order to keep the temperature range within the furnace within 10 deg.
There is a problem that the initial cost becomes high.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas heating tempering furnace having a temperature range within 10 deg within the furnace at a low cost.

[0005]

SUMMARY OF THE INVENTION The present invention has a radius r at the top.
In a tempering furnace having a centrifugal fan, a gas burner is provided outside the furnace, and combustion exhaust gas from the gas burner is guided by a duct to a lower part of the centrifugal fan and a distance of 1 / 2r to r from the centrifugal fan axis. It is a gas heating tempering furnace. Further, the present invention is provided with the centrifugal fan 3
The upper end of the duct is provided in the range of 0 to 60 mm.

[0006]

According to the present invention, the combustion exhaust gas from the burner provided outside the furnace is introduced into the tempering furnace by the duct. In this case, it was found that the temperature inside the tempering furnace can be made uniform by devising the position of the tip of the duct, that is, the outlet of the combustion exhaust gas. Further, since the burner is provided outside the furnace, the burner can be easily managed. In the tempering furnace, in order to stir the gas in the furnace, a centrifugal fan having a radius r is provided in the upper part of the furnace, and the air in the lower part is sucked and discharged to the outside in the radial direction. From the experimental results, the duct tip position is located in the lower part of the centrifugal fan and is located at 1 / 2r to r, preferably 2 / 3r from the axial center of the centrifugal fan. This is because if the tip of the duct is close to the axial center of the centrifugal fan, the combustion exhaust gas is not evenly sucked, and if it is outside the blade of the centrifugal fan, it is circulated without being sucked by the centrifugal fan.

According to the invention, the distance between the upper end of the duct and the centrifugal fan is preferably in the range of 30 to 60 mm. This is because if the distance is 30 mm or less, the blades may vibrate and hit the duct due to the rotation of the centrifugal fan, and if the distance is 60 mm or more, the space for accommodating the object to be processed cannot be increased.

[0008]

The present invention will be described in more detail with reference to the following examples.

FIG. 1 is a plan view of a gas heating tempering furnace 11 which is an embodiment of the present invention, and FIG. 2 is a section line II of FIG.
FIG. 3 is a sectional view taken along line II in FIG. 3, and FIG.
It is sectional drawing by I-III. The tempering furnace 11 is covered with a heat insulating material in its periphery, and an inner case 12 for accommodating an object to be processed is provided at a substantially central portion thereof. The inner case 12 has openings at the top and bottom and on the door side, and the periphery is a wall surface. On the front surface of the furnace 11, there is an opening 13 through which an object 31 to be processed is put into and taken out from the inner case 12, and a door 14 that can be opened and closed is provided here. On the ceiling 15 in the furnace 11,
A centrifugal fan 26 is provided and rotated by a motor 27.
On one side wall 18 of the furnace 11 a gas burner, for example C
An F burner 21 is provided, to which, for example, city gas is connected and burned. Flue gas is discharged from the duct 22 to the furnace 1.
Introduced in 1.

As shown in the perspective view of FIG. 4, the centrifugal fan 26 has a plurality of rectangular blades 28, for example, six blades 28, which are mounted parallel to the rotation axis. As a result, the air in the furnace 11 is sucked from below in the axial direction and discharged in the direction perpendicular to the axial center. That is, the air in the inner case 12 is sucked from the upper portion thereof, passes through the periphery of the inner case 12, and circulates from the furnace bottom 16 into the inner case 12. At this time, the high temperature combustion exhaust gas from the duct 22 is mixed with the in-furnace air from the inner case 12 to form a uniform circulating gas. The amount of combustion exhaust gas from the CF burner is about 1% of the circulating gas, and the excess exhaust gas is exhausted from the exhaust stack 17. As shown in FIG. 5, when the distance between the tip of the duct 22 and the shaft center 30 of the centrifugal fan 26 is x, x
By changing the temperature range in the furnace 11 by circulating 56.8 times /
Fig. 6 shows the result of an examination in an empty furnace having a set temperature of 180 ° C for min. In addition, the temperature range in the actual furnace with the circulation frequency of 30 times / min is
It is known from the experiment that the number of circulation is 56.8 times / minute, which corresponds to about twice the temperature range in the empty furnace. Therefore, from FIG. 6, in order to keep the temperature range in the empty furnace within 5 deg, x Is 1/2
It should be in the range of r to r, and in order to obtain the minimum temperature range, x≈2 / 3r. In addition, centrifugal fan 2
It is preferable that the lower surface of 6 and the upper surface of the duct 22 have a minimum distance in which the blades 28 do not contact the duct 22 due to the vibration caused by the rotation of the centrifugal fan 26. In this embodiment, the distance is 40 mm. The duct 22 is suspended from the ceiling 15 by a suspender 23 so that the tip of the duct 22 does not tilt downward due to gravity.

The size of the gas heating and tempering furnace 11 of the present embodiment is a furnace internal size, for example, height 1,160 mm, width 1,
The length is 300 mm, the length is 1,710 mm, and the treatment amount is 550 kg per treatment. Further, when the processing temperature is 180 ° C, it takes about 30 minutes to raise the temperature, and the 180 ° C processing time is 2.5
In terms of time, the total treatment time was 3 hours. On the other hand, in the case of conventional electric heating, it takes about 1 hour to raise the temperature under the same capacity and temperature conditions, and the total processing time is 3.5 hours.
The fuel cost for gas heating was about half that for electric heating. In the case of an empty furnace, the temperature range in the furnace is 4.4 deg with electric heating, whereas the above-mentioned x = 2 / g with gas heating.
If it is 3r, it becomes 3.8 deg. Further, the temperature range in the furnace used above is the difference between the highest temperature and the lowest temperature measured at 9 points in the furnace according to the method of JIS B 6901.

[0012]

As described above, according to the present invention, since the combustion gas is introduced into the tempering furnace by the duct from the burner provided outside the furnace, the maintenance of the burner is facilitated and the tip of the duct is radiused. 1 / 2r to r from the axial center of the centrifugal fan of r
The temperature difference in the tempering furnace can be made equal to or less than that of the conventional electrically heated tempering furnace, and the temperature rise time of the tempering furnace can be shortened by reducing the fuel cost to 1
It can be reduced to / 2.

[Brief description of drawings]

FIG. 1 is a plan view of a gas heating tempering furnace according to an embodiment of the present invention.

2 is a cross-sectional view taken along the section line II-II in FIG.

FIG. 3 is a sectional view taken along section line III-III in FIG.

FIG. 4 is a perspective view of a centrifugal fan 26.

5 is a diagram showing a relationship between a centrifugal fan 26 and a duct 22. FIG.

FIG. 6 is a graph showing the relationship between the tip position of the duct 22 and the temperature range in the furnace.

FIG. 7 is a cross-sectional view of a typical prior art electrically heated tempering furnace 1.

[Explanation of symbols]

 11 Gas Heating and Tempering Furnace 12 Inner Case 21 Gas Burner 22 Duct 26 Centrifugal Fan 27 Motor 28 Blade 30 Shaft Center 31 Workpiece

Claims (2)

[Claims] 1. A tempering furnace having a centrifugal fan with a radius r in the upper part, wherein a gas burner is provided outside the furnace, and combustion exhaust gas from the gas burner is ducted to the lower part of the centrifugal fan and 1/2 r from the centrifugal fan axis. A gas heating tempering furnace characterized by leading to a distance of ~ r. 2. The gas heating tempering furnace according to claim 1, wherein an upper end of the duct is provided within a range of 30 to 60 mm from a lower end of the centrifugal fan.