JPH0987043A - Method for firing ceramic and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the bending deformation of a work and to decrease the man-hours for working in finish polishing by oscillatably supplying the work in the position upper than the centroid position of the work and subjecting the work to a treatment, such as heating, while applying vibration thereon. SOLUTION: A mortar-shaped receiving surface 9-5 corresponding to the conical shape of the rear surface in the umbrella part of the work 8 is formed at the peripheral edge on the upper end side of a hole 9-6 formed at the upper beam 9-1 of a set jig 9 and the work 8 is inserted into the receiving surface 9-5, by which the work 8 is oscillatably supported in the position upper than the centroid position of the work 8. The front end of the work 8 is inserted into a hole 9-7 having a compliance guide 9-4 formed at a lower beam 9-2. The work 8 is subjected to the treatment, such as heating, while the work is continuously or intermittently vibrated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for firing various ceramics, for example, ceramics applied to manufacturing processes of engine valves, turbine rotor blades and the like.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a series of known ceramic manufacturing processes. As shown in the figure, the ceramic manufacturing process includes a molding process 11 for molding granulated powder that is a ceramic raw material by various methods, a machining process 12 before firing for removing extraneous meat during molding, and a predetermined strength. , A hardness and dimensional firing step 13, and a final polishing step 14 for finishing to a predetermined surface roughness and dimensional accuracy.

The molding step 11 shown in FIG. 3 is a method previously proposed by the inventors of the present application. (1) filling and sealing in a thin resin mold, and (2) CIP (low temperature hydrostatic pressure). However, it is not directly related to the firing method of the present invention, and any other molding method may be used.

FIG. 4 shows, as an example of a conventional firing method, sintering-HIP firing in an atmosphere gas of high temperature and high pressure.
Show the law. The outline is as follows.

An object to be treated 8 (here, an example of an engine valve which has been machined before firing is shown) is inserted into a set jig 19, and a bell jar type (one example) firing pressure container (base 12) is inserted.
And the upper lid 1), and the air in the firing pressurizing vessel is removed by the exhaust system 4, the valve 4-1 is closed, and the pressure is supplied from the pressurizing system 3 via the valve 3-1. The pressure is gradually increased with an inert gas such as nitrogen, and the heater 5 heats by supplying power from a power source 7 according to a predetermined heating program.

FIG. 5 shows an example of a jig for setting an object to be processed. The set jig 19 shown in FIG. 5 is made of Si when the ceramic material is, for example, Si ₃ N ₄ (silicon nitride).
Boron nitride (h-BN), which is hard to react with ₃ N ₄ and excellent in machinability and easy to manufacture, is used. Structurally, it has a predetermined shape and a predetermined shape for maintaining the posture of the object to be processed 8 during processing. An upper beam 19-1 and a lower beam 19-2 provided with a hole having a diameter and a column 19- for connecting these upper and lower beams 19-1 and 19-2
3 and 3.

[0007]

Recently, in automobile engines, ceramicization of engine valves is again in the limelight in view of high responsiveness, low fuel consumption, light weight, and quietness. There has been a long-felt demand for ceramics for the blades in terms of high temperature and high efficiency, and in recent years, remarkable progress has been made in terms of ceramic performance and quality. However, in terms of practical application, it is an urgent task to establish a mass production method that can realize a significant reduction in manufacturing costs.

Therefore, the inventors of the present invention have already used an expensive ceramic powder at a high yield as a molding method for granulated powder.
We have established and established a molding method that can be molded into est Net Shape and can significantly reduce the number of additional processing steps, and have eliminated the maximum neck process of cost reduction.

On the other hand, the next neck is the firing process, which has the following problems.

In the forming and mechanical finishing steps before firing,
Neare with uniform density and shrinkage deformation amount during firing
st Net Shape or Net Shape
Since the dimension is adjusted, the bending deformation due to external force such as gravity and self-weight during firing and its variation increase the dimensional defect rate, reduce the yield rate, and significantly increase the manufacturing cost.

Variation in the above-mentioned bending deformation (Min / Ma)
When taking measures to increase the bulkiness in consideration of x), the dimensional defect rate can be reduced, but the finishing allowance increases in the subsequent finishing polishing step and the polishing time required for finishing the ceramic hardened by firing remarkably increases. This will cause a significant increase in manufacturing costs and will not be established as a mass production method.

The cause of all the above-mentioned bending deformation is that the object to be processed is heated and held in an inclined state θ (see FIG. 5) while deviating from the gravity line during firing. As shown in FIG. 5, the engine valve 8 which is the object to be processed has an upper beam 19-1 and a lower beam 19-1.
-2 between the pair of holes, TopHovey, that is, by holding the umbrella part having a large weight on top and the shaft part having a small weight per length on the bottom, the influence of its own weight is reduced and the vertical position is maintained. Need to hold. However, it possible to maintain perfectly horizontal jig beam is difficult poles, and with respect to the shaft diameter d ₀ In consideration of the engine valve insertability into the jig hole diameter d ₁ of the lower beam 19-2 Is required to be slightly larger, and further, due to a slight discrepancy between the center axes of the upper and lower holes, variations in the hole diameter of the lower beam 19-2, and contraction of the shaft diameter during the firing process, the engine valve on the jig It is a very difficult technique to hold straight.

As a result of the above, the slight inclination angle θ = 0.1 °
Even if occurs, even if the valve length is 120 ^L mm, the bending amount of the tip is ΔL = L × 2πθ / 360 = 0.2 mm,
The finishing grinding time with the diamond grindstone after firing for a deformation amount of 200 μm becomes enormous.

Therefore, in view of the above-mentioned prior art, the present invention provides a ceramic firing method and apparatus capable of preventing the bending deformation of an object to be treated such as an engine valve, and reducing the processing man-hour in the finish polishing step. This is an issue.

[0015]

Means for Solving the Problems A first method for solving the above problems is described below.
In the firing method, the supporting means swingably supports the object to be processed above the center of gravity of the object to be processed, and the vibrating means continuously or intermittently applies vibration to the object to be processed. It is characterized in that treatment (heating, pressurization, reaction progress, etc.) is performed.

The second firing method is the same as the first firing method, except that the support means causes the object to be treated to be located above the position of the center of gravity of the object to be treated and the position of the center of gravity to be within the entire length of the object to be treated. It is characterized in that it is swingably supported so as to be positioned above the point.

The first baking apparatus for solving the above-mentioned problems is a support means for supporting the object to be processed in the baking furnace so as to be swingable above the position of the center of gravity of the object to be processed, and the object to be processed. A vibrating means attached to the firing furnace or the supporting means so as to continuously or intermittently vibrate the object to be processed when the object is treated (heating, pressurization, reaction progress, etc.) Is characterized by.

A second baking apparatus is the above-mentioned first baking apparatus, wherein the supporting means is located above the barycentric position of the object to be processed, and the barycentric position is the entire length of the object to be processed. It is characterized in that it is structured so as to be swingably supported in a form located above the midpoint.

The third firing device is the first or second firing device.
In the above baking apparatus, a supporting surface of the supporting means for supporting the object to be processed is formed with a receiving surface having a shape corresponding to the shape of the object to be processed.

A fourth baking apparatus is the above-mentioned first, second or third baking apparatus, wherein the supporting means is below a supporting portion for supporting the object to be processed and is on the lower end side of the object to be processed. And a hole for restricting the swinging motion range of the object to be processed at the time of vibrating.

A fifth baking apparatus is the same as the fourth baking apparatus, except that the diameter d ₂ of the hole of the supporting means is d ₀ when the diameter of the lower end of the object to be loosely inserted into the hole is d _0. It is characterized in that 1.0 <d ₂ / d ₀ ≦ 2.0.

According to the above-described baking method and apparatus, baking is performed continuously or intermittently while vibrating, so that the object to be processed has a precessive swinging motion (see FIG. 2).
Therefore, the object to be processed is not held in a state of being inclined only in one direction, that is, the object to be processed was statistically oriented in the gravity direction during firing.

When the position of the center of gravity of the object to be processed is above the midpoint of the entire length of the object to be processed, that is, in the case of TopHeavy, for example, in the engine valve, the weight of the umbrella portion is not added to the shaft portion of the object, so that the weight of the object is reduced. It is possible to prevent abnormal elongation of the shaft.

When the support surface of the support means is formed with a receiving surface having a shape corresponding to the shape of the object to be processed, the suspended posture of the object to be processed is stabilized.

When the lower end side of the object to be processed is loosely inserted into the hole provided below the support portion, this hole can prevent the swinging motion range of the object to be expanded excessively.
When 1.0 <d ₂ / d ₀ ≦ 2.0, d ₂ / d
By setting ₀ > 0, it is easy to insert the object to be processed into the hole of the supporting means, and by setting d ₂ / d ₀ ≦ 2.0, the swinging motion range is restricted within this range and the swinging motion range is set. To prevent the illness from spreading.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same parts as those of the related art are designated by the same reference numerals.

FIG. 1 is a sectional view showing a ceramic firing apparatus according to an embodiment of the present invention, and FIG. 2 is an explanation showing the shape of a setting jig and the behavior of an object to be treated on the setting jig during vibration firing. It is a figure.

As shown in FIG. 1, a heater 5 is provided in a firing pressurizing vessel consisting of a base 2 and an upper lid 1 provided on the base 2.
And a setting jig 9 are installed, and the upper portion of the firing pressure vessel is connected to the pressure system 3 and the exhaust system 4 via valves 3-1 and 4-1. The setting jig 9 is the beam 9-1.
And a lower beam 9-2 and a column 9-3 connecting the upper and lower beams 9-1, 9-2. And base 2
A vibration exciter 6 is attached to, and the vibration exciter 6 imparts fine vibration to the object to be processed. The power supply 7 is connected to the heater 5 and the vibrator 6.

Further, as shown in FIG. 2, a hole 9-6 is formed in the upper beam 9-1 of the setting jig 9, and this hole 9-
An engine valve 8 which is an object to be processed is provided on the peripheral portion of the upper end side of 6.
A mortar-shaped receiving surface 9-5 corresponding to the conical shape of the lower surface of the umbrella portion is formed. A hole 9-7 is formed in the lower beam 9-2, and a compliance guide 9-4 is provided on the upper end side of the hole 9-7. If the hole diameter d _{2 of the} hole 9-7 is the shaft diameter d _{0 of the} valve 8, 1.0 <d ₂ / d ₀ ≦ 2.
It is preferably 0. The engine valve 8 is swingably supported by the upper beam 9-1 in a state where the center of gravity is above the midpoint of the entire length with the umbrella portion up and the shaft portion down, that is, in the Top Heavy state. . At this time, the position of the center of gravity is below the supporting portion of the upper beam 9-1.

Next, an automobile engine valve will be described as an example of a ceramic product manufactured by using the firing method of the present invention.

Example 1 Preparation of Nearest Net Shape Body Before Firing Granulated powder composed of Si ₃ N ₄ , Y ₂ O ₃ , Al ₂ O ₃ and others was prepared in advance in a predetermined shape and size. 15 ^t m
After filling and sealing in a vinyl acetate capsule of m, C
IP (low temperature hydrostatic pressure) pressurization, removing capsules by machining, and taking into account the shrinkage amount during firing
Finished to Net Shape. The finished valve dimensions after firing are: Umbrella diameter: 28.0 mm, Shaft diameter: 6.2 φm
m, total length: 105 ^L mm.

Excitation firing The engine valve 8 in the green state (referred to as the state before firing) produced as described above is provided with a hole 9-of a setting jig 9 shown in FIG.
Many were automatically inserted in Nos. 6, 9-7. As the structure of the setting jig 9 at this time, two pieces of hBN (boron nitride) having a diameter of 750 mm are made to face each other with a span interval of 70 mm to form upper and lower beams 9-1 and 9-2. ，
9-2 was connected with the support | pillar 9-3. Further, the receiving surface 9-5 is formed on the upper end side of the hole 9-6 of the upper beam 9-1 as described above, and the compliance guide 9-4 and the diameter 1 are formed on the lower beam 9-2.
A hole 9-7 having a diameter of 1.5 mm was provided.

After the setting jig 9 is installed in the firing pressure container, the atmosphere in the firing pressure container is removed by a vacuum pump (not shown) of the exhaust system 4 to close the valve 4-1. High-pressure nitrogen gas was gradually supplied from the supply system 3 through the valve 3-1 to increase the pressure (Max 30 atm), and the power source 7 supplied power to the heater 5 to heat it. Then, at 1000 ° C. × 2 ^H, the exciter 6 started to vibrate for 10 seconds and then stopped in a cycle of 2 minutes to start 1500 ° C. × 2 ^H and 1800 ° C. × 2 ^{H.
During the H-} holding and furnace cooling process, the same vibration cycle as above was continued until the furnace temperature reached 900 ° C.

Example 2 In the above, as the vibration conditions, continuous vibration (30 Hz) was applied from the starting point of holding 1000 ° C. × 2 ^H to the time point when 900 ° C. was reached when the furnace was cooled.

(Operation / Effect) In the conventional method, as shown in FIG. 5, once the engine valve 8 has an inclination angle θ with respect to the gravity line on the set jig 19, the engine valve 8 is fired in the same posture as the shaft portion. Is deformed in the direction of gravity due to its own weight, resulting in bending of the shaft portion and poor straightness with respect to the umbrella portion. However, the engine valve 8 on the setting jig 9 is vibrated during the high temperature heat treatment, as shown in FIG. Lower beam 9-
2 hole diameter d ₂ (11.5φmm) (2δ <
d ₂₎ to produce a precession specific swinging motion to the shaft portion, the
It does not become a slope that is inclined only in one direction. That is, the engine valve 8 was statistically oriented in the gravity direction during firing. For this reason, the difference in straightness and bending deformation before and after firing was at a level that could not be grasped by measuring instruments.

The position of the engine valve 8 is set to Top He
Since the weight of the umbrella is not added to the shaft, the total length after firing in the case of avy is lower than the total length in the case of Bottom Heavy (when suspended by the cotter groove 8-1).
The average length was about 0.2 mm shorter, and abnormal elongation of the shaft due to its own weight could be prevented.

By providing the receiving surface 9-5 in the hole 9-6 of the upper beam 9-1, the suspension posture can be stabilized. In addition,
In the case of continuous vibration, the surface roughness of the neck portion of the engine valve 8 (the portion in contact with the upper beam 9-1) is slightly rougher than in the case of intermittent vibration, and the intermittent vibration method is slightly superior. There is.

Due to the above-mentioned effects (1) to (3), it is possible to completely prevent variations in straightness, bending deformation and elongation of the shaft in practical use, and it is possible to drastically reduce the processing man-hour in the finishing polishing step (1/8) and the polishing cycle time is within 20 seconds. I was able to.

Although the vibrator 6 is attached to the base 2 in the above embodiment, the present invention is not limited to this, and the vibrator may be attached to the upper lid 1 or the setting jig 9.

[0040]

According to the present invention as specifically described above together with the embodiments of the invention, the object to be processed is vibrated to cause a precession-like swinging motion in the object to be processed. The bending deformation of the can be prevented.

Further, the posture of the object to be processed is changed to Top Heavy.
By setting the state, for example, in the case of an engine valve, it is possible to prevent abnormal elongation of the shaft portion.

Further, by forming a receiving surface having a shape corresponding to the shape of the object to be processed on the supporting portion of the supporting means, the suspended posture of the object to be processed can be stabilized.

Further, by loosely inserting the lower end side of the object to be processed into the hole provided below the supporting portion (particularly 1.0 <d ₂ / d ₀
By setting ≦ 2.0), it is possible to prevent the swinging motion range of the workpiece from being excessively expanded by this hole.

Further, by preventing the bending deformation and the abnormal elongation as described above, it is possible to drastically reduce the processing man-hour in the finish polishing step.

[Brief description of drawings]

FIG. 1 is a sectional view showing a ceramic firing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the shape of the setting jig and the behavior of the object to be processed on the setting jig during vibration firing according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a series of ceramic manufacturing steps.

FIG. 4 is a sectional view showing a conventional ceramic firing apparatus.

FIG. 5 is an explanatory diagram showing a shape of a setting jig and a posture state of an object to be processed on the setting jig according to a conventional ceramic firing method.

[Explanation of symbols]

 1 Upper Lid 2 Platform 3 Pressurization System 4 Exhaust System 3-1 and 4-1 Valve 5 Heater 6 Vibrator 7 Power Supply 8 Engine Valve 8-1 Cotter Groove 9 Set Jig 9-1 Upper Beam 9-2 Lower Beam 9-3 Support post 9-4 Compliance guide 9-5 Receiving surface 9-6, 9-7 hole

Claims (7)

[Claims] 1. An object to be processed is swingably supported above the center of gravity of the object to be processed by a supporting means, and vibration is continuously or intermittently applied to the object to be processed by a vibrating means. A method for firing a semi-rack, which comprises performing a treatment such as heating. 2. The method for firing a ceramic according to claim 1, wherein the support means causes the object to be processed to be located above the position of the center of gravity of the object to be processed, and the position of the center of gravity being from the midpoint of the entire length of the object to be processed. A method for firing ceramics, characterized in that the ceramic is also supported so as to be swingable in a form positioned above. 3. A support means for swingably supporting an object to be processed in a firing furnace above a center of gravity of the object to be processed, and the above-mentioned method when the object to be processed is subjected to a treatment such as heating. A ceramic firing apparatus comprising: a firing furnace or a vibrating means attached to the supporting means so as to continuously or intermittently apply vibration to an object to be processed. 4. The ceramic firing apparatus according to claim 3, wherein the support means positions the object to be processed above a position of a center of gravity of the object to be processed, and the position of the center of gravity is within the entire length of the object to be processed. A ceramic firing apparatus, characterized in that it is configured to be swingably supported in a form located above a point. 5. The ceramic firing apparatus according to claim 3 or 4, wherein a receiving surface having a shape corresponding to the shape of the object to be processed is formed on a supporting portion of the supporting means for supporting the object to be processed. A method for firing a ceramic, which is characterized in that 6. The ceramic firing apparatus according to claim 3, 4, or 5, wherein the supporting means is below a supporting portion that supports the object to be processed, and a lower end side of the object to be processed is loosely inserted and added. A ceramic firing apparatus having a hole for restricting a swinging range of the object to be processed during shaking. 7. The ceramic firing apparatus according to claim 6, wherein the diameter d ₂ of the hole of the support means is 1. When the diameter of the lower end side of the object to be loosely inserted into the hole is d ₀ . 0 <d ₂
/ D ₀ ≦ 2.0 Ceramic firing apparatus.