Roller hearth type firing furnace

Abstract

The objective is to provide a roller hearth type firing furnace in which the rollers and drive unit are connected by a cap that has excellent shaft wobble prevention and durability. [Solution] A roller hearth type firing furnace that performs sintering while conveying a workpiece with a conveyor roller, the furnace having a cylindrical cap used to connect the output shaft of a drive device to the roller shaft portion of a conveyor roller arranged coaxially with the output shaft, the cap being made of metal, and having a plurality of slits formed on the outer surface of the cap, one of which is a long slit that penetrates from one end in the axial direction to the other, and the remaining slits are short slits shorter than the long slit.

Description

Technical Field

[0001] The present invention relates to a roller hearth type firing furnace.

Background Art

[0002] A roller hearth type firing furnace is a firing furnace that rotationally drives a large number of rollers arranged in the furnace and fires a workpiece placed thereon while conveying it, and can continuously and rapidly fire a large amount of workpieces. The rollers are made of ceramics, and the rollers and the driving device are connected to each other by a connecting member.

[0003] In FIGS. 3(B) and 3(C) of Patent Document 1, a method of connecting a roller and a driving device by a metal cap (connecting member) is disclosed. However, in the metal cap of Patent Document 1, a gap is formed between the roller and the metal cap, which may cause shaft play. Since shaft play is directly related to meandering and vibration of the workpiece, a cap that can prevent shaft play is required.

[0004] Patent Document 2 discloses a method of connecting a roller and a driving device by a silicone rubber cap. Although silicone has higher heat resistance than other rubbers, its heat resistance temperature is 200 to 300°C, so its durability was not sufficient when sintering workpieces with a high sintering temperature (for example, multilayer ceramic capacitors).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention aims to provide a roller hearth type firing furnace in which the rollers and drive unit are connected by a cap that has excellent axial wobble prevention effect and durability. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides (1) a roller hearth type firing furnace that performs sintering while conveying a workpiece with a conveyor roller, wherein the furnace has a cylindrical cap used to connect the output shaft of a drive device to the roller shaft portion of the conveyor roller which is arranged coaxially with the output shaft, the cap is made of metal, and a plurality of slits are formed on the outer surface of the cap, one of which is a long slit that penetrates from one end in the axial direction to the other, and the remaining slits are short slits which are shorter than the long slit.

[0008] (2) The roller hearth type firing furnace according to (1) above, characterized in that a plurality of short slits are provided on one end and the other end of the cap, and the central angle α of the spacing between the slits in the circumferential direction of the cap is 30 degrees or more and 60 degrees or less.

[0009] (3) The roller hearth type firing furnace according to (1) or (2) above, characterized in that the cap is fitted over both the tip of the output shaft and the tip of the roller shaft portion.

[0010] (4) A roller hearth type firing furnace according to any one of (1) to (3) above, characterized by having a clamping member for clamping the cap.

[0011] (5) The roller hearth type firing furnace according to any one of (1) to (4) above, characterized in that the conveying rollers include high-speed conveying rollers that rotate in a range of 800 rpm to 1000 rpm. [Effects of the Invention]

[0012] According to the present invention, by connecting the rollers and drive unit in a roller hearth type firing furnace with a cap that has excellent axial wobble prevention effect and durability, meandering of the processed material can be appropriately prevented. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view of a roller hearth type firing furnace. [Figure 2] This is a magnified view of the connection between the roller extension and the output shaft (with the cap removed). [Figure 3] This is a magnified view of the connection point between the roller extension and the output shaft (with the cap attached). [Figure 4] This is a perspective view of the cap. [Figure 5] This is a cross-section of the cap. [Figure 6] This is a perspective view of the clamping member. [Modes for carrying out the invention]

[0014] Figure 1 is a schematic cross-sectional view of a roller hearth firing furnace, cut in a direction perpendicular to the material transport direction. The furnace chamber 2 of the roller hearth firing furnace 1 includes the side walls 2a, top wall 2b, and bottom wall 2c, and extends in the material transport direction (corresponding to the direction normal to the plane of the paper). The materials to be processed include tiles, fine ceramics, multilayer ceramic capacitors, etc.

[0015] Numerous conveying rollers 4 are arranged inside the furnace chamber 2 in the direction of conveying the processed material (hereinafter abbreviated as "conveying direction"). Ceramics with excellent high-temperature durability are used for the conveying rollers 4. The ceramics may be silicon carbide, mullite, etc. The processed material can be conveyed by the rotation of these conveying rollers 4 around an axis extending in the thickness direction of the side wall 2a.

[0016] The furnace chamber 2 is divided into a plurality of small chambers by partition walls (not shown) intermittently installed in the conveying direction. Gas passages (not shown) are formed in the wall portions of each small chamber. By flowing gas in or out through this gas passage, the atmosphere (for example, non-oxidizing, mixing ratio of nitrogen and hydrogen) of each small chamber can be controlled.

[0017] The furnace chamber 2 can be configured, for example, by arranging a temperature-rising zone, a holding zone, and a cooling zone in this order from the upstream side in the conveying direction.

[0018] The furnace chamber 2 is adjacent to the drive-side accommodation chamber 9 across the side wall 2a. One end of the conveying roller 4 is provided with a roller extension portion 4a (corresponding to a roller shaft portion) extending into the drive-side accommodation chamber 9 and a universal joint 4b. However, the universal joint 4b may be omitted.

[0019] Figs. 2 and 3 are enlarged views of the connection portion between the roller extension portion 4a of the conveying roller 4 and the output shaft 6. Fig. 2 shows the state where the cap is removed, and Fig. 3 shows the state where the cap is attached. In Fig. 3, the elements inside the cap are shown in perspective. The output shaft 6 rotates by the power generated by a drive device (not shown). The output shaft 6 and the roller extension portion 4a face each other in the axial direction, and the cap 7 is put on so as to cover both the tip of the output shaft 6 and the tip of the roller extension portion 4a.

[0020] Fig. 4 is a perspective view of the cap. Fig. 5 is a cross-sectional view of the cap in Fig. 4 cut along the dotted line k. The cap 7 is cylindrical and made of metal. The metal may be stainless steel (for example, SUS304). By making the cap 7 of metal, the heat resistance can be enhanced compared to a silicone cap. Therefore, the present invention can also be applied to a roller hearth type firing furnace for processing an object whose sintering temperature reaches 1300°C, such as a multilayer ceramic capacitor.

[0021] Multiple slits 70 are formed on the outer circumferential surface of the cap 7. One of these slits 70 is a long slit 70a that penetrates from one axial end to the other of the cap 7, while the remaining slits 70 are short slits 70b that are shorter than the long slit 70a. Note that the slits 70 are omitted in Figures 1 and 3 to avoid making the drawings too complex. The width of the long slit 70a is preferably 0.8 mm or more and 1.2 mm or less.

[0022] The inventors also considered a method of connecting the roller extension 4a and the output shaft 6 using a cap with only a long slit 70a (through slit) formed on it. However, with this method, the cap 7 was difficult to deform, and if a certain amount of stress was applied to deform the cap 7, the conveyor roller 4 (ceramic roller) was damaged. Therefore, the inventors formed a short slit 70b in addition to the long slit 70a in order to deform the cap 7 to an extent that would not damage the conveyor roller 4.

[0023] Multiple short slits 70b are provided on both the axial end and the other end of the cap 7. The width of the short slits 70b is preferably 0.8 mm or more and 1.2 mm or less. When the length of each short slit 70b located on one end of the cap 7 is defined as L1, the length of each short slit 70b located on the other end of the cap 7 is defined as L2, and the length of the area without slits between these short slits 70b is defined as L3, preferably, both lengths L1 and L2 are greater than length L3. If length L3 is made greater than lengths L1 and L2, the short slits 70b become excessively short, making the cap 7 less susceptible to deformation.

[0024] The length L3 is preferably 5 mm or more. If the length L3 is excessively short (in other words, if the lengths L1 and L2 are excessively long), the rigidity of the cap 7 will decrease, making it more prone to breakage. Preferably, lengths L1 and L2 are approximately equal to each other. By making lengths L1 and L2 equal, the cap 7 can be deformed uniformly overall.

[0025] When the spacing of the slits 70 in the circumferential direction is expressed by the central angle α, the central angle α is a divisor of 360 degrees, preferably between 30 and 60 degrees, and more preferably between 45 and 60 degrees. If the central angle α is excessively large, the number of short slits 70b decreases, making the cap 7 less susceptible to deformation. Conversely, if the central angle α is excessively small, the rigidity of the cap 7 decreases, and processing costs increase. For example, if the central angle α is set to 30 degrees, 22 short slits 70b (11 on each side x 2) can be formed. If the central angle α is set to 45 degrees, 14 short slits 70b (7 on each side x 2) can be formed. If the central angle α is set to 60 degrees, 10 short slits 70b (5 on each side x 2) can be formed.

[0026] The clamp member 8 tightens the cap 7 in the diameter-reducing direction at two points on the outer circumferential surface of the cap 7. Figure 6 is a perspective view of the clamp member. The clamp member 8 comprises a clamp body 8a and a pair of ear-shaped handles 8b and 8c, the clamp body 8a being formed in a ring shape from steel. When the pair of handles 8b and 8c are moved toward each other against elastic force, the clamp body 8a expands in diameter, and when the handles 8b and 8c are separated from the expanded state, the inner diameter of the clamp body 8a shrinks due to elastic recovery.

[0027] When the clamp member 8 shrinks in diameter, the cap 7 held in the clamp member 8 deforms and presses against the output shaft 6 and the roller extension 4a. In this embodiment, since a cap 7 with a short slit 70b is used, the cap 7 can be appropriately deformed with a stress that does not damage the ceramic conveyor roller 4. Because the cap 7 is fastened using a clamp, it is easy to attach and detach, and the conveyor roller 4 can be easily replaced. However, the clamp member 8 is not limited to the configuration shown in Figure 6; for example, a general hose clamp may be used to fasten the cap 7.

[0028] The cap 7 presses against the output shaft 6 and the roller extension 4a, allowing the processed material to be transported with these components aligned on the same axis (in other words, without meandering of the processed material). The inventors have separately confirmed that this effect can also be obtained during high-speed transport. High-speed transport is defined as a rotational speed of approximately 800 to 1000 rpm for the transport roller 4. Normally, the rotational speed of the transport roller 4 is approximately 1 to 10 rpm (hereinafter also referred to as normal rotation), but there are cases where it is desirable to drive the transport roller 4 at a high-speed rotation exceeding normal rotation.

[0029] For example, multilayer ceramic capacitors have a structure in which nickel and barium titanate are layered, but the sintering temperature of nickel is around 800°C, and the sintering temperature of barium titanate is around 1300°C. When firing in a roller hearth type firing furnace 1, it is necessary to raise the temperature of the workpiece to the sintering temperature of nickel in the heating zone, and then raise the temperature of the workpiece to the sintering temperature of barium titanate in the holding zone. By shortening the time from when the nickel sintersects until the barium titanate sintersects, it is possible to prevent the nickel from continuing to expand for a long time, thereby reducing the possibility of product defects. Therefore, it is desirable to rotate the conveying rolls installed between the heating zone and the holding zone at high speed.

[0030] The present invention can be suitably used to connect such high-speed conveying rollers to drive devices. However, it goes without saying that the present invention can also be applied to normally rotating conveying rollers.

[0031] By using the cap 7 of this embodiment, even when the conveying roller 4 is rotated at high speed, the material to be processed can be conveyed without meandering while preventing axial wobble. [Explanation of Symbols]

[0032] 1. Roller hearth type firing furnace 2 Furnace room 4 Conveyor rollers 4a Roller extension 6 Output shaft 7 caps 8. Clamping member 70 slits 70a Long Slit 70b Short Slit

Claims

1. A roller hearth type firing furnace that performs sintering while conveying the material to be processed with conveyor rollers, It has a cylindrical cap used to connect the output shaft of the drive unit to the roller shaft portion of the conveying roller which is arranged coaxially with the output shaft, The aforementioned cap is made of metal. Multiple slits are formed on the outer surface of the cap, one of which is a long slit that penetrates from one end to the other in the axial direction, and the remaining slits are short slits that are shorter than the long slit. A roller hearth type firing furnace characterized by the following features.

2. Multiple short slits are provided on one end and the other end of the cap, The spacing between the slits in the circumferential direction of the cap is expressed by a central angle α, which is between 30 degrees and 60 degrees. The roller hearth type firing furnace according to feature 1.

3. The cap is fitted over both the tip of the output shaft and the tip of the roller shaft portion. A roller hearth type firing furnace according to claim 1 or 2, characterized in that it is as described above.

4. Having a clamping member for clamping the cap, A roller hearth type firing furnace according to claim 1 or 2, characterized in that it is as described above.

5. The aforementioned conveying roller includes a high-speed conveying roller that rotates in a range of 800 rpm to 1000 rpm. A roller hearth type firing furnace according to claim 1 or 2, characterized in that it is as described above.

6. The aforementioned conveying roller includes a high-speed conveying roller that rotates in a range of 800 rpm to 1000 rpm. The roller hearth type firing furnace according to feature 3.

7. The aforementioned conveying roller includes a high-speed conveying roller that rotates in a range of 800 rpm to 1000 rpm. The roller hearth type firing furnace according to feature 4.

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